Final Environmental Impact Statement

Corporate Average Fuel Economy Standards,

Passenger Cars and Light Trucks, 

Model Years 2012-2016

February 2010

National HighwayTraffic 

Safety Administration



FINAL ENVIRONMENTAL IMPACT STATEMENT

CORPORATE AVERAGE FUEL ECONOMY STANDARDS,

PASSENGER CARS AND LIGHT TRUCKS, MYS 2012-2016 

FEBRUARY 2010 

LEAD AGENCY: 

NATIONAL HIGHWAY TRAFFIC SAFETY ADMINISTRATION

COOPERATING AGENCY: 

U.S. ENVIRONMENTAL PROTECTION AGENCY

Table of Contents 

List of Acronyms and Abbreviations ......................................................................................................xii 

Glossary ..................................................................................................................................................xvi 

Summary .....................................................................................................................................................1 

Chapter 1 Purpose and Need for the Proposed Action.........................................................................1-1

1.1 Introduction ...............................................................................................................................1-1

1.2 Joint Rulemaking and NEPA Process........................................................................................1-2

1.2.1 Building Blocks of the National Program...................................................................1-3

1.2.2 Joint Proposal for a National Program........................................................................1-5

1.3 Proposed Action ........................................................................................................................1-8

1.4 Purpose and Need ......................................................................................................................1-8

1.5 Public Review and Comment ..................................................................................................1-10

1.5.1 Agency Consultation.................................................................................................1-11

1.5.2 Summary of Scoping Comments ..............................................................................1-12

1.5.3 Summary of Comments on the DEIS........................................................................1-17

1.5.4 Summary of Rulemaking Comments Relevant to the DEIS.....................................1-21

1.5.5 Next Steps in the NEPA Process and CAFE Rulemaking ........................................1-24

Chapter 2 Proposed Action and Alternatives........................................................................................2-1

2.1 Introduction ...............................................................................................................................2-1

2.2 Standards-setting .......................................................................................................................2-1

2.2.1 Volpe Model ...............................................................................................................2-2

2.2.2 Vehicle Market Forecast .............................................................................................2-4

2.2.3 Technology Assumptions............................................................................................2-5

2.2.4 Economic Assumptions ..............................................................................................2-9

2.3 Alternatives..............................................................................................................................2-11

2.3.1 Alternative 1: No Action...........................................................................................2-14

2.3.2 Alternative 2: 3-Percent Alternative .........................................................................2-14

2.3.3 Alternative 3: 4-Percent Alternative .........................................................................2-14

2.3.4 Alternative 4: Preferred Alternative..........................................................................2-14

2.3.5 Alternative 5: 5-Percent Alternative .........................................................................2-15

2.3.6 Alternative 6: MNB Alternative ...............................................................................2-15

2.3.7 Alternative 7: 6-Percent Alternative .........................................................................2-15

2.3.8 Alternative 8: 7-Percent Alternative .........................................................................2-15

2.3.9 Alternative 9: TCTB Alternative ..............................................................................2-15

2.3.10 Fuel Economy Levels for Each Alternative..............................................................2-16

2.3.11 Greenhouse Gas Emission Standards for Light-duty Vehicles .................................2-18

2.4 Sensitivity Analysis .................................................................................................................2-19

2.5 Alternatives Considered But Not Analyzed in Detail..............................................................2-23

2.6 Comparison of Alternatives.....................................................................................................2-25

2.6.1 Direct and Indirect Effects ........................................................................................2-26

2.6.2 Cumulative Effects....................................................................................................2-40 

Chapter 3 Affected Environment and Environmental Consequences ................................................3-1

3.1 Introduction ...............................................................................................................................3-1

i 
List of Acronyms and Abbreviations 

3.1.1 Direct and Indirect Impacts.........................................................................................3-2

3.1.2 Areas Not Affected .....................................................................................................3-2

3.1.3 Approach to Scientific Uncertainty and Incomplete Information...............................3-2

3.1.4 Common Methodologies.............................................................................................3-3

3.2 Energy........................................................................................................................................3-9 

3.2.1 Affected Environment.................................................................................................3-9

3.2.2 Methodology.............................................................................................................3-11 

3.2.3 Environmental Consequences...................................................................................3-12 

3.3 Air Quality...............................................................................................................................3-15

3.3.1 Affected Environment...............................................................................................3-15

3.3.2 Methodology.............................................................................................................3-23

3.3.3 Environmental Consequences...................................................................................3-36

3.4 Climate.....................................................................................................................................3-60

3.4.1 Introduction – Greenhouse Gases and Climate Change............................................3-60

3.4.2 Affected Environment...............................................................................................3-66

3.4.3 Methodology.............................................................................................................3-73

3.4.4 Environmental Consequences...................................................................................3-84

3.5 Other Potentially Affected Resource Areas...........................................................................3-111

3.5.1 Water Resources .....................................................................................................3-111

3.5.2 Biological Resources ..............................................................................................3-114

3.5.3 Land Use and Development....................................................................................3-117

3.5.4 Safety and Other Impacts to Human Health ...........................................................3-118

3.5.5 Hazardous Materials and Regulated Wastes...........................................................3-118

3.5.6 Land Uses Protected under U.S. Department of Transportation Act Section 4(f) ..3-121

3.5.7 Historic and Cultural Resources .............................................................................3-121

3.5.8 Noise .......................................................................................................................3-122

3.5.9 Environmental Justice.............................................................................................3-123

3.6 Unavoidable Impacts and Irreversible and Irretrievable Resource Commitment..................3-125

3.6.1 Unavoidable Adverse Impacts ................................................................................3-125

3.6.2 Short-term Uses and Long-term Productivity.........................................................3-126

3.6.3 Irreversible and Irretrievable Commitment of Resources.......................................3-126

3.7 EPA Proposed Action and Analysis ......................................................................................3-127

3.7.1 Overview.................................................................................................................3-127

3.7.2 Summary of EPA Proposal Impact Analysis ..........................................................3-128

Chapter 4 Cumulative Impacts...............................................................................................................4-1

4.1 Introduction ...............................................................................................................................4-1

4.1.1 Approach to Scientific Uncertainty and Incomplete Information...............................4-2

4.1.2 Temporal and Geographic Boundaries .......................................................................4-3

4.1.3 Reasonably Foreseeable Future Actions .....................................................................4-3

4.2 Energy........................................................................................................................................4-6 

4.2.1 Affected Environment......................................................................................................4-6 

4.2.2 Methodology....................................................................................................................4-6 

4.2.3 Environmental Consequences..........................................................................................4-7 

4.3 Air Quality...............................................................................................................................4-10 

4.3.1 Affected Environment....................................................................................................4-10 

4.3.2 Methodology..................................................................................................................4-10 

4.3.3 Environmental Consequences........................................................................................4-11 

4.4 Climate.....................................................................................................................................4-39 

4.4.1 Introduction – Greenhouse Gases and Climate Change.................................................4-39 

ii 
List of Acronyms and Abbreviations 

4.4.2 Affected Environment....................................................................................................4-39 

4.4.3 Methodology..................................................................................................................4-39 

4.4.4 Environmental Consequences........................................................................................4-49 

4.5 Health, Societal, and Environmental Impacts of Climate Change...........................................4-66

4.5.1 Introduction...............................................................................................................4-66

4.5.2 Methodology.............................................................................................................4-67

4.5.3 Freshwater Resources ...............................................................................................4-70

4.5.4 Terrestrial and Freshwater Ecosystems.....................................................................4-85

4.5.5 Marine, Coastal Systems, and Low-lying Areas.....................................................4-106

4.5.6 Food, Fiber, and Forest Products ............................................................................4-117

4.5.7 Industries, Settlements, and Society .......................................................................4-129

4.5.8 Human Health .........................................................................................................4-145

4.5.9 Tipping Points and Abrupt Climate Change ...........................................................4-154

4.6 Environmental Justice............................................................................................................4-166 

4.6.1 Affected Environment..................................................................................................4-166 

4.6.2 Environmental Consequences......................................................................................4-166 

4.7 Non-climate Cumulative Impacts of Carbon Dioxide ...........................................................4-169 

4.7.1 Affected Environment..................................................................................................4-169 

4.7.2 Environmental Consequences......................................................................................4-170 

Chapter 5 Mitigation ...............................................................................................................................5-1

5.1 Overview of Impacts .................................................................................................................5-1

5.2 Mitigation Measures ..................................................................................................................5-2

Chapter 6 Preparers ................................................................................................................................6-1 

6.1 National Highway Traffic Safety Administration .....................................................................6-1 

6.2 Consultant Team........................................................................................................................6-2 

Chapter 7 References...............................................................................................................................7-1

7.1 Purpose and Need References ...................................................................................................7-1

7.2 Proposed Action and Alternatives References...........................................................................7-1

7.3 Affected Environment and Environmental Consequences References .....................................7-1

7.3.1 Introduction References...................................................................................................7-1 

7.3.2 Energy References ...........................................................................................................7-2 

7.3.3 Air Quality References ....................................................................................................7-2 

7.3.4 Climate References ..........................................................................................................7-8 

7.3.5 Other Potentially Affected Resource References...........................................................7-14 

7.3.6 Unavoidable Impacts and Irreversible and Irretrievable Resource References .............7-20 

7.3.7 EPA Action and Analysis References............................................................................7-20 

7.4 Cumulative Impacts References ..............................................................................................7-20

7.4.1 Introduction References.................................................................................................7-20 

7.4.2 Energy References .........................................................................................................7-21 

7.4.3 Air Quality References ..................................................................................................7-21 

7.4.4 Climate Change References...........................................................................................7-21 

7.4.5 Health, Societal, and Environmental Impacts of Climate Change.................................7-23 

7.4.6 Environmental Justice References ...............................................................................7-109 

7.4.7 Non-climate Cumulative Impacts of CO2 References .................................................7-110 

7.5 Mitigation References............................................................................................................7-115

iii 
List of Acronyms and Abbreviations 

Chapter 8 Distribution List.....................................................................................................................8-1 

8.1 Federal Agencies .......................................................................................................................8-1 

8.2 State And Local Government Organizations.............................................................................8-5 

8.3 Elected Officials ........................................................................................................................8-6 

8.4 Native American Tribes.............................................................................................................8-8 

8.5 Stakeholders...............................................................................................................................8-8 

Chapter 9 Index........................................................................................................................................9-1 

Chapter 10 Responses to Public Comments ........................................................................................10-1 

10.1 Purpose And Need ...................................................................................................................10-4 

10.1.1 Purpose and Need Statement.....................................................................................10-4 

10.1.2 Public Review and Comment....................................................................................10-6 

10.1.3 Agency Consultation.................................................................................................10-7

10.1.4 Document Structure and Readability ......................................................................10-10 

10.1.5 Joint Rulemaking and the National Program ..........................................................10-10 

10.2 The Proposed Action and Alternatives ..................................................................................10-14 

10.2.1 Proposed Action......................................................................................................10-14 

10.2.2 Standards-setting.....................................................................................................10-16 

10.2.3 Volpe Model ...........................................................................................................10-19 

10.2.4 Alternatives.............................................................................................................10-37 

10.3 Affected Environment and Environmental Consequences ....................................................10-55 

10.3.1 Common Methodologies.........................................................................................10-55 

10.3.2 Air Quality ..............................................................................................................10-55 

10.3.3 Climate Tipping Points ...........................................................................................10-59 

10.3.4 Other Potentially Affected Resource Areas ............................................................10-61 

10.3.5 Unavoidable Impacts and Irreversible and Irretrievable Resource Commitment ...10-66 

10.4 Cumulative impacts ...............................................................................................................10-67 

10.4.1 Reasonably Foreseeable Future Actions .................................................................10-67 

10.4.2 Climate Methodology .............................................................................................10-69 

10.5 Mitigation ..............................................................................................................................10-72 

10.6 Rulemaking............................................................................................................................10-73 

10.6.1 Alternative Fuel Credits..........................................................................................10-73 

10.6.2 Regulatory Compliance Penalties ...........................................................................10-73 

10.6.3 Vehicle Performance Characteristics ......................................................................10-74 

10.6.4 Cost and Benefits of the Proposed Rule..................................................................10-75 

10.6.5 Vehicle Classification .............................................................................................10-75

List of Appendices 

The appendices to this Draft Environmental Impact Statement (DEIS) have been provided electronically 

on the accompanying CD. 

Appendix A Sources Identified in Scoping Comments and Sources Identified in DEIS Comments 

Appendix B Agency Consultation Letters 

Appendix C Air Quality Modeling Data 

Appendix D NHTSA Preliminary Regulatory Impact Assessment 

iv 
List of Acronyms and Abbreviations 

Appendix E EPA Draft Regulatory Impact Assessment 

Appendix F Air Quality Modeling and Health Impacts Assessment for the MY 2012-2016 NHTSA 

CAFE Standards 

Appendix G Endangered Species Act Consideration 

List of Tables 

Table 2.2-1 Forecasts, Assumptions, and Parameters Used to Analyze Impacts of 

Regulatory Alternatives .................................................................................................2-10

Table 2.3-1 Required MPG by Alternative .......................................................................................2-16

Table 2.3-2 Achieved MPG by Alternative.......................................................................................2-18

Table 2.3-3 Projected Fleet-Wide Emissions Compliance Levels under the Proposed 

Footprint-Based CO2 Standards (g/mi) ..........................................................................2-19

Table 2.3-4 Projected Fleet-Wide Achieved Emission Levels under the Proposed 

Footprint-Based CO2 Standards (g/mi) ..........................................................................2-19

Table 2.4-1 Sensitivity Analysis of Fuel Consumption (2012-2060; billion gallons) under 

Expected Value Model Input Assumptions versus other Model Input Assumptions 

for Selected Alternatives................................................................................................2-22

Table 2.6-1 Passenger Car Annual Fuel Consumption and Fuel Savings by Alternative 

(billion gallons gasoline equivalent)..............................................................................2-27

Table 2.6-2 Light Truck Annual Fuel Consumption and Fuel Savings by Alternative 

(billion gallons gasoline equivalent)..............................................................................2-27

Table 2.6-3 Car & Light Truck Annual Fuel Consumption and Fuel Savings by Alternative 

(billion gallons gasoline equivalent)..............................................................................2-28

Table 2.6-4 Nationwide Criteria Pollutant Emissions and Toxic Air Pollutant Emissions from 

Passenger Cars and Light Trucks (tons/year, Calendar Year 2030) by Alternative ......2-29

Table 2.6-5 Nationwide Changes in Health Outcomes from Criteria Pollutant Emissions 

(cases/year) from Passenger Cars and Light Trucks by Alternative ............................2-30

Table 2.6-7 Emissions and Emissions Reductions (MMTCO2) from 2012-2100 by 

Alternative ....................................................................................................................2-31

Table 2.6-8 CO2 Concentrations, Global Mean Surface Temperature Increase, and 

Sea-level Rise by Alternative .......................................................................................2-33

Table 2.6-9 Global Mean Precipitation (percent change) ................................................................2-39

Table 2.6-10 CO2 Concentrations, Global Mean Surface Temperature Increase, and Sea-level 

Rise for Varying Climate Sensitivities for Selected Alternatives ................................2-40

Table 2.6-11 Cumulative Effects of Passenger Car Annual Fuel Consumption and Fuel 

Savings by Alternative (billion gallons gasoline equivalent) ........................................2-41

Table 2.6-12 Cumulative Effects of Light Truck Annual Fuel Consumption and Fuel 

Savings by Alternative (billion gallons gasoline equivalent) .......................................2-42

Table 2.6-13 Cumulative Effects of Car & Light Truck Annual Fuel Consumption and 

Fuel Savings by Alternative (billion gallons gasoline equivalent) ................................2-42

Table 2.6-14 Cumulative Nationwide Criteria Pollutant Emissions (tons/year) from 

Passenger Cars and Light Trucks by Alternative..........................................................2-43

Table 2.6-15 Cumulative Nationwide Changes in Health Outcomes (cases/year) from 

Criteria Air Pollutant Emissions from Passenger Cars and Light Trucks 

by Alternative ...............................................................................................................2-44

v 
List of Acronyms and Abbreviations 

Table 2.6-16 Cumulative Nationwide Monetized Health Benefits (U.S. million dollars/year) 

from Criteria Air Pollutant Emissions from Passenger Cars and Light Trucks by 

Alternative ....................................................................................................................2-45

Table 2.6-17 Cumulative Effects of Emissions and Emissions Reductions (MMTCO2) 

from 2012-2100 by Alternative ....................................................................................2-46

Table 2.6-18 Cumulative Effects on CO2 Concentrations, Global Mean Surface Temperature 

Increase, and Sea-level Rise Using MAGICC (MiniCAM Level 3) by 

Alternative ....................................................................................................................2-48

Table 2.6-19 Cumulative Effects on Global Mean Precipitation (percent change) ............................2-53

Table 2.6-20 Cumulative Effects on CO2 Concentrations, Global Mean Surface 

Temperature Increase, and Sea-level Rise for Varying Climate Sensitivities 

for Selected Alternatives ...............................................................................................2-55

Table 3.2.1-1 Energy Consumption By Sector.....................................................................................3-10

Table 3.2.3-1 Passenger Car Annual Fuel Consumption and Fuel Savings (billion gallons of 

gasoline equivalent) .......................................................................................................3-13

Table 3.2.3-2 Light Truck Annual Fuel Consumption and Fuel Savings (billion gallons of 

gasoline equivalent) .......................................................................................................3-13

Table 3.2.3-3 Combined Passenger Car and Light Truck Annual Fuel Consumption and Fuel 

Savings (billion gallons of gasoline equivalent)............................................................3-14

Table 3.3.1-1 National Ambient Air Quality Standards .........................................................................3-16

Table 3.3.2-1 Nonattainment Areas for Ozone and PM2.5 ......................................................................3-27

Table 3.3.2-2 Human Health and Welfare Effects of PM2.5....................................................................3-32

Table 3.3.2-3 Benefits-per-ton Values (2007$) Derived Using the ACS Cohort Study for 

PM-related Premature Mortality (Pope et al. 2002) and a 3-Percent 

Discount Rate.................................................................................................................3-33

Table 3.3.2-4 Incidence-per-ton Values for Health Outcomes – Pope et al. 2002b 

Premature Mortality – Pope et al. 2002 .........................................................................3-33

Table 3.3.3-1 Nationwide Criteria Pollutant Emissions (tons/year) from Passenger Cars and 

Light Trucks by Alternative...........................................................................................3-38

Table 3.3.3-2 Nationwide Criteria Pollutant Emissions (tons/year) in 2030 from Passenger 

Cars and Light Trucks, by Vehicle Type and Alternative .............................................3-40

Table 3.3.3-3 Nationwide Changes in Criteria Pollutant Emissions (tons/year) from Passenger 

Cars and Light Trucks by Alternative............................................................................3-41

Table 3.3.3-4 Nationwide Toxic Air Pollutant Emissions (tons/year) from Passenger Cars and 

Light Trucks by Alternative...........................................................................................3-43

Table 3.3.3-5 Nationwide Toxic Air Pollutant Emissions (tons/year) in 2030 from Passenger 

Cars and Light Trucks, by Vehicle Type and Alternative .............................................3-46

Table 3.3.3-6 Nationwide Changes in Toxic Air Pollutant Emissions (tons/year) from Passenger 

Cars and Light Trucks by Alternative...........................................................................3-48

Table 3.3.3-7 Criteria Pollutant Emissions from Passenger Cars and Light Trucks, Maximum 

Changes by Nonattainment Area and Alternative.........................................................3-49

Table 3.3.3-8 Nationwide Changes in Health Outcomes from Criteria Pollutant Emissions 

(cases/year) from Passenger Cars and Light Trucks by Alternative.............................3-50

Table 3.3.3-9 Nationwide Monetized Health Benefits (U.S. million dollars/year) from Criteria 

Pollutant Emissions from Passenger Cars and Light Trucks by Alternative .................3-51

Table 3.3.3-10 Changes in Toxic Air Pollutant Emissions from Passenger Cars and Light Trucks, 

Maximum Changes by Nonattainment Area and Alternative........................................3-52

Table 3.4.4-1 Emissions and Emissions Reductions (MMTCO2) from 2012-2100 by 

Alternative .....................................................................................................................3-85

Table 3.4.4-2 Nationwide Emissions of Greenhouse Gases (MMT per Year) from Passenger 

Cars and Light Trucks by Alternative...........................................................................3-89

vi 
List of Acronyms and Abbreviations 

Table 3.4.4-3 Comparison of MAGICC Modeling Results and Reported IPCC Results 

(IPCC 2007)...................................................................................................................3-96

Table 3.4.4-4 CO2 Concentrations, Global Mean Surface Temperature Increase, and Sea-Level 

Rise Using MAGICC (RCP MiniCAM Reference) by Alternative...............................3-97

Table 3.4.4-5 Summary of Regional Changes to Warming and Seasonal Temperatures 

Extracted from the IPCC Fourth Assessment Report (Christensen et al. 2007)..........3-102

Table 3.4.4-6 Global Mean Precipitation Change (scaled, % per °C) (Meehl et al. 2007a) ..............3-104

Table 3.4.4-7 Global Mean Precipitation (Percent Change) Based on MiniCAM Reference 

Scenario Using Increases in Global Mean Surface Temperature Simulated by 

MAGICC by Alternative .............................................................................................3-105

Table 3.4.4-8 Summary of Regional Changes to Precipitation Extracted from the IPCC Fourth 

Assessment Report (Christensen et al. 2007) ..............................................................3-107

Table 3.4.4-9 CO2 Concentrations, Global Mean Surface Temperature Increases, and Sea-level 

Rise (cm) for Varying Climate Sensitivities for Selected Alternatives .......................3-110

Table 3.7.2-1 Impacts of Proposed Standards on Fuel Savings .........................................................3-130

Table 3.7.2-2 Impacts of Proposed Standards on Non-GHG Emissions (Short Tons Per Year) .......3-131

Table 4.1.3-1 AEO 2019-2030 Projected Gains in Fuel Economy Reflected in Analysis of 

Cumulative Impacts .........................................................................................................4-4

Table 4.2.3-1 Cumulative Effects of Passenger Car Annual Fuel Consumption and Fuel Savings 

(billion gallons of gasoline equivalent)............................................................................4-7

Table 4.2.3-2 Cumulative Effects of Light Truck Annual Fuel Consumption and Fuel Savings 

(billion gallons of gasoline equivalent)............................................................................4-8

Table 4.2.3-3 Cumulative Effects of Combined Passenger Car and Light Truck Annual Fuel 

Consumption and Fuel Savings .......................................................................................4-9

Table 4.3.3-1 Cumulative Nationwide Criteria Pollutant Emissions (tons/year) from Passenger 

Cars and Light Trucks by Alternative...........................................................................4-13

Table 4.3.3-2 Cumulative Nationwide Criteria Pollutant Emissions (tons/year) in 2030 from 

Passenger Cars and Light Trucks, by Vehicle Type and Alternative ............................4-15

Table 4.3.3-3 Cumulative Nationwide Criteria Pollutant Emission Changes (tons/year) from 

Passenger Cars and Light Trucks by Alternative Compared to No Action 

Alternative .....................................................................................................................4-16

Table 4.3.3-4 Cumulative Nationwide Toxic Air Pollutant Emissions (tons/year) from Passenger 

Cars and Light Trucks by Alternative...........................................................................4-18

Table 4.3.3-5 Cumulative Nationwide Toxic Air Pollutant Emissions (tons/year) in 2030 from 

Passenger Cars and Light Trucks, by Vehicle Type and Alternative ............................4-21

Table 4.3.3-6 Cumulative Nationwide Changes in Toxic Air Pollutant Emissions (tons/year) from 

Passenger Cars and Light Trucks by Alternative Compared to No Action 

Alternative .....................................................................................................................4-23

Table 4.3.3-7 Cumulative Criteria Pollutant Emissions from Passenger Cars and Light Trucks, 

Maximum Changes by Nonattainment Area and Alternative.......................................4-24

Table 4.3.3-8 Cumulative Nationwide Changes in Health Outcomes (cases/year) from Criteria 

Air Pollutant Emissions from Passenger Cars and Light Trucks by Alternative...........4-26

Table 4.3.3-9 Cumulative Nationwide Monetized Health Benefits (U.S. million dollars/year) 

 from Changes in Criteria Air Pollutant Emissions from Passenger Cars and 

Light Trucks by Alternative...........................................................................................4-27

Table 4.3.3-10 Cumulative Changes in Toxic Air Pollutant Emissions from Passenger Cars 

and Light Trucks, Maximum Changes by Nonattainment Area and Alternative...........4-29

Table 4.4.4-1 Cumulative Effects of Emissions and Emissions Reductions (MMTCO2) 

from 2012 to 2100 by Alternative..................................................................................4-51

Table 4.4.4-2 Cumulative Effects of Nationwide Emissions of Greenhouse Gases (MMT per year) 

from Passenger Cars and Light Trucks by Alternative..................................................4-53

vii 
List of Acronyms and Abbreviations 

Table 4.4.4-3 Comparison of MAGICC Results and Reported IPCC Results (IPCC 2007) ...............4-56

Table 4.4.4-4 Cumulative Effects on CO2 Concentrations, Global Mean Surface Temperature 

Increase, and Sea-level Rise Using MAGICC (MiniCAM Level 3) by 

Alternative .....................................................................................................................4-57

Table 4.4.4-5 Cumulative Effects on Global Mean Precipitation (Percent Change) Based on 

MiniCAM Level 3 Scenario Using Increases in Global Mean Surface 

Temperature Simulated by MAGICC by Alternative ....................................................4-63

Table 4.4.4-6 Cumulative Effects on CO2 Concentrations, Global Mean Surface Temperature 

Increase, and Sea-level Rise for Varying Climate Sensitivities for Selected 

Alternatives ...................................................................................................................4-65

Table 4.5.5-1 Common Coastal Ecosystem..........................................................................................4-107

Table 4.5.5-2 Common Marine Ecosystem Zones ...............................................................................4-108

Table 10-1 Outline of Issues Raised in Public Comments on the DEIS ..........................................10-2

Table 10-2 Index of Comments from Individuals, Federal and State Agencies, and 

Private Industry..............................................................................................................10-3

List of Figures 

Figure 2.6-1. Projected Annual Emissions (MMTCO2) by Alternative ..............................................2-32

Figure 2.6-2. CO2 Concentrations (ppm).............................................................................................2-34

Figure 2.6-3. Global Mean Surface Temperature Increase (°C)..........................................................2-35

Figure 2.6-4. Reduction in CO2 Concentrations (ppm) Compared to the No Action Alternative.......2-36

Figure 2.6-5. Reduction in Global Mean Temperature Compared to the No Action Alternative .......2-37

Figure 2.6-6. Cumulative Effects on CO2 Concentrations Using MAGICC .......................................2-49

Figure 2.6-7. Cumulative Effects on the Global Mean Surface Temperature Increase Using 

MAGICC by Alternative ...............................................................................................2-50

Figure 2.6-8. Cumulative Effects on CO2 Concentrations (Reduction Compared to the 

No Action Alternative) ..................................................................................................2-51

Figure 2.6-9. Cumulative Effects on Global Mean Temperature (Reduction Compared to 

the No Action Alternative).............................................................................................2-52

Figure 3.3.1-1. Vehicle Miles Traveled (VMT) vs. Vehicle Emissions (Source: Smith 2002).............3-21

Figure 3.3.3-1. Nationwide Criteria Pollutant Emissions (tons/year) from Passenger Cars and 

Light Trucks for 2030 by Alternative ............................................................................3-39

Figure 3.3.3-2. Nationwide Toxic Air Pollutant Emissions (tons/year) from Passenger Cars and 

Light Trucks for 2030 by Alternative ............................................................................3-44

Figure 3.4.1-1. Changes in Temperature, Sea Level, and Northern Hemisphere Snow Cover 

(Source: IPCC 2007b)...................................................................................................3-62

Figure 3.4.1-2. The Greenhouse Effect (Source: Le Treut et al. 2007) .................................................3-62

Figure 3.4.1-3. Contribution of Transportation to U.S. CO2 Emissions and Proportion Attributable 

by Mode, 2007 ...............................................................................................................3-64

Figure 3.4.3-1. Cascade of Uncertainty in Climate Change Simulations ..............................................3-75

Figure 3.4.3-2. Average GDP Growth Rates (1990 to 2030)..................................................................3-81

Figure 3.4.3-3. Global CO2 Emissions from Fossil Fuel Use .................................................................3-81

Figure 3.4.3-4. U.S. CO2 Emissions from Fossil Fuel Use.....................................................................3-82

Figure 3.4.3-5. World Primary Energy Use Forecast..............................................................................3-82

Figure 3.4.3-6. U.S. Primary Energy Use Forecast.................................................................................4-83

Figure 3.4.4-1. Emissions and Emissions Reductions (MMTCO2) from 2012 to 2100 by 

Alternative .....................................................................................................................4-86

viii 
List of Acronyms and Abbreviations 

Figure 3.4.4-2. Projected Annual Emissions (MMTCO2) by Alternative...............................................4-88

Figure 3.4.4-3. Projected Annual Emissions by Alternative, Compared to 2005 Levels for 

Cars and Light Trucks....................................................................................................3-91

Figure 3.4.4-4. Number of Passenger Cars and Light Trucks Equivalent to CO2 Reductions 

in 2016, Compared to the No Action Alternative ..........................................................3-92

Figure 3.4.4-5. Historical Carbon Emissions with Two Potential Pathways for the Future 

(Source: Socolow et al. 2004).......................................................................................3-94

Figure 3.4.4-6. Stabilization Wedges (Source: Socolow et al. 2004) .................................................. 3--94

Figure 3.4.4-7. CO2 Concentrations (ppm) ........................................................................................... 3--98

Figure 3.4.4-8. Global Mean Surface Temperature Increase (°C) ..........................................................3-99

Figure 3.4.4-9. Reduction in CO2 Concentrations (ppm) Compared to the No Action 

Alternative ...................................................................................................................3-100

Figure 3.4.4-10. Reduction in Global Mean Temperature Compared to the No Action 

Alternative ...................................................................................................................3-101

Figure 3.7.2-1. Estimated Projected Reductions in Global Mean Surface Temperatures from 

Baseline for Climate Sensitivities Ranging from 1.5–6 °C .........................................3-132

Figure 3.7.2-2. Estimated Projected Reductions in Global Mean Sea-Level Rise from 

Baseline for Climate Sensitivities Ranging from 1.5–6 °C ........................................3-132

Figure 4.3.3-1. Nationwide Criteria Pollutant Emissions (tons/year) from Passenger Cars and Light 

Trucks for 2030 by Alternative......................................................................................4-14

Figure 4.3.3-2. Cumulative Nationwide Toxic Air Pollutant Emissions (tons/year) from Passenger Cars 

and Light Trucks for 2030 by Alternative .....................................................................4-19

Figure 4.4.3-1. Average GDP Growth Rates (1990 to 2030) .................................................................4-47

Figure 4.4.3-2. Global Annual CO2 Emissions from Fossil Fuel Use ....................................................4-47

Figure 4.4.3-3. U.S. Annual CO2 Emissions from Fossil Fuel Use ........................................................4-48

Figure 4.4.3-4. World Primary Energy Use Forecast..............................................................................4-48

Figure 4.4.3-5. U.S. Primary Energy Use Forecast.................................................................................4-49

Figure 4.4.4-1. Cumulative Annual Emissions Under the MYs 2012-2016 Standards and Other 

Reasonably Foreseeable Future Actions (MMTCO2)....................................................4-52

Figure 4.4.4-2. Cumulative Effects on CO2 Concentrations...................................................................4-58

Figure 4.4.4-3. Cumulative Effects on Global Mean Surface Temperature Increase .............................4-59

Figure 4.4.4-4. Cumulative Effects on CO2 Concentrations (Reduction Compared to the 

No Action Alternative) ..................................................................................................4-60

Figure 4.4.4-5. Cumulative Effects on Global Mean Temperature (Reduction Compared to the 

No Action Alternative) ..................................................................................................4-61

Figure 4.5.3-1. Global Allocation of Water ............................................................................................4-70

Figure 4.5.4-1. Terrestrial Ecozones and Biomes of the World (Source: MA 2005c in 

Lettenmeier et al. 2008).................................................................................................4-86

Figure 4.5.4-2. Freshwater Major Habitat Types (MHTs) (Source: FEOW 2009)................................4-89

Figure 4.5.4-3. Level I Ecoregions in the North America (Source: CEC 1997)...................................4-92

ix 
List of Acronyms and Abbreviations 

List of Acronyms and Abbreviations 

+/- plus or minus 

°C degrees Celsius 

°F degrees Fahrenheit 

μg/m3 micrograms per cubic meter 

APA Administrative Procedures Act 

AEO Annual Energy Outlook 

AER Annual Energy Review 

AAM Alliance of Automobile Manufacturers 

AMFA Alternative Motor Fuels Act 

AMOC Atlantic Meridional Overturning Circulation 

AMT Automated Shift Manual Transmission 

AOGCM atmospheric-ocean general circulation models 

ATVM Advanced Technology Vehicles Manufacturing Loan Program 

BTU British thermal unit 

CAA Clean Air Act 

CAFE Corporate Average Fuel Economy 

CARB California Air Resources Board 

CBD Center for Biological Diversity 

CCSP Climate Change Science Program 

CEQ Council on Environmental Quality 

CFR Code of Federal Regulations 

CH4 methane 

cm centimeter 

CMAQ Congestion Mitigation and Air Quality Improvement 

CNG compressed natural gas 

CO carbon monoxide 

CO2 carbon dioxide 

CO2e carbon dioxide equivalent 

COP Conference of the Parties 

DEIS Draft Environmental Impact Statement 

DHHS U.S. Department of Health and Human Services 

DOE U.S. Department of Energy 

DOT U.S. Department of Transportation 

DPM diesel particulate matter 

DRIA Draft Regulatory Impact Assessment 

EA environmental assessment 

EIA Energy Information Administration 

EIS Environmental Impact Statement 

EISA Energy Independence and Security Act 

ENSO El Niño Southern Oscillation 

EO Executive Order 

EPA U.S. Environmental Protection Agency 

EPCA Energy Policy and Conservation Act 

EU European Union 

EU ETS European Union Greenhouse Gas Emission Trading System 

EV electric vehicle 

FAO Food and Agriculture Organization (United Nations) 

FEIS Final Environmental Impact Statement 

FEOW Freshwater Ecoregions of the World project 

FFV flexible fuel vehicle 

FONSI Finding of No Significant Impact 

FHWA Federal Highway Administration 

x 
List of Acronyms and Abbreviations 

FMCSA Federal Motor Carrier Safety Administration 

FR Federal Register 

FRIA Final Regulatory Impact Analysis 

FTA Federal Transit Administration 

g/mi gram per mile 

GAO General Accounting Office 

GDP Gross Domestic Product 

GHG greenhouse gases 

GIS Greenland ice sheet 

GREET Greenhouse Gases, Regulated Emissions, and Energy Use in Transportation 

GtC/year gigaton carbon per year 

GWP global warming potential 

HEV hybrid electric vehicle 

HFC hydrofluorocarbon 

HOP high oil price 

IARC International Agency for Research on Cancer 

IEO International Energy Outlook 

IGSM Integrated Global System Model

IPCC Intergovernmental Panel on Climate Change 

IRIS Integrated Risk Information System 

K kelvin 

ka kiloannum 

LNG liquefied natural gas 

LTCCS Large Truck Crash Causation Study 

LTV light trucks and vans 

MA Millennium Ecosystem Assessment 

MAGICC Model for Assessment of Greenhouse Gas-induced Climate Change 

mg/L milligram per liter 

mg/m3

 milligram per cubic meter 

MGA Midwestern Governors Association 

MHTs Major Habitat Types 

mm millimeter 

MMTCO2 million metric tons of carbon dioxide 

MNB Maximum Net Benefits 

MOC Meridional Overturning Circulation 

MOP moderate oil price 

MOVES Motor Vehicle Emission Simulator (U.S. EPA) 

mpg mile per gallon 

MSATs mobile source air toxics 

MTBE methyl tertiary butyl ether 

MY model year 

N2 nitrogen 

N2O nitrous oxide 

NAAQS National Ambient Air Quality Standards 

NADA National Automobile Dealers Association 

NATA National-scale Air Toxics Assessment 

NCD National County Database 

NCI National Cancer Institute 

NEI National Emissions Inventory 

NEPA National Environmental Policy Act 

NESHAP National Emission Standards for Hazardous Air Pollutants 

NERA National Environmental Research Associates 

NF3 nitrogen trifluoride 

NGO non-governmental organization 

NHTSA National Highway Traffic Safety Administration 

xi 
List of Acronyms and Abbreviations 

NMIM National Mobile Inventory Model 

NO nitric oxide 

NO2 nitrogen dioxide 

NOI Notice of Intent 

NOAA National Oceanic and Atmospheric Administration 

NOx nitrogen oxides 

Non-EGU Sources other than electric generating units (power plants). 

NPRM Notice of Proposed Rulemaking 

NRDC Natural Resources Defense Council 

NYSDOT New York State Department of Transportation 

OECD Organization for Economic Cooperation and Development 

OPEC Organization of Petroleum Exporting Countries 

OMB Office of Management and Budget 

PAH polycyclic aromatic hydrocarbon 

PFC perfluorocarbon 

PHEV Plug-In Hybrid Electric Vehicle 

POM polycyclic organic matter 

PM particulate matter 

PM10 particulate matter 10 microns diameter or less 

PM2.5 particulate matter 2.5 microns diameter or less 

ppm parts per million 

ppmv parts per million by volume 

PPR Prairie Pothole Region 

PRIA Preliminary Regulatory Impact Analysis 

RCP Representative Concentration Pathway 

RFS Renewable Fuels Standard 

RGGI Regional Greenhouse Gas Initiative 

RIA Regulatory Impact Analysis 

RPE retail price equivalent 

SAP Synthesis and Assessment Product 

SAB Science Advisory Board 

SCC social cost of carbon 

SCC source category code 

SF6 sulfur hexafluoride 

SIP State Implementation Plan 

SO sulfur oxide 

SOx sulfur oxides 

SO2 sulfur dioxide 

SRES Special Report on Emission Scenarios 

SUV sport utility vehicle 

TS&D Transportation, Storage, and Distribution 

TB total benefits 

TCTB Total Costs Equal Total Benefits 

TC total cost 

TgC/yr teragram carbon per year (1,000,000,000,000 grams carbon per year) 

THC thermohaline circulation 

TLAAS Temporary Lead-time Allowance Alternative Standards 

U.S.C. United States Code 

UCS Union of Concerned Scientists 

UMD University of Maryland 

UNESCO United Nations Educational Scientific and Cultural Organization 

UNFCCC United Nations Framework Convention on Climate Change 

USCCSP United States Climate Change Science Program 

USGCRP United States Global Change Research Program 

USGS United States Geological Survey 

xii 
List of Acronyms and Abbreviations 

xiii 

VMT vehicle-miles traveled 

VOC volatile organic compound 

VSL value of statistical life 

Volpe Center Volpe National Transportation Systems Center 

WAIS Western Antarctic ice sheet 

WCI Western Climate Initiative 

WGI IPCC Work Group I 

WGII IPCC Work Group II 

WHO World Health Organization 

WMO World Meteorological Organization 

WWF World Wildlife Fund 
Glossary 

To help readers more fully understand this Environmental Impact Statement, NHTSA has provided the 

following list of definitions for technical and scientific terms, as well as plain English terms used 

differently in the context of this EIS. 

Term Definition 

Adaptation Initiatives and measures to reduce the vulnerability of natural and human 

systems against actual or expected climate change effects. Various 

types of adaptation exist, including anticipatory and reactive, private and 

public, and autonomous and planned. 

Afforestation Planting of new forests on lands that historically have not contained 

forests (for at least 50 years). 

Anthropogenic Resulting from or produced by human beings. 

Aquaculture Farming of plants and animals that live in water. 

Benthic Describing habitat or organisms occurring at the bottom of a body of 

water. 

Biosphere The part of the Earth system comprising all ecosystems and living 

organisms, in the atmosphere, on land (terrestrial biosphere) or in the 

oceans (marine biosphere), including dead organic matter, such as litter, 

soil organic matter, and oceanic detritus. 

Carbon sink Any process, activity, or mechanism that removes a greenhouse gas, an 

aerosol, or a precursor of a greenhouse gas or aerosol from the 

atmosphere. 

Coral bleaching The paling in color that results if a coral loses its symbiotic, energy 

providing, organisms. 

Criteria pollutants Carbon monoxide (CO), airborne lead (Pb), nitrogen dioxide (NO2), 

ozone (O3), sulfur dioxide (SO2), and fine particulate matter (PM).

Cryosphere The portion of Earth’s surface that is frozen water, such as snow, 

permafrost, floating ice, and glaciers. 

Dansgaard-Oeschger events Very rapid climate changes – up to 7 °C in some 50 years – during the 

Quaternary geologic period, and especially during the most recent glacial 

cycle. 

Ecosystem A system of living organisms interacting with each other and their 

physical environment. The boundaries of what could be called an 

ecosystem are somewhat arbitrary, depending on the focus of interest or 

study. Thus, the extent of an ecosystem may range from very small 

spatial scales to, ultimately, all of Earth. 

xiv 
Glossary 

xv 

Term Definition 

El Niño-Southern Oscillation The term El Niño was initially used to describe a warm-water current that 

periodically flows along the coast of Ecuador and Peru, disrupting the 

local fishery. It has since become identified with a basinwide warming of 

the tropical Pacific east of the international dateline. This oceanic event 

is associated with a fluctuation of a global-scale tropical and subtropical 

surface pressure pattern called the Southern Oscillation. This coupled 

atmosphere-ocean phenomenon, with preferred time scales of two to 

about seven years, is collectively known as El Niño-Southern Oscillation, 

or ENSO. During an ENSO event, the prevailing trade winds weaken, 

reducing upwelling and altering ocean currents such that the sea surface 

temperatures warm, further weakening the trade winds. 

Emission rates Rate at which contaminants are discharged from a particular source, 

usually in weight unit per time period. 

Endemic Restricted to a region. 

EPCA factors for setting “maximum 

feasible” CAFE standards 

Technological feasibility, economic practicability, the effect of other motor 

vehicle standards of the government on fuel economy, and the need of 

the Nation to conserve energy. 

Eutrophication Enrichment of a water body with plant nutrients.

Evapotranspiration The combined process of water evaporation from Earth’s surface and 

transpiration from vegetation. 

Expected Value Model Inputs Model input scenario that uses the Energy Information Administration’s 

April 2009 Reference Case fuel price forecast, a 10-percent rebound 

effect, a domestic social cost of carbon of $20.00 per ton, a 3-percent 

discount rate, and a value of $0.17 per gallon for oil import externalities 

GREET model Model developed by Argonne National Laboratory that provides 

estimates of the energy and carbon contents of fuels as well as energy 

use in various phases of fuel supply. 

Hydrology The science dealing with the occurrence, circulation, distribution, and 

properties of Earth’s water. 

Hydrosphere The component of the climate system comprising liquid surface and 

subterranean water, such as oceans, seas, rivers, freshwater lakes, and 

underground water. 

Kiloannum A unit of time equal to 1000 years. Abbreviation is “ka.” 

Lake stratification The layering of warmer, less dense water over colder, denser water. 

Lifetime fuel consumption Total volume of fuel used by a vehicle over its lifetime. 

Maximum lifetime of vehicles The age after which less than 2 percent of the vehicles originally 

produced during a model year remains in service. 

NEPA scoping process An early and open process for determining the scope of issues to be 

addressed and for identifying the significant issues related to a proposed 

action. 
Glossary 

xvi 

Term Definition 

Nonattainment area Regions where concentrations of criteria pollutants exceed federal 

standards. Nonattainment areas are required to develop and implement 

plans to comply with the National Ambient Air Quality Standards within 

specified time periods.

Ocean acidification A decrease in the pH of sea water due to the uptake of anthropogenic 

carbon dioxide. 

Optimized standards Standards set at levels such that the cost of the last technology 

application (using the Volpe model) equals the benefits of the 

improvement in fuel economy resulting from that application, thereby 

maximizing net benefits (benefits minus costs). 

Overexploitation of species Exploitation of species to the point of diminishing returns. 

Paleoclimatology The study of climate change through the physical evidence left on Earth 

of historical global climate change (prior to the widespread availability of 

records to temperature, precipitation, and other data). 

Pathways of fuel supply Imports to the United States of refined gasoline and other transportation 

fuels, domestic refining of fuel using imported petroleum as a feedstock, 

and domestic fuel refining from crude petroleum produced within the 

United States. 

Permafrost Ground (soil or rock and included ice and organic material) that remains 

at or below zero degrees Celsius for at least two consecutive years. 

Phenology The study of natural phenomena in biological systems that recur 

periodically (development stages, migration) and their relationship to 

climate and seasonal changes. 

Rebound effect A situation in which improved fuel economy reduces the fuel cost of 

driving and leads to additional use of passenger cars and light trucks and 

thus increased emissions of criteria pollutants by passenger cars and 

light trucks.

Reformed CAFE Program Consists of two basic elements: (1) a process that sets fuel economy 

targets for different values of vehicle footprint; and (2) a Reformed CAFE 

standard for each manufacturer, which is equal to the productionweighted harmonic average of the fuel economy targets corresponding to 

the footprint values of each light truck model it produces.

Saltwater intrusion Displacement of fresh surface water or groundwater by the advance of 

saltwater due to its greater density. This process usually occurs in 

coastal and estuarine areas due to reducing land-based influence (either 

from reduced runoff and associated groundwater recharge, or from 

excessive water withdrawals from aquifers) or increasing marine 

influence (relative sea-level rise). 

Silviculture The management of forest resources. 

Survival rate The proportion of vehicles originally produced during a model year that 

are expected to remain in service at the age they will have reached 

during each subsequent year. 
Glossary 

xvii 

Term Definition 

Technologies Engine technologies, transmission, vehicle, electrification/accessory and 

hybrid technologies that influence fuel economy. 

Thermohaline circulation This term refers to the physical driving mechanism of ocean circulation, 

resulting from fluxes of heat and fresh water across the sea surface, 

subsequent interior mixing of heat and salt, and geothermal heat 

sources. 

Tipping point A situation where the climate system reaches a point at which is there is 

a strong and amplifying positive feedback from only a moderate 

additional change in a driver, such as CO2 or temperature increase. 

Total vehicle miles Total number of miles a vehicle will be driven over its lifetime. 

Track width The lateral distance between the centerlines of the base tires at ground, 

including the camber angle. 

Transpiration Water loss from plant leaves. 

Turbidity A decrease in the clarity of water due to the presence of suspended 

sediment. 

Vehicle footprint The product of track width times wheelbase divided by 144. 

Vehicle miles traveled Total number of miles driven. 

Volpe model CAFE Compliance and Effects Model developed by the U.S. Department 

of Transportation’s Volpe Center, that, for any given year, applies 

technologies to the manufacturer's fleet until the manufacturer achieves 

compliance with the standard under consideration. 

Wheelbase The longitudinal distance between front and rear wheel centerlines. 

Final Environmental Impact Statement 

Summary 1 

Summary 

Foreword 

The National Highway Traffic Safety Administration 

(NHTSA) prepared this Environmental Impact 

Statement (EIS) to analyze and disclose the potential 

environmental impacts of the proposed model years 

(MYs) 2012–2016 Corporate Average Fuel Economy 

(CAFE) standards for the total fleet of passenger and 

non-passenger automobiles (hereinafter referred to as 

passenger cars and light trucks, respectively) and 

reasonable alternative standards for the NHTSA CAFE 

program pursuant to Council on Environmental 

Quality (CEQ) regulations implementing the National 

Environmental Policy Act (NEPA), U.S. Department 

of Transportation (DOT) Order 5610.1C, and NHTSA 

regulations.1

 This EIS compares the potential 

environmental impacts of alternative mile-per-gallon 

(mpg) levels NHTSA will consider for the final rule, 

including the Preferred Alternative (i.e., the proposed 

standards) and a No Action Alternative. It also 

analyzes direct, indirect, and cumulative impacts and 

analyzes impacts in proportion to their significance. 

Background 

The Energy Policy and Conservation Act of 1975 

(EPCA) established a program to regulate automobile 

fuel economy and provided for the establishment of 

average fuel economy standards for passenger cars 

and separate standards for light trucks.2

 As part of that 

Act, the CAFE program was established to reduce 

national energy consumption by increasing the fuel 

economy of passenger cars and light trucks. The Act 

directs the Secretary of Transportation to set and 

implement fuel economy standards for passenger cars 

and light trucks sold in the United States. The 

Secretary delegated responsibility for implementing 

the CAFE program to NHTSA.3

 

In December 2007, Congress passed the Energy 

Independence and Security Act of 2007 (EISA),4

amending the EPCA CAFE program requirements and 

providing DOT additional rulemaking authority and 

responsibilities. Pursuant to EPCA, as amended by 

EISA, on April 22, 2008, NHTSA proposed CAFE 

standards for MYs 2011–2015 passenger cars and light 

trucks in a Notice of Proposed Rulemaking (NPRM).5

 

On October 10, 2008, NHTSA submitted to the U.S. 

Environmental Protection Agency (EPA) its Final 

Environmental Impact Statement, Corporate Average 

Fuel Economy Standards, Passenger Cars and Light 

Trucks, Model Years 2011–2015.6

 On March 30, 

2009, NHTSA issued a final rule adopting CAFE 

standards for MY 2011.7

 

On April 1, 2009, NHTSA published a Notice of 

Intent (NOI) to prepare an EIS for proposed MYs 

2012–2016 CAFE standards.8

 The NOI described the 

statutory requirements for the standards, provided 

initial information about the NEPA process, and 

initiated scoping by requesting public input on the 

scope of the environmental analysis to be conducted.9

On May 19, 2009, President Obama announced a 

National Fuel Efficiency Policy aimed at both 

increasing fuel economy and reducing greenhouse gas 

(GHG) emissions for all new cars and trucks sold in 

the United States, while also providing a predictable 

regulatory framework for the automotive industry. 

The policy seeks to set harmonized federal standards to 

regulate both fuel economy and GHG emissions. The 

policy covers MY 2012 to MY 2016 and ultimately 

requires the equivalent of an average fuel economy of 

35.5 mpg in 2016, if all carbon dioxide (CO2) 

reductions were achieved through fuel economy 

improvements. In conjunction with the President’s 

announcement, on May 19, 2009, DOT and EPA 

issued a Notice of Upcoming Joint Rulemaking to 

propose coordinated fuel economy and GHG standards 

for MYs 2012–2016 light-duty vehicles. 

On September 28, 2009, NHTSA and EPA announced 

in the Federal Register the Proposed Rulemaking To 

Establish Light-Duty Vehicle Greenhouse Gas 

Emission Standards and Corporate Average Fuel 

Economy Standards. The proposed rule calls for a 

strong and coordinated federal GHG and fuel 

economy program for passenger cars, light-duty 

trucks, and medium-duty passenger vehicles 

(hereinafter light-duty vehicles), referred to in this 

rulemaking as the National Program. The proposed 

rules would achieve substantial improvements in fuel 

economy and reductions of GHG emissions from 

light-duty vehicles, based on technology that is 

already being commercially applied in most cases and 

that can be incorporated at a reasonable cost. These 

joint proposed rules address the closely intertwined 

challenges of energy independence, energy security, 

and global warming. 

The proposed National Program makes it possible for 

the standards of two different federal agencies to act 

in a unified fashion, providing nationwide 

environmental and energy benefits, cost savings, and 
Final Environmental Impact Statement 

2 Summary 

administrative efficiencies. 10 Establishing a 

harmonized approach to regulating light-duty vehicle 

GHG emissions and fuel economy is critically 

important, given the interdependent goals of 

addressing climate change and ensuring energy 

independence and security. 

NEPA directs that “to the fullest extent possible,” 

federal agencies proposing “major federal actions 

significantly affecting the quality of the human 

environment” must prepare “a detailed statement” 

on the environmental impacts of the proposed 

action (including alternatives to the proposed 

action).11 To inform its development of the new 

MYs 2012–2016 CAFE standards, NHTSA prepared 

this EIS to analyze and disclose the potential 

environmental impacts of a proposed Preferred 

Alternative and other proposed alternative standards, 

including the No Action Alternative. 

Section 1501.6 of CEQ regulations emphasizes 

agency cooperation early in the NEPA process and 

allows a lead agency (in this case, NHTSA) to request 

the assistance of other agencies that either have 

jurisdiction by law or have special expertise regarding 

issues considered in an EIS.12 NHTSA invited EPA to 

become a cooperating agency, pursuant to CEQ 

regulations, because of its special expertise in the 

areas of climate change and air quality. On May 12, 

2009, EPA agreed to become a cooperating agency. 

The EPA environmental analysis of its proposed 

rulemaking is summarized and referenced in the 

appropriate sections of this EIS. 

Purpose and Need for 

the Proposed Action 

For purposes of this EIS, the Proposed Action is 

NHTSA’s action to set passenger car and light truck 

CAFE standards for MYs 2012–2016 in accordance 

with EPCA, as amended by EISA. NEPA requires that 

alternatives to a proposed action be developed based 

on the action’s purpose and need. 

EPCA and EISA set forth extensive requirements for 

the rulemaking, and those requirements form the 

purpose of and need for the standards. The 

requirements also were the basis for establishing the 

range of alternatives considered in this EIS. 

Specifically, the statute requires the Secretary of 

Transportation to establish average fuel economy 

standards for each model year at least 18 months 

before the beginning of that model year and to set 

them at “the maximum feasible average fuel 

economy level that the Secretary decides the 

manufacturers can achieve in that model year.”13

When setting maximum feasible fuel economy 

standards, the Secretary is required to “consider 

technological feasibility, economic practicability, the 

effect of other motor vehicle standards of the 

Government on fuel economy, and the need of the 

United States to conserve energy.”14 NHTSA interprets 

the statutory factors as including environmental issues 

and permitting the consideration of other relevant 

societal issues, such as safety.15

EPCA and EISA further direct the Secretary of 

Transportation, after consultation with the Secretary 

of Energy and the Administrator of EPA, to establish 

separate average fuel economy standards for 

passenger cars and for light trucks manufactured in 

each model year beginning with MY 2011 “to 

achieve a combined fuel economy average for MY 

2020 of at least 35 miles per gallon for the total fleet 

of passenger and non-passenger automobiles 

manufactured for sale in the United States for that 

model year.”16 In so doing, the Secretary of 

Transportation is to adopt “annual fuel economy 

standard increases,” but in any single rulemaking, 

standards may be established for not more than five 

model years.17 NHTSA also is acting pursuant to 

President Obama’s memorandum to DOT on January 

26, 2009, as described in Section 1.1 of this EIS. 

The purpose of this EIS is to identify proposed CAFE 

standards and regulatory alternatives, and to analyze 

and disclose the potential environmental impacts of 

the proposed standards and alternatives for 

consideration by NHTSA decisionmakers. 

Alternatives 

NEPA requires an agency to compare the potential 

environmental impacts of its proposed action and a 

reasonable range of alternatives. The EPCA fuel 

economy requirements, including the four statutory 

factors NHTSA must consider in determining 

maximum feasible CAFE levels—technological 

feasibility, economic practicability, the need of the 

United States to conserve energy, and the effect of 

other motor vehicle standards of the Government on 

fuel economy—form the purpose of and need for the 

MYs 2012–2016 CAFE standards and, therefore, 

inform the range of alternatives for consideration in 

this NEPA analysis. The NHTSA decision process 

balances the four statutory EPCA factors, along with 

considerations such as environmental impacts and 

safety. In developing a reasonable range of 

alternatives, NHTSA identified alternative stringencies 

that represent the spectrum of potential actions the 

agency could take. The environmental impacts of 

these alternatives, in turn, represent the spectrum of 

potential environmental impacts that could result 
Final Environmental Impact Statement 

Summary 3 

from NHTSA’s action of setting CAFE standards. This 

EIS analyzes the impacts of eight “action” alternatives 

as well as the impacts if the CAFE standards imposed 

no new requirements (the No Action Alternative). 

The specific alternatives NHTSA examined, described 

below and shown in Table S-1 and Table 2.3-1, 

encompass a reasonable range of alternative actions 

(i.e., CAFE standards) for which to evaluate the 

potential environmental impacts under NEPA, in view 

of EPCA requirements. At one end of this range is the 

No Action Alternative (Alternative 1), which assumes 

no action would occur under the National Program.18

The No Action Alternative assumes that average fuel 

economy levels in the absence of CAFE standards 

beyond MY 2011 would equal the higher of the 

agency’s collective market forecast or the 

manufacturers’ required level of average fuel 

economy for MY 2011. NHTSA also considers eight 

action alternatives, including NHTSA’s Preferred 

Alternative (Alternative 4), which requires 

approximately a 4.3-percent average annual increase 

in mpg from 2012 to 2016. This alternative and the 

EPA proposed rulemaking together comprise the 

National Program described in the NPRM. 

Alternatives 2, 3, 4, 5, 7, and 8 require average 

annual increases in mpg ranging from 3 percent 

(Alternative 2) to 7 percent (Alternative 8) from year 

to year. 19 

NHTSA added three alternatives to the list first 

proposed in the NOI: the agency’s Preferred 

Alternative (Alternative 4), an alternative that 

maximizes net benefits (MNB) (Alternative 6), and 

an alternative under which the total costs equal the 

total benefits (TCTB) (Alternative 9). The agency’s 

Preferred Alternative represents the required fuel 

economy level that NHTSA has tentatively determined 

to be the maximum feasible level under EPCA, based 

on balancing the four statutory factors and other 

relevant considerations. For a detailed explanation of 

the alternatives, see Section 2.3 of this EIS. 

The other two alternatives, the MNB and TCTB, 

represent fuel economy levels that depend on the 

agency’s best estimate of relevant economic variables 

(e.g., gasoline prices, social cost of carbon, discount 

rate, and rebound effect). For further discussion of the 

economic assumptions, see Section 2.2.4 of this EIS. 

The MNB Alternative and TCTB Alternative provide the 

decisionmaker and the public with useful information 

about where the standards would be set if costs and 

benefits were balanced in two different ways. 

The 6-Percent Alternative results in a required CAFE 

level in 2016 that is equal to the required CAFE level 

under the MNB Alternative, but the required CAFE 

levels in 2012 through 2015 under the 6-Percent 

Alternative are actually slightly lower than under the 

MNB Alternative. In general, the net result is that 

there is very little substantive difference in the 

required CAFE level under the 6-Percent and MNB 

Alternatives. The TCTB Alternative results in a 

required CAFE level in 2016 that is slightly lower 

than the required CAFE level under the 7-Percent 

Alternative, but the required CAFE levels in 2012 

through 2015 under the TCTB Alternative are slightly 

higher than under the 7-Percent Alternative. In 

general, the net result is that there is very little 

substantive difference in the required CAFE level 

under the 7-Percent and TCTB Alternatives. 

As discussed in Sections 1.2.2.2 and 2.2 of this EIS, 

the CAFE levels required under an attribute-based 

standard depend on the mix of vehicles produced for 

sale in the United States.20 The average fuel economy 

levels actually achieved by passenger cars and light 

trucks in a given model year may differ from the 

required CAFE levels for that model year. This occurs 

because some manufacturers’ average fuel economy 

levels for their vehicles are projected to exceed the 

applicable CAFE standards during certain model 

years,21 while other manufacturers’ fuel economy 

levels are projected to fall short of either the 

passenger car or light truck CAFE standards during 

some model years.22 Table S-1 shows the MY 2016 

required fuel economy levels for each alternative. 

Table 2.3-1 of this EIS shows the required fuel 

economy levels for each alternative in each model 

year, from MY 2012 to MY 2016. For additional 

detail and discussion of how NHTSA considers the 

EPCA statutory factors and other considerations that 

guide the agency’s determination of “maximum 

feasible” standards and inform an evaluation of the 

alternatives, see Section IV.F of the NPRM. For detailed 

calculations and discussions of manufacturer cost 

impacts and estimated benefits for each of the 

alternatives, see Sections VII and VIII of the NHTSA 

Preliminary Regulatory Impact Analysis. 

Table S-1 also shows the MY 2016 estimated23 achieved

fuel economy levels for each alternative. Table 2.3-2 

of this EIS shows the estimated achieved fuel 

economy levels for each alternative in each model 

year, from MY 2012 to MY 2016. Comparing the MY 

2016 achieved levels with the MY 2016 required 

levels in Table S-1 shows that estimated achieved 

mpg in 2016 would actually exceed the average 

required CAFE level under the No Action Alternative, 

indicating that some manufacturers would increase 

average mpg levels under the No Action Alternative. 
Final Environmental Impact Statement 

4 Summary 

Table S-1: Required and Achieved MPG by Alternative 

Alt. 1 Alt. 2 Alt. 3 Alt. 4 Alt. 5 Alt. 6 Alt. 7 Alt. 8 Alt. 9 

No 

Action*

3%/year 

Increase 

4%/year 

Increase 

~4.3%/year

Increase 

Preferred 

5%/year 

Increase 

~6.0%/year 

Increase MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.6%/year 

Increase 

 TCTB 

2016 – Required MPG 

Passenger Cars 30.5 35.5 37.2 37.8 39.1 40.9 40.9 42.9 42.3 

Light Trucks 24.4 26.9 28.2 28.7 29.6 31.0 31.0 32.6 31.8 

Combined 28.1 32.0 33.6 34.1 35.2 36.9 36.9 38.7 38.0 

2016 – Achieved MPG 

Passenger Cars 32.4 35.7 37.3 37.7 38.8 40.2 40.3 41.3 41.0 

Light Trucks 24.7 26.8 28.0 28.4 29.3 30.5 30.5 31.4 31.1 

Combined 29.3 32.1 33.5 33.9 34.9 36.3 36.3 37.2 37.0 

*The No Action Alternative assumes that average fuel economy levels in the absence of CAFE standards beyond MY 2011 would equal the higher of the agency’s vehicle market forecast 

or the manufacturers’ required level of average fuel economy for MY 2011. The numbers listed under Required MPG are representative of this scenario, but would not be implemented as 

CAFE standards under this alternative. 

Under most of the action alternatives, the estimated 

achieved mpg levels in 2016 would be somewhat 

lower than the required mpg levels because some 

manufacturers are not expected to comply fully with 

passenger car or light truck standards. 

Potential Environmental 

Consequences 

This section describes how the proposed action and 

alternatives could affect energy use, air quality, and 

climate, which are the resources for which NHTSA 

performed a quantitative assessment. This EIS 

describes potential additional impacts on water 

resources, vegetation, wildlife, land use and 

development, safety, hazardous materials and 

regulated wastes, noise, and environmental justice. 

NHTSA assesses those resource areas qualitatively.24 

The effects on energy use, air quality, and climate 

described in this section include direct, indirect, and 

cumulative effects. Direct effects occur at about the same 

time and place as the action. Indirect effects occur later 

in time or are farther removed in distance. Cumulative 

effects are the incremental impacts resulting from the 

action added to those of other past, present, and 

reasonably foreseeable future actions. 

When comparing direct and indirect effects with 

cumulative effects, it is important to understand that 

the methodology for evaluating direct effects 

compares the alternatives against a base case in which 

no further increases in average new passenger car or 

light truck mpg occur after 2016, whereas the 

evaluation of cumulative effects assumes that all the 

alternatives reach the EISA-mandated minimum level 

of 35 mpg by the year 2020 and ongoing gains in 

average new passenger car and light truck mpg 

through 2030. 

Energy Use 

Energy intensity in the United States (energy use per 

dollar of gross domestic product) has declined 

steadily at about 2 percent per year since 1973. 

Despite this continuing improvement in economywide energy efficiency, transportation fuel 

consumption has grown steadily through annual 

increases, and now represents the major use of 

petroleum in the U.S. economy. 

The transportation sector is the second largest 

consumer of energy in the United States (after the 

industrial sector), and as shown in Figure S-1, 

represents 28.7 percent of U.S. total energy use.25

This pattern of the industrial and transportation 

sectors being the first and second largest sectors by 

energy use, respectively, is also found globally, 

though at a slightly lower level, with transportation 

constituting 17.3 percent of non-U.S. world energy 

use. According to estimates from the U.S. Department 

of Energy (DOE) Energy Information Administration 

(EIA), this pattern will continue in the future with 

U.S. transportation use stabilizing as a percentage of 

total energy use and non-U.S. consumption 

increasing as a percentage of total energy use.26

Passenger cars and light trucks account for more than 

half of U.S. energy consumption in this sector, with 

the remaining consumption spread among heavy 

trucks, aviation, public transportation, and rail and 

marine transportation. 
Final Environmental Impact Statement 

Summary 5 

Figure S-1. U.S. Energy Consumption by Sector, 2007 

Source: http://www.eia.doe.gov/emeu/aer/txt/ptb0201a.html. 

As shown in Figure S-2, about 69 percent of the 

petroleum used in the United States is consumed by 

the transportation sector. While most U.S. gasoline 

and diesel is produced domestically, increasing 

volumes of crude oil are imported for processing in 

U.S. refineries as domestic crude oil production is 

steadily declining. Crude oil importssurpassed 10 

million barrels per day in 2007, with a high 

proportion coming from volatile and unstable 

regions.27 Despite efforts to increase the use of nonfossil fuels in transportation, fuel use remains largely 

petroleum based. Biofuels comprise slightly more 

than 2 percent of fuel use in the U.S. transportation 

sector and this component is expected to rise to 10 

percent by 2030. 

To calculate fuel savings for each alternative, NHTSA 

subtracted fuel consumption under that alternative 

from the No Action Alternative level. Fuel 

consumption estimates for 2012 to 2016 are based on 

the annual mpg increases specified by each alternative. 

For 2017 to 2060, the estimates for the direct and 

indirect effects analysis assume all new vehicles meet 

the MY 2016 CAFE standards for each action 

alternative. NHTSA’s cumulative effects analysis 

forces alternatives that are not at least 35 mpg in 

2016 to continue to increase so that those alternatives 

meet the EISA-mandated minimum of 35 mpg by 

2020. Once the EISA target is met, the estimates 

assume the same percent increases in new vehicle 

mpg for all alternatives through the year 2030. These 

percent increases are based on average annual mpg 

projections by the EIA’s Annual Energy Outlook 

(AEO). The AEO forecasts are regarded as the official 

U.S. government energy projections by both the 

public and the private sector. The projected mpg 

increases result from consumer demand and 

technology advances associated with ongoing 

projected increases in fuel prices.28 See Sections 3.1.4, 

3.2.2, 4.1.3, and 4.2.2 of this EIS for further details 

about the methodology used for NHTSA’s fuel 

savings calculations. 

Key Findings for Energy Use 

The fuel consumption figures below are shown for 

2060, the year when nearly the entire U.S. fleet is 

likely to be composed of MY 2016 and later vehicles. 

Direct and Indirect Effects 

Combined Passenger Cars and Light Trucks 

` Total annual fuel savings in 2060 range from 25.5 

billion gallons for Alternative 2 (3-Percent 

Alternative) to 59.6 billion gallons for Alternative 8 

(7-Percent Alternative), compared with fuel 

consumption under the No Action Alternative 

(Alternative 1).

Passenger Cars 

` Annual fuel savings in 2060 range from 17.2 billion 

gallons (Alternative 2) to 39.0 billion gallons

(Alternative 8), compared with fuel consumption 

under the No Action Alternative. 

` Fuel consumption under the No Action Alternative 

(Alternative 1) is 205.5 billion gallons in 2060. 

Consumption under the other alternatives ranges 

from 188.4 billion gallons for Alternative 2 (3-

Percent Alternative) to 166.5 billion gallons for 

Alternative 8 (7-Percent Alternative). 

Figure S-2. U.S. Petroleum Consumption by Sector, 2007

Source: http://www.eia.doe.gov/emeu/aer/petro.html. 
Final Environmental Impact Statement 

6 Summary 

` Fuel consumption under the Preferred Alternative 

(Alternative 4) is 179.4 billion gallons in 2060, 

representing a savings of 26.2 billion gallons, 

compared with fuel consumption under the No 

Action Alternative. 

Light Trucks 

` Annual fuel savings in 2060 range from 8.3 billion 

gallons (Alternative 2) to 20.6 billion gallons

(Alternative 8), compared with fuel consumption 

under the No Action Alternative. 

` Fuel consumption under the No Action Alternative 

is 113.0 billion gallons in 2060. Fuel consumption 

under the other alternatives ranges from 104.6 

billion gallons for Alternative 2 (3-Percent 

Alternative) to 92.4 billion gallons for Alternative 

8 (7-Percent Alternative). 

` Fuel consumption under the Preferred Alternative 

is 99.4 billion gallons in 2060, representing a 

savings of 13.5 billion gallons, compared with fuel 

consumption under the No Action Alternative. 

Cumulative Effects 

Combined Passenger Cars and Light Trucks 

` Total annual fuel savings in 2060 range from 37.5 

billion gallons for Alternative 2 (3-Percent 

Alternative) to 56.0 billion gallons for Alternative 8 

(7-Percent Alternative), compared with fuel 

consumption under the No Action Alternative. 

Passenger Cars 

` Annual fuel savings in 2060 range from 26.0 to 

36.9 billion gallons.

` Fuel consumption under the No Action 

Alternative is 193.2 billion gallons in 2060. 

Under the other alternatives, it ranges from 167.3 

billion gallons for Alternative 2 (3-Percent 

Alternative) to 156.3 billion gallons for 

Alternative 8 (7-Percent Alternative). 

` Fuel consumption under the Preferred Alternative 

is 167.2 billion gallons in 2060, representing a 

savings of 26.0 billion gallons compared with fuel 

consumption under the No Action Alternative. 

Light Trucks 

` Annual fuel savings in 2060 range from 11.5 billion 

gallons (Alternative 2) to 19.1 billion gallons

(Alternative 8). 

` Fuel consumption under the No Action Alternative 

is 103.8 billion gallons in 2060. Under the other 

alternatives it ranges from 92.2 billion gallons for 

Alternative 2 (3-Percent Alternative) to 84.6 billion 

gallons for Alternative 8 (7-Percent Alternative). 

` Fuel consumption under the Preferred Alternative 

is 91.2 billion gallons in 2060, representing a 

savings of 12.6 billion gallons. 

Figure S-3 illustrates each of the alternatives’ direct 

and indirect effects on annual fuel savings for passenger 

cars and light trucks in 2020, 2040, and 2060. For 

readers interested in additional details about the 

alternatives’ direct and indirect effects on annual fuel 

consumption, see Tables 3.2.3-1 and 3.2.3-2 in this 

EIS and the accompanying discussion. Figure S-4 

illustrates each of the alternatives’ cumulative effects 

on annual fuel savings for passenger cars and light 

trucks in 2020, 2040, and 2060. For readers 

interested in additional details about the alternatives’ 

cumulative effects on annual fuel consumption, see 

Tables 4.2.3-1 and 4.2.3-2 in this EIS and the 

accompanying discussion. 

Air Quality 

Air pollution and air quality can affect public health, 

public welfare, and the environment. The alternative 

MYs 2012–2016 CAFE standards under consideration 

would affect air pollutant emissions and air quality. 

This EIS air quality analysis assesses the impacts of the 

action alternatives in relation to emissions of 

pollutants of concern from mobile sources and the 

resulting health effects and monetized health benefits. 

Under the authority of the Clean Air Act and its 

amendments, EPA has established National Ambient 

Air Quality Standards (NAAQS) for six relatively 

common air pollutants—known as “criteria” 

pollutants because EPA regulates them by developing 

human-health-based and/or environmentally based 

criteria for setting permissible levels. The criteria 

pollutants are carbon monoxide, nitrogen dioxide 

(NO2), ozone, sulfur dioxide (SO2), particulate matter 

(PM10 and PM2.5), and lead. Ozone is not emitted 

directly from vehicles, but is formed from emissions 

of the ozone precursor pollutants nitrogen oxides 

(NOx) and volatile organic compounds (VOCs). 

In addition to criteria pollutants, motor vehicles emit 

some substances defined as hazardous air pollutants 

by the 1990 Clean Air Act Amendments. Hazardous 

air pollutants include certain VOCs, compounds in 

PM, pesticides, herbicides, and radionuclides that 

present tangible hazards, based on scientific studies 

of human (and other mammal) exposure. 
Final Environmental Impact Statement 

Summary 7 

Figure S-3. Annual Fuel Savings of Passenger Cars and Light Trucks by Alternative, Direct and Indirect Impacts 

2020 2040 2060

Billion gallons of gasoline equivalent

0

10

20

30

40

50

60

70

Alt. 2: 3%/year increase

Alt. 3: 4%/year increase

Alt. 4: ~4.3%/year increase, Preferred

Alt. 5: 5%/year increase

Alt. 6: ~6.0%/year increase, MNB

Alt. 7: 6%/year increase

Alt. 8: 7%/year increase

Alt. 9: ~6.6%/year increase, TCTB

Figure S-4. Annual Fuel Consumption of Passenger Cars and Light Trucks by Alternative, Cumulative Impacts 

2020 2040 2060

Billion gallons of gasoline equivalent

0

10

20

30

40

50

60

Alt. 2: 3%/year increase

Alt. 3: 4%/year increase

Alt. 4: ~4.3%/year increase, Preferred

Alt. 5: 5%/year increase

Alt. 6: ~6.0%/year increase, MNB

Alt. 7: 6%/year increase

Alt. 8: 7%/year increase

Alt. 9: ~6.6%/year increase, TCTB
Final Environmental Impact Statement 

8 Summary 

Hazardous air pollutants from vehicles are known as 

mobile source air toxics (MSATs). The MSATs 

included in this analysis are acetaldehyde, acrolein, 

benzene, 1,3-butadiene, diesel particulate matter 

(DPM), and formaldehyde. EPA and the Federal 

Highway Administration (FHWA) have identified 

these air toxics as the MSATs that typically are of 

greatest concern for impacts of highway vehicles. 

DPM is a component of exhaust from diesel-fueled 

vehicles and falls almost entirely within the PM2.5

particle-size class. 

Health Effects of the Pollutants 

The criteria pollutants assessed in this EIS have been 

shown to cause a range of health effects at various 

concentrations and exposures, including: 

` Damage to lung tissue (e.g., ozone, particulate 

matter); 

` Reduced lung function (e.g., ozone, nitrogen 

dioxide, sulfur dioxide, particulate matter); 

` Exacerbation of existing respiratory and 

cardiovascular diseases (e.g., ozone, nitrogen 

dioxide, particulate matter, sulfur dioxide); 

` Difficulty breathing (e.g., ozone, nitrogen dioxide, 

particulate matter, sulfur dioxide); 

` Irritation of the upper respiratory tract (e.g., ozone, 

nitrogen dioxide, sulfur dioxide); 

` Bronchitis and pneumonia (e.g., nitrogen dioxide); 

` Reduced resistance to respiratory infections (e.g., 

nitrogen dioxide); 

` Alterations to the body’s defense systems against 

foreign materials (e.g., particulate matter); 

` Reduced delivery of oxygen to the body’s organs 

and tissues (e.g., carbon monoxide); 

` Impairment of the brain’s ability to function 

properly (e.g., carbon monoxide); and 

` Cancer (e.g., particulate matter) and premature 

death (e.g., ozone, sulfur dioxide). 

MSATs are also associated with health effects. For 

example, acetaldehyde, benzene, 1-3 butadiene, 

formaldehyde, and certain components of DPM are 

all classified by EPA as either known or probable 

human carcinogens. In addition, many MSATs are 

also associated with noncancer health effects, such as 

respiratory irritation. 

Contribution of the U.S. Transportation 

Sector to Air Pollutant Emissions 

The U.S. transportation sector is a major source of 

emissions of certain criteria pollutants or their 

chemical precursors. Emissions of these pollutants 

from on-road mobile sources (passenger cars and 

light trucks) have declined dramatically since 1970 as 

a result of pollution controls on vehicles and 

regulation of the chemical content of fuels. 

Passenger cars and light trucks remain responsible for 

about 50 percent of total U.S. emissions of carbon 

monoxide, 4 percent of PM2.5 emissions, and 1 

percent of PM10 emissions. They also contribute about 

21 percent of total nationwide emissions of volatile 

organic compounds and 32 percent of NOx, both of 

which are chemical precursors of ozone. In addition, 

NOx is a PM2.5 precursor and VOCs can be PM2.5

precursors. Passenger cars and light trucks contribute 

only 1 percent of SO2, but SO2 and other oxides of 

sulfur (SOx) are important because they contribute to 

the formation of PM2.5 in the atmosphere. With the 

elimination of lead in gasoline, lead is no longer 

emitted from motor vehicles in more than negligible 

quantities, and thus is not assessed in this analysis. 

Key Findings for Air Quality 

The findings for direct and indirect effects are shown 

for the year 2030 when most of the fleet in operation 

would meet at least the MYs 2012–2016 standards. 

Findings for cumulative effects are shown for the 

year 2050 when most of the fleet would achieve the 

average fuel economy levels the agency projects in 

2030 based on AEO fuel economy forecasts. The No 

Action Alternative results in the highest emissions of 

most criteria pollutants. For hazardous air pollutants 

(MSATs), some of the alternatives result in slightly 

higher emissions of some hazardous air pollutants, 

when compared with emission levels under the No 

Action Alternative. 

With a few exceptions, cumulative emissions 

reductions are higher than noncumulative emissions 

reductions for the same combination of pollutant, year, 

and alternative, due to differences in vehicle miles 

traveled and fuel consumption under the cumulative 

case compared with the noncumulative case. 

Monetized PM2.5-related health benefits, and related 

incidence of reduced health effects from the 

emissions reductions, were estimated by multiplying 

direct PM2.5 and PM2.5 precursor emission reductions 

(NOx, SOx, and VOCs) by the pollutant-specific 

benefit-per-ton estimates supplied by EPA. Health 

outcomes include premature mortality, chronic 
Final Environmental Impact Statement 

Summary 9 

bronchitis, respiratory emergency room visits, and 

work-loss days. The economic benefits associated 

with reductions in health outcomes reflect a valuation 

of human health, as determined by EPA. 

EPA used the Value of Statistical Life (VSL) metric to 

calculate the economic benefits associated with 

reducing the risk of premature mortality. An 

estimated VSL of $6.3 million (in year 2000 dollars), 

as established by EPA in 2009, was used for this 

study. For other health-related effects, EPA used 

Willingness-to-Pay estimates derived from the 

valuation literature, estimated health care expenses, 

and lost wages in the valuation of economic benefits. 

Direct and Indirect Effects 

Criteria Pollutants 

` Emissions of PM2.5, SOx, NOx, and VOCs in 2030 

are highest in the No Action Alternative, and 

generally decline as fuel economy standards increase

across the alternatives. 

` Emissions of carbon monoxide are slightly higher 

under Alternatives 2 through 4 than under the No 

Action Alternative, but generally decline as fuel 

economy standards increase under Alternatives 5 

through 9. 

` Emissions of carbon monoxide, NOx, and VOCs in 

2030 are lowest under Alternative 8, emissions of 

SOx are lowest under Alternative 9, and emissions 

of PM2.5 are lowest under Alternative 4. 

Hazardous Air Pollutants 

` The changes in toxic air pollutant emissions, 

whether positive or negative, are generally small in 

relation to emission levels under the No Action Alternative.

` Emissions of acetaldehyde in 2030 increase with 

each successive alternative from the No Action 

Alternative to Alternative 4, decline from 

Alternative 5 to Alternative 8, and then increase 

slightly with Alternative 9. Acetaldehyde emissions 

in 2030 are highest under Alternative 4 and lowest 

under Alternative 8. 

` Emissions of acrolein and formaldehyde in 2030 

generally increase under each successive alternative 

from the No Action Alternative to Alternative 9, 

except for a slight decrease in formaldehyde 

emissions from the No Action Alternative to 

Alternative 2. 

` Emissions of benzene and diesel particulate matter 

in 2030 generally decrease under each successive 

alternative from the No Action Alternative to 

Alternative 9. Emissions are highest under the No 

Action Alternative and lowest under Alternative 8. 

` Emissions of 1,3-butadiene increase under each 

successive alternative from the No Action 

Alternative to Alternative 3 and then generally 

decrease from Alternative 4 to Alternative 9. 

Emissions of 1,3-butadiene are lowest under 

Alternative 8. 

Health and Health Benefits 

` Alternatives 2 through 9 would reduce adverse health 

effects nationwide compared with the No Action 

Alternative. Reductions become larger as fuel 

economy standards increase. 

` The monetized benefits also follow the same 

patterns as reductions in adverse health effects. 

When estimating quantified and monetized health 

impacts, EPA relies on results from two PM2.5-

related premature mortality studies it considers coequal (Pope et al., 2002 and Laden et al., 2006). EPA 

recommends that monetized benefits be shown 

using incidence estimates derived from each of 

these studies and valued using both a 3-percent 

and 7-percent discount rate to account for an 

assumed lag in the occurrence of mortality after 

exposure (EPA assumes a 20-year distributed 

“cessation lag”), for a total of four analyses. See

Sections 3.3.2.4.2, 3.3.3.3.3 of this EIS. Estimated 

benefits in annual health costs range from $1.2 billion 

for Alternative 2 (lowest of the four analyses) to $5.6 

billion for Alternative 9 (highest of the four analyses).

Cumulative Effects 

Criteria Pollutants 

` As with the direct effects, cumulative emissions of 

PM2.5, SOx, NOx, and VOCs in 2050 are highest 

under the No Action Alternative and generally 

decline (with some exceptions) as fuel economy 

standards increase across alternatives. In every case, 

emissions of these pollutants remain below those of the No 

Action Alternative.

` Cumulative emissions of carbon monoxide in 2050 

under Alternatives 2 through 4 are slightly higher 

than those of the No Action Alternative, and are 

lower than the No Action Alternative under 

Alternatives 5 through 9. 
Final Environmental Impact Statement 

10 Summary 

` Cumulative emissions of carbon monoxide, NOx, 

and VOC in 2050 are lowest under Alternative 8, 

emissions of SOx are lowest under Alternative 9, and 

emissions of PM2.5 are lowest under Alternative 4. 

Hazardous Air Pollutants 

` The changes in toxic air pollutant emissions, 

whether positive or negative, are generally small in 

relation to emission levels under the No Action Alternative.

` Annual cumulative emissions of acetaldehyde in 

2050 increase with each successive alternative 

from the No Action Alternative to Alternative 3 and 

then decline, though not consistently, from 

Alternative 4 to Alternative 9. Acetaldehyde 

emissions in 2050 are highest under Alternative 4 

and lowest under Alternative 8. 

` Annual cumulative emissions of acrolein and 

formaldehyde in 2050 generally increase under 

each successive alternative from the No Action 

Alternative to Alternative 6, and then decline, 

though not consistently, from Alternative 6 to 

Alternative 9. Acrolein emissions are highest under 

Alternative 8 and lowest under the No Action 

Alternative. Formaldehyde emissions are highest 

under Alternative 8 and lowest under Alternative 2. 

` Annual cumulative emissions of benzene and diesel 

particulate matter in 2050 decrease, though not 

consistently, across the alternatives, and are lowest 

under Alternative 8. 

` Annual cumulative emissions of 1,3-butadiene in 

2050 increase from the No Action Alternative to 

Alternative 2 and then decrease, though not 

consistently, under each successive alternative from 

Alternative 3 to Alternative 9. 

Health and Health Benefits 

` As with the direct effects, Alternatives 2 through 9 

would reduce adverse health effects nationwide 

compared with the No Action Alternative. 

` Estimated monetized health benefits range from 

$3.36 billion for Alternative 2 to $10.32 billion for 

Alternative 9 (lowest and highest of the four 

monetized health benefit analyses as explained 

above). 

For readers interested in additional detail, Tables 

3.3.3-1, 3.3.3-3, 3.3.3-4, 3.3.3-6, and 3.3.3-9 of 

this EIS provide data on direct effect criteria pollutant 

and hazardous air pollutant emissions, as well as 

monetized health benefits for the alternatives. Tables 

4.3.3-1 through 4.3.3-4 of this EIS provide 

cumulative effects data on criteria pollutant and 

hazardous air pollutant emissions. Table 4.3.3-9 of 

this EIS provides cumulative effects data on 

monetized health benefits from the alternatives. 

Climate 

The Earth’s natural greenhouse effect makes the 

planet habitable for life as we know it. See Figure S-5. 

Carbon dioxide (CO2) and other GHGs trap heat in 

the troposphere (the layer of the atmosphere that 

extends from Earth’s surface up to about 8 miles 

above the surface), absorb heat energy emitted by 

Earth’s surface and lower atmosphere, and reradiate 

much of it back to the surface. Without GHGs in the 

atmosphere, most of this heat energy would escape 

back to space. 

The amount of CO2 and other natural GHGs in the 

atmosphere, such as methane (CH4), nitrous oxide 

(N2O), water vapor, and ozone, has fluctuated over 

time, but natural emissions of GHGs are largely 

balanced by natural sinks, such as vegetation (which, 

when buried and compressed in the Earth over long 

periods of time, becomes fossil fuel) and the oceans, 

which remove the gases from the atmosphere. 

Since the industrial revolution, when fossil fuels 

began to be burned in increasing quantities, 

concentrations of GHGs in the atmosphere have 

increased. CO2 has increased by more than 38 percent 

since pre-industrial times, while methane’s 

concentration is now 149 percent above preindustrial levels.29

This buildup of GHGs in the atmosphere is upsetting 

Earth’s energy balance and causing the planet to 

warm, which in turn affects sea levels, precipitation 

patterns, cloud cover, ocean temperatures and 

currents, and other climatic conditions. Scientists 

refer to this phenomenon as “global climate change.” 

During the past century, Earth’s surface temperature 

has risen by an average of about 1.3 degrees Fahrenheit 

(0.74 °Celsius), and sea levels have risen 6.7 inches 

(0.17 meter), with a maximum rate of about 0.08 inch 

(2 millimeters) per year over the past 50 years on the 

northeastern coast of the United States.30 

Most scientists now agree that climate change is very 

likely due to GHG emissions from human activities.31

Human activities, such as the combustion of fossil 

fuel, the production of agricultural commodities, and 

the harvesting of trees, can contribute to increased 

concentrations of these gases in the atmosphere. 
Final Environmental Impact Statement 

Summary 11 

Figure S-5. The Greenhouse Effect32

Throughout this EIS, NHTSA has relied extensively 

on findings of the United Nations 

Intergovernmental Panel on Climate Change (IPCC), 

the U.S. Climate Change Science Program (CCSP), 

and EPA. Our discussion relies heavily on the most 

recent, thoroughly peer reviewed, and credible 

assessments of global and U.S. climate change − the 

IPCC Fourth Assessment Report (Climate Change 2007), 

the EPA Endangerment and Cause or Contribute 

Findings for Greenhouse Gases under Section 

202(a) of the Clean Air Act and the accompanying 

Technical Support Document (TSD), and CCSP and 

National Science and Technology Council reports 

that include Scientific Assessment of the Effects of Global 

Change on the United States and Synthesis and Assessment 

Products. 33 This EIS frequently cites these sources 

and the studies they review. 

Impacts of Climate Change 

Climate change is expected to have a wide range of 

impacts on temperature, sea level, precipitation 

patterns, severe weather events, and water resources, 

which in turn could affect human health and safety, 

infrastructure, food and water supplies, and natural 

ecosystems.

` Impacts to freshwater resources could include 

changes in precipitation patterns; decreasing 

aquifer recharge in some locations; changes in 

snowpack and timing of snowmelt; saltwater 

intrusion from sea-level changes; changes in 

weather patterns resulting in flooding or drought in 

certain regions; increased water temperature; and 

numerous other changes to freshwater systems that 

disrupt human use and natural aquatic habitats. 

` Impacts to terrestrial ecosystems could include shifts 

in species range and migration patterns, potential 

extinctions of sensitive species unable to adapt to 

changing conditions, increases in the occurrence of 

forest fires and pest infestation, and changes in 

habitat productivity due to increased atmospheric 

concentrations of CO2. 

` Impacts to coastal ecosystems could include the loss 

of coastal areas due to submersion and erosion, 

additional impacts from severe weather and storm 

surges, and increased salinization of estuaries and 

freshwater aquifers. 

` Impacts to land use could include flooding and 

severe-weather impacts to coastal, floodplain, and 

island settlements; extreme heat and cold waves; 

increases in drought in some locations; and 

weather- or sea-level-related disruptions of the 

service, agricultural, and transportation sectors. 

` Impacts to human health could include increased 

mortality and morbidity due to excessive heat, 

increases in respiratory conditions due to poor air 

quality, increases in water and food-borne 

diseases, changes to the seasonal patterns of vectorborne diseases, and increases in malnutrition. 
Final Environmental Impact Statement 

12 Summary 

In addition to its role as a GHG in the atmosphere, CO2

is transferred from the atmosphere to water, plants, 

and soil. In water, CO2 combines with water molecules 

to form carbonic acid. When CO2 dissolves in 

seawater, a series of well-known chemical reactions 

begins that increases the concentration of hydrogen 

ions and make seawater more acidic, which has 

adverse effects on corals and some other marine life. 

Increased concentrations of CO2 in the atmosphere 

can also stimulate plant growth to some degree, a 

phenomenon known as the CO2 fertilization effect. 

The available evidence indicates that different plants 

respond in different ways to enhanced CO2

concentrations. 

Contribution of the U.S. Transportation 

Sector to Climate Change 

Contributions to the build-up of GHG in the 

atmosphere vary greatly from country to country and 

depend heavily on the level of industrial and economic 

activity. Emissions from the United States account for 

about 17.2 percent of total global CO2 emissions. As 

shown in Figure S-6, the U.S. transportation sector 

contributed 31.5 percent of total U.S. CO2 emissions in 

2007, with passenger cars and light trucks accounting 

for 60.6 percent of total U.S. CO2 emissions from 

transportation.34 Thus, 19.1 percent of total U.S. CO2

emissions come from passenger cars and light trucks. 

Viewed globally, passenger cars and light trucks in the 

United States account for roughly 3.3 percent of total 

global CO2 emissions. 

Key Findings for Climate 

The proposed action and alternatives have the potential 

to substantially decrease the growth in GHG emissions, 

resulting in reductions in the anticipated increases in 

CO2 concentrations, temperature, precipitation, and 

sea level that are otherwise projected to occur. They 

would also, to a small degree, reduce the impacts and 

risks of climate change. 

Note that under all of the alternatives analyzed in this 

EIS, growth in the number of passenger cars and light 

trucks in use throughout the United States, combined 

with assumed increases in their average use (annual 

vehicle miles traveled per vehicle), is projected to 

result in growth in total passenger car and light truck 

travel. This growth in travel outpaces improvements 

in fuel economy for each of the action alternatives, 

resulting in projected increases in total fuel 

consumption by U.S. passenger cars and light trucks 

(see Figure S-7). 

Because CO2 emissions are a direct consequence of 

fuel consumption, the same result is projected for 

total CO2 emissions from passenger cars and light 

trucks. NHTSA estimates that the proposed CAFE 

standards will reduce fuel consumption and CO2

emissions from what they otherwise are estimated to 

be in the absence of the CAFE program (i.e., fuel 

consumption and CO2 emissions under the “no 

action” alternative). 

Figure S-6. U.S. Transportation Sector’s Contribution to U.S. Greenhouse Gas Emissions 

Source: Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990–2007. 
Final Environmental Impact Statement 

Summary 13 

Figure S-7. Projected Annual Greenhouse Gas Emissions by Alternative, Direct and Indirect Impacts 

2010 2020 2030 2040 2050 2060

MMTCO2

1500

2000

2500

3000

3500

4000

Alt. 1: No Action

Alt. 2: 3%/year increase

Alt. 3: 4%/year increase

Alt. 4: ~4.3%/year increase, Preferred

Alt. 5: 5%/year increase

Alt. 6: ~6.0%/year increase, MNB

Alt. 7: 6%/year increase

Alt. 8: 7%/year increase

Alt. 9: ~6.6%/year increase, TCTB

The global emissions scenario used in the cumulative 

effects analysis (and described in Chapter 4 of this 

EIS) differs from the global emissions scenario used 

for the climate change modeling for direct and 

indirect effects. In the cumulative analysis, the 

Reference Case climate change scenario used in the 

modeling analysis reflects reasonably foreseeable 

actions in global climate change policy; the global 

emissions scenario used for the analysis of direct and 

indirect effects assumes that no significant global 

controls on GHG emissions are adopted. See Section 

4.4.3.3 of this EIS for additional explanation of the 

cumulative effects methodology. 

The figures for GHG emissions and reductions below 

are summed for the period 2012 through 2100 

under each of the nine alternatives. 

Direct and Indirect Effects 

Greenhouse Gas Emissions 

` Compared with total projected U.S. CO2 emissions 

in 2100 of 7,886 million metric tons of carbon 

dioxide equivalent (MMTCO2), the action 

alternatives would reduce annual U.S. CO2 emissions by 

3.9 to 9.1 percent in 2100. See Figure S-7. 

` Compared with cumulative global emissions of 

5,293,896 MMTCO2 over this period, the action 

alternatives are expected to reduce annual global 

CO2 emissions by between 0.4 percent (Alternative 

2) and 0.9 percent (Alternative 9). 

` Average annual CO2 emission reductions from the 

CAFE alternatives range from 232 to 543 MMTCO2

over 2012–2100, equivalent to the annual CO2

emissions of 60 to 141 coal-fired power plants.

35
Final Environmental Impact Statement 

14 Summary 

` The emissions reductions from the alternatives are 

equivalent to the annual emissions of between 3.60 

million cars (Alternative 2) and 9.70 million cars 

(Alternative 9) in 2016, compared with the No Action 

Alternative. Emissions reductions in 2016 from the 

Preferred Alternative (Alternative 4) are equivalent 

to the annual emissions of 6.26 million cars. 

` President Obama recently submitted to the United 

Nations Framework Convention on Climate 

Change (UNFCCC) a GHG target for the United 

States in the range of 17 percent below 2005 levels 

by 2020,36 in association with the Copenhagen 

Accord, and in conformity with anticipated U.S. 

energy and climate legislation. While this 

rulemaking contributes to meeting that goal, the 

alternatives would result in projected CO2 emissions 

from the light duty vehicle sector in 2020 in the range of 

0.6 percent above (Alternative 2) to 5.4 percent below 

(Alternative 9) 2005 levels. Thus, no alternative would 

reduce 2020 emissions from cars and light trucks 

to 17 percent below 2005 levels, due to the fact 

that total vehicles miles traveled (VMT) increase 

under all scenarios.37 See Figure S-8. 

The President’s stated policy goal outlined above does 

not specify that every emitting sector of the economy 

must contribute equally proportional emissions 

reductions. Significantly, the action of setting fuel 

economy standards does not directly regulate total 

emissions from passenger cars and light trucks. 

NHTSA’s authority to promulgate new fuel economy 

standards is limited and does not allow regulation of 

other factors affecting emissions, including society’s 

driving habits. See Section 3.4.4.1 of this EIS for 

additional discussion relating NHTSA’s action to this 

policy goal. 

Figure S-8. Projected Annual CO2 Emissions by Alternative Compared with 17% below 2005 Levels, Direct and Indirect Impacts 

2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020

CO2 Emissions (MMTCO2)

1200

1300

1400

1500

1600

1700

1800

1900

Alt. 1: No Action

Alt. 2: 3%/year increase

Alt. 3: 4%/year increase

Alt. 4: ~4.3%/year increase, Preferred

Alt. 5: 5%/year increase

Alt. 6: ~6.0%/year increase, MNB

Alt. 7: 6%/year increase

Alt. 8: 7%/year increase

Alt. 9: ~6.6%/year increase, TCTB

17% below 2005 = 1,430.9 MMTCO2
Final Environmental Impact Statement 

Summary 15 

CO2 Concentration, Global Mean Surface 

Temperature, Sea-Level Rise, and Precipitation 

CO2 emissions affect the concentration of CO2 in the 

atmosphere, which in turn affects global temperature, 

sea level, and precipitation patterns. The impacts of 

the proposed action and alternatives on temperature, 

precipitation, or sea-level rise are small in absolute 

terms, because the action alternatives result in a small 

proportional change to the emissions trajectories in 

the reference scenario to which the alternatives were 

compared. Although these effects are small, they 

occur on a global scale and are long-lived. 

` Estimated CO2 concentrations in the atmosphere 

for the year 2100 range from 778.4 parts per million 

(ppm) under Alternative 8 to 783.0 ppm under the No 

Action Alternative. 

` For 2100, the reduction in temperature for the 

action alternatives, as compared to the No Action 

Alternative, ranges from 0.01 °F (0.007 °C) to 0.03 °F 

(0.018 °C). See Figure S-9. 

` Projected sea-level rise in 2100 ranges from 14.96 

inches (38.00 centimeters) under the No Action 

Alternative to 14.89 inches (37.84 centimeters) 

under the TCTB Alternative. Thus, the action 

alternatives will result in a maximum reduction of sea-level 

rise equal to 0.06 inches (0.16 centimeters) by 2100 from 

the level projected under the No Action Alternative. 

Cumulative Effects 

Greenhouse Gas Emissions 

` Compared with projected global emissions of 

3,919,462 MMTCO2 from 2012 through 2100, the 

incremental impact of this rulemaking is expected to 

reduce global CO2 emissions by about 0.8 to 1.2 percent

from their projected levels under the No Action 

Alternative. See Figure S-10. 

` Projections of emissions reductions over the 2012 

through 2100 period due to the MYs 2012–2016 

CAFE standards and other reasonably foreseeable 

future actions (i.e., forecasted fuel economy increases 

resulting from projected demand for fuel economy) 

ranged from 30,200 to 45,600 MMTCO2. 

Figure S-9. Reduction in Global Mean Temperature Compared with the No Action Alternative, 

Direct and Indirect Impacts 

2030 2050 2100

Degrees Celsius

0.000

0.002

0.004

0.006

0.008

0.010

0.012

0.014

0.016

0.018

0.020

Alt. 2: 3%/year increase

Alt. 3: 4%/year increase

Alt. 4: ~4.3%/year increase, Preferred

Alt. 5: 5%/year increase

Alt. 6: ~6.0%/year increase, MNB

Alt. 7: 6%/year increase

Alt. 8: 7%/year increase

Alt. 9: ~6.6%/year increase, TCTB
Final Environmental Impact Statement 

16 Summary 

Figure S-10. Projected Greenhouse Gas Emissions by Alternative, Cumulative Impacts 

2010 2020 2030 2040 2050 2060

MMTCO2

1500

2000

2500

3000

3500

4000

Alt. 1: No Action

Alt. 2: 3%/year increase

Alt. 3: 4%/year increase

Alt. 4: ~4.3%/year increase, Preferred

Alt. 5: 5%/year increase

Alt. 6: ~6.0%/year increase, MNB

Alt. 7: 6%/year increase

Alt. 8: 7%/year increase

Alt. 9: ~6.6%/year increase, TCTB

` This action contributes to meeting the President’s 

goal of returning GHG emissions to 17 percent 

below 2005 levels by 2020. The alternatives would 

reduce projected CO2 emissions from the light duty vehicle 

sector in 2020 by 0.7 percent (Alternative 2) to 5.7 percent 

(Alternative 9) below 2005 levels. See Figure S-11. 

CO2 Concentration, Global Mean Surface 

Temperature, Sea-Level Rise, and Precipitation 

` Estimated CO2 concentrations in the atmosphere for 

the year 2100 range from 653.4 ppm under Alternative 

8 to 657.4 ppm under the No Action Alternative.

` For 2100, the reduction in temperature increase for the 

action alternatives in relation to the No Action Alternative is 

about 0.02 to 0.04° F (0.01 to 0.02 °C). See Figure S-12. 

` Projected sea-level rise in 2100 ranges from 12.93 

inches (32.84 centimeters) under the No Action 

Alternative to 12.87 inches (32.68 centimeters) 

under the TCTB Alternative (Alternative 9). Thus, 

the CAFE action alternatives will result in a 

maximum reduction of sea level rise equal to 0.06 inches 

(0.16 centimeters) by 2100 from the level that would 

occur under the No Action Alternative. 

Readers interested in further details about the direct, 

indirect, and cumulative climate impacts should 

consult Sections 3.4 and 4.4 of this EIS. 

Health, Societal, and Environmental Impacts 

of Climate Change 

The magnitude of the changes in climate effects that 

the alternatives would produce (4 ppm of CO2, a few 

hundredths of a degree difference in temperature, a 

small percentage change in the rate of precipitation 

increase, and 1 or 2 millimeters of sea-level rise) are 
Final Environmental Impact Statement 

Summary 17 

Figure S-11. Projected Annual CO2 Emissions by Alternative Compared with 17% below 2005 Levels, Cumulative Impacts 

2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020

CO2 Emissions (MMTCO2)

1200

1300

1400

1500

1600

1700

1800

1900

Alt. 1: No Action

Alt. 2: 3%/year increase

Alt. 3: 4%/year increase

Alt. 4: ~4.3%/year increase, Preferred

Alt. 5: 5%/year increase

Alt. 6: ~6.0%/year increase, MNB

Alt. 7: 6%/year increase

Alt. 8: 7%/year increase

Alt. 9: ~6.6%/year increase, TCTB

17% below 2005 = 1,430.9 MMTCO2

too small to address quantitatively in terms of their 

impacts on health, society, and the environment. 

Given the enormous resource values at stake, these 

distinctions could be important, but they are too 

small for current quantitative techniques to resolve. 

For detailed discussion of climate change’s impacts 

on various resource sectors, see Section 4.5 of this EIS. 

The changes in non-climate impacts (such as ocean 

acidification by CO2) associated with the alternatives 

are also difficult to assess quantitatively. However, it 

is clear that a reduction in the rate of increase in 

atmospheric CO2, which all the action alternatives 

would provide to some extent, would reduce the 

ocean acidification effect and the CO2 fertilization 

effect. For additional discussion of non-climate 

environmental impacts, see Section 3.5 of this EIS. 

Mitigation 

CEQ regulations for implementing the procedural 

requirements of NEPA require that the discussion of 

alternatives in an EIS “[i]nclude appropriate 

mitigation measures not already included in the 

proposed action or alternatives.”38 In particular, an 

EIS should discuss the “[m]eans to mitigate adverse 

environmental impacts.”39 

Under NEPA, an agency does not have to formulate 

and adopt a complete mitigation plan, but should 

analyze possible measures that could be adopted. An 

agency should state in its Record of Decision whether 

all practicable means to avoid or reduce 

environmental harm have been adopted into the 

selected alternative.40 

Energy and Climate 

Each of the action alternatives would reduce energy 

consumption and GHG emissions from vehicles sold 

in the United States compared with the No Action 

Alternative, resulting in a net beneficial effect. 

Although an agency typically does not propose 

mitigation measures for an action resulting in a net 

beneficial effect, NHTSA would like to highlight 
Final Environmental Impact Statement 

18 Summary 

Figure S-12. Cumulative Effects on Global Mean Temperature (Reduction Compared with the No Action Alternative) 

2030 2050 2100

Degrees Celsius

0.000

0.005

0.010

0.015

0.020

Alt. 2: 3%/year increase

Alt. 3: 4%/year increase

Alt. 4: ~4.3%/year increase, Preferred

Alt. 5: 5%/year increase

Alt. 6: ~6.0%/year increase, MNB

Alt. 7: 6%/year increase

Alt. 8: 7%/year increase

Alt. 9: ~6.6%/year increase, TCTB

several other federal programs, which in conjunction 

with NHTSA CAFE standards, can make significant 

contributions in further reducing energy 

consumption and GHG emissions. 

The programs described below present the potential 

for future developments and advances that could 

provide further beneficial environmental effects. 

` EPA administers Renewable Fuel Standards under 

Section 211(o) of the Clean Air Act. EPA estimates 

that the greater volumes of biofuel mandated by 

proposed standards would reduce GHG emissions 

from transportation by approximately 160 

MMTCO2 equivalent per year. 

` DOT, in coordination with EPA and the U.S. 

Department of Housing and Urban Development, 

announced six livability principles around which 

the agencies will coordinate agency policies. One 

of the principles is focused on increasing 

transportation options, which aims to decrease 

energy consumption, improve air quality, and 

reduce GHG emissions. 

` DOT is one of more than a dozen agency members 

of the U.S. Climate Change Technology Program, 

led by DOE, which is aimed at the development 

and adoption of technologies designed to reduce 

the U.S. carbon footprint.41 

` In furtherance of DOT’s high-speed rail initiative, 

President Obama recently announced DOT’s 

American Recovery and Reinvestment Act HighSpeed Intercity Passenger Rail grants to 31 states 

and the District of Columbia to jump-start high-
Final Environmental Impact Statement 

Summary 19 

speed rail development in the United States. Highspeed rail development will help reduce vehicle 

miles traveled, a critical factor for reducing GHG 

emissions from the transportation sector. 

` The Federal Transit Administration is actively 

supporting the DOT Livability Initiative and the 

Federal Sustainable Communities Partnership with 

its programs to expand mass transit, another travel 

alternative that will reduce U.S. transportation 

sector GHG emissions. 

` Also within DOT, the Federal Aviation 

Administration is a sponsor of the Commercial 

Aviation Fuels Initiative (CAAFI), which is a 

coalition of the U.S. commercial aviation 

community that acts as a focal point for engaging 

the emerging alternative fuels industry. The CAAFI 

seeks to enhance energy security, and thereby 

reduce GHG emissions, in the transportation sector 

by promoting the development of alternative fuel 

options for use in aviation. 

` DOE’s Clean Cities Program develops governmentindustry partnerships designed to reduce 

petroleum consumption.42 

` DOE administers the Vehicle Technologies Program, 

which creates public-private partnerships that 

enhance energy efficiency and productivity and can 

bring clean technologies to the marketplace.43 

` Pursuant to Executive Order (EO) 13514 on 

Federal Sustainability, DOT and other federal 

agencies will be working to implement the 

President’s recently announced goal of federal 

government GHG emissions reductions of 28 

percent by 2020. The federal government is the 

single largest energy consumer in the U.S. 

economy. As such, the EO 13514 environmental 

performance goals for federal agencies focus on 

reducing GHG reductions from government 

operations and, thereby, leading by example. 

Air Pollution 

Generally, NHTSA’s analysis forecasts emissions from 

criteria pollutants and mobile source air toxics to 

decline under the action alternatives, although 

emissions of carbon monoxide, acetaldehyde, 

acrolein, 1,3-butadiene, and formaldehyde could 

increase under certain alternatives and analysis years, 

compared with the No Action Alternative. While 

carbon monoxide emissions are projected to increase 

in some cases, the associated harm might not increase 

measurably. There have been fewer than three 

violations of the carbon monoxide National Ambient 

Air Quality Standards per year since 2002, owing to 

the success of regulations governing fuel composition 

and vehicle emissions. Also, vehicle manufacturers 

can choose which technologies to employ to meet the 

new CAFE standards. Some of their choices result in 

higher or lower impacts for these emissions. 

There could be increases in criteria and toxic air 

pollutant emissions in some nonattainment areas as a 

result of implementation of the CAFE standards under 

the action alternatives. These increases would represent 

a slight decline in the rate of reductions achieved by 

implementation of Clean Air Act standards. 

There are several federal programs available to 

mitigate such impacts. Federal transportation funds 

administered by the Federal Highway Administration 

(FHWA) could be available to assist in funding 

projects to reduce increases in emissions. FHWA 

provides funding to states and localities specifically to 

improve air quality under the Congestion Mitigation 

and Air Quality Improvement (CMAQ) Program. The 

FHWA and the Federal Transit Administration also 

provide funding to states and localities under other 

programs that have multiple objectives, including air 

quality improvement. Specifically, the Surface 

Transportation Program provides flexible funding that 

states may use for projects on any federal-aid highway. 

As state and local agencies recognize the need to 

reduce emissions of carbon monoxide, acetaldehyde, 

acrolein, 1,3-butadiene, and formaldehyde (or other 

emissions eligible under the CMAQ Program, 

including the criteria pollutants and mobile source air 

toxics analyzed in this EIS), they have the ability to 

apply CMAQ funding to reduce impacts in most areas. 

Further, under the Clean Air Act, EPA has the authority 

to continue to improve vehicle emissions standards, 

which could result in future reductions as EPA 

promulgates new regulations. 
Final Environmental Impact Statement 

20 Summary 

Notes 

1

 NEPA is codified at 42 U.S.C. §§ 4321-4347. CEQ NEPA implementing regulations are codified at 40 CFR Parts 

1500-1508. NHTSA NEPA implementing regulations are codified at 49 CFR Part 520. 

2

 49 U.S.C. § 32901-32919.

3

 49 CFR §§ 1.50, 501.2(a)(8). 

4

 Pub. L. No. 110-140, 121 Stat. 1492 (Dec. 19, 2007). EISA amends and builds on EPCA by setting out a 

comprehensive energy strategy for the 21st Century addressing renewable fuels and CAFE standards. 

5

 Notice of Proposed Rulemaking, Average Fuel Economy Standards, Passenger Cars and Light Trucks; Model Years 

2011–2015, 73 Federal Register (FR) 24352 (May 2, 2008). At the same time, NHTSA requested updated product 

plan information from the automobile manufacturers. See Request for Product Plan Information, Passenger Car 

Average Fuel Economy Standards—Model Years 2008–2020 and Light Truck Average Fuel Economy Standards—

Model Years 2008–2020, 73 FR 21490 (May 2, 2008). 

6

 EPA published a Notice of Availability of the Final Environmental Impact Statement (FEIS) in the Federal Register on 

October 17, 2008. Environmental Impact Statements; Notice of Availability, 73 FR 61859 (Oct. 17, 2008). 

7

 Final Rule, Average Fuel Economy Standards Passenger Cars and Light Trucks Model Year 2011, 74 FR 14196 

(Mar. 30, 2009). On January 7, 2009, DOT announced that the Bush Administration would not issue the final 

rule. The DOT January 7, 2008 statement can be found at: http://www.dot.gov/affairs/dot0109.htm (last accessed Feb. 

2, 2009). President Obama issued a memorandum on January 26, 2009, to the Secretary of Transportation and 

the NHTSA Administrator requesting that NHTSA issue a final rule adopting CAFE standards for MY 2011 only, 

and to reconsider the standards for years after 2011. Memorandum for the Secretary of Transportation and the 

Administrator of the National Highway Traffic Safety Administration, 74 FR 4907 (Jan. 26, 2009). 

8 See Notice of Intent to Prepare an Environmental Impact Statement for New Corporate Average Fuel Economy 

Standards, 74 FR 14857 (Apr. 1, 2009). 

9

 Scoping, as defined under NEPA, is an early and open process for determining the scope of issues to be addressed 

in an EIS and for identifying the significant issues related to a proposed action. See 40 CFR § 1501.7. 

10 This would also achieve levels of emissions that would satisfy California’s standards. 

11 42 U.S.C. § 4332. 

12 40 CFR § 1501.6. 

13 49 U.S.C. § 32902(a). 

14 49 U.S.C. § 32902(f). 

15 See, e.g., Competitive Enterprise Inst. v. NHTSA, 956 F.2d 321, 322 (D.C. Cir. 1992) (citing Competitive Enterprise Inst. v. 

NHTSA, 901 F.2d 107, 120 n.11 (D.C. Cir. 1990)); and 73 FR 24352, 24364 (May 2, 2008). 

16 49 U.S.C. § 32902(b)(2)(A). 

17 49 U.S.C. §§ 32902(b)(2)(C), 32902(b)(3)(B). 

18 Although EISA’s recent amendments to EPCA direct NHTSA to increase the stringency of CAFE standards and do 

not permit the agency to take no action on fuel economy, CEQ regulations mandate analysis of a no action 

alternative. See 40 CFR § 1502.14(d). CEQ has explained that “the regulations require the analysis of the no 

action alternative even if the agency is under a court order or legislative command to act.” Forty Most Asked Questions Concerning 

CEQ’s National Environmental Policy Act Regulations, 46 FR 18026 (1981) (emphasis added). 
Final Environmental Impact Statement 

Summary 21 

19 Alternative 2 requires a 3% average annual increase in mpg. Alternative 3 requires a 4% average annual increase 

in mpg. Alternative 5 requires a 5% average annual increase in mpg. Alternative 7 requires a 6% average annual 

increase in mpg. Alternative 8 requires a 7% annual increase in mpg. 

20 In this rulemaking, NHTSA and EPA have chosen vehicle footprint as the most appropriate attribute on which to 

base fuel economy and GHG emissions standards as discussed in the NPRM. Thus, vehicles with larger footprints 

(i.e., generally larger vehicles) would be subject to less stringent standards than vehicles with smaller footprints 

(i.e., generally smaller vehicles). 

21 In NHTSA’s analysis, “overcompliance” occurs through multi-year planning: manufacturers apply some “extra” 

technology in early model years to carry that technology forward and thereby facilitate compliance in later 

model years. 

22 Consistent with EPCA, NHTSA has not accounted for manufacturers’ ability to earn CAFE credits for selling flexfuel vehicles (FFVs), to carry credits forward and back between model years, and to transfer credits between the 

passenger car and light truck fleets when setting standards. 49 U.S.C. § 32902(h). However, to assist in 

understanding the extent to which use of credits might reduce manufacturers’ compliance costs and the 

benefits of new CAFE standards, NHTSA does analyze the potential effects of FFV credits. See Section 3.1.4.1 of 

this EIS. 

23 The CAFE level required under an attribute-based standard depends on the mix of vehicles produced for sale in 

the United States. NHTSA has developed the average mpg levels under each alternative based on the vehicle 

market forecast that NHTSA and EPA have used to develop and analyze new CAFE and GHG emissions 

standards. 

24 See 42 U.S.C. § 4332 (requiring federal agencies to “identify and develop methods and procedures...which will 

insure that presently unquantified environmental amenities and values may be given appropriate 

consideration”); 40 CFR § 1502.23 (requiring an EIS to discuss the relationship between a cost-benefit analysis 

and any analyses of unquantified environmental impacts, values, and amenities); CEQ, Considering Cumulative Effects 

Under the National Environmental Policy Act (1984), available at http://ceq.hss.doe.gov/nepa/ccenepa/ccenepa.htm (last accessed 

July 22, 2009) (recognizing that agencies are sometimes “limited to qualitative evaluations of effects because 

cause-and-effect relationships are poorly understood” or cannot be quantified). 

25 U.S. Energy Information Administration, 2009. Annual Energy Review 2008. Report No. DOE/EIA-0384(2008), 

available at http://www.eia.doe.gov/emeu/aer/petro.html

26 Id.

27 U.S. Energy Information Administration, 2009. Annual Energy Review 2008. Washington, D.C. DOE/EIA0384(2008). 408 pgs. 

28 The AEO projections anticipate an average annual percentage gain of 0.51 percent in passenger car mpg and 0.86 

percent in light truck mpg from 2019 through 2030. 

29 U.S. EPA, Recent Atmospheric Changes page, Climate Change Site, http://www.epa.gov/climatechange/science/recentac.html

(last accessed December 17, 2009). 

30 Le Treut, H., R. Somerville, U. Cubasch, Y. Ding, C. Mauritzen, A. Mokssit, T. Peterson, and M. Prather. 2007. 

Historical Overview of Climate Change. Pgs. 93–128. In: Climate Change 2007: The Physical Science Basis. 

Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate 

Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor, and H.L. Miller 

(Eds.)] Cambridge University Press, Cambridge, United Kingdom and New York, New York. 996 pgs. 

31 EPA (U.S. Environmental Protection Agency). 2009. Technical Support Document for Endangerment and Cause or 

Contribute Findings for Greenhouse Gases under Section 202(a) of the Clean Air Act. Office of Atmospheric 

Programs Climate Change Division. U.S. Environmental Protection Agency, Washington, District of Columbia. 

December 7. 210 pgs. 

32 See Note 30. 
Final Environmental Impact Statement 

22 Summary 

33 Synthesis and assessment reports are issued by expert panels that have assessed numerous individual studies in 

order to draw general conclusions about the state of the science, have been reviewed and formally accepted by, 

commissioned by, or in some cases authored by U.S. government agencies and individual government scientists 

and provide assurances that the material has been well vetted by both the climate change research community 

and the U.S. government. 

34 EPA (U.S. Environmental Protection Agency). 2009. Inventory of U.S. Greenhouse Gas Emissions and Sinks. 

Washington, D.C. EPA 430-R-09-004. 441 pgs. Last Revised: July 14, 2009. Available at: 

http://www.epa.gov/climatechange/emissions/usinventoryreport.html (last accessed February 17, 2010). 

35 Estimated using EPA’s Greenhouse Gas Equivalencies Calculator, available at: http://www.epa.gov/cleanenergy/energyresources/calculator.html (last accessed Feb. 17, 2010). 

36 On January 28, 2010, the United States submitted this target to the U.N. Framework Convention on Climate 

Change as part of a January 31, 2010 deadline negotiated in Copenhagen in December 2009. See

http://unfccc.int/home/items/5264.php (last accessed Feb. 1, 2010). 

37 NHTSA may propose more stringent CAFE standards for MYs 2017-2020 that may help to achieve the President’s 

target. 

38 40 CFR § 1502.14(f). 

39 40 CFR § 1502.16(h). 

40 40 CFR § 1505.2(c). 

41 Office of Policy and International Affairs, Department of Energy, Climate Overview, available at

http://www.pi.energy.gov/climateoverview.html (last accessed Jul. 15, 2009). 

42 Office of Energy Efficiency and Renewable Energy, U.S. Department of Energy, Clean Cities: Fact Sheet (2009). 

43 Office of Energy Efficiency and Renewable Energy, U.S. Department of Energy, About the Program, available at

http://www1.eere.energy.gov/ vehiclesandfuels/about/index.html (last accessed Jul. 15, 2009). 
 1-1 

Chapter 1 Purpose and Need for the Proposed Action 

1.1 INTRODUCTION 

The Energy Policy and Conservation Act of 1975 (EPCA)1

 established a program to regulate 

automobile fuel economy and provided for the establishment of average fuel economy standards for 

passenger cars and light trucks.2

 As part of that Act, the Corporate Average Fuel Economy (CAFE) 

Program was established to reduce national energy consumption by increasing the fuel economy of 

passenger cars and light trucks. EPCA directs the Secretary of Transportation to set and implement fuel 

economy standards for passenger cars and light trucks sold in the United States.3

 The National Highway 

Traffic Safety Administration (NHTSA) is delegated responsibility for implementing EPCA fuel 

economy requirements assigned to the Secretary of Transportation.4

In December 2007, the Energy Independence and Security Act of 2007 (EISA)5

 amended 

EPCA’s CAFE program requirements, providing the U.S. Department of Transportation (DOT) ad

rulemaking authority and responsibilities. Pursuant to EISA, on April 22, 2008, NHTSA proposed CAFE 

standards for model years (MYs) 2011-2015 passenger cars and light trucks in a Notice of Proposed 

Rulemaking (NPRM).

ditional 

 

6

 On March 21, 2008, NHTSA issued a Notice of Intent (NOI) to prepare an EIS 

for the MYs 2011-2015 CAFE standards.7

 On October 10, 2008, NHTSA submitted to the U.S. 

Environmental Protection Agency (EPA) its Final Environmental Impact Statement, Corporate Average 

Fuel Economy Standards, Passenger Cars and Light Trucks, MYs 2011-2015. EPA published a Notice of 

Availability of the Final Environmental Impact Statement (FEIS) in the Federal Register (FR) on October 

17, 2008.8

 On January 7, 2009, DOT announced that the Bush Administration would not issue the final 

rule.9

 

In the context of calls for the development of new national policies to prompt sustained domestic 

and international actions to address the closely intertwined issues of energy independence, energy 

security, and climate change, President Obama issued a memorandum on January 26, 2009 to the 

1

 EPCA was enacted for the purpose of serving the Nation’s energy demands and promoting conservation methods 

when feasibly obtainable. EPCA is codified at 49 U.S.C. § 32901 et seq. 2

 49 U.S.C. §§ 32901-32919. 3

 49 CFR § 1.50. In addition, the U.S. Environmental Protection Agency (EPA) calculates the average fuel economy 

for each automobile manufacturer that sells vehicles in the United States. 49 U.S.C. § 32904. 4

 Accordingly, the Secretary of Transportation, DOT, and NHTSA are used interchangeably in this section of the 

DEIS. 

5

 EISA amends and builds on the Energy Policy and Conservation Act by setting out a comprehensive energy 

strategy for the 21st Century addressing renewable fuels and CAFE standards. Pub. L. No. 110-140, 121 Stat. 1492 

(Dec. 19, 2007). 

6

 Notice of Proposed Rulemaking, Average Fuel Economy Standards, Passenger Cars and Light Trucks; Model 

Years 2011-2015, 73 FR 24352 (May 2, 2008). At the same time, NHTSA requested updated product plan 

information from the automobile manufacturers. See Request for Product Plan Information, Passenger Car Average 

Fuel Economy Standards—Model Years 2008-2020 and Light Truck Average Fuel Economy Standards—Model 

Years 2008-2020, 73 FR 21490 (May 2, 2008). 7

 Notice of Intent to Prepare an Environmental Impact Statement for New Corporate Average Fuel Economy 

Standards, 73 FR 16615 (Mar. 28, 2008). 8

 Environmental Impact Statements; Notice of Availability, 73 FR 38204 (Jul. 3, 2008). 9

 The January 7, 2008 statement from the U.S. Department of Transportation can be found at: 

http://www.dot.gov/affairs/dot0109.htm (last accessed Jun. 9, 2009). 
Chapter 1 Purpose and Need for the Proposed Action 

 1-2 

Secretary of Transportation and the NHTSA Administrator.10 The memorandum requested that NHTSA 

divide the MYs 2011-2015 rulemaking into two parts: (1) MY 2011 standards, and (2) standards for MYs 

2012 and beyond.

 The request that the final rule establishing CAFE standards for MY 2011 passenger cars and light 

trucks be prescribed by March 30, 2009 was based on several factors. One was the requirement that the 

final rule regarding fuel economy standards for a given model year must be adopted at least 18 months 

before the beginning of that model year (49 U.S.C. § 32902(g)(2)). The other was that the beginning of 

MY 2011 is considered to be, for the purposes of CAFE standard setting, October 1, 2010. 

 For MYs 2012 and beyond, the President requested that, before promulgating a final rule 

concerning the model years after MY 2011, NHTSA

[C]onsider the appropriate legal factors under the EISA, the comments filed in response 

to the Notice of Proposed Rulemaking, the relevant technological and scientific 

considerations, and to the extent feasible, the forthcoming report by the National 

Academy of Sciences mandated under section 107 of EISA. 

In addition, the President requested that NHTSA consider whether any provisions regarding preemption 

are applicable. 

1.2 JOINT RULEMAKING AND NEPA PROCESS 

On September 28, 2009, NHTSA and EPA announced in the Federal Register the Proposed 

Rulemaking To Establish Light-Duty Vehicle Greenhouse Gas Emission Standards and Corporate 

Average Fuel Economy Standards.11 These joint proposed rules address the urgent and closely 

intertwined challenges of energy independence and security and global warming. These proposed rules 

call for a strong and coordinated federal greenhouse gas (GHG) and fuel economy program for passenger 

cars, light-duty trucks, and medium-duty passenger vehicles (also referred to as light-duty vehicles), 

referred to as the National Program. The proposed rules can achieve substantial improvements in fuel 

economy and reductions of GHG emissions from the light-duty vehicle part of the transportation sector, 

based on technology that is already being commercially applied in most cases and that can be 

incorporated at a reasonable cost. 

These joint proposed standards are consistent with the President’s announcement on May 19, 

2009 of a National Fuel Efficiency Policy for establishing consistent, harmonized, and streamlined 

requirements that would improve fuel economy and reduce GHG emissions for all new passenger cars 

and light trucks sold in the United States.12 The National Program holds out the promise of delivering 

additional environmental and energy benefits, cost savings, and administrative efficiencies on a 

nationwide basis that might not be available under a less coordinated approach. The proposed National 

Program also offers the prospect of regulatory convergence by making it possible for the standards of two 

 

10 Memorandum for the Secretary of Transportation and the Administrator of the National Highway Traffic Safety 

Administration, 74 FR 4907 (Jan. 26, 2009). 11 Proposed Rulemaking To Establish Light-Duty Vehicle Greenhouse Gas Emission Standards and Corporate 

Average Fuel Economy Standards, 74 FR 49454 (Sep. 28, 2009). 12 President Obama Announces National Fuel Efficiency Policy, The White House, May 19, 2009. Available at: 

http://www.whitehouse.gov/the_press_office/President-Obama-Announces-National-Fuel-Efficiency-Policy/ (last 

accessed August 18, 2009). Remarks by the President on National Fuel Efficiency Standards, The White House, 

May 19, 2009. Available at: http://www.whitehouse.gov/the_press_office/Remarks-by-the-President-on-nationalfuel-efficiency-standards/ (last accessed August 18, 2009). 
Chapter 1 Purpose and Need for the Proposed Action 

 1-3 

federal agencies and the standards of California and other states to act in a unified fashion in providing 

these benefits. This would allow automakers to produce and sell a single fleet nationally. Thus, it may 

also help to mitigate the additional costs that manufacturers would otherwise face in having to comply 

with multiple sets of federal and state standards. This joint notice is also consistent with the Notice of 

Upcoming Joint Rulemaking signed by DOT and EPA on May 19, 200913 and responds to the President’s 

January 26, 2009 memorandum on CAFE standards for MYs 2011 and beyond.14

1.2.1 Building Blocks of the National Program 

The National Program is both needed and possible because the relationship between improving 

fuel economy and reducing carbon dioxide (CO2) tailpipe emissions is a very direct and close one. The 

amount of those CO2 emissions is essentially constant per gallon combusted of a given type of fuel. 

Thus, the more fuel efficient a vehicle is, the less fuel it burns to travel a given distance. The less fuel it 

burns, the less CO2 it emits in traveling that distance (Committee on Science, Engineering and Public 

Policy 1992). While there are emission control technologies that reduce the pollutants (e.g., carbon 

monoxide) produced by imperfect combustion of fuel by capturing or destroying them, there is no such 

technology for CO2. Further, while some of those pollutants can also be reduced by achieving a mor

complete combustion of fuel, doing so only increases the tailpipe emissions of CO

e 

s as well. 

 

2. Thus, there is a 

single pool of technologies for addressing these twin problems, i.e., those that reduce fuel consumption

and thereby reduce CO2 emission

1.2.1.1 DOT’s CAFE Program 

In 1975, Congress enacted EPCA, mandating that NHTSA establish and implement a regulatory 

program for motor vehicle fuel economy to meet the various facets of the need to conserve energy, 

including those with energy independence and security, environmental, and foreign policy implications. 

Fuel economy gains since 1975, due both to standards and market factors, resulted in saving billions of 

barrels of oil and avoiding billions of metric tons of CO2 emissions. In December 2007, Congress 

enacted EISA, amending EPCA to require substantial, continuing increases in fuel economy standards. 

The CAFE standards address most, but not all, real-world CO2 emissions because EPCA requires 

the use of 1975 passenger car test procedures under which vehicle air conditioners are not turned on 

during fuel economy testing.15 Fuel economy is determined by measuring the amount of CO2 and other 

carbon compounds emitted from the tailpipe, not by attempting to measure directly the amount of fuel 

consumed during a vehicle test, a difficult task to accomplish with precision. The carbon content of the 

test fuel is then used to calculate the amount of fuel that had to be consumed per mile in order to produce 

that amount of CO2.

16 Finally, that fuel consumption figure is converted into a miles-per-gallon figure. 

CAFE standards also do not address the 5–8 percent of GHG emissions that are not CO2, i.e., nitrous 

oxide (N2O), and methane (CH4), as well as emissions from the operation of the air conditioning system 

such as CO2 and hydrofluorocarbons (HFCs). 

13 Notice of Upcoming Joint Rulemaking To Establish Vehicle GHG Emissions and CAFE Standards, 74 FR 24007 

(May 22, 2009). 

14 Available at: http://www.whitehouse.gov/the_press_office/Presidential_Memorandum_Fuel_Economy/ (last 

accessed August 18, 2009) 

15 EPCA does not require the use of 1975 test procedures for light trucks. 

16 This is the method that EPA uses to determine compliance with NHTSA’s CAFE standards. 
Chapter 1 Purpose and Need for the Proposed Action 

 1-4 

1.2.1.2 EPA’s Greenhouse Gas Standards for Light-Duty Vehicles 

Under the Clean Air Act (CAA), EPA is responsible for addressing air pollutants from motor 

vehicles. On April 2, 2007, the U.S. Supreme Court issued its opinion in Massachusetts v. EPA,

17 a case 

involving a 2003 EPA order denying a petition for rulemaking to regulate GHG emissions from motor 

vehicles under section 202(a) of the CAA.18 The Court held that GHGs were air pollutants for purposes 

of the CAA and further held that the Administrator must determine whether emissions from new motor 

vehicles cause or contribute to air pollution which may reasonably be anticipated to endanger public 

health or welfare, or whether the science is too uncertain to make a reasoned decision. The Court further 

ruled that, in making these decisions, the EPA Administrator is required to follow the language of section 

202(a) of the CAA. The Court rejected the argument that EPA cannot regulate CO2 from motor vehicles 

because to do so would de facto tighten fuel economy standards, authority over which has been assigned 

by Congress to DOT. The Court stated that “[b]ut that DOT sets mileage standards in no way licenses 

EPA to shirk its environmental responsibilities. EPA has been charged with protecting the public’s 

‘health’ and ‘welfare’, a statutory obligation wholly independent of DOT’s mandate to promote energy 

efficiency.” The Court concluded that “[t]he two obligations may overlap, but there is no reason to think 

the two agencies cannot both administer their obligations and yet avoid inconsistency.”19 The Court 

remanded the case back to the Agency for reconsideration in light of its findings.20 

EPA has since found that emissions of GHGs from new motor vehicles and motor vehicle engines 

cause or contribute to air pollution that may reasonably be anticipated to endanger public health and 

welfare.21 The forthcoming joint NHTSA-EPA Final Rule represents the second phase of EPA’s 

response to the U.S. Supreme Court’s decision. 

 

1.2.1.3 California Air Resources Board Greenhouse Gas Program 

In 2004, the California Air Resources Board approved standards for new light duty vehicles, 

which regulate the emission of CO2 and other GHGs. Since then, 13 states and the District of Columbia, 

comprising approximately 40 percent of the light duty vehicle market, have adopted California’s 

standards. These standards apply to MYs 2009 through 2016 and require reductions in CO2 emissions for 

passenger cars and some light trucks of 323 grams per mile (g/mi) in 2009 up to 205 g/mi in 2016 and 

439 g/mi for light trucks in 2009 up to 332 g/mi in 2016. On June 30, 2009, EPA granted California’s 

request for a waiver of preemption under the CAA.22 The granting of the waiver permits California and 

the other states to proceed with implementing the California emission standards. 

17 549 U.S. 497 (2007). 

18 See Notice of Denial of Petition for Rulemaking, Control of Emissions From New Highway Vehicles and 

Engines, 68 FR 52922 (Sep. 8, 2003). 

19549 U.S. at 531-32. 

20 For further information on Massachusetts v. EPA see the July 30, 2008 Advance Notice of Proposed Rulemaking, 

“Regulating Greenhouse Gas Emissions under the Clean Air Act,” 73 FR 44354 at 44397. This includes a 

comprehensive discussion of the litigation’s history, the U.S. Supreme Court’s findings, and subsequent actions 

undertaken by the Bush Administration and EPA from 2007–2008 in response to the Supreme Court remand. 

21 Final Rule, Endangerment and Cause or Contribute Findings for Greenhouse Gases Under Section 202(a) of the 

Clean Air Act, 74 FR 66496 (Dec. 15, 2009). 22 California State Motor Vehicle Pollution Control Standards, Notice of Decision Granting a Waiver of Clean Air 

Act Preemption for California’s 2009 and Subsequent Model Year Greenhouse Gas Emission Standards for New 

Motor Vehicles, 74 FR 32744 (Jul. 8, 2009). 
Chapter 1 Purpose and Need for the Proposed Action 

 1-5 

1.2.2 Joint Proposal for a National Program 

On May 19, 2009, DOT and EPA issued a Notice of Upcoming Joint Rulemaking to propose a 

strong and coordinated fuel economy and greenhouse gas National Program for MYs 2012-2016 lightduty vehicles. On September 28, 2009, NHTSA and EPA published the proposed rules in the Federal 

Register.

23 NHTSA and EPA proposed a harmonized and coordinated National Program with the 

following key elements. 

1.2.2.1 Level of the Standards 

NHTSA and EPA proposed two separate sets of standards, each under its respective statutory 

authority. NHTSA proposed CAFE standards for passenger cars and light trucks under 49 U.S.C. § 

32902. These standards would require these vehicles to meet an estimated combined average fuel 

economy level of 34.1 miles per gallon (mpg) in MY 2016. EPA proposed national CO2 emissions 

standards for light-duty vehicles under section 202(a) of the CAA. These standards would require these 

vehicles to meet an estimated combined average emissions level of 250 g/mi of CO2 in MY 2016. The 

proposed standards for both agencies begin with the 2012 model year, with standards increasing in 

stringency through MY 2016. They represent a harmonized approach that will allow industry to build a 

single national fleet that will satisfy both the GHG requirements under the CAA and CAFE requirements 

under EPCA/EISA.

Given differences in their respective statutory authorities, however, the agencies’ proposed 

standards include some important differences. Under the CO2 fleet average standard proposed under 

CAA section 202(a), EPA expects manufacturers to take advantage of the option to generate CO2-

equivalent credits by reducing emissions of HFCs and CO2 through improvements in their air conditioner 

systems. EPA accounted for these reductions in developing its proposed CO2 standard. EPCA does not 

allow vehicle manufacturers to use air conditioning credits in complying with CAFE standards for 

passenger cars.24 CO2 emissions due to air conditioning operation are not measured by the test procedure 

mandated by statute for use in establishing and enforcing CAFE standards for passenger cars. As a result, 

improvements in the efficiency of passenger car air conditioners would not be considered as a possible 

control technology for purposes of CAFE. 

The differences regarding the treatment of air conditioning improvements (related to CO2 and 

HFC reductions) affect the relative stringency of the EPA standard and the NHTSA standard. The 250 

g/mi of CO2 equivalent emissions limit is equivalent to 35.5 mpg25 if the automotive industry were to 

meet this CO2 level entirely through fuel economy improvements. As a consequence of the prohibition 

against NHTSA’s allowing credits for air conditioning improvements for purposes of passenger car 

CAFE compliance, NHTSA proposed fuel economy standards that are estimated to require a combined 

(passenger car and light truck) average fuel economy level of 34.1 mpg by MY 2016. 

 

23 Proposed Rulemaking To Establish Light-Duty Vehicle Greenhouse Gas Emission Standards and Corporate 

Average Fuel Economy Standards, 74 FR 49454 (Sep. 28, 2009). 24 There is no such statutory limitation with respect to light trucks. 

25 The agencies are using a common conversion factor between fuel economy in units of miles per gallon and CO2

emissions in units of grams per mile. This conversion factor is 8,887 grams CO2 per gallon gasoline fuel. Diesel 

fuel has a conversion factor of 10,179 grams CO2 per gallon diesel fuel though, for the purposes of this calculation, 

we are assuming 100% gasoline fuel. 
Chapter 1 Purpose and Need for the Proposed Action 

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1.2.2.2 Form of the Standards 

In this rulemaking, NHTSA and EPA proposed to establish attribute-based standards for 

passenger cars and light trucks. NHTSA adopted an attribute standard based on vehicle footprint in its 

Reformed CAFE program for light trucks for MYs 2008-2011,26 and recently extended this approach to 

passenger cars in the CAFE rule for MY 2011 as required by EISA.27 Under an attribute-based standard, 

every vehicle model has a performance target (fuel economy for the CAFE standards, and CO2 g/mi for 

the GHG emissions standards), the level of which depends on the vehicle’s attribute (for this rulemaking, 

footprint). The manufacturers’ fleet average performance is determined by the production-weighted28

average (for CAFE, harmonic average) of those targets. 

NHTSA and EPA proposed vehicle footprint as the attribute for the CAFE and GHG standards. 

Footprint is defined as a vehicle’s wheelbase multiplied by its track width – in other words, the area 

enclosed by the points at which the wheels meet the ground. The agencies believe that the footprint 

attribute is the most appropriate attribute on which to base the standards under consideration, as discussed 

in the NPRM and in Chapter 2 of the Draft Joint Technical Support Document (TSD) (EPA and NHTSA 

2009). 

Under the proposed footprint-based standards, each manufacturer would have a CAFE and GHG 

target unique to its fleet, depending on the footprints of the vehicle models produced by that 

manufacturer. A manufacturer would have separate footprint-based standards for cars and for trucks. 

Generally, larger vehicles (i.e., vehicles with larger footprints) would be subject to less stringent standards 

(i.e., higher CO2 g/mi standards and lower CAFE standards) than smaller vehicles. This is because, 

generally speaking, smaller vehicles are more capable of achieving higher standards than larger vehicles. 

Although a manufacturer’s fleet average standard could be estimated throughout the model year based on 

projected production volume of its vehicle fleet, the standard to which the manufacturer must comply 

would be based on its final model year production figures. A manufacturer’s calculation of fleet average 

emissions at the end of the model year would thus be based on the production-weighted average 

emissions of each model in its fleet. 

In designing the footprint-based standards, the agencies built upon the footprint standard curves 

for passenger cars and light trucks used in the CAFE rule for MY 2011.29 NHTSA and EPA worked 

together to design car and truck footprint curves that followed from logistic curves used in that rule. The 

agencies started by addressing two main concerns regarding the car curve. The first concern was that the 

2011 car curve was relatively steep near the inflection point and that, therefore, small variations in 

footprint could produce relatively large changes in fuel economy targets. A curve that was directionally 

less steep would reduce the potential for gaming. The second issue was that the inflection point of the 

logistic curve was not centered on the distribution of vehicle footprints across the industries’ fleet, thus 

resulting in a flat (universal or unreformed) standard for over half the fleet. The proposed car curve has 

been shifted and made less steep compared to the car curve adopted by NHTSA for 2011, such that it 

better aligns the sloped region with higher production volume vehicle models. Finally, both the car and 

truck curves are defined in terms of a constrained linear function for fuel consumption and, equivalently, 

a piece-wise linear function for CO2. NHTSA and EPA included a full discussion of the development of 

these curves in the joint TSD. In addition, a full discussion of the equations and coefficients that define 

 

26 Final Rule, Average Fuel Economy Standards for Light Trucks Model Years 2008-2011, 71 FR 17566 (Apr. 6, 

2006). 

27 Final Rule, Record of Decision, Average Fuel Economy Standards Passenger Cars and Light Trucks Model Year 

2011, 74 FR 14196 (Mar. 30, 2009). 28 Production for sale in the United States. 

29 74 FR at 14407-14409 (Mar. 30, 2009). 
Chapter 1 Purpose and Need for the Proposed Action 

 1-7 

the curves proposed by each agency was included in section III of the NPRM for the CO2 curves and 

section IV of the NPRM for the mpg curves. 

1.2.2.3 Program Flexibilities for Achieving Compliance 

NHTSA and EPA proposed standards that are intended to provide compliance flexibility to 

manufacturers, especially in the early years of the program. This flexibility would be expected to provide 

sufficient lead time to make necessary technological improvements and additions, and to reduce the 

overall cost of the program without compromising overall environmental and fuel economy objectives. 

The broad goal of harmonizing the NHTSA and EPA standards would include providing manufacturer 

flexibilities in meeting the standards. The flexibility provisions that the agencies jointly and separately 

contemplated in developing the program include CAFE/CO2 Credits Earned Based on Fleet Average 

Performance, Air Conditioning Credits, Flex-Fuel and Alternative Fuel Vehicle Credits, Temporary LeadTime Allowance Alternative Standards (TLAAS), and Additional Potential Credit Opportunities. Some 

of these flexibilities will be available to manufacturers in aiding compliance under both sets of standards, 

but some flexibilities, such as the air conditioning credits and TLAAS, will only be available under the 

EPA standard due to differences between the CAFE and CAA legal authorities.30

1.2.2.4 Compliance 

NHTSA and EPA proposed a program that recognizes and replicates as closely as possible the 

compliance protocols associated with the existing CAFE standards and CAA Tier 2 vehicle emission 

standards. The certification, testing, reporting, and associated compliance activities could closely track 

current practice and thus be familiar to manufacturers. EPA already oversees testing, collects and 

processes test data, and performs calculations to determine compliance with both CAFE and CAA 

standards. NHTSA determines compliance with the CAFE program, manages credits, issues letters of 

noncompliance, and collects civil penalties from manufacturers. In a coordinated approach, compliance 

mechanisms for both programs would be consistent and non-duplicative. 

Under the National Environmental Policy Act (NEPA)31 a federal agency must analyze 

environmental impacts if the agency implements a proposed action, provides funding for an action, or 

issues a permit for that action. Specifically, NEPA directs that “to the fullest extent possible,” federal 

agencies proposing “major federal actions significantly affecting the quality of the human environment” 

must prepare “a detailed statement” on the environmental impacts of the proposed action (including 

alternatives to the proposed action).32 To inform its development of the new MYs 2012-2016 CAFE 

standards required under EPCA, as amended by EISA, NHTSA prepared this EIS to analyze and disclose 

the potential environmental impacts of a proposed preferred alternative and other proposed alternative 

standards pursuant to CEQ NEPA implementing regulations, DOT Order 5610.1C, and NHTSA 

regulations.33 This EIS compares the potential environmental impacts among alternatives, including a no 

action alternative. It also analyzes direct, indirect, and cumulative impacts, and discusses impacts in 

proportion to their significance. 

Section 1501.6 of the CEQ regulations emphasizes agency cooperation early in the NEPA process 

and authorizes a lead agency (in this case, NHTSA) to request the assistance of other agencies that either 

 

30 See discussion of compliance flexibilities in Section 3.1.4.1 of the joint NHTSA-EPA NPRM. 31 42 U.S.C. §§ 4321-4347. 

32 42 U.S.C. § 4332. 

33 NEPA is codified at 42 U.S.C. §§ 4321-4347. CEQ NEPA implementing regulations are codified at 40 CFR Parts 

1500-1508, and NHTSA’s NEPA implementing regulations are codified at 49 CFR Part 520. 
Chapter 1 Purpose and Need for the Proposed Action 

 1-8 

have jurisdiction by law or have special expertise regarding issues considered in an EIS.34 NHTSA 

invited EPA to be a cooperating agency, pursuant to CEQ regulations, because of its special expertise in 

the areas of climate change and air quality. On May 12, 2009, EPA accepted NHTSA’s invitation and 

agreed to become a cooperating agency. 

EPA leads the Nation’s environmental science, research, education, and assessment efforts. The 

mission of EPA is to protect human health and the environment. EPA is legally required to comply with 

the procedural requirements of NEPA for its research and development activities, facilities construction, 

wastewater treatment construction grants under Title II of the Clean Water Act (CWA), EPA-issued 

National Pollutant Discharge Elimination System permits for new sources, and for certain projects funded 

through EPA annual Appropriations Acts. However, EPA actions under the CAA, including the EPA 

proposed vehicle GHG emission standards under the Joint Rulemaking, are not subject to the 

requirements of NEPA. Pursuant to the National Fuel Efficiency Policy announced by the President on 

May 19, 2009, NHTSA and EPA published their Notice of Upcoming Joint Rulemaking to ensure a 

coordinated national program on fuel economy and GHG emissions for passenger cars, light-duty trucks, 

and medium-duty passenger vehicles. In order to improve the usefulness of this EIS for NHTSA 

decisionmakers and the public, EPA’s environmental analysis of its proposed rulemaking is summarized 

and referenced within the appropriate sections of this EIS.35 

1.3 PROPOSED ACTION 

For this EIS, NHTSA’s Proposed Action is setting passenger car and light truck CAFE standards 

for MY 2012-2016, in accordance with EPCA, as amended by EISA. NHTSA and EPA proposed 

coordinated and harmonized CAFE standards and vehicle GHG emissions for passenger cars, light-duty 

trucks, and medium-duty passenger vehicles built in MY 2012 through 2016. 

1.4 PURPOSE AND NEED 

NEPA requires that a proposed action’s alternatives be developed based on the action’s purpose 

and need. The purpose and need statement explains why the action is needed, describes the action’s 

intended purpose, and serves as the basis for developing the range of alternatives to be considered in the 

NEPA analysis.36 In accordance with EPCA, as amended by EISA, one purpose of the Joint Rulemaking 

is to establish MYs 2012-2016 CAFE standards at “the maximum feasible average fuel economy level 

that the Secretary of Transportation decides the manufacturers can achieve in that model year.”37 When 

determining the level achievable by the manufacturers, EPCA requires that the agency consider the four 

statutory factors of technological feasibility, economic practicability, the effect of other motor vehicle 

 

34 40 CFR § 1501.6. 

35 Pursuant to the National Fuel Efficiency Policy announced by the President on May 19, 2009, EPA and NHTSA 

published their Notice of Upcoming Joint Rulemaking to ensure a coordinated National program on GHG emissions 

and fuel economy for passenger cars, light-duty trucks, and medium-duty passenger vehicles. NHTSA takes no 

position on whether EPA’s proposed rule on GHG emissions could be considered a “connected action” under the 

CEQ’s regulation at 40 CFR § 1508.25. For the purposes of this EIS, however, NHTSA has decided to treat EPA’s 

proposed rule as if it were a “connected action” under that regulation to improve the usefulness of the EIS for 

NHTSA decisionmakers and the public. NHTSA is aware that Section 7(c) of the Energy Supply and 

Environmental Coordination Act of 1974 (15 U.S.C. § 793(c)(1)) expressly exempts EPA action taken under the 

CAA from NEPA’s requirements. NHTSA’s discussion in this EIS of EPA’s proposed GHG regulation should not 

be construed to affect in any way the express NEPA exemption for action taken under the CAA and places no 

obligation on EPA to comply with NEPA in promulgating its rule or taking any other action covered by the 

exemption. 

36 40 CFR § 1502.13. 

37 49 U.S.C. § 32902(a). 
Chapter 1 Purpose and Need for the Proposed Action 

 1-9 

standards of the Government on fuel economy, and the need of the United States to conserve energy.38 In 

addition, the agency has the authority to—and traditionally does—consider other relevant factors, such as 

the effect of the CAFE standards on motor vehicle safety.39

NHTSA has defined these considerations as follows:40

• “Technological feasibility” refers to whether a particular method of improving fuel economy 

can be available for commercial application in the model year for which a standard is being 

established. 

• “Economic practicability” refers to whether a standard is one within the financial capability 

of the industry, but not so stringent as to lead to adverse economic consequences, such as 

significant job losses or unreasonable elimination of consumer choice. 

• “The effect of other motor vehicle standards of the Government on fuel economy,” involves 

an analysis of the effects of compliance with emission,41 safety, noise, or damageability 

standards on fuel economy capability and thus on average fuel economy. 

• “The need of the United States to conserve energy” means the consumer cost, national 

balance of payments, environmental, and foreign policy implications of the Nation’s need for 

large quantities of petroleum, especially imported petroleum. 

NHTSA must establish separate standards for MYs 2011-2020 passenger cars and light trucks, 

subject to two principal requirements.42 First, the standards are subject to a minimum requirement 

regarding stringency: they must be set at levels high enough to ensure that the combined U.S. passenger 

car and light truck fleet achieves an average fuel economy level of not less than 35 mpg not later than MY 

2020.43 Second, as discussed above and at length in the March 2009 final rule establishing the MY 2011 

CAFE standards, EPCA requires that the agency establish standards for all new passenger cars and light 

trucks at the maximum feasible average fuel economy level that the Secretary decides the manufacturers 

can achieve in that model year.44 

Additionally, EPCA, as amended by EISA, requires that the CAFE standards for passenger cars 

and light trucks increase ratably in each model year between MY 2011 and MY 2020. Standards must be 

“based on one or more vehicle attributes related to fuel economy,” and “expressed in the form of a 

 

38 49 U.S.C. §§ 32902(a), 32902(f). 

39 See, e.g., Competitive Enterprise Inst. v. NHTSA, 956 F.2d 321, 322 (D.C. Cir. 1992) (citing Competitive 

Enterprise Inst. v. NHTSA, 901 F.2d 107, 120 n.11 (D.C. Cir. 1990)); 73 FR 24352, 24364 (May 2, 2008). 40 Final Rule, Record of Decision, Average Fuel Economy Standards Passenger Cars and Light Trucks Model Year 

2011, 74 FR 14196 (Mar. 30, 2009). 41 In the case of emission standards, this includes standards adopted by the federal government and can include 

standards adopted by the states as well since in certain circumstances the CAA allows states to adopt and enforce 

state standards different from the federal standards. 

42 EISA added the following additional requirements: 

• Standards must be attribute-based and expressed in the form of a mathematical function. 49 U.S.C. § 

32902(b)(3)(A). 

• Standards for MYs 2011-2020 must “increase ratably” in each model year. 49 U.S.C. § 32902(b)(2)(C). 

NHTSA interprets this requirement, in combination with the requirement to set the standards for each model 

year at the level determined to be the maximum feasible level for that model year, to mean that the annual 

increases should not be disproportionately large or small in relation to each other. 43 49 U.S.C. § 32902(b)(2)(A). 

44 49 U.S.C. § 32902(a). 
Chapter 1 Purpose and Need for the Proposed Action 

 1-10 

mathematical function.”45 In any single rulemaking, standards may be established for not more than five 

model years.46 

NHTSA is also guided by President Obama’s memorandum to DOT on January 26, 2009, as 

described in Section 1.1. 

1.5 PUBLIC REVIEW AND COMMENT 

On April 1, 2009, NHTSA published an NOI to prepare an EIS for the MYs 2012-2016 CAFE 

standards. The NOI described the statutory requirements for the standards, provided initial information 

about the NEPA process, and initiated scoping47 by requesting public input on the scope of the 

environmental analysis to be conducted.48 Two important purposes of scoping are identifying the 

substantial environmental issues that merit in-depth analysis in the EIS and identifying and eliminating 

from detailed analysis the environmental issues that are not substantial and therefore require only brief 

discussion in the EIS.49 Scoping should “deemphasize insignificant issues, narrowing the scope of the 

environmental impact statement process accordingly.”50 Consistent with NEPA and its implementing 

regulations, on April 2, 2009, NHTSA mailed the NOI to: 

• 109 contacts at federal agencies having jurisdiction by law or special expertise with respect to 

the environmental impacts involved, or authorized to develop and enforce environmental 

standards, including other modes within DOT; 

• The Governors of every state and U.S. territory; 

• 65 organizations representing state and local governments; 

• 599 Native American tribal organizations and academic centers that issued reports on climate 

change and tribal communities; and 

• 265 contacts at other stakeholder organizations that NHTSA reasonably expected to be 

interested in the NEPA analysis for the MYs 2012-2016 CAFE standards, including 

automobile industry organizations, environmental organizations, and other organizations that 

expressed interest in prior CAFE rules. 

NHTSA used its letters transmitting the NOI to develop a contact list for future notices about the 

NEPA process for the MYs 2012-2016 CAFE standards. For instance, NHTSA asked each Governor to 

“share [the] letter and the enclosed [NOI] with the appropriate environmental agencies and other offices 

within your administration and with interested local jurisdictions and government organizations within 

your State.” NHTSA further requested that each Governor ask his or her representative to provide contact 

information for the state’s lead office for the CAFE EIS by returning a contact list form to NHTSA or by 

sending NHTSA an e-mail containing the information requested on the form. NHTSA asked federal 

agency contacts to share the NOI with other interested parties within their organizations and to complete 

 

45 49 U.S.C. § 32902(b)(3)(A). 

46 49 U.S.C. § 32902(b)(3)(B). 

47 Scoping, as defined under NEPA, is an early and open process for determining the scope of issues to be addressed 

in an EIS and for identifying the significant issues related to a proposed action. See 40 CFR § 1501.7.

48 See Notice of Intent to Prepare an Environmental Impact Statement for New Corporate Average Fuel Economy 

Standards, 74 FR 14857 (Apr. 1, 2009).

49 See 40 CFR §§ 1500.4(g), 1501.7(a).

50 40 CFR § 1500.4(g).
Chapter 1 Purpose and Need for the Proposed Action 

 1-11 

the contact list form. NHTSA asked contacts at other stakeholder organizations whether they wished to 

remain on the agency’s NEPA contact list for the CAFE EIS by returning a contact list form or sending 

NHTSA an e-mail containing the information requested on the form. NHTSA indicated that 

organizations that did not return the form would be removed from the NEPA contact list. 

NHTSA submitted to EPA the DEIS that disclosed and analyzed the potential environmental 

impacts of new CAFE standards and reasonable alternative standards in the context of NHTSA’s CAFE 

program pursuant to the CEQ NEPA implementing regulations, DOT Order 5610.1C, and NHTSA 

regulations.51 On September 25, 2009, NHTSA published a Federal Register Notice of Availability 

announcing the availability of the DEIS.52 NHTSA’s Notice of Availability also announced the date and 

location of a public hearing. Specifically, NHTSA’s Notice of Availability invited the public to 

participate at the NHTSA hearing on October 30, 2009 in Washington, DC. Also on September 25, 2009, 

EPA issued its Notice of Availability for the DEIS, triggering the 45-day public comment period.53 In 

accordance with CEQ implementing regulations, the public was invited to submit written comments on 

the DEIS until November 9, 2009. 

NHTSA mailed approximately 300 copies of the DEIS to interested parties, including federal, 

state, and local agencies; elected officials; environmental and public interest groups; Native American 

tribes; and other interested individuals, as listed in Chapter 8 of the DEIS. 

1.5.1 Agency Consultation 

On May 5, 2009, NHTSA invited EPA to become a cooperating agency with NHTSA in the 

development of the EIS for the CAFE rulemaking for MYs 2012-2016 passenger cars and light trucks in 

accordance with 40 CFR § 1501.6 of the NEPA implementing regulations issued by CEQ. Under 40 CFR 

§ 1501.6, a federal agency that has special expertise with respect to any environmental issue that should 

be addressed in the statement may be a cooperating agency upon request of the lead agency. In its 

invitation letter, NHTSA suggested that EPA’s role in the development of the EIS could include the 

following, as they relate to EPA’s areas of special expertise: 

• Providing input on determining the significant issues to be analyzed in the EIS from a climate 

change and air quality perspective. 

• Assisting NHTSA to “identify and eliminate from detailed study the issues which are not 

significant or which have been covered by prior environmental review (§ 1506.3), narrowing 

the discussion of these issues in the statement to a brief presentation of why they will not 

have a significant effect on the human environment or providing a reference to their coverage 

elsewhere.” 40 CFR § 1501.7(a)(3). 

• Participating in coordination meetings, as appropriate. 

• Reviewing and commenting on the DEIS and FEIS prior to publication. 

 

51 Under Section 309 of the CAA, EPA is required to review and publicly comment on the environmental impacts of 

major federal actions including actions that are the subject of EISs. If EPA determines that the action is 

environmentally unsatisfactory, it is required by Section 309 to refer the matter to CEQ. This is done by the Office 

of Federal Activities. 

52 Notice of Availability of a Draft Environmental Impact Statement (DEIS) for New Corporate Average Fuel 

Economy Standards; Notice of Public Hearing, 74 FR 48894 (Sep. 25, 2009). 53 Environmental Impact Statements; Notice of Availability, 74 FR 48951 (Sep. 25, 2009). 
Chapter 1 Purpose and Need for the Proposed Action 

On May 12, 2009, EPA accepted NHTSA’s invitation and agreed to become a cooperating 

agency. EPA staff participated in technical discussions and reviewed and commented on draft sections 

and the draft final version of the DEIS. 

To comply with NEPA’s requirements for agency consultation, on July 10, 2009, NHTSA mailed 

consultation letters to the following federal agencies: Bureau of Land Management, Centers for Disease 

Control and Prevention, Minerals Management Service, National Park Service, Advisory Council on 

Historic Preservation, U.S. Forest Service, and U.S. Army Corps of Engineers. On July 30, 2009, 

NHTSA received a response from the Centers for Disease Control and Prevention indicating that they are 

interested in consulting on this EIS. 

NHTSA received a comment on the DEIS asserting that NHTSA must consult under Section 

7(a)(2) of the ESA with the Services regarding consideration of potential effects of the CAFE standards 

on federally-listed endangered and threatened species. NHTSA has carefully considered the requirements 

of the ESA and determined that Section 7(a)(2) consultation with the Services is not required for this 

action. See Appendix G for an explanation of this determination. 

1.5.2 Summary of Scoping Comments 

NHTSA received seven responses to its scoping notice. Federal and state agencies, one 

automobile trade association, one environmental advocacy group, and three individuals provided 

comments. This section summarizes these scoping comments. 

1.5.2.1 Federal Agencies 

EPA was the only federal agency that provided scoping comments (Docket No. NHTSA-2009-

0059-0005). EPA suggested that NHTSA incorporate material from the October 10, 2008 FEIS in a 

judicious manner, recommending that NHTSA examine areas where the earlier analysis is no longer 

applicable, including key baseline assumptions, the social cost of carbon, and the predicted cost of fuel. 

Refer to Section 2 of this EIS for a discussion of NHTSA’s current approach and assumptions. NHTSA 

notes that while some material from the October 10, 2008 Final EIS may still be relevant and applicable 

to the current EIS, the present document is a new analysis with a new consideration of all issues and 

impacts. EPA further suggested that NHTSA be cautious when trying to incorporate future promulgated 

actions into the cumulative impacts assessment, as this could prove to be highly speculative and not 

appropriate in the current rapid flux of potential related legislative and regulatory action. Refer to Section 

4.4.3 (Cumulative Climate Methodology) of this EIS for a discussion of the methodology used to analyze 

cumulative impacts to climate. NHTSA notes that EPA’s scoping comment was submitted before EPA 

received NHTSA’s letter inviting EPA to become a cooperating agency on this EIS. 

1.5.2.2 States 

NHTSA received a letter from the Attorneys General of the States of California, Connecticut, 

Massachusetts, New Mexico, and Oregon, the Secretary of the New Mexico Environment Department, 

the Secretary of the Commonwealth of Pennsylvania Department of Environmental Protection, and the 

Corporation Counsel of the City of New York (Docket No. NHTSA-2009-0059-0006). 

The Attorneys General emphasized that rather than focusing on the effects of the rulemaking on 

global climate change, NHTSA should explain how this rule is consistent with, and essential to, the 

Nation’s efforts to address global warming. In this regard, they suggested that the 2008 EIS minimizes 

the effects of the CAFE program on global climate change and does not analyze cumulative impacts 

appropriately. Quoting the Ninth Circuit Court of Appeals, which stated in a 2007 ruling that “[a]ny 

 1-12 
Chapter 1 Purpose and Need for the Proposed Action 

 1-13 

given rule setting a CAFE standard might have an ‘individually minor’ effect on the environment but 

these rules are ‘collectively significant actions taking place over a period of time,’” they suggested that 

the 2008 EIS failed to meet this standard, and instead, minimized the effect of the rulemaking by stating 

that one set of CAFE rules by itself would have a negligible effect on global warming and public health 

and welfare. Refer to Sections 4.1.2 (Temporal and Geographic Boundaries) and 4.4.4 (Climate 

Cumulative Impacts) of this EIS, which discuss the temporal and geographic boundaries used for the 

analysis and the cumulative impacts to climate analysis, respectively. NHTSA notes that the agency is 

taking a fresh approach to placing its analysis in the context of global climate change in this EIS.

The letter cites the EPA “Proposed Endangerment and Cause or Contribute Findings for 

Greenhouse Gases Under Section 202(a) of the Clean Air Act,”54 which states that while no single GHG 

source category dominates on the global scale, many could be very significant contributors. In particular 

the letter cites EPA’s statement that motor vehicle source categories contribute 24 percent of total U.S. 

GHG emissions, and that total U.S. GHG emissions make up about 18 percent of the world’s GHG 

emissions. The Attorneys General concluded that NHTSA should put the CAFE rules in context by 

demonstrating their importance for reducing GHG emissions and reducing global warming. The 

Attorneys General listed some ways to provide the proper context, including: comparing CO2 emission 

reductions with the overall emission reduction goals that the President has endorsed (80 percent reduction 

by 2050); evaluating whether the automobile manufacturing industry is addressing global warming; and 

evaluating whether the rules will help prevent reaching a “tipping point” beyond which cataclysmic 

damages occur due to nonlinear changes in the climate. Refer to Sections 3.4 and 4.4 of this EIS, which 

discuss climate change due to direct or indirect and cumulative impacts. The Attorneys General also 

suggested evaluating whether new CAFE rules could constitute a “stabilization wedge.” Refer to Section 

2.5 of this EIS for a discussion of alternatives not included in the analysis and the reasons for their 

exclusion. 

The Attorneys General letter also incorporated by reference previous comments submitted to the 

2008 EIS docket, including their 2008 scoping comments (Docket No. NHTSA-2008-0060-0007); 2008 

DEIS comments (Docket No. NHTSA-2008-0060-0585); and 2008 Notice of Proposed Rulemaking 

comments (Docket Nos. NHTSA-2008-0060-0585, as an attachment to the 2008 DEIS comments, and 

NHTSA-2008-0089-0524). Comments received on the MY 2011 rulemaking and MYs 2011-2015 CAFE 

EIS were addressed in previous documents. NHTSA re-examined all of these comments and considered 

them in the development of this EIS. NHTSA is taking a fresh approach to this EIS. Thus, refer to the 

relevant sections of this EIS and the NPRM for MYs 2012-2016 CAFE standards for new discussions of 

these issues. 

1.5.2.3 Automobile Trade Associations 

NHTSA received a letter from the Alliance of Automobile Manufacturers (AAM) that provided 

scoping comments (Docket No. NHTSA-2009-0059-0007). AAM commented that the rate of fuel 

efficiency increase proposed by NHTSA – a 3- to 7-percent annual increase depending on the alternative 

– is substantially greater than historical fuel efficiency increases of approximately 1 percent annually and 

is too stringent for manufacturers undergoing difficult economic times. AAM noted that achieving the 

EISA-mandated minimum fuel efficiency increases, which equate to an increase in fuel efficiency of 3 

percent per year, represents a substantial challenge for manufacturers. Furthermore, AAM stated that the 

most aggressive standards suggested by NHTSA would require an average annual passenger car and light 

truck fuel economy of over 50 mpg in approximately 10 years, which no individual vehicle produced on a 

large scale can now achieve. These aggressive alternatives, AAM asserted, ignore the “economic 

 

54 74 FR 18886, 18907 (Apr. 24, 2009). 
Chapter 1 Purpose and Need for the Proposed Action 

 1-14 

practicability” provisions of EPCA and its case law. AAM suggested that NHTSA should keep in mind 

historical rates of fuel efficiency change when developing the alternatives in order to achieve a realistic 

increase in fuel efficiency. Refer to Section 2 (Alternatives) of this EIS for a discussion of the different 

alternatives selected for the analysis. 

AAM further suggested that more reasonable alternatives can be constructed by focusing on 

realistic variations of the 2020 MY endpoint under EISA, rather than incremental increases in average 

annual fuel economy improvement. Specifically, AAM suggests that Alternative 2 (as described in 

NHTSA’s April 1, 2009 NOI), could be redefined as improving fuel economy at a rate necessary to 

achieve 35-mpg fleet average fuel economy in MY 2020; Alternative 3 could be defined as improving 

fuel economy at a rate necessary to achieve a 36.75-mpg fleet average fuel economy in MY 2020; and 

Alternative 4 could be defined as improving fuel economy at the rate necessary to achieve a 38.5-mpg 

fuel economy in MY 2020. AAM noted that establishing a NEPA alternative based on a level of 

stringency tied to a “least capable manufacturer” analysis would provide important information to 

policymakers, especially regarding the effects of proposed standards on those companies which, they 

contended, are least likely to succeed under the new standards. AAM also suggested using increases 

based on only the reductions necessary to reach the MY 2020 endpoint under EISA. Refer to Section 2.5 

(Alternatives Considered but Not Analyzed in Detail) of this EIS for a discussion of alternatives not 

included in the analysis and the reasons for their exclusion. 

AAM highlighted that NHTSA’s NEPA regulations require the agency to apply a “systematic, 

interdisciplinary approach,”55 and that, pursuant to this approach, NHTSA should consider a number of 

factors resulting from CAFE increases, including the effects of the CAFE increases on local air quality – 

specifically due to fleet turnover and rebound effects; the socioeconomic consequences of CAFE 

increases, such as impacts on the quality of life for workers at companies, which would be adversely 

affected by the regulations; and the effect of CAFE standards on ground-level ozone concentrations. 

AAM also suggested that regulation of motor vehicle GHG emissions will increase the price of vehicles, 

thereby reducing fleet turnover and leading to increases in criteria pollutant emissions. It recommended 

that the EIS fully explore the relationships between fleet turnover, vehicle prices, and the continued air 

quality improvements that are expected to result from an increase in CAFE standards. Refer to Section 

3.3.3 (Air Quality Impacts) for a discussion of the air quality impacts of climate change. Refer to the 

NPRM for MYs 2012-2016 CAFE standards for new discussions of the updated Volpe model. 

AAM also suggested that the EIS should only use studies that have undergone “rigorous scientific 

peer review” and suggested that NHTSA should coordinate with EPA in choosing criteria to determine 

which scientific studies to rely upon. NHTSA recognizes the importance of peer review in the validation 

of scientific studies and analytic methods.56 Refer to Section 4.1 for an explanation of the unique expert 

and panel review process of climate change research in the scientific community. We also note above 

that NHTSA is coordinating with EPA via EPA’s role as a cooperating agency. 

AAM incorporated by reference its comments submitted during the 2008 scoping period. In the 

2008 comment letter, AAM raised questions regarding the requirement for and appropriate scope of an 

EIS for the CAFE rulemaking, the appropriate definition of the alternatives, and the scope of the 

cumulative effects analysis. Refer to Chapter 1, Section 1.3.3 in the 2008 FEIS, which summarizes the 

scoping comments and NHTSA’s responses, for an explanation of how NHTSA addressed these concerns 

 

55 49 CFR § 520.23(a). 

56 See 74 FR 14857, 14861 (explaining that scoping comments will be most useful when supported by reference to 

peer-reviewed scientific studies and reports). 
Chapter 1 Purpose and Need for the Proposed Action 

in the 2008 FEIS. NHTSA is taking a fresh approach to this EIS. In this EIS, these issues are addressed 

in Chapters 1, 2, and 4. 

AAM also incorporated by reference its comments on the 2008 DEIS. These comments 

addressed the requirement for and appropriate scope of an EIS for the CAFE rulemaking. AAM raised 

questions about the Volpe model and pointed out that the fleet turnover effect may result in an increase in 

air pollutant emissions. Please refer to Chapter 10, Responses to Public Comments, of the 2008 FEIS for 

complete responses as to how NHTSA addressed AAM’s concerns in the 2008 FEIS. Refer to Chapters 1 

and 2 in this EIS for a new discussion of these issues. 

1.5.2.4 Environmental Advocacy Groups 

The Center for Biological Diversity (CBD) was the only environmental advocacy group to 

provide scoping comments on the NOI to prepare an EIS (Docket No. NHTSA-2009-0059-0009). 

CBD stated that there is a need for fundamental changes to the process by which the CAFE 

standards are developed in issuing a final rule that complies with EISA and EPCA. One such change 

CBD recommended was to eliminate the use of the Volpe model. CBD suggested that NHTSA: revise 

the definition of light trucks to appropriately address their use as passenger cars; revise the Volpe model 

to accurately incorporate the benefits of lower vehicle weight for vehicle safety and fuel efficiency; revise 

the economic assumptions of the Volpe model to accurately reflect the feasibility of setting more 

aggressive standards; and develop an independent process to derive technology and capacity estimates. 

Refer to Sections 2.2.1 (Volpe Model), Section 2.2.3 (Technology Assumptions), and Section 2.2.4 

(Economic Assumptions) of this EIS for a discussion of the Volpe Model and the technology and 

economic assumptions used in the model. Refer to the NPRM for MYs 2012-2016 CAFE standards for 

detailed discussions of the updated Volpe model and the new assumptions. 

CBD maintained that limiting technology implementation to manufacturer “redesign” and 

“refresh” cycles as done in previous EISs goes against the technology-forcing principle mandated by 

EPCA. By not including a technology-forcing alternative, CBD contended that NHTSA artificially 

constrains the range of alternatives analyzed in this EIS. In CBD’s opinion, these development cycles 

should have no bearing on the considerations of technology implementation within the cost-benefit 

analysis. On a similar note, CBD suggested that NHTSA’s “technology exhaustion” alternative, defined 

by the criteria “whether a particular method of improving fuel economy can be available for commercial 

application in the MY for which the standard is being established,” cannot substitute for consideration of 

a technology-forcing alternative, because it does not include standards that may appear impossible today, 

but which would force innovation as industry strives to meet a more challenging standard. NHTSA notes 

that this EIS does not consider a technology exhaustion alternative. Refer to Section 2.5 (Alternatives 

Considered but Not Analyzed in Detail) of this EIS for a discussion of other alternatives not included in 

the analysis and the reasons for their exclusion. Again, refer to Sections 2.2.1 (Volpe Model) and Section 

2.2.3 (Technology Assumptions) of this EIS and to the NPRM for MYs 2012-2016 CAFE standards for 

discussions of the updated Volpe model. 

CBD suggested that the EIS must include a reasonable analysis of the combined impact of 

NHTSA’s rulemaking on U.S. transportation-sector emissions overall, as well as U.S. emissions overall. 

CBD recommended that NHTSA use the EIS to determine whether the impact of the proposed 

rulemaking is sufficient to ensure that the necessary emissions reductions from the U.S. transportation 

sector overall will be achievable. Citing recent published reports that contend that it will be necessary to 

limit CO2 concentrations to 350 parts per million (ppm) to avoid climate catastrophe, CBD requested that 

a maximum 350-ppm scenario be included as an upper limit for defining the range of alternatives. CBD 

suggested using the function in the Model for Assessment of Greenhouse Gas-induced Climate Change

 1-15 
Chapter 1 Purpose and Need for the Proposed Action 

(MAGGIC) that controls future emissions so that atmospheric CO2 concentrations do not exceed values 

ranging from 350 to 750 ppm. Refer to Section 3.4.2 (Affected Environment – Climate) of this EIS for a 

discussion of U.S. and global GHG emissions trends. Refer to Section 3.4.4.1 (Environmental 

Consequences – Greenhouse Gas Emissions) for a discussion of the effect of the proposed CAFE 

standards and the alternatives on GHG emissions. Refer to Section 4.4.3.3 (Global Emissions Scenarios) 

for a discussion of reasonably foreseeable global emissions scenarios in the cumulative effects analysis. 

Finally, CBD contended that NHTSA must initiate consultation with U.S. Fish and Wildlife 

Service and National Marine Fisheries Service on the impact of GHGs and other air pollutants on listed 

species. Specifically, CBD stated that NHTSA must further examine the impact of its action on species 

listed as threatened or endangered under Section 7 of the Endangered Species Act (ESA) and the National 

Environmental Policy Act. NHTSA is taking a fresh look at Section 7 consultations under the ESA for 

the MYs 2012-2016 CAFE rulemaking. As explained in Section 1.5.1, NHTSA has determined, in 

coordination with EPA, that consultation under the ESA is not required.

1.5.2.5 Individuals 

Three individuals provided scoping comments on the proposed rulemaking: Jean Public 

(NHTSA-2009-0059-0002), Michael Gordon (NHTSA-2009-0059-0003), and James Adcock (NHTSA2009-0059-0004). 

Jean Public suggested that NHTSA raise fuel economy standards to 100 mpg. Refer to Section 

2.5 of this EIS for a discussion of other alternatives not included in the analysis and the reasons for their 

exclusion. 

Michael Gordon stated his strong opposition to increasing CAFE standards, suggesting that 

CAFE standards should be controlled by consumer demand alone. Refer to Section 1.3 (Purpose and 

Need) of this EIS for a discussion of why CAFE standards must be increased. 

James Adcock suggested that, due to the rapidly changing world and unknown future events, 

NHTSA should consider issuing standards covering shorter time periods to allow the agency flexibility to 

re-address fuel economy standards. Refer to Section 1.3 of this EIS for a discussion of why the specific 

time scale was chosen. Mr. Adcock also suggested that NHTSA increase its fuel economy projections 

based on the leverage that the current administration has to impress change upon automobile 

manufacturers. Refer to the NPRM for a discussion of the current vehicle market. 

Mr. Adcock stated that the Volpe Model source code and output results should be published so 

that the public can determine if any errors exist. NHTSA has published the Volpe Model source code and 

output results. Refer to NHTSA’s website (www.nhtsa.gov) or the docket (NHTSA-2009-0059) for a 

publication of the Volpe Model source code and output results. 

Mr. Adcock contended that, contrary to the “footprint” model used by NHTSA, safety can be 

assured largely independent of fuel economy. He further highlighted techniques like sobriety checkpoints 

and enhanced traffic enforcement that can achieve safety improvements and help eliminate the perceived 

“size-based safety need” for large vehicles. Refer to Section 3.5.4 (Safety and Other Impacts to Human 

Health) of this EIS and Section IV.G.6 of the NPRM for MYs 2012-2016 CAFE standards for a 

discussion of the safety impacts of the proposed action and alternatives. 

Mr. Adcock commented on several assumptions used in the 2008 EIS. He recommended that 

NHTSA indicate which discount rate is used and why. Regarding gas price estimates, Mr. Adcock 

suggested that NHTSA use futures markets for oil and gas and up-to-date prices rather than relying on 

 1-16 
Chapter 1 Purpose and Need for the Proposed Action 

 1-17 

EIA estimates of future gas prices. Mr. Adcock also stated that a backstop may be necessary to combat 

large fluctuations in fuel economy year to year due to changes in fuel costs and individuals involved in 

the automobile market. Furthermore, he recommended that NHTSA consider the global costs of CO2

externalities instead of just the domestic costs. Similarly, he claimed that NHTSA should assume that 

CO2 reductions in the United States will be matched by carbon dioxide reductions in other nations. Refer 

to Sections 2.2.1 (Volpe Model), Section 2.2.3 (Technology Assumptions), and Section 2.2.4 (Economic 

Assumptions) of this EIS for a discussion of the Volpe Model, and the technology and economic 

assumptions used in the model. 

Mr. Adcock recommended that NHTSA allow an alternative certification path for vehicles in the 

United States, accept European Community vehicle certification standards, and permit the importation of 

higher fuel-efficiency European cars. The Vehicle Safety Act mandates that NHTSA set motor vehicle 

safety standards that are practicable, meet the need for motor vehicle safety, and are stated in objective 

terms.57 NHTSA has done so. While NHTSA appreciates the commenter’s suggestion, it is unable, 

pursuant to its statutory authority, to accept imported vehicles that do not comply with applicable federal 

motor vehicle safety standards.58 NHTSA believes that the federal motor vehicle safety standards 

incorporate the appropriate balance of the codified statutory considerations and that adoption of the 

European Community standards would be in contravention of congressional mandate. 

Mr. Adcock also suggested that NHTSA change its current approach and consider use of a depowered “environmental” mode to increase fuel efficiency. He stated that NHTSA should also 

acknowledge that U.S. demand has shifted to smaller, more efficient vehicles. Refer to the NPRM for a 

discussion of the market demand for fuel efficient vehicles. 

1.5.3 Summary of Comments on the DEIS 

NHTSA received 11 written comment submissions on the DEIS from interested stakeholders 

consisting of federal agencies, state agencies, environmental advocacy groups, and private citizens. In 

addition, three interested parties spoke at the public hearing. The transcript from the public hearing and 

written comments submitted during the public comment period are part of the administrative record and 

are available on the Federal Docket website at http://www.regulations.gov, Reference Docket No. 

NHTSA-2009-0059.59 In Chapter 10 of this FEIS, NHTSA provides excerpts of substantive comments 

on the DEIS, followed by NHTSA’s responses to those comments. The comments received on the DEIS 

are summarized by commenter type in the paragraphs below. 

 

1.5.3.1 Federal Agencies 

Three federal agencies provided comments on the DEIS: the Centers for Disease Control and 

Prevention (CDC) (Docket No. NHTSA-2009-0059-0042); the U.S. Department of Agriculture (USDA) 

Agricultural Research Service (Docket No. NHTSA-2009-0059-0043); and EPA (Docket No. NHTSA2009-0059-0052.1). 

CDC commented that the health-related consequences of concurrent factors resulting from the 

proposed action, such as increasing demand for and decreased availability of fossil fuels, should be 

included in the scope of analysis pursuant to NEPA. It stated that the associated health impacts include 

benefits to mental health and stress reduction. CDC suggested collaboration with public health 

professionals. It also noted that the potential fleet design and composition by which vehicle 

57 49 U.S.C. § 30111. The Secretary has delegated authority for these standards to NHTSA. See 49 CFR 1.50. 58 See 49 U.S.C. § 30112 (prohibiting the importation of vehicles that do not comply with applicable standards). 

59 See Docket No. NHTSA-2009-0059-0054. 
Chapter 1 Purpose and Need for the Proposed Action 

 1-18 

manufacturers will comply with new CAFE standards deserves further analysis, and that modeling these 

projections is critical to adequately analyzing the impact of new CAFE standards on the human 

environment. 

USDA Agricultural Research Service noted that it purchases the type of vehicles covered by the 

proposed action and stated, therefore, that the increase in fuel economy of vehicles on the market will 

help the agency achieve its fuel consumption and GHG emission reduction requirements under the Energy 

Policy Act of 2005, EISA, and several executive orders. 

EPA stated that it was supportive of the effort to raise fuel economy standards as part of the joint 

EPA/NHTSA National Program and noted that NHTSA’s proposed action would result in environmental 

benefits.60

1.5.3.2 State Agencies 

Three state agencies provided comments on the DEIS: the Tennessee Department of 

Transportation (Docket No. NHTSA-2009-0059-0046), the Missouri Department of Natural Resources 

(Docket No. NHTSA-2009-0059-0051), and the New York Department of Transportation (Docket No. 

NHTSA-2009-0059-0098). 

The Tennessee Department of Transportation commented on the appropriateness of the joint 

rulemaking and the National Program. It commended the joint effort as an effective way to develop 

regulations in a coordinated fashion. The agency applauded NHTSA for developing rules that meet 

Congress’ 2007 mandate for tighter CAFE standards and applying those standards by 2016, well in 

advance of the 2020 deadline mandated by Congress. It also stated that this initiative is the single largest 

step the United States can take to reduce energy consumption and GHG emissions and that the DEIS does 

not properly portray the significance of these reductions. The agency also cautioned that the final 

standards must guard against potential loopholes or other efforts to weaken the effectiveness of the 

program. 

The Missouri Department of Natural Resources expressed support for implementing a CAFE 

standard more stringent than the No Action Alternative, but questioned some of the findings in the air 

quality analysis. Most of the issues raised by the agency were related to the use of a 10 percent rebound 

effect, which it questioned as not being appropriate. It noted that, by assuming an increase in vehicle 

miles traveled due to improved fuel economy (i.e., the rebound effect), the DEIS is very conservative in 

estimating reductions of toxic pollutant air emissions. The agency also expressed concern regarding 

potential localized increases in emissions in nonattainment or maintenance areas due to the rebound effect 

and the uncertainty of estimating ozone levels. 

The New York Department of Transportation suggested that CAFE standards be set at as 

stringent a level as possible using technology-forcing standards and that implementing more aggressive 

standards more quickly would be appropriate. The Department also suggested that the economic benefits 

of improved fuel economy at the consumer level were not considered and that the way in which the 

discount rate is applied should be more clearly defined. In the Department’s opinion, the discount rate 

should be applied to both costs and benefits. The Department also stated that consideration should be 

given to the way in which the transportation sector might contribute to achieving an 80 percent reduction 

 

60 Under Section 309 of the CAA, EPA is required to review and publicly comment on the environmental impacts of 

major federal actions including actions that are the subject of EISs. If EPA determines that the action is 

environmentally unsatisfactory, it is required by Section 309 to refer the matter to CEQ. The Office of Federal 

Activities makes the referral. 
Chapter 1 Purpose and Need for the Proposed Action 

in GHG emissions by 2050. Finally, the Department also suggested that mitigation strategies for 

offsetting future emissions increases be discussed. 

1.5.3.3 Advocacy Groups 

Four advocacy groups provided comments on the DEIS. Environmental Consultants of Michigan 

submitted a comment (Docket No. NHTSA-2009-0059-0050.1), and, additionally, CBD, Sierra Club, and 

Public Citizen submitted joint written comments (Docket No. NHTSA-2009-0059-0053.1). Mark Cooper 

of the Consumer Federation of America, Ann Mensikoff of Sierra Club, and Lena Pons of Public Citizen 

provided testimony at the public hearing. 

In their combined comments, CBD, Sierra Club, and Public Citizen stated that the proposed 

rulemaking could substantially impact endangered species and that an analysis of these impacts was 

absent from the comparison of the impacts of each alternative in the DEIS. They stated that NHTSA 

must complete an Endangered Species Act Section 7 Consultation to ensure that its action will not 

jeopardize or adversely modify the critical habitat of threatened or endangered species. 

With regard to the structure and readability of the DEIS, CBD, Sierra Club, and Public Citizen 

specifically questioned the appropriateness of the DEIS comparison of alternatives in regard to GHG 

reductions and climate change. They stated that comparing the alternatives based on their contribution to 

the reduction in global temperature and sea-level rise in 2100 minimizes differences among alternatives to 

the point that climate change impacts of the agency’s proposed action are not shown in an appropriate or 

understandable context. They suggested that rather than being compared only to overall global 

concentrations, alternatives should be analyzed in a narrower context, for example, by analyzing their 

effects on emissions from motor vehicles in particular and on the U.S. transportation sector in general. 

Also with regard to readability, Environmental Consultants of Michigan expressed concern that 

the DEIS is not written in plain language, which prohibits decisionmakers and the public from fully 

comprehending the analysis. They suggested presenting the impacts analysis in a context that is relevant 

to the reader. Furthermore, they stated that requiring each agency to set its own standard under this joint 

rulemaking was duplicative and unnecessary. 

Additionally, CBD, Sierra Club, and Public Citizen expressed concern about how NHTSA’s 

alternatives relate to the EPCA requirement to establish the “maximum feasible average fuel economy.” 

They suggested that the DEIS fails to accurately describe maximum standards that are both 

technologically feasible and economically practicable, and that, consequently, the DEIS fails to propose 

standards at the maximum feasible level. They further criticized the DEIS for not considering a 

“technology forcing” alternative that is technologically exhaustive. 

CBD, Sierra Club, and Public Citizen also criticized the use of the Volpe model in setting CAFE 

standards. They stated that the Volpe model fails to adequately incorporate and respond to the real-world 

impacts and costs at stake as a result of the impacts of climate change. Additionally, they suggested that 

the Volpe model is insensitive to the social cost of carbon and therefore is an inappropriate tool to use in 

setting CAFE standards. 

CBD, Sierra Club, and Public Citizen also commented on the methodology for analyzing climate 

change impacts. They stated that the DEIS fails to adequately address climate change tipping points. 

They noted that under all scenarios considered in the DEIS, atmospheric CO2 concentrations would reach 

550 ppm or greater, which they stated is above the threshold for abrupt and catastrophic climate change 

caused by exceeding tipping points. They argued that none of the alternatives adequately addresses the 

need for deep reductions in CO2 emissions. They also suggested alternative scenarios for modeling 

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Chapter 1 Purpose and Need for the Proposed Action 

emission reduction impacts. Citing recent scientific evidence indicating that the avoidance of tipping 

points and climate catastrophe requires reductions in atmospheric CO2 concentrations to 350 ppm, they 

suggested modeling alternative scenarios in which future emissions are controlled so that atmospheric 

CO2 concentrations do not exceed values ranging from 350 to 750 ppm. 

Both the public testimony and written comments of CBD, Sierra Club, and Public Citizen 

suggested that the DEIS fails to consider all reasonably foreseeable actions that could affect fuel 

efficiency standards and GHG emissions from the transportation sector. They suggested that the DEIS 

ignores foreseeable actions including the continued regulation of GHGs by California and the states and 

the policies to reduce vehicle miles traveled. 

1.5.3.4 Individuals 

Four individuals provided comments on the DEIS: Gail Gilbert (Docket No. NHTSA-2009-

0059-0019), an anonymous commenter (Docket No. NHTSA-2009-0059-0044), Douglas Long (Docket 

No. NHTSA-2009-0059-0045), and James Adcock (Docket No. NHTSA-2009-0059-0049). 

All four commenters addressed the merits of the agency’s proposed action. Gail Gilbert stated 

that, despite her concern for loopholes, she considered the standards to be a big step forward. The 

anonymous commenter noted that the proposed action should not be under the control of the President or 

the U.S. Government in general. Douglas Long stated that NHTSA’s proposed action would establish 

regulations that would protect the American people by requiring that car manufacturers produce cleaner 

and more fuel-efficient vehicles than previously required. James Adcock stated that NHTSA’s proposed 

action does not represent a weighed consideration of climate change and that therefore NHTSA should 

change its proposal. 

James Adcock also raised several additional issues concerning the DEIS. One issue pertains to 

the availability of materials for public review. For example, Mr. Adcock expressed frustration that the 

2009 National Academy of Sciences update regarding the effectiveness and impact of CAFE standards 

was not available in time for the DEIS comment period. Additionally, Mr. Adcock expressed concern 

that the Volpe model could not be used on a personal computer for public validation of the model outputs. 

Mr. Adcock further suggested that NHTSA should not base fuel economy regulations on vehicle 

designs that manufacturers produce but never sell in great quantities. Rather, he claimed, NHTSA should 

focus on the vehicle models that make up most of the vehicle sales. Similarly, Mr. Adcock expressed 

concern regarding the technological assumptions used in the Volpe model. For example, he disagreed 

with NHTSA’s decision to exclude certain technologies, such as electric vehicles and plug-in hybrid 

electric vehicles, from consideration when setting CAFE standards for MYs 2012-2016. 

Mr. Adcock also critiqued the DEIS discussion of the safety impacts of new CAFE standards. He 

indicated that, although there might be a correlation between weight or footprint and safety, there is 

unlikely to be a significant correlation to miles per gallon, contrary to what is reported in the DEIS. 

Mr. Adcock also suggested that NHTSA fails to adequately account for species extinction when 

estimating the social cost of carbon. He believes NHTSA’s social cost of carbon is too low. Mr. Adcock 

also noted that the “environmentally preferred alternative” is not identified in the DEIS. 

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Chapter 1 Purpose and Need for the Proposed Action 

 1-21 

1.5.4 Summary of Rulemaking Comments Relevant to the DEIS 

On September 28, 2009, EPA and NHTSA published the joint NPRM in the Federal Register.

61 

The publication of the proposed rule opened a 60-day comment period, and the public was invited to 

submit comments on or before November 27, 2009 by posting to either the NHTSA or EPA docket 

(NHTSA-2009-0059 or EPA-HQ-OAR-2009-0472). A total of 247 rulemaking comments was submitted 

to the NHTSA docket and a total of 11,109 rulemaking comments was submitted to the EPA docket. 

NHTSA reviewed these submissions and has fully considered them in the development of the final rule. 

In addition, comments on the joint rulemaking were considered during the preparation of the EIS to 

ensure that any comments that could affect the content of the EIS were taken into account. For purposes 

of the EIS, NHTSA specifically looked for comments that were related to the EIS, such as comments 

about the Preferred Alternative, the range of alternatives considered, and the analysis of environmental 

impacts. Following is a brief description of the most common comments submitted on the rulemaking 

that are relevant to the EIS. 

Approximately 10,000 similar comments were received in support of the National Program. In 

these comments, commenters stated that they believed the benefits of the rulemaking would include: 

reducing GHG emissions from the transportation sector, thereby reducing climate change impacts; 

curbing dependence on foreign oil; improving national security; revitalizing the auto industry; reducing 

money spent on gasoline by consumers; encouraging the advancement and deployment of advanced 

technologies; and providing consumers with cleaner vehicle choices. Some comments were petitions that 

included signatures (more than 124,000 signatures were received). 

Although expressing support for the rulemaking, some commenters questioned why joint rules by 

two agencies were necessary. Many expressed the belief that NHTSA’s CAFE program is sufficient, 

while a few stated that the EPA GHG rule could replace the CAFE program. Several commenters had 

concerns about EPA’s regulation of GHG gases under CAA. Several states noted that the state waiver 

from EPA already grants California and other states the authority to regulate GHG emissions from 

vehicles. Several manufacturers and trade associations expressed appreciation that NHTSA and EPA 

were proposing one national joint rule. 

Although general support for the joint rulemaking was extensive, the second most frequent 

comment or recommendation was to adopt a more aggressive alternative for achieving higher levels of 

fuel economy and greater reductions in GHG emissions. These commenters were concerned that the 

proposed rulemakings were insufficient to avoid the adverse impacts of global warming and did not 

reflect fuel-saving technology advances that are currently or soon to be available. Commenters suggested 

CO2 reductions from vehicles should be in the 30–50 percent range. A frequent suggestion was to set 

standards that required vehicles to reach 50 mpg by 2016 as opposed to the proposed 33.8 mpg combined 

average in 2016Commenters also felt that the deadline for compliance with the EPA rule should be 2015, 

not 2030. In addition to more aggressive alternatives, many commenters offered new alternatives for the 

agencies to consider. These suggested alternatives covered a broad range of approaches, including ideas 

beyond the jurisdictions of NHTSA and EPA. Suggestions included eliminating the use of gasoline and 

relying on electric or hydrogen-powered vehicles; taxing gasoline at dramatically higher levels to reduce 

average vehicle use; returning to the 55 mile-per-hour speed limit on U.S. interstates and highways; 

rationing gasoline; promoting mass transit; retrofitting existing vehicles to improve their fuel economy; 

and placing higher fuel economy standards on government-owned vehicles. 

 

61 Proposed Rulemaking To Establish Light-Duty Vehicle Greenhouse Gas Emission Standards and Corporate 

Average Fuel Economy Standards, 74 FR 49454 (Sep. 28, 2009). 
Chapter 1 Purpose and Need for the Proposed Action 

Specific comments also were received on the components of the alternatives analyzed in the 

rulemaking. Some commenters expressed the belief that vehicle manufacturers have too much flexibility 

in compliance and cite the credits and the attribute-based standards as examples of this flexibility. These 

commenters are concerned that fully achieving the rule’s GHG reduction estimates will be undermined by 

including these components, especially the proposed credits. Several commenters specifically expressed 

concern regarding EPA’s credit for electric vehicles. Many stated that the benefit offered by this credit 

did not, through a life-cycle analysis, account for the GHGs emitted by the power plants that would 

provide these vehicles with their source of electricity. Other commenters, however, viewed the flexibility 

and credits as a benefit because they could reduce compliance costs for the automobile industry and allow 

for more consumer choice. Despite this compliance flexibility, other commenters noted that the rule’s 

compliance costs, as estimated by NHSTA and EPA, are understated for small-volume manufacturers 

because such manufacturers have fewer vehicles over which the costs can be spread. 

Commenters also raised questions about the adequacy of several cost and benefit measurements 

that are inputs into the Volpe model. In the EIS, the Volpe model establishes the mpg standard for the 

alternative that maximizes net benefits (MNB) (Alternative 6) and the alternative under which total cost 

equals total benefit (TCTB) (Alternative 9). Most notable were comments on the model’s estimate for the 

social cost of carbon. The $20 per metric ton cost that was used initially was generally reproved as being 

too low. These commenters expressed their belief that this cost does not adequately reflect the adverse 

impacts of CO2 emissions on society. Many of these commenters cited studies that used a much higher 

cost estimate. Similarly, comments were made regarding the undervaluation of national security benefits. 

These commenters believe that higher benefits should be claimed for reducing the nation’s dependence on 

foreign oil and the possible resulting future reduction in defense costs. NHTSA responds to the DEIS 

comments on the Volpe model in Section 10.2.3.4.2 of this EIS. 

Comments also were also received on the environmental impacts of the rule. A few commenters 

suggested that the environmental benefits of the rule in terms of climate change are inconsequential. 

Some suggested that there is evidence that climate change science is based on incorrect assumptions and 

data. One commenter suggested that the proposed rule relied too heavily on literature produced by the 

Intergovernmental Panel on Climate Change (IPCC) and that other peer-reviewed research also should be 

considered. Another commenter suggested that action is required now so that the climate tipping point is 

not passed. Some commenters suggested that only a world with a global concentration of 350-ppm CO2 

equivalent is sustainable. In this EIS, NHTSA discusses the effects of the rule on climate change in 

Sections 3.4, 4.4, and 4.5. NHTSA responds to similar comments received on the DEIS in Section 

10.2.4.6 on the comparison of alternatives and the context of the analysis, Section 10.3.3 on climate 

tipping points, and Section 10.4.2 on climate methodology. 

Several commenters suggested that a complete life cycle assessment of the rulemaking be 

completed. One commenter suggested that automobile manufacturers and their parts suppliers will need 

to retrofit their existing facilities or build new ones, which will require the extraction and processing of 

raw and recycled materials into useable building materials, transportation of those materials, and 

construction, which will produce GHG emissions. This commenter further suggested that vehicles will 

likely be manufactured from lighter weight materials to meet higher fuel economy requirements; some of 

these materials could require more energy to produce or recycle, leading to increased GHG emissions. 

NHTSA agrees with these commenters that a complete life cycle assessment of the impacts of the 

CAFE rulemaking, which would include estimates of energy use and emissions from both vehicle 

manufacturing and the construction or modification of facilities for producing and assembling vehicle 

components, would be an informative and interesting addition to its analysis of alternative increases in 

CAFE standards. However, such an analysis would require a number of largely arbitrary assumptions 

about uncertain variables – such as the number of facilities that would need to be constructed or modified 

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Chapter 1 Purpose and Need for the Proposed Action 

– and the behavior of vehicle manufacturers. The necessary assumptions would introduce sufficient 

uncertainty into the calculations of total energy use and emissions that NHTSA does not believe the 

resulting analysis would be reliable or useful to decisionmakers. For example, a complete life cycle 

analysis would require the agency to make assumptions about what fraction of manufacturers would build 

new facilities or modify existing ones as a result of increased CAFE standards, what specific materials 

and construction methods would be employed in building or modifying these facilities, and on what 

magnitude or scale these facilities would operate. The agency does not believe it has any reasonable basis 

for speculating about these parameters, or about other equally important assumptions that would be 

necessary to conduct a comprehensive life cycle analysis of energy use and emissions resulting from 

vehicle manufacturers’ responses to increases in CAFE standards for future model years. Therefore, 

NHTSA has not attempted a complete life cycle assessment as part of the analysis for the EIS or final rule 

establishing CAFE standards for MY 2012-2016 passenger cars and light trucks. 

Many commenters expressed support for the rule because they believe the reduction in emissions 

would improve public health by reducing asthma and other health issues related to poor air quality. 

However, two states expressed concern about the possible increases in emissions of criteria pollutants and 

air toxics, such as acetaldehyde, 1,3- butadiene ethylbenzene, toluene, and the xylene isomers, due to 

increased vehicle use, stating that increases in these emissions could have direct health impacts. Two 

states suggested that, in areas with little or no fuel-refining industry, the rebound effect would result in an 

increase in criteria pollutant emissions that are of critical importance for compliance with the National 

Ambient Air Quality Standard for ground-level ozone, primarily the emissions of volatile organic 

compounds (VOC) and nitrogen oxides (NOx). One state suggested that the emissions of all air toxics 

associated with the extraction, production, distribution, and combustion of fuel be examined and evidence 

be presented demonstrating that the proposed National Program will not increase air toxics emissions 

from mobile sources. 

NHTSA addresses air quality, including emissions of criteria pollutants and air toxics both 

nationwide and in nonattainment areas, in Sections 3.3 and 4.3 of the EIS and responds to comments 

about the air analysis in Section 10.3.2. The analysis shows that VOC emissions would decrease in every 

nonattainment area. NOx emissions would decrease in some nonattainment areas under Alternatives 2 

through 4 and would decrease in all nonattainment areas under Alternatives 5 through 9. Some 

nonattainment areas would have NOx emissions increases for some years and alternatives, but the 

increases would be very small compared to total NOx emissions in the affected nonattainment areas. The 

EIS air quality analysis covers the air toxics that EPA and the Federal Highway Administration have 

identified those that typically are of greatest concern for emissions from highway vehicles (acetaldehyde, 

acrolein, benzene, 1,3-butadiene, diesel particulate matter, and formaldehyde). The analysis includes 

downstream (combustion) and upstream (extraction, production, storage, and distribution) emissions and 

predicts both increases and decreases in emissions of air toxics depending on pollutant, calendar year, and 

alternative. NHTSA conducted a photochemical air quality modeling analysis of the alternatives which 

demonstrates beneficial impacts to health effects and health-related economic costs. The photochemical 

air quality analysis is included as Appendix F of this EIS.

Some commenters pointed out that the rulemaking could affect vehicle safety due to changes in 

vehicle size and weight. Commenters expressed satisfaction that the number of larger vehicles on the 

road was likely to diminish and the number of smaller cars was likely to grow; however, they connected 

this outcome to concerns about safety, citing tradeoffs between vehicle safety and weight reduction. 

Commenters also expressed concerns that NHTSA and EPA reached different conclusions regarding the 

safety-related impacts that could result from implementation of the proposed standards and that NHTSA 

might be using outdated data. NHTSA incorporated the safety discussion from the preamble and Chapter 

9 of the Preliminary Regulatory Impact Analysis on how future improvements in fuel economy might 

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Chapter 1 Purpose and Need for the Proposed Action 

 1-24 

affect human health and welfare into the EIS in Section 3.5.4 (NHTSA 2009). NHTSA received similar 

comments on the DEIS and provides a response in Section 10.3.4.1. 

Some commenters expressed concern that the cost of cars would increase, creating an 

affordability issue. Another commenter was concerned that the cost and availability of trucks would be 

negatively affected and thereby would negatively affect people such as farmers and ranchers whose jobs 

require trucks to haul heavy loads. Some commenters expressed concern that the cost for automobile 

manufacturers to implement the rule would force them to reduce the number of people they employ. 

Finally, commenters expressed general concerns about the affordability of cars manufactured to comply 

with the new standards. 

1.5.5 Next Steps in the NEPA Process and CAFE Rulemaking 

No sooner than 30 days after the availability of this EIS is announced in the Federal Register by 

EPA, NHTSA will execute a Record of Decision (ROD) and publish in the Federal Register the ROD and 

a final joint rule with EPA. The ROD will state and explain NHTSA’s decision. 

 
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Chapter 2 Proposed Action and Alternatives 

2.1 INTRODUCTION 

The National Environmental Policy Act1

 (NEPA) requires an agency to compare the 

environmental impacts of its proposed action and alternatives. An agency must rigorously explore and 

objectively evaluate all reasonable alternatives, including a No Action Alternative. For alternatives an 

agency eliminates from detailed study, the agency must “briefly discuss the reasons for their having been 

eliminated.”2

 The purpose of and need for the agency’s action provides the foundation for determining 

the range of reasonable alternatives to be considered in its NEPA analysis.3

For this EIS, the National Highway Traffic Safety Administration (NHTSA) Proposed Action is 

to set passenger car and light truck Corporate Average Fuel Economy (CAFE) standards for model years 

(MYs) 2012-2016 in accordance with the Energy Policy and Conservation Act (EPCA), as amended by 

the Energy Independence and Security Act (EISA). In developing the new proposed MYs 2012-2016 

CAFE standards and possible alternatives, NHTSA considered the four EPCA factors that guide the 

agency’s determination of “maximum feasible” standards: 

• Technological feasibility; 

• Economic practicability; 

• The effect of other standards of the Government on fuel economy; and 

• The need of the Nation to conserve energy.4

In addition, NHTSA considered relevant environmental and safety factors.5

 The NEPA analysis 

presented in the Environmental Impact Statement (EIS) informs the agency’s action in setting CAFE 

standards. During the standard-setting process, NHTSA consults with the U.S. Department of Energy 

(DOE) and the Environmental Protection Agency (EPA) regarding a variety of matters as required by 

EPCA. NHTSA also is guided by President Obama’s memorandum to the U.S. Department of 

Transportation (DOT) on January 26, 2009, and the NHTSA/EPA Joint Rulemaking announced on May 

19, 2009, as described in Chapter 1. 

2.2 STANDARDS-SETTING 

In developing the proposed MYs 2012-2016 standards, the agency developed and considered a 

wide variety of alternatives. NHTSA took a new approach to defining alternatives as compared to the 

most recent prior CAFE rulemaking. In the NOI, in response to comments received in the last round of 

rulemaking, NHTSA selected a range of candidate stringencies that increased annually, on average, 3 

percent to 7 percent. That same approach was carried over to this EIS and to the rulemaking. The 

majority of the alternatives considered by the agency are defined as average percentage increases in 

 

1 42 U.S.C. § 4332(2)(C). NEPA is codified at 42 U.S.C. § 4321, et seq. 2 40 CFR §§ 1502.14(a), (d). 

3 40 CFR § 1502.13. See Vermont Yankee Nuclear Power Corp. v. Natural Res. Def. Council, 435 U.S. 519, 551 

(1978); City of Alexandria v. Slater, 198 F.3d 862, 867-69 (D.C. Cir. 1999), cert. denied sub nom., 531 U.S. 820 

(2000). 

4 49 U.S.C. § 32902(f). 

5

 As mentioned in Chapter 1, NHTSA interprets the statutory factors as including environmental issues and 

permitting the consideration of other relevant societal issues, such as safety. See, e.g., Competitive Enterprise Inst. 

v. NHTSA, 956 F.2d 321, 322 (D.C. Cir. 1992) (citing Competitive Enterprise Inst. v. NHTSA, 901 F.2d 107, 120 

n.11 (D.C. Cir. 1990)); and 73 Federal Register (FR) 24352, 24364 (May 2, 2008). 
Chapter 2 Proposed Action and Alternatives 

stringency – 3 percent per year, 4 percent per year, 5 percent per year, and so on. NHTSA believes that 

this approach more clearly communicates the level of stringency of each alternative and is more intuitive 

than alternatives defined in terms of different cost-benefit ratios, and still allows us to identify alternatives 

that represent different ways to balance NHTSA’s statutory requirements under EPCA/EISA. 

In the NOI, we noted that each of the listed alternatives represents, in part, a different way in 

which NHTSA could conceivably balance conflicting policies and considerations in setting the standards. 

We were mindful that the agency would need to weigh and balance many factors, such as the 

technological feasibility, economic practicability (including lead-time considerations for the introduction 

of technologies and impacts on the auto industry), the impacts of the standards on fuel savings and CO2

emissions, as well as other relevant factors such as safety. For example, the 7-Percent Alternative, the 

most stringent alternative, weighs energy conservation and climate change considerations more heavily 

and technological feasibility and economic practicability less heavily. In contrast, the 3-Percent 

Alternative, the least stringent alternative, places more weight on technological feasibility and economic 

practicability. We recognized that the “feasibility” of the alternatives also may reflect differences and 

uncertainties in the way in which key economic (e.g., the price of fuel and the social cost of carbon) and 

technological inputs could be assessed and estimated or valued. 

After working with EPA in thoroughly reviewing and in some cases reassessing the effectiveness 

and costs of technologies, most of which are already being incorporated in at least some vehicles, market 

forecasts and economic assumptions, we used the Volpe model extensively to assess the technologies that 

the manufacturers could apply in order to comply with each of the alternatives. This permitted us to 

assess the variety, amount, and cost of the technologies that could be needed to enable the manufacturers 

to comply with each of the alternatives. NHTSA estimated how the application of these and other 

technologies could increase vehicle costs. The following sections describe the Volpe model and the 

inputs to the Volpe model, to help the reader gain an overview of the analytical pieces and tools used in 

the agency’s analysis of alternatives. 

2.2.1 Volpe Model 

Since 2002, NHTSA has employed, as part of its analysis, a modeling system developed 

specifically to assist NHTSA with applying technologies to thousands of vehicles and developing 

estimates of the costs and benefits of potential CAFE standards. The CAFE Compliance and Effects 

Modeling System, developed by the DOT Volpe National Transportation Systems Center and commonly 

referred to as “the Volpe model,” enables the agency to efficiently, systematically, and reproducibly 

evaluate many more regulatory options, including attribute-based CAFE standards required by EISA, than 

were previously possible, and to do so much more quickly. Generally speaking, the model assumes that 

manufacturers apply the most cost-effective technologies first, and as more stringent fuel economy 

standards are evaluated, the model recognizes that manufacturers must apply less cost-effective 

technologies. The model then compares the discounted present value of costs and benefits for any 

specific CAFE standard. However, while the Volpe model does calculate average changes in vehicle 

prices (corresponding to total technology outlays and, where applicable, civil penalties), it does not 

currently predict manufacturers’ decisions regarding the pricing or production of specific vehicle models. 

Nor does it currently estimate for consumer behavioral responses such as buying fewer vehicles or buying 

different types of vehicles. 

Model documentation, publicly available in the rulemaking docket and on NHTSA’s website, 

explains how the model is installed, how the model inputs and outputs are structured, and how the model 

is used. The model can be used on any Windows-based personal computer with Microsoft Office 2003 or 

2007 and the Microsoft .NET framework installed (the latter available without charge from Microsoft). 

The executable version of the model, with all of its underlying source code and accompanying 

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Chapter 2 Proposed Action and Alternatives 

demonstration files, is also available on NHTSA’s website for public download. The current version of 

the model was developed using Microsoft Development Environment 2003, and every line of computer 

code (primarily in C#

.NET) has been made available to individuals who have requested the code. 

The Volpe model requires the following types of input information: (1) a forecast of the future 

vehicle market; (2) estimates of the availability, applicability, and incremental effectiveness and cost of 

fuel-saving technologies; (3) estimates of vehicle survival and mileage accumulation patterns, the 

rebound effect, future fuel prices, the “social cost of carbon,” and many other economic factors; (4) fuel 

characteristics and vehicular emissions rates; and (5) coefficients defining the shape and level of CAFE 

curves to be examined. The model is a tool that the agency uses for analysis: it makes no a priori

assumptions regarding inputs such as fuel prices and available technology, and does not dictate the form 

or stringency of the CAFE standards to be examined. The agency makes those selections based on the 

best available information and data. 

Using inputs selected by the agency, NHTSA projects a set of technologies each manufacturer 

could apply in attempting to comply with the various levels of potential CAFE standards to be examined. 

The model then estimates the costs associated with this additional technology utilization, as well as 

accompanying changes in travel demand, fuel consumption, fuel outlays, emissions, and economic 

externalities related to petroleum consumption and other factors. 

Normally, the Volpe model uses technologies available on vehicles in the current year. For 

example, when modeling MY 2014, only vehicle models with technologies “enabled” in MY 2014 would 

be candidates for technology application. One of the updates to the model for the current rulemaking is 

the addition of a “multi-year planning” capability, developed in response to comments to prior CAFE 

rulemakings. When run in multi-year mode, the model is allowed to “look back” to earlier years when a 

technology was enabled on any vehicles but not used, and consider “back-dating” the application of that 

technology when calculating the effective cost. Thus, if the model did not apply an enabled technology in 

either MY 2012 or MY 2013, then that technology remains available for multi-year application in MY 

2014. Multi-year mode is anticipated to be most useful in situations where the model finds that a 

manufacturer is able to reach compliance in earlier years of the modeling period (e.g., MY 2012) but is 

challenged to reach compliance in later years (e.g., MY 2014). In these cases, the model can go back to 

the earlier year and over-comply in order to make compliance in the later year easier to achieve. 

Recognizing the uncertainty inherent in many of the underlying estimates in the model, such as 

the social cost of carbon, the discount rate, and so on, NHTSA has used the Volpe model to conduct both 

sensitivity analyses, by changing one factor at a time, and a probabilistic uncertainty analysis (a Monte 

Carlo analysis that allows simultaneous variation in these factors) to examine how key measures (e.g., 

mpg levels of the standard, total costs, and total benefits) vary in response to change in these factors. This 

type of analysis is used to estimate the uncertainty of the costs and benefits of a given set of CAFE 

standards. 

The model can also be used to estimate the stringency that (a) generates a specified average 

required CAFE level, (b) maximizes net benefits to society, (c) achieves a specified stringency at which 

total costs equal total benefits, or (d) results in a specified total incremental cost, etc. The agency uses 

this information from the Volpe model as a tool to assist in setting standards. For additional discussions 

of the Volpe model and its inputs, see the NPRM and the Draft Technical Support Document (TSD). Any 

changes made to the model inputs will be discussed in detail in the forthcoming joint NHTSA-U.S. 

Environmental Protection Agency (EPA) Final Rule promulgating MYs 2012-2016 CAFE standards and 

NHTSA’s forthcoming Regulatory Impact Analysis (RIA), as well as the forthcoming NHTSA-EPA joint 

TSD. 

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Chapter 2 Proposed Action and Alternatives 

Although NHTSA has used the Volpe model as a tool to inform its consideration of potential 

CAFE standards, the Volpe model does not determine the CAFE standards NHTSA will propose or 

promulgate as final regulations. NHTSA considers the results of analyses conducted using the Volpe 

model and external analyses, including assessments of greenhouse gases and air pollution emissions, and 

technologies that may be available in the long term. NHTSA also considers whether the standards could 

expedite the introduction of new technologies into the market, and the extent to which changes in vehicle 

prices and fuel economy might affect vehicle production and sales. Using all of this information, the 

agency considers the governing statutory factors, along with environmental issues and other relevant 

societal issues, such as safety, and promulgates the maximum feasible standards based on its best 

judgment on how to balance these factors. 

2.2.2 Vehicle Market Forecast 

To determine what levels of stringency are feasible in future model years, the agencies must 

project what vehicles and technologies will exist in those model years, and then evaluate what 

technologies can feasibly be applied to those vehicles to raise their fuel economy and lower their CO2

emissions. The agencies therefore establish a baseline vehicle fleet representing those vehicles, based on 

the best available information and a reasonable balancing of various policy concerns, against which they 

can analyze potential future levels of stringency and their costs and benefits. 

NHTSA has historically based its analysis of potential new CAFE standards on detailed product 

plans the agency has requested from manufacturers planning to produce passenger cars and light trucks 

for sale in the United States. For this rulemaking, and as explained in the Draft TSD prepared jointly by 

NHTSA and EPA, both agencies used a baseline vehicle fleet constructed beginning with CAFE 

certification data for the 2008 model year, the most recent model year for which final data is currently 

available from manufacturers. This data was used as the source for MY 2008 production volumes and 

some vehicle engineering characteristics, such fuel economy ratings, engine sizes, numbers of cylinders, 

and transmission types. 

Some information important for analyzing new CAFE standards is not contained in the CAFE 

certification data. EPA staff, in consultation with NHTSA staff, identified vehicle wheelbase and track 

widths using data from Motortrend.com and Edmunds.com. This information is necessary for calculating 

vehicle footprint, which is required for the analysis of footprint-based standards. Considerable additional 

information regarding vehicle engineering characteristics is also important for estimating the potential to 

add new technologies in response to new CAFE standards. In general, such information helps to avoid 

“adding” technologies to vehicles that already have the same or a more advanced technology. Examples 

include valvetrain configuration (e.g., overhead valve configuration [OHV], single overhead cam 

[SOHC], double overhead cam [DOHC]), presence of cylinder deactivation, and fuel delivery (e.g., 

stoichiometric gasoline direct injection [SGDI]). To the extent that such engineering characteristics were 

not available in certification data, EPA staff relied on data published by Ward’s Automotive, 

supplementing this with information from internet sites such as Motortrend.com and Edmunds.com. 

NHTSA staff also added some more detailed engineering characteristics (e.g., type of variable valve 

timing) using data available from ALLDATA® Online. Combined with the certification data, all of this 

information yielded a MY 2008 baseline vehicle fleet. 

After the baseline was created the next step was to project the sales volumes for 2011-2016 model 

years. The agencies used total projected light-duty vehicle volumes for this period from the Energy 

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Chapter 2 Proposed Action and Alternatives 

 2-5 

Information Administration (EIA) Annual Energy Outlook (AEO) 2010 Early Release (EIA 2009b).6 

However, AEO projects sales only at the car and truck level, not at the manufacturer and model-specific 

level, which are needed in order to estimate the effects new standards will have on individual 

manufacturers. Therefore, EPA purchased and shared with NHTSA data from CSM-Worldwide and used 

their projections of the number of vehicles of each type predicted to be sold by manufacturers in 2011-

2015.7

 This provided the year-by-year percentages of cars and trucks sold by each manufacturer as well 

as the percentages of each vehicle segment, although it was, therefore, necessary to assume the same 

manufacturer and segment shares in 2016 as in 2015. Using these percentages normalized to the AEO 

projected volumes then provided the manufacturer-specific market share and model-specific sales for 

MYs 2011-2016. 

The processes for constructing the MY 2008 baseline vehicle fleet and subsequently adjusting 

sales volumes to construct the MYs 2011-2016 baseline vehicle fleet are presented in detail in the Draft 

TSD. Any changes made to the agency’s baseline vehicle fleet will be fully explained in the forthcoming 

NHTSA-EPA joint TSD. For a detailed discussion of NHTSA’s prior product plan-based approach and 

the current baseline vehicle fleet approach used by NHTSA and EPA for this rulemaking, including the 

differences, advantages and disadvantages between the two approaches, see II.B.3 of the NPRM.

2.2.3 Technology Assumptions 

The analysis of costs and benefits employed in the Volpe model reflects NHTSA’s assessment of 

a broad range of technologies that can be applied to passenger cars and light trucks. In the agency’s 

rulemakings covering light truck CAFE standards for MYs 2005-2007 and MYs 2008-2011, the agency 

relied on the 2002 National Academy of Sciences’ report Effectiveness and Impact of Corporate Average 

Fuel Economy Standards for estimating potential fuel economy benefits and associated retail costs of 

applying combinations of technologies (NRC 2002). In developing its final rule adopting CAFE 

standards for MY 2011, NHTSA reviewed manufacturers’ technology data and comments it received on 

its fuel saving technologies, and conducted its own independent analysis which involved hiring an 

international engineering consulting firm that specializes in automotive engineering. This same 

engineering consulting firm was also used by EPA in developing its advance NPRM to regulate 

greenhouse gas (GHG) emissions under the Clean Air Act (CAA).8

In the MY 2011 CAFE Final Rule, as requested by the President in his January 2009 

memorandum, NHTSA also stated that it would continue to review these technology assumptions and the 

methodologies used to derive the costs and effectiveness values, in order to improve its assumptions. For 

the MYs 2012-2016 rulemaking, NHTSA worked with EPA to revise and update a common list of fuelsaving technology cost and effectiveness numbers. EPA is also using this list of fuel-saving technologies 

in its model for development of CO2 standards in the forthcoming joint NHTSA-EPA Final Rule. The 

revised technology assumptions – that is, estimates of the availability, applicability, cost, and 

effectiveness of fuel-saving technologies, and the order in which the technologies are applied – will be 

described in greater detail in the forthcoming NHTSA-EPA joint TSD and in NHTSA’s forthcoming RIA. 

 

6

 The agencies have also used the reference scenario fuel price forecast from the preliminary release of AEO 2010 

(EIA 2009b), and high and low fuel price forecasts from AEO 2009 (EIA 2009a). Both agencies regard AEO as a 

credible source not only of such forecasts, but also of many underlying forecasts, including forecasts of the size the 

future light vehicle market. 

7

 EPA also considered other sources of similar information, such as J.D. Powers, and concluded that CSM was better 

able to provide forecasts at the requisite level of detail for most of the model years of interest. 

8 See NHTSA, Average Fuel Economy Standards Passenger Cars and Light Trucks Model Year 2011, 74 FR 14196, 

14233-14300 (Mar. 30, 2009); Environmental Protection Agency, Regulating Greenhouse Gas Emissions Under the 

Clean Air Act, Proposed Rule, 73 FR 44354 (Jul. 30, 2008). 
Chapter 2 Proposed Action and Alternatives 

The technologies considered by the model are briefly described below, under the five broad 

categories of engine, transmission, vehicle, electrification/accessory, and hybrid technologies. 

Types of engine technologies that were considered under the benefit-cost analysis include the 

following:

• Low-friction lubricants – low-viscosity and advanced low-friction lubricants oils are now 

available with improved performance and better lubrication. 

• Reduction of engine friction losses – can be achieved through low-tension piston rings, roller 

cam followers, improved material coatings, more optimal thermal management, piston 

surface treatments, and other improvements in the design of engine components and 

subsystems that improve engine operation. 

• Conversion to dual overhead cam with dual cam phasing – as applied to overhead valves 

designed to increase the air flow with more than two valves per cylinder and reduce pumping 

losses.

• Cylinder deactivation – deactivates the intake and exhaust valves and prevents fuel injection 

into some cylinders during light-load operation. The engine runs temporarily as though it 

were a smaller engine which substantially reduces pumping losses 

• Variable valve timing – alters the timing or phase of the intake valve, exhaust valve, or both, 

primarily to reduce pumping losses, increase specific power, and control residual gases.

• Discrete variable valve lift – increases efficiency by optimizing air flow over a broader range 

of engine operation which reduces pumping losses. Accomplished by controlled switching 

between two or more cam profile lobe heights. 

• Continuous variable valve lift – is an electromechanically controlled system in which cam 

period and phasing is changed as lift height is controlled. This yields a wide range of 

performance optimization and volumetric efficiency, including enabling the engine to be 

valve throttled. 

• Stoichiometric gasoline direct-injection technology – injects fuel at high pressure directly into 

the combustion chamber to improve cooling of the air/fuel charge within the cylinder, which 

allows for higher compression ratios and increased thermodynamic efficiency. 

• Combustion restart – can be used in conjunction with gasoline direct-injection systems to 

enable idle-off or start-stop functionality. Similar to other start-stop technologies, additional 

enablers, such as electric power steering, accessory drive components, and auxiliary oil 

pump, might be required. 

• Turbocharging and downsizing – increases the available airflow and specific power level, 

allowing a reduced engine size while maintaining performance. This reduces pumping losses 

at lighter loads in comparison to a larger engine.

• Exhaust-gas recirculation boost – increases the exhaust-gas recirculation used in the 

combustion process to increase thermal efficiency and reduce pumping losses. 

 2-6 
Chapter 2 Proposed Action and Alternatives 

• Diesel engines – have several characteristics that give superior fuel efficiency, including 

reduced pumping losses due to lack of (or greatly reduced) throttling and a combustion cycle 

that operates at a higher compression ratio, with a very lean air/fuel mixture, than an 

equivalent-performance gasoline engine. This technology requires additional enablers, such 

as NOx trap catalyst after-treatment or selective catalytic reduction NOx after-treatment.

Types of transmission technologies considered include: 

• Improved automatic transmission controls – optimizes shift schedule to maximize fuel 

efficiency under wide-ranging conditions, and minimizes losses associated with torque 

converter slip through lock-up or modulation. 

• Six-speed automatic transmissions – the gear ratio spacing and transmission ratio are 

optimized to enable the engine to operate in a more efficient operating range over a broader 

range of vehicle operating conditions. 

• Dual clutch or automated shift manual transmissions – are similar to manual transmissions, 

but the vehicle controls shifting and launch functions. A dual-clutch automated shift manual 

transmission uses separate clutches for even-numbered and odd-numbered gears, so the next 

expected gear is pre-selected, which allows for faster and smoother shifting.

• Continuously variable transmission – commonly uses V-shaped pulleys connected by a metal 

belt rather than gears to provide ratios for operation. Unlike manual and automatic 

transmissions with fixed transmission ratios, continuously variable transmissions can provide 

fully variable and an infinite number of transmission ratios that enable the engine to operate 

in a more efficient operating range over a broader range of vehicle operating conditions.

• Manual 6-speed transmission – offers an additional gear ratio, often with a higher overdrive 

gear ratio, than a 5-speed manual transmission. 

Types of vehicle technologies considered include: 

• Low-rolling-resistance tires – have characteristics that reduce frictional losses associated 

with the energy dissipated in the deformation of the tires under load, therefore reducing the 

energy needed to move the vehicle. 

• Low-drag brakes – reduce the sliding friction of disc brake pads on rotors when the brakes 

are not engaged because the brake pads are pulled away from the rotors. 

• Front or secondary axle disconnect for four-wheel drive systems – provides a torque 

distribution disconnect between front and rear axles when torque is not required for the nondriving axle. This results in the reduction of associated parasitic energy losses. 

• Aerodynamic drag reduction – is achieved by changing vehicle shape or reducing frontal 

area, including skirts, air dams, underbody covers, and more aerodynamic side view mirrors. 

• Mass reduction and material substitution – Mass reduction encompasses a variety of 

techniques ranging from improved design and better component integration to application of 

lighter and higher-strength materials. Mass reduction is further compounded by reductions in 

engine power and ancillary systems (transmission, steering, brakes, suspension, etc.).

 2-7 
Chapter 2 Proposed Action and Alternatives 

Types of electrification/accessory and hybrid technologies considered include: 

• Electric power steering (EPS) – is an electrically-assisted steering system that has advantages 

over traditional hydraulic power steering because it replaces a continuously operated 

hydraulic pump, thereby reducing parasitic losses from the accessory drive.

• Improved accessories (IACC) – may include high efficiency alternators, electrically driven 

(i.e., on-demand) water pumps and cooling fans. This excludes other electrical accessories 

such as electric oil pumps and electrically driven air conditioner compressors.

• Air Conditioner Systems – These technologies include improved hoses, connectors, and seals 

for leakage control. They also include improved compressors, expansion valves, heat 

exchangers and the control of these components for the purposes of improving tailpipe CO2

emissions as a result of A/C use. These technologies are covered separately in the EPA RIA. 

• 12-volt micro-hybrid (MHEV) – also known as idle-stop or start stop and commonly 

implemented as a 12-volt belt-driven integrated starter-generator, this is the most basic hybrid 

system that facilitates idle-stop capability. Along with other enablers, this system replaces a 

common alternator with an enhanced power starter-alternator, both belt driven, and a revised 

accessory drive system.

• Higher Voltage Stop-Start/Belt Integrated Starter Generator (BISG) – provides idle-stop 

capability and uses a high voltage battery with increased energy capacity over typical 

automotive batteries. The higher system voltage allows the use of a smaller, more powerful 

electric motor and reduces the weight of the motor, inverter, and battery wiring harnesses. 

This system replaces a standard alternator with an enhanced power, higher voltage, higher 

efficiency starter-alternator, that is belt driven and that can recover braking energy while the 

vehicle slows down (regenerative braking).

• Integrated Motor Assist (IMA)/Crank integrated starter generator (CISG) – provides idlestop capability and uses a high voltage battery with increased energy capacity over typical 

automotive batteries. The higher system voltage allows the use of a smaller, more powerful 

electric motor and reduces the weight of the motor, inverter, and battery wiring harnesses. 

This system replaces a standard alternator with an enhanced power, higher voltage, higher 

efficiency starter-alternator that is crankshaft mounted and can recover braking energy while 

the vehicle slows down (regenerative braking).

• 2-mode hybrid (2MHEV) – is a hybrid electric drive system that uses an adaptation of a 

conventional stepped-ratio automatic transmission by replacing some of the transmission 

clutches with two electric motors that control the ratio of engine speed to vehicle speed, while 

clutches allow the motors to be bypassed. This improves both the transmission torque 

capacity for heavy-duty applications and reduces fuel consumption and CO2 emissions at 

highway speeds relative to other types of hybrid electric drive systems.

• Power-split hybrid (PSHEV) – a hybrid electric drive system that replaces the traditional 

transmission with a single planetary gearset and a motor/generator. This motor/generator 

uses the engine to either charge the battery or supply additional power to the drive motor. A 

second, more powerful motor/generator is permanently connected to the vehicle’s final drive 

and always turns with the wheels. The planetary gear splits engine power between the first 

motor/generator and the drive motor to either charge the battery or supply power to the 

wheels.

 2-8 
Chapter 2 Proposed Action and Alternatives 

• Plug-in hybrid electric vehicles (PHEV) – are hybrid electric vehicles with the means to 

charge their battery packs from an outside source of electricity (usually the electric grid). 

These vehicles have larger battery packs with more energy storage and a greater capability to 

be discharged. They also use a control system that allows the battery pack to be substantially 

depleted under electric-only or blended mechanical/electric operation.

• Electric vehicles (EV) – are vehicles with all-electric drive and with vehicle systems powered 

by energy-optimized batteries charged primarily from grid electricity.

2.2.4 Economic Assumptions 

The NHTSA analysis of the energy savings, emission reductions, and environmental impacts 

likely to result from alternative CAFE standards relies on a range of forecasts, economic assumptions, and 

estimates of parameters used by the Volpe CAFE model. These economic values play a significant role in 

determining the reductions in fuel consumption, changes in emissions of criteria air pollutants and GHGs, 

reductions in U.S. petroleum imports, and resulting economic benefits of alternative increases in CAFE 

standards. Under alternatives where standards would be established, in part, by reference to their costs 

and benefits (i.e., the Maximum Net Benefits Alternative, and the Total Cost Equals Total Benefit 

Alternative), these economic values also affect the levels of the CAFE standards themselves. 

The economic forecasts, assumptions, and parameters used in the Volpe CAFE model include the 

following: 

• Forecasts of sales of passenger cars and light trucks for MYs 2012-2016. 

• Assumptions about the fraction of these vehicles that remain in service at different ages, how 

rapidly average annual use of passenger cars and light trucks grows over time, and how 

passenger car and light truck use declines with their increasing age. 

• Forecasts of fuel prices over the expected lifetimes of MYs 2012-2016 passenger cars and 

light trucks. 

• Forecasts of expected future growth in total passenger car and light truck use, including 

vehicles of all model years comprising the U.S. vehicle fleet. 

• The size of the gap between test and actual on-road fuel economy. 

• The magnitude of the fuel economy rebound effect, or the increase in vehicle use that results 

from improved fuel economy. 

• Economic costs associated with U.S. consumption and imports of petroleum and refined 

petroleum products, over and above their market prices. 

• Changes in emissions of criteria air pollutants and GHGs that result from saving each gallon 

of fuel and from each added mile of driving. 

• The economic values of reductions in emissions of each criteria air pollutant and GHGs. 

• The value of increased driving range and less frequent refueling that results from increases in 

fuel economy. 

 2-9 
Chapter 2 Proposed Action and Alternatives 

• The costs of increased congestion, traffic accidents, and noise caused by added passenger car 

and light truck use. 

• The discount rate applied to future benefits. 

Table 2.2-1 presents many of the specific forecasts, assumptions, and parameter values used to 

calculate the energy savings, environmental impacts, and economic benefits of each alternative. The 

direct, indirect, and cumulative impacts of the proposed CAFE alternatives examined in this EIS reflect 

this specific combination of economic inputs in the Volpe model. Detailed descriptions of the sources of 

forecast information, the rationale underlying each economic assumption, and the agency’s choices of 

specific parameter values will be discussed in detail in the forthcoming joint NHTSA-EPA Final Rule and 

NHTSA’s forthcoming RIA, as well as the forthcoming joint EPA-NHTSA final TSD for fuel economy 

and motor vehicle CO2 emission standards. 

NHTSA’s main analysis of energy use and emissions resulting from alternative CAFE standards 

uses the forecasts, assumptions, and parameters reported in Table 2.2-1. The agency also analyzed the 

sensitivity of its estimates to plausible variations in the values of many of these variables. The specific 

alternative values of these variables that were used in the agency’s sensitivity analysis and their effects on 

its estimates of fuel consumption and GHG emissions are reported and discussed in Section 2.4 of this 

EIS. 

Table 2.2-1 

Forecasts, Assumptions, and Parameters 

Used to Analyze Impacts of Regulatory Alternatives 

Fuel Economy Rebound Effect 10%

"Gap" between Test and On-road MPG 20%

Value of Refueling Time ($ per vehicle-hour) $ 24.64

Annual growth in average vehicle use 1.15%

Fuel Prices (2012-50 average, $/gallon) 

Retail gasoline price $ 3.66

Pre-tax gasoline price $ 3.29

Economic Benefits from Reducing Oil Imports ($/gallon) $ 0.17

Emission Damage Costs (2020, $/ton or $/metric ton) 

Carbon monoxide (CO) $ 0

Volatile organic compounds (VOCs) $ 1,300

Nitrogen oxides (NOx) – vehicle use $ 5,300

Nitrogen oxides (NOx) – fuel production and distribution $ 5,100

Particulate matter (PM2.5) – vehicle use $ 290,000

Particulate matter (PM2.5) – fuel production and distribution $ 240,000

Sulfur dioxide (SO2) $ 31,000

Carbon dioxide (CO2) $ 56a/

Annual Increase in CO2 Damage Cost 3%

External Costs from Additional Automobile Use ($/vehicle-mile) 

Congestion $ 0.054

Accidents $ 0.023

Noise $ 0.001

Total External Costs $ 0.078

 2-10 
Chapter 2 Proposed Action and Alternatives 

 2-11 

Table 2.2-1 

Forecasts, Assumptions, and Parameters 

Used to Analyze Impacts of Regulatory Alternatives 

External Costs from Additional Light Truck Use ($/vehicle-mile) 

Congestion $ 0.048

Accidents $ 0.026

Noise $ 0.001

Total External Costs $ 0.075

Discount Rate Applied to Future Benefits 3%

Reduction in Consumer Benefits from Potential Welfare Losses b/ 0%

__________

a/ Federal government agencies are working toward, but do not yet have, an agreed-upon estimate 

for the social cost of carbon (SCC) to support federal regulatory activities where reducing CO2

emissions is an important potential outcome. Nevertheless, NHTSA is obligated under EPCA to 

issue a CAFE rule regardless of whether there is a uniform federal government view on the 

SCC. For the analysis in the FEIS, the agency modeled a primary SCC value of $56, and then 

conducted a sensitivity analysis using $10 (see Section 2.4). However, neither of these values 

is necessarily the estimate of SCC that the agency will ultimately select for valuing reductions in 

CO2 emissions in the final rule. The SCC used in the Volpe model in the Final EIS allows the 

stringency of the CAFE standards for the MNB Alternative and the TCTB Alternative to be higher 

than they would be for a lower valuation of SCC. This results in higher fuel savings and greater 

changes in environmental impacts for these alternatives than would result from using a lower 

SCC value in the model. The intent of this is to demonstrate the maximum differences in 

environmental impacts among the alternatives. The environmental impacts of the action 

alternatives other than the MNB Alternative and the TCTB Alternative are not significantly 

affected by the valuation of social cost of carbon in the model, as shown in Table 2.4-1. 

 In contrast, the SCC value that was used in the main NPRM and DEIS analysis was the $20/ton 

central value, based on interagency efforts to develop estimates of this value for governmentwide use. NHTSA notes that it was this $20/ton SCC value that was intended to represent the 

federal government’s interim “central” estimate of the SCC. The $56/ton SCC value was 

considered the “high” interim interagency SCC value for purposes of the NPRM and DEIS 

analysis. See section VI.C.3.l.iii of the NPRM, Chapter 4 of the draft joint TSD, and Chapter VIII 

of the PRIA for detail concerning the interim low, central, and high interagency guidance 

regarding SCC. NHTSA utilizes the $56 figure only in order to demonstrate the maximum 

potential environmental impacts, and not because the agency regards it as a more likely 

estimate of the “true” SCC. Detailed descriptions of the rationale underlying each economic 

assumption, and the agency’s choices of specific parameter values will be provided in the 

forthcoming joint NHTSA-EPA Final Rule and NHTSA’s forthcoming RIA, as well as the 

forthcoming joint EPA-NHTSA final TSD for fuel economy and motor vehicle CO2 emission 

standards. 

b/ The assumption used in the main analysis is that there is a zero percent reduction in consumer 

benefits from potential welfare losses to vehicle buyers or overestimation of the value of fuel 

savings, i.e., there are no losses in consumer welfare or errors in estimating the value of fuel 

savings that would reduce the agency’s estimates of the benefits to vehicle buyers from 

requiring higher fuel economy. This assumption is varied in the sensitivity analysis. See section 

2.4 (Sensitivity Analysis) for an explanation of why consumer benefits could theoretically be 

reduced due to potential welfare losses. 

2.3 ALTERNATIVES 

EPCA, as amended by EISA, requires NHTSA to adopt attribute-based fuel economy standards 

for passenger cars and light trucks. NHTSA first employed this approach (then called “Reformed 
Chapter 2 Proposed Action and Alternatives 

 2-12 

CAFE”) in establishing standards for MYs 2008-2011 light trucks.9 In May 2008, NHTSA proposed 

separate standards for MYs 2011-2015 passenger cars and light trucks, again using this approach.10 On 

March 30, 2009, NHTSA issued a final rule for MY 2011 passenger cars and light trucks, again using this 

approach.11 

Under the standards, fuel economy targets are established for vehicles of different sizes. Each 

manufacturer’s required level of CAFE is based on its distribution of vehicles among those sizes and the 

fuel economy target required for each size. Size is defined by vehicle footprint.12 The fuel economy 

target for each footprint reflects the technological and economic capabilities of the industry. These 

targets are the same for all manufacturers, regardless of the differences in their overall fleet mix. 

Compliance is determined by comparing a manufacturer’s harmonically averaged fleet fuel economy 

levels in a model year with an average required fuel economy level calculated using the manufacturer’s 

actual production levels and the targets for each footprint of the vehicles that it produces. 

NHTSA must establish separate standards for MYs 2011-2020 passenger cars and light trucks. 

The standards are subject to a minimum requirement regarding stringency: they must be set at levels high 

enough to ensure that the combined U.S. passenger-car and light-truck fleet achieves an average fuel 

economy level of not less than 35 mpg not later than MY 2020.13 Additionally, EPCA, as amended by 

EISA, requires that the CAFE standards for passenger cars and light trucks increase ratably in each model 

year between MY 2011 and MY 2020. Standards must be “based on one or more vehicle attributes 

related to fuel economy,” and “expressed in the form of a mathematical function.”14 

A large number of alternatives can be defined along a continuum from the least to the most 

stringent levels of potential CAFE standards. The specific alternatives NHTSA examined, described 

below, encompass a reasonable range to evaluate the potential environmental impacts of the CAFE 

standards and alternatives under NEPA, in view of EPCA requirements. 

At one end of this range is the No Action Alternative (Alternative 1), which assumes no action 

would occur under the National Program. Under that alternative, neither NHTSA nor EPA would issue a 

rule regarding the CAFE standard or GHG emissions for MYs 2012-2016. The No Action Alternative 

assumes that average fuel economy levels in the absence of CAFE standards beyond MY 2011 would 

equal the higher of the agencies’ collective market forecast or the manufacturer’s required level of 

average fuel economy for MY 2011. The MY 2011 fuel economy level represents the standard NHTSA 

believes manufacturers would continue to achieve, assuming NHTSA does not issue a rule. Costs and 

benefits of other alternatives are calculated relative to the baseline of the No Action Alternative. The No 

Action Alternative, by definition, would yield no incremental costs or benefits (and thus it would not 

satisfy the EPCA requirement to set standards such that the combined fleet achieves a combined average 

 

9 See Average Fuel Economy Standards for Light Trucks, Model Years 2008-2011, 71 FR 17566, 17587-17625, 

(Apr. 6, 2006) (describing this approach). 

10 Notice of Proposed Rulemaking; Average Fuel Economy Standards, Passenger Cars and Light Trucks; Model 

Years 2011-2015, 73 FR 24352 (May 2, 2008). The proposed standards include light truck standards for one model 

year (MY 2011) that were previously covered by a 2006 final rule, Average Fuel Economy Standards for Light 

Trucks, Model Years 2008-2011, 71 FR 17566 (Apr. 6, 2006). 

11 See Average Fuel Economy Standards Passenger Cars and Light Trucks Model Year 2011, 74 FR 14196 (Mar. 30, 

2009). 

12 A vehicle’s footprint is generally defined as “the product of track width [the lateral distance between the 

centerlines of the base tires at ground, including the camber angle] ... times wheelbase [the longitudinal distance 

between front and rear wheel centerlines] ... divided by 144 ....” 49 CFR § 523.2. 

13 49 U.S.C. § 32902(b)(2)(A). 

14 49 U.S.C. § 32902(b)(3)(A). 
Chapter 2 Proposed Action and Alternatives 

 2-13 

fuel economy of at least 35 mpg for MY 2020; nor would it satisfy the EPCA requirement to adopt annual 

fuel economy standard increases).15 

NHTSA is also considering eight action alternatives. Alternative 2 (3-Percent Alternative), 

Alternative 3 (4-Percent Alternative), Alternative 5 (5-Percent Alternative), Alternative 7 (6-Percent 

Alternative), and Alternative 8 (7-Percent Alternative), require the average fuel economy for the industrywide combined passenger car and light truck fleet to increase, on average, by a specified percentage for 

each model year from 2012-2016. Because the percentage increases in stringency are “average” 

increases, they may either be constant throughout the period or may vary from year to year. For a variety 

of reasons, the annual rates of increase in achieved mpg levels for passenger cars and light trucks 

separately will not exactly equal the rates of increase in combined passenger car and light truck required 

average mpg levels under each alternative. These include the fact that under some alternatives, separate 

required mpg levels for passenger cars and light trucks might not necessarily increase at annual rates that 

are identical to those for the combined standard. 

NHTSA also added three alternatives to the list of alternatives first proposed in the NOI – the 

agency’s Preferred Alternative (Alternative 4), an alternative that maximizes net benefits (MNB) 

(Alternative 6), and an alternative under which total cost equals total benefit (TCTB) (Alternative 9). The 

agency’s Preferred Alternative represents the required fuel economy level that we have tentatively 

determined to be the maximum feasible under EPCA, based on our balancing of statutory considerations. 

See Section 2.1. The other two alternatives, MNB and TCTB, represent fuel economy levels that are 

dependent on the agency’s best estimate of relevant economic variables (e.g., gasoline prices, social cost 

of carbon, the discount rate, and rebound effect). See Section 2.2.4. The MNB Alternative and TCTB 

Alternative provide the decisionmaker and the public with useful information about where the standards 

would be set if costs and benefits were balanced in two different ways. All three alternatives (Preferred 

Alternative, MNB Alternative, and TCTB Alternative) are placed in context by identifying 

the approximate, on average, annual percentage fuel economy increase, so that the public is able to see 

where they fall on the continuum of alternatives. 

Each of the alternatives considered by NHTSA represent, in part, a different way in which 

NHTSA conceivably could weigh EPCA’s statutory requirements and account for NEPA’s policies. For 

example, the 7-Percent Alternative weighs energy conservation and climate change considerations more 

heavily and technological feasibility and economic practicability less heavily. In contrast, the 3-Percent 

Alternative, the least stringent action alternative evaluated here, places more weight on technological 

feasibility and economic practicability. The “feasibility” of the alternatives also may reflect differences 

and uncertainties in the way in which key economic (e.g., the price of fuel and the social cost of carbon) 

and technological inputs could be assessed and estimated or valued. For additional detail and discussion 

of how NHTSA considers the EPCA statutory and other factors that guide the agency’s determination of 

“maximum feasible” standards, and inform an evaluation of the alternatives, we refer the reader to section 

IV.F of the NPRM. For detailed calculations and discussions of manufacturer cost impacts and estimated 

benefits for each of the DEIS alternatives, see Sections VII and VIII of NHTSA’s PRIA. 

 

15 Although EISA’s recent amendments to EPCA direct NHTSA to increase CAFE standards and do not permit the 

agency to take no action on fuel economy, CEQ regulations mandate analysis of a no action alternative. See 40 CFR 

§ 1502.14(d). CEQ has explained that “the regulations require the analysis of the no action alternative even if the 

agency is under a court order or legislative command to act.” Forty Most Asked Questions Concerning CEQ’s 

National Environmental Policy Act Regulations, 46 FR 18026 (1981) (emphasis added). 
Chapter 2 Proposed Action and Alternatives 

 2-14 

2.3.1 Alternative 1: No Action 

The No Action Alternative assumes that no action would occur under CAFE (or under the 

National Program).16 Under this alternative, NHTSA would not issue a rule regarding CAFE standards 

for MYs 2012-2016. As explained above, the No Action Alternative assumes that average fuel economy 

levels in the absence of CAFE standards beyond MY 2011 would equal the higher of the agencies’ 

collective market forecast or the manufacturer’s required level of average fuel economy for MY 2011. 

The No Action MY 2016 achieved mpg forecast represents the market forecast for mpg, assuming that 

NHTSA does not issue a rule.17 

NEPA requires agencies to consider a No Action Alternative in their NEPA analyses,18 although 

the recent amendments to EPCA direct NHTSA to set new CAFE standards and do not permit the agency 

to take no action on fuel economy. 19 In the NPRM, NHTSA refers to the No Action Alternative as the no 

increase or baseline alternative. 

2.3.2 Alternative 2: 3-Percent Alternative 

The 3-Percent Alternative requires a 3-percent average annual increase in mpg, resulting in a 

required MY 2016 fleetwide 35.5 mpg for passenger cars and 26.9 mpg for light trucks. The 3-Percent 

Alternative also results in a combined required fleetwide 32.0 mpg in MY 2016. 

2.3.3 Alternative 3: 4-Percent Alternative 

The 4-Percent Alternative requires a 4-percent average annual increase in mpg, resulting in a 

required MY 2016 fleetwide 37.2 mpg for passenger cars and 28.2 mpg for light trucks. The 4-Percent 

Alternative also results in a combined required fleetwide 33.6 mpg in MY 2016. 

2.3.4 Alternative 4: Preferred Alternative 

The Preferred Alternative requires approximately a 4.3-percent average annual increase in mpg, 

resulting in an estimated required MY 2016 fleetwide 37.8 mpg for passenger cars and 28.7 mpg for light 

trucks. The Preferred Alternative also results in a combined estimated required fleetwide 34.1 mpg in 

MY 2016. The agency’s Preferred Alternative represents the required fuel economy level that we have 

tentatively determined to be the maximum feasible under EPCA, based on our balancing of statutory 

considerations. A full discussion regarding the agency’s conclusion that Alternative 4 represents the 

“maximum feasible” average fuel economy level that the Secretary decides the manufacturers can 

achieve, considering the statutory and other relevant factors and is therefore the agency’s Preferred 

Alternative will be found in the forthcoming joint NHTSA-EPA Final Rule. 

 

16 Several commenters to the DEIS noted that the No Action Alternative should take into account state 

implementation of GHG standards in the absence of federal action. NHTSA has retained the No Action Alternative 

as defined in the DEIS without change. Although we agree that a number of states would likely enforce California 

GHG standards absent federal action, we believe that no change is necessary to the No Action Alternative under 

NEPA to properly inform the decisionmaker. For a full discussion of this issue, see the agency’s response to 

comments in section 10.2.4.2 of this EIS. 17 See 40 CFR §§ 1502.2(e) and 1502.14(d). 18 See 40 CFR § 1502.14(d). 

19 CEQ regulations mandate analysis of a no action alternative. See 40 CFR § 1502.14(d). CEQ has explained that 

“the regulations require the analysis of the no action alternative even if the agency is under a court order or 

legislative command to act.” Forty Most Asked Questions Concerning CEQ’s National Environmental Policy Act 

Regulations, 46 FR 18026 (1981) (emphasis added). 
Chapter 2 Proposed Action and Alternatives 

This alternative, along with EPA’s light-duty vehicle GHG emission standards, form the National 

Program and are consistent with the National Fuel Efficiency Policy announced by President Obama on 

May 19, 2009. Under the National Program, the overall light-duty vehicle fleet would reach 35.5 mpg in 

MY 2016, if all reductions were made through fuel economy improvements. 

2.3.5 Alternative 5: 5-Percent Alternative 

The 5-Percent Alternative requires a 5-percent average annual increase in mpg, resulting in a 

required MY 2016 fleetwide 39.1 mpg for passenger cars and 29.6 mpg for light trucks. The 5-Percent 

Alternative also results in a required achieved fleetwide 35.2 mpg in MY 2016. 

2.3.6 Alternative 6: MNB Alternative 

In the MNB Alternative, the Volpe model applies technologies to the vehicle market forecast 

until marginal benefits are estimated to equal marginal costs and net benefits are maximized. In this case, 

the model continues to include technologies until the marginal cost of adding the next technology exceeds 

the marginal benefit. This alternative requires approximately a 6.0-percent average annual increase in 

mpg, resulting in a required MY 2016 fleetwide 40.9 mpg for passenger cars and 31.0 mpg for light 

trucks. The MNB Alternative also results in a combined required fleetwide 36.9 mpg in MY 2016. 

2.3.7 Alternative 7: 6-Percent Alternative 

The 6-Percent Alternative requires a 6-percent average annual increase in mpg, resulting in a 

required MY 2016 fleetwide 40.9 mpg for passenger cars and 31.0 mpg for light trucks. The 6-Percent 

Alternative also results in a combined required fleetwide 36.9 mpg in MY 2016. 

The 6-Percent Alternative results in required mpg in 2016 that is equal to the required mpg under 

the MNB Alternative, but required mpg in 2012 through 2015 under the 6-percent Alternative is actually 

slightly lower than under the MNB Alternative. In general, the net result is that there is very little 

substantive difference in required mpg under the 6-percent and MNB Alternatives. 

2.3.8 Alternative 8: 7-Percent Alternative 

The 7-Percent Alternative requires a 7-percent average annual increase, resulting in a required 

MY 2016 fleetwide 42.9 mpg for passenger cars and 32.6 mpg for light trucks. The 7-Percent Alternative 

also results in a combined required fleetwide 38.7 mpg in MY 2016. 

2.3.9 Alternative 9: TCTB Alternative 

In the TCTB Alternative, the Volpe model applies technologies to the vehicle market forecast 

until total costs equal total benefits. In this case, the model increases the standard to a point where 

essentially total costs of the technologies added together over the baseline equals total benefits added over 

the baseline. This alternative requires approximately a 6.6-percent on average annual increase in mpg, 

resulting in a required MY 2016 fleetwide 42.3 mpg for passenger cars and 31.8 mpg for light trucks. 

The TCTB Alternative also results in a combined required fleetwide 38.0 mpg in MY 2016. 

The TCTB Alternative results in required mpg in 2016 that is just slightly lower than required 

mpg under the 7-Percent Alternative, but required mpg in 2012 through 2015 under the TCTB Alternative 

is slightly higher than under the 7-Percent Alternative. In general, the net result is that there is very little 

substantive difference in required mpg under the 7-Percent and TCTB Alternatives. 

 2-15 
Chapter 2 Proposed Action and Alternatives 

2.3.10 Fuel Economy Levels for Each Alternative 

As explained in Sections 1.2.2.2 and 2.2, the CAFE levels required under an attribute-based 

standard depend on the mix of vehicles produced for sale in the United States. The average fuel economy 

levels actually achieved by passenger cars and light trucks in a given model year may differ from the 

required CAFE levels for that model year. This occurs because some manufacturers’ average fuel 

economy levels for their vehicles are projected to exceed the applicable CAFE standards during certain 

model years, while other manufacturers’ fuel economy levels are projected to fall short of either the 

passenger car or light truck CAFE standards during some model years. Table 2.3-1 shows the fuel 

economy levels that would be required for each alternative not taking into account credits. 

Table 2.3-1 

Required MPG by Alternative 

Alt. 1 Alt. 2 Alt. 3 Alt. 4 Alt. 5 Alt. 6 Alt. 7 Alt. 8 Alt. 9 

No 

Action 

3%/year 

Increase 

4%/year 

Increase 

~4.3%/year

Increase 

Preferred 

5%/year 

Increase

~6.0%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.6%/year 

Increase 

 TCTB 

2012 

Passenger 

Cars 30.5 31.8 32.1 33.4 32.4 33.1 32.7 33.0 33.4

Light Trucks 24.4 24.3 24.3 25.3 24.6 26.3 24.8 25.1 26.3

Combined 27.8 28.4 28.6 29.7 28.8 30.1 29.1 29.4 30.3

2013 

Passenger 

Cars 30.5 32.6 33.3 34.2 33.9 36.1 34.6 35.2 36.7

Light Trucks 24.4 24.8 25.3 25.9 25.7 27.8 26.2 26.7 28.0

Combined 27.8 29.1 29.7 30.5 30.3 32.4 30.8 31.4 32.8

2014 

Passenger 

Cars 30.5 33.6 34.6 35.0 35.5 38.1 36.6 37.6 39.2

Light Trucks 24.5 25.5 26.2 26.6 27.0 29.2 27.8 28.6 29.7

Combined 28.0 30.1 30.9 31.3 31.8 34.3 32.7 33.7 35.0

2015 

Passenger 

Cars 30.5 34.4 35.8 36.2 37.2 39.6 38.6 40.1 40.7

Light Trucks 24.4 26.1 27.1 27.5 28.2 30.3 29.3 30.4 30.7

Combined 28.0 31.0 32.2 32.6 33.4 35.7 34.7 36.1 36.5

2016 

Passenger 

Cars 30.5 35.5 37.2 37.8 39.1 40.9 40.9 42.9 42.3

Light Trucks 24.4 26.9 28.2 28.7 29.6 31.0 31.0 32.6 31.8

Combined 28.1 32.0 33.6 34.1 35.2 36.9 36.9 38.7 38.0

Analyzing the environmental impacts of these alternatives provides information on the full 

spectrum of CAFE choices reasonably available to the decisionmaker. Although NEPA requires – and 

this EIS analyzes – a full spectrum of alternatives, NHTSA is obligated by EPCA to consider additional 

requirements and factors in setting “maximum feasible” CAFE standards: (1) technological feasibility, 

 2-16 
Chapter 2 Proposed Action and Alternatives 

 2-17 

(2) economic practicability, (3) the effect of other motor vehicle standards of the Government on fuel 

economy, and (4) the need of the Nation to conserve energy. 20 

Table 2.3-2 shows the estimated 21 achieved fuel economy levels for each alternative. Comparing 

Table 2.3-1 with Table 2.3-2 shows that estimated achieved combined mpg in 2016 would actually 

exceed required mpg under the No Action Alternative, indicating that some manufacturers would exceed 

the no action required mpg. Under other action alternatives, the estimated achieved mpg in 2016 would 

be somewhat lower than the required mpg levels because some manufacturers are not expected to meet 

passenger car or light truck standards under some alternatives.22 Estimated achieved and required fuel 

economy levels differ because manufacturers will, on average, undercomply23 in some model years and 

overcomply24 in others.25

 

20 49 U.S.C. § 32902(f). 

21 As discussed above, the CAFE level required under an attribute-based standard depends on the mix of vehicles 

produced for sale in the United States. NHTSA has developed the average mpg levels under each alternative based 

on the vehicle market forecast that NHTSA and EPA have used to develop and analyze new CAFE and CO2

emissions standards. 

22 Based on the agency’s analysis of technology application by manufacturers, given the different levels of 

stringency represented by the different alternatives, some of the more stringent alternatives might require so much 

more additional technology to be applied to vehicles that, although that level/amount of technology might be 

feasible for individual vehicle models, it would be beyond the realm of technological feasibility or economic 

practicability for the industry as a whole. Although NHTSA cannot predict how manufacturers will respond to the 

alternative CAFE standards, and although the agency’s Volpe model analysis evaluates only one possible way that 

manufacturers could comply with whatever given level of CAFE standards, NHTSA believes that some of the more 

stringent alternatives may involve levels of technology and cost that, considering the current state of the automotive 

industry, would not be technologically feasible or economically practicable. See joint NHTSA-EPA NPRM, 74 FR 

49454, 49695-49707. 

23 In NHTSA’s analysis, “undercompliance” is mitigated either through use of flex-fuel vehicle (FFV) credits, use of 

existing or “banked” credits, or through fine payment. Because NHTSA cannot consider availability of credits in 

setting standards, the estimated achieved CAFE levels presented here do not account for their use. In contrast, 

because NHTSA is not prohibited from considering fine payment, the estimated achieved CAFE levels presented 

here include the assumption that BMW, Daimler (i.e., Mercedes), Porsche, and Tata (i.e., Jaguar and Rover) will 

only apply technology up to the point that it would be less expensive to pay civil penalties. 

24 In NHTSA’s analysis, “overcompliance” occurs through multi-year planning: manufacturers apply some “extra” 

technology in early model years (e.g., MY 2014) in order to carry that technology forward and thereby facilitate 

compliance in later model years (e.g., MY 2016). 25 Consistent with EPCA, NHTSA has not accounted for manufacturers’ ability to earn CAFE credits for selling 

FFVs, carry credits forward and back between model years, and transfer credits between the passenger car and light 

truck fleets when setting standards. However, to begin understanding the extent to which use of credits might 

reduce manufacturers’ compliance costs and the benefits of new CAFE standards, NHTSA does analyze the 

potential effects of provisions regarding FFVs. See Section 3.1.4.1. 
Chapter 2 Proposed Action and Alternatives 

Table 2.3-2 

Achieved MPG by Alternative 

Alt. 1 Alt. 2 Alt. 3 Alt. 4 Alt. 5 Alt. 6 Alt. 7 Alt. 8 Alt. 9 

No 

Action 

3%/year 

Increase 

4%/year 

Increase 

~4.3%/year

Increase 

Preferred 

5%/year 

Increase

~6.0%/year 

Increase 

MNB 

6%/year 

Increase

7%/year 

Increase 

~6.6%/year 

Increase 

TCTB 

2012 

Passenger 

Cars 32.1 32.6 32.9 33.1 33.0 33.3 33.2 33.4 33.5

Light Trucks 24.3 24.5 24.6 25.0 24.9 25.5 25.0 25.1 25.5

Combined 28.5 28.9 29.1 29.4 29.3 29.8 29.5 29.6 29.8

2013 

Passenger 

Cars 32.4 33.8 34.4 34.9 35.1 36.1 35.6 36.1 36.4

Light Trucks 24.5 25.1 25.5 26.0 26.0 27.2 26.5 26.9 27.4

Combined 28.9 29.8 30.3 30.9 30.9 32.1 31.5 32.0 32.3

2014 

Passenger 

Cars 32.5 34.2 35.3 35.8 36.2 37.7 37.0 37.9 38.2

Light Trucks 24.7 25.8 26.4 26.9 27.3 28.8 28.1 28.8 29.1

Combined 29.1 30.6 31.4 31.9 32.4 33.9 33.1 33.9 34.2

2015 

Passenger 

Cars 32.4 34.8 36.3 36.7 37.4 38.9 38.4 39.3 39.4

Light Trucks 24.7 26.4 27.2 27.5 28.2 29.8 29.3 30.2 30.2

Combined 29.2 31.3 32.4 32.8 33.5 35.1 34.6 35.5 35.6

2016 

Passenger 

Cars 32.4 35.7 37.3 37.7 38.8 40.2 40.3 41.3 41.0

Light Trucks 24.7 26.8 28.0 28.4 29.3 30.5 30.5 31.4 31.1

Combined 29.3 32.1 33.5 33.9 34.9 36.3 36.3 37.2 37.0

2.3.11 Greenhouse Gas Emission Standards for Light-duty Vehicles 

As explained above, NHTSA’s proposed action is one part of a National Program consisting of 

new standards for light-duty vehicles that will improve fuel economy and reduce GHG emissions. EPA 

has proposed greenhouse gas emissions standards under Section 202(a) of the CAA, and NHTSA has 

proposed CAFE standards under EPCA, as amended. EPA’s proposed standards would require light-duty 

vehicles to meet an estimated combined average emissions level of 250 grams per mile (g/mi) of CO2 in 

MY 2016. The proposed standards for both agencies begin with MY 2012, with standards increasing in 

stringency through MY 2016. They represent a harmonized approach that will allow industry to build a 

single national fleet that will satisfy both the GHG requirements under the CAA and CAFE requirements 

under EPCA/EISA. Given differences in their respective statutory authorities, however, the agencies’ 

proposed standards include some important differences. Refer to Section 3.7 for a discussion of these 

differences. 

 2-18 
Chapter 2 Proposed Action and Alternatives 

 2-19 

EPA is proposing GHG emissions standards, and Table 2.3-3 provides EPA’s estimates of its 

projected overall fleet-wide CO2 equivalent emission levels.26 The g/mi values are CO2 equivalent values 

because they include the projected use of air conditioning credits by manufacturers. 

Table 2.3-3 

Projected Fleet-Wide Emissions Compliance Levels under the Proposed 

Footprint-Based CO2 Standards (g/mi) 

2012 2013 2014 2015 2016 

Passenger Cars 261 253 246 235 224 

Light Trucks 352 341 332 317 302 

Combined Cars & Trucks 295 286 276 263 250 

As shown in Table 2.3-3, fleet-wide CO2 emission level requirements for cars under the proposed 

approach are projected to increase in stringency from 261 to 224 grams per mile between MY 2012 and 

MY 2016. Similarly, fleet-wide CO2 equivalent emission level requirements for trucks are projected to 

increase in stringency from 352 to 302 g/mi. As shown, the overall fleet average CO2 level requirements 

are projected to be 250 g/mi in 2016. 

EPA anticipates that manufacturers will take advantage of program flexibilities such as flex 

fueled vehicle credits, and car/truck credit trading. Due to the credit trading between cars and trucks, the 

estimated improvements in CO2 emissions are distributed differently than shown in Table 2.3-3, where 

full manufacturer compliance is assumed. Table 2.3-4 shows EPA projection of the achieved emission 

levels of the fleet for MYs 2012-2016, which does consider the increase in emissions due to program 

flexibilities such as the flex fueled vehicle credits, as well as the impact of car/truck trading and optional 

air conditioning credits. As shown in Table 2.3-4, the projected achieved levels are slightly higher for 

MYs 2012-2015 due to the projected use of the proposed flexibilities, but in MY 2016 the achieved value 

is projected to be 250 g/mi for the fleet. 

Table 2.3-4 

Projected Fleet-Wide Achieved Emission Levels under the Proposed 

Footprint-Based CO2 Standards (g/mi) 

2012 2013 2014 2015 2016 

Passenger Cars 264 254 245 232 220 

Light Trucks 365 355 346 332 311 

Combined Cars & Trucks 302 291 281 267 250 

2.4 SENSITIVITY ANALYSIS 

There are many variations in economic assumptions that can be used to examine the sensitivity of 

costs and benefits for each of the alternatives, including future fuel prices, the value of reducing CO2

emissions (referred to as the social cost of carbon or SCC), the discount rate, the magnitude of the 

rebound effect, and the value of oil import externalities. Different combinations of economic assumptions 

can also affect the calculation of environmental impacts of the various action alternatives. This occurs 

partly because some economic inputs to the Volpe model – notably fuel prices and the size of the rebound 

effect – influence its estimates of vehicle use and fuel consumption, the main factors that determine 

 

26 These levels do not include the effect of flexible fuel credits, transfer of credits between cars and trucks, 

temporary lead time allowance, or any other credits with the exception of air conditioning. 
Chapter 2 Proposed Action and Alternatives 

 2-20 

emissions of GHGs, criteria air pollutants, and airborne toxics. In addition, changes in economic 

assumptions may affect the fuel economy levels required under the action alternatives established on the 

basis of economic benefits and costs (i.e., Alternative 6 (MNB) and Alternative 9 (TCTB)). 

The direct, indirect, and cumulative environmental impacts of the proposed CAFE Alternatives 

examined in this EIS reflect the following combination of economic inputs to the Volpe model, referred 

to as the “Expected Value27” model inputs: 

• Annual Energy Outlook (AEO) 2010 Early Release Reference Case fuel price forecast; 

• 3-percent discount rate used to determine present value of future costs and benefits; 

• 10-percent rebound effect (the estimated increase in driving due to higher fuel economy 

standards and its effect on the cost per mile traveled); 

• $56 SCC (dollar value of per metric ton of CO2 emission reductions);28

• $0.17 reduction in oil import externalities per gallon of fuel saved (reduction in 

macroeconomic costs of oil price shocks only; includes no reduction in monopsony payments 

to oil producers or in military security outlays associated with oil imports). 

NHTSA selected these values based on the best available information and data, but the agency 

recognizes that the forecasts and assumptions they reflect are subject to considerable uncertainty. For 

example, as noted in Table 2.2-1, the assumption used in the main analysis is that NHTSA’s estimates of 

consumer benefits accurately reflect those perceived by potential vehicle buyers, that is, the agency has 

correctly estimated the value of fuel savings that buyers will experience, and no potential welfare losses 

to vehicle buyers will result from manufacturers’ efforts to increase fuel economy. It is possible, 

 

27 The tern “Expected Value” is used as defined in this section and does not refer to the term’s normal mathematical 

definition. 

28 Federal government agencies are working toward, but do not yet have, an agreed-upon estimate for the social cost 

of carbon (SCC) to support federal regulatory activities where reducing CO2 emissions is an important potential 

outcome. Nevertheless, NHTSA is obligated under EPCA to issue a CAFE rule regardless of whether there is a 

uniform federal government view on the SCC. For the analysis in the FEIS, the agency modeled a primary SCC 

value of $56, and then conducted a sensitivity analysis using $10 (see Section 2.4). However, neither of these values 

is necessarily the estimate of SCC that the agency will ultimately select for valuing reductions in CO2 emissions in 

the final rule. The SCC used in the Volpe model in the FEIS allows the stringency of the CAFE standards for the 

MNB Alternative and the TCTB Alternative to be higher than they would be for a lower valuation of SCC. This 

results in higher fuel savings and greater changes in environmental impacts for these alternatives than would result 

from using a lower SCC value in the model. The intent of this is to demonstrate the maximum differences in 

environmental impacts among the alternatives. The environmental impacts of the action alternatives other than the 

MNB Alternative and the TCTB Alternative are not significantly affected by the valuation of SCC in the model, as 

shown in Table 2.4-1. 

In contrast, the SCC value that was used in the main NPRM and DEIS analysis was the $20/ton central value, based 

on interagency efforts to develop estimates of this value for government-wide use. NHTSA notes that it was this 

$20/ton SCC value that was intended to represent the federal government’s interim “central” estimate of the SCC. 

The $56/ton SCC value was considered the “high” interim interagency SCC value for purposes of the NPRM and 

DEIS analysis. See section VI.C.3.l.iii of the NPRM, Chapter 4 of the draft joint TSD, and Chapter VIII of the 

PRIA for detail concerning the interim low, central, and high interagency guidance regarding SCC. NHTSA utilizes 

the $56 figure only in order to demonstrate the maximum potential environmental impacts, and not because the 

agency regards it as a more likely estimate of the “true” SCC. Detailed descriptions of the rationale underlying each 

economic assumption, and the agency’s choices of specific parameter values will be provided in the forthcoming 

joint NHTSA-EPA Final Rule and NHTSA’s forthcoming RIA, as well as the forthcoming joint EPA-NHTSA final 

TSD for fuel economy and motor vehicle CO2 emission standards. 
Chapter 2 Proposed Action and Alternatives 

however, that the agency’s estimates of benefits from improving fuel efficiency overstate the benefits that 

potential vehicle buyers believe they will actually experience, or that the agency has failed to account for 

changes in other vehicle attributes that will be necessary for manufacturers to comply with higher fuel 

economy standards. 

Specifically, buyers might not value increased fuel economy as highly as the agency’s 

calculations suggest, either because they have shorter time horizons than the expected vehicle lifetimes 

assumed by NHTSA, or because they discount future fuel savings at rates higher than the 3-percent 

discount rate used by the agency. Potential buyers might also anticipate lower fuel prices in the future 

than those forecast by EIA, or they might expect larger differences between vehicles’ rated and actual onroad mpg levels than the agency projects. Achieving the fuel economy improvements required by stricter 

CAFE standards could also require manufacturers to compromise the performance, passenger- and cargocarrying capacity, safety, or other features of some vehicle models. This could reduce the overall utility 

that those models offer to their owners, despite the fact that the agency’s analysis of feasibility was 

designed to allow manufacturers to hold these attributes constant while still achieving the desired levels 

of fuel economy. If this occurs, it could be viewed by potential buyers as a loss in welfare associated with 

requiring higher fuel economy, which NHTSA would have failed to acknowledge or deduct from its 

estimates of benefits from requiring higher fuel economy. 

As a way of evaluating the potential effect of this issue, NHTSA has included several alternative 

estimates of reductions in consumer benefits in the sensitivity analysis. These runs are labeled in the last 

three lines of Table 2.4-1 as 25% Consumer Benefits, 50% Consumer Benefits, and 75% Consumer 

Benefits. The 25% Consumer Benefits sensitivity run assumes that the actual benefits to consumers from 

higher fuel economy are only 25 percent as large as NHTSA’s estimate, either because the agency has 

overestimated the value of fuel savings to vehicle owners or because of accompanying changes in vehicle 

attributes that result in losses in consumer welfare. Similarly, the 50% Consumer Benefits sensitivity run 

assumes that the true benefits of fuel savings to buyers are only half as large as the agency’s estimate, 

while the 75% Consumer Benefits sensitivity run assumes that 25 percent of consumer benefits from 

higher fuel economy represents an overestimate of the value of fuel savings, or are offset by losses in 

consumer welfare. All other model inputs used in these sensitivity runs are the Expected Value inputs. 

We emphasize that, as illustrated in Table 2.4-1, for most of the alternatives fuel consumption is 

not sensitive to this assumption. Alternative 6 and Alternative 9 (the MNB and TCTB alternatives) are 

sensitive to this assumption because the stringency of these alternatives is determined by relating benefits 

to costs. Therefore, any reduction in benefits will reduce the stringency of CAFE standards that would be 

established by each of these alternatives, thus increasing total fuel consumption under each alternative. 

Because environmental impacts associated with each action alternative are derived primarily from 

changes in total fuel consumption from its baseline level under the No Action Alternative, the 

environmental impacts associated with most action alternatives are not sensitive to changes in the 

assumption regarding reduced consumer benefits due to overestimation of the value of fuel savings, or 

potential welfare losses. 

The agency recognizes that, with respect to Alternatives 6 and 9, both the achieved fuel economy 

standards and resulting environmental impacts under Alternatives 6 and 9 depend, in part, on the choice 

of inputs utilized by the Volpe model. Table 2.4-1 presents a sensitivity analysis of how changes in key 

economic variables, including fuel price projections, the value of reducing CO2 emissions, oil import 

externalities, consumer benefits losses, and the rebound effect influence the estimates of total fuel 

consumption over the period from 2012 to 2060 for selected Alternatives. The change in projected 2012-

2060 fuel consumption associated with different economic inputs to the Volpe model also indicates the 

magnitude of related changes in emissions of criteria air pollutants, greenhouse gases, and airborne toxics, 

as well as in their associated environmental impacts. Table 2.4-1 shows that fuel consumption is 

 2-21 
Chapter 2 Proposed Action and Alternatives 

relatively sensitive to fuel price projections, and somewhat sensitive to the estimated rebound effect, but 

relatively insensitive to changes in model input values for the discount rate, SCC, consumer benefit 

losses, and oil import externalities. 

Table 2.4-1 

Sensitivity Analysis of Fuel Consumption (2012-2060; billion gallons) under Expected Value Model 

Input Assumptions versus other Model Input Assumptions for Selected Alternatives 

Alt. 1 Alt. 2 Alt. 4 Alt. 6 Alt. 9 

No 

Action 

3%/year 

Increase 

~4.3%/year Increase 

Preferred 

~6.0%/year Increase 

MNB 

~6.6%/year 

Increase 

TCTB 

Expected Value 

Model Inputs 10,180 9,479 9,081 8,613 8,488

High AEO Fuel 

Price Forecast 10,175 9,444 9,050 8,514 8,462

Low AEO Fuel 

Price Forecast 10,190 9,533 9,116 8,773 8,564

7% Discount 

Rate a/ 10,180 9,479 9,081 8,635 8,488

5% Rebound 

Effect 10,179 9,373 8,926 8,413 8,277

15% Rebound 

Effect 10,181 9,585 9,236 8,813 8,699

$10/ton CO2 b/ 10,180 9,479 9,081 8,607 8,488

5¢/gal Oil Import 

Externality 10,180 9,479 9,081 8,613 8,488

25% Consumer 

Benefits 10,180 9,479 9,081 8,789 8,489

50% Consumer 

Benefits 10,180 9,479 9,081 8,719 8,489

75% Consumer 

Benefits 10,180 9,479 9,081 8,633 8,488

__________

a/ Non-climate benefits in this sensitivity case are discounted at 7%. Non-climate benefits in the main 

analysis and all other sensitivity cases are discounted at 3% per guidance from the Office of Management 

and Budget. See Office of Management and Budget, Circular No. A-4 (2003), Docket No. NHTSA-2009-

0059-0041. 

b/ The sensitivity run using the $10/ton SCC estimate discounts climate-related benefits at the same 5% rate 

used to develop the $10/ton SCC estimate. In contrast, the $56/ton SCC estimate used in the 

environmental analysis of this EIS discounts climate-related benefits at 3%, because that is the discount 

rate that was used to develop the $56/ton SCC estimate. The discounting of climate-related benefits is 

explained in the joint NPRM. 74 FR 49454, 49677. The 7% discount rate is only used in the sensitivity 

analysis case labeled accordingly, and is only applied to non-climate benefits in that case. 

The Expected Value model inputs result in 10,180 billion gallons of fuel consumption from 2012 

to 2060 under the No Action Alternative, and 8,488 billion gallons under the TCTB Alternative, with fuel 

consumption under other action alternatives falling within this range. Changing the projected fuel price 

input to the AEO High Fuel Price Forecast (while leaving other model inputs the same) reduces projected 

2012-2060 fuel consumption under each alternative by 0.05 percent to 1.15 percent from its estimated 

level under that alternative with the Expected Value model inputs (including the AEO Reference Case 

fuel price forecast). In contrast, changing the projected fuel price input to the AEO Low Fuel Price 

Forecast (while leaving other model inputs the same) increases projected 2012-2060 fuel consumption for 

 2-22 
Chapter 2 Proposed Action and Alternatives 

 2-23 

each alternative by 0.10 percent to 1.86 percent from its level under that alternative using the Expected 

Value model inputs (including the AEO Reference Case fuel price forecast). 

Reducing the rebound effect to 5 percent (while leaving other model inputs values the same, 

including the Reference Case fuel price forecast) reduces projected 2012-2060 fuel consumption for each 

alternative by 0.01 percent to 2.49 percent from its level under the same alternative with a 10 percent 

rebound effect (the Expected Value model input). In contrast, increasing the rebound effect to 15 percent 

increases projected 2012-2060 fuel consumption for each alternative by 0.01 percent to 2,49 percent. The 

sensitivity analysis in Table 2.4-1 shows that changes in the input values for the discount rate, the SCC, 

and oil import externalities result in less than a 1-percent change in projected 2012-2060 fuel 

consumption under each alternative (and less than a 0.01-percent change under most alternatives). 

These results occur because variation in fuel prices and the magnitude of the rebound effect 

influence total vehicle use (as measured by the number of vehicle-miles traveled, or VMT), one of the 

two determinants of fuel consumption, under each alternative. This reflects the response of average 

vehicle use to changes in fuel cost per mile; variation in fuel prices directly affects fuel cost per mile, 

while the rebound effect expresses the sensitivity of average vehicle use to the resulting change in fuel 

cost per mile.29 In addition, changes in fuel prices and the rebound effect significantly change the 

stringency of CAFE standards under alternatives that would establish standards on the basis of benefits 

and costs (Alternatives 6 and 9), which reinforces the effect of changes in vehicle use on total fuel 

consumption under those alternatives. 

In contrast, variation in other economic assumptions, including the discount rate, the value of 

reducing CO2 emissions, the reduced consumer benefits assumptions, and the value of petroleum import 

externalities have almost no effect on vehicle use under any alternative. Further, changes in these 

variables have only modest effects on the stringency of CAFE standards under alternatives that would 

establish standards on the basis of the economic costs and benefits from requiring higher fuel economy. 

As a consequence, changes in assumptions about these variables have little effect on total fuel 

consumption, as Table 2.4-1 illustrates, although changes in these variables do have significant effects on 

the total economic benefits resulting from the different Action Alternatives. 

2.5 ALTERNATIVES CONSIDERED BUT NOT ANALYZED IN DETAIL 

As a result of the scoping process, several suggestions were made to NHTSA regarding 

alternatives that should be examined in this EIS. NHTSA considered these alternatives and discusses 

them below along with the reasons why we believe these alternatives do not warrant further analysis in 

this EIS. 

• 100 mpg 

One commenter suggested NHTSA examine an alternative of setting standards to achieve 100 

mpg within 5 years. NHTSA did not pursue this suggested alternative for two reasons. First, a 

fleet-wide 100-mpg average would require the production of vehicles different from those now 

made in volume at a rate that is not possible in 5 years, as well as the elimination of vehicles for 

which there is consumer demand and for which manufacturers currently have supply contracts 

established to build in the near future. Second, the suggested approach would not be an 

appropriate balancing of the statutory factors listed in EPCA since the measures are not 

economically practicable based on manufacturers’ limitations concerning retooling and 

 

29 Mathematically, the rebound effect is equal in magnitude to the elasticity of average vehicle use with respect to 

fuel cost per mile driven, although the rebound effect is customarily expressed as a positive percentage. 
Chapter 2 Proposed Action and Alternatives 

 2-24 

established supply contracts.30 Indeed, the suggested approach would result in a level that is 

substantially higher than the “maximum feasible” CAFE standard, as required by EPCA. 

• Wedge Approach 

The Attorneys General commented that NHTSA’s EIS should show how the MYs 2012-2016 

CAFE rules contribute to reducing GHG emissions and addressing global warming by evaluating 

whether the new CAFE rules could constitute a stabilization wedge. While this is an approach, 

the agency declines to pursue a wedge analysis to fulfill its obligations under NEPA. CEQ 

regulations require NHTSA to rigorously explore all reasonable alternatives and examine their 

direct and indirect effects on climate change.31 NHTSA’s current approach demonstrates changes 

in CO2 concentration, global mean surface temperature, regional temperature and precipitation, 

and sea level for each alternative. Analysis of stabilization wedges, and framing the alternatives 

in terms of fractions of a stabilization edge, would only allow for a conceptual analysis of CO2

reductions. NHTSA believes that framing the alternatives as average annual percentage increase 

over current fuel economy levels is more intuitive to the public and to decisionmakers than 

framing the alternatives as suggested by the commenter. Therefore, NHTSA believes its chosen 

approach for addressing global warming is best able to describe the direct and indirect effects of 

climate change on all reasonable alternatives in accordance with NEPA. NHTSA has added a 

discussion of the wedge theory and how NHTSA’s proposed action generally looks in terms of a 

stabilization wedge in Section 3.4.4.1. 

• Least Capable Manufacturer

In their scoping comments the Alliance of Automobile Manufacturers (“AAM”) suggested an 

alternative of NHTSA setting standards tailored to the “least capable manufacturer.” As NHTSA 

explained in the FEIS for MY 2011 CAFE standards, the agency chose not to pursue the 

suggested approach for two reasons. First, the approach would not result in the EISA mandated 

fuel economy increases – namely, 35 mpg by MY 2020. Second, tailoring to the least capable 

manufacturer is unnecessary in Reformed CAFE, which was codified when EISA required that all 

CAFE standards be based on one or more vehicle attributes.32 Reformed CAFE standards specify 

variable levels of CAFE depending on the production mix of each manufacturer, making it 

unnecessary to tailor to the least capable manufacturer. 

• Variations based on increases from EISA MY 2020 endpoint 

The AAM also suggested that NHTSA “consider crafting a couple of alternatives that would 

model increased CAFE stringency levels over the baseline level for MY 2020 as required by 

EISA. For instance: Alternative (2) could be redefined as improving fuel economy at the rate 

necessary to achieve 35 mpg fleet average fuel economy in MY 2020...Alternative (3) could be 

defined as improving fuel economy at the rate necessary to achieve a 36.75 mpg fleet average 

fuel economy in MY 2020, an increase of 5 [percent] above EISA’s baseline level in MY 2020.” 

Docket No. NHTSA-2009-0059-0007. NHTSA recognizes that this is one possible approach to 

creating regulatory alternatives, but instead prefers to establish regulatory alternatives by 

specifying average annual percentage increases over MY 2011 CAFE standards because the 

agency believes alternatives expressed this way are more intuitive and understandable to the 

 

30 49 U.S.C. § 32902(f) (the determination of maximum feasibility is based on: technological feasibility, economic 

practicability, the effect of other motor vehicle standards on fuel economy, and the need of the United States to 

conserve energy). 

31 See 40 CFR § 1502.14-16. 32 49 U.S.C. § 32902(b)(3)(A); see 73 FR 24352, 24354-24355 (May 2, 2008). 
Chapter 2 Proposed Action and Alternatives 

 2-25 

public. We believe this approach best fulfills the goals of NEPA to inform both decisionmakers 

and the general public. CEQ regulations instruct agencies to write an EIS using plain language to 

enable understandability of complex environmental analyses for both decisionmakers and the 

public.33 CEQ regulations also indicate that a major purpose of an EIS is to facilitate public 

involvement in and knowledge of the NEPA process.34 NHTSA believes the approach chosen for 

generating alternatives best presents understandable regulatory approaches to CAFE increases. 

• Technology Exhaustion 

In the 2008 EIS, NHTSA analyzed a “technology exhaustion” alternative, which was 

developed by using the Volpe model to progressively increase the stringency of the standard in 

each model year until every manufacturer (among those without a history of paying civil 

penalties) exhausted technologies estimated to be available during the relevant model years. In 

its scoping comments, the Center for Biological Diversity stated that NHTSA should include one 

or more “technology forcing” alternatives, which would include standards that may appear 

impossible today, but which would force innovation as industry strives to meet a challenging 

standard. We consider the upper range of alternatives presented in this EIS to be technology 

forcing in the sense that at these higher average annual percentage increases some manufacturers 

run out of technologies, which would provide encouragement to seek other technologies to 

improve fuel economy. Since these higher average annual percentage increase regulatory 

alternatives would tend to induce manufacturers to do something they could not do with available 

technologies, they are in that sense “technology forcing” as well. We consider our range of 

alternatives to represent a reasonable range of possible agency actions. 

2.6 COMPARISON OF ALTERNATIVES 

The CEQ NEPA regulations direct federal agencies to use the NEPA process to identify and 

assess the reasonable alternatives to proposed actions that would avoid or minimize adverse effects of 

these actions upon the quality of the human environment.35 CEQ regulations state: 

Based on the information and analysis presented in the sections on the Affected 

Environment (Sec. 1502.15) and the Environmental Consequences (Sec. 1502.16), [an 

EIS] should present the environmental impacts of the proposal and the alternatives in 

comparative form, thus sharply defining the issues and providing a clear basis for choice 

among options by the decisionmaker and the public. 36 

This section summarizes the direct, indirect, and cumulative effects of the proposed action and 

alternatives on energy resources, air quality, and climate. For more detailed discussions on assumptions 

and methodologies associated with the direct, indirect, and cumulative effects of the proposed action and 

alternatives on energy resources, air quality and climate, see Sections 3.1 and 4.1. Please note that 

assumptions and methodologies may differ for each regulatory alternative. No quantifiable, alternativespecific effects were identified for the other resources discussed in Chapters 3 and 4 of this EIS. Refer to 

the text in Chapter 3 and 4 for qualitative discussions of the potential direct and indirect effects of the 

alternatives on these other resources. 

 

33 See 40 CFR § 1502.8. 34 See 40 CFR § 1500.1(b). 35 See 40 CFR § 1500.2(e). 36 See 40 CFR § 1502.14. 
Chapter 2 Proposed Action and Alternatives 

The consideration of the effects goes beyond MYs 2012-2016 vehicles. In the alternatives 

analyzed in the EIS, the growth in the number of passenger cars and light trucks in use throughout the 

United States, combined with assumed increases in their average use (annual vehicle miles traveled per 

vehicle), is projected to result in growth in total passenger car and light truck travel. This growth in travel 

outpaces improvements in fuel economy for each of the action alternatives, resulting in projected 

increases in total fuel consumption by U.S. passenger cars and light trucks. Because CO2 emissions are a 

direct consequence of total fuel consumption, the same result is projected for total CO2 emissions from 

passenger cars and light trucks. NHTSA estimates that the proposed CAFE standards will reduce fuel 

consumption and CO2 emissions from what they otherwise are estimated to be in the absence of the 

CAFE program (i.e., fuel consumption and CO2 emissions under the “no action” alternative). For more 

detailed discussions on assumptions and methodologies associated with the direct, indirect, and 

cumulative effects of the proposed action and alternatives on energy resources, air quality and climate, 

see Sections 3.1 and 4.1. 

2.6.1 Direct and Indirect Effects 

Under NEPA, direct effects “are caused by the action and occur at the same time and place.” 40 

CFR § 1508.8. CEQ regulations define indirect effects as those that “are caused by the action and are 

later in time or father removed in distance but are still reasonably foreseeable. Indirect effects may 

include ... effects on air and water and other natural systems, including ecosystems.” 40 CFR § 1508.8. 

Below is a description of the direct and indirect effects of the CAFE alternatives on energy, air quality, 

and climate. 

2.6.1.1 Energy 

Tables 2.6-1 through 2.6-3 show the impact on annual fuel consumption for passenger cars and 

light trucks from 2020 through 2060, when the entire passenger car and light truck fleet is likely to be 

composed of MY 2016 or later passenger cars. Table 2.6-1 shows annual total fuel consumption (both 

gasoline and diesel gasoline equivalent) under the No Action Alternative and the eight action alternatives. 

For passenger cars, fuel consumption under the No Action Alternative is 205.5 billion gallons in 2060. 

Fuel consumption ranges from 188.4 billion gallons under Alternative 2 (3-Percent Alternative) to 166.5 

billion gallons under Alternative 8 (7-Percent Alternative). Fuel consumption is 179.4 billion gallons 

under the Preferred Alternative. 

For light trucks, fuel consumption under the No Action Alternative is 113.0 billion gallons in 

2060. Fuel consumption ranges from 104.6 billion gallons under Alternative 2 (3-Percent Alternative) to 

92.4 billion gallons under Alternative 8 (7-percent annual increase in mpg). Fuel consumption is 99.4 

billion gallons under the Preferred Alternative (Alternative 4). 

For passenger cars and light trucks combined, fuel consumption under the No Action Alternative 

is 318.5 billion gallons in 2060. Fuel consumption ranges from 293.0 billion gallons under Alternative 2 

(3-Percent Alternative) to 258.9 billion gallons under Alternative 8 (7-percent annual increase in mpg). 

Fuel consumption is 278.8 billion gallons under the Preferred Alternative (Alternative 4). 

 2-26 
Chapter 2 Proposed Action and Alternatives 

Table 2.6-1 

Passenger Car Annual Fuel Consumption and Fuel Savings by Alternative 

(billion gallons gasoline equivalent) 

Alt. 1 Alt. 2 Alt. 3 Alt. 4 Alt. 5 Alt. 6 Alt. 7 Alt. 8 Alt. 9 

Calendar 

Year 

No 

Action 

3%/year 

Increase 

4%/year 

Increase 

~4.3%/year

Increase 

Preferred

5%/year 

Increase 

~6.0%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.6%/year 

Increase 

TCTB 

Fuel Consumption 

2020 74.1 70.5 68.9 68.4 67.5 66.2 66.4 65.6 65.6

2030 103.9 95.5 92.0 91.1 89.0 86.5 86.5 84.8 85.2

2040 134.5 123.3 118.6 117.4 114.7 111.3 111.3 109.0 109.6

2050 167.6 153.6 147.7 146.2 142.8 138.6 138.6 135.8 136.5

2060 205.5 188.4 181.2 179.4 175.2 170.0 170.0 166.5 167.4

Fuel Savings Compared to No Action 

2020 -- 3.6 5.2 5.7 6.6 7.9 7.7 8.5 8.4

2030 -- 8.4 11.9 12.8 14.8 17.4 17.3 19.1 18.7

2040 -- 11.2 15.9 17.1 19.9 23.2 23.3 25.5 24.9

2050 -- 14.0 19.8 21.3 24.8 28.9 29.0 31.8 31.1

2060 -- 17.2 24.3 26.2 30.4 35.5 35.5 39.0 38.1

Table 2.6-2 

Light Truck Annual Fuel Consumption and Fuel Savings by Alternative 

(billion gallons gasoline equivalent) 

Alt. 1 Alt. 2 Alt. 3 Alt. 4 Alt. 5 Alt. 6 Alt. 7 Alt. 8 Alt. 9 

Calendar 

Year 

No 

Action 

3%/year 

Increase 

4%/year 

Increase 

~4.3%/year

Increase 

Preferred 

5%/year 

Increase

~6.0%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.6%/year 

Increase 

TCTB 

Fuel Consumption 

2020 75.8 73.5 72.4 71.9 71.4 70.2 70.5 69.8 69.8

2030 72.2 67.7 65.7 64.9 63.9 62.2 62.2 61.1 61.3

2040 78.6 73.1 70.5 69.6 68.3 66.2 66.1 64.8 65.1

2050 93.0 86.2 83.0 81.9 80.4 77.8 77.7 76.1 76.5

2060 113.0 104.6 100.7 99.4 97.5 94.4 94.3 92.4 92.8

Fuel Savings Compared to No Action 

2020 -- 2.3 3.4 3.9 4.4 5.6 5.4 6.0 6.1

2030 -- 4.4 6.5 7.2 8.2 10.0 10.0 11.0 10.9

2040 -- 5.6 8.2 9.1 10.3 12.4 12.5 13.8 13.5

2050 -- 6.8 10.0 11.1 12.6 15.2 15.3 16.9 16.5

2060 -- 8.3 12.3 13.5 15.5 18.6 18.7 20.6 20.2

 2-27 
Chapter 2 Proposed Action and Alternatives 

Table 2.6-3 

Car & Light Truck Annual Fuel Consumption and Fuel Savings by Alternative a/ 

(billion gallons gasoline equivalent) 

Alt. 1 Alt. 2 Alt. 3 Alt. 4 Alt. 5 Alt. 6 Alt. 7 Alt. 8 Alt. 9 

Calendar 

Year 

No 

Action 

3%/year 

Increase 

4%/year 

Increase

~4.3%/year

Increase 

Preferred 

5%/year 

Increase 

~6.0%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.6%/year 

Increase 

TCTB 

Fuel Consumption 

2020 149.9 144.0 141.3 140.3 139.0 136.5 136.9 135.4 135.4

2030 176.0 163.2 157.7 156.0 153.0 148.7 148.7 146.0 146.5

2040 213.2 196.4 189.1 187.0 183.0 177.5 177.4 173.9 174.7

2050 260.5 239.7 230.7 228.2 223.2 216.5 216.3 211.9 213.0

2060 318.5 293.0 281.9 278.8 272.7 264.5 264.3 258.9 260.3

Fuel Savings Compared to No Action 

2020 -- 6.0 8.7 9.7 10.9 13.5 13.0 14.5 14.5

2030 -- 12.8 18.4 20.0 23.1 27.4 27.3 30.1 29.5

2040 -- 16.8 24.1 26.2 30.2 35.7 35.8 39.3 38.4

2050 -- 20.8 29.9 32.4 37.4 44.1 44.3 48.6 47.5

2060 -- 25.5 36.6 39.7 45.8 54.0 54.2 59.6 58.3

__________ 

a/ Some of the values shown for car and light truck fuel consumption in this table vary slightly from the sum of 

 values shown separately for passenger cars and light trucks in previous tables due to rounding error. 

2.6.1.2 Air Quality 

Table 2.6-4 summarizes the total national criteria and air toxic pollutant emissions in 2030 for the 

nine alternatives, left to right in order of generally increasing fuel economy requirements. Changes in 

overall emissions between the No Action Alternative and Alternatives 2 through 4 are generally smaller 

than those between the No Action Alternative and Alternatives 5 through 9. In the case of particulate 

matter (PM2.5), sulfur oxides (SOx), nitrogen oxides (NOx), and volatile organic compounds (VOCs), the 

No Action Alternative results in the highest emissions, and emissions generally decline as fuel economy 

standards increase across alternatives. Across Alternatives 4 through 9 some emissions increase from one 

alternative to another, but emissions remain below the levels under the No Action Alternative. In the case 

of carbon monoxide (CO), emissions under Alternatives 2 through 4 are slightly higher than under the No 

Action Alternative. Emissions of CO generally decline as fuel economy standards increase across 

Alternatives 5 through 9. 

The trends for toxic air pollutant emissions across the alternatives are mixed. Annual emissions 

of acetaldehyde in 2030 increase under each successive alternative from the No Action Alternative to 

Alternative 4, and then decrease from Alternative 5 to Alternative 9. Annual emissions of acrolein in 

2030 are higher than under the No Action Alternative. Acrolein emissions increase, though not 

consistently, from the No Action Alternative to Alternative 8, and then decrease under Alternative 9. 

Annual emissions of 1,3-butadiene in 2030 increase under each successive alternative from the No Action 

Alternative to Alternative 3 and then decrease, though not consistently, from Alternative 3 to Alternative 

9. The minimum emissions of 1,3-butadiene occurs under Alternative 8. Annual emissions in 2030 of 

benzene and DPM decrease from the No Action Alternative to Alternative 9, though the decrease is not 

consistent between Alternatives 6 and 9. The minimum emissions of benzene and DPM occur under 

Alternative 8. Annual emissions of formaldehyde in 2030 decrease from the No Action Alternative to 

Alternative 2. Formaldehyde emissions increase, though not consistently, from Alternative 2 to 

Alternative 8, and then decrease slightly under Alternative 9. 

 2-28 
Chapter 2 Proposed Action and Alternatives 

Table 2.6-4 

Nationwide Criteria Pollutant Emissions and Toxic Air Pollutant Emissions from Passenger Cars and Light 

Trucks (tons/year, Calendar Year 2030) by Alternative 

Alt. 1 Alt. 2 Alt. 3 Alt. 4 Alt. 5 Alt. 6 Alt. 7 Alt. 8 Alt. 9 

No 

Action 

3%/year 

Increase 

4%/year 

Increase

~4.3%/year

Increase 

Preferred 

5%/year 

Increase 

~6.0%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.6%/year 

Increase 

TCTB 

Criteria Pollutant Emissions 

Carbon 

monoxide 

(CO) 20,516,692 20,625,314 20,653,244 20,611,910 19,847,892 19,203,414 19,361,096 18,867,420 19,034,022

Nitrogen 

oxides (NOx) 1,425,733 1,410,414 1,402,605 1,398,774 1,371,749 1,345,911 1,351,818 1,332,981 1,338,453

Particulate 

matter (PM2.5) 84,021 81,726 80,498 80,206 81,194 81,484 81,637 82,126 81,839

Sulfur oxides 

(SOx) 216,228 200,884 194,149 192,374 192,985 191,324 190,961 190,214 189,760

Volatile 

organic 

compounds 

(VOCs) 1,881,987 1,810,076 1,778,691 1,767,262 1,708,646 1,649,731 1,655,217 1,614,158 1,627,859

Toxic Air Pollutant Emissions 

Acetaldehyde 7,927 7,951 7,973 7,976 7,929 7,905 7,902 7,872 7,879

Acrolein 391 394 395 397 425 449 445 463 457

Benzene 28,961 28,900 28,863 28,815 28,203 27,673 27,788 27,388 27,519

1,3-butadiene 3,751 3,771 3,777 3,776 3,747 3,724 3,734 3,717 3,722

Diesel 

particulate 

matter (DPM) 113,884 105,735 102,053 100,991 99,301 96,641 96,743 95,220 95,595

Formaldehyde 9,190 9,173 9,194 9,224 9,580 9,911 9,818 10,051 9,964

The reductions in emissions are expected to lead to reductions in adverse health effects as 

compared to the No Action Alternative. Table 2.6-5 summarizes the national changes in health outcomes 

in 2030 for the nine alternatives, left to right in order of increasing fuel economy requirements. There 

would be reductions in adverse health effects nationwide under Alternatives 2 (3-Percent Alternative) 

through 9 (TCTB) compared to the No Action Alternative. The No Action Alternative results in no 

reductions in adverse health effects and the reductions become larger as fuel economy standards increase 

and emissions decrease across alternatives. These reductions primarily reflect the projected PM2.5

reductions, and secondarily the reductions in SO2. 

The economic value of health impacts would vary proportionally with changes in health 

outcomes. Table 2.6-6 lists the corresponding annual monetized health benefits in 2030 under 

Alternatives 2 (3-Percent Alternative) through 9 (TCTB) compared to the No Action Alternative. 

Monetized health benefits are given based on data from two alternative studies, which EPA considers coequal, and for two alternative assumptions of the discount rate, 3 percent and 7 percent, consistent with 

EPA policy for presentation of future health benefits. 

 2-29 
Chapter 2 Proposed Action and Alternatives 

Table 2.6-5 

Nationwide Changes in Health Outcomes from Criteria Pollutant Emissions (cases/year) 

from Passenger Cars and Light Trucks by Alternative a/ 

Alt. 1 Alt. 2 Alt. 3 Alt. 4 Alt. 5 Alt. 6 Alt. 7 Alt. 8 Alt. 9 

Out. 

and 

Year 

No 

Action 

b/ 

3%/year 

Increase 

4%/year 

Increase 

~4.3%/year

Increase 

Preferred 

5%/year 

Increase 

~6.0%/year 

Increase MNB

6%/year 

Increase 

7%/year 

Increase 

~6.6%/year 

Increase 

TCTB 

Mortality (ages 30 and older), Pope et al. 

2030 0 -149 -223 -243 -235 -257 -247 -251 -257

Mortality (ages 30 and older), Laden et al. 

2030 0 -380 -571 -623 -600 -658 -632 -643 -657

Chronic bronchitis 

2030 0 -97 -146 -160 -155 -170 -163 -166 -169

Emergency Room Visits for Asthma 

2030 0 -137 -204 -222 -211 -228 -221 -224 -230

Work Loss Days 

2030 0 -17,499 -26,298 -28,705 -27,756 -30,507 -29,237 -29,792 -30,423

__________ 

a/ Negative changes indicate reductions; positive emissions changes are increases. 

b/ Changes in health outcome for the No Action Alternative are shown as zero because the No Action Alternative is 

the baseline to which emissions under the action alternatives are compared. 

Table 2.6-6 

Nationwide Monetized Health Benefits (U.S. million dollars/year) from Criteria Pollutant Emissions 

from Passenger Cars and Light Trucks by Alternative a/ 

Alt. 1 Alt. 2 Alt. 3 Alt. 4 Alt. 5 Alt. 6 Alt. 7 Alt. 8 Alt. 9 

Rate 

and 

Year 

No 

Action 

b/ 

3%/year 

Increase 

4%/year 

Increase 

~4.3%/year

Increase 

Preferred 

5%/year 

Increase 

~6.0%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.6%/year 

Increase 

TCTB 

3% Discount Rate

Pope et al. 

2030 0 -1,322 -1,983 -2,164 -2,087 -2,287 -2,197 -2,235 -2,284

Laden et al. 

2030 0 -3,239 -4,860 -5,302 -5,112 -5,603 -5,382 -5,477 -5,596

7% Discount Rate

Pope et al. 

2030 0 -1,199 -1,799 -1,963 -1,893 -2,075 -1,993 -2,028 -2,072

Laden et al. 

2030 0 -2,926 -4,390 -4,789 -4,618 -5,061 -4,861 -4,947 -5,055

__________ 

a/ Negative changes indicate monetized health benefits; positive emissions changes indicate monetized health 

disbenefits. 

b/ Changes in outcome for the No Action Alternative are shown as zero because the No Action Alternative is the 

baseline to which impacts under the action alternatives are compared. 

2.6.1.3 Climate Change 

This EIS uses a climate model to estimate the changes in CO2 concentrations, global mean 

surface temperature, and changes in sea level for each alternative. NHTSA also estimated changes in 

global precipitation. 

 2-30 
Chapter 2 Proposed Action and Alternatives 

 2-31 

2.6.1.3.1 GHG Emissions 

Table 2.6-7 shows total GHG emissions and emissions reductions from new passenger cars and 

light trucks, summed for the period 2012 through 2100 under each of the nine alternatives. Although 

GHG emissions from this sector will continue to rise over the period (absent other reduction efforts) 

across all the alternatives, the effect of the alternatives is to slow this increase by varying amounts. 

Emissions for the period range from 227,700 million metric tons of CO2 (MMTCO2) for the 7%/year 

Increase (Alternative 8) to 276,000 MMTCO2 for the No Action Alternative (Alternative 1). Compared 

to the No Action Alternative, projections of emissions reductions over the period 2012 to 2100 due to the 

MYs 2012-2016 CAFE standards range from 20,700 to 48,300 MMTCO2. Compared to cumulative 

global emissions of 5,293,896 MMTCO2 over this period (projected by the RCP 4.5 MiniCAM reference 

scenario), this rulemaking is expected to reduce global CO2 emissions by about 0.4 to 0.9 percent. 

Table 2.6-7 

Emissions and Emissions Reductions (MMTCO2) from 2012-2100 by Alternative a/ 

Alternative Emissions 

Emissions Reductions 

Compared 

to No Action Alternative 

1 No Action 276,000 0 

2 3%/year Increase 255,300 20,700 

3 4%/year Increase 246,300 29,700 

4 ~4.3%/year Increase, Preferred 243,800 32,300 

5 5%/year Increase 238,900 37,100 

6 ~6.0%/year Increase, MNB 232,200 43,900 

7 6%/year Increase 232,100 43,900 

8 7%/year Increase 227,700 48,300 

9 ~6.6%/year Increase, TCTB 228,700 47,300 

__________

a/ The numbers in this table have been rounded for presentation purposes. As a result, the 

reductions might not reflect the exact difference of the values in all cases. 

To get a sense of the relative impact of these reductions, it can be helpful to consider the relative 

importance of emissions from passenger cars and light trucks as a whole and to compare them against 

emissions projections for the United States. U.S. passenger cars and light trucks currently account for 

approximately 19.1 percent of CO2 emissions in the United States (EPA 2009a). With the action 

alternatives reducing U.S. passenger car and light truck CO2 emissions by 7.5 to 17.5 percent of 

cumulative emissions from 2012 to 2100, the CAFE alternatives would have a noticeable impact on total 

U.S. CO2 emissions. Compared to total U.S. CO2 emissions in 2100 projected by the MiniCAM reference 

scenario of 7,886 MMTCO2 , the action alternatives would reduce annual U.S. CO2 emissions by 3.9 to 

9.1 percent in 2100. As another comparison of the magnitude of these reductions, average annual CO2

emission reductions from the CAFE alternatives range from 232 to 543 MMTCO2 over 2012 to 2100, 

equivalent to the annual CO2 emissions of 60 to 141 coal-fired power plants.37 Figure 2.6-1 shows 

projected annual emissions from passenger cars and light trucks under the MYs 2012-2016 alternative 

CAFE standards. 

 

37 Estimated using EPA’s Greenhouse Gas Equivalencies Calculator (EPA 2009b). 
Chapter 2 Proposed Action and Alternatives 

Figure 2.6-1. Projected Annual Emissions (MMTCO2) by Alternative 

0

500

10001500200025003000350040004500

2010 2020 2030 2040 2050 

MMTCO2

Alt. 1: No Action Alt. 2: 3%/year IncreaseAlt. 3: 4%/year Increase Alt. 4: ~4.3%/year Increase, PreAlt. 5: 5%/year Increase Alt. 6: ~6.0%/year Increase, MNAlt. 7: 6%/year Increase Alt. 8: 7%/year IncreaseAlt. 9: ~6.6%/year Increase, TCTB

2-32 
Chapter 2 Proposed Action and Alternatives 

 2-33 

Under all of the alternatives analyzed, growth in the number of passenger cars and light trucks in 

use throughout the United States, combined with assumed increases in their average use, is projected to 

result in growth in total passenger car and light truck travel. This growth in travel overwhelms 

improvements in fuel economy for each of the alternatives, resulting in projected increases in total fuel 

consumption by U.S. passenger cars and light trucks over most of the period shown in the table. Because 

CO2 emissions are a direct consequence of total fuel consumption, the same result is projected for total 

CO2 emissions from passenger cars and light trucks. 

Emissions of CO2, the primary gas that drives climate effects, from the U.S. passenger car and 

light truck fleet represented about 3.3 percent of total global emissions of CO2 in 2005.38 Although 

substantial, this source is still a small percentage of global emissions. The relative contribution of CO2

emissions from the U.S. passenger cars and light trucks is expected to decline in the future, due primarily 

to rapid growth of emissions from developing economies (which are due in part to growth in global 

transportation sector emissions). 

2.6.1.3.2 CO2 Concentration, Global Mean Surface Temperature, Sea-level Rise, 

and Precipitation 

Table 2.6-8 shows estimated CO2 concentrations, increase in global mean surface temperature, 

and sea-level rise in 2030, 2050, and 2100 under the No Action Alternative and the eight action 

alternatives. Figures 2.6-2 through 2.6-5 graphically illustrate estimated CO2 concentrations and 

reductions for the eight action alternatives. 

Table 2.6-8 

CO2 Concentrations, Global Mean Surface Temperature Increase, and Sea-level Rise 

by Alternative a/

CO2 Concentration 

(parts per million) 

Global Mean Surface 

Temperature Increase 

(°C) 

Sea-level Rise 

(centimeters) 

2030 2050 2100 2030 2050 2100 2030 2050 2100 

Totals by Alternative 

1 No Action 441.8 514.8 783.0 0.923 1.557 3.136 8.38 15.17 38.00

2 3%/year Increase 441.6 514.3 781.0 0.922 1.554 3.128 8.38 15.16 37.94

3 4%/year Increase 441.5 514.0 780.2 0.922 1.553 3.125 8.38 15.15 37.91

4 ~4.3%/year Increase, Preferred 441.5 514.0 779.9 0.922 1.553 3.124 8.38 15.15 37.90

5 5%/year Increase 441.5 513.8 779.5 0.921 1.552 3.122 8.38 15.15 37.88

6 ~6.0%/year Increase, MNB 441.4 513.7 778.8 0.921 1.551 3.120 8.38 15.14 37.86

7 6%/year Increase 441.4 513.7 778.8 0.921 1.551 3.120 8.38 15.14 37.86

8 7%/year Increase 441.4 513.6 778.4 0.921 1.551 3.118 8.38 15.14 37.84

9 ~6.6%/year Increase, TCTB 441.4 513.6 778.5 0.921 1.551 3.118 8.38 15.14 37.84

Reductions under Alternative CAFE Standards

2 3%/year Increase 0.2 0.5 2.0 0.001 0.002 0.007 0.00 0.01 0.06

3 4%/year Increase 0.3 0.8 2.8 0.001 0.003 0.011 0.00 0.02 0.09

4 ~4.3%/year Increase, Preferred 0.3 0.8 3.1 0.001 0.004 0.012 0.00 0.02 0.10

5 5%/year Increase 0.3 1.0 3.5 0.002 0.004 0.014 0.00 0.02 0.12

6 ~6.0%/year Increase, MNB 0.4 1.1 4.2 0.002 0.006 0.016 0.00 0.03 0.14

7 6%/year Increase 0.4 1.1 4.2 0.002 0.006 0.016 0.00 0.03 0.14

8 7%/year Increase 0.4 1.2 4.6 0.002 0.006 0.018 0.00 0.03 0.16

9 ~6.6%/year Increase, TCTB 0.4 1.2 4.5 0.002 0.006 0.017 0.00 0.03 0.16

__________

a/ The numbers in this table have been rounded for presentation purposes. As a result, the reductions might not 

reflect the exact difference of the values in all cases. 

 

38 Includes land-use change and forestry, and excludes international bunker fuels. 
Chapter 2 Proposed Action and Alternatives 

Figure 2.6-2. CO2 Concentrations (ppm) 

0

100200300400500600700800900

2030 2050 2100

ppm

No Acti on Al t. 2: 3%/yea r Increa seAl t. 3: 4%/yea r Increa se Al t. 4: ~4.3%/yea r Increa se, Pre ferredAl t. 5: 5%/yea r Increa se Al t. 6: ~6.0%/yea r Increa se, MNBAl t. 7: 6%/yea r Increa se Al t. 8: 7%/yea r Increa seAl t. 9: ~6.6%/yea r Increa se, TCTB

2-34 
Chapter 2 P

Figure 2.6-3. Global Mean Surface Temperature Increase (°C) 

0

0.5

1

1.5

2

2.5

3

3.5

2030 2050 2100

degrees Celsius

No Action Al t. 2: 3%/yea r Increa seAl t. 3: 4%/yea r Increa se Al t. 4: ~4.3%/yea r Increa se, Pre fe rredAl t. 5: 5%/yea r Increa se Al t. 6: ~6.0%/yea r Increa se, MNBAl t. 7: 6%/yea r Increa se Al t. 8: 7%/yea r Increa seAl t. 9: ~6.6%/yea r Increa se, TCTB

2-35 
Chapter 2 Proposed Action and Alternatives 

Figure 2.6-4. Reduction in CO2 Concentrations (ppm) Compared to the No Action Altern

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

2030 2050 2100

ppm

Al t. 2: 3%/yea r Increa se Al t. 3: 4%/yea r Increa se Al t. 4: ~4.3%/yea r Increa se, PAl t. 5: 5%/yea r Increa se Al t. 6: ~6.0%/yea r Increa se, MNB Al t. 7: 6%/yea r Increa seAl t. 8: 7%/yea r Increa se Al t. 9: ~6.6%/yea r Increa se, TCTB

2-36 
Chapter 2 P

2-37 

Figure 2.6-5. Reduction in Global Mean Temperature Compared to the No Action Alterna

0.0000.0020.0040.0060.0080.0100.0120.0140.0160.0180.020

2030 2050 2100

degrees Celsius

Al t. 2: 3%/yea r Increa se Al t. 3: 4%/yea r Increa se Al t. 4: ~4.3%/yea r Increa se, Pre ferrAl t. 5: 5%/yea r Increa se Al t. 6: ~6.0%/yea r Increa se, MNB Al t. 7: 6%/yea r Increa seAl t. 8: 7%/yea r Increa se Al t. 9: ~6.6%/yea r Increa se, TCTB
Chapter 2 Proposed Action and Alternatives 

 2-38 

Table 2.6-8 lists the impacts on sea-level rise under the scenarios and shows sea-level rise in 2100 

ranging from 38.00 centimeters under the No Action Alternative to 37.84 centimeters under Alternatives 

8 and 9, for a maximum reduction of 0.16 centimeters by 2100 from the No Action Alternative. 

Estimated CO2 concentrations for 2100 range from 778.4 ppm under Alternative 8 to 783.0 ppm 

under the No Action Alternative. For 2030 and 2050, the range is even smaller. Because CO2

concentration is the key driver of other climate effects (which in turn act as drivers on the resource 

impacts discussed in Section 4.5), this leads to small differences in these effects. For the No Action 

alternative, the temperature increase from 1990 is 0.92 °C (1.65 °F) for 2030, 1.56 °C (2.80 °F) for 2050, 

and 3.14 °C (5.65 °F) for 2100. The differences among alternatives are small, as shown in Figures 2.6-2 

through 2.6-5. For 2100, the reduction in temperature increase, in relation to the No Action Alternative, 

ranges from 0.007 °C (0.013 °F) to 0.018 °C (0.032 °F). 

Given that all the action alternatives reduce temperature increases slightly in relation to the No 

Action Alternative, they also slightly reduce predicted increases in precipitation, as shown in Table 2.6-9. 

In summary, the impacts of the proposed action and alternatives on global mean surface 

temperature, precipitation, or sea-level rise are small in absolute terms. This is because the action 

alternatives have a small proportional change in the emissions trajectories in the RCP 4.5 MiniCAM 

reference scenario.39 This is due primarily to the global and multi-sectoral nature of the climate problem. 

Although these effects are small, they occur on a global scale and are long-lived. 

NHTSA examined the sensitivity of climate effects to key assumptions used in the analysis. The 

sensitivity analysis is based on the results provided for two CAFE alternatives – the No Action 

Alternative (Alternative 1) and the Preferred Alternative (Alternative 4) – using climate sensitivities of 

2.0, 3.0, and 4.5 °C for a doubling of CO2 concentrations in the atmosphere. The sensitivity analysis was 

conducted for only two CAFE alternatives, as this was deemed sufficient to assess the effect of various 

climate sensitivities on the results. 

The use of different climate sensitivities (the equilibrium warming that occurs at a doubling of 

CO2 from pre-industrial levels) not only directly affects warming, it also indirectly affects CO2

concentration (through feedbacks on the solubility of CO2 in the oceans) and sea-level rise (through 

effects on thermal expansion and melting of land-based ice). 

As shown in Table 2.6-10, the sensitivity of the simulated CO2 emissions in 2030, 2050, and 2100 

to changes in climate sensitivity is low; the reduction of CO2 concentrations from the No Action 

Alternative to the Preferred Alternative in 2100 is from 3.0 to 3.2 ppm. 

 

39 These conclusions are not meant to be interpreted as expressing NHTSA’s views that impacts on global mean 

surface temperature, precipitation, or sea-level rise are not areas of concern for policymakers. Under NEPA, the 

agency is obligated to discuss “the environmental impact[s] of the proposed action.” 42 U.S.C. § 4332(2)(C)(i) 

(emphasis added). This analysis fulfills NHTSA’s obligations in this regard. 
Chapter 2 Proposed Action and Alternatives 

Table 2.6-9 

Global Mean Precipitation (percent change) a/ 

Scenario 2020 2055 2090 

Global Mean Precipitation Change (scaled, % per °C) 1.45 1.51 1.63 

Global Temperature above Average 1980-1999, Mid-level Results (oC) 

1 No Action 0.648 1.716 2.816 

2 3%/year Increase 0.648 1.713 2.809 

3 4%/year Increase 0.648 1.712 2.806 

4 ~4.3%/year Increase, Preferred 0.648 1.712 2.806 

5 5%/year Increase 0.648 1.711 2.804 

6 ~6.0%/year Increase, MNB 0.648 1.709 2.801 

7 6%/year Increase 0.648 1.709 2.801 

8 7%/year Increase 0.648 1.709 2.800 

9 ~6.6%/year Increase, TCTB 0.648 1.709 2.800 

Reduction in Global Temperature (oC) for Alternative CAFE Standards, Mid-level Results (Compared to 

No Action Alternative) 

2 3%/year Increase 0.000 0.003 0.006 

3 4%/year Increase 0.000 0.004 0.009 

4 ~4.3%/year Increase, Preferred 0.000 0.004 0.010 

5 5%/year Increase 0.000 0.005 0.012 

6 ~6.0%/year Increase, MNB 0.000 0.007 0.014 

7 6%/year Increase 0.000 0.007 0.014 

8 7%/year Increase 0.000 0.007 0.016 

9 ~6.6%/year Increase, TCTB 0.000 0.007 0.016 

Global Mean Precipitation Change (%) 

1 No Action 0.94% 2.59% 4.59% 

2 3%/year Increase 0.94% 2.59% 4.58% 

3 4%/year Increase 0.94% 2.58% 4.57% 

4 ~4.3%/year Increase, Preferred 0.94% 2.58% 4.57% 

5 5%/year Increase 0.94% 2.58% 4.57% 

6 ~6.0%/year Increase, MNB 0.94% 2.58% 4.57% 

7 6%/year Increase 0.94% 2.58% 4.57% 

8 7%/year Increase 0.94% 2.58% 4.56% 

9 ~6.6%/year Increase, TCTB 0.94% 2.58% 4.56% 

Reduction in Global Mean Precipitation Change for Alternative CAFE Standards (% Compared to 

No Action Alternative) 

2 3%/year Increase 0.00% 0.00% 0.01% 

3 4%/year Increase 0.00% 0.01% 0.02% 

4 ~4.3%/year Increase, Preferred 0.00% 0.01% 0.02% 

5 5%/year Increase 0.00% 0.01% 0.02% 

6 ~6.0%/year Increase, MNB 0.00% 0.01% 0.02% 

7 6%/year Increase 0.00% 0.01% 0.02% 

8 7%/year Increase 0.00% 0.01% 0.03% 

9 ~6.6%/year Increase, TCTB 0.00% 0.01% 0.03% 

__________________ 

a/ The numbers in this table have been rounded for presentation purposes. As a result, the reductions might not 

reflect the exact difference of the values in all cases. 

 

 2-39 
Chapter 2 Proposed Action and Alternatives 

Table 2.6-10 

CO2 Concentrations, Global Mean Surface Temperature Increase, and Sea-level Rise for Varying Climate 

Sensitivities for Selected Alternatives a/ 

CAFE 

Alternative 

Climate 

Sensitivity 

(°C for 2xCO2) CO2 Concentration (ppm) 

Global Mean Surface 

Temperature Increase (°C) 

Sea- level 

Rise (cm)

2030 2050 2100 2030 2050 2100 2100 

1 No Action 

2.0 440.2 510.7 765.1 0.699 1.168 2.292 28.68

3.0 441.8 514.8 783.0 0.923 1.557 3.136 38.00

4.5 443.6 519.5 805.3 1.168 1.991 4.132 48.67

4 Preferred 

2.0 439.9 509.9 762.1 0.698 1.166 2.283 28.60

3.0 441.5 514.0 779.9 0.922 1.553 3.124 37.90

4.5 443.3 518.7 802.1 1.166 1.987 4.118 48.54

Reduction compared to No Action 

2.0 0.3 0.8 3.0 0.001 0.003 0.009 0.08

3.0 0.3 0.8 3.1 0.001 0.004 0.012 0.10

4.5 0.3 0.8 3.2 0.001 0.005 0.015 0.13

__________

a/ Values in this table are rounded.

The sensitivity of the simulated global mean surface temperatures for 2030, 2050, and 2100 

varies, is also shown in Table 2.6-10. In 2030, the impact is low, due primarily to the slow rate at which 

the global mean surface temperature increases in response to increases in radiative forcing. The relatively 

slow response in the climate system explains the observation that even by 2100, when CO2 concentrations 

more than double in comparison to pre-industrial levels, the temperature increase is below the equilibrium 

sensitivity levels, i.e., the climate system has not had enough time to equilibrate to the new CO2

concentrations. Nonetheless, as of 2100 there is a larger range in temperatures across the different values 

of climate sensitivity: the reduction in global mean surface temperature from the No Action Alternative to 

the Preferred Alternative ranges from 0.009 °C (0.016 °F) for the 2.0 °C climate sensitivity to 0.015 °C 

(0.027 °F) for the 4.5 °C climate sensitivity. 

The sensitivity of the simulated sea-level rise to change in climate sensitivity and global GHG 

emissions mirrors that of global temperature, as shown in Table 2.6-10. Scenarios with lower climate 

sensitivities have lower increases in sea-level rise. The greater the climate sensitivity, the greater the 

decrement in sea-level rise for the Preferred Alternative as compared to the No Action Alternative. 

2.6.2 Cumulative Effects 

CEQ identifies the impacts that must be addressed and considered by federal agencies in 

satisfying the requirements of NEPA. These include permanent, temporary, direct, indirect, and 

cumulative impacts. CEQ regulations implementing the procedural provisions of NEPA define 

cumulative impacts as “the impact on the environment which results from the incremental impact of the 

action when added to other past, present, and reasonably foreseeable future actions regardless of what 

agency . . . or person undertakes such other actions.” 40 CFR § 1508.7. Following is a description of the 

cumulative effects of the proposed action and alternatives on energy, air quality, and climate. 

The cumulative effects evaluation assumes ongoing gains in average new passenger car and light 

truck mpg consistent with further increases in CAFE standards to an EISA-mandated minimum level of 

35 mpg combined for passenger car and light trucks by the year 2020. After 2020, all alternatives 

 2-40 
Chapter 2 Proposed Action and Alternatives 

 2-41 

continue to increase in fuel economy consistent with AEO 2010 Early Release Reference Case projections 

of annual percentage gains of 0.49 percent in passenger car mpg and 0.68 percent in light truck mpg 

through 2030.40 AEO Reference Case projections are regarded as the official U.S. government energy 

projections by both the public and private sector. 

2.6.2.1 Energy 

The nine alternatives examined in this EIS will result in different future levels of fuel use, total 

energy, and petroleum consumption, which will in turn have an impact on emissions of GHG and criteria 

air pollutants. Table 2.6-11 presents the cumulative fuel consumption and fuel savings of passenger cars 

from the onset of the proposed new CAFE standards. By 2060, fuel consumption reaches 193.2 billion 

gallons under the No Action Alternative (Alternative 1). Consumption falls across the alternatives, from 

167.3 billion gallons under Alternative 2 (3-percent annual increase in mpg) to 156.3 billion gallons under 

Alternative 8 (7-percent annual increase in mpg) representing a fuel savings of 26.0 to 36.9 billion gallons 

in 2060, as compared to fuel consumption projected under the No Action Alternative. 

Table 2.6-11 

Cumulative Effects of Passenger Car Annual Fuel Consumption and Fuel Savings by Alternative 

(billion gallons gasoline equivalent) 

Calendar Alt. 1 Alt. 2 Alt. 3 Alt. 4 Alt. 5 Alt. 6 Alt. 7 Alt. 8 Alt. 9 

Year No 

Action 

3%/year 

Increase 

4%/year 

Increase 

~4.3%/year

Increase 

Preferred

5%/year 

Increase

~6.0%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.6%/year 

Increase 

TCTB 

Fuel Consumption

2020 73.8 69.4 68.4 68.0 67.3 66.0 66.2 65.4 65.4

2030 100.4 88.0 87.6 87.5 86.0 83.6 83.6 81.9 82.3

2040 127.0 110.0 109.9 109.9 108.1 104.9 104.9 102.7 103.3

2050 157.5 136.4 136.3 136.3 134.1 130.2 130.1 127.5 128.2

2060 193.2 167.3 167.2 167.2 164.5 159.6 159.6 156.3 157.2

Fuel Savings Compared to No Action

2020 -- 4.4 5.5 5.8 6.5 7.8 7.6 8.4 8.4

2030 -- 12.4 12.8 12.9 14.4 16.8 16.8 18.5 18.1

2040 -- 17.0 17.1 17.1 18.9 22.0 22.1 24.2 23.7

2050 -- 21.2 21.2 21.2 23.4 27.4 27.4 30.1 29.4

2060 -- 26.0 26.0 26.0 28.7 33.6 33.6 36.9 36.0

Table 2.6-12 presents the cumulative fuel consumption and fuel savings for light trucks from the 

onset of the proposed new CAFE standards. Fuel consumption by 2060 reaches 103.8 billion gallons 

under the No Action Alternative (Alternative 1). Consumption declines across the alternatives, from 92.2 

billion gallons under Alternative 2 (3-percent annual increase in mpg) to 84.6 billion gallons under 

Alternative 8 (7-percent annual increase in mpg). This represents a fuel savings of 11.5 to 19.1 billion 

gallons in 2060, as compared to fuel consumption projected under the No Action Alternative. 

 

40 NHTSA considers these AEO projected mpg increases to be reasonably foreseeable future action under NEPA 

because the AEO projections reflect future consumer and industry actions that result in ongoing mpg gains through 

2030. The AEO projections of fuel economy gains beyond the EISA requirement of combined achieved 35 mpg by 

2020 result from a future forecasted increase in consumer demand for fuel economy resulting from projected fuel 

price increases. 
Chapter 2 Proposed Action and Alternatives 

Table 2.6-12 

Cumulative Effects of Light Truck Annual Fuel Consumption and Fuel Savings by Alternative 

(billion gallons gasoline equivalent) 

Calendar Alt. 1 Alt. 2 Alt. 3 Alt. 4 Alt. 5 Alt. 6 Alt. 7 Alt. 8 Alt. 9 

Year No 

Action 

3%/year 

Increase 

4%/year 

Increase

~4.3%/year

Increase 

Preferred 

5%/year 

Increase

~6.0%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.6%/year 

Increase 

TCTB 

Fuel Consumption

2020 75.6 72.8 72.2 71.7 71.2 70.0 70.2 69.6 69.6

2030 69.4 63.4 63.2 62.5 61.5 59.8 59.9 58.9 59.0

2040 73.1 65.4 65.4 64.7 63.5 61.5 61.4 60.2 60.5

2050 85.6 76.2 76.2 75.3 73.9 71.5 71.4 70.0 70.3

2060 103.8 92.2 92.3 91.2 89.4 86.6 86.4 84.6 85.1

Fuel Savings Compared to No Action

2020 -- 2.7 3.4 3.9 4.4 5.6 5.3 6.0 6.0

2030 -- 6.0 6.3 6.9 7.9 9.6 9.6 10.6 10.4

2040 -- 7.7 7.7 8.5 9.7 11.6 11.7 12.9 12.6

2050 -- 9.4 9.4 10.3 11.7 14.1 14.2 15.6 15.3

2060 -- 11.5 11.5 12.6 14.3 17.2 17.3 19.1 18.7

Table 2.6-13 presents the cumulative fuel consumption and fuel savings for passenger cars and 

light trucks combined from the onset of the proposed new CAFE standards. Fuel consumption by 2060 

reaches 297.0 billion gallons under the No Action Alternative (Alternative 1). Consumption declines 

across the alternatives, from 259.5 billion gallons under Alternative 2 (3-percent annual increase in mpg) 

to 241.0 billion gallons under Alternative 8 (7-percent annual increase in mpg). This represents a fuel 

savings of 37.5 to 56.0 billion gallons in 2060, as compared to fuel consumption projected under the No 

Action Alternative. 

Table 2.6-13 

Cumulative Effects of Car & Light Truck Annual Fuel Consumption and Fuel Savings by Alternative 

(billion gallons gasoline equivalent) 

Calendar Alt. 1 Alt. 2 Alt. 3 Alt. 4 Alt. 5 Alt. 6 Alt. 7 Alt. 8 Alt. 9 

Year No 

Action 

3%/year 

Increase 

4%/year 

Increase

~4.3%/year

Increase 

Preferred 

5%/year 

Increase

~6.0%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.6%/year 

Increase 

TCTB 

Fuel Consumption

2020 149.4 142.2 140.5 139.7 138.5 136.0 136.4 135.0 135.0

2030 169.9 151.5 150.7 150.0 147.6 143.4 143.5 140.8 141.4

2040 200.1 175.4 175.3 174.6 171.6 166.4 166.3 163.0 163.8

2050 243.1 212.5 212.5 211.7 208.0 201.7 201.5 197.4 198.4

2060 297.0 259.5 259.5 258.4 253.9 246.2 246.0 241.0 242.2

Fuel Savings Compared to No Action

2020 -- 7.1 8.9 9.7 10.9 13.4 13.0 14.4 14.4

2030 -- 18.4 19.1 19.9 22.3 26.4 26.4 29.1 28.5

2040 -- 24.7 24.8 25.5 28.5 33.7 33.8 37.1 36.3

2050 -- 30.6 30.6 31.5 35.2 41.4 41.6 45.7 44.7

2060 -- 37.5 37.5 38.5 43.1 50.8 51.0 56.0 54.7

 2-42 
Chapter 2 Proposed Action and Alternatives 

 2-43 

2.6.2.2 Air Quality 

Table 2.6-14 summarizes the cumulative impacts for national toxic and criteria pollutants in 

2050.41 The table lists the action alternatives (Alternatives 2 through 9) left to right in order of generally 

increasing fuel economy requirements. In the case of PM2.5, SOx, NOx, and VOCs, the No Action 

Alternative results in the highest annual emissions, and emissions generally decline as fuel economy 

standards increase across alternatives. Exceptions to this declining trend are NOx under Alternatives 7 

and 9; PM2.5 under Alternatives 5 through 8; SOx under Alternatives 3 and 5; and VOCs under 

Alternatives 7 and 9. Despite these individual increases, emissions of PM2.5, SOx, NOx, and VOCs remain 

below the levels under the No Action Alternative. In the case of CO, emissions under Alternatives 2 

through 4 are slightly higher than under the No Action Alternative and are lower than under the No 

Action Alternative under Alternatives 5 through 9. Emissions of CO decline as fuel economy standards 

increase across Alternatives 2 through 9. 

Table 2.6-14 

Cumulative Nationwide Criteria Pollutant Emissions (tons/year) from Passenger Cars and 

Light Trucks by Alternative 

Alt. 1 Alt. 2 Alt. 3 Alt. 4 Alt. 5 Alt. 6 Alt. 7 Alt. 8 Alt. 9 

No 

Action 

3%/year 

Increase 

4%/year 

Increase

~4.3%/year

Increase 

Preferred 

5%/year 

Increase 

~6.0%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.6%/year 

Increase 

TCTB 

Criteria Pollutant Emissions (Calendar Year 2050) 

Carbon 

monoxide 

(CO) 28,943,491 29,227,165 29,179,262 29,098,748 27,809,337 26,721,219 26,941,788 26,099,919 26,408,318

Nitrogen 

oxides (NOx) 1,736,474 1,699,529 1,697,706 1,693,875 1,649,549 1,606,445 1,614,485 1,582,550 1,593,216

Particulate 

matter (PM2.5) 123,444 117,742 117,605 117,478 118,957 119,187 119,450 120,068 119,763

Sulfur oxides 

(SOx) 298,565 261,582 261,779 261,029 262,851 260,415 259,761 258,601 258,142

Volatile 

organic compounds (VOC) 2,157,634 1,988,851 1,986,963 1,978,405 1,892,334 1,803,021 1,808,713 1,745,102 1,767,929

Toxic Air Pollutant Emissions (Calendar Year 2050) 

Acetaldehyde 10,061 10,138 10,144 10,143 10,024 9,951 9,947 9,871 9,894

Acrolein 494 500 501 504 547 585 579 609 585

Benzene 29,272 29,163 29,128 29,057 28,000 27,082 27,243 26,539 26,794

1,3-butadiene 4,376 4,426 4,422 4,418 4,359 4,310 4,325 4,289 4,304

Diesel 

particulate 

matter (DPM) 157,271 137,711 137,612 137,050 135,284 131,578 131,581 129,470 130,085

Formaldehyde 11,476 11,456 11,491 11,534 12,063 12,550 12,425 12,772 12,638

 

41 Because the Chapter 4 analysis assumes that new vehicles in model years beyond MY 2016 have a higher fleet 

average fuel economy based on AEO fuel economy projections, these assumptions result in emissions reductions 

and fuel savings that continue to grow as these new, more fuel-efficient vehicles are added to the fleet in each 

subsequent year, reaching their maximum values when all passenger cars and light trucks in the U.S. fleet have these 

higher mpg levels. Because of this, NHTSA analyzed the air emissions through 2050, when most of the fleet would 

achieve the average fuel economy levels the agency projects in 2030 (based on AEO fuel economy forecasts). By 

2050, 98 percent of passenger cars and 88 percent of light trucks will have been produced in 2030 or later. Because 

newer vehicles are utilized more than older ones, the fraction of total passenger car and light truck VMT that these 

vehicles account for would be even higher – 99 percent for passenger cars and 94 percent for light trucks. 
Chapter 2 Proposed Action and Alternatives 

The trends for cumulative emissions of toxic air pollutants across the alternatives are mixed. 

Annual emissions of acetaldehyde in 2050 increase under each successive alternative from the No Action 

Alternative to Alternative 3, and then decrease from Alternative 3 to Alternative 9. Annual emissions of 

acrolein are higher than the No Action Alternative, and increase under each successive alternative from 

the No Action Alternative to Alternative 9, though the increase is not consistent between Alternatives 6 

and 9. Annual emissions of 1,3-butadiene in 2050 increase from the No Action Alternative to Alternative 

2 and then decrease, though not consistently, from Alternative 3 to Alternative 9. The minimum 

emissions of 1,3-butadiene occurs under Alternative 8. Annual emissions in 2050 of benzene and DPM 

decrease from the No Action Alternative to Alternative 9, though the decrease is not consistent between 

Alternatives 6 and 9. The minimum emissions of benzene and DPM occur under Alternative 8. Annual 

emissions of formaldehyde in 2050 decrease from the No Action Alternative to Alternative 2, and then 

increase, though not consistently, from Alternative 2 to Alternative 9. 

Cumulative emissions in 2030 generally would be less than noncumulative emissions for the 

same combination of pollutant and alternative because of differing changes in VMT and fuel consumption 

under the cumulative case compared to the noncumulative case. The exceptions in 2030 are acetaldehyde 

for all alternatives, acrolein for all alternatives (except Alternatives 1 through 4 and Alternative 8), 1,3-

butadiene all alternatives, and CO for all alternatives.(See Section 4.3 for cumulative emissions data for 

2030. Cumulative emissions were compared to noncumulative emissions for 2030 rather 2050 because 

noncumulative emissions were not estimated for 2050.) 

The reductions in emissions are expected to lead to reductions in cumulative adverse health 

effects. Table 2.6-15 summarizes the national annual changes in health outcomes in 2050 for the nine 

alternatives, left to right in order of increasing fuel economy requirements. Reductions in mortality are 

given based on data from two alternative studies, which EPA considers co-equal, consistent with EPA 

policy for presentation of future health outcomes. There would be reductions in adverse health effects 

nationwide under all the action alternatives compared to the No Action Alternative. Reductions in 

adverse health effects increase from Alternative 2 through Alternative 4, with mixed results under 

Alternatives 5 through 7, and increase again under Alternatives 8 and 9. These reductions primarily 

reflect the projected PM2.5 reductions, and secondarily the reductions in SO2. 

Table 2.6-15 

Cumulative Nationwide Changes in Health Outcomes (cases/year) from Criteria Air Pollutant Emissions from 

Passenger Cars and Light Trucks by Alternative a/ 

Out- Alt. 1 Alt. 2 Alt. 3 Alt. 4 Alt. 5 Alt. 6 Alt. 7 Alt. 8 Alt. 9 

come 

and 

Year 

No 

Action b/ 

3%/year 

Increase 

4%/year 

Increase 

~4.3%/year

Increase 

Preferred 

5%/year 

Increase 

~6.0%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.6%/year 

Increase 

TCTB 

 Mortality (ages 30 and older), Pope et al. 2002 

2050 0 -410 -417 -430 -415 -466 -449 -465 -465

Mortality (ages 30 and older), Laden et al. 2006 

2050 0 -1,048 -1,067 -1,098 -1,062 -1,192 -1,147 -1,188 -1,190

Chronic bronchitis 

2050 0 -260 -265 -273 -265 -298 -286 -297 -297

Emergency Room Visits for Asthma 

2050 0 -362 -366 -376 -358 -394 -383 -394 -396

Work Loss Days 

2050 0 -44,853 -45,691 -47,074 -45,648 -51,374 -49,365 -51,187 -51,231

__________ 

a/ Negative changes indicate reductions; positive changes indicate increases. 

b/ Changes in health outcome under the No Action Alternative are shown as zero because the No Action 

Alternative is the baseline to which emissions under the action alternatives are compared. 

 2-44 
Chapter 2 Proposed Action and Alternatives 

The economic value of health impacts would vary proportionally with changes in health 

outcomes. Table 2.6-16 lists the corresponding annual monetized health benefits in 2050 under the action 

alternatives compared to the No Action Alternative. Monetized health benefits are given based on data 

from two alternative studies, which EPA considers co-equal, and for two alternative assumptions of the 

discount rate, 3 percent and 7 percent, consistent with EPA policy for presentation of future health 

benefits. 

Table 2.6-16 

Cumulative Nationwide Monetized Health Benefits (U.S. million dollars/year) from Criteria Air Pollutant 

Emissions from Passenger Cars and Light Trucks by Alternative a/ 

Alt. 1 Alt. 2 Alt. 3 Alt. 4 Alt. 5 Alt. 6 Alt. 7 Alt. 8 Alt. 9 

Disc. 

and 

Year 

No 

Action b/ 

3%/year 

Increase 

4%/year 

Increase 

~4.3%/year

Increase 

Preferred 

5%/year 

Increase 

~6.0%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.6%/year 

Increase 

TCTB 

3-% Discount Rate

Pope et al. 2002 

2050 0 -3,709 -3,775 -3,888 -3,760 -4,219 -4,061 -4,205 -4,212

Laden et al. 2006 

2050 0 -9,091 -9,253 -9,529 -9,214 -10,339 -9,952 -10,305 -10,322

7-% Discount Rate

Pope et al. 2002 

2050 0 -3,364 -3,424 -3,526 -3,410 -3,827 -3,683 -3,814 -3,820

Laden et al. 2006 

2050 0 -8,211 -8,358 -8,607 -8,322 -9,338 -8,989 -9,307 -9,323

__________ 

a/ Negative changes indicate monetized health benefits; positive emissions changes indicate monetized health 

disbenefits. 

b/ Changes in outcome for the No Action Alternative are shown as zero because the No Action Alternative is the 

baseline to which impacts under the action alternatives are compared. 

2.6.2.3 Climate Change 

The Reference Case global emissions scenario used in the cumulative impacts analysis (and 

described in Chapter 4 of this EIS) differs from the global emissions scenario used for the climate change 

modeling presented in Chapter 3. In Chapter 4, the Reference Case global emissions scenario reflects 

reasonably foreseeable actions in global climate change policy; in Chapter 3, the global emissions 

scenario used for the analysis assumes that there are no significant global controls. Given that the climate 

system is non-linear, the choice of a global emissions scenario could produce different estimates of the 

benefits of the proposed action and alternatives, if the emission reductions of the alternatives were held 

constant. See Section 4.4 for more information on the emissions scenarios chosen for this analysis. 

The SAP 2.1 MiniCAM Level 3 scenario assumes a moderate level of global GHG reductions, 

resulting in a global atmospheric CO2 concentration of roughly 650 parts per million by volume (ppmv) 

as of 2100. The following regional, national, and international initiatives and programs are reasonably 

foreseeable actions to reduce GHG emissions: Regional Greenhouse Gas Initiative (RGGI); Western 

Climate Initiative (WCI); Midwestern Greenhouse Gas Reduction Accord; EPA’s Proposed GHG 

Emissions Standards; Cap-and-Trade Bills in the 111th Congress; Renewable Fuel Standard (RFS2); 

White House Goal to Reduce U.S. GHG Emissions by 17 percent by 2020; United Nation’s Framework 

Convention on Climate Change (UNFCCC) – The Kyoto Protocol and the December 2009 Conference of 

 2-45 
Chapter 2 Proposed Action and Alternatives 

 2-46 

the Parties (COP)-15; The European Union Greenhouse Gas Emission Trading System (EU ETS); G8 

Declaration – Summit 2009; and the Asia Pacific Partnership on Clean Development and Climate.42 

NHTSA used the MiniCAM Level 3 scenario as the primary global emissions scenario for 

evaluating climate effects, and used the MiniCAM Level 2 scenario and the RCP 4.5 MiniCAM reference 

emissions scenario to evaluate the sensitivity of the results to alternative emission scenarios. The 

sensitivity analysis provides a basis for determining climate responses to varying levels of climate 

sensitivities and global emissions under the No Action Alternative (Alternative 1) and the Preferred 

Alternative (Alternative 4). Some responses of the climate system are believed to be non-linear; by using 

a range of emissions cases and climate sensitivities, it is possible to estimate the effects of the alternatives 

in relation to different reference cases. 

2.6.2.3.1 Cumulative GHG Emissions 

Table 2.6-17 shows total GHG emissions and emissions reductions from new passenger cars and 

light trucks from 2012-2100 under each of the nine alternatives. Projections of emissions reductions over 

the 2012 to 2100 period due to the MYs 2012-2016 CAFE standards and other reasonably foreseeable 

future actions ranged from 30,200 to 45,600 MMTCO2. Compared to global emissions of 3,919,462 

MMTCO2 over this period (projected by the SAP 2.1 MiniCAM Level 3 scenario), the incremental 

impact of this rulemaking is expected to reduce global CO2 emissions by about 0.8 to 1.2 percent from 

their projected levels under the No Action Alternative. 

Table 2.6-17 

Cumulative Effects of Emissions and Emissions Reductions (MMTCO2) from 2012-2100 

by Alternative 

Alternative Emissions 

Emissions Reductions Compared 

to No Action Alternative 

1 No Action 259,800 0 

2 3%/year Increase 229,600 30,200 

3 4%/year Increase 229,300 30,400 

4 ~4.3%/year Increase, Preferred 228,400 31,400 

5 5%/year Increase 224,700 35,100 

6 ~6.0%/year Increase, MNB 218,400 41,400 

7 6%/year Increase 218,300 41,500 

8 7%/year Increase 214,200 45,600 

9 ~6.6%/year Increase, TCTB 215,200 44,600 

Emissions of CO2, the primary gas that drives climate effects, from the U.S. passenger car and 

light truck fleet represented about 3.3 percent of total global emissions of CO2 in 2005. Although 

substantial, this source is a still small percentage of global emissions. The relative contribution of CO2

emissions from U.S. passenger cars and light trucks is expected to decline in the future, due primarily to 

 

42 The regional, national, and international initiatives and programs discussed above are those which NHTSA has 

tentatively concluded are reasonably foreseeable past, current, or future actions to reduce GHG emissions. Although 

some of the actions, policies, or programs listed are not associated with precise GHG reduction commitments, 

collectively they illustrate a current and continuing trend of U.S. and global awareness, emphasis, and efforts 

towards significant GHG reductions. Together they imply that future commitments for reductions are probable and, 

therefore, reasonably foreseeable under NEPA. 
Chapter 2 Proposed Action and Alternatives 

 2-47 

rapid growth of emissions from developing economies (which are due in part to growth in global 

transportation sector emissions). 

2.6.2.3.2 CO2 Concentration, Global Mean Surface Temperature, Sea-level Rise, 

and Precipitation 

The mid-range results of MAGICC model simulations for the No Action Alternative and the eight 

action alternatives in terms of CO2 concentrations and increase in global mean surface temperature in 

2030, 2050, and 2100 are presented in Table 2.6-18 and Figures 2.6-6 through 2.6-9. As Figures 2.6-8 

and 2.6-9 show, the impact on the growth in CO2 concentrations and temperature is just a fraction of the 

total growth in CO2 concentrations and global mean surface temperature. However, the relative impact of 

the action alternatives is illustrated by the reduction in growth of both CO2 concentrations and 

temperature in the TCTB Alternative (Alternative 9). 

As shown in the table and figures, there is a fairly narrow band of estimated CO2 concentrations 

as of 2100, from 653.4 ppm for Alternative 8 (7%/year increase in fuel economy) to 657.4 ppm for the No 

Action Alternative (Alternative 1). For 2030 and 2050, the range is even smaller. Because CO2

concentrations are the key driver of all other climate effects, this leads to small differences in these 

effects. Although these effects are small, they occur on a global scale and are long-lived. 

The MAGICC simulations of mean global surface air temperature increases are also shown in 

Table 2.6-18. For all alternatives, the cumulative global mean surface temperature increase is about 

0.80 °C to 0.81 °C (1.44 to 1.46 °F) as of 2030; 1.32 to 1.33 °C (2.38 to 2.39 °F) as of 2050; and 2.59 to 

2.61 °C (4.66 to 4.70 °F) as of 2100.43 The differences among alternatives are small. For 2100, the 

reduction in temperature increase for the action alternatives in relation to the No Action Alternative is 

about 0.01 to 0.02 °C (0.02 to 0.04 °F). 

The impact on sea-level rise from the scenarios is presented in Table 2.6-18, showing sea-level 

rise in 2100 ranging from 32.84 centimeters under the No Action Alternative (Alternative 1) to 32.68 

centimeters under Alternatives 8 and 9, for a maximum reduction of 0.16 centimeters (0.06 inches) by 

2100 from the action alternatives. 

Given that the action alternatives would reduce temperature increases slightly in relation to the 

No Action Alternative (Alternative 1), they also would reduce predicted increases in precipitation 

slightly, as shown in Table 2.6-19. 

In summary, the impacts of the proposed action and alternatives and other reasonably foreseeable 

future actions on global mean surface temperature, sea-level rise, and precipitation are relatively small in 

the context of the expected changes associated with the emissions trajectories in the SRES scenarios.44 

This is due primarily to the global and multi-sectoral nature of the climate problem. Although these 

effects are small, they occur on a global scale and are long-lived. 

 

43 Because the actual increase in global mean surface temperature lags the commitment to warming, the impact on 

global mean surface temperature increase is less than the long-term commitment to warming. 44 These conclusions are not meant to be interpreted as expressing NHTSA’s views that impacts on global mean 

surface temperature, precipitation, or sea-level rise are not areas of concern for policymakers. Under NEPA, the 

agency is obligated to discuss “the environmental impact[s] of the proposed action.” 42 U.S.C. § 4332(2)(C)(i) 

(emphasis added). This analysis fulfills NHTSA’s obligations in this regard. 
Chapter 2 Proposed Action and Alternatives 

 2-48 

Table 2.6-18 

Cumulative Effects on CO2 Concentrations, Global Mean Surface Temperature Increase, and Sea-level Rise 

Using MAGICC (MiniCAM Level 3) by Alternative a/ 

CO2 Concentration 

(ppm) 

Global Mean Surface 

Temperature Increase

(°C) Sea-level Rise (cm) 

Totals by Alternative 2030 2050 2100 2030 2050 2100 2030 2050 2100 

1 No Action 438.7 498.0 657.4 0.805 1.327 2.611 7.83 13.67 32.84 

2 3%/year Increase 438.5 497.2 654.8 0.805 1.323 2.599 7.83 13.65 32.74 

3 4%/year Increase 438.5 497.2 654.8 0.804 1.323 2.599 7.83 13.65 32.74 

4 ~4.3%/year Increase, Preferred 438.5 497.2 654.7 0.804 1.323 2.599 7.83 13.65 32.73 

5 5%/year Increase 438.4 497.1 654.3 0.804 1.322 2.597 7.83 13.65 32.72 

6 ~6.0%/year Increase, MNB 438.4 496.9 653.8 0.804 1.321 2.594 7.83 13.64 32.69 

7 6%/year Increase 438.4 496.9 653.8 0.804 1.321 2.594 7.83 13.64 32.69 

8 7%/year Increase 438.3 496.8 653.4 0.804 1.321 2.592 7.83 13.64 32.68 

9 ~6.6%/year Increase, TCTB 438.3 496.8 653.5 0.804 1.321 2.593 7.83 13.64 32.68 

Reductions Under Alternative CAFE Standards

2 3%/year Increase 0.2 0.8 2.7 0.001 0.004 0.012 0.00 0.02 0.10 

3 4%/year Increase 0.2 0.8 2.7 0.001 0.004 0.012 0.00 0.02 0.10 

4 ~4.3%/year Increase, Preferred 0.2 0.8 2.8 0.001 0.004 0.012 0.00 0.02 0.11 

5 5%/year Increase 0.3 0.9 3.2 0.001 0.004 0.014 0.00 0.02 0.12 

6 ~6.0%/year Increase, MNB 0.3 1.1 3.7 0.002 0.006 0.017 0.00 0.03 0.15 

7 6%/year Increase 0.3 1.1 3.7 0.002 0.005 0.017 0.00 0.03 0.15 

8 7%/year Increase 0.4 1.2 4.1 0.002 0.006 0.019 0.00 0.03 0.16 

9 ~6.6%/year Increase, TCTB 0.4 1.2 4.0 0.002 0.006 0.018 0.00 0.03 0.16 

__________

a/ Values in this table are rounded. 
Chapter 2 P

Figure 2.6-6. Cumulative Effects on CO2 Concentrations Using MAGICC 

0

100200300400500600700

2030 2050 2100

ppm

No Action Al t. 2: 3%/yea r Increa seAl t. 3: 4%/yea r Increa se Al t. 4: ~4.3%/yea r Increa se, Pre ferredAl t. 5: 5%/yea r Increa se Al t. 6: ~6.0%/yea r Increa se, MNBAl t. 7: 6%/yea r Increa se Al t. 8: 7%/yea r Increa seAl t. 9: ~6.6%/yea r Increa se, TCTB

2-49 
Chapter 2 Proposed Action and Alternatives 

Figure 2.6-7. Cumulative Effects on the Global Mean Surface Temperature Increase Us

MAGICC by Alternative 

0

0.5

1

1.5

2

2.5

3

2030 2050 2100

degrees Celsius

No Acti on Al t. 2: 3%/yea r Increa seAl t. 3: 4%/yea r Increa se Al t. 4: ~4.3%/yea r Increa se, Pre fe rredAl t. 5: 5%/yea r Increa se Al t. 6: ~6.0%/yea r Increa se, MNBAl t. 7: 6%/yea r Increa se Al t. 8: 7%/yea r Increa seAl t. 9: ~6.6%/yea r Increa se, TCTB

2-50 
Chapter 2 P

Figure 2.6-8. Cumulative Effects on CO2 Concentrations (Reduction Compared to the No Action 

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

2030 2050 2100

ppm

Al t. 2: 3%/yea r Increa se Al t. 3: 4%/yea r Increa se Al t. 4: ~4.3%/yea r Increa se, Al t. 5: 5%/yea r Increa se Al t. 6: ~6.0%/yea r Increa se, MNB Al t. 7: 6%/yea r Increa seAl t. 8: 7%/yea r Increa se Al t. 9: ~6.6%/yea r Increa se, TCTB

2-51 
Chapter 2 Proposed Action and Alternatives 

2-52 

Figure 2.6-9. Cumulative Effects on Global Mean Temperature (Reduction Compared 

the No Action Alternative) 

0.0000.0020.0040.0060.0080.0100.0120.0140.0160.0180.020

2030 2050 2100

degrees Celsius

Al t. 2: 3%/yea r Increa se Al t. 3: 4%/yea r Increa se Al t. 4: ~4.3%/yea r Increa se, Pre Al t. 5: 5%/yea r Increa se Al t. 6: ~6.0%/yea r Increa se, MNB Al t. 7: 6%/yea r Increa seAl t. 8: 7%/yea r Increa se Al t. 9: ~6.6%/yea r Increa se, TCTB
Chapter 2 Proposed Action and Alternatives 

Table 2.6-19 

Cumulative Effects on Global Mean Precipitation (percent change) a/ 

Scenario 2020 2055 2090 

Global Mean Precipitation Change (scaled, % per °C) 1.45 1.51 1.63 

Global Temperature Above Average 1980-1999 Levels (°C) 

1 No Action 0.586 1.466 2.415 

2 3%/year Increase 0.586 1.462 2.405 

3 4%/year Increase 0.585 1.461 2.405 

4 ~4.3%/year Increase, Preferred 0.585 1.461 2.405 

5 5%/year Increase 0.585 1.459 2.403 

6 ~6.0%/year Increase, MNB 0.585 1.459 2.401 

7 6%/year Increase 0.585 1.459 2.401 

8 7%/year Increase 0.585 1.459 2.399 

9 ~6.6%/year Increase, TCTB 0.585 1.459 2.400 

Reduction in Global Temperature (°C) for Alternative CAFE Standards, Mid-level Results (Compared to No 

Action Alternative) 

2 3%/year Increase 0.000 0.004 0.010 

3 4%/year Increase 0.000 0.004 0.010 

4 ~4.3%/year Increase, Preferred 0.000 0.005 0.011 

5 5%/year Increase 0.000 0.005 0.012 

6 ~6.0%/year Increase, MNB 0.000 0.007 0.015 

7 6%/year Increase 0.000 0.007 0.015 

8 7%/year Increase 0.000 0.007 0.016 

9 ~6.6%/year Increase, TCTB 0.000 0.007 0.016 

Global Mean Precipitation Change (%)

1 No Action 0.85% 2.21% 3.94% 

2 3%/year Increase 0.85% 2.21% 3.92% 

3 4%/year Increase 0.85% 2.21% 3.92% 

4 ~4.3%/year Increase, Preferred 0.85% 2.21% 3.92% 

5 5%/year Increase 0.85% 2.21% 3.92% 

6 ~6.0%/year Increase, MNB 0.85% 2.20% 3.91% 

7 6%/year Increase 0.85% 2.20% 3.91% 

8 7%/year Increase 0.85% 2.20% 3.91% 

9 ~6.6%/year Increase, TCTB 0.85% 2.20% 3.91% 

Reduction in Global Mean Precipitation Change for Alternative CAFE Standards (% Compared to 

No Action Alternative)

2 3%/year Increase 0.00% 0.01% 0.02% 

3 4%/year Increase 0.00% 0.01% 0.02% 

4 ~4.3%/year Increase, Preferred 0.00% 0.01% 0.02% 

5 5%/year Increase 0.00% 0.01% 0.02% 

6 ~6.0%/year Increase, MNB 0.00% 0.01% 0.02% 

7 6%/year Increase 0.00% 0.01% 0.02% 

8 7%/year Increase 0.00% 0.01% 0.03% 

9 ~6.6%/year Increase, TCTB 0.00% 0.01% 0.03% 

__________

a/ The numbers in this table have been rounded for presentation purposes. As a result, the reductions might not 

 reflect the exact difference of the values in all cases. 

NHTSA examined the sensitivity of climate effects on key assumptions used in the analysis. The 

two variables for which assumptions were varied were climate sensitivity and global emissions. 

 2-53 
Chapter 2 Proposed Action and Alternatives 

 2-54 

Climate sensitivities used included 2.0, 3.0, and 4.5 °C for a doubling of CO2 concentrations in 

the atmosphere. Global emissions scenarios used included the SAP 2.1 MiniCAM Level 3 (650 ppm as 

of 2100), the SAP 2.1 MiniCAM Level 2 (550 ppm as of 2100), and RCP 4.5 MiniCAM reference 

scenario (783 ppm as of 2100). The sensitivity analysis is based on the results provided for two 

alternatives – the No Action Alternative (Alternative 1) and the Preferred Alternative (Alternative 4). The 

sensitivity analysis was conducted only for two alternatives, as this was deemed sufficient to assess the 

effect of various climate sensitivities on the results. 

The results of these simulations illustrate the uncertainty due to factors influencing future global 

emissions of GHGs (factors other than the CAFE rulemaking). 

The use of different climate sensitivities45 (the equilibrium warming that occurs at a doubling of 

CO2 from pre-industrial levels) can affect not only warming but also indirectly affect sea-level rise and 

CO2 concentration. The use of alternative global emissions scenarios can influence the results in several 

ways. Emissions reductions can lead to larger reductions in the CO2 concentrations in later years because 

more anthropogenic emissions can be expected to stay in the atmosphere. 

As shown in Table 2.6-20, the sensitivity of the simulated CO2 emissions in 2030, 2050, and 2100 

to assumptions of global emissions and climate sensitivity is low; stated simply, CO2 emissions do not 

change much with changes in global emissions and climate sensitivity. For 2030 and 2050, the choice of 

global emissions scenario has little impact on the results. By 2100, the Preferred Alternative (Alternative 

4) has the greatest impact in the global emissions scenario with the highest CO2 emissions (MiniCAM 

Reference) and the least impact in the scenario with the lowest CO2 emissions (MiniCAM Level 2). The 

total range of the impact of the Preferred Alternative on CO2 concentrations in 2100 is from 2.6 to 3.1 

ppm. The Reference Case using the MiniCAM Level 3 scenario and a 3.0 °C climate sensitivity has an 

impact of 2.8 ppm. 

The sensitivity of the simulated global mean surface temperatures for 2030, 2050, and 2100 is 

also shown in Table 2.6-20. In 2030, the impact is low due primarily to the slow rate at which the global 

mean surface temperature increases in response to increases in radiative forcing. In 2100, the impact is 

large due not only to the climate sensitivity but also to the change in emissions. In 2030, the reduction in 

global mean surface temperature from the No Action Alternative to the Preferred Alternative is 0.001 to 

0.002 °C (0.002 to 0.004 °F) across the climate sensitivities and global emissions scenarios, as shown in 

Table 2.6-20. The impact on global mean surface temperature due to assumptions concerning global 

emissions of GHG is also important. The scenarios with the higher global emissions of GHGs, such as 

the MiniCAM Reference, have a lower reduction in global mean surface temperature and the scenarios 

with lower global emissions have a higher reduction. This is in large part due to the non-linear and nearlogarithmic relationship between radiative forcing and CO2 concentrations. At high emissions levels, CO2

concentrations are high; therefore, a fixed reduction in emissions yields a lower reduction in radiative 

forcing and global mean surface temperature. 

The sensitivity of simulated sea-level rise to change in climate sensitivity and global GHG 

emissions mirrors that of global temperature, as shown in Table 2.6-20. Scenarios with lower climate 

sensitivities have lower increases in sea-level rise; the increase in sea-level rise is lower under the 

 

45 Equilibrium climate sensitivity (or climate sensitivity) is the projected responsiveness of Earth’s global climate 

system to forcing from GHG drivers, and is often expressed in terms of changes to global surface temperature 

resulting from a doubling of CO2 in relation to pre-industrial atmospheric concentrations. According to IPCC, using 

a likely emissions scenario that results in a doubling of the concentration of atmospheric CO2, there is a 66- to 90-

percent probability of an increase in surface warming of 2.5 to 4.0 °C by the end of the century (relative to 1990 

average global temperatures), with 3 °C as the single most likely surface temperature increase. 
Chapter 2 Proposed Action and Alternatives 

 2-55 

Preferred Alternative (Alternative 4) than it would be under scenarios with higher climate sensitivities. 

Conversely, scenarios with higher climate sensitivities have higher sea-level rise; the increase of sea-level 

rise is higher under the Preferred Alternative than it would be under scenarios with lower climate 

sensitivities. Higher global GHG emissions have higher sea-level rise, but the impact of the Preferred 

Alternative is less than in scenarios with lower global emissions. Conversely, scenarios with lower global 

GHG emissions have lower sea-level rise, though the impact of the Preferred Alternative is greater than in 

scenarios with higher global emissions. 

Table 2.6-20 

Cumulative Effects on CO2 Concentrations, Global Mean Surface Temperature Increase, and Sea-level Rise 

for Varying Climate Sensitivities for Selected Alternatives a/ 

Emissions 

Scenario 

CAFE 

Alternative 

Climate 

Sensitivity 

(°C for 2xCO2)

CO2 concentration 

(ppm) 

Global Mean Surface 

Temperature Increase (°C) 

Sea-level 

Rise (cm)

2030 2050 2100 2030 2050 2100 2100 

MiniCAM Level 2 

1 No Action 2.0 434.5 483.8 553.5 0.613 0.989 1.555 22.40 

3.0 436.0 487.3 565.9 0.813 1.327 2.189 30.03 

4.5 437.6 491.3 581.3 1.035 1.709 2.963 38.88 

4 Preferred 2.0 434.3 482.9 550.9 0.612 0.986 1.545 22.31 

3.0 435.7 486.4 563.1 0.812 1.323 2.175 29.91 

4.5 437.3 490.4 578.5 1.033 1.704 2.946 38.74 

Reduction compared to No Action 

2.0 0.2 0.9 2.6 0.001 0.003 0.010 0.09 

3.0 0.3 0.9 2.8 0.001 0.004 0.014 0.12 

4.5 0.3 0.9 2.8 0.001 0.005 0.017 0.14 

MiniCAM Level 3 

1 No Action 2.0 437.3 494.5 643.4 0.607 0.990 1.888 24.68 

3.0 438.7 498.0 657.5 0.805 1.327 2.611 32.84 

4.5 440.3 502.0 675.2 1.024 1.706 3.475 42.24 

4 Preferred 2.0 437.0 493.7 640.6 0.606 0.987 1.879 24.59 

3.0 438.5 497.2 654.7 0.804 1.323 2.599 32.73 

4.5 440.0 501.2 672.2 1.023 1.701 3.459 42.10 

Reduction compared to No Action 

2.0 0.3 0.8 2.8 0.001 0.003 0.009 0.09 

3.0 0.2 0.8 2.8 0.001 0.004 0.012 0.11 

4.5 0.3 0.8 3.0 0.001 0.005 0.015 0.14 

MiniCAM Reference 

1 No Action 2.0 440.2 510.7 765.1 0.699 1.168 2.292 28.68 

3.0 441.8 514.8 783.0 0.923 1.557 3.136 38.00 

4.5 443.6 519.5 805.3 1.168 1.991 4.132 48.67 

4 Preferred 2.0 439.9 509.9 762.2 0.698 1.165 2.284 28.60 

3.0 441.5 514.0 780 0.922 1.553 3.124 37.90 

4.5 443.3 518.7 802.2 1.166 1.987 4.118 48.54 

Reduction compared to No Action 

2.0 0.3 0.8 2.9 0.001 0.003 0.008 0.08 

3.0 0.3 0.8 3.0 0.001 0.004 0.011 0.10 

4.5 0.3 0.8 3.1 0.002 0.005 0.014 0.13 

__________

a/ The numbers in this table have been rounded for presentation purposes. As a result, the reductions might not 

 reflect the exact difference of the values in all cases. 

Chapter 3 Affected Environment and Environmental 

Consequences 

3.1 INTRODUCTION 

Council on Environmental Quality (CEQ) regulations for implementing the National 

Environmental Policy Act (NEPA) suggest a standard format for an environmental impact statement 

(EIS) that includes a section to describe the affected environment (existing conditions) and a section to 

describe the potential environmental consequences (impacts) of a proposed action and alternatives. In 

this EIS, the National Highway Traffic Safety Administration (NHTSA) describes the affected 

environment and potential environmental consequences of the proposed action and alternatives in sections 

under the heading for each resource area – energy (Section 3.2), air quality (Section 3.3), climate (Section 

3.4), and various other potentially affected resource areas (Section 3.5). This structure enables the reader 

to readily learn about existing environmental conditions and potential environmental consequences 

related to each resource area. Section 3.6 identifies unavoidable impacts and irreversible and irretrievable 

commitments of resources associated with the implementation of the Corporate Average Fuel Economy 

(CAFE) standards evaluated in this EIS. 

The following table lists topics addressed in a typical EIS and the section(s) in this chapter that 

address each topic. 

Typical NEPA Topics EIS Sections

Water 3.4 Climate; 3.5.1 Water Resources 

Ecosystems 3.4 Climate; 3.5.1 Water Resources; 3.5.2 Biological Resources 

Threatened and endangered species 3.5.2.1.4 Endangered Species 

Publicly owned parklands, recreational 

areas, wildlife and waterfowl refuges, 

historic sites, Section 4(f)-related issues 

3.4 Climate; 3.5.1 Water Resources; 3.5.2 Biological Resources; 

3.5.3 Land Use and Development; 3.5.6 Land Uses Protected 

under Section 4(f); 3.5.7 Historic and Cultural Resources 

Properties and sites of historic and cultural 

significance 

3.4 Climate; 3.5.3 Land Use and Development; 3.5.6 Land Uses 

Protected under Section 4(f); 3.5.7 Historic and Cultural Resources 

Considerations relating to pedestrians and 

bicyclists 

3.4 Climate; 3.5.3 Land Use and Development 

Social impacts 3.2 Energy; 3.4 Climate; 3.5.3 Land Use and Development; 

3.5.9 Environmental Justice 

Noise 3.4 Climate; 3.5.3 Land Use and Development; 3.5.8 Noise 

Air 3.2 Energy; 3.3 Air Quality; 3.4 Climate 

Energy supply and natural resource 

development 

3.2 Energy; 3.3 Air Quality; 3.4 Climate; 3.5.1 Water Resources; 

3.5.2 Biological Resources; 3.5.3 Land Use and Development 

Floodplain management evaluation 3.4 Climate; 3.5.1 Water Resources 

Wetlands and coastal zones 3.4 Climate; 3.5.1 Water Resources; 3.5.2 Biological Resources 

Construction impacts 3.2 Energy; 3.3 Air Quality; 3.4 Climate; 3.5.1 Water Resources; 

3.5.2 Biological Resources; 3.5.3 Land Use and Development 

Land use and urban growth 3.2 Energy; 3.3 Air Quality; 3.4 Climate; 3.5.1 Water Resources; 

3.5.2 Biological Resources; 3.5.3 Land Use and Development 

Human environment involving community 

disruption and relocation 

3.2 Energy; 3.3 Air Quality; 3.4 Climate; 3.5.3 Land Use and 

Development; 3.5.4 Safety and Other Human Health Impacts; 

3.5.5 Hazardous Materials and Regulated Wastes; 3.5.9 

Environmental Justice 

 3-1 
3.1 Introduction Chapter 3 Affected Environment and Environmental Consequences 

 3-2 

3.1.1 Direct and Indirect Impacts 

CEQ regulations state that an EIS “shall succinctly describe” the environment to be affected by 

the alternatives under consideration and to provide data and analyses “commensurate with the importance 

of the impact[s].” 40 CFR §§ 1502.15, 1502.16. This chapter provides the analysis to determine and 

compare the significance of the direct and indirect effects of the proposed action and alternatives. Under 

NEPA, direct effects “are caused by the action and occur at the same time and place.” 40 CFR § 1508.8. 

CEQ regulations define indirect effects as those that “are caused by the action and are later in time or 

farther removed in distance but are still reasonably foreseeable. Indirect effects may include...effects on 

air and water and other natural systems, including ecosystems.” 40 CFR § 1508.8. Sections 3.2, 3.3, and 

3.4 provide a quantitative analysis of the direct and indirect effects of the proposed action and alternatives 

on energy, air, and climate, respectively. Section 3.5 qualitatively describes impacts to other resource 

areas typically addressed in an EIS and the areas required by U.S. Department of Transportation (DOT) 

Order 5610, such as biological resources, water resources, noise, land use, and environmental justice, 

because there were not enough data available in the literature for a quantitative analysis and because 

many of these effects are not localized. In this EIS, such qualitative analysis is sufficient for NEPA 

purposes (DOT 1979). 1

3.1.2 Areas Not Affected 

DOT NEPA procedures describe various areas that should be considered in an EIS. Many of 

these areas are addressed Sections 3.2 through 3.6. NHTSA has considered the impact of the proposed 

action and alternatives on all areas outlined in the procedures and has determined that the action 

alternatives would not directly or indirectly affect the human environment in relation to disruption and 

relocation, and considerations related to pedestrians and bicyclists, floodplain management, and 

construction impacts. However, the cumulative impacts of the proposed action and alternatives in 

combination with other foreseeable actions could affect some of these areas of the human environment 

(see Chapter 4). 

3.1.3 Approach to Scientific Uncertainty and Incomplete Information 

CEQ regulations recognize that many federal agencies encounter limited information and 

substantial uncertainties when they analyze the potential environmental impacts of their actions. 

Accordingly, the regulations provide agencies with a means of formally acknowledging incomplete or 

unavailable information in NEPA documents. Where “information relevant to reasonably foreseeable 

significant adverse impacts cannot be obtained because the overall costs of obtaining it are exorbitant or 

the means to obtain it are not known,” the regulations require an agency to include in its NEPA 

document: 

1. A statement that such information is incomplete or unavailable; 

2. A statement of the relevance of the incomplete or unavailable information to evaluating 

reasonably foreseeable significant adverse impacts on the human environment; 

3. A summary of existing credible scientific evidence relevant to evaluating the reasonably 

foreseeable significant adverse impacts on the human environment; and 

 

1 See 42 U.S.C. § 4332 (requiring federal agencies to “identify and develop methods and procedures...which will 

insure that presently unquantified environmental amenities and values may be given appropriate consideration”); 40 

CFR § 1502.23 (requiring an EIS to discuss the relationship between a cost-benefit analysis and any analyses of 

unquantified environmental impacts, values, and amenities); CEQ (1984) (recognizing that agencies are sometimes 

“limited to qualitative evaluations of effects because cause-and-effect relationships are poorly understood” or cannot 

be quantified). 
Chapter 3 Affected Environment and Environmental Consequences 3.1 Introduction 

4. The agency’s evaluation of such impacts based on theoretical approaches or research methods 

generally accepted in the scientific community. 

40 CFR § 1502.22(b). 

Relying on these provisions is appropriate when an agency is performing a NEPA analysis that 

involves potential environmental impacts due to carbon dioxide (CO2) emissions. See, e.g., Mayo Found. 

v. Surface Transp. Bd., 472 F.3d 545, 555 (8th Cir. 2006). CEQ regulations also authorize agencies to 

incorporate material into a NEPA document by reference to “cut down on bulk without impeding agency 

and public review of the action.” 40 CFR § 1502.21. 

Throughout this EIS, NHTSA uses these two mechanisms – acknowledging incomplete or 

unavailable information and incorporation by reference – to address areas for which NHTSA cannot 

develop a credible estimate of the potential environmental impacts of the proposed action and 

alternatives. In particular, NHTSA recognizes that information about the potential environmental impacts 

of changes in emissions of CO2 and other greenhouse gases (GHGs) and associated changes in 

temperature, including those expected to result from the proposed rule, is incomplete. NHTSA often 

relies on the Intergovernmental Panel on Climate Change (IPCC) 2007 Fourth Assessment Report (IPCC 

2007a, 2007b, 2007c) as a recent “summary of existing credible scientific evidence which is relevant to 

evaluating the reasonably foreseeable significant adverse impacts on the human environment.” 40 CFR § 

1502.22(b)(3). 

3.1.4 Common Methodologies 

The CAFE Compliance and Effects Modeling System (referred to herein as the Volpe model) is a 

peer-reviewed modeling system developed by the DOT Volpe National Transportation Systems Center 

(Volpe Center). The Volpe model enables NHTSA to efficiently, systematically, and reproducibly 

evaluate many regulatory options by projecting technologies each manufacturer could apply in a given 

year to comply with a specific set of standards and by calculating the costs and effects of manufacturers’ 

application of technologies, including changes in fuel use and therefore CO2 emissions. The Volpe model 

provides outputs that NHTSA used to analyze potential impacts to energy, air, and climate. 

The Volpe model begins with an initial state of the domestic vehicle market, which in this case is 

the market for passenger cars and light trucks. The model is designed to calculate incremental costs, 

effects, and benefits of alternative scenarios (i.e., regulatory alternatives) relative to a specified baseline 

scenario (i.e., a no-action alternative) and based on a specified market forecast. The market forecast, the 

baseline scenario, and all alternative scenarios are specified in model inputs – the model does not 

determine these inputs. For this analysis, the market forecast through model year (MY) 2016 specified as 

an input to the Volpe model is based on the MY 2008 fleet, with adjustments to sales volumes of specific 

vehicle models. NHTSA used the Volpe model to estimate the extent to which manufacturers could add 

technology under the baseline scenario, under which manufacturers are assumed to continue to comply 

with the MY 2011 CAFE standards. This baseline scenario forms NHTSA's no-action alternative. All 

environmental effects attributable to technologies added under this scenario are subtracted from those 

attributable to all the other scenarios (i.e., regulatory alternatives). 

For the model years covered under the current proposal, the combined passenger car and light 

truck market forecast developed by NHTSA and the U.S. Environmental Protection Agency (EPA) staff 

using MY 2008 CAFE compliance data includes about 1,100 vehicle models, about 400 specific engines, 

and about 200 specific transmissions. This level of detail in the representation of the vehicle market is 

similar to that NHTSA used in recent CAFE analyses, and to that NHTSA uses when determining actual 

compliance with CAFE standards. Within the limitations of information that can be made available to the 

public, it provides the foundation for a realistic analysis of manufacturer-specific costs and the analysis of 

 3-3 
3.1 Introduction Chapter 3 Affected Environment and Environmental Consequences 

 3-4 

footprint-based CAFE standards, and this level of detail is much greater than the level of detail used by 

other models and analyses relevant to combined passenger car and light truck fuel economy.2

 

The Volpe model also uses several additional categories of data and estimates provided in various 

external input files for all 12 vehicle subclasses (sub-compact, sub-compact performance, compact, 

compact performance, midsize, midsize performance, large, and large performance cars; small sport 

utility vehicles [SUVs]/pickup trucks/vans, midsize SUVs/pickup trucks/vans, large SUVs/pickup 

trucks/vans, and minivans) including: 

• Fuel-saving technology characteristics, such as: 

− Commercialization year; 

− Effectiveness and cost; 

− “Learning effect” cost coefficients; 

− “Technology path” inclusion/exclusion; 

− “Phase-in caps” on penetration rates; and 

− “Synergy” effects. 

• Vehicular emissions rates for criteria air pollutants and their chemical precursors, including 

carbon monoxide (CO), volatile organic compounds (VOCs), nitrogen oxides (NOx), 

particulate matter (PM), and sulfur dioxide (SO2); these emission rates are functions of either 

vehicle use, as measured by the number of vehicle miles traveled (VMT), or fuel 

consumption, economic, and other data and estimates, such as: 

− Vehicle survival (percent of vehicles of a given vintage that remain in service); 

− Mileage accumulation (annual travel by vehicles of a given vintage); 

− Price/fuel taxation rates for seven fuels (such as gasoline and diesel); 

− Pump prices (including taxes) for vehicle fuel savings/retail price; 

− Rebound effect coefficient (the elasticity of VMT in relation to per-mile cost of fuel); 

− Discount rate; “payback period” (the number of years purchasers consider when taking 

into account fuel savings); 

− Fuel economy “gap” (for example, laboratory versus actual); 

− Per-vehicle value of travel time (in dollars per hour); 

− The economic costs (in dollars per gallon) of petroleum consumption; 

− Various external costs (all in dollars per mile) associated with changes in vehicle use; 

− Damage costs (all on a dollar-per-ton basis) for each of the above-mentioned criteria 

pollutants; and 

− The civil-penalties rate for noncompliance. 

• Properties of different fuels, such as: 

− Upstream CO2 and criteria pollutant emissions rates (that is, U.S. emissions resulting 

from the production and distribution of each fuel); 

− Density (pounds per gallon); energy density (British thermal unit per gallon); 

− Carbon content; 

− Shares of fuel savings leading to reduced domestic refining; and 

− Relative shares of different gasoline blends. 

 

2

 Because CAFE standards apply to the average performance of each manufacturer’s fleet of passenger cars and light 

trucks, the impact of potential standards on individual manufacturers cannot be credibly estimated without analysis 

of the fleets that manufacturers can be expected to produce in the future. Furthermore, because required CAFE 

levels under an attribute-based CAFE standard depend on manufacturers’ fleet composition, the stringency of an 

attribute-based standard cannot be predicted without performing analysis at this level of detail. 
Chapter 3 Affected Environment and Environmental Consequences 3.1 Introduction 

 3-5 

• Sensitivity analysis coefficients; high and low fuel price forecasts. 

• CAFE scenarios 

− Baseline (no action or business-as-usual); and 

− Alternative scenarios defining coverage, structure, and stringency of CAFE standards. 

NHTSA estimates and specifies all of the input data, then uses the modeling system to project a 

set of technologies that each manufacturer could apply to its individual vehicle models in attempting to 

comply with the various levels of potential CAFE standards to be examined. The Volpe model then 

estimates the costs associated with this additional technology utilization, and accompanying changes in 

travel demand; fuel consumption; fuel outlays; emissions of criteria air pollutants; toxic air pollutants; 

and GHGs, and economic externalities related to petroleum consumption and other factors. 

One of the updates to the model for the current rulemaking is the addition of a “multi-year 

planning” capability, developed in response to comments on prior CAFE rulemakings. The version of the 

Volpe model used in the previous EIS did not have that capability. For example, when modeling MY 

2014, only vehicles with technologies “enabled” in MY 2014 would be candidates for technology 

application. When run in multi-year mode, the model “looks back” to earlier years when a technology 

was enabled on any vehicles but not used, and considers “back-dating” the application of that technology 

when calculating the effective cost. Thus, if the model did not apply an enabled technology in MYs 2012 

or 2013, then that technology remains available for multi-year application in MY 2014. 

The Volpe model’s multi-year analysis mode is anticipated to be most useful in situations where 

the model finds that a manufacturer is able to reach compliance in earlier years of the modeling period 

(e.g., MY 2012) but is challenged to reach compliance in later years (e.g., MY 2014). In these cases, the 

model can go back to the earlier year and over-comply to make compliance in the later year easier to 

achieve. Although this capability is computationally implemented in this “backward-looking” fashion, 

the approach simulates a manufacturer’s ability to apply foresight in earlier model years to facilitate 

compliance in later model years, adding “extra” technology to a given model year’s fleet to boost CAFE 

levels ahead of time, so that less technology needs to be added in years that are not major redesign years. 

The Volpe model completes this compliance simulation for all manufacturers and all model years 

and produces various outputs from the effects of changes in fuel economy. The outputs include: 

• Total cost (TC) of all applied technologies; 

• Year-by-year mileage accumulation, including increased vehicle use due to the rebound 

effect; 

• Year-by-year fuel consumption; 

• Benefits from additional travel due to the fuel economy rebound effect, as measured by 

consumer surplus;3

• Emissions of CO2, other GHGs, criteria air pollutants, and airborne toxics, including 

emissions from vehicle use and domestic emissions from fuel production and distribution,4

and the economic value of resulting damages to human health; 

• Total discounted/undiscounted national societal costs of year-to-year fuel consumption; 

 

3

 Consumer surplus measures the net benefits drivers receive from additional travel and refers to the amount by 

which the benefits from additional travel exceed its costs (for fuel and other operating expenses). 

4

 Domestic full-fuel-cycle emissions include the emissions associated with production, transportation, and refining 

operations, and the CO2 emissions from fuel combustion. 
3.1 Introduction Chapter 3 Affected Environment and Environmental Consequences 

• Economic externalities caused by increased vehicle use (congestion, accidents, noise); 

• Value of refueling time saved; and 

• Total discounted/undiscounted societal benefits, including net social benefits and benefit-cost 

ratio. 

The specific outputs associated with each action alternative examined in this EIS reflect the 

assumed values for key inputs to the Volpe model. The outputs of the Volpe model provide data used to 

analyze impacts to energy, air, and climate, so these environmental impacts also reflect the inputs into the 

Volpe model. Recognizing the uncertainty inherent in many of the underlying estimates in the model, 

NHTSA has used the Volpe model to conduct both sensitivity analyses (by changing the assumed value 

of one input at a time), and a probabilistic uncertainty analysis (a Monte Carlo analysis that allows 

simultaneous variation in these factors) to examine how key measures (e.g., miles-per-gallon [mpg] levels 

of the standard, total costs, and total benefits) vary in response to changes in these factors. This type of 

analysis is used to estimate the uncertainty surrounding the model’s estimates of the costs and benefits of 

a given set of CAFE standards. Chapter 2 describes the results of the sensitivity analysis. 

The model can also be used to estimate the stringency at which various criteria are satisfied, such 

as (a) a specified average required CAFE level, (b) maximum net benefits to society, (c) total costs equal 

to total benefits to society, or (d) a specified total incremental cost. However, while the Volpe model 

does calculate average changes in vehicle prices (corresponding to total technology outlays and, where 

applicable, civil penalties), it does not currently predict manufacturers’ decisions regarding the pricing or 

production of specific vehicle models. Nor does it currently estimate for consumer behavioral responses 

such as buying fewer vehicles or buying different types of vehicles. The agency uses information from 

the Volpe model, and analysis performed outside the model, to assist in setting standards. 

Although NHTSA has used the Volpe model as a tool to inform its consideration of potential 

CAFE standards, the Volpe model does not determine the CAFE standards NHTSA will propose or 

promulgate as final regulations. NHTSA considers the results of analyses conducted using the Volpe 

model and external analyses, including assessments of GHGs and air pollutant emissions, and 

technologies that might be available in the longer term. NHTSA also considers whether the standards 

could expedite the introduction of new technologies into the market, and the extent to which changes in 

vehicle prices and fuel economy might affect vehicle production and sales. Using all of this information, 

the agency considers the governing statutory factors, along with environmental issues and other relevant 

societal issues, such as safety, and promulgates the maximum feasible standards based on its best 

judgment on how to balance these factors. 

For additional detail on how the Volpe model works and the outputs it produces (and which 

outputs NHTSA uses to estimate environmental impacts), see the joint NHTSA-EPA Notice of Proposed 

Rulemaking (NPRM) (Sections II.A, II.B, and II.C) and the accompanying joint Technical Support 

Document. See Docket Nos. NHTSA-2009-0059-0015, NHTSA-2009-0059-0029. 

3.1.4.1 Effect of Credit Flexibility on Emissions 

Consistent with the Energy Independence and Security Act (EISA), NHTSA’s March 30, 2009 

MY 2011 CAFE final rule not only set MY 2011 CAFE standards for passenger cars and light trucks, but 

also revised and added new regulatory provisions regarding the creation and application of CAFE credits. 

See 74 FR , 14196, 14428-14436 (Mar. 30, 2009). CAFE credits are earned when a manufacturer exceeds 

an applicable CAFE standard. Manufacturers can then use those credits to achieve compliance in years in 

which their measured average fuel economy falls below the standards. In this context, CAFE credits refer 

to flexibilities allowed under the Energy Policy and Conservation Act (EPCA) provisions governing use 

of Alternative Motor Fuels Act (AMFA) credits, allowable banked credits, and transfers of credits 

 3-6 
Chapter 3 Affected Environment and Environmental Consequences 3.1 Introduction 

 3-7 

between the passenger car and light truck fleets allowed under EISA. Through MY 2019, AMFA credits 

allow manufacturers to increase their CAFE levels by producing alternative fuel vehicles, such as dualfueled/flexible-fueled vehicles (FFVs) that can run on both gasoline and E85 ethanol-based fuel. The 

AMFA amended EPCA in 1988 to provide an incentive for producing these vehicles by specifying that 

their fuel economy is to be determined using a special calculation procedure that results in those vehicles 

being assigned a high fuel economy level. The additional flexibility to transfer credits between 

manufacturing companies is addressed separately below. Because EPCA prohibits NHTSA from 

considering these flexibilities when determining the stringency of CAFE standards, NHTSA did not 

attempt to do so when it developed standards it has considered for this action. 

Under the EISA, AMFA credits are being phased out. The allowable credits are reduced so that, 

by law, by 2020 such credits will no longer be allowed. However, notwithstanding the EPCA constraints 

regarding the context for establishing CAFE standards, NHTSA could attempt to account for the creation 

and application of CAFE credits when evaluating the environmental impacts of new CAFE standards 

under NEPA. 

NHTSA believes that manufacturers are likely to take advantage of these flexibility mechanisms, 

thereby reducing benefits and costs. Manufacturers producing dual-fueled vehicles are entitled to a 

CAFE benefit of up to 1.2 mpg in 2012-2014, 1.0 mpg in 2015, and 0.8 mpg in 2016 for each fleet. 

NHTSA estimates that the impact of the use of AMFA credits could result in an average reduction of 

approximately 0.9 mpg in achieved average fuel economy in 2012-2016, and a related increase in CO2

emissions. Regarding credits other than AMFA credits (e.g., CAFE credits earned through overcompliance, credits transferred between fleets, and credits acquired from other manufacturers), NHTSA 

does not have a sound basis to predict the extent to which manufacturers might use them, particularly 

because the credit-transfer and credit-trading programs have been only recently authorized, and credit 

transfers could involve complex interactions and multi-year planning.5

3.1.4.2 Difficulties in Quantifying Emissions Implications of Credits 

Questions NHTSA might need to address in performing an analysis of potential credit use and the 

resulting emissions include the following: 

• Would manufacturers that have never used CAFE flexibilities do so in the future? 

• Would flexibility-induced increases in the sale of flexible-fuel vehicles (FFVs) lead to 

increases in the use of alternative fuels? 

• Having earned CAFE credits in a given model year, in what model year would a given 

manufacturer most likely apply those credits, and how might that affect technologies added 

through multi-year planning? 

• Having earned CAFE credits in one fleet (i.e., passenger car or light truck), to which fleet 

would a given manufacturer most likely apply those credits? 

Such questions are similar to, though possibly less tractable than, the behavioral and strategic 

questions that were entailed in representing manufacturers’ ability to “pull ahead” the implementation of 

some technologies, and that would be involved in attempting to estimate CAFE-induced changes in 

market shares. Although the Volpe model has been modified to account for multi-year planning effects, 

 

5

 For example, if a manufacturer is planning to redesign many vehicles in MY 2013, but few vehicles in MY 2015 

when standards will also be significantly more stringent, the benefits (in terms of reducing regulatory burden) of 

using some flexibilities in MY 2013 (e.g., credit transfers) could be outweighed by the benefits of applying extra 

technologies in MY 2013 to carry them forward to facilitate compliance in MY 2015. 
3.1 Introduction Chapter 3 Affected Environment and Environmental Consequences 

 3-8 

substantial concerns remain about how to develop a credible market-share model for integration into the 

modeling system NHTSA has used to analyze the costs and effects of CAFE standards. 

3.1.4.3 Market Behavior 

Some manufacturers make substantial use of current flexibilities. Other manufacturers regularly 

exceed CAFE standards applicable to one or both fleets, and allow the corresponding excess CAFE 

credits to expire. Some manufacturers transfer earned CAFE credits to future (or past) model years, but 

do not produce FFVs and create corresponding CAFE credits. Finally, still other manufacturers regularly 

pay civil penalties for noncompliance, even when producing FFVs would substantially reduce the 

magnitude of those penalties. 

Notwithstanding these uncertainties, NHTSA anticipates that manufacturers would make varied 

use of the flexibilities provided by EPCA, as amended by EISA. These flexibilities could result in 

somewhat lower benefits (that is, CO2 emissions reductions) than estimated here, because manufacturers’ 

actions would cause VMT levels, fuel consumption, and emissions to be higher than reported here. 

NHTSA expects that the nine alternatives evaluated in this EIS, including the No Action Alternative in 

relation to which NHTSA measures the effects of the eight action alternatives, would be affected. Insofar 

as the No Action Alternative would be affected, it is even less certain how the net effects of each of the 

eight action alternatives would change. 

NHTSA expects that use of flexibilities would tend to be greater under more stringent standards. 

As stringency increases, the potential for manufacturers to face greater cost increases, and for some, 

depending on their level of technological implementation, costs could rise substantially. The economic 

advantage of employing allowed CAFE increases through the use of flexibilities could affect 

manufacturer behavior in this regard. A critical factor in addressing the fuel and emissions impacts of 

such flexibilities is that the likely extent of utilization cannot be assumed constant across the alternatives. 

3.1.4.4 Trading Between Companies 

The allowable trading between manufacturers is categorically different from the case discussed 

above. The provisions in Section 104 of Title I of the EISA require that fuel savings, and thus, GHG 

emissions, be conserved in any trades between manufacturers.6 Therefore, there would not be an 

environmental impact of any such trades because any increases in fuel use or emissions would have to be 

offset by the manufacturer buying the credits. 

 

6

 “The Secretary of Transportation [by delegation, the Administrator of NHTSA] may establish by regulation a fuel 

economy credit trading program to allow manufacturers whose automobiles exceed the average fuel economy 

standards prescribed under section 32902 to earn credits to be sold to manufacturers whose automobiles fail to 

achieve the prescribed standards such that total oil savings associated with manufacturers that exceed the prescribed 

standards are preserved when trading credits to manufacturers that fail to achieve the prescribed standards.” 

49 U.S.C. § 32903(f)(1). 
Chapter 3 Affected Environment and Environmental Consequences 3.2 Energy 

 3-9 

3.2 ENERGY 

Energy intensity in the United States (energy use per dollar of gross domestic product [GDP]) has 

declined steadily at about 2 percent per year since 1973, when the U.S. Department of Energy (DOE) 

began tracking the statistic (EIA 2009a). Since 2000, energy intensity in the U.S. economy has fallen 

from 10.08 million British thermal units per dollar of “real” or inflation-adjusted GDP, measured in year 

2000 dollars to 8.52 million British thermal units per dollar of GDP (in year 2000 dollars), and DOE 

projections show a further steady decline through 2035, with energy intensity reaching 5.12 million 

British thermal units per dollar of GDP (in year 2000 dollars) in the latter year (EIA 2009c). Although 

U.S. population and economic activity have grown steadily, energy intensity has fallen due to a 

combination of increased efficiency and a structural shift in the economy toward less energy-intensive 

industries. The most recent projection from the DOE Energy Information Administration (EIA) has 

population increasing 28 percent between 2008 and 2030, but energy consumption per capita declining 

0.4 percent annually during the same period. Despite this continuing improvement in economy-wide 

energy efficiency, however, transportation fuel consumption has grown steadily, and now represents the 

major use of petroleum in the U.S. economy. 

3.2.1 Affected Environment 

NHTSA uses energy projections from the EIA, which collects and provides the official energy 

statistics for the United States. EIA is the primary source of data used by government agencies and 

private firms to analyze and model energy systems. Every year EIA issues projections of energy 

consumption and supply for both the United States (Annual Energy Outlook [AEO]) and for the world 

(International Energy Outlook [IEO]). EIA reports and projects energy consumption by energy mode, by 

sector, and by geographic region. The modeling used to formulate the EIA’s projections incorporates all 

federal and state laws and regulations that are in force at the time of the modeling. 

In the case of the AEO 2010, EIA issued an early release (December 14, 2009) update of the 

Reference Case released in April 2009 to incorporate the impacts of the American Recovery and 

Reinvestment Act of 2009,7

 the MY 2011 CAFE standards, and an update of the macroeconomic 

assumptions (EIA 2009c). Table 3.2.1-1 shows U.S. and global energy consumption by sector. Actual 

energy-consumption data show a steady increase in energy use in all U.S. sectors. By 2004, the 

transportation sector was the second largest consumer of energy after the industrial sector, and comprised 

27.8 and 17.3 percent of U.S. and global (less U.S.) energy use, respectively. Both very high oil prices 

and the beginning of the global recession resulted in data for 2006 and 2008 being somewhat atypical. 

Over half of U.S. energy consumption in the transportation sector can be attributed to passenger cars and 

light trucks, ranging from 60 percent in 2008 to 57 percent by 2035. Going forward in time, 

transportation energy consumption is expected to continue to be the largest component after the industrial 

sector, but in the forecasted outer years in the United States the gap between energy consumption in the 

two sectors first widens and then narrows. As a percentage of total economy-wide energy consumption, 

projected energy use in the U.S. transportation sector remains fairly constant throughout the projection 

years. 

 The EIA projections include all forms of energy, including renewable fuels and biofuels. Despite 

efforts to increase the use of non-fossil fuels in transportation, fuel use remains largely petroleum based. 

In 2007, finished motor gasoline and on-road diesel constituted 66 percent of all finished petroleum 

products consumed in the United States. If other transportation fuels (aviation fuels, marine and 

locomotive diesel, and bunkers) are included, transportation fuels constitute approximately 79 percent of 

the finished petroleum products used. In the same year, the biofuel component of the total U.S. 

transportation sector energy consumption was slightly more than 2 percent. According to AEO 

 

7

 Pub. L. No. 111-5, 123 Stat. 115 (Feb. 17, 2009). 
3.2 Energy Chapter 3 Affected Environment and Environmental Consequences 

 3-10 

projections, the biofuels share of energy consumption in the transportation sector will rise to 12 percent 

by 2035. 

Table 3.2.1-1 

Energy Consumption By Sector 

Sector Actual a/ Forecast b/ 

(Quadrillion BTU c/) 1990 1995 2000 2004 2010 2015 2020 2025 2030 

United States 

Residential 17.0 18.6 20.5 21.2 22.1 21.8 22.5 23.3 24.0 

Commercial 13.3 14.7 17.2 17.7 19.3 20.4 21.5 22.6 23.8 

Industrial 31.9 34.0 34.8 33.6 29.7 31.3 31.7 32.3 31.9 

Transportation 22.4 23.8 26.6 27.9 28.0 28.7 28.9 30.0 31.2 

Total 84.7 91.2 99.0 100.4 99.1 102.1 104.7 108.2 111.0 

Transportation (%) 26.5 26.2 26.8 27.8 28.3 28.1 27.6 27.7 28.1 

World 

Residential - - - - - - 47.7 52.8 55.6 58.9 62.1 65.7 

Commercial - - - - - - 24.5 27.8 29.8 32.2 34.9 37.7 

Industrial - - - - - - 163.6 185.9 205.8 219.4 233.7 245.5 

Transportation - - - - - - 87.7 96.0 102.8 111.0 118.9 127.7 

Total 347.4 365.0 398.1 446.7 508.3 551.5 595.7 637.3 678.3 

Transportation (%) - - - - - - 19.6 18.9 18.6 18.6 18.7 18.8 

International (World less United States) 

Residential - - - - - - 26.5 30.7 33.8 36.4 38.8 41.7 

Commercial - - - - - - 6.8 8.5 9.4 10.7 12.3 13.9 

Industrial - - - - - - 130.0 156.2 174.5 187.7 201.4 213.6 

Transportation - - - - - - 59.8 68.0 74.1 82.1 88.9 96.5 

Total 262.8 273.9 299.2 346.3 409.2 449.4 491.0 529.1 567.3 

Transportation (%) - - - - - - 17.3 16.6 16.5 16.7 16.8 17.0 

_______________ 

a/ Actual United States data: EIA (2009c). 

 Actual World data: EIA (2009d). 

b/ Forecasted United States data: EIA (2009c). 

 Forecasted World data: EIA (2009d). 

c/ Btu = British thermal unit. 

The analysis of fuel consumption and energy use conducted for this EIS assumes that fuel 

consumed by U.S. passenger cars and light trucks will consist predominantly of gasoline or diesel fuel 

derived from petroleum for the foreseeable future. Implicitly, ethanol FFVs are assumed to operate 

exclusively on gasoline, while diesel vehicles are assumed to operate exclusively on petroleum-based 

diesel rather than on biodiesel. The estimates of gasoline consumption reported in this analysis include 

ethanol used as a gasoline additive to increase its oxygen content, while the estimates of diesel fuel 

consumption include biodiesel used as a blending agent.8

 The analysis makes no other assumption about 

the use of renewable fuels or biofuels. 

Most U.S. gasoline and diesel is produced domestically (EIA 2009a). In 2007, 4 percent of 

finished motor gasoline and 6 percent of on-road diesel were imported. However, increasing volumes of 

crude oil are imported for processing in U.S. refineries because domestic production is steadily declining. 

By 2006, petroleum imports equaled 60 percent of total liquids supplied and by 2007, crude oil imports 

 

8

 EIA data indicate that during 2007, ethanol accounted for approximately 3.6 percent of the energy content of fuel 

labeled at retail as gasoline, while biodiesel accounted for about 1.2 percent of the energy content of fuel sold at 

retail as diesel. Computed from information reported in AEO 2009 (EIA 2009b), Reference Case, Table 17 and 

Supplemental Table 46. 
Chapter 3 Affected Environment and Environmental Consequences 3.2 Energy 

had surpassed 10 million barrels per day (EIA 2009a), a high proportion of it coming from volatile and 

unstable regions. 

A fall in the demand for transportation fuels likely would affect imports of crude oil more than 

motor gasoline. Over the last decade there has been a shift in product imports, with volumes of finished 

gasoline stabilizing and declining slightly. However, volumes of motor gasoline blending components 

have been rapidly increasing, so that by 2007, the imports of blending components were twice that of 

finished gasoline. 

According to EIA, net imports of crude oil – in part due to improvements in fuel efficiency 

required by the changes in CAFE standards, in part due to substitution of biofuels, in part due to high 

prices, and in part due to a steady increase in U.S. production from the offshore – will fall to 41 percent of 

liquid fuel supply in 2020 and then decline further to 39 percent in 2035. The further decrease in 2035 is 

due in part to a projected surge in domestic crude oil production. The impact of these anticipated 

developments on the petroleum industry is likely to be felt largely by overseas producers (EIA 2009c), 

although the net impact on petroleum production levels of overseas suppliers and the associated change in 

their emissions of air pollutants and GHGs will ultimately depend on whether demand for motor fuel in 

developing nations rises sufficiently to replace declining U.S. demand. 

3.2.2 Methodology 

The methodology for examining the impact of higher CAFE standards on gasoline and diesel 

consumption relies on outputs from the Volpe model. The Volpe model, as described in Section 3.1.4, 

requires the following types of input information: (1) a forecast of the future vehicle market; (2) 

estimates of the availability, applicability, and incremental effectiveness and cost of fuel-saving 

technologies; (3) estimates of vehicle survival and mileage accumulation patterns, the rebound effect, 

future fuel prices, the “social cost of carbon,” and many other economic factors; (4) fuel characteristics 

and vehicular emissions rates; and (5) coefficients defining the shape and level of CAFE curves to be 

examined. 

Using NHTSA-selected inputs, the agency projects a set of technologies each manufacturer could 

apply in attempting to comply with the various levels of potential CAFE standards to be examined. The 

model then estimates the costs associated with this additional technology utilization, and accompanying 

changes in travel demand, fuel consumption, fuel outlays, emissions, and economic externalities related to 

petroleum consumption and other factors. 

The analysis of costs and benefits employed in the Volpe model reflects the NHTSA assessment 

of a broad range of technologies that can be applied to passenger cars and light trucks. In the agency’s 

rulemakings covering light truck CAFE standards for MYs 2005-2007 and MYs 2008-2011, the agency 

relied on the 2002 National Academy of Sciences report, Effectiveness and Impact of Corporate Average 

Fuel Economy Standards (NRC 2002) for estimating potential fuel economy benefits and associated retail 

costs of applying combinations of technologies. In developing its final rule adopting CAFE standards for 

MY 2011, NHTSA reviewed manufacturers’ technology data and comments it received on its fuel-saving 

technologies, and conducted its own independent analysis, which involved hiring an international 

engineering consulting firm that specializes in automotive engineering, the same firm EPA used in 

developing its advance notice of proposed rulemaking to regulate GHG emissions under the Clean Air 

Act (CAA). Since then, NHTSA and EPA have collaborated on further updates to estimates of the cost, 

effectiveness, and availability of fuel-saving technologies the agencies expect to be available during MYs 

2012-2016. The revised technology assumptions – that is, estimates of the availability, applicability, cost, 

and effectiveness of fuel-saving technologies, and the order in which the technologies are applied – are 

described in greater detail in the NHTSA-EPA joint technical support document (TSD) and in NHTSA’s 

 3-11 
3.2 Energy Chapter 3 Affected Environment and Environmental Consequences 

 3-12 

preliminary RIA, Docket Nos. NHTSA-2009-0059-0016.1 (RIA), NHTSA-2009-0059-0029 (TSD). See

Section 3.1.4 for further information on the Volpe model. A full discussion of changes made to the 

technology assumptions since the joint NPRM will be detailed in the forthcoming joint NHTSA-EPA 

final rule. 

The Volpe model produces various outputs, including its estimates of year-by-year fuel 

consumption by U.S. passenger car and light truck fleets. The Volpe model estimates annual fuel 

consumption and fuel savings for each calendar year from 2012, when the CAFE standards considered in 

this EIS would first take effect, through 2060, when almost all passenger cars and light trucks in use 

would have met CAFE standards at least as stringent as those established for MY 2016.9

 Therefore, the 

estimated fuel savings during 2060 represents the maximum annual fuel savings resulting from the CAFE 

standards established by this rulemaking. 

To calculate fuel savings for each action alternative, NHTSA subtracted fuel consumption under 

that alternative from its level under the No Action Alternative. The Volpe model estimated fuel savings 

using the following mpg assumptions: for MYs 2012-2016, the fuel economy of new passenger cars and 

light trucks under each action alternative increases annually in accordance with the CAFE standards 

specified in that particular alternative.10 For MYs 2017-2060, all new vehicles were assumed to meet the 

MY 2016 CAFE standards that would be established under each action alternative. In effect, this means 

that fuel economy achieved by passenger cars and light trucks produced in MYs 2017-2060 remains 

constant at their levels estimated for MY 2016 under each action alternative.11 

3.2.3 Environmental Consequences 

Table 3.2.3-1, which lists the impact on fuel consumption for passenger cars from 2020 through 

2060, shows the increasing impact of alternative CAFE standards over time. The table reports total fuel 

consumption for passenger cars, both gasoline and diesel, under the No Action Alternative (Alternative 1) 

and each of the eight action alternatives, as described in Section 2.3. By 2060, when nearly the entire 

passenger car and light truck fleet is likely to be composed of MY 2016 or later passenger cars and light 

trucks, fuel consumption reaches 205.5 billion gallons under the No Action Alternative. Fuel 

consumption is less than that projected under the No Action alternative for all the action alternatives, 

ranging from 188.4 billion gallons under Alternative 2 (3-percent annual increase in mpg) to 166.5 billion 

gallons under Alternative 8 (7-percent annual increase in mpg). In 2060, fuel consumption under the 

TCTB Alternative (Alternative 9) amounts to 10.9 million barrels of fuel per day, while under Alternative 

4 (the Preferred Alternative), daily fuel consumption amounts to 11.7 million barrels per day.12 As a 

point of reference, NHTSA projects that fuel consumption under the No Action Alternative would be 13.4 

million barrels per day in 2060. In 2007, the United States consumed 9.3 million barrels of fuel per day 

(EIA 2009a). 

 

9

 This assumes that if NHTSA does not establish more stringent CAFE standards for model years after MY 2016, 

the standards established for MY 2016 as part of the current rulemaking would be extended to apply to subsequent 

model years. 

10 The average fuel economy levels actually achieved by passenger cars and light trucks produced during a model 

year do not necessarily equal the CAFE standards for that model year. This occurs because some manufacturers’ 

average fuel economy levels for their passenger cars or light trucks are projected to exceed the applicable CAFE 

standards during certain model years, while other manufacturers’ fuel economy levels are projected to fall short of 

either the passenger car or light truck CAFE standards during some model years. As explained in Section 3.1.4.1, 

manufacturers may earn or use credits in these situations, but EPCA prohibits NHTSA from considering these 

flexibilities when determining the stringency of CAFE standards. 

11 See footnote 8 in this chapter. 12 Billions of gallons (annual) are converted to millions of barrels per day by dividing by 365 and then dividing by 

42. 
Chapter 3 Affected Environment and Environmental Consequences 3.2 Energy 

Table 3.2.3-1 

Passenger Car Annual Fuel Consumption and Fuel Savings (billion gallons of gasoline equivalent) 

Alt. 1 Alt. 2 Alt. 3 Alt. 4 Alt. 5 Alt. 6 Alt. 7 Alt. 8 Alt. 9 

Calendar 

Year 

No 

Action 

3%/year 

Increase 

4%/year 

Increase

~4.3%/year

Increase 

Preferred

5%/year 

Increase 

~6.0%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.6%/year 

Increase 

TCTB 

Fuel Consumption 

2020 74.1 70.5 68.9 68.4 67.5 66.2 66.4 65.6 65.6

2030 103.9 95.5 92.0 91.1 89.0 86.5 86.5 84.8 85.2

2040 134.5 123.3 118.6 117.4 114.7 111.3 111.3 109.0 109.6

2050 167.6 153.6 147.7 146.2 142.8 138.6 138.6 135.8 136.5

2060 205.5 188.4 181.2 179.4 175.2 170.0 170.0 166.5 167.4

Fuel Savings Compared to No Action 

2020 -- 3.6 5.2 5.7 6.6 7.9 7.7 8.5 8.4

2030 -- 8.4 11.9 12.8 14.8 17.4 17.3 19.1 18.7

2040 -- 11.2 15.9 17.1 19.9 23.2 23.3 25.5 24.9

2050 -- 14.0 19.8 21.3 24.8 28.9 29.0 31.8 31.1

2060 -- 17.2 24.3 26.2 30.4 35.5 35.5 39.0 38.1

Table 3.2.3-2 lists comparable results for light trucks for the same period and for the same 

alternative CAFE standards. As in the previous table, reported fuel consumption includes light truck 

diesel and gasoline consumption. Fuel consumption under the No Action Alternative is estimated to total 

113.0 billion gallons in 2060, and to decline progressively under the action alternatives, from 104.6 

billion gallons under Alternative 2 to 92.4 billion gallons under Alternative 8. These represent fuel 

savings compared to the No Action Alternative that range from 8.3 billion gallons annually under 

Alternative 2 to 20.6 billion gallons annually under Alternative 8, or from 0.5 million to 1.3 million 

barrels of petroleum per day. 

Table 3.2.3-2 

Light Truck Annual Fuel Consumption and Fuel Savings (billion gallons of gasoline equivalent) 

Alt. 1 Alt. 2 Alt. 3 Alt. 4 Alt. 5 Alt. 6 Alt. 7 Alt. 8 Alt. 9 

Calendar 

Year 

No 

Action 

3%/year 

Increase 

4%/year 

Increase

~4.3%/year

Increase 

Preferred 

5%/year 

Increase 

~6.0%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.6%/year 

Increase 

TCTB 

Fuel Consumption 

2020 75.8 73.5 72.4 71.9 71.4 70.2 70.5 69.8 69.8

2030 72.2 67.7 65.7 64.9 63.9 62.2 62.2 61.1 61.3

2040 78.6 73.1 70.5 69.6 68.3 66.2 66.1 64.8 65.1

2050 93.0 86.2 83.0 81.9 80.4 77.8 77.7 76.1 76.5

2060 113.0 104.6 100.7 99.4 97.5 94.4 94.3 92.4 92.8

Fuel Savings Compared to No Action 

2020 -- 2.3 3.4 3.9 4.4 5.6 5.4 6.0 6.1

2030 -- 4.4 6.5 7.2 8.2 10.0 10.0 11.0 10.9

2040 -- 5.6 8.2 9.1 10.3 12.4 12.5 13.8 13.5

2050 -- 6.8 10.0 11.1 12.6 15.2 15.3 16.9 16.5

2060 -- 8.3 12.3 13.5 15.5 18.6 18.7 20.6 20.2

Table 3.2.3-3 shows the combined passenger car and light truck projected fuel consumption and 

fuel savings under the various alternatives. Combined passenger car and light truck fuel consumption 

under the No Action Alternative is estimated to total 318.5 billion gallons in 2060, and to decline 

progressively under the action alternatives, from 293.0 billion gallons under Alternative 2 to 258.9 billion 

 3-13 
3.2 Energy Chapter 3 Affected Environment and Environmental Consequences 

 3-14 

gallons under Alternative 8. These represent fuel savings compared to the No Action Alternative that 

range from 25.5 billion gallons annually under Alternative 2 to 59.6 billion gallons annually under 

Alternative 8. 

Table 3.2.3-3 

Combined Passenger Car and Light Truck Annual Fuel Consumption and Fuel Savings a/ 

 (billion gallons of gasoline equivalent) 

Alt. 1 Alt. 2 Alt. 3 Alt. 4 Alt. 5 Alt. 6 Alt. 7 Alt. 8 Alt. 9 

Calendar 

Year 

No 

Action 

3%/year 

Increase 

4%/year 

Increase

~4.3%/year

Increase 

Preferred 

5%/year 

Increase 

~6.0%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.6%/year 

Increase 

TCTB 

Fuel Consumption 

2020 149.9 144.0 141.3 140.3 139.0 136.5 136.9 135.4 135.4 

2030 176.0 163.2 157.7 156.0 153.0 148.7 148.7 146.0 146.5 

2040 213.2 196.4 189.1 187.0 183.0 177.5 177.4 173.9 174.7 

2050 260.5 239.7 230.7 228.2 223.2 216.5 216.3 211.9 213.0 

2060 318.5 293.0 281.9 278.8 272.7 264.5 264.3 258.9 260.3 

Fuel Savings Compared to No Action 

2020 -- 6.0 8.7 9.7 10.9 13.5 13.0 14.5 14.5 

2030 -- 12.8 18.4 20.0 23.1 27.4 27.3 30.1 29.5 

2040 -- 16.8 24.1 26.2 30.2 35.7 35.8 39.3 38.4 

2050 -- 20.8 29.9 32.4 37.4 44.1 44.3 48.6 47.5 

2060 -- 25.5 36.6 39.7 45.8 54.0 54.2 59.6 58.3 

_______________ 

a/ Some of the values shown for car & light truck fuel consumption in this table vary slightly from the 

sum of values shown separately for passenger cars and light trucks in previous tables due to rounding error. 

 The reductions in U.S. gasoline consumption and demand for crude petroleum projected to result 

from alternative increases in CAFE standards could lead to reductions in global petroleum prices, and 

thus to lower gasoline prices throughout the world. One consequence of lower prices would be increases 

in gasoline consumption outside the U.S., which would lead to increased emissions of greenhouse gases, 

criteria air pollutants, and airborne toxics from global fuel production and use. These increases have the 

potential to offset a modest share of the reductions in emissions projected to occur as a consequence of 

lower fuel production and consumption within the United States. A numerical example using Leiby’s 

(2008) mean estimate of the sensitivity of global petroleum prices to changes in U.S. import demand 

suggests that increases in fuel consumption outside the U.S. could offset about 8 percent of the emissions 

reductions projected to result from the alternative increases in CAFE standards analyzed in this FEIS.13

Given the various assumptions and uncertainties in our analyses, an 8 percent change would not change 

the overall conclusions or analysis of the alternatives made in this EIS. 

 

13 Using Leiby’s reported range of uncertainty surrounding his mean estimate of the sensitivity of global petroleum 

prices to U.S. import demand, increases in fuel consumption outside the U.S. could offset from 3 percent (under 

Alternative 2) to 15 percent (under Alternative 9) of the emissions reductions projected to result from alternative 

increases in CAFE standards (Leiby 2008). 
Chapter 3 Affected Environment and Environmental Consequences 3.3 Air Quality 

3-15 

3.3 AIR QUALITY 

3.3.1 Affected Environment 

3.3.1.1 Relevant Pollutants and Standards 

The proposed CAFE standards would affect air pollution and air quality, which in turn, have the 

potential to affect public health and welfare and the environment. The CAA is the primary federal 

legislation that addresses air quality. Under the authority of the CAA and its amendments, EPA has 

established National Ambient Air Quality Standards (NAAQS) for six criteria pollutants14 (relatively 

commonplace pollutants that can accumulate in the atmosphere as a result of normal levels of human 

activity). This EIS air quality analysis assesses the impacts of the No Action Alternative and action 

alternatives in relation to criteria pollutants and some hazardous air pollutants from mobile sources. 

The criteria pollutants are CO, nitrogen dioxide (NO2) (one of several oxides of nitrogen), ozone, 

SO2, PM with an aerodynamic diameter equal to or less than 10 microns (PM10) and 2.5 microns (PM2.5), 

and lead. Ozone is not emitted directly from vehicles, but is evaluated based on emissions of the ozone 

precursor pollutants nitrogen oxides (NOx) and VOCs.15

The U.S. transportation sector is a major source of emissions of certain criteria pollutants or their 

chemical precursors. Total emissions from on-road mobile sources (passenger cars and light trucks) have 

declined dramatically since 1970 as a result of pollution controls on vehicles and regulation of the 

chemical content of fuels, despite continuing increases in the amount of vehicle travel. From 1970 to 

2008, the most recent year for which data are available, emissions from on-road mobile sources declined 

76 percent for CO, 59 percent for NOx, 64 percent for PM10, 77 percent for SO2, and 80 percent for 

VOCs. Emissions of PM2.5 from on-road mobile sources declined 66 percent from 1990, the earliest year 

for which data are available, to 2008 (EPA 2009i). 

On-road mobile sources are responsible for 50 percent of total U.S. emissions of CO, 4 percent of 

PM2.5 emissions, and 1 percent of PM10 emissions (EPA 2009i). Almost all of the PM in motor-vehicle 

exhaust is PM2.5; therefore, this analysis focuses on PM2.5 rather than PM10. On-road mobile sources also 

contribute 21 percent of total nationwide emissions of VOCs and 32 percent of NOx, which are chemical 

precursors of ozone. In addition, NOx is a PM2.5 precursor and VOCs can be PM2.5 precursors. On-road 

mobile sources contribute only 1 percent of SO2, but SO2 and other oxides of sulfur (SOx) are important 

because they contribute to the formation of PM2.5 in the atmosphere; however, on-road mobile sources 

contribute only 1 percent of SO2. With the elimination of lead in automotive gasoline, lead is no longer 

emitted from motor vehicles in more than negligible quantities. Lead is not assessed further in this 

analysis. 

Table 3.3.1-1 lists the primary and secondary NAAQS for each criteria pollutant. Primary 

standards are set at levels intended to protect against adverse effects on human health; secondary 

standards are intended to protect against adverse effects on public welfare, such as damage to agricultural 

 

14 “Criteria pollutants” is a term used to collectively describe the six common air pollutants for which the CAA 

requires EPA to set NAAQS. EPA calls these pollutants “criteria” air pollutants because it regulates them by 

developing human-health-based and/or environmentally based criteria (science-based guidelines) for setting 

permissible levels. “Hazardous air pollutants,” by contrast, refer to substances defined as hazardous by the 1990 

CAA amendments. These substances include certain VOCs, compounds in PM, pesticides, herbicides, and 

radionuclides that present tangible hazards, based on scientific studies of human (and other mammal) exposure. 15 Ozone is a photochemical oxidant and the major component of smog. Ozone is not emitted directly into the air, 

but is formed through complex chemical reactions between precursor emissions of VOCs and NOx in the presence of 

the ultraviolet component of sunlight. 
3.3 Air Quality Chapter 3 Affected Environment and Environmental Consequences 

crops or vegetation, and damage to buildings or other property. Because each criteria pollutant has 

different potential effects on human health and public welfare, the NAAQS specify different permissible 

levels for each pollutant. NAAQS for some pollutants include standards for both short- and long-term 

average levels. Short-term standards, which typically specify higher levels of a pollutant, are intended to 

protect against acute health effects from short-term exposure to higher levels of a pollutant; long-term 

standards are established to protect against chronic health effects resulting from long-term exposure to 

lower levels of a pollutant. 

Table 3.3.1-1 

National Ambient Air Quality Standards 

Primary Standards Secondary Standards 

Pollutant Level a/ Averaging Time Level a/ Averaging Time 

9 ppm 

(10 mg/m3

) 

Carbon monoxide 8 hours b/ 

35 ppm 

(40 mg/m3

) 

1 hour b/ 

None 

Lead 0.15 μg/m3 Rolling 3-month average Same as Primary 

0.053 ppm 

(100 μg/m3

) 

Annual 

(Arithmetic Mean) 

Nitrogen dioxide Same as Primary 

0.100 ppm 

(200 μg/m3) 

1 hour c/ None 

Particulate matter (PM10) 150 μg/m3 24 hours d/ Same as Primary 

15.0 μg/m3 Annual e/ 

(Arithmetic Mean) 

Particulate matter (PM2.5) Same as Primary 

35 μg/m3 24 hours f/ Same as Primary 

0.075 ppm 

(2008 std.) 

Ozone 8 hours g/ Same as Primary 

0.08 ppm 

(1997 std.) 

8 hours h/ i/ Same as Primary 

0.03 ppm Annual 

(Arithmetic Mean) 

Sulfur dioxide 

0.14 ppm 24 hours b/ 

0.5 ppm 

(1300 μg/m3

) 

3 hours b/ 

_______________ 

a/ Units of measure for the standards are parts per million (ppm) by volume, milligrams per cubic meter of air 

(mg/m3

), and micrograms per cubic meter of air (μg/m3). 

b/ Not to be exceeded more than once per year. 

c/ To attain this standard, the 3-year average of the 98th percentile of the daily maximum 1-hour average at each 

monitor within an area must not exceed 0.100 ppm (effective January 22, 2010). 

d/ Not to be exceeded more than once per year on average over 3 years. 

e/ To attain this standard, the 3-year average of the weighted annual mean PM2.5 concentrations from single or 

multiple community-oriented monitors must not exceed 15.0 μg/m3

. 

f/ To attain this standard, the 3-year average of the 98th percentile of 24-hour concentrations at each populationoriented monitor within an area must not exceed 35 μg/m3

 (effective December 17, 2006). 

g/ To attain this standard, the 3-year average of the fourth-highest daily maximum 8-hour average ozone 

concentrations measured at each monitor within an area over each year must not exceed 0.075 ppm (effective 

May 27, 2008). 

h/ To attain this standard, the 3-year average of the fourth-highest daily maximum 8-hour average ozone 

concentrations measured at each monitor within an area over each year must not exceed 0.08 ppm. 

i/ The 1997 standard—and the implementation rules for that standard—will remain in place for implementation 

purposes as EPA undertakes rulemaking to address the transition from the 1997 ozone standard to the 2008 

ozone standard. 

Source: 40 CFR 50, as presented in EPA 2010. 

 3-16 
Chapter 3 Affected Environment and Environmental Consequences 3.3 Air Quality 

Under the CAA, EPA is required to review NAAQS every 5 years and to change the levels of the 

standards if warranted by new scientific information. NAAQS formerly included an annual PM10

standard, but EPA revoked the annual PM10 standard in 2006 based on an absence of evidence of health 

effects associated with annual PM10 levels. In September 2006, EPA tightened the 24-hour PM2.5

standard from 65 micrograms per cubic meter (μg/m3

) to 35 μg/m3. In March 2008, EPA tightened the 

8-hour ozone standard from 0.08 part per million (ppm) to 0.075 ppm. At present, EPA is considering 

further changes to the PM2.5 standards and changes to the ozone standard. 

The air quality of a geographic region is usually assessed by comparing the levels of criteria air 

pollutants found in the atmosphere to the levels established by NAAQS. Concentrations of criteria 

pollutants within the air mass of a region are measured in parts of a pollutant per million parts of air or in 

micrograms of a pollutant per cubic meter of air present in repeated air samples taken at designated 

monitoring locations. These ambient concentrations of each criteria pollutant are compared to the 

permissible levels specified by NAAQS to assess whether the region’s air quality could be unhealthful. 

When the measured concentrations of a criteria pollutant within a geographic region are below 

those permitted by NAAQS, EPA designates the region as an attainment area for that pollutant; regions 

where concentrations of criteria pollutants exceed federal standards are called nonattainment areas. 

Former nonattainment areas that have attained NAAQS are designated as maintenance areas. Each 

nonattainment area is required to develop and implement a State Implementation Plan (SIP), which 

documents how the region will reach attainment levels within periods specified in the CAA. In 

maintenance areas, the SIP documents how the state intends to maintain compliance with NAAQS. When 

EPA changes a NAAQS, states must revise their SIPs to address how they will attain the new standard. 

Compounds emitted from vehicles, which are known or suspected to cause cancer or other serious 

health and environmental effects, are known as mobile source air toxics (MSATs). The MSATs included 

in this analysis are acetaldehyde, acrolein, benzene, 1,3-butadiene, diesel particulate matter (DPM), and 

formaldehyde. EPA and the Federal Highway Administration (FHWA) have identified these air toxics as 

the MSATs that typically are of greatest concern for impacts of highway vehicles (EPA 2007, FHWA 

2006). DPM is a component of exhaust from diesel-fueled vehicles and falls almost entirely within the 

PM2.5 particle-size class. 

Section 3.4 addresses the major GHGs – CO2, methane (CH4), and nitrous oxides (N2O); these 

GHGs are not included in this air quality analysis, except the evaluation of NOx includes N2O because it 

is one of the oxides of nitrogen. 

3.3.1.2 Health Effects of Criteria Pollutants 

The following paragraphs briefly describe the health effects of the six federal criteria pollutants. 

This information is adapted from the EPA Green Book, Criteria Pollutants (EPA 2008b). EPA’s most 

recent technical reports and Federal Register notices for NAAQS reviews contain more information on 

the health effects of criteria pollutants (see http://www.epa.gov/ttn/naaqs/). 

Ozone is a photochemical oxidant and the major component of smog. Ozone is not emitted 

directly into the air, but is formed through complex chemical reactions between precursor emissions of 

VOCs and NOx in the presence of the ultraviolet component of sunlight. Ground-level ozone causes 

health problems because it irritates the mucous membranes, damages lung tissue, reduces lung function, 

and sensitizes the lungs to other irritants. Exposure to ozone for several hours at relatively low 

concentrations has been found to substantially reduce lung function and induce respiratory inflammation 

in normal, healthy people during exercise. There is also evidence that short-term exposure to ozone 

directly or indirectly contributes to non-accidental and cardiopulmonary-related mortality. 

3-17 
3.3 Air Quality Chapter 3 Affected Environment and Environmental Consequences 

 3-18 

PM is a generic term for a broad class of chemically and physically diverse substances that exist 

as discrete particles. PM includes dust, dirt, soot, smoke, and liquid droplets directly emitted into the air, 

and particles formed in the atmosphere by condensation or by the transformation of emitted gases such as 

NOx, SOx and VOCs. The definition of PM also includes particles composed of elemental carbon (carbon 

black or black carbon). Both gasoline-fueled and diesel-fueled vehicles emit PM. In general, the smaller 

the PM, the deeper it can penetrate into the respiratory system and the more damage it can cause. 

Depending on its size and composition, PM can damage lung tissue, aggravate existing respiratory and 

cardiovascular diseases, alter the body’s defense systems against foreign materials, and cause cancer and 

premature death. As noted above, EPA regulates PM according to two particle size classifications, PM10

and PM2.5. This analysis only considers PM2.5 because almost all of the PM emitted in exhaust from 

passenger cars and light trucks is PM2.5. 

CO is a colorless, odorless, poisonous gas produced by incomplete combustion of carbon in fuels. 

Motor vehicles are the single largest source of CO emissions nationally16. When CO enters the 

bloodstream, it acts as an asphyxiant by reducing the delivery of oxygen to the body’s organs and tissues. 

It can impair the brain’s ability to function properly. Health threats are most serious for those who suffer 

from cardiovascular disease, particularly those with angina or peripheral vascular disease. 

Lead is a toxic heavy metal used in industry, such as in battery manufacturing, and formerly in 

widespread use as an additive in paints. Lead gasoline additives (in piston-engine powered aircraft), nonferrous smelters, and battery plants are the most significant contributors to atmospheric lead emissions. 

Lead exposure can occur through multiple pathways, including inhalation of air and ingestion of lead in 

food, water, soil, or dust. Excessive lead exposure can cause seizures, mental retardation, behavioral 

disorders, severe and permanent brain damage, and death. Even low doses of lead can lead to central 

nervous system damage. Because of the prohibition of lead as an additive in motor vehicle liquid fuels, 

vehicles are no longer a major source of lead pollution. 

SO2, one of various oxides of sulfur (SOx), is a gas formed from combustion of fuels containing 

sulfur. Most SO2 emissions are produced by stationary sources such as power plants. SO2 is also formed 

when gasoline is extracted from crude oil in petroleum refineries, and in other industrial processes. High 

concentrations of SO2 cause severe respiratory distress (difficulty breathing), irritate the upper respiratory 

tract, and can aggravate existing respiratory and cardiovascular disease. SO2 also is a primary contributor 

to acid deposition, or acid rain, which causes acidification of lakes and streams and can damage trees, 

crops, historic buildings, and statues. 

NO2 is a reddish-brown, highly reactive gas, one of the oxides of nitrogen formed by 

high-temperature combustion (as in vehicle engines) of nitrogen and oxygen. Most NOx created in the 

combustion reaction consists of nitric oxide (NO), which oxidizes to NO2 in the atmosphere. NO2 can 

irritate the lungs and mucous membranes, cause bronchitis and pneumonia, and lower resistance to 

respiratory infections. Oxides of nitrogen are an important precursor both to ozone and acid rain, and can 

affect both terrestrial and aquatic ecosystems. 

3.3.1.3 Health Effects of Mobile Source Air Toxics (adapted from EPA 2009d) 

Motor vehicle emissions contribute to ambient levels of air toxics known or suspected as human 

or animal carcinogens, or that have noncancer health effects. The population experiences an elevated risk 

of cancer and other noncancer health effects from exposure to air toxics (EPA 1999a). These compounds 

include, but are not limited to, acetaldehyde, acrolein, benzene, 1,3-butadiene, and formaldehyde. These 

 

16 Highway motor vehicles accounted for 50 percent of national CO emissions in 2008. Passenger cars and light 

trucks accounted for about 76 percent of the CO emissions from highway motor vehicles (EPA 2009f) 
Chapter 3 Affected Environment and Environmental Consequences 3.3 Air Quality 

five air toxics, plus DPM, comprise the six priority MSATs analyzed in this EIS. These compounds, 

except acetaldehyde, plus polycyclic organic matter (POM) and naphthalene, were identified as national 

or regional risk drivers in the EPA 2002 National-scale Air Toxics Assessment (NATA) and have 

significant inventory contributions from mobile sources (EPA 2009a). This EIS does not analyze POM 

separately, but it can occur as a component of DPM and is addressed under DPM below. Naphthalene is 

not analyzed separately in this EIS; however, naphthalene is a member of the POM class of compounds 

discussed under DPM. 

Acetaldehyde is classified in EPA’s Integrated Risk Information System (IRIS) database as a 

probable human carcinogen, based on nasal tumors in rats, and is considered toxic by the inhalation, oral, 

and intravenous routes (EPA 1991). Acetaldehyde is reasonably anticipated to be a human carcinogen by 

the U.S. Department of Health and Human Services (DHHS) in the 11th Report on Carcinogens and is 

classified as possibly carcinogenic to humans (Group 2B) by the International Agency for Research on 

Cancer (IARC) (NTP 2005, IARC 1999). EPA is reassessing cancer risk from inhalation exposure to 

acetaldehyde. 

The primary noncancer effects of exposure to acetaldehyde vapors include eye, skin, and 

respiratory-tract irritation (EPA 1991). In short-term (4-week) rat studies, degeneration of olfactory 

epithelium was observed at various concentration levels of acetaldehyde exposure (Appleman et al. 1982, 

1986). EPA used data from these studies to develop an inhalation reference concentration. Some 

asthmatics have been shown to be a sensitive subpopulation to decrements in functional expiratory 

volume (FEV1 test) and bronchoconstriction upon acetaldehyde inhalation (Myou et al. 1993). EPA is 

reassessing the health hazards from inhalation exposure to acetaldehyde. 

Acrolein is extremely acrid and irritating to humans when inhaled, with acute exposure resulting 

in upper respiratory tract irritation, mucus hypersecretion, and congestion. Levels considerably lower 

than 1 ppm (2.3 mg/m3

) elicit subjective complaints of eye and nasal irritation and a decrease in the 

respiratory rate (Weber-Tschopp et al. 1977, Sim and Pattle 1957). Lesions to the lungs and upper 

respiratory tracts of rats, rabbits, and hamsters have been observed after subchronic exposure to acrolein. 

Based on animal data, individuals with compromised respiratory function (e.g., emphysema, asthma) are 

expected to be at increased risk of developing adverse responses to strong respiratory irritants such as 

acrolein. This was demonstrated in mice with allergic-airway disease by comparison to non-diseased 

mice in a study of the acute respiratory irritant effects of acrolein (Morris et al. 2003). The intense 

irritancy of this carbonyl has been demonstrated during controlled tests in human subjects, who suffer 

intolerable eye and nasal mucosal sensory reactions within minutes of exposure (Sim and Pattle 1957). 

EPA determined in 2003 that the human carcinogenic potential of acrolein could not be 

determined because the available data were inadequate. No information was available on the 

carcinogenic effects of acrolein in humans and the animal data provided inadequate evidence of 

carcinogenicity (EPA 2003). IARC determined in 1995 that acrolein was not classifiable as to its 

carcinogenicity in humans (IARC 1995). 

The EPA IRIS database lists benzene as a known human carcinogen (causing leukemia) by all 

routes of exposure, and concludes that exposure is associated with additional health effects, including 

genetic changes in both humans and animals and increased proliferation of bone marrow cells in mice 

(EPA 2000a, IARC 1982, Irons et al. 1992). EPA states in its IRIS database that data indicate a causal 

relationship between benzene exposure and acute lymphocytic leukemia and suggest a relationship 

between benzene exposure and chronic non-lymphocytic leukemia and chronic lymphocytic leukemia. 

IARC has determined that benzene is a human carcinogen and DHHS has characterized benzene as a 

known human carcinogen (IARC 1987, NTP 2005). 

3-19 
3.3 Air Quality Chapter 3 Affected Environment and Environmental Consequences 

A number of adverse noncancer health effects, including blood disorders such as preleukemia and 

aplastic anemia, have also been associated with long-term exposure to benzene (Askoy 1989, Goldstein 

1988). The most sensitive noncancer effect observed in humans, based on current data, is the depression 

of the absolute lymphocyte count in blood (Rothman et al 1996, EPA 2002a). In addition, recent work, 

including studies sponsored by the Health Effects Institute, provides evidence that biochemical responses 

are occurring at lower levels of benzene exposure than previously known (Qu et al. 2002, 2003; Lan et al.

2004; Turtletaub and Mani 2003) The EPA IRIS program has not yet evaluated these new data. 

EPA has characterized 1,3-butadiene as carcinogenic to humans by inhalation (EPA 2002b, 

2002c). IARC has determined that 1,3-butadiene is a human carcinogen, and DHHS has characterized 

1,3-butadiene as a known human carcinogen (IARC 1999, NTP 2005). There are numerous studies 

consistently demonstrating that animals and humans in experiments metabolize 1,3-butadiene into 

genotoxic metabolites. The specific mechanisms of 1,3-butadiene-induced carcinogenesis are not known; 

however, scientific evidence strongly suggests that the carcinogenic effects are mediated by genotoxic 

metabolites. Animal data suggest that females could be more sensitive than males for cancer effects 

associated with 1,3-butadiene exposure; there are insufficient data in humans from which to draw 

conclusions about sensitive subpopulations. 1,3-butadiene also causes a variety of reproductive and 

developmental effects in mice; no human data on these effects are available. The most sensitive effect 

was ovarian atrophy observed in a lifetime bioassay of female mice (Bevan et al. 1996). 

DPM is a component, along with diesel exhaust organic gases, of diesel exhaust. DPM particles 

are very fine, with most particles smaller than 1 micron, and their small size allows inhaled DPM to reach 

the lungs. Particles typically have a carbon core coated by condensed organic compounds such as POM, 

which include mutagens and carcinogens. DPM also includes elemental carbon (carbon black or black 

carbon) particles emitted from diesel engines. Diesel exhaust is likely to be carcinogenic to humans by 

inhalation from environmental exposure. 

DPM can contain POM, which is generally defined as a large class of organic compounds that 

have multiple benzene rings and a boiling point greater than 100 degrees Celsius (oC). EPA classifies 

many of the compounds included in the POM class as probable human carcinogens based on animal data. 

Polycyclic aromatic hydrocarbons (PAHs) are a subset of POM that contains only hydrogen and carbon 

atoms. A number of PAHs are known or suspected carcinogens. Recent studies have found that maternal 

exposures to PAHs in a population of pregnant women were associated with several adverse birth 

outcomes, including low birth weight and reduced length at birth, and impaired cognitive development at 

age 3 (Perera et al. 2002, 2006). EPA has not yet evaluated these recent studies. 

Since 1987, EPA has classified formaldehyde as a probable human carcinogen based on evidence 

in humans and in rats, mice, hamsters, and monkeys (EPA 1987). EPA is reviewing recently published 

epidemiological data. For example, National Cancer Institute (NCI) research found an increased risk of 

nasopharyngeal cancer and lymphohematopoietic malignancies such as leukemia among workers exposed 

to formaldehyde (Hauptmann et al. 2003, 2004). In an analysis of the lymphohematopoietic cancer 

mortality from an extended followup of these workers, NCI confirmed an association between 

lymphohematopoietic cancer risk and peak exposures to formaldehyde (Beane Freeman et al. 2009). A 

recent National Institute of Occupational Safety and Health study of garment workers also found 

increased risk of death due to leukemia among workers exposed to formaldehyde (Pinkerton 2004). 

Extended followup of a cohort of British chemical workers did not find evidence of an increase in 

nasopharyngeal or lymphohematopoietic cancers, but did report a continuing statistically significant 

excess in lung cancers (Coggon et al. 2003). Recently, IARC reclassified formaldehyde as a human 

carcinogen (Group 1) (IARC 2006). 

 3-20 
Chapter 3 Affected Environment and Environmental Consequences 3.3 Air Quality 

Formaldehyde exposure also causes a range of noncancer health effects, including irritation of the 

eyes (burning and watering), nose, and throat. Effects in humans from repeated exposure include 

respiratory-tract irritation, chronic bronchitis, and nasal epithelial lesions such as metaplasia and loss of 

cilia. Animal studies suggest that formaldehyde might also cause airway inflammation, including 

eosinophil infiltration into the airways. There are several studies suggesting that formaldehyde might 

increase the risk of asthma, particularly in the young (ATSDR 1999, WHO 2002). 

3.3.1.4 Clean Air Act and Conformity Regulations 

3.3.1.4.1 Vehicle Emission Standards 

Under the CAA, EPA has established emission standards for vehicles. EPA has tightened the 

emission standards over time as more effective emission-control technologies have become available. 

These reductions in the levels of the standards are responsible for the declines in total emissions from 

motor vehicles, as discussed above. The EPA Tier 2 Vehicle & Gasoline Sulfur Program, which went 

into effect in 2004 established the CAA emissions standards that will apply to MYs 2012-2016 passenger 

cars and light trucks (EPA 1999b). Under the Tier 2 standards, emissions from passenger cars and light 

trucks will continue to decline. In 2004, the Nation’s refiners and importers of gasoline began to 

manufacture gasoline with sulfur levels capped at 300 ppm, approximately a 15-percent reduction from 

the previous industry average of 347 ppm. By 2006, refiners met a 30-ppm average sulfur level with a 

cap of 80 ppm. These fuels enable post-2006 model year vehicles to use emissions controls that reduce 

tailpipe emissions of NOx by 77 percent for passenger cars and by as much as 95 percent for pickup 

trucks, vans, and SUVs, compared to 2003 levels. Figure 3.3.1-1 shows that cleaner vehicles and fuels 

will result in continued reductions in emissions from passenger cars and light trucks, despite increases in 

travel. Figure 3.3.1-1 illustrates current trends in travel and emissions from passenger cars and light 

trucks under the existing CAFE standards. Figure 3.3.1-1 does not show the effects of the proposed 

action and alternatives; see Section 3.3.3. 

Figure 3.3.1-1. Vehicle Miles Traveled (VMT) vs. Vehicle Emissions (Source: Smith 2002) 

From 1970 to 1999, aggregate emissions traditionally associated with vehicles substantially 

decreased (with the exception of NOx) even as VMT has increased by approximately 149 percent. NOx

3-21 
3.3 Air Quality Chapter 3 Affected Environment and Environmental Consequences 

emissions increased 16 percent between 1970 and 1999, due mainly to emissions from light trucks and 

heavy-duty vehicles. However, as future trends show, vehicle travel is having a smaller and smaller 

impact on emissions as a result of stricter EPA standards for vehicle emissions and the chemical 

composition of fuels, even with additional growth in VMT (Smith 2002). This general trend will 

continue, to a greater or lesser degree, with implementation of any of the proposed alternative CAFE 

standards. 

EPA is addressing air toxics through its MSAT rules (EPA 2007). These rules limit the benzene 

content of gasoline beginning in 2011. They also limit exhaust emissions of hydrocarbons (many VOCs 

and MSATs are hydrocarbons) from passenger cars and light trucks when they are operated at cold 

temperatures. The cold-temperature standard will be phased in from 2010 to 2015. The MSAT rules also 

adopt nationally the California evaporative emissions standards. EPA projects that these controls will 

substantially reduce emissions of acetaldehyde, acrolein, benzene, 1,3-butadiene, and formaldehyde. 

3.3.1.4.2 Conformity Regulations 

Section 176(c) of the CAA prohibits federal agencies from taking actions in nonattainment or 

maintenance areas that do not “conform” to the SIP. The purpose of this conformity requirement is to 

ensure that general activities do not interfere with meeting the emissions targets in SIPs, do not cause or 

contribute to new violations of NAAQS, and do not impede the ability to attain or maintain NAAQS. 

EPA has issued two sets of regulations to implement CAA Section 176(c), as follows: 

• The Transportation Conformity Rules (40 CFR Part 93, Subpart A), which apply to 

transportation plans, programs, and projects funded under U.S.C. Title 23 or the Federal 

Transit Act. Highway and transit infrastructure projects funded by FHWA or the Federal 

Transit Administration (FTA) usually are subject to transportation conformity. 

• The General Conformity Rule (40 CFR Part 51, Subpart W) apply to all other federal actions 

not covered under transportation conformity. The General Conformity Rule established 

emissions thresholds, or de minimis levels, for use in evaluating the conformity of a project. 

If the net emissions increases due to the project are less than these thresholds, then the project 

is presumed to conform and no further conformity evaluation is required. If the emissions 

increases exceed any of these thresholds, then a conformity determination is required. The 

conformity determination can entail air quality modeling studies, consultation with EPA and 

state air quality agencies, and commitments to revise the SIP or to implement measures to 

mitigate air quality impacts. 

The CAFE standards and associated program activities are not funded under U.S.C. Title 23 or 

the Federal Transit Act. Further, NHTSA establishes CAFE standards, not FHWA or FTA. Accordingly, 

the CAFE standards and associated rulemakings are not subject to transportation conformity. 

The General Conformity Rule contains several exemptions applicable to federal actions, which 

the conformity regulations define as “any activity engaged in by a department, agency, or instrumentality 

of the Federal Government, or any activity that a department, agency or instrumentality of the Federal 

Government supports in any way, provides financial assistance for, licenses, permits, or approves, other 

than activities [subject to transportation conformity].” 40 CFR 51.852. “Rulemaking and policy 

development and issuance” are exempted at 40 CFR 51.853(c)(2)(iii). Because NHTSA’s CAFE 

standards involve a rulemaking process, NHTSA’s action is exempt from general conformity. Also, 

emissions for which a federal agency does not have a “continuing program responsibility” are not 

considered “indirect emissions” subject to general conformity under 40 CFR 51.852. “Emissions that a 

Federal agency has a continuing program responsibility for means emissions that are specifically caused 

by an agency carrying out its authorities, and does not include emissions that occur due to subsequent 

 3-22 
Chapter 3 Affected Environment and Environmental Consequences 3.3 Air Quality 

3-23 

activities, unless such activities are required by the Federal agency.” 40 CFR 51.852. Emissions that 

occur as a result of the CAFE standards are not caused by NHTSA carrying out its statutory authorities 

and clearly occur due to subsequent activities, including vehicle manufacturers’ production of passenger 

car and light truck fleets and consumer purchases and driving behavior. Thus, changes in any emissions 

that result from NHTSA’s new CAFE standards are not those for which the agency has a “continuing 

program responsibility;” therefore, a general conformity determination is not required. Nonetheless, 

NHTSA is evaluating the potential impacts of air emissions for the purposes of NEPA. 

3.3.2 Methodology 

3.3.2.1 Overview 

To analyze impacts to air quality, NHTSA calculated the emissions of criteria pollutants and 

MSATs from passenger cars and light trucks that would occur under each alternative and assessed the 

changes in emissions in relation to the No Action Alternative (Alternative 1). 

For purposes of analyzing potential direct and indirect impacts (environmental consequences), the 

No Action Alternative in this EIS consists of the existing CAFE standards with no changes in the future. 

That is, the No Action Alternative assumes that average fuel economy levels in the absence of CAFE 

standards beyond MY 2011 would equal the higher of the agencies’ collective market forecast or the 

manufacturer’s required level of average fuel economy for MY 2011. See Section 2.3.2. The basic 

method used to estimate emissions entails multiplying activity levels of passenger cars and light trucks, 

expressed as the total VMT, by emission factors measured in grams of pollutant emitted per VMT. 

National emissions estimates for all passenger cars and light trucks projected to be in use during future 

years were developed using the Volpe model. The Volpe model utilizes emission factors developed using 

EPA’s draft MOVES2009 emission model (EPA 2009j) for light-duty gasoline vehicles, and MOBILE6.2 

(EPA 2004) for light-duty diesel vehicles. MOVES reflects EPA’s updated estimates of real-world 

emissions from passenger cars and trucks, and accounts for emission control requirements on exhaust 

(tailpipe) emissions and evaporative emissions, including the Tier 2 Vehicle & Gasoline Sulfur Program 

and Mobile Source Air Toxics (MSAT) rule. 

Impacts on upstream emissions (oil refining as well as fuel transport, storage, and distribution) 

were estimated using emission factors provided by EPA. These were based on the Greenhouse Gas, 

Regulated Emissions, and Energy Use in Transportation model (GREET, version 1.8) developed by DOE 

Argonne National Laboratory (Argonne 2002). EPA modified GREET for use in analyzing its 

Renewable Fuel Standard rulemaking17 analysis to account for recent EPA emission standards for 

gasoline transport and the addition of air toxics emission factors. 

By reducing the cost of fuel consumed per mile driven, setting future CAFE standards that require 

higher mpg levels would create an incentive for additional driving. The resulting increase in driving 

offsets part of the fuel savings that would otherwise result from requiring higher fuel economy; this 

phenomenon is known as the fuel economy “rebound effect.” The total amount of passenger car and light 

truck VMT would increase slightly due to the rebound effect, and emissions from these vehicles would 

increase in proportion to the increased VMT. Although higher CAFE standards would decrease the total 

amount of fuel consumed from its level under the No Action Alternative despite the rebound effect, the 

reduction in fuel usage cannot be linked directly to any decrease in emissions resulting directly from 

vehicle use. 

 

17 74 FR 24904, May 26, 2009. 
3.3 Air Quality Chapter 3 Affected Environment and Environmental Consequences 

 3-24 

The NHTSA CAFE standards and the EPA emissions standards impose separate requirements on 

motor-vehicle manufacturers. Although manufacturers must meet both the CAFE standards and the EPA 

emissions standards simultaneously, neither NHTSA nor EPA dictates the design and technology choices 

manufacturers must make to comply. For example, a manufacturer could use a technique that increases 

fuel economy but also increases emissions, as long as the manufacturer’s production still meets both the 

CAFE standards and the EPA emissions standards. For this reason, the air quality analysis methodology 

does not assume any reduction in direct emissions from motor vehicle use solely due to improvements in 

fuel economy. 

However, the proposed CAFE standards would lead to reductions in “upstream” emissions, which 

are emissions associated with petroleum extraction, refining, storage, and distribution of transportation 

fuels. Upstream emissions would decrease as a consequence of the proposed CAFE standards because the 

total amount of fuel used by passenger cars and light trucks would decrease. 

Although the rebound effect is assumed to result in identical percentage increases in VMT and 

emissions from vehicle use in all regions of the Nation, the associated changes in upstream emissions are 

expected to vary among regions because fuel refining and storage facilities are not uniformly distributed 

across the Country. Thus, an individual region could experience either a net increase or a net decrease in 

emissions of each pollutant due to the proposed CAFE standards, depending on the relative magnitudes of 

the increase in emissions from vehicle use and the regional reduction in emissions from fuel production 

and distribution. 

To assess regional differences in the effects of the alternatives, NHTSA estimated net emissions 

changes for individual nonattainment areas. NHTSA used nonattainment areas because these are the 

regions in which air quality problems have been greatest. All nonattainment areas assessed were in 

nonattainment for ozone or PM2.5 because these are the pollutants for which emissions from passenger 

cars and light trucks are of greatest concern. NHTSA did not quantify PM10 emissions separately from 

PM2.5 because almost all the PM in the exhaust from passenger cars and light trucks is PM2.5. The roaddust component of PM10 concentrations from passenger cars and light trucks would increase in proportion 

to the rebound effect. There are no longer any nonattainment areas for annual PM10 because EPA 

revoked the annual PM10 standard. Currently there are no NO2 nonattainment areas, and only one area 

remains designated nonattainment for CO. 

The air quality analysis is nationwide and regional and does not address the specific geographic 

locations of increases in emissions because emissions increases due to the rebound effect consist of higher 

emissions from passenger cars and light trucks operating on regional roadway networks. Thus, any 

emissions increases due to the VMT rebound effect would be distributed along a region’s entire road 

network. At any one location the increase would be small compared to total emissions near the source 

(i.e., existing emissions from traffic on the road), so the localized impacts on ambient concentrations and 

health should also be small. The aggregate of such small near-source impacts on ambient concentrations 

and health nationwide might be larger, but is not feasible to quantify. 

3.3.2.2 Time Frames for Analysis 

Ground-level concentrations of criteria and toxic air pollutants generally respond quickly to 

changes in emission rates. The longest averaging period for measuring whether ambient concentrations 

of a pollutant comply with the NAAQS is 1 year.18 The air quality analysis considers the emissions that 

 

18 Compliance with the ozone NAAQS is based on the average of the fourth highest daily maximum 8-hour 

concentration over a 3-year period; compliance with the 24-hour PM2.5 NAAQS is based on the average of the daily 
Chapter 3 Affected Environment and Environmental Consequences 3.3 Air Quality 

3-25 

would occur over annual periods, consistent with NAAQS. NHTSA selected calendar years that are 

meaningful for the timing of likely effects of the alternatives. 

Passenger cars and light trucks remain in use for many years, so the change in emissions due to 

any change in the CAFE standards for MYs 2012-2016 would also continue for many years. The 

influence of vehicles produced during a particular model year declines over time as those vehicles are 

gradually retired from service as they age, while those that remain in use are driven progressively less. 

The Volpe model defines vehicle lifetime as the point at which less than 2 percent of the vehicles 

originally produced in a model year remain in service. Under this definition, passenger cars survive in the 

fleet for as long as 26 years, while light trucks can survive for up to 37 years. Of course, any individual 

vehicle might not necessarily survive to these maximum ages; the typical or “expected” lifetimes for 

passenger cars and light trucks are approximately half of their respective maximum lifetimes, or 13 years 

for passenger cars and 18.5 years for light trucks. 

The survival of vehicles and the amount they are driven can be forecast with reasonable accuracy 

for a decade or two, while the influences of fuel prices and general economic conditions are less certain. 

To evaluate impacts to air quality, specific years must be selected for which emissions will be estimated 

and their effects on air quality calculated. NHTSA performed the air quality analysis in two ways that 

affect the choice of analysis years. For the NEPA direct and indirect impacts analysis, NHTSA assumed 

that the CAFE standards for MYs 2012-2016 would remain in force indefinitely at the 2016 level; 

NHTSA did not include potential CAFE standards for MYs 2017-2020 because they are not within the 

scope of this rulemaking. 

The paragraphs below describe the analysis years NHTSA used in this EIS and the rationales for 

each. 

• 2016 – First year of complete implementation of the MYs 2012-2016 CAFE standards; year 

of highest overall emissions from passenger cars and light trucks following complete 

implementation. 

• 2020 – Latest required attainment date for 8-hour ozone nonattainment areas (2020 is latest 

full year, because the last attainment date is June 2021 for South Coast Air Basin, 

California19); by this point a large proportion of passenger car and light truck VMT would be 

accounted for by vehicles that meet the MYs 2012-2016 standards; first year of complete 

implementation of potential MYs 2017-2020 CAFE standards (see Section 4.3). 

• 2030 – By 2030, almost all passenger cars and light trucks in operation would meet at least 

the MYs 2012-2016 standards, and the impact of these standards would be determined 

primarily by VMT growth rather than further tightening of the standards. The year-by-year 

impacts of the CAFE standards for MYs 2012-2016 and the EPA standards by 2030 will 

change little from model year turnover, and most changes in emissions from year to year will 

come from added driving due to the fuel economy rebound effect. 

 

98th percentile concentrations averaged over a 3-year period; and compliance with the annual PM2.5 NAAQS is 

based on the 3-year average of the weighted annual mean concentrations. 

19 The South Coast area is currently classified as severe-17; however, the California Air Resources Board has 

submitted a request to EPA to bump up the area to extreme. Clean Air Act section 181(b)(3) requires the 

Administrator to grant such requests. Once granted the area’s attainment date will be June 2024 and the last full 

year prior to that date will be 2023. 
3.3 Air Quality Chapter 3 Affected Environment and Environmental Consequences 

3.3.2.3 Treatment of Incomplete or Unavailable Information 

As noted throughout this methodology section, the estimates of emissions rely on models and 

forecasts that contain numerous assumptions and data that are uncertain. Examples of areas in which 

information is incomplete or unavailable include future emissions rates, vehicle manufacturers’ decisions 

on vehicle technology and design, the mix of vehicle types and model years comprising the passenger car 

and light truck fleet, VMT projections, emissions from fuel refining and distribution, and economic 

factors. To approximate the health benefits associated with each alternative, NHTSA used screeninglevel estimates of health outcomes in the form of cases per ton of criteria pollutant emissions reduced, and 

of monetized health benefits in the form of dollars per ton of criteria pollutant emissions reduced. The 

use of such dollars-per-ton numbers, however, does not account for all potential health and environmental 

benefits, because the information necessary to monetize all potential health and environmental benefits is 

unavailable. As a result, NHTSA has probably underestimated the total criteria pollutant benefits. 

Reductions in emissions of toxic air pollutants should result in health benefits as well, but scientific data 

that would support quantification and monetization of these benefits are not available. 

Where information in the analysis included in the EIS is incomplete or unavailable, NHTSA has 

relied on CEQ regulations regarding incomplete or unavailable information. See 40 CFR § 1502.22(b). 

NHTSA has used the best available models and supporting data. The models used for the EIS were 

subjected to scientific review and have received the approval of the agencies that sponsored their 

development. NHTSA believes that the EIS assumptions regarding uncertain conditions reflect the best 

available information and are valid and sufficient for this analysis. 

3.3.2.4 Allocation of Exhaust Emissions to Nonattainment Areas 

For each alternative, the Volpe model provided national emissions estimates for each criteria air 

pollutant (or its chemical precursors) and MSAT. National emissions were allocated to the county level 

using VMT data for each county. EPA provided passenger car and light truck VMT data for all counties 

in the United States for 2014, 2020, and 2030 and consistent with the EPA National Emissions Inventory 

(NEI) (EPA 2006 as cited in EPA 2009g). Data for 2014, 2020, and 2030 were based on growth from 

economic modeling and EIA (2006). The VMT data used in the NEI were projected from traffic counts 

taken by counties and states on major roadways, and therefore are subject to some uncertainty. NHTSA 

used the VMT data from the NEI only to allocate nationwide total emissions to counties, and not to 

calculate the emissions. The estimates of nationwide total emissions are based on the national VMT data 

used in the Volpe model. 

NHTSA used the county-level VMT allocations, expressed as fractions of national VMT for each 

county, to derive the county-level emissions from the estimates of nationwide total emissions. Emissions 

for each nonattainment area were derived by summing the emissions for the counties included in each 

nonattainment area. Most nonattainment areas comprise one or more counties, and because county-level 

emissions are aggregated for each nonattainment area, uncertainties in the country-level emissions 

estimates carry over to NHTSA’s estimates of emissions within each nonattainment area. Over time, 

some counties will grow faster than others, and VMT growth rates will also vary. EPA provided the 

VMT data which includes forecasts of the county allocation only as far as 2030. The EPA forecasts of 

county-level VMT allocation introduce some uncertainty into the nonattainment-area-level VMT 

estimates. Additional uncertainties that affect county-level exhaust emissions estimates arise 

from differences between counties or nonattainment areas other than VMT, such as ambient temperatures, 

vehicle age distributions, vehicle speed distributions, vehicle inspection and maintenance programs, and 

fuel composition requirements. This uncertainty increases as the projection period lengthens, such as 

analysis year 2030 compared to 2016. 

 3-26 
Chapter 3 Affected Environment and Environmental Consequences 3.3 Air Quality 

The geographic definitions of ozone and PM2.5 nonattainment areas came from the current EPA 

Greenbook list (EPA 2009e). For nonattainment areas that include portions of counties, NHTSA 

calculated the proportion of county population that falls within the nonattainment area boundary as a 

proxy for the proportion of county VMT within the nonattainment area boundary. This method assumes 

that per-capita VMT is constant within each county, so that the proportion of county population in the 

partial county area reflects the VMT in that area. This assumption introduces some uncertainty into the 

allocation of VMT to partial counties, because actual VMT per capita can vary according to the 

characteristics of land use and urban development. For example, VMT per capita can be lower than 

average in urban centers with mass transit and higher than average in suburban and rural areas where 

people tend to drive more (Cook et al. 2006). 

Partial county boundaries were taken from geographic information system files based on 2006 

nonattainment area definitions. In some cases, partial counties within nonattainment areas as currently 

defined were not included in the 2006 nonattainment areas. In those cases, NHTSA did not add any part 

of the missing counties’ VMT to the nonattainment area totals, on the basis that partial counties added to 

nonattainment areas between 2006 and 2009 are likely to represent relatively small additions to total 

nonattainment area VMT. Several urban areas are in nonattainment for both ozone and PM2.5. Where 

boundary areas differ between the two pollutants, NHTSA used the larger boundary. This approach is 

conservative (tending to overestimate emissions within the nonattainment area for the pollutant having the 

smaller boundary) because it assigns the larger area’s VMT (and thus, its emissions) to the smaller area. 

Table 3.3.2-1 lists the current nonattainment and maintenance areas. 

Table 3.3.2-1 

Nonattainment Areas for Ozone and PM2.5

Classification a/ 

General 

Conformity 

Threshold b/ 

Nonattainment/Maintenance Area O3 PM2.5 O3 PM2.5

Albany-Schenectady-Troy, NY Subpart 1 - 100 - 

Allegan Co., MI Subpart 1 - 100 - 

Amador and Calavaras Cos. (Central Mountain Counties), 

CA 

Subpart 1 - 100 - 

Atlanta, GA Moderate Nonattainment 100 100 

Baltimore, MD Moderate Nonattainment 100 100 

Baton Rouge, LA Moderate - 100 - 

Beaumont/Port Arthur, TX Moderate - 100 - 

Birmingham, AL - Nonattainment - 100 

Boston-Lawrence-Worcester (E. MA), MA Moderate - 100 - 

Boston-Manchester-Portsmouth, MA-SE. NH Moderate - 100 - 

Buffalo-Niagara Falls, NY Subpart 1 - 100 - 

Canton-Massillon, OH - Nonattainment - 100 

Charleston, WV - Nonattainment - 100 

Charlotte-Gastonia-Rock Hill, NC-SC Moderate - 100 - 

Chattanooga, AL-TN-GA - Nonattainment - 100 

Chicago-Gary-Lake Co., IL-IN Moderate Nonattainment 100 100 

Chico, CA Subpart 1 - 100 - 

Cincinnati-Hamilton, OH-KY-IN Subpart 1 Nonattainment 100 100 

Cleveland-Akron-Lorain, OH Subpart 1 Nonattainment 100 100 

Columbus, OH Subpart 1 Nonattainment 100 100 

Dallas-Fort Worth, TX Moderate - 100 - 

3-27 
3.3 Air Quality Chapter 3 Affected Environment and Environmental Consequences 

Table 3.3.2-1 (cont’d) 

Nonattainment Areas for Ozone and PM2.5

Classification a/ 

General 

Conformity 

Threshold b/ 

Nonattainment/Maintenance Area O3 PM2.5 O3 PM2.5

Dayton-Springfield, OH - Nonattainment - 100 

Denver-Boulder-Greeley-Ft. Collins, CO Subpart 1 - 100 - 

Detroit-Ann Arbor, MI Marginal Nonattainment 100 100 

Door Co., WI Subpart 1 - 100 - 

Essex Co., NY (Whiteface Mountain) Subpart 1 - 100 - 

Evansville, IN - Nonattainment - 100 

Greater Connecticut, CT Moderate - 100 - 

Greensboro-Winston Salem-High Point, NC - Nonattainment - 100 

Harrisburg-Lebanon-Carlisle, PA - Nonattainment - 100 

Haywood and Swain Cos. (Great Smoky Mountains National 

Park), NC 

Subpart 1 - 100 - 

Hickory, NC - Nonattainment - 100 

Houston-Galveston-Brazoria, TX Severe 15 - 100 - 

Huntington-Ashland, WV-KY-OH - Nonattainment - 100 

Imperial Co., CA Moderate - 100 - 

Indianapolis, IN - Nonattainment - 100 

Jamestown, NY Subpart 1 - 100 - 

Jefferson Co., NY Moderate - 100 - 

Johnstown, PA - Nonattainment - 100 

Kern Co. (Eastern Kern), CA Subpart 1 - 100 - 

Knoxville, TN Subpart 1 Nonattainment 100 100 

Lancaster, PA - Nonattainment - 100 

Las Vegas, NV Subpart 1 - 100 - 

Libby, MT - Nonattainment - 100 

Liberty-Clairton, PA - Nonattainment - 100 

Los Angeles South Coast Air Basin, CA Severe 17 Nonattainment 25 100 

Los Angeles-San Bernardino Cos. (W. Mojave Desert), CA Moderate - 100 - 

Louisville, KY-IN - Nonattainment - 100 

Macon, GA - Nonattainment - 100 

Manitowoc Co., WI Subpart 1 - 100 - 

Mariposa & Tuolumne Cos. (Southern Mountain Counties), 

CA Subpart 1 

- 100 - 

Martinsburg, WV-Hagerstown, MD - Nonattainment - 100 

Memphis, TN-AR Moderate - 100 - 

Milwaukee-Racine, WI Moderate - 100 - 

Nevada (Western Part), CA Subpart 1 - 100 - 

New York-N. New Jersey-Long Island, NY-NJ-CT Moderate Nonattainment 100 100 

Parkersburg-Marietta, WV-OH - Nonattainment - 100 

Philadelphia-Wilmington-Atlantic City, PA-DE-MD-NJ Moderate Nonattainment 100 100 

Phoenix-Mesa, AZ Subpart 1 - 100 - 

Pittsburgh-Beaver Valley, PA Subpart 1 Nonattainment 100 100 

Poughkeepsie, NY Moderate - 100 - 

Providence (All RI), RI Moderate - 100 - 

Reading, PA - Nonattainment - 100 

Riverside Co., CA (Coachella Valley) Serious - 50 - 

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Chapter 3 Affected Environment and Environmental Consequences 3.3 Air Quality 

Table 3.3.2-1 (cont’d) 

Nonattainment Areas for Ozone and PM2.5

Classification a/ 

General 

Conformity 

Threshold b/ 

Nonattainment/Maintenance Area O3 PM2.5 O3 PM2.5

Rochester, NY Subpart 1 - 100 - 

Rome, GA - Nonattainment - 100 

Sacramento Metro, CA Serious - 50 - 

San Diego, CA Subpart 1 - 100 - 

San Francisco Bay Area, CA Marginal - 100 - 

San Joaquin Valley, CA Serious Nonattainment 50 100 

Sheboygan, WI Moderate - 100 - 

Springfield (Western MA), MA Moderate - 100 - 

St. Louis, MO-IL Moderate Nonattainment 100 100 

Steubenville-Weirton, OH-WV - Nonattainment - 100 

Sutter County (Sutter Buttes), CA Subpart 1 - 100 - 

Ventura Co., CA Serious - 50 - 

Washington, DC-MD-VA Moderate Nonattainment 100 100 

Wheeling, WV-OH - Nonattainment - 100 

York, PA - Nonattainment - 100 

__________ 

a/ Pollutants for which the area is designated nonattainment or maintenance as of 2009, and severity classification. 

b/ Tons per year of VOCs or NOx in ozone nonattainment areas; primary PM2.5 in PM2.5 nonattainment areas. 

Source: EPA 2009e. 

3.3.2.4.1 Allocation of Upstream Emissions to Nonattainment Areas 

Upstream emissions associated with the production and distribution of fuels used by motor 

vehicles are generated when fuel products are produced, processed, and transported. Upstream emissions 

are typically divided into four categories: 

• Feedstock recovery (mainly petroleum extraction); 

• Feedstock transportation; 

• Fuel refining; and 

• Fuel transportation, storage, and distribution (TS&D). 

Feedstock recovery refers to the extraction or production of fuel feedstocks. In the case of 

petroleum, this is the stage of crude-oil extraction. During the next stage, feedstock transportation, crude 

oil, or other feedstocks are shipped to fuel refineries. Fuel refining refers to the processing of crude oil 

into gasoline and diesel fuel. TS&D refers to the movement of gasoline and diesel from refineries to bulk 

terminals, storage at bulk terminals, and transportation of fuel from bulk terminals to retail outlets. 

Emissions of pollutants at each stage are associated with expenditure of energy, as well as with leakage or 

spillage and evaporation of fuel products. 

To analyze the impact of the alternatives on individual nonattainment areas, NHTSA allocated 

emissions reductions to geographic areas according to the following methodology:

• Feedstock recovery – NHTSA assumed that little to no extraction of crude oil occurs in 

nonattainment areas. Of the top 50 highest producing oil fields in the United States, only 

nine are in nonattainment areas. These nine fields account for just 10 percent of domestic 

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3.3 Air Quality Chapter 3 Affected Environment and Environmental Consequences 

production, or 3 percent of total crude-oil imports plus domestic production (EIA 2006, EIA 

2008). Therefore, because relatively little extraction occurs in nonattainment areas, NHTSA 

ignored emissions reductions from feedstock recovery in nonattainment areas. As a result of 

not quantifying the upstream emissions reductions associated with feedstock recovery, this 

part of the analysis is conservative (tending to underestimate the emission reduction benefits 

of the proposed CAFE standards). 

• Feedstock transportation – NHTSA assumed that little to no crude oil is transported through 

nonattainment areas. Most refineries are outside of, or on the outskirts of, urban areas. 

Crude oil is typically transported hundreds of miles from extraction points and ports to reach 

refineries. Most transportation is by ocean tanker and pipeline. Probably only a very small 

proportion of criteria pollutants emitted in the transport of crude oil occur in nonattainment 

areas. Therefore, NHTSA ignored emissions reductions from feedstock transportation within 

nonattainment areas. 

Because NHTSA ignores emissions changes from the first two upstream stages, our assumptions 

produce conservative estimates of emission reductions in nonattainment areas (i.e., the estimates slightly 

underestimate the emissions benefits reductions associated with lower fuel production and use). 

• Fuel refining – Fuel refining is the largest source of upstream emissions of criteria pollutants. 

Depending on the specific fuel and pollutant, fuel refining accounts for between one third and 

three quarters of all upstream emissions (based on outputs of the Volpe model). NHTSA 

used projected emissions data for 2022 from EPA’s 2005-based air quality modeling platform 

(EPA 2009h) to allocate fuel refining emission reductions to nonattainment areas. The NEI 

estimates emissions of criteria and toxic pollutants by county and by source category code 

(SCC). Because there are specific SCCs for fuel refining processes, it is possible to 

determine the share of national fuel refining emissions allocated to each nonattainment area. 

It is assumed that the share of fuel refining emissions allocated to each nonattainment area 

does not change over time, and that fuel refining emissions will change uniformly across all 

refineries nationwide as a result of the alternatives. 

• TS&D – NHTSA used data from the EPA modeling platform (EPA 2009h) to allocate TS&D 

emissions to nonattainment areas in the same way as for fuel refining emissions. It is 

assumed that the share of TS&D emissions allocated to each nonattainment area does not 

change over time, and that TS&D emissions will change uniformly nationwide as a result of 

the alternatives. 

The data provided by EPA was missing county-level data for acetaldehyde, benzene, and 

formaldehyde. Therefore, for these three pollutants, NHTSA allocated national emissions based on the 

allocation of the pollutant that is believed to behave most similarly to the pollutant in question, as 

follows: 

• For acetaldehyde, the data provided by EPA did not report TS&D emissions at the national or 

county level, so NHTSA assumed there are no acetaldehyde emissions associated with TS&D 

(i.e., that 100 percent of upstream acetaldehyde emissions come from refining). The EPA 

data included national fuel-refining emissions of acetaldehyde, but data by county are not 

available. To allocate acetaldehyde emissions to counties, NHTSA used the county 

allocation of acrolein, because acrolein is the toxic air pollutant which has, among those for 

which county-level data were available, the highest proportion of its emissions coming from 

refining. Thus, the use of acrolein data for allocation of acetaldehyde emissions to counties is 

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Chapter 3 Affected Environment and Environmental Consequences 3.3 Air Quality 

most consistent with the assumption that 100 percent of acetaldehyde emissions come from 

refining 

• For benzene, the EPA data included nationwide fuel refining and TS&D emissions, and 

TS&D emissions at the county level, but not refining emissions at the county level. To 

allocate fuel refining emissions of benzene to counties, NHTSA used the same county 

allocation as butadiene because, among toxic air pollutants for which county-level data were 

available, butadiene has the ratio of fuel refining and TS&D emissions that is closest to the 

ratio for benzene emissions. 

• For formaldehyde, the EPA data included national fuel refining and TS&D emissions, but 

county-level data were not available. To allocate formaldehyde emissions to counties, 

NHTSA used the same county allocation as for butadiene because, among toxic air pollutants 

for which county-level data were available, butadiene has the ratio of fuel refining and TS&D 

emissions that is closest to the ratio for formaldehyde emissions. 

3.3.2.4.2 Health Outcomes and Monetized Benefits 

Overview

This section describes the NHTSA approach to addressing public comments on the need to 

provide more quantitative estimates of adverse health effects of conventional air pollutants associated 

with each alternative. 

In this analysis, NHTSA quantified and monetized impacts to human health for each alternative. 

The agency evaluated the health impacts of CAFE alternatives for four health outcomes – premature 

mortality, chronic bronchitis, respiratory emergency-room visits, and work-loss days. For each analysis 

year, this methodology estimates the health impacts of each alternative, expressed as the number of 

additional or avoided outcomes per year. The general approach to calculating health outcomes associated 

with each alternative is to multiply the pollutant-specific incidence-per-ton value (number of annual 

outcomes avoided per ton of pollutant emissions reduced) by the emissions of the pollutant (tons per 

year), summed across all pollutants. Similarly, the general approach to calculating the monetary value of 

the health outcomes for each alternative is to multiply the pollutant-specific benefits-per-ton value (dollar 

value of human health benefits per ton of pollutant emissions reduced) by the emissions of the pollutant 

(tons per year), summed across all pollutants. The impact of a CAFE action alternative is calculated as 

the difference in the monetized value of benefits or the number of health outcomes between that 

alternative and the No Action Alternative. 

NHTSA estimated only the PM2.5-related human health impacts that are expected to result from 

reduced population exposure to atmospheric concentrations of PM2.5. The estimates are derived from 

PM2.5-related dollar-per-ton estimates that include only quantifiable reductions in health impacts likely to 

result from reduced population exposure to particular matter (PM). Three other pollutants – NOx, SO2, 

and VOCs – are included in the analysis as precursor emissions that contribute to PM2.5 not emitted 

directly from a source, but instead formed by chemical reactions in the atmosphere (secondary PM2.5). 

The dollar-per-ton estimates do not include all health impacts related to reduced exposure to PM, nor do 

they include any reductions in health impacts resulting from lower population exposure to other criteria 

air pollutants (particularly ozone) and air toxics. 

3-31 
3.3 Air Quality Chapter 3 Affected Environment and Environmental Consequences 

 3-32 

Monetized Health Impacts

The PM2.5 benefit-per-ton estimates provide the total monetized human health benefits (the sum 

of premature mortality and premature morbidity) of reducing one ton of directly emitted PM2.5, or its 

precursors (such as NOx, SO2, and VOCs), from a specified source. NHTSA followed the benefit-per-ton 

technique used in the EPA recent Ozone NAAQS Regulatory Impact Analysis (RIA) (EPA 2008a), 

Portland Cement National Emission Standards for Hazardous Air Pollutants (NESHAP) RIA (EPA 

2009b), and NO2 NAAQS (EPA 2009c). Table 3.3.2-2 lists the quantified and unquantified PM2.5-related 

benefits captured in those benefit-per-ton estimates. 

Table 3.3.2-2 

Human Health and Welfare Effects of PM2.5

Effects Quantified and Monetized 

in Primary Estimates 

Unquantified Effects 

Changes in: 

Adult premature mortality 

Bronchitis: chronic and acute 

Hospital admissions: respiratory and cardiovascular 

Emergency room visits for asthma 

Nonfatal heart attacks (myocardial infarction) 

Lower and upper respiratory illness 

Minor restricted-activity days 

Work loss days 

Asthma exacerbations (asthmatic population) 

Infant mortality 

Subchronic bronchitis cases 

Low birth weight 

Pulmonary function 

Chronic respiratory diseases other than chronic 

bronchitis 

Non-asthma respiratory emergency room visits 

Visibility 

Household soiling 

The benefits estimates utilize the concentration-response functions as reported in the 

epidemiology literature. Readers interested in reviewing the complete methodology for creating the 

benefit-per-ton estimates used in this analysis can consult the EPA Technical Support Document 

accompanying the final ozone NAAQS RIA (EPA 2008a). Readers can also refer to Fann et al. (2009) 

for a detailed description of the benefit-per-ton methodology.20

As described in the documentation for the benefit-per-ton estimates cited above, national per-ton 

estimates are developed for selected pollutant/source category combinations. The per-ton values 

calculated therefore apply only to tons reduced from those specific pollutant/source combinations (e.g., 

NO2 emitted from mobile sources; direct PM emitted from stationary sources). The NHTSA estimate of 

PM2.5 benefits is therefore based on the total direct PM2.5 and PM2.5-related precursor emissions controlled 

by sector and multiplied by this per-ton value. 

The benefit-per-ton coefficients were derived using modified versions of the health impact 

functions used in the EPA PM NAAQS RIA. Specifically, this analysis incorporated functions directly 

from the epidemiology studies without an adjustment for an assumed threshold. 

PM-related mortality provides most of the monetized value in each benefit-per-ton estimate. 

NHTSA calculated the premature-mortality-related effect coefficients that underlie the benefits-per-ton 

estimates from epidemiology studies that examined two large population cohorts – the American Cancer 

 

20 The values included in this analysis are different from those in Fann et al. (2009) cited above. Benefits methods 

change to reflect new information and evaluation of the science. Since publication of Fann et al. (2009), EPA has 

made two significant changes to its benefits methods: (1) EPA no longer assumes that there is a threshold in PMrelated models of health impacts and (2) EPA has revised the Value of a Statistical Life to equal $6.3 million (in 

year 2000 dollars), up from an estimate of $5.5 million (in year 2000 dollars) used in Fann et al. (2009). Refer to 

the following website for updates to the dollar-per-ton estimates: http://www.epa.gov/air/benmap/bpt.html. 
Chapter 3 Affected Environment and Environmental Consequences 3.3 Air Quality 

3-33 

Society cohort (Pope et al. 2002) and the Harvard Six Cities cohort (Laden et al. 2006). These are logical 

choices for anchor points when presenting PM-related benefits because, while both studies are well 

designed and peer reviewed, there are strengths and weaknesses inherent in each, which argues for using 

both studies to generate benefits estimates. However, due to the analytical limitations associated with this 

analysis, NHTSA chose to use the benefit-per-ton value derived from the American Cancer Society study 

and note that benefits would be approximately 145 percent (or almost two-and-a-half times) larger if the 

agency used the Harvard Six Cities values. 

The benefits-per-ton estimates used in this analysis are based on a value of statistical life (VSL) 

estimate that was vetted and endorsed by EPA’s Science Advisory Board (SAB) in the Guidelines for 

Preparing Economic Analyses (EPA 2000b).21 This approach calculates a mean value across VSL 

estimates derived from 26 labor market and contingent valuation studies published between 1974 and 

1991. The mean VSL across these studies is $6.3 million (in 2000 dollars). The dollar-per-ton estimates 

NHTSA used in this analysis are based on this VSL and listed in Table 3.3.2-3. 

Table 3.3.2-3 

Benefits-per-ton Values (2007$) Derived Using the ACS Cohort Study for PM-related Premature Mortality 

(Pope et al. 2002) a/ and a 3-Percent Discount Rate b/ 

All Sources d/ 

Stationary (Non-EGU e/) 

Sources Mobile Sources 

Year c/ SOx VOC NOx Direct PM2.5 NOx Direct PM2.5

2016 $29,000 $1,200 $4,800 $220,000 $4,900 $270,000 

2020 $31,000 $1,300 $5,100 $240,000 $5,300 $290,000 

2030 $36,000 $1,500 $6,100 $280,000 $6,400 $350,000 

2040 $43,000 $1,800 $7,200 $330,000 $7,600 $420,000 

_______________ 

a/ The benefit-per-ton estimates in this table are based on an estimate of premature mortality derived from the 

American Cancer Society study (Pope et al. 2002). If the benefit-per-ton estimates were based on the Six Cities 

study (Laden et al. 2006), the values would be approximately 145 percent (nearly two-and-a-half times) larger. 

b/ The benefit-per-ton estimates in this table assume a 3-percent discount rate in the valuation of premature 

mortality to account for a 20-year segmented cessation lag. If a 7-percent discount rate had been used, the 

values would be approximately 9 percent lower. 

c/ Benefit-per-ton values were estimated for the years 2015, 2020, and 2030. For 2016, NHTSA interpolated 

exponentially between 2015 and 2020. For 2040, NHTSA extrapolated exponentially based on the growth 

between 2020 and 2030. 

d/ Note that the benefit-per-ton value for SOx is based on the value for Stationary (Non-EGU) sources; no SOx value 

was estimated for mobile sources. The benefit-per-ton value for VOCs was estimated across all sources. 

e/ Non-EGU = Sources other than electric generating units (power plants). 

Quantified Health Impacts

Table 3.3.2-4 lists the incidence-per-ton estimates for select PM-related endpoints (derived by the 

same process as described above for the dollar-per-ton estimates). 

For the analysis of direct and indirect impacts (see Section 3.4), NHTSA used the values for 

2016, 2020, and 2030 (see Section 3.3.2.2). For the analysis of cumulative impacts (see Section 4.3), 

which also includes estimated impacts for 2050, NHTSA used the same values and used the values for 

2040 for the 2050 analysis. 

 

21 In the (draft) update of the Economic Guidelines (EPA 2008c), EPA retained the VSL endorsed by the SAB with 

the understanding that further updates to the mortality risk valuation guidance would be forthcoming in the near 

future. Therefore, this report does not represent final agency policy. 
3.3 Air Quality Chapter 3 Affected Environment and Environmental Consequences 

Table 3.3.2-4 

Incidence-per-ton Values for Health Outcomes – Pope et al. 2002b 

All Sources b/ 

Stationary (Non-EGU c/) 

Sources Mobile Sources 

Year a/ SOx VOC NOx Direct PM2.5 NOx Direct PM2.5

Premature Mortality – Pope et al. 2002b/ 

2016 0.003325787 0.000137288 0.000547035 0.025732657 0.000569579 0.031175340 

2020 0.003458671 0.000143397 0.000570861 0.026715546 0.000596007 0.032639009 

2030 0.003975998 0.000167016 0.000663928 0.030515150 0.000697373 0.038060658 

2040 0.004570704 0.000194525 0.000772167 0.034855151 0.000815979 0.044382895 

Chronic Bronchitis 

2016 0.002277723 0.000096601 0.000397136 0.017420574 0.000414238 0.022207886 

2020 0.0023816082 0.0001012424 0.0004171427 0.0181752796 0.0004359040 0.0232993398 

2030 0.0026209886 0.0001118571 0.0004635162 0.0199109220 0.0004858213 0.0258578276 

2040 0.002884430 0.000123585 0.000515045 0.021812309 0.000541455 0.028697262 

Emergency Room Visits – Respiratory 

2016 0.003099058 0.000103060 0.000451637 0.025462154 0.000441076 0.025601267 

2020 0.0032303276 0.0001070418 0.0004698051 0.0265119244 0.0004597436 0.0266615404 

2030 0.0035320012 0.0001164697 0.0005108599 0.0289098974 0.0005019649 0.0291780116 

2040 0.003861848 0.000126728 0.000555502 0.031524764 0.000548064 0.031932002 

Work Loss Days 

2016 0.438375533 0.018707314 0.077980894 3.360146515 0.081423310 4.305601155 

2020 0.4465435076 0.0190630849 0.0796512748 3.4161853728 0.0832854645 4.3980698724 

2030 0.4691223356 0.0199715639 0.0839602703 3.5832489831 0.0879939906 4.6493469302 

2040 0.492842829 0.020923338 0.088502375 3.758482598 0.092968712 4.914980322 

_______________ 

a/ Benefit-per-ton values were estimated for the years 2015, 2020, and 2030. For 2016, NHTSA interpolated 

exponentially between 2015 and 2020. For 2040, NHTSA extrapolated exponentially based on growth between 

2020 and 2030. 

b/ The PM-related premature mortality incidence-per-ton estimates presented in this table are based on an estimate 

of premature mortality derived from the ACS study (Pope et al. 2002). If the incidence-per-ton estimates were 

based on the Six Cities study (Laden et al. 2006), the values would be approximately 145 percent (nearly twoand-a-half times) larger. 

c/ Non-EGU = Sources other than electric generating units (power plants).

Assumptions and Uncertainties

The benefit-per-ton estimates are subject to a number of assumptions and uncertainties, as 

follows: 

• They do not reflect local variability in population density, meteorology, exposure, baseline 

health incidence rates, or other local factors that might lead to an overestimate or 

underestimate of the actual benefits of controlling fine particulates. Emissions changes and 

benefits-per-ton estimates alone are not a good indication of local or regional air quality and 

health impacts, because there could be localized impacts associated with the proposed action. 

Because the atmospheric chemistry related to ambient concentrations of PM2.5, ozone, and air 

toxics is very complex, full-scale photochemical air quality modeling would be necessary to 

control for local variability. Full-scale photochemical modeling would provide the needed 

spatial and temporal detail to more completely and accurately estimate changes in ambient 

levels of these pollutants and their associated health and welfare impacts. To support and 

confirm the screening-level, benefit-per-ton estimates, NHTSA performed full-scale 

photochemical air quality modeling of a selection of alternatives as discussed below and in 

Appendix F. This modeling provides insight into the uncertainties associated with the use of 

benefits-per-ton estimates. EPA is conducting full-scale photochemical modeling for its 

 3-34 
Chapter 3 Affected Environment and Environmental Consequences 3.3 Air Quality 

rulemaking on vehicle GHG standards, which is an element of the joint NHTSA-EPA 

rulemaking for CAFE (NHTSA) and GHG (EPA) standards for MYs 2012-2016 passenger 

cars and light trucks. It should be noted that the air quality modeling presented in Appendix F 

differs in a number of key respects from the modeling EPA is conducting for the analysis of 

the final standard, as discussed in Appendix E. These differences include: 

– Use of a more recent version of CMAQ by EPA (this version was not publicly available 

at the time NHTSA performed its modeling), 

– Use of a 2005 base year modeling platform compared to the 2002 platform used in the 

NHTSA modeling, 

– Use of a finer 12-km U.S. spatial modeling grid compared to the 36-km resolution used 

in the NHTSA modeling, 

– Estimation of global boundary conditions from a global chemistry model compared to the 

static boundary conditions used in the NHTSA modeling, and 

– EPA’s modeling of vehicle emissions accounts for geographic variations in factors such 

as ambient temperature, age distribution of the fleet, and fuel composition (especially 

with regard to the ethanol fraction), while the NHTSA modeling of vehicle emissions is 

based on national average characteristics. 

• NHTSA assumed that all fine particles, regardless of their chemical composition, are equally 

potent in causing premature mortality. This is an important assumption, because PM2.5

produced via transported precursors emitted from stationary sources might differ significantly 

from direct PM2.5 released from diesel engines and other industrial sources, but there are no 

clear scientific grounds to support estimating differential effects by particle type. 

• NHTSA assumed that the health impact function for fine particles is linear within the range of 

ambient concentrations under consideration. Thus, the estimates include health benefits from 

reducing fine particles in areas with varied concentrations of PM2.5, including both regions 

that are in attainment with the fine-particle standard and those that do not meet the standard 

down to the lowest modeled concentrations. 

• There are several health-benefits categories NHTSA was unable to quantify due to limitations 

associated with using benefits-per-ton estimates, several of which could be substantial. 

Because NOx and VOCs are also precursors to ozone, reductions in NOx and VOC emissions 

would also reduce ozone formation and the health effects associated with ozone exposure. 

Unfortunately, there are no benefits-per-ton estimates because of issues associated with the 

complexity of the atmospheric air chemistry and nonlinearities associated with ozone 

formation. The PM-related benefits-per-ton estimates also do not include any human welfare 

or ecological benefits. 

Photochemical Air Quality Modeling and Risk Assessment

To support and confirm the health effects and health-related economic estimates in this EIS, a 

national-scale photochemical air quality modeling and heath risk assessment was conducted for a 

representative subset of the DEIS alternatives. The study used air quality modeling and health benefits 

analysis tools to quantify the air quality and health-related benefits associated with the alternative CAFE 

standards. Four alternatives from the DEIS were modeled: the No Action Alternative and Alternative 2 

(the 3-Percent Alternative) to represent fuel economy requirements at the lower end of the range; 

Alternative 4 (the Preferred Alternative); and Alternative 8 (the 7 Percent Alternative) to represent fuel 

economy requirements at the higher end of the range. The photochemical air quality study is included as 

Appendix F to this EIS. 

3-35 
3.3 Air Quality Chapter 3 Affected Environment and Environmental Consequences 

 3-36 

NHTSA used the DEIS Volpe model data and the photochemical air quality modeling tools to 

determine whether NHTSA’s EIS scaling approach to estimating health effects and monetized health 

benefits – using the EPA incidence-per-ton and benefits-per-ton data – is sufficient to determine the 

differences among the alternatives as NEPA requires. Because the photochemical air quality analysis is a 

detailed analysis that takes several months to complete, the FEIS Volpe data were not available when the 

agency began its analysis. The photochemical air quality modeling is a more detailed examination of the 

air quality impacts already analyzed using the EIS benefits-per-ton estimates scaling approach. Because 

NHTSA’s analysis shows agreement between the scaling method and the results of the photochemical 

modeling, the new information confirms the adequacy of the air quality analysis methodology NHTSA 

uses in its EIS as sufficient to distinguish air quality impacts among the alternatives. Therefore, the 

photochemical modeling did not reveal significant effects not previously considered. This analysis is an 

appropriate tool to confirm NHTSA’s air quality and health effects methodology and results, and a 

supplemental EIS is not required.22

The photochemical air quality modeling analysis provides the most detailed, comprehensive, and 

accurate estimates available on the potential health effects and health-related economic effects of the 

CAFE alternatives. The analysis demonstrates that the health and economic effects calculated in the EIS 

using EPA’s incidence-per-ton and benefits-per-ton data are comparable to the detailed estimates from the 

photochemical air quality analysis. 

3.3.3 Environmental Consequences 

3.3.3.1 Results of the Emissions Analysis 

The CAA has been a success in reducing emissions from on-road mobile sources. As discussed 

in Section 3.3.1, pollutant emissions from vehicles have been declining since 1970 and EPA projects that 

they will continue to decline. However, as future trends show, vehicle travel is having a smaller and 

smaller impact on emissions as a result of stricter EPA standards for vehicle emissions and the chemical 

composition of fuels, even with additional growth in VMT (Smith 2002). This general trend will 

continue, to a greater or lesser degree, with implementation of any of the alternative CAFE standards. 

The analysis by alternative in this section shows that the CAFE action alternatives will lead to both 

reductions and increases in emissions from passenger cars and light trucks, compared to current trends 

without the proposed CAFE standards. The amounts of the reductions and increases would vary by 

pollutant, calendar year, and action alternative. The more restrictive action alternatives generally would 

result in greater emissions reductions compared to the No Action Alternative. 

Sections 3.3.3.2 through 3.3.3.10 describe the results of the emissions analysis for Alternatives 1 

through 9. 

 

22 See Marsh v. Oregon Natural Resources Council, 490 U.S. 360, 374 (1989) (noting that application of the rule of 

reason in the supplemental EIS context turns on the value of the new information to the decisionmaking process). 

An agency must prepare a supplement to a draft EIS if there “are significant new circumstances or information 

relevant to environmental consequences and bearing on the proposed action or its impacts.” 40 CFR § 1502.9(c). 

See Sierra Club v. L. Van Antewerp, 526 F.3d 1353, 1360 (11th Cir. 2008) (noting that an agency must prepare a 

supplemental EIS when the receipt of additional information reveals new, significant effects on the quality of the 

human environment not previously considered). 
Chapter 3 Affected Environment and Environmental Consequences 3.3 Air Quality 

3-37 

3.3.3.2 Alternative 1: No Action 

3.3.3.2.1 Criteria Pollutants 

Under the No Action Alternative, average fuel economy levels in the absence of CAFE standards 

beyond MY 2011 would equal the higher of the agencies’ collective market forecast or the manufacturers’ 

required level of average fuel economy for MY 2011. Current trends in the levels of emissions from 

vehicles would continue, with emissions continuing to decline due to the EPA emissions standards, 

despite a growth in total VMT. The EPA vehicle emissions standards regulate all criteria pollutants 

except SO2, which is regulated through fuel sulfur content. The No Action Alternative would not result in 

any change in criteria pollutant emissions, other than current trends, in nonattainment and maintenance 

areas throughout the United States. 

Table 3.3.3-1 summarizes the total national emissions from passenger cars and light trucks by 

alternative for each of the criteria pollutants and analysis years. The table presents the action alternatives 

(Alternatives 2 through 9) left to right in order of increasing fuel economy requirements. Figure 3.3.3-1 

illustrates this information. Table 3.3.3-1 and Figure 3.3.3-1 show that changes in overall emissions 

between the No Action Alternative and Alternatives 2 through 4 are generally smaller than those between 

the No Action Alternative and Alternatives 5 through 9. In the case of NOx, PM2.5, SOx, and VOCs, the 

No Action Alternative results in the highest emissions, and emissions generally decline as fuel economy 

standards increase across alternatives. Across Alternatives 4 through 9 there are some emissions 

increases from one alternative to another, but emissions remain below the levels under the No Action 

Alternative. In the case of CO, emissions under Alternatives 2 through 4 are slightly higher than under 

the No Action Alternative. Emissions of CO generally decline, though unevenly, as fuel economy 

standards increase across Alternatives 5 through 9. 

Total emissions are composed of four components: tailpipe emissions and upstream emissions 

for passenger cars, and tailpipe emissions and upstream emissions for light trucks. To show the 

relationship among these four components for criteria pollutants, Table 3.3.3-2 breaks down the total 

emissions of criteria pollutants by component for calendar year 2030. 

Table 3.3.3-3 lists the net change in nationwide emissions from passenger cars and light trucks 

compared to the No Action Alternative for each of the criteria pollutants and analysis years. The table 

lists the action alternatives (Alternatives 2 through 9) left to right in order of increasing fuel economy 

requirements. In Table 3.3.3-3, the nationwide emissions reductions of NOx, SOx, and VOCs generally 

become greater from left to right, reflecting the increasing fuel economy requirements assumed under 

successive alternatives, although the decreases are smaller for some pollutants and years under 

Alternatives 5 through 9 due to the interaction of VMT, fuel economy, and the share of VMT accrued by 

diesel vehicles. Emissions of PM2.5 follow the same trend to a lesser extent, with the reductions becoming 

smaller from Alternative 5 to Alternative 8 before increasing again under Alternative 9. Emissions of CO 

under Alternatives 2 through 4 are exceptions, showing increases compared to the No Action Alternative, 

because increases in VMT more than offset increases in fuel efficiency and declines in CO emission rates 

per vehicle. 

One of the ways that the Volpe model projects vehicle manufacturers can achieve higher fuel 

economy is to increase the share of new vehicles that use diesel engines. The resulting increase in the use 

of diesel fuel as mpg standards become more stringent across action alternatives can interact with other 

factors, such as changes in VMT, the car and light truck shares, and the shares of other technologies such 

as hybrids, to affect emissions of different pollutants in different ways across Alternatives. Another result 

of increasing forecasted use of diesel engines can be that differing upstream emission rates might change 
3.3 Air Quality Chapter 3 Affected Environment an

Table 3.3.3-1 

Nationwide Criteria Pollutant Emissions (tons/year) from Passenger Cars and Light Trucks by Alternativ

Alt. 1 Alt. 2 Alt. 3 Alt. 4 Alt. 5 Alt. 6 Alt. 7 

Poll. 

and 

Year 

No 

Action 

3%/year 

Increase 

4%/year 

Increase 

~4.3%/year 

Increase 

Preferred 

5%/year 

Increase 

~6.0%/year 

Increase 

MNB 

6%/year 

Increase 

7

In

Carbon monoxide (CO) 

2016 20,380,537 20,393,938 20,394,480 20,383,598 20,272,923 20,182,256 20,228,025 22020 19,129,794 19,168,534 19,173,637 19,152,242 18,857,762 18,607,550 18,702,398 12030 20,516,692 20,625,314 20,653,244 20,611,910 19,847,892 19,203,414 19,361,096 1

Nitrogen oxides (NOx) 

2016 2,210,405 2,207,302 2,205,558 2,204,404 2,201,606 2,197,765 2,199,718 2020 1,756,741 1,749,121 1,745,092 1,742,950 1,733,886 1,724,211 1,727,891 2030 1,425,733 1,410,414 1,402,605 1,398,774 1,371,749 1,345,911 1,351,818 

Particulate matter (PM2.5) 

2016 68,793 68,374 68,122 68,024 68,424 68,603 68,606 2020 68,906 67,821 67,223 67,055 67,782 68,113 68,159 2030 84,021 81,726 80,498 80,206 81,194 81,484 81,637 

Sulfur Oxides (SOx) 

2016 176,518 173,665 172,306 171,666 172,232 171,378 171,729 2020 184,239 177,076 173,851 172,779 173,439 172,286 172,419 2030 216,228 200,884 194,149 192,374 192,985 191,324 190,961 

Volatile organic compounds (VOCs) 

2016 2,505,277 2,491,567 2,484,860 2,480,794 2,470,902 2,455,914 2,461,292 2020 2,163,685 2,129,680 2,114,100 2,107,249 2,082,209 2,052,680 2,058,723 2030 1,881,987 1,810,076 1,778,691 1,767,262 1,708,646 1,649,731 1,655,217 

3-38 
Chapter 3 Affected Environment and Environmental Consequences 

Figure 3.3.3-1. Nationwide Criteria Pollutant Emissions (tons/year) 

from Passenger Cars and Light Trucks for 2030 by Alternative 

0

400,000800,000

1,200,0001,600,0002,000,000

Alt. 1

No Action

Alt. 2 

3%/year

Increase

Alt. 3 

4%/year

Increase

Alt. 4 

~4.3%/year

Increase

Preferred

Alt. 5 

5%/year

Increase

Alt. 6 

~6.0%/year

Increase MNB

Alt. 7 

6%/year

Increase

Alt. 8 

7%/year

Increase

Alt 

~6.6%

Incr

TC

Alternative

Tons/Year (NOx, PM, SOx, VOC) 

Nitrogen Oxides (NOx) Particulate Matter (PM) Sulfur Oxides (SOx) Volatile Organic Compounds (VOC) Carbon Mono

3-39 
3.3 Air Quality Chapter 3 Affected Environment an

Table 3.3.3-2 

Nationwide Criteria Pollutant Emissions (tons/year) in 2030 from Passenger Cars and Light Trucks, by Vehicle Type a

Alt. 1 Alt. 2 Alt. 3 Alt. 4 Alt. 5 Alt. 6 Alt. 7 Al

Poll. and 

Source 

No 

Action 

3%/year 

Increase 

4%/year 

Increase 

~4.3%/year

Increase 

Preferred 

5%/year 

Increase 

~6.0%/year 

Increase 

MNB 

6%/year 

Increase 

7%/

Incr

Carbon monoxide (CO) 

Car Tail 10,045,431 10,056,403 10,114,957 10,117,191 9,852,164 9,676,743 9,646,119 9,4Car Up 56,362 52,139 50,141 49,671 49,712 49,083 49,198 Truck Tail 10,375,524 10,479,934 10,452,279 10,409,473 9,909,803 9,441,137 9,629,644 9,3Truck Up 39,375 36,839 35,868 35,576 36,214 36,451 36,135 Total 20,516,692 20,625,314 20,653,244 20,611,910 19,847,892 19,203,414 19,361,096 18,8

Nitrogen oxides (NOx)

Car Tail 360,141 360,706 362,717 362,816 354,215 348,510 347,521 3Car Up 176,443 163,055 156,849 155,362 154,888 152,523 152,828 1Truck Tail 766,002 771,372 770,883 769,408 750,084 732,206 739,610 7Truck Up 123,148 115,280 112,157 111,188 112,563 112,673 111,859 1Total 1,425,733 1,410,414 1,402,605 1,398,774 1,371,749 1,345,911 1,351,818 1,3

Particulate matter (PM2.5) 

Car Tail 22,502 22,920 22,931 22,976 23,924 24,585 24,689 Car Up 24,026 22,234 21,380 21,180 21,231 20,984 21,036 Truck Tail 20,703 20,867 20,890 20,874 20,558 20,299 20,441 Truck Up 16,790 15,706 15,297 15,175 15,481 15,616 15,472 Total 84,021 81,726 80,498 80,206 81,194 81,484 81,637 

Sulfur Oxides (SOx) 

Car Tail 19,460 17,814 17,180 17,000 16,330 15,662 15,642 Car Up 107,889 99,867 96,023 95,130 95,437 94,385 94,624 Truck Tail 13,465 12,669 12,239 12,077 11,592 10,957 11,045 Truck Up 75,414 70,534 68,708 68,168 69,625 70,319 69,649 Total 216,228 200,884 194,149 192,374 192,985 191,324 190,961 1

Volatile organic compounds (VOCs)  Car Tail 289,746 290,863 292,113 292,259 288,769 286,519 286,102 2 Car Up 588,841 537,102 518,485 512,862 485,595 460,751 459,531 4 Truck Tail 597,298 599,279 599,260 598,828 592,877 587,618 590,056 5 Truck Up 406,101 382,832 368,833 363,313 341,405 314,844 319,529 3 Total 1,881,987 1,810,076 1,778,691 1,767,262 1,708,646 1,649,731 1,655,217 1,6

3-40 
Chapter 3 Affected Environment and Environmental Consequences 

3-41 

Table 3.3.3-3 

Nationwide Changes in Criteria Pollutant Emissions (tons/year) from Passenger Cars and Light Trucks by Altern

Alt. 1 Alt. 2 Alt. 3 Alt. 4 Alt. 5 Alt. 6 Alt. 7 Al

Poll. 

and 

Year 

No 

Action c/ 

3%/year 

Increase 

4%/year 

Increase 

~4.3%/year 

Increase 

Preferred 

5%/year 

Increase 

~6.0%/year 

Increase 

MNB 

6%/year 

Increase 

7%/

Incr

Carbon monoxide (CO) 

2016 0 13,402 13,943 3,062 -107,614 -198,280 -152,511 2020 0 38,740 43,844 22,448 -272,031 -522,244 -427,396 2030 0 108,622 136,552 95,218 -668,801 -1,313,279 -1,155,596 -1

Nitrogen oxides (NOx) 

2016 0 -3,103 -4,847 -6,001 -8,799 -12,640 -10,687 2020 0 -7,620 -11,649 -13,791 -22,855 -32,530 -28,850 2030 0 -15,319 -23,128 -26,959 -53,984 -79,822 -73,915 

Particulate matter (PM2.5) 

2016 0 -420 -672 -770 -369 -191 -187 2020 0 -1,085 -1,683 -1,851 -1,125 -793 -747 2030 0 -2,295 -3,523 -3,816 -2,827 -2,537 -2,384 

Sulfur Oxides (SOx) 

2016 0 -2,853 -4,212 -4,852 -4,286 -5,140 -4,788 2020 0 -7,163 -10,388 -11,460 -10,800 -11,953 -11,820 2030 0 -15,344 -22,079 -23,854 -23,243 -24,904 -25,267 

Volatile organic compounds (VOCs) 

2016 0 -13,710 -20,417 -24,484 -34,375 -49,363 -43,985 2020 0 -34,005 -49,585 -56,436 -81,475 -111,004 -104,961 2030 0 -71,911 -103,296 -114,725 -173,341 -232,255 -226,770 

__________ a/ Emissions changes have been rounded to the nearest whole number. 

b/ Negative emissions changes indicate reductions; positive emissions changes are increases. 

c/ Emissions changes for the No Action Alternative are shown as zero because the No Action Alternative is the baseline to which the emissions for the 

compared.
3.3 Air Quality Chapter 3 Affected Environment and Environmental Consequences 

pollutant emissions estimates, as compared to those rates for gasoline fueled engines. Projected changes 

in the share of diesel vehicles appear to be a factor in the results for CO that show increases in emissions 

compared to the No Action Alternative under Alternatives 2 through 4 and decreases in emissions 

compared to the No Action Alternative under Alternatives 6 through 9. 

3.3.3.2.2 Toxic Air Pollutants 

Under Alternative 1 (No Action), the average fuel economy would remain at the MY 2011 level 

in future years. As with the criteria pollutants, current trends in the levels of toxic air pollutant emissions 

from vehicles would continue, with emissions continuing to decline due to the EPA emissions standards, 

despite a growth in total VMT. An exception to this general trend is DPM, for which emissions are 

projected to increase over time under the No Action Alternative due to increasing use of diesel vehicles 

and increasing VMT. EPA regulates toxic air pollutants from motor vehicles through vehicle emissions 

standards and fuel quality standards, as discussed in Section 3.3.1. The No Action Alternative would not 

change the current CAFE standards and therefore would not result in any change in toxic air pollutant 

emissions, other than current trends in emissions and VMT, in nonattainment and maintenance areas 

throughout the United States. 

Table 3.3.3-4 summarizes the total national emissions of toxic air pollutants from passenger cars 

and light trucks by alternative for each of the pollutants and analysis years. Figure 3.3.3-2 lists the total 

national emissions of toxic air pollutants from passenger cars and light trucks by alternative. Emissions 

of benzene and DPM are highest under the No Action Alternative, and emissions of acrolein and 

formaldehyde are highest under Alternative 8. Emissions of acetaldehyde are highest under Alternatives 

8 and 9 in 2016, Alternative 8 in 2020, but highest under Alternative 4 in 2030. Emissions of 1,3-

butadiene is highest under Alternative 8 in 2016, Alternative 8 in 2020,, and highest under Alternative 3 

in 2030. 

The trends for toxic air pollutant emissions across the alternatives are mixed. Table 3.3.3-4 

shows the emissions of acetaldehyde increase under each successive alternative from Alternative 1 to 

Alternative 9, except for Alternatives 2, 7, and 9 in 2016, Alternatives 7 and 9 in 2020, and Alternatives 5 

through 8 in 2030. In Alternatives 6 through 9 in 2030, acetaldehyde emissions are below those in the No 

Action alternative. Emissions of acrolein remain constant or increase under each successive alternative 

from Alternative 1 to Alternative 9, except for Alternatives 7 and 9. Emissions of benzene decrease under 

each successive alternative from Alternative 1 to Alternative 9, except for Alternatives 7 and 9. 

Emissions of 1,3-butadiene in 2016 increase under each successive alternative from Alternative 1 to 

Alternative 9, except under Alternatives 7 and 9; emissions of 1,3-butadiene in 2020 increase under each 

successive alternative from Alternative 1 to Alternative 9, except under Alternative 9; emissions of 1,3-

butadiene in 2030 increase under each successive alternative from Alternative 1 to Alternative 9, except 

for Alternatives 4 through 6 and 8. Emissions of DPM decrease under each successive alternative from 

Alternative 1 to Alternative 9, except for Alternative 7 in 2016, Alternatives 7 and 9 in 2020 and 2030. 

Emissions of formaldehyde decrease under each successive alternative from Alternative 1 to Alternative 

9, except for Alternatives 3 through 6 and 8. These trends are accounted for by the interaction between 

the share of VMT accrued by diesel vehicles, which increases across successive years as well as 

successive alternatives in the Volpe model, and fuel economy, which increases across successive 

alternatives except for Alternative 9. 

 3-42 
Chapter 3 Affected Environment and Environmental Consequences 3.3 Air Quality 

3-43 

Table 3.3.3-4 

Nationwide Toxic Air Pollutant Emissions (tons/year) from Passenger Cars and Light Trucks by Alternative 

Alt. 1 Alt. 2 Alt. 3 Alt. 4 Alt. 5 Alt. 6 Alt. 7 Alt. 8 Alt. 9 

Poll. 

and 

Year 

No 

Action 

3%/year 

Increase 

4%/year 

Increase

~4.3%/year

Increase 

Preferred 

5%/year 

Increase 

~6.0%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.6%/year 

Increase 

TCTB 

Acetaldehyde 

2016 10,921 10,919 10,924 10,928 10,955 10,976 10,960 10,977 10,977

2020 9,024 9,027 9,036 9,041 9,069 9,098 9,084 9,104 9,097

2030 7,927 7,951 7,973 7,976 7,929 7,905 7,902 7,872 7,879

Acrolein 

2016 561 561 561 562 569 576 572 577 576

2020 455 456 456 458 472 486 482 491 488

2030 391 394 395 397 425 449 445 463 457

Benzene 

2016 56,184 56,162 56,150 56,139 56,080 56,019 56,045 56,008 56,010

2020 43,121 43,075 43,049 43,025 42,840 42,669 42,729 42,613 42,635

2030 28,961 28,900 28,863 28,815 28,203 27,673 27,788 27,388 27,519

1,3-butadiene 

2016 6,100 6,101 6,102 6,103 6,107 6,112 6,109 6,113 6,112

2020 4,874 4,879 4,881 4,882 4,883 4,887 4,888 4,891 4,889

2030 3,751 3,771 3,777 3,776 3,747 3,724 3,734 3,717 3,722

Diesel particulate patter (DPM) 

2016 93,117 91,618 90,856 90,463 90,213 89,313 89,679 89,227 89,075

2020 97,085 93,300 91,516 90,865 90,117 88,550 88,862 88,008 88,018

2030 113,884 105,735 102,053 100,991 99,301 96,641 96,743 95,220 95,595

Formaldehyde 

2016 13,700 13,685 13,692 13,707 13,833 13,937 13,874 13,948 13,943

2020 10,980 10,956 10,968 10,990 11,223 11,434 11,351 11,498 11,457

2030 9,190 9,173 9,194 9,224 9,580 9,911 9,818 10,051 9,964
3.3 Air Quality Chapter 3 Affected Environment an

Figure 3.3.3-2. Nationwide Toxic Air Pollutant Emissions (tons/year) 

from Passenger Cars and Light Trucks for 2030 by Alternative 

0

2,0004,0006,0008,000

10,00012,000

Alt. 1

No Action

Alt. 2 

3%/year

Increase

Alt. 3 

4%/year

Increase

Alt. 4 

~4.3%/year

Increase

Preferred

Alt. 5 

5%/year

Increase

Alt. 6 

~6.0%/year

Increase MNB

Alt. 7 

6%/year

Increase

Alt. 8 

7%/year

Increase

A

~6.6%

Incr

TC

Alternative

Tons/Year (Acetaldehyde, Acrolein, 1,3-

Butadiene, Formaldehyde) 

Acetaldehyde Acrolein 1,3-Butadiene Formaldehyde Benzene Diesel Particulate Matter (DPM

3-44 
Chapter 3 Affected Environment and Environmental Consequences 3.3 Air Quality 

One of the ways that the Volpe model projects vehicle manufacturers can achieve higher fuel 

economy is to increase the share of new vehicles that use diesel engines. The resulting increase in the use 

of diesel fuel as mpg standards become more stringent across action alternatives can interact with other 

factors, such as changes in VMT, the car and light truck shares, and the shares of other technologies such 

as hybrids, to affect emissions of different pollutants in different ways across Alternatives. Another result 

of increasing forecasted use of diesel engines can be that differing upstream emission rates might change 

pollutant emissions estimates, as compared to those rates for gasoline fueled engines. Projected changes 

in the share of diesel vehicles appear to be a factor in the results for acetaldehyde and 1,3-butadiene that 

show increases in emissions compared to the No Action Alternative under Alternatives 2 through 4 and 

decreases in emissions compared to the No Action Alternative under Alternatives 6 through 9. 

Total emissions are composed of four components: tailpipe emissions and upstream emissions 

for passenger cars, and tailpipe emissions and upstream emissions for light trucks. To show the 

relationship among these four components for air toxic pollutants, Table 3.3.3-5 breaks down the total 

emissions of air toxic pollutants by component for calendar year 2030. 

Table 3.3.3-6 lists the net change in nationwide emissions from passenger cars and light trucks 

for each of the toxic air pollutants and analysis years. After the No Action Alternative (Alternative 1), the 

table presents the action alternatives (Alternatives 2 through 9) left to right; this corresponds to the order 

of increasing fuel economy except for Alternative 9. In Table 3.3.3-6, the nationwide emissions changes 

are uneven in relation to pollutant and alternative, although some demonstrate reductions, reflecting the 

changes in VMT and emissions by passenger cars versus light trucks and gasoline versus diesel engines 

projected to occur with the increasing fuel economy requirements assumed under successive alternatives. 

3.3.3.2.3 Health Outcomes and Monetized Benefits 

Under Alternative 1 (No Action), average fuel economy would remain at the MY 2011 level in 

future years. Current trends in the levels of criteria pollutants and toxic air pollutants emissions from 

vehicles would continue, with emissions continuing to decline due to the EPA emissions standards, 

despite a growth in total VMT. The human health-related impacts that occur under current trends would 

continue. The No Action Alternative would not result in any other increase or decrease in human health 

impacts throughout the United States. 

3.3.3.3 Alternative 2: 3-Percent Annual Increase 

3.3.3.3.1 Criteria Pollutants 

Under the 3-Percent Alternative (Alternative 2), generally the CAFE standards would require 

increased fuel economy compared to the No Action Alternative (Alternative 1). Alternative 2 would 

increase fuel economy less than would Alternatives 3 through 9. There would be reductions in 

nationwide emissions of NOx, PM2.5, SOx, and VOCs under Alternative 2 compared to the No Action 

Alternative. Depending on the year, NOx emissions would be reduced 0.1 to 1.1 percent, PM2.5 emissions 

would be reduced 0.6 to 2.7 percent, SOx emissions would be reduced 1.6 to 7.1 percent, and VOC 

emissions would be reduced 0.5 to 3.8 percent. There would be increases of CO emissions. CO 

emissions would increase 0.1 to 0.5 percent under Alternative 2, depending on the year. 

3-45 
3.3 Air Quality Chapter 3 Affected Environment an

Table 3.3.3-5 

Nationwide Toxic Air Pollutant Emissions (tons/year) in 2030 from Passenger Cars and Light Trucks, by Vehicle Type 

Alt. 1 Alt. 2 Alt. 3 Alt. 4 Alt. 5 Alt. 6 Alt. 7 Alt. 8 

Poll. and 

Source 

No 

Action 

3%/year 

Increase 

4%/year 

Increase 

~4.3%/year 

Increase 

Preferred 

5%/year 

Increase 

~6.0%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

Acetaldehyde Car Tail 3,453 3,467 3,484 3,486 3,435 3,403 3,397 3,36Car Up 63 58 56 55 54 52 52 5Truck Tail 4,367 4,385 4,394 4,397 4,401 4,413 4,415 4,42Truck Up 44 41 40 39 39 37 37 3Total 7,927 7,951 7,973 7,976 7,929 7,905 7,902 7,87Acrolein Car Tail 162 166 166 166 178 187 188 19Car Up 9 8 8 8 7 7 7 Truck Tail 215 214 216 218 234 250 244 25Truck Up 6 6 5 5 5 5 5 Total 391 394 395 397 425 449 445 46Benzene Car Tail 9,427 9,447 9,495 9,498 9,310 9,185 9,163 9,03Car Up 1,274 1,165 1,124 1,112 1,064 1,017 1,015 98Truck Tail 17,378 17,458 17,443 17,415 17,076 16,764 16,896 16,68Truck Up 881 829 801 790 753 707 714 68Total 28,961 28,900 28,863 28,815 28,203 27,673 27,788 27,381,3-butadiene Car Tail 1,518 1,529 1,534 1,536 1,532 1,530 1,529 1,52Car Up 14 13 12 12 12 12 12 1Truck Tail 2,210 2,220 2,221 2,220 2,194 2,173 2,183 2,16Truck Up 10 9 9 9 9 9 9 Total 3,751 3,771 3,777 3,776 3,747 3,724 3,734 3,71Diesel particulate matter (DPM) Car Tail 15 269 193 218 1,204 1,883 1,992 2,67Car Up 67,202 61,635 59,410 58,800 56,920 54,897 54,865 53,43Truck Tail 88 49 95 138 572 996 841 1,12Truck Up 46,580 43,781 42,355 41,835 40,605 38,865 39,045 37,98Total 113,884 105,735 102,053 100,991 99,301 96,641 96,743 95,22

3-46 
Chapter 3 Affected Environment and Environmental Consequences 

 3-47 

Table 3.3.3-5 (cont’d) 

Nationwide Toxic Air Pollutant Emissions (tons/year) in 2030 from Passenger Cars and Light Trucks, by Vehicle Type 

Alt. 1 Alt. 2 Alt. 3 Alt. 4 Alt. 5 Alt. 6 Alt. 7 Alt. 8 

Pollutant and 

Source 

No 

Action 

3%/year 

Increase 

4%/year 

Increase 

~4.3%/year 

Increase 

Preferred 

5%/year 

Increase 

~6.0%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

Formaldehyde  Car Tail 3,564 3,612 3,619 3,624 3,698 3,754 3,761 3,81 Car Up 472 434 418 414 405 394 394 38 Truck Tail 4,827 4,820 4,859 4,891 5,186 5,480 5,379 5,57 Truck Up 328 308 298 295 291 284 284 27 Total 9,190 9,173 9,194 9,224 9,580 9,911 9,818 10,05
3.3 Air Quality Chapter 3 Affected Environment and Environmental Consequences 

Table 3.3.3-6 

Nationwide Changes in Toxic Air Pollutant Emissions (tons/year) from Passenger Cars 

and Light Trucks by Alternative a/ b/

Alt. 1 Alt. 2 Alt. 3 Alt. 4 Alt. 5 Alt. 6 Alt. 7 Alt. 8 Alt. 9 

Poll. 

and 

Year 

No 

Action c/

3%/year 

Increase 

4%/year 

Increase 

~4.3%/year

Increase 

Preferred 

5%/year 

Increase 

~6.0%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.6%/year 

Increase 

TCTB 

Acetaldehyde 

2016 0 -2 3 7 33 55 39 56 56

2020 0 2 12 16 44 74 60 80 73

2030 0 24 46 50 2 -21 -25 -54 -48

Acrolein 

2016 0 0 0 1 8 15 11 16 15

2020 0 0 1 3 17 30 26 36 33

2030 0 3 4 6 34 58 53 72 66

Benzene 

2016 0 -21 -33 -45 -104 -165 -139 -175 -174

2020 0 -46 -72 -96 -282 -452 -393 -508 -486

2030 0 -61 -98 -146 -757 -1,288 -1,172 -1,572 -1,441

1,3-Butadiene 

2016 0 1 2 3 7 12 10 13 13

2020 0 5 7 8 9 13 14 17 15

2030 0 20 25 25 -4 -27 -17 -34 -29

Diesel particulate matter (DPM) 

2010 0 -1,499 -2,261 -2,654 -2,904 -3,804 -3,438 -3,890 -4,042

2020 0 -3,786 -5,570 -6,220 -6,969 -8,536 -8,223 -9,078 -9,068

2030 0 -8,150 -11,832 -12,894 -14,584 -17,243 -17,141 -18,665 -18,290

Formaldehyde 

2010 0 -15 -7 8 134 237 175 249 243

2020 0 -24 -11 10 244 454 371 518 477

2030 0 -18 4 33 390 721 627 861 774

__________ 

a/ Emissions changes have been rounded to the nearest whole number. 

b/ Negative emissions changes indicate reductions; positive emissions changes are increases. 

c/ Emissions changes for the No Action Alternative are shown as zero because the No Action Alternative is the 

baseline to which emissions from the action alternatives are compared. 

At the national level, the reduction in upstream emissions of criteria air pollutants tends to offset 

the increase in VMT and emissions due to the rebound effect. However, the reductions in upstream 

emissions are not uniformly distributed to individual nonattainment areas. For example, a nonattainment 

area that contains petroleum-refining facilities, such as Houston-Galveston-Brazoria, Texas, would 

experience more reductions in upstream emissions than an area that has none. There can be net emissions 

reductions if the reduction in upstream emissions in the nonattainment area more than offsets the increase 

within the area due to the rebound effect. Under Alternative 2, all nonattainment areas would experience 

reductions in emissions of SOx and VOCs. Some nonattainment areas would experience increases of CO, 

NOx, and PM2.5 emissions. The increases in CO, NOx, and PM2.5 emissions are the result of increased 

tailpipe emissions due to the rebound effect, particularly for CO emissions, which are dominated by 

tailpipe emissions rather than upstream emissions. Although NOx and PM2.5 emissions would increase in 

some nonattainment areas, the increase in each area is generally quite small. The decreases in nationwide 

NOx and PM2.5 emissions are the result of the decreases in upstream emissions and do not occur in all 

nonattainment areas. Although NOx and PM2.5 emissions would decrease in fewer nonattainment areas, 

 3-48 
Chapter 3 Affected Environment and Environmental Consequences 3.3 Air Quality 

the decreases in each area are much larger. The net result is decreased NOx and PM2.5 emissions 

nationwide. 

Tables in Appendix C list the emissions reductions for each nonattainment area. Table 3.3.3-7 

summarizes the criteria air pollutant results by nonattainment area. 

Table 3.3.3-7 

Criteria Pollutant Emissions from Passenger Cars and Light Trucks, Maximum Changes 

by Nonattainment Area and Alternative a/ 

Criteria 

Pollutant 

Increase/ 

Decrease 

Change 

(tons/year) Year Alt. No. Nonattainment Area 

Maximum Increase 5,420 2030 2 New York-N. New Jersey-Long Island, NY-NJ-CT CO Maximum Decrease 56,925 2030 9 Los Angeles South Coast Air Basin, CA 

Maximum Increase 149 2030 2 Dallas-Fort Worth, TX NOx Maximum Decrease 4,350 2030 8 Houston-Galveston-Brazoria, TX 

Maximum Increase 23 2020 8 New York-N. New Jersey-Long Island, NY-NJ-CT PM2.5 Maximum Decrease 402 2030 6 Houston-Galveston-Brazoria, TX 

Maximum Increase No increases are predicted for any alternatives. SOx Maximum Decrease 1,713 2030 6 Chicago-Gary-Lake Co, IL-IN 

Maximum Increase No increases are predicted for any alternatives. VOCs Maximum Decrease 7668 2030 9 Houston-Galveston-Brazoria, TX 

__________ 

a/ Emissions changes have been rounded to the nearest whole number. 

3.3.3.3.2 Toxic Air Pollutants 

There would be reductions in nationwide emissions of benzene, DPM, and formaldehyde in all 

analysis years under Alternative 2 compared to the No Action Alternative. Emissions for the other toxic 

air pollutants and years are constant or higher under Alternative 2 than under Alternative 1. 

Compared to Alternatives 3 through 9, Alternative 2 would have higher emissions of benzene and 

DPM, but the same or lower emissions of acrolein and formaldehyde. For acetaldehyde and 1,3-

butadiene, Alternative 2 would have lower emissions than Alternatives 3 through 9 in 2016 and 2020, 

lower emissions than Alternatives 3 and 4 in 2030, and higher emissions than Alternatives 5 through 9 in 

2030. 

At the national level, the reduction in upstream emissions of toxic air pollutants tends to offset the 

increase in VMT and emissions due to the rebound effect. However, as noted above, the reductions in 

upstream emissions are not uniformly distributed to individual nonattainment areas. For example, a 

nonattainment area that contains petroleum-refining facilities, such as Houston-Galveston-Brazoria, 

Texas, would experience more reductions in upstream emissions than an area that has none. There can be 

net emissions reductions if the reduction in upstream emissions in the nonattainment area more than 

offsets the increase within the area due to the rebound effect. 

Under Alternative 2, many nonattainment areas would experience net increases in emissions of 

one or more toxic air pollutants in at least one of the analysis years (see Appendix C). However, the sizes 

of the emissions increases would be quite small, as shown in Appendix C, and emissions increases would 

be distributed throughout each nonattainment area. 

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3.3 Air Quality Chapter 3 Affected Environment and Environmental Consequences 

3.3.3.3.3 Health Outcomes and Monetized Benefits 

There would be reductions in adverse health effects nationwide under Alternative 2 compared to 

the No Action Alternative (see Table 3.3.3-8). These reductions primarily reflect the projected PM2.5

reductions, and secondarily the reductions in SOx (while the magnitude of PM2.5 reductions under this 

alternative is smaller than that of SOx, the pollutant is the largest contributor to adverse health effects on a 

per-ton basis). Compared to the No Action Alternative, Alternative 2 would reduce cases of premature 

mortality by 149 (under Pope et al.; reductions would be 155 percent greater under Laden et al.) in year 

2030. In the same year, the number of work-loss days would be reduced by 17,499. 

Table 3.3.3-8 

Nationwide Changes in Health Outcomes from Criteria Pollutant Emissions (cases/year) 

from Passenger Cars and Light Trucks by Alternative a/ 

Alt. 1 Alt. 2 Alt. 3 Alt. 4 Alt. 5 Alt. 6 Alt. 7 Alt. 8 Alt. 9 

Out. 

and 

Year 

No 

Action b/ 

3%/year 

Increase 

4%/year 

Increase 

~4.3%/year

Increase 

Preferred 

5%/year 

Increase 

~6.0%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.6%/year 

Increase 

TCTB 

Mortality (ages 30 and older), Pope et al.

2016 0 a/ -23 b/ -36 -42 -31 -32 -29 -29 -34

2020 0 -61 -93 -103 -88 -90 -85 -83 -91

2030 0 -149 -223 -243 -235 -257 -247 -251 -257

Mortality (ages 30 and older), Laden et al.

2016 0 -60 -93 -107 -80 -83 -75 -73 -87

2020 0 -157 -239 -265 -225 -231 -219 -212 -232

2030 0 -380 -571 -623 -600 -658 -632 -643 -657

Chronic bronchitis 

2016 0 -16 -25 -29 -21 -22 -20 -19 -23

2020 0 -42 -64 -71 -60 -62 -58 -56 -62

2030 0 -97 -146 -160 -155 -170 -163 -166 -169

Emergency Room Visits for Asthma 

2016 0 -22 -34 -40 -30 -31 -29 -28 -33

2020 0 -59 -89 -99 -84 -86 -82 -80 -88

2030 0 -137 -204 -222 -211 -228 -221 -224 -230

Work Loss Days 

2016 0 -3,047 -4,750 -5,510 -4,110 -4,201 -3,821 -3,708 -4,430

2020 0 -7,900 -11,994 -13,323 -11,313 -11,627 -10,945 -10,602 -11,634

2030 0 -17,499 -26,298 -28,705 -27,756 -30,507 -29,237 -29,792 -30,423

__________ 

a/ Negative changes indicate reductions; positive emissions changes are increases. 

b/ Changes in health outcome for the No Action Alternative are shown as zero because the No Action 

Alternative is the baseline to which emissions under the action alternatives are compared. 

Table 3.3.3-9 lists the corresponding monetized health benefits under Alternative 2 compared to 

the No Action Alternative. Health-related benefits under Alternative 2 would be $1.32 billion in 2030, 

using a 3-percent discount rate and estimates from Pope et al. Using Laden et al., health-related benefits 

would be 145 percent greater. Using a 7-percent discount rate, health-related benefits would be 9.3 to 9.7 

percent less. 

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Chapter 3 Affected Environment and Environmental Consequences 3.3 Air Quality 

Table 3.3.3-9 

Nationwide Monetized Health Benefits (U.S. million dollars/year) from Criteria Pollutant Emissions 

from Passenger Cars and Light Trucks by Alternative a/ 

Alt. 1 Alt. 2 Alt. 3 Alt. 4 Alt. 5 Alt. 6 Alt. 7 Alt. 8 Alt. 9 

Rate 

and 

Year 

No 

Action b/ 

3%/year 

Increase 

4%/year 

Increase 

~4.3%/year

Increase 

Preferred 

5%/year 

Increase 

~6.0%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.6%/year 

Increase 

TCTB 

3-Percent Discount Rate

Pope et al. 

2016 0 a/ -196 b/ -304 -353 -264 -272 -248 -241 -287

2020 0 -534 -809 -898 -763 -785 -741 -719 -788

2030 0 -1,322 -1,983 -2,164 -2,087 -2,287 -2,197 -2,235 -2,284

Laden et al. 

2016 0 -480 -746 -865 -648 -666 -607 -591 -704

2020 0 -1,308 -1,982 -2,200 -1,870 -1,922 -1,816 -1,761 -1,930

2030 0 -3,239 -4,860 -5,302 -5,112 -5,603 -5,382 -5,477 -5,596

7-Percent Discount Rate

Pope et al. 

2016 0 -178 -276 -320 -240 -247 -225 -219 -260

2020 0 -484 -734 -815 -693 -712 -672 -652 -715

2030 0 -1,199 -1,799 -1,963 -1,893 -2,075 -1,993 -2,028 -2,072

Laden et al. 

2016 0 -433 -674 -781 -585 -602 -549 -534 -636

2020 0 -1,182 -1,790 -1,987 -1,689 -1,737 -1,640 -1,591 -1,743

2030 0 -2,926 -4,390 -4,789 -4,618 -5,061 -4,861 -4,947 -5,055

__________ 

a/ Negative changes indicate monetized health benefits; positive emissions changes indicate monetized health 

disbenefits. 

b/ Changes in outcome for the No Action Alternative are shown as zero because the No Action Alternative is the 

 baseline to which impacts under the action alternatives are compared. 

3.3.3.4 Alternative 3: 4-Percent Annual Increase 

3.3.3.4.1 Criteria Pollutants 

Under the 4-Percent Alternative (Alternative 3), generally the CAFE standards would increase 

fuel economy more than would Alternative 2 but less than would Alternatives 4 through 9. There would 

be reductions in nationwide emissions of NOx, PM2.5, SOx, and VOCs under Alternative 3 compared to 

the No Action Alternative. Depending on the year, NOx emissions would be reduced 0.2 to 1.6 percent, 

PM2.5 emissions would be reduced 1.0 to 4.2 percent, SOx emissions would be reduced 2.4 to 10.2 

percent, and VOC emissions would be reduced 0.8 to 5.5 percent. The NOx, SOx, and VOC emissions 

reductions are generally greater than would occur under Alternative 2 but less than would occur under 

Alternatives 4 through 9. The PM2.5 emissions reductions are greater than would occur under Alternative 

2 and Alternatives 5 through 9, but less than would occur under Alternative 4. There would be increases 

of CO emissions from 0.1 to 0.7 percent, depending on the year. Under Alternative 3, all nonattainment 

areas would experience reductions in emissions of SOx and VOCs. Most nonattainment areas would 

experience increases of CO, NOx, and PM2.5 emissions compared to the No Action Alternative. The 

increases in CO, NOx, and PM2.5 emissions are the result of increased tailpipe emissions due to the 

rebound effect. Although NOx and PM2.5 emissions would increase in many nonattainment areas, the 

increase in each area is quite small. The decreases in nationwide NOx and PM2.5 emissions are the result 

of the decreases in upstream emissions and do not occur in all nonattainment areas. There would be 

fewer nonattainment areas with decreases in NOx and PM2.5 emissions than with increases, but the 

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3.3 Air Quality Chapter 3 Affected Environment and Environmental Consequences 

decreases would be much larger than the increases. The net result is decreased NOx and PM2.5 emissions 

nationwide. Tables in Appendix C list the emissions reductions for each nonattainment area. 

3.3.3.4.2 Toxic Air Pollutants 

Alternative 3 would reduce emissions of toxic air pollutants compared to the No Action 

Alternative for benzene and DPM in all years. For formaldehyde, Alternative 3 would reduce emissions 

in 2016 and 2020, but increase emissions in 2030. Emissions of acetaldehyde, acrolein, and 1,3-butadiene 

would remain constant or increase in all years under Alternative 3 compared to the No Action Alternative. 

Alternative 3 would have higher emissions of benzene and DPM but lower emissions of acrolein and 

formaldehyde compared to Alternatives 4 through 9 in all years. Alternative 3 would have lower 

emissions of 1,3-butadiene compared to Alternatives 4 through 9 in 2016 and 2020, but higher than under 

Alternatives 4 through 9 in 2030. Results would be mixed for acetaldehyde, depending on the year and 

alternative. 

At the national level, emissions of toxic air pollutants could decrease because the reduction in 

upstream emissions more than offsets the increase in VMT and emissions due to the rebound effect. 

However, as with Alternative 2, the reductions in upstream emissions would not be uniformly distributed 

to individual nonattainment areas. Under Alternative 3, most nonattainment areas would experience net 

increases in emissions of one or more toxic air pollutants in at least one of the analysis years (see

Appendix C). However, the sizes of the emissions increases would be quite small, as shown in Appendix 

C, and emissions increases would be distributed throughout each nonattainment area. Table 3.3.3-10 

summarizes the air toxic results by nonattainment area. 

Table 3.3.3-10 

Changes in Toxic Air Pollutant Emissions from Passenger Cars and Light Trucks, 

Maximum Changes by Nonattainment Area and Alternative a/ 

Hazardous Air 

Pollutant 

Increase/ 

Decrease 

Change

(tons/year) Year Alt. No. Nonattainment Area 

Maximum Increase 4.25 2020 8 New York-N. New Jersey-Long Island, NY-NJ-CT Acetaldehyde Maximum Decrease -7.57 2030 8 Houston-Galveston-Brazoria, TX 

Maximum Increase 3.47 2030 8 New York-N. New Jersey-Long Island, NY-NJ-CT Acrolein 

Maximum Decrease -0.49 2030 8 Beaumont/Port Arthur, TX 

Maximum Increase 4.97 2030 3 Los Angeles South Coast Air Basin, CA Benzene 

Maximum Decrease -63.2 2030 8 New York-N. New Jersey-Long Island, NY-NJ-CT 

Maximum Increase 1.30 2030 3 New York-N. New Jersey-Long Island, NY-NJ-CT 1,3-Butadiene Maximum Decrease -1.51 2030 8 Los Angeles South Coast Air Basin, CA 

Diesel Maximum Increase 76 2030 8 Atlanta, GA 

particulate 

matter Maximum Decrease -2,104 2030 8 Houston-Galveston-Brazoria, TX 

Maximum Increase 47 2030 8 New York-N. New Jersey-Long Island, NY-NJ-CT Formaldehyde Maximum Decrease -38 2030 9 Houston-Galveston-Brazoria, TX 

__________ 

a/ Emissions changes have been rounded to the nearest whole number except to present values greater 

 than zero but less than one. 

3.3.3.4.3 Health Outcomes and Monetized Benefits 

There would be reductions in adverse health effects nationwide under Alternative 3 compared to 

the No Action Alternative, as shown in Table 3.3.3-8. These reductions primarily reflect the projected 

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Chapter 3 Affected Environment and Environmental Consequences 3.3 Air Quality 

PM2.5 reductions, and secondarily the reductions in SOx (while the magnitude of PM2.5 reductions under 

this alternative is smaller than that of SOx, the pollutant is the largest contributor to adverse health effects 

on a per-ton basis). Compared to the No Action Alternative, Alternative 3 would reduce cases of 

mortality by 223 (under Pope et al.; reductions would be 156 percent greater under Laden et al.) and the 

number of work-loss days by 26,289 in 2030. 

Table 3.3.3-9 lists the corresponding monetized health benefits under Alternative 3 compared to 

the No Action Alternative. Monetized health benefits under Alternative 3 would be $1.98 billion in 2030, 

using a 3-percent discount rate and estimates from Pope et al. Using Laden et al., economic benefits 

would be 145 percent greater. Using a 7-percent discount rate, monetized health benefits would be 9.3 to 

9.7 percent less. 

3.3.3.5 Alternative 4: Preferred Alternative 

3.3.3.5.1 Criteria Pollutants 

Under the Preferred Alternative (Alternative 4), the CAFE standards would increase fuel 

economy more than would Alternatives 1 through 3 but less than would Alternatives 5 through 9. There 

would be reductions in nationwide emissions of NOx, PM2.5, SOx, and VOCs under Alternative 4 

compared to the No Action Alternative. Depending on the year, NOx emissions would be reduced 0.3 

to1.9 percent, PM2.5 emissions would be reduced 1.1 to 4.5 percent, SOx emissions would be reduced 2.7 

to 11.0 percent, and VOC emissions would be reduced 1.0 to 6.1 percent. These emissions reductions are 

greater than would occur under Alternative 3 but less than would occur under Alternatives 5 through 9 

(except for PM2.5, and SOx under Alternative 5). There would be increases of CO emissions of 0.02 to 0.5 

percent, depending on the year. 

Under Alternative 4, all nonattainment areas would experience reductions in emissions of SOx

and VOCs. Most nonattainment areas would experience increases of CO, NOx, and PM2.5 emissions 

compared to the No Action Alternative. The increases in CO, NOx, and PM2.5 emissions are the result of 

increased tailpipe emissions due to the rebound effect. Although NOx and PM2.5 emissions would 

increase in some nonattainment areas, the increase in each area is quite small. The decreases in 

nationwide NOx and PM2.5 emissions are the result of the decreases in upstream emissions and do not 

occur in all nonattainment areas. Although NOx and PM2.5 emissions would decrease in fewer 

nonattainment areas, the decreases in each area are much larger. The net result is decreased NOx and 

PM2.5 emissions nationwide. Tables in Appendix C list the emissions reductions for each nonattainment 

area. 

3.3.3.5.2 Toxic Air Pollutants 

Alternative 4 would result in reduced emissions of benzene and DPM, and increased emissions of 

acetaldehyde, acrolein, 1,3-butadiene, and formaldehyde, compared to the No Action Alternative. 

Compared to Alternatives 5 through 9, Alternative 4 would have lower emissions of acrolein and 

formaldehyde, and higher emissions of benzene and DPM. Emissions of acetaldehyde would be lower in 

2016 and 2020, but higher in 2030 than under Alternatives 5 through 9. Emissions of 1,3-butadiene under 

Alternative 4 would be lower than under Alternatives 5 through 9 in 2016 and 2020, but higher than under 

Alternatives 5 through 9 in 2030. 

At the national level, emissions of toxic air pollutants might decrease because the reduction in 

upstream emissions more than offsets the increase in VMT and emissions due to the rebound effect. 

However, as with prior alternatives, the reductions in upstream emissions would not be uniformly 

distributed to individual nonattainment areas. Under Alternative 4, most nonattainment areas would 

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3.3 Air Quality Chapter 3 Affected Environment and Environmental Consequences 

experience net increases in emissions of one or more toxic air pollutants in at least one of the analysis 

years (see Appendix C). However, the sizes of the emissions increases would be quite small, as shown in 

Appendix C. Potential air quality impacts from these increases would be minor, because the VMT and 

emissions increases would be distributed throughout each nonattainment area. 

3.3.3.5.3 Health Outcomes and Monetized Benefits 

There would be reductions in adverse health effects nationwide under Alternative 4 compared to 

the No Action Alternative, as shown in Table 3.3.3-8. These reductions primarily reflect the projected 

PM2.5 reductions, and secondarily the reductions in SOx (while the magnitude of PM2.5 reductions under 

this alternative is smaller than that of SOx, the pollutant is the largest contributor to adverse health effects 

on a per-ton basis). Compared to the No Action Alternative, Alternative 4 would reduce cases of 

premature mortality by 243 (under Pope et al.; reductions would be 156 percent greater under Laden et 

al.) in year 2030. In the same year, the number of work-loss days would be reduced by 28,705. 

Table 3.3.3-9 lists the corresponding monetized health benefits under Alternative 4 compared to 

the No Action Alternative. Monetized health benefits under Alternative 4 would be $2.16 billion in 2030, 

using a 3-percent discount rate and estimates from Pope et al. Using Laden et al., economic benefits 

would be 145 percent greater. Using a 7-percent discount rate, monetized health benefits would be 9.3 to 

9.7 percent less. 

3.3.3.6 Alternative 5: 5-Percent Annual Increase 

3.3.3.6.1 Criteria Pollutants 

Under the 5-Percent Alternative (Alternative 5), the CAFE standards would increase fuel 

economy more than would Alternatives 1 through 4 but less than would Alternatives 6 through 9. There 

would be reductions in nationwide emissions of all criteria pollutants under Alternative 5 compared to the 

No Action Alternative. Reductions would be greater than under Alternative 4 (except for PM2.5 and SOx), 

but less than under Alternatives 6 through 9 (except for PM2.5). Depending on the year, CO emissions 

would be reduced0.5 to 3.3 percent, NOx emissions would be reduced 0.4 to 3.8 percent, PM2.5 emissions 

would be reduced 0.5 to 3.4 percent, SOx emissions would be reduced 2.4 to 10.7 percent, and VOC 

emissions would be reduced 1.4 to 9.2 percent. All individual nonattainment areas would experience 

reductions in emissions of CO, NOx, SOx, and VOCs. PM2.5 emissions would increase in some 

nonattainment areas and would decrease in others compared to the No Action Alternative. Tables in 

Appendix C list the emissions reductions for each nonattainment area. 

3.3.3.6.2 Toxic Air Pollutants 

Alternative 5 would result in reduced emissions of benzene and DPM, and increased emissions of 

acetaldehyde, acrolein, and formaldehyde, compared to the No Action Alternative. Emissions of 1,3-

butadiene would be increased in 2016 and 2020, but be reduced in 2030 compared to the No Action 

Alternative. Compared to Alternatives 6 through 9, Alternative 5 would have lower emissions of acrolein 

and formaldehyde, and higher emissions of benzene and DPM. For acetaldehyde and 1,3-butadiene, 

Alternative 5 would have lower emissions in 2016 and 2020, and higher emissions in 2030. At the 

national level, emissions of toxic air pollutants could decrease because the reduction in upstream 

emissions more than offsets the increase in VMT and emissions due to the rebound effect. However, as 

with prior alternatives, the reductions in upstream emissions would not be uniformly distributed to 

individual nonattainment areas. Under Alternative 5, most nonattainment areas would experience net 

increases in emissions of one or more toxic air pollutants in at least one of the analysis years (see

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Chapter 3 Affected Environment and Environmental Consequences 3.3 Air Quality 

Appendix C). However, the sizes of the emissions increases would be quite small, as shown in Appendix 

C, and emissions increases would be distributed throughout each nonattainment area. 

3.3.3.6.3 Health Outcomes and Monetized Benefits 

There would be reductions in adverse health effects nationwide under Alternative 5 compared to 

the No Action Alternative, as shown in Table 3.3.3-8. These reductions primarily reflect the projected 

PM2.5 reductions, and secondarily the reductions in SOx (while the magnitude of PM2.5 reductions under 

this alternative is smaller than that of SOx, the pollutant is the largest contributor to adverse health effects 

on a per-ton basis). Compared to the No Action Alternative, Alternative 5 would reduce cases of 

premature mortality by 235 (under Pope et al.; reductions would be 155 percent greater under Laden et 

al.) in year 2030. In the same year, the number of work-loss days would be reduced by 27,756. 

Table 3.3.3-9 lists the corresponding monetized health benefits under Alternative 5 compared to 

the No Action Alternative. Monetized health benefits under Alternative 5 would be $2.09 billion in 2030, 

using a 3-percent discount rate and estimates from Pope et al. Using Laden et al., economic benefits 

would be 145 percent greater. Using a 7-percent discount rate, monetized health benefits would be 9.3 to 

9.7 percent less. 

3.3.3.7 Alternative 6: MNB 

3.3.3.7.1 Criteria Pollutants 

Under the MNB (Alternative 6), the CAFE standards would increase fuel economy more than 

would Alternatives 1 through 5 but less than would Alternatives 7 through 9. There would be reductions 

in nationwide emissions of all criteria pollutants under Alternative 6 compared to the No Action 

Alternative. Reductions in CO, NOx, and VOC emissions would be greater than under Alternatives 5 and 

7, but less than under Alternatives 8 through 9. For PM2.5 and SOx, the emissions would be similar for 

Alternatives 5 through 9; the reductions under Alternative 6 are slightly greater or less than the reductions 

under Alternatives 5 and 7 through 9, depending on the year and alternative. Depending on the year, CO 

emissions would be reduced 1.0 to 6.4 percent, NOx emissions would be reduced 0.6 to 5.6 percent, PM2.5

emissions would be reduced 0.3 to 3.0 percent, SOx emissions would be reduced 2.9 to 11.5 percent, and 

VOC emissions would be reduced 2.0 to 12.3 percent. All individual nonattainment areas would 

experience reductions in emissions of CO, NOx, SOx, and VOCs. PM2.5 emissions would increase in 

some nonattainment areas and would decrease in others compared to the No Action Alternative. Tables 

in Appendix C list the emissions reductions for each nonattainment area. 

3.3.3.7.2 Toxic Air Pollutants 

Alternative 6 would result in reduced emissions of benzene and DPM, and increased emissions of 

acrolein and formaldehyde, compared to the No Action Alternative. For acetaldehyde and 1,3-butadiene, 

Alternative 6 would result in higher emissions in 2016 and 2020, and lower emissions in 2030, compared 

to the No Action Alternative. Compared to Alternative 7, Alternative 6 would have higher emissions of 

acetaldehyde, acrolein, and formaldehyde, and lower emissions of benzene and DPM. Compared to 

Alternatives 8 and 9, Alternative 6 would have the same or lower emissions of acrolein and 

formaldehyde, and higher emissions of benzene and DPM. Results are mixed for acetaldehyde and 1,3-

butadiene depending on year and alternative. At the national level, emissions of toxic air pollutants could 

decrease for many combinations of pollutant, year, and alternative because the reduction in upstream 

emissions more than offsets the increase in VMT and emissions due to the rebound effect. However, as 

with prior alternatives, the reductions in upstream emissions would not be uniformly distributed to 

individual nonattainment areas. Under Alternative 6, most nonattainment areas would experience net 

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3.3 Air Quality Chapter 3 Affected Environment and Environmental Consequences 

increases in emissions of one or more toxic air pollutants in at least one of the analysis years (see

Appendix C). However, the sizes of the emissions increases would be quite small, as shown in Appendix 

C, and emissions increases would be distributed throughout each nonattainment area. 

3.3.3.7.3 Health Outcomes and Monetized Benefits 

There would be reductions in adverse health effects nationwide under Alternative 6 compared to 

the No Action Alternative, as shown in Table 3.3.3-8. The reductions in mortality, chronic bronchitis, 

and work loss days primarily reflect the projected PM2.5 reductions, and secondarily the reductions in 

SOx. The reductions in emergency room visits for asthma primarily reflect the projected SOx reductions, 

and secondarily the reductions in PM2.5. Compared to the No Action Alternative, Alternative 6 would 

reduce cases of premature mortality by 257 (under Pope et al.; reductions would be 156 percent greater 

under Laden et al.) in year 2030. In the same year, the number of work-loss days would be reduced by 

30,507. 

Table 3.3.3-9 lists the corresponding monetized health benefits under Alternative 6 compared to 

the No Action Alternative. Monetized health benefits under Alternative 6 would be $2.29 billion in 2030, 

using a 3-percent discount rate and estimates from Pope et al. Using Laden et al., economic benefits 

would be 145 percent greater. Using a 7-percent discount rate, monetized health benefits would be 9.3 to 

9.7 percent less. 

3.3.3.8 Alternative 7: 6-Percent Annual Increase 

3.3.3.8.1 Criteria Pollutants 

Under the 6-Percent Alternative (Alternative 7), the CAFE standards would increase fuel 

economy more than would Alternatives 1 through 6 but less than would Alternatives 8 and 9. There 

would be reductions in nationwide emissions of all criteria pollutants under Alternative 7 compared to the 

No Action Alternative. Reductions in emissions of all criteria pollutants under Alternative 7 would be 

less than under Alternative 6 (except for SOx in 2030).emissions of all criteria pollutants under 

Alternative 7 would be less than under Alternatives 8 and 9 (except for PM2,5). Depending on the year, 

CO emissions would be reduced 0.7 to 5.6 percent, NOx emissions would be reduced 0.5 to 5.2 percent, 

PM2.5 emissions would be reduced 0.3 to 2.8 percent, SOx emissions would be reduced 2.7 to 11.7 

percent, and VOC emissions would be reduced 1.8 to 12.0 percent. All individual nonattainment areas 

would experience reductions in emissions of CO, NOx, SOx, and VOCs under Alternative 7. PM2.5

emissions would increase in some nonattainment areas and would decrease in others compared to the No 

Action Alternative. Tables in Appendix C list the emissions reductions for each nonattainment area. 

3.3.3.8.2 Toxic Air Pollutants 

Alternative 7 would result in reduced emissions of benzene and DPM, and increased emissions of 

acrolein and formaldehyde, compared to the No Action Alternative. For acetaldehyde and 1,3-butadiene, 

Alternative 7 would result in higher emissions in 2016 and 2020, and lower emissions in 2030, compared 

to the No Action Alternative. Compared to Alternatives 8 and 9, Alternative 7 would have lower 

emissions of acrolein and formaldehyde, and higher emissions of benzene and DPM. For acetaldehyde 

and 1,3-butadiene, Alternative 7 would result in lower emissions in 2016 and 2020, and higher emissions 

in 2030, compared to Alternatives 8 and 9. 

At the national level, emissions of toxic air pollutants could decrease because the reduction in 

upstream emissions more than offsets the increase in VMT and emissions due to the rebound effect. 

However, as with previous alternatives, the reductions in upstream emissions would not be uniformly 

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Chapter 3 Affected Environment and Environmental Consequences 3.3 Air Quality 

distributed to individual nonattainment areas. Under Alternative 7, most nonattainment areas would 

experience net increases in emissions of one or more toxic air pollutants in at least one of the analysis 

years (see Appendix C). However, the sizes of the emissions increases would be quite small, as shown in 

Appendix C, and emissions increases would be distributed throughout each nonattainment area. 

3.3.3.8.3 Health Outcomes and Monetized Benefits 

There would be reductions in adverse health effects nationwide under Alternative 7 compared to 

the No Action Alternative, as shown in Table 3.3.3-8. The reductions in mortality, chronic bronchitis, 

and work loss days primarily reflect the projected PM2.5 reductions, and secondarily the reductions in 

SOx. The reductions in emergency room visits for asthma primarily reflect the projected SOx reductions, 

and secondarily the reductions in PM2.5. Compared to the No Action Alternative, Alternative 7 would 

reduce cases of premature mortality by 247 (under Pope et al.; reductions would be 156 percent greater 

under Laden et al.) in 2030. In the same year, the number of work-loss days would be reduced by 29,237. 

Table 3.3.3-9 lists the corresponding monetized health benefits under Alternative 7 compared to 

the No Action Alternative. Monetized health benefits under Alternative 7 would be $2.20 billion in 2030, 

using a 3-percent discount rate and estimates from Pope et al. Using Laden et al., economic benefits 

would be 145 percent greater. Using a 7-percent discount rate, monetized health benefits would be 9.3 to 

9.7 percent less. 

3.3.3.9 Alternative 8: 7-Percent Annual Increase 

3.3.3.9.1 Criteria Pollutants 

Under the 7-Percent Alternative (Alternative 8), the CAFE standards would increase fuel 

economy more than all the other alternatives. There would be reductions in nationwide emissions of all 

criteria pollutants under Alternative 8 compared to the No Action Alternative. Compared to Alternative 

7, reductions in emissions under Alternative 8 would be greater for CO, NOx, SOx, and VOC, but less for 

PM2.5. Reductions in emissions under Alternative 8 would be greater than under Alternative 9 for CO, 

NOx in 2020 and 2030, and VOC in 2020 and 2030, but would be less than under Alternative 9 for NOx in 

2016, PM2.5 and SOx in all years, and VOC in 2016. CO emissions would be reduced 1.0 to 8.0 percent, 

NOx emissions would be reduced 0.6 to 6.5 percent, PM2.5 emissions would be reduced 0.1 to 2.3 percent, 

SOx emissions would be reduced 2.9 to 12.0 percent, and VOC emissions would be reduced 2.1 to 14.2 

percent compared to the No Action Alternative, depending on the year. All individual nonattainment 

areas would experience reductions in emissions of CO, NOx, SOx, and VOCs. PM2.5 emissions would 

increase in some nonattainment areas and would decrease in others compared to the No Action 

Alternative. Tables in Appendix C list the emissions reductions for each nonattainment area. 

3.3.3.9.2 Toxic Air Pollutants 

Alternative 8 would result in reduced emissions of benzene and DPM, and increased emissions of 

acrolein and formaldehyde, compared to the No Action Alternative. For acetaldehyde and 1,3-butadiene, 

Alternative 8 would result in higher emissions in 2016 and 2020, and lower emissions in 2030, compared 

to the No Action Alternative. Compared to Alternative 9, Alternative 8 would have higher emissions of 

acetaldehyde (in 2020), acrolein, 1,3-butadiene (in 2016 and 2020), DPM (in 2016), and formaldehyde. 

Emissions reductions of acetaldehyde (in 2030), benzene, 1,3-butadiene (in 2030), and DPM under 

Alternative 8 would be greater than with any other alternative. Similarly, emissions increases of 

acetaldehyde (in 2016 and 2020), acrolein, 1,3-butadiene (in 2016 and 2020), and formaldehyde under 

Alternative 8 would be the same or greater than with any other alternative. 

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3.3 Air Quality Chapter 3 Affected Environment and Environmental Consequences 

At the national level, emissions of toxic air pollutants could decrease because the reduction in 

upstream emissions more than offsets the increase in VMT and emissions due to the rebound effect. 

However, as with prior alternatives, the reductions in upstream emissions would not be uniformly 

distributed to individual nonattainment areas. Under Alternative 8, most nonattainment areas would 

experience net increases in emissions of one or more toxic air pollutants in at least one of the analysis 

years (see Appendix C). However, the sizes of the emissions increases would be quite small, as shown in 

Appendix C, and emissions increases would be distributed throughout each nonattainment area. 

3.3.3.9.3 Health Outcomes and Monetized Benefits 

There would be reductions in adverse health effects nationwide under Alternative 8 compared to 

the No Action Alternative, as shown in Table 3.3.3-8. The reductions in mortality, chronic bronchitis, 

and work loss days primarily reflect the projected PM2.5 reductions, and secondarily the reductions in 

SOx. The reductions in emergency room visits for asthma primarily reflect the projected SOx reductions, 

and secondarily the reductions in PM2.5. In comparison to the No Action Alternative, Alternative 8 would 

reduce cases of premature mortality by 251 (under Pope et al.; reductions would be 156 percent greater 

under Laden et al.) in year 2030. In the same year, the number of work-loss days would be reduced by 

29,792. 

Table 3.3.3-9 lists the corresponding monetized health benefits under Alternative 8 compared to 

the No Action Alternative. Monetized health benefits under Alternative 8 would be $2.24 billion in 2030, 

using a 3-percent discount rate and estimates from Pope et al. Using Laden et al., economic benefits 

would be 145 percent greater. Using a 7-percent discount rate, monetized health benefits would be 9.3 to 

9.7 percent less. 

3.3.3.10 Alternative 9: TCTB 

3.3.3.10.1 Criteria Pollutants 

Under the TCTB Alternative (Alternative 9), the CAFE standards would increase fuel economy 

more than would Alternatives 1 through 7 but less than would Alternative 8. There would be reductions 

in nationwide emissions of all criteria pollutants under Alternative 9 compared to the No Action 

Alternative. Emissions reductions under Alternative 9 would be greater than with any other alternative 

for NOx in 2016, SOx in all years, and VOC in 2016. Emission reductions under Alternative 9 would be 

greater than the reductions under Alternatives 2 through 7, but less than the reductions under Alternative 

8, for CO in all years, NOx in 2020 and 2030, and VOC in 2020 and 2030. Emission reductions under 

Alternative 9 would be less than the reductions under Alternatives 2 through 6, but greater than the 

reductions under Alternatives 7 and 8, for PM2.5 in 2016; in 2020 and 2030 the PM2.5 reductions under 

Alternative 9 would be less than the reductions under Alternatives 2 through 7, but greater than the 

reductions under Alternative 8. Depending on the year, CO emissions would be reduced 1.0 to 7.2 

percent, NOx emissions would be reduced 0.6 to 6.1 percent, PM2.5 emissions would be reduced 0.3 to 2.6 

percent, SOx emissions would be reduced 3.2 to 12.2 percent, and VOC emissions would be reduced 2.1 

to 13.5 percent compared to the No Action Alternative. All individual nonattainment areas would 

experience reductions in emissions of CO, NOx, SOx, and VOCs. PM2.5 emissions would increase in 

some nonattainment areas and would decrease in others compared to the No Action Alternative. Tables 

in Appendix C list the emissions reductions for each nonattainment area. 

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Chapter 3 Affected Environment and Environmental Consequences 3.3 Air Quality 

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3.3.3.10.2 Toxic Air Pollutants 

Alternative 9 would result in reduced emissions of acetaldehyde (in 2030), benzene, 1,3-

butadiene (in 2030), and DPM, and increased emissions of acetaldehyde (in 2016 and 2020), acrolein, 

1,3-butadiene (in 2016 and 2020), and formaldehyde, compared to the No Action Alternative. 

At the nationwide level, emissions of toxic air pollutants could decrease because the reduction in 

upstream emissions more than offsets the increase in VMT and emissions due to the rebound effect. 

However, as with prior alternatives, the reductions in upstream emissions would not be uniformly 

distributed to individual nonattainment areas. Under Alternative 9, most nonattainment areas would 

experience net increases in emissions of one or more toxic air pollutants in at least one of the analysis 

years (see Appendix C). However, the sizes of the emissions increases would be quite small, as shown in 

Appendix C, and emissions increases would be distributed throughout each nonattainment area. 

3.3.3.10.3 Health Outcomes and Monetized Benefits 

There would be reductions in adverse health effects nationwide under Alternative 9 compared to 

the No Action Alternative, as shown in Table 3.3.3-8. The reductions in mortality, chronic bronchitis, 

and work loss days primarily reflect the projected PM2.5 reductions, and secondarily the reductions in 

SOx. The reductions in emergency room visits for asthma primarily reflect the projected SOx reductions, 

and secondarily the reductions in PM2.5. Compared to the No Action Alternative, Alternative 9 would 

reduce cases of premature mortality by 257 (under Pope et al.; reductions would be 156 percent greater 

under Laden et al.) in 2030. In the same year, the number of work-loss days would be reduced by 30.423 

days. 

Table 3.3.3-9 lists the corresponding monetized health benefits under Alternative 9 compared to 

the No Action Alternative. Monetized health benefits under Alternative 9 would be $2.29 billion in 2030, 

using a 3-percent discount rate and estimates from Pope et al. Using Laden et al., economic benefits 

would be 145 percent greater. Using a 7-percent discount rate, monetized health benefits would be 9.3 to 

9.7 percent less. 
3.4 Climate Chapter 3 Affected Environment and Environmental Consequences 

3.4 CLIMATE 

This section describes how the MYs 2012-2016 CAFE standards would affect the anticipated 

pace and extent of future changes in the global climate. Because there is little precedent for addressing 

climate change within the structure of an EIS, several reasonable judgments were required to distinguish 

the direct and indirect effects of alternative CAFE standards (Chapter 3) from the cumulative impacts 

associated with those same alternatives (Chapter 4). 

NHTSA determined that the scope of climate change issues covered in Chapter 3 would be 

narrower than the scope of those addressed in Chapter 4 in two respects: (1) the discussion in Chapter 3 

focuses on impacts associated with reductions in GHG emissions due exclusively to the MYs 2012-2016 

CAFE standards (which are then assumed to remain in place at the MY 2016 levels from 2016 through 

2060) and (2) the Chapter 3 discussion of consequences focuses on GHG emissions and their effects on 

the climate system, for example, atmospheric CO2 concentrations, temperature, sea level, and 

precipitation. The analysis presented in Chapter 4 is more comprehensive in that (1) it addresses the 

effects of the MYs 2012-2016 standards together with those of reasonably foreseeable future actions, 

including the continuing increases in CAFE standards for MYs 2017-2020 that are necessary under some 

alternatives to reach the EISA-mandated target of a combined 35 mpg; and (2) continuing market-driven 

increases in fuel economy based on AEO projections through 2030 as a reasonably foreseeable future 

action (since the AEO forecasted fuel economy increases result from projections of rising future demand 

for fuel economy, as opposed to future increases in CAFE standards). These reasonably foreseeable 

future actions would affect fuel consumption and emissions attributable to passenger cars and light trucks 

through 2060. The climate modeling in Chapter 4 applies different assumptions about the effect of 

broader global GHG policies on emissions outside the U.S. transportation sector, and it extends the 

discussion of consequences to include not only the immediate effects of emissions on the climate system, 

but also the impacts of changes in the climate system on key resources (such as freshwater resources, 

terrestrial ecosystems, and coastal ecosystems). Thus, the reader is encouraged to explore the cumulative 

impacts discussion in Chapter 4 to fully understand NHTSA’s approach to climate change in this EIS. 

Section 3.4.1 introduces key topics on GHGs and climate change, while Section 3.4.2 outlines the 

methodology NHTSA used to evaluate climate effects. Section 3.4.3 describes the affected environment, 

and Section 3.4.4 describes the direct and indirect environmental consequences of the proposed action and 

alternative actions that were considered by NHTSA. 

3.4.1 Introduction – Greenhouse Gases and Climate Change 

This document primarily draws upon panel-reviewed synthesis and assessment reports from the 

IPCC and U.S. Global Change Research Program (USGCRP). It also cites EPA’s Technical Support 

Document for Endangerment and Cause or Contribute Findings for GHGs under the Clean Air Act (EPA 

2009b) – which heavily relied on these panel reports. NHTSA similarly relies on panel reports because 

they have assessed numerous individual studies to draw general conclusions about the state of science; 

have been reviewed and formally accepted by, commissioned by, or in some cases authored by, U.S. 

government agencies and individual government scientists and provide NHTSA with assurances that this 

material has been well vetted by both the climate change research community and by the U.S. 

government; and in many cases, they reflect and convey the consensus conclusions of expert authors. 

These reports therefore provide the overall scientific foundation for U.S. climate policy at this time. 

This document also refers to new peer-reviewed literature that has not been assessed or 

synthesized by an expert panel. This new literature supplements but does not supersede the findings of 

the panel-reviewed reports. 

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Chapter 3 Affected Environment and Environmental Consequences 3.4 Climate 

NHTSA’s consideration of newer studies and highlighting of particular issues responds to 

previous public comments received on the scoping document and the prior EIS for the MY 2011 CAFE 

standard, as well as the Ninth Circuit’s decision in CBD v. NHTSA, 538 F.3d 1172 (9th Cir. 2008). The 

level of detail regarding the science of climate change in this draft EIS, and NHTSA’s consideration of 

other studies that show illustrative research findings pertaining to the potential impacts of climate change 

on health, society, and the environment, are provided to help inform the public and the decisionmaker, 

consistent with the agency’s approach in the prior EIS for the MY 2011 CAFE standards. 

3.4.1.1 Uncertainty within the IPCC Framework 

The IPCC reports communicate uncertainty and confidence bounds using descriptive words in 

italics, such as likely and very likely, to represent likelihood of occurrence. The IPCC Fourth Assessment 

Synthesis Report and the IPCC Fourth Assessment Report Summary for Policymakers (IPCC 2007c, 

IPCC 2007b) briefly explain this convention. The IPCC Guidance Notes for Lead Authors of the IPCC 

Fourth Assessment Report on Addressing Uncertainties (IPCC 2005) provides a more detailed discussion 

of the IPCC treatment of uncertainty. 

This EIS uses the IPCC uncertainty language (always noted in italics) throughout Chapters 3 

and 4 when discussing qualitative environmental impacts on certain resources. The reader should refer to 

the referenced IPCC documents to gain a full understanding of the meaning of those uncertainty terms, 

because they might be used differently than similar language describing uncertainty in the EIS, as 

required by the CEQ regulations described in Section 3.1.3.1. Section 4.5.2.2 of this EIS summarizes the 

IPCC treatment of uncertainty. 

3.4.1.2 What is Climate Change? 

Global climate change refers to long-term (i.e., multi-decadal) trends in global average surface 

temperature, precipitation, ice cover, sea level, cloud cover, sea-surface temperatures and currents, and 

other climatic conditions. Scientific research has shown that over the 20th century, Earth’s global-average 

surface temperature rose by an average of about 0.74 °C (1.3 °F) (EPA 2009b, IPCC 2007b); global 

average sea level has been gradually rising, increasing about 0.17 meters (6.7 inches) during the 20th

Century (IPCC 2007b) with a maximum rate of about 2 millimeters (0.08 inch) per year over the last 50 

years on the northeastern coast of the United States (EPA 2009b); Arctic sea ice cover has been 

decreasing at a rate of about 4.1 percent per decade, with faster decreases of 7.4 percent per decade in 

summer; and the extent and volume of mountain glaciers and snow cover have also been decreasing (EPA 

2009b, IPCC 2007b) (see Figure 3.4.1-1). 

3.4.1.3 What Causes Climate Change? 

Earth absorbs heat energy from the sun and returns most of this heat to space as terrestrial 

infrared radiation. Accumulated GHGs trap heat in the troposphere (the layer of the atmosphere that 

extends from Earth’s surface up to about 8 miles above the surface), absorb heat energy emitted by 

Earth’s surface and lower atmosphere, and reradiate much of it back to Earth’s surface, thereby causing 

warming. This process, known as the “greenhouse effect,” is responsible for maintaining surface 

temperatures warm enough to sustain life (see Figure 3.4.1-2). Human activities, particularly fossil-fuel 

combustion, lead to the presence of increased concentrations of GHGs in the atmosphere; this buildup of 

GHGs in the atmosphere is upsetting Earth’s energy balance. 

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3.4 Climate Chapter 3 Affected Environment and Environmental Consequences 

Figure 3.4.1-1. Changes in Temperature, Sea Level, and Northern 

Hemisphere Snow Cover (Source: IPCC 2007b) 

Figure 3.4.1-2. The Greenhouse Effect (Source: Le Treut 

et al. 2007) 

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Chapter 3 Affected Environment and Environmental Consequences 3.4 Climate 

 3-63 

The observed changes in the global climate described in Section 3.4.1.2 are largely a result of 

GHG emissions from human activities. Both EPA and the IPCC have recently concluded that “[m]ost of 

the observed increase in global average temperatures since the mid-20th Century is very likely due to the 

observed increase in anthropogenic [human-caused] GHG concentrations” (EPA 2009b, IPCC 2007b).23 

Most GHGs, including CO2, methane (CH4), nitrous oxide (N2O), water vapor, and ozone, occur 

naturally. Human activities such as the combustion of fossil fuel for transportation and electric power, the 

production of agricultural and industrial commodities, and the loss of soil fertility and the harvesting of 

trees can contribute to very significant increases in the concentrations of these gases in the atmosphere. 

In addition, several very potent anthropogenic GHGs, including hydrofluorocarbons (HFCs), 

perfluorocarbons (PFCs), and sulfur hexafluoride (SF6), are created and emitted through industrial 

processes and emitted as a result, for example, of leaks in refrigeration and air-conditioning systems. 

3.4.1.4 What are the Anthropogenic Sources of Greenhouse Gases? 

Human activities that emit GHGs to the atmosphere include the combustion of fossil fuels, 

industrial processes, solvent use, land-use change and forestry, agricultural production, and waste 

management. Atmospheric concentrations of CO2, CH4, and N2O − the most important anthropogenic 

GHGs, comprising over 99 percent of anthropogenic emissions (WRI 2009)24 − have increased 

approximately 38, 149, and 23 percent, respectively, since the beginning of the Industrial Revolution in 

the mid-1700s. During this time, the atmospheric CO2 concentration has increased from 280 ppm to 386 

ppm in 2008 (EPA 2009b). Isotopic and inventory-based studies make clear that this rise in the CO2

concentration is largely a result of combustion of fossil fuels (coal, petroleum, and gas) used to produce 

electricity, heat buildings, and run motor vehicles and airplanes, among other uses. 

Contributions to the build up of GHGs in the atmosphere vary greatly from country to country, 

and depend heavily on the level of industrial and economic activity, the population, the standard of living, 

the character of a country’s buildings and transportation system, energy options that are available, and the 

climate. Emissions from the United States account for about 17.2 percent of total global CO2 emissions 

(WRI 2009). The U.S. transportation sector contributed 31.5 percent of total U.S. CO2 emissions in 2007, 

with passenger cars and light trucks accounting for 60.6 percent of total U.S. CO2 emissions from 

transportation (EPA 2009a). Thus, approximately 19.1 percent of total U.S. CO2 emissions are from 

passenger cars and light trucks, and passenger cars and light trucks in the United States account for 

roughly 3.3 percent of total global CO2 emissions.25 Figure 3.4.1-3 shows the proportion of U.S. 

emissions attributable to the transportation sector and the contribution of each mode to U.S. transportation 

emissions. 

 

23 As mentioned above, the IPCC uses standard terms to “define the likelihood of an outcome or result where this 

can be estimated probabilistically.” The term “very likely,” cited in italics above and elsewhere in this section, 

corresponds to a greater than 90-percent probability of an occurrence or outcome, whereas the term “likely” 

corresponds to a greater than 66-percent probability. This section uses these two terms; Section 4.5 uses and defines 

a more expansive set of IPCC terminology regarding likelihood. 

24 This calculation is weighted by global warming potential. 

25 Percentages include land-use change and forestry, and exclude international bunker fuels (i.e., international 

marine and aviation travel). 
3.4 Climate Chapter 3 Affected Environment and Environmental Consequences 

Figure 3.4.1-3. Contribution of Transportation to U.S. CO2 Emissions and Proportion 

Attributable by Mode, 2007 

3.4.1.5 Evidence of Climate Change 

Observations and studies across the globe are reporting evidence that Earth is undergoing climatic 

change much more quickly than would be expected from natural variations. The global average 

temperature is rising, with 8 of the 10 warmest years on record occurring since 2001 (EPA 2009b). Colddependent habitats are shifting to higher altitudes and latitudes and growing seasons are becoming longer 

(EPA 2009b). Sea level is rising, caused by thermal expansion of the ocean and melting of snow and ice. 

More frequent weather extremes such as droughts, floods, severe storms, and heat waves have also been 

observed (EPA 2009b, IPCC 2007b). Oceans are becoming more acidic as a result of increasing 

absorption of CO2, driven by higher atmospheric concentration of CO2, (EPA 2009b). Statistically 

significant indicators of climate change have been observed on every continent (Rosenzweig et al. 2008). 

Additional evidence of climate change is discussed throughout this section. 

3.4.1.6 Future Climatic Trends and Expected Impacts 

As the world population grows and developing countries industrialize and bring their populations 

out of poverty, fossil-fuel use and resulting GHG emissions are expected to grow substantially over the 

21st century unless there is a significant shift away from deriving energy from fossil fuels. Based on the 

current trajectory, the IPCC projects that the atmospheric CO2 concentration could rise to more than three 

times the pre-industrial level by 2100 (EPA 2009b, IPCC 2007b). 

If there is an unchecked rise in the atmospheric CO2 concentration out to 2100, the average global 

surface temperature is likely to rise by 2.0 to 11.5 °F by that time (EPA 2009b). In addition, EPA (2009b) 

projects that sea level is likely to rise 0.19 to 0.58 meters (0.6 to 1.9 feet) by 2100 due just to thermal 

expansion and the melting of glaciers and small ice caps; even greater rise is projected if ice streams 

draining the Greenland and Antarctic ice sheets accelerate. If this happens, and satellite observation 

suggest such changes are beginning, recent studies indicate that sea-level rise could be even higher, and 

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Chapter 3 Affected Environment and Environmental Consequences 3.4 Climate 

 3-65 

have estimated ranges of 0.8 to 2 meters (2.6 to 6.6 feet) (Pfeffer et al. 2008) and 0.5 to 1.4 meters (1.6 to 

4.6 feet) (Rahmstorf 2007) by 2100. In addition to increases in global-average temperature and sea level, 

climate change is expected to have many environmental, human health, and economic consequences. 

For a more in-depth analysis of the future impacts of climate change on various sectors, see 

Section 4.5 of this EIS. 

3.4.1.7 Black Carbon 

This EIS does not model the climatic impacts of black carbon.26 Therefore, the direct effects (the 

radiative properties) and indirect effects (the impacts on clouds and surface snow/ice) of black carbon are 

qualitatively discussed here. 

Black carbon is an aerosol that forms during incomplete combustion of certain fossil fuels 

(primarily coal and diesel) and biomass (primarily fuel wood and crop waste). Developing countries are 

the primary emitters of black carbon because they depend more heavily on biomass-based fuel sources for 

cooking and heating and on diesel vehicles for transport, and have less stringent air emission control 

standards and technologies. The United States contributes about 7 percent of the world’s black carbon 

emissions, with about 19 percent of those emissions coming from on-road vehicles (or just over 1 percent 

of the world total) (Battye et al. 2002, Bond et al. 2004).27 

While black carbon has been an air pollutant of concern for years due to its direct human health 

effects, climate change experts are now paying attention to it for its influence on climate change (EPA 

2009b). Black carbon has a warming effect on the climate by (1) absorbing solar radiation, (2) reducing 

the albedo28 of clouds while suspended in the air, and (3) reducing the albedo of snow and ice when it 

falls onto snow and ice fields (EPA 2009b; Ramanathan and Carmichael 2008). 

The scientific literature is far from conclusive as to what effect black carbon has on the climate. 

In the IPCC Fourth Assessment Report (IPCC 2007b), the scientific knowledge level of black carbon’s 

effect on the climate was classified as medium to low (CCSP 2008b). Another study estimates that there 

is a 50-percent uncertainty in global emissions estimates, while the uncertainty in regional emissions 

estimates can range from factors of two to five (Ramanathan and Carmichael 2008). Although emission 

estimates are uncertain, recent studies suggest that black carbon might be a major contributor to climate 

change. 

In a recent study, black carbon was estimated to have more than half of the positive radiative 

forcing effect of CO2, and a larger forcing than from other GHGs, including CH4 and N2O (Ramanathan 

 

26 Black carbon is often referred to as “soot” or “particulate matter,” when in fact it is only one component of soot, 

and one type of particulate matter. It is sometimes referred to as “elemental carbon,” although it is actually a 

slightly impure form of elemental carbon. As noted by Andreae and Gelencser (2006), “black carbon” is often used 

interchangeably with other terms that are similar, but whose definitions are slightly different. Furthermore, 

definitions across literature sources are not always consistent. 

27 Battye et al. (2002) calculated total U.S. (433 Gg) and U.S. motor vehicle (81 Gg) black carbon in fine particles 

(PM2.5) from EPA’s 2001 National Emission Inventory (NEI) database. Bond et al. (2004) estimated global black 

carbon emissions (in PM2.5) to be 6.5 Tg. (Note that the same year of data was not available – Bond used fuel data 

from 1996, while EPA calculated black carbon emissions for 2001. So these calculations assume black carbon 

emissions in the 2 years were equivalent.) 

28 Surfaces on Earth reflect solar radiation back to space. This reflective characteristic, known as albedo, indicates 

the proportion of incoming solar radiation that the surface reflects. High albedo has a cooling effect because the 

surface reflects rather than absorbs most solar radiation. Black carbon can reduce the albedo of water and ice in 

clouds and snow and ice on the ground. 
3.4 Climate Chapter 3 Affected Environment and Environmental Consequences 

and Carmichael 2008). Recent research indicates that black carbon has contributed approximately 0.5 to 

1.4 °C (0.9 to 2.52 °F) to Arctic warming since 1890 (Shindell and Faluvegi 2009). Other research 

suggests that black carbon might have a played a role in droughts in the northern part of China and floods 

in the southern part of China (Menon et al. 2002). 

Some aerosols suppress formation of larger cloud drops, which can extend the lifetime of the 

cloud and increase cloud cover (Ramanathan and Carmichael 2008). Black carbon, on the other hand, 

radiatively warms the surrounding air, which leads to evaporation of cloud drops and reduces cloud cover 

(Ramanathan and Carmichael 2008). An important issue, which can vary by region, is whether the nonblack carbon aerosols or the black carbon aerosols dominate in cloud effects (Ramanathan and 

Carmichael 2008). Meanwhile, it is also believed that black carbon-related warming might induce 

convection and ultimately lead to cloud formation (Rudich et al. 2003 in Ramanathan and Carmichael 

2008). 

Black carbon has a much shorter atmospheric lifespan than GHGs. CCSP (2009) estimates the 

lifetime of black carbon in the atmosphere as being between 5.3 and 15 days, generally depending on the 

meteorological situation. Because the atmospheric loading of black carbon depends on being continually 

replenished, reductions in black-carbon emissions can have an almost immediate effect on radiative 

forcing. Meanwhile, the lifespan of CO2 in the atmosphere is hundreds of years. Therefore, due to the 

long lifespan of CO2, mitigation of its emissions in the short-term will have long-lasting impacts. 

The impact that the new CAFE standards will have on black carbon emissions is uncertain. 

Historically, diesel vehicles have emitted more black carbon than gasoline vehicles on a per-mile basis. 

Thus, a shift to diesel vehicles could increase black carbon emissions, resulting in increased warming. 

Widespread deployment of recent, more effective control technologies for particulate-matter emissions 

from diesel vehicles could minimize any increase in warming due to this shift. NHTSA estimates that the 

fraction of MY 2016 passenger cars that are diesel-powered would rise from less than 1 percent under the 

No Action Alternative to about 1 percent under the Preferred Alternative and would reach 7 to 10 percent 

under those alternatives that would establish the most stringent CAFE standards. At the same time, the 

agency projects that the diesel fraction of light trucks sold during MY 2016 would rise from less than 1 

percent under the No Action Alternative to more than 12 percent under the Preferred Alternative and 

would range as high as 25 percent under alternatives that would establish the highest CAFE standards. 

Using estimates of U.S. on-road emissions of black carbon in fine particles (PM 2.5) (Battye et al.

2002) and global emissions of black carbon in PM 2.5 (Bond et al. 2004), U.S. motor vehicles contribute 

just over 1 percent of global black carbon emissions. As noted above, the effects of the alternative CAFE 

standards considered in this analysis on U.S. and global black carbon emissions have not been 

established. The precise amount by which CAFE standards will increase black carbon emissions depends 

on the increase in the presence of diesel vehicles in the future U.S. vehicle fleet that results from 

manufacturers’ efforts to comply with higher CAFE standards, particularly under those alternatives that 

would impose the most stringent standards. It also depends on future improvements in the effectiveness 

of emissions control technology for diesel vehicles, including both light duty diesel vehicles and the 

heavy-duty diesel trucks that are used extensively for fuel distribution to retail stations. 

3.4.2 Affected Environment 

This section describes the affected environment in terms of current and anticipated trends in GHG 

emissions and climate. Effects of emissions and the corresponding processes that affect climate involve 

very complex processes with considerable variability, which complicates the measurement and detection 

of change. Recent advances in the state of the science, however, are contributing to an increasing body of 

evidence that anthropogenic GHG emissions are affecting climate in detectable and quantifiable ways. 

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Chapter 3 Affected Environment and Environmental Consequences 3.4 Climate 

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This section begins with a discussion of emissions, and then turns to climate. Both discussions 

start with a description of conditions in the United States, followed by a description of global conditions. 

Many themes in the U.S. discussions reappear in the global discussions.29 

3.4.2.1 Greenhouse Gas Emissions (Historic and Current) 

3.4.2.1.1 U.S. Emissions 

GHG emissions for the United States in 200730 were estimated at 7,150.1 million metric tons of 

carbon dioxide (MMTCO2)

31 (EPA 2009a), and, as noted earlier, contributes about 18 percent of total 

global emissions32 (WRI 2009). Annual U.S. emissions, which have increased 17 percent since 1990 and 

typically increase each year, are heavily influenced by “general economic conditions, energy prices, 

weather, and the availability of non-fossil alternatives” (EPA 2009a). 

CO2 is by far the primary GHG emitted in the United States, representing almost 85.4 percent of 

all U.S. GHG emissions in 2007 (EPA 2009a). The other gases include CH4, N2O, and a variety of 

fluorinated gases, including HFCs, PFCs, and SF6. The fluorinated gases are collectively referred to as 

high global warming potential (GWP) gases. CH4 accounts for 8.2 percent of the remaining GHGs on a 

GWP-weighted basis, followed by N2O (4.4 percent), and the high-GWP gases (2.1 percent) (EPA 

2009a). 

GHGs are emitted from a wide variety of sectors, including energy, industrial processes, waste, 

agriculture, and forestry. Most U.S. emissions are from the energy sector, largely due to CO2 emissions 

from the combustion of fossil fuels, which alone account for 80 percent of total U.S. emissions (EPA 

2009a). These CO2 emissions are due to fuels consumed in the electric power (42 percent of fossil fuel 

emissions), transportation (33 percent), industry (15 percent), residential (6 percent), and commercial (4 

percent) sectors (EPA 2009a). However, when U.S. CO2 emissions are apportioned by end use, 

transportation is the single leading source of U.S. emissions from fossil fuels, causing approximately onethird of total CO2 emissions from fossil fuels (EPA 2009a). 

As noted earlier, the U.S. transportation sector contributed 31.5 percent of total U.S. CO2

emissions in 2007, with passenger cars and light trucks accounting for 60.6 percent of total U.S. CO2

emissions from transportation. Thus, 19.1 percent of total U.S. CO2 emissions are from passenger cars 

and light trucks. With the United States accounting for 17.2 percent of global CO2 emissions, passenger 

cars and light trucks in the United States account for roughly 3.3 percent of global CO2 emissions.33

Passenger cars and light trucks, which include SUVs, pickup trucks, and minivans, account for 

more than half of U.S. transportation CO2 emissions, and CO2 emissions from these vehicles have 

increased by 21 percent since 1990 (EPA 2009a). This increase was driven by two factors − (1) an 

increase in use of passenger cars and light trucks and (2) relatively little improvement in their average 

fuel economy. Population growth and expansion, economic growth, and low fuel prices led to more 

 

29 For NEPA purposes, it is appropriate for NHTSA to consider global environmental impacts. See Council on 

Environmental Quality Guidance on NEPA Analyses for Transboundary Impacts (July 1, 1997), available at 

http://ceq.hss.doe.gov/nepa/regs/transguide.html (last visited July 22, 2009) (stating that “agencies must include 

analysis of reasonably foreseeable transboundary effects of proposed actions in their [NEPA] analysis of proposed 

actions in the United States”). 

30 Most recent year for which an official EPA estimate is available. 31 Each GHG has a different level of radiative forcing, that is, the ability to trap heat. To compare their relative 

contributions, gases are converted to carbon dioxide equivalent using their unique global warming potential (GWP). 

32 Based on 2005 data and excludes carbon sinks from forestry and agriculture. 

33 Percentages include land-use change and forestry, and exclude international bunker fuels. 
3.4 Climate Chapter 3 Affected Environment and Environmental Consequences 

 3-68 

VMT, while the rising popularity of SUVs and other light trucks kept the average combined fuel economy 

of new passenger cars and light trucks relatively constant (EPA 2009a). 

3.4.2.1.2 Global Emissions 

Although humans have always contributed to some level of GHG emissions to the atmosphere 

through activities like farming and land clearing, substantial contributions did not begin until the mid1700s, with the onset of the Industrial Revolution. People began burning coal, oil, and natural gas to light 

their homes, power trains and cars, and run factories and industrial operations. Today the burning of 

fossil fuels is still the predominant source of GHG emissions. 

Levels of atmospheric CO2 have been rising rapidly. For about 10,000 years before the Industrial 

Revolution, atmospheric CO2 levels were 280 ppm (+/- 20 ppm). Since the Industrial Revolution, CO2

levels have risen to 386 ppm in 2008 (EPA 2009b). In addition, the concentrations of CH4 and N2O in the 

atmosphere have increased 149 and 23 percent, respectively (EPA 2009b). 

In 2000, gross global GHG emissions were calculated to be 41,638.5 MMTCO2 equivalent, an 8-

percent increase since 199034 (WRI 2009). In general, global GHG emissions have increased regularly, 

though annual increases vary according to a variety of factors (weather, energy prices, and economic 

factors). 

As in the United States, the primary GHGs emitted globally are CO2, CH4, N2O, and the 

fluorinated gases HFCs, PFCs, and SF6. In 2000, CO2 emissions comprised 77 percent of global 

emissions on a GWP-weighted basis, followed by CH4 (14.5 percent) and N2O (7.5 percent). 

Collectively, fluorinated gases represented 1.1 percent of global emissions (WRI 2009). 

Various sectors contribute to global GHG emissions, including energy, industrial processes, 

waste, agriculture, land-use change, and forestry. The energy sector is the largest contributor of global 

GHG emissions, accounting for 59 percent of global emissions in 2000. In this sector, the generation of 

electricity and heat accounts for 25 percent of total global emissions. The next highest contributors to 

emissions are land-use change and forestry (18 percent), agriculture (14 percent), and transportation (12 

percent, which is included in the 59 percent for the energy sector) (WRI 2009). 

Emissions from transportation are primarily due to the combustion of petroleum-based fuels to 

power vehicles such as cars, trucks, trains, airplanes, and ships. In 2005, transportation represented 14 

percent of total global GHG emissions and 20 percent of CO2 emissions; in absolute terms, global 

transportation CO2 emissions increased 30 percent from 1990 to 2005 (WRI 2009).35

3.4.2.2 Climate Change Effects and Impacts (Historic and Current) 

3.4.2.2.1 U.S. Climate Change Effects 

This section describes observed historical and current climate change effects and impacts for the 

United States. Much of the material that follows is drawn from the following sources, including the 

citations therein: Technical Support Document for Endangerment and Cause or Contribute Findings for 

Greenhouse Gases under Section 202(a) of the Clean Air Act (EPA 2009b), Scientific Assessment of the 

Effects of Global Change on the United States (National Science and Technology Council 2008), and 

 

34 All GHG estimates cited in this section include contributions from land-use change and forestry, unless noted 

otherwise. 

35 Values in this paragraph exclude land-use change and forestry. 
Chapter 3 Affected Environment and Environmental Consequences 3.4 Climate 

Global Climate Change Impacts in the United States (GCRP 2009). The impacts associated with these 

observed trends are further discussed in Section 4.5. 

Increased Temperatures

The past decade has been the warmest in more than a century of direct observations, with average 

temperatures for the contiguous United States rising at a rate near 0.58 °F per decade in the past few 

decades. U.S. average temperatures are now 1.25 °F warmer than they were at the beginning of the 20th

Century with an average warming of 0.13 °F per decade over 1895–2008, and the rate of warming is 

increasing (EPA 2009b). 

Since 1950, the frequency of heat waves has increased, although those recorded in the 1930s 

remain the most severe. There were also fewer unusually cold days in the past few decades with fewer 

severe cold waves for the most recent 10-year period in the record (GCRP 2009). 

Sea-level Rise

Relative sea level is rising 0.8 to 1.2 inches per decade along most of the Atlantic and Gulf 

Coasts, and a few inches per decade along the Louisiana Coast (due to land subsidence); sea level is 

falling (due to land uplift) at the rate of a few inches per decade in parts of Alaska (National Science and 

Technology Council 2008, EPA 2009b). These observations demonstrate that sea level does not rise 

uniformly across the globe. 

Sea-level rise extends the zone of impact from storm surge and waves from tropical and other 

storms farther inland, causing coastal erosion and other damage. Resulting shoreline erosion is well 

documented. Since the 1970s, half of the coastal area in Mississippi and Texas has been eroding by an 

average of 2.6 to 3.1 meters (8.5 to 10.2 feet) per year. In Louisiana, a full 90 percent of the shoreline has 

been eroding at an average rate of more than 12.0 meters (39 feet) per year (Nicholls et al. 2007 in EPA 

2009). 

Changes in Precipitation Patterns

Higher temperatures cause higher rates of evaporation and plant transpiration, meaning that more 

water vapor is available in the atmosphere for precipitation events. Depending on atmospheric 

conditions, increased evaporation means that some areas experience increases in precipitation events, 

while other areas are left more susceptible to droughts. 

Over the contiguous United States, total annual precipitation increased about 6 percent from 1901 

to 2005, with the greatest increases in the northern Midwest and the South. Heavy precipitation events 

also increased, primarily during the last 3 decades of the 20th Century, and mainly over eastern regions 

(GCRP 2009). Most regions experienced decreases in drought severity and duration during the second 

half of the 20th Century, although there was severe drought in the Southwest from 1999 to 2008 (EPA 

2009b); the Southeast has also recently experienced severe drought (GCRP 2009). 

Increased Incidence of Severe Weather Events

It is likely that the numbers of tropical storms, hurricanes, and major hurricanes each year in the 

North Atlantic have increased during the past 100 years (CCSP 2008c in National Science and 

Technology Council 2008) and that Atlantic sea-surface temperatures have increased over the same 

period. However, these trends are complicated by multi-decadal variability and data-quality issues. In 

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3.4 Climate Chapter 3 Affected Environment and Environmental Consequences 

addition, there is evidence of an increase in extreme wave-height characteristics over the past 2 decades, 

associated with more frequent and more intense hurricanes (CCSP 2008a). 

Changes in Water Resources

Melting snow and ice, increased evaporation, and changes in precipitation patterns all affect 

surface water. Stream flow decreased about 2 percent per decade over the past century in the central 

Rocky Mountain region (Rood et al. 2005 in Field et al. 2007), while in the eastern United States it 

increased 25 percent in the past 60 years (Groisman et al. 2004 in Field et al. 2007). Annual peak stream 

flow (dominated by snowmelt) in western mountains is occurring at least a week earlier than in the 

middle of the 20th Century. Winter stream flow is increasing in seasonal snow-covered basins and the 

fraction of annual precipitation falling as rain (rather than snow) has increased in the past half century 

(National Science and Technology Council 2008). 

Changes in temperature and precipitation are also affecting frozen surface water. Spring and 

summer snow cover has decreased in the West. In mountainous regions of the western United States, 

April snow water equivalent has declined 15 to 30 percent since 1950, particularly at lower elevations and 

primarily due to warming (Field et al. 2007 in National Science and Technology Council 2008). 

However, total snow-cover area in the United States increased in the November-to-January season from 

1915 to 2004 (National Science and Technology Council 2008). 

Barnett et al. (2008) found that human-induced climate change was responsible for 60 percent of 

the observed changes in river flows, winter air temperature, and snow pack in the western United States. 

Annual average Arctic sea ice extent decreased 2.7 (+/- 0.6) percent per decade from 1978 to 

2005. In 2007, sea ice extent was approximately 23 percent less than the previous all-time minimum 

observed in 2005. Average sea ice thickness in the central Arctic very likely has decreased by 

approximately 3 feet from 1987 to 1997. These area and thickness reductions allow winds to generate 

stronger waves, which have increased shoreline erosion along the Alaskan coast. Alaska has also 

experienced increased thawing of the permafrost base of up to 1.6 inches per year since 1992 (EPA 

2009b, National Science and Technology Council 2008). 

Rivers and lakes are freezing over later, at an average rate change of 5.8 (+/- 1.6) days per 

century, with ice breakup taking place earlier, at an average rate of 6.5 (+/- 1.2) days per century. Loss of 

glacier mass is occurring in the mountainous regions of the Pacific Northwest and has been especially 

rapid in Alaska since the mid-1990s (National Science and Technology Council 2008). 

Snowpack is also changing. At high elevations that remain below freezing in winter, 

precipitation increases have resulted in increased snowpack. Warmer temperatures at mid-elevations 

have decreased snowpack and led to earlier snowmelt, even with precipitation increases (Kundzewicz et 

al. 2007). An empirical analysis of available data indicated that temperature and precipitation impact 

mountain snowpack simultaneously, with the nature of the impact strongly dependent on factors such as 

geographic location, latitude, and elevation (Stewart 2009). 

3.4.2.2.2 Global Climate Change Effects 

In their most recent assessment of climate change, the IPCC states that, “Warming of the climate 

system is unequivocal, as is now evident from observations of increases in global average air and ocean 

temperatures, widespread melting of snow and ice, and rising global average sea level” (IPCC 2007b). 

The IPCC concludes that, “At continental, regional and ocean basin scales, numerous long-term changes 

in climate have been observed. These include changes in arctic temperatures and ice, widespread changes 

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Chapter 3 Affected Environment and Environmental Consequences 3.4 Climate 

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in precipitation amounts, ocean salinity, wind patterns and aspects of extreme weather including droughts, 

heavy precipitation, heat waves and the intensity of tropical cyclones” (IPCC 2007b). 

This section describes observed historical and current climate-change effects and impacts at a 

global scale. As with the discussion of effects for the United States, much of the material that follows is 

drawn from the following studies, including the citations therein: Summary for Policymakers (IPCC 

2007b), Technical Support Document for Endangerment and Cause or Contribute Findings for 

Greenhouse Gases under Section 202(a) of the Clean Air Act (EPA 2009b), Scientific Assessment of the 

Effects of Global Change on the United States (National Science and Technology Council 2008), and 

Global Climate Change Impacts in the United States (GCRP 2009). 

Increased Temperatures

The IPCC states that scientific evidence shows that the increase in GHGs (specifically, CO2, CH4, 

and N2O) since 1750 has led to an increase in global positive radiative forcing of 2.30 W/m2

 (+/- 0.23 

W/m2) (EPA 2009b). The radiative forcing from increased CO2 concentrations alone increased by 20 

percent between 1995 and 2005, which is the largest increase in the past 200 years (IPCC 2007b). 

This increase in radiative forcing results in higher temperatures, which are already being 

observed. Global temperature has been increasing over the past century. In the past 100 years, global 

mean surface temperatures have risen by 0.74 +/- 0.18 °C (1.3 +/- 0.32 °F) (EPA 2009b). Temperatures 

are rising at an increasing rate. The average rate of increase over the past century was 0.07 +/- 0.02 °C 

(0.13 +/- 0.04 °F) per decade. Over the past 50 years, temperatures have been rising at nearly twice that 

average rate or 0.13 +/- 0.03 °C (0.23 +/- 0.05 °F) per decade (EPA 2009b). Over the past 30 years, 

average global temperatures have risen even faster, for an average of 0.29 °F per decade (NOAA 2009 in 

EPA 2009). Average Arctic temperatures have increased at almost twice the global average rate in the 

past 100 years. Temperature increases are more pronounced over land, because air temperatures over 

oceans are warming at about half the rate as air over land (EPA 2009b). 

Extreme temperatures have changed significantly over the past 50 years. Hot days, hot nights, 

and heat waves have become more frequent; cold days, cold nights, and frost have become less frequent 

(EPA 2009b). 

Weather balloons, and now satellites, have directly recorded increases in temperatures since the 

1940s (GCRP 2009). In addition, higher temperatures are also independently confirmed by other global 

observations. For example, scientists have documented shifts to higher latitudes and elevations of certain 

flora and fauna habitat. In high and mid latitudes, the growing season increased on average by about 2 

weeks during the second half of the 20th Century (EPA 2009b), and plant flowering and animal spring 

migration patterns are occurring earlier (EPA 2009b). Permafrost top layer temperatures have generally 

increased since the 1980s (about 3 °C [5 °F] in the Arctic), while the maximum area covered by seasonal 

frozen ground has decreased since 1900 by about 7 percent in the Northern Hemisphere, with a decrease 

in spring of up to 15 percent (EPA 2009b). 

Some temperature-related climate variables are not changing. The diurnal temperature range has 

not changed from 1979 to 2004; 36 day- and night-time temperatures have risen at similar rates. Antarctic 

sea-ice extent shows no substantial average trends, despite inter-annual variability and localized changes, 

consistent with the lack of warming across the region from average atmospheric temperatures (GCRP 

2009). 

 

36 Diurnal temperature range is a meteorological term that relates to the variation in temperature that occurs from the 

maximum (high) temperatures of the day to the minimum (lowest) temperatures of nights. 
3.4 Climate Chapter 3 Affected Environment and Environmental Consequences 

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Sea-level Rise

Higher temperatures cause sea level to rise due to both thermal expansion of water and to an 

increased volume of ocean water from melting glaciers and ice sheets. EPA estimates that between 1993 

and 2003, thermal expansion and melting ice were roughly equal in their effect on sea-level rise (EPA 

2009b). 

Between 1961 and 2003, observations of global ocean temperature indicate that it warmed by 

about 0.18 °F from the surface to a depth of 700 meters (0.43 mile). This warming contributed an 

average of 0.4 +/- 0.1 millimeter (0.016 +/- 0.0039 inch) per year to sea-level rise (EPA 2009b), because 

seawater expands as it warms. Mountain glaciers, ice caps, and snow cover have declined on average, 

contributing further to sea-level rise. Losses from the Greenland and Antarctic ice sheets have very likely 

contributed to sea-level rise from 1993 to 2003 and satellite observations indicate that they have 

contributed to sea-level rise in the years since (Shepherd and Wingham 2007). Dynamical ice loss 

explains most of the Antarctic net mass loss and about half of the Greenland net mass loss; the other half 

occurred because melting has exceeded snowfall accumulation (IPCC 2007b). 

Global average sea level rose at an average rate of 1.8 +/- 0.5 millimeters (0.07 +/- 0.019 inch) 

per year from 1961 to 2003 with the rate increasing to about 3.1 +/- 0.7 millimeters (0.12 inch +/- 0.027) 

per year from 1993 to 2003 (EPA 2009b). Total 20th-Century rise is estimated at 0.17 +/- 0.05 meter 

(0.56 +/- 0.16 foot) (EPA 2009b). However, since the IPCC Fourth Assessment Report was published in 

2007, a recent study improved the historical estimates of upper-ocean (300 meters to 700 meters [0.19 to 

0.43 mile]) warming from 1950 to 2003 (by correcting for expendable bathy-thermographs instrument 

bias). Domingues et al. (2008) found the improved estimates demonstrate clear agreement with the 

decadal variability of the climate models that included volcanic forcing. Furthermore, this study 

estimated the globally averaged sea-level trend from 1961 to 2003 to be 1.5 +/- 0.4 millimeters (0.063 +/- 

0.01 inch) per year with a rise of 2.4 millimeters (0.094 inch) per year evident from 1993 to 2003, 

consistent with the estimated trend of 2.3 millimeters (0.091 inch) per year from tide gauges after taking 

into account thermal expansion in the upper ocean and deep ocean, variations in the Antarctica and 

Greenland ice sheets, glaciers and ice caps, and terrestrial storage. 

Sea-level rise is not uniform across the globe. The largest increases since 1992 have been in the 

western Pacific and eastern Indian Oceans; meanwhile, sea level in the eastern Pacific and western Indian 

Oceans has actually been falling (EPA 2009b).37 

Changes in Precipitation Patterns

Average atmospheric water vapor content has increased since at least the 1980s over land and the 

oceans, and in the upper troposphere, largely consistent with air temperature increases. As a result, heavy 

precipitation events have increased in frequency over most land areas (National Science and Technology 

Council 2008). 

Long-term trends in global precipitation amounts have been observed since 1900. Precipitation 

has substantially increased in eastern parts of North and South America, northern Europe, and northern 

and central Asia. Drying has been observed in the Sahel, the Mediterranean, southern Africa, and parts of 

southern Asia. Spatial and temporal variability for precipitation is high, and data are limited for some 

regions (EPA 2009b). 

 

37 Note that parts of the United States’ West Coast – which is part of the eastern Pacific – are experiencing a rise in 

sea level (see Section 3.4.2.2.1). Local changes in sea-level rise depend on a variety of factors, including land 

subsidence. 
Chapter 3 Affected Environment and Environmental Consequences 3.4 Climate 

Droughts that are more intense and longer have been observed since the 1970s, particularly in the 

tropics and subtropics, and were caused by higher temperatures and decreased precipitation. Changes in 

sea-surface temperatures, wind patterns, and decreased snowpack and snow cover have also been linked 

to droughts (EPA 2009b). 

Increased Incidence of Severe Weather Events

Long-term trends in tropical cyclone activity have been reported, but there is no clear trend in the 

number of tropical cyclones each year. There is observational evidence of an increase in intense tropical 

cyclone activity in the North Atlantic since about 1970, correlated with increases of tropical sea surface 

temperatures. However, concerns about data quality and multi-decadal variability persist (EPA 2009b). 

The World Meteorological Organization (WMO) Sixth International Workshop on Tropical Cyclones in 

2006 agreed that “no firm conclusion can be made” on anthropogenic influence on tropical cyclone 

activity because “there is evidence both for and against the existence of a detectable anthropogenic signal 

in the tropical cyclone climate record” (WMO 2006). 

There is also insufficient evidence to determine whether there are trends in large-scale 

phenomena such as the meridional overturning circulation (MOC) (a mechanism for heat transport in the 

North Atlantic Ocean, where warm waters are carried north and cold waters are carried toward the 

equator) or in small-scale phenomena such as tornadoes, hail, lightning, and dust storms (IPCC 2007b). 

Changes in Ice Cover

Changes in air and ocean temperatures, precipitation onto the ice mass, and water salinity are 

affecting glaciers and ice sheets. Numerous studies have confirmed that glaciers and ice sheets have 

significantly shrunk in the past half century. Satellite images have documented the shrinking of the 

Greenland ice sheet and the West Antarctic ice sheet (NASA 2009); since 1979, the annual average Arctic 

sea ice area has been declining at a rate of 4.1 percent per decade (EPA 2009b). Additionally, some 

Arctic ice that previously was thick enough to last through summer has now thinned enough that it melts 

completely in summer. In 2003, 62 percent of the Arctic’s total ice volume was stored in multi-year ice; 

in 2008, only 32 percent was stored in multi-year ice (NASA 2009). 

Acidification of Oceans

Oceans have absorbed some of the increase in atmospheric CO2, which lowers the pH of the 

water. When CO2 dissolves in seawater, there is an increase in the hydrogen ion concentration of the 

water, measured as a decline in pH. Relative to the pre-industrial period, the pH of the world’s oceans 

has dropped 0.1 pH units (EPA 2009b). Because pH is measured on a logarithmic scale, this represents a 

30% increase in the hydrogen ion concentration of seawater, a significant acidification of the oceans. 

Although research on the ultimate impacts of ocean acidification is limited, scientists believe that the 

acidification is likely to interfere with the calcification of coral reefs and thus inhibit the growth and 

survival of coral reef ecosystems (EPA 2009b). 

3.4.3 Methodology 

The methodology NHTSA used to characterize the effects of the alternatives on climate has two 

key elements, as follows: 

1. Analyzing the effects of the proposed action and alternatives on GHG emissions; and 

2. Analyzing how GHG emissions affect the climate system (climate effects). 

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3.4 Climate Chapter 3 Affected Environment and Environmental Consequences 

For both effects on GHG emissions and effects on the climate system, this EIS expresses results – 

for each alternative – in terms of the environmental attribute being characterized (emissions, CO2

concentrations, temperature, precipitation, and sea level). Comparisons between the No Action 

Alternative (Alternative 1) and each action alternative (Alternatives 2 through 9) are also presented to 

illustrate the differences in environmental effects among the alternative CAFE standards. The impact of 

each action alternative on these results is measured by the difference in its value under the No Action 

Alternative and its value under that action alternative. For example, the reduction in CO2 emissions 

attributable to an action alternative is measured by the difference in emissions under that alternative and 

emissions under the No Action Alternative. 

The methods used to characterize emissions and climate effects involve considerable uncertainty. 

Sources of uncertainty include the pace and effects of technology change in the transportation sector and 

other sectors that emit GHGs; changes in the future fuel supply and fuel characteristics that could affect 

emissions; sensitivity of climate to increased GHG concentrations; rate of change in the climate system in 

response to changing GHG concentrations; potential existence of thresholds in the climate system (which 

cannot be predicted or simulated); regional differences in the magnitude and rate of climate changes; and 

many other factors. 

Moss and Schneider (2000) characterize the “cascade of uncertainty” in climate change 

simulations (Figure 3.4.3-1). As indicated in the figure, the emissions estimates used in this EIS have 

narrower bands of uncertainty than the global climate effects, which are less uncertain than the regional 

climate change effects. The effects on climate are, in turn, less uncertain than the impacts of climate 

changes on affected resources (such as terrestrial and coastal ecosystems, human health, and other 

resources discussed in Section 4.5). Although the uncertainty bands get broader with each successive step 

in the analytic chain, this is not to say that all values within the bands are equally likely – it is still the 

case that the mid-range values have the highest likelihood. 

Where information in the analysis in this EIS is incomplete or unavailable, NHTSA has relied on 

the CEQ regulations regarding incomplete or unavailable information (see 40 CFR § 1502.22(b)). The 

scientific understanding of the climate system is incomplete; like any analysis of complex, long-term 

changes to support decisionmaking, evaluating reasonably foreseeable significant adverse impacts on the 

human environment involves many assumptions and uncertainties. This EIS uses methods and data that 

represent the best and most up-to-date information available on this topic, and have been subjected to 

peer-review and scrutiny. In fact, the information cited throughout this section that is extracted from the 

most recent EPA, IPCC, and CCSP reports on climate change has endured a more thorough and 

systematic review process than information on virtually any other topic in environmental science and 

policy. The tools used to perform the climate change impacts analysis in this EIS, including MAGICC 

(Model for the Assessment of Greenhouse-gas Induced Climate Change) and the Representative 

Concentration Pathway (RCP) and CCSP Final Report of Synthesis and Assessment Product (SAP) 2.1 

emissions scenarios described below, are widely available and generally accepted in the scientific 

community. 

CCSP SAP 3.1 on the strengths and limitations of climate models (CCSP 2008d) provides a 

thorough discussion of the methodological limitations regarding modeling. Readers interested in a 

detailed treatment of this topic can find the SAP 3.1 report useful in understanding the issues that 

underpin the modeling of environmental impacts of the proposed action and the range of alternatives on 

climate change. 

 3-74 
Chapter 3 Affected Environment and Environmental Consequences 3.4 Climate 

 3-75 

Figure 3.4.3-1. Cascade of Uncertainty in Climate Change Simulations a/ 

emission

scenarios

carbon cycle

response

global climate

sensitivity

regional climate

change

scenarios

range of

possible

impacts

emission

scenarios

carbon cycle

response

global climate

sensitivity

regional climate

change

scenarios

range of

possible

impacts

a/ Source: Moss and Schneider (2000) – “Cascade of uncertainties typical in impact assessments showing the 

‘uncertainty explosion’ as these ranges are multiplied to encompass a comprehensive range of future consequences, 

including physical, economic, social, and political impacts and policy responses.” 

3.4.3.1 Methodology for Modeling Greenhouse Gas Emissions 

GHG emissions were estimated using the Volpe model, as described in Section 3.1.4. The 

emissions estimates include global CO2, CH4, and N2O emissions resulting from direct fuel combustion 

and from the production and distribution of fuel (upstream emissions) in the United States. The Volpe 

model also accounted for and estimated the following non-GHGs: SO2, NOx, CO, and VOCs. 

Fuel savings from stricter CAFE standards result in lower emissions of CO2, the main GHG 

emitted as a result of refining, distribution, and use of transportation fuels.38 There is a direct relationship 

among fuel economy, fuel consumption, and CO2 emissions. Lower fuel consumption reduces CO2

emissions directly because the primary source of vehicle-related CO2 emissions is fuel combustion in 

internal-combustion engines. Therefore, fuel consumption is directly related to CO2 emissions and CO2

emissions are directly related to fuel economy. NHTSA estimates reductions in CO2 emissions resulting 

from fuel savings by assuming that the carbon content of gasoline, diesel, and other fuels is converted 

entirely to CO2 during the combustion process.39 Specifically, NHTSA estimates CO2 emissions from 

fuel combustion as the product of the volume of each type of fuel consumed (in gallons), its mass density 

(in grams per gallon), the fraction of its total mass represented by carbon (measured as a proportion), and 

CO2 emissions per gram of fuel carbon (the ratio of the molecular weights of CO2 and elemental carbon). 

Reduced fuel consumption also lowers CO2 emissions that result from the use of carbon-based 

energy sources during fuel production and distribution. NHTSA currently estimates the global reductions 

in CO2 emissions during each phase of fuel production and distribution using CO2 emissions rates 

obtained from the Greenhouse Gases, Regulated Emissions, and Energy Use in Transportation (GREET) 

 

38 For this rulemaking, NHTSA estimated emissions of vehicular CO2, CH4, and N2O emissions, but did not estimate 

vehicular emissions of HFCs. CH4 and N2O account for 2.2 percent of the tailpipe GHG emissions from passenger 

cars and light trucks, and CO2 emissions account for the remaining 97.8 percent. Of the total (including nontailpipe) GHG emissions from passenger cars and light trucks, tailpipe CO2 represents about 93.5 percent, tailpipe 

CH4 and N2O represent about 2.1 percent, and HFCs (from air-conditioner leaks) represent about 4.3 percent. 

(Values calculated from EPA 2009a.) 

39 This assumption results in a slight overestimate of CO2 emissions, because a small fraction of the carbon content 

of gasoline is emitted as CO and unburned hydrocarbons. However, the magnitude of this overestimation is likely to 

be extremely small. This approach is consistent with the recommendation of the IPCC for “Tier 1” national GHG 

emissions inventories (IPCC 2006). 
3.4 Climate Chapter 3 Affected Environment and Environmental Consequences 

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version 1.8b model using the previous assumptions about how fuel savings are reflected in reductions in 

activity during each phase of fuel production and distribution. The total reduction in CO2 emissions from 

improving fuel economy under each CAFE alternative is the sum of the reductions in motor vehicle 

emissions from reduced fuel combustion, plus the reduction in upstream emissions from a lower volume 

of fuel production and distribution. 

3.4.3.2 Methodology for Estimating Climate Effects 

This EIS estimates and reports on four direct and indirect effects of climate change, driven by 

alternative scenarios of GHG emissions, as follows: 

1. Changes in CO2 concentrations; 

2. Changes in global mean surface temperature; 

3. Changes in regional temperature and precipitation; and 

4. Changes in sea level. 

The change in CO2 concentration is a direct effect of the changes in GHG emissions and 

influences each of the other factors. 

This EIS uses a simple climate model to estimate the changes in CO2 concentrations, global mean 

surface temperature, and changes in sea level for each CAFE alternative and uses increases in global 

mean surface temperature combined with an approach and coefficients from the IPCC Fourth Assessment 

Report (IPCC 2007a) to estimate changes in global precipitation. NHTSA used the publicly available 

modeling software MAGICC 5.3.v2 (Wigley 2008) to estimate changes in key direct and indirect effects. 

The application of MAGICC 5.3.v2 uses the estimated reductions in emissions of CO2, CH4, N2O, CO, 

NOx, SO2, and VOCs produced by the Volpe model. A sensitivity analysis was completed to examine the 

relationship among selected CAFE alternatives and likely climate sensitivities, and the associated direct 

and indirect effects for each combination. These relationships can be used to infer the effect of emissions 

associated with the CAFE alternatives on direct and indirect climate effects. 

This section describes MAGICC, the climate sensitivity analysis, and the emissions scenario used 

in the analysis. 

3.4.3.2.1 MAGICC Version 5.3.v2 

The selection of MAGICC for this analysis was driven by a number of factors, as follows: 

• MAGICC has been used in the peer-reviewed literature to evaluate changes in global mean 

surface temperature and sea-level rise, including the IPCC Fourth Assessment Report for 

Working Group I (WGI) (IPCC 2007a) in which it was used to scale the results from the 

atmospheric-ocean general circulation models (AOGCMs)40 to estimate the global mean 

surface temperature and the sea-level rise for global emissions scenarios that the AOGCMs 

did not run. 

• MAGICC is publicly available and was designed for the type of analysis performed in this 

EIS. 

• More complex AOGCMs are not designed for the type of sensitivity analysis performed here 

and are best used to provide results for groups of scenarios with much greater differences in 

emissions. 

 

40 For a discussion of AOGCMs, see WGI, Chapter 8 in IPCC (2007a). 
Chapter 3 Affected Environment and Environmental Consequences 3.4 Climate 

 3-77 

• MAGICC has been updated to version 5.3.v2 to incorporate the science from the IPCC 

Fourth Assessment Report (Wigley 2008). 

• EPA is also using MAGICC 5.3.v2 for their vehicle GHG emissions standards Regulatory 

Impact Analysis (RIA), which accompanies the joint NHTSA and EPA NPRM. 

NHTSA assumed that global emissions under the No Action Alternative (Alternative 1) follow 

the trajectory provided by the RCP 4.5 MiniCAM (Mini Climate Assessment Model) reference scenario. 

This scenario represents a reference case, in which future global emissions continue to rise unchecked 

assuming no additional climate policy. It is based on the CCSP SAP 2.1 MiniCAM reference scenario, 

and has been revised by the Joint Global Change Research Institute to update emission estimates of nonCO2 gases. Section 3.4.3.3 describes the RCP 4.5 MiniCAM reference scenario. 

3.4.3.2.2 Reference Case Modeling Runs 

The modeling runs and sensitivity analysis are designed to use information on CAFE alternatives, 

climate sensitivities, and the RCP 4.5 MiniCAM reference emissions scenario (Clarke et al. 2007, Smith 

and Wigley 2006)41 to model relative changes in atmospheric concentrations, global mean surface 

temperature, precipitation, and sea-level rise likely to result under each alternative. 

The modeling runs are based on the results provided for the nine CAFE alternatives, a climate 

sensitivity of 3 °C (5.4 °F) for a doubling of CO2 concentrations in the atmosphere, and the RCP 4.5 

MiniCAM reference scenario. 

The approach uses the following steps to estimate these changes: 

1. NHTSA assumed that global emissions under the No Action Alternative follow the trajectory 

provided by the RCP 4.5 MiniCAM reference scenario. 

2. NHTSA assumed that global emissions for the CAFE alternatives are equal to the global 

emissions from the No Action Alternative minus the emissions reductions from the Volpe 

model for CO2, CH4, N2O, SO2, NOx, CO, and VOCs. (For example, the global emissions 

scenario under Alternative 2 equaled the RCP 4.5 MiniCAM reference scenario minus the 

emission reductions from that Alternative). All SO2 reductions were applied to the Aerosol 

region 1 of MAGICC, which includes North America. 

3. NHTSA used MAGICC 5.3.v2 to estimate the changes in global CO2 concentrations, global 

mean surface temperature, and sea-level rise through 2100 using the global emissions 

scenario under each CAFE alternative, developed in Steps 1 and 2 above. 

4. NHTSA used the increase in global mean surface temperature, along with factors relating 

increase in global average precipitation to this increase in global mean surface temperature, to 

estimate the increase in global averaged precipitation for each CAFE alternative using the 

RCP 4.5 MiniCAM reference scenario. 

Section 3.4.4 presents the results of the model runs for the alternatives. 

 

41 The use of different emissions scenarios provides insight into the impact of alternative global emissions scenarios 

on the effect of the CAFE alternatives. 
3.4 Climate Chapter 3 Affected Environment and Environmental Consequences 

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3.4.3.2.3 Sensitivity Analysis 

NHTSA conducted a sensitivity analysis to examine the effect of various equilibrium climate 

sensitivities on the results. Equilibrium climate sensitivity42 (or climate sensitivity) is the projected 

responsiveness of Earth’s global climate system to forcing from GHG drivers, and is often expressed in 

terms of changes to global surface temperature resulting from a doubling of CO2 in relation to preindustrial atmospheric concentrations (280 ppm CO2) (NRC 2001 in EPA 2009). In the past 8 years, 

confidence in climate sensitivity projections has increased significantly (Meehl et al. 2007b in EPA 

2009). According to IPCC, with a doubling of the concentration of atmospheric CO2, there is a 66- to 90-

percent probability of an increase in surface warming of 2.0 to 4.5 °C (3.6 to 8.1 °F), with 3 °C (5.4 °F) as 

the single most likely surface temperature increase (EPA 2009b, Meehl et al. 2007a). 

Climate sensitivities of 2.0, 3.0, and 4.5 °C (3.6, 5.4, and 8.1 °F) for a doubling of CO2

concentrations in the atmosphere were assessed. NHTSA conducted the sensitivity analysis around two 

of the CAFE alternatives, the No Action Alternative (Alternative 1) and the Preferred Alternative 

(Alternative 4), as this was deemed sufficient to assess the effect of various climate sensitivities on the 

results. 

The approach uses the following steps to estimate the sensitivity of the results to alternate 

estimates of the climate sensitivity: 

1. NHTSA used the RCP 4.5 MiniCAM reference scenario to represent emissions from the No 

Action Alternative. 

2. Starting with the RCP 4.5 MiniCAM reference scenario from step 1, NHTSA assumed that 

the reductions in global emissions of CO2, CH4, N2O, SO2, NOx, CO, and VOCs resulting 

from the Preferred Alternative are equal to the global emissions of each pollutant under the 

No Action Alternative, minus emissions of each pollutant under the Preferred Alternative. 

All SO2 reductions were applied to Aerosol region 1 of MAGICC, which includes North 

America. 

3. NHTSA assumed climate sensitivity values consistent with the likely range from the IPCC 

Fourth Assessment Report (IPCC 2007a) of 2.0, 3.0, and 4.5 °C (3.6, 5.4, and 8.1 °F). 

4. For each climate sensitivity in step 3, NHTSA used MAGICC 5.3.v2 to estimate the resulting 

changes in CO2 concentrations, global mean surface temperature, and sea-level rise through 

2100 for the global emissions scenarios in step 1 and 2. 

Section 3.4.4.2.5 presents the results of the model runs for the alternatives. 

3.4.3.3 Global Emissions Scenarios 

As described above, MAGICC uses long-term emissions scenarios representing different 

assumptions about key drivers of GHG emissions. The RCP 4.5 MiniCAM reference scenario is based on 

the MiniCAM reference scenario developed for the SAP 2.1 report. This scenario was created as part of 

the CCSP effort to develop a set of long-term (2000 to 2100) global emissions scenarios that incorporate 

an update of economic and technology data and utilize improved scenario-development tools compared to 

the IPCC Special Report on Emissions Scenarios (SRES) (IPCC 2000) developed more than a decade 

ago. 

 

42 In this document, the term “climate sensitivity” refers to “equilibrium climate sensitivity.” 
Chapter 3 Affected Environment and Environmental Consequences 3.4 Climate 

 3-79 

The Strategic Plan for the U.S. Climate Change Science Program (CCSP 2003) called for the 

preparation of 21 synthesis and assessment products and noted that emissions scenarios are essential for 

comparative analysis of future climate change and for analyzing options for mitigating and adapting to 

climate change. The Plan includes Product 2.1, Scenarios of Greenhouse Gas Emissions and 

Atmospheric Concentrations and Review of Integrated Scenario Development and Application (Clarke et 

al. 2007), which presents 15 scenarios, five from each of the three modeling groups (IGSM, MiniCAM, 

and MERGE).43 

Each climate modeling group independently produced a unique emissions reference scenario 

based on the assumption that no climate policy would be implemented beyond the current set of policies 

in place using a set of assumptions about drivers such as population changes, economic growth, land and 

labor productivity growth, technological options, and resource endowments. In addition, each group 

produced four additional stabilization scenarios, which are defined in terms of the total long-term 

radiative impact of the suite of GHGs that includes CO2, N2O, CH4, HFCs, PFCs, and SF6. These 

stabilization scenarios represent various levels of implementation of global GHG emissions reduction 

policies. 

 The results rely primarily on the RCP 4.5 MiniCAM reference scenario (which is based on the 

MiniCAM reference scenario developed for SAP 2.1) to represent a reference case emissions scenario; 

that is, future global emissions assuming no additional climate policy. NHTSA chose the RCP 4.5 

MiniCAM reference scenario based on the following factors: 

• The RCP 4.5 MiniCAM reference scenario is a slightly updated version of the scenario 

developed by the MiniCAM Model of the Joint Global Change Research Institute, which is a 

partnership between the Pacific Northwest National Laboratory and the University of 

Maryland, and is one of three reference climate scenarios described in the SAP 2.1. The 

MiniCAM reference scenario is based on a set of assumptions about drivers such as 

population, technology, and socioeconomic changes in the absence of global action to 

mitigate climate change. 

• In terms of global emissions of CO2 from fossil fuels and industrial sources, the MiniCAM 

reference scenario illustrates a pathway of emissions between the IGSM and MERGE 

reference scenarios for most of the 21st Century. In essence, out of the three SAP 2.1 

reference case scenarios, the MiniCAM reference scenario is the “middle ground” scenario. 

• CCSP SAP 2.1 is more than a decade newer than the IPCC SRES, and therefore has updated 

economic and technology data and assumptions and uses improved integrated assessment 

models that account for advances in economics and science over the past 10 years. 

• EPA is also using the RCP 4.5 MiniCAM reference scenario for their vehicle GHG emissions 

standards RIA, which accompanies the joint NHTSA and EPA NPRM. 

The RCP 4.5 MiniCAM reference scenario provides a global context for emissions of a full suite 

of GHGs and ozone precursors. There are some inconsistencies between the overall assumptions that 

SAP 2.1 and the Joint Global Change Research Institute used to develop the global emissions scenario 

and the assumptions used in the Volpe model in terms of economic growth, energy prices, energy supply, 

and energy demand. However, these inconsistencies affect the characterization of each CAFE alternative 

in equal proportion, so the relative estimates provide a reasonable approximation of the differences in 

environmental impacts among the alternatives. 

 

43 IGSM is the Massachusetts Institute of Technology’s Integrated Global System Model. MERGE is A Model for 

Evaluating the Regional and Global Effects of GHG Reduction Policies. 
3.4 Climate Chapter 3 Affected Environment and Environmental Consequences 

 3-80 

Each of the alternatives was simulated by calculating the difference between annual GHG 

emissions under that alternative and emissions under the No Action Alternative, and subtracting this 

change from the RCP 4.5 MiniCAM reference scenario to generate modified global-scale emissions 

scenarios, which show the effects of the various regulatory alternatives on the global emissions path. For 

example, CO2 emissions from U.S. passenger cars and light trucks in 2020 under Alternative 1, No 

Action, are 1,810 MMTCO2; the emissions in 2020 under the Alternative 4 (Preferred) are 1,690 

MMTCO2 (see Table 3.4.4-2). The difference of 120 MMTCO2 represents the reduction in emissions 

projected to result from adopting the Preferred Alternative. Global emissions for the RCP 4.5 MiniCAM 

reference scenario in 2020 are 38,020 MMTCO2, which are assumed to incorporate the level of emissions 

from U.S. passenger cars and light trucks under the No Action Alternative. Global emissions under the 

Preferred Alternative are thus estimated to be 120 MMTCO2 less than this reference level or 37,900 

MMTCO2 in 2020. 

Many of the economic assumptions used in the Volpe model (such as fuel price, VMT, U.S. 

GDP) are based on EIA’s Annual Energy Outlook (AEO) 2010 Early Release (EIA 2009a) and 

International Energy Outlook (IEO) 2009 (EIA 2009b), which forecast energy supply and demand in the 

U.S. and globally to 2030. Figures 3.4.3-2 to 3.4.3-6 show how the EIA forecasts of global and U.S. 

GDP, CO2 emissions from energy use, and primary energy use compare against the assumptions used to 

develop the SAP 2.1 MiniCAM reference scenario.44,45 Both forecasts presented here are for reference 

scenarios. 

The GDP growth assumptions for the IEO reference scenario are slightly higher than those in 

SAP scenarios by about 0.6 percent annually for the world and 0.9 percent annually for the United States 

(see Figure 3.4.3-2). 

Despite this IEO assumption of higher economic growth, the growth in primary energy use is 

similar between the IEO and MiniCAM with the total primary energy use in MiniCAM slightly lower 

than that of the IEO, as shown in Figure 3.4.3-5. Thus, the global primary liquids energy use in SAP 2.1 

and the IEO 2009 compare well. Much of the difference in energy use in the IEO forecast is due to 

assumptions of higher coal use, which results in higher CO2 emissions, as shown in Figure 3.4.3-4. 

Additionally, the IEO reference scenario estimates have a lower share of “other” fuels, which include 

biomass and renewable fuels, and is likely due to different treatments of non-commercial fuels in the two 

sets of forecasts. 

The primary energy use projections for the United States show a different trend than the global 

numbers. The AEO 2010 Early Release (EIA 2009a)46 projection shows an increase in total primary 

energy use in the United States, but much of the increase is from the use of coal and liquid fuels. On the 

other hand, the MiniCAM reference scenario has a higher share of natural gas (see Figure 3.4.3-6). 

However, the AEO reference scenario has a greater share of other fuels47 than the MiniCAM reference 

scenario, resulting in lower CO2 emissions (see Figure 3.4.3-4). 

 

44 The MiniCAM reference scenario from SAP 2.1 uses the same assumptions for GDP, energy use, and CO2

emissions as the RCP MiniCAM reference scenario. 

45 The IEO 2009 uses energy supply and consumption from the AEO 2009 for the United States and the same 

forecast for world oil prices. The IEO nuclear primary energy forecast numbers were adjusted to account for 

differences in reporting primary energy use for nuclear energy and all IEO energy-use estimates were converted to 

exajoules (EJ). 

46 AEO 2010 Early Release estimates were used for U.S. primary energy consumption. 47 For AEO reference scenario, “other” includes biomass, hydropower, and other renewable fuels. 
Chapter 3 Affected Environment and Environmental Consequences 3.4 Climate 

Figure 3.4.3-2. Average GDP Growth Rates (1990 to 2030) 

Figure 3.4.3-3. Global CO2 Emissions from Fossil Fuel Use 

0

5

10

15

20

25

30

35

40

45

2010 2020 2030

Billion tonnes of CO2

IEO

MINICAM_REF

 3-81 
3.4 Climate Chapter 3 Affected Environment and Environmental Consequences 

Figure 3.4.3-4. U.S. CO2 Emissions from Fossil Fuel Use 

0

1

2

3

4

5

6

7

2010 2020 2030

Billion tonnes of CO2

IEO

MINICAM_REF

Figure 3.4.3-5. World Primary Energy Use Forecast 

0

100

200

300

400

500

600

700

800

IEO

MINICAM_REF

IEO

MINICAM_REF

IEO

MINICAM_REF

2010                                                             2020                                                        2030

Exajoules (EJ)

Other

Nuclear

Natural Gas

Coal

Liquids

 3-82 
Chapter 3 Affected Environment and Environmental Consequences 3.4 Climate 

Figure 3.4.3-6. U.S. Primary Energy Use Forecast 

0

20

40

60

80

100

120

140

AEO (year 2008 value)

MINICAM_REF

AEO

MINICAM_REF

AEO

MINICAM_REF

2010                                                       2020                                                        2030

Exajoules (EJ)

Other

Nuclear

Natural Gas

Coal

Liquids

Where information in the analysis included in this EIS is incomplete or unavailable, NHTSA has 

relied on the CEQ regulations regarding incomplete or unavailable information (see 40 CFR § 

1502.22(b)). In this case, despite the inconsistencies between the MiniCAM assumptions on global trends 

across all GHG-emitting sectors (and the drivers that affect them) and the particularities of the emissions 

estimates for the U.S. transportation sector provided by the Volpe model, the approach used is valid for 

this analysis. These inconsistencies affect all alternatives equally; therefore, they do not hinder a 

comparison of the alternatives in terms of their relative effects on climate. 

The approaches focus on marginal changes in emissions that affect climate. Thus, the approaches 

result in a reasonable characterization of climate change for a given set of emissions reductions, 

regardless of the underlying details associated with those emissions reductions. Section 3.4.4 

characterizes projected climate change under the No Action Alternative (Alternative 1) and the action 

alternatives (Alternatives 2 through 9). 

The climate sensitivity analysis provides a basis for determining climate responses to varying 

climate sensitivities under the No Action Alternative (Alternative 1) and the Preferred Alternative 

(Alternative 4). Section 3.4.3.2.2 discusses the methodology for the sensitivity analysis. Though the 

MAGICC model does not simulate abrupt climate change processes, some responses of the climate 

system represented in MAGICC are slightly non-linear, primarily due to carbon cycle feedbacks and the 

logarithmic response of equilibrium temperature to CO2 concentration. Therefore, by using a range of 

emissions cases and climate sensitivities, the effects of the alternatives in relation to different scenarios 

and sensitivities can be estimated 

3.4.3.3.1 Tipping Points and Abrupt Climate Change 

The phrase “tipping point” is most typically used, in the context of climate change and its 

consequences, to describe situations in which the climate system (the atmosphere, oceans, land, 

 3-83 
3.4 Climate Chapter 3 Affected Environment and Environmental Consequences 

 3-84 

cryosphere,48 and biosphere) reaches a point at which there is a disproportionally large or singular 

response in a climate-affected system as a result of only a moderate additional change in the inputs to that 

system (such as an increase in the CO2 concentration). Exceeding one or more tipping points, which 

“occur when the climate system is forced to cross some threshold, triggering a transition to a new state at 

a rate determined by the climate system itself and faster than the cause” (NRC 2002 in EPA 2009), could 

result in abrupt changes in the climate or any part of the climate system. Abrupt climate changes could 

occur so quickly and unexpectedly that human systems would have difficulty adapting to them (NRC 

2002 in EPA 2009). 

The methodology used to address tipping points is based on an analysis of climate change science 

synthesis reports – including the Technical Support Document for EPA’s Endangerment Finding for 

GHGs (EPA 2009b), the IPCC WGI report (Meehl et al. 2007a) and CCSP SAP 3.4: Abrupt Climate 

Change – and recent literature on the issue of tipping points and abrupt climate change. The analysis 

identifies vulnerable systems, possible temperature thresholds, and estimates of the likelihood, timing, 

and impacts of abrupt climate events. While there are methodological approaches to estimate 

temperatures resulting from a reduction in GHG emissions and associated radiative forcing, the present 

state of the art does not allow for quantification of how emission reductions from a specific policy or 

action might affect the probability and timing of abrupt climate change. This is one of the most complex 

and scientifically challenging areas of climate science, and given the difficulty of simulating the largescale processes involved in these tipping points – or inferring their characteristics from paleoclimatology 

– considerable uncertainties remain as to the tipping points and rate of change. Despite the lack of a 

precise quantitative methodological approach, Section 4.5.9 presents a qualitative and comparative 

analysis of tipping points and abrupt climate change.49

3.4.4 Environmental Consequences 

This section describes the environmental consequences of the proposed action and alternatives in 

relation to GHG emissions and climate effects. 

3.4.4.1 Greenhouse Gas Emissions 

To estimate the emissions resulting from changes in passenger car and light truck CAFE 

standards, NHTSA uses the Volpe model (see Sections 2.2.1 through 2.2.4 and Section 3.1.4 for 

descriptions of the model). The change in fuel use projected to result from each alternative CAFE 

standard determines the resulting impacts on total and petroleum energy use, which in turn affects the 

amount of CO2 emissions. Reducing fuel use also lowers CO2 emissions from the use of fossil carbonbased energy during crude-oil extraction, transportation, and refining, and in the transportation, storage, 

and distribution of refined fuel. Because CO2 accounts for such a large fraction of total GHGs emitted 

during fuel production and use – more than 95 percent, even after accounting for the higher global 

 

48 The cryosphere describes the portion of Earth’s surface that is frozen water, such as snow, permafrost, floating 

ice, and glaciers. 

49 See 42 U.S.C. § 4332 (requiring federal agencies to “identify and develop methods and procedures ... which will 

insure that presently unquantified environmental amenities and values may be given appropriate consideration”); 40 

CFR § 1502.23 (requiring an EIS to discuss the relationship between a cost-benefit analysis and any analyses of 

unquantified environmental impacts, values, and amenities); CEQ, Considering Cumulative Effects Under the 

National Environmental Policy Act (1984), available at http://ceq.hss.doe.gov/nepa/ccenepa/ccenepa.htm 

(recognizing that agencies are sometimes “limited to qualitative evaluations of effects because cause-and-effect 

relationships are poorly understood” or cannot be quantified). 
Chapter 3 Affected Environment and Environmental Consequences 3.4 Climate 

 3-85 

warming potentials of other GHGs – NHTSA’s consideration of GHG impacts focuses on reductions in 

CO2 emissions resulting from the savings in fuel use that accompany higher fuel economy.50

NHTSA estimated GHG emissions for each alternative using the economic assumptions 

described in Section 2.2.4. In the discussion and table that follows, emissions reductions represent the 

differences in total annual emissions by all passenger cars or light trucks in use between their estimated 

future levels under the No Action Alternative (Alternative 1) and each action alternative (Alternatives 2 

through 9). Emissions reductions resulting from the proposed action and alternatives for MYs 2012-2016 

passenger cars and light trucks were estimated from 2012 to 2100. For each alternative, all vehicles after 

MY 2016 were assumed to meet the MY 2016 CAFE standards. Emissions were estimated for all 

alternatives through 2060, and emissions from 2061 through 2100 were assumed to remain constant at 

their levels estimated for 2060.51 Emissions under each action alternative were then compared against 

those under the No Action Alternative to determine its impact on emissions. 

Table 3.4.4-1 and Figure 3.4.4-1 show total emissions and emissions reductions resulting from 

applying the nine alternative CAFE standards to new passenger cars and light trucks from 2012 to 2100. 

Emissions for this period range from a low of 227,700 MMTCO2 under the 7%/year Increase (Alternative 

8) to 276,000 MMTCO2 under the No Action Alternative (Alternative 1). Compared to the No Action 

Alternative, projections of emissions reductions over the period 2012 to 2100 due to the MYs 2012-2016 

CAFE standards ranged from 20,700 to 48,300 MMTCO2. Compared to cumulative global emissions of 

5,293,896 MMTCO2 over this period (projected by the RCP 4.5 MiniCAM reference scenario), this 

rulemaking is expected to reduce global CO2 emissions by about 0.4 to 0.9 percent from their projected 

levels under the No Action Alternative. 

Table 3.4.4-1 

Emissions and Emissions Reductions (MMTCO2) from 2012-2100 by Alternative a/ 

Alternative Emissions 

Emissions Reductions 

Compared to No 

Action Alternative 

1 No Action 276,000 0 

2 3%/year Increase 255,300 20,700 

3 4%/year Increase 246,300 29,700 

4 ~4.3%/year Increase, Preferred 243,800 32,300 

5 5%/year Increase 238,900 37,100 

6 ~6.0%/year Increase, MNB 232,200 43,900 

7 6%/year Increase 232,100 43,900 

8 7%/year Increase 227,700 48,300 

9 ~6.6%/year Increase, TCTB 228,700 47,300 

__________

a/ The numbers in this table have been rounded for presentation purposes. As a result, the reductions 

 might not reflect the exact difference of the values in all cases. 

 

50 Although this section includes a discussion of CO2 emissions only, the climate modeling discussion in Section 

3.4.4.4 assesses the direct and indirect effects associated with emissions reductions of multiple gases, including CO2, 

CH4, N2O, SO2, CO, NOx, and VOCs. 51 See Section 3.1.3 for a summary of the scope and parameters of the Volpe model. 
3.4 Climate Chapter 3 Affected Environment an

Figure 3.4.4-1. Emissions and Emissions Reductions (MMTCO2) 

from 2012 to 2100 by Alternative 

‐

50,000

100,000150,000200,000250,000300,000

Alt. 1:

No Action

Alt. 2:

3%/year Increase

Alt. 3:

4%/year Increase

Alt. 4:

~4.3%/year

Increase, Preferred

Alt. 5:

5%/year Increase

Alt. 6:

~6.0%/year

Increase, MNB

Alt. 7:

6%/year Increase

Alt. 8:

7%/year Incre

3-86 
Chapter 3 Affected Environment and Environmental Consequences 3.4 Climate 

 3-87 

To get a sense of the relative impact of these reductions, it can be helpful to consider the relative 

importance of emissions from passenger cars and light trucks as a whole and to compare them against 

emissions projections from the transportation sector, and expected or stated goals from existing programs 

designed to reduce CO2 emissions. As mentioned earlier, U.S. passenger cars and light trucks currently 

account for a significant amount of CO2 emissions in the United States. With the action alternatives 

reducing U.S. passenger car and light truck CO2 emissions by 7.5 to 17.5 percent of cumulative emissions 

from 2012-2100, they will have a noticeable impact on total U.S. CO2 emissions. Compared to total U.S. 

CO2 emissions in 2100 of 7,886 MMTCO2 projected by the MiniCAM reference scenario (Clarke et al.

2007), the action alternatives would reduce total U.S. CO2 emissions by 3.9 to 9.1 percent in 2100. 

Figure 3.4.4-2 shows projected annual emissions from passenger cars and light trucks under the MYs 

2012-2016 alternative CAFE standards. 

As Table 3.4.4-2 shows, total CO2 emissions accounted for by the U.S. passenger car and light 

truck fleets are projected to increase substantially after 2020 under the No Action Alternative, which 

assumes average fuel economy would remain at the 2011 level for all future model years. The table also 

shows that each of the action alternatives would reduce total passenger car and light truck CO2 emissions 

in future years significantly from their projected levels under the No Action Alternative. Progressively 

larger reductions in CO2 emissions from their levels under the No Action Alternative are projected to 

occur during each future year because the action alternatives require successively higher fuel economy 

levels for MYs 2012-2016 and later passenger cars and light trucks. 

Under all of the alternatives analyzed, growth in the number of passenger cars and light trucks in 

use throughout the United States, combined with assumed increases in their average use, is projected to 

result in growth in total passenger car and light truck travel. This growth in travel overwhelms 

improvements in fuel economy for each of the alternatives, resulting in projected increases in total fuel 

consumption by U.S. passenger cars and light trucks over most of the period shown in the table. Because 

CO2 emissions are a direct consequence of total fuel consumption, the same result is projected for total 

CO2 emissions from passenger cars and light trucks. 

Emissions of CO2, the primary gas that drives climate effects, from the U.S. passenger car and 

light truck fleet represented about 3.3 percent of total global emissions of all CO2 emissions in 2005 (EPA 

2009a, WRI 2009).52 Although substantial, this source contributes a small percentage of global 

emissions, and the relative contribution of CO2 emissions from the U.S. combined passenger car and light 

truck fleet is expected to decline in the future. This expected decline is due primarily to rapid growth of 

emissions from developing economies (which result in part from growth in global transportation sector 

emissions). In the CCSP SAP 2.1 MiniCAM reference scenario, the share of liquid fuel use – mostly oil 

– from the United States as a percent of total primary energy consumption declines from 40 percent in 

2000 to 24 percent in 2100.53

As another way to provide context these GHG results, President Obama recently submitted to the 

United Nations Framework Convention on Climate Change (UNFCCC) a GHG target for the United 

States in the range of 17 percent below 2005 levels by 2020, in association with the Copenhagen Accord, 

 

52 Includes land-use change and forestry, and excludes international bunker fuels. 

53 The RCP 4.5 MiniCAM reference scenario used in the climate modeling is based on the CCSP SAP 2.1 

MiniCAM reference scenario. Both versions of the MiniCAM reference scenario in these models use the same 

assumptions for GDP, energy use, and CO2 emissions. 
3.4 Climate Chapter 3 Affected Environment an

Figure 3.4.4-2. Projected Annual Emissions (MMTCO2) by Alternative 

0

500

10001500200025003000350040004500

2010 2020 2030 2040 2050 

MMTCO2

Alt. 1: No Action Alt. 2: 3%/year IncreaseAlt. 3: 4%/year Increase Alt. 4: ~4.3%/year Increase, PreAlt. 5: 5%/year Increase Alt. 6: ~6.0%/year Increase, MNAlt. 7: 6%/year Increase Alt. 8: 7%/year IncreaseAlt. 9: ~6.6%/year Increase, TCTB

3-88 
Chapter 3 Affected Environment and Environmental Consequences 3.4 Climate 

 3-89 

Table 3.4.4-2 

Nationwide Emissions of Greenhouse Gases (MMT per Year) from Passenger Cars and 

Light Trucks by Alternative 

Alt. 1 Alt. 2 Alt. 3 Alt. 4 Alt. 5 Alt. 6 Alt. 7 Alt. 8 Alt. 9 

GHG 

and 

Year 

No 

Action 

3%/year 

Increase 

4%/year 

Increase 

~4.3%/year

Increase

Preferred 

5%/year 

Increase

~6.0%/year 

Increase

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.6%/year 

Increase 

TCTB 

Carbon dioxide (CO2) 

2010 1,730 1,730 1,730 1,730 1,730 1,730 1,730 1,730 1,730 

2020 1,810 1,730 1,700 1,690 1,670 1,640 1,650 1,630 1,630 

2030 2,120 1,970 1,900 1,880 1,840 1,790 1,790 1,760 1,770 

2040 2,570 2,360 2,280 2,250 2,200 2,140 2,140 2,100 2,100 

2050 3,140 2,890 2,780 2,750 2,690 2,610 2,610 2,550 2,570 

2060 3,840 3,530 3,400 3,360 3,280 3,190 3,180 3,120 3,140 

Methane (CH4) 

2010 2.03 2.03 2.03 2.03 2.03 2.03 2.03 2.03 2.03 

2020 2.11 2.02 1.99 1.97 1.95 1.92 1.92 1.90 1.90 

2030 2.48 2.30 2.22 2.20 2.15 2.09 2.09 2.05 2.06 

2040 3.00 2.77 2.66 2.64 2.57 2.49 2.49 2.44 2.45 

2050 3.66 3.38 3.25 3.22 3.14 3.04 3.04 2.97 2.99 

2060 4.48 4.13 3.97 3.93 3.84 3.71 3.71 3.63 3.65 

Nitrous oxide (N2O) 

2010 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.06 

2020 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 

2030 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 

2040 0.05 0.05 0.05 0.05 0.04 0.04 0.04 0.04 0.04 

2050 0.06 0.06 0.06 0.06 0.05 0.05 0.05 0.05 0.05 

2060 0.07 0.07 0.07 0.07 0.07 0.06 0.06 0.06 0.06 

and in conformity with anticipated U.S. energy and climate legislation.54 While the proposed action 

contributes to meeting that goal, the action alternatives would result in projected CO2 emissions from the 

light duty vehicle sector in 2020 in the range of 0.6 percent above (Alternative 2) to 5.4 below 

(Alternative 9) 2005 levels. Thus, none of the alternatives considered would reduce 2020 emissions from 

passenger cars and light trucks by 17 percent from their 2005 level.55 This occurs because the increases 

in fuel economy required by even those alternatives that would increase CAFE standards most rapidl

(Alternatives 7, 8, and 9) are insufficient to offset the effect on total emissions from projected increases in 

total VMT by passenger cars and light trucks. 

y 

 

NHTSA emphasizes that the President’s stated policy goal outlined above does not specify that 

every emitting sector of the economy must contribute equally proportional emissions reductions. 

Significantly, the action of setting fuel economy standards does not directly regulate total emissions from 

54 On January 28, 2010, the U.S. submitted this target to the U.N. Framework Convention on Climate Change as part 

of a January 31 deadline negotiated in Copenhagen in December 2009, “in conformity with anticipated U.S. energy 

and climate legislation, recognizing that the final target will be reported to the [U.N.] in light of enacted legislation.” 

(U.S. Department of State 2010) 

55 A 17% reduction would mean a reduction of 293 MMTCO2 from 2005 levels, or 375 from the No Action baseline. 
3.4 Climate Chapter 3 Affected Environment and Environmental Consequences 

 3-90

passenger cars and light trucks. NHTSA’s authority to promulgate new fuel economy standards is a 

limited authority and does not allow NHTSA to regulate other factors affecting emissions, including 

society’s driving habits. Specifically, NHTSA notes that under all of the alternatives analyzed, growth in 

the number of passenger cars and light trucks in use throughout the U.S., combined with assumed 

increases in their average use (annual vehicle-miles traveled per vehicle), is projected to result in growth 

in total passenger car and light truck travel. 

This projected growth in travel is expected to more than offset the effect of improvements in fuel 

economy required under each of the alternatives, resulting in increases in total fuel consumption by U.S. 

passenger cars and light trucks. Because CO2 emissions are a direct consequence of total fuel 

consumption, the same result is projected for total CO2 emissions from passenger cars and light trucks. 

As Figure 3.4.4-3 shows, NHTSA estimates that the proposed CAFE standards will reduce CO2

emissions significantly from the future levels that would otherwise be estimated to occur in the absence of 

the CAFE program. These reductions in emissions are also sufficient to reduce total passenger car and 

light truck emissions during 2020 below their 2005 levels (for all alternatives except Alternative 2); 

however, none of the alternatives would reduce emissions sufficiently to achieve the target reduction of 

17 percent from 2005 levels. These calculations are meant to present the agency’s action as compared to 

some stated national policy goal to which a decisionmaker or reader might relate. 

Figure 3.4.4-4 shows CO2 reductions from the alternatives in 2016 expressed as equivalent to the 

number of passenger cars and light trucks that would produce those emissions in that year. The emissions 

reductions from the action alternatives are equivalent to the annual emissions of between 3.60 million cars 

(Alternative 2) and 9.70 million cars (Alternative 9) in 2016, as compared to the annual emissions that 

would occur in the absence of CAFE standards under the No Action Alternative. Emissions reductions in 

2016 from the Preferred Alternative (Alternative 4) are equivalent to the annual emissions of 6.26 million 

cars. Annual CO2 reductions, their equivalent in vehicles, and differences among alternatives grow larger 

in future years as older vehicles are increasingly replaced by newer ones meeting the progressively higher 

CAFE standards required by each alternative.56 

These emissions reductions can also be compared to existing programs designed to reduce GHG 

emissions in the United States. In 2007, Arizona, California, New Mexico, Oregon, and Washington 

formed the Western Climate Initiative (WCI) to develop regional strategies to address climate change. 

The WCI stated a goal of reducing 350 MMTCO2 equivalent over the period 2009 to 2020 (WCI 

2007a).57 If this goal is achieved, emissions levels in 2020 would be 33-percent lower than projected 

2020 emissions levels under a business as usual scenario, and 15-percent lower than those at the 

beginning of the WCI action (WCI 2007b). By comparison, the proposed CAFE rulemaking is expected 

to reduce CO2 emissions by 290 to 730 MMTCO2 over the same period (depending on alternative), with 

emissions levels in 2020 representing a 4- to 10-percent reduction from the future baseline emissions for 

passenger cars and light trucks. 

 

56 The passenger vehicle equivalency is based on an average per-vehicle emissions estimate, which includes both 

tailpipe CO2 emissions and associated upstream emissions from fuel production and distribution. The average light 

duty vehicle accounts for approximately 7.94 metric tons of CO2 in the year 2016 based on Volpe model analysis. 57 Since this goal was initially stated, Montana, Quebec, and Ontario joined the WCI. Thus, the total emissions 

reduction is likely to be greater than 350 MMTCO2. A revised estimate was not available as of January 25, 2010. 
Chapter 3 Affected Environment and Environmental Consequences 

Figure 3.4.4-3. Projected Annual Emissions by Alternative, Compared to 2005 Levels for C

Light Trucks 

12001300140015001600170018001900

2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 

CO2 Emissions(MMTCO2)

Alt. 1 Alt. 2 Alt. 3 Alt. 4 Alt. 5 Alt. 6 Alt. 7 Alt. 8 Alt. 9 17% below 

17% below 2005 = 1,430.9 MMTCO2

Note: 2005 CO2 emissions from light‐duty vehicles are 1,723.9 MMTCO2.

3-91 
3.4 Climate Chapter 3 Affected Environment an

3-92 

Figure 3.4.4-4. Number of Passenger Cars and Light Trucks Equivalent to CO2 Reductions in 2016, C

No Action Alternative 
Chapter 3 Affected Environment and Environmental Consequences 3.4 Climate 

 3-93 

Nine northeast and mid-Atlantic states have formed the Regional Greenhouse Gas Initiative 

(RGGI) to reduce CO2 emissions from power plants in the northeast. Emissions reductions from 2006 to 

2024 were estimated at 268 MMTCO2 (RGGI 2006).58 This represents a 23-percent reduction from the 

future baseline and a 10-percent reduction in 2024 emissions from their levels at the beginning of the 

action (RGGI 2006). By comparison, NHTSA forecasts that the proposed CAFE rulemaking would 

reduce CO2 emissions by 670 to 1,650 MMTCO2 over this period (depending on alternative), with 

emissions levels in 2024 representing a 6- to 14-percent reduction from the future baseline emissions for 

passenger cars and light trucks. 

Two features of these comparisons are extremely important to emphasize. First, emissions from 

the sources addressed in the WCI and RGGI plans are projected to decrease compared to the beginning of 

the action, while emissions from passenger cars and light trucks are projected to increase under all 

alternatives for this proposed rulemaking due to increases in vehicle ownership and use. Second, these 

projections are only estimates, and the scope of these climate programs differs from that in the scope of 

the proposed rulemaking in terms of geography, sector, and purpose. 

In 2004, Robert Socolow and Stephen Pacala first introduced the concept of stabilization 

“wedges” − idealizing a new scheme of dividing necessary emissions reductions to prevent atmospheric 

CO2 levels from doubling in the next 50 years (Pacala and Socolow 2004). In 2004, the concentration of 

atmospheric CO2 was about 375 ppm. Socolow and Pacala proposed to stabilize atmospheric CO2 at a 

maximum concentration of approximately 500 ppm for the next 50 years to prevent the most damaging 

forms of climate change. Stabilization at 500 ppm would require that emissions be held near the present 

level of 7 billion tons of carbon59 per year (GtC/year) for the next 50 years. Socolow and Pacala depicted 

the necessary reductions in emissions from their projected increase over the next 50 years as a triangle, 

with progressively larger reductions in emissions from their projected level required during each 

successive future year (see Figure 3.4.4-5). 

Socolow and Pacala divided the stabilization triangle into wedges, with each wedge representing 

an activity that reduces projected growth in carbon emissions by progressively larger amounts each year 

over a 50-year period ending in 2055, with the reduction reaching 1 billion tons annually in 2055. 

Socolow and Pacala estimated that approximately seven wedges of this size would be needed to fill the 

stabilization triangle (see Figure 3.4.4-6). 

Wedges can be achieved from improvements in energy efficiency, decarbonization of energy 

sources, decarbonization of fuels, and from forests and agricultural soils. For example, approximately 

one wedge could be achieved from improvements in either fuel efficiency, reduced reliance on passenger 

cars, storing CO2 from power and hydrogen plants, or reduced deforestation. Note that this wedge 

approach does not assess what the most appropriate global reduction should be, nor does it include an 

assessment of the economic costs of achieving that goal (whatever it may be), and the wedges could look 

fundamentally different depending on the approach taken, for example, mandating reductions versus an 

economy-wide market-based approach. 

 

58 Emissions reductions were estimated by determining the difference between the RGGI Cap and the Phase III 

RGGI reference case. These estimates do not include offsets. Offsets are credits that are created by projects outside 

of the cap system that decrease or sequester emissions in a way that is additional, verifiable, and permanent. 

Capped/regulated entities can use these offsets for compliance, thus allowing regulated entities to emit more, but 

allow reductions elsewhere. 

59 Socolow and Pacala present their analysis in terms of carbon, whereas this EIS discusses emissions in terms of 

CO2. One ton of carbon equals roughly 3.67 tons of CO2. 
3.4 Climate Chapter 3 Affected Environment and Environmental Consequences 

 3-94 

Figure 3.4.4-5. Historical Carbon Emissions with Two Potential 

Pathways for the Future (Source: Socolow et al. 2004) 

Figure 3.4.4-6. Stabilization Wedges (Source: Socolow et al. 2004) 

 

Socolow and Pacala estimate that improving the average fuel economy of the world’s combined 

passenger car and light truck fleet from an average of 30 mpg on conventional fuel to 60 mpg in 50 years 

(i.e., by 2055) would achieve one wedge.60 Their estimate is based on a global fleet of approximately 2 

billion passenger cars and light trucks, averaging 10,000 miles per year. 

 

60 Id.; see also http://www.princeton.edu/~cmi/resources/wedgesumtb.htm (listing 15 examples of potential wedges). 
Chapter 3 Affected Environment and Environmental Consequences 3.4 Climate 

 3-95 

By comparison, NHTSA estimates that the number of passenger cars and light trucks in use 

throughout the United States will increase to more than 310 million by 2055, the same year Socolow and 

Pacala analyzed, and that under the No Action alternative these vehicles will be driven an average of 

almost 22,000 miles. Thus, in total, NHTSA projects that passenger cars and light trucks in the United 

States will be driven more than 6.8 trillion miles during 2055 under the No Action Alternative. NHTSA 

estimates that the progressively higher fuel economy levels required by the eight action alternatives 

considered in this EIS (allowing for the accompanying increases in average vehicle use) would reduce 

total passenger car and light truck fuel consumption during 2055 by 23 billion gallons (under Alternative 

2) to as much as 57 billion gallons (under Alternative 8). As a consequence, CO2 emissions attributable 

to U.S. passenger car and light truck use in 2055 would decline by the equivalent of 8 percent (Alternative 

2) to 19 percent (Alternative 9) of the emissions reductions corresponding to one “stabilization wedge.”61 

NHTSA emphasizes that the action of setting fuel economy standards does not directly regulate 

emissions from passenger cars and light trucks. NHTSA’s authority to promulgate new fuel economy 

standards does not allow it to regulate other factors affecting emissions, including society’s driving 

habits. NHTSA does not have the authority to control the increase of vehicles on the road or the amount 

of miles people drive. NHTSA’s authority is to establish average fuel economy standards for each model 

year at “the maximum feasible average fuel economy that the Secretary decides the manufacturers can 

achieve in that model year.” 49 U.S.C. § 32902(a). NHTSA estimates that the various alternatives being 

considered will decrease emissions from what they otherwise would be if the agency did not increase 

CAFE standards. However, due to the continued growth of VMT that the government forecasts, 

increased efficiency of internal combustion engines will not decrease total emissions from passenger cars 

and light trucks, although it will significantly slow the rate at which emissions from these vehicles 

increase, as mentioned above and as illustrated in Figure 3.4.4-2. 

Where information in the analysis included in this EIS is incomplete or unavailable, NHTSA has 

relied on the CEQ regulations regarding incomplete or unavailable information (see 40 CFR § 

1502.22(b)). In this case, the comparison of emissions reductions from the alternative CAFE standards to 

emissions reductions associated with other programs is intended to benefit decisionmakers by providing 

relative benchmarks, rather than absolute metrics, for selecting among alternatives. In summary, the 

alternatives analyzed herein deliver GHG emissions reductions that are on the same scale as many of the 

most progressive and ambitious GHG emissions reduction programs underway in the United States. 

3.4.4.2 Direct and Indirect Effects on Climate Change 

Sections 3.4.4.2.1 through 3.4.4.2.5 describe the direct and indirect effects of the alternatives on 

four relevant climate change indicators: atmospheric CO2 concentrations, temperature, precipitation, and 

sea-level rise. 

3.4.4.2.1 Atmospheric CO2 Concentrations 

MAGICC 5.3.v2 is a simple climate model that is well calibrated to the mean of the multi-model 

ensemble results for three of the most commonly used emissions scenarios – B1 (low), A1B (medium), 

and A2 (high) from the IPCC SRES series – as shown in Table 3.4.4-3.62 As the table indicates, the 

results of the model runs developed for this analysis agree relatively well with IPCC estimates for both 

CO2 concentrations and surface temperature. 

 

61 These “wedge equivalents” of the alternative CAFE standards considered in this EIS account for the fact that the 

emissions reductions they would produce would not begin until 2012, later than the 2005 initial year for emissions 

reductions assumed in the Socolow Pacala analysis. 

62 NHTSA used the default climate sensitivity in MAGICC of 3.0 °C (5.4 °F). 
3.4 Climate Chapter 3 Affected Environment and Environmental Consequences 

Table 3.4.4-3 

Comparison of MAGICC Modeling Results and Reported IPCC Results 

(IPCC 2007) a/ 

CO2 Concentration 

(ppm) 

Global Mean Increase 

in Surface Temperature 

(°C) Sea-Level Rise (cm) 

Scenario

IPCC 

WGI 

(2100) 

MAGICC 

(2100) 

IPCC WGI 

(2080-2099) 

MAGICC 

(2090) 

IPCC WGI 

(2090-2099) a/

MAGICC 

(2095) 

B1 (low) 550 538.3 1.79 1.81 28 26 

A1B (medium) 715 717.2 2.65 2.76 35 35 

A2 (high) 836 866.8 3.13 3.31 37 38 

_______________ 

a/ The IPCC values represent the average of the 5- to 95-percent range of the rise of sea level between 1980 to 

 1989 and 2090 to 2099. 

A comparison of sea-level rise from MAGICC 5.3.v2 and the IPCC Fourth Assessment Report is 

presented in the release documentation for MAGICC 5.3.v2 (Wigley 2008). In Table 3 of the 

documentation, Wigley presents the results for six SRES scenarios, which show that the comparable value 

for sea-level rise from MAGICC 5.3.v2 (total sea-level rise minus estimates for contributions from nonmelt sources such as warming of the permafrost) within 0.01 centimeter in 2095. 

As discussed in Section 3.4.3, NHTSA used the RCP 4.5 MiniCAM reference scenario to 

represent the No Action Alternative in the MAGICC modeling runs. Table 3.4.4-4 and Figures 3.4.4-7 

through 3.4.4-10 present the results of MAGICC simulations for the No Action Alternative and the eight 

action alternatives in terms of CO2 concentrations and increases in global mean surface temperature in 

2030, 2050, and 2100. As Figures 3.4.4-9 and 3.4.4-10 show, the reduction in the increases in projected 

CO2 concentrations and temperature from each of the action alternatives amounts to a small fraction of 

the total increases in CO2 concentrations and global mean surface temperature. However, the relative 

impact of the action alternatives is shown by the reduction in increases of both CO2 concentrations and 

temperature under Alternative 9. As shown in Figures 3.4.4-9 and 3.4.4-10, the reduction in increase of 

CO2 concentrations by 2100 under Alternative 9 is more than twice that of Alternative 2. Similarly, the 

reduction in increase of temperature under Alternative 9 is more than twice that of Alternative 2. 

As shown in Table 3.4.4-4 and Figures 3.4.4-7 through 3.4.4-10, estimated CO2 concentrations 

for 2100 range from 778.4 ppm under Alternative 8 to 783.0 ppm under the No Action Alternative. For 

2030 and 2050, the corresponding range is even smaller. Because CO2 concentrations are the key driver 

of other climate effects (which in turn act as drivers on the resource impacts discussed in Section 4.5), this 

leads to small differences in these effects. While these effects are small, they occur on a global scale and 

are long-lived. 

 3-96 
Chapter 3 Affected Environment and Environmental Consequences 3.4 Climate 

 3-97 

Table 3.4.4-4 

CO2 Concentrations, Global Mean Surface Temperature Increase, and Sea-Level Rise Using MAGICC (RCP 

MiniCAM Reference) by Alternative a/

CO2 Concentration 

(ppm) 

Global Mean Surface 

Temperature Increase

(°C) Sea-Level Rise (cm) 

Totals by Alternative 2030 2050 2100 2030 2050 2100 2030 2050 2100 

1 No Action 441.8 514.8 783.0 0.923 1.557 3.136 8.38 15.17 38.00 

2 3%/year Increase 441.6 514.3 781.0 0.922 1.554 3.128 8.38 15.16 37.94 

3 4%/year Increase 441.5 514.0 780.2 0.922 1.553 3.125 8.38 15.15 37.91 

4 ~4.3%/year Increase, Preferred 441.5 514.0 779.9 0.922 1.553 3.124 8.38 15.15 37.90 

5 5%/year Increase 441.5 513.8 779.5 0.921 1.552 3.122 8.38 15.15 37.88 

6 ~6.0%/year Increase, MNB 441.4 513.7 778.8 0.921 1.551 3.120 8.38 15.14 37.86 

7 6%/year Increase 441.4 513.7 778.8 0.921 1.551 3.120 8.38 15.14 37.86 

8 7%/year Increase 441.4 513.6 778.4 0.921 1.551 3.118 8.38 15.14 37.84 

9 ~6.6%/year Increase, TCTB 441.4 513.6 778.5 0.921 1.551 3.118 8.38 15.14 37.84 

Reductions Under Alternative CAFE Standards

2 3%/year Increase 0.2 0.5 2.0 0.001 0.002 0.007 0.00 0.01 0.06 

3 4%/year Increase 0.3 0.8 2.8 0.001 0.003 0.011 0.00 0.02 0.09 

4 ~4.3%/year Increase, Preferred 0.3 0.8 3.1 0.001 0.004 0.012 0.00 0.02 0.10 

5 5%/year Increase 0.3 1.0 3.5 0.002 0.004 0.014 0.00 0.02 0.12 

6 ~6.0%/year Increase, MNB 0.4 1.1 4.2 0.002 0.006 0.016 0.00 0.03 0.14 

7 6%/year Increase 0.4 1.1 4.2 0.002 0.006 0.016 0.00 0.03 0.14 

8 7%/year Increase 0.4 1.2 4.6 0.002 0.006 0.018 0.00 0.03 0.16 

9 ~6.6%/year Increase, TCTB 0.4 1.2 4.5 0.002 0.006 0.017 0.00 0.03 0.16 

__________ 

a/ The numbers in this table have been rounded for presentation purposes. As a result, the reductions might not 

reflect the exact difference of the values in all cases. 
3.4 Climate Chapter 3 Affected Environment an

Figure 3.4.4-7. CO2 Concentrations (ppm) 

0

100200300400500600700800900

2030 2050 2100

ppm

No Action Al t. 2: 3%/yea r Increa seAl t. 3: 4%/yea r Increa se Al t. 4: ~4.3%/yea r Increa se, Pre ferredAl t. 5: 5%/yea r Increa se Al t. 6: ~6.0%/yea r Increa se, MNBAl t. 7: 6%/yea r Increa se Al t. 8: 7%/yea r Increa seAl t. 9: ~6.6%/yea r Increa se, TCTB

3-98 
Chapter 3 Affected Environment and Environmental Consequences 

Figure 3.4.4-8. Global Mean Surface Temperature Increase (°C) 

0

0.5

1

1.5

2

2.5

3

3.5

2030 2050 2100

degrees Celsius

No Action Al t. 2: 3%/yea r Increa seAl t. 3: 4%/yea r Increa se Al t. 4: ~4.3%/yea r Increa se, Pre ferredAl t. 5: 5%/yea r Increa se Al t. 6: ~6.0%/yea r Increa se, MNBAl t. 7: 6%/yea r Increa se Al t. 8: 7%/yea r Increa seAl t. 9: ~6.6%/yea r Increa se, TCTB

3-99 
3.4 Climate Chapter 3 Affected Environment an

Figure 3.4.4-9. Reduction in CO2 Concentrations (ppm) Compared to the No Action Altern

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

2030 2050 2100

ppm

Al t. 2: 3%/yea r Increa se Al t. 3: 4%/yea r Increa se Al t. 4: ~4.3%/yea r Increa seAl t. 5: 5%/yea r Increa se Al t. 6: ~6.0%/yea r Increa se, MNB Al t. 7: 6%/yea r Increa seAl t. 8: 7%/yea r Increa se Al t. 9: ~6.6%/yea r Increa se, TCTB

3-100 
Chapter 3 Affected Environment and Environmental Consequences 

3-101 

Figure 3.4.4-10. Reduction in Global Mean Temperature Compared to the No Action Alter

0.0000.0020.0040.0060.0080.0100.0120.0140.0160.0180.020

2030 2050 2100

degrees Celsius

Al t. 2: 3%/yea r Increa se Al t. 3: 4%/yea r Increa se Al t. 4: ~4.3%/yea r Increa se, Pre feAl t. 5: 5%/yea r Increa se Al t. 6: ~6.0%/yea r Increa se, MNB Al t. 7: 6%/yea r Increa seAl t. 8: 7%/yea r Increa se Al t. 9: ~6.6%/yea r Increa se, TCTB
3.4 Climate Chapter 3 Affected Environment and Environmental Consequences 

3.4.4.2.2 Temperature 

Table 3.4.4.4 lists MAGICC simulations of mean global surface air temperature increases. Under 

the No Action Alternative, the temperature increase from 1990 is 0.92 °C (1.65 °F) for 2030, 1.56 °C 

(2.80 °F) for 2050, and 3.14 °C (5.65 °F) for 2100. The differences among alternatives are small. For 

2100, the reduction in temperature increase in relation to the No Action Alternative ranges from 0.007 °C 

(0.013 °F) to 0.018 °C (0.032 °F). 

Table 3.4.4-5 summarizes the regional changes in warming and seasonal temperatures presented 

in the IPCC Fourth Assessment Report. At this time, quantifying the changes to regional climate from the 

CAFE alternatives is not possible due to the limitations of existing climate models, but the alternatives 

would be expected to reduce the impacts in proportion to the amount of reduction in global mean surface 

temperature. 

Table 3.4.4-5 

Summary of Regional Changes to Warming and Seasonal Temperatures 

Extracted from the IPCC Fourth Assessment Report (Christensen et al. 2007) 

Land Area Sub-region Mean Warming 

Maximum Summer 

Temperatures 

Mediterranean area 

and northern Sahara 

Southern Africa and 

western margins 

Africa 

East Africa 

Likely larger than global 

mean throughout continent 

and in all seasons 

Northern Europe 

Southern and Central 

Europe 

Maximum summer temperatures likely to 

increase more than the average 

Mediterranean 

and Europe 

Mediterranean area 

Likely to increase more than 

the global mean with largest 

warming in winter 

Asia Central Asia Likely to be well above the 

global mean 

Tibetan Plateau Likely to be well above the 

global mean 

Northern Asia Likely to be well above the 

global mean 

Eastern Asia Likely to be above the 

global mean 

Very likely that heat waves/hot spells in 

summer will be longer, more intense, and 

more frequent 

Very likely fewer very cold days 

South Asia Likely to be above the 

global mean 

Very likely fewer very cold days 

Southeast Asia Likely to be similar to the 

global mean 

North America Northern 

regions/Northern North 

America 

Likely to exceed the global 

mean warming 

Warming is likely to be greatest in winter. 

Minimum winter temperatures are likely 

to increase more than the average 

Southwest Warming is likely to be greatest in 

summer 

Maximum summer temperatures are 

likely to increase more than the average 

 3-102 
Chapter 3 Affected Environment and Environmental Consequences 3.4 Climate 

 3-103 

Table 3.4.4-5 (cont’d) 

Summary of Regional Changes to Warming and Seasonal Temperatures 

Extracted from the IPCC Fourth Assessment Report (Christensen et al. 2007)

Land Area Sub-region Mean Warming 

Maximum Summer 

Temperatures 

Northeast USA 

Southern Canada 

Canada 

Northernmost part of 

Canada 

Central and South 

America 

Southern South 

America 

Likely to be similar to the 

global mean warming 

Central America Likely to be larger than 

global mean warming 

Southern Andes 

Tierra del Fuego 

Southeastern South 

America 

Northern South 

America 

Australia and New 

Zealand 

Southern Australia Likely comparable to the 

global mean but less than in 

the rest of Australia 

Increased frequency of extreme high 

daily temperatures and decreased 

frequency of cold extremes are very 

likely

Southwestern Australia Likely comparable to the 

global mean 

Rest of Australia Likely comparable to the 

global mean 

New Zealand, South 

Island 

Likely less than the global 

mean 

Rest of New Zealand Likely comparable to the 

global mean 

Polar Regions Arctic Very likely to warm during 

this century more than the 

global mean 

Warming greatest in winter and smallest 

in summer 

Antarctic Likely to warm 

Small Islands Likely to be smaller than the 

global annual mean 

MAGICC 5.3.v2 estimates radiative forcing from black carbon, a primary aerosol emitted 

through the incomplete combustion of fossil fuel and biomass burning. However, emissions trends for 

black carbon are “hard-wired” in the model to follow emissions of SO2 and cannot be specified as 

separate inputs to the model.63 The radiative forcing of black carbon is difficult to accurately quantify 

because it is a function of microphysical properties of the geographic and vertical placement, and lifetime 

 

63 Accurately determining the magnitude of mobile source emissions of black carbon is difficult because the 

emissions vary with fuel properties and fluctuations in the combustion environment. MOBILE6.2 outputs 

particulate matter mass that is then incorporated in the Volpe model. This particulate matter is based on tailpipe 

emissions and therefore includes carbon emissions from the combustion process. Because the carbon emissions are 

included as part of the particular matter and are not treated independently, the Volpe model does not provide direct 

results of the impact of the carbon emissions. 
3.4 Climate Chapter 3 Affected Environment and Environmental Consequences 

 3-104 

of the aerosol; however, it is not clear that black carbon contributes substantially to global warming 

(Jacobson 2001). Total global black carbon emissions are estimated to be approximately 8 Teragrams of 

carbon per year (Tg C/yr) (Bond et al. 2004 in Forster et al. 2007) with estimates of fossil fuel 

contributions ranging from 2.8 Tg C/yr (Ito and Penner 2005 in Forster et al. 2007) to 8.0 Tg C/yr 

(Haywood and Boucher in Forster et al. 2007).64 In summary, the climate modeling accounts for the 

effects of black carbon on climate variables. 

3.4.4.2.3 Precipitation 

In some areas, higher temperatures might increase precipitation. Increases in precipitation are a 

result of higher temperatures causing greater water evaporation, which causes more water vapor to be 

available for precipitation (EPA 2009b). Increased evaporation leads to increased precipitation in areas 

where there is sufficient surface water, such as over oceans and lakes. In drier areas, the increased 

evaporation can actually accelerate surface drying, which can lead to drought conditions (EPA 2009b). 

Overall, according to IPCC (Meehl et al. 2007a), global mean precipitation is expected to increase under 

all scenarios. However, there will be considerable spatial and seasonal variations. Generally, 

precipitation increases are very likely to occur in high latitudes, and decreases are likely to occur in the 

sub-tropics (EPA 2009b). 

Where information in the analysis included in this EIS is incomplete or unavailable, NHTSA has 

relied on the CEQ regulations regarding incomplete or unavailable information (see 40 CFR § 

1502.22(b)). As noted earlier in the methodology section, MAGICC does not directly simulate changes 

in precipitation, and it was not feasible to undertake precipitation modeling with a full AtmosphericOcean General Circulation Model within the time and resources available for this EIS. In this case, the 

IPCC (Meehl et al. 2007a) summary of precipitation represents the most thoroughly reviewed, credible 

means of producing an assessment of this highly uncertain factor. NHTSA expects that the proposed 

action and alternatives would reduce anticipated changes in precipitation (i.e., in a reference case with no 

GHG emission reduction policies) in proportion to the alternatives’ effects on temperature. 

The global mean change in precipitation provided by the IPCC for the A2 (high), A1B (medium), 

and B1 (low) scenarios (Meehl et al. 2007a) is given as the scaled change in precipitation (as a percentage 

change from 1980 to 1999 averages) divided by the increase in global mean surface warming for the same 

period (per °C) as shown in Table 3.4.4-6. The IPCC provides scaling factors in the year ranges of 2011 

to 2030, 2046 to 2065, 2080 to 2099, and 2180 to 2199. NHTSA used the scaling factors for the RCP 4.5 

MiniCAM reference scenario in this analysis because MAGICC does not directly estimate changes in 

global mean precipitation.65

Table 3.4.4-6 

Global Mean Precipitation Change (scaled, % per °C) (Meehl et al. 2007a) 

Scenario 2011-2030 2046-2065 2080-2099 2180-2199 

A2 (high) 1.38 1.33 1.45 NA 

A1B (medium) 1.45 1.51 1.63 1.68 

B1 (low) 1.62 1.65 1.88 1.89 

Applying these scaling factors to the reductions in global mean surface warming provides 

estimates of changes in global mean precipitation. Given that the CAFE action alternatives reduce 

 

64 Bond et al. 2004 estimates black carbon in PM10 to be 8.0 Tg/yr, with black carbon in PM2.5 at 6.5 Tg/yr. 65 Although MAGICC does not estimate changes in precipitation, SCENGEN does. 
Chapter 3 Affected Environment and Environmental Consequences 3.4 Climate 

temperature increases slightly in relation to the No Action Alternative, they also slightly reduce predicted 

increases in precipitation, as shown in Table 3.4.4-7 (again based on the A1B [medium] scenario). 

In addition to changes in mean annual precipitation, climate change is anticipated to affect the 

intensity of precipitation, as described below (Meehl et al. 2007a): 

Intensity of precipitation events is projected to increase, particularly in tropical and high 

latitude areas that experience increases in mean precipitation. Even in areas where mean 

precipitation decreases (most subtropical and mid-latitude regions), precipitation intensity 

is projected to increase but there would be longer periods between rainfall events. There 

is a tendency for drying of the mid-continental areas during summer, indicating a greater 

risk of droughts in those regions. Precipitation extremes increase more than does the 

mean in most tropical and mid- and high-latitude areas. 

Table 3.4.4-7 

Global Mean Precipitation (Percent Change) Based on MiniCAM Reference Scenario Using Increases in 

Global Mean Surface Temperature Simulated by MAGICC by Alternative a/ 

Scenario 2020 2055 2090 

Global Mean Precipitation Change (scaled, % K-1) 1.45 1.51 1.63 

Global Temperature Above Average 1980-1999 Levels (K) for the MiniCAM reference Scenario and 

Alternative CAFE Standards, Volpe Reference Results 

1 No Action 0.648 1.716 2.816 

2 3%/year Increase 0.648 1.713 2.809 

3 4%/year Increase 0.648 1.712 2.806 

4 ~4.3%/year Increase, Preferred 0.648 1.712 2.806 

5 5%/year Increase 0.648 1.711 2.804 

6 ~6.0%/year Increase, MNB 0.648 1.709 2.801 

7 6%/year Increase 0.648 1.709 2.801 

8 7%/year Increase 0.648 1.709 2.800 

9 ~6.6%/year Increase, TCTB 0.648 1.709 2.800 

Reduction in Global Temperature (K) for Alternative CAFE Standards, Mid-level Results (Compared to No 

Action Alternative) 

2 3%/year Increase 0.000 0.003 0.006 

3 4%/year Increase 0.000 0.004 0.009 

4 ~4.3%/year Increase, Preferred 0.000 0.004 0.010 

5 5%/year Increase 0.000 0.005 0.012 

6 ~6.0%/year Increase, MNB 0.000 0.007 0.014 

7 6%/year Increase 0.000 0.007 0.014 

8 7%/year Increase 0.000 0.007 0.016 

9 ~6.6%/year Increase, TCTB 0.000 0.007 0.016 

Volpe Reference level Global Mean Precipitation Change (%)

1 No Action 0.94% 2.59% 4.59% 

2 3%/year Increase 0.94% 2.59% 4.58% 

3 4%/year Increase 0.94% 2.58% 4.57% 

4 ~4.3%/year Increase, Preferred 0.94% 2.58% 4.57% 

5 5%/year Increase 0.94% 2.58% 4.57% 

6 ~6.0%/year Increase, MNB 0.94% 2.58% 4.57% 

7 6%/year Increase 0.94% 2.58% 4.57% 

8 7%/year Increase 0.94% 2.58% 4.56% 

9 ~6.6%/year Increase, TCTB 0.94% 2.58% 4.56% 

 3-105 
3.4 Climate Chapter 3 Affected Environment and Environmental Consequences 

Table 3.4.4-7 (cont’d) 

Global Mean Precipitation (Percent Change) Based on MiniCAM Reference Scenario Using Increases in 

Global Mean Surface Temperature Simulated by MAGICC by Alternative a/ 

Scenario 2020 2055 2090 

Reduction in Global Mean Precipitation Change for Alternative CAFE Standards (% Compared to 

No Action Alternative)

2 3%/year Increase 0.00% 0.00% 0.01% 

3 4%/year Increase 0.00% 0.01% 0.02% 

4 ~4.3%/year Increase, Preferred 0.00% 0.01% 0.02% 

5 5%/year Increase 0.00% 0.01% 0.02% 

6 ~6.0%/year Increase, MNB 0.00% 0.01% 0.02% 

7 6%/year Increase 0.00% 0.01% 0.02% 

8 7%/year Increase 0.00% 0.01% 0.03% 

9 ~6.6%/year Increase, TCTB 0.00% 0.01% 0.03% 

____________________

a/ Note: The numbers in this table have been rounded for presentation purposes. As a result, the reductions 

might not reflect the exact difference of the values in all cases. 

Regional variations and changes in the intensity of precipitation events cannot be quantified 

further, primarily due to the unavailability of AOGCMs required to estimate these changes. These 

models are typically used to provide results among scenarios with very large changes in emissions, such 

as the SRES B1 (low), A1B (medium), and A2 (high) scenarios; very small changes in emissions profiles 

would produce results that would be difficult to resolve among scenarios with small changes in emissions. 

Also, the multiple AOGCMs produce results that are regionally consistent in some cases but inconsistent 

for other areas. 

Table 3.4.4-8 summarizes the regional changes in precipitation from the IPCC Fourth Assessment 

Report. Quantifying the changes in regional climate from the alternative CAFE standards is not possible 

at present, but they would be expected to reduce the changes in relation to the reduction in global mean 

surface temperature. 

3.4.4.2.4 Sea-level Rise 

IPCC identifies four primary components of sea-level rise: (1) thermal expansion of ocean water, 

(2) melting of glaciers and ice caps, (3) loss of land-based ice in Antarctica, and (4) loss of land-based ice 

in Greenland (IPCC 2007b). Ice-sheet discharge is an additional factor that could influence sea level over 

the long term. Ocean circulation, changes in atmospheric pressure, and geological processes can also 

influence sea-level rise at a regional scale (EPA 2009b). MAGICC calculates the oceanic thermal 

expansion component of global mean sea-level rise using a nonlinear temperature- and pressuredependent expansion coefficient (Wigley 2008). It also addresses the other three primary components 

through ice-melt models for small glaciers and the Greenland and Antarctic ice sheets, and excludes nonmelt sources, which the IPCC Fourth Assessment Report also excluded. Neither MAGICC 5.3.v2 nor the 

IPCC Fourth Assessment Report includes more recent information, suggesting that ice flow from 

Greenland and Antarctica will be accelerated. The Fourth Assessment Report estimates the ice flow to be 

between 9 and 17 centimeters (3.5 and 6.7 inches) by 2100 (Wigley 2008). 

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Chapter 3 Affected Environment and Environmental Consequences 3.4 Climate 

Table 3.4.4-8 

Summary of Regional Changes to Precipitation Extracted from the IPCC Fourth Assessment Report 

(Christensen et al. 2007) 

Land Area Sub-region Precipitation 

Snow Season and 

Snow Depth 

Mediterranean area 

and northern Sahara 

Very likely to decrease 

Southern Africa and 

western margins 

Winter rainfall likely to decrease in southern 

parts 

Africa 

East Africa Likely to be an increase in annual mean 

rainfall 

Northern Europe Very likely to increase and extremes are 

likely to increase 

Southern and Central 

Europe 

Mediterranean 

and Europe 

Mediterranean area Very likely to decrease and precipitation days 

are very likely to decrease 

Likely to decrease. 

Asia Central Asia Precipitation in summer is likely to decrease 

Tibetan Plateau Precipitation in boreal winter is very likely to 

increase 

Northern Asia Precipitation in boreal winter is very likely to 

increase 

Precipitation in summer is likely to increase 

Eastern Asia Precipitation in boreal winter is likely to 

increase 

Precipitation in summer is likely to increase 

Very likely to be an increase in the frequency 

of intense precipitation 

Extreme rainfall and winds associated with 

tropical cyclones are likely to increase 

South Asia Precipitation in summer is likely to increase 

Very likely to be an increase in the frequency 

of intense precipitation 

Extreme rainfall and winds associated with 

tropical cyclones are likely to increase 

Southeast Asia Precipitation in boreal winter is likely to 

increase in southern parts 

Precipitation in summer is likely to increase 

in most parts 

Extreme rainfall and winds associated with 

tropical cyclones are likely to increase 

North America Northern 

regions/Northern North 

America 

Southwest Annual mean precipitation is likely to 

decrease 

Northeast USA Annual mean precipitation is very likely to 

increase 

Southern Canada 

Canada Annual mean precipitation is very likely to 

increase 

Snow season length 

and snow depth are 

very likely to decrease 

 3-107 
3.4 Climate Chapter 3 Affected Environment and Environmental Consequences 

Table 3.4.4-8 (cont’d) 

Summary of Regional Changes to Precipitation Extracted from the IPCC Fourth Assessment Report 

(Christensen et al. 2007) 

Land Area Sub-region Precipitation 

Snow Season and 

Snow Depth 

Northernmost part of 

Canada 

Snow season length 

and snow depth are 

likely to increase 

Central and 

South America 

Southern South 

America 

Central America Annual precipitation is likely to decrease 

Southern Andes Annual precipitation is likely to decrease 

Tierra del Fuego Winter precipitation is likely to increase 

Southeastern South 

America 

Summer precipitation is likely to increase 

Northern South 

America 

Uncertain how rainfall would change 

Australia and 

New Zealand 

Southern Australia Precipitation is likely to decrease in winter 

and spring 

Southwestern 

Australia 

Precipitation is very likely to decrease in 

winter 

Rest of Australia 

New Zealand, South 

Island 

Precipitation is likely to increase in the west 

Rest of New Zealand 

Polar Regions Arctic Annual precipitation is very likely to 

increase. 

Very likely that the relative precipitation 

increase would be largest in winter and 

smallest in summer 

Antarctic Precipitation likely to increase 

Small Islands Mixed, depending on the region 

The state of the science reflected as of the publication of the IPCC Fourth Assessment Report 

projects a sea-level rise of 18 to 59 centimeters (0.6 to 1.9 feet) by 2090 to 2099 (EPA 2009b). Several 

recent studies have found the IPCC estimates of potential sea-level rise might be underestimated 

regarding ice loss from the Greenland and Antarctic ice sheets (Shepherd and Wignham 2007, Csatho et 

al. 2008) and ice loss from mountain glaciers (Meier et al. 2007). Further, IPCC results for sea-level 

projections might underestimate sea-level rise due to changes in global precipitation (Wentz et al. 2007, 

Zhang et al. 2007). Rahmstorf (2007) used a semi-empirical approach to project future sea-level rise. 

The approach yielded a proportionality coefficient of 3.4 millimeters per year per degree Centigrade of 

warming, and a projected sea-level rise of 0.5 to 1.4 meters (1.6 to 4.6 feet) above 1990 levels in 2100 

when applying IPCC Third Assessment Report warming scenarios. Rahmstorf (2007) concludes that “[a] 

rise over 1 meter (3.3 feet) by 2100 for strong warming scenarios cannot be ruled out.” None of these 

studies takes into account the potential complex changes in ocean circulation that might further influence 

sea-level rise. Section 4.5.5 discusses sea-level rise in more detail. 

Table 3.4.4-4 lists the impacts on sea-level rise under the scenarios and shows sea-level rise in 

2100 ranging from 38.00 centimeters (14.96 inches) under the No Action Alternative to 37.84 centimeters 

(14.89 inches) under the TCTB (Alternative 9), for a maximum reduction of 0.16 centimeters (0.063 

inches) by 2100 under the No Action Alternative. 

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Chapter 3 Affected Environment and Environmental Consequences 3.4 Climate 

 3-109 

In summary, the impacts of the proposed action and alternatives on global mean surface 

temperature, precipitation, or sea-level rise are small in relation to the expected changes associated with 

the emissions trajectories in the RCP 4.5 MiniCAM reference scenario.66 This is due primarily to the 

global and multi-sectoral nature of the climate problem. Although these effects are small, they occur on a 

global scale and are long-lived. 

3.4.4.2.5 Climate Sensitivity Variations 

NHTSA examined the sensitivity of projected climate effects to key technical or scientific 

assumptions used in the analysis. This examination included reviewing the impact of various climate 

sensitivities on the climate effects due to the No Action Alternative (Alternative 1) and the Preferred 

Alternative (Alternative 4) with the RCP 4.5 MiniCAM reference scenario. Table 3.4.4-9 lists the results 

from the sensitivity analysis (3.0 °C [5.4 °F] for a doubling of CO2 climate sensitivity). 

The use of different climate sensitivities (the equilibrium warming that occurs at a doubling of 

CO2 from pre-industrial levels) can affect not only warming but also sea-level rise and CO2 concentration 

indirectly. 

As shown in Table 3.4.4-9, the sensitivity of the simulated CO2 emissions in 2030, 2050, and 

2100 to changes in climate sensitivity is low; the reduction of CO2 concentrations from the No Action 

Alternative to the Preferred Alternative in 2100 is from 3.0 to 3.2 ppm. 

The sensitivity of the simulated global mean surface temperatures for 2030, 2050, and 2100 

varies, as shown in Table 3.4.4-9. In 2030, the impact is low due primarily to the rate at which the global 

mean surface temperature increases in response to increases in radiative forcing. In 2100, the impact is 

larger due not only to the climate sensitivity but also to the change in emissions. In 2100, the reduction in 

global mean surface temperature from the No Action Alternative to the Preferred Alternative in 2100 

ranges from 0.009 oC (0.016 °F) for the 2.0 °C (3.6 °F) climate sensitivity to 0.015 oC (0.027 °F) for the 

4.5 °C (8.1 °F) climate sensitivity, as listed in Table 3.4.4-9. The impact on global mean surface 

temperature due to assumptions concerning global emissions of GHG is also important. 

The sensitivity of the simulated sea-level rise to change in climate sensitivity and global GHG 

emissions mirrors that of global temperature, as shown in Table 3.4.4-9. Scenarios with lower climate 

sensitivities have lower increases in sea-level rise. Also, the reduction in the increase in sea-level rise is 

lower under the Preferred Alternative compared to the No Action Alternative. Conversely, scenarios with 

higher climate sensitivities have higher sea-level rise. The reduction in the increase of sea-level rise is 

greater under the Preferred Alternative compared to the No Action Alternative. The range in reduction of 

sea-level rise under the Preferred Alternative compared to the No Action Alternative is 0.08 to 0.13 

centimeters (0.03 to 0.05 inch), depending on the climate sensitivity. 

 

66 These conclusions are not meant to be interpreted as expressing NHTSA’s views that impacts on global mean 

surface temperature, precipitation, or sea-level rise are not areas of concern for policymakers. Under NEPA, the 

agency is obligated to discuss “the environmental impact[s] of the proposed action.” 42 U.S.C. § 4332(2)(C)(i) 

(emphasis added). This analysis fulfills NHTSA’s obligations in this regard. 
3.4 Climate Chapter 3 Affected Environment and Environmental Consequences 

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Table 3.4.4-9 

CO2 Concentrations, Global Mean Surface Temperature Increases, and Sea-level Rise (cm) for Varying 

Climate Sensitivities for Selected Alternatives a/ 

CAFE 

Alternative 

Climate 

Sensitivity 

(°C for 2xCO2) CO2 Concentration (ppm) 

Global Mean Surface 

Temperature Increase (°C) 

Sea-level 

Rise (cm)

2030 2050 2100 2030 2050 2100 2100 

1 No Action 

2.0 440.2 510.7 765.1 0.699 1.168 2.292 28.68

3.0 441.8 514.8 783.0 0.923 1.557 3.136 38.00

4.5 443.6 519.5 805.3 1.168 1.991 4.132 48.67

4 Preferred 

2.0 439.9 509.9 762.1 0.698 1.166 2.283 28.60

3.0 441.5 514.0 779.9 0.922 1.553 3.124 37.90

4.5 443.3 518.7 802.1 1.166 1.987 4.118 48.54

Reduction compared to No Action 

2.0 0.3 0.8 3.0 0.001 0.003 0.009 0.08

3.0 0.3 0.8 3.1 0.001 0.004 0.012 0.10

4.5 0.3 0.8 3.2 0.001 0.005 0.015 0.13

__________

a/ The numbers in this table have been rounded for presentation purposes. As a result, the reductions might not 

 reflect the exact difference of the values in all cases. 
Chapter 3 Affected Environment and Environmental Consequences 3.5 Other Potentially Affected Resource Areas 

3.5 OTHER POTENTIALLY AFFECTED RESOURCE AREAS 

This section describes the affected environment and environmental consequences of the proposed 

action and alternatives on water resources (Section 3.5.1), biological resources (Section 3.5.2), land use 

and development (Section 3.5.3), safety and other impacts to human health (Section 3.5.4), hazardous 

materials and regulated wastes (Section 3.5.5), land uses protected under U.S. Department of 

Transportation Act Section 4(f) (Section 3.5.6), historic and cultural resources (Section 3.5.7), noise 

(Section 3.5.8), and environmental justice (Section 3.5.9). These sections describe the current and 

projected future threats to those resources from non-global climate change impacts relevant to the CAFE 

alternatives and provide primarily qualitative assessments of any potential consequences of the 

alternatives, positive or negative, on these resources. 

This section does not describe the affected environment in relation to, or address potential 

environmental consequences resulting from, global climate change. For a description of potential impacts 

resulting from global climate change, see Chapter 4. 

3.5.1 Water Resources 

3.5.1.1 Affected Environment 

Water resources include surface water and groundwater. Surface waters are water bodies open to 

the atmosphere, such as rivers, streams, lakes, oceans, and wetlands; surface waters can contain either 

fresh or salt water. Groundwater is found in natural reservoirs or aquifers below Earth’s surface. Sources 

of groundwater include rainfall and surface water, which penetrate the ground and recharge the water 

table. Sections 3.5.1.1.1 through 3.5.1.1.3 describe existing and projected future threats to these resources 

from non-global climate change impacts related to the proposed action. The production and combustion 

of fossil fuels, the production of biofuels, and shifts in the location of mining activities are the identified 

relevant sources of impact. Section 3.5.2 describes relevant aspects of surface water resources from a 

habitat perspective. For a discussion of the effects of global climate change on freshwater and coastal 

systems, see Sections 4.5.3 and 4.5.5. 

Impacts to water resources during recent decades have come from a number of sources, including 

increased water demand for human and agricultural use, pollution from point and non-point sources, and 

climatic changes. One of the major human-caused impacts to water quality has been the extraction, 

refining, and combustion of petroleum products, or oil. 

3.5.1.1.1 Oil Extraction and Refining 

Oil refineries, which produce gasoline and diesel fuel, and the motor vehicles that combust 

petroleum-based fuels, are major sources of VOCs, SO2, NOx, CO, and other air pollutants (EPA 1995a, 

EPA 1997a). In the atmosphere, SO2 and NOx contribute to the formation of acid rain (the wet, dry, or 

fog deposition of SO2 and NOx), which enters water bodies either directly or as runoff from terrestrial 

systems (see Section 3.3 for more information on air quality). Once in surface waters, these pollutants 

can cause acidification of the water body, changing the acidity or alkalinity (commonly called pH) of the 

system and affecting the function of freshwater ecosystems (Van Dam 1996, Baum 2001, EPA 2007). An 

EPA survey of sensitive freshwater lakes and streams (those with a low capacity to neutralize or buffer 

against decreases in pH) found that 75 percent of the lakes and 50 percent of the streams had experienced 

acidification as a result of acid rain (EPA 2007). EPA has identified the areas of the United States most 

sensitive to acid rain as the Adirondacks and Catskill Mountains in New York State, the mid-Appalachian 

highlands along the east coast, the upper Midwest, and mountainous areas of the western United States 

(EPA 2007). 

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3.5 Other Potentially Affected Resource Areas Chapter 3 Affected Environment and Environmental Consequences 

Water quality might also be affected by petroleum products released during the refining and 

distribution process. Oil spills can lead to contamination of surface water and groundwater and can result 

in impacts to drinking water and marine and freshwater ecosystems (see Section 3.5.2.1.1). EPA 

estimates that, of the volume of oil spilled in “harmful quantities,” as defined under the CAA, 83.8 

percent was deposited in internal/headland waters and within 3 miles of shore, with 17.5 percent spilled 

from pipelines, often in inland areas (EPA 2004). The environmental impacts to and recovery time for 

individual waterbodies vary based on several factors (e.g., salinity, water movement, wind, temperature), 

with locations of faster-moving and warm water recovering more quickly (EPA 2008a). 

During oil extraction, the primary waste product is highly saline liquid called “produced water,” 

which can contain metals and other potentially toxic components (see Section 3.5.5.1.1 for more on 

produced water). Produced water and other oil extraction wastes are most commonly disposed of by 

reinjecting them to the well, which increases pressure and can force out more oil. Potential impacts from 

these wastes generally occur when large amounts are spilled and they enter surface waters, when 

decommissioned wells are improperly sealed, or when saline water from the wells intrudes into fresh 

surface water or groundwater (Kharaka and Otton 2003). 

Water quality impacts also occur as a result of contamination by VOCs. A nationwide USGS 

study of groundwater aquifers found VOCs in 90 of 98 major aquifers sampled (Zogorski et al. 2006). 

The study concluded that “...[t]he widespread occurrence of VOCs indicates the ubiquitous nature of 

VOC sources and the vulnerability of many of the Nation’s aquifers to low-level VOC contamination.” 

Several of the most commonly identified VOCs were a gasoline additive (gasoline oxygenate – methyl 

tertiary butyl ether [MTBE]) and a gasoline hydrocarbon (toluene). USGS notes, however, that only 1 to 

2 percent of the well samples had concentrations of VOCs at levels that would be of potential concern to 

human health; none of the VOCs found in potentially hazardous quantities were primarily used in the 

manufacture of fuels or as fuel additives (Zogorski et al. 2006). Section 3.5.5 describes toxic chemicals 

released during fuel production and combustion. 

3.5.1.1.2 CO2 Emissions 

Oceanic concentrations of CO2 from anthropogenic (human-made) sources, primarily the 

combustion of fossil fuels, have increased since the Industrial Revolution and will likely continue to 

increase. In addition to its role as a GHG, atmospheric CO2 plays a key role in the biogeochemical cycle 

of carbon. Atmospheric CO2 concentrations influence the chemistry of natural waters. 

Atmospheric concentrations of CO2 are in equilibrium with aqueous (dissolved in water) carbonic 

acid, which in turn influences the aqueous concentrations of bicarbonate ion and carbonate ion. In natural 

waters, the carbonate system controls pH, which in turn controls the availability of some nutrients and 

toxic materials in freshwater and marine systems. 

One of the large-scale non-climatic effects of an increase in CO2 emissions is the potential for 

ocean acidification. The ocean exchanges huge quantities of CO2 with the atmosphere, and when 

atmospheric concentrations rise (due to anthropogenic emissions), there is a net flux from the atmosphere 

into the oceans. This decreases the pH of the oceans, reducing the availability of calcium. According to 

Richardson and Poloczanska (2008), “declines in ocean pH may impact calcifying organisms, from corals 

in the tropics to pteropods (winged snails) in polar ecosystems, and will take tens of thousands of years to 

reequilibrate to preindustrial conditions.” Section 4.7 provides more information on the non-climate 

effects of CO2 on plant and animal communities. 

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Chapter 3 Affected Environment and Environmental Consequences 3.5 Other Potentially Affected Resource Areas 

 3-113 

3.5.1.1.3 Biofuel Cultivation and Mining Activity 

The need to supply agricultural products for a growing population will continue to affect water 

resources; future irrigation needs are likely to include increased production of both food and biofuel crops 

(Simpson et al. 2008). Global demand for water is increasing as a result of population growth and 

economic development and irrigation currently accounts for around 70 percent of global water 

withdrawals (Shiklomanov and Rodda 2003 in Kundzewicz et al. 2007). EPA states that “[d]emand for 

biofuels is also likely to have impacts on water including increasing land in agricultural production, 

resulting in increased risk of runoff of sediments, nutrients, and pesticides...[p]roduction of biofuels also 

uses significant amounts of water” (EPA 2008b). Runoff from agricultural sources often contains 

nitrogen, phosphorus, and other fertilizers and chemicals that harm water quality and can lead to 

eutrophication (the enrichment of a water body with plant-essential nutrients that can ultimately lead to 

oxygen depletion) (Vitousek et al. 1997, as in Fischlin et al. 2007). If biofuel production in the United 

States continues to be based on input-intensive crops like corn and soybeans, projected expansions to 

meet demand likely will result in significantly increased runoff of fertilizer and sediment (Simpson 2008). 

Shifts toward fuel-saving lighter vehicles, either as a result of consumer preference for fuelefficient vehicles or downweighting-design decisions by manufacturers, might result in changes in mining 

land-use patterns with resulting impacts to water quality (see Section 3.5.3.1.1). Metal mining results in 

impacts to water resources via run-off sedimentation from cleared mining sites and degradation of 

groundwater quality or quantity due to excavation and extraction activities (EPA 1995a). Shifts in 

demand for lighter vehicles could mean that areas with iron deposits would experience less mining 

activity, while areas where commonly used light-weight metals (such as aluminum or magnesium) might 

experience an increase in mining and related water impacts. 

3.5.1.2 Environmental Consequences 

As discussed in Section 3.3, each action alternative is generally expected to decrease the amount 

of VOCs, SO2, NOx, and other air pollutants in relation to No Action Alternative (Alternative 1) levels. 

Reductions in these pollutant levels would be the result of lower petroleum fuel consumption by 

passenger cars and light trucks, and a potential for reduced extraction, transportation, and refining of 

crude oil. NHTSA expects that lower pollutant emissions would decrease the formation of acid rain in the 

atmosphere compared to the No Action Alternative, which in turn would have a beneficial impact on the 

quality of freshwater by decreasing eutrophication67 and acidification. As discussed in Section 3.4, the 

impact of the alternative CAFE standards on CO2 is relatively small compared to global emissions of 

CO2. The U.S. passenger car and light truck fleet represents less than 4 percent of the global emissions of 

CO2 from passenger cars and light trucks, and this contribution is projected to decline in the future, due 

primarily to rapid growth of emissions from developing countries. 

Each alternative could lead to an indirect increase in the use of more light-weight materials in 

vehicles, depending on the mix of methods manufacturers use to meet the increased CAFE standards, 

economic demand, and technological capabilities. If manufacturers opted for increased production of 

downweighted vehicles, shifts in the location of metal extraction could alternatively benefit water quality 

in locations of decreased activity, while negatively affecting it in areas of increased activity. However, 

due to uncertainty about how manufacturers would meet the new requirements, and the fact that none of 

 

67 Eutrophication is a process whereby water bodies, such as lakes, estuaries, or slow-moving streams receive excess 

nutrients that stimulate excessive plant growth (algae, periphyton attached algae, and nuisance plants and weeds). 

This enhanced plant growth reduces dissolved oxygen in the water when dead plant material decomposes and can 

cause other organisms to die. See http://toxics.usgs.gov/definitions/eutrophication.html (last visited Jul. 22, 2009). 
3.5 Other Potentially Affected Resource Areas Chapter 3 Affected Environment and Environmental Consequences 

the alternative CAFE standards prescribe vehicle downweighting, these potential impacts are not 

quantifiable. Section 3.5.4 provides additional information on vehicle downweighting.

3.5.2 Biological Resources 

3.5.2.1 Affected Environment 

Biological resources include vegetation, wildlife, and special status species (those classified as 

“threatened” or “endangered” under the Endangered Species Act). The U.S. Fish and Wildlife Service 

has jurisdiction over terrestrial and freshwater special status species and the National Marine Fisheries 

Service has jurisdiction over marine special status species. States and federal agencies, such as the 

Department of the Interior’s Bureau of Land Management, also have species of concern to which they 

have assigned additional protections. Sections 3.5.2.1.1 through 3.5.2.1.3 describe the existing and 

projected future threats to these biological resources from non-global climate change impacts related to 

the proposed action and alternatives. As discussed below, the production and combustion of fossil fuels, 

the cultivation and production of biofuels from agricultural crops, and shifts in the location of mining 

activities are the identified relevant sources of impacts to biological resources. Section 4.5 describes the 

effects of global climate change on ecosystems. 

3.5.2.1.1 Petroleum Extraction and Refining 

Oil extraction activities could impact biological resources through habitat destruction and 

encroachment, raising concerns about their effects on the preservation of animal and plant populations 

and their habitats. Oil exploration and extraction result in intrusions into onshore and offshore natural 

habitats and can involve construction within natural habitats. “The general environmental effects of 

encroachment into natural habitats and the chronic effects of drilling and generating mud and discharge 

water on benthic (bottom-dwelling) populations, migratory bird populations, and marine mammals 

constitute serious environmental concerns for these ecosystems” (Borasin et al. 2002, in O’Rourke and 

Connolly 2003). 

Oil extraction and transportation can also result in spills of oil and hazardous materials. Oil 

contamination of aquatic and coastal habitats can directly smother small species and is dangerous to 

animals and fish if ingested or coated on their fur, skin, or scales. Oil refining and related activities result 

in chemical and thermal pollution of water, both of which can be harmful to animal and plant populations 

(Borasin et al. 2002, in O’Rourke and Connolly 2003). Offshore and onshore drilling and oil transport 

can lead to spills, vessel or pipeline breakage, and other accidents that release petroleum, toxic chemicals, 

and highly saline water into the environment and affect plant and animal communities. 

Oil extraction, refining, and transport activities, and the combustion of fuel during motor-vehicle 

operation, result in air emissions that affect air quality and can contribute to the production of acid rain. 

These effects can result in negative impacts to plants and animals. Once present in surface waters, air 

pollutants can cause acidification of waterbodies, changing the pH of the system and affecting the 

function of freshwater ecosystems. EPA (2009) states: 

...plants and animals living within an ecosystem are highly interdependent...Because of 

the connections between the many fish, plants, and other organisms living in an aquatic 

ecosystem, changes in pH or aluminum levels affect biodiversity as well. Thus, as lakes 

and streams become more acidic, the numbers and types of fish and other aquatic plants 

and animals that live in these waters decrease. 

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Chapter 3 Affected Environment and Environmental Consequences 3.5 Other Potentially Affected Resource Areas 

Acid rain has also been shown to affect forest ecosystems negatively, both directly and indirectly. 

These impacts include stunted tree growth and increased mortality, primarily as a result of the leaching of 

calcium and other soil nutrients (Driscoll et al. 2001, DeHayes et al. 1999, Baum 2001). Declines in 

biodiversity of aquatic species and changes in terrestrial habitats likely have ripple effects on other 

wildlife that depend on these resources. 

The combustion of fossil fuels and certain agricultural practices have lead to a disruption in the 

nitrogen cycle (the process by which gaseous nitrogen from the atmosphere is used and recycled by 

organisms) with serious repercussions for biological resources. Nitrogen-cycle disruption has occurred 

through the introduction of large amounts of anthropogenic nitrogen in the form of ammonium and 

nitrogen oxides to aquatic and terrestrial systems (Vitousek 1994). Increased availability of nitrogen in 

these systems is a major cause of eutrophication in freshwater and marine waterbodies. Eutrophic 

systems typically contain communities dominated by phytoplankton (free-floating microscopic plants). 

Eutrophication can ultimately result in the death of fish and other aquatic animals, as well as harmful 

algal blooms. Acid rain enhances eutrophication of aquatic systems through the deposition of additional 

nitrogen (Lindberg 2007). 

3.5.2.1.2 CO2 Emissions 

Ocean acidification as a result of increasing concentrations of atmospheric CO2, primarily from 

the combustion of fossil fuels, is expected to affect calciferous marine organisms. In conjunction with 

rapid climate change, ocean acidification could pose severe threats to coral reef ecosystems. HoeghGuldberg et al. (2007) state that “[u]nder conditions expected in the 21st century, global warming and 

ocean acidification will compromise carbonate accretion, with corals becoming increasingly rare on reef 

systems. The result will be less diverse reef communities and carbonate reef structures that fail to be 

maintained.” 

In contrast to its potential adverse effect on the productivity of marine ecosystems, higher CO2

concentrations in the atmosphere could increase the productivity of terrestrial systems, because plants use 

CO2 as an input to photosynthesis. The IPCC Fourth Assessment Report states that “[o]n physiological 

grounds, almost all models predict stimulation of carbon assimilation and sequestration in response to 

rising CO2, called CO2 fertilization” (Denman et al. 2007). 

Under bench-scale and field-scale experimental conditions, several investigators have found that 

higher concentrations have a “fertilizer” effect on plant growth (e.g., Long et al. 2006, Schimel et al.

2000). IPCC reviewed and synthesized field and chamber studies, finding that: 

There is a large range of responses, with woody plants consistently showing NPP [net 

primary productivity] increases of 23 to 25 percent (Norby et al. 2005), but much smaller 

increases for grain crops (Ainsworth and Long 2005)...Overall, about two-thirds of the 

experiments show positive response to increased CO2 (Ainsworth and Long 2005, 

Denman et al. 2007). Since saturation of CO2 stimulation due to nutrient or other 

limitations is common (Dukes et al. 2005, Körner et al. 2005, both in Denman et al.

2007), it is not yet clear how strong the CO2 fertilization effect actually is. 

The CO2 fertilization effect could mitigate some of the increase in atmospheric CO2

concentrations by resulting in more storage of carbon in vegetation. 

Increased atmospheric CO2, in conjunction with other environmental factors and changes in plant 

communities, could alter growth, abundance, and respiration rates of some soil microbes (Lipson et al.

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2005, Chung et al. 2007, Lesaulnier et al. 2008). Section 4.7 provides more information on the nonclimate effects of CO2 on plant and animal communities. 

3.5.2.1.3 Land Disturbances Due to Biofuel Production and Mining 

Future demands for biofuel production are predicted to require increased commitments of land to 

agricultural production (EPA 2008b). Placing additional land into agricultural production or returning 

marginal agricultural land to production to grow perennial grass or trees for use in cellulosic ethanol 

production would decrease the area available as natural habitat. A decrease in habitat and potential 

habitat for plants and animal species would likely result in negative impacts to certain species. Increased 

agriculture production would also likely result in increased surface runoff of sediments and fertilizers. 

Additional fertilizer inputs to water could increase eutrophication and associated impacts. Sediment 

runoff can settle to the bottom of waterbodies and degrade essential habitat for some species of aquatic 

organisms, bury food sources and areas used for spawning, and kill benthic organisms (EPA 2000a). 

As stated in Section 3.5.1.1.3, a shift toward lighter vehicles would likely result in changes to 

mining land-use patterns and impacts to water quality; such changes could affect aquatic and terrestrial 

ecosystems. EPA notes that mining activities could result in the destruction of terrestrial habitat, loss of 

fish populations due to water-quality impacts, and a loss of plants due to increased dust (EPA 1995a). As 

previously stated, such a shift would likely be beneficial in areas of decreased activity and detrimental in 

areas of increased activity. 

3.5.2.1.4 Endangered Species 

Off-shore drilling, on-shore oil and gas drilling, and roads created to access remote extraction 

sites through habitats used by threatened or endangered species may be relevant considerations for these 

plants and animals both directly, through loss of individual animals or habitat, and indirectly, through 

water-quality degradation or cumulative impacts with other projects. Loss of potential habitat to the 

production of biofuels could also result in issues for some species (e.g., diminished potential for habitat 

expansion, increased runoff-related issues). 

Increased anthropogenic inputs of nitrogen to terrestrial, aquatic, and microbial communities 

containing rare plants and animals could also be relevant considerations for threatened and endangered 

species. In ecosystems with certain vegetation and soil types, this increased nitrogen availability can 

result in reduced biodiversity or the exclusion of certain endemic species in favor of those adapted to 

make use of these nutrients to their competitive advantage (Bobbink et al. 1998, Fenn et al. 2003, Weiss 

1999). For example, the decline of certain nutrient-poor native grasslands in California, which serve as 

critical habitat for the Bay checkerspot butterfly, is likely partially due to an increase in invasive grass 

species made possible by such nutrient inputs (Weiss 1999). 

3.5.2.2 Environmental Consequences 

The decrease in overall fuel consumption by passenger cars and light trucks, anticipated under all 

of the alternatives except the No Action Alternative, could lead to reductions in oil exploration, 

extraction, transportation, and refining. NHTSA expects that a reduction in these activities would result 

in decreased impacts to on- and off-shore habitat and plant and animal species. This decrease could have 

a small overall benefit to plants and animals, primarily through decreased levels of direct ground 

disturbance and releases of oil and hazardous materials. Reductions in the rate of fuel consumption 

increase under all of the alternatives compared to the No Action Alternative would lead to overall 

decreases in the release of SO2 and NOx. Reductions in acid rain and anthropogenic nutrient deposition 

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could lower levels of eutrophication in surface waters and could slow direct impacts to ecosystems and to 

soil leaching. 

Reductions in the rate of fuel consumption increase would also lead to a decrease in the release of 

CO2 compared to the No Action Alternative. Lower levels of atmospheric CO2 could slow projected 

effects to terrestrial plant growth, calciferous marine organisms, and microorganisms. However, as 

discussed in Section 3.5.1.2, the reduction in CO2 as a result of the proposed action and alternatives 

would be relatively small compared to current and projected global CO2 releases (see Chapter 2 and 

Section 3.3). 

The alternatives could lead to an increase in mining for light-weight raw materials, depending on 

the mix of methods manufacturers use to meet the new CAFE standards, economic demands from 

consumers and manufacturers, and technological developments. Depending on these factors, increased 

mining land-disturbance activities could affect aquatic health due to increased sedimentation. However, 

due to the uncertainty surrounding how manufacturers would meet the new requirements and the fact that 

none of the alternatives analyzed prescribe vehicle downweighting, these potential effects are not 

quantifiable. It would be speculative to associate any of these potential general impacts to any particular 

location or to any particular biological resource. 

NHTSA has carefully considered the requirements of the Endangered Species Act and determined 

that Section 7(a)(2) consultation is not required for this action. See Appendix G for more information. 

3.5.3 Land Use and Development 

3.5.3.1 Affected Environment 

Land use and development refers to human activities that alter land (e.g., industrial and 

residential construction in urban and rural settings, clearing of natural habitat for agricultural or industrial 

use) and could affect the amount of carbon or biomass in existing forest or soil stocks in the affected 

areas. For purposes of this analysis, shifts in agricultural and mining production and changes to 

manufacturing plants that produce passenger cars and light trucks are the identified relevant sources of 

impact. 

3.5.3.1.1 Changes in Agricultural Production and Mining 

Biofuel production is predicted to require increased devotion of land to agricultural production 

(EPA 2008b, Keeney and Hertel 2008). Converting areas into cropland would decrease the overall land 

area kept in a natural state and the potential area available for other uses (such as commercial 

development or pastureland) (Keeney and Hertel 2008). There is uncertainty regarding how much 

additional land could be required to meet projected biofuel needs in the United States, and how an 

increase in biofuel production could affect other land uses (Keeney and Hertel 2008). 

Shifts toward fuel-saving lighter vehicles, either as a result of consumer preference for fuelefficient vehicles or downweighting design decisions by manufacturers, might result in changes in mining 

land-use patterns. Mining for the minerals needed to construct these lighter vehicles (primarily aluminum 

and magnesium) could shift some metal-extraction activities to areas rich in these resources. 

Schexnayder et al. (2001) noted that such a shift in materials “could reduce mining for iron ore in the 

United States, but increase the mining of bauxite for aluminum, magnesium, titanium, and other materials 

in such major countries as Canada, China, and Russia and in many small, developing countries, such as 

Guinea, Jamaica, and Sierra Leone.” 

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3.5.3.1.2 Manufacturing Changes 

Recent shifts in consumer demand in the United States away from less-fuel-efficient vehicles 

have begun to change the types of vehicles produced and the manufacturing plants where they are made. 

Sharp decreases in demand for trucks and SUVs have recently resulted in plant closures and production 

shifts to plants where small cars and gas-electric hybrid vehicles are made (WWJ News Radio 2008, 

Keenan and Mckenna 2008, Bunkley 2008). 

3.5.3.2 Environmental Consequences 

Depending on how manufacturers achieve reductions in vehicle weight, downweighted vehicles 

could result in shifts in mining from areas containing iron to those containing aluminum and magnesium, 

and shifts from facilities that process iron ore (for iron and steel) to those that process bauxite (for 

aluminum) and brine (for magnesium). These changes would have implications for environmental issues 

associated with land use and development, and material processing. However, due to the uncertainty 

surrounding how manufacturers would meet the new requirements and the fact that none of the analyzed 

alternatives prescribe vehicle downweighting (much less specific engineering and materials shifts to 

reduce vehicle mass), these potential environmental impacts are not quantifiable. See Section 3.5.4 for 

more information on vehicle downweighting. 

Major changes to manufacturing facilities, such as those occurring with the apparent shift in 

consumer demand toward more fuel-efficient vehicles, might have implications for environmental issues 

associated with land use and development. However, NHTSA’s review of existing and available 

technologies and capabilities shows that the CAFE standards under all the action alternatives can be met 

by existing and planned manufacturing facilities. Because of the availability of sufficient existing and 

planned capacity, and because none of the alternatives prescribe particular technologies for meeting these 

standards, the various alternatives are not projected to force changes in product mixes that would result in 

plant changes. 

3.5.4 Safety and Other Impacts to Human Health 

NHTSA has analyzed how future improvements in fuel economy might affect human health and 

welfare through vehicle safety performance and the rate of traffic fatalities. The agency also considered 

how the new standards might affect energy concerns, which could have ramifications for family health 

and welfare. For more details on this analysis, see Section IV of the joint preamble and Chapter 9 of the 

RIA. 

3.5.5 Hazardous Materials and Regulated Wastes 

3.5.5.1 Affected Environment 

Hazardous wastes are defined here as solid wastes, which also include certain liquid or gaseous 

materials, that because of their quantity and concentration, or their physical, chemical, or infectious 

characteristics, could cause or contribute to an increase in mortality or an increase in serious irreversible 

or incapacitating reversible illness or could pose a substantial hazard to human health or the environment 

when improperly treated, stored, used, transported, disposed of, or otherwise managed. Hazardous wastes 

are generally designated as such by individual states or EPA under the Resource Conservation and 

Recovery Act of 1976. Additional federal and state legislation and regulations, such as the Federal 

Insecticide, Fungicide, and Rodenticide Act, determine handling and notification standards for other 

potentially toxic substances. For purposes of this analysis, hazardous materials and wastes generated 

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during the oil-extraction and refining processes and by agricultural production and mining activities are 

the identified relevant sources of impact. 

3.5.5.1.1 Wastes Produced during the Extraction Phase of Oil Production 

The primary waste created during the extraction of oil is “produced water,” highly saline water 

pumped from oil and gas wells during mining (American Petroleum Institute 2000, EPA 2000b). In 1995, 

the onshore oil and gas industry produced approximately 15 billion barrels of produced water (American 

Petroleum Institute 2000). Produced water is generally “highly saline (total dissolved solids may exceed 

350,000 milligrams per liter [mg/L]), may contain toxic metals, organic and inorganic components, and 

radium-226/228 and other naturally occurring radioactive materials” (Kharaka and Otton 2003). Drilling 

wastes, primarily mud and rock cuttings, account for 149 million barrels of extraction wastes. 

“Associated wastes,” generally the most hazardous wastes produced during extraction (often containing 

benzenes, arsenic, and toxic metals), account for another 22 million barrels (The American Petroleum 

Institute 2000, EPA 2000b). 

Wastes produced during oil and gas extraction have been known to have serious environmental 

effects on soil, water, and ecosystems (Kharaka and Otton 2003, O’Rourke and Connolly 2003). Onshore 

environmental effects result “primarily from the improper disposal of large volumes of saline water 

produced with oil and gas, from accidental hydrocarbon and produced water releases, and from 

abandoned oil wells that were not correctly sealed” (Kharaka and Otton 2003). Offshore effects result 

from improperly treated produced water released into the waters surrounding the oil platform (EPA 

2000b). 

3.5.5.1.2 Wastes Produced during the Refining Phase of Oil Production 

Wastes produced during the petroleum-refining process are primarily released to the air and 

water, accounting for 75 percent (air emissions) and 24 percent (wastewater discharges) of the total (EPA 

1995a). EPA defines a release as the “on-site discharge of a toxic chemical to the environment... 

emissions to the air, discharges to bodies of water, releases at the facility to land, as well as contained 

disposal into underground injection wells” (EPA 1995a). EPA reports that nine of the 10 most common 

toxic substances released by the petroleum-refining industry are volatile chemicals, highly reactive 

substances prone to state changes or combustion, that include benzene, toluene, ethylbenzene, xylene, 

cyclohexane, 1,2,4-trimethylbenzene and ethylbenze (EPA 1995a). These substances are present in crude 

oil and in finished petroleum products. Other potentially dangerous substances commonly released 

during the refining process include ammonia, gasoline additives (methanol, ethanol, and MTBE), and 

chemical feedstocks (propylene, ethylene, and napthalene) (EPA 1995a). Spent sulfuric acid is by far the 

most commonly produced toxic substance; however, it is generally reclaimed instead of released or 

transferred for disposal (EPA 1995a). 

Wastes released during the oil-refining process can cause environmental impacts to water quality, 

air quality, and human health. The volatile chemicals released during the refining process are known to 

react in the atmosphere and contribute to ground-level ozone and smog (EPA 1995a). Several of the 

produced volatile chemicals are also known or suspected carcinogens and many others are known to 

cause respiratory problems and impair internal-organ functions, particularly in the liver and kidneys (EPA 

1995a). Ammonia is a form of nitrogen and can contribute to eutrophication in surface waters. 

3.5.5.1.3 Agricultural Materials 

Agricultural production, especially of the type required to grow the corn and soybeans most 

commonly used to produce biofuels in the United States, also results in the release of potentially 

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hazardous materials and wastes. Wastes from agricultural production can include pesticide (insecticides, 

rodenticides, fungicides, and herbicides) and fertilizer runoff and leaching, wastes used in the 

maintenance and operation of agricultural machinery (used oil, fuel spills, organic solvents, metal 

machining wastes, spent batteries), and other assorted process wastes (EPA 2000c). 

Agricultural wastes in the form of runoff from agricultural fields can cause environmental 

impacts to water and human health. Fertilizers can run off into surface waters and cause eutrophication, 

while pesticides can directly affect beneficial insects and wildlife (EPA 2000c). A National Renewable 

Energy Lab report concludes that the negative environmental impacts on soil and water due to impacts of 

increased biofuel production are likely to occur disproportionately in the Midwest, where most of these 

crops are grown (Powers 2005). Human health can also be affected by improperly handled or applied 

pesticides, with potential effects ranging from minor respiratory or skin inflammation to death (EPA 

2000c). Nitrogen fertilizer runoff to drinking-water sources can lead to methemoglobinemia, the 

potentially fatal binding of a form of nitrogen to hemoglobin in infants (Powers 2005). 

Ethanol, as a biofuel additive to gasoline, is suspected of enhancing the plume size after a 

gasoline-blended ethanol spill and might decrease degradation of the spilled hydrocarbon and related 

compounds, such as benzene (Powers et al. 2001, Deeb et al. 2002, Williams et al. 2003). 

3.5.5.1.4 Automobile Production and Assembly 

Motor vehicles and the motor vehicle equipment industry, and businesses engaged in the 

manufacture and assembly of cars, trucks, and buses produce hazardous materials and toxic substances. 

EPA reports that solvents (xylene, methyl ethyl ketone, acetone, etc.) are the most commonly released 

toxic substances it tracks for this industry (EPA 1995a). These solvents are used to clean metal and in the 

vehicle-finishing process during assembly and painting (EPA 1995a). Other industry wastes include 

metal paint and component-part scrap. 

In addition, studies have suggested that the substitution of lighter-weight materials (such as 

aluminum, magnesium, titanium, or plastic) for steel and iron to increase fuel efficiency could increase 

the total waste stream resulting from automobile manufacturing (Schexnayder et al. 2001). Mining 

wastes generated during the extraction of these lighter raw materials would likely increase substantially, 

primarily due to aluminum mining, and other production wastes (e.g., from refining of aluminum and 

plastic manufacturing) could also increase (Schexnayder et al. 2001, Dhingra et al. 1999). The extraction 

and processing of these metals and the production of manmade fibers and plastics also generate various 

hazardous wastes (EPA 1995b, EPA 1997b). An assessment of the solid and hazardous wastes generated 

during the production of three light-weight concept cars concluded the net generation of waste would 

increase versus conventional vehicles; however, the study also noted that the generation of most 

hazardous materials of particular concern to human health (e.g., cadmium, chlorine, lead) emitted during 

the production of vehicles appeared to decrease in the vehicle models analyzed (Schexnayder et al. 2001). 

Recycling of vehicles at the end of the vehicle life could help to offset some of the projected net increase 

in waste production versus primarily steel/iron construction vehicles. 

3.5.5.1.5 CO2 Emissions 

CO2 is not classified as a hazardous material or regulated waste. For a discussion of the release 

of CO2 relevant to the proposed action and alternatives and its impacts on climate change, see Section 3.4. 

For a discussion of the impacts of CO2 on water resources, see Section 3.5.1.1.2. For a discussion of the 

impacts of CO2 on biological resources, see Section 3.5.2.1.2. 

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3.5.5.2 Environmental Consequences 

The projected reduction in fuel production and consumption as a result of the proposed action and 

alternatives could lead to a reduction in the amount of hazardous materials and wastes created by the oilextraction and refining industries. NHTSA expects corresponding decreases in the associated 

environmental and health impacts of these substances. However, these effects would likely be small if 

they occurred, because of the limited overall effect of the proposed action and alternatives on these areas. 

All of the alternatives could lead to the use of more light-weight materials in vehicles, depending 

on the mix of methods manufacturers use to meet the new CAFE standards, economic demands from 

consumers and manufacturers, and technological developments. If manufacturers pursued vehicle 

downweighting, these could be a net increase in the waste stream. However, due to the uncertainty 

surrounding how manufacturers would meet the new requirements and the fact that none of the 

alternatives analyzed prescribes vehicle downweighting (or specific means of vehicle downweighting), 

these potential impacts are not quantifiable. See Section 3.5.4 for additional information on vehicle 

downweighting. 

3.5.6 Land Uses Protected under U.S. Department of Transportation Act Section 4(f) 

3.5.6.1 Affected Environment 

Section 4(f) resources are publicly owned parks, recreational areas, wildlife and waterfowl 

refuges, or public and private historical sites to which the DOT gives special consideration. Originally 

included as part of the Department of Transportation Act of 1966, Section 4(f) stipulates that DOT 

agencies cannot approve the use of land from publicly owned parks, recreational areas, wildlife and 

waterfowl refuges, or public and private historical sites unless “(1) there is no feasible and prudent 

alternative to the use of such land, and (2) such program includes all possible planning to minimize harm 

to such park, recreational area, wildlife and waterfowl refuge, or historic site resulting from such use.” 49 

U.S.C. 303. 

3.5.6.2 Environmental Consequences 

“Section 4(f) only applies where land is permanently incorporated into a transportation facility 

and when the primary purpose of the activity on the 4(f) resource is for transportation” (FHWA 2005). 

Because the proposed action in this EIS does not meet these criteria, Section 4(f) does not apply. 

3.5.7 Historic and Cultural Resources 

3.5.7.1 Affected Environment 

The National Historic Preservation Act of 1966 (16 U.S.C. 470 et seq.), Section 106, states that 

agencies of the Federal Government must take into account the impacts of their action to historic 

properties; the regulations to meet this requirement can be found at 36 CFR Part 800. This process, 

known as the “Section 106 process,” is intended to support historic preservation and mitigate impacts to 

significant historical or archeological properties through the coordination of federal agencies, states, and 

other affected parties. Historic properties are generally identified through the National Register of 

Historic Places, which lists properties of significance to the United States or a particular locale because of 

their setting or location, contribution to or association with history, or unique craftsmanship or materials. 

National Register-eligible properties must also be sites “A. That are associated with events that have 

made a significant contribution to the broad patterns of our history; or B. That are associated with the 

lives of persons significant in our past; or C. That embody the distinctive characteristics of a type, period, 

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or method of construction, or that represent the work of a master, or that possess high artistic values, or 

that represent a significant and distinguishable entity whose components may lack individual distinction; 

or D. That have yielded, or may be likely to yield, information important in prehistory or history.” 

36 CFR 60.4. Acid rain as a result of the processing of petroleum products and the combustion of 

petroleum-based fuels is the identified relevant source of impact to historic and cultural resources for this 

analysis. 

Acid rain, the primary source of which is the combustion of fossil fuels, is one cause of 

degradation to exposed cultural resources and historic sites. EPA states that “[a]cid rain and the dry 

deposition of acidic particles contribute to the corrosion of metals (such as bronze) and the deterioration 

of paint and stone (such as marble and limestone). These effects substantially reduce the societal value of 

buildings, bridges, cultural objects (such as statues, monuments, and tombstones), and cars” (EPA 2007). 

3.5.7.2 Environmental Consequences 

The projected reduction in fuel production and combustion as a result of the proposed action and 

alternatives could lead to a minor reduction in the amount of pollutants that cause acid rain. A decrease in 

the production of such pollutants could result in a corresponding decrease in the amount of damage to 

historic and other structures caused by acid rain. However, such effects are not quantifiable. 

3.5.8 Noise 

3.5.8.1 Affected Environment 

Excessive amounts of noise, which is measured in decibels, can present a disturbance and a 

hazard to human health at certain levels. Potential health hazards from noise range from annoyance 

(sleep disturbance, lack of concentration, and stress) to hearing loss at high levels (Delucchi and Hsu 

1998, Geary 1998, Fleming et al. 2005). Motor-vehicle noise also affects property values. A study of the 

impacts of roadway noise on property values estimated this cost to be roughly 3 billion dollars in 1991 

dollars (Delucchi and Hsu 1998). The noise from motor vehicles has been shown to be one of the primary 

causes of noise disturbance in homes (OECD 1988, in Delucchi and Hsu 1998, and Geary 1998). Noise 

generated by vehicles causes inconvenience, irritation, and potentially even discomfort to occupants of 

other vehicles, to pedestrians and other bystanders, and to residents or occupants of surrounding property. 

3.5.8.2 Environmental Consequences 

As a result of the rebound effect (the increase in VMT as the cost per mile for fuel decreases), 

NHTSA predicts that there will be increased vehicle use under all of the alternatives; higher overall VMT 

would result in increases in vehicle road noise. However, location-specific analysis of noise impacts is 

not possible based on available data. Noise levels are location specific, meaning factors such as the time 

of day at which increases in traffic occur, existing ambient noise levels, the presence or absence of noise 

abatement structures, and the location of schools, residences, and other sensitive noise receptors all 

influence whether there will be noise impacts. 

All of the alternatives could lead to an increase in use of hybrid vehicles, depending on the mix of 

methods manufacturers use to meet the new CAFE standards, economic demands from consumers and 

manufacturers, and technological developments. An increased percentage of hybrid vehicles could result 

in reduced road noise, potentially offsetting some of the increase in road noise predicted to result from 

increased VMT. However, due to the uncertainty surrounding how manufacturers would meet the new 

requirements, the fact that none of the alternatives prescribes increased production of hybrid vehicles, and 

the location-specific nature of noise impacts, these potential impacts are not quantifiable. 

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3.5.9 Environmental Justice 

3.5.9.1 Affected Environment 

Federal agencies must identify and address disproportionately high and adverse impacts to 

minority and low-income populations in the United States (Executive Order 12898, Federal Actions to 

Address Environmental Justice in Minority Populations and Low-Income Populations). DOT Order 

5610.2 establishes the process the Department uses to “incorporate environmental justice principles (as 

embodied in the Executive Order) into existing programs, policies, and activities.” The production and 

use of fossil fuels and the production of biofuels are the identified relevant sources of impact to 

environmental populations for this analysis. For a discussion of the effects of climate change on 

environmental justice populations, see Section 4.6. 

Numerous studies have noted that there appears to be a historic and ongoing relationship between 

the environmental impacts of petroleum extraction, processing, and use and environmental justice 

populations (Pastor et al. 2001, O’Rourke and Connolly 2003, Lynch et al. 2004, Hymel 2007, Srinivasan 

et al. 2003). 

Potential impacts of the oil exploration and extraction process on environmental justice 

communities include “human health and safety risks for neighboring communities and oil industry 

workers, and displacement of indigenous communities” (O’Rourke and Connolly 2003). Subsistence-use 

activities (collecting plants or animals to fulfill basic needs for food, clothing, or shelter) can also be 

affected by extraction and exploration through the direct loss of subsistence-use areas or impacts to 

culturally/economically important plants and animals as a result of a spill or hazardous-material release 

(O’Rourke and Connolly 2003, Kharaka and Otton 2003). 

It has been shown that minority and low income populations often disproportionately reside near 

high-risk polluting facilities, such as oil refineries (Pastor et al. 2001, Graham et al. 1999, O’Rourke and 

Connolly 2003), and “mobile” sources of air toxins and pollutants, as in the case of populations residing 

near highways (Morello-Frosch 2002, Jerrett et al. 2001, O’Neill et al. 2003). Populations near refineries 

could be disproportionately affected by exposure to potentially dangerous petroleum and by-products of 

the refining process, such as benzene (Borasin et al. 2002). Exposure to the toxic chemicals associated 

with refineries, primarily by refinery workers, has been shown to be related to increases in certain 

diseases and types of cancer (Pukkala 1998, Chan et al. 2006); the precise nature and severity of these 

health impacts are still under debate. Pollutants emitted primarily by transportation sources, such as NOx

and CO, are often found in higher concentrations near roadways and other emission sources (Zhou and 

Levy 2007). These pollutants have been reported in higher concentrations in areas with high fractions of 

disadvantaged populations, such as minorities and low-income groups (Jerret et al. 2001, Morello-Frosch 

2002). Recent reviews by health and medical researchers indicate a general consensus that proximity to 

high-traffic roadways could result in adverse cardiovascular and respiratory effects, among other possible 

impacts ( HEI 2010; Heinrich and Wichmann, 2004; Salam et al., 2008; Adar and Kaufman, 2007). The 

exact nature of the relationship between these health impacts, traffic-related emissions, and the influence 

of confounding factors or modifying factors such as traffic noise are not fully understood at this time 

(Samet 2007; HEI 2010). 

The production of biofuels could, depending on the mix of agricultural crops or crop residues 

used in its production, affect food prices. The International Food Policy Research Institute states, “An 

aggressive biofuel scenario that assumes that current plans for expansion of the sector in Africa, Asia, 

Europe, and North and South America are actually realized could lead to substantial price increases for 

some food crops by 2020 – about 80 percent for oilseeds and about 40 percent for maize – unless new 

technologies are developed that increase efficiency and productivity in both crop production and biofuel 

processing” (von Braun and Pachauri 2006). Such an increase in food prices would disproportionately 

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affect low income populations, because these groups typically spend a larger share of their incomes on 

food. 

3.5.9.2 Environmental Consequences 

The projected reduction in fuel production and consumption as a result of the action alternatives 

could lead to a minor reduction in the amount of direct land disturbance as a result of oil exploration and 

extraction, and the amount of air pollution produced by the oil refineries. There could be corresponding 

decreases in impacts on environmental justice populations as a result of the alternatives, but the effects of 

any such decreases are not quantifiable and would likely be minor, if they occurred. 

As discussed in Section 3.3, the overall decrease in emissions predicted to occur as a result of the 

proposed new CAFE standards is not evenly distributed due to the increase in VMT from the rebound 

effect and regional changes in upstream emissions. As a result, some criteria and toxic air pollutants are 

predicted to increase in some air quality nonattainment areas. The large size of each nonattainment area 

and the minor emissions increases in affected nonattainment and other areas make it unlikely that there 

would be disproportionate effects to environmental justice populations. 
Chapter 3 Affected Environment and Environmental Consequences 3.6 Unavoidable Impacts 

3.6 UNAVOIDABLE IMPACTS AND IRREVERSIBLE AND IRRETRIEVABLE RESOURCE 

COMMITMENT 

3.6.1 Unavoidable Adverse Impacts 

The National Highway Traffic Safety Administration (NHTSA) proposed action is to implement 

new Corporate Average Fuel Economy (CAFE) standards for model years (MYs) 2012-2016. Under 

Alternative 1 (No Action), neither NHTSA nor EPA would issue a rule regarding fuel economy or GHG 

emissions for MYs 2012-2016. Each of the eight action alternatives (Alternatives 2 through 9) would 

result in a decrease in carbon dioxide (CO2) emissions and associated climate change effects and a 

decrease in energy consumption as compared to the No Action Alternative. However, total energy 

consumption and CO2 emissions by U.S. passenger cars and light trucks are projected to continue to 

increase under all of the alternatives as a result of projected increases in the number of these vehicles in 

use and the total number of miles they are driven each year (as measured by vehicle miles traveled, or 

VMT). 

Based on NHTSA’s current understanding of global climate change, certain effects are likely to 

occur as a consequence of accumulated total greenhouse gas (GHG) emissions in Earth’s atmosphere. 

Neither the proposed action nor its alternatives would prevent these effects. As described in Section 

3.4.4.2, each of the action alternatives could contribute to reductions in global GHG emissions from the 

levels that would occur if average fuel economy were to continue at its current levels, thus diminishing 

these anticipated changes in the global climate. 

Oxides of nitrogen (NOx), particulate matter (PM2.5), oxides of sulfur (SOx), volatile organic 

compounds (VOCs), benzene, 1,3-butadiene, and diesel particulate matter (DPM) exhibit decreases in 

emissions for all action alternatives and analysis years as compared to their levels under the No Action 

Alternative. Any negative health impacts associated with these emissions are expected to be similarly 

reduced, and there would be no unavoidable negative impacts of these emissions. 

According to NHTSA’s analysis, emissions of carbon monoxide (CO) acetaldehyde, acrolein, 

1,3-butadiene, and formaldehyde could increase under certain alternatives from the levels that are 

projected under the No Action Alternative. Thus, the potential for unavoidable impacts depends on the 

selection of the final standards. The CO increases would occur only under Alternatives 2 through 4 and 

would be approximately 0.7 percent or less over the No Action Alternative. The increases in emissions of 

acetaldehyde, acrolein, 1,3-butadiene, and formaldehyde could occur under any of the action alternatives 

depending on the pollutant and analysis year. The maximum projected increases in emissions, compared 

to the No Action Alternative, are 0.9 percent for acetaldehyde (under Alternative 8 in 2020), 18.4 percent 

for acrolein (under Alternative 8 in 2030), 0.7 percent for 1,3-butadiene (under Alternative 3 in 2030), 

and 9.4 percent for formaldehyde (under Alternative 8 in 2030). Under the Preferred Alternative 

(Alternative 4) the increases in emissions in 2030 compared to the No Action Alternative would be 50 

tons (0.6 percent) for acetaldehyde, 6 tons (1.5 percent) for acrolein, 25 tons (0.7 percent) for 1,3-

butadiene, and 33 tons (0.4 percent) for formaldehyde. 

Increases in criteria and toxic air pollutant emissions could occur in some nonattainment areas as 

a result of implementation of the CAFE standards under the action alternatives, largely due to increases in 

vehicle miles traveled. These increases represent a slight decline in the rate of reductions being achieved 

by implementation of Clean Air Act standards. 

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3.6 Unavoidable Impacts Chapter 3 Affected Environment and Environmental Consequences 

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3.6.2 Short-term Uses and Long-term Productivity 

The eight action alternatives (Alternatives 2 through 9) would result in a decrease in energy 

(crude oil) consumption and reductions in CO2 emissions and associated climate change impacts 

compared to those of Alternative 1, No Action. Manufacturers would need to apply various technologies 

to the production of passenger cars and light trucks to meet the MYs 2012-2016 CAFE standards under 

the eight action alternatives. NHTSA cannot predict which specific technologies manufacturers would 

apply to meet the CAFE standards under any of the eight action alternatives; however, NHTSA estimates 

that existing technologies and existing vehicle production facilities can be applied to meet the standards 

under the eight action alternatives. Some vehicle manufacturers might need to commit additional 

resources to existing, redeveloped, or new production facilities to meet the CAFE standards. Such shortterm uses of resources by vehicle manufacturers to meet the CAFE standards would enable the long-term 

reduction of national energy consumption and would enhance long-term national productivity. 

3.6.3 Irreversible and Irretrievable Commitment of Resources 

Energy consumption in the United States would decrease under all the action alternatives 

compared to the No Action Alternative. Tables 3.2.3-1, 3.2.3-2 and 3.2.3-3 (see Section 3.2 of this EIS) 

summarize fuel consumption under each alternative. For the Preferred Alternative (Alternative 4) the fuel 

savings68 over the No Action Alternative in 2060 would be 21.9 billion gallons for passenger cars and 

another 13.1 billion gallons for light trucks. 

As discussed in Section 3.6.2, manufacturers would need to apply various technologies to the 

production of passenger cars and light trucks to meet the MYs 2012-2016 CAFE standards under the 

eight action alternatives. NHTSA cannot predict which specific technologies manufacturers would apply 

to meet the CAFE standards under any of the eight action alternatives. Existing technologies and existing 

vehicle production facilities can be applied to meet the CAFE standards under the eight action 

alternatives. However, some vehicle manufacturers might need to commit additional resources to 

existing, redeveloped, or new production facilities to meet the standards. The specific amounts and types 

of irretrievable resources (such as electricity and other energy consumption) manufacturers would expend 

in meeting the CAFE standards would depend on the specific methods and technologies manufacturers 

choose to implement. Commitment of resources for manufacturers to comply with the CAFE standards 

would tend to be offset by the fuel savings from implementing the standards. 

 

68 Fuel savings are expressed as the sum of the number of gallons of diesel fuel and gasoline without adjustment for 

the energy content per gallon of each fuel. 
Chapter 3 Affected Environment and Environmental Consequences 3.7 EPA Proposed Action and Analysis 

 3-127 

3.7 EPA PROPOSED ACTION AND ANALYSIS 

3.7.1 Overview 

As explained in Chapter 1, in a joint rulemaking being issued in parallel with this EIS, NHTSA 

and EPA are proposing a strong and coordinated federal greenhouse gas and fuel economy program for 

light-duty vehicles (passenger cars, light-duty trucks, and medium-duty passenger), referred to as the 

National Program. This rule proposes to increase vehicle fuel economy and reduce vehicle GHG 

emissions. NHTSA is proposing CAFE standards under EPCA, as amended by EISA 2007, and EPA is 

proposing its first-ever GHG emissions standards under the CAA. This joint proposal is consistent with 

the President’s announcement on May 19, 2009 of a National Fuel Efficiency Policy that will improve 

fuel economy and reduce greenhouse gas emissions for all new cars and light-duty trucks sold in the 

United States, and the Notice of Upcoming Joint Rulemaking issued by DOT and EPA on that date.69

This section of the EIS presents EPA’s proposal analysis of its proposed action under the CAA, 

and attempts to place EPA’s proposed action in context of NHTSA’s proposed action (setting CAFE 

standards) and the National Program. Section 1501.6 of CEQ regulations emphasize agency cooperation 

early in the NEPA process and allow a lead agency (in this case, NHTSA) to request the assistance of 

other agencies that either have jurisdiction by law or have special expertise regarding issues considered in 

an EIS. NHTSA invited EPA to be a cooperating agency, pursuant to CEQ regulations, because of its 

special expertise in the areas of climate change and air quality.70 On May 12, 2009, the EPA accepted 

NHTSA’s invitation and agreed to become a cooperating agency.

In developing their respective proposals, NHTSA and EPA considered many of the same issues. 

Given differences in their respective statutory authorities, however, the agencies’ proposals include some 

important differences. Significantly, under the CO2 fleet average standard proposed under CAA section 

202(a), EPA expects manufacturers to take advantage of the option to generate CO2-equivalent credits by 

reducing emissions of hydrofluorocarbon (HFC) refrigerant and CO2 through improvements to their air 

conditioner systems. EPA accounted for these reductions in developing its proposed CO2 standard. 

However, EPCA does not permit NHTSA to consider air conditioning credits in developing a proposed 

CAFE standard for passenger cars. CO2 emissions due to air conditioning operation are not measured by 

the test procedure mandated by statute for use in establishing and enforcing CAFE standards for 

passenger cars. As a result, improvements in the efficiency of passenger car air conditioners would not be 

considered as a possible control technology for the purposes of CAFE. 

In addition, in its analysis of the impacts of the program, EPA took into consideration three 

compliance flexibilities that are proposed with the program: full transfer of credits between car and truck 

fleets; flex fueled vehicle credits; and the Temporary Lead-time Allowance Alternative Standards 

 

69 See Notice of Upcoming Joint Rulemaking To Establish Vehicle GHG Emissions and CAFE Standards, 74 FR 

24007 (May 22, 2009). 

70 40 CFR § 1501.6. NHTSA takes no position on whether EPA’s proposed rule on GHG emissions could be 

considered a “connection action” under the Council of Environmental Quality’s regulations at 40 CFR § 1508.25. 

For the purposes of this EIS, however, NHTSA has decided to treat EPA’s proposed rule as if it were a “connected 

action” under those regulations to ensure coordination under the National Program and because we believe such 

treatment will prove beneficial and add value to the EIS. NHTSA is aware that Section 7(c) of the Energy Supply 

and Environmental Coordination Act of 1974 (15 U.S.C. § 793(c)(1)) expressly exempts EPA actions under the 

Clean Air Act from NEPA’s requirements. NHTSA’s discussion in this EIS of EPA’s proposed GHG regulation 

should not be construed as a waiver of EPA’s express NEPA exemption and places no obligation on EPA to comply 

with NEPA in promulgating this or any other rule covered by the exemption. 
3.7 EPA Proposed Action and Analysis Chapter 3 Affected Environment and Environmental Consequences 

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program. NHTSA’s CAFE program has its own compliance flexibilities, and as discussed below, 

NHTSA’s analysis accounts for the potential that some manufacturers (e.g., most European OEMs) would 

pay civil penalties rather than complying with CAFE standards. However, because EPCA prohibits 

NHTSA from considering CAFE credits compliance flexibilities when determining the stringency of 

CAFE standards, NHTSA did not attempt to do so when it developed standards it has considered for this 

action. 71 

Finally, under the proposed EPA GHG emissions standards, there is no ability for a manufacturer 

to intentionally plan to pay a set fine in lieu of meeting the standard. However, under EPCA, automotive 

manufacturers are allowed to pay a fine for every 0.1 mpg they fall short of meeting the CAFE standard 

as a method of compliance. In NHTSA’s analysis prepared for this EIS, there is some level of voluntary 

fine payment reflected in the impacts which reduce the estimated benefits of the alternative CAFE 

standards analyzed. Since intentional noncompliance is not permitted under the CAA, this consideration 

justifies proposing more stringent GHG emissions standards, and is not reflected in EPA’s impacts 

analysis. 

For the above reasons, the proposed CAFE standards (under the Preferred Alternative) are 

somewhat lower than the proposed EPA GHG standard. However, together, NHTSA’s proposed CAFE 

standards and EPA’s GHG emissions standards would represent a harmonized and consistent National 

Program under each agency’s respective statutory framework. They require vehicles to meet an estimated 

combined average emissions level of 250 grams of CO2 per mile in MY 2016 under EPA’s GHG 

program, and 34.1 mpg in MY 2016 under NHTSA’s CAFE program. Under the National Program, the 

overall light-duty vehicle fleet would reach 35.5 mpg in MY 2016, if all reductions were made through 

fuel economy improvements and result in significant reductions in both greenhouse gas emissions and oil 

consumption. For more details, see the NHTSA and EPA joint preamble and the EPA Draft Regulatory 

Impact Analysis (DRIA) (see Appendix E) and the NHTSA Preliminary Regulatory Impact Analysis (see

Appendix D) associated with the joint proposal. 

3.7.2 Summary of EPA Proposal Impact Analysis 

The action EPA is proposing as a part of the National Program would reduce GHG emissions 

emitted directly from vehicles due primarily to reduced fuel use and secondarily to improved air 

conditioning systems. In addition to these “downstream” emissions, reducing CO2 emissions through 

reducing fuel use translates directly to reductions in the emissions associated with the processes involved 

in getting petroleum to the pump, including the extraction and transportation of crude oil, and the 

production and distribution of finished gasoline (termed “upstream” emissions). Reductions from tailpipe 

GHG standards grow over time as the fleet turns over to vehicles affected by these standards, meaning the 

benefit of the standards will continue as long as the oldest vehicles in the fleet are replaced by newer, 

lower CO2 emitting vehicles. 

As detailed in the EPA DRIA (see Appendix E), EPA estimated calendar year tailpipe CO2

reductions based on pre- and post-control CO2 gram per mile levels from EPA’s vehicle technology and 

cost model (which relates manufacturer technology choices and GHG emission reductions) and VMT 

 

71 As documented in NHTSA’s regulatory impact analysis, NHTSA did perform analysis accounting for the 

potential that some manufacturers would earn credits for the production of flexible fuel vehicles (FFVs), and would 

use these credits toward compliance with CAFE standards. 
Chapter 3 Affected Environment and Environmental Consequences 3.7 EPA Proposed Action and Analysis 

 3-129 

projections described in the draft Joint Technical Support Document.72 These estimates reflect the CO2

emissions reductions projected for the entire U.S. vehicle fleet in a specified calendar year. 

As in NHTSA’s analysis, EPA projected expected changes in both “downstream” (vehicle 

tailpipe) and “upstream” (fuel production and distribution) emissions, including the effects of additional 

driving (“VMT rebound”). EPA analyzed the expected effects of the standards on emissions of the 

vehicle-related greenhouse gases: CO2, air conditioning related emissions of HFC refrigerant and CO2, 

N2O, and CH4. EPA also analyzed the effect of the proposed program on “criteria” air pollutants and 

precursors (including CO, PM2.5, SOx, VOC, NOx); and air toxics (including benzene, 1,3-butadiene, 

formaldehyde, acetaldehyde, and acrolein). 

EPA developed downstream emission impacts using a spreadsheet analysis based on data from 

two EPA models. EPA derived computation algorithms and achieved CO2 levels from EPA’s vehicle 

model, coupled with non-CO2 emission rates from EPA’s MOVES. 

EPA calculated upstream emission changes resulting from the decreased fuel consumption using 

a spreadsheet model based on emission factors from Argonne National Laboratory’s GREET Model. 

EPA and NHTSA shared common data inputs for their parallel analyses, as described in the Joint 

Technical Support Document associated with the proposed National Program. For full details of EPA’s 

subsequent analyses and results, please refer to Chapter 5 of EPA’s DRIA, also associated with the 

proposed National Program. 

In addition, EPA estimated changes in projected global mean surface temperature and sea-level 

rise to 2100 using the MiniCAM integrated assessment model coupled with the MAGICC, version 5.3 

climate model. MiniCAM was used to create the globally and temporally consistent set of emission 

scenarios required for running MAGICC. MAGICC was then used to estimate the change in the global 

mean surface temperature and sea-level rise over time (at five-year time steps). Given the magnitude of 

the estimated emissions reductions associated with the proposal, a simple climate model such as 

MAGICC is reasonable for estimating the climate response. 

To capture some key uncertainties in the climate system with the MAGICC model, the changes in 

projected temperatures and sea level were estimated across the most current IPCC range of climate 

sensitivities, 1.5 °C to 6.0 °C.73 To compute the change in temperature and sea-level rise attributable to 

the proposal, the output from the proposal’s emissions scenario were subtracted from an existing 

MiniCAM emission scenario. Details about the models used, reference case scenario, and how the 

emissions reductions were applied to generate the proposal scenario can be found in chapter 7.4 of EPA’s 

DRIA (see Appendix E). 

3.7.2.1 Energy 

EPA anticipates its proposal would create significant fuel savings as compared to the baseline. 

Projected fuel savings are shown in Table 3.7.2-1. 

 

72 Both NHTSA’s and EPA’s regulatory impact analyses can be found in appendices to this EIS. They can also be 

found in the docket for this rulemaking, along with the Joint Technical Support Document. 

73 In IPCC reports, equilibrium climate sensitivity refers to the equilibrium change in the annual mean global surface 

temperature following a doubling of the atmospheric equivalent carbon dioxide concentration. The IPCC states that 

climate sensitivity is “likely” to be in the range of 2 °C to 4.5 °C, “very unlikely” to be less than 1.5 °C, and “values 

substantially higher than 4.5 °C cannot be excluded.” IPCC (2007). 
3.7 EPA Proposed Action and Analysis Chapter 3 Affected Environment and Environmental Consequences 

In calendar year 2030, EPA analysis projects its proposal to reduce light-duty fuel consumption 

approximately 17 percent relative to the reference scenario. 

Table 3.7.2-1 

Impacts of Proposed Standards on Fuel Savings 

Calendar Year 

Annual Fuel Savings due to Proposed 

Standards 

(Billion Gallons Of Gasoline 

Equivalent) 

No Action Fuel Consumption 

(Billion Gallons Of Gasoline 

Equivalent) 

2020 13.4 142.2 

2030 26.2 161.9 

2040 33.9 196.2 

2050 42.6 244.1 

3.7.2.2 Air Quality 

EPA estimates that its proposed standards would result in emission reductions of NOx, VOC, 

PM2.5 and SOx, but would slightly increase CO emissions. The overall impact of its proposal would be 

relatively small compared to total U.S. inventories across all sectors for these pollutants. In 2030, its 

proposed standards would reduce these total NOx, PM and SOx inventories by 0.2 to 0.3 percent and 

reduce the VOC inventory by 1.2 percent, while increasing the total national CO inventory by 0.4 percent. 

EPA estimates that the proposed GHG standards would result in mixed impacts on air toxic 

emissions. Again, the overall impact of the proposal would be relatively small for these pollutants 

compared to total U.S. inventories across all sectors. In 2030, EPA estimates that its standards would 

reduce total acrolein, benzene, and formaldehyde emissions by less than 0.1 percent. Total 1,3-butadiene 

and acetaldehyde emissions would increase by 0.1 to 0.2 percent. 

Table 3.7.2-2 presents the impacts of the proposed standards on each of the non-GHG pollutants 

that EPA analyzed. 

For its final rule, EPA will perform a national-scale air quality modeling analysis to analyze the 

impacts of the proposed vehicle GHG standards on PM2.5, ozone, and selected air toxics (i.e., benzene, 

formaldehyde, acetaldehyde, acrolein and 1,3-butadiene). The length of time needed to prepare the 

necessary emissions inventories, in addition to the processing time associated with the modeling itself, 

has precluded EPA from performing air quality modeling for the proposed rule. 

The atmospheric chemistry related to ambient concentrations of PM2.5, ozone and air toxics is 

very complex, and making predictions based solely on emissions changes is extremely difficult. 

However, based on the magnitude of the emissions changes predicted to result from the proposed vehicle 

GHG standards, EPA expects that there will be an improvement in ambient air quality, pending a more 

comprehensive analysis for the final rule. 

Table 3.7.2-2 

Impacts of Proposed Standards on Non-GHG Emissions (Short Tons Per Year) 

Pollutant Calendar Year % Change vs. Calendar Year % Change vs. 

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Chapter 3 Affected Environment and Environmental Consequences 3.7 EPA Proposed Action and Analysis 

2020 2020 Reference 2030 2030 Reference 

Δ Carbon Monoxide 70,614 0.13% 227,832 0.38%

Δ NOx -17,206 -0.14% -27,726 -0.23%

Δ PM2.5 -2,856 -0.08% -5,431 -0.16%

Δ SOx -16,307 -0.18% -31,965 -0.34%

Δ VOC -73,739 -0.60% -142,347 -1.17%

Δ 1,3-Butadiene 11.5 0.07% 36.8 0.22%

Δ Acetaldehyde 16.8 -0.04% 60.6 0.13%

Δ Acrolein 0.2 -0.00% 1.8 -0.03%

Δ Benzene -83.6 -0.04% -77.5 -0.04%

Δ Formaldehyde -28.3 -0.03% -15.7 -0.02%

3.7.2.3 Climate Change 

The results, in both Figures 3.7.2-1 and 3.7.2-2, of EPA’s climate change modeling analysis show 

a small, but quantifiable, reduction in projected global mean surface temperature and sea level as a result 

of this proposal across all climate sensitivities. Global mean temperature is projected to be reduced by 

approximately 0.007–0.016 °C by 2100 and global mean sea-level rise is projected to be reduced by 

approximately 0.06–0.15 cm by 2100. The reductions are small relative to the IPCC’s 2100 “best 

estimates” for global mean temperature increases (1.8–4.0 oC) and sea-level rise (0.20–0.59 m) for all 

global GHG emissions sources for a range of emissions scenarios. These projected reductions are 

proportionally representative of changes to U.S. GHG emissions in the transportation sector. 

As a substantial portion of CO2 emitted into the atmosphere is not removed by natural processes 

for millennia, each unit of CO2 not emitted into the atmosphere avoids essentially permanent climate 

change on centennial time scales. While not formally estimated for the joint proposed rule, a reduction in 

projected global mean temperature and sea-level rise implies a reduction in the adverse risks associated 

with climate change. Both figures illustrate that the distribution for projected global mean temperature 

and sea-level rise increases has shifted downward as a result of the proposal. 

 3-131 
3.7 EPA Proposed Action and Analysis Chapter 3 Affected Environment and Environmental Consequences 

Figure 3.7.2-1. Estimated Projected Reductions in Global Mean 

Surface Temperatures from Baseline for Climate Sensitivities 

Ranging from 1.5–6 °C 

Global Mean Temperature Change

-0.0200

-0.0150

-0.0100

-0.0050

0.0000

2000 2050 2100

Year

Difference (°C)

ClimSens=1.5

ClimSens=2.0

ClimSens=2.5

ClimSens=3.0

ClimSens=4.5

ClimSens=6.0

Figure 3.7.2-2. Estimated Projected Reductions in Global Mean 

Sea-Level Rise from Baseline for Climate Sensitivities 

Ranging from 1.5–6 °C 

Global Mean Sea Level Rise Change

-0.20

-0.15

-0.10

-0.05

0.00

2000 2050 2100

Year

Difference (cm)

ClimSens=1.5

ClimSens=2.0

ClimSens=2.5

ClimSens=3.0

ClimSens=4.5

ClimSens=6.0

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Chapter 4 Cumulative Impacts 

4.1 INTRODUCTION 

The Council on Environmental Quality (CEQ) identifies the impacts federal agencies must 

address and consider in satisfying the requirements of the National Environmental Policy Act (NEPA). 

This includes permanent, short-term and long-term direct, indirect, and cumulative impacts. 

CEQ NEPA implementing regulations at 40 CFR § 1508.7 define cumulative impact as “the 

impact on the environment which results from the incremental impact of the action when added to other 

past, present, and reasonably foreseeable future actions regardless of what agency (federal or non-federal) 

or person undertakes such other actions.” Cumulative impacts should be evaluated along with the overall 

impacts of each alternative. The range of alternatives considered should include a No Action Alternative 

as a baseline against which to evaluate cumulative effects. The range of actions to be considered includes 

not only the proposed action but all connected and similar actions that could contribute to cumulative 

effects. Connected actions should be addressed in the same analysis. CEQ recommends that an agency’s 

analysis accomplish the following: 

• Focus on the effects and resources within the context of the proposed action. 

• Present a concise list of issues that have relevance to the anticipated effects of the proposed 

action or eventual decision. 

• Reach conclusions based on the best available data at the time of the analysis. 

• Rely on information from other agencies and organizations on reasonably foreseeable 

projects or activities that are beyond the scope of the analyzing agency’s purview. 

• Relate to the geographic scope of the proposed project. 

• Relate to the temporal period of the proposed project. 

A cumulative impacts analysis involves assumptions and uncertainties. Monitoring programs and 

research can be identified to supplement the available information and thus enhance analyses for the 

future. The absence of an ideal database should not prevent the completion of a cumulative effects 

analysis. 

Chapter 4 addresses areas of the quantitative analyses presented in Chapter 3, with particular 

attention to energy, air, and climate, and describes the indirect cumulative effects of climate change on a 

global scale. This chapter is organized according to the conventions of the climate change literature 

rather than the conventions of an Environmental Impact Statement (EIS) format. To assist the reader, the 

table on the following page maps topics found in U.S. Department of Transportation (DOT) NEPA 

documents (DOT Order 5610.1C) to the sections in this EIS. 

 4-1 
4.1 Introduction Chapter 4 Cumulative Impacts 

Typical NEPA Topics EIS Subsections 

Water 4.4 Climate; 4.5.3 Freshwater Resources; 4.5.5 Coastal Systems 

and Low-lying Areas 

Ecosystems 4.5.3 Freshwater Resources; 4.5.4 Terrestrial Ecosystems; 

4.5.5 Coastal Systems and Low-lying Areas; 4.5.6 Food, Fiber, and 

Forest Products; 4.7 Non-climate Cumulative Impacts of CO2 

Threatened and endangered species 4.5.4 Terrestrial Ecosystems; 4.5.5 Coastal Systems and Low-lying 

Areas; 4.7 Non-climate Cumulative Impacts of CO2

Publicly owned parklands, recreational 

areas, wildlife and waterfowl refuges, and 

historic sites, Section 4(f) related issues 

4.5.3 Freshwater Resources; 4.5.4 Terrestrial Ecosystems; 

4.5.5 Coastal Systems and Low-lying Areas; 4.5.7 Industries, 

Settlements, and Society 

Properties and sites of historic and cultural 

significance 

4.5.7 Industries, Settlements, and Society 

Considerations relating to pedestrians and 

bicyclists 

4.5.7 Industries, Settlements, and Society 

Social impacts 4.5.7 Industries, Settlements, and Society; 4.6 Environmental 

Justice 

Noise 4.5.7 Industries, Settlements, and Society 

Air 4.3 Air Quality 

Energy supply and natural resource 

development 

4.2 Energy; 4.5.4 Terrestrial Ecosystems; 4.5.6 Food, Fiber, and 

Forest Products; 4.5.7 Industries, Settlements, and Society 

Floodplain management evaluation 4.5.3 Freshwater Resources; 4.5.5 Coastal Systems and Low-lying 

Areas 

Wetlands or coastal zones 4.5.3 Freshwater Resources; 4.5.5 Coastal Systems and Low-lying 

Areas 

Construction impacts 4.3 Air Quality; 4.4 Climate; 4.5.7 Industries, Settlements, and 

Society; 4.5.8 Human Health 

Land use and urban growth 4.4 Climate; 4.5.6 Food, Fiber, and Forest Products; 

4.5.7 Industries, Settlements, and Society 

Human environment involving community 

disruption and relocation 

4.3 Air Quality; 4.4 Climate; 4.5.5 Coastal Systems and Low-lying 

Areas; 4.5.7 Industries, Settlements, and Society; 4.5.8 Human 

Health; 4.6 Environmental Justice 

4.1.1 Approach to Scientific Uncertainty and Incomplete Information 

4.1.1.1 CEQ Regulations 

CEQ regulations recognize that many federal agencies confront limited information and 

substantial uncertainties when analyzing the potential environmental impacts of their actions under 

NEPA. 40 CFR § 1502.22. Accordingly, the regulations provide agencies with a means to formally 

acknowledge incomplete or unavailable information in NEPA documents. Where “information relevant 

to reasonably foreseeable significant adverse impacts cannot be obtained because the overall costs of 

obtaining it are exorbitant or the means to obtain it are not known,” the regulations require an agency to 

include in its NEPA document: 

1. A statement that such information is incomplete or unavailable; 

2. A statement of the relevance of the incomplete or unavailable information to evaluating 

reasonably foreseeable significant adverse impacts on the human environment; 

 4-2 
Chapter 4 Cumulative Impacts 4.1 Introduction 

3. A summary of existing credible scientific evidence that is relevant to evaluating the 

reasonably foreseeable significant adverse impacts on the human environment; and 

4. The agency’s evaluation of such impacts based on theoretical approaches or research methods 

generally accepted in the scientific community. 

Relying on these provisions is appropriate when an agency is performing a NEPA analysis that 

involves potential environmental impacts resulting from carbon dioxide (CO2) emissions (e.g., Mayo 

Found. v. Surface Transp. Bd., 472 F.3d 545, 555 (8th Cir. 2006). CEQ regulations at 40 CFR § 1502.21 

also authorize agencies to incorporate material into a NEPA document by reference to “cut down on bulk 

without impeding agency and public review of the action.” 

Throughout this EIS, the National Highway Transportation Safety Administration (NHTSA) uses 

these two mechanisms – acknowledging incomplete or unavailable information and incorporation by 

reference – to address areas for which the agency cannot develop a credible estimate of the potential 

environmental impacts of the standards or reasonable alternatives. In particular, NHTSA recognizes that 

information about the potential environmental impacts of changes in emissions of CO2 and other 

greenhouse gases (GHGs) and associated changes in temperature, including those expected to result from 

the proposed rule, is incomplete. In this EIS, NHTSA often relies on the EPA Technical Support 

Document entitled Endangerment and Cause or Contribution Findings for Greenhouse Gases under 

Section 202(a) of the Clean Air Act (EPA 2009), the Intergovernmental Panel on Climate Change (IPCC) 

Fourth Assessment Report by Working Group II (WGII) entitled Climate Change 2007 – Impacts, 

Adaptation, and Vulnerability (IPCC 2007), and the U.S. Climate Change Science Program (CCSP) 

Synthesis and Assessment Product (SAP) reports as a recent “summary of existing credible scientific 

evidence which is relevant to evaluating the reasonably foreseeable significant adverse impacts on the 

human environment.” See 40 CFR § 1502.22(b)(3). 

4.1.2 Temporal and Geographic Boundaries 

When evaluating cumulative effects, the analysis must consider expanding the geographic study 

area beyond that of the proposed action, and expanding the temporal (time) limits to consider past, 

present, and reasonably foreseeable future actions that might affect the environmental resources of 

concern. The timeframe for this cumulative impacts analysis extends through 2050 for the air quality 

analysis and through 2100 for energy and climate change. The analysis considers potential cumulative 

impacts on a national and global basis. 

4.1.3 Reasonably Foreseeable Future Actions 

The methodology for evaluating cumulative effects includes the reasonably foreseeable future 

actions of projected average annual passenger car and light truck mile-per-gallon (mpg) estimates from 

2016 through 2030 that differ from mpg estimates reflected in the Chapter 3 analysis. The Chapter 3 

analysis reflects the direct impacts of fuel economy requirements for model years (MYs) 2012 through 

2016 under each of the action alternatives, assuming no further increases in average new passenger car or 

light truck mpg after 2016. For Chapter 3, this is a reasonable assumption because Chapter 3 is intended 

to show the direct and indirect effects of the proposed action. The Chapter 3 analysis does not show the 

environmental effects of fuel economy improvements beyond those made under the proposed action by 

MY 2016. 

However, the Chapter 4 evaluation of cumulative effects projects ongoing gains in average new 

passenger car and light truck mpg consistent with Annual Energy Outlook (AEO) 2010 Early Release 

(EIA 2009) Reference Case projections because those projected gains are reasonably foreseeable future 

 4-3 
4.1 Introduction Chapter 4 Cumulative Impacts 

actions. AEO Reference Case projections are regarded as the official U.S. Government energy 

projections by both the public and private sector. Chapter 3, Section 3.2.1 provides an expanded 

description of the AEO. In general, the AEO Reference Case projections tend to fall in the middle of 

similar publicly available projections. The AEO projections for average new passenger car and light 

truck mpg assume that combined new passenger cars and light trucks surpass an average of 35 mpg in 

2019, and reach 35.5 mpg in 2020, slightly exceeding the Energy Independence and Security Act (EISA) 

2007 requirement of 35 mpg in 2020. The AEO Reference Case projections also anticipate an average 

annual percentage gain of 0.49 percent in passenger car mpg and 0.68 percent in light truck mpg from 

2019 through 2030, due to consumer demand and technology advances associated with ongoing increases 

in fuel prices through 2030. The analysis of cumulative effects in this chapter reflects these AEO mpg 

projections as reasonably foreseeable future actions, associated with future government actions as needed 

to achieve the EISA 2007 requirement of 35 mpg in 2020, and future consumer and industry actions that 

result in ongoing mpg gains through 2030. Table 4.1.3-1 shows the AEO projected total and annual 

percentage increases for fuel economy. 

Table 4.1.3-1 

AEO 2019-2030 Projected Gains in Fuel Economy Reflected in Analysis of Cumulative Impacts 

2019-2030 Total % Increase in Fuel 

Economy 

2019-2030 Average Annual % Increase in 

Fuel Economy 

New Passenger Car 6.8 0.49 

New Light Truck 8.8 0.68 

The specific manner in which the AEO mpg projections are applied varies across the action 

alternatives to ensure that all action alternatives achieve the EISA 2007 requirement of 35 mpg in 2020. 

The increase in fuel economy from 2016 to 2030 is expected to be at least equal to a gain of 0.49 percent 

in passenger car mpg and 0.68 percent in light truck mpg under all action alternatives. Also, an even 

faster rate of mpg gain is expected from 2016 to 2020 for two action alternatives that would have to 

increase mpg at a faster rate after 2016 to achieve the EISA 2007 requirement of 35 mpg in 2020. 

Alternatives 4 through 9 would exceed the EISA requirement of 35 mpg in 2020, with an average annual 

percentage gain of 0.51 percent in passenger car mpg and 0.86 percent in light truck mpg after 2016. 

Therefore, the analysis of cumulative impacts projects annual percentage gains of 0.49 percent in 

passenger car mpg and 0.68 percent in light truck mpg for 2016 through 2030 under Alternatives 4 

through 9. Alternatives 2 and 3 would require larger percentage gains in mpg from 2016 to 2020 to 

achieve the EISA requirement of 35 mpg in 2020. Therefore, the analysis of cumulative impacts projects 

annual gains in mpg from 2016 to 2020 under Alternatives 2 and 3 that are large enough to achieve the 

EISA requirement of 35 mpg in 2020. The projected actual achieved mpg in 2020 (fleet-wide average) 

actually slightly exceeds 35 mpg in 2020 (consistent with the AEO projection) under Alternatives 2 and 3 

(and under other action alternatives) because some manufacturers would exceed the EISA requirement of 

35 mpg in 2020. The analysis of cumulative impacts also projects annual percentage gains of 0.49 

percent in passenger car mpg and 0.68 percent in light truck mpg under Alternatives 2 and 3 from 2020 

through 2030. 

The assumption that all Action Alternatives reach the EISA 35 mpg target by 2020, with mpg 

growth at the AEO forecast rate from 2020 to 2030, results in estimated cumulative impacts for 

Alternatives 2, 3, and 4 that are substantially equivalent, with any minor variation in cumulative impacts 

across these Alternatives due to the specific modeling assumptions used to ensure that each Alternative 

achieves at least 35 mpg by 2020. Therefore, the cumulative impacts analysis in Chapter 4 adds 

substantively to the analysis of direct impacts in Chapter 3 when comparing cumulative impacts between 

Alternatives 4 through 9, but not when comparing cumulative impacts between Alternatives 2 through 4. 

 4-4 
Chapter 4 Cumulative Impacts 4.1 Introduction 

 4-5 

Another important difference in the methodology for evaluating cumulative effects is that the No 

Action Alternative (Alternative 1) also reflects projected annual percentage gains of 0.49 percent in 

passenger car mpg and 0.68 percent in light truck mpg for 2016 through 2030, whereas the Chapter 3 

analysis assumed no increases in average new passenger car or light truck mpg after 2016 under any 

alternative, including the No Action Alternative. Chapter 2 explained that the No Action Alternative 

(Alternative 1) assumes no action occurs under the National Program (i.e., NHTSA and EPA do not act, 

and in the absence of standards, manufacturers continue to meet the NHTSA MY 2011Corporate Average 

Fuel Economy (CAFE) standards), so average fuel economy levels in the absence of CAFE standards 

beyond MY 2011 would equal the higher of the agencies’ collective market forecast or the manufacturer’s 

required level of average fuel economy for MY 2011. The No Action Alternative, by definition, would 

not satisfy the Energy Conservation and Policy Act (EPCA) (as updated by EISA) requirement to set 

standards such that the combined fleet of passenger cars and light trucks achieves a combined average 

fuel economy of at least 35 mpg for MY 2020 (nor would it satisfy the EPCA, as updated by EISA, 

requirement to adopt annual fuel economy standard increases).1

 The evaluation of cumulative effects in 

this chapter is consistent in that the projected annual percentage gains of 0.49 percent in passenger car 

mpg and 0.68 percent in light truck mpg for 2016 through 2030 under the No Action Alternative still do 

not reflect any action under the National Program, but only the annual AEO projected gain in mpg 

through 2030 due to consumer demand and technology advances associated with ongoing increases in 

fuel prices. 

Even with this projected annual percentage gain in mpg for 2016 through 2030, the No Action 

Alternative would still not achieve the EISA requirement of 35 mpg in 2020. The annual AEO projected 

gain in mpg through 2030 due to consumer demand and technology advances is applied to the No Action 

Alternative and to each of the action alternatives so that the difference between fuel use, emissions, and 

other projections under the No Action Alternative and the action alternatives can be meaningfully 

compared (e.g., by calculating fuel saved by any action alternative in relation to the No Action 

Alternative). 

NHTSA also considered other reasonably foreseeable actions that would affect greenhouse gas 

emissions (GHGs). Section 4.4.3.3 discusses these actions and their incorporation into the analysis. 

 

1

 Although EISA’s recent amendments to EPCA direct NHTSA to increase CAFE standards and do not permit the 

agency to take no action on fuel economy, CEQ regulations mandate analysis of a no action alternative. See 40 CFR 

§ 1502.14(d). CEQ has explained that “the regulations require the analysis of the no action alternative even if the 

agency is under a court order or legislative command to act.” Forty Most Asked Questions Concerning CEQ’s 

National Environmental Policy Act Regulations, 46 FR 18026 (1981) (emphasis added). The MY 2011 fuel 

economy level represents the standard NHTSA believes manufacturers would continue to abide by, assuming 

NHTSA does not issue a rule. 
4.2 Energy Chapter 4 Cumulative Impacts 

4.2 ENERGY 

A NEPA analysis must consider the cumulative impacts of the proposed action. For this EIS, 

such considerations include evaluating the cumulative fuel consumption of the vehicle fleet from the 

onset of the proposed new CAFE standards. 

4.2.1 Affected Environment 

According to the Energy Information Administration (EIA), net imports of total liquid fuels, 

including crude oil, refined products, and biofuels, which in 2007 amounted to 58 percent of total 

consumption, will fall to 48 percent of total consumption in 2020 and then fall further to 45 percent of 

consumption in 2035 (EIA 2009). This change is attributed in part to expected changes in the CAFE 

standards and to the increased use of biofuels. The steep decline predicted in imports by 2025 is also 

driven by the surge in U.S. domestic crude-oil production in the previous decade. After 2025, imports of 

crude oil and biofuels are forecasted to grow slowly through 2035, although imports of finished products 

continue to decline. The predicted shift in crude oil imports in the period leading up to 2030 could have 

some effect on the global price of crude oil, but the United States is a price taker not a pricemaker when it 

comes to petroleum. In addition, over time the U.S. share of global demand for liquid fuels will decline 

due to rapid increases in demand in developing economies, including China and India, reducing the 

relative impact of the CAFE standards on global markets. EIA projections show that U.S. consumption of 

petroleum liquids amounted to 24 percent of global liquid consumption in 2007 and falls to 20 percent by 

2035 (EIA 2009). 

Over time, a larger share of liquid fuels is expected to be produced from unconventional sources 

such as biofuels, shale oil, coal-to-liquids, and gas-to-liquids. These alternative sources would affect CO2

and other emissions reductions from the CAFE alternatives. This shift would be driven by changes to the 

Renewable Fuels Standard (RFS) in EISA, which forecasts that 36 billion gallons of renewable fuels will 

be required by 2022 for use primarily in the transportation sector. The EIA AEO 2010 forecasts that 

domestic production of non-hydro renewable energy (biomass, landfill gas, biogenic municipal waste, 

wind, photovoltaic, and solar thermal sources) will increase from just over 4 quadrillion British thermal 

units in 2007 to almost 14 quadrillion British thermal units in 2035 (EIA 2009). In the United States, 

liquid fuels from gas, coal, and biomass are projected to increase from 0.00 quadrillion British thermal 

units in 2007 to 1.18 quadrillion British thermal units by 2035. 

Changes to the CAFE standards are unlikely to affect domestic production, given the level of 

crude oil imports. Impacts on production would occur outside of the United States, and would be 

determined by the balance between the decline in U.S. imports and the increase in demand from 

developing countries. Impacts on petroleum products would be mixed. U.S. imports of petroleum 

products are often targeted for specific product requirements, for logistical reasons, or to optimize the 

inputs and outputs from refineries. Petroleum imports depend on specific product demands and the mix 

of crudes processed in the refineries, which are projected to change considerably over time. 

Consequently, any decline in demand for petroleum products is likely to have some effect on both 

overseas and domestic refineries. 

4.2.2 Methodology 

As explained in Section 4.1.3, AEO mpg projections through 2030 are reflected in the analysis of 

cumulative impacts. In particular, this analysis projects annual gains in mpg from 2016 to 2020 under 

Alternatives 2 and 3 large enough to achieve the EISA requirement of 35 mpg combined for passenger 

cars and light trucks in 2020. Additionally, the analysis projects annual percentage gains of 0.49 percent 

in passenger car mpg and 0.68 percent in light truck mpg from 2019 through 2030 under Alternatives 2 

 4-6 
Chapter 4 Cumulative Impacts 4.2 Energy 

and 3, and from 2016 through 2030 under the No Action Alternative and Alternatives 4 through 9. The 

compound annual gains of 0.49 percent in passenger car mpg and 0.68 percent in light truck mpg through 

2030 reflect the total percentage gains projected by AEO from 2019 through 2030 (see Table 4.1.3-1 in 

Section 4.1.3). 

4.2.3 Environmental Consequences 

Implementing alternative CAFE standards would result in different future levels of fuel use, total 

energy, and petroleum consumption, which in turn would have an impact on emissions of GHGs and 

criteria air pollutants. An important measure of the impact of alternative CAFE standards is the impact on 

the fuel consumption of the vehicle fleet from the onset of the new standards. Passenger cars and light 

trucks are considered separately; total fuel consumption encompasses gasoline and diesel. CAFE 

standards for MYs 2012-2020 are assumed to apply to all subsequent additions to the vehicle fleet. 

Table 4.2.3-1 shows the fuel consumption of passenger cars under the No Action Alternative 

(Alternative 1) and the eight action alternatives (Alternatives 2 through 9), as described in Section 2.3. 

By 2060, fuel consumption reaches 193.2 billion gallons under the No Action Alternative. Consumption 

falls across the alternativesfrom 167.2 billion gallons under Alternatives 3 and 4 to 156.3 and 157.2 

billion gallons under Alternatives 8 and 9, representing a fuel savings of 26.0 to 36.9 billion gallons in 

2060. 

Table 4.2.3-2 shows the fuel consumption of light trucks under the CAFE alternatives examined. 

Fuel consumption by 2060 reaches 103.8 billion gallons under the No Action Alternative. Consumption 

declines across the alternatives, from 92.2 billion gallons under Alternative 2 to 84.6 billion gallons under 

Alternative 8. This represents a fuel savings of 11.5 to 19.1 billion gallons in 2060. 

Table 4.2.3-1 

Cumulative Effects of Passenger Car Annual Fuel Consumption and Fuel Savings 

(billion gallons of gasoline equivalent) 

Alt. 1 Alt. 2 Alt. 3 Alt. 4 Alt. 5 Alt. 6 Alt. 7 Alt. 8 Alt. 9 

Calendar 

Year 

No 

Action 

3%/year 

Increase 

4%/year 

Increase 

~4.3%/year

Increase 

Preferred

5%/year 

Increase

~6.0%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.6%/year 

Increase 

TCTB 

Fuel Consumption 

2020 73.8 69.4 68.4 68.0 67.3 66.0 66.2 65.4 65.4

2030 100.4 88.0 87.6 87.5 86.0 83.6 83.6 81.9 82.3

2040 127.0 110.0 109.9 109.9 108.1 104.9 104.9 102.7 103.3

2050 157.5 136.4 136.3 136.3 134.1 130.2 130.1 127.5 128.2

2060 193.2 167.3 167.2 167.2 164.5 159.6 159.6 156.3 157.2

Fuel Savings Compared to No Action 

2020 -- 4.4 5.5 5.8 6.5 7.8 7.6 8.4 8.4

2030 -- 12.4 12.8 12.9 14.4 16.8 16.8 18.5 18.1

2040 -- 17.0 17.1 17.1 18.9 22.0 22.1 24.2 23.7

2050 -- 21.2 21.2 21.2 23.4 27.4 27.4 30.1 29.4

2060 -- 26.0 26.0 26.0 28.7 33.6 33.6 36.9 36.0

 4-7 
4.2 Energy Chapter 4 Cumulative Impacts 

Table 4.2.3-2 

Cumulative Effects of Light Truck Annual Fuel Consumption and Fuel Savings 

(billion gallons of gasoline equivalent) 

Alt. 1 Alt. 2 Alt. 3 Alt. 4 Alt. 5 Alt. 6 Alt. 7 Alt. 8 Alt. 9 

Calendar 

Year 

No 

Action 

3%/year 

Increase 

4%/year 

Increase

~4.3%/year

Increase 

Preferred

5%/year

Increase

~6.0%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.6%/year 

Increase 

TCTB 

Fuel Consumption 

2020 75.6 72.8 72.2 71.7 71.2 70.0 70.2 69.6 69.6

2030 69.4 63.4 63.2 62.5 61.5 59.8 59.9 58.9 59.0

2040 73.1 65.4 65.4 64.7 63.5 61.5 61.4 60.2 60.5

2050 85.6 76.2 76.2 75.3 73.9 71.5 71.4 70.0 70.3

2060 103.8 92.2 92.3 91.2 89.4 86.6 86.4 84.6 85.1

Fuel Savings Compared to No Action 

2020 -- 2.7 3.4 3.9 4.4 5.6 5.3 6.0 6.0

2030 -- 6.0 6.3 6.9 7.9 9.6 9.6 10.6 10.4

2040 -- 7.7 7.7 8.5 9.7 11.6 11.7 12.9 12.6

2050 -- 9.4 9.4 10.3 11.7 14.1 14.2 15.6 15.3

2060 -- 11.5 11.5 12.6 14.3 17.2 17.3 19.1 18.7

Table 4.2.3-3 summarizes the fuel consumption and savings for both passenger cars and light 

trucks. Fuel consumption reaches 297.0 billion gallons under the No Action Alternative in 2060 and 

declines across the alternatives, from 259.5 billion gallons under Alternative 2 to 241.0 billion gallons 

under Alternative 8. This represents a fuel savings of 37.5 to 56.0 billion gallons in 2060. 

As a result of the assumptions in fuel economy growth after 2016, annual fuel consumption is 

reduced compared to the fuel consumption results reported in the direct and indirect effects analysis in 

Section 3.2.3. Fuel savings for Alternatives 2 and 3 are greater in this analysis than in Section 3.2.3. 

Alternatives 2 and 3 have a fast annual growth in mpg from 2016 to 2020 in order to achieve the EISA 

requirement of 35 mpg whereas the No Action Alternative increases at a rate consistent with AEO 

projections. Alternative 4 through 9 show reduced fuel savings as compared to the analysis in Section 

3.2.3 because the No Action Alternative, from which the fuel savings is calculated, has lower fuel 

consumption due to the growth in mpg assumed in this analysis. 

 4-8 
Chapter 4 Cumulative Impacts 4.2 Energy 

 4-9 

Table 4.2.3-3 

Cumulative Effects of Combined Passenger Car and Light Truck Annual Fuel Consumption 

and Fuel Savings a/ 

(billion gallons of gasoline equivalent) 

Alt. 1 Alt. 2 Alt. 3 Alt. 4 Alt. 5 Alt. 6 Alt. 7 Alt. 8 Alt. 9 

Calendar 

Year 

No 

Action 

3%/year 

Increase 

4%/year 

Increase

~4.3%/year

Increase 

Preferred 

5%/year 

Increase 

~6.0%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.6%/year 

Increase 

TCTB 

Fuel Consumption 

2020 149.4 142.2 140.5 139.7 138.5 136.0 136.4 135.0 135.0 

2030 169.9 151.5 150.7 150.0 147.6 143.4 143.5 140.8 141.4 

2040 200.1 175.4 175.3 174.6 171.6 166.4 166.3 163.0 163.8 

2050 243.1 212.5 212.5 211.7 208.0 201.7 201.5 197.4 198.4 

2060 297.0 259.5 259.5 258.4 253.9 246.2 246.0 241.0 242.2 

Fuel Savings Compared to No Action 

2020 -- 7.1 8.9 9.7 10.9 13.4 13.0 14.4 14.4 

2030 -- 18.4 19.1 19.9 22.3 26.4 26.4 29.1 28.5 

2040 -- 24.7 24.8 25.5 28.5 33.7 33.8 37.1 36.3 

2050 -- 30.6 30.6 31.5 35.2 41.4 41.6 45.7 44.7 

2060 -- 37.5 37.5 38.5 43.1 50.8 51.0 56.0 54.7 

_______________ 

a/ Some of the values shown for car & light truck fuel consumption in this table vary slightly from the 

sum of values shown separately for passenger cars and light trucks in previous tables due to rounding error. 
4.3 Air Quality Chapter 4 Cumulative Impacts 

 4-10 

4.3 AIR QUALITY 

4.3.1 Affected Environment 

Section 3.3.1 describes the air quality affected environment. 

4.3.2 Methodology 

4.3.2.1 Overview 

The analysis methodology for air quality cumulative impacts and consequent health outcomes is 

the same as described in Section 3.3.2, except that the cumulative impacts analysis assumes annual 

average percentage gains in average fuel economy from 2016 through 2030 consistent with the AEO 2010 

Early Release (EIA 2009) Reference Case projections, with all action alternatives exceeding the 

combined EISA target of 35 mpg in 2020 (see Section 4.1.3). These AEO mpg projections reflect 

reasonably foreseeable future government actions as needed to achieve the EISA 2007 requirement, and 

future consumer and industry actions that result in ongoing mpg gains through 2030. Because there are 

no valid projections that go past calendar year 2030, the average fuel economy estimates for MYs 2030-

2050 remain constant. NHTSA analyzed the cumulative air quality impacts of the action alternatives by 

calculating the emissions from passenger cars and light trucks that would occur under each alternative, 

including the effects of percentage gains in mpg from 2016 through 2030 consistent with AEO 

projections, and assessing the changes in emissions in relation to the No Action Alternative, to which the 

AEO forecasted fuel economy increases were also applied. 

This analysis considers the following cumulative impacts of alternative CAFE standards for MYs 

2012-2016 and other reasonably foreseeable actions projected to affect fuel economy through 2030, as 

described in Section 4.1.3. Because CAFE standards and ongoing mpg gains apply to new vehicles, this 

assumption results in emissions reductions and fuel savings that continue to grow as new vehicles with 

higher average mpg are added to the fleet in each subsequent year, reaching their maximum values when 

all passenger cars and light trucks in the U.S. fleet meet the mpg projection for new passenger cars and 

light trucks in 2030. To account for these effects on emissions beyond calendar year 2030, NHTSA 

analyzed cumulative impacts through 2050. Because the cumulative impacts analysis assumes that new 

vehicles in model years beyond MY 2016 have a higher fleet average fuel economy based on AEO fuel 

economy projections, these assumptions result in emissions reductions and fuel savings that continue to 

grow as these new, more fuel efficient vehicles are added to the fleet in each subsequent year, reaching 

their maximum values when all passenger cars and light trucks in the U.S. fleet have these higher mpg 

levels. Because of this, NHTSA analyzed the air emissions through 2050, when most of the fleet would 

achieve the average fuel economy levels the agency projects in 2030 (based on AEO fuel economy 

forecasts).2

 For comparison, the Chapter 3 analysis only examines the direct and indirect effects of the 

proposed MYs 2012-2016 standards and analyzes the effect of this rule through 2030. 

4.3.2.2 Treatment of Incomplete or Unavailable Information 

As noted in Section 3.3.2, the estimates of emissions rely on models and forecasts that contain 

numerous assumptions and data that are uncertain. Examples of areas in which information is incomplete 

or unavailable include future emission rates, vehicle manufacturers’ decisions on vehicle technology and 

design, the mix of vehicle types and model years, projections of vehicle miles traveled (VMT), emissions 

 

2

 By 2050, 98 percent of passenger cars and 88 percent of light trucks will have been produced in 2030 or later. 

Because newer vehicles are utilized more than older ones, the fraction of total passenger car and light truck VMT 

that these vehicles account for would be even higher – 99 percent for passenger cars and 94 percent for light trucks. 
Chapter 4 Cumulative Impacts 4.3 Air Quality 

from fuel refining and distribution, and economic factors. NHTSA used screening-level estimates of 

health outcomes in the form of cases per ton of criteria pollutant emissions reduced, and of monetized 

health benefits in the form of dollars per ton of criteria pollutant emissions reduced, to approximate the 

health benefits associated with each alternative. The use of such dollar-per-ton numbers, however, does 

not account for all potential health and environmental benefits because the information necessary to 

monetize all potential health and environmental benefits is unavailable (e.g., health effects per ton of 

emissions of pollutants other than PM, values of property damage, and effects on vegetation), which leads 

to an underestimate of total criteria pollutant benefits. Reductions in emissions of toxic air pollutants 

should result in health benefits as well, but scientific data are not available that would allow 

quantification and monetization of these benefits. 

Where information in the analysis included in this EIS is incomplete or unavailable, the agency 

has relied on CEQ regulations regarding incomplete or unavailable information. 40 CFR § 1502.22(b). 

NHTSA used the best available models and supporting data in preparing this EIS. The models used have 

been scientifically reviewed and have been approved by the agencies that sponsored their development. 

NHTSA believes that the assumptions in this EIS regarding uncertain conditions reflect the best available 

information and are valid and sufficient for this analysis. 

4.3.2.3 Photochemical Air Quality Modeling and Risk Assessment 

The national-scale photochemical air quality modeling and health risk assessment, Appendix F, 

was also conducted with the cumulative impacts data from the DEIS. The analysis methodology for the 

photochemical modeling and risk assessment of cumulative impacts is the same as described in Section 

3.3.2, except that the cumulative impacts analysis assumes annual average percentage gains in average 

fuel economy from 2016 through 2030 as described in Section 4.3.2.1. The analysis showed comparable 

results to the health and economic effects calculated in the DEIS. 

4.3.3 Environmental Consequences 

4.3.3.1 Results of Emissions Analysis 

The Clean Air Act (CAA) has been a success in reducing emissions from on-road mobile sources. 

As discussed in Section 3.3.1, pollutant emissions from vehicles have been declining since 1970 and the 

U.S. Environmental Protection Agency (EPA) projects that they will continue to decline. However, as 

future trends show, vehicle travel is having a smaller and smaller impact on emissions as a result of 

stricter EPA standards for vehicle emissions and the chemical composition of fuels, even with additional 

growth in VMT (Smith 2002). This general trend will continue, to a greater or lesser degree, with 

implementation of any of the alternative CAFE standards. The analysis by alternative in this section 

shows that the alternative CAFE standards will lead to both reductions and increases in emissions from 

passenger cars and light trucks (depending on the pollutant), compared to current trends (i.e., the No 

Action Alternative). The amounts of the reductions and increases would vary by pollutant, calendar year, 

and alternative. The more restrictive alternatives generally would result in greater emissions reductions 

compared to the No Action Alternative. This trend is shown in the analysis of the MYs 2012-2016 CAFE 

standards in Section 3.3.3. 

4.3.3.2 Alternative 1: No Action 

4.3.3.2.1 Criteria Pollutants 

Under the No Action Alternative, average fuel economy levels in the absence of CAFE standards 

beyond MY 2011 would equal the higher of the agencies’ collective market forecast or the manufacturer’s 

 4-11 
4.3 Air Quality Chapter 4 Cumulative Impacts 

required level of average fuel economy for MY 2011. Average fuel economy is assumed to increase from 

2012 through 2030 due to projected rising demand for fuel economy, consistent with AEO projections 

(see Section 4.1.3). Current trends in the levels of emissions from vehicles would continue through 2030, 

with emissions continuing to decline due to the EPA emissions standards, despite a growth in total VMT. 

By 2050, however, VMT growth more than offsets decreases due to emission standards and total 

emissions increase. The EPA vehicle emissions standards regulate all criteria pollutants except sulfur 

dioxide (SO2), which is regulated through the fuel sulfur content. The No Action Alternative would not 

change the MY 2011 CAFE standards; therefore, any change in criteria pollutant emissions in 

nonattainment and maintenance areas throughout the United States would be attributable to current 

emissions regulatory programs and the assumed future trends in fuel economy increases in accordance 

with the AEO projections. 

Table 4.3.3-1 summarizes the total national emissions of criteria pollutants from passenger cars 

and light trucks under the No Action Alternative. Figure 4.3.3-1 illustrates this information. Table 4.3.3-

1 lists the action alternatives (Alternatives 2 through 9) left to right in order of generally increasing fuel 

economy requirements. In the case of particulate matter with an aerodynamic diameter less than or equal 

to 2.5 microns (PM2.5), sulfur oxides (SOx), nitrogen oxides (NOx), and volatile organic compounds 

(VOCs), the No Action Alternative results in the highest emissions, and emissions generally decline as 

fuel economy standards increase across alternatives. Due to the interaction of VMT, fuel economy, and 

the share of VMT accrued by diesel vehicles, there are some exceptions to this declining trend (emissions 

increase from one individual alternative to the next higher fuel economy alternative), although emissions 

of these pollutants would remain below the levels under the No Action Alternative. These exceptions are 

NOx under Alternative 7, and under Alternative 9 in 2020, 2030, and 2050; PM2.5 under Alternatives 5 

through 8; SOx under Alternative 3 in 2050, Alternative 5, and Alternative 7 in 2016 and 2020; and VOCs 

under Alternative 7, and under Alternative 9 in 2020, 2030, and 2050. Despite these individual increases, 

emissions of PM2.5, SOx, NOx, and VOCs remain below the levels under the No Action Alternative. In 

the case of CO, emissions under Alternatives 2 through 4 are slightly higher than under the No Action 

Alternative, and are lower than under the No Action Alternative for Alternatives 5 through 9. Appendix 

C presents cumulative emissions of criteria pollutants for each nonattainment area. 

Total emissions are composed of four components: tailpipe emissions and upstream emissions 

for passenger cars, and tailpipe emissions and upstream emissions for light trucks. To show the 

relationship among these four components for criteria pollutants, Table 4.3.3-2 breaks down the total 

emissions of criteria pollutants by component for calendar year 2030. 

Table 4.3.3-3 lists the net changes in nationwide cumulative emissions from passenger cars and 

light trucks as compared to the No Action Alternative for each criteria pollutant and analysis year. The 

table lists Alternatives 2 through 9 from left to right in order of generally increasing fuel economy 

requirements. The reductions in nationwide cumulative emissions from the No Action Alternative 

generally increase from left to right, though unevenly, as noted above, due to the interaction of VMT, fuel 

economy, and the share of VMT accrued by diesel vehicles. There are some increases in CO emissions 

under Alternatives 2 through 4, as noted above, because increases in VMT more than offset declines in 

CO emission rates and increases in fuel economy. 

As discussed in Section 3.3.3.2.1, one of the ways that the Volpe model projects vehicle 

manufacturers can achieve higher fuel economy is to increase the share of new vehicles that use diesel 

engines. The resulting increase in the use of diesel fuel as mpg standards become more stringent across 

action alternatives can interact with other factors, such as changes in VMT, the car and light truck shares, 

and the shares of other technologies such as hybrids, to affect emissions of different pollutants in different 

ways across Alternatives. Another result of increasing forecasted use of diesel engines can be that 

 4-12 
Chapter 4 Cumulative Impacts 4.3 Air Quality 

 4-13 

Table 4.3.3-1 

 Cumulative Nationwide Criteria Pollutant Emissions (tons/year) from Passenger Cars 

and Light Trucks by Alternative 

Alt. 1 Alt. 2 Alt. 3 Alt. 4 Alt. 5 Alt. 6 Alt. 7 Alt. 8 Alt. 9 

Poll. 

and 

Year 

No 

Action 

3%/year 

Increase 

4%/year 

Increase 

~4.3%/year

Increase 

Preferred

5%/year 

Increase 

~6.0%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.6%/year 

Increase 

TCTB 

Carbon monoxide (CO) 

2016 20,380,537 20,393,938 20,394,480 20,383,598 20,272,923 20,182,256 20,228,025 20,168,102 20,173,726

2020 19,133,013 19,178,024 19,177,706 19,155,494 18,860,312 18,609,878 18,704,744 18,527,238 18,568,972

2030 20,569,714 20,730,187 20,711,222 20,662,019 19,890,055 19,242,112 19,400,043 18,904,057 19,071,598

2050 28,943,491 29,227,165 29,179,262 29,098,748 27,809,337 26,721,219 26,941,788 26,099,919 26,408,318

Nitrogen oxides (NOx) 

2016 2,210,405 2,207,302 2,205,558 2,204,404 2,201,606 2,197,765 2,199,718 2,197,430 2,196,989

2020 1,755,985 1,746,692 1,744,016 1,742,112 1,733,189 1,723,506 1,727,191 1,720,739 1,721,297

2030 1,417,997 1,395,535 1,393,715 1,391,027 1,364,556 1,338,602 1,344,552 1,325,627 1,331,170

2050 1,736,474 1,699,529 1,697,706 1,693,875 1,649,549 1,606,445 1,614,485 1,582,550 1,593,216

Particulate matter (PM2.5) 

2016 68,793 68,374 68,122 68,024 68,424 68,603 68,606 68,737 68,605

2020 68,785 67,443 67,057 66,925 67,672 68,003 68,049 68,373 68,137

2030 82,714 79,237 79,031 78,919 80,004 80,289 80,448 80,932 80,653

2050 123,444 117,742 117,605 117,478 118,957 119,187 119,450 120,068 119,763

Sulfur oxides (SOx) 

2016 176,518 173,665 172,306 171,666 172,232 171,378 171,729 171,422 170,947

2020 183,552 174,936 172,914 172,039 172,820 171,669 171,805 171,336 170,802

2030 208,630 186,377 185,643 184,922 186,154 184,521 184,182 183,444 183,012

2050 298,565 261,582 261,779 261,029 262,851 260,415 259,761 258,601 258,142

Volatile organic compounds (VOCs) 

2016 2,505,277 2,491,567 2,484,860 2,480,794 2,470,902 2,455,914 2,461,292 2,453,075 2,452,838

2020 2,160,591 2,120,074 2,109,903 2,103,946 2,079,646 2,050,297 2,056,326 2,037,883 2,041,620

2030 1,848,278 1,746,212 1,741,205 1,734,534 1,680,701 1,623,692 1,629,059 1,589,318 1,602,520

2050 2,157,634 1,988,851 1,986,963 1,978,405 1,892,334 1,803,021 1,808,713 1,745,102 1,767,929
4.3 Air Quality 

Figure 4.3.3-1. Nationwide Criteria Pollutant Emissions (tons/year) 

from Passenger Cars and Light Trucks for 2030 by Alternative 

0

400,000800,000

1,200,0001,600,0002,000,000

Alt. 1

No Action

Alt. 2 

3%/year

Increase

Alt. 3 

4%/year

Increase

Alt. 4 

~4.3%/year

Increase

Preferred

Alt. 5 

5%/year

Increase

Alt. 6 

~6.0%/year

Increase MNB

Alt. 7 

6%/year

Increase

Alt. 8 

7%/year

Increase

A

~6.6

Inc

T

Alternative

Tons/Year (NOx, PM, SOx, VOC) 

Nitrogen Oxides (NOx) Particulate Matter (PM) Sulfur Oxides (SOx) Volatile Organic Compounds (VOC) Carbon Mono

4-14 
Chapter 4 Cumulative Impacts 

4-15 

Table 4.3.3-2 

Cumulative Nationwide Criteria Pollutant Emissions (tons/year) in 2030 from Passenger Cars and Light Trucks, by Ve

Alternative 

Alt. 1 Alt. 2 Alt. 3 Alt. 4 Alt. 5 Alt. 6 Alt. 7 Alt. 8 

Poll. and Source 

No 

Action 

3%/year 

Increase 

4%/year 

Increase 

~4.3%/year

Increase 

Preferred 

5%/year 

Increase 

~6.0%/year 

Increase 

MNB 

6%/year 

Increase 

7%/ye

Increa

Carbon monoxide (CO) 

Car Tailpipe 16,600,120 16,696,233 16,735,859 16,722,906 16,237,744 15,938,196 15,879,787 15,553Car Upstream 85,473 74,450 74,308 74,357 74,945 73,966 74,106 73Truck Tailpipe 12,211,183 12,415,064 12,327,431 12,260,170 11,454,514 10,666,524 10,945,836 10,430Truck Upstream 46,714 41,418 41,664 41,315 42,133 42,533 42,059 42Total 28,943,491 29,227,165 29,179,262 29,098,748 27,809,337 26,721,219 26,941,788 26,099

Nitrogen oxides (NOx)

Car Tailpipe 588,874 592,580 593,895 593,465 577,426 567,584 565,648 554Car Upstream 267,576 232,825 232,448 232,575 233,465 229,789 230,142 228Truck Tailpipe 733,930 744,512 741,099 738,733 707,841 677,887 688,775 669Truck Upstream 146,095 129,611 130,264 129,102 130,816 131,185 129,921 130Total 1,736,474 1,699,529 1,697,706 1,693,875 1,649,549 1,606,445 1,614,485 1,582

Particulate matter (PM2.5) 

Car Tailpipe 38,294 39,167 39,059 39,095 40,552 41,586 41,750 42Car Upstream 36,435 31,749 31,685 31,707 32,010 31,625 31,690 31Truck Tailpipe 28,795 29,169 29,092 29,051 28,377 27,738 27,987 27Truck Upstream 19,921 17,658 17,769 17,624 18,019 18,237 18,023 18Total 123,444 117,742 117,605 117,478 118,957 119,187 119,450 120

Sulfur Oxides (SOx) 

Car Tailpipe 29,513 25,434 25,459 25,446 24,571 23,541 23,490 22Car Upstream 163,612 142,602 142,307 142,410 143,897 142,254 142,557 142Truck Tailpipe 15,966 14,246 14,198 13,998 13,319 12,457 12,544 12Truck Upstream 89,475 79,301 79,816 79,175 81,063 82,163 81,171 81Total 298,565 261,582 261,779 261,029 262,851 260,415 259,761 258

Volatile organic compounds (VOCs)  Car Tailpipe 441,191 445,208 445,814 445,617 438,503 434,412 433,530 428 Car Upstream 893,064 766,825 768,339 767,652 730,099 691,833 689,276 659 Truck Tailpipe 341,942 346,317 345,099 344,301 333,296 322,707 326,643 319 Truck Upstream 481,437 430,501 427,712 420,835 390,437 354,068 359,264 336 Total 2,157,634 1,988,851 1,986,963 1,978,405 1,892,334 1,803,021 1,808,713 1,745
4.3 Air Quality Chapter 4 Cumulative Impacts 

 Table 4.3.3-3 

 Cumulative Nationwide Criteria Pollutant Emission Changes (tons/year) from Passenger Cars and Light 

Trucks by Alternative Compared to No Action Alternative a/ b/ 

Alt. 1 Alt. 2 Alt. 3 Alt. 4 Alt. 5 Alt. 6 Alt. 7 Alt. 8 Alt. 9 

Poll. 

and 

Year 

No 

Action 

c/ 

3%/year 

Increase 

4%/year 

Increase 

~4.3%/year

Increase 

Preferred 

5%/year 

Increase 

~6.0%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.6%/year 

Increase 

TCTB 

Carbon monoxide (CO) 

2016 0 13,402 13,943 3,062 -107,614 -198,280 -152,511 -212,434 -206,811

2020 0 45,011 44,693 22,481 -272,701 -523,135 -428,268 -605,774 -564,041

2030 0 160,473 141,508 92,306 -679,658 -1,327,602 -1,169,671 -1,665,657 -1,498,116

2050 0 283,674 235,771 155,258 -1,134,154 -2,222,272 -2,001,703 -2,843,572 -2,535,173

Nitrogen oxides (NOx) 

2016 0 -3,103 -4,847 -6,001 -8,799 -12,640 -10,687 -12,976 -13,416

2020 0 -9,294 -11,969 -13,873 -22,796 -32,479 -28,795 -35,246 -34,689

2030 0 -22,462 -24,282 -26,970 -53,441 -79,395 -73,445 -92,370 -86,827

2050 0 -36,945 -38,767 -42,599 -86,925 -130,029 -121,989 -153,924 -143,258

Particulate matter (PM2.5) 

2016 0 -420 -672 -770 -369 -191 -187 -57 -189

2020 0 -1,342 -1,728 -1,861 -1,114 -783 -736 -412 -648

2030 0 -3,477 -3,683 -3,795 -2,710 -2,425 -2,266 -1,782 -2,061

2050 0 -5,701 -5,838 -5,966 -4,486 -4,256 -3,993 -3,375 -3,681

Sulfur oxides (SOx) 

2016 0 -2,853 -4,212 -4,852 -4,286 -5,140 -4,788 -5,096 -5,571

2020 0 -8,616 -10,638 -11,513 -10,732 -11,883 -11,747 -12,216 -12,750

2030 0 -22,253 -22,987 -23,708 -22,475 -24,109 -24,447 -25,185 -25,617

2050 0 -36,983 -36,786 -37,537 -35,715 -38,151 -38,804 -39,964 -40,423

Volatile organic compounds (VOCs) 

2016 0 -13,710 -20,417 -24,484 -34,375 -49,363 -43,985 -52,202 -52,439

2020 0 -40,518 -50,688 -56,645 -80,946 -110,295 -104,265 -122,708 -118,971

2030 0 -102,066 -107,073 -113,743 -167,577 -224,585 -219,218 -258,960 -245,758

2050 0 -168,783 -170,670 -179,228 -265,299 -354,612 -348,921 -412,532 -389,704

__________ 

a/ Emissions changes have been rounded to the nearest whole number. 

b/ Negative emissions changes indicate reductions; positive emissions changes are increases. 

c/ Emissions changes for the No Action Alternative are shown as zero because the No Action Alternative is the 

 baseline to which the emissions for the other alternatives are compared. 

differing upstream emission rates might change pollutant emissions estimates, as compared to those rates 

for gasoline-fueled engines. Projected changes in the share of diesel vehicles appear to be a factor in the 

results for CO that show increases in cumulative emissions compared to the No Action Alternative under 

Alternatives 2 through 4 and decreases in cumulative emissions compared to the No Action Alternative 

under Alternatives 6 through 9. 

Cumulative emissions in 2016 would be equivalent to the noncumulative emissions in all cases. 

Cumulative emissions of NOx, PM2.5, SO2, and VOCs in 2020 and 2030 would be less than 

noncumulative emissions for the same combination of pollutant, year, and alternative because of differing 

changes in VMT and fuel consumption under the cumulative case compared to the noncumulative case 

(i.e., because of the impact of projected higher average fuel economy in the cumulative analysis). 

Cumulative emissions of CO in 2020 and 2030 would be greater than the corresponding noncumulative 

emissions.

 4-16 
Chapter 4 Cumulative Impacts 4.3 Air Quality 

4.3.3.2.2 Toxic Air Pollutants 

As with the criteria pollutants, current trends in the levels of toxic air pollutant emissions from 

vehicles would continue, with emissions of most toxic air pollutants continuing to decline through 2050, 

despite a growth in total VMT, as a result of the EPA emission standards. By 2050, however, VMT 

growth more than offsets decreases due to emission standards and total emissions increase. In addtion, 

with current trends, emissions of diesel particulate matter (DPM) nationwide would increase in 2020, 

2030, and 2050 over 2016 levels under the No Action Alternative. Nationwide emissions of 

acetaldehyde, acrolein, benzene, 1,3-butadiene, and formaldehyde would decrease in 2020, 2030, and 

2050 from 2016 levels under the No Action Alternative. Cumulative emissions would increase in at least 

one nonattainment area in each year for each toxic air pollutant. 

Table 4.3.3-4 summarizes the cumulative national toxic air pollutant emissions from passenger 

cars and light trucks under each alternative for each toxic air pollutant and analysis year. The table lists 

Alternatives 2 through 9 from left to right in order of generally increasing fuel economy requirements. 

Figure 4.3.3-2 lists the total national emissions of toxic air pollutants from passenger cars and light trucks 

by alternative. Emissions of most toxic air pollutants would increase in each alternative as compared to 

the No Action Alternative. The exceptions are acetaldehyde emissions, which would decrease under 

Alternative 2 in 2016, Alternatives 6 through 9 in 2030, and Alternatives 5 though 9 in 2050; acrolein 

emissions, which would remain the same under alternatives 2 and 3 in 2016; benzene emissions, which 

would decrease under all alternatives and years; 1,3-butadiene emissions, which would increase under all 

alternatives and years except Alternatives 5 through 9 in 2030 and 2050; DPM emissions, which would 

decrease under all alternatives in all years; and formaldehyde emissions, which would decrease under 

Alternative 2 in all years and under Alternative 3 in 2016 and 2020. The changes in toxic air pollutant 

emissions, positive or negative, would generally be small (less than 10 percent) in relation to the No 

Action Alternative emissions levels. The exceptions are acrolein emissions, which would increase by 

more than 10 percent under Alternatives 6 through 9 in 2030 and Alternatives 5 through 9 in 2050; DPM 

emissions, which would decrease by more than 10 percent under all action alternatives in 2030 and 2050; 

and formaldehyde emissions, which would increase by more than 10 percent under Alternatives 8 and 9 in 

2050. Appendix C presents the cumulative emissions of toxic air pollutants for each nonattainment area 

for the No Action Alternative. 

As discussed in Section 3.3.3.2.2, one of the ways that the Volpe model projects vehicle 

manufacturers can achieve higher fuel economy is to increase the share of new vehicles that use diesel 

engines. The resulting increase in the use of diesel fuel as mpg standards become more stringent across 

action alternatives can interact with other factors, such as changes in VMT, the car and light truck shares, 

and the shares of other technologies such as hybrids, to affect emissions of different pollutants in different 

ways across Alternatives. Another result of increasing forecasted use of diesel engines can be that 

differing upstream emission rates might change pollutant emissions estimates, as compared to those rates 

for gasoline-fueled engines. Projected changes in the share of diesel vehicles appear to be a factor in the 

results for acetaldehyde and 1,3-butadiene that show increases in cumulative emissions compared to the 

No Action Alternative under Alternatives 2 through 4 and decreases in cumulative emissions compared to 

the No Action Alternative under Alternatives 6 through 9. 

Cumulative emissions after 2016 would be lower than noncumulative emissions for acrolein 

under Alternative 9 in 2020 and 2030, benzene, DPM, and formaldehyde because of differing changes in 

VMT and fuel consumption under the cumulative case compared to the noncumulative case (i.e., because 

of the impact of projected higher fuel economy in the cumulative analysis). Cumulative emissions after 

2016 would be the same or higher than noncumulative emissions for acetaldehyde, acrolein under 

Alternatives 1 through 8, and 1,3-butadiene. 

 4-17 
4.3 Air Quality Chapter 4 Cumulative Impacts 

 4-18 

Table 4.3.3-4 

 Cumulative Nationwide Toxic Air Pollutant Emissions (tons/year) from Passenger Cars 

and Light Trucks by Alternative 

Alt. 1 Alt. 2 Alt. 3 Alt. 4 Alt. 5 Alt. 6 Alt. 7 Alt. 8 Alt. 9 

Poll. 

and 

Year 

No 

Action 

3%/year 

Increase 

4%/year 

Increase 

~4.3%/year

Increase 

Preferred 

5%/year 

Increase 

~6.0%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.6%/year 

Increase 

TCTB 

Acetaldehyde 

2016 10,921 10,919 10,924 10,928 10,955 10,976 10,960 10,977 10,977

2020 9,025 9,028 9,037 9,041 9,069 9,099 9,085 9,105 9,098

2030 7,939 7,978 7,987 7,989 7,940 7,916 7,912 7,882 7,889

2050 10,061 10,138 10,144 10,143 10,024 9,951 9,947 9,871 9,894

Acrolein 

2016 561 561 561 562 569 576 572 577 576

2020 455 456 456 458 472 486 482 491 486

2030 392 395 396 398 425 449 445 464 449

2050 494 500 501 504 547 585 579 609 585

Benzene 

2016 56,184 56,162 56,150 56,139 56,080 56,019 56,045 56,008 56,010

2020 43,117 43,061 43,043 43,020 42,836 42,665 42,725 42,609 42,631

2030 28,927 28,843 28,826 28,782 28,174 27,645 27,760 27,361 27,491

2050 29,272 29,163 29,128 29,057 28,000 27,082 27,243 26,539 26,794

1,3-butadiene 

2016 6,100 6,101 6,102 6,103 6,107 6,112 6,109 6,113 6,112

2020 4,874 4,880 4,881 4,882 4,883 4,887 4,888 4,891 4,889

2030 3,758 3,784 3,784 3,782 3,753 3,729 3,739 3,722 3,727

2050 4,376 4,426 4,422 4,418 4,359 4,310 4,325 4,289 4,304

Diesel particulate matter (DPM) 

2016 93,117 91,618 90,856 90,463 90,213 89,313 89,679 89,227 89,075

2020 96,724 92,177 91,025 90,479 89,807 88,252 88,565 87,719 87,726

2030 109,888 98,126 97,596 97,096 95,875 93,354 93,454 92,024 92,369

2050 157,271 137,711 137,612 137,050 135,284 131,578 131,581 129,470 130,085

Formaldehyde 

2016 13,700 13,685 13,692 13,707 13,833 13,937 13,874 13,948 13,943

2020 10,978 10,951 10,966 10,988 11,222 11,433 11,350 11,497 11,456

2030 9,179 9,154 9,182 9,213 9,571 9,904 9,810 10,044 9,957

2050 11,476 11,456 11,491 11,534 12,063 12,550 12,425 12,772 12,638
Chapter 4 Cumulative Impacts 

Figure 4.3.3-2. Cumulative Nationwide Toxic Air Pollutant Emissions (tons/year) 

from Passenger Cars and Light Trucks for 2030 by Alternative 

0

2,0004,0006,0008,000

10,00012,000

Alt. 1

No Action

Alt. 2 

3%/year

Increase

Alt. 3 

4%/year

Increase

Alt. 4 

~4.3%/year

Increase

Preferred

Alt. 5 

5%/year

Increase

Alt. 6 

~6.0%/year

Increase

MNB

Alt. 7 

6%/year

Increase

Alt. 8 

7%/year

Increase

Alt 9 

~6.6%/y

Increas

TC=TB

Alternative

Tons/Year (Acetaldehyde, Acrolein, 1,3-

Butadiene, Formaldehyde) 

Acetaldehyde Acrolein 1,3-Butadiene Formaldehyde Benzene Diesel Particulate Matter (DPM) .

4-19 
4.3 Air Quality Chapter 4 Cumulative Impacts 

Most emissions changes with the cumulative analysis (compared to the No Action Alternative) 

would be the same as or greater than the corresponding emissions changes with the noncumulative 

analysis for most toxic air pollutants. The exceptions are acetaldehyde in 2020 under Alternatives 4 and 

5, and in 2030 under Alternative 5; acrolein in 2020 under Alternative 9, and in 2030 under Alternatives 5 

through 7 and 9; benzene in 2030 under Alternatives 4 through 9; 1,3-butadiene in 2030 under Alternative 

4; DPM under Alternatives 5 through 9 in 2020, and under Alternatives 4 through 9 in 2030; and 

formaldehyde under Alternative 3 in 2030. 

Total emissions are composed of four components: tailpipe emissions and upstream emissions 

for passenger cars, and tailpipe emissions and upstream emissions for light trucks. To show the 

relationship among these four components for air toxic pollutants, Table 4.3.3-5 breaks down the total 

emissions of air toxic pollutants by component for calendar year 2030. 

Table 4.3.3-6 lists the net changes in nationwide cumulative emissions from passenger cars and 

light trucks compared to Alternative 1 (No Action) for each toxic air pollutant and analysis year. The 

table lists Alternatives 2 through 9 left to right in order of generally increasing fuel economy 

requirements. 

4.3.3.2.3 Health Outcomes and Monetized Benefits 

Under Alternative 1 (No Action), average fuel economy would remain at the 2011 level until 

2016, increase as projected by AEO until 2030, and then remain at the 2030 level through 2050. 

Emissions of criteria pollutants and toxic air pollutants would change as described above. Human health 

effects of emissions are tied to specific pollutants, and will vary as emissions of these pollutants vary. 

The No Action Alternative would result in no other increase or decrease in human health effects 

throughout the United States compared to current trends because the No Action Alternative represents 

maintaining the status quo (i.e., no action by either NHTSA or the EPA). 

The economic value of health impacts would vary proportionally with changes in health 

outcomes under the methodology defined in Section 3.3.2.4.2. The monetized health benefits analyzed 

here are the result of changes in ambient PM concentrations caused by changes in the precursor criteria 

pollutants NOx, VOCs, SO2, and PM2.5. Alternative 1 (No Action) would result in no other change in 

health-related impacts throughout the United States, compared to current trends because the No Action 

Alternative represents maintaining the status quo (i.e., no action by either NHTSA or EPA). 

4.3.3.3 Alternative 2: 3-Percent Annual Increase 

4.3.3.3.1 Criteria Pollutants 

Under the 3-Percent Alternative (Alternative 2), generally the CAFE standards would require 

increased fuel economy compared to the No Action Alternative (Alternative 1). Alternative 2 would 

increase fuel economy less than Alternatives 3 through 9. There would be reductions in nationwide 

emissions of NOx, PM2.5, SOx, and VOCs under Alternative 2 compared to the No Action Alternative. 

Depending on the year, NOx emissions would be reduced 0.1 to 2.1 percent, PM2.5 emissions would be 

reduced 0.6 to 4.6 percent, SOx emissions would be reduced 1.6 to 12.4 percent, and VOC emissions 

would be reduced 0.5 to 7.8 percent, compared to emissions projected under the No Action Alternative. 

There would be increases of CO emissions. CO emissions would increase 0.1 to 1.0 percent under 

Alternative 2, depending on the year, compared to emissions projected under the No Action Alternative. 

 4-20 
Chapter 4 Cumulative Impacts 

Table 4.3.3-5 

Cumulative Nationwide Toxic Air Pollutant Emissions (tons/year) in 2030 from Passenger Cars and Light Trucks, by V

Alternative 

Alt. 1 Alt. 2 Alt. 3 Alt. 4 Alt. 5 Alt. 6 Alt. 7 Alt. 8 

Pollutant and 

Source 

No 

Action 

3%/year 

Increase

4%/year 

Increase 

~4.3%/year 

Increase 

Preferred 

5%/year 

Increase 

~6.0%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

Acetaldehyde Car Tailpipe 5,771 5,822 5,831 5,828 5,728 5,670 5,658 5,59Car Upstream 95 82 82 82 81 79 78 7Truck Tailpipe 4,143 4,188 4,186 4,187 4,171 4,159 4,168 4,16Truck Upstream 52 46 46 45 45 43 43 4Total 10,061 10,138 10,144 10,143 10,024 9,951 9,947 9,87Acrolein Car Tailpipe 272 281 279 280 300 315 317 33Car Upstream 13 11 11 11 11 11 11 1Truck Tailpipe 202 202 204 207 230 253 246 26Truck Upstream 7 6 6 6 6 6 6 Total 494 500 501 504 547 585 579 60Benzene Car Tailpipe 15,004 15,109 15,139 15,130 14,766 14,546 14,502 14,25Car Upstream 1,933 1,664 1,666 1,665 1,600 1,528 1,524 1,47Truck Tailpipe 11,291 11,457 11,394 11,347 10,770 10,208 10,409 10,04Truck Upstream 1,044 933 929 915 864 801 808 76Total 29,272 29,163 29,128 29,057 28,000 27,082 27,243 26,531,3-butadiene Car Tailpipe 2,511 2,541 2,543 2,542 2,530 2,526 2,525 2,51Car Upstream 21 18 18 18 18 18 18 1Truck Tailpipe 1,833 1,856 1,851 1,848 1,800 1,755 1,772 1,74Truck Upstream 11 10 10 10 10 11 11 1Total 4,376 4,426 4,422 4,418 4,359 4,310 4,325 4,28Diesel particulate matter (DPM) Car Tailpipe 22 442 314 356 2,020 3,134 3,326 4,48Car Upstream 101,917 88,002 88,042 88,017 85,674 82,554 82,441 80,21Truck Tailpipe 94 37 107 169 820 1,468 1,249 1,67Truck Upstream 55,238 49,229 49,149 48,508 46,771 44,423 44,565 43,10Total 157,271 137,711 137,612 137,050 135,284 131,578 131,581 129,47

4-21 
4.3 Air Quality 

4-22 

Table 4.3.3-5 (cont’d) 

Cumulative Nationwide Toxic Air Pollutant Emissions (tons/year) in 2030 from Passenger Cars and Light Trucks, by V

Alternative 

Alt. 1 Alt. 2 Alt. 3 Alt. 4 Alt. 5 Alt. 6 Alt. 7 Alt. 8 

Pollutant and 

Source 

No 

Action 

3%/year 

Increase

4%/year 

Increase 

~4.3%/year 

Increase 

Preferred 

5%/year 

Increase 

~6.0%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

Formaldehyde  Car Tailpipe 5,967 6,077 6,068 6,071 6,192 6,282 6,296 6,38 Car Upstream 715 619 619 619 610 593 593 58 Truck Tailpipe 4,405 4,414 4,458 4,502 4,924 5,349 5,211 5,48 Truck Upstream 389 346 346 342 336 327 326 32 Total 11,476 11,456 11,491 11,534 12,063 12,550 12,425 12,77
Chapter 4 Cumulative Impacts 4.3 Air Quality 

Table 4.3.3-6 

Cumulative Nationwide Changes in Toxic Air Pollutant Emissions (tons/year) from Passenger Cars and Light 

Trucks by Alternative Compared to No Action Alternative a/ b/ 

Alt. 1 Alt. 2 Alt. 3 Alt. 4 Alt. 5 Alt. 6 Alt. 7 Alt. 8 Alt. 9 

Poll. 

and 

Year 

No 

Action c/ 

3%/year 

Increase 

4%/year 

Increase 

~4.3%/year

Increase 

Preferred 

5%/year 

Increase 

~6.0%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.6%/year 

Increase 

TCTB 

Acetaldehyde 

2016 0 -2 3 7 33 55 39 56 56

2020 0 3 12 16 44 74 60 80 73

2030 0 39 48 49 0 -24 -27 -57 -51

2050 0 78 84 82 -36 -110 -114 -190 -166

Acrolein 

2016 0 0 0 1 8 15 11 16 15

2020 0 0 1 3 17 30 26 36 30

2030 0 3 4 6 34 58 53 72 58

2050 0 6 7 10 54 91 86 115 91

Benzene 

2016 0 -21 -33 -45 -104 -165 -139 -175 -174

2020 0 -56 -74 -97 -281 -451 -392 -507 -486

2030 0 -84 -101 -145 -753 -1,282 -1,167 -1,566 -1,436

2050 0 -109 -144 -215 -1,271 -2,190 -2,028 -2,733 -2,478

1,3-butadiene 

2016 0 1 2 3 7 12 10 13 13

2020 0 6 7 8 9 13 14 17 15

2030 0 26 26 25 -5 -28 -19 -36 -30

2050 0 50 46 42 -17 -66 -51 -87 -73

Diesel particulate matter (DPM) 

2016 0 -1,499 -2,261 -2,654 -2,904 -3,804 -3,438 -3,890 -4,042

2020 0 -4,547 -5,699 -6,246 -6,917 -8,472 -8,159 -9,006 -8,998

2030 0 -11,762 -12,292 -12,792 -14,013 -16,534 -16,434 -17,864 -17,519

2050 0 -19,559 -19,659 -20,220 -21,986 -25,693 -25,690 -27,801 -27,185

Formaldehyde 

2016 0 -15 -7 8 134 237 175 249 243

2020 0 -27 -12 10 244 455 372 519 478

2030 0 -25 3 34 392 725 631 865 778

2050 0 -20 15 58 586 1,074 949 1,296 1,162

__________ 

a/ Emissions changes have been rounded to the nearest whole number. 

b/ Negative emissions changes indicate reductions; positive emissions changes are increases. 

c/ Emissions changes for the No Action Alternative are shown as zero because the No Action Alternative is the 

baseline to which emissions from the action alternatives are compared. 

Emissions in individual nonattainment areas might follow different patterns from nationwide 

emissions. Emissions of criteria pollutants vary due to interrelations among upstream emissions, VMT 

increases, and diesel share of VMT and fuel usage. Compared to Alternative 1, cumulative emissions of 

SOx and VOCs under Alternative 2 would decrease in all nonattainment areas. In contrast, CO emissions 

would increase in almost all nonattainment areas, while NOx and PM emissions would decrease in some 

 4-23 
4.3 Air Quality Chapter 4 Cumulative Impacts 

nonattainment areas and increase in others. Tables in Appendix C list emissions reductions for each 

nonattainment area. 

Cumulative fuel economy standards would lead to lower emissions of most pollutants compared 

to noncumulative standards, due to the impact of higher projected average fuel economy in the cumulative 

case. Under Alternative 2, cumulative emissions of NOx, PM2.5, SOx, and VOCs are lower than 

noncumulative emissions. However, emissions of CO are higher under the cumulative case than the 

noncumulative case, because increases in VMT more than offset declines in CO emission rates and 

increases in fuel economy. 

Emissions reductions (compared to the No Action Alternative) under the Alternative 2 

cumulative analysis would be greater than the corresponding emissions reductions under the Alternative 2 

noncumulative analysis for NOx, PM2.5, SO2, and VOCs. For CO, emissions increases under Alternative 2 

cumulative analysis would be greater than the corresponding emissions increases under Alternative 2 

noncumulative analysis. 

Tables in Appendix C list the emissions reductions for each nonattainment area. Table 4.3.3-7 

summarizes the criteria air pollutant results by nonattainment area. 

Table 4.3.3-7 

Cumulative Criteria Pollutant Emissions from Passenger Cars and Light Trucks, Maximum Changes 

by Nonattainment Area and Alternative a/ 

Criteria 

Pollutant 

Increase/ 

Decrease 

Change 

(tons/year) Year Alt. No. Nonattainment Area 

Maximum Increase 13,975 2050 2 New York-N. New Jersey-Long Island, NY-NJ-CT CO Maximum Decrease -132,472 2050 8 Los Angeles South Coast Air Basin, CA 

Maximum Increase 291 2050 2 Dallas-Fort Worth, TX NOx Maximum Decrease -6,860 2050 8 Houston-Galveston-Brazoria, TX 

Maximum Increase 105 2050 8 New York-N. New Jersey-Long Island, NY-NJ-CT PM2.5 Maximum Decrease -663 2050 4 Houston-Galveston-Brazoria, TX 

Maximum Increase No increases are predicted for any alternatives. SOx Maximum Decrease -2,732 2050 4 Chicago-Gary-Lake Co, IL-IN 

Maximum Increase No increases are predicted for any alternatives. VOCs Maximum Decrease -13,344 2050 8 Houston-Galveston-Brazoria, TX 

__________ 

a/ Emissions changes have been rounded to the nearest whole number. 

4.3.3.3.2 Toxic Air Pollutants 

Under Alternative 2, cumulative emissions of acetaldehyde, acrolein (except in 2020), and 1,3-

butadiene would be greater than noncumulative emissions for the same combinations of pollutant and 

year. Cumulative emissions of acrolein (in 2020), benzene, DPM, and formaldehyde would be less than 

noncumulative emissions for the same combinations of pollutant and year. 

Alternative 2 would reduce toxic air pollutant emissions compared to the No Action Alternative 

for acetaldehyde (in 2016), benzene, DPM, and formaldehyde, and would increase emissions of 

acetaldehyde (except in 2016), acrolein (except in 2016), and 1,3-butadiene. Compared to Alternatives 3 

through 9, Alternative 2 would result in lower emissions of acetaldehyde (except under Alternatives 5 

through 9 in 2030 and 2050), acrolein (except under Alternative 3 in 2016 and 2020), 1,3-butadiene 

 4-24 
Chapter 4 Cumulative Impacts 4.3 Air Quality 

(except in 2030 and 2050), and formaldehyde (in all years). Alternative 2 would result in higher 

emissions of benzene (in all years) and DPM (in all years) compared to Alternatives 3 through 9. 

Emissions changes (compared to the No Action Alternative) under the Alternative 2 cumulative 

analysis would be the same as or greater than the corresponding emissions changes under the Alternative 

2 noncumulative analysis for all toxic air pollutants. 

Nationwide, the reduction in upstream emissions of toxic air pollutants tends to offset the 

increase in VMT and emissions due to the rebound effect. However, as noted above, the reductions in 

upstream emissions are not uniformly distributed to individual nonattainment areas. There can be net 

emission reductions if the reduction in upstream emissions in the nonattainment area more than offsets the 

increase within the area due to the rebound effect. Under Alternative 2, most nonattainment areas would 

experience net increases in emissions of one or more toxic air pollutant in at least one of the analysis 

years (see Appendix C). However, the emissions increases would be quite small, as shown in 

Appendix C, and emissions increases would be distributed throughout each nonattainment area. 

4.3.3.3.3 Health Outcomes and Monetized Benefits 

Compared to Alternative 1 (No Action), the cumulative impact of Alternative 2 would result in 

410 fewer mortalities and 44,853 fewer work-loss days in 2050. Mortality benefits are measured 

according to Pope et al. (2002); reductions would be 156 percent greater using the Laden et al. (2006) 

benefit-per-ton values. 

Table 4.3.3-8 lists the net changes in health outcomes due to nationwide cumulative emissions in 

each analysis year. The table lists Alternatives 1 through 9 left to right in order of generally increasing 

fuel economy requirements. The health impacts of vehicle emissions decrease successively (i.e., the 

benefits increase) in each analysis year, and generally decrease across more stringent alternatives through 

Alternative 4, with mixed results under Alternatives 5 through 7, and decreasing again under Alternatives 

8 and 9. 

Table 4.3.3-8 expresses the health impacts of each alternative in terms of changes in health 

outcomes compared to the No Action Alternative. The health impacts of each alternative represent 

predicted changes from the baseline incidence (or prevalence) rates. To provide context for the estimated 

health impacts given in Table 4.3.3-8, it is helpful to compare the impacts to sample baseline incidence 

rates. These sample baseline incidence rates provide an estimate of the typical prevalence rates of each 

outcome nationwide under the No Action Alternative. The EPA Report to Congress on The Benefits and 

Costs of the Clean Air Act 1990 to 2010 (EPA 1999) estimated baseline rates for particulate matter (PM)-

related mortality and morbidity for 2010. Generally, the EPA extrapolated these baseline rates from the 

health effect concentration-response function, or estimated them using hospital admissions rates for 

respiratory and cardiovascular conditions. The EPA analysis estimated the following mean baseline 

incidence rates (cases per year) for PM-related effects nationwide in 2010: 2.3 million cases of premature 

mortality, 640,000 cases of chronic bronchitis, 870,000 hospital emergency room visits for asthma, and 

440 million work loss days. 

Table 4.3.3-9 lists the nationwide changes in monetized health impacts from cumulative 

emissions from passenger cars and light trucks. Results for each analysis year are shown for the No 

Action Alternative in the left column, and for the other alternatives from left to right in order of generally 

increasing fuel economy requirements. Monetized health impacts follow the trends established with 

health outcomes above, generally decreasing (i.e., benefits increasing) across more stringent alternatives 

through Alternative 4, with mixed results under Alternatives 5 through 7, and decreasing again under 

Alternatives 8 and 9. 

 4-25 
4.3 Air Quality Chapter 4 Cumulative Impacts 

Table 4.3.3-8 

Cumulative Nationwide Changes in Health Outcomes (cases/year) from Criteria Air Pollutant Emissions from 

Passenger Cars and Light Trucks by Alternative a/ 

Alt. 1 Alt. 2 Alt. 3 Alt. 4 Alt. 5 Alt. 6 Alt. 7 Alt. 8 Alt. 9 

Out. 

and 

Year 

No 

Action b/ 

3%/year 

Increase 

4%/year 

Increase 

~4.3%/year

Increase 

Preferred 

5%/year 

Increase 

~6.0%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.6%/year 

Increase 

TCTB 

Mortality (ages 30 and older) 

Pope et al. 2002 

2016 0 a/ -23 b/ -36 -42 -31 -32 -29 -29 -34

2020 0 -75 -95 -104 -87 -90 -85 -82 -90

2030 0 -221 -233 -242 -227 -249 -239 -243 -248

2050 0 -410 -417 -430 -415 -466 -449 -465 -465

Laden et al. 2006 

2016 0 -60 -93 -107 -80 -83 -75 -73 -87

2020 0 -193 -245 -266 -224 -230 -217 -210 -231

2030 0 -566 -596 -619 -580 -638 -611 -622 -635

2050 0 -1,048 -1,067 -1,098 -1,062 -1,192 -1,147 -1,188 -1,190

Chronic Bronchitis 

2016 0 -16 -25 -29 -21 -22 -20 -19 -23

2020 0 -51 -65 -71 -60 -61 -58 -56 -61

2030 0 -145 -153 -159 -149 -165 -157 -160 -164

2050 0 -260 -265 -273 -265 -298 -286 -297 -297

Emergency Room Visits for Asthma 

2016 0 -22 -34 -40 -30 -31 -29 -28 -33

2020 0 -72 -91 -99 -83 -86 -82 -80 -87

2030 0 -202 -212 -220 -204 -221 -214 -217 -222

2050 0 -362 -366 -376 -358 -394 -383 -394 -396

Work Loss Days 

2016 0 -3,047 -4,750 -5,510 -4,110 -4,201 -3,821 -3,708 -4,430

2020 0 -9,663 -12,301 -13,391 -11,232 -11,543 -10,859 -10,515 -11,543

2030 0 -26,037 -27,455 -28,551 -26,834 -29,566 -28,261 -28,812 -29,409

2050 0 -44,853 -45,691 -47,074 -45,648 -51,374 -49,365 -51,187 -51,231

__________ 

a/ Negative changes indicate reductions; positive emissions changes are increases. 

b/ Changes in health outcome for the No Action Alternative are shown as zero because the No Action Alternative is 

the baseline to which emissions under the action alternatives are compared. 

Table 4.3.3-9 lists the corresponding monetized health benefits under Alternative 2 compared to 

the No Action Alternative. In 2050, health-related benefits under Alternative 2 would be $3.7 billion 

annually using a 3-percent discount rate and estimates from Pope et al. (2002). With the Laden et al.

(2006) method, health-related benefits would be 145 percent greater. Using a 7-percent discount rate, 

health-related benefits would be 9.3 to 9.7 percent less. Alternative 2 would result in less health and 

economic benefit than other more stringent alternatives. 

 4-26 
Chapter 4 Cumulative Impacts 4.3 Air Quality 

Table 4.3.3-9 

Cumulative Nationwide Monetized Health Benefits (U.S. million dollars/year) from Changes in Criteria Air 

Pollutant Emissions from Passenger Cars and Light Trucks by Alternative a/ 

Alt. 1 Alt. 2 Alt. 3 Alt. 4 Alt. 5 Alt. 6 Alt. 7 Alt. 8 Alt. 9 

Disc. 

and 

Year 

No 

Action b/ 

3%/year 

Increase 

4%/year 

Increase 

~4.3%/year

Increase 

Preferred 

5%/year 

Increase 

~6.0%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.6%/year 

Increase 

TCTB 

3-% Discount Rate

Pope et al. 2002 

2016 0 a/ -196 b/ -304 -353 -264 -272 -248 -241 -287

2020 0 -653 -830 -903 -758 -779 -735 -713 -782

2030 0 -1,965 -2,070 -2,152 -2,017 -2,216 -2,123 -2,161 -2,208

2050 0 -3,709 -3,775 -3,888 -3,760 -4,219 -4,061 -4,205 -4,212

Laden et al. 2006 

2016 0 -480 -746 -865 -648 -666 -607 -591 -704

2020 0 -1,599 -2,032 -2,211 -1,856 -1,909 -1,801 -1,746 -1,915

2030 0 -4,815 -5,073 -5,273 -4,942 -5,429 -5,201 -5,295 -5,409

2050 0 -9,091 -9,253 -9,529 -9,214 -10,339 -9,952 -10,305 -10,322

7-% Discount Rate

Pope et al. 2002 

2016 0 -178 -276 -320 -240 -247 -225 -219 -260

2020 0 -592 -753 -819 -688 -707 -667 -647 -709

2030 0 -1,782 -1,878 -1,952 -1,830 -2,010 -1,926 -1,961 -2,003

2050 0 -3,364 -3,424 -3,526 -3,410 -3,827 -3,683 -3,814 -3,820

Laden et al. 2006 

2016 0 -433 -674 -781 -585 -602 -549 -534 -636

2020 0 -1,444 -1,836 -1,997 -1,677 -1,724 -1,627 -1,578 -1,730

2030 0 -4,349 -4,582 -4,763 -4,464 -4,904 -4,698 -4,783 -4,885

2050 0 -8,211 -8,358 -8,607 -8,322 -9,338 -8,989 -9,307 -9,323

__________ 

a/ Negative changes indicate monetized health benefits; positive emissions changes indicate monetized health 

disbenefits. 

b/ Changes in outcome for the No Action Alternative are shown as zero because the No Action Alternative is the 

baseline to which impacts under the action alternatives are compared. 

4.3.3.4 Alternative 3: 4-Percent Annual Increase 

4.3.3.4.1 Criteria Pollutants 

Under the 4-Percent Alternative (Alternative 3), the CAFE standards generally would increase 

fuel economy more than Alternative 2 but less than Alternatives 4 through 9. There would be reductions 

in nationwide emissions of NOx, PM2.5, SOx, and VOCs under Alternative 3 compared to the No Action 

Alternative. Depending on the year, NOx emissions would be reduced 0.2 to 2.2 percent, PM2.5 emissions 

would be reduced 1.0 to 4.7 percent, SOx emissions would be reduced 2.4 to 12.3 percent, and VOC 

emissions would be reduced 0.8 to 7.9 percent, compared to emissions projected under the No Action 

Alternative. Except for emissions SOx in 2050, these emissions reductions are generally greater than 

would occur under Alternative 2. Except for emissions of PM2.5 under Alternatives 5 through 9, and SOx

under Alternative 5 in 2030 and 2050, these emissions reductions are generally less than would occur 

under Alternatives 4 through 9. There would be increases of CO emissions from 0.1 to 0.8 percent, 

depending on the year, compared to emissions projected under the No Action Alternative. 

 4-27 
4.3 Air Quality Chapter 4 Cumulative Impacts 

Emissions in individual nonattainment areas might follow different patterns from nationwide 

emissions. Emissions of criteria pollutants vary due to interrelations among upstream emissions, VMT 

increases, and diesel share of fuel consumption. Compared to Alternative 1, cumulative emissions of SOx

and VOCs under Alternative 3 would decrease in all nonattainment areas. In contrast, CO emissions 

would increase in almost all nonattainment areas, while NOx and PM2.5 emissions would would decrease 

in some nonattainment areas and increase in others. Tables in Appendix C list the emissions reductions 

for each nonattainment area. 

Cumulative fuel economy standards would lead to lower emissions of most pollutants compared 

to noncumulative standards, due to the impact of higher projected average fuel economy in the cumulative 

case. Under Alternative 3, cumulative emissions of NOx, PM2.5, SOx, and VOCs would be lower than 

noncumulative emissions. However, emissions of CO are higher under the cumulative case than the 

noncumulative case, because increases in VMT more than offset declines in CO emission rates and 

increases in fuel economy. 

Emissions reductions (compared to the No Action Alternative) under the Alternative 3 cumulative 

analysis would be greater than the corresponding emissions reductions under the Alternative 3 

noncumulative analysis for NOx, PM2.5, SO2, and VOCs. For CO, emissions increases under the 

Alternative 3 cumulative analysis would be greater than the corresponding emissions increases under the 

Alternative 3 noncumulative analysis. 

4.3.3.4.2 Toxic Air Pollutants 

Alternative 3 would reduce toxic air pollutant emissions compared to the No Action Alternative 

for benzene, DPM, and formaldehyde (in 2016 and 2020), and would increase emissions of acetaldehyde, 

acrolein, 1,3-butadiene, and formaldehyde (in 2030 and 2050) compared to the No Action Alternative. 

Compared to Alternatives 4 through 9, Alternative 3 would result in higher emissions of benzene and 

DPM, and lower emissions of acetaldehyde (except under Alternatives 5 through 9 in 2030 and 2050), 

acrolein, 1,3-butadiene (except in 2030 and 2050), and formaldehyde. 

Emissions changes (compared to the No Action Alternative) under the Alternative 3 cumulative 

analysis would be the same as or greater than the corresponding emissions changes under the Alternative 

3 noncumulative analysis for all toxic air pollutants except formaldehyde (in 2030). For formaldehyde in 

2030, emissions changes (compared to the No Action Alternative) under the Alternative 3 cumulative 

analysis would be less than the corresponding emissions changes under the Alternative 3 noncumulative 

analysis. 

Nationwide, emissions of toxic air pollutants can decrease because the reduction in upstream 

emissions more than offsets the increase in VMT and emissions due to the rebound effect. However, the 

reductions in upstream emissions are not uniformly distributed to individual nonattainment areas. Under 

Alternative 3, most nonattainment areas would experience net increases in emissions of one or more toxic 

air pollutant in at least one of the analysis years (see Appendix C). However, the emissions increases 

would be quite small, as shown in Appendix C, and emissions increases would be distributed throughout 

each nonattainment area. Table 4.3.3-10 summarizes the air toxic results by nonattainment area. 

4.3.3.4.3 Health Outcomes and Monetized Benefits 

Compared to Alternative 1 (No Action), the cumulative impact of Alternative 3 would result in 

417 fewer mortalities and 45,691 fewer work-loss days in 2050. Mortality benefits are measured 

according to Pope et al. (2002); reductions would be 156 percent greater under the Laden et al. (2006) 

methodology. 

 4-28 
Chapter 4 Cumulative Impacts 4.3 Air Quality 

Table 4.3.3-10 

Cumulative Changes in Toxic Air Pollutant Emissions from Passenger Cars and Light Trucks, 

Maximum Changes by Nonattainment Area and Alternative 

Hazardous Air 

Pollutant 

Increase/ 

Decrease 

Change

(tons/year) Year Alt. No. Nonattainment Area 

Maximum Increase 4.78 2050 3 New York-N. New Jersey-Long Island, NY-NJ-CT Acetaldehyde 

Maximum Decrease -13.33 2050 8 Houston-Galveston-Brazoria, TX 

Maximum Increase 5.56 2050 8 New York-N. New Jersey-Long Island, NY-NJ-CT Acrolein 

Maximum Decrease -0.74 2050 8 Beaumont/Port Arthur, TX 

Maximum Increase 10.64 2050 2 Los Angeles South Coast Air Basin, CA Benzene 

Maximum Decrease -112.2 2050 8 New York-N. New Jersey-Long Island, NY-NJ-CT

Maximum Increase 2.51 2050 2 New York-N. New Jersey-Long Island, NY-NJ-CT 1,3-Butadiene 

Maximum Decrease -3.91 2050 8 New York-N. New Jersey-Long Island, NY-NJ-CT

Diesel particulate Maximum Increase 124 2050 8 Atlanta, GA 

matter Maximum Decrease -3,177 2050 8 Houston-Galveston-Brazoria, TX 

Maximum Increase 70 2050 8 New York-N. New Jersey-Long Island, NY-NJ-CT Formaldehyde 

Maximum Decrease -58 2050 9 Houston-Galveston-Brazoria, TX 

Table 4.3.3-9 lists the corresponding monetized health benefits under Alternative 3 compared to 

the No Action Alternative. In 2050, health-related benefits under Alternative 3 would be $3.8 billion 

annually, using a 3-percent discount rate and estimates from Pope et al. (2002). With the Laden et al. 

(2006) method, health-related benefits would be 145 percent greater. Using a 7-percent discount rate, 

health-related benefits would be 9.3 to 9.7 percent less. 

4.3.3.5 Alternative 4: Preferred Alternative 

4.3.3.5.1 Criteria Pollutants 

Under the Preferred Alternative (Alternative 4), the CAFE standards would increase fuel 

economy more than Alternatives 1 through 3 but less than Alternatives 5 through 9. There would be 

reductions in nationwide emissions of NOx, PM2.5, SOx, and VOCs under Alternative 4 compared to the 

No Action Alternative. Depending on the year, NOx emissions would be reduced 0.3 to 2.5 percent, 

PM2.5 emissions would be reduced 1.1 to 4.8 percent, SOx emissions would be reduced 2.8 to 12.6 

percent, and VOC emissions would be reduced 1.0 to 8.3 percent, compared to emissions projected under 

the No Action Alternative. The emissions reductions for these pollutants are generally greater than would 

occur under Alternative 3, except for SOx in 2050 . Emissions reductions of these four pollutants under 

Alternative 4 would be less than would occur under Alternatives 5 through 9, except for PM2,5 in all 

years, and SOx under Alternative 5 in all years and Alternative 7 in 2016. There would be increases of 

CO emissions of 0.02 to 0.5 percent, depending on the year, compared to emissions projected under the 

No Action Alternative. 

Emissions in individual nonattainment areas might follow different patterns from nationwide 

emissions. Emissions of criteria pollutants vary due to interrelations among upstream emissions, VMT 

increases, and diesel share of fuel consumption. Compared to Alternative 1, cumulative emissions of SOx

and VOCs under Alternative 4 would decrease in all nonattainment areas. In contrast, CO emissions 

would increase in almost all nonattainment areas, while NOx and PM emissions would decrease in some 

 4-29 
4.3 Air Quality Chapter 4 Cumulative Impacts 

nonattainment areas and increase in others. Tables in Appendix C list the emissions reductions for each 

nonattainment area. 

Cumulative fuel economy standards would lead to lower emissions of most pollutants compared 

to noncumulative standards, due to the impact of higher projected average fuel economy in the cumulative 

case. Under Alternative 4, cumulative emissions of NOx, PM2.5, SOx, and VOCs are lower than 

noncumulative emissions. However, emissions of CO are higher under the cumulative case than the 

noncumulative case, because increases in VMT more than offset declines in CO emission rates and 

increases in fuel economy. 

Emissions reductions (compared to the No Action Alternative) under the Alternative 4 cumulative 

analysis would be greater than the corresponding emissions reductions under the Alternative 4 

noncumulative analysis for NOx, PM2.5, SO2, and VOCs, except for PM2.5, SO2, and VOCs in 2030. For 

CO, emissions increases under the Alternative 4 cumulative analysis would be greater than the 

corresponding emissions increases under the Alternative 4 noncumulative analysis, except in 2030. 

4.3.3.5.2 Toxic Air Pollutants 

Under Alternative 4, cumulative emissions would be less than noncumulative emissions for 

benzene, DPM and formaldehyde and the same as or greater than noncumulative emissions for 

acetaldehyde, acrolein, and 1,3-butadiene. 

Alternative 4 would reduce toxic air pollutant emissions compared to the No Action Alternative 

for benzene and DPM, and would increase emissions of acetaldehyde, acrolein, 1,3-butadiene, and 

formaldehyde. Compared to Alternatives 5 through 9, Alternative 4 would result in higher emissions of 

acetaldehyde (in 2030 and 2050), benzene, DPM, and 1,3-butadiene (in 2030 and 2050), and lower 

emissions of acetaldehyde (in 2016 and 2020), acrolein, 1,3-butadiene (in 2016 and 2020), and 

formaldehyde. 

Emissions changes (compared to the No Action Alternative) under the Alternative 4 cumulative 

analysis would be the same as or greater than the corresponding emissions changes under the Alternative 

4 noncumulative analysis, for all toxic air pollutants except acetaldehyde (in 2020), and benzene, 1,3-

butadiene, and DPM in 2030. 

Nationwide, emissions of toxic air pollutants can decrease because the reduction in upstream 

emissions more than offsets the increase in VMT and emissions due to the rebound effect. However, the 

reductions in upstream emissions would not occur uniformly in all nonattainment areas. Under 

Alternative 4, most nonattainment areas would experience net increases in emissions of one or more toxic 

air pollutant in at least one of the analysis years (see Appendix C). However, the emissions increases 

would be quite small, as shown in Appendix C, and emissions increases would be distributed throughout 

each nonattainment area. 

4.3.3.5.3 Health Outcomes and Monetized Benefits 

Compared to Alternative 1 (No Action), the cumulative impact of Alternative 4 would result in 

430 fewer mortalities and 47,074 fewer work-loss days in 2050. Mortality benefits are measured 

according to Pope et al. (2002); reductions would be 155 percent greater using the Laden et al. (2006) 

methodology. 

Table 4.3.3-9 lists the corresponding monetized health benefits under Alternative 4 compared to 

the No Action Alternative. In 2050, health-related benefits under Alternative 4 would be $3.9 billion 

 4-30 
Chapter 4 Cumulative Impacts 4.3 Air Quality 

annually, using a 3-percent discount rate and estimates from Pope et al. (2002). With the Laden et al. 

(2006) method, health-related benefits would be 145 percent greater. Using a 7-percent discount rate, 

health-related benefits would be 9.3 to 9.7 percent less. 

Compared to more stringent alternatives, health and economic benefits are less than for all 

successive alternatives. 

4.3.3.6 Alternative 5: Five Percent Annual Increase 

4.3.3.6.1 Criteria Pollutants 

Under the 5-Percent Alternative (Alternative 5), the CAFE standards would increase fuel 

economy more than Alternatives 1 through 4 but less than Alternatives 6 through 9. There would be 

reductions in nationwide emissions of all criteria pollutants under Alternative 5 compared to the No 

Action Alternative. Reductions under Alternative 5 would be greater than under Alternative 4 (except for 

PM2.5 and SOx), and less than under Alternative 6 through 9 (except for PM2.5 in all years). Depending on 

the year, CO emissions would be reduced 0.5 to 3.9 percent, NOx emissions would be reduced 0.4 to 5.0 

percent, PM2.5 emissions would be reduced 0.5 to 3.6 percent, SOx emissions would be reduced 2.4 to 

12.0 percent, and VOC emissions would be reduced 1.4 to 12.3 percent, compared to emissions projected 

under the No Action Alternative. 

Emissions in individual nonattainment areas could follow different patterns from nationwide 

emissions. Emissions of criteria pollutants vary due to interrelations among upstream emissions, VMT 

increases, and diesel share of fuel. Compared to Alternative 1, cumulative emissions of CO, NOx, SOx, 

and VOCs under Alternative 5 would decrease in all nonattainment areas. PM2.5 results would be mixed, 

with emissions increasing in some nonattainment areas and decreasing in others. Tables in Appendix C 

list the emissions reductions for each nonattainment area. 

Cumulative fuel economy standards would lead to lower emissions of most pollutants compared 

to noncumulative standards, due to the impact of higher projected average fuel economy in the cumulative 

case. Under Alternative 5, cumulative emissions of NOx, PM2.5, SOx, and VOCs are lower than 

noncumulative emissions. However, emissions of CO are higher under the cumulative case than the 

noncumulative case, because increases in VMT more than offset declines in CO emission rates and 

increases in fuel economy. 

Emissions reductions (compared to the No Action Alternative) under the Alternative 5 cumulative 

analysis would be less than the corresponding emissions reductions under the Alternative 5 

noncumulative analysis for NOx, PM2.5, SO2, and VOCs. For CO, emissions reductions under the 

Alternative 5 cumulative analysis would be greater than the corresponding emissions reductions under the 

Alternative 5 noncumulative analysis. 

4.3.3.6.2 Toxic Air Pollutants 

Under Alternative 5, cumulative emissions would be less than noncumulative emissions for 

benzene, DPM, and formaldehyde ; the same as noncumulative emissions for acetaldehyde in 2020, 

acrolein in all years, and 1,3-butadiene in 2020; and greater than noncumulative emissions for 

acetaldehyde and 1,3-butadiene in 2030. 

Alternative 5 would reduce toxic air pollutant emissions compared to the No Action Alternative 

for acetaldehyde (in 2050), benzene, 1,3-butadiene (in 2030 and 2050), and DPM, and would increase 

emissions of acetaldehyde (except in 2050), acrolein, 1,3-butadiene (in 2016 and 2020), and 

 4-31 
4.3 Air Quality Chapter 4 Cumulative Impacts 

formaldehyde compared to the No Action Alternative. Compared to Alternatives 6 through 9, Alternative 

5 would result in higher emissions of acetaldehyde (in 2030 and 2050), benzene, 1,3-butadiene (in 2030 

and 2050), and DPM, and lower emissions of acetaldehyde (in 2016 and 2020), acrolein, 1,3-butadiene (in 

2016 and 2020), and formaldehyde. 

Emissions changes (compared to the No Action Alternative) under the Alternative 5 cumulative 

analysis would be the same or greater than the corresponding emissions changes under the Alternative 5 

noncumulative analysis, for all toxic air pollutants except acetaldehyde (in 2020 and 2030), acrolein (in 

2030), enzene (in 2030), and DPM (in 2020 and 2030). 

Nationwide, emissions of toxic air pollutants can decrease because the reduction in upstream 

emissions more than offsets the increase in VMT and emissions due to the rebound effect. However, the 

reductions in upstream emissions are not uniformly distributed to individual nonattainment areas. Under 

Alternative 5, most nonattainment areas would experience net increases in emissions of one or more toxic 

air pollutant in at least one of the analysis years (see Appendix C). However, the emissions increases 

would be quite small, as shown in Appendix C, and emissions increases would be distributed throughout 

each nonattainment area. 

4.3.3.6.3 Health Outcomes and Monetized Benefits 

Compared to Alternative 1 (No Action), the cumulative impact of Alternative 5 would result in 

415 fewer mortalities and 45,648 fewer work-loss days in 2050. Mortality benefits are measured 

according to Pope et al. (2002); reductions would be 156 percent greater using the Laden et al. (2006) 

methodology. 

Table 4.3.3-9 lists the corresponding monetized health benefitsunder Alternative 5 compared to 

the No Action Alternative. Health-related benefits underAlternative 5 in 2050 would be $3.8 billion 

annually, using a 3-percent discount rate and estimates from Pope et al. (2002). With the Laden et al. 

(2006) method, health-related benefits would be 145 percent greater. Using a 7-percent discount rate, 

health-related benefits would be 9.3 to 9.7 percent less. 

Compared to Alternative 5, health and economic benefits would be greater under Alternative 6, 

Alternatives 7 and 8 in 2030 and 2050, and Alternative 9, but less under Alternatives 7 and 8 in 2016 and 

2020. 

4.3.3.7 Alternative 6: MNB 

4.3.3.7.1 Criteria Pollutants 

Under the MNB (Alternative 6), the CAFE standards would increase fuel economy more than 

Alternatives 1 through 4 but less than Alternatives 7 through 9. There would be reductions in nationwide 

emissions of all criteria pollutants under Alternative 6 compared to the No Action Alternative. 

Reductions under Alternative 6 would be greater than under Alternative 5 except for PM2.5 for all years. 

Depending on the year, CO emissions would be reduced 1.0 to 7.7 percent, NOx emissions would be 

reduced 0.6 to 7.5 percent, PM2.5 emissions would be reduced 0.3 to 3.4 percent, SOx emissions would be 

reduced 2.9 to 12.8 percent, and VOC emissions would be reduced 2.0 to 16.4 percent, compared to 

emissions projected under the No Action Alternative. 

Emissions in individual nonattainment areas could follow different patterns from nationwide 

emissions. Emissions of criteria pollutants vary due to interrelations among upstream emissions, VMT 

increases, and diesel share of fuel consumption. Compared to Alternative 1, cumulative emissions of CO, 

 4-32 
Chapter 4 Cumulative Impacts 4.3 Air Quality 

NOx, SOx, and VOCs under Alternative 6 would decrease in all nonattainment areas. PM2.5 results are 

mixed, with emissions increasing in some nonattainment areas and decreasing in others. Tables in 

Appendix C list the emissions reductions for each nonattainment area. 

Cumulative fuel economy standards would lead to lower emissions of most pollutants compared 

to noncumulative standards, due to the impact of higher projected average fuel economy in the cumulative 

case. Under Alternative 6, cumulative emissions of NOx, PM2.5, SOx, and VOCs would be lower than 

noncumulative emissions. However, emissions of CO would be higher under the cumulative case than 

the noncumulative case, because increases in VMT more than offset declines in CO emission rates and 

increases in fuel economy. 

Emissions reductions (compared to the No Action Alternative) under the Alternative 6 cumulative 

analysis would be less than the corresponding emissions reductions under the Alternative 6 

noncumulative analysis for for NOx, PM2.5, SOx, and VOCs. Emissions reductions (compared to the No 

Action Alternative) under the Alternative 6 cumulative analysis would be greater than the corresponding 

emissions reductions under the Alternative 6 noncumulative analysis for CO in all years 

4.3.3.7.2 Toxic Air Pollutants 

Under Alternative 6, cumulative emissions would be less than noncumulative emissions for 

benzene, DPM, and formaldehyde; greater than noncumulative emissions for acetaldehyde in all years, 

acrolein, and 1,3-butadiene in 2030; and the same as noncumulative emissions for acrolein. Alternative 6 

would reduce toxic air pollutant emissions compared to the No Action Alternative for acetaldehyde (in 

2030 and 2050), benzene, 1,3-butadiene (in 2030 and 2050), and DPM, and would increase emissions of 

acetaldehyde (in 2016 and 2020), acrolein, 1,3-butadiene (in 2016 and 2020), and formaldehyde 

compared to the No Action Alternative. Compared to Alternatives 7 through 9, results for all pollutants 

under Alternative 6 would be mixed, depending on year, pollutant, and alternative. 

Emissions changes (compared to the No Action Alternative) under the Alternative 6 cumulative 

analysis would be greater than the corresponding emissions changes under the Alternative 6 

noncumulative analysis for all toxic air pollutants except acrolein (in 2030), benzene (in 2030), and DPM 

(in 2020 and 2030). 

Nationwide, emissions of toxic air pollutants can decrease because the reduction in upstream 

emissions more than offsets the increase in VMT and emissions due to the rebound effect. However, the 

reductions in upstream emissions are not uniformly distributed to individual nonattainment areas. Under 

Alternative 6, most nonattainment areas would experience net increases in emissions of one or more toxic 

air pollutant in at least one of the analysis years (see Appendix C). However, the emissions increases 

would be quite small, as shown in Appendix C, and emissions increases would be distributed throughout 

each nonattainment area. 

4.3.3.7.3 Health Outcomes and Monetized Benefits 

Compared to Alternative 1 (No Action), the cumulative impact of Alternative 6 would result in 

466 fewer mortalities and 51,374 fewer work-loss days in 2050. Mortality benefits are measured 

according to Pope et al.; reductions would be 156 percent greater using the Laden et al. methodology 

Table 4.3.3-9 lists the corresponding monetized health benefits under Alternative 6 compared to 

the No Action Alternative. In 2050, health-related benefits under Alternative 6 would be $4.2 billion 

annually, using a 3-percent discount rate and estimates from Pope et al. (2002). With the Laden et al. 

 4-33 
4.3 Air Quality Chapter 4 Cumulative Impacts 

(2006) method, health-related benefits would be 145 percent greater. Using a 7-percent discount rate, 

health-related benefits would be 9.3 to 9.7 percent less. 

Compared to Alternative 6, health and economic benefits would be greater under Alternative 9 in 

2016 and 2020, but less under Alternatives 7 and 8 in all years, and Alternative 9 in 2030 and 2050. 

4.3.3.8 Alternative 7: 6-Percent Annual Increase 

4.3.3.8.1 Criteria Pollutants 

Under the 6-Percent Alternative (Alternative 7), the CAFE standards would increase fuel 

economy more than Alternatives 1 through 6 but less than Alternatives 8 and 9. There would be 

reductions in nationwide emissions of all criteria pollutants under Alternative 7 compared to the No 

Action Alternative. Reductions would be less than under Alternative 6 (except for SOx in 2030 and 

2050). Reductions also would be less than under Alternatives 8 and 9 (except for PM2.5 under Alternative 

8). Depending on the year, CO emissions would be reduced 0.7 to 6.9 percent, NOx emissions would be 

reduced 0.5 to 7.0 percent, PM2.5 emissions would be reduced 0.3 to 3.2 percent, SOx emissions would be 

reduced 2.7 to 13.0 percent, and VOC emissions would be reduced 1.8 to 16.2 percent, compared to 

emissions projected under the No Action Alternative. 

Emissions in individual nonattainment areas could follow different patterns from nationwide 

emissions. Emissions of criteria pollutants vary due to interrelations among upstream emissions, VMT 

increases, and diesel share of fuel consumption. Compared to Alternative 1, cumulative emissions of CO, 

NOx, SOx, and VOCs under Alternative 7 would decrease in all nonattainment areas. PM2.5 results are 

mixed, with emissions increasing in some nonattainment areas and decreasing in others. Tables in 

Appendix C list the emissions reductions for each nonattainment area. 

Cumulative fuel economy standards would lead to lower emissions of most pollutants compared 

to noncumulative standards, due to the impact of higher projected average fuel economy in the cumulative 

case. Under Alternative 7, cumulative emissions of NOx, PM2.5, SOx, and VOCs are lower than 

noncumulative emissions. However, emissions of CO are higher under the cumulative case than the 

noncumulative case, because increases in VMT more than offset declines in CO emission rates and 

increases in fuel economy. 

Emissions reductions (compared to the No Action Alternative) under the Alternative 7 cumulative 

analysis would be less than the corresponding emissions reductions under the Alternative 7 

noncumulative analysis for NOx, PM2.5, SOx, and VOCs. Emissions reductions (compared to the No 

Action Alternative) under the Alternative 7 cumulative analysis would be greater than the corresponding 

emissions reductions under the Alternative 7 noncumulative analysis for CO. 

4.3.3.8.2 Toxic Air Pollutants 

Under Alternative 7, cumulative emissions would be less than noncumulative emissions for 

benzene, DPM, and formaldehyde, and greater than noncumulative emissions for acetaldehyde in 2020 

and 2030, and 1,3-butadiene in 2030, and the same as noncumulative emissions for for acrolein in all 

years and 1,3-butadiene in 2020. 

Alternative 7 would reduce toxic air pollutant emissions compared to the No Action Alternative 

for acetaldehyde (in 2030 and 2050), benzene, 1,3-butadiene (in 2030 and 2050), and DPM, and would 

increase emissions of acetaldehyde (in 2016 and 2020), acrolein, 1,3-butadiene (in 2016 and 2020), and 

formaldehyde. Compared to Alternatives 8 and 9, Alternative 7 would result in higher emissions of 

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Chapter 4 Cumulative Impacts 4.3 Air Quality 

acetaldehyde (in 2030 and 2050), benzene, 1,3-butadiene (in 2030 and 2050), and DPM, and lower 

emissions of acetaldehyde (in 2016 and 2020), acrolein, 1,3-butadiene (in 2016 and 2020), and 

formaldehyde. 

Emissions changes (compared to the No Action Alternative) under the Alternative 7 cumulative 

analysis would be the same as or greater than the corresponding emissions changes under the Alternative 

7 noncumulative analysis for all toxic air pollutants except benzene (in 2020 and 2030) , and DPM (in 

2020 and 2030). 

Nationwide, emissions of toxic air pollutants can decrease because the reduction in upstream 

emissions more than offsets the increase in VMT and emissions due to the rebound effect. However, the 

reductions in upstream emissions are not uniformly distributed to individual nonattainment areas. Under 

Alternative 7, most nonattainment areas would experience net increases in emissions of one or more toxic 

air pollutant in at least one of the analysis years (see Appendix C). However, the emissions increases 

would be quite small, as shown in Appendix C, and emissions increases would be distributed throughout 

each nonattainment area. 

4.3.3.8.3 Health Outcomes and Monetized Benefits 

Compared to Alternative 1 (No Action), the cumulative impact of Alternative 7 would result in 

449 fewer mortalities and 49,365 fewer work-loss days in 2050. Mortality benefits are measured 

according to Pope et al. (2002); reductions would be 155 percent greater using the Laden et al. (2006) 

methodology. 

Table 4.3.3-9 lists the corresponding monetized health benefits under Alternative 7 compared to 

the No Action Alternative. In 2050, health-related benefits under Alternative 7 would be $4.1 billion 

annually, using a 3-percent discount rate and estimates from Pope et al. (2002). With the Laden et al. 

(2006) method, health-related benefits would be 145 percent greater. Using a 7-percent discount rate, 

health-related benefits would be 9.3 to 9.7 percent less. 

Compared to Alternative 7, health and economic benefits would be greater under Alternative 8 in 

2030 and 2050, and Alternative 9 in all years, but less under Alternative 8 in 2016 and 2020. 

4.3.3.9 Alternative 8: 7-Percent Annual Increase 

4.3.3.9.1 Criteria Pollutants 

Under the 7-Percent Alternative (Alternative 8), the CAFE standards would increase fuel 

economy more than Alternatives 1 through 7 and also more than Alternative 9. There would be 

reductions in nationwide emissions of all criteria pollutants under Alternative 8 compared to the No 

Action Alternative. Reductions would be greater than under Alternative 7 (except for PM2.5). Reductions 

would be greater than under Alternative 9 for CO, NOx (except in 2016), and VOC (except in 2016). 

Reductions would be less than under Alternative 9 for NOx in 2016, PM2.5 in all years, SOx in all years, 

and VOC in 2016. Depending on the year, CO emissions would be reduced 1.0 to 9.8 percent, NOx

emissions would be reduced 0.6 to 8.9 percent, PM2.5 emissions would be reduced 0.1 to 2.7 percent, SOx

emissions would be reduced 2.9 to 13.4 percent, and VOC emissions would be reduced 2.1 ro 19.1 

percent, compared to emissions projected under the No Action Alternative. 

Emissions in individual nonattainment areas could follow different patterns from nationwide 

emissions. Emissions of criteria pollutants vary due to interrelations among upstream emissions, VMT 

increases, and diesel share of fuel. Compared to Alternative 1, cumulative emissions of CO, NOx, SOx, 

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4.3 Air Quality Chapter 4 Cumulative Impacts 

and VOCs under Alternative 8 would decrease in all nonattainment areas. PM2.5 results are mixed, with 

emissions increasing in some nonattainment areas and decreasing in others. Tables in Appendix C list the 

emissions reductions for each nonattainment area. 

Cumulative fuel economy standards would lead to lower emissions of most pollutants compared 

to noncumulative standards, due to the impact of higher projected fuel economy in the cumulative case. 

Under Alternative 8, cumulative emissions of NOx, PM2.5, SOx, and VOCs would be lower than 

noncumulative emissions. However, emissions of CO would be higher under the cumulative case than 

the noncumulative case, because increases in VMT more than offset declines in CO emission rates and 

increases in fuel economy. 

Emissions reductions (compared to the No Action Alternative) under the Alternative 8 cumulative 

analysis would be greater than the corresponding emissions reductions under the Alternative 8 

noncumulative analysis for CO in all years. Emissions reductions (compared to the No Action 

Alternative) under the Alternative 8 cumulative analysis would be less than the corresponding emissions 

reductions under the Alternative 8 noncumulative analysis for NOx, PM2.5, SOx, and VOCs in all years. 

4.3.3.9.2 Toxic Air Pollutants 

Under Alternative 8, cumulative emissions would be less than noncumulative emissions for 

benzene, DPM, and formaldehyde, and the same or greater than noncumulative emissions for 

acetaldehyde, acrolein, and 1,3-butadiene. 

Alternative 8 would reduce toxic air pollutant emissions compared to the No Action Alternative 

for acetaldehyde (in 2030 and 2050), benzene, 1,3-butadiene (in 2030 and 2050), and DPM, and would 

increase emissions of acetaldehyde (in 2016 and 2020), acrolein, 1,3-butadiene (in 2016 and 2020), and 

formaldehyde compared to the No Action Alternative. Compared to Alternative 9, Alternative 8 would 

result in the same or higher emissions of acetaldehyde (in 2016 and 2020), acrolein, 1,3-butadiene (in 

2016 and 2020), DPM (in 2016), and formaldehyde, and lower emissions of acetaldehyde (in 2030 and 

2050), benzene, 1,3-butadiene (in 2030 and 2050), and DPM (in 2020 through 2050). 

Emissions changes (compared to the No Action Alternative) under the Alternative 8 cumulative 

analysis would be the same as or greater than the corresponding emissions changes under the Alternative 

8 noncumulative analysis for all toxic air pollutants except benzene (in 2020 and 2030), and DPM (in 

2020 and 2030). 

Nationwide, emissions of toxic air pollutants can decrease because the reduction in upstream 

emissions more than offsets the increase in VMT and emissions due to the rebound effect. However, the 

reductions in upstream emissions are not uniformly distributed to individual nonattainment areas. Under 

Alternative 8, most nonattainment areas would experience net increases in emissions of one or more toxic 

air pollutant in at least one of the analysis years (see Appendix C). However, the emissions increases 

would be quite small, as shown in Appendix C, and emissions increases would be distributed throughout 

each nonattainment area. 

4.3.3.9.3 Health Outcomes and Monetized Benefits 

Compared to Alternative 1 (No Action), the cumulative impact of Alternative 8 would result in 

465 fewer mortalities and 51,187 fewer work-loss days in 2050. Mortality benefits are measured 

according to Pope et al. (2002); reductions would be 155 percent greater using the Laden et al. (2006) 

methodology. 

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Chapter 4 Cumulative Impacts 4.3 Air Quality 

Table 4.3.3-9 lists the corresponding monetized health benefits under Alternative 8 compared to 

the No Action Alternative. In 2050, health-related benefits under Alternative 8 would be $4.2 billion 

annually, using a 3-percent discount rate and estimates from Pope et al. (2002). With the Laden et al. 

(2006) method, health-related benefits would be 145 percent greater. Using a 7-percent discount rate, 

health-related benefits would be 9.3 to 9.7 percent less. Compared to Alternative 9, health and economic 

benefits would be smaller under Alternative 8. 

4.3.3.10 Alternative 9: TCTB 

4.3.3.10.1 Criteria Pollutants 

Under the TCTB Alternative (Alternative 9), the CAFE standards would increase fuel economy 

more than Alternatives 1 through 7, but less than Alternative 8. There would be reductions in nationwide 

emissions of all criteria pollutants under Alternative 9 compared to the No Action Alternative. Emission 

reductions of all criteria pollutants under Alternative 9 would be greater than with any other alternative 

for NOx in 2016, PM2.5 and SOx in all years, and VOCs in 2016. Depending on the year, CO emissions 

would be reduced 1.0 to 8.8 percent, NOx emissions would be reduced 0.6 to 8.2 percent, PM2.5 emissions 

would be reduced 0.3 to 3.0 percent, SOx emissions would be reduced 3.2 to 13.5 percent, and VOC 

emissions would be reduced 2.1 to 18.1 percent, compared to emissions projected under the No Action 

Alternative. 

Emissions in individual nonattainment areas could follow different patterns from nationwide 

emissions. Emissions of criteria pollutants vary due to interrelations among upstream emissions, VMT 

increases, and diesel share of fuel. Compared to Alternative 1, cumulative emissions of CO, NOx, SOx, 

and VOCs under Alternative 9 decrease in all nonattainment areas. PM2.5 results are mixed, with 

emissions increasing in some nonattainment areas and decreasing in others. Tables in Appendix C list the 

emissions reductions for each nonattainment area. 

Cumulative fuel economy standards would lead to lower emissions of most pollutants compared 

to noncumulative standards, due to the impact of higher projected average fuel economy in the cumulative 

case. Under Alternative 9, cumulative emissions of NOx, PM2.5, SOx, and VOCs are lower than 

noncumulative emissions. However, emissions of CO are higher under the cumulative case than the 

noncumulative case, because increases in VMT more than offset declines in CO emission rates and 

increases in fuel economy. 

Emissions reductions (compared to the No Action Alternative) under the Alternative 9 cumulative 

analysis would be greater than the corresponding emissions reductions under the Alternative 9 

noncumulative analysis for CO in all years. Emissions reductions (compared to the No Action 

Alternative) under the Alternative 9 cumulative analysis would be less than the corresponding emissions 

reductions under the Alternative 9 noncumulative analysis for NOx, PM2.5, SOx, and VOCs in all years. 

4.3.3.10.2 Toxic Air Pollutants 

Under Alternative 9, cumulative emissions would be less than noncumulative emissions for 

acrolein (in 2020 and 2030), benzene (in 2020 and 2030), DPM (in 2020 and 2030), and formaldehyde (in 

2020 and 2030), and the same as greater than noncumulative emissions for acetalehyde and 1,3-butadiene 

in all years. 

Alternative 9 would reduce toxic air pollutant emissions compared to the No Action Alternative 

for acetaldehyde (in 2030 and 2050), benzene, 1,3-butadiene (in 2030 and 2050), and DPM, and would 

 4-37 
4.3 Air Quality Chapter 4 Cumulative Impacts 

 4-38 

increase emissions of acetaldehyde (in 2016 and 2020), acrolein, 1,3-butadiene (in 2016 and 2020), and 

formaldehyde compared to the No Action Alternative. 

Emissions changes (compared to the No Action Alternative) under the Alternative 9 cumulative 

analysis would be the same as or greater than the corresponding emissions changes under the Alternative 

9 noncumulative analysis for acetalehyde, benzene (in 2016 and 2020), 1,3-butadiene, and formaldehyde. 

Emissions changes (compared to the No Action Alternative) under the Alternative 9 cumulative analysis 

would be less than the corresponding emissions changes under the Alternative 9 noncumulative analysis 

for acrolein (in 2020 and 2030), benzene (except in 2016 and 2020), and DPM (except in 2016). 

Nationwide, emissions of toxic air pollutants can decrease because the reduction in upstream 

emissions more than offsets the increase in VMT and emissions due to the rebound effect. However, the 

reductions in upstream emissions are not uniformly distributed to individual nonattainment areas. Under 

Alternative 9, most nonattainment areas would experience net increases in emissions of one or more toxic 

air pollutant in at least one of the analysis years (see Appendix C). However, the emissions increases 

would be quite small, as shown in Appendix C, and emissions increases would be distributed throughout 

each nonattainment area. 

4.3.3.10.3 Health Outcomes and Monetized Benefits 

Compared to Alternative 1 (No Action), the cumulative impact of Alternative 9 would result in 

465 fewer mortalities and 51,231 fewer work-loss days in 2050. Mortality benefits are measured 

according to Pope et al. (2002); reductions would be 156 percent greater using the Laden et al. (2006) 

methodology. 

Table 4.3.3-9 lists the corresponding monetized health benefits under Alternative 9 compared to 

the No Action Alternative. In 2050, health-related benefits under Alternative 9 would be $4.2 billion 

annually, using a 3-percent discount rate and estimates from Pope et al. (2002). With the Laden et al. 

(2006) method, health-related benefits would be 145 percent greater. Using a 7-percent discount rate, 

health-related benefits would be 9.3 to 9.7 percent less. 
Chapter 4 Cumulative Impact 4.4 Climate 

4.4 CLIMATE 

As noted earlier, a cumulative impact is defined as “the impact on the environment which results 

from the incremental impact of the action when added to other past, present, and reasonably foreseeable 

future actions regardless of what agency or person undertakes such other actions. Cumulative impacts 

can result from individually minor but collectively significant actions taking place over a period of time.” 

40 CFR § 1508.70. 

This section on the cumulative impacts of the proposed action and alternatives on climate covers 

many of the same topics as Section 3.4. However, the analysis in Chapter 4 is broader than the analysis in 

Chapter 3 because it addresses (1) the effects of the MYs 2012-2016 standards together with those of

reasonably foreseeable future actions, including the continuing increases in CAFE standards for MYs 

2017-2020 that are necessary under some alternatives to reach the EISA-mandated target of a combined 

mpg of 35 mpg (see Section 4.1.3), and (2) continuing market-driven annual average percentage gains in 

mpg from 2016 through 2030 consistent with the AEO projections as a reasonably foreseeable future 

action. These reasonably foreseeable future actions would affect fuel consumption and emissions 

attributable to passenger cars and light trucks through 2060. Because these mpg projections apply to new 

vehicles, this assumption results in emissions reductions and fuel savings that continue to grow as new 

vehicles are added to the fleet in each subsequent year, and as VMT continue to grow. This is the case 

under the No Action Alternative and each of the action alternatives. Like Chapter 3, Chapter 4 addresses 

the consequences of emissions and effects on the climate system. However, Chapter 4 goes beyond this 

to discuss the impacts of changes in the climate system on key resources (e.g., freshwater resources, 

terrestrial ecosystems, and coastal ecosystems). 

Understanding that many readers do not read through an EIS in linear fashion, but instead focus 

on the sections of most interest, this section repeats some of the information in Section 3.4 with 

modifications to reflect the slightly different scope (cumulative impacts versus the direct and indirect 

effects of the proposed action and alternatives). However, this section also refers the reader to Section 3.4 

in many cases, to minimize replication of background information on climate science or modeling 

methodologies. 

4.4.1 Introduction – Greenhouse Gases and Climate Change 

Section 3.4.1 provides a discussion of the science of climate change, uncertainty within the IPCC 

framework, and NHTSA’s reliance on panel- and peer-reviewed literature for this EIS. 

4.4.2 Affected Environment 

The affected environment can be characterized in terms of GHG emissions and climate. Section 

3.4.2 provides a discussion of both topics, including a description of conditions in the United States as 

well as globally. Because there is no distinction between the affected environment for purposes of the 

analysis of direct and indirect effects and the analysis of cumulative impacts, NHTSA refers readers to 

Section 3.4.2 for a discussion of this topic. 

4.4.3 Methodology 

The methodology NHTSA used to characterize the effects of the proposed action and alternatives 

on climate has two key elements: (1) analyzing the effects of the proposed action and alternatives on 

GHG emissions and (2) analyzing how GHG emissions affect the climate system (climate effects). 

 4-39 
4.4 Climate Chapter 4 Cumulative Impacts 

This cumulative impacts analysis of each alternative includes the effects of the proposed CAFE 

standards for MYs 2012-2016 and other reasonably foreseeable actions, including ongoing gains in mpg 

through 2030 consistent with AEO projections (see Section 4.1.3). This EIS expresses results for each 

alternative in terms of the environmental attribute being characterized (emissions, CO2 concentrations, 

temperature, precipitation, and sea level). Comparisons between the No Action Alternative (Alternative 

1) and each action alternative (Alternatives 2 through 9) illustrate the differences in environmental effects 

among the alternative CAFE standards. The impact of each action alternative on these results is measured 

by the difference in its value under the No Action Alternative and its value under that action alternative. 

For example, the reduction in CO2 emissions attributable to an action alternative is measured by the 

difference in emissions under that alternative and emissions under the No Action Alternative. 

The methods NHTSA used to characterize emissions and climate-change impacts involve 

considerable uncertainty. See Section 3.4.3 for a discussion of uncertainty in emissions scenarios, the 

global climate system, and climate models. 

4.4.3.1 Methodology for Modeling Greenhouse Gas Emissions 

GHG emissions were estimated using the Volpe model, which is described in Section 3.1.4. The 

methodology for modeling GHG emissions is described in Section 3.4.3.1. This analysis of cumulative 

impacts uses the Volpe model to estimate GHG emissions, but includes reasonably foreseeable actions 

beyond this proposed action. See Sections 4.1.4 and 4.4.3.3 for a detailed description of these additional 

actions. 

4.4.3.2 Methodology for Estimating Climate Effects 

This EIS estimates and reports four direct and indirect effects of climate change driven by 

alternative scenarios of GHG emissions – changes in CO2 concentrations, changes in global temperature, 

changes in regional temperature and precipitation, and changes in sea level. 

The change in CO2 concentration is a direct effect of the changes in GHG emissions, and 

influences each of the other factors. 

This EIS uses a climate model to estimate the changes in CO2 concentrations, global mean 

surface temperature, and changes in sea level for each alternative CAFE standard, and uses increases in 

global mean surface temperature combined with an approach and coefficients from the IPCC Fourth 

Assessment Report (IPCC 2007) to estimate changes in global precipitation. NHTSA used the publicly 

available modeling software MAGICC version 5.3.v2 (Wigley 2008) to estimate changes in key direct 

and indirect effects. MAGICC 5.3.v2 uses the estimated reductions in emissions of CO2, CH4, N2O, CO, 

NOx, SO2, and VOCs produced by the Volpe model. Sensitivity analyses examined the relationship 

among various CAFE alternatives, likely climate sensitivities, and scenarios of global emissions paths and 

the associated direct and indirect effects for each combination. These relationships can be used to infer 

the effect of the emissions associated with the regulatory alternatives on direct and indirect climate 

effects. 

Sections 4.4.3.2.1, 4.4.3.2.2, and 4.4.3.2.3 describe MAGICC, the Reference Case modeling runs, 

the sensitivity analysis, and the emissions scenarios NHTSA used in the analysis. 

4.4.3.2.1 MAGICC Version 5.3.v2 

The selection of MAGICC for this analysis was driven by a number of factors, as described in Section 

3.4.3.2.1. 

 4-40 
Chapter 4 Cumulative Impact 4.4 Climate 

 4-41 

NHTSA assumed that global emissions consistent under the No Action Alternative (Alternative 

1) would follow the trajectory provided by the CCSP SAP 2.1 MiniCAM Level 3 scenario. This scenario 

represents a Reference Case where future global emissions assume significant global actions to address 

climate change. Section 4.4.3.2.2 describes the CCSP SAP 2.1 scenarios. 

4.4.3.2.2 Reference Case Modeling Runs 

The approach for the Reference Case modeling runs was based on the approach described in 

Section 3.4.3.2.2. For this analysis, NHSTA assumed that global emissions under the No Action 

Alternative (Alternative 1) follow the trajectories provided by the CCSP SAP 2.1 MiniCAM Level 3 

scenario, rather than the RCP 4.5 MiniCAM reference scenario used in Section 3.4. 

Section 4.4.4 presents the results of the Reference Case modeling runs. 

4.4.3.2.3 Sensitivity Analysis 

The approach for the sensitivity analysis was based on the same approach described in Section 

3.4.3.2.3. In the Chapter 4 analysis, NHTSA assumed multiple global emissions scenarios that include 

the SAP 2.1 MiniCAM Level 3 (650 ppm as of 2100); the SAP 2.1 MiniCAM Level 2 (550 ppm as of 

2100); and RCP 4.5 MiniCAM reference scenario (783 ppm as of 2100). The Section 3.4 analysis did not 

assess the sensitivity around different global emissions scenarios. These global emissions scenarios 

represent various levels of implementation of global GHG emissions reduction policies. 

Section 4.4.4.2.5 presents the results of the sensitivity analysis. 

4.4.3.3 Global Emissions Scenarios 

As described above, MAGICC uses long-term emissions scenarios representing different 

assumptions about key drivers of GHG emissions. All scenarios used are based on the CCSP effort to 

develop a set of long-term (2000 to 2100) emissions scenarios that incorporate an update of economic and 

technology data and utilize improved scenario development tools compared with the IPCC Special Report 

on Emissions Scenarios (SRES) (IPCC 2000) developed more than a decade ago. See Section 3.4.3.3 for 

background on the development of the CCSP scenarios. 

The results in this chapter rely primarily on the CCSP SAP 2.1 MiniCAM Level 3 scenario to 

represent a Reference Case global emissions scenario; that is, future global emissions assuming 

significant global actions to address climate change. This Reference Case global emissions scenario 

serves as a baseline against which the climate benefits of the various CAFE alternatives can be 

measured.3

 NHTSA chose the SAP 2.1 MiniCAM Level 3 scenario to represent reasonably foreseeable 

actions based on the following factors: 

• The SAP 2.1 MiniCAM Level 3 scenario was developed by the MiniCAM Model of the Joint 

Global Change Research Institute (which is a partnership between the Pacific Northwest 

National Laboratory and the University of Maryland) and is one of three Level 3 climate 

 

3

 Note that the Reference Case global emissions scenario used in Chapter 4 differs from the global emissions 

scenario used for the climate change modeling presented in Chapter 3. In Chapter 4, the Reference Case global 

emission scenario reflects reasonably foreseeable actions in global climate change policy; in Chapter 3, the global 

emissions scenario used for the analysis assumes that there are no significant global controls or large efforts to 

mitigate the projected continued growth of global GHG emissions. Given that the climate system is non-linear, the 

choice of a global emissions scenario could produce different estimates of the benefits of the proposed action and 

alternatives, if the emissions reductions under the alternatives were held constant. 
4.4 Climate Chapter 4 Cumulative Impacts 

 4-42 

scenarios described in the SAP 2.1. MiniCAM Level 3 is based on a set of assumptions about 

drivers such as population, technology, and socioeconomic changes, and global climate 

policies that correspond to total radiative forcing stabilization by 2100 and associated CO2

concentrations at roughly 650 parts per million by volume (ppmv), after accounting for the 

contributions to radiative forcing from the non-CO2 GHGs. It therefore represents an 

illustration of a plausible future pathway of global emissions in response to significant global 

action to mitigate climate change. 

• CCSP SAP 2.1 is more than a decade newer than the IPCC SRES, and therefore has updated 

economic and technology data/assumptions. It also uses improved integrated assessment 

models that account for advances in economics and science over the past 10 years. 

The SAP 2.1 MiniCAM Level 3 scenario assumes a moderate level of global GHG reductions, 

resulting in a global atmospheric CO2 concentration of roughly 650 ppmv by 2100. The regional, 

national, and international initiatives and programs discussed below are those NHTSA has tentatively 

concluded are reasonably foreseeable past, current, or future actions to reduce GHG emissions. Although 

many of these actions, policies, or programs are not associated with precise GHG reduction commitments, 

collectively they illustrate an existing and continuing trend of U.S. and global awareness, emphasis, and 

efforts toward significant GHG reductions. Together they imply that future commitments for reductions 

are probable and, therefore, reasonably foreseeable under NEPA. 

Reasonably Foreseeable Actions Included in the Cumulative Impacts Analysis 

United States: Regional Actions4

• Regional Greenhouse Gas Initiative (RGGI). Beginning January 1, 2009, RGGI is the first 

mandatory, market-based effort in the United States to reduce GHG emissions (RGGI 2009a). 

Ten Northeastern and Mid-Atlantic states (Connecticut, Delaware, Maine, Maryland, 

Massachusetts, New Hampshire, New Jersey, New York, Rhode Island, and Vermont) have 

capped annual emissions from power plants in the region at 188 million tons of CO2 (RGGI 

2009b). Beginning in 2015, this cap will be reduced 2.5 percent each year through 2019, for 

a total of a 10-percent emissions reduction from the 2015 cap from the power sector by 2018 

(RGGI 2009c). Thus, the cap is comprised of two phases: the first is a stabilization phase 

from 2009 to 2014, and the second is a reduction phase from 2015 through 2018. 

• Western Climate Initiative (WCI) – The WCI includes seven states (Arizona, California, 

Montana, New Mexico, Oregon, Utah, and Washington) and four Canadian provinces (British 

Columbia, Manitoba, Ontario, and Quebec). Set to begin on January 1, 2012, the WCI capand-trade program will cover emissions of the six main greenhouse gases (CO2, CH4, N2O, 

HFC’s, PFC’s, and SF6) from the following sectors of the economy: electricity generation, 

including imported electricity; industrial and commercial fossil fuel combustion; industrial 

process emissions; gas and diesel consumption for transportation; and residential fuel use. 

Covered entities and facilities will be required to surrender enough allowances to cover 

emissions that occur within each 3-year “compliance period.” This multi-sector program is 

the most comprehensive carbon-reduction strategy designed to date in the United States. This 

program is an important component of the WCI comprehensive regional effort to reduce 

GHG emissions to 15 percent below 2005 levels by 2020. The program will be rolled out in 

two phases. The first phase will begin on January 1, 2012, and will cover emissions from 

electricity, including imported electricity, industrial combustion at large sources, and 

industrial process emissions for which adequate measurement methods exist. The second 

 

4

 Two of the three regional actions include Canadian provinces as participants and observers. 
Chapter 4 Cumulative Impact 4.4 Climate 

phase begins in 2015, when the program expands to include transportation fuels and 

residential, commercial, and industrial fuels not otherwise covered (WCI 2009). When fully 

implemented in 2015, the program will cover nearly 90 percent of greenhouse gas emissions 

in the 11 WCI Partner states and provinces. 

• Midwestern Greenhouse Gas Reduction Accord – The Accord includes six states (Illinois, 

Iowa, Kansas, Michigan, Minnesota, and Wisconsin) and one Canadian province (Manitoba). 

Signed on November 15, 2007, the Midwestern Greenhouse Gas Reduction Accord serves as 

a regional strategy to achieve energy security and reduce GHG emissions (Midwestern 

Governors Association 2009). The Accord will establish GHG-reduction targets and time 

frames consistent with member states’ targets; develop a market-based and multi-sector capand-trade mechanism to help achieve those reduction targets; establish a system to enable 

tracking, management, and crediting for entities that reduce GHG emissions; and develop and 

implement additional steps as needed to achieve the reduction targets, such as low-carbon 

fuel standards and regional incentives and funding mechanisms (Midwestern Greenhouse Gas 

Reduction Accord 2009). 

United States: Federal Actions 

• EPA Proposed GHG Emissions Standards. In a joint NHTSA and EPA notice of proposed 

rulemaking published concurrently with this Draft EIS, EPA will propose a national CO2

vehicle emissions standard under Section 202(a) of the Clean Air Act, which will be 

coordinated and harmonized with NHTSA proposed CAFE standards. These standards 

would apply to passenger cars, light-duty trucks, and medium-duty passenger vehicles (lightduty vehicles) built in MYs 2012-2016. These vehicle categories are responsible for almost 

60 percent of all U.S. transportation-related GHG emissions. EPA is considering proposing 

standards that would, if made final, achieve an average of 250 grams per mile of CO2 in MY 

2016. The standards would begin with the 2012 model year and the program is intended to 

reduce GHG emissions from the U.S. light-duty vehicle fleet by 19 percent by 2030 (EPA 

2009d).

• Cap-and-Trade Bills in the 111th Congress. H.R. 2454, the American Clean Energy and 

Security Act of 2009 (“Waxman-Markey Bill”), passed in the House June 26, 2009. The bill 

amends the Clean Air Act to require the EPA Administrator to promulgate regulations to cap 

and reduce GHG emissions, annually, to yield GHG emission reductions from capped sources 

of 17 percent (below 2005 levels) by 2020, 42 percent by 2030, and 83 percent by 2050; and 

establish a federal GHG registry, among other amendments. In the U.S. Senate, S. 1733, 

Clean Energy Jobs and American Power Act, (“Kerry-Boxer Bill”), proposes to cut U.S. 

GHG emissions by 20 percent by 2020, and 83 percent by 2050, when compared to the 2005 

baseline. Included in its key elements are: a coordinated approach to geological sequestration 

of carbon dioxide, new performance standards for coal-fired plants, programs to research 

furthering of nuclear power use, water-use efficiency programs, and new energy efficiency 

standards for buildings. The Kerry-Boxer bill passed out of the Senate Environment and 

Public Works Committee on November 5, 2009. 

• Renewable Fuel Standard (RFS2). Section 211(o) of the Clean Air Act requires that a 

renewable fuel standard be determined annually that is applicable to refiners, importers, and 

certain blenders of gasoline (73 FR 70643). On the basis of this standard, each obligated 

party determines the volume of renewable fuel that it must ensure is consumed as motor 

vehicle fuel. RFS2 will increase the volume of renewable fuel required to be blended into 

gasoline from 9 billion gallons in 2008 to 36 billion gallons by 2022 (EPA 2009b), and the 

renewable fuel standard for 2009 is 10.21 percent (73 FR 70643). EPA estimates that the 

 4-43 
4.4 Climate Chapter 4 Cumulative Impacts 

 4-44 

greater volumes of biofuel mandated by RFS2 will reduce life-cycle GHG emissions by an 

annual average of 150 million tons CO2 equivalent (EPA 2009c). 

• United States GHG Emissions Target in Association with the Copenhagen Accord. 

Building on the pledge made at the December 2009 U.N. climate change conference in 

Copenhagen (COP-15), President Obama recently submitted to the United Nations 

Framework Convention on Climate Change (UNFCCC) a GHG target for the United States in 

the range of 17 percent below 2005 levels by 2020, in association with the Copenhagen 

Accord. This target is in conformity with anticipated U.S. energy and climate legislation, and 

recognizes that the final target will be reported to the Secretariat in light of enacted 

legislation. Initial activities toward this goal include an $80 billion investment in clean energy 

through the American Recovery and Reinvestment Act of 2009, more stringent energy 

efficiency standards for commercial and residential appliances, and development of wind 

energy on the Outer Continental Shelf, among other federal initiatives. On January 28, 2010, 

the U.S. submitted this target to the U.N. Framework Convention on Climate Change as part 

of a January 31 deadline negotiated in Copenhagen in December 2009, “in conformity with 

anticipated U.S. energy and climate legislation, recognizing that the final target will be 

reported to the [U.N.] in light of enacted legislation” (U.S. Department of State 2010). 

International Actions 

• United Nation’s Framework Convention on Climate Change (UNFCCC) – The Kyoto 

Protocol, and the December 2009 Conference of the Parties (COP)-15. UNFCCC is an 

international treaty signed by many countries around the world (including the United States5

), 

which entered into force on March 21, 1994, and sets an overall framework for 

intergovernmental efforts to tackle the challenge posed by climate change (UNFCCC 2002). 

The Kyoto Protocol is an international agreement linked to the United Nations Framework 

Convention on Climate Change. The major feature of the Kyoto Protocol is that it sets 

binding targets for 37 industrialized countries and the European community for reducing 

GHG emissions, which covers more than half of the world’s GHG emissions. These amount 

to an average of 5 percent of 1990 levels over the 5-year period 2008 through 2012 

(UNFCCC 2005). At COP-15, and for the first time ever, all major developed and 

developing countries agreed to pledge specific emission reductions. However, the pledges 

will not be legally binding, and much remains to be negotiated. 

• The European Union Greenhouse Gas Emission Trading System (EU ETS) - In January 

2005 the EU ETS commenced operation as the largest multi-country, multi-sector 

Greenhouse Gas Emission Trading System world-wide (European Union 2009). The aim of 

the EU ETS is to help European Union Member States achieve compliance with their 

commitments under the Kyoto Protocol (European Union 2005). This trading system does 

not entail new environmental targets; instead, it allows for less expensive compliance with 

existing targets under the Kyoto Protocol. 

The scheme is based on Directive 2003/87/EC, which entered into force on October 25, 2003 

 

5

 Although a signatory to the Kyoto Protocol, the United States has neither ratified nor withdrawn from the Protocol. 

Treaties are nonbinding on the United States unless ratified by the Senate by a two-thirds majority, and neither the 

Clinton Administration nor the Bush Administration submitted the Kyoto Protocol to the Senate for ratification. On 

July 25, 1997, before the Kyoto Protocol was finalized, the Senate passed (by a 95-0 vote) the Byrd-Hagel 

Resolution, which stated the Senate position that the United States should not be a signatory to any treaty that did 

not include binding targets and timetables for developing nations as well as industrialized nations or “would result in 

serious harm to the economy of the United States.” See S. Res. 98, 105th Cong. (1997). 
Chapter 4 Cumulative Impact 4.4 Climate 

(European Union 2009), and covers over 11,500 energy-intensive installations across the 

European Union, which represent almost half of Europe’s emissions of CO2. These 

installations include combustion plants, oil refineries, coke ovens, iron and steel plants, and 

factories making cement, glass, lime, brick, ceramics, pulp and paper (European Union 

2005). 

• G8 Declaration – Summit 2009. During the July 2009 G8 Summit in Italy, the group 

officially recognized the importance of the outcome of COP-15, issuing the following 

statement regarding GHG emissions reductions: “We recognize the broad scientific view that 

the increase in global average temperature above pre-industrial levels ought not to exceed 

2 °C. Because this global challenge can only be met by a global response, we reiterate our 

willingness to share with all countries the goal of achieving at least a 50 percent reduction of 

global emissions by 2050, [recognizing] that this implies that global emissions need to peak 

as soon as possible and decline thereafter. As part of this, we also support a goal of 

developed countries reducing emissions of greenhouse gases in aggregate by 80 percent or 

more by 2050 compared to 1990 or more recent years” (G8 Summit 2009, page 19). 

• Asia Pacific Partnership on Clean Development and Climate. The Asia-Pacific 

Partnership on Clean Development and Climate is an effort to accelerate the development and 

deployment of clean energy technologies. The Asia-Pacific Partnership partners (Australia, 

Canada, China, India, Japan, Korea, and the United States) have agreed to work together and 

with private-sector partners to meet goals for energy security, national air pollution reduction, 

and climate change in ways that promote sustainable economic growth and poverty reduction. 

These seven partner countries collectively account for more than half of the world's economy, 

population, and energy use, and they produce about 65 percent of the world's coal, 62 percent 

of the world's cement, 52 percent of world's aluminum, and more than 60 percent of the 

world's steel (APP 2009a). The Partnership aims to be consistent with and contribute to the 

members’ efforts under the UNFCCC and will complement, but not replace, the Kyoto 

Protocol (APP 2009b). 

The SAP 2.1 MiniCAM Level 3 scenario provides a global context for emissions of a full suite of 

GHGs and ozone precursors for a Reference Case harmonious with implementation of the above policies 

and initiatives. There are some inconsistencies between the overall assumptions used by CCSP in SAP 

2.1 (Clarke et al. 2007) to develop global emissions scenarios and the assumptions used in the Volpe 

model in terms of economic growth, energy prices, energy supply, and energy demand. However, these 

inconsistencies affect the characterization of each CAFE alternative in equal proportion, so the relative 

estimates provide a reasonable approximation of the differences in environmental impacts among the 

alternatives. 

NHTSA used the MiniCAM Level 3 scenario as the primary global emissions scenario for 

evaluating climate effects in the Chapter 4 analysis, but used the MiniCAM Level 2 scenario and the RCP 

4.5 MiniCAM reference emissions scenario to evaluate the sensitivity of the results to alternative 

emissions scenarios. The RCP 4.5 MiniCAM reference emissions scenario assumes that no climate 

policy would be implemented beyond the current set of policies in place, whereasthe SAP 2.1 MiniCAM 

Level 2 and 3 scenarios correspond to total radiative forcing stabilization by 2100 and associated CO2

concentrations at roughly 550 ppmv and 650 ppmv, respectively, after accounting for the contributions to 

radiative forcing from the non-CO2 GHGs. 

Separately, each of the other alternatives was simulated by calculating the difference between 

annual GHG emissions under that alternative and emissions under the No Action Alternative (Alternative 

1), and subtracting this change in the MiniCAM Level 3 scenario to generate modified global-scale 

emissions scenarios, which show the effect of the various CAFE alternatives on the global emissions path. 

 4-45 
4.4 Climate Chapter 4 Cumulative Impacts 

 4-46 

For example, emissions from U.S. passenger cars and light trucks in 2020 under the No Action 

Alternative are 1,800 million metric tons of CO2 (MMTCO2); emissions in 2020 under the Preferred 

Alternative (Alternative 4) are 1,680 MMTCO2 (see Table 4.4.4-2). The difference of 120 MMTCO2 

represents the reduction in emissions projected to result from adopting the Preferred Alternative. Global 

emissions for the MiniCAM Level 3 scenario in 2020 are 34,060 MMTCO2, which are assumed to 

incorporate the level of emissions from U.S. passenger cars and light trucks under the No Action 

Alternative. Global emissions under the Preferred Alternative are thus estimated to be 120 MMTCO2 less 

than this reference level, or 33,940 MMTCO2 in 2020. 

Many of the economic assumptions used in the Volpe model (such as fuel price, VMT, U.S. gross 

domestic product [GDP]) are based on the EIA Annual Energy Outlook (AEO) 2010 Early Release (EIA 

2009a) and International Energy Outlook (IEO) 2009 (EIA 2009b), which forecast energy supply and 

demand in the United States and globally to 2030. Figures 4.4.3-1 through 4.4.3-5 show how the EIA 

forecasts of global and U.S. GDP, CO2 emissions from energy use, and primary energy use compare 

against the assumptions used to develop the SAP 2.1 MiniCAM scenarios.6,7

 The IEO forecast is for a 

reference case, while the SAP 2.1 forecasts are for a reference case and two climate policy cases. 

The GDP growth assumptions for the IEO reference scenario are slightly higher than those in the 

SAP scenarios, by about 0.6 percent annually for the world and 0.9 percent annually for the United States 

(see Figure 4.4.3-1). 

Despite this IEO assumption of higher economic growth, the growth in primary energy use is 

similar between the IEO and MiniCAM, with the primary energy use in MiniCAM slightly lower than 

that of the IEO, as shown in Figure 4.4.3-4. The global primary liquids energy use in SAP 2.1 and the 

IEO 2009 (EIA 2009b) compare well. Much of the difference in energy use in the IEO forecast is due to 

assumptions of higher coal use that result in higher CO2 emissions, as shown in Figure 4.4.3-2. 

Additionally, the IEO reference scenario estimates have a particularly low share of “other” fuels, which 

includes biomass and renewable fuels, and is likely due to different treatments of non-commercial fuels in 

the two sets of forecasts. 

The primary energy use projections for the United States show a different trend than the global 

numbers. The AEO 2010 Early Release (EIA 2009a)8

 projection shows an increase in total primary 

energy use in the United States, but much of the increase is from the use of coal and liquid fuels. On the 

other hand, the SAP MiniCAM scenarios have a higher share of natural gas (Figure 4.4.3-5). However, 

the AEO reference scenario has a larger share of other fuels9

 than the SAP MiniCAM scenarios, resulting 

in lower CO2 emissions (Figure 4.4.3-3). 

The approaches focus on the marginal climate effects of marginal changes in emissions. Thus, 

they generate a reasonable characterization of climate changes for a given set of emissions reductions, 

regardless of the underlying details associated with those emissions reductions. The discussion in Section 

4.4.4 characterizes projected climate change under the No Action Alternative and the changes associated 

with each action alternative.

 

6

 The MiniCAM reference scenario from SAP 2.1 uses the same assumptions for GDP, energy use, and CO2

emissions as the RCP MiniCAM reference scenario. 

7

 The IEO 2009 (EIA 2009b) uses energy supply and consumption from the AEO 2009 for the United States and the 

same forecast for world oil prices. The IEO nuclear primary energy forecast numbers were adjusted to account for 

differences in reporting primary energy use for nuclear energy. All IEO energy-use estimates were converted to 

exajoules. 

8

 AEO 2010 Early Release (EIA 2009a) estimates were used for U.S. primary energy consumption. 9

 For the AEO reference scenario, “other” includes biomass, hydropower, and other renewable fuels. 
Chapter 4 Cumulative Impact 4.4 Climate 

Figure 4.4.3-1. Average GDP Growth Rates (1990 to 2030) a/ 

a/ GDP growth rates were not available for the United States under MiniCAM Level 3 and MiniCAM Level 2 

scenario 

Figure 4.4.3-2. Global Annual CO2 Emissions from Fossil Fuel Use 

0

5

10

15

20

25

30

35

40

45

2010 2020 2030

Billion tonnes of CO2

IEO

MINICAM_REF

MINICAM_L3

MINICAM_L2

 4-47 
4.4 Climate Chapter 4 Cumulative Impacts 

Figure 4.4.3-3. U.S. Annual CO2 Emissions from Fossil Fuel Use 

0

1

2

3

4

5

6

7

2010 2020 2030

Billion tonnes of CO2

IEO

MINICAM_REF

MINICAM_L3

MINICAM_L2

Figure 4.4.3-4. World Primary Energy Use Forecast 

0

100

200

300

400

500

600

700

800

IEO

MINICAM_REF

MINICAM_L3

MINICAM_L2

IEO

MINICAM_REF

MINICAM_L3

MINICAM_L2

IEO

MINICAM_REF

MINICAM_L3

MINICAM_L2

2010                                                                  2020                                                               2030

Exajoules (EJ)

Other

Nuclear

Natural Gas

Coal

Liquids

 4-48 
Chapter 4 Cumulative Impact 4.4 Climate 

Figure 4.4.3-5. U.S. Primary Energy Use Forecast 

0

20

40

60

80

100

120

140

AEO (year 2008 value)

MINICAM_REF

MINICAM_L3

MINICAM_L2

AEO

MINICAM_REF

MINICAM_L3

MINICAM_L2

AEO

MINICAM_REF

MINICAM_L3

MINICAM_L2

2010                                                                    2020                                                                     2030

Exajoules (EJ)

Other

Nuclear

Natural Gas

Coal

Liquids

The climate sensitivity analysis (see Section 4.4.3.2.3) also uses the MiniCAM Level 2 emissions 

scenario (Clarke et al. 2007) and the RCP 4.5 MiniCAM reference emissions scenario as possible global 

emissions scenarios. This provides a basis for determining climate responses to varying levels of global 

emissions and climate sensitivities under the No Action Alternative (Alternative 1) and the Preferred 

Alternative (Alternative 4). Some responses of the climate system are believed to be non-linear; by using 

a range of emissions cases and climate sensitivities, it is possible to estimate the effects of the alternatives 

in relation to different scenarios and sensitivities. 

Where information in the analysis included in this EIS is incomplete or unavailable, NHTSA has 

relied on CEQ regulations regarding incomplete or unavailable information (see 40 CFR § 1502.22(b)). 

For this analysis, despite the inconsistencies between the MiniCAM assumptions on global trends across 

all GHG-emitting sectors (and the drivers that affect them) and the particularities of the emissions 

estimates for the U.S. transportation sector provided by the Volpe model, the approach used is valid; these 

inconsistencies affect all alternatives equally, and thus do not hinder a comparison of the alternatives in 

terms of their relative effects on climate. 

4.4.3.3.1 Tipping Points and Abrupt Climate Change 

Tipping points and abrupt climate change are discussed in Section 3.4.3.3.1 and the same 

conclusions apply to this cumulative impact analysis. A qualitative survey of the current state of climate 

science on tipping points and abrupt climate change is presented in Section 4.5.9. 

4.4.4 Environmental Consequences 

This section describes the consequences of the proposed action and alternatives, and other 

reasonably foreseeable future actions, in relation to GHG emissions and the consequences of global 

climate change. 

4.4.4.1 Greenhouse Gas Emissions 

To estimate the emissions resulting from changes in passenger car and light truck CAFE 

standards, NHTSA uses the Volpe model (see Sections 2.2.1 through 2.2.4 and Section 3.1.4 for 

 4-49 
4.4 Climate Chapter 4 Cumulative Impacts 

 4-50 

descriptions of the model). The change in fuel use projected to result from each alternative CAFE 

standard determines the resulting impacts on total energy and petroleum energy use, which in turn affects 

the amount of CO2 emissions. These CO2 emissions estimates also include upstream emissions, which 

occur from the use of carbon-based energy during crude oil extraction, transportation, and refining, and in 

the transportation, storage, and distribution of refined fuel. Because CO2 accounts for such a large 

fraction of total GHG emitted during fuel production and use – more than 95 percent, even after 

accounting for the higher global warming potentials (GWPs) of other GHGs – NHTSA’s consideration of 

GHG impacts focuses on reductions in CO2 emissions resulting from the savings in fuel use that 

accompany higher fuel economy.10

NHTSA considers the following measures of the cumulative impact of alternative CAFE 

standards for MYs 2012-2016 and other reasonably foreseeable actions affecting CO2 emissions: 

• CO2 emissions from MYs 2012-2016 passenger cars and light trucks, which are directly 

affected by the new CAFE standards; 

• CO2 emissions from MYs 2017-2030 passenger cars and light trucks, assuming annual 

average percentage gains in mpg consistent with the AEO 2010 Early Release Reference 

Case projections (EIA 2009a), with all action alternatives exceeding the combined EISA 

target of 35 mpg in 2020 (see Section 4.1.3); 

• CO2 emissions from MYs 2031-2060 passenger cars and light trucks, for which the overall 

fuel economy of the fleet continues to improve as new vehicles enter the fleet with an average 

fuel economy equivalent to MY 2030 vehicles,11 and older vehicles leave the fleet; and 

• CO2 emissions from MYs 2061-2100 passenger cars and light trucks, for which emissions are 

held constant.12 

Cumulative emissions reductions from each action alternative increase across alternatives, with 

Alternative 2 having the lowest cumulative emissions reductions and Alternative 9 having the highest 

cumulative emissions reductions. Emissions reductions represent the differences in total annual 

emissions by all passenger cars or light trucksin use between their estimated future levels under the No 

Action Alternative (baseline), and with each alternative CAFE standard in effect. 

Emissions reductions resulting from applying the reasonably foreseeable future actions to the 

proposed CAFE standards for MYs 2012-2016 passenger cars and light trucks and the eight action 

alternatives were estimated from 2012 to 2060. Emissions were estimated for all alternatives through 

2060, and these emissions were compared against the No Action Alternative (which assumes post-MY 

2011 fuel economy levels grow at the rates projected by the AEO fuel economy forecasts) to estimate 

emissions reductions. Annual emissions reductions from 2061 to 2100 were held constant at 2060 levels. 

Emissions under each action alternative were then compared against those under the No Action 

Alternative to determine its impact on emissions. 

Table 4.4.4-1 shows total GHG emissions and emissions reductions from new passenger cars and 

light trucks from 2012-2100 under each of the nine alternatives. Projections of emissions reductions over 

 

10 Although this section includes only a discussion of CO2 emissions, the climate modeling discussion in Section 

4.4.4.4 assesses the direct and indirect effects associated with emissions reductions of multiple gases, including CO2, 

CH4, N2O, SO2, CO, NOx, and VOCs. 11 As explained in Section 4.1.3, because AEO fuel economy projections end at 2030, this analysis assumes that all 

post-2030 vehicles continue to achieve the average fuel economy levels projected for new vehicles in 2030. 12 The year 2060 is the last year the Volpe model provides estimates of fleet fuel efficiency, fuel use, VMT, and the 

other factors required to calculate GHG emissions. Because this information is not available post 2060, emissions 

are held constant after that year. 
Chapter 4 Cumulative Impact 4.4 Climate 

 4-51 

the 2012 to 2100 period due to the MYs 2012-2016 CAFE standards and other reasonably foreseeable 

future actions ranged from 30,200 to 45,600 MMTCO2. Compared to cumulative global emissions of 

3,919,462 MMTCO2 over this period (projected by the SAP 2.1 MiniCAM Level 3 scenario), the 

incremental impact of this rulemaking is expected to reduce global CO2 emissions by about 0.8 to 1.2 

percent from their projected levels under the No Action Alternative. 

Table 4.4.4-1 

Cumulative Effects of Emissions and Emissions Reductions (MMTCO2) 

from 2012 to 2100 by Alternative a/ 

Alternative Emissions 

Emissions Reductions 

Compared to No 

Action Alternative 

1 No Action 259,800 0 

2 3%/year Increase 229,600 30,200 

3 4%/year Increase 229,300 30,400 

4 ~4.3%/year Increase, Preferred 228,400 31,400 

5 5%/year Increase 224,700 35,100 

6 ~6.0%/year Increase, MNB 218,400 41,400 

7 6%/year Increase 218,300 41,500 

8 7%/year Increase 214,200 45,600 

9 ~6.6%/year Increase, TCTB 215,200 44,600 

__________

a/ Note: The numbers in this table have been rounded for presentation purposes. As a result, the 

 reductions might not reflect the exact difference of the values in all cases. 

To get a sense of the relative impact of these reductions, it can be helpful to consider the relative 

importance of emissions from passenger cars and light trucks as a whole and to compare them against 

emissions projections from the United States, and expected or stated goals from existing programs 

designed to reduce CO2 emissions. As mentioned earlier, U.S. passenger cars and light trucks currently 

account for approximately 19.1 percent of CO2 emissions in the United States. With the action 

alternatives reducing U.S. passenger car and light truck CO2 emissions by 11.6. to 17.6 percent over 

2012-2100, the CAFE alternatives will have a noticeable impact on total U.S. CO2 emissions. Compared 

to total U.S. CO2 emissions in 2100 projected by the MiniCAM reference scenario of 7,886 MMTCO2 

(Clarke et al. 2007), the action alternatives would reduce total U.S. CO2 emissions by 5.7 to 8.5 percent in 

2100. Figure 4.4.4-1 shows projected annual emissions from passenger cars and light trucks under MYs 

2012-2016 standards and other reasonably foreseeable future actions. 

As Table 4.4.4-2 shows, total CO2 emissions accounted for by the U.S. passenger car and light 

truck fleets are projected to increase substantially from their level in 2011 under the No Action 

Alternative, which would assume that passenger cars and light trucks continue to achieve the level of fuel 

economy required by MY 2011 CAFE standards. The table also shows that each of the action alternatives 

would reduce total passenger car and light truck CO2 emissions in future years significantly from their 

projected levels under the No Action Alternative. Progressively larger reductions in CO2 emissions from 

their levels under the No Action Alternative are projected to occur during each future year because the 

action alternatives require successively higher fuel economy levels for MYs 2012-2016 and later 

passenger cars and light trucks. For example, Alternative 9 (which results in 37.0 mpg in 2016) will get 

much larger by 2030 growing at 0.51 percent a year than Alternative 2 (which results in 32 mpg in 2016) 

will get by 2030 growing at 0.51 percent a year. 
4.4 Climate 

Figure 4.4.4-1. Cumulative Annual Emissions Under the MYs 2012-2016 Standards and Other R

Foreseeable Future Actions (MMTCO2) 

0

500

1000150020002500300035004000

2010 2020 2030 2040 2050 

MMTCO2

Alt. 1: No Action Alt. 2: 3%/year IncreaseAlt. 3: 4%/year Increase Alt. 4: ~4.3%/year Increase, PreferreAlt. 5: 5%/year Increase Alt. 6: ~6.0%/year Increase, MNBAlt. 7: 6%/year Increase Alt. 8: 7%/year IncreaseAlt. 9: ~6.6%/year Increase, TCTB

4-52 
Chapter 4 Cumulative Impacts 

4-53 

Table 4.4.4-2 

Cumulative Effects of Nationwide Emissions of Greenhouse Gases (MMT per year) from Passenger Cars and Light Truc

Alt. 1 Alt. 2 Alt. 3 Alt. 4 Alt. 5 Alt. 6 Alt. 7 Alt

GHG 

and 

Year 

No 

Action 

3%/year 

Increase 

4%/year 

Increase 

~4.3%/year 

Increase 

Preferred 

5%/year 

Increase 

~6.0%/year 

Increase 

MNB 

6%/year 

Increase 

7%/y

Incre

Carbon dioxide (CO2) 

2010 1,730 1,730 1,730 1,730 1,730 1,730 1,730 1,72020 1,800 1,710 1,690 1,680 1,670 1,640 1,640 1,62030 2,050 1,820 1,820 1,890 1,780 1,730 1,730 1,72040 2,410 2,110 2,110 2,100 2,070 2,010 2,000 1,92050 2,930 2,560 2,560 2,550 2,510 2,430 2,430 2,32060 3,580 3,120 3,130 3,110 3,060 2,970 2,960 2,9

Methane (CH4) 

2010 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.02020 1.92 2.00 1.98 1.97 1.95 1.91 1.92 1.82030 2.39 2.14 2.13 2.12 2.08 2.02 2.08 1.92040 2.82 2.48 2.48 2.46 2.42 2.34 2.34 2.22050 3.42 3.00 3.00 2.99 2.93 2.84 2.84 2.72060 4.18 3.67 3.65 3.58 3.46 3.46 3.46 3.3

Nitrous oxide (N2O) 

2010 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.02020 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.02030 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.02040 0.05 0.05 0.05 0.05 0.04 0.04 0.04 0.02050 0.06 0.06 0.06 0.06 0.05 0.05 0.05 0.02060 0.07 0.07 0.07 0.07 0.06 0.06 0.06 0.0
4.4 Climate Chapter 4 Cumulative Impacts 

 4-54 

Under all of the alternatives, projected growth in the number of passenger cars and light trucks in 

use throughout the United States, combined with assumed increases in their average use (VMT per 

vehicle), is projected to result in growth in total passenger car and light truck travel (VMT). As a result, 

despite increases in fuel economy, total fuel consumption and CO2 emissions by U.S. passenger cars and 

light trucks is projected to increase under each of the action alternatives, as shown in the Figure 4.4.4-1. 

Because CO2 emissions are a direct consequence of total fuel consumption, the same result is projected 

for total CO2 emissions from passenger cars and light trucks. 

Emissions of CO2, the primary gas that drives climate effects, from the U.S. passenger car and 

light truck fleet represented about 3.3 percent of total global emissions of CO2 in 2005 (EPA 2009a, WRI 

2009).13 Although substantial, this source is still a small percentage of global emissions. The relative 

contribution of CO2 emissions from U.S. passenger cars and light trucks is expected to decline in the 

future, due primarily to rapid growth of emissions from developing economies (which are due in part to 

growth in global transportation sector emissions). These conclusions are not meant to be interpreted as 

expressing NHTSA views that the U.S. vehicle fleet’s contribution to global CO2 emissions is not an area 

of concern for policymakers. Under NEPA, the agency is obligated to discuss “the environmental 

impact[s] of the proposed action.” 42 U.S.C. § 4332(2)(C)(i) (emphasis added). The analysis in this EIS 

fulfills NHTSA obligations in this regard. 

These emissions reductions can also be compared to existing programs designed to reduce GHG 

emissions in the United States. In 2007, Arizona, California, New Mexico, Oregon, and Washington 

formed the WCI to develop regional strategies to address climate change. WCI has a stated goal of 

reducing 350 MMTCO2 equivalent over the period from 2009 to 2020 (WCI 2007) By comparison, this 

rulemaking is expected to reduce CO2 emissions by 310 to 730 MMTCO2 over the same period. In the 

Northeast and Mid-Atlantic, nine states have formed the RGGI to reduce CO2 emissions from power 

plants. Emissions reductions from 2006 to 2024 are estimated at 268 MMTCO2 from what they were 

otherwise projected to be (RGGI 2006).14 By comparison, NHTSA forecasts that this rulemaking will 

reduce CO2 emissions by 820 to 1,630 MMTCO2 over this period. 

Two features of these comparisons are extremely important to emphasize. First, emissions from 

the sources addressed in the WCI and RGGI plans are projected to decrease compared to the beginning of 

the action, while emissions from passenger cars and light trucks are projected to increase under all 

alternatives for this rulemaking due to increases in vehicle ownership and use. Second, these projections 

are only estimates, and the scope of these climate programs differs from that in this rulemaking in terms 

of geography, sector, and purpose. 

Where information in the analysis included in this EIS is incomplete or unavailable, NHTSA has 

relied on CEQ regulations regarding incomplete or unavailable information (see 40 CFR § 1502.22(b)). I 

n this case, the comparison of emissions reductions from the action alternatives to emissions reductions 

associated with other programs is intended to aid decisionmakers by providing relative benchmarks, 

rather than absolute metrics, for selecting among alternatives. In summary, the alternatives analyzed here 

deliver GHG emissions reductions that are on a scale similar to many of the most progressive and 

ambitious GHG emissions reduction programs underway in the United States. However, due to projected 

increases in VMT, increases in CAFE standards are not projected to provide absolute emissions 

reductions from today’s levels of passenger car and light truck emissions, whereas some regional 

programs do predict such absolute reductions. 

 

13 Includes land-use change and forestry, and excludes international bunker fuels. 

14 Emissions reductions were estimated by determining the difference between the RGGI Cap and the Phase III 

RGGI Reference Case. These estimates do not include offsets. 
Chapter 4 Cumulative Impacts 4.4 Climate 

 4-55 

4.4.4.2 Cumulative Effects on Climate Change 

The approach to estimating the cumulative effects of climate change from the MYs 2012-2016 

CAFE standards combined with other reasonably foreseeable future actions mirrors that used to estimate 

the direct and indirect effects of the MYs 2012-2016 CAFE standards. 

Again, because EISA directs NHTSA to increase CAFE standards to reach a combined fleet 

average CAFE level of at least 35 mpg by MY 2020, MYs 2017-2020 CAFE standards are reasonably 

foreseeable and must be accounted for when analyzing the cumulative impacts of the MYs 2012-2016 

CAFE standards. Many of the action alternatives surpass the target of 35 mpg in 2016. For action 

alternatives that do not reach 35 mpg by MY 2016 (Alternative 2, Alternative 3, Alternative 4, and 

Alternative 5), the Chapter 4 cumulative impacts mpg is expected to continue to rise from 2017 to 2020 

so that the MY 2020 EISA target 35 mpg is at least met. Once the 35 mpg target is met or exceeded, 

NHTSA assumes that the overall fuel economy of the fleet continues to improve until 2030 at a pace 

consistent with the AEO 2010 Early Release Reference Case projections (see Section 4.1.3). NHTSA 

also assumes fuel economy increases consistent with the AEO projections under the No Action 

Alternative. 

Because the CAFE standards apply to new vehicles, this assumption results in emissions 

reductions and fuel savings that continue to grow after 2030 as new vehicles meeting the 2030 mpg 

average are added to the fleet in each subsequent year, reaching their maximum values when all passenger 

cars and light trucks in the U.S. fleet meet the 2030 average mpg. Overall, the emissions reductions for 

the MYs 2012-2016 CAFE standards have a small impact on climate change. The emissions reductions 

and resulting climate impacts for the MYs 2012-2016 CAFE standards and other reasonably foreseeable 

future actions are larger, although they are still relatively small in absolute terms. While these effects are 

small, they occur on a global scale and are long-lived. These conclusions are not meant to be interpreted 

as expressing NHTSA views that anthropogenic climate change is not an area of concern for 

policymakers. Under NEPA, the agency is obligated to discuss “the environmental impact[s] of the 

proposed action.” 42 U.S.C. § 4332(2)(C)(i) (emphasis added). The analysis in this EIS fulfills NHTSA 

obligations in this regard. 

Sections 4.4.4.2.1 through 4.4.4.2.4 describe cumulative effects of the alternatives on climate 

change in terms of atmospheric CO2 concentrations, temperature, precipitation, and sea-level rise. 

4.4.4.2.1 Atmospheric Carbon Dioxide Concentrations 

MAGICC is a simple climate model that is well calibrated to the mean of the multi-model 

ensemble results for three of the most commonly used emissions scenarios – B1 (low), A1B (medium), 

and A2 (high) from the IPCC SRES series – as shown in Table 4.4.4-3.15 As the table indicates, the 

model runs developed for this analysis achieve relatively good agreement with IPCC WGI estimates in 

terms of both CO2 concentrations and surface temperature. 

A comparison of sea-level rise from MAGICC 5.3.v2 and the IPCC Fourth Assessment Report 

can be found in the release documentation for MAGICC 5.3.v2 (Wigley 2008). In Table 3 of the 

documentation, Wigley (2008) presents the results for six SRES scenarios that show the comparable value 

for sea-level rise from MAGICC 5.3.v2 (total sea-level rise minus estimates for contributions from nonmelt sources such as warming of the permafrost) within 0.01 centimeters (0.04 inch) in 2095. 

 

15 NHTSA used the default climate sensitivity in MAGICC of 3.0 °C (5.4 °F) 
4.4 Climate Chapter 4 Cumulative Impacts 

 4-56 

Table 4.4.4-3 

Comparison of MAGICC Results and Reported IPCC Results (IPCC 2007) 

CO2 Concentration 

(ppm) 

Global Mean Increase 

in Surface Temperature (°C) Sea-level Rise (cm) 

Scenario 

IPCC WGI 

(2100) 

MAGICC 

(2100) 

IPCC WGI 

(2080-2099) 

MAGICC 

(2090) 

IPCC WGI 

(2090-2099) a/ 

MAGICC 

(2095) 

B1 550 538.3 1.79 1.81 28 26 

A1B 715 717.2 2.65 2.76 35 35 

A2 836 866.8 3.13 3.31 37 38 

_______________ 

a/ The IPCC values represent the average of the 5- to 95-percent range of the rise of sea level from 1980 to 

1989 and from 2090 to 2099.

The MiniCAM Level 3 scenario, which is a radiative forcing stabilization scenario with a 

corresponding CO2 concentration level of roughly 650 ppmv in 2100, was used to represent the No 

Action Alternative (Alternative 1) in the MAGICC runs for this EIS.16 Table 4.4.4-4 and Figures 4.4.4-2 

through 4.4.4-5 show the mid-range results of MAGICC model simulations for Alternative 1 and the eight 

action alternatives for CO2 concentrations and increase in global mean surface temperature in 2030, 2050, 

and 2100. As Figures 4.4.4-2 and 4.4.4-3 show, the reduction impact on the growth in projected CO2

concentrations and temperature amounts to a small fraction of the total growth in CO2 concentrations and 

global mean surface temperature. However, the relative impact of the action alternatives is illustrated by 

the reduction in growth of both CO2 concentrations and temperature under the TCTB Alternative 

(Alternative 9). 

As shown in the Table 4.4.4-4 and Figures 4.4.4-2 through 4.4.4-5, there is a fairly narrow band 

of estimated CO2 concentrations as of 2100, from 653.4 ppm under Alternative 8 (7%/year increase in 

fuel economy) to 657.4 ppm under the No Action Alternative (Alternative 1). For 2030 and 2050, the 

corresponding range is even smaller. Because CO2 concentrations are the key driver of all other climate 

effects, this leads to small differences in these effects. Although these effects are small, they occur on a 

global scale and are long-lived. 

4.4.4.2.2 Temperature 

MAGICC simulations of mean global surface air temperature increases are shown below in Table 

4.4.4-4. For all alternatives, the cumulative global mean surface temperature increase is about 0.80 °C to 

0.81 °C (1.44 to 1.46 °F) as of 2030; 1.32 to 1.33 °C (2.38 to 2.39 °F) as of 2050; and 2.59 to 2.61 °C 

(4.66 to 4.70 °F) as of 2100.17 The differences among alternatives are small. For 2100, the reduction in 

temperature increase under the action alternatives in relation to the No Action Alternative is about 0.01 to 

0.02 °C (0.02 to 0.04 °F). Although these effects are small, they occur on a global scale and are longlived. 

Quantifying the changes to regional climate from the CAFE alternatives is not possible at this 

point due to the limitations of existing climate models, but it is expected that the alternatives would 

reduce the changes in relation to the reduction in global mean surface temperature. Regional changes to 

warming and seasonal temperatures as described by the IPCC Fourth Assessment Report are summarized 

in Table 3.4.4-5 in Section 3.4.4.2.2. 

 

16 The No Action Alternative does not reach a CO2 concentration level of exactly 650 ppm in 2100 because the 

MiniCAM Level 3 scenario was developed using an assumed total long-term radiative forcing stabilization level, 

which includes radiative forcing from other non-CO2 GHGs. The scientists who designed the scenario are using 650 

ppm as convenient shorthand for a condition that is considerably more complicated. 

17 Because the actual increase in global mean surface temperature lags the commitment to warming, the impact on 

global mean surface temperature increase is less than the impact on the long-term commitment to warming. 
Chapter 4 Cumulative Impacts 4.4 Climate 

 4-57 

Table 4.4.4-4 

Cumulative Effects on CO2 Concentrations, Global Mean Surface Temperature Increase, and Sea-level Rise 

Using MAGICC (MiniCAM Level 3) by Alternative a/ 

CO2 Concentration 

(ppm) 

Global Mean Surface 

Temperature Increase 

(°C) Sea-level Rise (cm) Totals by 

Alternative 2030 2050 2100 2030 2050 2100 2030 2050 2100 

1 No Action 438.7 498.0 657.4 0.805 1.327 2.611 7.83 13.67 32.84 

2 3%/year Increase 438.5 497.2 654.8 0.805 1.323 2.599 7.83 13.65 32.74 

3 4%/year Increase 438.5 497.2 654.8 0.804 1.323 2.599 7.83 13.65 32.74 

4 ~4.3%/year 

Increase, Preferred 438.5 497.2 654.7 0.804 1.323 2.599 7.83 13.65 32.73 

5 5%/year Increase 438.4 497.1 654.3 0.804 1.322 2.597 7.83 13.65 32.72 

6 ~6.0%/year 

Increase, MNB 438.4 496.9 653.8 0.804 1.321 2.594 7.83 13.64 32.69 

7 6%/year Increase 438.4 496.9 653.8 0.804 1.321 2.594 7.83 13.64 32.69 

8 7%/year Increase 438.3 496.8 653.4 0.804 1.321 2.592 7.83 13.64 32.68 

9 ~6.6%/year 

Increase, TCTB 438.3 496.8 653.5 0.804 1.321 2.593 7.83 13.64 32.68 

Reductions Under Alternative CAFE Standards

2 3%/year Increase 0.2 0.8 2.7 0.001 0.004 0.012 0.00 0.02 0.10 

3 4%/year Increase 0.2 0.8 2.7 0.001 0.004 0.012 0.00 0.02 0.10 

4 ~4.3%/year 

Increase, Preferred 0.2 0.8 2.8 0.001 0.004 0.012 0.00 0.02 0.11 

5 5%/year Increase 0.3 0.9 3.2 0.001 0.004 0.014 0.00 0.02 0.12 

6 ~6.0%/year 

Increase, MNB 0.3 1.1 3.7 0.002 0.006 0.017 0.00 0.03 0.15 

7 6%/year Increase 0.3 1.1 3.7 0.002 0.005 0.017 0.00 0.03 0.15 

8 7%/year Increase 0.4 1.2 4.1 0.002 0.006 0.019 0.00 0.03 0.16 

9 ~6.6%/year 

Increase, TCTB 0.4 1.2 4.0 0.002 0.006 0.018 0.00 0.03 0.16 

_______________ 

a/ The numbers in this table have been rounded for presentation purposes. Therefore, the reductions might not 

 reflect the exact difference of the values in all cases. 
4.4 Climate 

Figure 4.4.4-2. Cumulative Effects on CO2 Concentrations 

0

100200300400500600700

2030 2050 2100

ppm

No Action Al t. 2: 3%/yea r Increa seAl t. 3: 4%/yea r Increa se Al t. 4: ~4.3%/yea r Increa se, Pre fe rreAl t. 5: 5%/yea r Increa se Al t. 6: ~6.0%/yea r Increa se, MNBAl t. 7: 6%/yea r Increa se Al t. 8: 7%/yea r Increa seAl t. 9: ~6.6%/yea r Increa se, TCTB

4-58 
Chapter 4 Cumulative Impacts 

Figure 4.4.4-3. Cumulative Effects on Global Mean Surface Temperature Increase 

0

0.5

1

1.5

2

2.5

3

2030 2050 2100

degrees Celsius

No Action Al t. 2: 3%/yea r Increa seAl t. 3: 4%/yea r Increa se Al t. 4: ~4.3%/yea r Increa se, Pre ferredAl t. 5: 5%/yea r Increa se Al t. 6: ~6.0%/yea r Increa se, MNBAl t. 7: 6%/yea r Increa se Al t. 8: 7%/yea r Increa seAl t. 9: ~6.6%/yea r Increa se, TCTB

4-59 
4.4 Climate 

Figure 4.4.4-4. Cumulative Effects on CO2 Concentrations (Reduction Compared to the No Actio

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

2030 2050 2100

ppm

Al t. 2: 3%/yea r Increa se Al t. 3: 4%/yea r Increa se Al t. 4: ~4.3%/yea r Increa Al t. 5: 5%/yea r Increa se Al t. 6: ~6.0%/yea r Increa se, MNB Al t. 7: 6%/yea r Increa seAl t. 8: 7%/yea r Increa se Al t. 9: ~6.6%/yea r Increa se, TCTB

4-60 
4-61 

Chapter 4 Cumulative Impacts 

Figure 4.4.4-5. Cumulative Effects on Global Mean Temperature (Reduction Compared t

No Action Alternative) 

0.0000.0020.0040.0060.0080.0100.0120.0140.0160.0180.020

2030 2050 2100

degrees Celsius

Al t. 2: 3%/yea r Increa se Al t. 3: 4%/yea r Increa se Al t. 4: ~4.3%/yea r Increa se, Pre feAl t. 5: 5%/yea r Increa se Al t. 6: ~6.0%/yea r Increa se, MNB Al t. 7: 6%/yea r Increa seAl t. 8: 7%/yea r Increa se Al t. 9: ~6.6%/yea r Increa se, TCTB
4.4 Climate Chapter 4 Cumulative Impacts 

 4-62 

4.4.4.2.3 Precipitation 

The effects of higher temperatures on the amount of precipitation and the intensity of 

precipitation events, as well as the IPCC scaling factors to estimate global mean precipitation change, are 

discussed in Section 3.4.4.2.3. 

Applying these scaling factors to the reductions in global mean surface warming provides 

estimates of changes in global mean precipitation. Given that the action alternatives would reduce 

temperature increases slightly in relation to the No Action Alternative, they also would reduce predicted 

increases in precipitation slightly, as shown in Table 4.4.4-5 (again, based on the A1B [medium] 

scenario). 

Regional variations and changes in the intensity of precipitation events cannot be quantified 

further. This inability is due primarily to the lack of availability of AOGCMS required to estimate these 

changes. AOGCMS are typically used to provide results among scenarios having very large changes in 

emissions such as the SRES B1 (low), A1B (medium), and A2 (high) scenarios; very small changes in 

emissions profiles produce results that would be difficult to resolve among scenarios having relatively 

small changes in emissions. Also, the multiple AOGCMs produce results that are regionally consistent in 

some cases but are inconsistent in others. 

Quantifying the changes to regional climate from the action alternatives is not possible at this 

point, but the action alternatives would reduce the changes in relation to the reduction in global mean 

surface temperature. Regional changes to precipitation as described by the IPCC Fourth Assessment 

Report are summarized in Table 3.4.4-8 in Section 3.4.4.2.3. 

4.4.4.2.4 Sea-level Rise 

The components of sea-level rise, MAGICC treatment of these components, and recent scientific 

assessments are discussed in Section 3.4.4.2.4. 

Table 4.4.4-4 presents the impact on sea-level rise from the scenarios and show sea-level rise in 

2100 ranging from 32.84 centimeters (12.93 inches) under the No Action Alternative (Alternative 1) to 

32.68 centimeters (12.87 inches) under Alternatives 8 and 9, for a maximum reduction of 0.16 

centimeters (0.06 inches) by 2100. 

In summary, the impacts of the proposed action and alternatives and other reasonably foreseeable 

future actions on global mean surface temperature, sea-level rise, and precipitation are relatively small in 

the context of the expected changes associated with the emissions trajectories in the SRES scenarios.18 

This is due primarily to the global and multi-sectoral nature of the climate problem. Although these 

effects are small, they occur on a global scale and are long-lived. 

 

18 These conclusions are not meant to be interpreted as expressing NHTSA views that impacts on global mean 

surface temperature, precipitation, or sea-level rise are not areas of concern for policymakers. Under NEPA, the 

agency is obligated to discuss “the environmental impact[s] of the proposed action.” 42 U.S.C. § 4332(2)(C)(i) 

(emphasis added). This analysis fulfills NHTSA obligations in this regard. 
Chapter 4 Cumulative Impacts 4.4 Climate 

Table 4.4.4-5 

Cumulative Effects on Global Mean Precipitation (Percent Change) Based on MiniCAM Level 3 Scenario 

Using Increases in Global Mean Surface Temperature Simulated by MAGICC by Alternative a/ 

Scenario 2020 2055 2090 

Global Mean Precipitation Change (scaled, % K-1) 1.45 1.51 1.63 

Global Temperature Above Average 1980-1999 Levels (K) for the MiniCAM reference Scenario and 

Alternative CAFE Standards, Volpe Reference Results 

1 No Action 0.586 1.466 2.415 

2 3%/year Increase 0.586 1.462 2.405 

3 4%/year Increase 0.585 1.461 2.405 

4 ~4.3%/year Increase, Preferred 0.585 1.461 2.405 

5 5%/year Increase 0.585 1.459 2.403 

6 ~6.0%/year Increase, MNB 0.585 1.459 2.401 

7 6%/year Increase 0.585 1.459 2.401 

8 7%/year Increase 0.585 1.459 2.399 

9 ~6.6%/year Increase, TCTB 0.585 1.459 2.400 

Reduction in Global Temperature (K) for Alternative CAFE Standards, Mid-level Results (Compared to 

No Action Alternative) 

2 3%/year Increase 0.000 0.004 0.010 

3 4%/year Increase 0.000 0.004 0.010 

4 ~4.3%/year Increase, Preferred 0.000 0.005 0.011 

5 5%/year Increase 0.000 0.005 0.012 

6 ~6.0%/year Increase, MNB 0.000 0.007 0.015 

7 6%/year Increase 0.000 0.007 0.015 

8 7%/year Increase 0.000 0.007 0.016 

9 ~6.6%/year Increase, TCTB 0.000 0.007 0.016 

Global Mean Precipitation Change (%)

1 No Action 0.85% 2.21% 3.94% 

2 3%/year Increase 0.85% 2.21% 3.92% 

3 4%/year Increase 0.85% 2.21% 3.92% 

4 ~4.3%/year Increase, Preferred 0.85% 2.21% 3.92% 

5 5%/year Increase 0.85% 2.21% 3.92% 

6 ~6.0%/year Increase, MNB 0.85% 2.20% 3.91% 

7 6%/year Increase 0.85% 2.20% 3.91% 

8 7%/year Increase 0.85% 2.20% 3.91% 

9 ~6.6%/year Increase, TCTB 0.85% 2.20% 3.91% 

Reduction in Global Mean Precipitation Change for Alternative CAFE Standards (% Compared to 

No Action Alternative)

2 3%/year Increase 0.00% 0.01% 0.02% 

3 4%/year Increase 0.00% 0.01% 0.02% 

4 ~4.3%/year Increase, Preferred 0.00% 0.01% 0.02% 

5 5%/year Increase 0.00% 0.01% 0.02% 

6 ~6.0%/year Increase, MNB 0.00% 0.01% 0.02% 

7 6%/year Increase 0.00% 0.01% 0.02% 

8 7%/year Increase 0.00% 0.01% 0.03% 

9 ~6.6%/year Increase, TCTB 0.00% 0.01% 0.03% 

_______________ 

a/ The numbers in this table have been rounded for presentation purposes. Therefore, the reductions might not 

 reflect the exact difference of the values in all cases. 

 4-63 
4.4 Climate Chapter 4 Cumulative Impacts 

4.4.4.2.5 Climate Sensitivity Variations 

NHTSA examined the sensitivity of climate effects on key assumptions used in the analysis. This 

examination included reviewing the impact of various climate sensitivities and global emissions scenarios 

on the climate effects under the No Action Alternative (Alternative 1) and the Preferred Alternative 

(Alternative 4). Table 4.4.4-6 presents the results from the sensitivity analysis. 

The use of alternative global emissions scenarios can influence the results in several ways. 

Emissions reductions can lead to larger reductions in the CO2 concentrations in later years because more 

of the anthropogenic emissions can be expected to stay in the atmosphere. The use of different climate 

sensitivities (the equilibrium warming that occurs at a doubling of CO2 from pre-industrial levels) can 

affect not only warming but also indirectly affect sea-level rise and CO2 concentration. 

As shown in Table 4.4.4-6, the sensitivity of simulated CO2 emissions in 2030, 2050, and 2100 to 

assumptions of global emissions and climate sensitivity is low; stated simply, CO2 emissions do not 

change much with changes in global emissions and climate sensitivity. For 2030 and 2050, the choice of 

global emissions scenario has little impact on the results. By 2100, the Preferred Alternative (Alternative 

4) has the greatest impact in the global emissions scenario with the highest CO2 emissions (MiniCAM 

Reference) and the least impact in the scenario with the lowest CO2 emissions (MiniCAM Level 2). The 

total range of the impact of the Preferred Alternative on CO2 concentrations in 2100 is from 2.6 to 

3.1 ppm. The Reference Case using the MiniCAM Level 3 scenario and a 3.0 °C (5.4 °F) climate 

sensitivity has an impact of 2.8 ppm. 

The sensitivity of the simulated global mean surface temperatures for 2030, 2050, and 2100 

varies, as shown in Table 4.4.4-6. In 2030, the impact is low due primarily to the rate at which global 

mean surface temperature increases in response to increases in radiative forcing. In 2100, the impact is 

large due not only to the climate sensitivity but also to the change in emissions. In 2030, the reduction in 

global mean surface temperature from the No Action Alternative to the Preferred Alternative is 0.001 to 

0.002 °C (0.002 to 0.004 °F) across the climate sensitivities and global emissions scenarios, as shown in 

Table 4.4.4-9. The impact on global mean surface temperature due to assumptions concerning global 

emissions of GHG is also important. The scenarios with the higher global emissions of GHGs, such as 

the MiniCAM Reference, have a lower reduction in global mean surface temperature and the scenarios 

with lower global emissions have a higher reduction. This is in large part due to the non-linear and nearlogarithmic relationship between radiative forcing and CO2 concentrations. At high emissions levels, CO2

concentrations are high; therefore, a fixed reduction in emissions yields a lower reduction in radiative 

forcing and global mean surface temperature. 

The sensitivity of simulated sea-level rise to change in climate sensitivity and global GHG 

emissions mirrors that of global temperature, as shown in Table 4.4.4-6. Scenarios with lower climate 

sensitivities have lower increases in sea-level rise; the increase in sea-level rise is lower under the 

Preferred Alternative (Alternative 4) than it would be under scenarios with higher climate sensitivities. 

Conversely, scenarios with higher climate sensitivities have higher sea-level rise; the increase of sea-level 

rise is higher under the Preferred Alternative than it would be under scenarios with lower climate 

sensitivities. Higher global GHG emissions have higher sea-level rise, but the impact of the Preferred 

Alternative is less than in scenarios with lower global emissions. Conversely, scenarios with lower global 

GHG emissions have lower sea-level rise, though the impact of the Preferred Alternative is greater than in 

scenarios with higher global emissions. 

 4-64 
Chapter 4 Cumulative Impacts 4.4 Climate 

 4-65 

Table 4.4.4-6 

Cumulative Effects on CO2 Concentrations, Global Mean Surface Temperature Increase, and Sea-level Rise 

for Varying Climate Sensitivities for Selected Alternatives a/ 

Emissions 

Scenario 

CAFE 

Alternative 

Climate 

Sensitivity 

(°C for 2xCO2) CO2 concentration (ppm)

Global Mean Surface 

Temperature Increase (°C) 

Sealevel 

Rise 

(cm) 

2030 2050 2100 2030 2050 2100 2100 

MiniCAM Level 2 

1 No 

Action 2.0 434.5 483.8 553.5 0.613 0.989 1.555 22.40 

3.0 436.0 487.3 565.9 0.813 1.327 2.189 30.03 

4.5 437.6 491.3 581.3 1.035 1.709 2.963 38.88 

4 

Preferred 2.0 434.3 482.9 550.9 0.612 0.986 1.545 22.31 

3.0 435.7 486.4 563.1 0.812 1.323 2.175 29.91 

4.5 437.3 490.4 578.5 1.033 1.704 2.946 38.74 

Reduction compared to No Action 

2.0 0.2 0.9 2.6 0.001 0.003 0.010 0.09 

3.0 0.3 0.9 2.8 0.001 0.004 0.014 0.12 

4.5 0.3 0.9 2.8 0.001 0.005 0.017 0.14 

MiniCAM Level 3 

1 No 

Action 2.0 437.3 494.5 643.4 0.607 0.990 1.888 24.68 

3.0 438.7 498.0 657.5 0.805 1.327 2.611 32.84 

4.5 440.3 502.0 675.2 1.024 1.706 3.475 42.24 

4 

Preferred 2.0 437.0 493.7 640.6 0.606 0.987 1.879 24.59 

3.0 438.5 497.2 654.7 0.804 1.323 2.599 32.73 

4.5 440.0 501.2 672.2 1.023 1.701 3.459 42.10 

Reduction compared to No Action 

2.0 0.3 0.8 2.8 0.001 0.003 0.009 0.09 

3.0 0.2 0.8 2.8 0.001 0.004 0.012 0.11 

4.5 0.3 0.8 3.0 0.001 0.005 0.015 0.14 

MiniCAM Reference 

1 No 

Action 2.0 440.2 510.7 765.1 0.699 1.168 2.292 28.68 

3.0 441.8 514.8 783.0 0.923 1.557 3.136 38.00 

4.5 443.6 519.5 805.3 1.168 1.991 4.132 48.67 

4 

Preferred 2.0 439.9 509.9 762.2 0.698 1.165 2.284 28.60 

3.0 441.5 514.0 780 0.922 1.553 3.124 37.90 

4.5 443.3 518.7 802.2 1.166 1.987 4.118 48.54 

Reduction compared to No Action 

2.0 0.3 0.8 2.9 0.001 0.003 0.008 0.08 

3.0 0.3 0.8 3.0 0.001 0.004 0.011 0.10 

4.5 0.3 0.8 3.1 0.002 0.005 0.014 0.13 

_______________ 

a/ The numbers in this table have been rounded for presentation purposes. Therefore, the reductions might not 

 reflect the exact difference of the values in all cases. 
4.5 Health, Societal, and Environmental Impacts of Climate Change Chapter 4 Cumulative Impacts 

4.5 HEALTH, SOCIETAL, AND ENVIRONMENTAL IMPACTS OF CLIMATE CHANGE 

4.5.1 Introduction 

The effects of the proposed action and alternatives on climate as described in Section 4.4 – CO2

concentrations, temperature, precipitation, and sea-level rise – can translate to impacts to key natural and 

human resources. Section 4.5.2 describes the methodology NHTSA used to evaluate the cumulative 

impacts stemming from climate change on key natural and human resources. Sections 4.5.3 through 4.5.8 

address cumulative impacts to the following key natural and human resources: 

• Freshwater resources (the availability, practices, and vulnerabilities of freshwater as a 

function of climate); 

• Terrestrial and freshwater ecosystems (existing and potential vulnerabilities and benefits of 

the respective species and communities in response to climate change); 

• Marine, coastal systems, and low-lying areas (the interplay between climate, environment, 

species, and communities within coastal and open-ocean waters, including coastal wetlands 

and coastal human settlements); 

• Food, fiber, and forest products (the environmental vulnerabilities of farming, forestry, and 

fisheries that could be affected by climate change); 

• Industries, settlements, and society (covers a broad range of human institutions and systems, 

including industrial and service sectors; large and small urban areas and rural communities; 

transportation systems; energy production; and financial, cultural, and social institutions in 

the context of how these elements might be affected by climate change; and 

• Human health (how a changing climate might affect human mortality and morbidity). 

 Each section discusses the affected environment, provides an overview of the resource within the 

U.S. and globally, and addresses the consequences and observed changes of climate change on that 

resource. The section also includes a discussion of both the beneficial and adverse consequences of 

climate change, as they are represented in the literature. Although the approach is systematic, these topics 

do not exist in isolation and there is some overlap between discussions. 

The sections generally follow the organization of topic areas in the climate literature, notably by 

IPCC, which is a key source for much of the information presented in this section, and by EPA and 

CCSP. These categories do not follow the classification of resources typically found in an EIS. See the 

chart in Section 4.1 to find where specific NEPA topics are covered. 

As shown in Section 4.4, although the alternatives could substantially decrease GHG emissions, 

they would not prevent climate change; instead they would result in reductions to the anticipated 

increases of global CO2 concentrations, temperature, precipitation, and sea level. NHTSA’s assumption 

is that these reductions in climate effects would be reflected in reduced impacts to affected resources. 

However, the magnitude of the changes in climate effects that the alternatives would produce – 4 ppm of 

CO2, a few hundredths of a degree Centigrade difference in temperature, a small percentage change in the 

rate of precipitation increase, and 1 or 2 millimeters of sea-level rise, see Section 4.4.4 – are too small to 

address quantitatively in terms of their impacts on resources. Given the enormous resource values at 

stake, these distinctions could be important – very small percentages of huge numbers can yield 

substantial results – but they are too small for current quantitative techniques to resolve. Consequently, 

the discussion of resource impacts does not distinguish among the CAFE alternatives; rather it provides a 

 4-66 
Chapter 4 Cumulative Impacts 4.5 Health, Societal, and Environmental Impacts of Climate Change 

 4-67 

qualitative review of the benefits of reducing GHG emissions and the magnitude of the risks involved in 

climate change. 19

4.5.2 Methodology 

This document primarily draws upon panel-reviewed synthesis and assessment reports from the 

IPCC and U.S. Global Change Research Program (USGCRP). It also cites EPA’s Technical Support 

Document for Endangerment and Cause or Contribute Findings for Greenhouse Gases under Section 

202(a) of the Clean Air Act – which heavily relied on these panel reports. NHTSA similarly relies on

panel reports because they have assessed numerous individual studies in order to draw general 

conclusions about the state of science; have been reviewed and formally accepted by, commissioned by, 

or in some cases authored by, U.S. government agencies and individual government scientists and provide 

NHTSA with assurances that this material has been well vetted by both the climate change research 

community and by the U.S. government; and in many cases, they reflect and convey the consensus 

conclusions of expert authors. These reports therefore provide the overall scientific foundation for U.S. 

climate policy at this time. 

This document also refers to new peer-reviewed literature that has not been assessed or 

synthesized by an expert panel. This new literature supplements but does not supersede the findings of 

the panel-reviewed reports. 

NHTSA’s consideration of newer studies and highlighting of particular issues responds to 

previous public comments received on the scoping document and the prior EIS for the MY 2011 CAFE 

standard, as well as the Ninth Circuit’s decision in CBD v. NHTSA, 538 F.3d 1172 (9th Cir. 2008). The 

level of detail regarding the science of climate change in this draft EIS, and NHTSA’s consideration of 

other studies that show illustrative research findings pertaining to the potential impacts of climate change 

on health, society, and the environment, are provided to help inform the public and the decisionmaker, 

consistent with the agency’s approach in the prior EIS for the MY 2011 CAFE standards. 

NHTSA compiled research on freshwater resources; terrestrial and freshwater ecosystems and 

biodiversity; marine, coastal, and low-lying areas; industry, settlement, and society; food, fiber, and forest 

products; and human health. Each section includes an introduction and addresses the impacts anticipated 

for both the United States and the global environment. 

To accurately reflect the likelihood of climate-change impacts for each sector, NHTSA 

referenced the IPCC uncertainty guidelines (see Section 4.4.1.1 and Section 4.5.2.2). This approach 

provided a consistent methodology to define confidence levels and percent probability of a predicted 

outcome or impact. More information on the uncertainty guidelines is provided in the Treatment of 

Uncertainties in the IPCC’s Working Group II Assessment in Solomon et al. (2007). Section 4.5.2.2 

summarizes the IPCC treatment of uncertainty. 

4.5.2.1 Cumulative Climate-change Impacts 

As described in Chapter 3, the proposed action and alternatives result in different periods of CO2

emissions associated with the operation of U.S. vehicles. These emissions, in combination with U.S. 

 

19 See 42 U.S.C. § 4332 (requiring federal agencies to “identify and develop methods and procedures...which will 

insure that presently unquantified environmental amenities and values may be given appropriate consideration”); 40 

CFR § 1502.23 (requiring an EIS to discuss the relationship between a cost-benefit analysis and any analyses of 

unquantified environmental impacts, values, and amenities); CEQ (1984) (recognizing that agencies are sometimes 

“limited to qualitative evaluations of effects because cause-and-effect relationships are poorly understood” or cannot 

be quantified). 
4.5 Health, Societal, and Environmental Impacts of Climate Change Chapter 4 Cumulative Impacts 

GHG emissions from other sources (such as power plants, natural gas use, and agricultural production) 

and with emissions of all GHGs globally, would alter atmospheric concentrations of GHGs. As the 

modeling results presented in Section 4.4 show, different atmospheric concentrations of GHGs will be 

associated with long-term changes in global climate variables, including global average temperature, 

precipitation, and rising sea level. In turn, these climate changes would result in changes to a range of 

natural and human resources and systems, including water supplies, human health, the built environment, 

and a host of others. 

The most common approach to assessing the impacts of climate change is to construct future 

scenarios that represent combinations of changes in levels, and sometimes patterns or variability, of 

temperature, precipitation, sea-level rise, and other relevant climatic and related variables (IPCC 2007b). 

In some cases these scenarios will represent the results of specific climate modeling (the output of 

General Circulation Models), often downscaled to provide results at a finer level of geographic resolution. 

In other cases, scenarios might be designed to be representative of the types and ranges of effects 

expected to occur under climate change, and not the results of specific models (Parson et al. 2007). 

Impacts associated with these scenarios are then estimated using a variety of techniques, including models 

of individual systems (specific ecosystems or geographic areas, such as a park) and examination of 

performance under similar historical conditions. 

Climate impacts literature suggests that some regions and sectors will likely experience positive 

effects of future climate change, particularly at lower levels of temperature change (less than 1 to 3 °C 

[1.8 to 5.4 degrees Fahrenheit {°F} above 1990 levels), while others will experience negative effects 

(IPCC 2007b). The IPCC WGII for the Fourth Assessment Report found that, at higher levels of 

temperature, on balance the net global effects are expected to be negative: “while developing countries 

are expected to experience larger percentage losses, global mean losses could be 1 to 5 percent GDP for 4 

°C [7.2 °F] of warming” (IPCC 2007b). The modeling results presented in Section 4.4 suggest that, for 

the CAFE alternatives, the cumulative climate effects in terms of temperature rise under a moderate 

emissions scenario lie in the range of 2.59 to 2.61 °C (4.66 to 4.70 °F) as of 2100. 

NHTSA’s presumption, consistent with the general literature cited above and reviewed for 

Section 4.5, is that reducing emissions and concomitant climate effects will reduce the net negative 

long-term effects that have been projected for climate change. NHTSA has not, however, performed a 

quantitative comparison of the climate impacts of the alternative CAFE standards on individual resource 

areas, for several reasons. 

First, as indicated above, analyses of impacts often focus on discrete climate scenarios, rather 

than a continuum of climate outcomes; the information to analyze small changes in climate variables is 

not, therefore, generally available in the literature. Moreover, as the global climate changes, so will 

regional and local climates. Changes in global climate variables will be reflected in regional and local 

changes in average climate variables, and in the variability and patterns of climate, such as seasonal and 

annual variations, the frequency and intensity of extreme events, and other physical changes, such as the 

timing and amount of snowmelt. Impacts assessments often rely on highly localized data for both climate 

and other conditions and circumstances (CCSP 2008d). Thus, changes in impacts due to changes in 

global average climate, as projected in this analysis, likely will not be adequately represented by a simple 

scaling of results. Where information in the analysis included in the EIS is incomplete or unavailable, the 

agency has relied on CEQ regulations regarding incomplete or unavailable information (see 40 CFR § 

1502.22(b)). Information on the effect of very small changes in temperature, precipitation, and sea-level 

rise (at the scale of the distinctions among the alternative CAFE standards) is not currently available. 

Nevertheless, NHTSA’s qualitative characterization – that the greater the reductions in GHG emissions, 

the lower the environmental impact – is consistent with theoretical approaches and research methods 

generally accepted in the scientific community. 

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Chapter 4 Cumulative Impacts 4.5 Health, Societal, and Environmental Impacts of Climate Change 

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Second, there is considerable debate about the likely shape of a global climate impacts damage 

function. Although many believe the function to be upwardly sloped (so that marginal net damages 

increase with increasing levels of climate change), fewer agree on its shape, that is, how rapidly net 

climate damages increase as temperature and other variables increase (IPCC 2007b). There is also the 

important question of whether there are thresholds, that is, stress points at which ecosystems collapse or 

the negative impacts rapidly accelerate – a topic important enough to warrant attention in a SAP Report 

for which the USGS is the lead agency (CCSP 2009c). Finally, much of the work on impacts – both 

global and more localized – is, in and of itself, qualitative and so does not lend itself to further 

quantification.20 

4.5.2.2 Treatment of Uncertainties in the Working Group I Assessment 

Uncertainties can be classified in several different ways. “Value uncertainties” and “structural 

uncertainties” are two primary types of uncertainties. When data are inaccurate or do not fully represent 

the phenomenon of interest, value uncertainties arise. These types of uncertainties are typically estimated 

with statistical techniques, and then expressed probabilistically. An incomplete understanding of the 

process that controls particular values or results generates structural uncertainties. These types of 

uncertainties are described by presenting the authors’ collective judgment of their confidence in the 

correctness of a result. As stated in the WGI assessment, a “careful distinction between levels of 

confidence in scientific understanding and the likelihoods of specific results” are drawn in the uncertainty 

guidance provided for the Fourth Assessment Report. 

The standard terms used to define levels of confidence are: 

Confidence Terminology Degree of Confidence in Being Correct 

 Very high confidence At least 9 out of 10 chance 

 High confidence About 8 out of 10 chance 

 Medium confidence About 5 out of 10 chance 

 Low confidence About 2 out of 10 chance 

 Very low confidence Less than 1 out of 10 chance 

The standard terms used to define the likelihood of an outcome or result where the outcome or 

result can be estimated probabilistically are: 

Likelihood Terminology Likelihood of the Occurrence/Outcome 

 Virtually certain Greater than 99% probability 

 Extremely likely Greater than 95% probability 

 Very likely Greater than 90% probability 

 Likely Greater than 66% probability 

 More likely than not Greater than 50% probability 

 About as likely as not 33 to 66% probability 

 Unlikely Less than 33% probability 

 Very unlikely Less than 10% probability 

 Extremely unlikely Less than 5% probability 

 Exceptionally unlikely Less than 1% probability 

 

20 NHTSA’s qualitative discussion of these impacts also does not attempt to analyze the consequences that these 

impacts may have in terms of economic impacts stemming from the differential abilities that different populations 

may have to adapt to the consequences resulting from climate change. The ability to adapt will vary with sector, 

country, and how sudden or disruptive the impact.
4.5 Health, Societal, and Environmental Impacts of Climate Change Chapter 4 Cumulative Impacts 

4.5.3 Freshwater Resources 

In 2008, IPCC concluded that “Observational records and climate projections provide abundant 

evidence that freshwater resources are vulnerable and have the potential to be strongly impacted by 

climate change, with wide-ranging consequences for human societies and ecosystems” (Bates et al. 2008). 

In the United States, according to EPA (2009b), the vulnerability of these resources varies regionally. 

This section summarizes current global and U.S. observations of freshwater resources and the most recent 

projections of future changes. 

4.5.3.1 Affected Environment 

4.5.3.1.1 Freshwater Systems and Storage 

Without water, there would be no life on Earth. Climate change implications for water resources 

are therefore of fundamental interest. As seen in Figure 4.5.3-1, water covers about 70 percent of Earth’s 

surface, and most of this water (97.5 percent) is contained in the oceans. The remaining 2.5 percent is 

fresh water, most of which (68.7 percent) is ice and permanent snow cover in the Antarctic, the Arctic, 

and mountainous regions. Another 29.9 percent is fresh groundwater. Only 0.26 percent of the total 

amount of fresh water is contained in lakes, reservoirs, and river systems (UNESCO 2003). 

Figure 4.5.3-1. Global Allocation of Water 

The largest volume of fresh water is stored in the cryosphere, and consists of snow, glaciers, ice, 

and frozen ground. Most glaciers and ice sheets are found in Antarctica (almost 90 percent), with the 

remainder found in Greenland (almost 10 percent) and in mountain glaciers. Permafrost extends over 

northeastern Europe and the northern and northeastern parts of Asia, including the Arctic islands, northern 

Canada, the fringes of Greenland and Antarctica, and the high-altitude areas of South America (UNESCO 

2003). 

Groundwater occurs in the pores of soils and fractures of rocks and is the second largest source of 

fresh water. Groundwater feeds springs, streams, and lakes; supports wetlands; and is a critical source of 

water for human consumption. Groundwater also includes aquifers, underground strata of water-bearing 

permeable rock or unconsolidated materials (sand, gravel, and some silts and clays) from which water is 

extracted by well systems (UNESCO 2003). 

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Chapter 4 Cumulative Impacts 4.5 Health, Societal, and Environmental Impacts of Climate Change 

Lakes, which can be broadly defined as bodies of water collected in depressions in Earth’s 

surface, are widespread and numerous (there are approximately 15 million) and store the largest volume 

of fresh surface waters. Reservoirs – human-made lakes – are constructed for the storage of water, and 

are typically created by damming a river channel in a valley (UNESCO 2003). 

Rivers are bodies of flowing water that drain surface runoff from land to the seas and oceans. 

They begin in higher elevations such as mountains and hills where rainwater and snowmelt collect, 

forming small tributary streams that flow into larger streams and rivers (UNESCO 2003). 

4.5.3.1.2 Non-climate Threats to Freshwater Resources 

Freshwater resources during recent decades are threatened by non-climatic and climatic drivers. 

The non-climate threats include population growth and economic development, which create increasing 

demands for water from the residential, industrial, municipal, and agricultural sectors. In particular, 

irrigation of agricultural lands accounts for nearly 70 percent of global freshwater withdrawals and for 

more than 90 percent of global consumptive use (Bates et al. 2008). The extent of irrigated areas, which 

is expected to expand in areas that are already water-stressed, will determine the effect that this use will 

have on global water use in the future (EPA 2009b, Bates et al. 2008, Kundzewicz et al. 2007a). 

Other pressures on freshwater resources include infrastructure development (dams, dikes, levees, 

and river diversions); poor land use (urbanization, conversion to crop or grazing lands, wetland removal 

or reduction, and deforestation); overexploitation (groundwater aquifer depletion and reduced water levels 

in lakes, rivers, and wetlands); water pollution from industrial, municipal, and agricultural sources 

(pathogens and microbial contaminants, pesticides, phosphorus and nitrogen from fertilizers, heavy 

metals, toxic organic compounds and microorganic pollutants); silt and suspended particles (from soil 

erosion); acidification (from air pollution); and thermal pollution (from industrial discharges and slow 

flows caused by dams and reservoirs) (EPA 2009b, Bates et al. 2008, Kundzewicz et al. 2007a). 

4.5.3.2 Environmental Consequences 

Although there will be water-supply increases in some areas and decreases in others, there will be 

an overall net negative impact of climate change on water resources and freshwater ecosystems 

worldwide. The effects of climate change on freshwater resources will exacerbate the impacts of other 

stressors, such as increases in population growth, economic activity, land-use change, and urbanization. 

In some areas, including regions as diverse as the Rhine basin, southeastern Michigan, Pennsylvania, and 

central Ethiopia, models project that land-use change will have a small effect compared to climate change 

(Kundzewicz et al. 2007a). 

Areas in which runoff is projected to decline are likely to face a reduction in the value of the 

services provided by freshwater resources. The beneficial impacts of increased annual runoff in other 

areas will be offset to some extent by the negative effects of increased precipitation variability and 

seasonal runoff shifts on water supply, water quality, and flood risks (EPA 2009b). 

Chemical and microbial inputs, biogeochemical processes, water temperature, and water levels 

control water quality. Climate changes can affect water quality from increases in temperature or through 

changes in precipitation and water quantity. Negative impacts from water temperature increases include 

algal blooms, increased microbial concentrations, and out-gassing of volatile and semi-volatile 

compounds like ammonia, mercury, dioxins, and pesticides (EPA 2009b). Negative impacts on water 

quality from changes in water quantity include resuspension of bottom sediments, increased turbidity 

(suspended solids), pollutant introduction, and reduced dilution. Increased stream flow can dilute 

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4.5 Health, Societal, and Environmental Impacts of Climate Change Chapter 4 Cumulative Impacts 

pollutant concentrations or transport additional pollutants into surface-water sources, while extreme 

events – floods and droughts – generally exacerbate water quality problems (EPA 2009b). 

In general, consequences of changes in snow, ice, and frozen ground (including permafrost) 

include (Rosenzweig et al. 2007): 

• Ground instability in permafrost regions; 

• A shorter travel season for vehicles over frozen roads in the Arctic; 

• Increase in the number and size of glacial lakes in mountain regions; 

• Destabilization of moraines damming glacial lakes; 

• Changes in Arctic and Antarctic Peninsula flora and fauna; 

• Limitations on mountain sports in lower-elevation alpine areas; and 

• Changes in indigenous livelihoods in the Arctic. 

4.5.3.2.1 Observed Impacts of Climate Change on Freshwater Resources in the 

United States 

Precipitation and Stream Flow

Conditions across the United States tend to be increasingly dry from east to west. Upslope areas 

in the Cascade and coastal mountain ranges are more humid, with relatively low precipitation variability. 

The Intermountain West and Southwest are driest, and the greatest precipitation variability is in the arid 

and semi-arid West (EPA 2009b, Lettenmaier et al. 2008). Stream gauge data show increases in stream 

flow from 1939 through 1998 in the eastern United States (Mauget 2003 in Lettenmeier et al. 2008) and a 

more or less reverse pattern in the western United States (Lettenmaier et al. 2008a, National Science and 

Technology Council 2008). Stream flow in the eastern United States has increased 25 percent in the past 

60 years, and has decreased by about 2 percent per decade in the central Rocky Mountain region over the 

past century (EPA 2009b). Since 1950, stream discharge in both the Colorado and Columbia River 

Basins has decreased, while over the same period annual evapotranspiration from the conterminous 

United States increased by 55mm (2.2 inches) (Walter et al. 2004). 

The observed impacts to precipitation and streamflow also include: 

• In regions with winter snow, warming has shifted the magnitude and timing of hydrologic 

events (Mote et al. 2005, Regonda et al. 2005, Stewart et al. 2005 in National Science and 

Technology Council 2008). From 1949 to 2004, the fraction of annual precipitation falling as 

rain (rather than snow) increased at 74 percent of the weather stations studied in the western 

mountains of the United States (EPA 2009b). 

• Streamflow peaks in the snowmelt-dominated western mountains of the United States 

occurred 1 to 4 weeks earlier in 2002 than in 1948 (Stewart et al. 2005 in National Science 

and Technology Council 2008). 

• Precipitation in the Arctic has increased 8 percent on average over the past century. Much of 

that increase has occurred as rain (EPA 2009b). 

Precipitation variability and subsequent surface-water availability vary regionally across the 

United States depending on a catchment’s (watershed) physical, hydrological, and geological 

characteristics (National Science and Technology Council 2008). EPA has identified the Great Lakes, 

Chesapeake Bay, Gulf of Mexico, and Columbia River Basin as large water bodies for which climate 

change is a particular concern (EPA 2009b). 

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Chapter 4 Cumulative Impacts 4.5 Health, Societal, and Environmental Impacts of Climate Change 

The IPCC Fourth Assessment Report summarized the current precipitation and water supply 

trends in the United States as follows (EPA 2009b): 

• Annual precipitation has increased throughout most of North America. 

• Stream flow has increased in the eastern United States in the last 60 years, but has decreased 

in the central Rocky Mountain region over the last century. 

• Since 1950, stream discharge in both the Colorado and Columbia River basins has decreased. 

• In regions with winter snow, warming has shifted the magnitude and timing of hydrologic 

events. 

• The fraction of annual precipitation falling as rain (rather than snow) increased at 74 percent 

of the weather stations studied in the western mountains of the United States from 1949 

through 2004. 

Snow Cover

There is a trend toward reduced mountain snowpack and earlier spring snowmelt runoff peaks 

across much of the western United States. Evidence suggests this trend is very likely attributable, at least 

in part, to long-term warming, although decadal-scale variability, including a shift in Pacific Decadal 

Oscillation (PDO) in the 1970s, might have played some part. Where shifts to earlier snowmelt peaks and 

reduced summer and fall low flows have already been detected, continuing shifts in this direction are 

expected and could have substantial impacts on the performance of reservoir systems (EPA 2009b). 

Snowpack in the mountainous headwater regions of the western United States generally declined 

over the second half of the 20th Century, especially at lower elevations and in locations where average 

winter temperatures are close to or above 0o

C (32 °F). These trends toward reduced winter snow 

accumulation and earlier spring melt are also reflected in a tendency toward earlier runoff peaks in spring, 

a shift that has not occurred in rainfall-dominated watersheds in the same region (Lettenmaier et al. 2008b 

in National Science and Technology Council 2008). 

Spring and summer snow cover has decreased in the western United States (Groisman et al.

2004). April snow water equivalent has declined 15 to 30 percent since 1950 in the western mountains of 

North America, particularly at lower elevations and primarily due to warming rather than changes in 

precipitation (Mote et al. 2003, 2005 and Lemke et al. 2007b, all in National Science and Technology 

Council 2008). Additionally, the break-up of river and lake ice in North America is now occurring 

earlier, with an advance of 0.2 to 12.9 days over the last century (EPA 2009b). 

Groundwater

The effects of climate on groundwater – especially groundwater recharge – is a topic that requires 

further research to determine current effects from climate change. The available literature (Vaccaro 1992, 

Loaiciga et al. 2000, Hanson and Dettinger 2005, Scibek and Allen 2006, Gurdak et al. 2007, all in 

Lettenmaier et al. 2008) implies that groundwater systems generally respond more slowly to climate 

change than do surface-water. However, a 2.5 °C (4.5 °F) or greater warming scenario is projected to 

decrease the recharge of the Ogallala aquifer region by 20 percent (EPA 2009b). 

Groundwater levels correlate most strongly with precipitation. Temperature is a more important 

factor for shallow aquifers during warm periods (National Science and Technology Council 2008). 

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4.5 Health, Societal, and Environmental Impacts of Climate Change Chapter 4 Cumulative Impacts 

Groundwater and surface water might also be affected by sea-level rise. Saltwater intrusion into 

aquifers might occur in coastal areas, and increased salinity of ground and estuary water might reduce 

freshwater availability. 

Water Quality

Chemical and microbial inputs, biogeochemical processes, water temperature, and water levels 

control water quality. Water temperature and water quantity are sensitive to climate change. However, 

pollution from land use – especially agricultural runoff, urban runoff, and thermal pollution from energy 

production – have caused most of the observed changes in water quality (National Science and 

Technology Council 2008). 

Rising water temperatures negatively affect aquatic biota, especially certain fish species such as 

salmon (Bartholow 2005, Crozier and Zabel 2006, both in Lettenmaier et al. 2008). Rising temperatures 

also affect dissolved oxygen, oxidation/reduction potentials, lake stratification, and mixing rates. 

However, the direction of climate change effects associated with water quantity on water quality is not as 

evident. Increased streamflow can dilute pollutant concentrations or transport additional pollutants into 

surface water sources. Extreme events – floods and droughts – generally exacerbate water quality 

problems. 

Extreme Events – Floods and Drought

Extreme events such as floods and drought affect freshwater resources. Climatic phenomena 

(intense/long-lasting precipitation, snowmelt, ice jams) and non-climatic phenomena (dam failure, 

landslides) can exacerbate floods and drought. 

As previously mentioned, research to date has not provided clear evidence for a climate-related 

trend in floods during past decades. However, evidence suggests that the observed increase in 

precipitation intensity and other observed climate changes could have affected floods (National Science 

and Technology Council 2008). 

There is some evidence of long-term drying and increase in drought severity and duration in the 

West and Southwest (National Science and Technology Council 2008) that is probably a result of 

decadal-scale climate variability and long-term change (EPA 2009b). 

Over-allocation and continuing competition for freshwater resources for agriculture, cities, and 

industry increases vulnerability to extended drought in North America (EPA 2009b), despite the fact that 

per-capita water consumption has declined over the past 2 decades in the United States (Lettenmaier et al.

2008a). 

4.5.3.2.2 Globally Observed Impacts of Climate Change on Freshwater Resources 

Trends associated with climate change have already been observed in various inputs, throughputs, 

and outputs to the global freshwater system, including (Kundzewicz et al. 2007a): 

• Precipitation – increasing over northern (30 degrees north) latitudes, decreasing over middle 

(10 degrees south to 30 degrees north) latitudes, increasing in intensity; 

• Stream flow – increasing in Eurasian Arctic, measurable increases or decreases in some river 

basins, earlier spring peak flows and increased winter-based flows in North America and 

Eurasia; 

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Chapter 4 Cumulative Impacts 4.5 Health, Societal, and Environmental Impacts of Climate Change 

• Evapotranspiration – increased actual evapotranspiration in some areas; 

• Lakes – warming, substantial increases and decreases in some lake levels, and reduction in 

ice cover; 

• Snow cover – decreasing in most regions; 

• Glaciers – decreasing almost everywhere; and 

• Permafrost – thawing between 0.08 inch per year (Alaska) and 1.8 inches per year (Tibetan 

plateau). 

For other anticipated changes in the freshwater system, data are often insufficient to observe a 

climate trend, especially when compared to the non-climatic pressures mentioned previously. The lack of 

an observed trend does not necessarily indicate a lack of sensitivity to climate change. The current 

hydrologic observing system was not designed specifically for detecting the effects of climate change on 

water resources (Lettenmaier et al. 2008a). In addition, there are large-scale climate variations, such as 

ENSO events, occurring at the same time as global and regional climate changes. For these reasons, it 

can be difficult to detect a climate change signal within the climate variability without observations of a 

decade or longer (Rosenzweig et al. 2007). 

Snow Cover and Frozen Regions

Temperature increases lead to declines in snow cover, and where most of winter precipitation 

currently falls as snow, hydrologic impact studies have shown that warming leads to changes in the 

seasonality of river flows. Areas vulnerable to these changes include the European Alps, the Himalayas, 

western North America, central North America, eastern North America, the Russian territory, 

Scandinavia, and Baltic regions (Kundzewicz et al. 2007a). 

Precipitation is also an important driver of changes in snow cover. At high elevations that remain 

below freezing in winter, precipitation increases have resulted in increased snowpack. Warmer 

temperatures at mid-elevations have decreased snowpack and led to earlier snowmelt, even with 

precipitation increases (Kundzewicz et al. 2007a). An empirical analysis of available data indicated that 

both temperature and precipitation impact mountain snowpack simultaneously, with the nature of the 

impact strongly dependent on factors such as geographic location, latitude, and elevation (Stewart 2009). 

Global warming is increasing glacier melt worldwide and decreasing snow cover in most regions. 

More than one-sixth of the world’s population lives in glacier- or snowmelt-fed river basins and will be 

affected by a seasonal shift in stream flow, an increase in the ratio of winter to annual flows, and a 

reduction in low flows caused by decreased glacier extent or snow water storage (Kundzewicz et al.

2007a). 

Glacier melt sustains many rivers during summer in the Hindu Kush Himalaya and the South 

American Andes (Singh and Kumar 1997, Mark and Seltzer 2003, Singh 2003, Barnett et al. 2005 in 

Kundzewicz et al. 2007,). The mass of some northern hemisphere glaciers is projected to decrease up to 

60 percent by 2050 (Schneeberger et al. 2003 in Kundzewicz et al. 2007). 

From 2010 to 2015, the ice cover on Siberian rivers is expected to melt 15 to 27 days sooner than 

it did from 1950 to 1979. The maximum ice cover is also expected to be 20 to 40 percent thinner 

(Vuglinsky and Gronskaya 2005 in Kundzewicz et al. 2007). 

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4.5 Health, Societal, and Environmental Impacts of Climate Change Chapter 4 Cumulative Impacts 

Permafrost is thawing in many regions, with variations among regions in the degree of thawing. 

In Alaska, permafrost is declining 0.08 inch per year, while permafrost melting is 1.8 inches per year on 

the Tibetan plateau (Kundzewicz et al. 2007a). 

Surface Waters

A recent analysis of streamflow records for 925 of the world’s largest ocean-discharging rivers 

from 1948 through 2004 indicated significant trends for about one-third of the top 200 rivers. There were 

significant downward trends in annual streamflow in low- and mid-altitude regions, consistent with the 

general drying trend over global lands for the past half-century, whereas there was a large upward trend 

for annual discharge into the Arctic Ocean. The data also indicated that ENSO events are important for 

rivers discharging into the Atlantic, Pacific, Indian and global oceans as a whole, but not for the Arctic 

Ocean and the Mediterranean and Black Seas. Significantly, the effect of human activities on annual 

stream flow and streamflow trends was found to be small for most of the world’s large rivers compared to 

the influence of climate change (Dai et al. 2009). 

Climate models consistently project precipitation increases in high latitudes and parts of the 

tropics, and decreases in lower mid-latitude regions (Milly et al. 2005c, Nohara et al. 2006 in Ebi et al.

2008). Projections for the area in between remain highly uncertain (Kundzewicz et al. 2007a). Data from 

24 climate model runs generated by 12 different general circulation models generally agreed that by 2050 

annual average river runoff and water availability will increase by 10 to 40 percent at high latitudes 

(North America, Eurasia) and in some wet tropical areas, and decrease by 10 to 30 percent over some dry 

regions at mid-latitudes and in the dry tropics (Milly et al. 2005a). 

Semi-arid and arid areas are particularly vulnerable to precipitation declines. Many of these areas 

are water stressed, including the Mediterranean, southern Africa, and northeastern Brazil. In southeastern 

Australia and southern India, climate change has the potential to exacerbate reductions in runoff caused 

by forestation (Bates et al. 2008, Kundzewicz et al. 2007a). 

In snow-dominated basins, where most precipitation occurs in winter in the form of snow, it is 

projected that winter snows will be reduced and snowmelt will occur earlier, resulting in reduced spring 

runoff and summer flows (Bates et al. 2008). Projections for rain-fed basins describe higher flows in the 

peak-flow season, with either lower flows in low-flow seasons or extended dry periods (Kundzewicz et 

al. 2007a). 

Water Quality

A brief overview of the effects of climate change on the availability and quality of drinking water 

is provided by Epstein et al. (2005). Many countries are experiencing water-quality issues in their water 

and wastewater treatment plants. Increased filtration is required in drinking water plants to address 

microorganism outbreaks following intense rain, thus increasing some operating costs by 20 to 30 percent 

(AWWA 2006 in Kundzewicz 2007). Other stressors on water quality noted by the IPCC include 

(Kundzewicz et al. 2007a): 

• More water impoundments for hydropower (Kennish 2002 in Kundzewicz et al. 2007, 

Environment Canada 2004 in Fischlin et al. 2007); 

• Stormwater drainage operation and sewage disposal disturbances in coastal areas resulting 

from sea-level rise (Haines et al. 2000); 

• Increasing water withdrawals from low-quality sources; 

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Chapter 4 Cumulative Impacts 4.5 Health, Societal, and Environmental Impacts of Climate Change 

• Greater pollutant loads resulting from increased infiltration rates to aquifers or higher runoff 

to surface waters (resulting from high precipitation); 

• Water infrastructure malfunctioning during floods (GEO-LAC 2003); and 

• Increased amounts of polluted storm water. 

Higher water temperatures, increased precipitation intensity, and longer periods of low flows 

exacerbate existing water pollution, with impacts on ecosystems, human health, water system reliability, 

and operating costs. Pollutants include sediments, nutrients, dissolved organic carbon, pathogens, 

pesticides, salt, and thermal pollution. Rising temperatures also have adverse effects on dissolved oxygen 

levels, oxidation/reduction potentials, and lake stratification and mixing rates (EPA 2009b, Kundzewicz 

et al. 2007a). 

4.5.3.2.3 Projected Impacts of Climate Change on Freshwater Resources in the 

United States 

Most freshwater resource analyses are keyed either to climate scenarios (what happens if 

temperature increases by 6 °F and precipitation declines by 10 percent) or to global climate model outputs 

pegged to IPCC-reported emission scenarios. This section summarizes the projected impacts resulting 

from such analyses, current sensitivities, and potential vulnerabilities (including extreme events). 

The climate-change impacts on freshwater resources in the United States are described by 

National Science and Technology Council (2008), Lettenmaier et al. (2008a), and Field et al. (2007a). 

“In regards to the hydrologic observing systems on which these sections are based, Lettenmaier et al.

(2008a) found that the current hydrologic observing system was not designed specifically for the purpose 

of detecting the effects of climate change on water resources. In many cases, the resulting data are unable 

to meet the predictive challenges of a rapidly changing climate” (National Science and Technology 

Council 2008). 

Precipitation

Recent climate model simulations reported by the IPCC indicate that, in general, current patterns 

will continue, with increases in runoff over the eastern United States, gradually transitioning to little 

change in the Missouri and lower Mississippi, to substantial decreases in annual runoff in the interior 

West (Colorado and Great Basin) (Bates et al. 2008, Kundzewicz et al. 2007a). Many areas in the 

western and southwestern United States already stressed are expected to suffer from additional decreases 

in precipitation and runoff from future climate changes (EPA 2009b). In eastern North America, 

meanwhile, precipitation may increase. Under a mid-range scenario, daily precipitation so heavy that it 

now occurs only every 20 years is likely to occur every 8 years by 2100 (EPA 2009b). 

Additionally, several recent state and regional studies have examined specific climate-change 

impacts on freshwater resources. For example, many impacts on freshwater resources described above 

have been projected for New Jersey (EPA 1997). “Projections for the western mountains of the United 

States suggest that warming, and changes in the form, timing, and amount of precipitation will very likely

lead to earlier melting and significant reductions in snowpack by the middle of the 21st Century (high 

confidence). In mountainous snowmelt-dominated watersheds, projections suggest advances in the timing 

of snowmelt runoff, increases in winter and early spring flows (raising flooding potential), and 

substantially decreased summer flows. Heavily utilized water systems of the western United States that 

rely on capturing snowmelt runoff, such as the Columbia River system, will be especially vulnerable” 

(Field et al. 2007b in National Science and Technology Council 2008). 

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Although uncertainties in climate model projections of precipitation changes make future 

projections of stream flow uncertain, watersheds dominated by spring and summer snowmelt are an 

exception. In mountainous snowmelt-dominated watersheds, projections suggest advances in the timing 

of snowmelt runoff, increases in winter and early spring flows (raising flooding potential), and 

substantially decreased summer flows (Stewart 2009). 

Snowpack

Trends in declining snowpack are perhaps best illustrated from studies conducted for California. 

Reduced snowpack has been identified as a major concern for the State (California Energy Commission 

2006 in National Science and Technology Council 2008). Several authors anticipate a coming crisis in 

water supply for the western United States (Barnett et al. 2008), and have projected that Lake Mead (on 

the Colorado River system) might go dry (Barnett and Pierce 2008 in CCSP 2008). While these studies 

focus on issues already identified in the literature, their findings suggest that freshwater resources might 

be more sensitive to climate change than previously projected. A recent article by Rauscher et al. (2008) 

used a high-resolution nested climate model to investigate future changes in snowmelt-driven runoff over 

the western United States and modeled increases in seasonal temperature of approximately 3 to 5 °C (5.4 

to 9 °F) by 2100, which could cause snowmelt-driven runoff to occur as much as 2 months earlier than at 

present – twice as early as other projections – affecting reservoir water storage and hydroelectric 

generation, and impacting land use, agriculture, and water management. 

In the western United States, where water supplies are already strained, continuing shifts toward 

drier conditions will have significant implications for water supplies and water management (Brekke et 

al. 2009, Lettenmaier et al. 2008a). Projections for the western mountains of the United States suggest 

that warming, and changes in the form, timing, and amount of precipitation will very likely lead to earlier 

melting and significant reductions in snowpack by the middle of the 21st Century. Heavily utilized water 

systems of the western United States that rely on capturing snowmelt runoff, such as the Columbia River 

system, will be especially vulnerable (EPA 2009b). 

Snowpack is also decreasing in Alaska. Snow cover in that area is expected to decrease 10 to 20 

percent by the 2070s (EPA 2009b). 

Groundwater

Future groundwater supplies will depend on both climate-related changes in recharge rates and 

withdrawals for human uses. Many parts of the United States depend on groundwater supplies for 

drinking water, irrigating agriculture, and a variety of residential uses, and increased demands due to 

population growth, increased temperature, and reduced precipitation could draw down groundwater 

supplies faster than it can be recharged (GCRP 2009). In arid and semi-arid regions, groundwater 

supplies are more vulnerable than elsewhere, and in some areas it might not be possible to rely on 

groundwater to make up declines in surface-water supplies resulting from climate change and other 

stressors. Projections for the Ogallala aquifer, for example, indicate a 20 percent decrease in groundwater 

recharge based on simulations of future warming using a number of different climate models (EPA 

2009b). 

Water Quality

Climate change will make achieving existing water quality goals more difficult. Historically, 

agricultural runoff, urban runoff, and thermal pollution from energy production have caused most of the 

observed changes in water quality in the United States (Kundzewicz et al. 2007a, The National Science 

and Technology Council 2008). EPA cites siltation, excess nutrients, and metals (e.g., mercury) as the 

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main pollutants in U.S. waters, primarily because of nonpoint source pollution from runoff from urban 

and agricultural lands (EPA 2000, EPA 2007). 

Based on simulations, phosphorus remediation targets for the Bay of Quinte (Lake Ontario) and 

the surrounding watershed could be compromised as 5.4 to 7.2 °F warmer water temperatures contribute 

to 77 to 98 percent increases in summer phosphorus concentrations in the Bay (Nicholls 1999, in National 

Science and Technology Council 2008), and as changes in precipitation, streamflow, and erosion lead to 

increases in average phosphorus concentrations in streams of 25 to 35 percent (Walker 2001 in Field et al.

2007). 

Projected impacts on water quality also include (National Science and Technology Council 

2008): 

• Changes in precipitation could increase nitrogen loads from rivers in the Chesapeake and 

Delaware Bay regions by up to 50 percent by 2030 (Kundzewicz et al. 2007a). 

• Decreases in snow cover and increases in winter rain on bare soil will likely lengthen the 

erosion season and enhance erosion intensity. This will increase the potential for sedimentrelated water quality impacts in agricultural areas (Field et al. 2007a). 

• Increased precipitation amounts and intensities will lead to greater rates of erosion in the 

United States and in other regions unless protection measures are taken (Kundzewicz et al.

2007a). Soil-management practices (crop residue, no-till) in some regions (e.g., the Corn 

Belt) might not provide sufficient erosion protection against future intense precipitation and 

associated runoff (Field et al. 2007a). 

• For the Midwest, simulations project that the low flows used to develop pollutant discharge 

limits (Total Maximum Daily Loads) would decrease by more than 60 percent were there to 

be a 25 percent decrease in mean precipitation; adding on irrigation demand, the effective 

decline is projected to reach 100 percent (Eheart et al. 1999 in National Science and 

Technology Council 2008). 

• Based on simulations, phosphorus remediation targets for the Bay of Quinte (Lake Ontario) 

and the surrounding watershed could be compromised as 5.4 to 7.2 °F warmer water 

temperatures contribute to 77 to 98 percent increases in summer phosphorus concentrations in 

the Bay (Nicholls 1999 in National Science and Technology Council 2008), and as changes in 

precipitation, streamflow, and erosion lead to increases in average phosphorus concentrations 

in streams of 25 to 35 percent (Walker 2001 in Field et al. 2007). 

Kundzewicz et al. (2007a) also concluded (high confidence) that climate change is likely to make 

achieving existing water quality goals for North America more difficult (National Science and 

Technology Council 2008). 

Extreme Events – Floods and Drought

Climate change is expected to increase the frequency and intensity of extreme events such as 

floods and drought. Research to date has not provided clear evidence for a climate-related trend in floods 

in the United States during past decades. However, evidence suggests that the observed increase in 

precipitation intensity and other observed climate changes could have affected floods (National Science 

and Technology Council 2008). Climatic phenomena (intense/long-lasting precipitation, snowmelt, ice 

jams) and non-climatic phenomena (dam failure, landslides) can exacerbate floods and droughts. In the 

United States, the frequency of heavy precipitation events was at a minimum in the 1920s and 1930s, and 

then increased during most of the rest of the 20th Century (Field et al. 2007a). 

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Because the intensity and mean amount of precipitation is projected to increase across the United 

States at middle and high latitudes, the risk of flash flooding and urban flooding will increase in these 

areas (EPA 2009b). At the same time, greater temporal variability in precipitation increases the risk of 

drought (Christensen et al. 2007a). There is some evidence of long-term drying and increase in drought 

severity and duration in the West and Southwest (National Science and Technology Council 2008) that is 

probably a result of decadal-scale climate variability and long-term change (EPA 2009b). 

Water Availability and Water Use

Regionally, the IPCC concluded that large changes in irrigation water demand are likely due to 

climate change (Kundzewicz et al. 2007a). Irrigation continues to be the largest use of water, accounting 

for 70 percent of global water use and 90 percent of consumptive use. Over-allocation and continuing 

competition for freshwater resources for agriculture, cities, and industry increases vulnerability to climate 

changes. Federal agencies have identified a number of areas, mostly in the western half of the United 

States, where there could be conflicts over growing water shortages in a changing climate (U.S. DOI 

2005, Brekke et al. 2009). For example, in southern California, 41 percent of the water supply will be 

vulnerable by the 2020s due to loss of snowpack in the Sierra Nevada and Colorado River Basin (EPA 

2009b). 

4.5.3.2.4 Projected Impacts of Climate Change on Global Freshwater Resources 

The IPCC report is the most recent, comprehensive, and peer-reviewed summary of impacts on 

global freshwater resources available. Kundzewicz et al. (2007a) summarized the conclusions from the 

freshwater resources and management chapter as follows: 

• The impacts of climate change on freshwater systems and their management are mainly due 

to the observed and projected increases in temperature, sea level, and precipitation variability 

(very high confidence). 

• More than one-sixth of the world’s population lives in glacier- or snowmelt-fed river basins 

and will be affected by the seasonal shift in streamflow, an increase in the ratio of winter to 

annual flows, and possibly the reduction in low flows caused by decreased glacier extent or 

snow-water storage (high confidence). 

• Sea-level rise will extend areas of salinization of groundwater and estuaries, resulting in a 

decrease in freshwater availability for humans and ecosystems in coastal areas (very high 

confidence). 

• Increased precipitation intensity and variability is projected to increase the risks of flooding 

and drought in many areas (high confidence). 

• Semi-arid and arid areas are particularly exposed to the impacts of climate change on 

freshwater (high confidence). 

• Many of these areas (Mediterranean basin, western United States, southern Africa, and 

northeastern Brazil) will suffer a decrease in water resources due to climate change (very high 

confidence). 

• Efforts to offset declining surface-water availability due to increasing precipitation variability 

will be hampered by the fact that groundwater recharge will decrease considerably in some 

already water-stressed regions (high confidence), where vulnerability is often exacerbated by 

the rapid increase in population and water demand (very high confidence). 

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• Higher water temperatures, increased precipitation intensity, and longer periods of low flows 

exacerbate many forms of water pollution, with impacts on ecosystems, human health, watersystem reliability, and operating costs (high confidence). 

• These pollutants include sediments, nutrients, dissolved organic carbon, pathogens, 

pesticides, salt, and thermal pollution. 

• Climate change affects the function and operation of existing water infrastructure and water 

management practices (very high confidence). 

• Adverse effects of climate on freshwater systems aggravate the impacts of other stresses, 

such as population growth, changing economic activity, land use change, and urbanization 

(very high confidence). 

• Globally, water demand will grow in the coming decades, primarily due to population growth 

and increased affluence; regionally, large changes in irrigation water demand as a result of 

climate change are likely (high confidence). 

• Current water management practices are very likely to be inadequate to reduce the negative 

impacts of climate change on water supply reliability, flood risk, health, energy, and aquatic 

ecosystems (very high confidence). 

• Improved incorporation of current climate variability into water-related management would 

make adaptation to future climate change easier (very high confidence). 

• Adaptation procedures and risk management practices for the water sector are being 

developed in some countries and regions (the Caribbean, Canada, Australia, Netherlands, 

United Kingdom, United States, and Germany) that have recognized projected hydrological 

changes with related uncertainties (very high confidence). 

• Since the IPCC Third Assessment, uncertainties have been evaluated, their interpretation has 

improved, and new methods (e.g., ensemble-based approaches) are being developed for their 

characterization (very high confidence). 

• Nevertheless, quantitative projections of changes in precipitation, river flows, and water 

levels at the river-basin scale remain uncertain (very high confidence). 

• The negative impacts of climate change on freshwater systems outweigh its benefits (high 

confidence). 

• All IPCC regions (see Chapters 3 through 16 of the IPCC report) show an overall net 

negative impact of climate change on water resources and freshwater ecosystems (high 

confidence). 

• Areas in which runoff is projected to decline are likely to face a reduction in the value of the 

services provided by water resources (very high confidence). 

• The beneficial impacts of increased annual runoff in other areas will be tempered by the 

negative effects of increased precipitation variability and seasonal runoff shifts on water 

supply, water quality, and flood risks (high confidence). 

Observed global climate-related trends affecting freshwater resources were identified previously. 

The following discussion identifies key projected impacts to surface waters, groundwater, extreme events, 

and water quality. 

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Surface Water

Data from 24 climate model runs generated by 12 different general circulation models (Milly et 

al. 2005b in Kundzewicz et al. 2007) generally agreed that by 2050: 

• Annual average river runoff and water availability will increase by 10 to 40 percent at high 

latitudes (North America, Eurasia) and in some wet tropical areas. 

• Annual average river runoff and water availability will decrease by 10 to 30 percent over 

some dry regions at mid-latitudes and in the dry tropics, some of which are presently waterstressed areas (Mediterranean, southern Africa, and western United States/northern Mexico). 

Hydrological impact studies have shown that warming leads to changes in the seasonality of river 

flows where much winter precipitation currently falls as snow, including the European Alps, the 

Himalayas, western North America, central North America, eastern North America, the Russian territory, 

Scandinavia, and Baltic regions. Winter flows will increase, summer flows will decrease, and peak flow 

will occur at least 1 month earlier in many cases (Kundzewicz et al. 2007a). 

Higher temperatures increase glacier melt. Glacier melt sustains many rivers during summer in 

the Hindu Kush Himalaya and the South American Andes (Singh and Kumar 1997, Mark and Seltzer 

2003, Singh 2003, Barnett et al. 2005, all in Kundzewicz et al. 2007). The mass of some northern 

hemisphere glaciers is projected to decrease up to 60 percent by 2050 (Schneeberger et al. 2003 in 

Kundzewicz et al. 2007). 

Projections for rain-fed basins describe higher flows in peak-flow season with either lower flows 

in low-flow season or extended dry periods (Kundzewicz et al. 2007a). 

Lake levels are determined by river and rain water inputs and evaporation outputs. By the end of 

the 21st Century, water levels are projected to change between −4.5 feet and +1.15 feet in the Great Lakes 

(Lofgren et al. 2002, Schwartz et al. 2004, both in Kundzewicz et al. 2007) and to drop about 29.5 feet in 

the Caspian Sea (Elguindi and Giorgi 2006 in Kundzewicz et al. 2007). 

From 2010 to 2015, the ice cover on Siberian rivers is expected to melt 15 to 27 days sooner than 

it did from 1950 to 1979. The maximum ice cover is also expected to be 20 to 40 percent thinner 

(Vuglinsky and Gronskaya 2005 in Kundzewicz et al. 2007). 

A combination of land-use changes and climate change could affect annual runoff. Land-use 

changes are projected by model studies to have a small effect compared to climate change in the Rhine 

basin, southeastern Michigan, Pennsylvania, and central Ethiopia. In southeastern Australia and southern 

India, projections are comparable, with climate change having the potential to exacerbate reductions in 

runoff caused by afforestation (Kundzewicz et al. 2007a). 

Evapotranspiration (water loss from plant leaves) responds to increases in carbon dioxide in two 

distinct ways. First, higher CO2 concentrations cause leaf stomata to close, reducing evapotranspiration. 

Second, CO2 fertilization encourages plant growth, increasing total leaf area and subsequent 

evapotranspiration. Considering these vegetation effects, global mean runoff has been projected to 

increase by 5 percent for a doubling of CO2 concentration (Betts et al. 2007, Leipprand and Gerten 2006, 

both in Kundzewicz et al. 2007) compared to a 5 to 17 percent increase under climate change alone 

(Kundzewicz et al. 2007a). 

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Chapter 4 Cumulative Impacts 4.5 Health, Societal, and Environmental Impacts of Climate Change 

 Small islands are especially vulnerable to future change in water availability. Most small islands 

already have limited availability of freshwater, and changes in their hydrologic cycle can pose serious 

threats for their water supply (EPA 2009b). 

Groundwater

Climate change will mainly affect groundwater recharge rates, although very little research has 

been done on the issue. Groundwater levels could change as a result of thawing permafrost, vegetation 

changes, changes in river level (where hydraulic connection is adequate), and changes in floods. Global 

hydrological models project that globally averaged groundwater recharge will increase less (2 percent) 

than total runoff (9 percent) in the 2050s compared to recharge and runoff rates from 1961 to 1990. In 

northeastern Brazil and southwestern Africa, and along the southern Mediterranean coast, groundwater 

recharge is projected to decrease by more than 70 percent. In contrast, recharge is projected to increase 

by more than 30 percent in the Sahel, Near East, northern China, Siberia, and the western United States 

(Döll and Flörke 2005 in Kundzewicz et al. 2007). Projected impacts on individual aquifers return very 

site-specific results. 

Any decrease in groundwater recharge will exacerbate the effect of saltwater intrusion. Saltwater 

intrusion has been projected for a sea-level rise of 0.33 foot on two coral islands off the Indian coast – the 

thickness of the freshwater lens decreasing from 82 feet to 32 feet and from 118 feet to 92 feet (Bobba et 

al. 2000 in Kundzewicz et al. 2007). Saltwater intrusion from sea-level rise might also affect 

groundwater/aquifer water supplies on similar small islands. 

Some areas might try to offset decreases in surface water availability by increasing withdrawals 

of groundwater. However, decreases in groundwater discharge will hamper such efforts (EPA 2009b). 

Extreme Events – Floods and Droughts

Increased precipitation intensity and variability are projected to increase the risks of flooding and 

drought in many areas, and extreme floods and extreme droughts are projected to become more frequent 

(EPA 2009b). The proportion of total rainfall from heavy precipitation events is likely to increase over 

most areas, particularly in tropical and high-latitude regions, while droughts are expected to increase in 

subtropical and mid-latitude regions. Precipitation changes between these regions are uncertain (Bates et 

al. 2008). More floods are projected for northern and northeastern Europe, while more drought is 

projected for southern and southeastern Europe (Lehner et al. 2005 in Kundzewicz et al. 2007). 

Projections of climate-change impacts on flood magnitude and frequency can be both positive 

and negative, depending on the global climate model used, snowmelt contributions, catchment 

characteristics, and location (Reynard et al. 2004 in Kundzewicz et al. 2007). Up to 20 percent of the 

world’s population lives in river basins at risk from increased flooding (Kleinen and Petschel-Held 2007 

in Kundzewicz et al. 2007). The area flooded in Bangladesh is projected to increase by 23 to 29 percent 

with a global temperature rise of 3.6 °F (Mirza 2003 in Kundzewicz et al. 2007). 

A recent study by Allen and Soden (2008) using a combination of satellite observations and 

model simulations showed a link between rainfall extremes and temperature. The observed amplification 

of rainfall extremes was larger than other model projections, leading the authors to infer that “projections 

of future changes in rainfall extremes due to anthropogenic global warming may be underestimated.” 

Globally, it is projected that by the 2090s, there will be an increase in drought-affected areas, 

with the land area in extreme drought at a given time expected to be ten times what it is today (Bates et al. 

2008, Kundzewicz et al. 2007a). By the 2090s, the proportion of the total land surface in extreme drought 

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4.5 Health, Societal, and Environmental Impacts of Climate Change Chapter 4 Cumulative Impacts 

is projected to increase ten-fold, from the current rate of 1 to 3 percent to 30 percent; extreme drought 

events per 100 years are projected to double; and mean drought duration is projected to increase by a 

factor of six (Burke et al. 2006a in Kundzewicz et al. 2007). 

Water Quality

Higher water temperatures and runoff variations are likely to affect water quality negatively (Patz 

2001, Lehman 2002, O’Reilly et al. 2003, Hurd et al. 2004, all in Kundzewicz et al. 2007). Negative 

impacts on water quality from changes in water quantity include resuspension of bottom sediments, 

increased turbidity (suspended solids), pollutant introduction, and reduced dilution. Negative impacts 

from water temperature include algal blooms, increased microbial concentrations, and out-gassing of 

volatile and semi-volatile compounds like ammonia, mercury, dioxins, and pesticides (Kundzewicz et al.

2007a). 

Acidic atmospheric deposition is projected to increase acidification in rivers and lakes (Ferrier 

and Edwards 2002, Gilvear et al. 2002, Soulsby et al. 2002, all in Kundzewicz et al. 2007a). 

Salt concentration is expected to increase in estuaries and inland reaches under decreasing 

streamflows. For example, salinity is projected to increase in the tributary rivers above irrigation areas in 

Australia’s Murray-Darling Basin by 13 to 19 percent by 2050 and by 21 to 72 percent by 2100 

(Kundzewicz et al. 2007a). 

No quantitative studies projecting the impact of climate change on microbiological water quality 

for developing countries are cited by the IPCC. However, climate change will be an additional stressor 

affecting water quality and public health. Potential impacts include increased waterborne disease with 

increases in extreme rainfall, and great incidence of diarrheal and water-related diseases in regions with 

increased drought (Kundzewicz et al. 2007a). A brief overview of the effects of climate change on the 

availability and quality of drinking water is provided by Epstein et al. (2005). 

Developed countries are also experiencing water-quality issues in their water and wastewater 

treatment plants. Increased filtration is required in drinking water plants to address microorganism 

outbreaks following intense rain, thus increasing some operating costs by 20 to 30 percent (AWWA 2006 

in Kundzewicz et al. 2007a). Other stressors on water quality include (Kundzewicz et al. 2007a): 

• More water impoundments for hydropower (Kennish 2002 in Kundzewicz et al. 2007, 

Environment Canada 2004 in Fischlin et al. 2007); 

• Stormwater drainage operation and sewage disposal disturbances in coastal areas resulting 

from sea-level rise (Haines et al. 2000); 

• Increasing water withdrawals from low-quality sources; 

• Greater pollutant loads resulting from increased infiltration rates to aquifers or higher runoff 

to surface waters (resulting from high precipitation); 

• Water infrastructure malfunctioning during floods (GEO-LAC 2003); and 

• Increased amounts of polluted storm water. 

In many regions, there is no alternative supply even as water quality declines, and reusing 

wastewater (e.g., to irrigate crops) can introduce other public health problems. 

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4.5.4 Terrestrial and Freshwater Ecosystems 

This section addresses climate-related impacts on terrestrial and freshwater ecosystems, including 

non-coastal wetlands. An ecosystem is defined as a complex of biological communities (plants, animals, 

and microorganisms) and their non-living environments, which act together as a unit (MA 2005c in 

Lettenmeier et al. 2008 and MA 2005b in Fischlin et al. 2007). By definition, relationships within an 

ecosystem are strong, while relationships with components outside the ecosystem boundaries are weak 

(MA 2005b in Fischlin et al. 2007). Ecosystems are critical, in part, because they supply humans with 

services that sustain life and are beneficial to the functioning of society (Fischlin et al. 2007). 

In addition to anthropogenic stressors, such as extraction of natural resources and changes in land 

use (Bush et al. 2004 in Fischlin et al. 2007), climate change poses a threat to the wellbeing of 

ecosystems. Many terrestrial and freshwater ecosystems have demonstrated resilience to historical 

changes in climate; however, their ability to maintain resilience in response to more rapid and profound 

changes in climate, such as those expected to occur over the next century, is uncertain (Chapin et al. 

2004, Jump and Peñuelas 2005, both in Fischlin et al. 2007). Projected climate change and other 

ecosystem stressors generated by humans in the next century are “virtually certain to be unprecedented” 

(Forster et al. 2007 in Fischlin et al. 2007). While some climate-change impacts are expected to 

exacerbate existing ecosystem stressors, others represent entirely new stressors. For example, increasing 

surface temperatures or changes in snow cover will sometimes result in a mismatch in timing between 

predators and their prey, constraining the ability of populations to sustain themselves via a limited food 

supply (EPA 2009b, UNEP 2006). Impacts projected for species biodiversity “are significant and of key 

relevance, since global losses in biodiversity are irreversible (very high confidence)” (EPA 2009b). 

4.5.4.1 Affected Environment 

Earth’s biosphere is an interconnected network of individuals, populations, and interacting natural 

systems, referred to as ecosystems. Ecosystems provide society benefits such as supporting services, 

such as biodiversity, “a resource that...sustain[s] many of the goods and services that humans enjoy from 

ecosystems”; provisioning services, such as food and building/clothing materials; regulating services, 

such as the sequestration of carbon, regulation of climate and water, and protection from natural hazards 

(floods, landslides, pest regulation); and cultural services, which allow humans the opportunity to 

appreciate the aesthetics of ecosystems components (Hassan et al. 2005b in Fischlin et al. 2007). The 

focus of this section is on non-marine ecosystems only. Section 4.5.5 addresses marine and coastal 

ecosystems. 

Ecosystems addressed in this section include (EPA 2009b, EPA 2001) terrestrial communities, 

such as forests, grasslands, shrublands, savanna, and tundra; aquatic communities, such as rivers, lakes, 

and ponds; and freshwater wetlands, such as marshes, swamps, and bogs. 

4.5.4.1.1 Global Ecoregions and Ecozones 

Terrestrial Communities

The World Wildlife Fund (WWF) has developed a widely accepted classification scheme for 

global terrestrial ecosystems; the classification includes ecozones, biomes, and ecoregions. Similar to the 

classification of Miklos Udvary’s (1975) biogeographical realm, the ecozone is the biogeographic 

division of Earth's surface at the largest scale. Terrestrial ecozones follow the floral and faunal 

boundaries that separate the world's major plant and animal communities. The WWF has identified eight 

terrestrial ecozones, as indicated in Figure 4.5.4-1. 

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4.5 Health, Societal, and Environmental Impacts of Climate Change Chapter 4 Cumulative Impacts 

Figure 4.5.4-1. Terrestrial Ecozones and Biomes of the World (Source: MA 2005c in 

Lettenmeier et al. 2008)

Biomes are climatically and geographically defined areas of ecologically similar communities of 

plants, animals, and microorganisms. These habitat types are defined by factors such as plant structures, 

leaf types, plant spacing, and climate. The land classification system developed by WWF identifies 14 

major terrestrial habitat types, which can be further divided into 825 smaller, more distinct terrestrial 

ecoregions (WWF 2008a). 

The 14 primary terrestrial habitats recognized by WWF are as follows: 

• Tundra is a treeless polar desert found at high latitudes in the Polar Regions, primarily in 

Alaska, Canada, Russia, Greenland, Iceland, and Scandinavia, and sub-Antarctic islands. 

These regions are characterized by long, dry winters, months of total darkness, and extremely 

frigid temperatures. The vegetation is composed of dwarf shrubs, sedges and grasses, 

mosses, and lichens. A wide variety of animals thrive in the tundra, including herbivorous 

and carnivorous mammals and migratory birds. 

• Boreal Forests and Taiga are forests found at northerly latitudes in inland Alaska, Canada, 

Sweden, Finland, Norway, and Russia, and parts of the extreme northern continental United 

States, northern Kazakhstan, and Japan. Annual temperatures are low and precipitation 

ranges from 15 to 40 inches per year and can fall mainly as snow. Vegetation includes 

coniferous and deciduous trees, lichens, and mosses. Herbivorous mammals and small 

rodents are the predominant animal species; however, predatory birds and mammals also 

occupy this habitat type. 

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Chapter 4 Cumulative Impacts 4.5 Health, Societal, and Environmental Impacts of Climate Change 

• Temperate coniferous forests are found predominantly in areas with warm summers and cool 

winters. Plant life varies greatly across temperate coniferous forests. In some forests, 

needleleaf trees dominate, while others consist of broadleaf evergreen trees or a mix of both 

tree types. Typically, there are two vegetation layers in a temperate coniferous forest: an 

understory dominated by grasses and shrubs and an overstory of large tree species. 

• Temperate broadleaf and mixed forests experience a wide range of variability in temperature 

and precipitation. In regions where rainfall is distributed throughout the year, deciduous trees 

are mixed with evergreens. Species such as oak, beech, birch, and maple typify the tree 

composition of this habitat type. Diversity is high for plants, invertebrates, and small 

vertebrates. 

• Mediterranean forests, woodlands, and shrub ecoregions are characterized by hot and dry 

summers, while winters tend to be cool and moist. Most precipitation arrives during winter. 

Only five regions in the world experience these conditions: the Mediterranean, south-central 

and southwestern Australia, the fynbos of southern Africa, the Chilean matorral, and the 

Mediterranean ecoregions of California. These regions support a tremendous diversity of 

habitats and species. 

• Tropical and subtropical coniferous forests are found predominantly in North and Central 

America and experience low levels of precipitation and moderate variability in temperature. 

These forests are characterized by diverse species of conifers, whose needles are adapted to 

deal with the variable climate conditions. These forests are wintering ground for a variety of 

migratory birds and butterflies. 

• Tropical and subtropical moist broadleaf forests are generally found in large, discontinuous 

patches centered on the equatorial belt and between the Tropics of Cancer and Capricorn. 

They are characterized by low variability in annual temperature and high levels of rainfall. 

Forest composition is dominated by semi-evergreen and evergreen deciduous tree species. 

These forests are home to more species than any other terrestrial ecosystem. A square 

kilometer can support more than 1,000 tree species. Invertebrate diversity is extremely high, 

and dominant vertebrates include primates, snakes, large cats, amphibians, and deer. 

• Tropical and subtropical dry broadleaf forests are found in southern Mexico, southeastern 

Africa, the Lesser Sundas, central India, Indochina, Madagascar, New Caledonia, eastern 

Bolivia, central Brazil, the Caribbean, valleys of the northern Andes, and along the coasts of 

Ecuador and Peru. Deciduous trees predominate in most of these forests and they are home 

to a wide variety of wildlife, including monkeys, large cats, parrots, various rodents, and 

ground-dwelling birds. 

• Temperate grasslands, savannas, and shrublands are known as prairies in North America, 

pampas in South America, veld in southern Africa, and steppe in Asia. They differ from 

tropical grasslands in species composition and the annual temperature regime under which 

they thrive. These regions are devoid of trees, except for riparian or gallery forests associated 

with streams and rivers. Biodiversity in these habitats includes a number of large grazing 

mammals and associated predators, burrowing mammals, numerous bird species, and a 

diversity of insects. 

• Tropical and subtropical grasslands, savannas, and shrublands are found in the large 

expanses of land in the tropics that do not receive enough rainfall to support extensive tree 

cover. However, there could be great variability in soil moisture throughout the year. 

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Grasses dominate the species composition of these ecoregions, although scattered trees can be 

common. Large mammals that have evolved to take advantage of the ample forage typify the 

biodiversity associated with these habitats. 

• Montane grasslands and shrublands include high-elevation grasslands and shrublands, such 

as the puna and paramo in South America, subalpine heath in New Guinea and East Africa, 

steppes of the Tibetan plateaus, and other similar subalpine habitats around the world. 

Montane grasslands and shrublands are tropical, subtropical, and temperate. Mountain 

ecosystem services such as water purification and climate regulation extend beyond the 

geographical boundaries of the grasslands and shrublands and affect all continental mainlands 

(Woodwell 2004). Characteristic plants of these habitats display features such as rosette 

structures, waxy surfaces, and abundant pilosity (WWF 2008b). 

• Deserts and xeric shrublands across the world vary greatly with respect to precipitation and 

temperature. Generally, rainfall is less than 10 inches annually and evaporation exceeds 

precipitation. Temperature variability is also extremely diverse in these remarkable lands. 

Many deserts, such as the Sahara, are hot year-round, but others, such as Asia’s Gobi, 

become quite cold in winter. Woody-stemmed shrubs and plants evolved to minimize water 

loss characterize vegetation in these regions. Animal species are equally well-adapted to the 

dry conditions, and species are quite diverse. 

• Mangroves occur in the waterlogged, salty soils of sheltered tropical and subtropical shores, 

where they stretch from the intertidal zone to the high tide mark. Associated with these tree 

species is a whole host of aquatic and salt-tolerant plants. Mangroves provide important 

nursery habitats for a vast array of aquatic animal species. 

• Flooded grasslands and savannas are common to four continents. These vast areas support 

numerous plants and animals adapted to the unique hydrologic regimes and soil conditions. 

Large congregations of migratory and resident water birds can be found in these regions. 

Ecosystem services include breeding habitat and the buffering of inland areas from the effects 

of wave action and storms (MA 2005c in Lettenmeier et al. 2008). 

Freshwater Aquatic Communities

According to the Freshwater Ecoregions of the World (FEOW) project, although freshwater 

biodiversity is more imperiled overall than terrestrial biodiversity, conservation efforts have largely 

focused on terrestrial ecosystems. This is due, in large part, to a lack of comprehensive data on 

freshwater species distribution (FEOW 2009). FEOW has worked to identify and classify Earth’s many 

freshwater habitats into larger, more manageable groupings. From the 426 freshwater ecoregions 

identified in Abell et al. (2008), FEOW has defined 12 Major Habitat Types (MHTs), which represent 

groups of “ecoregions with similar biological, chemical, and physical characteristics and are roughly 

equivalent to biomes for terrestrial systems” (FEOW 2009). These are presented in Figure 4.5.4-2 and are 

described below. 

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Figure 4.5.4-2. Freshwater Major Habitat Types (MHTs) (Source: FEOW 2009) 

The 12 MHTs recognized by FEOW are as follows (FEOW 2009): 

• Large lakes are dominated and defined by lentic (still or standing water) systems. 

Ecosystems in this MHT include areas of in-flow and out-flow from rivers and adjacent 

wetlands in addition to the lakes themselves. These regions include large tropical, temperate, 

and polar lakes. 

• Large river deltas contain deltaic features such as those from tidal influences and their 

associated fish species, which are different from those found upstream. Regions containing 

deltaic features, but that aren’t defined by specific fish species, are not included in these 

ecoregions.

• Montane freshwaters are composed on streams, rivers, lakes or wetlands at higher elevations. 

Included are high gradient, fast-flowing streams, and complexes of higher elevation wetlands 

and lakes.

• Xeric freshwaters and endorheic (closed) basins contain freshwater systems found in arid, 

semi-arid, or sub-humid environments. They usually contain plant and animal species that 

are adapted to ephemeral regimes, intermittent flooding, or lower levels of water periodically 

throughout the year.

• Temperate coastal rivers usually contain small to medium coastal basins at middle latitudes. 

While characterized by river systems, they can also include wetlands, small lakes, and 

lagoons. Migratory animal species that live in both fresh and marine ecosystems may be 

present. Island ecoregions with these characteristics are included here.

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• Temperate upland rivers include non-floodplain rivers at middle latitudes, along with 

headwater drainages and tributaries of large rivers. These rivers typically flow over moderate 

gradients and do not flood cyclically.

• Temperate floodplain rivers and wetland complexes each contain a single large river system 

at a middle latitude, including its associated sub-basins, which are or have historically been 

cyclically flooded. These regions can contain wetland complexes with deltas, swamps, and 

marshes.

• Tropical and subtropical coastal river ecoregions contain several tropical small or medium 

coastal basins that drain into the ocean. The areas are characterized by river systems but can 

also contain lakes, lagoons, and wetlands. Islands with these characteristics are included 

here.

• Tropical and subtropical upland rivers contain non-floodplain rivers in the tropics, including 

headwater drainages and tributaries of larger rivers. These rivers flow over moderate 

gradients.

• Tropical and subtropical floodplain rivers and wetland complexes are characterized by a 

single tropical large river and include that river’s main stem drainage and its sub-basins, 

which are or have historically been cyclically flooded. Internal deltas, marshes, and swamps 

may be included in these areas.

• Polar freshwaters are high-latitude ecoregions that contain the entire drainage from the 

headwaters to the mouth of the system. The Yukon in Alaska is one example of this MHT.

• Oceanic islands include the ecoregions of one or more islands, and above high tide. The 

plant and animal species found here are freshwater, but have evolved from marine ancestors. 

Freshwater Wetlands

As the barriers between terrain and water, wetlands are typically not only rich sources of 

biodiversity, but also provide services critical to humans, such as mitigation of flooding and storm runoff, 

erosion control, and filtration of pollutants from water and sediments. The roles of particular wetlands 

vary depending on the location and main water source of the wetland. Those that are dominated by 

precipitation supply water to streams and replenish groundwater reservoirs while riparian wetlands are 

dominated by surface flow and may remove, store, or release water, nutrients, and sediments. Types of 

wetlands, excluding those associated with marine systems or estuaries (which are addressed in Section 

4.5.5), are as follows (EPA 2001): 

• Precipitation-dominated Wetlands 

− Bogs form where peat accumulates at a faster rate than it decomposes. These receive 

little to no surface water in-flow due to their elevation above surrounding areas due to the 

peat accumulation. Due to this lack of in-flow, they have low rates of primary 

productivity. The dominant plant matter in bogs, Sphagnum moss, releases organic acids, 

usually resulting in acidification of the bogs, with a pH as low as 3.0. Also found in bogs 

are evergreen trees and shrubs. This environment has produced unique plants that 

evolved to thrive in conditions that are acidic and lacks nutrients. 

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− Vernal pools are low-lying areas in grasslands and forests that are underlain by clay or 

bedrock, which acts to pool the water, rather than allowing any accumulated water to 

drain away. While covered by shallow water during some periods, they can be 

completely dry during some months of the summer and fall. 

− Playas are small, low-lying marshlike ponds that collect rainfall and storm runoff from 

surrounding areas. These form in arid regions such as the Southern Great Plains in the 

United States. 

− Prairie potholes are holes generated by past glacial events in northern North America 

that subsequently fill up with rainwater and snowmelt. The potholes contribute to 

groundwater recharge, at times. 

− Wet meadows are grasslands formed in poorly drained areas that get waterlogged after 

precipitation events, such as basins and depressions, between marshes and upland areas. 

They are often dry during summer months. 

− Wet prairies are similar to wet meadows but remain waterlogged longer than do wet 

meadows. Additionally, they receive water not only from precipitation but also from 

groundwater and intermittent streams. 

• Groundwater-dominated Wetlands 

− Fens form in low-lying areas or near slopes where groundwater meets the soil surface. 

These wetlands accumulate peat, similar to bogs, but are supplied with groundwater, 

rather than precipitation and, as such, are provided with a year-round water supply. Fens 

are typically found at higher latitudes and in previously-glaciated locations. 

• Surface Water-dominated Wetlands 

− Freshwater marshes are formed in depressions around lakes and rivers and can contain 

permanent or periodic shallow water with little or no accumulation of peat. They usually 

have the greatest biodiversity of the types of wetlands (along with tidal marshes). Much 

of a marsh’s water is from surface sources, but some is from groundwater. They are 

dominated by floating-leaf plants, such as lilies, and soft-stemmed plants like cattails. 

− Riparian forested wetlands (swamps) are linear systems formed along rivers and lakes. 

They are typically saturated during the winter while plants are dormant and 

evapotranspiration is low. During the summer, they are usually dry, except during 

periods of flooding. The pH and nutrient load of riparian wetlands vary, depending on 

the inputs, but they are almost always very productive ecosystems. Many bird and fish 

species are known to be solely dependent on riparian wetlands. 

− Tidal freshwater marshes are influenced by tides only in terms of water levels, and 

receive little, if any, saline water from the ocean. These are found upstream from 

estuarine systems and receive most water from upstream sources, with some additional 

input from storm runoff and precipitation. These marshes have very high primary 

productivity and are known for their rich biodiversity. A key function performed by tidal 

freshwater marshes is the prevention of nitrogen entering in to estuaries; they can filter 

out as much of 50 percent of the nitrogen that enters the marsh.

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4.5.4.1.2 Ecosystems in the United States 

Published in 1976, Ecoregions of the United States represented one of the first attempts to 

systematically divide the Country’s terrestrial ecosystems into more manageable regions. Subsequently, 

Bailey (1980) provided, for each region, a brief description of the dominant physical and biological 

characteristics based on land-surface form, climate, vegetation, soils, and fauna. Bailey defined four 

major domains, 12 divisions, and 30 provinces. Since then, the terrestrial ecoregions of North America 

have been further refined by the international working group of the Commission of Environmental 

Cooperation (CEC 1997). Their system divides the continent into 15 broad level I ecoregions, 52 level II 

ecoregions, and approximately 200 level III ecoregions. The level I terrestrial ecoregions present in the 

United States include tundra, taiga, northern forests, northwestern forested mountains, marine west coast 

forests, eastern temperate forests, great plains, North American deserts, Mediterranean California, 

southern semi-arid highlands, temperate sierras, and tropical humid forests (see Figure 4.5.4-3). 

Figure 4.5.4-3. Level I Ecoregions in the North America 

(Source: CEC 1997) 

 There are 50 freshwater ecoregions in the United States. These ecoregions are divided among 

eight of the 12 MHTs recognized in the FEOW project − polar freshwaters (two), temperate coastal rivers 

(12), temperate upland rivers (12), large lakes (two), temperate floodplain rivers and wetlands (seven), 

xeric freshwaters and endorheic basins (11), tropical and subtropical coastal rivers (three), and oceanic 

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Chapter 4 Cumulative Impacts 4.5 Health, Societal, and Environmental Impacts of Climate Change 

islands (one) (FEOW 2009). One of the most ecologically valuable freshwater resources in the United 

States is the Prairie Pothole Region (PPR) of the Great Plains, which falls primarily within the temperate 

floodplain rivers and wetlands MHT. This region contains as many as eight million acres of wetlands, 

providing crucial ecosystem services to the Country in addition to habitat critical to waterfowl (EPA 

2009b, CCSP 2009c). Almost 90 percent of variation in the mallard duck reproductive variability 

depends on breeding activities within the PPR (Johnson et al. 2005a). Historically, the climate of this 

area has fluctuated, sometimes between extremes such as devastating droughts and periodic flooding. 

Both ends of the climate spectrum resulted in widespread tree and grassland mortality (CCSP 2009c). 

More than 90 percent of the eastern PPR wetlands have been drained for agricultural purposes and, 

although restoration activities have been underway for more than 20 years, less than 1 percent of drained 

basins have been restored (Johnson et al. 2005a). 

The Great Lakes region is an ecologically and economically significant area that spreads across 

the northern United States and southern Canada in eastern North America. The lakes (Erie, Huron, 

Michigan, Ontario, and Superior) contain 18 percent of the world’s fresh water. They not only supply 

water to millions of people, but also are home to some of the richest ecosystems on the continent (Kling et 

al. 2003). The lakes themselves provide habitat for large populations of trout, salmon, and other popular 

game fish, while the surrounding marsh and coniferous forests sustain grey wolves, moose, peregrine 

falcons, bald eagles, and black bears. The Upper Peninsula of Michigan has a 1,700-mile shoreline and 

16,500 square miles of largely intact forests. The Peninsula contains rich populations of both aquatic and 

terrestrial species, including 300 bird species, of which 25 to 30 percent are year-round residents; the rest 

are migratory (Kling et al. 2003). 

Ecosystems are dynamic and can change naturally over time as a result of drivers such as climate 

change (natural or anthropogenic), geological processes (volcanic eruptions, earthquakes, landslides, 

erosion, stream migration), fire, disease or pest outbreaks, and evolution. All organisms modify their 

environment to some extent; however, in the past century and especially in the past 50 years, human 

population growth and technological innovations have affected ecosystems drastically (Vitousek et al.

1997). In fact, the structure of the world’s ecosystems have changed more rapidly in the second half of 

the 20th Century than in any time in recorded human history (MA 2005c in Lettenmeier et al. 2008). It is 

expected that during the course of the 21st Century, the resilience of many ecosystems is likely to be 

exceeded by anthropogenic pressures (Fischlin et al. 2007). 

4.5.4.2 Environmental Consequences 

This section discusses existing climate and non-climate related impacts that have already been 

observed, and projected impacts. Climate-change impacts are discussed globally, and with specific 

attention to impacts in the United States. The EPA Technical Support Document for Endangerment and 

Cause or Contribute Findings for Greenhouse Gases Under Section 202(a) of the Clean Air Act was 

released in 2009 (EPA 2009b), the IPCC WGI Fourth Assessment Report (Fischlin et al. 2007) was 

released in 2007, the CCSP report on climate sensitive ecosystems was released in 2008 (CCSP 2008a). 

The 2009 EPA findings and the 2007 IPCC report are the most comprehensive recent summaries of 

projected impacts of climate change. Many of the impacts discussed in this section were gathered from 

these reports, which provide analyses and discussions on both global and U.S. scales. Information about 

impacts specific to ecosystems in the United States was obtained from the EPA findings and the 2008 

CCSP report, along with information from several other recent reports. The projected impacts described 

in Sections 4.5.4.2.1 through 4.5.4.2.5 were forecast with varying degrees of certainty. Where relevant, 

the descriptions include the level of certainty as defined by IPCC. 

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4.5.4.2.1 Non-climate Threats to Terrestrial and Freshwater Ecosystems 

The Millennium Ecosystem Assessment (MA), a United Nations research project, focuses on 

identifying the current inventory and conditions of 10 categories of global ecosystems and projecting 

changes and trends into the future. 

In 2005, the MA released five technical volumes and six synthesis reports, providing a scientific 

appraisal of the condition and trends in the world’s ecosystems (terrestrial, marine, and freshwater) and 

the services they provide. From 2001 to 2005, the MA involved the work of more than 1,360 experts 

worldwide. The MA included the following conclusions regarding the current state of global ecosystems 

(MA 2005c in Lettenmeier et al. 2008): 

• Cultivated systems now cover one quarter of Earth’s terrestrial surface. More than two thirds 

of the area of two of the world’s 14 major terrestrial biomes and more than half of the area of 

four other biomes had been converted by 1990, primarily to agriculture. 

• Across a range of taxonomic groups, for most species, either the population size or range or 

both is currently declining. 

• The distribution of species on Earth is becoming more homogenous; in other words, the set of 

species in any one region of the world is becoming more similar to the set in other regions 

primarily as a result of introductions of species, both intentionally and inadvertently in 

association with increased travel and shipping. 

• The number of species on the planet is declining. Over the past few hundred years, humans 

have increased the species extinction rate by as much as 1,000 times over background rates 

typical over Earth’s history. Some 10 to 30 percent of mammal, bird, and amphibian species 

are currently threatened with extinction. 

• Only four of the 24 ecosystem services examined in this assessment have been enhanced, 

while 15 have been degraded (Hassan et al. 2005a). 

The MA concluded that biodiversity changes due to human activities were more rapid in the past 

50 years than at any time in human history. Moreover, the forces causing biodiversity loss and leading to 

changes in ecosystem services are either steady, show no evidence of declining over time, or are 

increasing in intensity. The MA examined four plausible future scenarios and projected that the rates of 

biodiversity change will continue or accelerate (MA 2005c in Lettenmeier et al. 2008). The changes in 

ecosystems identified in the MA can have impacts on ecological processes, species composition, and 

genetic diversity. Ecosystem processes, which include water, nitrogen, carbon, and phosphorous cycling, 

have all changed more rapidly in the second half of the 20th Century than at any time in recorded human 

history (MA 2005c in Lettenmeier et al. 2008). Human actions have not only changed the structure of 

ecosystems, but also the processes as functions of the ecosystems. 

A change in ecosystem structure also affects the species within the system and vice versa. 

Historically, the natural processes of evolution and the combination of natural barriers to species 

migration and local adaptation resulted in substantial phenotypic differences in plant and animal species 

of different ecosystems. These regional differences are now becoming rare. 

Some ecosystem changes have been the inadvertent result of activities unrelated to the use of 

ecosystem services, such as the construction of roads, ports, and cities and the discharge of pollutants. 

However, most ecosystem changes were the direct or indirect result of changes made to meet growing 

demands for food, water, timber, fiber, and fuel (MA 2005c in Lettenmeier et al. 2008). In addition to 

climate change, ecosystem dynamics can be affected by a variety of human and natural drivers, including, 

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Chapter 4 Cumulative Impacts 4.5 Health, Societal, and Environmental Impacts of Climate Change 

land use change, hydrologic modification, wildfires, insect outbreaks, species decline and extinctions, and 

pollution. These drivers can act independently or in concert with each other (EPA 2009b, Lepers et al.

2004), and are summarized below.

Land-use Change

Land-use change represents the anthropogenic replacement of one land use type by another, such 

as forest converted to cultivated land (or the reverse), and subtle changes of management practices within 

a given land use type, such as intensification of agricultural practices. Both forms of land-use change are 

affecting 40 percent of the terrestrial surface (Foley et al. 2005 in Easterling et al. 2007). Land-use 

change can lead to habitat loss and fragmentation and is an important driver in ecosystem change 

(Heywood and Watson 1995 in Fischlin et al. 2007, Fahrig 2003 in Fischlin et al. 2007). Overall, land 

transformation represents the primary driving force in the loss of biological diversity (Vitousek et al.

1997). In nine of the 14 terrestrial biomes studied by the MA, more than half the area has been 

transformed, largely by agricultural cultivation (Hassan et al. 2005a). Only the biomes that are less 

suitable for agriculture, such as deserts, boreal forests, and tundra, have remained largely untransformed 

by human activity. 

Virtually all of Earth’s ecosystems have now been substantially transformed through human 

actions (MA 2005c in Lettenmeier et al. 2008). Approximately 70 percent of original temperate 

grasslands and forests and Mediterranean forests were lost by 1950, primarily from conversion to 

agricultural lands. More land was converted to cropland in the 30 years after 1950 than in the 150 years 

between 1700 and 1850 (MA 2005a in Kundzewicz et al. 2007, Hassan et al. 2005a). 

Historically, terrestrial ecosystems that have been most substantially altered by human activity 

include temperate broadleaf forests, temperate grasslands, Mediterranean forests, and tropical dry forests 

(Hassan et al. 2005a). Of these, more than two thirds of the temperate grasslands and Mediterranean 

forests, and more than half of tropical dry forests, temperate broadleaf forests, and tropical grasslands 

have been converted to agriculture (Hassan et al. 2005a). Forest systems in general have been reduced by 

half over the past 3 centuries, and have effectively disappeared in 25 countries. Another 29 countries 

have lost 90 percent or more of their forest cover (Hassan et al. 2005a). 

Globally, the rate of ecosystem conversion has begun to decelerate, mainly because the rate of 

expansion of cultivated land has declined. Ecosystems are beginning to return to conditions and species 

compositions similar to their pre-conversion states. However, rates of ecosystem conversion remain high 

or are increasing for specific ecosystems and ecoregions (MA 2005c in Lettenmeier et al. 2008). Landuse changes and land degradation are important drivers of ecosystem change globally and in the United 

States. For example, “between 1982 and 1997, 11 million acres of nonfederal grasslands and shrublands 

were converted to other uses” (The H. John Heinz III Center for Science 2002). 

The increase in cultivated land, especially for the purpose of grazing, has led to an increase in 

desertification. Desertification involves the expansion of deserts into semi-arid and subhumid regions, 

and the loss of productivity in arid zones. Desertification is characterized by loss of groundcover and 

soils, replacement of palatable, mesophytic grasses by unpalatable xerophytic shrubs, or both (Ryan et al.

2008a). Desertification affects the livelihoods of millions of people, including a large portion of the poor 

residents of drylands (Hassan et al. 2005a). While desertification can certainly be exacerbated by 

changes in climate, there has been long-standing controversy over the relative contributions of climatic 

and anthropogenic factors as drivers of desertification (National Science and Technology Council 2008). 

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Hydrologic Modification

An ongoing and significant threat to freshwater ecosystems is the practice of hydrologic 

modification, including the damming of lakes and rivers for hydroelectric power and re-routing stream 

systems for the purposes of agricultural irrigation. At present, there are 45,000 large dams (more than 

about 50 feet high) and as many as 800,000 smaller dams around the world (MA 2005a in Kundzewicz et 

al. 2007). These practices can negatively impact migratory patterns of aquatic species, interfering with 

reproductive patterns, for example. The tight control of waterways through damming, though partially 

intended to help prevent the damages from periodic flooding, has also worked to prevent the positive 

impacts of flooding, such as the replacement of soil nutrients to agricultural lands and terrestrial 

ecosystems (Heino et al. 2008, MA 2005a in Kundzewicz et al. 2007). In recent years, decisionmakers in 

the United States have realized the damages to aquatic ecosystems and the surrounding landscape caused 

by such modifications. Therefore, fewer dams are being constructed and some are being dismantled. 

However, most remain intact. 

Wildfires

Fire influences ecosystem structure by promoting species that tolerate fire or even enhance the 

spread of fire, resulting in a relationship between the relative flammability of a species and its relative 

abundance in a particular community (Bond and Keeley 2005). Intensified and increasing wildfire 

occurrences appear to be changing vegetation structure and composition in some ecoregions (Kasischke 

and Turetsky 2006). 

Insect Outbreaks

Invasive alien species represent a major threat to endemic or native biodiversity in terrestrial and 

aquatic systems. Invasions of alien species also interact with other drivers, sometimes resulting in 

unexpected outcomes. The impact of insect damage is substantial and can exceed the impacts of fire in 

some ecosystems, but especially in boreal forests (EPA 2009b, Logan et al. 2003). For example, spruce 

budworm defoliated more than 20 times the area burned in eastern Ontario between 1941 and 1996 

(Fleming et al. 2002). Fires tended to occur 3 to 9 years after a spruce budworm outbreak (Fleming et al.

2002), suggesting that insect outbreaks can be a driver of increased fire events. 

Species Decline and Extinction

Although extinction is a natural part of Earth’s history, observed modern rates of extinction are 

not part of natural cycles. Over the past few hundred years, humans have increased the extinction rate by 

as much as 1,000 times over the rate expected based on natural history (Hassan et al. 2005a). A decrease 

in global genetic diversity is linked to extinction. The loss of unique populations has resulted in the loss 

of genetic diversity. The loss of genetic diversity among terrestrial species has also declined among 

cultivated species as farmers have shifted from locally adapted crop populations to more widely adapted 

varieties produced through formal breeding practices. For most species across a wide range of taxonomic 

groups, either the population size, population range, or both is in decline (MA 2005c in Lettenmeier et al.

2008). 

Pollution

Pollution is another substantial threat to ecosystems. Over the past 4 decades, excessive nutrient 

loading has emerged as one of the most important direct drivers of ecosystem change in terrestrial, 

freshwater, and marine systems. A known cause is the use of increasing amounts of synthetic nitrogen 

and phosphorous fertilizers, which can be lost to the environment after application (EPA 2009b). 

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Consumption of nitrogen fertilizer grew almost 800 percent between 1960 and 2003 (MA 2005c in 

Lettenmeier et al. 2008). In terrestrial ecosystems, excessive nitrogen flows contribute to acidification. 

Nitrogen also plays a role in ground-level ozone, which can lead to a loss of forest and agricultural 

productivity (EPA 2009b, MA 2005c in Lettenmeier et al. 2008). In aquatic systems, excessive nitrogen 

and phosphorus loads often result in eutrophication of both surface and deeper waters (Poff et al. 2002). 

As the nutrient enrichment encourages growth of aquatic vegetation in the surface layers of water bodies, 

the result is that natural processes that occur as the plants die, sink to the lower layers of water, and decay 

lead to depleted oxygen. The depletion of oxygen makes it more difficult for many species to thrive and 

sometimes results in large areas of “dead zones,” in which no species are able to thrive. In one example, 

in the 1960s, Lake Erie experienced such significant phosphorus pollution that algal bloom decay used up 

almost all of the dissolved oxygen in the lake and the lake was almost entirely unable to support any fish 

and other aquatic life (Kling et al. 2003). 

4.5.4.2.2 Observed Impacts on Terrestrial and Freshwater Ecosystems in the 

United States 

Changes and impacts on ecosystems in the United States are similar to those occurring globally. 

During the 20th Century, the United States already had begun to experience the effects of climate change. 

Precipitation over the contiguous United States increased 6.1 percent over long-term averages (EPA 

2009b), while a sea-level rise of 0.08 to 0.12 inch per year has occurred at most of the country’s 

coastlines; the Louisiana coast has experienced an even greater rise in sea level at a rate of 0.36 inches per 

year (EPA 2009b). It should be noted that while global sea level rise is relatively smooth across the 

globe, the amount at any particular location can be affected by many factors. 

Examples of observed changes to non-marine ecosystems in the United States attributable to 

anthropogenic climate change include: 

• Many plant species are expanding leaves or flowering earlier, for example: earlier flowering 

in lilac, 1.8 days per decade (Schwartz and Reiter 2000) and honeysuckle, 3.8 days per 

decade (Cayan et al. 2001). 

• Warmer springs have led to earlier nesting for 28 migrating bird species on the east coast of 

the United States and to earlier egg laying for Mexican jays and tree swallows (EPA 2009b). 

• In lowland California, 70 percent of 23 butterfly species advanced the date of first spring 

flights by an average of 24 days over 31 years (Forister and Shapiro 2003 in Easterling et al.

2007). 

• Many North American plant and animal species have shifted their ranges, typically to the 

north or to higher elevations (EPA 2009b, Parmesan and Yohe 2003a). 

• Edith’s checkerspot butterfly has become locally extinct in the southern, low-elevation 

portion of its western North American range but has extended its range 56 miles north and 

394 feet higher in elevation (EPA 2009b, Parmesan 1996, Crozier 2003). Forty percent of the 

populations below 2,400 feet elevation are now extinct (GCRP 2009). 

• The frequency of large forest fires and the length of the fire season in the western United 

States have increased substantially since 1985. These phenomena are related to the advances 

in the timing of spring snowmelt and increases in spring and summer air temperatures (EPA 

2009b, Westerling et al. 2006b in CCSP 2008). 

• The vegetation growing season has increased on average by about 2 days per decade since 

1948, with the largest increase happening in the West (Easterling 2002, Feng and Hu 2004 in 

Rosenzweig et al. 2007). 

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• Recently, spruce budworm in Alaska has completed its lifecycle in 1 year, rather than the 2 

years previously (EPA 2009b). This allows many more individuals to survive the 

overwintering period with impacts on the boreal forests of North America. 

• Over the past 3 to 5 decades, all the major continental mountain chains exhibited upward 

shifts in the height of the freezing level (Diaz et al. 2003). 

• Populations of the American pika, a mountain-dwelling relative of the rabbit, are in decline 

(EPA 2009b). The pika might be the first North American mammal to become extinct as a 

result of anthropogenic climate change. Several populations of the pika, in the Rocky 

Mountain region, appear to have been extirpated as of the 1990s, compared to those that 

existed in the early 20th Century. One of the important factors in this occurrence is climate 

change that affected food supply and habitat availability (Janetos et al. 2008). 

• Reproductive success in polar bears has declined as a result of melting Arctic Sea ice. 

Without ice, polar bears cannot hunt seals, their preferred prey (Derocher et al. 2004). On 

May 15, 2008, the U.S. Fish and Wildlife Service listed the polar bear as a threatened species 

(EPA 2009b), reflecting the loss of sea ice habitat that once encompassed more than 90 

percent of the polar bear’s habitat range (Federal Register 73, 28212-28303, May 15, 2008). 

• Between 1970 and 2000, much of Alaska has experienced approximately 10 additional snowfree days. The response to this is variable throughout the state. In northern Alaska, aboveground vegetation is increasing on the tundra while decreasing in the boreal forest regions in 

the interior of the state (CCSP 2009c). 

• Permafrost in Alaska is warming and thawing in some areas and large areas of thermokarst 

terrain (subsidence from thawing) are observed. Estimates of the surface warming thus far 

are 0.5 to 1.5 °C (0.9 to 2.7 °F) and the subsidence is averaging 1 to 2 meters, and is as much 

as 6 meters in some locations (CCSP 2009c). 

• In northern Alaska, shrub cover has increased by 16 percent since 1950. In 200 Arctic 

locations, there has been a 70 percent increase in shrub cover (EPA 2009b). This is already 

resulting in decreased surface albedo, reinforcing the warming trend (CCSP 2009c). The 

northward-shifting tree line into the tundra is encroaching on habitat for a number of 

migratory birds and land mammals, such as caribou (GCRP 2009). 

• Northeastern birds that winter in the southern United States arrive home 13 days earlier than 

they did in the early 20th Century. Those that migrate to South America arrive home 4 days 

earlier, on average (GCRP 2009). 

• In the past decade, the percentage of Rocky Mountain wildflower buds that are exposed to 

frost has doubled, hindering their reproductive ability (GCRP 2009). 

• Since 1906, climate in the PPR has been generally been warmer and wetter. Minimum daily 

temperatures have been increasing in winter while maximum daily temperatures in the 

summer have been decreasing. Average annual precipitation over the same time period 

increased by 9 percent. The moisture gradient (wet in the east, dry in the west) steepened, as 

well. This trend is threatening the productive are of wetlands (Millett et al. 2009). 

• There have been major changes in plant species abundance in Thoreau’s Walden Woods in 

Concord, MA. Meticulous records of species have been kept for 150 years. Much of the 

change is thought due to changes in climate. The mean annual temperature in the Concord 

area has risen 2.4 °C (4.3 °F) in the last 100 years. Species in the area are now flowering 7 

days earlier than they were during Thoreau’s record-keeping days (Willis et al. 2008). 

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4.5.4.2.3 Observed Impacts of Climate Change on Terrestrial and Freshwater 

Ecosystems Globally 

Because all ecosystems are defined by the interactions of biotic factors (plants, animals, and 

microorganisms) and abiotic factors (geology, hydrology, weather), climate is a key factor in determining 

the different characteristics and distributions of natural systems. 

Studies have noted the response of biological and chemical characteristics of ecosystems to 

climate conditions, especially temperature change. Substantial research has examined the effects of 

climate change on vegetation and wildlife, leading to the conclusion that the changing climate is already 

having a real and demonstrable effect on a variety of ecosystem types (EPA 2009b, CCSP 2008b). As 

noted in the IPCC report, plants and animals can reproduce, grow, and survive only within specific ranges 

of climate and environmental conditions (EPA 2009b, Fischlin et al. 2007). Changes in climate can affect 

terrestrial ecosystems in any of the following ways (EPA 2009b): 

• Shifting the timing of life cycle events such as blooming or migration; 

• Shifting range boundaries or densities of individuals within their ranges; 

• Changing species morphology (body size, egg size), reproduction, or genetics; and 

• Causing extirpation or extinction. 

These changes are a result of many factors. Phenology – the timing of seasonal activities of 

animals and plants – is perhaps the simplest process by which to track changes in the ecology of species 

in response to climate change (EPA 2009b, Rosenzweig et al. 2007). Observed phenological events 

include spring leaf unfolding, flowering, fruit ripening, autumn leaf coloring, leaf fall of plants, bird 

migration, chorusing of amphibians, and appearance or emergence of butterflies. Global daily satellite 

data, available since 1981, indicate an earlier onset of spring by 10 to 14 days over 19 years, particularly 

across temperate latitudes of the northern hemisphere (EPA 2009b, Lucht et al. 2002). Leaf unfolding 

and flowering in spring and summer have, on average, advanced by 1 to 3 days per decade in Europe, 

North America, and Japan over the last 30 to 50 years (Fischlin et al. 2007). The seasonal timing of bird 

migration and egg-laying has also changed, associated with the increase of temperature in breeding 

grounds and migration routes (EPA 2009b). According to IPCC (Rosenzweig et al. 2007), “Many small 

mammals have been observed to come out of hibernation and to breed earlier in the spring than they did a 

decade ago (Inouye et al. 2000, Franken and Hik 2004) and even larger mammals such as reindeer are 

showing phenological changes (Post and Forchhammer 2002), as are butterflies, crickets, aphids, and 

hoverflies (Forister and Shapiro 2003 in Easterling et al. 2007, Stefanescu et al. 2003, Hickling et al.

2005, and Newman 2005). Increasing regional temperatures are also associated with earlier calling and 

mating and shorter time to maturity of amphibians (Gibbs and Breisch 2001, Reading 2003, and 

Tryjanowski et al. 2003).” Frogs have been documented initiating mating calls as many as 10 to 13 days 

earlier then they were a century ago in some areas (EPA 2009b). 

Rapid global warming can directly affect the size of a species’ range, the density of individuals 

within the range, and the abundance of preferred habitat within the range. Climate changes have affected 

the location of suitable habitat for several species of plants and animals. Changes in the distribution of 

species have occurred across a wide range of taxonomic groups and geographical locations (Rosenzweig 

et al. 2007). Several different bird species no longer migrate out of Europe in the winter as the 

temperature continues to warm (Rosenzweig et al. 2007). Over the past decades, a poleward extension of 

various species has been observed, which is probably attributable to increases in temperature (Parmesan 

and Yohe 2003b in Rosenzweig et al. 2007). Many Arctic and tundra communities are affected and have 

been replaced by trees and dwarf shrubs (Kullman 2002 in Rosenzweig et al. 2007, and EPA 2009b). In 

some mountainous areas of the northern hemisphere, including in Alaska, tree lines have shifted to higher 

altitudes over the past century (Sturm et al. 2001 in Rosenzweig et al. 2007). 

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Decreases in the size of a species’ range, the density of individuals within the range, and the 

abundance of its preferred habitat factors can lower species population size (Wilson et al. 2004 in 

Rosenzweig et al. 2007) and can increase the risk of extinction. Examples of declines in populations and 

subsequent extinction or extirpation are found in amphibians around the world (Alexander and Eischeid 

2001, Middleton et al. 2001, Ron et al. 2003, and Burrowes et al. 2004, all in Rosenzweig et al. 2007). 

Increased toad mortality in freshwater systems in recent years has been attributed, in part, to exposure of 

their eggs to ultraviolet B radiation, which increases susceptibility to certain fungal parasites (EPA 

2009b). 

Changes in morphology and reproduction rates have been attributed to climate change. For 

example, the egg sizes of many bird species are changing with increasing regional temperatures (Jarvinen 

1996 and Tryjanowski et al. 2003). Several studies conducted in Asia and Europe found that some birds 

and mammals are experiencing increases in body size as temperatures increase, on a regional scale, most 

likely due to the increasing availability of food (Nowakowski 2002, Yom-Tov 2003, Kanuscak et al.

2004, and Yom-Tov and Yom-Tov 2004 in Rosenzweig et al. 2007). Many northern insects have a 2-

year life cycle, and warmer winter temperatures allow a larger fraction of overwintering larvae to survive. 

The mountain pine beetle has expanded its range in British Columbia into areas previously considered too 

cold (Carroll et al. 2004) for its survival. 

Examples of observed changes to non-marine ecosystems attributable to changes in climate also 

include: 

• In lakes around the world, disruptions of trophic interactions among phytoplankton and 

zooplankton species with different temperature requirements have been observed (Winder 

and Schindler, 2004). 

• Forest growth has increased over the last several decades due to increasing CO2 in the 

atmosphere, an earlier onset of the growing season, and increased atmospheric nitrogen 

deposition (GCRP 2009). 

• Changes in the relative timing of caterpillar food supplies for European woodland birds, 

including the Great Tit and the Pied Flycatcher, are impacting the reproductive success for 

those that cannot adjust their phenological timing, accordingly (UNEP 2006). 

• In Northern Scotland, some populations of seabirds have had failures of close to 100 percent 

in recent years, due primarily to warmer waters becoming more hostile to phytoplankton, 

providing less food to the fish, which are the seabirds’ food source (UNEP 2006). 

• New species of fish, such as pacific salmon, have been identified in aquatic systems of the 

Canadian Arctic in recent years as a result of expanded ranges from warming waters (UNEP 

2006). 

4.5.4.2.4 Projected Impacts of Climate Change on Terrestrial and Freshwater 

Ecosystems in the United States 

The United States is projected to experience changes in average temperature and precipitation 

over the 21st Century of an even greater magnitude than those experienced in the 20th Century. Although 

the entire Country is projected to experience some degree of change, particular regions of the United 

States could experience changes of a greater-than-average magnitude. For example, the greatest changes 

in temperature are projected for Alaska and the western continental United States (EPA 2009b, CCSP 

2008a). In northern Alaska, the average temperatures are projected to increase 5.0 °C (9.0 °F) by the end 

of the 21st Century. Areas near coasts are projected to witness an increase of approximately 2.0 °C 

(3.6 °F) over the same period; summer temperatures nationwide could increase 3.0 to 5.0 °C (5.4 to 9.0 

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°F); and winter temperatures are projected to increase 7.0 to 10.0 °C (12.6 to 18.0 °F) (CCSP 2008a). 

Additionally, the northeastern United States could experience a rise in sea level that is greater than the 

projected global average of 0.8 to 2.0 meters (2.6 to 6.6 feet) (EPA 2009b, Pfeffer et al. 2008). 

Additional expected changes in United States climate include: 

• More frequent hot days and hot nights (EPA 2009b); 

• Heavier precipitation events, primarily in the form of rain rather than snow (EPA 2009b). 

Annual precipitation in the northeastern United States is projected to increase while 

precipitation in the Southwest is expected to decrease (EPA 2009b, Christensen et al. 2007a); 

and 

• A decline in spring snow cover, leading to decreased availability of water in reservoirs (EPA 

2009b). 

Ecosystems across the United States are projected to experience both positive and negative 

impacts from climate change over the next century. The degree of impacts will vary by region. Wildlife 

species have already responded to climate change and its effects on migration patterns, reproduction, and 

geographic ranges (EPA 2009b). Future, more substantial changes in climate are projected to affect many 

ecosystem services negatively (EPA 2009b, CCSP 2008a). The IPCC WGII has projected, with a high 

level of confidence, “that recent regional changes in temperature have had discernible impacts on many 

physical and biological systems” (National Science and Technology Council 2008). 

The IPCC has determined that areas of the United States that experience temperature increases of 

1.5 to 2.5 °C (2.7 to 4.5 °F) are at highest risk for modifications to ecosystem structure and composition 

(IPCC 2007c in CCSP 2008). Over the next century, it is projected that species could move northward 

and to higher elevations (Field et al. 2007b in National Science and Technology Council, 2008). In one 

example of possible future threats to ecosystem vegetation, the upward move in elevation of species as 

the snow and tree line advances suggests that alpine ecosystems could be endangered by the introduction 

of invasive species (National Science and Technology Council 2008). 

Rather than experiencing impacts of climate change directly, most animals could experience the 

effects of climate change indirectly through changes to their habitat, food sources, and predators 

(Schneider and Root 1996 in National Science and Technology Council 2008). A changing climate 

facilitates migration of certain species into non-native habitats, potentially affecting current goods and 

services (EPA 2009b, CCSP 2008a). 

Ecosystems in the United States are projected to experience a variety of climate-change impacts. 

For example: 

• The area of drought-limited ecosystems is projected to expand in the U.S. 11 percent for 

every 1.0 °C (1.8 °F) (EPA 2009b). 

• Changes in hydrology as a result of changes in precipitation patterns could interrupt the 

breeding cycles of amphibians, which depend on the ability to migrate to breeding ponds. 

The production of their eggs is also highly dependent on temperature and moisture 

availability (Fischlin et al. 2007 in National Science and Technology Council 2008). 

• Changes in climate that occur over at least several years are likely to affect the reproductive 

success of migratory birds and their ability to survive. A mismatch in timing between the 

migration and reproduction periods and peak food availability is the potential pathway for 

such impacts (EPA 2009b). 

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• The migration of butterflies is highly dependent on spring temperatures, and anthropogenic 

climate change is likely to lead to earlier spring arrivals. As with migratory birds, an earlier 

butterfly migration could result in a mismatch with food supply, thus threatening 

reproduction and survival (Forister and Shapiro 2003 in National Science and Technology 

Council, 2008). 

• Shifts in migration ranges could result in disease entering new areas, for example, avian 

malaria in Hawaii could move upslope as climate changes (CCSP 2008a). 

In one well-publicized example of mammals experiencing the effects of a warming climate, the 

polar bear is specifically adapted to conditions in a narrow ecological slot niche (an environment with 

cold temperatures and access to snow, ice, and open water) and depends on this sea ice environment to 

hunt ice-breeding seals (EPA 2009b). Two thirds of polar bears could be gone from Alaska by the middle 

of this century (GCRP 2009). Polar bears were listed as threatened under the Endangered Species Act on 

May 15, 2008, due to the ongoing and projected loss of their sea-ice habitat from global warming (EPA 

2009b). 

The vegetation of terrestrial ecosystems in the United States is projected to experience a variety 

of direct impacts from climate change. For example, national forests, which harbor much of the Nation’s 

biodiversity, and national grasslands are expected to experience an exacerbation of preexisting stressors, 

such as wildfires, invasive species, extreme weather events, and air pollution (CCSP 2008a). 

Warmer, drier climates weaken resistance of trees to insect infestation, as they are more likely to 

be wilted and weakened under those conditions. In a healthy state, trees can typically fight off beetle 

infestation by drowning them with resin (sap) as they bore through the bark. Drought reduces the flow of 

resin and beetles that are able to penetrate the bark introduce decay-causing fungus. This problem has 

already been documented. Since 1994, winter mortality of beetle larvae in Wyoming has been cut due to 

mild winters (from 80 percent to less than 10 percent mortality). As a result, the beetles have been able to 

strip four million acres of Wyoming forests (Egan 2002 in Epstein et al. 2005). The U.S. Forest Service 

reports that bark beetles have now impacted over 1.5 million acres in northern Colorado and southern 

Wyoming, killing lodgepole pines and affecting watersheds, timber production, and wildlife habitats, 

along with other human activities (USFS 2008). 

Additional impacts on vegetation in ecosystems in the United States could include: 

• Water management in the West would be complicated by increases in temperatures and 

changes in precipitation patterns, which lead to reduced snow pack, earlier snowmelt, and 

modified hydrology (EPA 2009b). 

• High latitudes would experience increased vegetation productivity. Regions in the midlatitudes would experience either increased or decreased productivity, depending on whether 

the primary impact is more precipitation or higher temperatures (increasing evaporation and 

dryness) (Bachelet et al. 2001b, Berthelot et al. 2002, Gerber et al. 2004, Woodward and 

Lomas 2004, all in National Science and Technology Council 2008, EPA 2009b). 

• Terrestrial ecosystems in the East would be statistically “likely to become carbon sources, 

while those in the west would be likely to remain carbon sinks” (Bachelet et al. 2004 in 

National Science and Technology Council 2008). 

• The jet stream would move northward with increasing atmospheric temperatures. The 

consequence of this shift is a drying of the Southeast. Closed-canopy forest ecosystems could 

be converted to savanna ecosystems, woodlands, or grasslands, measurably increasing the 

threat of fire occurrence (CCSP 2008a). 

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• Growing seasons would lengthen, according to several predictive models; this would 

beneficially act to sustain carbon sinks (EPA 2009b). 

• In the Olympic Range, a temperature increase of 2 °C (3.6 °F) would move tree species 

upwards 0.20 to 0.38 mile. Temperate species would replace subalpine species over 300 to 

500 years (Zolbrod and Peterson 1999). 

By 2050, coldwater stream fish habitat is projected to decline by 20 percent in the U.S. as a whole 

and 50 percent in the Rocky Mountain Region (Preston 2006). More than half of the wild trout 

populations of the southern Appalachian Mountains are projected to disappear as streams warm. Some 

studies project that losses of western trout populations could exceed 60 percent (Keleher and Rahel 1996 

in Poff et al. 2002; Rahel et al. 1996 in Mohseni et al. 2003; Rahel 2002 in Battin et al. 2007). Models of 

Pacific Northwest salmon populations project losses of 20 to 40 percent by 2050 (Battin et al. 2007). 

The millions of wetlands in the North American Prairie Pothole region, which provide essential 

breeding habitat to waterfowl, are considered particularly vulnerable to a warmer and drier climate. The 

wetlands of this region are considered the most productive habitat for waterfowl in the world, and it is 

estimated that the wetlands in the area support up to 80 percent of North American ducks. Simulations 

suggest that under a drier climate, the most productive habitat for breeding waterfowl would shift from 

the center of the region in the Dakotas and southeastern Saskatchewan to the wetter eastern and northern 

fringes, areas that are less productive or where most wetlands have been drained, resulting in significant 

declines in productivity (Johnson et al. 2005a). 

Seasonal migrations of wetland species will be disrupted, with reduced survival and possible 

extinctions of some species. Boreal peatlands are considered particularly vulnerable (Wrona et al. 2006; 

Heino et al. 2008). Declines in abundance and local and global extinctions of arctic fish species are 

projected for this century. 

4.5.4.2.5 Projected Impacts of Climate Change on Global Terrestrial and 

Freshwater Ecosystems 

The IPCC concludes (very high confidence) that anthropogenic temperature rises have visibly 

altered ecosystems (Parry et al. 2007). The exact impacts of climate changes are difficult to discern, 

however, because they are mediated by other stressors and the capabilities of natural systems to adapt to 

changing climates to some degree (Parry et al. 2007). 

Some regions of the world are more vulnerable to changes in climate than others. Regions of 

snow, ice, and tundra have been visibly altered by changes in global temperature. Observations of frozen 

regions already show larger glacial lakes and the destabilization of glacial debris that dam these lakes; 

changes in ecosystems at both poles; and increased melting of ice sheets, glaciers, and ice caps (Parry et 

al. 2007). 

Ecosystems in all regions of the world are expected to respond to climate-change impacts with 

poleward and upward shifts of plants and animals; earlier onset of migration of terrestrial species such as 

birds and butterflies; and localized disappearance of particular species (EPA 2009b). 

Additional factors, such as projected growth in human populations, are expected to exacerbate the 

effects of climate change. For example, river basin ecosystems that are already experiencing high levels 

of stress are projected, with medium confidence, to witness growth in human populations from 

approximately 1.4 to 1.6 billion in 1995 to roughly 4.3 to 6.9 billion by 2050 (Parry et al. 2007). River 

basins experience the stress of increasing human populations as manifested in increasing demands for 

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water (CCSP 2008b) and more inputs of pollutants. A warmer, drier climate could increase these 

stressors and reduce access to other water sources (EPA 2009b). 

Other projected global impacts of climate change include: 

• The hardiness of the world’s ecosystems is expected (high confidence) to be challenged over 

the 21st Century with “an unprecedented combination of climate change, associated 

disturbances (e.g., flooding, drought, wildfire, insects, and ocean acidification), and other 

global change drivers (especially land use, pollution, and over-exploitation of resources) 

(Fischlin et al. 2007). 

• Declines in keystone species populations are projected to be the primary factor in causing 

ecological cascades, which are “sequential chains of ecological effects, including starvation 

and death, beginning at the bottom levels of the food chain and ascending to higher levels, 

including apex predators” (EPA 2009b). 

• Eighty-four percent of the species listed in the Convention on Migratory Species could be 

impacted in some way by climate change: 53 percent are susceptible to changes in water 

regime, 24 percent to mismatched water supply, 18 percent to sea-level rise, 17 percent to 

changes in prey range, 17 percent to habitat shifts, and seven percent to increased storm 

severity. The number of species threatened due to climate change is greater than the total 

number that are threatened by all other anthropogenic effects (UNEP 2006). 

• By 2050, the Amazon forest is likely committed to losing 50 percent of its area. Even if all 

further forcing were to discontinue, projections indicate that almost all of the Amazon forest 

would be committed to loss (Jones et al. 2009). 

• Fifty to 70 percent of the global climate models utilized by IPCC in 2007 project a 20-percent 

reduction in dry season precipitation in the eastern Amazon region, 40 percent in the central 

region, and 20 percent in the west. The Amazon forest seems resilient short-term droughts 

but large tree mortality begins after 3 years of drought (Betts et al. 2008). 

• Global average temperature increases in excess of 1.5 to 2.5 °C (2.7 to 4.5 °F) are statistically 

likely to threaten 20 to 30 percent of plant and animal species with extinction by 2100 (GCRP 

2009). 

• Carbon uptake by ecosystems such as forests and grasslands is statistically likely to peak 

during the 21st Century and might ultimately even reverse (forests and grasslands would emit 

carbon, rather than taking it in), which would amplify climate change due to increased 

atmospheric CO2 (Fischlin et al. 2007 in National Science and Technology Council 2008). 

In addition to other anthropogenic stressors, “such as extractive use of goods, and increasing 

fragmentation and degradation of natural habitats” (Bush et al. 2004 in Fischlin et al. 2007), climate 

change poses a threat to the wellbeing of ecosystems. Although many ecosystems have been resilient to 

historical changes in climate, it is not clear whether their resilience is enough to withstand the more rapid 

and profound changes that are projected given the buildup of GHGs in the atmosphere (Chapin et al.

2004, Jump and Peñuelas 2005 in Fischlin et al. 2007). Projected climate change and other anthropogenic 

stressors are “virtually certain to be unprecedented” (Forster et al. 2007 in Fischlin et al. 2007). While 

some of the impacts expected with climate change serve to exacerbate existing stressors on ecosystems, 

other expected impacts could be altogether new. For example, increasing temperatures could cause some 

current sinks for GHGs, such as forest vegetation, to actually become sources for these gases (including 

CO2 and methane) (Fischlin et al. 2007). 

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Effects of anthropogenic climate change on ecosystems are anticipated at different levels of 

severity and over varying time scales (decades to centuries) (Lischke et al. 2002 in Fischlin et al. 2007). 

Some of the broad impacts on ecosystems associated with climate change are expected to include species 

extinctions, loss of habitat due to more severe tropical storms (Wiley and Wunderle 1994 in Fischlin et al.

2007), changes in the types and abundance of vegetation present in an ecosystem (Schröter et al. 2005, 

Metzger et al. 2006, both in Fischlin et al. 2007), and increased susceptibility of land to desertification 

(Burke et al. 2006b in Fischlin et al. 2007). 

Aquatic species will be vulnerable to changes in precipitation, hydrologic regimes, and water 

temperatures that alter or reduce habitat. Southern species of mammals and waterfowl are among the 

species groups expected to move north as the climate warms (Wrona et al. 2006), with the potential for 

some extinctions of fishes that are already at the northern limits of their range (Chu et al. 2005 in Heino et 

al. 2008). It has been estimated that with a warming of 4.0 °C (7.2 °F), there would be a shift in thermal 

regimes northward by about 422 miles (Sweeney et al. 1992 in Heino et al. 2008). Eaton and Scheller 

(1996) in Mohseni et al. 2003 estimated that with this degree of warming, thermally suitable habitat for 

57 stream fishes requiring cold or cool water would decline by 50 percent. 

Foreseeable pathways of climate change-induced impacts on ecosystems include: 

• CO2 fertilization effects on vegetation (EPA 2009b). 

• Higher atmospheric temperatures that could lead to more frequent insect and disease 

outbreaks (EPA 2009b). 

• Increased radiation due to a projected decrease in tropical cloud cover (Nemani et al. 2003 in 

Fischlin et al. 2007). This is linked to warming, which can directly affect ecosystems and 

increase the frequency and severity of storms originating in the tropics. 

Increased water temperatures in freshwater systems sometimes make aquatic species more 

susceptible to pathogens. Increasing evaporation of lakes and stream systems can also increase 

concentrations of pollutants in water bodies. 

Ecological Thresholds

Ecosystems have thresholds, similar to climatic or oceanic system tipping points, over which any 

small stressors on an ecosystem could result in abrupt changes in the quality or properties of the whole 

system. “Threshold phenomena are particular nonlinear behaviors that involve a rapid shift from one 

ecosystem state (or dynamic regime) to another that is the result of, or provokes, instability in any 

ecosystem” attribute (CCSP 2009c). This kind of instability is associated with some type of positive, 

runaway feedback, which differentiates a threshold from other types of changes in the ecosystem that are 

the result of environmental modifications. 

Crossing over a threshold, an ecosystem makes a well defined break from previous trends in the 

system’s behaviors and overall characteristics (CCSP 2009c). An example cited in CCSP (2009a) that 

illustrates this is the observed impact to grasslands that was the result of interactions between drought and 

livestock overgrazing. As soon as a component critical to the wellbeing of the grassland ecosystem 

failed, that failure triggered “runaway desertification...a domino-like cascade of instability that 

substantially alter[ed] the rest of the system” (Groffman et al. 2006 in CCSP 2009c). Another example is 

that of the previously cited rapid die-off of forests in the southwestern United States. The primary trigger 

to runaway changes, sudden tree mortality from the drought-bark beetle stressors, led to other nonlinear 

changes in the ecosystem, such as erosion and the increased incidence of forest fires. Similarly, in the 

1990s, southern Alaska experienced a world-record-breaking onslaught of spruce bark beetles, which was 

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linked to a threshold response to observed changes in climate, primarily milder winter seasons that 

reduced the beetles’ winter mortality and allowed the beetles to complete their life cycles in 1 year, rather 

than the historical 2 years. The beetle outbreak occurred on top of a 9-year drought that had already 

pushed spruce trees to the limits of their resilience; the trees were unable to protect themselves from 

insect pests at that time, leading to widespread tree mortality (CCSP 2009c). 

In the future, facing changes in precipitation, temperature, and sea level, it might not be possible 

for ecosystems to meet historic benchmarks. Therefore, managers of ecosystem resources will likely have 

to modify their goals to accommodate these changes. For example, it could be necessary to foster the 

growth of more resilient components of ecosystems, such as those with only a few strong connections 

between them, which would build a “fire-break” into the systems and help to protect them from collapse 

(CCSP 2009c). 

4.5.5 Marine, Coastal Systems, and Low-lying Areas 

This section addresses climate-related impacts to marine and coastal ecosystems and low-lying 

areas. Coastal zones, commonly included as part of the marine intertidal and neritic zones, are unique 

environments where land and water meet. Though there is no single definition for coastal zones, all 

coastal zones include an area of land with a portion covered by saltwater. Burke et al. (2001) defines 

coastal zones as the “intertidal and subtidal areas on and above the continental shelf (to a depth of about 

200m (650 feet)) – areas routinely inundated by saltwater – and immediately adjacent lands.” Marine 

zones are also varied, often categorized according to both water depth and distance from land. In general, 

most geographic categorizations make clear delineations among shallow zones near the coast, open ocean 

areas, and the deepest areas of the sea; however, there is no one universal definition applicable to 

establishing the different subboundaries of marine zones. Alternatively, marine zones can also be defined 

by the ecosystems they support; NOAA has identified 64 Large Marine Ecosystems that each represent 

vast marine areas with distinct physical characteristics and where plant and animal populations are 

inextricably linked in the food chain (NOAA 2009a). 

This section introduces the marine and coastal environments and discusses the observed and 

projected impacts of climate change. These environments are particularly vulnerable to warming water 

temperatures, sea-level rise, melting of freshwater ice, storm events, and water acidification (see Section 

4.7.2. for discussion of water acidification). 

4.5.5.1 Affected Environment 

The world’s coastal length is estimated to be 1,015,756 miles, with North America having the 

longest coastal length of all continents (Pruett and Cimino 2000 in Burke et al. 2001). Canada has the 

longest coastal length of any country in the world and the United States has the second longest, at 

265,523 km (164,988 miles) and 133,312 km (82,836 miles), respectively (Pruett and Cimino 2000 in 

Burke et al. 2001). Important ecosystems found in coastal zones can include estuaries, coral reefs, coastal 

lagoons, mangroves, seagrass meadows, upwelling areas, salt marshes, beaches, bays, deltas, kelp forests, 

and barrier islands. A variety of terminology exists for describing coastal zone ecosystems. Table 4.5.5-1 

lists some of the more commonly described ecosystems found in coastal zones. 

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Table 4.5.5-1 

Common Coastal Ecosystem 

Coastal Ecosystem Description 

Coastal Wetlands The broadest definition of wetlands occurring along coastal zones. They include a number 

of natural communities that share the unique combination of aquatic, semi-aquatic, and 

terrestrial habitats that results from periodic flooding by tidal waters, rainfall, or runoff. 

Sandy Shorelines Sandy areas along coastlines where high-energy wave actions deposit and move around 

sand and sediment. 

Barrier Islands Long narrow islands running parallel to the mainland that provide protection to the coast. 

Tidal Wetlands A type of coastal wetland that is affected by both tides and freshwater runoff. 

Estuaries Bodies of water and their surrounding coastal habitats typically found where rivers meet the 

ocean. 

Mangroves Coastal wetlands found in tropical and subtropical regions typically characterized by shrubs 

and trees with an affinity to saline tidal waters. 

Tidal Salt Marshes A type of coastal wetland frequently or continually inundated with water, characterized by 

soft-stemmed vegetation adapted to saturated soil conditions. a/ 

Coral Reefs A large underwater calcium carbonate formation that includes a diverse collection of 

biological communities. 

Coastal Deltas Typically a triangular deposit of silt and sand deposited at the mouth of a river along a coast.

Coastal Wetlands The broadest definition of wetlands occurring along coastal zones. They include a number 

of natural communities that share the unique combination of aquatic, semi-aquatic, and 

terrestrial habitats that results from periodic flooding by tidal waters, rainfall, or runoff. 

Sandy Shorelines Sandy areas along coastlines where high-energy wave actions deposit and move around 

sand and sediment. 

Barrier Islands Long narrow islands running parallel to the mainland that provide protection to the coast. 

Tidal Wetlands A type of coastal wetland that is affected by both tides and freshwater runoff. 

Estuaries Bodies of water and their surrounding coastal habitats typically found where rivers meet the 

ocean. 

Mangroves Coastal wetlands found in tropical and subtropical regions typically characterized by shrubs 

and trees with an affinity to saline tidal waters. 

Tidal Salt Marshes A type of coastal wetland frequently or continually inundated with water, characterized by 

soft-stemmed vegetation adapted to saturated soil conditions. a/ 

Coral Reefs A large underwater calcium carbonate formation that includes a diverse collection of 

biological communities. 

Coastal Deltas Typically a triangular deposit of silt and sand deposited at the mouth of a river along a coast.

_________________

a/ EPA (2006)

Coastal zones are areas of substantial biological productivity that provide food, shelter, spawning 

grounds, and nurseries for fish, shellfish, birds, and other wildlife. The interaction between aquatic and 

terrestrial components of coastal ecosystems creates a unique environment that is critical to the life cycles 

of many plant and animal species. In the United States, 85 percent of commercially harvested fish depend 

on estuaries and coastal waters at some stage in their life cycle (Summers et al. 2005), while as much as 

95 percent of the world’s marine fish harvest is caught or reared in coastal waters (Sherman 1993 in 

Burke et al. 2001). Most historical information available on coastal ecosystems focuses on data related to 

fisheries (see Section 4.5.6, Food, Fiber, and Forests, for a detailed discussion on fisheries). As more 

research is conducted on other increasingly important coastal ecosystems, new data and information are 

becoming available. For example, coral reefs alone, while representing only 0.2 percent of the total area 

of oceans (Bryant et al. 1998), harbor more than 25 percent of all known marine fish (Tibbetts 2004). In 

addition, the species in some coral reefs can reach densities of 1,000 per square meter (Tibbetts 2004). In 

the United States, coastal ecosystems provide the Country’s essential nesting, feeding, and breeding 

habitat for 85% of the waterfowl and other migratory birds (Summers et al. 2005). Coastal zones have 

also been found to support a much higher percentage of the world’s threatened and endangered species. 

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4.5 Health, Societal, and Environmental Impacts of Climate Change Chapter 4 Cumulative Impacts 

Because a disproportionate percentage of the world’s population lives in coastal zones, the 

activities of humans have created environmental pressures that threaten the very resources that make the 

coastal zones desirable (Summers et al. 2005). The impact of these activities varies from place to place 

and depends on the types and sensitivity of coastal ecosystems involved. A wide range of pressures has 

been identified as causing adverse changes in coastal ecosystems, but the leading causes of coastal 

ecosystem degradation include physical alteration, habitat degradation and destruction, water withdrawal, 

overexploitation, pollution, and the introduction of non-native species (UNESCO and WWAP 2006). In 

addition, climate change might compound these pressures (UNESCO and WWAP 2006). 

 There are numerous ways to define marine zones. Table 4.5.5-2 illustrates some commonly used 

zones (note that many of zones are similar in definition or overlap with other zones). Zonal 

characteristics include their proximity to land and their depth. Water zones close to land tend to be 

shallower, warmer, and have greater exposure to sunlight compared to deeper waters; thus, these different 

zones support very distinct ecosystems. Note the intertidal and neritic zones can also be defined as 

coastal zones. 

Table 4.5.5-2 

Common Marine Ecosystem Zones a/ 

Marine Ecosystem Description 

Intertidal or Littoral The area where ocean meets land. Tidal variations mean some intertidal 

parts are submerged in water for only part of the day. The length of time 

an area is submerged can influence the ecosystem it supports. For this 

reason, intertidal zones can be further stratified vertically. 

Neritic The shallow ocean area over the continental shelf. Sometimes 

differentiated from the intertidal zone by the fact that it is continuously 

submerged. Sometimes included as part of the intertidal zone. 

Shallow, near land 

Coral reefs, estuaries, mangroves, and other coastal ecosystems often grouped under intertidal or 

neritic zones, but sometimes are defined separately. 

Upper 

open 

ocean 

Oceanic or Pelagic Upper part of open ocean. Colder water, but still receives sunlight. 

Supports plankton and the fish and other organisms that feed upon them. 

Benthic Lower part of open ocean, but excludes the deepest parts. Cold water, 

with little sunlight. Supports seaweed, bacteria, sea stars, and other 

bottom dwellers. 

Abyssal Very cold and nutrient poor. Ecosystem consists mainly of bottom dwellers 

that feed on organic matter that drifts down from upper parts of ocean. 

Hydrothermal Vents Found in abyssal zones. Support chemosynthetic bacteria that live on 

minerals emitted by the vents. 

Deep open ocean 

Profundal Deep zone below the point light can penetrate. Could include the other 

deep ocean zones above. 

_________________

a/ Different categorizations might further stratify these zones, group some zones together, apply different names, 

or define them somewhat differently.

Marine ecosystems play critical roles in global ecology. Marine ecosystems support almost half 

of all known species on Earth, and contribute 5 percent of the protein in the human diet (NOAA 2009b). 

Plankton and seaweed growing in shallower waters are the primary resource for many marine and coastal 

food chains/webs. Marine zones also play an important role in climate change through absorption of CO2. 

Plankton absorb CO2 as they grow, and ultimately will sequester some of that carbon when they die and 

fall to the ocean bottom. Additionally, ocean water itself absorbs some of the CO2 in the atmosphere, 

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Chapter 4 Cumulative Impacts 4.5 Health, Societal, and Environmental Impacts of Climate Change 

increasing water acidity and contributing to reduced concentrations of dissolved oxygen, both of which 

can harm marine ecosystems (see Section 4.7.2 for more information on ocean acidification) (EPA 

2009b). 

4.5.5.2 Environmental Consequences 

4.5.5.2.1 Observed Trends and Impacts of Climate Change 

Many marine and coastal ecosystems around the globe have been substantially degraded, and 

many have been lost altogether. Quantifying the changes in coastal ecosystems is difficult because 

historical data describing the previous extent of these ecosystems are very limited. More and higherquality data characterizing the world’s marine and coastal zones are needed (Burke et al. 2001). 

Ecosystem Conditions

A warming climate is already affecting the ocean. Increasing water temperatures have caused a 

rapid poleward shift in fish and plankton populations in the North Atlantic (EPA 2009b). As ice melts 

and precipitation increases at varying degrees around the globe, freshwater enters the ocean system, 

decreasing salinity and increasing the temperatures. Boyer et al. (2005) found that salinity levels of the 

oceans have changed when comparing 5 year periods from 1955-1959 and 1994-1998 (investigating the 

ocean surface vertically down to a depth of 3 km), and found that some areas are experiencing freshening 

while others are experiencing increases in salinity; in some parts, it is reasoned that the increase in salinity 

is due to increased evaporation. This study concludes that some parts of the Atlantic and Pacific Oceans 

are decreasing in salinity, while other parts are increasing; in most areas of the Indian Ocean, the upper 

layers are increasing in salinity, while the subsurface layers are freshening. Hegerl et al. (2006 in Fischlin 

et al. 2007) found that observed changes in salinity are consistent with simulations of warming and an 

increase of the hydrologic cycle. Less saline waters can inhibit the vertical mixing of ocean waters 

interfering with the distribution of nutrients, although the ultimate impact of this phenomenon remains 

unclear (Denman et al. 2007). 

Ocean ecosystems are being pressured by overfishing, pollution, and other human-induced 

stressors. The United Nations estimates that 75 percent of the world’s fish stocks are fully exploited, 

overexploited, or depleted (FAO 2004 in Easterling et al. 2007) (see Section 4.5.6). Even where fish 

populations are stable, fishing alters marine ecosystems by reducing the age, size, geographic diversity, 

and biodiversity of the populations. Brander (2007) finds that this decrease in diversity leaves the 

ecosystems more vulnerable to environmental stressors such as climate change. 

Recent studies using relatively new data collection methods link changes in temperature to the 

productivity in the world’s oceans. Based on a decade of data from National Aeronautics and Space 

Administration satellite ocean-color sensors launched in 1997, Behrenfeld et al. (2006) in Doney (2006) 

show that trends in chlorophyll productivity closely follow changes in temperature, and that in general, 

phytoplankton biomass and growth decline as surface waters warm. In addition, excess amounts of 

decaying plankton and elevated dissolved CO2 concentrations can cause and expand hypoxic (lowoxygen) zones, or oceanic dead zones, which could physiologically stress marine animals (Brewer and 

Peltzer 2009 in Kundzewicz et al. 2007). Additionally, as the oceans absorb CO2, they become more 

acidic, threatening coral reef ecosystems (EPA 2009b) (see Section 4.7.2. for more information on ocean 

acidification). A recent study found that one-third of the 704 zooxanthellate reef-building coral species 

assessed are at increased risk of extinction (Carpenter et al. 2008). This number has risen dramatically in 

recent decades due to bleaching and diseases driven by elevated sea-surface temperatures. 

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The conditions of coastal ecosystems vary from place to place and depend on many factors. 

Attempts have been made to assess the global extent and distribution of aquatic habitats, but estimates 

vary considerably depending on the type and source of data (UNESCO and WWAP 2006). While 

inventories of coastal zones exist, no high-quality data sets or indicators are available at the global level 

that track changes in condition over time (UNESCO and WWAP 2006). Despite the lack of high-quality 

data, it is safe to assume that coastal zones with substantial human populations are vulnerable to a range 

of human activities that can increase pressure and cause adverse changes to coastal ecosystems. As 

mentioned above, typical coastal ecosystem degradation would include physical alteration, habitat 

degradation and destruction, water withdrawal, overexploitation, pollution, and the introduction of nonnative species. The effects of sea-level rise from climate change could compound these potential impacts. 

EPA considers the current overall coastal condition of the United States to be fair (Summers et al.

2005). EPA evaluated six geographic coastal regions (Great Lakes Coastal Area, Northeast Coastal Area, 

Southeast Coastal Area, Gulf Coast Coastal Area, West Coastal Area, and Alaska, Hawaii, and Island 

Territories) using five ecological health indicators (water quality, sediment quality, benthic, coastal 

habitat, and fish tissue contaminants) to assess estuarine coastal conditions as good, fair, or poor. Of the 

five indicators, only the coastal habitat index received an overall poor rating. The benthic and sediment 

quality indices rated fair to poor, while the water quality and fish tissue contaminants indices received fair 

ratings. Of the six coastal regions, the Southeast Coastal Area ranked highest, with all indicators rating 

fair to good. The region with the worst coastal condition was the Northeast Coastal Area, with four of the 

five indicators rating poor or fair to poor. In terms of human and aquatic life use, 21 percent of the 

assessed coastal resources of the Country are considered unimpaired (good condition), whereas 35 percent 

are impaired (poor condition) and 44 percent threatened (fair condition). 

Burke et al. (2001) found the following trends affecting the conditions of marine and coastal 

ecosystems: 

• Many coastal habitats are disappearing at a fast pace, with extensive losses in the past 

50 years. 

• Although some industrial countries have improved coastal water quality, chemical pollutant 

discharges are increasing overall as agriculture intensifies and new synthetic compounds are 

developed. 

• Pollution-filtering capacities are lost as coastal ecosystems are lost. 

• Nutrient inputs to coastal waters appear to be increasing because of population increase and 

agricultural intensification. 

• The frequency of harmful algal blooms resulting in mass mortality of marine organisms has 

increased substantially over the past few decades. 

• More than 25 different coral reef diseases have been recorded since 1970, and reports of coral 

bleaching have increased measurably in recent years. 

• The capacity of coastal ecosystems to produce fish for human harvest has been highly 

degraded by overfishing, destructive trawling techniques, and loss of coastal nursery areas. 

• An increased number of invasive species is being reported throughout the world’s coastal 

ecosystems. 

• Increased occurrences of hypoxia (shortage of oxygen in water) have been reported. 

• Many commercial fish species and other marine wildlife have become threatened. 

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Chapter 4 Cumulative Impacts 4.5 Health, Societal, and Environmental Impacts of Climate Change 

• Large-scale marine oil spills have been declining, but oil discharges from land-based sources 

are believed to be increasing. 

• The number of protected marine and coastal areas has increased, indicating greater awareness 

of the need to protect these environments. 

• Global marine fish production has increased six-fold since 1950. 

• Notable ecosystem changes have occurred over the last half-century in some fishery areas, 

such as the North Atlantic and Northeast Pacific. 

Sea-level Rise

There is strong evidence that temperature increases caused a rise in global sea level during the 

20th Century (Parry et al. 2007). Because each coastal area has its own unique geographic and 

environmental characteristics, consequences from adaptations to climate change are expected to differ for 

each community. Areas of critical sensitivity on the global scale include Tokyo, Shanghai, London, 

Thailand, India, and Vietnam (Nicholls et al. 2007a in National Science and Technology Council 2008). 

These areas share the characteristics of coastal location, low elevation, large population, and stressed 

resources. Because of their proximity to the water’s edge and the high level of infrastructure typical of 

many coastal communities, these urban centers are sensitive to changes in sea-level rise (National Science 

and Technology Council 2008). 

Recent data suggest that the rise in global sea level has had an effect on some U.S. coastal zones. 

Sea-level rise is non-uniform around the world. In some regions, rates of rise have been as much as 

several times the global mean, while other regions have experienced falling sea level. This might be the 

result of variations in thermal expansion and exchanges of water between oceans and other reservoirs, 

ocean and atmospheric circulation, and geologic processes (EPA 2009b). Satellite measurements provide 

unambiguous evidence of regional variability of sea-level change from 1993 to 2003, with the largest sealevel rise occurring in the western Pacific and eastern Indian Oceans (EPA 2009b). 

Tide gauges have measured the average rate of sea-level rise to be 1.8 millimeters (0.07 inch) +/−

0.5 millimeter (0.019 inch) per year from 1961 to 2003 and 1.7 millimeters (0.07 inch) +/− 0.5 

millimeter (0.02 inch) per year over the past century (EPA 2009b). These changes are attributed to 

thermal expansion associated with rising global temperature, thawing of permafrost, and loss of sea ice 

(EPA 2009b). The global ocean temperature averaged from the surface to a depth of approximately 700 

meters (2,300 feet) has increased by 0.10 °C (0.18 °F) over the period of 1961 to 2003, contributing to an 

average increase in sea level of 0.4 millimeter (0.02 inch) +/− 0.1 millimeter (0.004 inch) per year (EPA 

2009b). This contribution increased from 1993 to 2003, with a rate of sea-level rise of 1.6 millimeters 

(0.06 inch) +/− 0.5 millimeter (0.02 inch) per year (EPA 2009b). Melting of mountain glaciers, ice caps, 

and land ice have also contributed to the measured sea-level rise. From 1961 to 2003, the melting of land 

ice has contributed approximately 0.7 millimeter (0.03 inch) +/− 0.5 millimeter (0.02 inch) per year to 

sea-level rise, with an accelerated rate of 1.2 millimeter (0.05 inch) +/− 0.4 millimeter (0.02 inch) per year 

between 1993 and 2003 (EPA 2009b). Recent global sea-level data from satellite altimetry show an 

accelerated rate of sea-level rise of 2.4 millimeters (0.094 inch) per year evident from 1993 to 2003 

(Domingues et al. 2008 in Epstein et al. 2005), and a rate of 3.36 millimeters (0.13 inch) +/− 0.4 

millimeter (0.02 inch) from 1993 to 2007 (Beckley et al. 2007 in Chao et al. 2008), although it is 

uncertain whether this more recent rate increase is part of a long-term trend or decadal variability (EPA 

2009b). 

Sea-level data show a rise of 0.8 to 1.2 inches per decade since 1958 along most of the Atlantic 

and Gulf Coasts in the United States (EPA 2009b), with the Gulf Coast experiencing a rise of a few 

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4.5 Health, Societal, and Environmental Impacts of Climate Change Chapter 4 Cumulative Impacts 

inches per decade (primarily due to land subsidence) and parts of the Alaskan coasts experiencing 

decreases in relative sea level (due to land rising) of a few inches per decade (National Science and 

Technology Council 2008 and EPA 2009b). Approximately one-sixth of U.S. land that is close to sea 

level is in the mid-Atlantic region; consequently, much of the reporting on effects focuses on that region 

(National Science and Technology Council 2008). Over the past century, the highest rate of sea-level rise 

has been observed in the mid-Atlantic region, in part resulting from subsidence of the land surface 

(Gutierrez et al. 2007). For example, Virginia has observed sea-level rise at 4.4 millimeters (0.17 inch) 

per year compared to 1.8 millimeters (0.07 inch) per year in Maine (Zervas 2001 in Gutierrez et al. 2007). 

New Jersey, with 60 percent of its population living along the 127 miles of coastline, has experienced 

coastline subsidence and beach erosion, threatening communities and coastal wetlands (Union of 

Concerned Scientists 2007 in Kundzewicz et al. 2007, Aucott and Caldarelli 2006, Jacob et al. 2000). 

Sea level on the California coast rose by almost 18 centimeters (7.1 inches) over the last century (EPA 

2009b). 

Enhanced storm surge is an associated stressor directly related to sea-level rise. In one example, 

Frumhoff et al. (2007) discusses the impacts of surging waters during a coastal storm in December 1992, 

when strong winds and rising water levels disrupted the New York City public transit system and required 

the evacuation of communities in New Jersey and Long Island. Sea-level rise in the Chesapeake Bay has 

accelerated erosion rates, resulting in wetland destruction (National Science and Technology Council 

2008). According to the Maryland Geological Survey, Tropical Storm Isabel resulted in the loss of an 

estimated 20 acres or more of land on the western shore of Chesapeake Bay, causing significant damages 

to shoreline structures (Maryland Department of Planning 2004). 

Coastal wetland loss is occurring where ecosystems are squeezed between natural and artificial 

landward boundaries and rising sea levels (EPA 2009b). Rise in sea level could be contributing to coastal 

erosion across the eastern United States (Zhang et al. 2004 in Rosenzweig et al. 2007). In Mississippi 

and Texas, more than half of the shorelines have eroded at average rates of 2.6 meters (8.5 feet) to 3.1 

meters (10.2 feet) per year since the 1970s, while 90 percent of the Louisiana shoreline has eroded at a 

rate of 12.0 meters (39.4 feet) per year (EPA 2009b). Areas in Louisiana are experiencing barrier island 

erosion, resulting in an increased height of waves (Nicholls et al. 2007a in National Science and 

Technology Council 2008). Furthermore, regional sea-level rise has contributed to increased storm-surge 

impacts along the North American eastern coast (National Science and Technology Council 2008). 

Particularly because subsidence is occurring in parts of this area, areas such as the Louisiana and Gulf 

coasts are considered at high risk from erosion and storm surges, and any area along the coast with low 

elevation, large populations, and stressed resources could be expected to be at risk from any future sealevel rise. Saltwater intrusion is a projected threat to estuarine and mangrove ecosystems. The decline of 

bald cypress forests in Louisiana and cabbage palm forests in Florida has already been linked with 

saltwater intrusion. (EPA 2009b) Low-lying areas of the United States Pacific coast are also at increasing 

risk of flooding as sea level rises. 

4.5.5.2.2 Projected Impacts of Climate Change for the United States 

Impacts to marine and coastal ecosystems are expected to continue due to climate and nonclimate stressors, particularly where coastal populations increase and demand more coastal space and 

resources. As of 2003, 153 million people (53 percent of the total population) lived in coastal counties of 

the United States, an increase of 33 million people since 1980. The U.S. coastal population was projected 

to rise to 160 million by 2008. It is also estimated that an additional 25 million people will live in the 

coastal United States in the next 25 years (EPA 2009b). This change in population is expected to 

compound the anticipated adverse effects of climate change on coastal communities, placing heavier 

demand on already stressed ecosystems (EPA 2009b). Nicholls et al. (2007b) in (EPA 2009b) suggests 

that “The major non-climate impacts for the U.S. and other world regions include drainage of coastal 

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Chapter 4 Cumulative Impacts 4.5 Health, Societal, and Environmental Impacts of Climate Change 

wetlands, resource extraction, deforestation, introductions of invasive species, shoreline protection, and 

the discharge of sewage, fertilizers, and contaminants into coastal waters,” and further notes “The 

cumulative effect of these non-climate, anthropogenic impacts increases the vulnerability of coastal 

systems to climate-related stressors.” 

Sea-level Rise

A range of adverse effects from climate change is expected in the United States, one of the most 

damaging of which is expected to be sea-level rise. Sea-level rise in the 21st Century is expected to 

exceed that of past years, with potential adverse consequences for coastal communities and the 

infrastructures they support. Recent studies have shown that global sea level does not rise uniformly and 

that the coastal United States is expected to experience significantly higher sea levels than the global 

average (Bamber et al. 2009b, Yin et al. 2009, both in Pew Center on Global Climate Change 2009). 

Some general effects associated with rising sea levels include:

• Loss of land area due to submergence and erosion of lands in the coastal zone; 

• Changes to coastal environments; 

• More flooding due to storm surges; and 

• Salinization of estuaries and groundwater (National Science and Technology Council 2008). 

For islands such as those in Hawaii and other U.S. territories in the Pacific, outcomes could 

include a reduction in island size and the abandonment of inundated areas (National Science and 

Technology Council 2008, EPA 2009b). 

The effects of sea-level rise on some coastal communities could be devastating because of 

increased flooding and erosion. As much as 21 percent of the U.S. mid-Atlantic coastal wetlands are 

potentially at risk of inundation between 2000 and 2100 (EPA 2009b), and coastal wetlands already 

experiencing submergence are “virtually certain” to continue to shrink due to accelerated sea-level rise, 

among other climate- and non-climate-related factors (EPA 2009b). Additionally, the melting of the 

Greenland ice sheet could have an effect on ocean circulation and sea-level rise dynamics, which might 

exacerbate sea-level rise experienced on the northeast North American coast (Hu et al. 2009). Extensive 

erosion has already been documented across the East Coast, as have notable decreases in the coastal 

wetlands of Louisiana, the mid-Atlantic region, New England, and New York (Rosenzweig et al. 2007 in 

National Science and Technology Council 2008). Erosion is expected to be worse in sandy environments 

along the mid-Atlantic coast, Mississippi, and Texas (National Science and Technology Council 2008, 

Nicholls et al. 2007a in National Science and Technology Council 2008). Over the past fifty years, 

Alaska’s western and northeastern coastline has experienced a doubling in the rate of erosion as highwind events have occurred more frequently (GCRP 2009). Over this century, the Pacific storm track may 

move northward as projected sea surface temperatures increase and sea ice cover decreases accelerating 

coastal erosion (GCRP 2009). The IPCC notes that sandy shorelines are already retreating and that sealevel rise due to climate change is an underlying cause. Furthermore, areas in Louisiana are experiencing 

barrier-island erosion, resulting in increases in the height of waves that make it to shore (EPA 2009b). A 

large storm can affect the shoreline position for weeks to a decade or longer (Morton 1994, Zhang et al.

2004, List et al. 2006, Riggs and Ames 2003, all in Gutierrez et al. 2007). Tidal wetlands, estuarine 

beaches, marshes, and deltas are expected to be inundated with water in areas such as the Mississippi 

River, Louisiana Delta, and the Blackwater River marshes in Maryland (Titus et al. 2008 in National 

Science and Technology Council 2008). The “coastal squeeze” phenomenon, where wetlands are trapped 

between natural and human-made land boundaries, is causing wetland loss and habitat destruction (EPA 

2009b). Freshwater resources are also at risk given the likely intrusion of saltwater into groundwater 

supplies, adversely affecting water quality and salinization rates (Kundzewicz et al. 2007b in National 

Science and Technology Council 2008). 

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4.5 Health, Societal, and Environmental Impacts of Climate Change Chapter 4 Cumulative Impacts 

The most devastating impacts related to increased mean sea level are associated with impacts of 

storm surge (EPA 2009b). The height of storm surges will increase if sea level rises, regardless of storm 

frequency and intensity increases; thus, a storm of similar behavior will cause greater damage with rising 

sea level (Fisher et al. 2000 in Easterling et al. 2007). One study suggests the 100-year flood might 

actually occur every 25 to 30 years (Najjar et al. 1999 in Easterling et al. 2007). By mid-century, Boston 

and Atlantic City could experience a 100-year flood event every 2 to 4 years and annually by the end of 

the century (Frumhoff et al. 2007). 

Sections of the California coastal ecosystems are at risk due to sea-level rise. The historic rate of 

sea-level rise observed at San Francisco and San Diego during the past 100 years was 15 to 20 

centimeters (5.9 to 7.9 inches). Parts of the California coast are at risk for flood damage, which could 

further jeopardize levees in the City of Santa Cruz (California Environmental Protection Agency 2009). 

Santa Cruz is 20 feet above sea level and has levees built to contain the 100-year flood. The ENSO 

events of 1982-1983 and 1997-1998 corresponded to high sea level episodes (Flick 1998 in Cayan et al.

2006). The most severe coastal impacts occur as a result of coinciding factors including (a) elevated 

storm surge during, (b) high astronomical tide with (c) higher sea levels due to monthly-to-annual sealevel fluctuations associated with ENSO events, and (d) higher mean sea levels (Cayan et al. 2008). 

In the San Francisco Bay Area, by 2050, 180,000 acres of shoreline will be vulnerable to 

inundation with a 16-inch rise in sea level, which is the lower of two sea-level rise scenarios considered 

by the Bay Area Conservation and Development Commission. Additionally, a 16-inch rise in sea level 

would impact 90 to 95 percent of existing tidal marshes and tidal flats, 20 percent of which would be 

vulnerable to permanent submersion and erosion. (Heberger et al. 2009 in BCDC 2009) 

Storm Events 

The frequency and intensity of storms are expected to increase at the same time sea levels rise 

and sea surface temperatures increase (Nicholls et al. 2007a in National Science and Technology Council 

2008). 

One ecological effect of intense storms is the loss of coastal wetlands, which has been 

documented on many occasions. A prominent recent example is the loss of coastal lands as a result of 

Hurricane Katrina in 2005. In Louisiana alone, the loss of land during Hurricane Katrina was 

approximately 217 square miles. The Chandeleur Islands, which New Orleans relied on as a tropical 

storm buffer, lost 85 percent of their surface area (CCSP 2008b). Parts of New Orleans and surrounding 

areas are 1.5 to 3 meters (4.9 to 9.8 feet) below sea level. Using a mid-range estimate of sea-level rise of 

480 millimeters (roughly 1.6 feet) and accounting for land subsidence, the region could be 2.5 to 4.0 

meters (8.2 to 13.1 feet) or more below mean sea level by 2100. Further, in this scenario, a storm surge of 

3 to 4 meters (9.8 to 13.1 feet) (an estimated storm surge from a Category 3 hurricane), without the effect 

of waves, could be 6 to 7 meters (19.7 to 23.0 feet) above areas that were heavily populated in 2004. 

(EPA 2009b) 

Severe storms and sea-level rise have had detrimental effects on coastal ecosystems in areas with 

sandy beaches. Many species rely on the wellbeing of, and accessibility to, beaches. Examples include: 

• Diamondback terrapins and horseshoe crabs rely on beach sands to bury their eggs. The eggs 

not only act to propagate the species, but some shorebirds, such as the piping plover, rely on 

these eggs as a food source (USFWS 1988 in CCSP 2009b). 

• Horseshoe crabs rarely spawn unless sand is deep enough to nearly cover their bodies, about 

10 centimeters (4 inches) (Weber 2001). Shoreline protection structures designed to slow 

beach loss can also block horseshoe crab access to beaches and can trap or strand spawning 

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Chapter 4 Cumulative Impacts 4.5 Health, Societal, and Environmental Impacts of Climate Change 

crabs when wave energy is high (Doctor and Wazniak 2005). In this case, both the loss of 

beach and the adaptation strategy selected by the community can harm local species. 

• A rare firefly, Photuris bethaniensis, is found only in areas between dunes on Delaware’s 

barrier beaches. Its habitat is at risk due to beach stabilization and hardening of shorelines, 

which limits migration of dunes and the formation of the swales between dunes where the 

firefly is found (CCSP 2009b). 

Because the distribution of marine fish and plankton is largely driven by climate-related factors, 

climate change is causing significant ecosystem alterations, including marine species shifts and effects on 

fisheries. The IPCC estimates that 20 to 30 percent of marine species studied would be in climate zones 

outside their current ranges with a temperature rise of 3.5 to 5.5 °F, and would likely be at risk of 

extinction (CCSP 2009a). Rising water temperatures and other climate-driven changes (e.g., salinity, 

dissolved oxygen levels, ocean circulation) have been associated with the movement of plankton by 10° 

latitude toward the poles over a period of 4 decades in the North Atlantic (EPA 2009b). Tuna stocks in 

the Pacific are expected to shift eastward due to climate change, and marine ecosystems in Alaska are 

already experiencing significant alterations (CCSP 2009a). The Bering Sea produces the largest 

commercial fishery harvests in the United States and supports subsistence economies of the indigenous 

peoples of Alaska (ACIA 2005). Current observations indicate that continued climate-related changes in 

the north Bering Sea could result in major shifts in marine fish stocks, including commercially important 

species such as Pollock, upon which Alaskan Natives depend (Grebmeier et al. 2006). 

4.5.5.2.3 Projected Global Impacts of Climate Change 

Globally, coastal systems and low-lying areas are experiencing adverse effects related to climate 

change and sea-level rise, such as coastal inundation, erosion, ecosystem loss, coral bleaching and 

mortality at low latitudes, thawing of permafrost, and associated coastal retreat at high latitudes (very high 

confidence) (Nicholls et al. 2007c in Ebi et al. 2008). To further exacerbate the stressors, human 

settlement and encroachment on coastal systems and low-lying areas have been increasing, with an 

estimated 23 percent of the world’s population living within about 60 to 65 miles of the coast and no 

more than about 330 feet above sea level (Small and Nicholls 2003 in National Science and Technology 

Council 2008). 

Sea-level Rise

Although non-uniform around the world, global sea level is estimated to have risen by 1.7 

millimeters (0.07 inch) +/− 0.5 millimeter (0.02 inch) per year over the past century, with the western 

Pacific Ocean and the eastern Indian Ocean experiencing the greatest rise (Nicholls et al. 2007c in Ebi et 

al. 2008). Sea-level rise, coupled with both projected sea surface temperatures increasing 1 oC (1.8 oF) to 

3 °C (5.4 °F) and intensified cyclonic activity, could lead to larger waves and storm surges, which would 

impact coastal systems and low-lying areas across the globe (Nicholls et al. 2007c in Ebi et al. 2008). 

The loss or degradation of coastal ecosystems has a direct impact on societies that depend on coastalrelated goods and services such as freshwater and fisheries and has the potential to impact hundreds of 

millions of people (Parry et al. 2007). 

There is variability in the projected effects from climate change and sea-level rise on an 

international scale. For instance, if the global mean annual temperature increases above 1980 to 1999 

levels, coastal systems and low-lying areas are anticipated to sustain increased damage due to floods and 

storms; an additional increase of 2 °C (3.6 °F) would lead to an increase of millions of people that could 

experience coastal flooding each year; an increase of 3 °C (5.4 °F) is estimated to cause a loss of 

30 percent of the global coastal wetlands (high confidence; IPCC 2007d, Figure SPM.2). Coastal wetland 

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ecosystems are at substantial risk from sea-level rise if they are sediment-starved or prevented from 

migrating inland. As sea water temperatures increase, it is likely that coral bleaching and mortality will 

rise unless corals demonstrate thermal adaptation (Nicholls et al. 2007c in Ebi et al. 2008). These adverse 

impacts are expected to increase in severity as the global mean annual temperature increases. 

IPCC (2007d) and EPA (2009b) state that sea level will likely rise 0.18 to 0.59 meter (0.6 to 2.0 

feet) by 2100 relative to 1980-1999 (these numbers represent the 5 to 95% range across all SRES 

scenarios). However, this estimate does not fully account for effects from loss of land-surface ice flowing 

into the ocean; it might also underestimate ice losses from the Greenland and Antarctic ice sheets (Pfeffer 

et al. 2008, Meier et al. 2007 in Kundzewicz et al. 2007, Rahmstorf 2007, Shepherd and Wingham 2007); 

and it does not account for adjustments to water volume due to changes in global precipitation (Wentz et 

al. 2007, Zhang et al. 2007). Recent studies that account for some of these effects indicate that sea-level 

rise might be even higher. For example, Pfeffer et al. (2008) estimates sea level could rise 0.8 to 2.0 

meters (2.6 to 6.6 feet) by 2100 compared to present day, while Rahmstorf (2007) uses a semi-empirical 

approach to estimates a rise of 0.5 to 1.4 meters (1.6 to 4.6 feet) by 2100 compared to 1990 levels. None 

of these studies account for the potential complex changes in ocean circulation that could further 

influence sea-level rise. 

Complete melting of the Greenland ice sheet could occur from a sustained summertime warming 

in the region of 5 °C (9 °F) (with a range of uncertainty from 2 °C to 7 °C [4 °F to 13 °F]) (CCSP 2009a), 

which would exacerbate coastal sea-level rise (Hu et al. 2009). This scenario raises concern regarding the 

viability of coastal communities, salt marshes, corals, and mangroves. A sea-level rise of about 36 

centimeters (14 inches) from 2000 to 2080 is projected to reduce coastal wetlands by 33 percent, with the 

largest impact on the Atlantic and Gulf of Mexico coasts of the Americas, on the Mediterranean, on the 

Baltic, and on small-islands (Nicholls et al. 2007c in Ebi et al. 2008). 

IPCC SRES estimated that the coastal population could grow from 1.2 billion people in 1990 to 

between 1.8 billion and 5.2 billion people by the 2080s, with this range dependent on coastal migration. 

Although the impact of sea-level rise on a specific region can be difficult to quantify given regional and 

local variations (Parry et al. 2007), the IPCC describes the following coastal regions as the most 

vulnerable to the impact of climate change: South Asia, Southeast Asia, East Asia, Africa, and small 

islands (Nicholls et al. 2007c in Ebi et al. 2008). 

Many of the coastal cities that are most vulnerable to adverse impacts of climate change are at 

further risk due to human activities such as agriculture, aquaculture, silviculture, industrial uses, and 

residential uses that have degraded the natural protective qualities of the coastal systems (Nicholls et al.

2007c in Ebi et al. 2008). Examples of coastal countries at risk for shoreline retreat and flooding due to 

degradation associated with human activity include Thailand (Durongdej 2001, Saito 2001, both in 

National Science and Technology Council 2008); India (Mohanti 2000 in National Science and 

Technology Council 2008); Vietnam (Thanh et al. 2004 in National Science and Technology Council 

2008); and the United States (Scavia et al. 2002 in National Science and Technology Council 2008), with 

emphasis on the seven Asian megadeltas that have a combined population of more than 200 million 

(Nicholls et al. 2007c in Ebi et al. 2008). Of particular concern are those highly populated coastal regions 

in countries with limited financial resources to protect or relocate its populations (Nicholls et al. 2007c in 

Ebi et al. 2008). 

Small islands are particularly vulnerable to climate change and sea-level rise, especially those 

prone to subsidence (Parry et al. 2007). Beach erosion is projected to increase as sea level rises and sea 

water temperature increases. Arctic islands could experience increased erosion and volume loss as 

permafrost and ground ice warms in response to rising global temperatures (Mimura et al. 2007). Coastal 

stability in the Arctic is influenced by a combination of factors, including shoreline exposure, relative sea-

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level change, local geology, temperatures, ground ice, and sea ice (EPA 2009b). Rising temperatures 

reduce the thickness and spatial extent of sea ice creating more open water, this allows for winds to 

generate stronger waves thereby increasing shoreline erosion (EPA 2009b). This dynamic process is 

exacerbated by relative sea-level rise and thawing of permafrost (EPA 2009b). 

Changes in Sea Ice and Ocean Warming

Annual average temperature in the Arctic has increased at twice the rate of the rest of the world, 

and additional warming of 4 to 7 °F is expected over the next century. The stronger warming is primarily 

a result of the positive feedback due to decreased surface albedo as sea ice is lost (EPA 2009b). Annual 

average Arctic sea ice extent decreased 2.7 +/− 0.6 percent per decade from 1978 to 2005. In 2007, sea 

ice extent was approximately 23 percent less than the previous all-time minimum observed in 2005. 

Average sea ice thickness in the central Arctic very likely has decreased up to approximately 3 feet from 

1987 to 1997 (EPA 2009b). Recent results indicate that summer Arctic sea ice could be gone as early as 

2037 (Wang and Overland 2009). Sea ice dynamics are nonlinear and many thermodynamic processes 

will affect potential threshold behavior (Eisenman and Wettlaufer 2009). 

Ocean warming and sea-ice decline is leading to a change from arctic to subarctic conditions in 

the northern Bering Sea. This is having significant impacts on Arctic sea-ice ecosystems. Phytoplankton 

(algae) that form the base of the Arctic food web bloom on the underside of sea ice. The timing and 

distribution of plankton blooms are regulated by the ice edge in spring, and as the extent and location of 

the ice edge changes with warming sea surface temperatures, the timing of blooms change. This leads to 

more consumption at the surface by zooplankton and less organic material reaching the sea bed. As a 

result, there is a decline in benthic production of clams and other small mollusks and crustaceans, which 

are the food source for many bottom-feeding sea ducks and marine mammals, including walrus and gray 

whales. (Janetos et al. 2008) 

As a result of these dynamics, the trend toward more subarctic ecosystem conditions in the 

northern Bering Sea is contributing to declines in Arctic marine mammal and diving seabird populations, 

and in commercial and subsistence fisheries (Grebmeier et al. 2006). In other ocean basins, there is 

evidence of changes in important prey species of zooplankton, with resulting food-web changes. For 

example, in the North Atlantic the distribution of warm-water copepods (aquatic crustaceans) has shifted 

north by 10° latitude as a result of a change in the North Atlantic Oscillation and climate (Beaugrand et 

al. 2002a). In the southwest Atlantic, the distribution of emperor and Adelie penguins, which depend on 

ice habitat, has shifted to the north and contracted (Forcada and Trathan 2009 in Easterling et al. 2007). 

Positive impacts anticipated to be experienced in high latitudes include a longer tourist season 

and better navigability (Mimura et al. 2007). 

4.5.6 Food, Fiber, and Forest Products 

This section defines food, fiber, and forest product resources and the existing conditions and 

potential vulnerability of each to the impacts of climate change. The primary source of information in 

this section is the IPCC Fourth Assessment Report (Easterling et al. 2007), specifically, Chapter 5 for 

food, fiber, and forest products. 

The food, fiber, and forest sector is a substantial source of livelihood and food for large numbers 

of the world’s population and a major land cover type at a global level. Cropland, pasture, or natural 

forests account for approximately 70 percent of Earth’s land cover. The United Nations Food and 

Agriculture Organization (FAO) estimates that approximately 450 million of the world’s poorest people 

depend entirely on this sector for their livelihood (Easterling et al. 2007). 

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According to IPCC, this sector includes agriculture, forestry, and fisheries and the IPCC describes 

the climate-change impacts to these systems and their capacity to provide food and sustenance for human 

consumption. This sector also includes subsistence and smallholder agriculture, defined as rural 

producers who farm or fish primarily with family labor and for whom this activity provides the primary 

source of income (Easterling et al. 2007). 

4.5.6.1 Affected Environment 

An estimated 40 percent of Earth’s land surface is used for cropland and pasture (Foley et al.

2005 in Easterling et al. 2007). The FAO estimates that natural forests cover another 30 percent of the 

land surface, and that 5 percent of that natural forest area generates 35 percent of global timber production 

(FAO 2000 in Easterling et al. 2007). Almost 70 percent of people in lower-income countries around the 

world live in rural areas where agriculture is the primary source of livelihood. Growth in agricultural 

incomes in developing countries fuels the demand for non-basic goods and services fundamental to 

human development. The FAO estimates that the livelihoods of roughly 450 million of the world’s 

poorest people depend entirely on managed ecosystem services. Fish provide more than 2.6 billion 

people with at least 20 percent of their average per-capita animal protein intake, but 75 percent of global 

fisheries are fully exploited, overexploited, or depleted (FAO 2004 in Easterling et al. 2007). 

4.5.6.1.1 Terrestrial Systems 

The distribution of crop, pasture, and forest species between the polar and equatorial latitudes is a 

function of existing climatic and atmospheric conditions, and a function of photoperiod. Agricultural, 

pastoral, and forestry systems depend on total seasonal precipitation and its pattern of variability, and on 

wind and humidity. Crops exhibit threshold responses to their climatic environment, which affect their 

growth, development, and yield (Porter and Semenov 2005 in Easterling et al. 2007). Short-term natural 

extremes, such as storms and floods, interannual and decadal climate variations, and large-scale 

circulation changes, such as ENSO, all have important effects on crop, pasture, and forest production 

(Tubiello 2005 in Easterling et al. 2007). 

For example, Europe experienced a particularly extreme climate event during the summer of 

2003, with temperatures up to 6 °C (11 °F) above long-term means, and precipitation deficits up to 12 

inches (Trenberth et al. 2007 in Easterling et al. 2007). Associated with this extreme climate event was a 

decline in corn yield of 36 percent in the Po River valley in Italy and 30 percent in France. In addition, 

French fruit harvests declined by 25 percent, winter wheat yields declined by 21 percent, and hay and 

other forage production declined by an average of 30 percent (Ciais et al. 2005 in Easterling et al. 2007). 

The impacts to the terrestrial biosphere (e.g., increased tree death) could increase due to the lag effect of 

the heat wave in the years following an extreme event (Heimann and Reichstein 2008). African droughts 

between 1981 and 1999 caused livestock mortality from 20 percent to more than 60 percent in countries 

such as Botswana, Niger, Ethiopia, and Kenya (Easterling et al. 2007). 

Total forest productivity might rise modestly, with considerable global variation, due to extended 

growing seasons and elevated CO2 concentrations. Nitrogen deposition and warmer temperatures have 

likely increased forest growth in locations not water limited. For example, in regions that are historically 

limited by low temperatures and short growing seasons, forest growth seems to be slowly accelerating 

(less than 1 percent per decade). Conversely, growth is slowing in areas subject to drought. For example, 

in the southwestern United States, growth rates have decreased since 1895, correlating to drought caused 

by warming temperatures. Similarly, increased drought stress has lowered the growth of white spruce on 

Alaska’s dry south-facing slopes (EPA 2009b). 

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Wildfires have been increasing in some areas, limiting forest productivity. The wildfire season in 

the western United States has increased by 78 days in the last 3 decades. Burn durations of large fires 

(more than 2,470 acres) has increased from 7.5 to 37.1 days due to an increase in spring and summer 

temperatures of 1.4 °F (EPA 2009b). 

Overall, climate change might benefit crop and pasture yields in mid- to high-latitude regions, 

while decreasing yields in dry and low-latitude regions. Local extinctions of fish species are expected, 

particularly at the edges of habitat ranges (Easterling et al. 2007). 

Agricultural and forest lands are experiencing multiple stresses that increase their vulnerability to 

climate-change impacts. Examples include soil erosion, salinization of irrigated areas, overgrazing, overextraction of groundwater, loss of biodiversity, and erosion of the genetic resource base in agricultural, 

forest, and pasture areas. Overfishing, loss of biodiversity, and water pollution in aquatic areas are 

stresses that increase the vulnerability of fishery resources to climate-change impacts (Easterling et al.

2007). 

The vulnerability of these resources depends on both the exposure to climate conditions and 

capacity to cope with changing conditions. Exposure to conditions highly depends on local geography 

and environment. Adaptive capacity is dynamic and depends on wealth, human capital, information and 

technology, material resources and infrastructure, and institutions and entitlements (Easterling et al.

2007). 

Sub-Saharan Africa offers one example of a region that is highly vulnerable to food insecurity 

(Vogel 2005 in Easterling et al. 2007). Drought conditions, flooding, and pest outbreaks are some of the 

existing stressors on food security that could be influenced by future climate change. Options for 

addressing food insecurity in this region (and overall development initiatives related to agriculture, 

fisheries, and forestry) could be constrained by health status, lack of information, and ineffective 

institutional structures. These constraints could limit future adaptations to periods of heightened climate 

stress (Reid and Vogel 2006 in Easterling et al. 2007). 

4.5.6.1.2 Aquatic Systems 

Spatial adaptation of marine ecosystems to climate change is in some ways less geographically 

constrained than for terrestrial systems. The rates at which planktonic ecosystems have shifted their 

distribution have been very rapid over the past 3 decades, which can be regarded as natural adaptation to a 

changing physical environment (Beaugrand et al. 2002b in Easterling et al. 2007). Most fishing 

communities use stocks that fluctuate due to interannual and decadal climate variability, and consequently 

have developed considerable coping capacity (King 2005 in Easterling et al. 2007). 

Research on the relationship between water temperature and the health of freshwater fishes 

indicates different impacts in summer and winter. Although temperature increases might cause seasonal 

increases in growth in winter, mortality risks to fish populations occur at the upper end of their thermal 

tolerance zone in summer. 

World capture production of finfish and shellfish in 2004 was more than twice that of 

aquaculture, but since 1997, capture production decreased by 1 percent whereas aquaculture increased by 

59 percent (Easterling et al. 2007). The increasingly important aquaculture sector allows for the 

application of similar types of management adaptations to climate change suggested for crop, livestock, 

and forestry sectors. This is not the case, however, for marine capture fisheries, which are shared 

resources subject to varying degrees of effective governance. Adaptation options for marine capture 

fisheries include altering catch size and effort. Three-quarters of world marine fish stocks are exploited at 

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levels close to or above their productive capacity (Bruinsma 2003 in Easterling et al. 2007). Reductions 

in level of effort and harvest are required to sustain yields. Such a course of action might also benefit fish 

stocks that are sensitive to climate variability when their population age-structure and geographic 

substructure are reduced (Brander 2005 in Easterling et al. 2007). 

4.5.6.2 Environmental Consequences 

Earth’s land surface is composed mostly of managed cropland and pasture (40 percent) and 

natural forests (30 percent) (Foley et al. 2005 in Easterling et al. 2007). These sectors provide important 

commodities that are produced in a variety of geographic and climatic regions (CCSP 2008c). Continued 

growth and productivity of the world’s agriculture and forests is necessary to sustain human economic 

and social development. 

The discussion below focuses on impacts to food and industrial crops, fisheries, agricultural 

pastures, commercial forestry, and subsistence farming (Easterling et al. 2007). The key drivers for 

climate impacts in this sector are higher temperatures, changed precipitation and transpiration dynamics, 

the effects of increased CO2 concentrations on vegetative growth and yield, greater frequency in extreme 

weather events, and increased stressors to forests and agriculture in the form of pests and weeds 

(Easterling et al. 2007). 

The world’s food crops, forests, and fisheries have evolved to be in tune with the present climatic 

environment. The productivity of these systems ultimately relies on the interaction of various climate 

factors, including temperature, radiation, precipitation, wind speed, and water vapor pressure (Easterling 

et al. 2007). Threshold climatic conditions for crops and forests affect their growth and yield, and 

climatic conditions and their interaction influence the global distribution of agricultural and forest species 

(Porter and Semenov 2005 in Easterling et al. 2007). Extreme weather events, including droughts and 

intense rainfall episodes, can adversely impact crop yields due to the increases and decreases of water 

associated with these events (CCSP 2008c). 

The sensitivity to climate change and exposure to various other stressors increases the 

vulnerability of the forest, food, and fiber systems (Easterling et al. 2007). Non-climate stressors such as 

soil erosion, overgrazing, loss of biodiversity, decreased availability of water resources, increased 

economic competition among regions, and the adaptive capacity of various species increase overall 

sensitivity to the climate and thus exacerbate the adverse effects of climate change (CCSP 2008c). 

Climate change could also benefit agriculture and silviculture through the CO2 fertilization effect. 

CO2 is essential for plant growth; some research suggests that higher atmospheric concentrations lead to 

higher productivity of some food, fiber, and forest crops. Milder winters and longer growing seasons 

could also increase productivity in some regions. 

Important examples that highlight the link between large-scale climate changes and the sensitivity 

of the food, fiber, and forest systems include the effects of ENSO, a relatively well-known phenomenon, 

on crop yield. In Australia, during ENSO years there is increased probability of a decline in farmers’ 

incomes by as much as 75 percent below the median income compared to non-ENSO years (Tubiello 

2005 in Easterling et al. 2007). Another example is the extreme heat wave that occurred in Europe in 

2003, which lowered maize yield by 36 percent in Italy and 30 percent in France (Ciais et al. 2005 in 

Easterling et al. 2007). Uninsured losses for the entire European Union agriculture sector were estimated 

at 13 billion euros; 4 billion euros was lost in France alone (Sénat 2004 in Easterling et al. 2007). 

In the United States, particularly in the north, the average increase in temperature is expected to 

lead to a longer growing season. However, temperature increases could also lead to increased sensitivity 

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to climate change in the southeast and the corn belt (Carbone et al. 2003 in National Science and 

Technology Council 2008). The Great Plains region is not expected to experience increased sensitivity to 

climate change (Mearns et al. 2003 in National Science and Technology Council 2008). 

The most recent comprehensive and peer-reviewed literature about global climate impacts on the 

food and forestry sectors is from the IPCC Fourth Assessment Report. The SAP 4.3 Report (CCSP 

2008c) provides an additional source of information on the impacts of climate change on agriculture, land 

resources, and biodiversity in the United States. Most of the evidence cited in this section focuses on the 

results of the IPCC Fourth Assessment Report and SAP 4.3 (CCSP 2008c). Additionally, this section 

includes information from EPA’s Technical Support Document for Endangerment and Cause or 

Contribute Findings for Greenhouse Gases under Section 202 (a) of the Clean Air Act (EPA 2009b). 

However, because new evidence is continuously emerging on the subject of climate-change impacts on 

the agriculture and forest systems, the discussion below also draws on results reported in more recent 

studies. 

4.5.6.2.1 Projected Impacts of Climate Change for the United States 

Forests

In the United States, the combination of human management and temperate climate has resulted 

in a productive and healthy forest system, as exemplified by the southern pine plantations (CCSP 2000). 

Forests are generally considered the most productive of the terrestrial ecosystems and provide important 

commodities like timber products. They are also key biodiversity sanctuaries and providers of ecosystem 

services. Forests cover roughly one third of the land in the United States. Net growth of these forests 

(growth minus removals minus decomposition) accounts for removing about 910.7 MMTCO2 per year 

from the atmosphere, about 12.7 percent of gross national GHG emissions (EPA 2009a). Globally, 

forests account for the largest fraction of terrestrial ecosystem sequestered carbon, estimated to be 

roughly 1,640 petagrams (3,615 trillion pounds) of carbon (Sabine et al. 2004 in CCSP 2008). Climate 

change could directly affect the ability of forests to provide key services and commodities in several 

ways. 

Overall, forest productivity could increase through the CO2 fertilization effect, the warming of 

colder climates associated with increased CO2 concentrations, and increased precipitation, especially in 

arid regions (EPA 2009b). Forest growth in North America will likely increase between 10 and 20 

percent throughout the 21st Century, but with noticeable variation both temporally and regionally (EPA 

2009b). The productivity gains will be temporally and regionally dependent. For example, the growth of 

high elevation forests in the Cascade Mountains in the Northwest United States is expected to increase in 

the short terms. However, over the long term, deficits in soil moisture will adversely impact tree growth 

and productivity (GCRP 2009).The expected productivity benefits from increased CO2 concentrations can 

be counteracted by water shortages and drought, which in turn are affected by increased nitrogen 

deposition rates and ozone concentrations (Malmsheimer et al. 2008). Additionally, new studies indicate 

that the direct CO2 fertilization effect on tree growth is less than previously believed (EPA 2009b). 

One key impact of climate change is the extended risk and increased burn area of forest fires 

coupled with pathogenic stressors that damage fragile forest systems (EPA 2009b). It is projected that the 

forest fire season (summer) could be extended by 10 to 30 percent as a result of warmer temperatures 

(Parry et al. 2007). Certain forest types including the pinon pine-juniper forests in the Southwest region 

will be especially susceptible to forest fire risk because of current drought conditions in the region (GCRP 

2009). In the western states, the anticipated warmer spring and summer temperatures are expected to 

reinforce longer fire seasons and increased frequency of large wildfires. In turn, the carbon pools within 

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forests are expected to be affected by changes in forest composition and reduced tree densities 

(Westerling et al. 2006 in CCSP 2008). 

More specifically, the Hadley and Canadian climate and ecological models project an increase in 

the fire season hazard by 10 percent in the 21st Century in the United States, with small regional decreases 

in the Great Plains and a 30-percent increase in Alaska and the Southeast (CCSP 2000). Highlighting the 

geographic differences even within a state, two climate models (the Geophysical Fluid Dynamics 

Laboratory model and the Parallel Climate Model) were run using “business as usual” (A2) and 

“transition to a low GHG emissions” (B1) IPCC SRES emissions scenarios. The results showed increases 

in fire risk in Northern California (15 to 90 percent), increasing with temperature, whereas, in Southern 

California, the change in fire risks ranged from a decrease of 29 percent to an increase of 28 percent. 

These results were largely driven by differences in precipitation between the different scenarios. In 

Southern California the drier conditions simulated in both the Geophysical Fluid Dynamics Laboratory 

model scenarios led to reduced fire risks in large parts of southern California, with fire risks increased in 

parts of the San Bernardino Mountains (Westerling and Bryant 2006a). 

Historical evidence indicates that the warmer periods in the past millennium correlated with 

increased frequency in wildfires, particularly in western forests (CCSP 2008c). General circulation 

models project increased wildfire activity in the western states, particularly from 2010 through 2029 

(Flannigan et al. 2000, Brown et al. 2004a, both in CCSP 2008). In 2060, models have projected forest 

fire severity increases of 10 to 30 percent in southeastern states and 10 to 20 percent in northeastern states 

(Flannigan et al. 2000 in CCSP 2008). Some models have projected even larger increases in wildfire 

activity, particularly in the southeastern region of the United States (Bachelet et al. 2001a in CCSP 2008). 

Potential losses to North American producers from increased disturbances (including wildfires, insects, 

and diseases) coupled with climate-change impacts have been estimated to range from $1 to $2 billion per 

year averaged throughout the 21st Century (Sohngen and Sedjo 2005 in Field et al. 2007). 

Ancillary consequences of the projected increase in wildfire frequency across the United States 

include an increase in GHG emissions and criteria air pollutant emissions. Although the GHGs released 

through wildfires could eventually be sequestered by forest regrowth, this carbon release might not be 

fully recovered in the short term and thus might be an important source of CO2 in the atmosphere 

(Kashian et al. 2006 in CCSP 2008). Particularly in forests in the western United States, “If wildfire 

trends continue, at least initially this biomass burning will result in carbon release, suggesting that the 

forests of the western United States could become a source of increased atmospheric carbon dioxide 

rather than a sink, even under a relatively modest temperature increase scenario” (Westerling et al. 2006b 

in CCSP 2008). 

Invasive Species 

The increasing occurrence of forest fires, which is likely to continue with projected warming 

temperatures, would impact ecosystem services, reduce the potential for carbon storage via forest 

management, and provide increased potential habitat for invasive species and insect outbreaks (Parry et 

al. 2007). 

Because invasive species and pests are not constrained by the need for pollinators or seed 

spreaders, these species are more adaptable to the warming climate (Vila et al. 2007 in CCSP 2008). The 

northward movement of weed species, especially invasive weeds, is likely to be a result of higher 

projected temperatures and increased CO2 concentration. This movement northward could further be 

accelerated, because some studies that have shown that the responsiveness of weeds to glyphosate, an 

important herbicide used in the United States, diminishes with increases in CO2 concentration levels 

(Ziska et al. 1999 in CCSP 2008). 

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Disease and Pathogens

Warming temperatures might be allowing for the migration of diseases and pathogens (CCSP 

2008c). More specifically, increases in temperature are influencing the development of insect lifecycles, 

reducing winter mortality rates (EPA 2009b) and “influence[ing] synchronization of mass attacks required 

to overcome tree defenses” (Ryan et al. 2008b in CCSP 2008). EPA (2009b) states that the impacts of 

climate change on North American commercial forestry are likely to be sensitive to changes in 

disturbances from insects and diseases. 

Warming trends in the United States have already allowed for earlier spring insect activity and 

increased proliferation of certain species (CCSP 2008c). In the Great Plains region, red fire ant and 

rodent populations are projected to increase due to warming temperatures associated with climate change 

(GCRP 2009). These warming trends have also allowed for an increase in the survival rates of diseases 

and pathogens that affect crops and plant and animal species. Recent research has linked rising 

temperatures to increased outbreaks of the mountain pine beetle, the southern pine beetle, and the spruce 

beetle (EPA 2009b). Rising temperatures have also been correlated with the expansion of suitable range 

for the hemlock wooly adelgid and the gypsy moth (Ryan et al. 2008b in CCSP 2008). Not only are the 

boundaries of insects being shifted by climate change, but “tree physiology and tree defense mechanisms” 

are being altered (Kirilenko and Sedjo 2007). The damage to forests is expected to depend on seasonal 

warming − increases in winter and spring temperatures might increase losses to insects such as the 

southern pine beetle (Gan 2004 in Field et al. 2007). 

The control of increased insect populations, especially in the projected warmer winters and in the 

southern regions, might require increased applications of insecticides. It is important to control these 

insect populations because of their ability to spread other pathogens, especially the flea beetle, which is 

known to be a conduit for the corn damaging bacterium Stewart’s Wilt (CCSP 2008c). 

Migration

Under future climate-warming scenarios, plant and animal species are expected to shift northward 

and to migrate to higher elevations, thus redistributing North American ecosystems (Parry et al. 2007). 

The projected increases in precipitation over dry regions might encourage forest growth and displace 

some grasslands (CCSP 2008c). Recent bioclimate modeling indicates that over the long term the 

diversity of tree species in the Northwest will increase while in the Southwest tree species richness will 

decrease. Plants and trees which are native to the Southeast region will likely shift northward into the 

Midwest region as temperatures rise (GSCRP 2009). However, the benefit of increased diversity of 

species in the North over the long term might lead to decreases in the short term because migration of 

new species northward might be slower than the disappearance of species who have not adapted to local 

conditions (EPA 2009b). 

As an example of species migration as a result of climate change, the United States has 

experienced an incursion of perennial herbaceous species that limit the soil moisture available for other 

crops throughout the growing season (CCSP 2008c). The invasion of these non-native species could 

impact how these regions adapt to climate change and could lead to the potential for more frequent 

wildfires by increasing vegetation density (Fenn et al. 2003 and Wisdom et al. 2005 both in CCSP 2008). 

As another example, aspen trees in Colorado have been encroaching on the more cold-tolerant spruce-fir 

forests over the past century (EPA 2009b). Additionally, certain habitats like the mountain forests are 

losing ground due to lowland encroachment and high-altitude habitat loss as a result of warming (EPA 

2009b). In the Southwest, grasslands are expected to expand and shift into some forest areas as a result of 

increasing temperatures and changing precipitation profiles in this region (GCRP 2009). 

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A marked change in forest composition and distribution has been noted in Alaska, as indicated by 

a northward migration of the subarctic boundary tree line by 6 miles, and the displacement of 2 percent of 

the Alaskan tundra in the past 50 years (EPA 2009b). Also, as evidenced by remote sensing analysis, the 

growing season is increasing in length by roughly 3 days per decade (CCSP 2008c). Arctic vegetation is 

expected to shift northward and cause forests to overtake tundra (EPA 2009b). 

Crops and Agriculture 

The agriculture sector in the United States is vulnerable to climate change due to the many factors 

that affect crops and agriculture, including the availability of water resources, the adaptive capacity of the 

agricultural sector, technological improvements in farming practices, economic competition, and existing 

climate and soil conditions (EPA 2009b). 

In the early part of the 21st Century, moderate climate change could increase crop yields on 

agricultural land by 5 to 20 percent (Easterling et al. 2007). However, this increase would depend on 

crops that rely on already highly utilized water resources (Parry et al. 2007). Crops that are near the 

threshold of their productive temperature range (i.e., crops that are “near the warm end of their suitable 

range”), such as wine grapes, apricots, alomonds, artichokes, figs, kiwis, olives and walnuts in California, 

are expected to decrease in yield or quality based on moderate climate-change scenarios (EPA 2009b and 

GCRP 2009). The probability of the loss of popular and recognizable plants such as saguaro cacti and 

Joshua trees will increase because temperature increases will increasingly affect the reproductive 

development of various crops, particularly in arid regions (CCSP 2008c). 

Grain crops in the United States are likely to initially benefit from the increased temperature and 

CO2 levels. However, as temperatures continue to rise, sensitivity of these grain crops could increase. 

This sensitivity is expected to an even greater extent for horticultural crops such as tomatoes and onions, 

compromising their productive yield (CCSP 2008c). Various studies have found differing thresholds for 

maize production in the United States, with one in particular showing a 17-percent reduction of maize 

yield per 1 °C (1.8 °F) increase in temperature (Lobell and Asner 2003 in CCSP 2008). Other crops, such 

as wheat, are regionally and temporally dependent. Studies show that wheat yield in the Great Plains “is 

estimated to decline 7 percent per 1 °C increase in air temperature between 18 and 21 °C [50 and 53 °F] 

and about 4 percent per 1 °C increase in air temperature above 21 °C” (Lobell and Field 2007 in CCSP 

2008). Similarly, rice yields are projected to decline about 10 percent per 1 °C increase for temperature 

profiles that are above current summer mean air temperatures (CCSP 2008c). 

Using an assumed 1.2 °C (2.2 °F) warming over the next 30 years, maize, wheat, sorghum, and 

dry bean yields are projected to each decrease by 4.0 to 9.4 percent in their major production areas of the 

United States. Soybean yield, on the other hand, is projected to increase 2.5 percent in the Midwest. 

However, crop yields in the South will likely decrease. (EPA 2009b) 

In the Great Lakes region, fruit production might benefit from climate change, although there 

might be increased risk of winter thaws and spring frost (Bélanger et al. 2002, Winkler et al. 2002, both 

in Field et al. 2007). In New Jersey, higher summer temperatures are expected to depress the yields of a 

number of other economically important crops adapted to cooler conditions (e.g., spinach, lettuce) by 

mid-century, while rising winter temperatures are expected to drive the continued northward expansion of 

agricultural pests and weeds (such as kudzu) (Frumhoff et al. 2007). Cranberries are especially 

susceptible because of their requirement to be subjected to long periods of cold winter temperatures for 

development (Frumhoff et al. 2007). 

Climate changes could result in significant impacts to irrigation needs. Decreased rainfall, 

increased evaporation from higher temperatures, and longer growing seasons can all increase irrigation 

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needs. Recent studies indicate that by 2030, changes in irrigation requirements could range from -1 to 

+451 percent for corn in the United States. Overall, irrigation requirements in the U.S. are projected to 

increase by 35 to 64 percent (EPA 2009b). 

Agriculture could also be affected by the impact of climate change on pests and weeds. Warming 

trends have in some cases led to earlier spring activity and proliferation of some species. Warmer winters 

also might allow for higher survival rates of pathogens and parasites. Further, weeds might respond more 

favorably to elevated CO2 levels than cash crops. However, further research is needed on this topic 

before conclusions can be drawn on the effects of elevated CO2 levels on pests and weeds (EPA 2009b). 

Extreme Weather Events 

The negative impacts of increased frequency of extreme weather events on crop yield might 

temper the beneficial effects of increased CO2 concentrations (CCSP 2008c). Extreme weather events, 

including droughts and intense rainfall episodes, might adversely impact crop yields due to the increases 

and decreases of water associated with these events (CCSP 2008c). 

Multi-year droughts, which could have been a result of increased temperature conditions in 

lower-elevation forests in the southwestern region, have had a large impact on forest mortality rates 

(Breshears et al. 2005 in CCSP 2008). The mortality rate continued to increase even though growth at the 

forest tree line had been increasing previously (Swetnam and Betancourt 1998 in CCSP 2008). Forest 

productivity has decreased from climate change-induced warming in drought-prone regions (McKenzie et 

al. 2001 in CCSP 2008) and in subalpine regions (Monson et al. 2005, Sacks et al. 2007, both in CCSP 

2008). Droughts are more prevalent in the western U.S. but the East could also be affected by drought 

and the associated reductions in water supply (EPA 2009b). In the Great Plains region, the projected 

increase in drought frequency and severity will stress the region’s water resources that, in turn, supply 

water for the agriculture sector. The irrigated agricultural areas in the southern Great Plains will 

especially be vulnerable to these water resource impacts, particularly because the region is already 

experiencing unsustainable water use (GCRP 2009). 

Intense rainfall events will also cause crop losses via soil compaction and increased susceptibility 

to root diseases. Intense rainfall also causes more runoff and leaching. In turn, this will delay spring 

planting for crops, which influences economic profits of the agriculture sector (EPA 2009b). Surface 

waters could be inundated by sediments, pathogens, and pesticides as increased runoff from crop fields 

and animal agriculture operations result from intense rainfall events (EPA 2009b). 

Livestock

The livestock production infrastructure in the United States is likely to be influenced by the 

climate-change-induced distributional and productivity changes to plant species. Livestock production 

during the summer season would very likely be reduced due to higher temperatures, but livestock 

production during winter months could increase, again due to the projected increase in temperatures 

(CCSP 2008c). 

The expected elevated CO2 concentrations could diminish the quality of grass feed. An increase 

in the carbon-to-nitrogen ratio would decrease the nutritional value of feed. In turn, grazing livestock that 

feed on lower-quality grasses might be affected in terms of decreased weight and health (EPA 2009b). 

For example, an experiment conducted on shortgrass prairie found that increased CO2 concentrations 

reduced the protein concentration, which in turn reduced the digestibility of forage by 14 percent in midsummer (CCSP 2008c). Expected future average climate-change conditions could have less effect on 

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livestock productivity and potential livestock loss than the effects of increased weather variability (e.g., 

droughts and temperature extremes) (EPA 2009b). 

Models of the impact of climate change on agriculture have projected decreases in livestock 

productivity in the United States simply due to projected temperature increases. In 2050, such a model 

projects an average decrease in swine, beef, and milk production of 0.9 to 1.2 percent, 0.7 to 2.0 percent, 

and 2.1 to 2.2 percent, respectively (Frank et al. 2001 in CCSP 2008). Higher temperatures directly affect 

animals’ abilities to maintain homeostasis; consequently, livestock must engage in altered metabolic 

thermoregulatory processes (Mader et al. 1997, Davis et al. 2003c, both in CCSP 2008). The induced 

thermal stress on livestock often results in a reduction in physical activity and ultimately diminishes feed 

intake. Livestock production losses and associated economic losses might be attributed to increasing 

temperatures that are “beyond the ability of the animal to dissipate [and] result in reduced performance 

(i.e., production and reproduction), health, and well-being” (Hahn et al. 1992, Mader 2003, both in 

National Science and Technology Council 2008). However, EPA (2009b) points out that decreases in 

livestock production from hotter summers will likely be partly offset by increased production from 

warmer winters (EPA 2009b). 

The increased temperature expected as a result of climate change could allow for easier migration 

of animal pathogens and diseases, especially in the northward transition from the low to mid-latitudes, 

which would adversely affect livestock wellbeing in the United States (White et al. 2003, Anon 2006, van 

Wuijckhuise et al. 2006, all in CCSP 2008). 

Fisheries

Freshwater fisheries are sensitive to changes in water temperature, and to changes in river flows 

and lake levels caused by changes in surface water (EPA 2009b). Although fisheries in cold freshwater 

regions are expected to be adversely affected, fisheries in warm freshwater regions could benefit from 

climate change (EPA 2009b). The effects of temperature increases have caused northward shifts of 

fisheries systems and this is expected to continue in the future (CCSP 2008c). According to IPCC, “many 

warm-water and cool-water species will shift their ranges northward or to higher altitudes” (Clark et al.

2001, Mohseni et al. 2003, both in Field et al. 2007). It has been observed that Pacific salmon species 

have been recently appearing in Arctic rivers (EPA 2009b). In the Southeastern region of the United 

States, a reduction in dissolved oxygen associated with warmer water temperatures could potentially lead 

to increased mortality rates for certain fish species (GCRP 2009). 

An example of negative impacts that result from large-scale species migration is the recent 

migration of two protozoan parasites from the Gulf of Mexico northward into Delaware Bay. This 

parasitic incursion, possibly as a result of climate change, has led to a substantially increased mortality 

rate of oysters in the region (Hofmann et al. 2001 in CCSP 2008). 

According to IPCC, the survival of brook trout in the United States is directly correlated to the 

availability of its preferred cold-water habitat. As temperatures increase, mortality rates also increase for 

certain species of trout (EPA 2009b). Other cold-water salmonid species are likely to be negatively 

affected by rising temperatures (EPA 2009b). It is likely that other coldwater species could disappear 

from all but the deeper lakes; cool-water species will be lost mainly from shallow lakes; and warm-water 

species will thrive, except in the far south, where temperatures in shallow lakes will exceed survival 

thresholds (EPA 2009b). Stocks of the river-spawning walleye will likely decline due to lower lake levels 

and climate-change impacts in Lake Erie (Jones et al. 2006 in Field et al. 2007). 

Coastal fisheries are also expected to experience the negative impacts of climate change, 

including coral reef bleaching, due to increased ocean temperatures (EPA 2009b). 

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4.5.6.2.2 Projected Global Impacts of Climate Change 

Although the preceding section highlights anticipated impacts of climate change in the United 

States, there are additional impacts that could affect forest and agriculture systems elsewhere in the world. 

Crops

Globally, climate change will affect the agriculture and forest sectors. A recent Harvard report on 

Climate Change Futures states that a “changing climate will alter the hydrological regime, the timing of 

seasons, the arrival of pollinators and the prevalence, extent, and type of crop diseases and pests” (Epstein 

et al. 2005). Throughout the mid- to high-latitudinal regions, crop-specific productivity increases are 

projected for global mean temperature increases of 1 to 3 oC (1.8 to 5.4 oF). Beyond a 3-oC increase in 

global mean temperature, crop productivity is expected to decrease in some regions (Easterling et al.

2007). Depending on crop type, experiments on the effects of increased CO2 concentrations (namely, 550 

ppm as opposed to existing levels of roughly 380 ppm) suggest that crop yields could increase by 0 to 25 

percent (EPA 2009b). In the lower-latitude dry regions, cereal crop productivity is projected to decrease 

with temperature increases of 1 to 2 oC (1.8 to 3.6 oF), thereby exacerbating hunger issues for the 

population living in these regions (Parry et al. 2007). 

In a modest warming climate scenario, adaptive practices such as using various cultivars and 

altering planting and harvesting times might maintain cereal crop yields and possibly allow for an 

increase in productivity in the high latitudinal and temperate regions (Easterling et al. 2007). The 

adaptive practice in regions with 1 to 2 oC temperature increases corresponds to an avoidance of a 10- to 

15-percent reduction in yield for cereal crops (Parry et al. 2007). 

According to IPCC, the “projected changes in the frequency and severity of extreme climate 

events will have more serious consequences for food and forestry production, and food insecurity, than 

will changes in projected means of temperature and precipitation” (Easterling et al. 2007). The low 

latitudinal regions might experience an increase in the frequency of extreme weather events like floods 

and droughts, which could adversely affect crop production, especially in subsistence farming regions 

(Easterling et al. 2007). Extreme weather events “reduce crop yield and livestock productivity beyond 

the impacts due to changes in mean variables alone, creating the possibility for surprises” (Parry et al.

2007). The reduced adaptive capacity of small-scale farmers such as subsistence and artisanal fisherfolk 

could result in increased vulnerability to extreme weather events, sea-level rise, and the spread of human 

disease, which could negatively affect agricultural and fish yields (Parry et al. 2007). Existing climatechange models do not yet include recent findings on precipitation extremes that are expected to impact 

agricultural production in areas such as southern Asia, northern Europe, and eastern Australia. These 

areas are expected to experience an impact on agricultural productivity as a result of projected increased 

precipitation extremes such as floods and droughts (Christensen et al. 2007b in Easterling et al. 2007). 

Certain crops, such as wheat, are impacted by high precipitation events because wheat is “susceptible to 

insects and diseases (especially fungal diseases) under rainy conditions” (Rosenzweig and Hillel 1998 in 

Epstein et al. 2005). On the other hand, during droughts, certain fungi, such as Aspergillus flavus, are 

stimulated and will feed on drought-weakened crops (Epstein et al. 2005). 

Decreases in crop and forest yields in moderate warming scenarios for the low latitudes will 

likely result in increased dependence on food imports in these typically the developing countries. As 

such, agricultural exports to lower latitude countries are likely to increase in the short term (Parry et al.

2007). 

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There could be a marginal increase in the population at risk of hunger due to climate change, but 

this would occur in the context of an overall decrease in the global population at risk of hunger as a result 

of anticipated economic development (Parry et al. 2007). 

Forests

Globally, commercially grown forests for use in timber production are expected to increase 

modestly in the short term, depending on geographic region (Easterling et al. 2007). Large regional and 

local differences are anticipated, as is a shift in terms of production increase from the lower latitudes to 

the higher latitudes (Parry et al. 2007). This poleward shift of forests and vegetation is estimated at 

roughly 500 kilometers (about 310 miles) or more for the boreal zones for climate scenarios with CO2

concentrations of double present levels (Kirilenko and Sedjo 2007). In terms of distributional production, 

net benefits will accrue to regions experiencing increased forest production, whereas regions with 

declining activity will likely face net losses (Kirilenko and Sedjo 2007). 

Due to increases in CO2 concentration, there is potential for a carbon fertilization effect on the 

growth of trees, with some experiments showing up to an 80-percent increase in wood production for 

orange trees (Kirilenko and Sedjo 2007). There is evidence to support elevated growth for young, 

immature forests in response to higher CO2 concentration levels (Parry et al. 2007). However, free-air 

CO2 enrichment experiments indicate that mature forests show no appreciable response to elevated CO2

concentrations. However, young, immature forests show elevated growth in response to higher CO2

concentrations (Parry et al. 2007). It should be noted that one study regarding forest free-air CO2

enrichment of 100-year-old tree stands found little to no enhanced stem growth, but this lack of growth 

might be explained by the relative difficulty of controlling for constant CO2 levels (Kirilenko and Sedjo 

2007). 

Many forest models have projected increases in forest production in certain geographic regions 

(with a few exceptions). For example, the Terrestrial Ecosystem Model and the Center for International 

Trade in Forest Products Global Trade Model have simulated a future harvest increase of 2 to 11 percent 

in western North America, a 10- to 12-percent increase in New Zealand, a 10- to 13-percent increase in 

South America, and a harvest decrease in Canada (Kirilenko and Sedjo 2007). 

It is important to contrast these possible short-term benefits with the negative implications of a 

warming climate, because “continued warming favors more fungal and insect of forests, and more harsh 

weather will further weaken tree defenses against pests” (Epstein et al. 2005). For example, in Europe the 

spruce bark beetle will likely produce more broods more frequently than in the past due to the warmer 

climate (Schlyter et al. 2006 in Malmsheimer et al. 2008). The ability of forests to continue to function 

as providers of agriculture and energy and sequester carbon will be affected by climate change (Epstein et 

al. 2005). The extreme weather events causing drought and decreased soil moisture, in concert with 

increased damage from insect and pathogen outbreaks and wildfires, might result in large-scale 

deforestation, as evidenced by recent trends in the Amazon basin (Kirilenko and Sedjo 2007). Climatevegetation models have indicated that at CO2 concentration levels of roughly three times present levels, 

the Amazon rainforests will eventually be lost due to climate change (Cox et al. 2004 in Kirilenko and 

Sedjo 2007). 

Fisheries

The aquaculture and fisheries sector is expected to experience negative impacts as a result of the 

regional changes in the distribution and proliferation of various marine species (Easterling et al. 2007). 

As the distribution of certain fish species continues to be regionally rearranged, there is the potential for 

notable extinctions in the fisheries system, especially in freshwater species, in temperature ranges at the 

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margin (Parry et al. 2007). Recent evidence indicates that the Meridional Overturning Circulation, which 

supplies nutrients to the upper layers of the Pacific and Atlantic Oceans, is slowing and therefore 

adversely affecting regional production of primary food supply for fisheries systems (McPhaden and 

Zhang 2002, Curry and Mauritzen 2005, Gregg et al. 2003, Lehodey et al. 2003b, all in Easterling et al.

2007). In the North Sea, a shift in the distribution of warm-water species such as zooplankton has 

resulted in a shift of fish species from whiting to sprat (Beaugrand 2004 in CCSP 2008). 

The largest economic impacts associated with the fisheries sector as a result of climate change are 

expected to occur in coastal regions of Asia and South America (Allison et al. 2005 in CCSP 2008). 

Specifically, regional climate change could most affect species such as tuna and Peruvian anchovy 

(Barber 2001, Lehodey et al. 2003a, both in CCSP 2008). 

Earlier spring ice melts in the Arctic and diminishing sea ice are affecting the distribution and 

productivity of marine species, particularly the upper-level sea organisms. In turn, fish harvests in the 

Arctic region are expected to change in the warming future. Freshwater species in the Arctic region are 

expected to be most affected by increasing temperatures (Wrona et al. 2005 in Field et al. 2007). 

4.5.7 Industries, Settlements, and Society 

This section defines industries, settlements, and society resources and describes the existing 

conditions and potential vulnerability of each to climate-change impacts. In addition, this section briefly 

describes the potential vulnerability of cultural resources, including archaeological resources and 

buildings of historic significance, to climate-change impacts. The primary source for the information in 

this section is the IPCC Fourth Assessment Report (Wilbanks et al. 2007), specifically, Chapter 7 for 

industry, settlement, and society. 

The industries, settlements, and society sector encompasses resources and activities that describe 

how people produce and consume goods and services, deliver and receive public services, and live and 

relate to each other in society. 

As defined by IPCC, this sector includes: 

• Industry − manufacturing, transport, energy supply and demand, mining, construction, and 

related informal production activities (Wilbanks et al. 2007); 

• Services − trade, retail, and commercial services, tourism, risk financing/insurance (IPCC 

2007a); 

• Utilities/infrastructure − systems designed to meet relatively general human needs, often 

through largely or entirely public utility-type institutions (Wilbanks et al. 2007); 

• Human settlement − urbanization, urban design, planning, rural settlements (Wilbanks et al.

2007); and 

• Social issues − demography, migration, employment, livelihood, and culture (Wilbanks et al.

2007). 

4.5.7.1 Affected Environment 

The industry, settlements, and society sector covers a very broad range of human institutions and 

systems, including the industrial and services sectors, large and small urban areas and rural communities, 

transportation systems, energy production, and financial, cultural, and social institutions. 

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A principal objective of human societies is to reduce their sensitivity to weather and climate. 

Recent experience with storms such as Hurricane Katrina reveals the limits to human control over 

climate-related impacts on industries, settlements, and society. Systems that are sensitive to climate 

change include air and water quality, linkage systems (transportation and transmission networks), 

building structures, resource supplies, social networks, and economic systems (Wilbanks et al. 2007). 

This sector normally experiences and is generally resilient to variability in environmental 

conditions. Industries, settlements, and human society, however, can be vulnerable to extreme or 

persistent changes. Vulnerability increases when changes are unexpected or if resources or other factors 

inhibit the ability of this sector to respond to changes (EPA 2009b). 

Together, industry and economic services account for more than 95 percent of gross domestic 

product in highly developed economies and between 50 and 80 percent of gross domestic product in lessdeveloped economies (World Bank 2006 in Wilbanks et al. 2007). Industrial activities are vulnerable to 

temperature and precipitation changes. For example, in Canada, weather-related road accidents translate 

into annual losses of at least $1 billion Canadian annually, and more than a quarter of air travel delays in 

the United States are weather related (Andrey and Mills 2003 in Wilbanks et al. 2007). Buildings, linking 

systems, and other infrastructure are often in areas vulnerable to extreme weather events (flooding, 

drought, high winds). Trapp et al. (2007) found a net increase in the number of days in which severe 

thunderstorm environmental conditions could occur during the late 21st Century using global and highresolution regional climate models. The analysis suggests a future increase in these conditions of 100 

percent or more in Atlanta, Georgia, and New York, New York. Such extreme events that can threaten 

linkage infrastructures such as bridges, roads, pipelines, or transportation networks could cause industry 

to experience substantial economic losses (Wilbanks et al. 2007). In one example of non-storm-related 

impacts of climate change to infrastructure, in Russia there have been documented structural failures due 

to unusual levels of permafrost thaw from warming trends (EPA 2009b). 

Institutional infrastructure is generally considered to be less vulnerable to weather and climate 

variation, as it embodies less fixed investment and is more readily adapted within the time scale of 

climate change. In some cases, experience with climatic variability can enhance the resilience of 

institutional infrastructure by triggering adaptive responses (Wilbanks et al. 2007). 

Vulnerability to climate-change impacts is determined by local geography and social context, 

rather than by large-scale or aggregate factors (Wilbanks et al. 2007). A trend toward urbanization can 

also increase the vulnerability of an area when that urbanization concentrates people in areas at risk for 

negative climate-change impacts. Sections 4.5.7.1.1 through 4.5.7.1.3 briefly describe risk factors 

associated with local geography, social context, and urbanization. 

4.5.7.1.1 Geography 

Extreme weather events are more likely to pose risks to industry, settlements, and society than 

gradual climate change (Wilbanks et al. 2007). Resources and activities in areas with higher 

susceptibility to extreme weather events (high temperatures, high winds, and flooding) are more 

vulnerable to the impacts of climate change. The most vulnerable areas are likely to be Alaska, coastal 

and river basins susceptible to flooding, arid areas, and areas where the economic bases are climate 

sensitive (EPA 2009b). Extreme weather events can damage transportation routes and other 

infrastructure, damage property, dislocate settlement patterns, and disrupt economic activity (EPA 

2009b). Gradual climate change can change patterns of consumption, decrease or increase the availability 

of inputs for production, and affect public-health needs. Such impacts are experienced locally, but can be 

linked to impacts on national and global systems (Wilbanks et al. 2007). 

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Archaeological resources and buildings of historic significance are fixed in location and are 

therefore vulnerable to the effects of extreme weather events and gradual changes associated with local 

geography. Extreme weather events can expose archaeological resources and damage structures. Over 

time, gradual changes to weather patterns can also erode protective cover around archaeological resources 

and increase the rate of deterioration of historic buildings. Vulnerability of these resources to climatechange impacts is tied to the susceptibility of location and local geography to extreme and gradual 

changes to weather. 

4.5.7.1.2 Social Context 

Worldwide, many of the places where people live are under pressure from a combination of 

growth, social inequity, jurisdictional fragmentation, fiscal shortfalls, and aging infrastructure. These 

stresses can include scarcity of water, poor sanitation, inadequate governance structures, unmet resource 

requirements, economic inequities, and political instability. While these types of stresses vary greatly 

across localities, they can combine with climate-change impacts to result in substantial additional stress at 

local, national, and global levels (Wilbanks et al. 2007). 

The social impacts associated with climate change will be mainly determined by how the changes 

interact with economic, social, and institutional processes to minimize or magnify the stresses. From an 

environmental justice perspective, the most vulnerable populations include the poor, the very old and very 

young, the disabled, and other populations that have limited resources and ability to adapt to changes 

(EPA 2009b). Environmental justice issues are made apparent as warmer temperatures in urban summers 

have more direct impact on those living and working without air conditioning (EPA 2009b). Section 4.6 

addresses environmental justice. 

4.5.7.1.3 Urbanization 

It is estimated that one third of the world’s urban population (almost 1 billion people) lives in 

overcrowded and unserviced slums, and 43 percent of the urban population is in developing countries. 

More generally, human settlements are often situated in risk-prone regions such as steep slopes, ravines, 

and coastal areas. These risk-prone settlements are expected to experience an increase in population, 

urbanized area, and economic activity. The population in the near-coastal zone (i.e., within 330 feet 

elevation and 60 to 65 miles distance from the coast) has been estimated to be between 600 million and 

1.2 billion, or 10 to 23 percent of the world’s population (Adger et al. 2005a, McGranahan et al. 2006, 

both in Wilbanks et al. 2007). Migration from rural to urban areas is a common response to calamities 

such as floods and famines (Wilbanks et al. 2007). 

4.5.7.2 Environmental Consequences 

Key climate-change impacts on this set of human systems are likely to vary widely and depend on 

a range of location-specific characteristics and circumstances. Moreover, potential climate-change 

impacts on this sector could be particularly challenging to determine because effects tend to be indirect 

rather than direct. For example, changes in temperature, a direct effect of climate change, affect air 

pollution concentrations in urban areas, thereby affecting human health and health care systems. These 

are all indirect effects (Wilbanks et al. 2007). The significance of climate-change impacts on human 

systems will largely be determined through its interaction with other processes, driving forces, and 

stresses (CCSP 2008d). This type of multi-stress perspective indicates that changes in climate extremes 

are very often of more concern than changes in climate averages (EPA 2009b). 

The human institutions and systems that comprise the industry, settlements, and society sector 

tend to be quite resilient to fluctuations in environmental conditions that are within the range of normal 

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occurrence. However, when environmental changes are more extreme or persistent, these systems can 

exhibit a range of vulnerabilities “especially if the changes are not foreseen and/or if capacities for 

adaptation are limited” (Wilbanks et al. 2007). For this reason industry, settlements, and society in 

developing countries are expected to be more vulnerable to direct and indirect climate-change impacts 

than they are in industrialized countries (Wilbanks et al. 2007). 

Climate change is expected to affect industry, settlements, and society via a range of physical 

effects, including the frequency and intensity of tropical cyclones and storms, extreme rainfall and floods, 

heat and cold waves, drought, temperature extremes, precipitation, and sea-level rise. Following the 

approach in Wilbanks et al. (2007), the categories of human systems addressed in this section include 

industry, services, utilities and infrastructure, settlements, and social issues. The following paragraphs 

describe each category and potential climate impacts on each category. Subsequent sections describe in 

more detail key systems within these categories that are expected to experience impacts associated with 

climate change. 

Industry – This category includes manufacturing, transport, energy supply and demand, mining, 

construction, and related informal production activities (Wilbanks et al. 2007). These activities can be 

vulnerable to climate change when (a) facilities are in climate-sensitive areas such as coasts and 

floodplains, (b) the sector depends on climate-sensitive inputs such as food processing, or (c) the sector 

has long-lived capital assets (Ruth et al. 2004 in Wilbanks et al. 2007). For the energy sector, in addition 

to possible infrastructure damage or destruction from the effects of climate change (e.g., as could happen 

due to extreme weather events) effects could include climate-driven changes in demands for energy. For 

example, demand for heating could decline in winter months while demand for cooling could rise in 

summer months (CCSP 2008d). 

Services – This category includes trade, retail and commercial services, tourism, and risk 

financing or insurance (Wilbanks et al. 2007). Possible climate-change impacts on trade include impacts 

on transportation from extreme weather events like snow and ice storms that could impede the ability to 

transport goods, or impacts on comparative advantage of a region or country due to temperature shifts that 

affect production. Climate-change impacts on transportation could also affect retail and commercial 

services. Retail and commercial services could also be affected by climatic conditions that affect prices 

of raw materials and by potential damage to infrastructure, such as facilities in climate-sensitive areas like 

coastal regions. Extreme events such as hurricanes can also affect tourism infrastructure. Tourism 

services could also be affected by climate-change impacts through temperature shifts and changes that 

affect the natural landscape of tourist destinations. Potential indirect effects of climate change on tourism 

include changes in availability of water and energy prices. Regarding the insurance sector, climatechange impacts could lead to increasing risk, which could trigger higher premiums and more conservative 

coverage. A reduction in availability of or ability to afford insurance could in turn lead to impacts on 

local and regional economies. 

Utilities and infrastructure – This category includes systems that are “designed to meet relatively 

general human needs, often through largely or entirely public utility-type institutions” (Wilbanks et al.

2007). This includes physical infrastructure such as water, transportation, energy, and communications 

systems, and institutional infrastructure such as shelters, public health-care systems, and police, fire, and 

emergency services. “These infrastructures are vulnerable to climate change in different ways and to 

different degrees depending on their state of development, their resilience, and their adaptability” 

(Wilbanks et al. 2007). In general, institutional infrastructure tends to be less vulnerable to climate 

change than physical infrastructure because it typically involves less investment in fixed assets and is 

more flexible over timeframes that are relevant to climate change. There are numerous points where 

impacts on different infrastructures interact and the failure of one system can put pressure on others. At 

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the same time, however, “this means that measures to protect one sector can also help to safeguard the 

others” (Wilbanks et al. 2007). 

Human settlement – Climate change interacts with other stresses in its impact on human 

settlements (Wilbanks et al. 2007). Potential impacts on human settlements could be experienced through 

several pathways. Sea-level rise threatens populations in coastal areas by accelerating the inundation of 

coastal wetlands, threatening vital infrastructure and water supplies, augmenting summertime energy 

demand, and affecting public health (Wilbanks et al. 2007). Changes in precipitation patterns could alter 

the availability of potable water, while changes in temperature could affect air quality and contribute to an 

increase in incidents of heat stress and respiratory illnesses (Wilbanks et al. 2007). In urban areas, the 

Urban Heat Island effect (Wilbanks et al. 2007), which relates to the “degree to which built and paved 

areas are associated with higher temperatures than surrounding rural areas” (National Science and 

Technology Council 2008), might affect the manner in which climate change affects these areas. For 

example, imbalances in the urban metabolism could aggravate climate-change impacts such as the role of 

the Urban Heat Index in the formation of smog in cities (CCSP 2008d). 

Social Issues – Within human settlements, society could also experience a variety of effects 

associated with climate change. For example, communities could experience increasing stress on 

management and budget requirements for public services if demands on public health care and disaster 

risk reduction grow (CCSP 2008d). There could be a loss of cultural and traditional groups of people, 

e.g. “indigenous societies in polar regions” (Wilbanks et al. 2007). Societal concerns that might be 

affected by the impacts of climate change include socioeconomic issues relating to developed versus 

developing areas and rich versus poor. As poorer populations tend to have weaker infrastructure and 

economies tied to climate-sensitive resources, their vulnerability to climate-change impacts is expected to 

be higher and their capacity to cope or adapt are expected to be lower than wealthier populations (EPA 

2009b). 

4.5.7.2.1 Projected Impacts of Climate Change for the United States 

The research literature on climate-change impacts on U.S. industry, settlements, and society is 

relatively sparse. “At the current state of knowledge, vulnerabilities to possible impacts are easier to 

project than actual impacts because they estimate risks or opportunities associated with possible 

consequences rather than estimating the consequences themselves” (CCSP 2008d). In general, “climate 

change effects on human settlements in the United States are expected to occur as a result of interaction 

with other processes” (National Science and Technology Council 2008). These effects include those on 

health, water resources, physical infrastructure (notably transportation systems), energy systems, human 

settlements, and economic opportunities. 

Impacts on human health and human health care systems are expected to arise because of 

temperature-related stress. Increases in cases of respiratory illness associated with high concentrations of 

ground-level ozone; water-, food-, and vector-borne diseases; and allergies related to higher 

concentrations of plant species are expected. 

Effects on water are expected to include reductions in snowpack, river flows, and groundwater 

levels, saline intrusion in rivers and groundwater, an increase in water demand due to increasing 

temperatures, and impacts on sanitation, transportation, food and energy, and communication 

infrastructures from severe weather events. 

The U.S. coastline, deltas, and coastal cities such as the Mississippi Delta and surrounding cities, 

are vulnerable to sea-level rise. “Rapid development, including an additional 25 million people in the 

coastal United States over the next 25 years will further reduce the resilience of coastal areas to rising sea 

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levels and increase the economic resources and infrastructure vulnerable to impacts” (Field et al. 2007b in 

National Science and Technology Council 2008). 

Effects on other key human systems are discussed in greater detail below. Because this section 

deals with such a broad set of human systems, the potential impacts of climate change and potential 

adaptations available to key human systems are discussed together. Given the enormous range of human 

systems that could be affected by climate change, the discussion here is focused on a few key systems for 

which impacts can best be characterized or supported by sufficient information. 

Impacts on Transportation Infrastructure

Climate affects the design, construction, operation, safety, reliability, and maintenance of 

transportation infrastructure, services, and systems (EPA 2009b). The potential for climate change raises 

critical questions about how changes in temperature, precipitation, storm events, sea-level rise, and other 

climate variables could affect the system of roads, airports, rail, public transit, pipelines, ports, 

waterways, and other elements of the nation’s and the world’s complex transportation systems. 

Climate changes anticipated during the next 50 to 100 years include higher temperatures, changes 

in precipitation patterns, increased storm frequency and intensity, and rising sea levels globally, resulting 

from the warming of Earth’s oceans and decline in polar ice sheets. These changes could affect the 

transportation system in a wide variety of ways. The following paragraphs summarize those of greatest 

relevance for the United States. 

• Increases in very hot days and heat waves. It is very likely that heat extremes and heat waves 

will continue to become more frequent, more intense, and last longer in most regions during 

the 21st Century. This could increase the cost of transportation construction, operations, and 

maintenance. 

• Increases in Arctic temperatures. Arctic warming is virtually certain because temperature 

increases are expected to be greatest over land and at most high northern latitudes. As much 

as 90 percent of the upper layer of permafrost could thaw under more pessimistic emissions 

scenarios. 

• Rising sea levels. It is virtually certain that sea levels will continue to rise in the 21st Century 

as a result of thermal expansion and loss of mass from ice sheets. This could make much of 

the existing transportation infrastructure in coastal areas prone to frequent, severe, and/or 

permanent inundation. 

• Increases in intense precipitation events. It is very likely that intense precipitation events 

will continue to become more frequent in widespread areas of the United States. 

Transportation networks, safety, and reliability could be disrupted by visibility problems for 

drivers, and by flooding, which could result in substantial damage to the transportation 

system. 

• Increases in hurricane intensity. Increased tropical storm intensities, with larger peak wind 

speeds and more intense precipitation, are likely. This could result in increased travel 

disruption, impacts on the safety and reliability of transportation services and facilities, and 

increased costs for construction, maintenance, and repair (Transportation Research Board 

2008). 

Numerous studies have examined ways of mitigating the transportation sector’s contribution to 

global warming from GHG emissions. However, far less attention has been paid to the potential impacts 

of climate change on U.S. transportation systems and on how transportation professionals can best adapt 

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to climate changes that are already occurring, and will continue to occur into the foreseeable future even 

if drastic mitigation measures were taken today. Because GHGs have long life spans, they continue to 

impact global climate change for decades (Transportation Research Board 2008). 

Scientific evidence reports that climate change is already occurring, and that it will trigger new, 

extreme weather events and could lead to surprises, such as more rapid than expected rises in sea levels or 

temperature changes. Every mode of transportation will be affected as climate change poses new and 

often unfamiliar challenges to infrastructure providers (Transportation Research Board 2008). 

Consideration of climate-change-related factors in transportation planning and investment 

decisions should lead to a more resilient, reliable, and cost-effective transportation system in the coming 

decades. When decisionmakers better understand the risks associated with climate change, they can make 

better decisions about potential adaptation strategies and the tradeoffs involved in planning, designing, 

constructing, operating, and maintaining transportation systems (Transportation Research Board 2008). 

Projected climate changes have profound implications for transportation in the United States 

(Transportation Research Board 2008). Climate change is likely to increase costs for construction and 

maintenance of transportation infrastructure; impact safety through reduced visibility during storms and 

destruction of elements of the transportation system during extreme weather events; disrupt transportation 

networks with flooding and visibility problems; inundate substantial portions of the transportation system 

in low-lying coastal areas; increase the length and frequency of disruptions in transportation service; 

cause substantial damage and incur costly repairs to transportation infrastructure; and impact the overall 

safety and reliability of the Nation’s transportation system (Transportation Research Board 2008). 

Transportation systems across the United States are projected to experience both positive and 

negative impacts from climate change over the next century; the degree of impacts will be determined, in 

part, by the geographic region (Transportation Research Board 2008). Coastal communities are 

especially vulnerable to impacts associated with sea-level rise, increased frequency or intensity of storms, 

and damage to the transportation system due to storm surges and flooding. The literature indicates that 

the intensity of major storms could increase by 10 percent or more, which could result in more frequent 

Category 3 (or higher) storms along the Gulf Coast and the Atlantic Coast (Transportation Research 

Board 2008). Warming temperatures might require changes in the kinds of materials used for 

construction of transportation facilities, and in the operation and maintenance of transportation facilities 

and services. Higher temperatures could require the development and use of more heat-tolerant materials 

(Transportation Research Board 2008). Restrictions on work rules could increase the time and costs for 

labor for construction and maintenance of transportation facilities. Rail lines could be affected by higher 

temperatures and more frequent rail buckling, which would affect service reliability, safety, and overall 

system costs and performance. Costs could increase for ports, maintenance facilities, and transportation 

terminals if higher temperatures require an increase in refrigeration and cooling (Transportation Research 

Board 2008); and higher temperatures could affect aircraft performance and the runway lengths required 

for safe operation (Transportation Research Board 2008). In addition, due to the potential global nature 

of the changes in severe weather, climate change could profoundly affect the operational aspects of 

aviation and overall air traffic and air space management (CCSP 2008b). On the positive side, higher 

temperatures might open up northern transportation routes for longer periods and allow more direct 

routing for marine transportation (Transportation Research Board 2008). In addition, warmer or less 

snowy winters could be beneficial by reducing delays, improving ground and air transportation reliability, 

and decreasing the need for winter road maintenance (EPA 2009b). 

Changes in precipitation patterns could increase short-term flooding, resulting in decreased 

safety, disruptions in transportation services, and costly damage to transportation infrastructure. Hotter 

climates could exhibit reduced soil moisture and average runoff, which might require changes in the 

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management and maintenance of publicly owned rights-of-way. The potential increase in heavy rainfall 

might exceed the capacity of existing drainage systems, resulting in more frequent flooding and 

associated disruptions in transportation system reliability and service, increased costs for maintenance of 

existing facilities, and increased costs for construction of new facilities (Transportation Research Board 

2008). 

Relative sea-level rise might inundate existing transportation infrastructure and substantially 

increase the cost of providing new transportation facilities and services. Some portions of the 

transportation infrastructure in coastal areas, or in areas prone to flooding, might have to be protected 

with dikes or levees – increasing the cost for construction and maintenance, and the potential for more 

serious flooding incidents associated with the failure of such dikes and levees (Transportation Research 

Board 2008). 

Increased storm frequency and intensity might lead to more disruption to greater transportation 

services, and damage to transportation infrastructure in coastal and inland areas. Model results for the 

study of the Gulf Coast conservatively estimated a 22- to 24-foot potential surge for major hurricanes 

(Transportation Research Board 2008). During Hurricane Katrina (a Category 3 storm at landfall) surges 

exceeded these heights in some locations (Transportation Research Board 2008). While the specific 

location and strength of storm surges are difficult to project due to the variation of the scale and trajectory 

of individual tropical storms, substantial portions of the coastal infrastructure across the United States are 

vulnerable to increased damage resulting from the impacts of climate change (Transportation Research 

Board 2008). The central Gulf Coast is particularly vulnerable because of the frequency of hurricanes, its 

loss of natural protection (e.g., barrier islands and wetlands), and that much of its land is sinking in 

relation to mean sea level (EPA 2009b). 

Disruptions in transportation-system availability could result in substantial economic impacts 

associated with increased costs to construct or repair transportation infrastructure, and costs associated 

with disruptions in transportation for goods and services. Increasing fuel costs and delays in 

transportation service result in increased transport costs, which are then passed on to consumers. A 

substantial disruption in transportation (e.g., destruction of a major transportation facility by hurricane, 

flood, or other extreme weather event) could affect the regional economy in many different ways. 

Communities are likely to require long periods of time to recover from these events, and some 

communities could be permanently affected (Transportation Research Board 2008). 

The analysis to date raises clear cause for concern regarding the vulnerability of transportation 

infrastructure and services in coastal areas, and across the United States. Addressing the risks associated 

with a changing climate in the planning and design of transportation facilities and services can help public 

agencies and private investors to minimize disruptions to the smooth and safe provision of transportation 

services; and can protect the substantial investments made in the Nation’s transportation infrastructure 

now and in the future (Transportation Research Board 2008). 

According to the CCSP Impacts of Climate Change and Variability on Transportation Systems 

and Infrastructure Report (Transportation Research Board 2008), four key factors are critical to 

understanding how climate change might affect transportation: 

• Exposure. What is the magnitude of stress associated with a climate factor (sea-level rise, 

temperature change, severe storms, and precipitation) and the probability that this stress will 

affect a transportation segment or facility? 

• Vulnerability. Based on the structural strength and integrity of the infrastructure, what is the 

potential for damage and disruption in transportation services from this exposure? 

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• Resilience. What is the capacity of a system to absorb disturbances and retain transportation 

performance? 

• Adaptation. What response(s) can be taken to increase resilience at both the facility (e.g., a 

specific bridge) and system levels? 

New approaches to address climate-change factors in transportation planning and decisionmaking 

could include: 

• Extending planning timeframes. To address the long time frame over which climate changes 

and environmental processes occur, planning time frames might need to be extended beyond 

the typical 20- to 30-year planning horizon. The fact that transportation infrastructure can 

last for many decades (or even more than 100 years) argues for planning for much longer 

time frames to examine the potential impacts of climate change and other elements of the 

natural environment on the location, construction techniques, and costs for transportation 

infrastructure investments that are expected to last for many decades (Transportation 

Research Board 2008). 

• Conducting risk assessment analysis for transportation investments. Transportation 

investments face many uncertainties, including the potential impacts of climate change on 

construction, operations, and maintenance. Planners and decisionmakers can use iterative 

risk management analysis to evaluate potential risks of all types, and to identify potential 

ways to minimize the risks and increase the resiliency of transportation infrastructure. 

Transportation structures and facilities can be hardened, raised, or even relocated if needed. 

Where it is critical to safety, reliability, and mobility, redundant systems might be necessary 

for the most critical elements of the transportation system (Transportation Research Board 

2008). 

Impacts on Energy Systems

Although the energy sector has been seen as a driver of climate change, the energy sector is also 

subject to the effects of climate change (Wilbanks et al. 2007, EPA 2009b). All major energy sources are 

subject to a variety of climate change effects, including temperature, wind, humidity, precipitation, and 

extreme weather events (Bhatt et al. 2007; EPA 2009b). The most direct climate-change impacts for 

fossil fuel and nuclear power plants, for example, are related to power-plant cooling and water availability 

(Bhatt et al. 2007). Each kilowatt of electricity generated by thermoelectric generation requires about 25 

gallons of water. Power plants rank only slightly behind irrigation in freshwater withdrawals in the 

United States (USGS 2004 in Bhatt et al. 2007). In addition, about 10 percent of all U.S. coal shipments 

were delivered by barge in 2003; consequently, low river flows can create shortfalls in coal supplies at 

power plants (Bhatt et al. 2007). 

CCSP identified potential effects of climate change on energy production and use in the United 

States, which are stated in terms of likelihood (Wilbanks et al. 2007). Principal impacts and their 

likelihood are as follows: 

• Climate change will reduce total energy demand for space heating; effects will differ by 

region (virtually certain). 

• Climate change will increase total energy demand for space cooling; effects will differ by 

region (virtually certain). 

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• Net effects on energy use will differ by region. Overall impacts will be affected by patterns 

of interregional migration – which are likely to be in the direction of net cooling load 

regions – and investments in new building stock (virtually certain). 

• Temperature increases will increase peak demands for electricity (very likely). 

• Changes in the distribution of water availability will affect power plants; in areas with 

decreased water availability, competition for water supplies between energy and other sectors 

will increase (virtually certain). 

• Temperature increases will reduce overall efficiency of thermoelectric power generation 

(virtually certain). 

• In some regions, energy resource production and delivery systems will be vulnerable to the 

effects of sea-level rise and extreme weather events, especially the Gulf Coast and the East 

Coast (virtually certain). 

• Hydropower production will be directly and substantially affected by climate change, 

especially in the West and Northwest (very likely). 

• Climate change concerns will affect perceptions and practices related to risk management 

behavior in investment by energy institutions (very likely). 

• Climate change concerns are almost certain to affect public and private sector energy 

technology research and development investments and energy resource and technology 

choices by energy institutions, along with associated emissions (virtually certain). 

CCSP concluded that there is very little literature on adaptation of the energy sector to effects of 

climate change, and its following discussion is therefore largely speculative (Wilbanks et al. 2007). Both 

energy users and providers are accustomed to changing conditions that affect their decisions. The energy 

sector is among the most resilient of all economic sectors in terms of responding to changes within the 

range of historical experience (Wilbanks et al. 2007). Adaptations to the effects of climate change on 

energy use could focus on increased demands and rising costs for space cooling; likely responses include 

investing in more efficient cooling equipment and building envelopes. Increased demands for both peak 

and average electricity demands could lead to contingency planning for load leveling, more efficient and 

expanded generation capacity, expanded interties, and increased storage capacity (Wilbanks et al. 2007). 

In terms of energy production and supply, the most likely near-term adaptation is expected to be 

an increase in perceptions of uncertainty and risk in long-term strategic planning and investment, with 

investors seeking to reduce risks through such approaches as diversifying supply sources and 

technologies, and risk-sharing arrangements (Wilbanks et al. 2007). 

Impacts on Human Settlements

The impacts of climate change on human settlements are expected to be substantial in a number 

of ways. “Settlements are important because they are where most of the [U.S.] population lives, often in 

concentrations that imply vulnerabilities to location-specific events and processes” (Wilbanks et al.

2007). Among the general effects of climate change are increased stress on human settlements due to 

higher summer temperatures and decreased stress associated with warmer winter temperatures. Changes 

in precipitation and water availability, rising sea levels in coastal regions, and greater risks from extreme 

weather events such as storms, flooding, and droughts are also expected to affect human settlements to 

various degrees (EPA 2009b). At the same time, stresses due to extreme cold weather events, such as 

blizzards and ice storms, are expected to decrease (Wilbanks et al. 2007). In addition to climate change 

itself, climate-change mitigation measures could affect human settlements. For example, policies related 

to energy sources and uses, environmental emissions, and land use could have direct and short-term 

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effects on settlements in regions where the economies are closely related to the production and 

consumption of large quantities of fossil fuels (CCSP 2008d). 

Predicting climate-change impacts on U.S. settlements is difficult because climate change is not 

forecast on a scale that is appropriate for local decisionmaking, and because climate is not the only 

change that settlements are confronting. A key example is the continuing population shift, particularly 

among persons who have reached retirement, toward the Sun Belt and coastal areas. This means an ever 

larger elderly population could be at risk, especially from extreme weather events such as tropical storms, 

and some types of vector-borne diseases and heat-related illnesses (CCSP 2008d). 

Anticipated human impacts include: 

• Increased water demands associated with warming accompanied by changes in precipitation 

that alters access to water (Gleick 2000, Kirshen 2002, Ruth et al. 2007, all in CCSP 2008d). 

• Damages or disruptions to services associated with urban infrastructure such as sanitation 

systems, electricity transmission networks, communication systems, and the like could occur 

as a result of storms, floods, and fires (CCSP 2008d). 

• Sea-level rise could jeopardize many of the 673 coastal counties and threaten population 

centers (Neumann et al. 2000, Kirshen et al. 2004, both in CCSP 2008d). 

• Vulnerable populations such as the poor, elderly, those in ill health, the disabled, persons 

living alone, and individuals with limited rights (e.g., recent migrants) are expected to be at 

greater risk from climate change (CCSP 2008d). 

The vulnerability of human settlements and infrastructure in coastal areas to natural disasters such 

as hurricanes and tropical storms was demonstrated through the damages Hurricanes Katrina and Rita 

caused along the U.S. Gulf Coast. 

There is considerable potential for adaptation through technological and institutional 

development, in addition to behavioral changes, in particular where such developments meet other 

sustainable development needs (CCSP 2008d). There are various possible adaptation strategies for 

human settlements including assuring effective governance; increasing the resilience of physical and 

linkage infrastructures; changing settlement locations over time; changing settlement form; reducing heatisland effects; reducing emissions and industry effluents; improving waste handling; providing financial 

mechanisms for increasing resiliency; targeting assistance programs for especially impacted segments of 

the population; and adopting sustainable community development practices (Wilbanks et al. 2005 in 

Wilbanks et al. 2007). The choice of strategies and policies for adaptation depend on their relationships 

with other social and ecological processes and level of economic development (O’Brien and Leichenko 

2000 in Wilbanks et al. 2007). 

Impacts on Economic Opportunities and Risks

Communities or regions that depend on climate-sensitive resources or goods or whose 

comparative advantage could be affected are expected to be particularly vulnerable to climate change. 

The insurance sector is an example of an industry that could be highly vulnerable to climate impacts. 

Overall risk exposure of insurers’ has grown considerably (e.g., the National Flood Insurance Program’s 

exposure increased four-fold since 1980 to nearly $1 trillion in 2005 and the Federal Crop Insurance 

Corporation’s exposure grew up to $44 billion) (U.S. GAO 2007). In the United States, of the $19 trillion 

in insured commercial and residential properties, 41 percent are in coastal communities (EPA 2009b). In 

Florida, this portion is 79 percent; in New York 63 percent; and in Connecticut 61 percent (EPA 2009b). 

To the extent that climate change increases costs for insurers or increases the difficulty of forecasting 

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risks, the insurance sector might “withdraw (or make much more expensive) private insurance coverage 

from areas vulnerable to climate change impacts” (National Science and Technology Council 2008). 

Trade, retail, and commercial services, and tourism are other economic areas that are expected to 

be affected by climate-change impacts, largely as a result of impacts on the transportation and energy 

sectors. For example, impacts on transportation will affect distribution and receipt of goods for retail 

services. A decline in water levels could jeopardize this mode of transporting manufacturing. Future 

low-flow conditions in some areas could affect the ability of ships to navigate waterways and use some 

ports (EPA 2009b). 

Tourism could be affected by “changes in the landscape of areas of tourist interest” and by 

changes in the availability of resources and energy costs (Wilbanks et al. 2007). In the United States, 

climate-change impacts could affect winter recreation and tourism in the Northeast. Warmer winters 

would “shorten the average ski and snowboard seasons, increase snow making requirements, and drive up 

operating costs,” possibly “prompting further closures and consolidation of ski areas northward toward 

the Canadian border” (Frumhoff et al. 2007). 

Historical and Cultural Resources

A variety of cultural and historical resources are at risk from climate change. Alaska is the region 

expected to be most affected by climate change, largely because of location (warming is more pronounced 

closer to the poles) and way of life (settlement and economic activities based around Arctic conditions) 

(CCSP 2008d). Indigenous communities in Alaska are facing major economic and cultural impacts 

because they depend for subsistence on various climate-sensitive animals such as polar bears, walruses, 

seals, and caribou (National Science and Technology Council 2008). “Changes in species’ ranges and 

availability, access to these species, a perceived reduction in weather predictability, and travel safety in 

changing ice and weather conditions present serious challenges to human health and food security, and 

possibly even the survival of some cultures” (EPA 2009b). 

Impacts on National Security

This section draws heavily from national security reports, as peer-reviewed studies are 

unavailable. These reports represent a collection of security assessments based on congressional 

testimonies, and assessments from military advisory boards and councils on foreign relations. The 

following reports were consulted: the Center for Naval Analyses (CNA) Corporation report, “National 

Security and the Threat of Climate Change” (The CNA Corporation 2007), which was researched and 

written under the direction of 11 retired senior military officers; the Center for Strategic and International 

Studies and the Center for a New American Security’s report, “The Age of Consequences: The Foreign 

Policy and National Security Implications of Global Climate Change” (Campbell et al. 2007); the Council 

on Foreign Affairs’ special report, “Climate Change and National Security: An Agenda for Action” 

(Busby 2007); the Pew Center on Climate Change report, “National Security Implications of Global 

Climate Change” (Pew Center on Global Climate Change 2009); the paper for the European Council, 

“Climate Change and International Security” (ECEC 2008); and the Department of Defense’s 

“Quadrennial Defense Review Report” (DOD 2010). 

Climate change has profound implications for America’s national security both domestically and 

abroad. Sea-level rise, storm surges, extreme weather events, and changes in temperature and 

precipitation patterns all pose serious threats to global stability. Regions in Asia, Africa, and the Middle 

East with marginal living standards will be particularly vulnerable as economic and environmental 

conditions worsen (NIC 2008; The CNA Corporation 2007). Further, climate change acts as a threat 

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multiplier21 for instability in volatile regions of the world (Campbell et al. 2007; DOD 2010); NIC 2008; 

The CNA Corporation 2007). 

Areas of conflict driven by climate change that might impact U.S. and international security 

include the following: 

• increased conflict over resources, stemming from changes in agricultural production and 

freshwater availability (Brown and Crawford 2009; The CNA Corporation 2007; ECEC 

2008; Pew Center on Global Climate Change 2009); 

• risk of economic damage to coastal cities and critical infrastructure from sea-level rise and an 

increase in natural disasters (The CNA Corporation 2007; Pew Center on Global Climate 

Change 2009; Busby 2007); 

• loss of territory and border disputes resulting from sea-level rise; 

• environmentally-induced migration from loss of coastal land, desertification, and a decreased 

availability of resources due to climate change (Pew Center on Global Climate Change 2009; 

ECEC 2008); 

• potential for tension and instability over energy supplies (The CNA Corporation 2007; ECEC 

2008); 

• increasing pressure on international governance, stemming from the potential resentment of 

those impacted by climate change towards those considered responsible for climate change 

(ECEC 2008). 

These areas of conflict could add political and social tension, as well as an economic burden, to 

the United States and other stable countries, for example, if such countries were to accept large immigrant 

and refugee populations (The CNA Corporation 2007; DOD 2010; ECEC 2008; Busby 2007). In 

addition, the U.S. military could become overextended as it responds to extreme weather events and 

natural disasters, as along with current or future national security threats (The CNA Corporation 2007; 

Pew Center on Global Climate Change 2009; DOD 2010; Busby 2007). As a result of the risks described 

above, the National Intelligence Council has expressed increasing concern regarding the geopolitical and 

national security consequences of climate change (NIC 2008). 

4.5.7.2.2 Projected Global Impacts of Climate Change 

As the discussion above suggests, the three major ways in which industry, settlements, and 

society are vulnerable to climate change are through impacts on economics, infrastructure, and health. 

The magnitude of impacts on industry, settlements, and society largely depends on location and the level 

of development of the area or region. The following discussion highlights anticipated impacts on key 

human systems at the global level. 

Global Energy Sector Impacts

Regarding energy production and use, expected global impacts will likely be similar to those 

described above for the United States. When the climate warms, less heating will be needed for 

industrial, commercial, and residential buildings, with changes varying by region and by season 

(Wilbanks et al. 2007). Electricity is used in areas around the world for cooling; coal, oil, gas, biomass, 

and electricity provide energy for heating. Regions with substantial requirements for both cooling and 

 

21 “Threat multiplier” refers to an action that further intensifies the instability of a system that poses a security 

concern. 
4.5 Health, Societal, and Environmental Impacts of Climate Change Chapter 4 Cumulative Impacts 

heating could see net increases in electricity demands while demands for other energy sources decline 

(Hadley et al. 2006 in Wilbanks et al. 2007). 

According to one study, by 2100 the benefits (reduced heating) will be about 0.75 percent of 

gross domestic product, and impacts (increased cooling) will be approximately 0.45 percent (Tol 2002a, 

2002b, both in Wilbanks et al. 2007). These percentages could be affected by migration from heatingintensive regions to cooling-intensive regions (Wilbanks et al. 2007). 

Climate change could also affect global energy production and distribution if extreme weather 

events become more frequent or intense (EPA 2009b); and in regions that depend on water supplies for 

hydropower or thermoelectric generation if there are substantial changes in rainfall/snowfall locations and 

seasonality. Reduced stream flows are expected to jeopardize hydropower production in some areas, but 

higher precipitation rates resulting in greater or more sustained stream flows could be beneficial (Casola 

et al. 2005, Viosin et al. 2006, both in Wilbanks et al. 2007). More frequent or intense extreme weather 

events could threaten coastal energy infrastructures, including electricity transmission and distribution 

facilities (Bull et al. 2007). 

Warming temperatures resulting in melting of permafrost threaten petroleum production facilities 

and pipelines, electrical transmission towers, and nuclear power plants in the Arctic region (EPA 2009b). 

As with Alaska’s North Slope facilities, structural failures in transportation and industrial infrastructure 

are becoming more common in northern Russia due to melting permafrost (EPA 2009b). 

Global Transportation Sector Impacts

The IPCC concludes, with very high confidence, that data since 1970 have demonstrated 

anthropogenic temperature rises have visibly altered ecosystems (Parry et al. 2007). Other stressors on 

the built environment and the ability of cities and countries to adapt to a changing climate make it 

difficult to discern the exact impacts of climate change on transportation systems around the world. 

Additional factors, such as projected population growth, are expected to exacerbate the effects of climate 

change. Development typically occurs in coastal regions, especially in the newly developing third-world 

countries. These areas are particularly vulnerable to the impacts of projected increases in extreme 

weather events such as hurricanes, cyclones, unusually heavy precipitation, and flooding. In addition, 

these developing countries are less able to adapt to expected changes due to their limited resources and 

other pressing needs (Wilbanks et al. 2007). 

Transportation-system vulnerabilities in more-developed countries often focus on physical assets 

and infrastructures and their economic value and replacement costs, along with linkages to global 

markets. Vulnerabilities in less-developed countries often focus on human populations and institutions 

that are likely to have very different transportation needs and resources (Wilbanks et al. 2007). A 

warmer, drier climate could exacerbate many of the problems of developing countries, including drought 

and decreases in food production in areas of Africa and Asia (Wilbanks et al. 2007). 

At a national scale, industrialized countries such as Norway can cope with most kinds of gradual 

climate change, but localized differences can show considerable variability in stresses and capacities to 

adapt (Kates and Wilbanks 2003 in National Science and Technology Council 2008, O’Brien et al. 2004, 

Kirshen et al. 2006). 

Impacts on the U.S. transportation systems described above apply in other countries as well. 

Based on information developed by the Transportation Research Board (2008) the potential impacts of 

climate change on transportation fall into the two major categories, as follows: 

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• Climate change will affect transportation primarily through increases in several types of 

weather and climate extremes, such as very hot days, intense precipitation events, intense 

hurricanes, drought, and rising sea levels, coupled with storm surges and land subsidence. 

The impacts will vary by mode of transportation and region, but they will be widespread and 

costly in both human and economic terms and will require substantial changes in the 

planning, design, construction, operation, and maintenance of transportation systems. 

• Potentially, the greatest impact of climate change on global transportation systems will be 

flooding of coastal roads, railways, transit systems, and runways because of rising sea levels 

coupled with storm surges, and exacerbated in some locations by land subsidence (National 

Science and Technology Council 2008). 

Given the global nature of the impacts of climate change and the world economy, coordination 

within and among nations will become increasingly important (Wilbanks et al. 2007). Strong and 

complex global linkages and interactions occur throughout the world today and are likely to increase in 

the future. Climate-change effects cascade through interlinked systems for international trade, migration, 

and communication patterns, producing a variety of direct and indirect effects. Some of these impacts 

might be anticipated. However, many might not, especially if the globalized economy becomes less 

resilient and more interdependent (Wilbanks et al. 2007). 

The impacts of an extreme weather event in one location (e.g., Hurricane Katrina in Louisiana) 

causes ripple effects throughout the transportation system in the United States and in areas around the 

world linked to the United States through the ports in the affected area (Transportation Research Board 

2008). 

There are now incidences in Europe, North America, and Japan of new transportation 

infrastructure being designed and constructed with potential climate change in mind. For example, 

designing bridges and other infrastructure at higher elevations in anticipation of sea-level rise over the life 

span of these transportation-system elements (Wilbanks et al. 2007). 

Global Human Settlements Impacts

Human settlements are vulnerable to the effects of climate change in three major ways: (1) 

through economic sectors affected by changes in input resource productivity or market demands for goods 

and services, (2) through impacts on certain physical infrastructure, and (3) through impacts of weather 

and extreme events on the health of populations. The degree of vulnerability tends to be a function of the 

location (coastal and riverine areas are most at risk), economy (economies most dependent on weatherrelated sectors are at highest risk), and size (larger settlements are at greater aggregate risk, but they likely 

have greater resources to prevent the impacts of climate change and respond to events that result from 

climate changes, such as hurricanes, floods, or other extreme weather events) (EPA 2009b). 

Shifts in precipitation patterns might affect already stressed environments. For example, mean 

precipitation in all four seasons has tended to decrease in all main arid and semi-arid regions of the world 

(northern Chile and northeast Brazil, West Africa, and Ethiopia, drier parts of southern Africa, and 

western China) (Folland et al. 2001 in Wilbanks et al. 2007). Increasing temperature could aggravate 

ozone pollution in many cities, which could affect quickly growing urban areas that are experiencing 

more air pollution problems, especially those in developing countries (Wilbanks et al. 2007). 

Additionally, sea-level rise will threaten the habitability of island nations in the Caribbean and Pacific, 

where 50 percent of populations live within 0.9 mile of the shoreline (EPA 2009b). 

Extreme weather events affect settlements and society in developing countries just as they do 

developed countries − through damage and destruction of infrastructure and loss of human life − although 

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perhaps in slightly different ways. For example, in some urban areas of developing countries, informal 

settlements develop. These informal settlements are especially vulnerable because they tend to be built 

on hazardous sites and be susceptible to floods, landslides, and other climate-related disasters (Cross 

2001, UN-Habitat 2003, both in Wilbanks et al. 2007). Another example is how “[i]n developing 

countries, a common cause of death associated with extreme weather events in urban areas is 

electrocution by fallen power cables” (Few et al. 2004 in Wilbanks et al. 2007). 

Generally, low-income and other vulnerable populations would experience the same impacts from 

climate change as populations in comparable geographic areas described in this section and Sections 

4.5.6, Food, Fiber, and Forest Products, and 4.5.8, Human Health. However, as with environmental 

justice populations in the United States, vulnerable populations would likely experience climate-change 

impacts differentially. The magnitude of climate-change impacts on residents of poorer countries would 

be expected to be greater (EPA 2009b). For example, IPCC notes that the continent of Africa’s “major 

economic sectors are vulnerable to current climate sensitivity, with huge economic impacts, and this 

vulnerability is exacerbated by existing developmental challenges such as endemic poverty, complex 

governance and institutional dimensions; limited access to capital, including markets, infrastructure and 

technology; ecosystem degradation; and complex disasters and conflicts. These in turn have contributed 

to Africa’s weak adaptive capacity, increasing the continent’s vulnerability to projected climate change” 

(Wilbanks et al. 2007). 

As discussed in this section, the danger to human health from climate change will affect 

developing countries differentially. The IPCC states that “Adverse health impacts will be greatest in lowincome countries. Those at greater risk include, in all countries, the urban poor, the elderly and children, 

traditional societies, subsistence farmers, and coastal populations” (Wilbanks et al. 2007). Section 4.5.8 

describes in detail the potential health effects from climate change on developing countries, which 

include: 

• Increases in malnutrition, and related health impacts, in developing regions of the world due 

to declining crop yields; 

• Potential increases in water-related diseases, such as diarrhea-causing pathogens, due to 

higher temperatures; 

• Potential for continuation of upward trends in certain vector-borne diseases, such as malaria 

in Africa, which have been attributed to temperature increases; and 

• Increases in temperature leading to increased ozone and air pollution levels in large cities 

with vulnerable populations. 

Section 4.5.6 and this section describe the effects of climate change on developing countries that 

would differ or be substantially more severe than similar effects experienced by developed nations. 

Because the developing world tends to depend more on small-scale farming and subsistence economic 

activities, individuals in these areas would be disproportionately affected by climate-change impacts on 

agricultural and subsistence resources. In particular, these impacts could include: 

• Decreases in precipitation in developing parts of the world, such as southern Africa and 

northern South America, leading to decreases in agricultural production and increased food 

insecurity; 

• Substantial potential for impacts on small-scale subsistence farmers resulting from increases 

in extreme weather events projected under global climate change, reducing agricultural 

production in some areas of the globe; 

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• Changes in the range of fish and animals and species extinctions, affecting populations in 

developing nations that depend economically on these resources; 

• Declines in tourism, especially to coastal and tropical areas heavily affected by sea-level rise, 

with severe economic consequences for smaller, developing nations; and 

• Sea-level rise and severe weather-related events affecting the long-term habitability of atolls 

(low coral reef-formed islands) (Barnet and Adger 2003). 

Global Impacts on Economic Opportunities and Risks

Impacts vary by region and locality and cannot be generalized for all nations. Although impacts 

are expected to vary, a factor that developed countries have in common is that their access to material and 

financial resources provides them opportunities to adapt to the effects of a changing climate. In contrast, 

poorer countries are expected to be less able to adapt to climate change because they lack both the 

physical and financial resources needed to bolster their resilience to the same extent possible in wealthier 

countries (EPA 2009b). 

In developing countries “industry includes a greater proportion of enterprises that are small-scale, 

traditional, and informally organized...Impacts of climate change on these businesses are likely to depend 

on...location in vulnerable areas, dependence on inputs sensitive to climate, and access to resources to 

support adaptive actions” (Wilbanks et al. 2007). One specific industry that could become more 

vulnerable to direct and indirect impacts of climate change is tourism. Impacts on this industry can be 

“especially significant for smaller, tourist-oriented countries often in the developing world” (Wilbanks et 

al. 2007). It seems “likely that tourism based on natural environments will see the most substantial 

changes due to climate change...Tropical island nations and low-lying coastal areas may be especially 

vulnerable as they may be affected by sea-level rise, changes in storm tracks and intensities, changes in 

perceived climate-related risks, and changes in transport costs...” (Wilbanks et al. 2007). The 

implications are most notable for areas in which tourism is a relatively large share of the local or regional 

economy, and those for which adaptation would represent a relatively substantial need and a relatively 

substantial cost (Wilbanks et al. 2007). Trade is another industry that could be affected by extreme 

weather events that temporarily close ports or transportation routes and damage infrastructure critical to 

trade, both domestic and international. There could be “linkages between climate change scenarios and 

international trade scenarios, such as a number of regional and sub-regional free trade agreements” 

(Wilbanks et al. 2007). However, research on this topic is lacking. 

4.5.8 Human Health 

4.5.8.1 Affected Environment 

Climate change has contributed to human mortality and morbidity (very high confidence; IPCC 

2007b) with further projected increases (EPA 2009b). Climate change could increase the risk of flooding; 

increase incidence of heat waves; change the severity, duration, and location of extreme weather; increase 

surface temperature; and alter precipitation intensity and frequency. These events can affect human 

health either directly through temperature and weather or indirectly though changes in water, air, food 

quality, vector ecology, ecosystems, agriculture, industry, and settlements. Climate change can also 

affect health through social and economic disruption. Malnutrition, death, and disease brought on by 

climate change are projected to affect millions of people (Confalonieri et al. 2007). 

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4.5.8.2 Environmental Consequences 

4.5.8.2.1 Observed Health Impacts and Vulnerabilities Associated with Climate 

Change 

Heat Waves

A heat wave is a period of abnormally high temperatures that can be accompanied by unusual 

humidity. This weather phenomenon is not formally specified by a time period or temperature reading. 

Conventionally, a heat wave lasts several days to several weeks, though a 1-day event can qualify as a 

heat wave. The temperature to qualify as a heat wave depends on what is considered unusually hot for 

that region, because increases in mortality can occur below temperatures considered extremely hot (Ebi et 

al. 2008). IPCC has found the number of hot days, hot nights, and heat waves to have increased 

(Confalonieri et al. 2007). Global warming has increased the intensity of heat waves (Houghton et al.

2001 in Epstein et al. 2005), due in part to disproportionate warming at night (Easterling et al.1997 in 

Epstein et al. 2005). Heat waves can trigger poor air quality and forest fires, leading to further increases 

in human mortality and morbidity (Bates. 2005, Goodman et al. 2004, Keatinge and Donaldson 2001, 

O’Neill et al. 2005, Ren et al. 2006, all in Ebi et al. 2008). 

The impact of a heat wave on the affected population depends on the population’s health and 

economic status. Globally, those most sensitive to heat waves include the rural population, the elderly, 

outdoor workers, the very young, city dwellers, those with less education, those who are socially isolated, 

medicated, or mentally ill, and those without available air conditioning (Chaudhury et al. 2000 in 

Confalonieri et al. 2007; Diaz et al. 2002, Klinenberg 2002, McGeehin and Mirabelli 2001, Semenza et 

al. 1996, Whitman et al. 1997, Basu et al. 2005, Gouveia et al. 2003, Greenberg et al. 1983, O’Neill et al.

2003, Schwartz 2005, Jones et al. 1982, Kovats et al. 2004, Schwartz et al. 2004, Semenza et al. 1999, 

Watkins et al. 2001, all in Ebi 2008; EPA 2009b). People in developed areas also can be impacted 

substantially by heat waves. Existing electricity grids in the United States would be severely stressed by 

a major heat wave, leading to brownouts and blackouts and further contributing to increased heat-related 

illnesses (Epstein et al. 2005). In addition, increased electricity demand during heat waves and summer 

months can compound health issues because air pollutant levels from electrical generating units increase 

(IPCC, 2007b). Populations identified to be vulnerable to heat waves in the United States include those 

with diabetes, mobility constraints, and cognitive constraints (Schwartz 2005 in Ebi et al. 2008; EPA 

2006 in Ebi et al. 2008). 

The urban heat island effect could increase temperatures experienced in cities by 2 to 10 oF 

compared to neighboring rural and suburban areas (EPA 2009c in Ebi et al. 2008). This increase in 

temperature occurs, in part, as the city pavement and buildings absorb a greater amount of incoming solar 

radiation compared to vegetation and trees; in addition, heat is also emitted from buildings and 

transportation (EPA 2009c, Pinho and Orgaz 2000, Vose et al. 2004, Xu and Chen 2004, all in Ebi et al.

2008). However, it has been demonstrated that during a heat wave, not all urban areas experience greater 

heat-related mortality than the surrounding rural and suburban areas (Sheridan and Dolney, 2003 in Ebi et 

al. 2008). In addition, a sociological analysis of a 1995 Chicago heat wave found populations were at 

higher risk in neighborhoods without public gathering places and active street life (Klinenberg 2002 in 

Ebi et al. 2008). Population growth over the next 50 years is projected to occur primarily in cities, 

thereby increasing the number of people exposed to heat waves (EPA 2009b). 

Cold Waves

Human mortality and morbidity can also be caused by cold waves. Cold waves affect human 

health through death, hypothermia, frostbite, damage to organs such as kidneys, pancreas, and liver, with 

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the greatest risk to infants and the elderly (NOAA 2001). Cold waves can cause further complications of 

heavy snow, ice, coastal flooding, and stranded motorists. As with a heat wave, the classification of a 

cold wave varies by region, with no formal definition for the minimum temperature reached, the rate of 

temperature fall, or the duration of the event. Populations in temperate countries that do not traditionally 

experience cold waves tend to be more sensitive (Honda et al. 1998 in Confalonieri et al. 2007); however, 

populations in cold environments are considered vulnerable if electricity or heating systems fail (EPA 

2009b). The human-health reaction of a population to a cold wave can vary depending on income, (Healy 

2003 in Ebi et al. 2008), age, topography, climate (Curriero et al. 2002, Hajat 2006, both in Confalonieri 

et al. 2007), race (Fallico et al. 2005 in Ebi et al. 2008), sex (Wilkinson et al. 2004 in Ebi et al. 2008), 

health (Wilkinson et al. 2004 in Ebi et al. 2008), dress (Donaldson et al. 2001 in Ebi et al. 2008), and 

access to fuel (Healy 2003 in Ebi et al. 2008). Cold days, cold nights, and frost days have become less 

common (IPCC 2007b), with the winter season projected to continue to decrease in duration and intensity 

(IPCC 2007e in Ebi et al. 2008). This could lead to a decrease in cold-related health impacts, 

notwithstanding external factors, such as influenza outbreaks (Ebi et al. 2008, EPA 2009b). It has not 

been determined if the reduced mortality associated with cold waves will be more or less than the 

increased heat-related mortality projected to occur in response to climate change (CCSP 2008d, EPA 

2009b). 

Extreme Weather Events

Climate change is anticipated to affect the number, severity, and duration of extreme weather 

events (Fowler and Hennessey 1995 in Sussman et al. 2008). Extreme weather events include floods, 

tropical and extra-tropical cyclones, tornadoes, windstorms, and drought. Extreme weather can further 

trigger additional extreme events such as wildfires, negatively affecting infrastructure, including 

sanitation, human mortality and morbidity, and mental health (Confalonieri et al. 2007). The loss of 

shelter, large-scale population displacement, damage to community sanitation and health care, and 

reduction in food availability can extend the level of mortality and morbidity beyond the actual event 

(Curriero et al. 2001b in Sussman et al. 2008). Factors that influence population vulnerability to extreme 

weather include location, population density, land use, age, income, education, health, health-care 

response, and disaster preparedness (Blaikie et al. 1994, Menne 2000, Olmos 2001, Adger et al. 2005b, 

Few and Matthies 2006, all in Confalonieri et al. 2007; EPA 2009b). 

Adverse weather conditions create safety hazards and delays in the Nation’s transportation 

systems, especially on its highways. The Federal Highway Administration estimates that about 28 

percent of highway crashes occur during adverse weather, resulting in about 19 percent of highway 

fatalities (AMS, 2004), while the Federal Motor Carrier Safety Administration found that the factor 

“environmental conditions” was the critical reason22 for 3 percent of large truck crashes (FMCSA, 2007). 

Extreme weather events that increase adverse weather conditions on the Nation’s highways could affect 

highway safety. 

Floods occur with the greatest frequency compared to other extreme weather events (EM-DAT 

2006 in Confalonieri et al. 2007). The intensity of a flood depends on rainfall, surface runoff, 

evaporation, wind, sea level, and local topography (Confalonieri et al. 2007). Health impacts related to 

flood events include deaths and injuries sustained during a flood event; increased transmission and 

prevalence of infectious diseases; toxic contamination of supplies and food; and post-traumatic stress 

disorders (EPA 2009b). Additional health impact stressors such as geographic displacement and damage 

 

22 The Federal Motor Carrier Safety Administration conducted the Large Truck Crash Causation Study sample of 963 crashes 

involving 1,123 large trucks and 959 motor vehicles that were not large trucks between 2001 and 2003. The Study defines the 

Critical Reason as the immediate reason for the critical event (i.e., the failure leading to the critical event). The critical reason is 

assigned to the vehicle coded with the critical event in the crash. It can be coded as a driver error, vehicle failure, or 

environmental condition (roadway or weather). Other causal coding includes a Critical Event and Associated Factors.
4.5 Health, Societal, and Environmental Impacts of Climate Change Chapter 4 Cumulative Impacts 

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to possessions and property can occur after the initial event, leading to continued disruption and anxiety 

regarding the recurrence of the event (Tapsell et al. 2002 in Ebi et al. 2008). Coastal storms can cause 

drowning by the associated storm surge particularly in regions of high-density populations living in lowlying coastal sections, as evidenced in the U.S. Gulf Coast during 2005 Hurricane Katrina (EPA 2009b). 

Drought is an abnormal period of dry weather that has led to substantial decrease in water 

availability for a given location (Huschke 1959). The health impacts associated with a drought include 

mortality, malnutrition, infectious diseases, and respiratory diseases (Menne and Bertollini 2000 in 

Confalonieri et al. 2007). Aggravating this situation, malnutrition increases the susceptibility of 

contracting an infectious disease (Confalonieri et al. 2007) and drought-related population displacement 

can reduce access to adequate and safe water, food, and shelter, leading to increased malnutrition and 

infectious diseases. Further health impacts can spiral, such as a change in the transmission of mosquitoborne diseases during and after the drought event (Confalonieri et al. 2007). Impacts on agricultural 

productivity affect health through risk of under- and malnutrition (Epstein et al. 2005), and increased dust 

storm activity and frequency of forest fires. Drought conditions weaken trees’ defenses against pests and 

can result in increased threats to human health from forest fires (Mattson and Haack 1987, Boyer 1995, 

Holsten et al. 2000, all in Epstein et al. 2005). Health impacts associated with drought tend to be more 

prevalent in drier climates with poor populations and where there is human-induced water scarcity. 

Therefore, the most severe drought-related health impacts are likely to be in developing countries rather 

than in the United States (EPA 2009b). 

Air Quality

Climate change can affect air quality through altering local weather patterns and/or pollution 

concentrations. Ground-level ozone, PM, and airborne allergens contribute to poor air quality, leading to 

respiratory ailments and premature mortality. Increasing exposure to these pollutants would have 

substantial negative health impacts (Confalonieri et al. 2007). 

Ground-level ozone contributes to urban smog, and occurs both naturally and as a secondary 

pollutant formed through photochemical reactions of NOx and VOCs.23 These reactions are accelerated 

with increasing sunlight and temperatures. Ozone concentrations tend to peak around 3pm through 6pm 

depending and in the warmer season. EPA (2009b) states that ozone generally increases with higher 

temperatures. Studies have already found increasing levels of ground-level ozone in most regions (Wu 

and Chan 2001, Chen et al. 2004, both in Confalonieri et al. 2007). A recent study found increases in 

CO2 concentrations contribute to increased water vapor and temperatures and separately increase ozone 

more with higher ozone (Jacobson 2008). These lead to an increase in U.S. annual air pollution deaths by 

about 1,000 (350-1,800) where about 40% of the additional death may be due to ozone (the remaining 

60% to particles). The study further extrapolates the findings to a global scale estimating 21,600 (7,500-

39,000) excess CO2-caused annual pollution deaths 

Ozone exposure is associated with respiratory ailments such as pneumonia, chronic obstructive 

pulmonary disease, asthma, allergic rhinitis, chest pain and other respiratory diseases (Mudway and Kelly 

2000, Gryparis et al. 2004, Bell et al. 2005, 2006, Ito et al. 2005, Levy et al. 2005, all in Confalonieri et 

al. 2007). Asthmatics are considered a sensitive population (Ebi et al. 2008). Long-term exposure to 

elevated amounts of ozone has been shown to affect lung efficiency (Ebi et al. 2008). 

PM comprises solid and liquid particles suspended in the atmosphere varying in both chemical 

composition and origin. Concentrations of PM are affected by emission rates and local weather 

 

23 NOx is emitted, in part, through the burning of fossil fuels. VOCs are emitted from varying sources, including burning of fossil 

fuels, transpiration, evaporation from stored fuels, solvents and other chemicals.
Chapter 4 Cumulative Impacts 4.5 Health, Societal, and Environmental Impacts of Climate Change 

conditions such as atmospheric stability, wind, and topography. Some particulates display seasonal 

variability directly linked to seasonal weather patterns (Alvarez et al. 2000, Kassomenos et al. 2001, 

Hazenkamp-von Arx et al. 2003, Nagendra and Khare 2003, Eiguren-Fernandez et al. 2004, all in 

Confalonieri et al. 2007). In Mexico City and Los Angeles, local weather conditions can create a stagnant 

air mass, restricting dispersion of pollution. Seasonal weather patterns can further enhance the chemical 

reactions of emissions, thereby increasing secondary PM (Rappengluck et al. 2000, Kossmann and 

Sturman 2004, both in Confalonieri et al. 2007; EPA 2009b). 

Breathing PM can cause respiratory ailments, heart attack, and arrhythmias (Dockery et al. 1993, 

Samet et al. 2000, Pope et al. 1995, 2002, 2004, Pope and Dockery 2006, Dominici et al. 2006, Laden et 

al. 2006, all in Ebi et al. 2008). Populations at greatest risk could include children, the elderly, and those 

with heart and lung disease, diabetes (Ebi et al. 2008), and high blood pressure (Künzli et al. 2005 in Ebi 

et al. 2008). Chronic exposure to PM could decrease lifespan by 1 to 3 years (Pope 2000 in American 

Lung Association 2008). Increasing PM concentrations are expected to have a measurable adverse 

impact on human health (Confalonieri et al. 2007). 

Forest fires contribute to poor air quality conditions. During the fifth largest U.S. wildfire, in 

1999, medical visits at the Hoopa Valley National Indian Reservation increased by 52 percent, with 

symptoms affecting lower respiratory tract and preexisting cardiopulmonary conditions (Mott et al. 2002). 

Human-health ailments associated with forest fires include burns, smoke inhalation, mortality, eye 

illnesses, and respiratory illnesses (Confalonieri et al. 2007, Ebi et al. 2008). One study found there is an 

increase in the number of patients requesting emergency services for smoke and ash inhalation when there 

are large fires (EPA 2009b). Certain regions are anticipated to experience an increase in frequency and 

intensity of fire events with projected changes in temperature and precipitation. Pollutants from forest 

fires can affect air quality for thousands of miles (EPA 2009b). Pollution from forest fires along with 

other pollutants, such as carbon monoxide, ozone, desert dust, mould spores and pesticides, can be 

transported thousands of kilometers on time scales of 4 to 6 days and affecting populations far from the 

sources (Gangoiti et al. 2001, Stohl et al. 2001, Buchanan et al. 2002, Chan et al. 2002, Martin et al.

2002, Ryall et al. 2002, Ansmann et al. 2003, He et al. 2003, Helmis et al. 2003, Moore et al. 2003, 

Shinn et al. 2003, Unsworth et al. 2003, Kato et al. 2004, Liang et al. 2004, Tu et al. 2004, all in 

Confalonieri et al. 2007). 

Water-borne and Food-borne Diseases

Substantial morbidity and childhood mortality has been linked to water- and food-borne diseases. 

Climate change is projected to alter temperature and the hydrologic cycle through changes in 

precipitation, evaporation, transpiration, and water storage. These changes, in turn, potentially affect 

water-borne and food-borne diseases, such as salmonellosis, campylobacter, leptospirosis, and pathogenic 

species of vibrio. They also have a direct impact on surface-water availability and water quality. It has 

been estimated that more than 1 billion people in 2002 did not have access to adequate clean water 

(McMichael et al. 2003 in Epstein et al. 2005). Increased temperatures, greater evaporation, and heavyrain events have been associated with adverse impacts on drinking water through increased waterborne 

diseases, algal blooms, and toxins (Chorus and Bartram 1999, Levin et al. 2002, Johnson and Murphy 

2004, all in Epstein et al. 2005). A seasonal signature has been associated with waterborne disease 

outbreaks (EPA 2009b). In the United States, 68 percent of all waterborne diseases between 1948 and 

1994 were observed after heavy rainfall events (Curriero et al. 2001a in Epstein et al. 2005). 

Climate change could further impact a pathogen by directly affecting its life cycle (Ebi et al.

2008). The global increase in the frequency, intensity, and duration of red tides could be linked to local 

impacts already associated with climate change (Harvell et al. 1999 in Epstein et al. 2005); toxins 

associated with red tide directly affect the nervous system (Epstein et al. 2005). 

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Many people do not report or seek medical attention for their ailments of water-borne or foodborne diseases; hence, the number of actual cases with these diseases is greater than clinical records 

demonstrate (Mead et al. 1999 in Ebi et al. 2008). Many of the gastrointestinal diseases associated with 

water-borne and food-borne diseases can be self-limiting; however, vulnerable populations include young 

children, those with a compromised immune system, and the elderly. 

Vector-borne Diseases

Infections can be spread by the bite of an infected arthropod (termed vector-borne) such as 

mosquitoes, ticks, sandflies, and blackflies, or through non-human vertebrates such as rodents, canids, 

and other mammals. Such diseases include typhus, malaria, yellow fever, dengue fever, West Nile virus, 

Western Equine encephalitis, Eastern Equine encephalitis, Bluetongue virus, and Lyme disease. 

Increased insect density has been correlated with milder seasonal variability (Confalonieri et al. 2007) 

and tick distributions tend to expand with higher minimum temperatures (Ebi et al. 2008). In the United 

States, the greatest transmissions of West Nile virus occurred during the 2002 through 2004 summers 

associated with above average temperatures (EPA 2009b). In general, climate and weather are important 

constraints on the range of transmission for vector-borne diseases. For example, temperature and 

flooding are key constraints on the range of mosquitoes, which serve as a primary vector for malaria and 

other diseases (Epstein et al. 2005). Changes in seasonal duration and increases in weather variability 

reduce or eliminate these constraints (Epstein et al. 2005). In southern Mozambique, the number of 

malaria cases increased four to five times over long-term averages in the days and weeks following a 

severe flooding event in 2000 (Epstein et al. 2005). Temperature and the availability of water can both 

play key roles in regulating population size. For the deer tick, the disease vector for Lyme disease, offhost survival is strongly affected by these two variables; therefore, climate is the primary factor 

determining size and distribution of deer tick populations (Needham and Teel 1991, Bertrand and Wilson 

1996, both in Epstein et al. 2005). Changes in land-use practices or to the habitat and behavior of wildlife 

hosts of the insect can also impact latitudinal or altitudinal shifts in the disease-carrying species 

(Confalonieri et al. 2007). 

4.5.8.2.2 Projected Health Impacts of Climate Change on the United States 

Human health is projected to be adversely affected by rising temperatures, increasing groundlevel ozone concentrations, changes in extreme weather events, and increasing food- and water-borne 

pathogens. The impact of the varying health-related event is dependent on location. The United States is 

anticipated to sustain fewer cases of illness and death associated with climate change compared with the 

developing world (CCSP 2008d). The existing health infrastructure Federal Government disaster 

planning and emergency response systems are key assets to enable the United States to meet changing 

health-effect demands associated with climate change. These health impacts will vary in scope across the 

United States. 

In the United States, there were 20,000 heat and solar-related deaths from 1936 to 1975, with the 

heat wave of 1980 accounting for more than 1,250 of these deaths (NOAA 2005 in Kundzewicz et al.

2007). There could be a rise in heat-related morbidity and mortality in the coming decades (CCSP 2008d) 

due, in part, to an aging population. By 2010, 13 percent of the population of the United States is 

projected to be over the age of 65 (Day 1996 in Ebi et al. 2008), and this proportion will grow 

dramatically as Baby Boomers age (EPA 2009b). Additionally, most population growth will occur in the 

cities, where temperatures tend to be higher due to the urban heat island effect (EPA 2009b). This shift 

toward an older, and more urban population, could increase heat-related health risks. 

 Studies have shown a decline in heat-related mortality over the past decades, possibly due to 

increased air conditioning usage and improved health care (Davis et al. 2002, Davis et al. 2003a, Davis et 

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al. 2003b, Carson et al. 2006, all in Ebi et al. 2008). Heat waves are anticipated to increase in severity, 

frequency and duration, particularly in the Midwest and Northeast (CCSP 2008d). In U.S. regions where 

severe heat waves already occur, these events are projected (high confidence) to intensify in magnitude 

and duration. Tor example, in 2080 through 2099, Chicago could experience a 25-percent increase in the 

annual frequency of heat waves under the business-as-usual (A1B) emissions scenario (EPA 2009b). 

The northern latitudes of the United States are likely to experience the greatest increases in 

average temperature and concentrations of many of the airborne pollutants (CCSP 2008d). A regional 

climate simulation projected air quality to worsen in Texas but to improve in the Midwest in 2045 to 2055 

compared to 1995 to 2005 (Leung and Gustafson 2005 in Ebi et al. 2008). In urban areas, ground-level 

ozone concentrations are anticipated to increase in response to higher temperatures and increases in water 

vapor concentration (CCSP 2008d, Jacobson 2008). Climate change could further cause stagnant air 

masses that increase pollution concentrations of ground-level ozone and PM in populated areas. For 

example, one study projected an increase in upper Midwest stagnant air between 2000 and 2052 (Mickley 

et al. 2004 in Ebi et al. 2008). An alternative study found an increase in evaporative losses from nitrate 

particles reduces PM levels (Aw and Kleeman 2003 in Ebi et al. 2008). A recent study concluded that 

continuous local outdoor CO2 emissions can increase the respective CO2 concentration for that area, 

thereby increasing ozone levels (Jacobson 2008). 

The spring pollen season has recently been shown to begin earlier than usual in the Northern 

Hemisphere (D’Amato et al. 2002, Weber 2002, Beggs 2004, all in Confalonieri et al. 2007). There is 

further evidence suggesting a lengthening of the pollen season for some plant species (Confalonieri et al.

2007). A recent study determined that the density of air-borne pollen for some species has increased, 

however, it is not understood what the allergenic content of this additional pollen is (Huynen and Menne 

2003, Beggs and Bambrick 2005, both in Confalonieri et al. 2007). Additionally, climate change could 

alter the pollen concentration of a given plant species as the species reacts to increased concentrations of 

CO2. Current findings demonstrate that ragweed pollen production and the length of the ragweed pollen 

season increase with rising CO2 concentrations and temperatures (Wan et al. 2002, Wayne et al. 2002, 

Singer et al. 2005, Ziska et al. 2005, Rogers et al. 2006a, all in Confalonieri et al. 2007). Invasive plant 

species with high allergenic content, such as ragweed and poison ivy, have been found to be spreading in 

particular locations around the world, increasing potential health risks (Rybnicek and Jaeger 2001, 

Huynen and Menne 2003, Taramarcaz et al. 2005, Cecchi et al. 2006, all in Confalonieri et al. 2007). For 

example, a field study determined urban locations could experience an increase in ragweed pollen 

compared to rural locations due to the projected temperature and CO2 concentrations in these locations 

(Field et al. 2007d in EPA 2009). Scientific findings are not conclusive about how climate change might 

impact allergenic illnesses in the United States, particularly in relation to other factors such as changes in 

land use, air pollution, and adaptation practices (EPA 2009b). 

Extreme weather events are likely to be altered by climate change, though there is uncertainty 

projecting the frequency and severity of events. Some regions in the United States might experience 

drought conditions due to the reduction in rainfall, while other sections of the Country are likely to 

experience increased frequency of heavy rainfall events, leading to potential flood risk (GCRP 2009). It 

is considered very likely (greater than 90 percent certainty) that over the course of this century there will 

be an increase in the frequency of extreme precipitation (IPCC 2007a). The Southeast, Intermountain 

West, and West are likely to experience an increase in frequency, severity, and duration of forest fires 

(CCSP 2008d, Brown et al. 2004b, Fried et al. 2004, all in Ebi et al. 2008). Impacts to respective 

vulnerable populations could change in the future as shifts occur in population, suburban development, 

and community preparedness. It is very likely that a large portion of the projected growth of the United 

States population will occur in areas considered to be at risk for future extreme weather events (Ebi et al.

2008). Hence, even if the rate of health impacts decreased, the growth in population in risk areas would 

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still cause an increase in the total number of people affected. Intense tropical cyclone activity is “likely” 

to intensify, increasing the risk of death, injuries, diseases, and mental health disorders (EPA 2009b). 

Pathogen transmission depends on many climate-related factors such as temperature, 

precipitation, humidity, water salinity, extreme weather events, and ecological shifts, and could display 

seasonal shifts (Ebi et al. 2008). Few studies have projected the health impact of vector-borne diseases. 

Vector-borne illnesses are likely to shift or expand northward and to higher elevations with the possible 

introduction of new vector-borne diseases (CCSP 2008d), while decreasing the range of tick-borne 

encephalitis in low latitudes and elevation (Randolph and Rogers 2000 in Ebi et al. 2008). For example, 

the northern range limit of Lyme disease could shift north by as much as 200 kilometers (about 124 

miles) by 2020 and 1,000 kilometers (about 621 miles) by 2080 (Field et al. 2007a; EPA 2009b). Malaria 

in the United States is unlikely to be affected by climate change variables given public intervention and 

vector control (EPA 2009b). 

Food- and water-borne pathogens might spread with a warmer climate. Increases in temperature, 

precipitation, and extreme events could spread these pathogens, depending on their survival, persistence, 

habitat range, and transmission under changing climate and environmental conditions. While the quality 

of the U.S. water supply is well maintained by the Safe Drinking Water Act and the Clean Water Act, 

individuals can still be exposed to these pathogens through other means (e.g., swimming) (EPA 2009b). 

Climate change is anticipated to increase ozone-related diseases (Sussman et al. 2008). However, 

it is important to note that the concentration of ground-level ozone for a particular location varies as a 

function of temperature, wind, solar radiation, atmospheric moisture, atmospheric mixing, and cloud 

cover. The impact climate change has on some of these variables could have a positive effect on ozone 

concentrations, while simultaneously the impact of climate change on other variables could have a 

negative effect on ozone concentrations (EPA 2009b). Therefore, when estimating the impact climate 

change will have on ground-level ozone, it is necessary to account for all of these factors, and not just 

temperature (EPA 2009b). That said, climate change is projected to increase surface layer ozone 

concentrations in urban and polluted rural environments (EPA 2009b). 

Climate change could also have opposing effects on PM. On the one hand, increased 

precipitation and humidity in some areas could lower PM concentrations. On the other hand, increased 

forest fires could increase PM concentrations. Preliminary modeling indicates an overall small decrease 

in PM concentrations due to climate change; however, there are significant regional variations. In the 

United States, the Midwest and Northeast, for example, could experience noteworthy increases in PM 

concentrations (EPA 2009b). 

Overall, populations within certain regions of the United States regions could experience climate 

change-induced health impacts from a number of pathways simultaneously. For instance, populations in 

coastal communities could experience an extreme weather event, such as a tropical cyclone and flooding, 

adding to health burdens associated with sea-level rise or coastal erosion. 

4.5.8.2.3 Projected Global Health Impacts of Climate Change 

Globally, climate change is anticipated to contribute to both adverse and beneficial health 

impacts. Projected adverse health impacts include malnutrition leading to disease susceptibility (high 

confidence); increased heat-wave-, flood-, storm- and fire-induced mortality (high confidence); decrease 

in cold-related deaths (high confidence); increased diarrheal disease burden (medium confidence); 

increased levels of ground-level ozone (high confidence); and altered geographic distribution of some 

infectious disease vectors (high confidence) (Confalonieri et al. 2007). A decrease in cold-related 

mortality and some pollutant-related mortality, increased crop yields in certain areas, and restriction of 

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certain diseases in certain areas (if temperatures or precipitation rise above the critical threshold for vector 

or parasite survival) are examples of projected beneficial health impacts (Confalonieri et al. 2007). The 

adverse impacts, however, greatly outweigh the beneficial impacts, particularly after mid-century 

(Confalonieri et al. 2007). 

Regionally, the impact on human health will vary. Some Asian countries could experience 

increasing malnutrition by 2030, with crop yields decreasing later in the century, rendering the population 

in the region particularly vulnerable to malnutrition-associated diseases and disorders (Confalonieri et al.

2007). Certain coastal areas will experience flooding by 2030, impacting human mortality (Confalonieri 

et al. 2007). By 2080, Lyme disease is projected to have moved northward into Canada, due to a two- to 

four-fold increase in tick abundance (Confalonieri et al. 2007). By 2085, climate change is projected to 

increase the population at risk to dengue fever to a total of 3.5 billion people (Confalonieri et al. 2007). 

Heat waves have been experienced globally; thousands of deaths incurred in India over the 18 

heat waves recorded between 1980 and 1998 (De and Mukhopadhyay 1998, Mohanty and Panda 2003, 

De et al. 2004, all in Confalonieri et al. 2007). In August 2003, approximately 35,000 deaths were linked 

to a heat wave in Europe, with France alone incurring more than 14,800 deaths (Hemon and Jougla 2004, 

Martinez-Navarro et al. 2004, Michelozzi et al. 2004, Vandentorren et al. 2004, Conti et al. 2005, Grize 

et al. 2005, Johnson et al. 2005b, all in Confalonieri et al. 2007). About 60 percent of the heat-waverelated deaths in France were people at or over 75 years of age (Hemon and Jougla 2004 in Confalonieri 

et al. 2007). Overall, studies have linked high temperatures to about 0.5 to 2 percent of annual mortality 

in the elderly European population (Pattenden et al. 2003, Hajat et al. 2006, both in Confalonieri et al.

2007). 

In 2003, floods in China affected 130 million people (EM-DAT 2006 in Confalonieri et al.2007). 

In 1999, storms with floods and landslides in Venezuela killed 30,000 people (Confalonieri et al. 2007). 

The World Health Organization (WHO) estimates that a high proportion of those in dry regions 

(approximately 2 billion) experience malnutrition, infant mortality, and water-related diseases (WHO 

2005 in Confalonieri et al. 2007). Children in low-income countries are particularly vulnerable to loss of 

life due to diarrhea. The transmission of the enteric pathogen appears to increase during the rainy season 

for children in sub-Saharan Africa (Nchito et al. 1998, Kang et al. 2001, both in Confalonieri et al. 2007). 

In Peru, higher temperatures have been linked to periods of increased diarrhea incidence experienced by 

adults and children (Checkley et al. 2000, Speelmon et al. 2000, Checkley et al. 2004, Lama et al. 2004, 

all in Confalonieri et al. 2007). 

Cholera outbreaks associated with floods can occur in areas of poor sanitation. A study of seasurface temperatures in the Bay of Bengal demonstrated a bimodal seasonal pattern that translated to 

increased plankton activity and leading to increases in cholera in nearby Bangladesh (Colwell 1996, 

Bouma and Pascual 2001, both in Confalonieri et al. 2007). 

Dengue is considered the most important vector-borne viral disease (Confalonieri et al. 2007). 

There is a strong correlation between climate-based factors such as temperature, rainfall, and cloud cover 

with the observed disease distribution in Colombia, Haiti, Honduras, Indonesia, Thailand and Vietnam 

(Hopp and Foley 2003 in Confalonieri et al. 2007). About one-third of the world’s population lives in 

areas with climate conditions favorable for dengue (Hales et al. 2002, Rogers et al. 2006b, both in 

Confalonieri et al. 2007). 

Malaria is a vector-borne disease spread by mosquitoes. Depending on location, malaria 

outbreaks could be influenced by rainfall amounts and sea-surface temperatures in southern Asia, 

Botswana, and South America (Kovats et al. 2003, Thompson et al. 2005, DaSilva et al. 2004, all in 

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Confalonieri et al. 2007). A recent study of malaria in East Africa found that the measurable warming 

trend the area has experienced since the 1970s can be correlated with the potential of disease 

transmission. (Pascual et al. 2006 in Confalonieri et al. 2007). However, southern Africa was not shown 

to exhibit the same trend (Craig et al. 2004 in Confalonieri et al. 2007). External factors are also 

influencing the number of cases of the disease in Africa, such as drug-resistant malaria, and parasite and 

HIV infections. Studies did not provide clear evidence that malaria in South America or the continental 

regions of the Russian Federation have been affected by climate change (Benitez et al. 2004, Semenov et 

al. 2002, both in Confalonieri et al. 2007). In general, however, higher temperatures and more frequent 

extreme weather occurrences (such as floods and droughts) are projected to have a stronger influence on 

the wider spread of malaria with increasing climate change (McMichael et al. 1996 in Epstein et al.

2005). 

Temperature has been shown to affect food- and water-borne diseases (EPA 2009b). Several 

studies have found increases in salmonellosis cases (food poisoning) within 1 to 6 weeks of the hightemperature peaks (controlled by season). This could be due in part to the processing of food products 

and the population varying its eating habits during warmer months (Fleury et al. 2006b, Naumova et al.

2006, Kovats et al. 2004a, D’Souza et al. 2004a, all in Ebi et al. 2008). High temperatures have been 

shown to increase common types of food poisoning (D’Souza et al. 2004b, Kovats et al. 2004b, Fleury et 

al. 2006a, all in Confalonieri et al. 2007). Increasing global temperatures could contribute to a rise in 

salmonellosis cases (Ebi et al. 2008). There is further concern that projected increasing temperatures 

from climate change will also increase leptospirosis cases, a disease that is resurging in the United States. 

The effects of climate change on air quality are expected to adversely impact people suffering 

from asthma and other respiratory ailments. Increases in temperature, humidity, the prevalence and 

frequency of wildfires, and other factors are expected to result in more smog, dust, and particulates that 

exacerbate asthma. Widespread respiratory distress throughout many regions of the world is a possible 

result of climate change. Existing asthma treatment and management plans might be overwhelmed, 

leading to major increases in asthma-related morbidity and mortality (Epstein et al. 2005). 

Warm climates are more apt to support the growth of the pathogenic species of Vibrio, leading to 

shell-fish related death and morbidity that might affect the United States, Japan and Southeast Asia (Janda 

et al. 1988, Lipp et al. 2002, both in Ebi et al. 2008, 2-10; Wittmann and Flick 1995, Tuyet et al. 2002, 

both in Confalonieri et al. 2007). If temperatures increase, the geographic range and concentration of the 

Vibrio species could expand. For example, as the waters of the northern Atlantic have warmed, the 

concentration of Vibrio species has increased (Thompson et al. 2004 in Ebi et al. 2008). Future ocean 

warming might also lead to the proliferation of harmful algal blooms, releasing toxins that contaminate 

shellfish and lead to food-borne diseases (Confalonieri et al. 2007). 

In 2000, WHO estimated that climate change has caused the loss of more than 150,000 lives 

(Campbell-Lendrum et al. 2003, Ezzati et al. 2004, McMichael 2004, all in Confalonieri et al. 2007). The 

projected risks in 2030 described by WHO study vary by health outcome and region; most of the increase 

in disease is due to diarrhea and malnutrition. More cases of malaria are projected in countries situated at 

the edge of the existing distribution. The projected health impact associated with malaria is mixed, with 

some regions demonstrating increased burden and others exhibiting decreased burden. 

4.5.9 Tipping Points and Abrupt Climate Change 

This section starts by providing an overview of tipping points and abrupt climate change, then 

discusses specific climate systems that could be affected, and concludes with a summary. 

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4.5.9.1 Overview 

The phrase “tipping point” is most typically used in the context of climate change and its 

consequences to describe situations in which the climate system (the atmosphere, oceans, land, 

cryosphere,24 and biosphere) reaches a point at which there is a disproportionately large or singular 

response in a climate-affected system as a result of only a moderate additional change in the inputs to that 

system (such as an increase in the CO2 concentration). Exceeding one or more tipping points, which 

“occurs when the climate system is forced to cross some threshold, triggering a transition to a new state at 

a rate determined by the climate system itself and faster than the cause” (NRC 2002b in EPA 2009), could 

result in abrupt changes in the climate or any part of the climate system. These changes would likely 

produce impacts at a rate and intensity far greater than the slower, steady changes currently being 

observed (and in some cases, planned for) in the climate system (EPA 2009b). 

The phrase tipping point is also used outside the climate-modeling community. In addition to 

climate scientists, many others – including biologists, marine chemists, engineers, and policymakers – are 

concerned about tipping points because it is not just the climate that can change abruptly. The same type 

of non-linear responses exists in the physical, environmental, and societal systems that climate affects. 

For example, ocean acidity resulting from an elevated atmospheric concentration of CO2 might reach a 

point at which there would be a dramatic decline in coral ecosystems. 25 Consideration of possible tipping 

points could therefore encompass sharp changes in climate-affected resources and not be restricted to 

climatic parameters and processes. 

Using the broad definition of the term tipping point to include both climate change and its 

consequences, the scale of spatial responses can range from global (e.g., a “supergreenhouse” atmosphere 

with higher temperatures worldwide), to continental or subcontinental changes (such as dramatically 

altering the Asian monsoon), to regional (e.g., drying in the southwestern United States, leading to 

drought and increases in the frequency of fires), to local (such as loss of the Sierra Nevada snowpack). 

The definition of tipping point used by Lenton et al. (2008) (discussed below) specifically applies only to 

subcontinental or larger features, whereas public policy is concerned with a wider range of scales, as the 

IPCC analysis (discussed below) suggests. 

The temporal scales considered are also important. On crossing a tipping point, the evolution of 

the climate-affected system is no longer controlled by the time scale of the climate forcing (such as the 

heat absorption by GHGs), but rather is determined by its internal dynamics, which can either be much 

faster than the forcing, or substantially slower. The much faster case – abrupt climate change – might be 

said to occur when the: 

• Rate of change is sharply greater than (or a different sign than) what has prevailed over 

previous decades; 

• State of the system exceeds the range of variations experienced in the past; or 

• Rate has accelerated to a pace that exceeds the resources and ability of nations to respond to 

it. 

Climate changes could occur in many ways as tipping points are reached. These mechanisms 

range from the appearance or unusual strengthening of positive feedbacks – self-reinforcing cycles – and 

 

24 The cryosphere describes the portion of Earth’s surface that is frozen water, such as snow, permafrost, floating 

ice, and glaciers. 

25 For example, climate-related thresholds for ecosystems are discussed in CCSP SAP 4.2. 
4.5 Health, Societal, and Environmental Impacts of Climate Change Chapter 4 Cumulative Impacts 

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reversible-phase transitions in climate-affected systems to irreversible-phase transitions – where a 

threshold has been crossed that could lead to either abrupt or unexpected changes in the rate or direction 

of change in climate-affected systems. Although climate models incorporate many positive (and 

negative, or dampening) feedback mechanisms, the magnitude of these effects and the threshold at which 

the feedback-related tipping points are reached are only roughly known, especially regarding global 

impacts. In addition, models of climate and climate-affected systems do not contain all feedback 

processes. As subsequently shown in this section, substantial progress has been made in understanding 

the qualitative processes associated with tipping points, although there are limits to the quantitative 

understanding of many of these systems. 

In recent years, the concept of a tipping point (or a set of tipping points) and abrupt change (or 

abrupt changes) in Earth’s climate system has been attracting increased attention among climate scientists 

and policymakers. For example, information on Abrupt Climate Change and High Impact Events was 

recently presented in the Technical Support Document for Endangerment and Cause or Contribute 

Findings for Greenhouse Gases under Section 202(a) of the Clean Air Act (EPA 2009b). The information 

that follows provides a brief survey of tipping points and abrupt climate change, drawing on perspectives 

from key analyses of the issue and other relevant research − IPCC, CCSP, Lenton et al. (2008), and 

paleoclimate26 evidence − and uses much of the same available literature as used in EPA (2009b) and 

recent peer-reviewed research. 

In its Fourth Assessment Report, the IPCC addresses the issue of tipping points in the discussion 

of “major or abrupt climate changes” (Meehl et al. 2007) and highlights three large systems: the 

meridional overturning circulation (MOC) system that drives Atlantic Ocean circulation, the collapse of 

the West Antarctic ice sheet, and the loss of the Greenland ice sheet. The IPCC states that there is 

uncertainty in the understanding of these systems but concludes that these systems are unlikely to reach 

their tipping points within the 21st Century (Meehl et al. 2007). The IPCC also mentions additional 

systems that might have tipping points (as noted below), but does not include estimates for them. 

The IPCC WGII report provides insight on the uncertainties surrounding tipping points, their 

systemic and impact thresholds, and the value judgments required to select a critical level of warming 

(Carter et al. 2007). The presence of these thresholds can also present their own physical and ecological 

limits and informational and cognitive barriers to adaptation (Adger et al. 2007). In the case of this EIS, 

uncertainty prevents NHTSA from being able to quantify the impacts of the alternatives under 

consideration on specific tipping-point thresholds. 

In the IPCC WGII report, certain thresholds are assumed and then used with analyses of 

emissions scenarios and stabilization targets to assess how certain impacts might be avoided (Schneider et 

al. 2007). For example, several authors hypothesize that a large-scale climatic event or other impacts (for 

example, widespread coral-reef bleaching; deglaciation of West Antarctica) would be likely if 

atmospheric CO2 concentrations stabilize at levels exceeding 450 ppm, although the location of the 

tipping points and thresholds is uncertain (O’Neill and Oppenheimer 2002, Lowe et al. 2006, and CorfeeMorlot and Höhne 2003, all in Schneider et al. 2007). 

The CCSP reaches similar conclusions in its report Scientific Assessment of the Effects of Global 

Change on the United States (National Science and Technology Council 2008). The CCSP report 

summarizes scientific studies suggesting that there are several “triggers” of abrupt climate change and 

that “anthropogenic forcing could increase the risk of abrupt climate change;” however, “future abrupt 

 

26 Paleoclimatology is the study of climate change through the physical evidence left on Earth of historical global 

climate change (prior to the widespread availability of records to temperature, precipitation, and other data). See

generally http://www.giss.nasa.gov/research/paleo/. 
Chapter 4 Cumulative Impacts 4.5 Health, Societal, and Environmental Impacts of Climate Change 

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changes cannot be predicted with confidence” because of the insufficiencies of current climate models, 

which reflect the limits of current understanding.27 However, the CCSP report does reiterate the 

conclusions of the Committee on Abrupt Climate Change (NRC 2002a) that anthropogenic forcing could 

increase the risk of abrupt climate change and that (1) “greenhouse warming and other human alterations 

of the Earth system may increase the possibility of large, abrupt, and unwelcome regional or global 

climatic events;” (2) “abrupt changes of the past are not fully explained yet, and climate models typically 

underestimate the size, speed, and extent of those changes;” and (3) “future abrupt changes cannot be 

predicted with confidence, and climate surprises are to be expected” (EPA 2009b). 

The CCSP report (National Science and Technology Council 2008) considers the susceptibility of 

the same three systems to abrupt change as IPCC highlighted − the Atlantic MOC (AMOC) system that 

drives Atlantic Ocean circulation, the collapse of the West Antarctic ice sheet, and the loss of the 

Greenland ice sheet. The report also suggests that there are thresholds in non-climate systems influenced 

by CO2 emissions, such as ocean acidification, where there could be a threshold beyond which existing 

coral reef ecosystems cannot survive (National Science and Technology Council 2008). The CCSP report 

concludes that these impacts, including climate-related thresholds, could occur in groups as thresholds are 

crossed, but, due to the uncertainty, more research is needed to quantify the impacts of crossing particular 

thresholds and to determine when these thresholds would be reached (National Science and Technology 

Council 2008). 

The IPCC WGI report (Meehl et al. 2007) describes various climate and climate-affected systems 

that might undergo abrupt change, contribute to “climate surprises,” or experience irreversible impacts, as 

follows: AMOC and other ocean circulation changes, Arctic sea ice, glaciers, and ice caps, Greenland 

and West Antarctic ice sheets, vegetation cover, and atmospheric and ocean-atmosphere regimes. 

In the Fourth Assessment Report, IPCC also reiterated five “reasons for concerns” categorizing 

impacts of a similar type to provide a set of metrics reflecting severity of risk.28 These reasons for 

concern include the risks of large-scale discontinuities (also referred to as singularities or tipping 

points).29 Recently, Smith et al. (2008), the authors of the reasons for concern, describe revised 

sensitivities to increases in global mean temperature for the reasons for concern, and present a more 

thorough understanding of the concept of vulnerability based on expert judgment about findings in the 

literature assessed in the Fourth Assessment Report and additional research published since. In the case 

of the likelihood of large-scale discontinuities, including partial or complete deglaciation of the Greenland 

ice sheet or the West Antarctic ice sheet and substantial reduction or collapse of the AMOC, the authors 

acknowledge that “no single metric could adequately describe the diversity of impacts and associated risk 

for any one [reason for concern], let alone aggregate across all of them into a single “dangerous” global 

temperature threshold.” However, based on “growing evidence that even modest increases in [global 

mean temperature] could commit the climate system to the risk of very large impacts on multiple-century 

time scales,”30 the risks of large-scale discontinuities were expertly judged to begin being a source of 

substantial risk around 1 °C (around 2 °F). Smith et al. (2008) projected 2.5 °C (4.5 °F) – the midpoint of 

the warming range cited for partial deglaciation – to be the “possible trigger for commitment to largescale global impacts over multiple-century time scales.” 

 

27 See CCSP 2008d. 28 The “reasons for concern” were originally introduced and discussed in the IPCC Third Assessment Report. 29 The IPCC Third Assessment Report assessed the risks of abrupt and/or irreversible changes under the rubic of 

large-scale singularities or discontinuities, and this usage is retained in the Smith et al. (2008) paper. The other 

reasons for concern are (1) risks to unique and threatened systems, (2) risks of extreme weather events, (3) 

distribution of impacts (and vulnerabilities), and (4) net aggregate impacts. 30 The term “commit’ is used as in IPCC Fourth Assessment Report WGII and is derived from the possibility of 

crossing thresholds or irreversible change, but ones for which the actual impact could be substantially delayed. 
4.5 Health, Societal, and Environmental Impacts of Climate Change Chapter 4 Cumulative Impacts 

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Building on the IPCC and early CCSP research, at a workshop entitled “Tipping Points in the 

Earth System” experts identified several climate systems that have tipping points, and tested and refined a 

questionnaire subsequently distributed electronically to 193 international scientists. Fifty-two scientists 

(among them 16 workshop participants and 22 contributors to the IPCC Fourth Assessment Report) 

returned a completed questionnaire. Lenton et al. (2008) published the findings from this expert 

elicitation identifying nine systems facing separate tipping points due to increased CO2 and temperature 

levels that met four scientifically based criteria to be considered “policy-relevant potential future tipping 

elements in the climate system” (Lenton et al. 2008). Additional systems were identified, but insufficient 

information precluded these systems from meeting the definition of policy relevant. The systems at risk 

that the researchers identified are: Arctic sea ice, Greenland ice sheet, West Antarctic ice sheet, Atlantic 

thermohaline circulation (a component of the AMOC), El-Niño-Southern Oscillation, Indian summer 

monsoon, Sahara/Sahel and West African monsoon, Amazon rainforest, and boreal forest. 

The CCSP report SAP 3.4, Abrupt Climate Change 31 (CCSP 2008e), provides additional 

information on the topic of abrupt climate change, focusing on rapid change in glaciers, ice sheets, and 

hence sea level; widespread and sustained changes to the hydrologic cycle; abrupt change in the AMOC; 

and rapid release to the atmosphere of methane trapped in permafrost and on continental margins. 

The report updates “the state and strength of existing knowledge, both from the paleoclimate and 

historical records, and from model predictions for future change” and “reflects the significant progress in 

understanding abrupt climate change that has been made since” the report by the Committee on Abrupt 

Climate Change (NRC 2002a) and the IPCC WGI report (Meehl et al. 2007). 

4.5.9.2 Affected Climate Systems 

The list of affected climate systems covered by the key analyses and peer-reviewed research 

identified above includes: 

• Rapid changes in glaciers and ice sheets (including paleoclimate evidence on sea-level rise 

from previous ice-sheet melt); 

• Hydrologic variability and change; 

• Potential for abrupt change in the AMOC and Atlantic Thermohaline Circulation (a 

component of the AMOC); 

• Potential for abrupt changes in atmospheric methane; 

• El-Niño-Southern Oscillation; 

• Indian summer monsoon; 

• Sahara/Sahel and West African monsoon; 

• Amazon rainforest; and 

• Boreal forest. 

Each system is described below. 

Rapid Changes in Glaciers and Ice Sheets. Based on an assessment of the published scientific 

literature, Clark et al. (2008) found that “observations demonstrate that it is extremely likely that the GIS 

 

31 SAP 3.4 defines abrupt climate change as a “large-scale change in the climate system that takes place over a few 

decades or less, persists (or is anticipated to persist) for at least a few decades, and causes substantial disruptions in 

human and natural systems.” (CCSP 2008e) 
Chapter 4 Cumulative Impacts 4.5 Health, Societal, and Environmental Impacts of Climate Change 

[Greenland ice sheet] is losing mass and that this has very likely been accelerating since the mid-1990s” 

(EPA 2009b). Another recent CCSP report, SAP 1.2, Past Climate Variability and Change in the Arctic 

and High Latitudes (CCSP 2009a), finds a threshold for ice-sheet removal from sustained summertime 

warming in relation to pre-industrial temperatures of 5 °C (9 °F) (with a range of uncertainty from 2 to 7 

°C [4 to 13 °F]) comparable to the range of required sustained warming of 1.9 to 4.6 °C (3.4 to 8.3 °F) 

suggested by Meehl et al. (2007) for the complete melting of the Greenland ice sheet, albeit over many 

hundreds of years (see EPA 2009b). 

The surface of Arctic sea ice has a higher albedo (reflectivity) than the darker ocean surface. As 

sea ice melts from higher air and ocean temperatures, more of the ocean is exposed, which allows more 

radiation to be absorbed, amplifying the sea-ice melt. In summer, Arctic sea-ice loss could lead to the ice 

cap melting beyond a certain size/thickness, making it unstable and leading to an ice-free Arctic. Recent 

record ice losses and modeling studies have led some researchers to suggest that the summer Arctic will 

be ice-free within a decade or less, that there is a critical threshold for summer Arctic sea-ice loss, and 

that this threshold has already been crossed (Borenstein and Joling 2008 in Lenton et al. 2008). 

The USGS estimates that a complete disintegration of the neighboring, predominantly land-based 

Greenland ice sheet would raise sea level by 6.55 meters (21.5 feet; Williams and Hall 1993 in USGS 

2000). However, a recent paper by Pfeffer et al. (2008) studying Kinematic Constraints on Glacier 

Contributions to 21st-Century Sea-Level Rise and taking dynamic land ice loss into account, postulates 

projections in sea-level rise of between 0.8 and 2.0 meters (2.6 and 6.6 feet), compared to the 0.18 to 0.59 

meters (0.6 to 1.9 feet) projected in the IPCC Fourth Assessment Report. Pfeffer et al. (2008) conclude 

that “increases in excess of 2 meters [6.6 feet] are physically untenable” by 2100. Rahmstorf (2007) 

projects that sea-level rise in 2100 could be 0.5 to 1.4 meters (1.6 to 4.6 feet) above the 1990 level. The 

dynamic land ice-loss processes credited with accelerated ice loss include enhanced surface melt-water 

production penetrating to the glacier base lubricating motion; and buttressing ice-shelf removal, ice-front 

retreat, and glacier un-grounding that reduce resistance to glacier flow. 

The Greenland ice sheet is also susceptible to positive feedbacks. Melting at the glacial margins 

lowers the edge of the ice sheet to elevations that are warmer and where more melting will occur. The 

IPCC estimated the Greenland ice sheet threshold for negative surface mass at 1.9 to 4.6 °C (3.4 to 8.3 °F) 

above pre-industrial temperature, well within the predicted temperature range for this century. Dynamic 

ice-melting processes, regional temperatures, warming surrounding oceans, and recent observations 

indicating that both Greenland and Antarctica are now losing mass have led researchers to conclude that 

the timescale for Greenland ice sheet collapse is conceivably on a scale of hundreds rather than thousands 

of years (Lenton et al. 2008). 

The USGS (2005) estimates the collapse of the West Antarctic ice sheet would raise sea level by 

approximately 6 meters (approximately 20 feet) although the most recent reassessment by Bamber et al. 

(2009a) obtains a value of 3.3 meters (10.8 feet). The processes of surface melt and glacier un-grounding 

from melting at the base from a warmer ocean are implicated in the potential destabilization of the West 

Antarctic ice sheet (EPA 2009b). However, ice-sheet models do not include all the small-scale dynamical 

processes involving the glacier base and the ocean at the edge of the ice sheet (EPA 2009b, Meehl et al. 

2007) and dynamic ice loss was not represented in the models used by the IPCC to project sea-level rise 

(EPA 2009b). Therefore, while these models suggest that Antarctica will gain in mass due to increased 

snowfall, Clark et al. (2008) indicate that substantial ice losses from West Antarctica and the Antarctic 

Peninsula are very likely occurring, so that Antarctica is losing ice mass on balance despite ice thickening 

over some higher-elevation regions (EPA 2009b). Lemke et al. (2007a) have presented satellite and in 

situ observations of dynamic ice-sheet reactions behind disintegrating ice shelves, and found no 

significant continent-wide trends in snow accumulation over the past several decades (EPA 2009b). 

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Because the present generation of models does not capture all these processes, Clark et al. (2008) 

state that “it is unclear whether [glacier accelerations of flow and thinning are] a short-term natural 

adjustment or a response to recent climate change,” however, “accelerations are enabled by warming, so 

these adjustments will very likely become more frequent in a warmer climate.” 

Because the West Antarctic ice sheet is grounded below sea level, positive feedbacks could result 

from the loss of buttressing sea-ice shelves and the ingress of warmer ocean water. While centuries or 

millennia could pass before a collapse, the thresholds for ocean and surface atmospheric warming 

temperature are likely to be crossed this century (Lenton et al. 2008). A recent study of ice-core records 

suggests strong links between past West Antarctic climate, and potentially its ice sheet, to large-scale 

changes in global climate, particularly major El Niño events (Schneider and Steig 2008 in Lenton et al. 

2008). 

The paleoclimate record cited by IPCC, CCSP, and others gives an indication of sea-level rise 

from previous ice-sheet melt, and the corresponding temperature for these periods. For example, 

geological evidence showing the presence of elevated beaches suggests that global sea level was 4 to 6 

meters (13 to 20 feet) higher during the most recent interglacial period about 125,000 years ago (Jansen et 

al. 2007). Paleoclimatic reconstructions suggest that global average temperature then was about 1 °C (1.8 

°F) warmer than during the present interglacial period (Hansen et al. 2007). Corings from the ice sheets 

to determine their ages, supplemented by simulations of ice-sheet extent, suggest that large-scale retreat 

of the southern half of the Greenland ice sheet and other Arctic ice fields likely contributed roughly 2 to 4 

meters (6.6 to 13.1 feet) of sea-level rise during the last interglacial period, with most of any remainder 

likely coming from the Antarctic ice sheet (Jansen et al. 2007). Schneider et al. (2007) assess similar 

paleoclimatic evidence for a sea-level rise of 4 to 6 meters (13.1 to 19.7 feet) during the last interglacial 

period, with polar temperatures 3 to 5 °C (5.4 to 9.0 °F) warmer than at present (and global mean 

temperature not notably warmer than at present) (EPA 2009b). Schneider et al. (2007) go on to conclude 

with medium confidence that partial melting of the Greenland ice sheet (and possibly the West Antarctic 

ice sheet) would occur over a timescale of centuries to millennia for a global average temperature increase 

of 1 to 4 °C (1.8 to 7.2 °F) in relation to 1990 to 2000 temperatures, causing the same rise in sea level 

(EPA 2009b). 

Paleoclimatic reconstructions also indicate occurrences of abrupt changes in the terrestrial, ice, 

and oceanic climatic records. For example, ice-core records suggest that temperatures atop the Greenland 

ice sheet warmed by up to 8 to 16 °C (14.4 to 28.8 °F) within a few decades (EPA 2009b) during 

Dansgaard-Oeschger events,32 which were likely caused by the North Atlantic Ocean being covered by 

catastrophic outflows of glacial meltwater from the North American ice sheet that was present during 

glacial times (Jansen et al. 2007). A more recent study (Steffensen et al. 2008) provides more detail, 

indicating that there was a sharp warming over 1 to 3 years (that is, “abrupt climate change happens in [a] 

few years”), followed by a more gradual warming over 50 years. 

For the future, Hansen et al. (2007) and Hansen et al. (2008) suggest that climate feedback 

processes not included in most climate models (e.g., slower surface albedo and ice-sheet feedbacks) have 

the potential to cause large and rapid shifts in climate and in factors like glacial melt and sea-level rise 

that are closely dependent on the climate. 

 

32 Dansgaard-Oeschger events are very rapid climate changes – up to 7.0 °C (12.6 °F) in some 50 years – during the 

Quaternary geologic period, and especially during the most recent glacial cycle. (A Dictionary of Geography. 

Oxford University Press, 1992, 1997, 2004.) Sedimentary evidence suggests that they were driven, at least on some 

occasions, by the rapid draining of melt-water lakes when ice dams burst. 
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In a study utilizing model simulations and paleoclimatic data,33 Hansen et al. (2007) conclude 

that “...a CO2 level exceeding about 450 ppm is ‘dangerous,’” where “dangerous” is defined by the 

authors to be global warming of more than 1 oC (1.8 oF) above the level in 2000, potentially leading to 

highly disruptive effects. Although this 450-ppm estimate has limitations and uncertainties, Hansen’s 

more recent publications have suggested a target atmospheric CO2 concentration of 350 ppm (Hansen et 

al. 2008) – lower than the CO2-equivalent concentration, including the offsetting effects of aerosols, is 

today. 

The range of views linking past and future sea-level rise is clearly broad, with uncertainty 

attributable to each view. 

Hydrologic Variability and Change. Clark et al. (2008) state that “there is no clear evidence to 

date of human-induced global climate change on North American precipitation amounts,” however, 

“further analysis [since the IPPC Fourth Assessment Report] of climate models scenarios of future 

hydrological change over North America and the global subtropics indicate that subtropical aridity is 

likely to intensify and persist due to future greenhouse gas warming.” The projected drying would extend 

into the southwest United States and potentially increase the likelihood of future severe and persistent 

drought in the region, and while model results indicate that this drying might have already begun, it 

cannot be definitively distinguished from the natural variability of hydro-climate for the region (EPA 

2009b). 

A recent paper by Solomon et al. (2009) also demonstrates the potential for substantial – and 

irreversible – decreases in dry-season rainfall in a number of already-dry areas (including the southwest 

United States), and while these impacts are not expressly related to a specific tipping point or an 

associated abrupt climate change, the magnitude and irreversibility of these impacts makes them policy 

relevant. The paper shows that the climate change resulting from an increase in atmospheric CO2 levels 

from near present-day values – 385 ppm – to a peak of 450 to 600 ppm over the coming century is largely 

irreversible. Solomon et al. (2009) used a suite of AOGCM projections to characterize precipitation 

changes. More than 80 to 90 percent of the models project increased drying of respective dry seasons for 

the regions of southern Europe, northern Africa, southern Africa, southwestern United States, eastern 

South America, and western Australia; and long-term irreversible warming and mean rainfall changes. 

For example, changes in dry-season precipitation in southwestern North America would be about 10 

percent for 2 °C (3.6 °F) of global mean warming, comparable to the American “dust bowl,” with average 

rainfall decreases of around 10 percent over about 10 to 20 years. 

Potential for Abrupt Change in the Atlantic Meridional Overturning Circulation. The AMOC is 

the northward flow of warm, salty water in the upper layers of the Atlantic Ocean coupled to the 

southward flow of colder water in the deep layers, and transports oceanic heat from low to high latitudes. 

Clark et al. (2008) state, “it is very likely that the strength of the AMOC will decrease over the course of 

the 21st Century in response to increasing greenhouse gases, with a best estimate decrease of 25–30 

percent.” They go on to say that the AMOC is very unlikely to undergo an abrupt transition to a 

weakened state during the course of the 21st Century, and is unlikely to collapse during this period, 

although they do not entirely exclude the possibility (EPA 2009b). 

 

33 The authors compare the corresponding GHG concentrations and associated temperature increases to 

paleoclimatology research to demonstrate that abrupt changes have occurred in Earth’s past, resulting from a similar 

range in increased temperature as those being projected, and to argue the existence of a CO2 concentration 

equivalent level (in atmospheric GHG concentration) at which the probability of abrupt, irreversible changes in 

climate-affected systems might occur. 
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The term thermohaline circulation (THC) refers to the physical driving mechanism of ocean 

circulation, resulting from fluxes of heat and fresh water across the sea surface, subsequent interior 

mixing of heat and salt, and geothermal heat sources. The MOC, discussed in the IPCC and CCSP 

reports, is the observed response in an ocean basin to this type of ocean circulation coupled with winddriven currents. The Lenton et al. (2008) paper refers to risk to the Atlantic THC instead of the AMOC 

because they are discussing the influence of climate change on the underlying cooling or freshwater 

forcing of the Atlantic Ocean circulation, even though this in turn dramatically affects the AMOC. 

If enough fresh water enters the North Atlantic (such as from melting sea ice or the Greenland ice 

sheet), the density-driven sinking of North Atlantic waters might be reduced or even stopped, as 

apparently occurred during the last glacial cycle (Stocker and Wright 1991 in Lenton et al. 2008). This 

would likely reduce the northward flow of thermal energy in the Gulf Stream and result in less heat 

transport to the North Atlantic. At the same time, reduced formation of very cold water would likely slow 

the global ocean THC, leading to impacts on global climate and ocean currents. The IPCC review of the 

results of model simulations suggests that an abrupt transition of the Atlantic Ocean’s component of the 

global THC is very unlikely this century. However, more recent modeling that includes increased 

freshwater inputs suggests there could be initial changes this century, with larger and more intense 

reductions in the overturning circulation persisting for many centuries (Mikolajewicz et al. 2007 in 

Lenton et al. 2008). 

Potential for Abrupt Changes in Atmospheric Methane. A “catastrophic” release of CH4 to the 

atmosphere from clathrate hydrates34 in the sea bed and permafrost, and from northern high-latitude and 

tropical wetlands, has been identified as a potential cause of abrupt climate change (EPA 2009b). Clark 

et al. (2008) state that the size of the hydrate reservoir is uncertain (perhaps by up to a factor of 10), 

making judgments about risk difficult to assess (EPA 2009b). This uncertainty is borne out by a recent 

study by Tanocai et al. (2009) estimating soil organic carbon pools in the northern circumpolar 

permafrost regions. The study reports new estimates − including deeper layers and pools not previously 

accounted for − about double those reported in previous analyses for the first meter of soil.

Clark et al. (2008) conclude that despite suggestions in the literature of a possible dramatic abrupt 

release of CH4 to the atmosphere, modeling and isotopic fingerprinting of ice-core CH4 do not support 

such a release over the last 100,000 years or in the near future, and “the risk of catastrophic release of 

methane to the atmosphere in the next century appears very unlikely” (EPA 2009b). However, Clark et 

al. (2008) also state “it is very likely that climate change will accelerate the pace of persistent emissions 

from both hydrate sources and wetlands. Current models suggest wetland emissions could double in the 

next century. However, because these models do not realistically represent all of the processes thought to 

be relevant to future northern high-latitudes CH4 emissions, much larger (or smaller) increases cannot be 

discounted. Acceleration of persistent release from hydrate reservoirs is likely, but its magnitude is 

difficult to estimate” (EPA 2009b).

 

34 Clathrate hydrates are “inclusion compounds” in which a hydrogen-bonded water framework – the host lattice – 

traps “guest” molecules (typically gases) within ice cages. Naturally occurring gas hydrate on Earth is primarily 

methane hydrate and forms under high pressure–low temperature conditions in the presence of sufficient methane. 

These conditions are most often found in relatively shallow marine sediments on continental margins, but also in 

some high-latitude terrestrial sediments (permafrost). Although the amount of methane stored as hydrate in 

geological reservoirs is not well quantified, it is very likely that very large amounts are sequestered in comparison to 

the present total atmospheric methane burden (Brook et al. 2008). 
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El-Niño-Southern Oscillation (ENSO).

35 The changes that might lead to increasingly persistent 

(and frequent) El Niño (or La Niña) conditions are particularly uncertain. Increases in ocean heat content 

could have an effect on ENSO conditions, but predictive and paleoclimate modeling studies do not agree 

on the magnitude, frequency, and direction of these effects. However, ENSO has substantial and largescale effects on the global climate system (Lenton et al. 2008).36

Indian Summer Monsoon. The Indian summer monsoon is the result of land-to-ocean pressure 

gradients and advection of moisture from ocean to land. By warming the land more than the ocean, 

climate change generally strengthens the monsoon. However, reductions in the amount of solar radiation 

that is absorbed by the land surface, due to some types of land-use change, generally weaken it. An 

albedo greater than roughly 50 percent is necessary to simulate the collapse of the Indian summer 

monsoon in a simple model (Zickfield et al. 2005 in Lenton et al. 2008). IPCC projections do not project 

passing a threshold this century, although paleoclimatic reconstructions do indicate that the monsoon has 

changed substantially in the past (Lenton et al. 2008). 

West African Monsoon. Sahara/Sahel rainfall depends on the West African monsoon circulation, 

which is affected by sea-surface temperature. By warming the land more than the ocean and therefore 

causing greater upward movement of the air, GHG forcing is expected to draw more moist oceanic air 

inland and thereby increase rainfall in the region, which as simulated by some models. Other models, 

however, project a less productive monsoon. The reasons for this inconsistency are not clear (Lenton et 

al. 2008).

Amazon Rainforest. The recycling of precipitation in the Amazon rainforest implies that 

deforestation, reductions in precipitation, a longer dry season, and increased summer temperature could 

contribute to forest dieback. These conditions are thought to be linked to a more persistent El Niño and 

an increase of global average temperature by 3 to 4 °C (5.4 to 7.2 °F). Important additional stressors also 

present include forest fires and human activity (such as land clearing). A critical threshold might exist in 

canopy cover, which could be reached through changes in land use or regional precipitation, ENSO 

variability, and global forcing (Lenton et al. 2008). 

Boreal Forest. The dieback of boreal forest could result from a combination of increased heat 

stress and water stress, leading to decreased reproduction rates, increased disease vulnerability, and 

subsequent fire. Although highly uncertain, studies suggest a global warming of 3 °C (5.4 °F) could be 

the threshold for loss of the boreal forest (Lenton et al. 2008).

4.5.9.3 Summary 

The IPCC, CCSP, and Lenton et al. (2008) conclude that the loss of the Greenland ice sheet, the 

collapse of the West Antarctic ice sheet, and the disruption of the Atlantic THC systems are not expected 

to cross their estimated tipping elements in this century (though actions this century could create enough 

momentum in the climate system to cross the threshold in future centuries37). Lenton et al. (2008) 

determined that several other systems (loss of Arctic sea ice, Indian summer monsoon disruption, 

 

35 ENSO describes the full range of the Southern Oscillation (see-saw of atmospheric mass or pressure between the 

Pacific and Indo-Australian regions) that includes both sea-surface temperature increases and decreases compared to 

the long-term average. El Niño is the oceanic component – used on its own to describe the warming of sea-surface 

temperatures in the central and eastern equatorial pacific – and the Southern Oscillation is the atmospheric 

component. 

36 ENSO influences patterns of tropical sea surface temperature, and has been implicated in historical episodes of 

extreme drought, including the “mega-droughts” (900 to 1600 A.D.). 

37 See Lenton et al. (2008). 
4.5 Health, Societal, and Environmental Impacts of Climate Change Chapter 4 Cumulative Impacts 

Sahara/Sahel and West African monsoon changes, drying of the Amazon rainforest, and warming of the 

boreal forest) could reach a tipping threshold within the century, however. 

A factor that might accelerate climate change at rates faster than those currently observed is the 

possible shift of soil and vegetation-carbon feedbacks, causing the soil and vegetation to become carbon 

sources rather than carbon sinks. At present, soil and vegetation act as sinks, absorbing carbon from the 

atmosphere as plant material and storing carbon in the soil when the plants die. However, by mid-century 

(about the time the IPCC projects the global average temperature reaches 2.0 oC [3.6 oF] above preindustrial levels), increasing temperatures and precipitation could cause increased rates of transpiration, 

resulting in soil and vegetation becoming a potential source of carbon emissions (Cox et al. 2000 in 

Meehl et al. 2007). Warming could also thaw frozen Arctic soils (permafrost), causing the wet soils to 

emit more CH4, a GHG. This suggestion is supported by the findings of the most recent CCSP reports, 

with Clark et al. (2008) suggesting that it is very likely that climate change will accelerate the pace of 

persistent emissions from hydrate sources and wetlands (EPA 2009b). In fact, there is evidence that 

permafrost is already melting (Walter et al. 2007). 

Across all of the climate systems for which tipping points have been hypothesized or observed 

from the paleoclimatological record, uncertainties exist, especially for timing estimates, and the 

uncertainties are at least partly responsible for the broad spectrum of views regarding tipping points. 

Exactly where these tipping points exist, and the levels at which they occur, are still a matter in need of 

further scientific investigation before precise quantitative conclusions can be made. 

Where information in this EIS analysis is incomplete or unavailable, as here due to current 

climate modeling limitations, NHTSA has relied on the CEQ regulations regarding incomplete or 

unavailable information (see 40 CFR § 1502.22(b)). CEQ regulations state, in part, that when an agency 

is evaluating “reasonably foreseeable significant adverse impacts on the human environment and 

...information relevant to...[the] impacts cannot be obtained because the overall costs of obtaining it are 

exorbitant or the means to obtain it are not known, the agency shall include within the [EIS]: 

(1) a statement that such information is incomplete or unavailable; 

(2) a statement of the relevance of the incomplete or unavailable information to evaluating 

reasonably foreseeable significant adverse impacts on the human environment; 

(3) a summary of existing credible scientific evidence which is relevant to evaluating the 

reasonably foreseeable significant adverse impacts on the human environment; and 

(4) the agency’s evaluation of such impacts based upon theoretical approaches or research 

methods generally accepted in the scientific community. For the purposes of this section, 

“reasonably foreseeable” includes impacts which have catastrophic consequences, even if 

their probability of occurrence is low, provided that the analysis of the impacts is supported 

by credible scientific evidence, is not based on pure conjecture, and is within the rule of 

reason.” 

40 CFR § 1502.22 (b). 

This EIS addresses the requirements of 40 CFR § 1502.22 appropriately. The above survey of the 

current state of climate science tipping points provides a “summary of existing credible scientific 

evidence which is relevant to evaluating the...adverse impacts of the CAFE standards.” In Colorado 

Environmental Coalition v. Dombeck, the Tenth Circuit found that the ultimate goal of the agency is to 

ensure that the EIS’s “form, content, and preparation foster both informed decision making and informed 

public participation” (185 F.3d 1162, 1172 [10th Cir. 1999] [quoting Oregon Envtl. Council v. Kunzman, 

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Chapter 4 Cumulative Impacts 4.5 Health, Societal, and Environmental Impacts of Climate Change 

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817 F.2d 484, 492 (9th Cir. 1987)]). The Tenth Circuit held that 40 CFR § 1502.22 could not be read as 

imposing a “data gathering requirement under circumstances where no such data exists.” Id.

In this case, this EIS acknowledges that information on tipping points or abrupt climate change is 

incomplete, and the state of the science does not allow for a characterization of how the CAFE 

alternatives influence these risks, beyond emission levels serving as a reasonable proxy for the risks and 

impacts of climate change, including tipping point risks. This action alone, even as analyzed for the most 

stringent alternative, is very unlikely to produce sufficient CO2 emissions reductions to avert emission 

levels corresponding to abrupt and severe climate change. Under EPCA, as amended by EISA, NHTSA 

has the authority to set fuel economy standards for U.S. passenger cars and light trucks, which account for 

roughly 3.3 percent of global annual CO2 emissions. Even if NHTSA could set standards that reduced 

emissions from this sector to zero, tipping-point thresholds (whether they occur at 550 ppm or any other 

level of that general order of magnitude) would not likely be avoided without other significant global 

actions. 

To the degree that the action in this rulemaking reduces the rate of CO2 emissions, the rule 

contributes to the general reduction or delay of reaching these tipping-point thresholds. Moreover, while 

NHTSA’s action alone does not produce sufficient CO2 emissions reductions, it is one of several other 

federal programs, which, in conjunction with NHTSA CAFE standards, could make substantial 

contributions in averting levels of abrupt and severe climate change. These conclusions are not meant to 

be read as expressing NHTSA views that tipping points in climate-related systems are not areas of 

concern for policymakers. Under NEPA, the agency is obligated to discuss “the environmental impact[s] 

of the proposed action.” 42 U.S.C. § 4332(2)(C)(i) (emphasis added). The discussion above fulfills 

NHTSA’s NEPA obligations regarding this issue. 
4.6 Environmental Justice Chapter 4 Cumulative Impacts 

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4.6 ENVIRONMENTAL JUSTICE 

4.6.1 Affected Environment 

Executive Order (EO) 12898, Federal Actions to Address Environmental Justice in Minority 

Populations and Low Income Populations, directs federal agencies to “promote nondiscrimination in 

federal programs substantially affecting human health and the environment, and provide minority and low 

income communities access to public information on, and an opportunity for public participation in, 

matters relating to human health or the environment.” EO 12898 also directs agencies to identify and 

consider disproportionately high and adverse human health or environmental effects of their actions on 

minority and low-income communities, and provide opportunities for community input in the NEPA 

process, including input on potential effects and mitigation measures. CEQ, the entity responsible for 

compliance with EO 12898, has provided agencies with general guidance on how to meet the 

requirements of the EO as it relates to NEPA in Environmental Justice Guidance Under the National 

Environmental Policy Act (CEQ 1997). This guidance document also defines the terms “minority” and 

“low-income community” in the context of environmental justice analysis. Members of a minority are 

defined as: American Indians or Alaskan Natives, Asian or Pacific Islanders, Blacks, and Hispanics. 

Low-income communities are defined as those below the poverty thresholds from the U.S. Census 

Bureau. The term “environmental justice populations” refers to the group comprised of minorities and 

low-income communities as defined. 

In compliance with EO 12898, NHTSA provides in this EIS a qualitative analysis of the 

cumulative effects of the proposed action in regard to air pollutant discharges and climate change on these 

populations.38 

As described in Section 3.5.10, research studies have shown that minority and low-income 

populations often disproportionately reside near high-risk polluting facilities, such as oil refineries, and 

“mobile” sources of air toxins and pollutants, as in the case of populations residing near highways. 

Environmental justice populations also tend to be concentrated in areas with a higher risk of climaterelated impacts. CCSP notes that this geographic placement might put these communities at higher risk, 

“from climate variability and climate-related extreme events such as heat waves, hurricanes, and tropical 

and riverine flooding” (CCSP 2008). 

4.6.2 Environmental Consequences 

4.6.2.1 Air Quality 

NHTSA predicts that upstream emissions from oil refining would decrease, which could cause a 

local improvement in air quality for residents near oil refineries. This improvement could represent a 

small positive impact on environmental justice populations living or working near these facilities. 

Emissions of all but one of the criteria air pollutants analyzed and all but one of the MSATs 

analyzed would decrease overall with adoption of any of the action alternatives and the foreseeable fuel 

economy improvements (see Section 4.3). However, increases in VMT due to the rebound effect are still 

projected to cause increases in emissions of some criteria and toxic air pollutants in some air quality 

 

38 See 42 U.S.C. § 4332 (requiring federal agencies to “identify and develop methods and procedures...which will 

insure that presently unquantified environmental amenities and values may be given appropriate consideration”); 40 

CFR § 1502.23 (requiring an EIS to discuss the relationship between a cost-benefit analysis and any analyses of 

unquantified environmental impacts, values, and amenities); CEQ (1984) (recognizing that agencies are sometimes 

“limited to qualitative evaluations of effects because cause-and-effect relationships are poorly understood” or cannot 

be quantified). 
Chapter 4 Cumulative Impacts 4.6 Environmental Justice 

nonattainment areas. These emissions would be distributed throughout the roadway network. The large 

size of each nonattainment area and the minor emissions increases in affected nonattainment and other 

areas make it unlikely that there would be disproportionate effects to environmental justice populations. 

4.6.2.2 Effects of Climate Change in the United States 

Environmental justice populations in the United States, as defined by EO 12898, would 

experience the same general impacts as a result of global climate change felt by the U.S. population as a 

whole and described in Sections 4.5.6, Food, Fiber, and Forest Products; 4.5.7, Industries, Settlements, 

and Society; and 4.5.8, Human Health. However, the CCSP notes that the general climate change impacts 

to the U.S. population might be differentially experienced by environmental justice populations, 

explaining that “[e]conomic disadvantage, lower human capital, limited access to social and political 

resources, and residential choices are social and economic reasons that contribute to observed differences 

in disaster vulnerability by race/ethnicity and economic status” (CCSP 2008). These impacts are similar 

to those that would be experienced globally, although the severity of impacts experienced by developing 

countries would likely be disproportionately larger than those experienced in developed nations, such as 

the United States. 

Within the United States, some environmental justice populations are likely to be affected. Citing 

GCRP (2009), EPA (2009) adds, “climate-related changes will add further stress to an existing host of 

social problems that cities experience, including neighborhood degradation, traffic congestion, crime, 

unemployment, poverty, and inequities in health and well-being. Climate change impacts on cities are 

further compounded by aging infrastructure, buildings, and populations, as well as air pollution and 

population growth”. 

The remainder of this section discusses, qualitatively, the most substantial areas of potential 

disproportionate impacts for these populations in the United States. 

4.6.2.2.1 Human Health 

Low-income and minority communities exposed to the direct effects of extremes in climatic 

conditions might also experience synergistic effects with preexisting health risk factors, such as limited 

availability of preventative medical care and inadequate nutrition (CCSP 2008). 

As described in Section 4.5.7, increases in heat-related morbidity and mortality as a result of 

higher overall and extreme temperatures is likely to disproportionately affect minority and low-income 

populations, partially as a result of limited access to air conditioning and a result of high energy costs 

(CCSP 2008, EPA 2009, O’Neill et al. 2005). Urban areas, which often have relatively large 

environmental justice populations, would likely experience the most substantial temperature increase due 

to the urban “heat island” effect and could be particularly vulnerable to this type of health impact (CCSP 

2008, Knowlton et al. 2007). 

The IPCC notes that many human diseases are sensitive to weather. Increasing temperatures 

could lead to expanded ranges for a number of diseases (CCSP 2008). As described in Section 4.5.8, the 

number and severity of outbreaks for vector-borne illnesses, such as the West Nile Virus, could become 

more frequent and severe. Because the vectors of these diseases (such as mosquitoes) are more likely to 

come into contact with environmental justice populations, there could be disproportionate impacts. For 

example, an outbreak of the mosquito-borne dengue fever in Texas primarily affected low-income 

Mexican immigrants living in lower-quality housing without air conditioning, leading a team researching 

the outbreak to conclude that the low prevalence of dengue in the United States is primarily due to 

economic, rather than climatic, factors (Reiter et al. 2003). 

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4.6 Environmental Justice Chapter 4 Cumulative Impacts 

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4.6.2.2.2 Land Use 

In the United States, two primary types of geographical environmental justice communities are 

likely to be affected by global climate change: urban areas, because of their relatively high 

concentrations of low-income and minority residents, and indigenous communities. Environmental 

justice communities in urban areas, because of previously mentioned heat exposure and health issues, are 

likely to experience climate change impacts more acutely. Additionally, environmental justice 

populations in coastal urban areas (vulnerable to increases in flooding as a result of projected sea-level 

rise, larger storm surges, and human settlement in floodplains) are less likely to have the means to quickly 

evacuate in the event of a natural disaster (CCSP 2008, GCRP 2009). CCSP, as an example, notes that 

flooding in Louisiana following the 2005 Hurricane Katrina primarily killed poor and elderly residents 

having no means to flee (GCRP 2009). In Alaska, more than 100 Native American villages on the coast 

and in low-lying areas along rivers are subject to increased flooding and erosion due to climate change 

(GCRP 2009). These indigenous communities could face major impacts on their subsistence economies 

from climate change. These impacts would result from their partial reliance on arctic animals, such as 

seals and caribou, for food and the potential destruction of transportation infrastructure due to ground 

thaw. 

As of 2003, about half of the U.S. population lived in the country’s 673 coastal counties (EPA 

2009). In coastal and floodplain areas prone to flooding because of larger storm surges and generally 

more extreme weather, increases in flood insurance premiums could disproportionately affect 

environmental justice populations unable to absorb the additional cost. Lack of sufficient insurance 

coverage might render these populations more financially vulnerable to severe weather events. 

Potential food insecurity as a result of global climate change, particularly among low-income 

populations in the United States and abroad, is an often mentioned concern (Wilbanks et al. 2007, CCSP 

2008). Climate change is likely to affect agriculture by changing the growing season, limiting rainfall, 

and water availability, or increasing the prevalence of agricultural pests (see Section 4.5.6 for more 

information). In the United States, the most vulnerable segment of the population to food insecurity is 

likely to be low-income children (Cook and Frank 2008 in CCSP 2008). 
Chapter 4 Cumulative Impacts 4.7 Non-Climate Cumulative Impacts of CO2

4.7 NON-CLIMATE CUMULATIVE IMPACTS OF CARBON DIOXIDE 

4.7.1 Affected Environment 

In addition to its role as a GHG in the atmosphere, CO2 is exchanged from the atmosphere to 

water, plants, and soil. CO2 dissolves easily in water and more easily in salt water, such as oceans. In 

water, CO2 combines with water molecules to form carbonic acid. The amount of CO2 dissolved in the 

upper ocean is related to its concentration in the air. As the atmospheric concentration continues to 

increase, this process takes up about 30% of each year’s emissions (Canadell et al. 2007). This reduces 

the increase in the atmospheric concentration of CO2, but also increases the acidity of the ocean. Although 

ocean uptake is slowly decreasing, the increasing CO2 concentration will have a global effect on the 

oceans. It is estimated that by 2100, ocean pH could drop 0.3 to 0.5 units in relation to pre-industrial 

levels (Caldeira and Wickett 2005). 

Terrestrial plants remove CO2 from the atmosphere through photosynthesis and use the carbon for 

plant growth. This uptake by plants can influence annual fluctuations of CO2 on the order of 3 percent 

from growing season to non-growing season (Schneider and Londer 1984 in Perry 1994). Increased 

levels of CO2 essentially act as a fertilizer, influencing normal annual terrestrial plant growth. Over recent 

decades, terrestrial uptake has amounted to about 30% of each year’s emissions (Canadell et al. 2007). 

In addition, CO2 concentrations affect soil microorganisms. Only recently have the relationships 

between above-ground and below-ground components of ecosystems been considered significant; there is 

increasing awareness that feedbacks between the above-ground and below-ground components play a 

fundamental role in controlling ecosystem processes. For example, plants provide most of the organic 

carbon required for below-ground decomposition. Plants also provide the resources for root-associated 

microorganisms (Wardle et al. 2004). The “decomposer subsystem in turn breaks down dead plant 

material and indirectly regulates plant growth and community composition by determining the supply of 

available root nutrients” (Wardle et al. 2004). 

Specific plant species, depending on the quantity and quality of resources provided to belowground components, might have greater impacts on soil biota and the processes regulated by those biota 

than do other plants. Variation in the quality of forest litter produced by co-existing species of trees, for 

example, “explains the patchy distribution of soil organisms and process rates that result from ‘single 

tree’ effects” (Wardle et al. 2004). The composition of plant communities has a consistent and substantial 

impact on the composition of root-associated microbes; however, the effects of plant community 

composition on decomposer systems are apparently context-dependent. In one study, manipulating the 

composition of plant communities in five sites in Europe produced distinctive effects on decomposer 

microbes, while root-related soil microbes experienced no clear effect (Wardle et al. 2004). 

The amount of carbon stored in soils of temperate and boreal forests is about four times greater 

than the carbon that is stored by vegetation and is “33 percent higher than total carbon storage in tropical 

forests” (Heath et al. 2005). Terrestrial communities contain as much carbon as the atmosphere. Forest 

soils are also the longest lived carbon pools in terrestrial ecosystems (King et al. 2004). Several 

experiments involving increases of atmospheric CO2 resulted in increased carbon mass in trees, but a 

reduction of carbon sequestration in soils. This is associated with increasing soil microorganism 

respiration (Heath et al. 2005); respiration is associated with “root herbivory, predation, consumption of 

root exudates, and the decomposition of root and leaf litter” (King et al. 2004). 

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4.7 Non-Climate Cumulative Impacts of CO2 Chapter 4 Cumulative Impacts 

 4-170 

NHTSA provides in this EIS a qualitative analysis of the cumulative effects of the proposed 

action regarding to non-climate cumulative impacts of CO2.

39

4.7.2 Environmental Consequences 

4.7.2.1 Ocean Acidification 

Ocean acidification occurs when CO2 dissolves in seawater, initiating a series of well-known 

chemical reactions that increases the concentration of hydrogen ions and makes seawater less basic (and 

therefore more acidic), measured as a decline in pH (Bindoff et al. 2007, Denham et al. 2007). An 

important consequence of this change in ocean chemistry is that the excess hydrogen ions bind with 

carbonate ions, making the carbonate ions unavailable to marine organisms for forming the calcium 

carbonate minerals (mostly aragonite or calcite) that make up their shells, skeletons, and other hard parts. 

Once formed, aragonite and calcite will dissolve back into the surrounding seawater, unless the water 

contains a sufficiently high concentration of carbonate ions (recent reviews by Doney 2009, Doney et al. 

2009, EPA 2009, Fabry et al. 2008, Fischlin et al. 2007, Guinotte and Fabry 2008, Royal Society 2005). 

For many millennia before present, there was little change in ocean pH. Even during the warm 

Cretaceous period, about a 100 million years ago, when atmospheric CO2 concentrations were between 

three and ten times higher than at present, it is considered unlikely that there was any significant decrease 

in ocean pH. This is because the rate at which atmospheric CO2 changed in the past was much slower 

than at present, and during slow natural changes, the carbon system in the oceans has time to reach a 

steady state with sediments. If the ocean starts to become more acidic, some carbonate will be dissolved 

from sediments, buffering the chemistry of the seawater so that pH changes are lessened (Royal Society 

2005). 

However, as anthropogenic emissions have increased there has been an accumulation of CO2 in 

the atmosphere and a net flux of CO2 from the atmosphere to the oceans. As a result, the pH and 

carbonate ion concentrations of the world’s oceans have declined and are now lower than at any time in 

the past 420,000 years (Hoegh-Guldberg et al. 2007). It is estimated that the pH of today’s oceans has 

declined in relation to the pre-industrial period by 0.1 pH units (on a log scale), representing a 30-percent 

increase in ocean acidity (Caldeira and Wickett 2003; EPA 2009). Regionally, high latitude ocean water 

has experienced greater reduction in pH due to low buffer capacity, compared to low latitude ocean water 

(EPA 2009). Scientists predict that as early as 2050, ocean pH could be lower than at any time during the 

past 20 million years (Feely et al., 2004). This rate of change is at least a hundred times greater than during 

the past hundreds of millennia (Royal Society 2005). By 2100, depending on the emissions scenario 

modeled, the average ocean pH could decline by 0.3 to 0.5 pH units in relation to pre-industrial levels 

(Fischlin et al. 2007; EPA 2009). Atmospheric CO2 would need to be stabilized under 500 parts per 

million (ppm) for the decline in locally measured ocean pH to remain below the 0.2 pH unit limit 

established by EPA in 1976 for the protection of marine life (Caldeira et al. 2007). 

At present, ocean surface waters are super-saturated with respect to the two prevalent calcium 

carbonate forms – aragonite and calcite (Bindoff et al. 2007) – but the saturation horizon (the depth above 

which supersaturation occurs and within which, for example, all near surface reef systems were located in 

pre-industrial times) is becoming shallower (Feely et al. 2004). As the oceans absorb increasing amounts 

 

39 See U.S.C § 4332 (requiring federal agencies to “identify and develop methods and procedures...which will 

insure that presently unquantified environmental amenities and values may be given appropriate consideration”); 40 

CFR § 1502.23 (requiring an EIS to discuss the relationship between a cost-benefit analysis and any analyses of 

unquantified environmental impacts, values, and amenities); CEQ (1984) (recognizing that agencies are sometimes 

“limited to qualitative evaluations of effects because cause-and-effect relationships are poorly understood” or cannot 

be quantified). 
Chapter 4 Cumulative Impacts 4.7 Non-Climate Cumulative Impacts of CO2

of CO2, the greatest pH decline in relation to the global average will occur in polar and subpolar regions. 

CO2 dissolves more readily in cold water, which is naturally low in carbonate ion concentration and more 

acidic than surface waters (Meehl et al. 2007). Under the IPCC IS92a “business as usual” scenario 

(Pepper et al. 1992), the multi-model projection of 788 ppm of atmospheric CO2 by 2100 indicates that as 

early as 2050, Southern Ocean surface waters would begin to become undersaturated with respect to 

aragonite; by 2100 all of the Southern Ocean south of 60 degrees south and portions of the Subarctic 

North Pacific could become undersaturated (Orr et al. 2005; EPA 2009). Simulation of the IPCC IS92a 

scenario predicted wintertime aragonite undersaturation in the Southern Ocean between 2030 and 2038 

(McNeil and Matear 2008). Simulation of the SRES A2 scenario (IPCC 2000) predicts aragonite 

undersaturation in Arctic surface waters once the CO2 concentration increases above 450 ppm (Steinacher 

et al. 2009). Under this scenario, the ocean volume that is saturated with respect to aragonite, and 

therefore contains much of the ocean’s biodiversity, could decrease from about 42 percent today to 25 

percent by 2100, resulting in a significant loss of marine life (Steinacher et al. 2009). 

Recent observations indicate that ocean acidification is increasing in some areas faster than 

expected. Hydrographic surveys have found that this occurs when, for example, wind-induced upwelling 

of seawater that is undersaturated with respect to aragonite spreads out over the continental shelf; 

evidence of this is reported from western North America during unusual weather conditions, decades 

earlier than model predictions for average weather conditions (Feely et al. 2008). Measurements of ocean 

pH off the coast of Washington State over a period of 8 years, for example, found that acidity in the 

region has increased more than 10 times faster than other areas (Wootton et al. 2008). 

4.7.2.1.1 Effects of Ocean Acidification on Marine Calcifiers 

Laboratory and observational studies make clear that, with few exceptions, the reduction in 

calcium carbonate resulting from ocean acidification reduces the calcification rates of marine organisms, 

a finding that holds over a wide range of taxa (reviewed by Doney 2009, Doney et al. 2009, EPA 2009, 

Fabry et al. 2008, Guinotte and Fabry 2008, Fischlin et al. 2007, Royal Society 2005). Table 1 in Fabry 

et al. (2008) and Table 2 in Guinotte and Fabry (2008) provide citations for the available literature. Here 

we provide representative results, ranging from the individual to ecosystem level, for a variety of marine 

taxa. 

Warmwater Corals. Studies indicate that a doubling of the CO2 concentration from pre-industrial 

levels to 560 ppm will result in a 20- to 60-percent decrease in the calcification rates of tropical reefbuilding corals, with the percent decrease depending on the species (Kleypas et al. 1999, Guinotte and 

Fabry 2008, Hoegh-Guldberg 2007). Langdon et al. (2000) and Leclerq et al. (2000) showed that 

saturation state was the primary factor determining calcification rates of coral reef ecosystems grown in a 

large mesocosm (i.e., an outdoor cage). Fine and Tchernov (2007) showed that two species of coral 

experienced complete dissolution of their shells in highly acidified water but were able to regrow their 

shells when returned to water of normal pH. Under the SRES A2 scenario, ocean waters with an 

aragonite saturation level considered suitable for coral growth are projected to disappear in the second 

half of this century; water considered optimal for coral growth, which covered about 16 percent of the 

ocean surface in pre-industrial times, could be gone within the next few years (Guinotte et al. 2006). 

As a result of the combined effects of increased CO2 and “bleaching” events resulting from 

elevated sea surface temperatures, tropical and subtropical corals could become rare by 2050 (HoeghGuldberg 2007). Bleaching occurs when corals eject their symbiotic algae when the temperature of 

surface waters increase above a threshold near 30 °C. Increases in sea surface temperatures have 

contributed to major bleaching events of subtropical and tropical coral reefs (EPA 2009). These 

bleaching events increase the risk of disease among surviving coral (EPA 2009). For example, in Virgin 

Islands National Park, fifty percent of the corals have died from bleaching or subsequent disease 

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4.7 Non-Climate Cumulative Impacts of CO2 Chapter 4 Cumulative Impacts 

outbreaks (EPA 2009). The IPCC concluded that it is “very likely” that a projected future increase in sea 

surface temperature of 1 to 3 degrees °C will result in more frequent bleaching events and widespread 

coral mortality, unless there is long-term thermal adaptation by corals and their algal symbionts (Nicholls 

et al. 2007; EPA 2009). A group of 39 coral experts from around the world estimated that one-third of 

reef-building corals face elevated risk of extinction. A group of 39 coral experts from around the world 

estimated that one-third of reef-building corals face elevated extinction risk from climate change and local 

anthropogenic stressors (Carpenter et al. 2008). The vulnerability of these corals to thermal stress will 

also be dependent on the existence of additional adverse factors stressing the corals such as overfishing, 

pollution, invasive species, and available nutrients (EPA 2009). 

Coldwater Corals. As the saturation horizon becomes shallower, saturated waters are becoming 

limited to the warm surface layers of the world’s oceans. As a result, under the IPCC “business as usual” 

scenario, it is projected that by 2100, only 30 percent of coldwater corals will remain in saturated waters

(Guinotte et al. 2006). 

Marine Algae. Crustose coralline algae are critical for coral reefs because they cement together 

carbonate fragments. Under high CO2 conditions in an outdoor mesocosm experiment, the recruitment 

rate and percentage cover of crustose coralline algae decreased by 78 percent and 92 percent, 

respectively, whereas that of non-calcifying algae increased by only 52 percent (Kuffner et al. 2008). 

While some marine phytoplankton grow well over a wide range of pH, others have growth rates that vary 

greatly over a narrow 0.5 to 1.0 pH unit change (Hinga 2002). Eutrophication and ocean acidification 

might interact to increase the frequency of blooms of those species that tolerate extreme pH (Hinga 2002). 

Coccolithophores, planktonic microalgae that are the main calcifiers in the ocean, show a mix of 

responses. In one study, coccolithophores show reduced calcification when grown at 750 ppm CO2

(Riebesell et al. 2000), while in another study they showed no change (Langer et al., 2006). 

Molluscs. Gazeau et al. (2007) found that calcification in a mussel species and Pacific oyster 

declined by 25 percent and 10 percent, respectively, when grown in seawater at 740 ppm CO2, which is 

the concentration expected by 2100 under the IPCC IS92a scenario. Pteropods, small marine snails, show 

shell dissolution in seawater undersaturated with respect to aragonite (Feely et al. 2004, Orr et al. 2005). 

When live pteropods were collected in the Subarctic Pacific and exposed to a level of aragonite 

undersaturation similar to that projected for the Southern Ocean by 2100 under the IPCC IS92a emissions 

scenario, shell dissolution occurred within 48 hours (Orr et al. 2005). Declines in pteropods are a 

particular concern in high-latitude oceans, where they are a critical food source for marine animals 

ranging from krill (small shrimp-like organisms) to whales, and including highly valued fish such as 

salmon. Therefore, their loss could have significant effects on high-latitude food webs (Guinotte and 

Fabry 2008).

Echinoderms. Sea urchins show reduced early development (Kurihara and Shirayama 2004) and 

shell growth (Shirayama and Thornton 2005) in seawater with elevated CO2 concentrations. 

Field observations are limited but consistent with the results of laboratory and mesocosm studies, 

as follows: 

• Shifts in community composition were observed in a mussel-dominated rocky intertidal 

community experiencing rapid declines in pH. Years of low pH were accompanied by 

declines in calcerous species (e.g., mussels, stalked barnacles) and increases in non-calcerous 

species (e.g., acorn barnacles, algae) (Wootton et al. 2008). 

• Near-subsurface areas with natural, volcanic venting of CO2, stony corals are absent and the 

abundance of calcifying sea urchins, coralline algae, and gastropods is greatly reduced (HallSpencer et al. 2008). 

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Chapter 4 Cumulative Impacts 4.7 Non-Climate Cumulative Impacts of CO2

• Moy et al. (2009) provided direct evidence that ocean acidification is affecting shell 

formation, finding that the shells of foraminifera in the Southern Ocean are lighter than shells 

of the same species in core samples from ocean sediments that predate the industrial 

revolution. Modern shells were found to be 30 to 35 percent lighter than older shells of the 

same size. 

• De’ath et al. (2009) examined growth patterns of 328 massive coral colonies from the Great 

Barrier Reef of Australia and found that their rates of calcification have declined by almost 

15 percent since 1990, to values lower than any seen for the past 400 years. The investigators 

believe that the main causes of this continuing decline are increasing sea surface temperatures 

and ocean acidification. 

4.7.2.1.2 Changes in the Effectiveness of the Ocean Sink 

In addition to its role in calcium carbonate formation, carbonate ion concentration also controls 

the uptake of CO2. As CO2 increases in surface waters and carbonate concentration declines, the 

effectiveness of the ocean as a “sink” for CO2 will decrease (Bindoff et al. 2007, Denham et al. 2007, 

Sabine et al. 2004). In addition, ocean warming decreases the solubility of CO2 in seawater (Binhoff et 

al. 2007, Denham et al. 2007). Observations and modeling studies indicate that the sinks in the North 

Atlantic (Lefèvre et al. 2004, Schuster and Watson 2009) and Southern Ocean (LeQuéré et al. 2007, 

Lovenduski et al. 2008) have declined in recent decades, consistent with expectations. From 2000 to 

2006, it is estimated that the oceans absorbed about 25 percent of anthropogenic CO2 emissions, 

representing a decline in the ocean sink from earlier decades (Canadell et al. 2007). 

4.7.2.1.3 IPCC Conclusions about Ocean Acidification 

The IPCC conclusions about ocean acidification are as follows (EPA 2009, Denman et al. 2007): 

• The biological production of corals, and calcifying phytoplankton and zooplankton within the 

water column, could be inhibited or slowed down as a result of ocean acidification. 

• Cold-water corals are likely to show large reductions in geographic range this century. 

• The dissolution of calcium carbonate at the ocean floor will be enhanced, making it difficult 

for benthic calcifiers to develop protective structures. 

• Acidification can influence the marine food web at higher trophic levels. 

4.7.2.2 Plant Growth and Soil Microorganisms 

In contrast to its potential adverse effect on the productivity of marine ecosystems, higher CO2

concentrations in the atmosphere could increase the productivity of terrestrial systems. CO2 can have a 

stimulatory or fertilization effect on plant growth (EPA 2009). Plants use CO2 as an input to 

photosynthesis. The IPCC Fourth Assessment Report states that “[o]n physiological grounds, almost all 

models predict stimulation of carbon assimilation and sequestration in response to rising CO2, referred to 

as ‘CO2 fertilization’” (Denman et al. 2007). IPCC projects with medium confidence that forest growth in 

North America will likely increase 10 to 20 percent, due to both CO2 fertilization and longer growing 

seasons, over this century (EPA 2009, Field et al. 2007). 

Under bench-scale and field-scale experimental conditions, several investigators have found that 

higher CO2 concentrations have a fertilizing effect on plant growth (e.g., Long et al. 2006, Schimel et al.

2000). Through free air CO2 Enrichment experiments, at an ambient atmospheric concentration of 550 

ppm CO2, unstressed C3 crops (e.g., wheat, soybeans, and rice) yielded 10 to 25 percent more than under 

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4.7 Non-Climate Cumulative Impacts of CO2 Chapter 4 Cumulative Impacts 

current CO2 conditions, while C4 crops (e.g., maize) yielded up to 10 percent more (EPA 2009). In 

addition, IPCC reviewed and synthesized field and chamber studies, finding that: 

There is a large range of responses, with woody plants consistently showing net primary 

productivity (NPP) increases of 23 to 25 percent (Norby et al. 2005), but much smaller 

increases for grain crops (Ainsworth and Long 2005). Overall, about two-thirds of the 

experiments show positive response to increased CO2 (Ainsworth and Long 2005; Luo et 

al. 2004). Since saturation of CO2 stimulation due to nutrient or other limitations is 

common (Dukes et al. 2005; Köerner et al. 2005), the magnitude, and effect of the CO2

fertilization is not yet clear. 

Forest productivity gains that might result through the CO2 fertilization effect can be reduced by 

other changing factors, but the magnitude of this effect remains uncertain over the long term (EPA 2009). 

Easterling et al. (2007) discussed studies suggesting that the CO2 fertilization effect might be lower than 

assumed previously, with the initial increases in growth potentially limited by competition, disturbance 

(e.g., storm damage, forest fires, and insect infestation), air pollutants (primarily tropospheric ozone), 

nutrient limitations, ecological processes, and other factors (EPA 2009). 

The CO2 fertilization effect could mitigate some of the increase in atmospheric CO2

concentrations by resulting in more storage of carbon in biota. It should also be noted that while CO2 

fertilization can result in a greater mass of available vegetation, it can also increase the carbon-to-nitrogen 

ratio in plants. In one study, such fertilization of forage grasses for livestock increased their abundance, 

but reduced their nutritional value, affecting livestock “weight and performance” (EPA 2009). 

Additionally, there is evidence that long-term exposure to elevated ambient CO2 levels, such as areas near 

volcano outgassing, will result in a die-off of some plants. Although, under typical atmospheric CO2

concentrations, soil gas is 0.2 to 0.4 percent CO2, while in areas of observed die-off, CO2 concentration 

comprised as much as 20 to 95 percent of soil gas (EPA 2009). Any CO2 concentration above 5 percent 

is likely to adversely impact vegetation, and if concentrations reach 20 percent, CO2 is observed to have a 

phytotoxic effect (EPA 2009). 

The current annual exchange in CO2 between the atmosphere and terrestrial ecosystems is 

estimated at nine to 10 times greater than annual emissions produced as a result of burning fossil fuels. 

Even a small shift in the magnitude of this exchange could have a measurable impact on atmospheric CO2

concentration (Heath et al. 2005). The above-ground/below-ground processes and components in 

terrestrial ecosystems typically sequester carbon. Studies are now confirming that variations in 

atmospheric CO2 have impacts not only on the above-ground plant components, but also on the belowground microbial components of these systems. 

In one study, an increase in CO2 directly resulted in increased soil microbial respiration. 

However, after 4 to 5 years of increased exposure to CO2, “the degree of stimulation declined” to only a 

10 to 20 percent increase in respiration over the base rate (King et al. 2004). Additionally, the degree of 

stimulation was linked to variability in seasonal and interannual weather (King et al. 2004). Ryan et al. 

(2008) suggest that for forest ecosystems, several unresolved questions prevent a definitive assessment of 

the effect of elevated CO2 on components of the carbon cycle other than carbon sequestration, mostly in 

wood (EPA 2009). 

The increase in microbe respiration could, therefore, diminish the carbon sequestration role of 

terrestrial ecosystems. Because of the number of factors involved in determining soil respiration and 

carbon sequestration, the threshold for substantial changes in these activities varies spatially and 

temporally (King et al. 2004). 

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Chapter 4 Cumulative Impacts 4.7 Non-Climate Cumulative Impacts of CO2

 4-175 

As with the climatic effects of CO2, the changes in non-climatic impacts associated with the 

alternatives is difficult to assess quantitatively. In the possible climate scenarios presented by IPCC, 

atmospheric CO2 concentrations increase from current levels of approximately 380 ppm to as much as 800 

ppm in 2100 (Kleypas et al. 2006). Whether the distinction in concentrations is substantial across 

alternatives is not clear because the damage functions and potential existence of thresholds for CO2

concentration are not known. However, what is clear is that a reduction in the rate of increase in 

atmospheric CO2, which all the action alternatives would provide to some extent, would reduce the ocean 

acidification effect and the CO2 fertilization effect. 

 5-1 

Chapter 5 Mitigation 

Council on Environmental Quality (CEQ) regulations for implementing the procedural 

requirements of the National Environmental Policy Act (NEPA) require that the discussion of alternatives 

in an Environmental Impact Statement (EIS) “[i]nclude appropriate mitigation measures not already 

included in the proposed action or alternatives.” 40 CFR § 1502.14(f). In particular, an EIS should 

discuss the “[m]eans to mitigate adverse environmental impacts.” 40 CFR § 1502.16(h). As defined in 

the CEQ regulations, mitigation includes: 

(a) Avoiding the impact altogether by not taking a certain action or parts of an action. 

(b) Minimizing impacts by limiting the degree or magnitude of the action and its implementation. 

(c) Rectifying the impact by repairing, rehabilitating, or restoring the affected environment. 

(d) Reducing or eliminating the impact over time by preservation and maintenance operations 

during the life of the action. 

(e) Compensating for the impact by replacing or providing substitute resources or environments. 

40 CFR § 1508.20. 

Under NEPA, an EIS should contain “a reasonably complete discussion of possible mitigation 

measures.”1

 Essentially, “[t]he mitigation must ‘be discussed in sufficient detail to ensure that 

environmental consequences have been fairly evaluated.’”2

 Under NEPA, an agency does not have to 

formulate and adopt a complete mitigation plan,3

 but should analyze possible measures that could be 

adopted. An agency should state in its Record of Decision whether all practicable means to avoid or 

reduce environmental harm have been adopted in the selected alternative. 40 CFR § 1505.2(c). 

Generally, an agency does not propose mitigation measures for an action resulting in beneficial effects. 

5.1 OVERVIEW OF IMPACTS 

The National Highway Traffic Safety Administration’s (NHTSA’s) proposed action is to 

implement Corporate Average Fuel Economy (CAFE) standards for model years (MYs) 2012-2016, as 

required by the Energy Independence and Security Act of 2007 (EISA). The cumulative impacts analysis 

(see Chapter 4) considers the implementation of CAFE standards for MYs 2012-2016 and for MYs 2017-

2030.4

 Under Alternative 1, No Action, there would be no action under the National Program, and thus 

NHTSA would take no action to implement the MYs 2012-2016 CAFE standards. The No Action 

Alternative (Alternative 1) assumes that average fuel economy levels in the absence of CAFE standards 

beyond 2011 would equal the manufacturer’s required level of average fuel economy for MY 2011. 

Compared to the No Action Alternative, each of the eight action alternatives (Alternatives 2 through 9) 

 

1 Northern Alaska Environmental Center v. Kempthorne, 457 F.3d 969, 979 (9th Cir. 2006) (citing Robertson v. 

Methow Valley Citizens Council, 490 U.S. 332, 352 (1989)). 2 Id. (citing City of Carmel-By-The-Sea v. U.S. Dept. of Transp., 123 F.3d 1142, 1154 (9th Cir. 1997)). 

3

Id. (citing Robertson, 490 U.S. at 352 (noting that NEPA does not contain a substantive requirement that a 

complete mitigation plan be actually formulated and adopted)). See also Valley Community Preservation Com'n v. 

Mineta, 231 F. Supp. 2d 23, 41 (D.D.C. 2002) (noting that NEPA does not require that a complete mitigation plan be 

formulated and incorporated into an EIS). 4

 Although NHTSA will set CAFE standards for MYs 2017 and beyond in a future rulemaking, this NEPA analysis 

makes assumptions about the MYs 2017-2030 standards based on the MYs 2012-2016 standards, the EISA 

requirements, and the Annual Energy Outlook 2009 assumptions regarding projected vehicle fuel economy 

increases. 
Chapter 5 Mitigation 

 5-2 

would result in a decrease in energy consumption, carbon dioxide (CO2) emissions, and associated 

climate-change effects. 

As analyzed in this EIS, emissions from criteria air pollutants and mobile source air toxics 

(MSATs) are generally anticipated to decline. According to the analyses described in Sections 3.3 and 

4.3, some emissions would increase under some alternatives and for some analysis years, while most 

would demonstrate declines compared to the No Action Alternative (Alternative 1). Health effects are 

estimated to be reduced, and monetized health benefits would occur under all action alternatives. 

Nitrogen oxides (NOx), particulate matter (PM2.5), sulfur oxides (SOx), volatile organic 

compounds (VOCs), benzene, and diesel particulate matter (DPM), exhibit decreases in emissions under 

all action alternatives for all analysis years, compared to the No Action Alternative (Alternative 1). 

Therefore, any negative health impacts associated with these emissions are similarly expected to be 

reduced, and mitigation is not necessary. 

According to the NHTSA analysis, emissions of carbon monoxide (CO), acetaldehyde, acrolein, 

1,3-butadiene, and formaldehyde could increase under certain alternatives and analysis years, which 

requires further examination regarding the need for mitigation. The potential for harm depends on the 

selection of the final standards, the magnitude of the increases, and other factors. In all cases except for 

acrolein and formaldehyde, the increases are less than 1 percent; approximately 0.9 percent or less for 

acetaldehyde; and 0.7 percent or less for 1,3-butadiene, compared to emissions under the No Action 

Alternative (Alternative 1). Under the Preferred Alternative (Alternative 4) the increases in emissions in 

2030 compared to the No Action Alternative would be 3,062 tons (0.5 percent) for CO, 50 tons (0.6 

percent) for acetaldehyde, 6 tons (1.5 percent) for acrolein, 25 tons (0.7 percent) for 1,3-butadiene, and 33 

tons (0.4 percent) for formaldehyde. 

5.2 MITIGATION MEASURES 

As noted above, NEPA does not obligate an agency to adopt a mitigation plan. Rather, NEPA 

requires an agency to discuss possible measures that could be adopted.5

 In accordance with NEPA and 

CEQ regulations, the following is a discussion of possible measures that could mitigate the effects of 

NHTSA’s action. These include current and future actions that NHTSA or other federal agencies could 

take. Any of these actions would mitigate the environmental impacts associated with some of the action 

alternatives and provide even greater environmental benefits. 

It should be noted that even if CO emissions show some level of increase, the associated harm 

might not increase concomitantly. After a long downward trend, there have been fewer than three 

violations of the CO standards per year since 2002, owing to the success of regulations governing fuel 

composition and vehicle emissions (EPA 2009c). Also, vehicle manufacturers can choose which 

technologies to employ to reach the new CAFE standards. Some of their technology choices result in 

higher or lower impacts for these emissions. Nevertheless, there is the potential that some air pollutant 

emissions will increase in some years for some alternatives. 

Beyond these considerations, at the national level there could also be increases in criteria and 

toxic air pollutant emissions in some nonattainment areas as a result of implementation of the CAFE 

 

5 Id. (citing Robertson, 490 U.S. at 352 (noting that NEPA does not contain a substantive requirement that a 

complete mitigation plan be actually formulated and adopted)). See also Valley Community Preservation Com'n v. 

Mineta, 231 F. Supp. 2d 23, 41 (D.D.C. 2002) (noting that NEPA does not require that a complete mitigation plan be 

formulated and incorporated into an EIS). 
Chapter 5 Mitigation 

 5-3 

standards under the action alternatives. These increases would represent a slight decline in the rate of 

reductions being achieved by implementation of Clean Air Act (CAA) standards. 

In regard to air quality, federal transportation funds administered by the Federal Highway 

Administration (FHWA) could be available to assist in funding projects to reduce increases in emissions. 

FHWA provides funding to states and localities specifically to improve air quality under the Congestion 

Mitigation and Air Quality Improvement (CMAQ) Program. The FHWA and the Federal Transit 

Administration (FTA) also provide funding to states and localities under other programs that have 

multiple objectives including air quality improvement. Specifically, the Surface Transportation Program 

provides flexible funding that may be used by states for projects on any federal-aid highway (DOE 

2009a). As state and local agencies recognize the need to reduce emissions of CO, acetaldehyde, 

acrolein, 1,3-butadiene, and formaldehyde (or other emissions eligible under the CMAQ Program, 

including the criteria pollutants and MSATs analyzed in this EIS), they have the ability to apply CMAQ 

funding to reduce impacts in most areas. Further, the U.S. Environmental Protection Agency (EPA) has 

the authority to continue to improve vehicle emissions standards under CAA, which could result in future 

reductions as EPA promulgates new regulations. 

Each of the proposed alternatives would reduce energy consumption and greenhouse gas (GHG) 

emissions compared to the No Action Alternative (Alternative 1), resulting in a net beneficial effect. 

Regardless of these reductions, passenger cars and light trucks are a major contributor to energy 

consumption and GHG emissions in the United States. Although an agency typically does not propose 

mitigation measures for an action resulting in a net beneficial effect, NHTSA would like to highlight 

several other federal programs, which in conjunction with NHTSA CAFE standards, can make significant 

contributions in further reducing energy consumption and GHG emissions. 

The programs discussed below are ongoing and at various stages of completing their goals. All 

these programs present the potential for future developments and advances that could further increase the 

net beneficial effect of the environmental impacts identified in this EIS. 

Regarding energy consumption, EPA administers Renewable Fuel Standards (RFS) under Section 

211(o) of the CAA. EPA is required to determine the standard applicable to refiners, importers, and 

certain blenders of gasoline annually. The renewable fuel standard for 2009 is 10.21 percent.6

 The 

current proposed standard would increase the volume of renewable fuel required to be blended into 

gasoline from 9 billion gallons in 2008 to 36 billion gallons by 2022 (EPA 2009a). EPA estimates that 

the greater volumes of biofuel mandated by proposed standards would reduce GHG emissions from 

transportation by a total of 6.8 billion tons CO2 equivalent when measured over a 100-year timeframe and 

discounted at 2 percent. This is equivalent to approximately 160 million tons CO2 equivalent per year. 

See Section 4.4.3.3 for further details. 

In addition, the U.S. Department of Transportation (DOT), in coordination with EPA and the U.S. 

Department of Housing and Urban Development, announced six livability principles around which the 

agencies will coordinate agency policies. One of the principles is focused on increasing transportation 

options, which aims to decrease energy consumption, improve air quality, and reduce GHG emissions 

(EPA 2009b). Known as the Federal Sustainable Communities Partnership, this agency coordination 

establishes the basis upon which DOT, with assistance from EPA and the Department of Housing and 

Urban Development, can embark on future projects and direct existing programs toward further 

achievements in the areas of energy consumption, air quality, and climate change. Specifically, DOT has 

a Secretarial goal to lower the number of vehicle miles traveled (VMT). In support of this goal, Secretary 

 

6

 Environmental Protection Agency, Federal Register Environmental Documents: Renewable Fuel Standard for 

2009, http://www.epa.gov/fedrgstr/EPA-AIR/2008/November/Day-21/a27613.htm (last visited on Jul. 28, 2009). 
Chapter 5 Mitigation 

 5-4 

LaHood testified before the Senate Committee on Environment and Public Works detailing a 

departmental policy of cooperation and community planning, aimed at developing livable communities 

and improving multi-modal transportation, which is anticipated to result in decreasing VMT (LaHood 

2009). Similarly, the Smart Growth movement presents great potential for mitigating environmental 

effects caused by fuel consumption for transportation. EPA provides information and support for Smart 

Growth, further encouraging its growth (EPA 2010). 

DOT and other federal agencies are currently working to implement Executive Order (EO) 13514 

issued by President Obama.7

 This Executive Order on Federal Sustainability sets measurable 

environmental performance goals for federal agencies and focuses on making improvements in their 

environmental, energy, and economic performance. EO 13514 required each federal agency to submit a 

2020 GHG emissions reduction target from its estimated 2008 baseline to CEQ and to the Office of 

Management and Budget (OMB) by January 4, 2010. On January 28, 2010, President Obama announced 

that the federal government will reduce its GHG emissions by 28 percent by 2020.8

 This federal target is 

the aggregate of 35 federal agency self-reported targets. As the single largest energy consumer in the 

U.S. economy, the White House estimates that achieving the federal agency GHG emissions reduction 

target will reduce federal energy use by the equivalent of 646 trillion BTUs, equal to 205 million barrels 

of oil, and taking 17 million cars off the road for one year. 

DOT is also one of more than a dozen agency members of the U.S. Climate Change Technology 

Program, which the Department of Energy (DOE) leads, that is aimed at the development and adoption of 

technologies designed to reduce the U.S. carbon footprint (DOE 2009b). Additionally, DOE administers 

programs that provide mitigating effects, such as the Section 1605b Voluntary Reporting of Greenhouse 

Gases. Section 1605b reporting provides a forum for recording strategies and reductions in GHGs and is 

a voluntary program that facilitates information sharing (DOE 2009b). Such programs can provide a 

source of information and strategy for future programs. 

DOT’s high speed rail initiative will provide a travel alternative that will reduce U.S. GHG 

emissions. The overall strategy involves two parts: improving existing rail lines to make current train 

service faster and identifying potential corridors for the creation of high-speed rail. In furtherance of 

these goals, on January 28, 2010, President Obama announced DOT’s American Recovery and 

Reinvestment Act High-Speed and Inter-city Passenger Rail grants.9

 With 31 states and the District of 

Columbia receiving awards, these grants are jump-starting high-speed rail development in the United 

States. 

The FTA is actively supporting the DOT Livability Initiative and the Federal Sustainable 

Communities Partnership with its programs to expand mass transit, another travel alternative that will 

reduce U.S. GHG emissions (FTA 2010a). The FTA works with public transportation providers and 

other key stakeholders to implement strategies that reduce GHG emissions from the transportation sector. 

FTA’s grants, technical assistance, research, and policy leadership all play a role in the agency’s efforts to 

address climate change (FTA 2010b). For example, FTA’s grant programs support purchases of fuel 

efficient and alternative fuel transit vehicles. 

Also within DOT, the FAA is a sponsor of the Commercial Aviation Fuels Initiative (CAAFI), 

which is a coalition of the U.S. commercial aviation community that acts as a focal point for engaging the 

 

7

 Federal Leadership in Environmental, Energy, and Economic Performance, Exec. Order No. 13514, 74 FR 52117 

(Oct. 8, 2009). 

8 See http://www.whitehouse.gov/the-press-office/president-obama-sets-greenhouse-gas-emissions-reduction-targetfederal-operations (last accessed Feb. 3, 2010). 9 See http://www.whitehouse.gov/blog/2010/01/28/president-obama-delivers-american-high-speed-rail (last accessed 

Feb. 3 2010). 
Chapter 5 Mitigation 

 5-5 

emerging alternative fuels industry (FAA 2009). The CAAFI seeks to enhance energy security, and 

thereby reduce GHG emissions, in the transportation sector by promoting the development of alternative 

fuel options for use in aviation. Similarly, the Maritime Administration (MARAD) is exploring 

alternative fuels for ferries and other vessels via workshops with key stakeholders. 

Regarding carbon emissions, DOE administers programs designed to give consumers and 

industries information required to make environmentally conscious decisions. Specifically, the DOE 

Clean Cities program develops government-industry partnerships designed to reduce petroleum 

consumption (DOE 2009a). The focus on urbanized areas overlaps with some of the nonattainment areas 

identified in Sections 3.3.2 and 4.3.2. Also, DOE administers the Vehicle Technologies Program, which 

creates public-private partnerships that enhance energy efficiency and productivity and bring clean 

technologies to the marketplace (DOE 2009c). 

As NHTSA notes throughout the EIS, annual passenger car and light truck GHG emissions will 

continue to increase regardless of what level NHTSA sets CAFE standards. NHTSA’s setting of CAFE 

standards will reduce the rate at which these emissions will increase. See Figure 2.6-1. NHTSA 

recognizes the importance of mitigating GHG emissions in this sector, and in the transportation sector 

more generally. Emissions mitigation in the transportation sector can only be discussed in the context of 

larger national emissions reductions policies and strategies. GHG emission reductions of the order of 

magnitude necessary to mitigate climate change will require concurrent efforts from many different 

international actors, from both the public and private sectors. For this reason, mitigation of global GHG 

emissions presents a unique set of challenges far beyond this rulemaking. That said, in the light duty 

vehicle sector, some policies that could be explored to contribute to this sector’s GHG mitigation include 

expanding and improving mass transit, raising gas taxes or other driving-associated fees to deter VMT 

growth, and setting lower speed limits. When appropriate, increased motor fuel taxes or VMT fees could 

provide incentives to travelers to reduce trip lengths and shift to less carbon-intensive modes. A federal 

policy to reduce speed limits on national highways could reduce transportation GHG emissions because 

reducing highway traveling speeds generally increases vehicle fuel economy. For example, reducing 

speed from 70 to 55 miles per hour increases fuel economy for an average vehicle by over 6 miles per 

gallon. However, achieving these benefits would require strong enforcement. 

Chapter 6 Preparers 

6.1 NATIONAL HIGHWAY TRAFFIC SAFETY ADMINISTRATION 

Name Qualifications/Experience 

PREPARERS 

Angel Jackson, Contracting Officer’s Technical Representative (FEIS) 

J.D., University of Cincinnati College of Law; M.S., Mechanical Engineering, B.S., Mechanical 

Engineering, Florida Agricultural and Mechanical University 

2 years of legal experience; 3 years experience in regulatory analysis and drafting; 7 years of 

engineering experience 

Carol Hammel-Smith, Contracting Officer’s Technical Representative (DEIS) 

M.P.A., Environmental Management and Policy, University of Colorado; B.A., Political Science, 

University of Colorado 

21 years of experience in environmental impact assessment 

Sarah Alves 

J.D., Boston University School of Law; B.A., Astronomy and Physics, Boston University 

2 years of legal experience; 2 years of experience in macroeconomic analysis 

Amanda Fuller (DEIS) 

J.D. Candidate, Georgetown University Law Center; B.A., Government (Honors), Philosophy, and 

History, Wesleyan University 

1 year of legal experience 

Carrie Gage (FEIS) 

J.D., University of Washington School of Law; B.A., Psychology, Whitman College 

2 years of legal experience; 2 years of policy/legislative experience 

Anita Ghosh (DEIS) 

J.D. Candidate, American University Washington College of Law; M.S. Electrical Engineering, 

Johns Hopkins University; B.S., Computer Engineering, University of Maryland – College Park 

1 year of legal experience; 4 years of engineering experience 

Kevin Green 

M. Eng., Applied & Engineering Physics; B.S., Applied & Engineering Physics, Cornell University 

18 years of experience in vehicle emissions analysis and regulation 

Don H. Pickrell 

Ph.D., Urban Planning, M.A., Urban Planning, University of California – Los Angeles; B.A., 

Economics and Mathematics (High Honors), University of California – San Diego 

31 years of experience in applied transportation economics, including 15 years of experience in 

analysis of environmental impacts of transportation activity 

Greg Powell (FEIS) 

M.S., Computer Engineering and Science, University of Michigan – Dearborn; B.S., Technical 

Communication, Ferris State University 

15 years of automotive engineering and regulatory experience 

Peter Prout 

M.B.A., University of Michigan- Dearborn; B.S., Eastern Michigan University

25 years of automotive engineering and regulatory compliance experience 

 6-1 
Chapter 6 Preparers 

 6-2 

Name Qualifications/Experience 

PREPARERS (continued) 

Henrietta Dandy 

D.B.A., California Coast University; M.B.A., Howard University; B.S., Virginia State University 

20 years of fuel-economy and regulatory experience; 10 years of budgeting and quantitative 

analysis experience 

Jessica G. Wilson (DEIS)

J.D., College of William & Mary; B.A., International Affairs, James Madison University 

5 years of legal experience 

REVIEWERS 

Julie Abraham, Director, Office of International Policy, Fuel Economy and Consumer Programs (DEIS) 

M.S., Bioengineering, University of Michigan – Ann Arbor; M.S., Electrical Engineering, Wayne 

State University 

17 years of experience in domestic and international vehicle safety and fuel economy rulemaking 

John Donaldson, Assistant Chief Counsel, Legislation and General Law 

J.D., Boston College Law School; B.A., Economics, Cornell University 

25 years of experience in vehicle safety issues, including environmental impact assessments 

Stephen R. Kratzke, Associate Administrator, Rulemaking (FEIS) 

J.D., Georgetown University; B.A., Political Science, Duke University 

33 years experience in vehicle safety and fuel economy regulatory matters 

Helen L. Serassio, Senior Attorney Advisor 

J.D., S.J. Quinney College of Law, University of Utah; B.S., Political Science, University of Utah 

9 years of legal experience in NEPA and environmental issues 

O. Kevin Vincent, Chief Counsel (FEIS) 

J.D., University of Alabama School of Law; B.S. Electrical Engineering, University of Alabama 

23 years of legal experience in contracts and administrative law issues 

Stephen P. Wood, Assistant Chief Counsel, Vehicle Safety Standards and Harmonization 

J.D., Columbia Law School; B.A., Political Science, Williams College 

40 years of experience in vehicle safety rulemaking; 33 years in fuel economy rulemaking 

6.2 CONSULTANT TEAM 

ICF International supported the National Highway Traffic Safety Administration (NHTSA) in 

conducting its environmental analysis and preparing this Environmental Impact Statement (EIS). 

Name/Role Qualifications/Experience 

PROJECT MANAGEMENT 

Alan Summerville, Officer in Charge 

M.A., City Planning, University of Pennsylvania; B.A., Economics and Political Science, University 

of Vermont – Burlington 

19 years of experience participating in and managing the preparation of NEPA documents 

Michael Smith, Project Manager 

Ph.D., Sociology, Utah State University; M.A., Geography, University of Wyoming; B.A., 

Environmental Studies (Honors), University of California – Santa Cruz 

16 years of experience in environmental impact assessment 
Chapter 6 Preparers 

 6-3 

Name/Role Qualifications/Experience 

PROJECT MANAGEMENT (continued) 

Karen Fadely, Deputy Project Manager 

M.E.M., Conservation Science and Policy, Duke University; B.S., Biology, Bucknell University 

9 years of environmental experience; 3 years participating in and managing the preparation of 

NEPA documents 

TECHNICAL AND OTHER EXPERTISE (alphabetically) 

Nicholas Baker, Technical Data Quality Control Team 

M.E.M., Conservation Science and Policy, Duke University; B.S., Wildlife Biology, Colorado State 

University 

2 years of experience in preparing NEPA documents 

Aaron Beaudette, Climate Change Modeling 

B.S., Natural Resources, Research, Law & Society Concentration (Honors), Cornell University 

2 years of experience in climate change modeling and analysis 

Leiran Biton, Air Quality Analyst 

M.S., Environmental Science, University of North Carolina – Chapel Hill; B.A., Environmental 

Science & Policy and Theater Arts, Clark University 

3 years of experience in environmental analysis 

Adam Brundage, Climate Change Modeling Analyst 

M.E.M., Environmental Management, Duke University; B.S., Atmospheric Science, McGill 

University – Canada 

4 years of experience assessing and analyzing climate change issues 

Howard Chang, Energy Analyst 

B.S., Industrial and Operations Engineering, University of Michigan – Ann Arbor 

2 years of experience in asset valuation, GHG regulation impacts, and fuel pricing 

Elizabeth Diller, Quality Assurance Lead 

B.S., Environmental Science (Honors), University of Ulster – Ireland 

9 years of environmental experience; 7 years of NEPA experience 

David Ernst, Team Leader, Air Quality 

M.C.R.P., Environmental Policy, Harvard University; B.S., Urban Systems Engineering; B.A., 

Ethics and Politics, Brown University 

29 years of experience preparing air quality analysis for NEPA documents 

Cristiano Facanha, Air Quality Analyst 

Ph.D., Civil and Environmental Engineering; M.S., Transportation Engineering, University of 

California – Berkeley; M.S., Management of Transportation, Chalmers University of Technology – 

Sweden; B.S., Industrial Engineering, Federal University of Rio de Janeiro – Brazil

5 years of experience in transportation analysis 

Mark Flugge, Climate Change Analyst 

Ph.D., Atmospheric Chemistry, and M.C., Chemistry, University of Oxford – United Kingdom 

11 years of experience analyzing atmospheric chemistry, greenhouse-gas, and climate-change 

issues 

Randall J. Freed, Senior Technical Climate Change Advisor 

M.S., Water Resource Management, B.S., Zoology, University of Maryland – College Park 

34 years of experience in assessing and managing environmental risk; 14 years of experience 

assessing climate-change issues 
Chapter 6 Preparers 

 6-4 

Name/Role Qualifications/Experience 

TECHNICAL AND OTHER EXPERTISE (alphabetically) (continued) 

Frank Gallivan, Air Quality Analyst 

M.A., City Planning, University of California – Berkeley; B.A., Economics and Classical 

Archaeology, Dartmouth College 

3 years of experience preparing economic and environmental analyses for NEPA documents 

Kelly Hammerle, Technical Data Quality Control Team 

M.P.A., Emphasis in Environmental Policy, East Carolina University; B.S., Fisheries and Wildlife 

Sciences, North Carolina State University 

5 years of experience in environmental analysis 

John Hansel, Senior NEPA Advisor 

J.D., Cum Laude, American University Washington College of Law; B.A., Economics, University 

of Wisconsin – Madison 

31 years of experience managing the preparation of NEPA documents 

William Hartley, Air Quality Analyst 

M.S., Atmospheric Sciences, University of Washington – Seattle; B.S., Physics, North Carolina 

State University 

11 years of experience in air quality analysis 

Joseph Herr, Climate Change Analyst 

B.S., Natural Resources and Business Administration, University of Vermont – Burlington 

4 years of experience in air quality analysis 

David Johnson, Other Environmental Impact Analyst 

B.S., Biology, University of Minnesota – Twin Cities 

10 years of experience in assessing aquatic resources, resource inventory and classification, 

impact assessment, permitting assistance, and regulatory compliance 

Penelope Kellar, Technical Editor 

M.S., Ecology (Honors), University of California – Davis; B.S., Conservation of Natural Resources 

(Highest Honors), University of California – Berkeley 

26 years of experience in environmental science writing and editing, with extensive expertise in 

communication of environmental assessments; 2 years in NEPA document preparation 

Whitney Kihlstrom, Research Assistant 

B.S., Environmental Science, University of North Carolina – Chapel Hill 

2 years of experience assisting with NEPA document production 

Jean Kim, Climate Change Analyst 

M.E.M., Water and Air Resources, Duke University; B.A., Environmental Studies and International 

Relations, University of Pennsylvania

3 years of experience in climate change analysis 

Tanvi Lal, Technical Data Quality Control Team 

M.S., Environmental Science, M.P.A., Indiana University – Bloomington; B.S., Life Sciences, St. 

Xavier’s College – India

4 years of experience in environmental impact analysis and document production 

Robert Lanza, P.E., Technical Data QA/QC Lead 

M. Eng., Chemical Engineering, B.S., Chemical Engineering, Cornell University 

21 years of experience in preparing and reviewing NEPA documents 

Suzanne Martos, Research Assistant 

B.S., Science of Earth Systems & Biology, Cornell University 

2 years of experience assisting in NEPA document preparation 
Chapter 6 Preparers 

 6-5 

Name/Role Qualifications/Experience 

TECHNICAL AND OTHER EXPERTISE (alphabetically) (continued)

Rawlings Miller, Human Health Analyst 

Ph.D., Atmospheric Sciences, University of Arizona; M.S., Aerospace Engineering, Boston 

University; B.S., Physics, Union College 

9 years of experience with climate change modeling and impacts analysis 

Chris Moelter, Technical Data Quality Control Team 

M.E.M., Environmental Tourism, University of Queensland – Australia; B.S., Zoology, University 

of Wisconsin – Madison 

6 years of consulting on environmental issues; 2 years of experience in preparing NEPA 

documents 

Beth Moore, Climate Change Analyst 

M.E.M., Environmental Management, Yale University; B.A., Economics and Environmental 

Science, Duke University 

5 years of experience in climate change analysis 

Rick Nevin, Alternatives Analyst 

M.B.A., Finance, Managerial Economics, and Strategy, J.L. Kellogg Graduate School of 

Management, Northwestern University; M.A., Economics, B.A., Economics and Mathematics, 

Boston University 

26 years of experience managing and preparing environmental, energy, and economic analyses 

Andrew Papson, Air Quality Analyst 

M. Eng., Transportation Engineering, University of California – Berkeley; B.S., Materials Science, 

Stanford University 

3 years of experience analyzing vehicle emissions and fuel efficiency 

Melissa Pauley, Project Coordinator 

M.S., Environmental Science and Management, Duquesne University; B.S., Environmental 

Studies, Bucknell University 

5 years of environmental consulting experience; 2 years of experience in environmental impact 

assessment 

Bill Pepper, Climate Change Team Leader 

M.A., Mathematics, Temple University; B.S., Mathematics, University of Maryland – College Park 

21 years of experience modeling and evaluating climate change issues 

Annah Peterson, Technical Data Quality Control Team 

M.E.M., Environmental Economics and Policy, Duke University; B.A., Biology, Reed College 

2 years of experience preparing NEPA documents 

Arlene Rosenbaum, Technical Director 

M.P.H., Environmental Health Planning, University of Michigan – Ann Arbor; M.S., EngineeringEconomic Systems, Stanford University; B.S., Chemistry, University of Michigan – Ann Arbor 

26 years of experience in environmental health analysis, population exposure assessment for air 

pollutants; 2 years of experience preparing NEPA documents 

Zeta Rosenberg, Energy Analyst 

Ph.D., (less dissertation) History; M.A., Economics, George Washington University; M.A., History, 

University of Toronto – Canada; B.A., History (Honors), University of New Brunswick – Canada 

32 years of experience in energy analysis 

Judith Shipman, Technical Editor 

A.A., General Studies, University of South Carolina – Aiken 

31 years of experience in NEPA document preparation, including technical writing and editing, 

document production support; document production coordination 
Chapter 6 Preparers 

 6-6 

Name/Role Qualifications/Experience 

TECHNICAL AND OTHER EXPERTISE (alphabetically) (continued)

Allison Stork, Technical Data Quality Control Team 

M.S., Geography, University of Tennessee – Knoxville; B.A. Geography and English, State 

University of New York – Geneseo 

2 years of experience in preparing NEPA documents 

Elizabeth Strange, Water Resources Analyst 

Ph.D., Ecology, University of California – Davis; M.S., Ecology, University of California – Davis; 

B.A., Biology, San Francisco State University; 

15 years of experience in analysis of impacts of human stressors on water resources and aquatic 

ecosystems 

Audrey Turley, Human Health Analyst 

M.S., Mechanical Engineering, North Carolina State University; B.A., Mathematics, Texas A&M 

University 

3 years of experience analyzing toxicological effects of inhaled particulate matter and executing 

models to calculate human exposure and risk based on air quality data 

Alex Uriarte, Environmental Justice Analyst and Administrative Record Coordinator 

Ph.D., Development Studies, M.S., Economics, University of Wisconsin-Madison; M.A., Business 

Economics, Getulio Vargas Foundation – Brazil; B.A., Economics, University of Sao Paulo – 

Brazil 

11 years of experience in socioeconomic assessments and studies, as well as management and 

monitoring of economic development projects

John Venezia, Climate Change and Economics Analyst 

M.S., Environmental Science and Policy, Johns Hopkins University; B.S., Biology and 

Environmental Science & Policy, Duke University 

11 years of experience analyzing the technical and economic aspects of global climate change 

issues 

Satish Vutukuru, Air Quality Analyst 

Ph.D., Mechanical and Aerospace Engineering, M.S., Chemical Engineering, University of 

California – Irvine; B. Tech., Chemical Engineering, Indian Institute of Technology – India 

5 years of experience in air quality modeling, health risk assessment, and environmental impact 

analysis 
Chapter 7 References 

7.1 PURPOSE AND NEED REFERENCES 

Committee on Science, Engineering, and Public Policy. 1992. Policy Implications of Greenhouse 

Warming : Mitigation, Adaptation, and the Science Base. National Academy of Sciences. 918 

pgs. 

EPA (U.S. Environmental Protection Agency) and NHTSA (National Highway Traffic Safety 

Administration). 2009. Draft Joint Technical Support Document: Proposed Rulemaking to 

Establish Light-Duty Vehicle Greenhouse Gas Emission Standards and Corporate Average Fuel 

Economy Standards. EPA-420-D-09-901. September. 203 pgs. 

NHTSA (National Highway Traffic Safety Administration). 2009. Preliminary Regulatory Impact 

Analysis: Corporate Average Fuel Economy for MY 2012-MY2016 Passenger Cars and Light 

Trucks. Office of Regulatory Analysis and Evaluation, National Center for Statistics and 

Analysis. August. 501 pgs. 

7.2 PROPOSED ACTION AND ALTERNATIVES REFERENCES 

EIA (Energy Information Administration). 2009a. An Updated Annual Energy Outlook 2009 Reference 

Case Reflecting Provisions of the American Recovery and Reinvestment Act and Recent Changes 

in the Economic Outlook. U.S. Department of Energy. Washington, District of Columbia. 

SR/OIAF/2009-03. April. 56 pgs. 

EIA (Energy Information Administration). 2009b. Annual Energy Outlook 2010 Early Release. Summary 

Reference Case. U.S. Department of Energy. Washington, District of Columbia. December. 41 

pgs. 

EPA (U.S. Environmental Protection Agency). 2009a. Inventory of U.S. Greenhouse Gas Emissions and 

Sinks. Washington, District of Columbia. EPA 430-R-09-004. 441 pgs. Last Revised: July 14, 

2009. Available: <http://www.epa.gov/climatechange/emissions/usinventoryreport.html>. 

Accessed: August 5, 2009. 

EPA (U.S. Environmental Protection Agency). 2009b. Greenhouse Gas Equivalencies Calculator. 

Available: < http://www.epa.gov/RDEE/energy-resources/calculator.html >. Accessed: August 

26, 2009. 

NRC (National Research Council). 2002. Effectiveness and Impact of Corporate Average Fuel Economy 

(CAFE) Standards. National Academy Press. Washington, District of Columbia. 166 pgs. 

7.3 AFFECTED ENVIRONMENT AND ENVIRONMENTAL CONSEQUENCES 

REFERENCES 

7.3.1 Introduction References 

CEQ (Council on Environmental Quality). 1984. Considering Cumulative Effects Under the National 

Environmental Policy Act. Washington, District of Columbia. 64 pgs. 

DOT (U.S. Department of Transportation). 1979. Procedures for Considering Environmental Impacts. 

Order DOT 5610.1C. September 18. 

 7-1 
Chapter 7 References 

IPCC (Intergovernmental Panel on Climate Change). 2007a. Climate Change 2007: The Physical Science 

Basis. Contribution of Working Group I to the Fourth Assessment Report of the 

Intergovernmental Panel on Climate Change. [Solomon, S., D. Qin, M. Manning, Z. Chen, M. 

Marquis, K.B. Averyt, M. Tignor and H.L. Miller (Eds.).] Cambridge University Press, 

Cambridge, United Kingdom and New York, NY, USA. 996 pgs. 

IPCC (Intergovernmental Panel on Climate Change). 2007b. Climate Change 2007: Impacts, Adaptation 

and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the 

Intergovernmental Panel on Climate Change. [Parry, M. L., O.F. Canziani, J.P. Palutikof, P.J. van 

der Linden and C.E.Hanson (Eds)]. Cambridge University Press, Cambridge, United Kingdom 

and New York, NY, USA. 976 pgs. 

IPCC (Intergovernmental Panel on Climate Change). 2007c. Climate Change 2007: Mitigation. 

Contribution of Working Group III to the Fourth Assessment Report of the Intergovernmental 

Panel on Climate Change. [B. Metz, O.R. Davidson, P.R. Bosch, R. Dave, L.A. Meyer (Eds)] 

Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.. 851 pgs. 

7.3.2 Energy References 

EIA (Energy Information Administration). 2009a. Annual Energy Review 2008. Washington, District of 

Columbia. DOE/EIA-0384(2008). 408 pgs. 

EIA (Energy Information Administration). 2009b. An Updated Annual Energy Outlook 2009 Reference 

Case Reflecting Provisions of the American Recovery and Reinvestment Act and Recent Changes 

in the Economic Outlook. U.S. Department of Energy. Washington, District of Columbia. 

SR/OIAF/2009-03. April. 56 pgs. 

EIA (Energy Information Administration). 2009c. Annual Energy Outlook 2010 Early Release. Summary 

Reference Case. U.S. Department of Energy. Washington, District of Columbia. December. 41 

pgs. 

EIA (Energy Information Administration). 2009d. International Energy Outlook 2009. Washington, 

District of Columbia. DOE/EIA-0484-(2009). 274 pgs. 

Leiby, Paul N. 2008. Estimating the Energy Security Benefits of Reduced U.S. Oil Imports. Report 

ORNL/TM-2007/028. Oak Ridge National Laboratory, March 14. 

NRC (National Research Council). 2002. Effectiveness and Impact of Corporate Average Fuel Economy 

(CAFE) Standards. National Academy Press. Washington, District of Columbia. 166 pgs. 

7.3.3 Air Quality References 

Aksoy, M. 1989. Hematotoxicity and Carcinogenicity of Benzene. Environmental Health Perspectives 

92:193–197. 

Appleman, L.M., R.A. Woutersen, and V.J. Feron. 1982. Inhalation Toxicity of Acetaldehyde in Rats. I. 

Acute and Subacute Studies. Toxicology 23:293–297. 

Appleman, L.M., R.A. Woutersen, V.J. Feron, R.N. Hooftman, and W.R.F. Notten. 1986. Effects of the 

Variable Versus Fixed Exposure Levels on the Toxicity of Acetaldehyde in Rats. Journal of 

Applied Toxicology 6:331–336. 

 7-2 
Chapter 7 References 

Argonne (Argonne National Laboratories). 2002. The Greenhouse Gas and Regulated Emissions from 

Transportation (GREET) Model. Version 1.8a. February 2002. 

ATSDR (Agency for Toxic Substances and Disease Registry). 1999. Toxicological Profile for 

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7.3.7 EPA Action and Analysis References 

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7.4.2 Energy References 

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7.4.3 Air Quality References 

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7.4.5 Health, Societal, and Environmental Impacts of Climate Change 

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AMS (American Meterological Society). 2004. Weather and Highways Report of a Policy Forum. 

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Canziani, J.P. Palutikof, P.J. van der Linden, and C.E. Hanson (Eds.)] Cambridge University 

Press, Cambridge, United Kingdom. 976 pgs. 

Norby, R.J., E.H. DeLucia, B. Gielen, C. Calfapietra, C.P. Giardina, J.S. King, J. Ledford, H.R. 

McCarthy, D.J.P. Moore, R. Ceulemans, P. DeAngelis, A.C. Finzi, D.F. Karnosky, M. Kubiske, 

M. Lukac, K.S. Pregitzer, and G.E. Scarascia-Mugnoz. 2005. Forest Response to Elevated CO2 is 

Conserved Across a Broad Range of Productivity. Proceedings of the National Academy of 

Sciences 102(50):18052–18056. 

Orr, J.C., V.J. Fabry, O. Aumont, L. Bopp, S.C. Doney, R.A. Feely, A. Gnanadesikan, N. Gruber, A. 

Ishida, F. Joos, R.M. Key, K. Lindsay, E. Maier-Reimer, R. Matear, P. Monfray, A. Mouchet, 

R.G. Najjar, G.K. Plattner, and K.B. Rodgers. 2005. Anthropogenic Ocean Acidification Over the 

Twenty-first Century and its Impact on Calcifying Organisms. Nature 437:681–686. 

Pepper, W.J. J. Leggett, W.J. Pepper, R.J. Swart, J. Edmonds, L.G. Meira Filho, I. Mintzer, M.X. Wang, 

and J. Watson. 1992. Emissions Scenarios for the IPCC: An Update. Assumptions, Methodology, 

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and Results. Prepared for the Intergovernmental Panel on Climate Change Working Group I. 

Cambridge University Press, Cambridge, United Kingdom. 68–95. 

Riebessell, U., I. Zondervan, B. Rost, P.D. Tortell, R.E. Zeebe, and F.M.M. Morel. 2000. Reduced 

Calcification of Marine Plankton in Response to Increased Atmospheric CO2. Nature 

407(6802):364–367. 

Royal Society. 2005. Ocean Acidification due to Increasing Atmospheric Carbon Dioxide. Policy 

Document 12/05. London. 68 pgs. 

Ryan, M.G., S.R. Archer, R. Birdsey, C. Dahm, L. Heath, J. Hicke, D. Hollinger, T. Huxman, G. Okin, R. 

Oren,J. Randerson, and W. Schlesinger. 2008. Land Resources. In: The Effects of Climate 

Change on Agriculture, Land Resources, Water Resources, and Biodiversity in the United States.

Prepared by the U.S. Climate Change Science Program and the Subcommittee on Global Change 

Research. Washington, District of Columbia. 362 pgs. 

Sabine, C.L., R.A. Feely, N. Gruber, R.M. Key, and K. Lee. 2004. The Oceanic Sink for Anthropogenic 

CO2. Science 305(5682):367–371. 

Schimel, D., J. Melillo, H. Tian, A.D. McGuire, D. Kicklighter, T. Kittel, N. Rosenbloom, S. Running, P. 

Thornton, D. Ojima, W. Parton, R. Kelly, M. Sykes, R. Neilson, and B. Rizzo. 2000. Contribution 

of Increasing CO2 and Climate to Carbon Storage by Ecosystems in the United States. Science 

287(5460):2004–2006. 

Schneider, S.H., and R. Londer. 1984. The Coevolution of Climate and Life, San Francisco. Sierra Club 

Books, San Francisco, California. 563 pgs. [As cited in: Perry, D.A. 1994. Forest Ecosystems. 

Johns Hopkins University Press: Baltimore, Maryland. 59 pgs.] 

Schuster, U., and A.J. Watson. 2009. A Variable and Decreasing Sink for Atmospheric CO2 in the North 

Atlantic. Journal of Geophysical Research 112(C11006):1–10. 

Shirayama, Y., and H. Thornton. 2005. Effect of Increased Atmospheric CO2 on Shallow Water Marine 

Benthos. Journal of Geophysical Research 110(C9):1–7. 

Steinacher, M., F. Joos, T.L. Frölicher, G.K. Plattner, and S.C. Doney. 2009. Imminent Ocean 

Acidification in the Arctic Projected with the NCAR Global Coupled Carbon Cycle-Climate 

Model. Biogeosciences 6(4):515–533. 

Wardle, D.A., R.D. Bardgett, J.N. Klironomos, H. Setälauml, W.H. van der Putten, and D.H. Wall. 2004. 

Ecological Linkages Between Aboveground and Belowground Biota. Science 304(5677):1629–

1633. 

Wootton, T.J., C.A. Pfister, and J.D. Foerester. 2008. Dynamic Patterns and Ecological Impacts of 

Declining Ocean pH in a High-resolution Multi-year Dataset. Proceedings of the National 

Academy of Sciences 105(48):18848–18853. 

7.5 MITIGATION REFERENCES 

DOE (U.S. Department of Energy). 2009a. Fact Sheet: Clean Cities. Last Revised: July 9, 2009. 

Available: <http://www1.eere.energy.gov/cleancities/pdfs/44929.pdf>. Accessed August 5, 2009. 

 7-115 
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 7-116 

DOE (U.S. Department of Energy). 2009b. Climate Overview. Available: 

<http://www.pi.energy.gov/climateoverview.html>. Accessed: July 22, 2009. 

DOE (U.S. Department of Energy). 2009c. About the Program. Last Revised: June 15, 2009. Available: 

<http://www1.eere.energy.gov/vehiclesandfuels/about/index.html>. Accessed August 5, 2009. 

EPA (U.S. Environmental Protection Agency). 2009a. Fuels and Fuel Additives: Renewable Fuel 

Standard Program. Last Revised: July 13, 2009. Available: 

<http://www.epa.gov/OMS/renewablefuels/>. Accessed August 5, 2009. 

EPA (U.S. Environmental Protection Agency). 2009b. Press Release: EPA Administrator Lisa Jackson, 

DOT Secretary Ray LaHood and HUD Secretary Shaun Donovan Announce Interagency 

Partnership for Sustainable Communities, Partnership Sets Forth 6 ‘Livability Principles’ to 

Coordinate Policy. Last Revised: June 16. 2008. Available: 

<http://yosemite.epa.gov/opa/admpress.nsf/0/F500561FBB8D5A08852575D700501350>. 

Accessed August 5, 2009. 

EPA (U.S. Environmental Protection Agency). 2009c. Monitor Trends Report – Criteria Air Pollutants. 

Last Revised: July 2, 2009. Available: <http://www.epa.gov/air/data/montrnd.html>. Accessed: 

August 5, 2009. 

EPA (U.S. Environmental Protection Agency). 2010. Smart Growth. Last Revised: February 3, 2010. 

Available: <http://www.epa.gov/smartgrowth/index.htm>. Accessed: February 4, 2010. 

FAA (Federal Aviation Administration). 2009. Fact Sheet. Commercial Aviation Alternatives Fuel 

Initiative: Supporting Soultions for Secure and Sustainable Aviation. September. Available: 

<http://www.faa.gov/news/fact_sheets/news_story.cfm?newsId=10112>. Accessed: February 4, 

2010 

FTA (Federal Transit Administration). 2010a. Livable and Sustainable Communities. Available: 

<http://fta.dot.gov/publications/publications_10935.html>. Accessed: February 4, 2010 

FTA (Federal Transit Administration). 2010b. FTA Activities that Promote Environmental Sustainability. 

Available: <http://fta.dot.gov/planning/planning_environment_8513.html>. Accessed: February 

4, 2010 

LaHood, R. 2009. Statement of the Hon. Ray LaHood, Secretary of Transportation: Transportation’s Role 

in Climate Change and Greenhouse Gases. Committee on Environment and Public Works, United 

States Senate. July 14, 2009. 
Chapter 8 Distribution List 

The Council on Environmental Quality (CEQ) regulations for implementing the National 

Environmental Policy Act (NEPA) (40 Code of Federal Regulations 1501.19) specify requirements for 

circulating an Environmental Impact Statement (EIS). In accordance with those requirements, NHTSA is 

mailing this EIS to the agencies, officials, and other interested persons listed in this chapter. 

8.1 FEDERAL AGENCIES 

• Advisory Council on Historic Preservation 

• Council on Environmental Quality 

• Council on Environmental Quality, NEPA Oversight 

• Delaware River Basin Commission 

• Denali Commission 

• Federal Energy Regulatory Commission, Division of Gas - Environmental and Engineering 

• Federal Energy Regulatory Commission, Division of Hydropower, Environment and 

Engineering 

• Federal Energy Regulatory Commission, Office of Energy Projects 

• International Boundary and Water Commission 

• International Boundary and Water Commission, Environmental Management Division 

• Marine Mammal Commission 

• National Capital Planning Commission, Office of Urban Design and Plan Review 

• National Science Foundation, Office of the General Counsel 

• Office of Science and Technology Policy, National Science and Technology Council, 

Executive Office of the President 

• Presidio Trust, NEPA Compliance Division 

• Susquehanna River Basin Commission 

• Tennessee Valley Authority, NEPA Policy 

• U.S. Agency for International Development, Bureau for Economic growth, Agriculture, and 

Trade 

• U.S. Department of Agriculture, Agricultural Research Service 

 8-1 
Chapter 8 Distribution List 

• U.S. Department of Agriculture, Animal and Plant Health Inspection Service, Environmental 

Services 

• U.S. Department of Agriculture, Cooperative State Research, Education and Extension 

Service 

• U.S. Department of Agriculture, Farm Service Agency 

• U.S. Department of Agriculture, Natural Resources Conservation Service 

• U.S. Department of Agriculture, Rural Business-Cooperative Service 

• U.S. Department of Agriculture, Rural Housing Services, Technical Support Branch 

• U.S. Department of Agriculture, Rural Utilities Service, Engineering and Environmental Staff 

• U.S. Department of Agriculture, U.S. Forest Service 

• U.S. Department of Commerce, Economic Development Administration, Legislative and 

Intergovernmental Affairs 

• U.S. Department of Commerce, National Oceanic and Atmospheric Administration, National 

Marine Fisheries Service 

• U.S. Department of Commerce, National Oceanic and Atmospheric Administration, National 

Climatic Data Center 

• U.S. Department of Commerce, National Oceanic and Atmospheric Administration, Planning 

and Integration Office 

• U.S. Department of Defense, Army Corps of Engineers, Office of Environmental Policy 

• U.S. Department of Defense, Office of Deputy Undersecretary of Defense of Installations and 

Environment, Environmental Security 

• U.S. Department of Energy, Office of Climate Change Policy (PI-63) 

• U.S. Department of Energy, Office of NEPA Policy and Compliance (EH-42) 

• U.S. Department of Energy, Western Energy and Waste Management Unit 

• U.S. Department of Health and Human Services, Centers for Disease Control and Prevention 

• U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, 

Building and Facilities Office 

• U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, 

National Center for Environmental Health, Agency for Toxic Substances and Disease 

Registry, Environmental Public Health Readiness Branch 

• U.S. Department of Health and Human Services, Food and Drug Administration, Center for 

Food Safety and Applied Nutrition 

 8-2 
Chapter 8 Distribution List 

• U.S. Department of Health and Human Services, Food and Drug Administration, Office of 

Commissioner 

• U.S. Department of Health and Human Services, Health Resources and Services 

Administration 

• U.S. Department of Health and Human Services, Indian Health Service, Division of 

Sanitation Facilities Construction 

• U.S. Department of Health and Human Services, National Institutes of Health, Division of 

Environmental Protection, ORF, Environmental Quality Branch 

• U.S. Department of Health and Human Services, Office of the Secretary, Office for Facilities 

Management and Policy, Division of Real Property 

• U.S. Department of Homeland Security, Federal Emergency Management Agency 

• U.S. Department of Homeland Security, Office of Safety and Environment 

• U.S. Department of Homeland Security, U.S. Coast Guard, Environmental Management 

Division (G-SEC-3) 

• U.S. Department of Housing and Urban Development, Office of Environment and Energy 

• U.S. Department of Justice, Environment and Natural Resources Division 

• U.S. Department of Labor, Mine Safety and Health Administration, Office of Standards, 

Regulations, and Variances 

• U.S. Department of Labor, Occupational Safety and Health Administration, Office of the 

Assistant Secretary 

• U.S. Department of State, Bureau of Oceans and International Environmental and Scientific 

Affairs 

• U.S. Department of the Interior 

• U.S. Department of the Interior, Bureau of Indian Affairs 

• U.S. Department of the Interior, Bureau of Land Management, Renewable Resources 

Planning Division, Planning and Science Policy 

• U.S. Department of the Interior, Bureau of Reclamation 

• U.S. Department of the Interior, Main Interior 

• U.S. Department of the Interior, Minerals Management Service, Environmental Assessment 

Branch 

• U.S. Department of the Interior, National Park Service, Cultural Resources GIS Facility 

• U.S. Department of the Interior, National Park Service, Environmental Quality Division 

 8-3 
Chapter 8 Distribution List 

• U.S. Department of the Interior, Office of Environmental Policy and Compliance 

• U.S. Department of the Interior, Office of Environmental Policy and Compliance, Natural 

Resources Management Team, Transportation Projects 

• U.S. Department of the Interior, Office of Surface Mining 

• U.S. Department of the Interior, U.S. Fish and Wildlife Service 

• U.S. Department of the Interior, U.S. Geological Survey, Office of Environmental Affairs 

Program 

• U.S. Department of State, Bureau of Oceans and International Environmental and Scientific 

Affairs 

• U.S. Department of Transportation 

• U.S. Department of Transportation, Federal Aviation Administration 

• U.S. Department of Transportation, Federal Aviation Administration, Office of Environment 

& Energy (AEE-400) 

• U.S. Department of Transportation, Federal Highway Administration 

• U.S. Department of Transportation, Federal Highway Administration, Office of NEPA 

Facilitation 

• U.S. Department of Transportation, Federal Maritime Administration 

• U.S. Department of Transportation, Federal Motor Carrier Safety Administration 

• U.S. Department of Transportation, Federal Railroad Administration 

• U.S. Department of Transportation, Federal Railroad Administration, Office of Railroad 

Development 

• U.S. Department of Transportation, Federal Transit Administration 

• U.S. Department of Transportation, Maritime Administration, Office of Environmental 

Activities 

• U.S. Department of Transportation, Office of the Assistant Secretary for Transportation 

Policy 

• U.S. Department of Transportation, Office of the Secretary 

• U.S. Department of Transportation, Pipeline & Hazardous Materials Safety Administration 

• U.S. Department of Transportation, Research and Innovative Technology Administration 

• U.S. Department of Transportation, Research and Innovative Technology Administration, 

Volpe Center, Environmental Engineering Division 

 8-4 
Chapter 8 Distribution List 

• U.S. Department of Transportation, Saint Lawrence Seaway Development Corporation 

• U.S. Department of Transportation, Surface Transportation Board, Section of Environmental 

Analysis 

• U.S. Environmental Protection Agency 

• U.S. Environmental Protection Agency, NEPA Compliance Division 

• U.S. Environmental Protection Agency, Office of Federal Activities, EIS Filing Section 

• U.S. Environmental Protection Agency, Office of Transportation and Air Quality 

• U.S. Institute for Environmental Conflict Resolution, ECR Policy and Leadership 

• U.S. Nuclear Regulatory Commission 

• Valles Caldera Trust 

8.2 STATE AND LOCAL GOVERNMENT ORGANIZATIONS 

• American Samoa Department of Public Safety 

• Assistant Corporation Counsel of the City of New York, Environmental Law Division 

• California Attorney General’s Office 

• Connecticut Office of the Attorney General 

• Corporation Counsel of the City of New York 

• Georgia Environmental Protection Division 

• Massachusetts Attorney General’s Office 

• Missouri Department of Natural Resources 

• Montana Department of Environmental Quality 

• New Mexico Department of Attorney General 

• New Mexico Environment Department 

• New York State Department of Transportation 

• Oregon Department of Attorney General 

• Pennsylvania Department of Environmental Protection 

• Tennessee Department of Transportation 

• Vermont Attorney General, Environmental Division 

 8-5 
Chapter 8 Distribution List 

• Washington State Department of Ecology 

8.3 ELECTED OFFICIALS 

• The Honorable Bob Riley, Governor of Alabama 

• The Honorable Sean Parnell, Governor of Alaska 

• The Honorable Togiola T.A. Tulafono, Governor of American Samoa 

• The Honorable Janice Brewer, Governor of Arizona 

• The Honorable Mike Beebe, Governor of Arkansas 

• The Honorable Arnold Schwarzenegger, Governor of California 

• The Honorable Bill Ritter, Governor of Colorado 

• The Honorable M. Jodi Rell, Governor of Connecticut 

• The Honorable Jack Markell, Governor of Delaware 

• The Honorable Adrian Fenty, Mayor of the District of Columbia 

• The Honorable Charlie Crist, Governor of Florida 

• The Honorable Sonny Perdue, Governor of Georgia 

• The Honorable Felix P. Camacho, Governor of Guam 

• The Honorable Linda Lingle, Governor of Hawaii 

• The Honorable C.L. “Butch” Otter, Governor of Idaho 

• The Honorable Pat Quinn, Governor of Illinois 

• The Honorable Mitchell E. Daniels, Governor of Indiana 

• The Honorable Chet Culver, Governor of Iowa 

• The Honorable Mark Parkinson, Governor of Kansas 

• The Honorable Steven Beshear, Governor of Kentucky 

• The Honorable Bobby Jindal, Governor of Louisiana 

• The Honorable John E. Baldacci, Governor of Maine 

• The Honorable Martin O’Malley, Governor of Maryland 

• The Honorable Deval Patrick, Governor of Massachusetts 

 8-6 
Chapter 8 Distribution List 

• The Honorable Jennifer M. Granholm, Governor of Michigan 

• The Honorable Tim Pawlenty, Governor of Minnesota 

• The Honorable Haley Barbour, Governor of Mississippi 

• The Honorable Jay Nixon, Governor of Missouri 

• The Honorable Brian D. Schweitzer, Governor of Montana 

• The Honorable Dave Heineman, Governor of Nebraska 

• The Honorable Jim Gibbons, Governor of Nevada 

• The Honorable John Lynch, Governor of New Hampshire 

• The Honorable Chris Christie, Governor of New Jersey 

• The Honorable Bill Richardson, Governor of New Mexico 

• The Honorable David A. Paterson, Governor of New York 

• The Honorable Bev Perdue, Governor of North Carolina 

• The Honorable John Hoeven, Governor of North Dakota 

• The Honorable Benigno R. Fitial, Governor of the Commonwealth of the Northern Mariana 

Islands 

• The Honorable Ted Strickland, Governor of Ohio 

• The Honorable Brad Henry, Governor of Oklahoma 

• The Honorable Ted Kulongoski, Governor of Oregon 

• The Honorable Edward G. Rendell, Governor of Pennsylvania 

• The Honorable Luis Fortuño, Governor of Puerto Rico 

• The Honorable Donald L. Carcieri, Governor of Rhode Island 

• The Honorable Mark Sanford, Governor of South Carolina 

• The Honorable Mike Rounds, Governor of South Dakota 

• The Honorable Phil Bredesen, Governor of Tennessee 

• The Honorable Rick Perry, Governor of Texas 

• The Honorable Gary Herbert, Governor of Utah 

• The Honorable Jim Douglas, Governor of Vermont 

 8-7 
Chapter 8 Distribution List 

• The Honorable Bob McDonnell, Governor of Virginia 

• The Honorable John P. deJongh, Jr., Governor of the United States Virgin Islands 

• The Honorable Chris Gregoire, Governor of Washington 

• The Honorable Joe Manchin, III, Governor of West Virginia 

• The Honorable Jim Doyle, Governor of Wisconsin 

• The Honorable Dave Freudenthal, Governor of Wyoming 

8.4 NATIVE AMERICAN TRIBES 

• Cedarville Rancheria 

• Leisnoi Village aka Woody Island Tribal Council 

• Mille Lacs Band of Ojibwe 

• Native Village of Point Hope 

• Natives of Larsen Bay 

• Table Mountain Rancheria 

8.5 STAKEHOLDERS 

• Alliance of Automobile Manufacturers 

• American Association of Blacks in Energy 

• American Council for an Energy Efficient Economy 

• American International Automobile Dealers Association 

• American Jewish Committee 

• American Jewish Committee, Washington Chapter, Office of Government and International 

Affairs 

• BG Automotive Group, Ltd. 

• BMW (US) Holding Corp. 

• BMW of North America, LLC 

• California Air Pollution Control Officers Association 

• Cambridge Consumers’ Council 

• Cambridge Consumers’ Council, Massachusetts Consumers Council 

 8-8 
Chapter 8 Distribution List 

• Center for Biological Diversity 

• Chrysler LLC 

• Conservation Law Foundation 

• Conservation Law Foundation, Vermont Advocacy Center 

• Consumer Action 

• Consumer Federation of America 

• Consumers for Auto Reliability and Safety 

• Consumers Union 

• Douglas Long 

• Environment America 

• Environmental Council of the States 

• Environmental Defense Fund 

• Evangelical Lutheran Church in America 

• Ford Motor Company 

• Ford Motor Company, Environmental and Safety Engineering 

• Fred T. Teal, Jr. 

• Friends Committee on National Legislation 

• Fuji Heavy Industries USA/Subaru 

• General Motors Corporation 

• General Motors, Public Policy Center 

• Gibson, Dunn & Crutcher LLP 

• Insurance Institute for Highway Safety 

• James L. Adcock 

• Jean Public 

• Jewish Community Relations Council of Greater Washington 

• Kirkland & Ellis LLP 

 8-9 
Chapter 8 Distribution List 

• Maryknoll Office of Global Concerns 

• Michael Gordon 

• Missionary Society of St. Columban 

• Missionary Society of St. Columban, Columban Justice Peace and Integrity of Creation 

Office 

• National Automobile Dealers Association 

• National Council of Churches USA 

• National Tribal Environmental Council 

• Natural Resources Canada 

• Natural Resources Defense Council 

• Natural Resources Defense Council, Vehicles Campaign 

• Nissan North America, Inc. 

• Northeast States for Coordinated Air Use Management 

• Presbyterian Church (USA) 

• Public Citizen 

• Ray Koonuk, Jr. 

• Sierra Club 

• Sierra Club Global Warming and Energy Program 

• Sierra Club Legislative Office 

• Stratacomm on behalf of Aluminum Association Auto & Light Truck Group 

• The Consumer Alliance 

• The Episcopal Church 

• The Mountaineers – Conservation Executive Committee 

• The United Methodist Church General Board of Church and Society 

• U.S. PIRG 

• U.S. PIRG, Illinois PIRG 

• U.S. PIRG, MASSPIRG 

 8-10 
Chapter 8 Distribution List 

 8-11 

• Union for Reform Judaism 

• Union of Concerned Scientists 

• Union of Concerned Scientists, Washington Office 

• United Church of Christ 

• University of Colorado School of Law 

• Volkswagen Group of America 

• Volkswagen of America, Industry-Government Relations 

• Western Governors’ Association 

• Western Regional Air Partnership 

Chapter 9 Index 

adaptation, 2-8, 4-3, 4-81, 4-94, 4-115, 4-116, 4-119, 4-132, 4-135, 4-137, 4-138, 4-139, 4-145, 4-151, 4-

156 

afforestation, 4-82 

air pollutants, 1-4, 1-15, 1-16, 2-9, 2-20, 2-21, 2-28, 2-41, 2-44, 3-4, 3-5, 3-6, 3-11, 3-14, 3-15, 3-17, 3-

24, 3-26, 3-30, 3-31, 3-42, 3-45, 3-48, 3-49, 3-52, 3-53, 3-54, 3-55, 3-56, 3-58, 3-59, 3-65, 3-111, 3-

113, 3-114, 3-124, 3-125, 3-129, 4-7, 4-11, 4-17, 4-20, 4-24, 4-25, 4-28, 4-30, 4-31, 4-32, 4-33, 4-34, 

4-35, 4-36, 4-37, 4-38, 4-122, 4-146, 4-166, 5-2 

albedo, 3-65, 4-98, 4-117, 4-159, 4-160, 4-163 

Alliance of Automobile Manufacturers, 1-13, 2-24 

Alternative 1, 1-18, 2-1, 2-12, 2-14, 2-16, 2-17, 2-18, 2-21, 2-22, 2-26, 2-27, 2-28, 2-29, 2-30, 2-31, 2-33, 

2-36, 2-37, 2-38, 2-39, 2-40, 2-41, 2-42, 2-43, 2-44, 2-45, 2-46, 2-47, 2-48, 2-51, 2-52, 2-53, 2-54, 2-

55, 3-8, 3-12, 3-13, 3-14, 3-15, 3-23, 3-31, 3-35, 3-36, 3-37, 3-38, 3-40, 3-41, 3-42, 3-43, 3-45, 3-46, 3-

47, 3-48, 3-49, 3-50, 3-51, 3-52, 3-53, 3-54, 3-55, 3-56, 3-57, 3-58, 3-59, 3-66, 3-74, 3-77, 3-78, 3-80, 

3-83, 3-85, 3-87, 3-89, 3-90, 3-92, 3-95, 3-96, 3-97, 3-100, 3-101, 3-102, 3-105, 3-106, 3-108, 3-109, 

3-110, 3-113, 3-116, 3-117, 3-125, 3-126, 3-130, 4-1, 4-5, 4-7, 4-8, 4-9, 4-10, 4-11, 4-12, 4-13, 4-15, 4-

16, 4-17, 4-18, 4-20, 4-21, 4-22, 4-23, 4-24, 4-25, 4-26, 4-27, 4-28, 4-29, 4-30, 4-31, 4-32, 4-33, 4-34, 

4-35, 4-36, 4-37, 4-38, 4-39, 4-40, 4-41, 4-45, 4-46, 4-49, 4-50, 4-51, 4-53, 4-55, 4-56, 4-57, 4-60, 4-

61, 4-62, 4-63, 4-64, 4-65, 5-1, 5-2, 5-3 

Alternative 2, 1-14, 2-2, 2-13, 2-14, 2-16, 2-18, 2-22, 2-26, 2-27, 2-28, 2-29, 2-30, 2-31, 2-33, 2-39, 2-41, 

2-42, 2-43, 2-44, 2-45, 2-46, 2-48, 2-53, 3-12, 3-13, 3-14, 3-35, 3-38, 3-40, 3-41, 3-43, 3-45, 3-46, 3-

47, 3-48, 3-49, 3-50, 3-51, 3-52, 3-77, 3-85, 3-89, 3-90, 3-95, 3-96, 3-97, 3-105, 3-106, 4-7, 4-8, 4-9, 4-

13, 4-15, 4-16, 4-17, 4-18, 4-20, 4-21, 4-22, 4-23, 4-24, 4-25, 4-26, 4-27, 4-50, 4-51, 4-53, 4-55, 4-57, 

4-63 

Alternative 3, 1-14, 2-13, 2-14, 2-16, 2-18, 2-27, 2-28, 2-29, 2-30, 2-31, 2-33, 2-39, 2-41, 2-42, 2-43, 2-

44, 2-45, 2-46, 2-48, 2-53, 3-13, 3-14, 3-38, 3-40, 3-41, 3-42, 3-43, 3-46, 3-47, 3-48, 3-50, 3-51, 3-52, 

3-53, 3-85, 3-89, 3-97, 3-105, 3-106, 3-125, 4-7, 4-8, 4-9, 4-12, 4-13, 4-15, 4-16, 4-17, 4-18, 4-20, 4-

21, 4-22, 4-23, 4-24, 4-26, 4-27, 4-28, 4-29, 4-51, 4-53, 4-55, 4-57, 4-63 

Alternative 4, 1-14, 1-21, 2-13, 2-14, 2-26, 2-28, 2-38, 2-40, 2-44, 2-46, 2-54, 3-12, 3-35, 3-42, 3-51, 3-

53, 3-54, 3-66, 3-78, 3-80, 3-83, 3-90, 3-109, 3-125, 3-126, 3-128, 4-8, 4-20, 4-25, 4-29, 4-30, 4-31, 4-

46, 4-49, 4-55, 4-64, 5-2 

Alternative 5, 2-13, 2-15, 2-16, 2-18, 2-27, 2-28, 2-29, 2-30, 2-31, 2-33, 2-39, 2-41, 2-42, 2-43, 2-44, 2-

45, 2-46, 2-48, 2-53, 3-13, 3-14, 3-37, 3-38, 3-40, 3-41, 3-43, 3-46, 3-47, 3-48, 3-50, 3-51, 3-53, 3-54, 

3-55, 3-85, 3-89, 3-97, 3-105, 3-106, 4-7, 4-8, 4-9, 4-12, 4-13, 4-15, 4-16, 4-18, 4-20, 4-21, 4-22, 4-23, 

4-26, 4-27, 4-29, 4-31, 4-32, 4-51, 4-53, 4-55, 4-57, 4-63 

Alternative 6, 1-22, 2-11, 2-13, 2-15, 2-20, 2-21, 3-55, 3-56, 4-31, 4-32, 4-33, 4-34 

Alternative 7, 2-13, 2-15, 2-16, 2-18, 2-22, 2-27, 2-28, 2-29, 2-30, 2-31, 2-33, 2-39, 2-41, 2-42, 2-43, 2-

44, 2-45, 2-46, 2-48, 2-53, 3-13, 3-14, 3-38, 3-40, 3-41, 3-42, 3-43, 3-46, 3-47, 3-48, 3-50, 3-51, 3-55, 

 9-1 
Chapter 9 Index 

3-56, 3-57, 3-85, 3-89, 3-97, 3-105, 3-106, 4-7, 4-8, 4-9, 4-12, 4-13, 4-15, 4-16, 4-18, 4-21, 4-22, 4-23, 

4-26, 4-27, 4-29, 4-34, 4-35, 4-51, 4-53, 4-57, 4-63 

Alternative 8, 2-2, 2-13, 2-15, 2-16, 2-18, 2-26, 2-27, 2-28, 2-29, 2-30, 2-31, 2-33, 2-38, 2-39, 2-41, 2-42, 

2-43, 2-44, 2-45, 2-46, 2-47, 2-48, 2-53, 3-12, 3-13, 3-14, 3-35, 3-37, 3-38, 3-40, 3-41, 3-42, 3-43, 3-

46, 3-47, 3-48, 3-50, 3-51, 3-57, 3-58, 3-85, 3-89, 3-95, 3-96, 3-97, 3-105, 3-106, 3-125, 4-7, 4-8, 4-9, 

4-13, 4-15, 4-16, 4-18, 4-21, 4-22, 4-23, 4-26, 4-27, 4-34, 4-35, 4-36, 4-37, 4-51, 4-53, 4-56, 4-57, 4-63 

Alternative 9, 1-22, 2-11, 2-13, 2-15, 2-20, 2-21, 2-22, 2-28, 2-44, 2-47, 3-12, 3-14, 3-37, 3-42, 3-45, 3-

57, 3-58, 3-59, 3-89, 3-90, 3-95, 3-96, 3-108, 4-12, 4-17, 4-20, 4-32, 4-34, 4-35, 4-36, 4-37, 4-38, 4-50, 

4-51, 4-56 

Alternative Motor Fuels Act (AMFA), 3-7 

Annual Energy Outlook (AEO), 2-5, 2-20, 2-22, 2-40, 2-41, 2-43, 3-9, 3-10, 3-60, 3-80, 4-3, 4-4, 4-5, 4-6, 

4-8, 4-10, 4-12, 4-20, 4-39, 4-40, 4-46, 4-50, 4-55, 5-1 

anthropogenic, 2-54, 3-63, 3-66, 3-73, 3-112, 3-115, 3-116, 4-55, 4-64, 4-83, 4-85, 4-93, 4-95, 4-97, 4-98, 

4-102, 4-103, 4-104, 4-105, 4-113, 4-142, 4-156 

aquaculture, 4-116, 4-119, 4-128 

atmospheric-ocean general circulation model (AOGCM), 3-76, 3-106, 4-62, 4-161 

Attorney General, 1-12, 1-13, 2-24 

benthic, 3-114, 3-116, 4-108, 4-110, 4-117 

biofuel, 3-9, 3-10, 3-11, 3-111, 3-113, 3-114, 3-116, 3-117, 3-119, 3-120, 3-123, 4-6, 4-44, 5-3 

biosphere, 3-84, 4-85, 4-118, 4-155 

carbon sink, 3-67, 4-102, 4-103, 4-164 

Center for Biological Diversity (CBD), 1-15, 1-16, 1-19, 1-20, 2-25, 3-61, 4-67 

Centers for Disease Control and Prevention (CDC), 1-12, 1-17 

Clean Air Act (CAA), 1-4, 1-5, 1-7, 1-8, 1-9, 1-11, 1-13, 1-18, 1-21, 2-5, 2-18, 3-11, 3-15, 3-17, 3-21, 3-

22, 3-25, 3-27, 3-28, 3-29, 3-36, 3-60, 3-68, 3-71, 3-89, 3-112, 3-125, 3-127, 3-128, 4-3, 4-11, 4-25, 4-

43, 4-44, 4-67, 4-93, 4-121, 4-156, 5-3 

climate change, 1-1, 1-8, 1-10, 1-11, 1-12, 1-13, 1-14, 1-19, 1-20, 1-21, 1-22, 2-2, 2-13, 2-24, 2-45, 3-60, 

3-61, 3-64, 3-65, 3-68, 3-70, 3-74, 3-76, 3-79, 3-83, 3-84, 3-90, 3-93, 3-95, 3-105, 3-111, 3-114, 3-115, 

3-120, 3-123, 3-125, 3-126, 3-127, 3-131, 4-1, 4-3, 4-39, 4-40, 4-41, 4-42, 4-44, 4-45, 4-46, 4-49, 4-54, 

4-55, 4-66, 4-67, 4-68, 4-69, 4-70, 4-71, 4-72, 4-73, 4-74, 4-75, 4-76, 4-77, 4-78, 4-79, 4-80, 4-81, 4-

82, 4-83, 4-84, 4-85, 4-93, 4-94, 4-97, 4-98, 4-99, 4-100, 4-101, 4-102, 4-103, 4-104, 4-105, 4-106, 4-

108, 4-109, 4-110, 4-111, 4-112, 4-113, 4-115, 4-116, 4-117, 4-119, 4-120, 4-121, 4-123, 4-124, 4-125, 

4-126, 4-127, 4-128, 4-129, 4-130, 4-131, 4-132, 4-133, 4-134, 4-135, 4-136, 4-137, 4-138, 4-139, 4-

140, 4-141, 4-142, 4-143, 4-144, 4-145, 4-147, 4-148, 4-149, 4-150, 4-151, 4-152, 4-153, 4-154, 4-155, 

4-156, 4-158, 4-160, 4-161, 4-162, 4-163, 4-164, 4-165, 4-166, 4-167, 4-168, 5-3, 5-4, 5-5 

 9-2 
 Chapter 9 Index 

coastal, 3-1, 3-111, 4-2, 4-66, 4-106, 4-107, 4-108, 4-109, 4-110, 4-111, 4-113, 4-115, 4-116 

Code of Federal Regulations (CFR), 1-1, 1-7, 1-8, 1-10, 1-11, 1-14, 1-17, 2-1, 2-12, 2-13, 2-14, 2-24, 2-

25, 2-26, 2-40, 3-2, 3-3, 3-22, 3-26, 3-36, 3-74, 3-83, 3-84, 3-95, 3-104, 3-121, 3-127, 4-1, 4-2, 4-3, 4-

5, 4-11, 4-39, 4-49, 4-54, 4-67, 4-68, 4-164, 4-166, 5-1 

cold wave, 3-69, 4-132, 4-146 

coral bleaching, 4-110, 4-115, 4-116 

Corporate Average Fuel Economy (CAFE), 1-1, 1-2, 1-3, 1-5, 1-6, 1-7, 1-8, 1-9, 1-10, 1-11, 1-12, 1-13, 

1-14, 1-15, 1-16, 1-18, 1-19, 1-20, 1-21, 1-22, 1-24, 2-1, 2-2, 2-3, 2-4, 2-5, 2-9, 2-10, 2-11, 2-12, 2-13, 

2-14, 2-16, 2-17, 2-18, 2-20, 2-21, 2-23, 2-24, 2-26, 2-31, 2-33, 2-38, 2-39, 2-40, 2-41, 2-42, 2-46, 2-

48, 2-53, 2-54, 2-55, 3-1, 3-3, 3-4, 3-5, 3-6, 3-7, 3-8, 3-9, 3-11, 3-12, 3-13, 3-14, 3-15, 3-21, 3-22, 3-

23, 3-24, 3-25, 3-30, 3-31, 3-35, 3-36, 3-37, 3-42, 3-45, 3-51, 3-53, 3-54, 3-55, 3-56, 3-57, 3-58, 3-60, 

3-61, 3-66, 3-74, 3-75, 3-76, 3-77, 3-78, 3-79, 3-84, 3-85, 3-87, 3-89, 3-90, 3-93, 3-95, 3-97, 3-102, 3-

104, 3-105, 3-106, 3-110, 3-111, 3-113, 3-117, 3-118, 3-121, 3-122, 3-124, 3-125, 3-126, 3-127, 3-128, 

4-5, 4-6, 4-7, 4-10, 4-11, 4-20, 4-27, 4-29, 4-31, 4-32, 4-34, 4-35, 4-37, 4-39, 4-40, 4-41, 4-43, 4-45, 4-

49, 4-50, 4-51, 4-54, 4-55, 4-56, 4-57, 4-63, 4-65, 4-66, 4-67, 4-68, 4-164, 4-165, 5-1, 5-2, 5-3, 5-5 

Council on Environmental Quality (CEQ), 1-7, 1-8, 1-11, 1-18, 2-13, 2-14, 2-24, 2-25, 2-26, 2-40, 3-1, 3-

2, 3-3, 3-26, 3-61, 3-67, 3-74, 3-83, 3-84, 3-95, 3-104, 3-127, 4-1, 4-2, 4-3, 4-5, 4-11, 4-49, 4-54, 4-67, 

68, 4-164, 4-166, 5-1, 5-2, 5-4 

criteria pollutants, 1-23, 2-43, 3-4, 3-15, 3-17, 3-23, 3-30, 3-37, 3-42, 3-45, 3-54, 3-55, 3-56, 3-57, 3-58, 

4-12, 4-17, 4-20, 4-23, 4-28, 4-29, 4-31, 4-32, 4-34, 4-35, 4-37, 5-3 

crude oil, 3-10, 3-11, 3-18, 3-29, 3-30, 3-113, 3-119, 3-126, 3-128, 4-6, 4-50 

cryosphere, 3-84, 4-70, 4-155 

Department of Transportation Act of 1966, 3-121 

desertification, 4-95, 4-105, 4-141 

diesel particulate matter, 1-23, 2-28, 2-29, 2-43, 2-44, 3-17, 3-19, 3-20, 3-42, 3-43, 3-46, 3-48, 3-49, 3-52, 

3-53, 3-54, 3-55, 3-56, 3-57, 3-59, 3-125, 4-17, 4-18, 4-20, 4-21, 4-23, 4-24, 4-28, 4-29, 4-30, 4-31, 4-

32, 4-33, 4-34, 4-35, 4-36, 4-37, 4-38, 5-2 

disease, 1-12, 3-18, 3-19, 3-32, 3-123, 4-84, 4-93, 4-102, 4-105, 4-109, 4-110, 4-122, 4-123, 4-125, 4-

126, 4-127, 4-133, 4-139, 4-144, 4-145, 4-147, 4-148, 4-149, 4-150, 4-152, 4-153, 4-154, 4-163, 4-167 

downweighting of vehicles, 3-113, 3-114, 3-117, 3-118, 3-121 

drought, 3-64, 3-66, 3-69, 3-71, 3-73, 3-104, 3-105, 4-72, 4-74, 4-79, 4-80, 4-83, 4-84, 4-93, 4-101, 4-

102, 4-104, 4-105, 4-118, 4-119, 4-120, 4-121, 4-125, 4-126, 4-127, 4-128, 4-130, 4-132, 4-138, 4-142, 

4-143, 4-147, 4-148, 4-151, 4-154, 4-155, 4-161, 4-163 

ecosystem, 2-26, 3-1, 3-2, 3-18, 3-60, 3-73, 3-74, 3-111, 3-112, 3-114, 3-115, 3-116, 3-117, 3-119, 4-2, 4-

39, 4-66, 4-67, 4-68, 4-69, 4-70, 4-71, 4-77, 4-80, 4-81, 4-85, 4- 88, 4-89, 4-91, 4-92, 4-93, 4-94, 4-95, 

4-96, 4-97, 4-99, 4-100, 4-101, 4-102, 4-103, 4-104, 4-105, 4-106, 4-107, 4-108, 4-109, 4-110, 4-111, 

 9-3 
Chapter 9 Index 

4-112, 4-114, 4-115, 4-116, 4-117, 4-118, 4-119, 4-121, 4-122, 4-123, 4-128, 4-142, 4-144, 4-145, 4-

155, 4-157 

El Nino Southern Oscillation, 4-75, 4-76, 4-114, 4-118, 4-120, 4-163 

electric vehicle, 1-20, 1-22, 2-9 

emission rates, 3-4, 3-24, 3-37, 3-45, 3-129, 4-10, 4-12, 4-16, 4-17, 4-24, 4-28, 4-30, 4-31, 4-33, 4-34, 4-

36, 4-37, 4-148 

emissions, global, 1-16, 2-31, 2-33, 2-45, 2-46, 2-53, 2-54, 2-55, 3-65, 3-66, 3-67, 3-68, 3-76, 3-77, 3-78, 

3-79, 3-80, 3-85, 3-87, 3-109, 3-113, 4-40, 4-41, 4-42, 4-45, 4-49, 4-51, 4-54, 4-64 

emissions, United States, 1-15, 3-4, 3-15, 3-63, 3-67 

Energy Independence and Security Act (EISA), 1-1, 1-2, 1-3, 1-5, 1-6, 1-7, 1-8, 1-9, 1-13, 1-14, 1-15, 1-

18, 2-1, 2-2, 2-11, 2-12, 2-13, 2-18, 2-24, 2-40, 2-41, 3-6, 3-7, 3-8, 3-60, 3-127, 4-4, 4-5, 4-6, 4-8, 4-

10, 4-39, 4-50, 4-55, 4-165, 5-1 

Energy Information Administration (EIA), 1-17, 2-5, 2-21, 3-9, 3-10, 3-11, 3-12, 3-26, 3-29, 3-80, 4-3, 4-

6, 4-10, 4-46, 4-50 

Energy Policy and Conservation Act (EPCA), 1-1, 1-3, 1-5, 1-7, 1-8, 1-9, 1-14, 1-15, 1-19, 2-1, 2-2, 2-11, 

2-12, 2-13, 2-14, 2-16, 2-17, 2-18, 2-20, 2-23, 3-7, 3-8, 3-12, 3-127, 3-128, 4-5, 4-165 

environmental justice, 3-2, 3-111, 3-123, 3-124, 4-131, 4-144, 4-166, 4-167, 4-168 

eutrophication, 3-113, 3-115, 3-116, 3-117, 3-119, 3-120, 4-97 

Executive Order (EO), 2-5, 3-80, 3-123, 4-46, 4-166, 4-167, 5-4 

Federal Highway Administration (FHWA), 1-23, 3-17, 3-22, 3-121, 4-147, 5-3 

Federal Register (FR), 1-1, 1-2, 1-3, 1-4, 1-5, 1-6, 1-9, 1-10, 1-11, 1-13, 1-14, 1-21, 1-24, 2-1, 2-5, 2-12, 

2-13, 2-14, 2-17, 2-22, 2-24, 3-7, 3-17, 3-23, 3-127, 4-5, 4-43, 4-98, 5-3, 5-4 

Federal Transit Administration (FTA), 3-22, 5-3, 5-4 

feedstock recovery, 3-29, 3-30 

fisheries, 1-16, 3-114, 4-66, 4-107, 4-111, 4-115, 4-117, 4-118, 4-119, 4-120, 4-126, 4-128, 4-129 

flexible fuel vehicle, 2-17, 3-128 

flood, 3-64, 3-66, 4-71, 4-72, 4-74, 4-77, 4-79, 4-81, 4-83, 4-84, 4-85, 4-90, 4-114, 4-115, 4-118, 4-127, 

4-131, 4-132, 4-136, 4-139, 4-143, 4-144, 4-147, 4-151, 4-152, 4-153, 4-154, 4-168 

food production, 3-18, 3-113, 3-116, 3-123, 4-2, 4-66, 4-67, 4-85, 4-94, 4-98, 4-100, 4-101, 4-102, 4-104, 

4-106, 4-107, 4-108, 4-114, 4-117, 4-118, 4-119, 4-120, 4-121, 4-127, 4-129, 4-132, 4-133, 4-140, 4-

142, 4-144, 4-145, 4-147, 4-148, 4-149, 4-150, 4-152, 4-154, 4-167, 4-168 

 9-4 
 Chapter 9 Index 

forest products, 1-12, 3-93, 3-115, 3-117, 4-2, 4-66, 4-67, 4-85, 4-86, 4-87, 4-91, 4-92, 4-93, 4-95, 4-96, 

4-97, 4-98, 4-100, 4-102, 4-104, 4-105, 4-106, 4-107, 4-112, 4-117, 4-118, 4-119, 4-120, 4-121, 4-122, 

4-123, 4-124, 4-125, 4-127, 4-128, 4-144, 4-146, 4-148, 4-149, 4-151, 4-152, 4-158, 4-163, 4-164, 4-

167 

freshwater resources, 3-60, 3-111, 3-112, 3-113, 3-114, 3-115, 4-2, 4-39, 4-66, 4-67, 4-70, 4-71, 4-72, 4-

74, 4-75, 4-77, 4-78, 4-80, 4-81, 4-83, 4-85, 4-88, 4-89, 4-90, 4-91, 4-92, 4-94, 4-96, 4-97, 4-99, 4-100, 

4-103, 4-105, 4-106, 4-107, 4-109, 4-113, 4-115, 4-119, 4-126, 4-128, 4-129, 4-137, 4-141, 4-162 

Fuel Transportation, Storage, and Distribution, 3-24, 3-26, 3-29, 3-30, 3-31, 4-11 

glacier, 3-61, 3-64, 3-70, 3-72, 3-73, 3-84, 3-106, 3-108, 4-70, 4-75, 4-80, 4-82, 4-103, 4-111, 4-155, 4-

157, 4-158, 4-159, 4-160 

global warming potential, 3-63, 3-67, 3-68, 3-85, 4-50 

greenhouse gas, 1-2, 1-3, 1-4, 1-5, 1-6, 1-8, 1-13, 1-14, 1-16, 1-18, 1-19, 1-20, 1-21, 1-22, 2-4, 2-5, 2-9, 

2-10, 2-12, 2-14, 2-15, 2-18, 2-19, 2-20, 2-21, 2-24, 2-31, 2-40, 2-41, 2-45, 2-46, 2-54, 3-3, 3-5, 3-6, 3-

8, 3-11, 3-14, 3-17, 3-35, 3-60, 3-61, 3-63, 3-64, 3-65, 3-66, 3-67, 3-68, 3-71, 3-73, 3-74, 3-75, 3-76, 3-

77, 3-78, 3-79, 3-80, 3-83, 3-84, 3-85, 3-87, 3-89, 3-90, 3-95, 3-104, 3-109, 3-112, 3-125, 3-127, 3-

128, 3-129, 3-130, 3-131, 4-3, 4-5, 4-7, 4-39, 4-40, 4-41, 4-42, 4-43, 4-44, 4-45, 4-49, 4-50, 4-53, 4-

54, 4-56, 4-64, 4-66, 4-68, 4-104, 4-121, 4-122, 4-134, 4-155, 4-161, 4-163, 4-164, 5-3, 5-4, 5-5 

Greenhouse Gases, Regulated Emissions, and Energy Use in Transportation Model (GREET), 3-23, 3-75, 

3-129 

groundwater, 3-111, 3-112, 3-113, 4-70, 4-71, 4-73, 4-74, 4-78, 4-80, 4-81, 4-83, 4-90, 4-91, 4-113, 4-

119, 4-133 

heat wave, 3-64, 3-69, 3-71, 3-102, 4-118, 4-120, 4-134, 4-145, 4-146, 4-147, 4-150, 4-151, 4-153, 4-166 

human health, 1-8, 1-24, 3-5, 3-15, 3-31, 3-45, 3-65, 3-74, 3-111, 3-112, 3-118, 3-119, 3-120, 3-122, 3-

123, 4-20, 4-66, 4-67, 4-68, 4-77, 4-81, 4-131, 4-133, 4-140, 4-144, 4-145, 4-146, 4-148, 4-149, 4-150, 

4-153, 4-166 

hybrid electric vehicle, 2-9 

hydrology, 4-99, 4-101, 4-102 

ice sheets, 3-64, 3-72, 3-73, 3-106, 3-108, 4-70, 4-103, 4-113, 4-116, 4-134, 4-156, 4-157, 4-158, 4-159, 

4-160, 4-162, 4-163 

Intergovernmental Panel on Climate Change (IPCC), 1-22, 2-54, 3-3, 3-60, 3-61, 3-62, 3-63, 3-64, 3-65, 

3-70, 3-71, 3-72, 3-73, 3-74, 3-75, 3-76, 3-77, 3-78, 3-79, 3-84, 3-95, 3-96, 3-102, 3-103, 3-104, 3-106, 

3-107, 3-108, 3-115, 3-129, 3-131, 4-3, 4-39, 4-40, 4-41, 4-42, 4-55, 4-56, 4-62, 4-66, 4-67, 4-68, 4-69, 

4-70, 4-73, 4-76, 4-77, 4-80, 4-81, 4-84, 4-93, 4-99, 4-101, 4-103, 4-104, 4-113, 4-115, 4-116, 4-117, 

4-118, 4-121, 4-122, 4-126, 4-127, 4-129, 4-142, 4-144, 4-145, 4-146, 4-147, 4-151, 4-155, 4-156, 4-

157, 4-158, 4-159, 4-160, 4-162, 4-163, 4-164, 4-167 

International Energy Outlook (IEO), 3-9, 3-80, 4-46 

 9-5 
Chapter 9 Index 

Laden et al. 2006, 3-32 

land use, 3-1, 3-2, 3-27, 3-111, 3-117, 3-118, 4-2, 4-71, 4-74, 4-78, 4-81, 4-85, 4-95, 4-104, 4-138, 4-147, 

4-151, 4-163 

MAGICC model, 2-47, 2-48, 2-49, 2-50, 3-74, 3-76, 3-77, 3-78, 3-83, 3-95, 3-96, 3-97, 3-102, 3-103, 3-

104, 3-105, 3-106, 3-129, 4-40, 4-41, 4-55, 4-56, 4-57, 4-62, 4-63 

Millennium Ecosystems Assessment (MA), 3-27, 3-29, 4-85, 4-86, 4-88, 4-93, 4-94, 4-95, 4-96, 4-97, 4-

98 

mitigation, 1-19, 3-66, 4-90, 4-135, 4-138, 4-166, 5-1, 5-2, 5-3, 5-5 

mobile source air toxics (MSATs), 3-17, 3-19, 3-22, 3-23, 3-26, 3-103,4-166, 5-2, 5-3 

National Ambient Air Quality Standards (NAAQS), 3-15, 3-16, 3-17, 3-22, 3-24, 3-31, 3-32 

National Environmental Policy Act of 1969 (NEPA), 1-2, 1-7, 1-8, 1-10, 1-11, 1-12, 1-14, 1-16, 1-17, 1-

24, 2-1, 2-12, 2-13, 2-14, 2-16, 2-24, 2-25, 2-26, 2-38, 2-40, 2-41, 2-46, 2-47, 3-1, 3-2, 3-3, 3-7, 3-23, 

3-25, 3-36, 3-67, 3-84, 3-109, 3-127, 4-1, 4-2, 4-3, 4-5, 4-6, 4-42, 4-54, 4-55, 4-62, 4-66, 4-165, 4-166, 

5-1, 5-2 

National Highway Traffic Safety Administration (NHTSA), 1-1, 1-2, 1-3, 1-4, 1-5, 1-6, 1-7, 1-8, 1-9, 1-

10, 1-11, 1-12, 1-13, 1-14, 1-15, 1-16, 1-17, 1-18, 1-19, 1-20, 1-21, 1-22, 1-23, 1-24, 2-1, 2-2, 2-3, 2-4, 

2-5, 2-9, 2-10, 2-11, 2-12, 2-13, 2-14, 2-16, 2-17, 2-18, 2-20, 2-21, 2-22, 2-23, 2-24, 2-25, 2-26, 2-30, 

2-38, 2-41, 2-43, 2-46, 2-47, 2-53, 3-1, 3-2, 3-3, 3-5, 3-6, 3-7, 3-8, 3-9, 3-11, 3-12, 3-22, 3-23, 3-24, 3-

25, 3-26, 3-27, 3-29, 3-30, 3-31, 3-32, 3-33, 3-34, 3-35, 3-36, 3-60, 3-61, 3-66, 3-67, 3-73, 3-74, 3-75, 

3-76, 3-77, 3-78, 3-79, 3-83, 3-84, 3-85, 3-89, 3-90, 3-93, 3-95, 3-96, 3-104, 3-109, 3-113, 3-116, 3-

117, 3-118, 3-121, 3-122, 3-125, 3-126, 3-127, 3-128, 3-129, 4-3, 4-5, 4-10, 4-11, 4-20, 4-39, 4-40, 4-

41, 4-42, 4-43, 4-45, 4-49, 4-50, 4-54, 4-55, 4-62, 4-64, 4-66, 4-67, 4-68, 4-69, 4-156, 4-164, 4-165, 4-

166, 5-1, 5-2, 5-3, 5-5 

National Register of Historic Places (NRHP), 3-121 

nonattainment, 1-18, 1-23, 3-17, 3-22, 3-24, 3-25, 3-26, 3-27, 3-28, 3-29, 3-30, 3-37, 3-42, 3-48, 3-49, 3-

51, 3-52, 3-53, 3-54, 3-55, 3-56, 3-57, 3-58, 3-59, 3-124, 3-125, 4-12, 4-17, 4-23, 4-24, 4-25, 4-28, 4-

29, 4-30, 4-31, 4-32, 4-33, 4-34, 4-35, 4-36, 4-37, 4-38, 4-167, 5-2, 5-5 

nonattainment area (NAA), 1-23, 3-17, 3-24, 3-25, 3-26, 3-27, 3-29, 3-30, 3-48, 3-49, 3-51, 3-52, 3-53, 3-

54, 3-55, 3-56, 3-57, 3-58, 3-59, 3-124, 3-125, 4-12, 4-17, 4-23, 4-24, 4-25, 4-28, 4-29, 4-30, 4-31, 4-

32, 4-33, 4-34, 4-35, 4-36, 4-37, 4-38, 4-167, 5-2, 5-5 

Notice of Intent (NOI), 1-1, 1-10, 1-14, 1-15, 2-1, 2-2, 2-13 

Notice of Proposed Rulemaking (NPRM), 1-1, 1-2, 1-4, 1-6, 1-7, 1-13, 1-14, 1-15, 1-16, 1-17, 1-21, 2-3, 

2-5, 2-11, 2-12, 2-13, 2-14, 2-17, 2-20, 2-22, 3-6, 3-12, 3-77, 3-79 

ocean acidification, 3-73, 3-112, 3-115, 4-104, 4-109, 4-157 

ocean circulation, 3-73, 3-106, 3-108, 4-113, 4-115, 4-116, 4-129, 4-156, 4-157, 4-161, 4-162 

Organization for Economic Cooperation and Development (OECD), 3-122 

 9-6 
 Chapter 9 Index 

permafrost, 3-70, 3-71, 3-84, 3-96, 4-55, 4-70, 4-72, 4-75, 4-76, 4-83, 4-98, 4-111, 4-115, 4-116, 4-130, 

4-134, 4-142, 4-155, 4-158, 4-162, 4-164 

plug-in hybrid electric vehicle, 1-20 

polar bear, 4-98, 4-102, 4-140 

polar regions, 3-61, 3-64, 3-66, 3-70, 3-71, 3-72, 3-73, 3-103, 3-106, 3-108, 4-70, 4-72, 4-74, 4-76, 4-86, 

4-98, 4-99, 4-100, 4-116, 4-117, 4-124, 4-126, 4-129, 4-133, 4-134, 4-140, 4-142, 4-156, 4-157, 4-158, 

4-159, 4-160, 4-163, 4-164 

Pope et al. 2002, 3-32 

precipitation, change in, 2-24, 2-30, 2-33, 2-38, 2-39, 2-47, 2-53, 3-60, 3-61, 3-69, 3-70, 3-71, 3-72, 3-73, 

3-74, 3-76, 3-77, 3-95, 3-104, 3-105, 3-106, 3-107, 3-108, 3-109, 4-40, 4-55, 4-62, 4-63, 4-66, 4-68, 4-

71, 4-72, 4-73, 4-74, 4-75, 4-76, 4-77, 4-78, 4-79, 4-80, 4-81, 4-82, 4-83, 4-84, 4-86, 4-87, 4-88, 4- 90, 

4-91, 4-97, 4-98, 4-100, 4-101, 4-102, 4-104, 4-105, 4-106, 4-109, 4-116, 4-118, 4-120, 4-121, 4-122, 

4-123, 4-127, 4-130, 4-132, 4-133, 4-134, 4-135, 4-136, 4-137, 4-138, 4-139, 4-140, 4-142, 4-143, 4-

144, 4-145, 4-149, 4-151, 4-152, 4-153, 4-156, 4-161, 4-163, 4-164 

Preliminary Regulatory Impact Analysis (PRIA), 1-24, 2-11, 2-13, 2-20, 3-128 

rebound effect, 1-14, 1-18, 1-23, 2-3, 2-9, 2-13, 2-19, 2-20, 2-21, 2-23, 3-4, 3-5, 3-11, 3-23, 3-24, 3-25, 3-

48, 3-49, 3-51, 3-52, 3-53, 3-54, 3-55, 3-56, 3-58, 3-59, 3-122, 3-124, 4-25, 4-28, 4-30, 4-32, 4-33, 4-

35, 4-36, 4-38, 4-166 

Reference Case, 2-20, 2-22, 2-23, 2-40, 2-45, 2-46, 2-54, 3-9, 3-10, 3-77, 3-79, 3-93, 3-104, 3-129, 4-3, 

4-10, 4-40, 4-41, 4-45, 4-46, 4-50, 4-54, 4-55, 4-64 

Reformed CAFE Program, 1-6, 2-12, 2-24 

safety, 1-9, 1-15, 1-16, 1-17, 1-20, 1-23, 2-1, 2-2, 2-4, 2-21, 3-1, 3-6, 3-20, 3-111, 3-118, 3-123, 4-3, 4-

134, 4-135, 4-137, 4-140, 4-147 

saltwater intrusion, 4-74, 4-83, 4-112 

sea level rise, 4-97, 4-112, 4-114, 4-116 

Secretary of Transportation, 1-1, 1-2, 1-8, 3-8 

sensitivity analyses, 2-3, 2-10, 2-11, 2-20, 2-21, 2-22, 2-23, 2-38, 2-46, 2-54, 3-5, 3-6, 3-76, 3-77, 3-78, 

3-83, 3-109, 4-40, 4-41, 4-49, 4-64 

Social Cost of Carbon (SCC), 1-12, 1-19, 1-20, 1-22, 2-2, 2-3, 2-11, 2-13, 2-19, 2-20, 2-22, 2-23, 3-11, 3-

30 

Special Report on Emission Scenarios (SRES), 2-47, 3-78, 3-79, 3-95, 3-96, 3-106, 4-41, 4-42, 4-55, 4-

62, 4-116, 4-122 

State Implementation Plan (SIP), 3-17, 3-22 

survival rate, 4-123, 4-125 

 9-7 
Chapter 9 Index 

 9-8 

Synthesis and Assessment Product (SAP), 2-45, 2-46, 2-53, 3-74, 3-77, 3-78, 3-79, 3-80, 3-84, 3-87, 4-3, 

4-41, 4-42, 4-45, 4-46, 4-51, 4- 69, 4-121, 4-155, 4-158, 4-159 

temperature, change in, 1-19, 2-24, 2-30, 2-33, 2-35, 2-37, 2-38, 2-39, 2-40, 2-47, 2-48, 2-50, 2-52, 2-53, 

2-54, 2-55, 3-3, 3-18, 3-22, 3-35, 3-60, 3-61, 3-62, 3-64, 3-70, 3-71, 3-72, 3-74, 3-76, 3-77, 3-78, 3-83, 

3-84, 3-95, 3-96, 3-97, 3-99, 3-101, 3-102, 3-104, 3-105, 3-106, 3-109, 3-110, 3-112, 3-129, 3-131, 4-

3, 4-40, 4-45, 4-55, 4-56, 4-57, 4-59, 4-61, 4-62, 4-63, 4-64, 4-65, 4-66, 4-68, 4-69, 4-71, 4-73, 4-74, 4-

75, 4-77, 4-78, 4-80, 4-83, 4-84, 4-87, 4-88, 4-98, 4-99, 4-100, 4-101, 4-103, 4-104, 4-106, 4-109, 4-

111, 4-115, 4-116, 4-117, 4-119, 4-120, 4-122, 4-123, 4-124, 4-125, 4-126, 4-127, 4-128, 4-130, 4-131, 

4-132, 4-133, 4-134, 4-135, 4-136, 4-137, 4-138, 4-140, 4-142, 4-143, 4-144, 4-145, 4-146, 4-147, 4-

149, 4-150, 4-151, 4-152, 4-153, 4-154, 4-156, 4-157, 4-158, 4-159, 4-160, 4-161, 4-162, 4-163, 4-164, 

4-167 

terrestrial ecosystems, 3-60, 3-116, 4-39, 4-85, 4-87, 4-88, 4-92, 4-95, 4-96, 4-97, 4-99, 4-102, 4-121 

tipping point, 1-13, 1-19, 1-22, 3-83, 3-84, 4-49, 4-105, 4-154, 4-155, 4-156, 4-157, 4-158, 4-161, 4-164, 

4-165 

United Nations Food and Agriculture Organization (FAO), 4-109, 4-117, 4-118 

U.S. Department of Energy (DOE), 2-1, 3-9, 3-23, 5-3, 5-4, 5-5 

U.S. Department of Health and Human Services (DHHS), 3-19, 3-20 

U.S. Department of Transportation (DOT), 1-1, 1-3, 1-4, 1-5, 1-7, 1-10, 1-11, 2-1, 2-2, 3-2, 3-3, 3-111, 3-

121, 3-123, 3-127, 4-1, 5-3, 5-4 

U.S. Environmental Protection Agency (EPA), 1-1, 1-2, 1-3, 1-4, 1-5, 1-6, 1-7, 1-8, 1-11, 1-12, 1-13, 1-

14, 1-16, 1-17, 1-18, 1-21, 1-22, 1-23, 1-24, 2-1, 2-2, 2-3, 2-4, 2-5, 2-8, 2-10, 2-11, 2-12, 2-14, 2-15, 2-

17, 2-18, 2-19, 2-20, 2-29, 2-31, 2-44, 2-45, 3-1, 3-3, 3-6, 3-11, 3-15, 3-16, 3-17, 3-18, 3-19, 3-20, 3-

21, 3-22, 3-23, 3-24, 3-25, 3-26, 3-29, 3-30, 3-31, 3-32, 3-33, 3-35, 3-36, 3-37, 3-42, 3-45, 3-60, 3-61, 

3-63, 3-64, 3-65, 3-67, 3-68, 3-69, 3-70, 3-71, 3-72, 3-73, 3-74, 3-75, 3-77, 3-78, 3-79, 3-84, 3-87, 3-

104, 3-106, 3-108, 3-111, 3-112, 3-113, 3-114, 3-116, 3-117, 3-118, 3-119, 3-120, 3-122, 3-125, 3-127, 

3-128, 3-129, 3-130, 3-131, 4-1, 4-3, 4-5, 4-11, 4-12, 4-17, 4-20, 4-25, 4-43, 4-54, 4-66, 4-67, 4-70, 4-

71, 4-72, 4-73, 4-74, 4-77, 4-78, 4-80, 4-83, 4-85, 4-90, 4-93, 4-95, 4-96, 4-97, 4-98, 4-99, 4-100, 4-

101, 4-102, 4-103, 4-104, 4-105, 4-107, 4-109, 4-110, 4-111, 4-112, 4-113, 4-114, 4-115, 4-116, 4-117, 

4-118, 4-119, 4-121, 4-123, 4-124, 4-125, 4-126, 4-127, 4-130, 4-131, 4-133, 4-134, 4-135, 4-136, 4-

137, 4-138, 4-139, 4-140, 4-142, 4-143, 4-144, 4-145, 4-146, 4-147, 4-148, 4-149, 4-150, 4-151, 4-152, 

4-154, 4-155, 4-156, 4-157, 4-159, 4-160, 4-161, 4-162, 4-164, 4-167, 4-168, 5-2, 5-3 

U.S. Geological Survey (USGS), 4-112 

Volpe model, 1-14, 1-15, 1-16, 1-17, 1-19, 1-20, 1-22, 2-2, 2-3, 2-4, 2-5, 2-9, 2-10, 2-11, 2-15, 2-17, 2-

19, 2-20, 2-21, 2-25, 3-3, 3-4, 3-5, 3-6, 3-8, 3-11, 3-12, 3-23, 3-25, 3-26, 3-30, 3-36, 3-37, 3-42, 3-45, 

3-75, 3-76, 3-77, 3-79, 3-80, 3-83, 3-84, 3-85, 3-90, 3-103, 3-105, 4-12, 4-17, 4-40, 4-45, 4-46, 4-49, 4-

50, 4-63 

World Meteorological Organization (WMO), 3-73 
 

 10-1 

Chapter 10 Responses to Public Comments 

The National Highway Traffic Safety Administration (NHTSA) submitted to the U.S. 

Environmental Protection Agency (EPA) a draft Environmental Impact Statement (DEIS) to disclose and 

analyze the potential environmental impacts of the new Corporate Average Fuel Economy (CAFE) 

standards for Model Years (MYs) 2012-2016 and reasonable alternative standards in the context of 

NHTSA’s CAFE Program pursuant to National Environmental Policy Act (NEPA) implementing 

regulations issued by Council of Environmental Quality (CEQ), U.S. Department of Transportation 

(DOT) Order 5610.1C, and NHTSA regulations. On September 25, 2009, NHTSA published in the 

Federal Register (FR) a Notice of Availability of its DEIS. NHTSA’s Notice of Availability also made 

public the date and location of a public hearing, and invited the public to participate at the hearing on 

October 30, 2009, in Washington, DC. The Notice of Availability of the DEIS triggered a 45-day public 

comment period. In accordance with CEQ NEPA implementing regulations, the public was invited to 

submit comments on the DEIS until November 9, 2009. NHTSA mailed approximately 300 copies of the 

DEIS to interested parties, including federal, state, and local officials and agencies; elected officials, 

environmental and public interest groups; Native American tribes; and other interested individuals, as 

listed in Chapter 8 of the DEIS. 

On Monday, September 28, 2009, EPA and NHTSA published in the Federal Register (FR) the 

Proposed Rulemaking To Establish Light-Duty Vehicle Greenhouse Gas Emission Standards and 

Corporate Average Fuel Economy Standards; Proposed Rule. The publication of the proposed rule 

opened a 60-day comment period and the public was invited to comment submit comments on or before 

November 27, 2009 by posting to either the EPA or NHTSA docket (EPA-HQ-OAR-2009-0472 or 

NHTSA-2009-0059). Comments submitted to the EPA docket were considered as comments submitted 

to the NHTSA docket and are under consideration for the final rule. A combined total of 11,356 public 

submissions were received on the NHTSA and EPA dockets. NHTSA and EPA also held three public 

hearings to receive comments on the rulemaking. NHTSA reviewed all of the rulemaking comments 

during preparation of this final Environmental Impact Statement (FEIS). Comments that were considered 

substantive to the EIS are summarized in Section 1.5.3. Comments received on the rulemaking will be 

responded to in the final rule. 

NHTSA received 11 written comments from interested stakeholders on the DEIS. In addition, 

during the public comment hearing in Washington, DC, three people provided oral statements. In this 

chapter of the FEIS, NHTSA has quoted substantive excerpts from these comments and responded to the 

comments received, as required by NEPA (40 CFR § 1503.4). 

NHTSA considered and evaluated all written and oral comments received during the public 

comment period in the preparation of this FEIS. NHTSA changed the EIS, in part, to respond to 

comments on the DEIS. NHTSA also changed the EIS as a result of updated information that became 

available after issuance of the DEIS. 

NHTSA appreciates the comments provided during development of the EIS. The transcript from 

the public hearing and written comments submitted to NHTSA are part of the administrative record and 

are available on the Federal Docket, which can be found on the Web at http://www.regulations.gov, 

Reference Docket No.: NHTSA-2009-0059. Written comments and the public hearing transcript can also 

be viewed in their entirety in Appendix G of this FEIS. Sections 10.1 through 10.6 provide comments on 

the DEIS and NHTSA’s responses to those comments. Table 10-1 lists the topics addressed in this 

chapter. Table 10-2 is an index of the comments from individuals, federal and state agencies, and private 

industry and the location in this chapter of NHTSA’s responses to those comments. 
Introduction Chapter 10 Responses to Public Comments 

 10-2 

Table 10-1 

Outline of Issues Raised in Public Comments on the DEIS 

10.1 PURPOSE AND NEED 

10.1.1 Purpose and Need Statement 

10.1.2 Public Review and Comment 

10.1.3 Agency Consultation 

10.1.4 Document Structure and Readability 

10.1.5 Joint Rulemaking and the National Program 

10.2 THE PROPOSED ACTION AND ALTERNATIVES 

10.2.1 Proposed Action 

10.2.2 Standards-setting 

10.2.2.1 Technological Feasibility 

10.2.3 Volpe Model 

10.2.3.1 General 

10.2.3.2 Vehicle Market Forecast 

10.2.3.3 Technology Assumptions 

10.2.3.4 Economic Assumptions 

10.2.3.4.1 Rebound Effect 

10.2.3.4.2 Social Cost of Carbon 

10.2.3.4.3 Military Costs 

10.2.3.4.4 Fuel Prices 

10.2.3.4.5 Consumer Demand 

10.2.3.4.6 Consumer Welfare 

10.2.3.4.7 Discount Rate 

10.2.4 Alternatives 

10.2.4.1 Environmentally Preferred Alternative 

10.2.4.2 No Action Alternative 

10.2.4.3 Suggestions for New Alternatives 

10.2.4.4 Adoption of More Aggressive Alternatives 

10.2.4.5 Sensitivity Analysis 

10.2.4.6 Comparison of Alternatives and Context of Analysis 

10.3 AFFECTED ENVIRONMENT AND ENVIRONMENTAL CONSEQUENCES 

10.3.1 Common Methodologies 

10.3.2 Air Quality 

10.3.2.1 Methodology 

10.3.2.2 Consequences 

10.3.3 Climate Tipping Points 

10.3.4 Other Potentially Affected Resource Areas 

10.3.4.1 Safety and Other Human Health Impacts 

10.3.4.2 Environmental Justice 

10.3.5 Unavoidable Impacts and Irreversible and Irretrievable Resource Commitment 

10.4 CUMULATIVE IMPACTS 

10.4.1 Reasonably Foreseeable Future Actions 

10.4.2 Climate Methodology 

10.5 MITIGATION

10.6 RULEMAKING 

10.6.1 Alternative Fuel Credits 

10.6.2 Regulatory Compliance Penalties 

10.6.3 Vehicle Performance Characteristics 

10.6.4 Cost and Benefits of the Proposed Rule 

10.6.5 Vehicle Classification 
Chapter 10 Responses to Public Comments Introduction 

 10-3 

Table 10-2 

Index of Comments from Individuals, Federal and State Agencies, and Private Industry 

Commenter 

Document 

ID 

Number a/ 

Location of Comment Excerpts 

and NHTSA’s Responses 

Federal Agencies 

Centers for Disease Control and 

Prevention 

0042 10.3.4.1 

Environmental Protection Agency, 

Susan Bromm 

0052.1 10.2.3.4.1 

USDA Agricultural Research Service, 

Facilities Division 

0043 Non-substantive 

State Agencies 

Tennessee Department of 

Transportation, Gerald Nicely 

0046 10.1.5, 10.2.1, 10.2.2.1, 10.2.4.6, 10.3.4.1, 10.6.5 

Missouri Department of Natural 

Resources, Dru Buntin 

0051.1 10.2.1, 10.2.3.4.1, 10.3.2.1, 10.3.2.2 

New York Department of 

Transportation, Stanley Gee 

0098 10.2.2, 10.2.3.4, 10.2.3.4.7, 10.2.4.3, 10.2.4.6, 10.5 

Industry 

Environmental Consultants of Michigan 0050.1 10.1.5, 10.2.4.3, 10.6.4 

Organizations 

Center for Biological Diversity, Public 

Citizen, and the Sierra Club, Brian 

Nowicki 

0053.1 10.1.3, 10.2.1, 10.2.2.1, 10.2.4.2, 10.2.4.3, 10.2.4.5, 

10.2.4.6, 10.3.3, 10.4.1, 10.4.2 

Sierra Club, Ann Mensikoff TRANS01 10.1.5, 10.2.4.2, 10.2.4.6, 10.4.1 

Public Citizen, Lena Pons TRANS02 10.1.4, 10.2.4.2, 10.2.4.6, 10.4.1 

Consumer Federation of America, Mark 

Cooper 

TRANS03 10.2.2, 10.2.3.4.1, 10.2.3.4.3, 10.2.3.4.5, 10.2.3.4.6, 

10.2.4.4, 10.2.4.6 

Individuals 

Gail Gilbert 0019 10.2.1, 10.3.1 

Douglas Long 0045 10.1.1, 10.2.1 

James Adcock 0049 10.1.2, 10.1.3, 10.2.1, 10.2.2, 10.2.2.1, 10.2.3.1, 

10.2.3.2, 10.2.3.3, 10.2.3.4, 10.2.3.4.2, 10.2.3.4.3, 

10.2.3.4.4, 10.2.3.4.5, 10.2.4.1, 10.3.4.1, 10.3.4.2, 

10.3.5, 10.6.1, 10.6.2, 10.6.3, 10.6.5 

_______________

a/ Documents may be found at http://www.regulations.gov, Reference Docket No.: NHTSA-2009-0059. 
10.1 Purpose and Need Chapter 10 Responses to Public Comments 

 10-4 

10.1 PURPOSE AND NEED 

10.1.1 Purpose and Need Statement 

Comments

Docket Number: 0045 

Organization: Individual 

Commenter: Douglas Long 

The American people need energy independence, more fuel efficient vehicles and cleaner air to breathe. 

To do that, President Barack Obama has introduced a plan to reduce vehicle fuel emissions and increase 

fuel mileage for vehicles in the model year 2012 to 2016. As an American citizen, tax payer and 

registered voter I want to establish that I support this plan by saying that we have to find alternative ways 

to conserve petroleum usage, either by improving fuel mileage from fossil fuel burning vehicles or by 

using energy sources such as electric or hydrogen alternatives, or by combining both technologies in 

future vehicles we will drive to achieve this goal. 

We need to allow our country to achieve the increased benefits of a single, nationwide program to reduce 

light duty vehicle Green House Gas (GHG) emissions and reduce the country's dependence on fossil fuels 

by improving fuel economy . . . . 

Oil prices have increased dramatically over the past several years, causing financial stress globally. In 

2008, the United States really felt the punch of high fuel costs. In some areas, the price of a gallon of 

gasoline rose to over $4.00 per gallon. . . . When gasoline prices go up, it causes a ripple effect through 

the transportation industry, food industry, retail sales, and the car manufacturing industry as examples. 

...After experiencing such high costs of fuel and feeling the economic effects, it's time the American 

public support our government’s stance in developing policies that will assist in decreasing air pollution 

and increasing fuel economy at the same time. 

Docket Number: 0044.1 

Organization: Anonymous 

Commenter: Anonymous

How will car dealers guarantee to consumers that cars will last and run when they themselves are not sure 

because this mile per gallon regulation has been pushed ahead by Obama. I see that these fuel standards 

are to help the issue of global warming. Global warming is only natural on earth, and will happen 

regardless of cars having an increase in car mileage. The President placing these new regulations on auto 

makers is not his job to do in my opinion. Why is the government just now proposing these new 

guidelines? The government has known about global warming for a long time-- why get in a hurry now? 

Having more fuel efficient cars will preserve more oil, but really how much oil is out there for us to use? 

While there are many theories out there about global warming and how much oil is available it is all a 

matter of opinion. 

This regulation has many positive aspects, but it should not have been pushed ahead by the government. 

Oil running out or global warming getting worse is not going to be rescued by moving up these 

regulations four years. The President should not have control over the miles per gallon on a vehicle and 

cause auto makers more money that will ultimately trickle down to consumers. 

* * * * * 
Chapter 10 Responses to Public Comments 10.1. Purpose and Need 

 10-5 

The new standards regarding miles per gallon on vehicles are a great benefit to society to help increase 

better fuel mileage, greenhouse emissions, and save consumers money. There are a lot more negatives to 

this new regulation than positives. As the prices of gas continue to raise it will help people still be able to 

afford the cars or trucks they want and have better gas mileage at the same time. People currently buy 

trucks although the gas mileage is not good and gas is very expensive, so these new standards may 

increase sales slightly. These new regulations will cost auto makers money, and this cost will then be 

placed on the consumer. The money consumers will save on gas may be eaten up with the increase in car 

prices because they have to be fuel efficient. Many fuel efficient cars are not American cars right now, so 

people currently have the option to buy fuel efficient without the government forcing each car dealer to 

have a more fuel efficient car. Some car dealers are just catching up on other regulations, so now having 

this regulation moved up four years will only require research and development teams to work harder and 

longer to make sure they meet the deadline. 

Docket Number: 0049 

Organization: Individual 

Commenter: James Adcock 

NHTSA ought to reduce the period of years covered by this regulation to a minimum in order to be able 

to respond to assumed forthcoming cap and trade treaties and legislation. For this reason we ask that the 

regulations be set for the minimum allowed number of years, not the maximum.

Response

Energy conservation is a core consideration of the agency in setting fuel economy standards. In 

proposing standards for MYs 2012-2016, NHTSA is acting pursuant to the Energy Policy and 

Conservation Act (EPCA), 49 U.S.C. § 32901 et seq., as amended by the Energy Independence and 

Security Act of 2007 (EISA), which requires the agency to set “maximum feasible” fuel economy 

standards for passenger cars and light trucks, taking into account four factors – technological feasibility, 

economic practicability, the effect of other standards of the Government on fuel economy, and the need of 

the Nation to conserve energy. Id. at § 32902(f). NHTSA has carefully balanced these considerations and 

believes that the proposed action represents the maximum feasible fuel economy standards. 

NHTSA recognizes that the proposed action alone will not avert climate change. A suite of many GHG 

emission reduction policies in numerous countries—across numerous sectors of their economies—would 

need to be implemented to mitigate climate change substantially. Nonetheless, EPCA does not limit 

NHTSA’s duty under the National Environmental Policy Act (NEPA) to consider the environmental 

impacts of its rule. This FEIS reflects NHTSA’s careful consideration of the environmental impacts of its 

proposed action and a reasonable range of alternatives. 

In response to the comment regarding the timeframe of the proposed action, we note that in enacting 

EISA, Congress granted NHTSA the discretion to set CAFE standards anywhere from 1 model year to 5 

model years at a time. See 49 U.S.C. § 32902(b)(3)(B). We believe setting standards five years at a time 

has benefits. By doing so, NHTSA promotes regulatory stability and provides significantly more lead 

time, which enables manufacturers to achieve and NHTSA to set more ambitious CAFE standards. If 

NHTSA waited until just 18 months before a model year to set standards for that model year, rather than 

setting standards for multiple years, the agency would have little ability to require the manufacturers to 

make more than relatively modest improvements to the products they would already have established for 

that year. Changing plans and making substantial improvements requires lead time. Due to the nature of 

automobile production, manufacturers generally set production and supply contracts years in advance. 

While modest changes can be made in 18 months, substantial changes would be impracticable in such a 
10.1 Purpose and Need Chapter 10 Responses to Public Comments 

 10-6 

short time. Because NHTSA believes that the best approach is to set CAFE standards for 5 model years, 

NHTSA has proposed standards for MYs 2012-2016. 

10.1.2 Public Review and Comment 

Comments 

Docket Number: 0049 

Organization: Individual 

Commenter: James Adcock

We wish to express up front great disappointment and frustration that the NAS 2009 update was not made 

available in time for the comment period of the DEIS. We believe this is inappropriate, given that 

Congress specifically called for NAS input to enlighten these controversial issues. . . . Further the DEIS 

and the reviews of the DEIS do not incorporate the Congressionally called for 2009 revision of the NAS 

document. We believe the clock should be stopped until the NAS 2009 report has been delivered and 

NHTSA and the DEIS reviewers have had a chance to respond. 

* * * * * 

While NAS 2002 valued reducing the risk of GHG highly, NHTSA and EPA list GHG as by far a weaker 

reason to increase CAFE. EPA and NHTSA need to explain why they are ignoring NAS in these matters. 

* * * * * 

Given NHTSA's great reliance on IPCC we suggest that NHTSA needs to formally invite IPCC to 

comment on NHTSA's chosen levels of CAFE stringency. 

Response 

In accordance with EPCA, as amended by EISA, NHTSA must go forward with setting fuel economy 

standards as directed by Congress. Because of the requirement to set standards for MY 2012 by the end 

of March 2010, the agency cannot wait for the National Academy of Sciences (NAS) report. See 49 

U.S.C. § 32902(a) (requiring the agency to set CAFE standards for any model year at least 18 months in 

advance of the start of that model year). For both the joint Notice of Proposed Rulemaking (NPRM) and 

for the alternatives described in this FEIS, NHTSA has a considerable body of information, including the 

comments it received on the NPRM. 

However, as explained in the joint NPRM, NHTSA plans to continue to work with the National Academy 

of Sciences to update the list of fuel-saving technologies and their associated costs and effectiveness 

numbers on a 5-year interval. To ensure that the combined passenger car and light truck fleets meet the 

statutorily mandated floor of 35 mpg in 2020, NHTSA will continue to assess whether the industry is on 

track during the 5 years covered by this rulemaking. 

With regard to IPCC, NHTSA has provided multiple opportunities for interested parties to be heard. See

DEIS Section 1.5; FEIS Section 1.5. On April 1, 2009, NHTSA informed the public through notice in the 

Federal Register regarding its plans to prepare an EIS. The April Notice initiated scoping1

 by requesting 

public input on the scope of the environmental analysis to be conducted. See 74 Federal Register (FR) 

14857. On September 25, 2009, EPA published a Notice of Availability of the DEIS, which reflected our 

 

1 Scoping, as defined under NEPA, is an early and open process for determining the scope of issues to be addressed 

in an EIS and for identifying the significant issues related to a proposed action. See 40 CFR § 1501.7.
Chapter 10 Responses to Public Comments 10.1. Purpose and Need 

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review and consideration of public scoping comments and the studies suggested by the commenters. See

74 FR 48951. Also on September 25, 2009, NHTSA published its own Notice of Availability of a Draft 

Environmental Impact Statement (DEIS) for New Corporate Average Fuel Economy Standards and 

Notice of Public Hearing. See 74 FR 48894. NHTSA’s notice instructed the public where they could find 

the DEIS, invited comment on the DEIS, and announced details concerning how interested members of 

the public could participate in an October 30, 2009 public hearing on the DEIS. 

On September 28, 2009, NHTSA and EPA published a joint NPRM, with NHTSA proposing CAFE 

standards, and EPA proposing GHG standards for MYs 2012-2016 light-duty vehicles. See 74 FR 49454. 

The NPRM informed the public that an EIS process was underway, and sought comments on the proposed 

rule. After issuing the DEIS, NHTSA provided a 45-day public-comment period, which closed on 

November 9, 2009. On October 30, 2009, before the close of the comment period, NHTSA held a public 

hearing on the DEIS in Washington, DC, during which interested parties were invited to testify. 

Like the rest of the public, the Intergovernmental Panel on Climate Change (IPCC) was alerted to 

NHTSA’s development of an EIS and was free to comment at any of the stages noted above. 

10.1.3 Agency Consultation 

Comments 

Docket Number: 0053.1 

Organization: Center for Biological Diversity, Public Citizen, and the Sierra Club 

Commenter: Brian Nowicki 

NHTSA must complete an Endangered Species Act Section 7 Consultation to ensure that its action will 

not jeopardize or adversely modify the critical habitat of any species listed as “threatened” or 

“endangered.” 

The DEIS is non-committal with regard to its responsibilities under the federal Endangered Species Act to 

consult with U.S. Fish and Wildlife Service and National Oceanic and Atmospheric Administration 

Fisheries Service to ensure that this action will not jeopardize or adversely modify the critical habitat of 

any species listed as “threatened” or “endangered.” “NHTSA is also currently exploring its obligations 

under Section 7 of the Endangered Species Act with U.S. Fish and Wildlife Service and National Oceanic 

and Atmospheric Administration Fisheries Service.” DEIS at 1-11. 

Section 4.5 of the DEIS includes a long discussion of the likely impacts of climate change on plant and 

animal species, including species protected under the federal Endangered Species Act. “Global average 

temperature increases in excess of 1.5 to 2.5 °C (2.7 to 4.5 °F) are statistically likely to threaten 20 to 30 

percent of plant and animal species with extinction by 2100 (EPA 2009b, GCRP et al. 2009).” DEIS at 4-

110. In addition, Section 3.4 includes a discussion of the effects on climate change that are likely to result 

from the rule. 

Congress enacted the Endangered Species Act (“ESA”) to conserve endangered and threatened species 

and the ecosystems upon which they depend. 16 U.S.C. § 1531(b). The Supreme Court’s review of the 

ESA’s “language, history, and structure” convinced the Court “beyond a doubt” that “Congress intended 

endangered species to be afforded the highest of priorities.” Tennessee Valley Authority v. Hill, 437 U.S. 

153, 174 (1978). . . . Once a species is listed under the ESA, Section 7 requires all federal agencies to 

“insure” that their actions neither “jeopardize the continued existence” of any listed species nor “result in 

the destruction or adverse modification” of its “critical habitat.” 16 U.S.C. § 1536(a)(2). In addition, the 

“take” of listed species is generally prohibited. Id. at § 1538(a); 50 C.F.R. § 17.31(a). “Take” means “to 
10.1 Purpose and Need Chapter 10 Responses to Public Comments 

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harass, harm, pursue, hunt, shoot, wound, kill, trap, capture, or collect, or to attempt to engage in any such 

conduct.” 16 U.S.C. § 1532(19). The Services may, however, permit “incidental” take on a case-by-case 

basis if it finds, among other things, that such take will be minimized and mitigated and that such take 

will not “appreciably reduce the likelihood of survival and recovery of the species.” Id. at § 1539(a). 

Section 7 consultation is required for “any action [that] may affect listed species or critical habitat.” 50 

C.F.R. § 402.14. Agency “action” is defined in the ESA’s implementing regulations to include “all 

activities or programs of any kind authorized, funded, or carried out, in whole or in part, by Federal 

agencies in the United States or upon the high seas. Examples include, but are not limited to: (a) actions 

intended to conserve listed species or their habitat; (b) the promulgation of regulations; (c) the granting of 

licenses, contracts, leases, easements, rights-of-way, permits, or grants-in-aid; or (d) actions directly or 

indirectly causing modifications to the land, water, or air.” 50 C.F.R. § 402.02. This regulatory definition 

of “action” clearly encompasses NHTSA’s rulemaking, since the emissions from the regulated 

automobiles unquestionably will cause “modification to the land, water, or air.” The U.S. Fish and 

Wildlife Service’s and National Marine Fisheries Service’s Consultation Handbook, Procedures for 

Conducting Consultation and Conference Activities under Section 7 of the Endangered Species Act 

(March 1998) explains the above terms and definitions. There can also be no question that the enormous 

volume of direct, indirect, and cumulative emissions from the regulated vehicles “may affect” listed 

species, and therefore the NHTSA must consult. 

NHTSA’s rulemaking will impact species listed as threatened and endangered in several ways, yet 

NHTSA has failed to initiate the required Section 7 consultations with [U.S. Fish and Wildlife Service 

and NOAA Fisheries] on its impact. NHSTA must initiate and complete the required Section 7 

consultations on the rulemaking, or it may be held liable for take of listed species from the impacts of its 

action, including increased greenhouse gas emissions and other emissions such as NOx. On May 15, 

2008, the U.S. Fish and Wildlife Service listed the polar bear as a threatened species throughout is range 

due to global warming. Endangered and Threatened Wildlife and Plants, Determination of Threatened 

Status for the Polar Bear (Ursus maritimus) Throughout its Range, 73 Fed. Reg. 28212-28303 (May 15, 

2008). NHTSA must consult on the impact of its rulemaking, and its proposal to set fuel economy 

standards far below what is technologically achievable, on the polar bear. 

On May 9, 2006, the National Marine Fisheries Service listed the staghorn and elkhorn corals as 

threatened due in part to increasing ocean temperature and ocean acidification due to anthropogenic 

greenhouse emissions. 71 Fed. Reg. 26852. NHTSA must consult on the impact of its rulemaking on 

these coral species. NHTSA must also consult on the impact of its rulemaking on the polar bear’s and the 

corals’ critical habitat, once such habitat is designated. 

Global warming was cited by the U.S. Fish and Wildlife Service in its critical habitat rulemakings for the 

Quino Checkerspot and Bay Checkerspot butterflies. See 73 Fed. Reg. 3328-3373 and 72 Fed. Reg. 

48178-48218. NHTSA must consult on the impact of its rulemaking on these species and their critical 

habitat. 

NHTSA must not limit its consultation, however, to species like the polar bear, corals, and checkerspot 

butterflies for which anthropogenic greenhouse emissions were cited as a reason for listing or as an 

impact in the listing or critical habitat rules. The Center has identified 143 listed species for which a 

recovery plan has been adopted that specifically identifies climate change or a projected impact of climate 

change as a direct or indirect threat to the species, as a critical impact to be mitigated, as a critical issue to 

be monitored, and/or as a component of the recovery criteria. See Exhibit A. This is clear evidence that 

the NHTSA’s rulemaking “may affect” these species. The NHTSA must consult on the impact of its 

action on all listed species which may be affected. 
Chapter 10 Responses to Public Comments 10.1. Purpose and Need 

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The direct, indirect, and cumulative impacts of setting fuel economy standards for all cars and light trucks 

nationally are extraordinarily significant, and therefore a large number of species may be implicated. 

Where, as here, NHTSA’s rulemaking is national in scope, NHTSA should conduct a nationally focused 

consultation. . . . If anything, a nationally focused consultation will provide the opportunity to most 

efficiently analyze the impact of the rulemaking on species and groups of species. 

The rulemaking will impact listed species in ways beyond global warming and ocean acidification. For 

example, vehicles are a primary source of excess nitrogen in the environment. Excess nitrogen contributes 

to major environmental problems including reduced water quality, eutrophication of estuaries, nitrateinduced toxic effects on freshwater biota, changes in plant community composition, disruptions in 

nutrient cycling, and increased emissions from soil of nitrogenous greenhouse gases. Nitrogen deposition 

therefore impacts species listed under the Endangered Species Act in a number of ways. [Citation 

omitted]. 

Docket Number: 0049 

Organization: Individual 

Commenter: James Adcock

DEIS does not adequately describe impact of CAFE decisions on West Coast species extinction risks, 

including the Polar Bear, Pacific Northwest Salmon, Mtn Pika, Eastern Pacific Northwest Native Pine 

Species, etc . . . . 

DEIS fails to explain how NHTSA and EPA avoid responsibility to ESA by monetizing SCC - and then 

ignoring the value of species extinction in that estimate of SCC! We believe SCC needs to include a 

valuation of species extinction and explanation of how the agencies reconcile these particular choices 

with ESA. 

Response

Under Section 7(a)(2) of the Endangered Species Act (ESA) federal agencies must ensure that actions 

they authorize, fund, or carry out are “not likely to jeopardize” federally listed threatened or endangered 

species or result in the destruction or adverse modification of the designated critical habitat of these 

species. 16 U.S.C. § 1536(a)(2). If a federal agency determines that an agency action may affect a listed 

species or designated critical habitat, it must initiate consultation with the appropriate Service – the U.S. 

Fish and Wildlife Service (FWS) of the Department of the Interior and/ or National Oceanic and 

Atmospheric Administration’s National Marine Fisheries Service (NOAA Fisheries Service) of the 

Department of Commerce, depending on the species involved—in order to ensure that the action is not 

likely to jeopardize the species or destroy or adversely modify designated critical habitat. See 50 CFR § 

402.14. Under this standard, the federal agency taking action evaluates the possible effects of its action 

and determines whether to initiate consultation. See 51 FR 19926, 19949 (Jun. 3, 1986). 

NHTSA has reviewed applicable ESA regulations, case law, guidance, and rulings in assessing the 

potential for impacts to threatened and endangered species from the proposed CAFE standards. NHTSA 

believes that the agency’s action of setting CAFE standards, which will result in nationwide fuel savings 

and, consequently, emissions reductions from what would otherwise occur in the absence of the agency’s 

CAFE standards, does not require consultation with NOAA Fisheries Service or the FWS under section 

7(a)(2) of the ESA. For additional discussion of the agency’s rationale, see Section 3.5.2.1.4 of the FEIS. 

Accordingly, NHTSA has concluded its review of this action under Section 7 of the ESA. 
10.1 Purpose and Need Chapter 10 Responses to Public Comments 

 10-10 

10.1.4 Document Structure and Readability 

Comments 

Docket Number: TRANS02 

Organization: Public Citizen 

Commenter: Lena Pons 

The agency has not produced a document that adequately informs the public. The DEIS is a long, 

complex document that assumes a great deal of familiarity with fuel economy standards, transportation 

energy policy, and climate change policy. For a layperson, the document is inaccessible and daunting. 

However, the agency is charged with producing a document that is written in plain language and written 

so that decision-makers and the public can readily understand it. The complexity of the rulemaking, the 

process by which the agency sets the standards, the coordination of multiple agencies in developing the 

standards and the global nature of impacts considered in the document ensure that even the best effort to 

present the impacts of the range of alternatives would not be considered plain language by many. 

In order to meaningfully talk about the range of alternatives, some familiarity of the reader with the 

subject matter must be assumed. And we do not suggest that the agency make no mention of technical 

elements in its analysis in presenting environmental impacts. However, presenting the impacts in a 

context that is relatable and relevant to the reader would significantly improve the usefulness of the 

document, guiding decision-making and informing the public. 

Response 

NHTSA has worked to make this EIS reader-friendly. As the commenter recognized, however, the 

extreme complexity of the subject matter warrants significant technical discussion. In response to this 

comment, NHTSA has revised the Summary to focus on communicating the importance of the impacts of 

the agency’s action in a non-technical, and average-reader-friendly way. This summary contains (1) a 

general discussion of the greenhouse effect and climate change, (2) a summary of impacts expected with 

climate change, (3) a brief discussion of the direct, indirect, and cumulative effects of alternatives on 

GHG emissions as well as atmospheric CO2 concentration, global mean surface temperature, sea-level 

rise, and precipitation, (4) graphical depictions of impacts of the agency action on U.S. light-duty vehicle 

fleet emissions, and (5) additional context to help decisionmakers and the public understand the 

differences among the alternatives and how this action fits into larger U.S. GHG reduction goals. 

NHTSA has formatted the Summary to make use of layout and fonts that are easier to read. 

For ease of access, in addition to the Summary included with the complete EIS, NHTSA will also publish 

the Summary on its website as a stand-alone document. We believe readers will find this new summary 

helpful in their understanding of the FEIS. 

10.1.5 Joint Rulemaking and the National Program 

Comments

Docket Number: 0046 

Organization: Tennessee Department of Transportation 

Commenter: Gerald Nicely 

EPA and NHTSA jointly proposed this rule establishing a national program that would improve fuel 

economy and reduce greenhouse gas emissions. The proposed rule contains two separate sets of standards 
Chapter 10 Responses to Public Comments 10.1. Purpose and Need 

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applying to passenger cars, light-duty trucks and medium-duty passenger vehicles, covering model years 

2012 through 2016. TDOT applauds this harmonized approach that will align the CAFE standards and 

EPA's greenhouse gas regulations. It makes sense to develop these regulations in a coordinated fashion, 

and this alignment of regulations affecting automobiles should provide significant benefits. TDOT hopes 

the two agencies will continue to work together to improve the efficiency, safety and environmental 

performance of motor vehicles sold in the United States. 

* * * * * 

Creating a strong national program will meet the president's commitment, provide U.S. consumers with 

clean vehicle choices, and allow the struggling auto industry to emerge as the model for a clean energy 

economy. The proposed rule to strengthen the CAFE standards is a strong step forward for fuel economy, 

and one of the centerpieces of a sound national energy policy. 

Docket Number: 0050.1 

Organization: Environmental Consultants of Michigan 

Commenter: 

In setting up separate rules for tailpipe greenhouse gases and fuel economy these two federal agencies 

establish unique sets of flexibilities, credit schemes, penalties, and administrative compliance 

requirements. Inevitably one of these standards will be more stringent compared to the other for 

individual manufacturers. Situations will arise wherein a corporation or individual will fail both sets of 

requirements for a single offense. This is unprecedented, unnecessary, overly bureaucratic, redundant and 

a violation of both common law and the Fifth Amendment to the U. S. Constitution which prohibits the 

government from prosecuting more than one time for a single offense and from imposing more than one 

punishment for a single offense. [Citations omitted]. 

Nowhere is this multiple punishment for a single offense more evident than in the case of a manufacturer 

electing to pay a statutorily permitted fine in lieu of changing their business strategy to meet a CAFE 

standard. BMW, Daimler, Porsche, Tata and VW among other companies routinely pay CAFE fines. 

Under the proposal, after paying the normal CAFE fine, these companies would be subject to a separate 

action wherein EPA voids ab initio the certificate of conformity necessary to sell a motor vehicle. Not 

only does this proposal impose more than one punishment for a single offense, but this administrative 

action renders the statute permitting the paying of CAFE fines in lieu of meeting the standard meaningless 

as no company would risk the administrative penalties imposed for selling a vehicle without a certificate 

of conformity. [Citations omitted]. 

Depending on the compliance strategy adopted by a manufacturer, one of these two standards will be 

more stringent. For example, the Alternative Motor Fuel Act encourages automobile manufacturers to 

produce flexible fueled vehicles that can operate on more than one fuel. CAFE laws provide an incentive 

to produce these vehicles. Under the proposed rule, the EPA standard would impose barriers to the 

production of these vehicles negating the counting of these vehicles for compliance with the GHG 

standard. On the flip side, the EPA proposal selects other technologies to incentivize, including "advanced 

technology" credits wherein the qualifying vehicles are given a multiplier of 1.2 to 2.0 for each vehicle 

produced, air conditioning credits and credits for qualifying "off-cycle" technologies. These credits do not 

apply to CAFE compliance. 

EPA argues that the Supreme Court required the Agency to determine if greenhouse emissions contribute 

to health and welfare concerns and if so to take appropriate action. The Agency on April 17, 2009 signed 

The Proposed Endangerment and Cause or Contribute Findings for Greenhouse Gases under the Clean 

Air Act. After making this finding, EPA has arbitrarily and capriciously jumped to the conclusion that the 
10.1 Purpose and Need Chapter 10 Responses to Public Comments 

 10-12 

only recourse is to regulate tailpipe GHG emissions in duplication of the NHTSA regulation of vehicle 

fuel economy required under EISA. [Citations omitted]. 

Arbitrarily jumping to the conclusion that tailpipe standards are necessary is a misreading of the decision 

handed down by the Supreme Court and a complete abdication of any objective policy review. 

* * * * * 

Thus there will continue to be a single National Program with no need for separate state standards with or 

without a duplicative national tailpipe greenhouse gas standard. 

Docket Number: TRANS01 

Organization: Sierra Club 

Commenter: Ann Mensikoff 

As Congress continues to debate climate legislation, NHTSA along with EPA are taking perhaps what is 

the most significant step this administration can take to curb global warning and saving oil. 

Response

NHTSA must issue a CAFE standard under EPCA, as amended by EISA. For each future model year, 

EPCA requires that NHTSA establish standards at “the maximum feasible average fuel economy level 

that it decides the manufacturers can achieve in that model year,” based on the agency's consideration of 

four statutory factors: technological feasibility, economic practicability, the effect of other standards of 

the Government on fuel economy, and the need of the Nation to conserve energy. See 49 U.S.C. §§ 

32902(a), 32902(f). 

In addition, section 202(a)(1) of the Clean Air Act states that “the Administrator shall by regulation 

prescribe (and from time to time revise) . . . standards applicable to the emission of any air pollutant from 

any class or classes of new motor vehicles . . . which in his judgment cause, or contribute to, air pollution 

which may reasonably be anticipated to endanger public health or welfare.” 42 U.S.C. § 7521(a). If 

EPA makes the appropriate endangerment and cause or contribute findings, then section 202(a) 

authorizes EPA to issue standards applicable to emissions of those pollutants. In Massachusetts v. EPA, 

the Supreme Court directed the EPA to determine whether or not emissions from new motor vehicles 

cause or contribute to air pollution which may reasonably be anticipated to endanger public health or 

welfare, or whether the science is too uncertain to make a reasoned decision. 549 U.S. 497, 532-35 

(2007). The Court explained that EPA’s mandate to protect public health and welfare is wholly 

independent from NHTSA’s mandate to promote energy efficiency, but there is no reason to think the two 

agencies cannot both administer their obligations and yet avoid inconsistency. Massachusetts v. EPA, 

549 U.S. at 532. 

On December 15, 2009, EPA finalized its finding that CO2 (one of six atmospheric GHGs) endangers the 

public health and welfare, and is therefore a CAA pollutant for purposes of vehicle GHG emissions. See

74 FR 66496; see also the EPA Endangerment Finding and Technical Support Document for a detailed 

discussion of these findings. Because EPA has issued both what is known as an “endangerment finding” 

and a “cause and contribute finding,” it must now set emissions standards under Title II of the CAA, as 

described above. 

NHTSA does not agree with the commenter’s view that the National Program could lead to “multiple 

punishment for a single offense” in violation of the Fifth Amendment. A single act can violate different 
Chapter 10 Responses to Public Comments 10.1. Purpose and Need 

 10-13 

statutes, and if so, may be appropriately penalized. Violations of EPCA and the CAA are proven 

differently, and so would constitute separately punishable offenses. 

Because both NHTSA and EPA have statutory obligations to regulate the related standards of vehicle fuel 

economy and CO2 and other vehicle GHG emissions, President Obama announced the National Fuel 

Efficiency Policy on May 19, 2009.2

 In the announcement of this national policy, the President directed 

that the two agencies establish consistent, harmonized, and streamlined requirements that would improve 

fuel economy and reduce GHG emissions for all new passenger cars and light trucks sold in the United 

States. The agencies have reasonably done so in this joint rulemaking, based on their respective statutory 

authorities. 

Finally, the statement that the proposed treatment of FFV credits under the joint proposal impermissibly 

eliminates the incentive in EISA to produce FFVs is incorrect. In fact, the proposal states that because 

FFV credits are part of manufacturers’ compliance strategy in the initial years of the National Program, 

EPA will accept the FFV credits under EISA for purposes of the CAA program through and including MY 

2015 vehicles in order to provide these manufacturers sufficient lead time. See 74 FR at 49531. 

Thereafter, these vehicles would be evaluated based on their actual performance, in keeping with the 

overall requirement of CAA section 202(a) to require achievable reductions of air pollutants emitted by 

motor vehicles at reasonable cost. The requirement is independent of the EPCA/EISA treatment of FFVs, 

and therefore EPA is not bound to follow that scheme. See Massachusetts v. EPA, 549 U.S. at 532 (EPA 

obligation to protect the public health and welfare are “wholly independent of DOT’s mandate to 

promote energy efficiency”). 

 

2 President Obama Announces National Fuel Efficiency Policy, The White House, May 19, 2009. Available at: 

http://www.whitehouse.gov/the_press_office/President-Obama-Announces-National-Fuel-Efficiency-Policy/ (last 

accessed Dec. 28, 2009). Remarks by the President on National Fuel Efficiency Standards, The White House, May 

19, 2009. Available at: http://www.whitehouse.gov/the_press_office/Remarks-by-the-President-on-national-fuelefficiency-standards/ (last accessed Dec. 28, 2009). 
10.2 The Proposed Action and Alternatives Chapter 10 Responses to Public Comments 

 10-14 

10.2 THE PROPOSED ACTION AND ALTERNATIVES 

10.2.1 Proposed Action 

Comments 

Docket Number: 0019 

Organization: Individual 

Commenter: Gail Gilbert 

These standards are a big step forward and I urge you to keep them strong to ensure that we reap their full 

benefit. 

Docket Number: 0045 

Organization: Individual 

Commenter: Douglas Long 

This proposal would establish regulations that would protect the American people by enforcing car 

manufacturers to produce even cleaner and more fuel efficient vehicles than ever before. Reducing GHGs 

would serve to protect the environment in which all humans and animals live. Increasing fuel mileage 

would allow the U.S. dollar to go further by Americans not having to spend it at the gas stations so often. 

These two positive attributes of this proposal only leave me with a belief that I have to support. Cleaner 

more fuel efficient vehicles are something the American people need. 

* * * * * 

The proposal is intended to enhance vehicle fuel economy, while protecting motor vehicle safety and 

being mindful of the risk of harm to the overall United States economy. Let it be known, I support this 

proposal. 

Docket Number: 0046 

Organization: Tennessee Department of Transportation 

Commenter: Gerald Nicely 

I would like to begin by commending the National Highway Traffic Safety Administration (NHTSA) for 

developing rules that meet Congress' 2007 mandate for tighter CAFE standards, and to apply those 

standards in 2016 well in advance of the 2020 Congressional mandate. 

Docket Number: 0051.1 

Organization: Missouri Department of Natural Resources 

Commenter: Dru Buntin 

Overall, the Department supports the proposal by the National Highway Traffic Safety Administration 

(NHTSA) and Environmental Protection Agency (EPA) to implement a more stringent CAFE standard 

than the no additional action alternative to reducing emissions from mobile sources. 
Chapter 10 Responses to Public Comments 10.2 The Proposed Action and Alternatives 

 10-15 

Docket Number: 0053.1 

Organization: Center for Biological Diversity, Public Citizen, and the Sierra Club 

Commenter: Brian Nowicki 

Setting fuel economy standards for all cars and light trucks nationally is one of the single most important 

actions that the government can take to reduce greenhouse emissions. NHTSA should correct the flaws 

[we have] identified . . . in the EPCA and NEPA analyses, and promptly propose and then finalize new 

fuel economy levels which actually achieve the “maximum feasible” level. 

Docket Number: 0049

Organization: Individual 

Commenter: James Adcock 

In general we believe EPA and NHTSA are offering way too many loopholes, credits, and footprint 

“gaming” opportunities to make for an effective regulation actually reducing fuel consumption. 

* * * * * 

We suggest that NHTSA needs to compare how the US is lagging behind on fuel economy compared to 

the rest of the world in order to determine whether or not US fuel economy forms a “gating function” for 

the success or failure of US diplomatic climate change negotiations and whether a greater show of “good 

faith” on the part of the US isn’t necessary in order for other nations to take or negotiations on climate 

change seriously. 

* * * * * 

We believe that NHTSA should set higher MPG CAFE targets leading to lower environmental damage. 

Response 

Individual commenters noted that the standards were “a big step forward,” that they would ensure the 

production of “cleaner and more fuel efficient vehicles than ever before,” and that they significantly 

speed up the timetable set by Congress in EISA requiring the U.S. fleet to reach a combined average 

CAFE standard of 35 mpg in MY 2020, although some thought the agency should set higher CAFE 

standards. 

One commenter suggested that, while a national standard for fuel economy was of great importance to 

the reduction of GHG emissions, NHTSA should finalize fuel economy levels which achieve the 

“maximum feasible” level. NHTSA believes that the preferred alternative achieves the maximum feasible 

average fuel economy level as required by EPCA, 49 U.S.C. § 32902(a), considering the four statutory 

factors (technological feasibility, economic practicability, the effect of other standards of the Government 

on fuel economy, and the need of the Nation to conserve energy). 

Finally, we note that NHTSA’s action is to set maximum feasible CAFE standards for vehicles for sale in 

the United States, based on the four factors noted above, not to establish a “gating function” for other 

efforts. 
10.2 The Proposed Action and Alternatives Chapter 10 Responses to Public Comments 

 10-16 

10.2.2 Standards-setting 

Comments 

Docket Number: 0049 

Organization: Individual 

Commenter: James Adcock 

The assumptions for fuel stringency set for 2012 have already been met by Mfg by 2010, indicating 2 

years loss without reason. 

* * * * * 

Do the proposed standards "increase ratably"? No: the standards DO NOT increase ratably if the required 

level of fuel economy for 2012 has already been accomplished by Mfgs by 2010, leading to two years 

where the Mfgs do not have to do anything, or alternatively that they can use to "get ahead in the game" 

which in turn will lead to greater effective stringency in the 2016 timeframe. 

Docket Number: TRANS03 

Organization: Consumer Federation of America 

Commenter: Mark Cooper 

First, we must balance the goals of the underlying statutes: technical feasibility, economic practicability -- 

which actually appear in both statutes almost identically -- the need to conserve energy -- which appears 

in NHTSA's governing statute -- and the need to reduce the environmental harm of gasoline consumption, 

which is obviously the purpose of the Clean Air Act being implemented. Reconciling those four goals we 

believe is achieved by setting the standard at the halfway point between the maximum economic benefit 

and the maximum practicable environmental benefit. We call this the 50/50 approach in the 2008 

proceeding. We think that's the way you resolve the statutes. 

Docket Number: 0098 

Organization: New York Department of Transportation 

Commenter: Stanley Gee 

Since the proposed standards assume a 10% rebound effect on future vehicle miles traveled, and the DEIS 

assumes that VMT is projected to increase significantly over the next 10-50 years, it is imperative that 

fuel economy standards be set at a level that is as stringent as the broadly defined "four factors" allow. 

Thus, the proposed CAFE standards should not simply rely on current market trends. It is appropriate for 

the standards to decrease oil dependence to the greatest extent possible with technology-forcing standards. 

* * * * * 

The proposal appears to place a greater emphasis on economic practicality than it places on the other 

statutory factors that NHTSA is required to consider in setting the CAFE standards. 

Response

The agency does not agree with the comment that manufacturers will already meet the MY 2012 CAFE 

standards by 2010. With attribute-based standards, which are required by EPCA as amended by EISA, 

each manufacturer has its own fuel economy requirement in each model year based on the mix of vehicles 

it produces and where those vehicles fall along the footprint target curves. A manufacturer need not meet 
Chapter 10 Responses to Public Comments 10.2 The Proposed Action and Alternatives 

 10-17 

the target for every single vehicle it produces, but may distribute its compliance burden among the 

vehicles it produces through averaging. Thus, a manufacturer may produce vehicles that are above their 

individual target fuel economy values at that point on the footprint curve, while also producing other 

vehicles that are below their target values, as long as the manufacturer’s fleet averages out to the 

harmonic average required of that manufacturer based on its vehicle mix. While NHTSA agrees, 

therefore, that there are individual vehicles that may exceed the overall proposed MY 2012 passenger car 

fleet-wide average of 33.4 miles per gallon in MY 2010, the fleet as a whole is unlikely to exceed that 

level in MY 2012, based on Volpe model simulation and analysis. 

EISA requires ratable increases in CAFE standards starting in MY 2011, which the agency interprets to 

mean, in combination with the requirement to set the standards for each model year at the level 

determined to be the maximum feasible level that manufacturers can achieve for that model year, that the 

annual increases should not be disproportionately large or small in relation to each other. See Proposed 

Rulemaking to Establish Light-Duty Vehicle Greenhouse Gas Emission Standards and Corporate 

Average Fuel Economy Standards, 74 FR 49454, 49463, 49635 (Sep. 28, 2009). The proposed standards 

substantially meet this condition. In any case, we estimate that achieved CAFE levels for both passenger 

cars and light trucks (and thus their combined average fuel economy levels) will increase each year from 

2012-2016, at least for the industry as a whole if not for each manufacturer individually.

Consumer Federation of America suggests a “50/50 approach in the 2008 proceeding,” where the 

agencies would set the standard “at the halfway point between the maximum economic benefit and the 

maximum practicable environmental benefit” by taking into account four factors: technical feasibility, 

economic practicability, the need to conserve energy, and the need to reduce the environmental harm of 

gasoline consumption. The agencies have worked closely to ensure that their respective programs work 

in a coordinated fashion and provide regulatory compatibility that allows auto manufacturers to build a 

single national light-duty fleet that complies with both the GHG and the EPCA-based CAFE standards. 

NHTSA’s action falls under the mandate of EPCA, rather than the Clean Air Act, and the agency’s action 

must be guided by the requirements and factors contained in our statute. 

EPCA requires the Secretary of Transportation to establish average fuel economy standards for each 

model year and to set them at “the maximum feasible average fuel economy level that the Secretary 

decides the manufacturers can achieve in that model year.” 49 U.S.C. § 32902(a). When setting 

“maximum feasible” fuel economy standards, the Secretary is required to “consider technological 

feasibility, economic practicability, the effect of other motor vehicle standards of the Government on fuel 

economy, and the need of the United States to conserve energy.” 49 U.S.C. § 32902(f). NHTSA has 

carefully balanced the statutory factors and believes that the stringency levels of the Preferred Alternative 

(Alternative 4) most reasonably reflect these requirements. For further explanation of NHTSA’s 

balancing of the statutory factors, see section IV.F of the NPRM. That said, the fundamental purpose of 

this EIS is to evaluate the environmental impacts of the alternatives to inform the decisionmaker, so that 

these impacts can be taken into account. 

10.2.2.1 Technological Feasibility 

Comments 

Docket Number: 0046 

Organization: Tennessee Department of Transportation 

Commenter: Gerald Nicely 

The standards can be met through the use of available technologies, such as improvements in energy 

efficiency, transmissions and tires as well as in air conditioning systems. Some critics believe that 
10.2 The Proposed Action and Alternatives Chapter 10 Responses to Public Comments 

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technologies exist to meet even tighter standards, and argue that NHTSA should have proposed tighter 

standards that would have forced new advances in technology. As they are, these standards are still likely 

to promote more widespread use of advanced fuel-saving technologies like hybrid vehicles and clean 

diesel engines. In addition, with the certainty of a national policy in place, the standards should spur more 

technological innovations, which may ultimately reduce the costs of meeting the standards. 

Docket Number: 0053.1 

Organization: Center for Biological Diversity, Public Citizen, and the Sierra Club 

Commenter: Brian Nowicki 

In addition, the upper range of alternatives presented in the DEIS fails to accurately describe a 

technologically feasible level. The highest stringency alternative analyzed in the DEIS would result in 

average fuel economy of 37.1 mpg in 2016. It is clear that this cannot, by any stretch of the imagination, 

be equated with what is “technologically feasible.” First, cars on the road in the U.S. today already 

achieve approximately the same or better gas mileage than what NHTSA has defined as the combined 

fleet “technology exhaustion” for model year 2016. These include the Toyota Prius (48/45; city/highway) 

and the Honda Civic Hybrid (40/45; city/highway). Many more vehicles already surpass the upper range 

of alternatives in the DEIS (30.0 mpg) for the combined fleet in MY 2012: smartcar (33/41; 

city/highway); Toyota Yaris (29/36); Toyota Corolla (28/37); Nissan Altima Hybrid (35/33); Toyota 

Camry Hybrid (33/34); Hyundai Accent (27/32); Kia Rio (27/32); Mazda Tribute Hybrid 2WD (34/30); 

and Honda Fit (28/34). Second, the upper range of alternatives results in standards significantly lower 

than those currently in use in many other countries. Europe and Japan had average fuel economy 

standards of approximately 42 mpg in 2008—over 15 mpg higher than U.S. standards. Both Europe and 

Japan are predicted to continue increasing their fuel standards; even their high standards are not the 

technology maximum. The fact that other countries have achieved higher fuel standards indicates that 

there are eminently feasible technology options available today that have not been included in the DEIS. 

[Citations omitted]. 

Docket Number: 0049

Organization: Individual 

Commenter: James Adcock 

We disagree with the decisions by NHTSA and EPA to in practice exclude Strong Hybrid, PHEV, and 

EV technology during this time frame. Prius Strong Hybrid technology is now about 15 years old, and 

has been adopted by many Mfgs. EV Tesla is selling commercially. PHEV Volt and EV Leaf have been 

firmly announced by major manufacturers. To assume that these technologies will not exist in the 

marketplace even by 2016 flies in the face of the evidence. NHTSA assumes PHEV range of 20 MPG 

where the one announced PHEV has a range of 40 MPG. By choosing an artificially low range NHTSA 

artificially deflates the MPG possible via PHEV technology. 

Response 

EPCA requires that NHTSA establish standards at “the maximum feasible average fuel economy level 

that it decides the manufacturers can achieve in that model year,” 49 U.S.C. § 32902(a), based on the 

agency’s consideration of four statutory factors: technological feasibility, economic practicability, the 

effect of other standards of the Government on fuel economy, and the need of the nation to conserve 

energy, id. at § 32902(f). EPCA does not define these terms or specify the weight to give each factor in 

balancing them. As defined by the agency, technological feasibility refers to whether a particular method 

of improving fuel economy can be available for commercial application in the model year for which a 

standard is being established. 74 FR at 49461. 
Chapter 10 Responses to Public Comments 10.2 The Proposed Action and Alternatives 

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The commenters suggest that NHTSA’s alternatives do not reflect technological feasibility because 

certain individual vehicle models currently on the road surpass the average fuel economy standards of 

each of the alternatives. CAFE standards are not measured by the performance of a single vehicle in a 

manufacturer’s fleet. Rather, they are measured as the production-weighted average of the 

manufacturer’s fleet-wide fuel economy. As explained in the NPRM, CAFE standards for each 

manufacturer are a function of their product mix. 

Technological feasibility is but one factor the agency must consider. In setting CAFE standards, NHTSA 

must also consider the additional statutory factors. One of the other four statutory factors is “economic 

practicability.” As set forth in the NPRM, “economic practicability” does not permit the CAFE 

standards to cause substantial economic hardship for automakers. See 74 FR at 49461. 

As the commenter notes, some manufacturers have already incorporated more advanced diesel and 

hybrid technologies. However, NHTSA believes that requiring increased technology penetration beyond 

what the agency has already modeled would exceed maximum feasibility, for reasons set forth in the 

PRIA. Making substantial product changes requires lead time. Thus, the fact that some manufacturers 

are using a technology now does not mean it can be added fleetwide in the lead time necessary. NHTSA 

believes that it is not practicable for all manufacturers to incorporate these technologies across their 

entire fleets by MY 2016. 

The commenters also suggest that NHTSA’s alternatives do not properly reflect “technological 

feasibility” because other countries currently have higher fuel economy standards in place than those 

considered in the DEIS for the model years covered by this rulemaking. We disagree. Setting aside 

regulatory differences between these nations, this argument ignores the fact that the United States does 

not have the same fleet profile – including the distribution of various vehicle footprints – as other 

countries, and that average fuel economy is strongly dependent on fleet profile. EPCA requires NHTSA 

to set maximum feasible CAFE standards for passenger cars and light trucks produced for sale in the 

United States, not to set standards that require manufacturers to replicate the fleet profiles of other 

countries. NHTSA’s determination of the technological feasibility and economic practicability tests must 

be applied within the context of the fleet of vehicles to be regulated – the projected U.S. fleet. 

10.2.3 Volpe Model 

10.2.3.1 General 

Comments 

Docket Number: 0049 

Organization: Individual 

Commenter: James Adcock 

While NHTSA has improved its "openness" to meaningful public review of its actions . . . . We find 

numerous cases where documentation referred to in the case documents is NOT at the location specified. 

We have contacted NHTSA and EPA for help in locating these "missing" supporting documents and we 

DID NOT receive credible assistance in locating these "missing" documents. 

* * * * * 

We continue to have problems in practice with the "openness" of the Volpe Model . . . 
10.2 The Proposed Action and Alternatives Chapter 10 Responses to Public Comments 

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NHTSA states that Volpe has been open to review, including input and output files. This is false. We 

asked via FOIA 1/22/09 for the input and output parameters to Volpe and our request was denied by 

NHTSA . . . . The denied files corresponded to about 150,000 numerical values without which it was 

impossible to repeat Volpe results. Denial based on the fact that some of these 150,000 values were 

"proprietary." 

* * * * * 

The economic lifetime of PCs is 2 to 3 years. Thus Volpe targeting "PC 2003" is expecting a PC that is 2 

to 3 generations old as its target machine. Volpe should be updated to compile correctly on contemporary 

PCs, versions of Excel and development environments. 

Response 

The Volpe model is a tool NHTSA uses to apply technologies and assess costs and benefits given a range 

of input assumptions, including vehicle market forecast information, technology costs and effectiveness, 

and economic externalities. NHTSA selects the input assumptions based on the available information at 

the time of the rulemaking. NHTSA provides interested parties and the public with relevant data and 

information used to develop inputs to the Volpe model and the rationale for selecting those inputs. FEIS 

Section 3.1.4 (detailing Volpe model inputs); NPRM, 74 FR 49454, 49646-49684 (Sep. 28, 2009). The 

NPRM contains detailed instructions on obtaining Volpe model software and documentation on NHTSA’s 

website (available at 

http://www.nhtsa.gov/staticfiles/DOT/NHTSA/Rulemaking/The%20Volpe%20Model/volpe_documentatio

n_draft.pdf). See e.g., 74 FR 49454, 49637, n. 432. 

NHTSA staff is aware of no attempts by Mr. Adcock to contact the agency for assistance locating 

supporting material related to the MYs 2012-2016 CAFE rulemaking. The Freedom of Information Act 

(FOIA) request Mr. Adcock references relates to the earlier MY 2011 CAFE rulemaking. In that FOIA 

request, Mr. Adcock requested files associated with NHTSA’s MY 2011 CAFE rulemaking and the MYs 

2011-2015 CAFE FEIS and, except for confidential business information, NHTSA provided Mr. Adcock 

with the requested files. The agency is prohibited by federal law from disclosing confidential business 

information; making this information publicly available would cause competitive harm to manufacturers. 

See 5 U.S.C. § 552(b)(4); 18 U.S.C. § 1905; 49 U.S.C. § 30167(a); 49 CFR Part 512; Critical Mass 

Energy Project v. Nuclear Regulatory Comm’n, 975 F.2d 871 (D.C. Cir. 1992). 

NHTSA has increased transparency. The MY 2011 CAFE Final Rule, which was issued in March of 2009, 

was based significantly on confidential product planning information submitted by manufacturers to the 

agency. Notwithstanding this restriction, in its publicly available documents for the MY 2011 Final Rule, 

NHTSA provided aggregated information (compiled from individual manufacturer submissions) 

regarding its forecasts of the future vehicle market. In the MYs 2012-2016 rulemaking, the agency’s 

vehicle market forecast does not contain confidential business information as previous baseline market 

forecasts did. See 74 FR 49454, 49484-49490, 49646-49654. Instead, the vehicle fleet currently used as 

an input to Volpe, like that used as an input to similar analysis by the EPA, is based on 2008 vehicle 

certification data as supplied by EPA. Therefore, as explained in the DEIS and joint NPRM, any 

interested party may obtain all files necessary to replicate the agency’s analysis from NHTSA’s website 

for the MYs 2012-2016 rulemaking. See DEIS Section 2.2.1; 74 FR 49454, 49637, n. 432. This change 

was made in response to comments on the previous rulemaking to enhance public transparency of the 

agency’s modeling analysis. 

The Volpe model and accompanying inputs used to conduct analysis documented in the DEIS for MYs 

2012-2016 was made available on the NHTSA website within days of the DEIS release. The material 
Chapter 10 Responses to Public Comments 10.2 The Proposed Action and Alternatives 

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posted on the website included the model executable and model source code, as well as model 

documentation, model input and output files (excluding confidential business information) from analysis 

documented in the DEIS, and model log files documenting every model setting applied as actually 

operated by Volpe Center staff. Since the agency has used the Volpe model for CAFE rulemakings, both 

NHTSA and Volpe Center staff have made efforts to support individuals and groups inquiring of the 

agency regarding difficulties working with the Volpe model, and will continue to do so upon request. 

Users should encounter no difficulties installing and running the model, as the model documentation 

provides specific minimum hardware requirements and also indicates operating environment 

requirements, both of which have remained materially unchanged for more than a year. Also, Volpe 

Center staff members routinely install and run the model successfully on new laptops, desktops, and 

servers as part of normal equipment refreshes and interagency support activities. We believe, therefore, 

that if the minimum hardware and operating environment requirements are met, installing and running 

the model should be straightforward and successful. The model documentation notes that some of the 

development and operating environment used by the Volpe model (e.g., the software environment rather 

than the hardware on which that software environment operates), particularly the version of Microsoft 

Excel used by the model, is Microsoft Office 2003. The current model documentation states that “the 

software makes use of encryption algorithms available in Excel 2003” and that these “algorithms are not 

available in older versions of Excel.” See Corporate Average Fuel Economy Compliance and Effects 

Modeling System Documentation, p.38. 

We recognize that some users may have more recent versions of Microsoft Office. However, as in the 

case of other large organizations, software licensing decisions, including the version of Microsoft Office, 

is centralized in the Office of the Chief Information Officer. Nonetheless, the Volpe Model is proven on 

both Microsoft Office version 2003 and the newer 2007 version. 

10.2.3.2 Vehicle Market Forecast 

Comments 

Docket Number: 0049 

Organization: Individual 

Commenter: James Adcock 

We find that the Volpe Model ("Volpe") does not do a reasonably good job of predicting the future when 

it fails to predict the emergence of PHEVs and EVs -- and Mfgs are announcing product plans for such. 

The fact that Volpe under-predicts these available fuel efficiencies indicates that NHTSA assumptions 

underlying the design of Volpe are false. . . . The Volpe projections are inconsistent with the rate that 

hybrids are actually being introduced into the market. If Volpe cannot correctly predict "in the future" that 

which is already happening TODAY then Volpe cannot be relied upon. Volpe failure to predict 

technology we know is happening prior to 2012: PHEVs and EVs which implies there is something 

fundamentally wrong with NHTSA's understanding and modeling of the reality of the market. 

* * * * * 

We do not think it is rational to include in the design of the regulations vehicles from Mfgs who choose 

not to meet CAFE Stds. . . . Rather, stringency should be based solely on those who show reasonable 

intent to meet the standards, and the resulting penalties to those who choose "not to play the game" should 

be allowed to fall where they lie. 

* * * * * 
10.2 The Proposed Action and Alternatives Chapter 10 Responses to Public Comments 

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135 Car models and 104 truck models corresponds to 80 percent of total vehicle sales. Rather than putting 

equal weight on all vehicle models NHTSA should concentrate on the approx 250 models that actually 

sell in any appreciable quantity . . . . It does not make sense to base regulations on designs that in practice 

Mfgs do not sell, and citizens do not buy. 

* * * * * 

We disagree with the decisions by NHTSA and EPA to in practice exclude Strong Hybrid, PHEV, and 

EV technology during this time frame. Prius Strong Hybrid technology is now about 15 years old, and has 

been adopted by many Mfgs. EV Tesla is selling commercially. PHEV Volt and EV Leaf have been 

firmly announced by major manufacturers. To assume that these technologies will not exist in the 

marketplace even by 2016 flies in the face of the evidence. 

* * * * * 

If Strong HEVs thus represent the rational choice of consumers, then agency CAFE requiring LESS than 

Strong HEVs do not represent rational regulatory choices. 

Response 

The vehicle fleet currently used as an input to the Volpe model, like that used as an input to similar 

analysis by the Environmental Protection Agency (EPA), is based on 2008 vehicle certification data as 

supplied by EPA. The use of 2008 certification data is a change in this rulemaking from the confidential 

business information used as an input to the Volpe model for the MY 2011 Final Rule. This change was 

made in response to comments on the previous rulemaking to enhance transparency in the agency’s 

modeling analysis. 

For this rulemaking, the baseline vehicle fleet developed by EPA in consultation with NHTSA is 

comprised of MY 2008 data. MY 2008 was used for the baseline vehicle fleet because it is the most recent 

model year for which full data are publicly available. Vehicle manufacturers have 90 days after their last 

vehicle is produced for a model year to submit CAFE data to EPA. For most manufacturers, this is 90 

days after the end of the calendar year. For example, in calendar year 2008, MY 2009 vehicles were 

tested and certified by the EPA. These MY 2009 vehicles were then sold in the latter part (often Fall) of 

2008 until the following Fall of 2009. In early 2010 (calendar year), manufacturers will submit their 

total sales of MY 2009 vehicles. After these sales figures are submitted, the sales are combined with the 

previously measured and reported fuel economies for individual models of vehicles with particular drive 

trains to calculate the sales-weighted average fleet fuel economy. The analysis for this present 

rulemaking was conducted in the 2009 calendar year. At that time the full sales figures for MY 2009 

vehicles were not yet submitted. Even though the fuel economies (and some other specifications) of the 

MY 2009 vehicles were known because they were tested earlier, the exact sales were not yet known for 

each company. Therefore, because MY 2008 data were the most complete and transparent dataset 

available, the agencies chose to use that data as the baseline. 

As the commenter noted, using the MY 2008 certification data can result in the agencies’ analyses 

counting vehicles that are no longer in production and excluding vehicles that will be in production 

during the timeframe of this rulemaking. The MY 2008 baseline dataset will only include vehicles that 

were in production during that model year and, conversely, not include vehicles introduced to the 

marketplace in subsequent model years. As the commenter stated, this means vehicles such as recently 

announced pure electric vehicles (EV) and plug-in hybrid electric vehicles (PHEV) along with other 

manufacturer-announced forward models, are not included in the dataset as these vehicles are not in 

production and, therefore, have not been certified by EPA. Having the MY 2008 baseline exclude these 
Chapter 10 Responses to Public Comments 10.2 The Proposed Action and Alternatives 

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vehicles doesn’t prevent advanced technologies from being considered in the reference fleet or the final 

rule. The reference fleet is the MY 2008 baseline modeled to meet 2011 CAFE. The Volpe model (and 

EPA’s OMEGA model) adds technology to vehicles to have the vehicle fleet meet current or future 

standards. If advanced technologies are necessary for a manufacturer to meet the standard, the model 

will simulate having that technology on a vehicle. This allows the agencies to determine the cost of the 

rule for each manufacturer based on the most cost effective fleet. Manufacturers’ introduction of 

technology for reasons other than meeting the standard (such as marketing, image, or to gain experience) 

is not considered since these actions would not be properly attributable to the rule. Also, the agencies 

include certain modeling constraints on the addition of various technologies (including strong hybrids) 

based on the need for sufficient lead time (and other technical reasons) to introduce these technologies 

throughout the fleet. 

Manufacturer announcements regarding forward models pose difficulty for use as model inputs. 

Manufacturers tend to limit production projections in these releases in order to protect product planning 

information and to better manage press coverage. In any event, commenters have not shown that the 

market for and sales of electric vehicles would be sufficiently large during the period covered by this 

rulemaking to change the analysis. There are substantial questions—including driving range, limited 

utility, cost and infrastructure—associated with these vehicles. 

NHTSA has evaluated the use of public manufacturer forward model press information to update the 

vehicle fleet inputs to the agency’s modeling analysis. The challenges in this approach are evidenced by 

the continuous stream of manufacturer press releases throughout a defined rulemaking period. 

Consistency in the vehicle inputs is necessary throughout the rulemaking process. Maintaining vehicle 

fleet consistency across both NHTSA and EPA lends to the harmonized approach for this rulemaking. 

With this in mind, continual modification to the vehicle fleet based on release of non-specific information 

on future models and, most likely not finalized, product press releases would lead to potential 

inconsistencies in not only the model analysis throughout the rulemaking period but also to a loss of 

synchronization across both agencies. 

More information on and explanation of the reasons for the baseline fleet used in the agency’s modeling 

analysis as part of this rulemaking are located in the Draft Joint Technical Support Document. Docket 

No. NHTSA-2009-0059-0029. See also 74 FR 49454, 49484-49490, 49646-49654; DEIS Section 

2.2.1.2008 

The commenter suggested excluding from the agency’s analysis vehicles produced by manufacturers that 

historically choose to pay fines instead of meeting CAFE targets. However, excluding all of these 

manufacturers of vehicles manufactured for sale in the US market from the analysis could compromise 

NHTSA’s statutory obligation to “consider technological feasibility, economic practicability, the effect of 

other motor vehicle standards of the Government on fuel economy, and the need of the United States to 

conserve energy.” 49 U.S.C. § 32902(f). Manufacturers that have historically chosen to pay fines are a 

real part of the fleet and NHTSA properly considers the capabilities of the existing vehicle fleet in 

determining what levels of stringency would be the maximum feasible for the industry as a whole. In the 

analysis, manufacturers that traditionally pay fines are still subject to the increased standards. 

Some commenters may misunderstand the agency’s use of the Volpe model. The Volpe model is not used 

to set the stringency of the standards. The model is a tool that allows the agency to estimate what it 

would take to comply with, as well as the costs and benefits of, CAFE standards at various stringencies. 

One of the inputs required by the model is a forecast of the future vehicle market for each manufacturer, 

from which NHTSA projects a set of technologies each manufacturer could apply in attempting to comply 

with the various levels of potential CAFE standards to be examined. The model then estimates the costs 

associated with the additional technology utilization, as well as accompanying changes in travel demand, 
10.2 The Proposed Action and Alternatives Chapter 10 Responses to Public Comments 

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fuel consumption, fuel outlays, emissions, and economic externalities related to petroleum consumption 

and other factors. Although NHTSA uses the Volpe model as a tool to inform its consideration of 

potential CAFE standards, the Volpe model does not determine the CAFE standards NHTSA will 

promulgate as final regulations. See Section 2.2.1 of this EIS. NHTSA considers the results of the 

analyses conducted using the Volpe model and external analyses, including assessments of greenhouse 

gases and air pollution emissions, and technologies that may be available in the long term. NHTSA also 

considers whether the standards could expedite the introduction of new technologies into the market, and 

the extent to which changes in vehicle prices and fuel economy might affect vehicle production and sales. 

Using all of this information, the agency considers the governing statutory factors, along with 

environmental issues and other relevant societal issues, such as safety, and promulgates the maximum 

feasible standards based on its judgment. 

10.2.3.3 Technology Assumptions 

Comments 

Docket Number: 0049 

Organization: Individual 

Commenter: James Adcock 

ROLL can reasonably be accommodated in any model year by bolting on more efficient rubber 

compounds, and thus should be assumed for all models all model years. 

We believe AERO can be applied to all vehicles. 

Re Intelligent Cooling of LT: Since these vehicles actually tow or carry loads less than 1 percent of the 

time (based on this reviewers' traffic surveys in the Seattle Area) electrified cooling WOULD actually be 

effective in trucks 99 percent of the time. 

Response 

The application rate of low rolling resistance tires is constrained by two factors: (1) the development 

efforts required for each tire specification a manufacturer affixes to a vehicle it sells, and (2) the vehicle 

type offered by the manufacturer. As discussed below, given these constraints, NHTSA does not believe 

that low rolling resistance tires can feasibly be applied fleet-wide in MY 2012. 

A manufacturer typically offers more than one specification of tire per vehicle it sells to balance supplier 

capacity, geographic needs and consumer interests. For each tire specification offered, manufacturers 

must commit substantial resources in terms of materials, facilities and engineering efforts to meet vehicle 

handling, ride, and comfort requirements and to accommodate Anti-lock Braking Systems and Electronic 

Stability Control systems. This effort and expenditure is typically associated with re-design and refresh 

cycles to balance necessary costs, facilities, development time and engineering resources—it is not a 

simple matter for a manufacturer to apply low rolling resistance tires to a vehicle. In light of NHTSA’s 

statutory requirement to take into account technical feasibility and economic practicability in setting 

CAFE standards, NHTSA continues to apply this technology at the redesign or refresh milestones. 

NHTSA does not apply this technology to vehicles in the Large Truck class due to the increased traction 

and handling requirements for off-road and braking performance at payload and towing limits. Likewise, 

this technology is not applied to vehicles in the performance car categories due to increased traction 

requirements for braking and handling, which cannot be met with low rolling resistance designs. Low 
Chapter 10 Responses to Public Comments 10.2 The Proposed Action and Alternatives 

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rolling resistance tires can sometimes sacrifice traction for increased fuel efficiency. Manufacturers have 

confirmed that they do not equip these vehicles with low rolling resistance tires. 

For the most part, aerodynamic improvements can most practicably and feasibly be applied at the vehicle 

redesign milestone event, with some minor modification possible at the vehicle refresh milestone. In most 

cases, improvements to vehicle aerodynamics require modification of the vehicle’s body stampings and 

other stylistic external vehicle components. These changes involve extensive and non-adaptable 

manufacturing tooling revisions for implementation. Manufacturing tooling for a vehicle program is 

primarily developed, purchased and amortized for the planned vehicle lifecycle by both vehicle 

manufacturers and suppliers. In addition, underbody trays, reduced grill openings and other 

aerodynamic improvement techniques result in system-wide effects to airflow and heat management 

properties requiring component and engineering development efforts to ensure proper vehicle operation 

and serviceability. 

In recognition of these constraints, the Volpe model incorporates vehicle redesign and refresh 

mechanisms in an attempt to accurately reflect how aerodynamic improvements can be applied 

throughout the rulemaking period to the vehicle fleet used as an input to the Volpe model analysis. 

NHTSA believes the redesign and refresh milestones for the vehicle fleet are set appropriately for this 

technology during this rulemaking period. The agency also expects that further aerodynamic 

improvements will not be applicable to performance cars, considering the extent to which the 

aerodynamic characteristics of such vehicles have already been optimized to balance fuel consumption 

and high-speed handling. 

In assessing the application of Intelligent Cooling to vehicle classifications, NHTSA consulted with a 

globally recognized engineering services firm. NHTSA concluded that Intelligent Cooling should not be 

applied to Large Trucks and SUVs based on the manufacturer development principle that vehicles are 

developed and tested to perform at their designed limits. 

In the Large Truck and SUV segment, manufacturers develop vehicle capabilities such as towing and 

hauling. As NHTSA noted in the MY 2011 CAFE Final Rule, Large Vehicles with towing capacity present 

a challenge for intelligent cooling systems, as these vehicles have higher cooling fan loads in comparison 

to passenger cars. See 74 FR 14196, 14297. To ensure the Large Truck and SUV towing and hauling 

capabilities the consumer is purchasing, manufacturers need to make them fully available throughout the 

vehicle lifecycle regardless of actual customer usage. For these reasons, NHTSA is continuing to exclude 

Intelligent Cooling application from the Large Truck vehicle segment in the agency’s analysis. 

10.2.3.4 Economic Assumptions 

Comments

Docket Number: 0049 

Organization: Individual 

Commenter: James Adcock 

5-year cutoff on payback period on the assumption that consumers only value a vehicle’s MPG 

technology on the first five years - is not a rational assumption because consumers well know how hard it 

is to unload gas guzzlers . . . . Choosing this irrational 5-year cutoff assumption in turn represents a large 

reduction in "duration" effectively causing a much higher depreciation rate than the claim 3 percent 

societal discount rate. 
10.2 The Proposed Action and Alternatives Chapter 10 Responses to Public Comments 

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Assuming a 5-year horizon for the consumer’s valuation of MPG improvements is the same as assuming 

vehicle purchasers assume that they will sell their vehicles in 5 years and be able to receive no premeium 

on that sale for high MPG. But, on the contrary consumers are well aware and it has been well reported 

that higher MPG vehicles hold their resale value better than lower MPG vehicles—and that low MPG 

SUVs and trucks are hard to unload at all! 

Docket Number: 0098 

Organization: New York Department of Transportation 

Commenter: Stanley Gee 

The proposal does not appear to give due consideration to the economic benefits of improved fuel 

economy at the consumer level. It is not reasonable to assume that the only effect of fuel-costs savings 

will be a rebound effect. The only economic benefit that appears to be considered in the impact analysis is 

a $0.17/gallon benefit from reducing oil imports. Unfortunately, this anticipated benefit is difficult to 

comprehend since the DEIS indicates that fuel consumption will increase significantly in the future 

whether or not the proposed CAFE standards are implemented. 

Response 

The CAFE model applies a “payback period,” specified as an input to the model, for the purpose of 

choosing from among available technology applications (where each technology application involves the 

application of a specific technology to one or more specific vehicle models). In making such choices, the 

model assigns each option an “effective cost,” calculated by considering (1) the hardware cost that 

would be incurred, (2) the amount by which civil penalties would be reduced, and (3) the amount by 

which the manufacturer estimates vehicle price can be raised based on the projected reduction in fuel 

consumption. In calculating the third of these components, the model applies the input value of the 

“payback period,” specifying the number of years manufacturers estimate that first purchasers “count” 

in making their purchasing decisions, to the extent supportable by increased fuel prices. 

For the current rule, NHTSA has applied a payback period of five years. While less than the average full 

useful life of a vehicle, this is considerably longer than the three year period some manufacturers have 

cited. NHTSA does not assume that consumers would necessarily sell their vehicles after five years (the 

average loan period). Rather, NHTSA uses the five-year estimate to simulate the period of time 

manufacturers assume that potential vehicle buyers typically value fuel economy improvements in making 

their purchasing decisions. 

In contrast, when estimating the actual value of fuel savings to both individual buyers and to society as a 

whole, NHTSA assumes that fuel savings are valued over the full expected lifetimes of vehicles. In effect, 

this assumes that the initial purchaser and any subsequent purchasers save fuel over the lifetime of the 

vehicle. In analysis conducted outside the CAFE model, the agency further assumes that, on average 

across each manufacturer’s fleet, the resale value of a more fuel-efficient model increases by 35 percent 

of the increase in its original purchase price that was attributable to its higher fuel economy, irrespective 

of whether manufacturers believe they can correspondingly increase prices charged to first purchasers. 

Thus, the agency assumes that purchasing a new vehicle with higher fuel economy does increase 

its resale by a significant fraction of the increase in its original purchase price. 

Contrary to the commenter’s assumption, NHTSA considers the primary benefit to consumers from 

increased fuel economy to be the value of the fuel saved by owners over the expected lifetimes of their 

vehicles. NHTSA includes as additional consumer benefits from higher fuel economy the value of 

increased driving range and reduction in the frequency of refueling, as well as the value of added 

mobility afforded by additional driving due to the fuel economy rebound effect. The value of fuel savings 
Chapter 10 Responses to Public Comments 10.2 The Proposed Action and Alternatives 

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accounts for by far the largest share of total consumer benefits. In addition to consumer benefits, NHTSA 

includes the value of various other benefits that will result from requiring passenger cars and light trucks 

to achieve higher fuel economy, but that will be realized by the economy as a whole rather than by vehicle 

buyers. These include reductions in environmental and energy security externalities that result from 

producing, distributing, and consuming a lower volume of fuel. 

10.2.3.4.1 Rebound Effect 

Comments 

Docket Number: 0051.1 

Organization: Missouri Department of Natural Resources 

Commenter: Dru Buntin 

The DEIS attributes the majority of the reductions in pollution emissions to the actual production, 

transport, and refining operations for fuel. These findings are based on the emissions reductions, 

assuming a decrease in number of barrels of crude oil required to be processed into fuel, compared to the 

no action alternative. It is assumed by the report that the majority, if not all, emissions reductions 

attributable to cars and trucks getting better mileage per gallon will be balanced by more miles traveled in 

a process referred to as the "rebound effect". This study used an across the board value of 10% rebound 

effect in all studies. The theory behind the rebound effect is that vehicles with higher fuel mileage will be 

driven more than the older vehicles they replaced, thus increasing their vehicle miles traveled (VMT). 

This increase in VMT is theorized to increase the emissions from actual driving to nearly the same level 

as the no action alternative. 

Although it is reasonable to assume that some people will drive more if their vehicles get better gas 

mileage, there is no evidence presented in the report showing that the average consumer automatically 

increases the amount they drive when they get more miles per gallon. Nor does the report fully explain 

why 10% is assumed to be the estimated increase. In addition, the report's assumption that this effect will 

result in no overall emissions reductions from the actual driving of vehicles appears to be extremely 

conservative in the estimation of emissions reductions resulting from higher CAFE standards. 

Docket Number: 0052.1 

Organization: United States Environmental Protection Agency3

Commenter: Susan Bromm 

We do have one area of clarification regarding the “rebound effect” which we suggest for inclusion in the 

Final EIS. While Appendix C recommends a rebound effect of 10 to 20 percent, and other sections of the 

DEIS recommend using an effect of 5 to 15 percent, a rebound effect of 10 percent was utilized in the 

analysis. EPA recommends that the FEIS include a paragraph providing a clarifying synopsis of the 

methodology and values of the rebound effect used in the analysis. 

 

3

 Under Section 309 of the Clean Air Act, EPA is required to review and publicly comment on the environmental 

impacts of major federal actions including actions which are the subject of EISs. If EPA determines that the action 

is environmentally unsatisfactory, it is required by Section 309 to refer the matter to CEQ. This is done by the 

Office of Federal Activities. 
10.2 The Proposed Action and Alternatives Chapter 10 Responses to Public Comments 

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Docket Number: TRANS03 

Organization: Consumer Federation of America 

Commenter: Mark Cooper 

It must properly value fuel savings, we think, by removing the rebound effect from the consumer private 

welfare analysis and setting it at a lower level for the societal analysis. 

Response 

Missouri DNR suggests that incorporating the rebound effect into NHTSA’s analysis increases the 

vehicle-miles traveled sufficiently to offset the effect of reductions in emissions that would be expected to 

result from higher fuel economy. However, the estimates of emissions per vehicle-mile used in NHTSA’s 

analysis, which were derived from EPA’s MOBILE6.2 and MOVES motor vehicle emission models, do 

not vary significantly in response to changes in fuel economy. 

Thus the only effect of higher fuel economy on emissions of criteria air pollutants, non-CO2 GHGs, and 

airborne toxics incorporated into NHTSA’s analysis is the increase in vehicle emissions that results from 

added driving as a consequence of the rebound effect. This rebound-effect driving occurs in response to 

increases in fuel economy from its level under the No Action Alternative, and results in estimated 

emissions of criteria air pollutants, non-CO2 GHGs, and airborne toxics from increased vehicle use under 

each action alternative. 

The net effect of each action alternative on combined emissions from fuel production and vehicle use is 

thus the difference between (1) the reduction in emissions from fuel production that results from the 

decline in fuel use under that alternative, and (2) the increase in emissions that results from added 

driving due to the rebound effect from higher fuel economy. As the DEIS reported and described in 

detail, and as the FEIS also reports, component (1) of the net change in emissions typically outweighs 

component (2), so that this calculation results in net declines in emissions of most, but not all, criteria air 

pollutants, non-CO2 GHGs, and airborne toxics.

The commenter also suggests that NHTSA has not cited evidence that vehicle use actually increases in 

response to increased fuel economy, and has not fully explained the basis for its rebound effect estimates. 

To derive an estimate of the rebound effect for use in assessing the fuel savings and other impacts of more 

stringent CAFE standards, NHTSA reviewed 22 studies of the effect of fuel economy on vehicle use. See

PRIA Section VIII. As NHTSA’s review indicated, 21 of these studies concluded that vehicle use increases 

in response to higher fuel economy. NHTSA then performed a detailed analysis of these studies’ 

estimates of the extent to which it does so, by tabulating and analyzing variation among the 66 estimates 

of the long-run rebound effect reported in these studies. The 66 estimates range from as low as 7 percent 

to as high as 75 percent, with a mean value of 23 percent. Approximately two-thirds of all 66 estimates 

reviewed range from 10 to 30 percent, as do two-thirds of all published estimates, and two-thirds of 

authors’ preferred estimates.

NHTSA also developed new estimates of the rebound effect using national data on passenger car and 

light truck travel over the period from 1950 through 2006. The agency estimated various econometric 

models of the relationship between vehicle miles-traveled and factors likely to influence it, including 

household income, fuel prices, vehicle fuel efficiency, road and highway capacity, the number of vehicles 

in use, vehicle prices, and other factors. The results of NHTSA’s analysis are generally consistent with 

the findings from other recent research in two respects: (1) they show that the average long-run rebound 

effect ranged from 16 percent to 30 percent over the period from 1950 through 2007, and (2) they 

indicate that the magnitude of the rebound effect declined throughout this period. However, the agency 

estimates that the decline in the rebound effect over this period was considerably less rapid than reported 
Chapter 10 Responses to Public Comments 10.2 The Proposed Action and Alternatives 

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in other recent research, and that its magnitude in 2007 ranged from 8 percent to 14 percent, well above 

the estimates reported in some recent studies. 

Projected values of the rebound effect for the period from 2010 through 2030, which the agency 

developed using forecasts of personal income, fuel prices, and fuel efficiency from AEO 2009’s Reference 

Case, range from 4 percent to 16 percent, depending on the specific model used to generate them. In light 

of these results, the agency believes that the apparent decline over time in the magnitude of the rebound 

effect justifies using a value for future analysis that is lower than historical estimates. Because the 

lifetimes of vehicles affected by the alternative CAFE standards considered in this rulemaking will extend 

from 2012 until nearly 2050, a value that is significantly lower than historical estimates appears to be 

appropriate. Thus NHTSA has elected to use a 10 percent rebound effect in its analysis of fuel savings 

and other benefits from higher CAFE standards for this NPRM. 

In response to EPA’s recommendation, NHTSA has added a paragraph to the FEIS explaining the 

agency’s choice of a single estimate of the rebound effect and identifying the 10 percent figure as that 

estimate, as discussed above. 

In response to the comment provided by Consumer Federation of America, NHTSA believes that it is 

important to incorporate the rebound effect in its consideration of potential consumer welfare impacts 

and the analysis of social benefits resulting from higher fuel economy. The rebound effect is important to 

recognize in the analysis of consumer welfare impacts because the resulting increase in vehicle travel 

provides additional benefits (i.e., additional opportunities to participate in activities outside the home) to 

purchasers of new vehicles beyond those resulting from lower fuel consumption. At the same time, it is 

important to incorporate the rebound effect into the analysis of social benefits from requiring higher fuel 

economy, because doing so recognizes the partial offset of fuel savings and resulting social benefits – 

including reductions in environmental and energy security externalities that result from lower fuel 

production, distribution, and consumption – that occurs as a consequence of increased rebound-effect 

driving. 

10.2.3.4.2 Social Cost of Carbon 

Comments 

Docket Number: 0049 

Organization: Individual 

Commenter: James Adcock 

The US Government Agencies et al need to agree upon a SCC and a discount rate associated with the 

economics and morality of intergenerational costs. We suggest that consumers need to be polled on 

THEIR "economic valuation" of the possible premature deaths of their children or grandchildren due to 

global warming. . . . C02 reduction efforts in the US results in designs and technologies that Mfgs can and 

do apply worldwide, reducing C02 emissions and fuel prices worldwide. To assume zero correlation 

between US actions and results overseas is not rational. Measuring only US environmental damages 

caused by only US vehicle emissions does not form a rational measure of the damages because applying 

this measurement technique on a nation-by-nation basis worldwide would not form a total equal to the 

total world-wide damages caused by vehicles worldwide. . . . Instead EPA and NHTSA either need to 

calculate world-wide SCC of US Vehicle Emissions, or alternatively calculate US SCC based on global 

vehicle C02 emissions. . . . CAFE's effects on global warming cannot sensibly be analyzed in isolation, 

but rather only as part of a national and international program to reduce GHG emissions. 

* * * * * 
10.2 The Proposed Action and Alternatives Chapter 10 Responses to Public Comments 

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We do not believe NHTSA has reasonably resolved the issue of species extinction and ESA with the SCC 

assumption of $20/ton. On the contrary, finding ESA and the issue of species extinction inconvenient, 

NHTSA simply chooses to ignore these issues when setting SCC! We believe provisions of the ESA are 

most consistent with an intergenerational discount rate of 0 percent -- since ESA expects that species 

available to one generation ought to be available to future generations. 

* * * * * 

NHTSA asks for input on how to calculate SCC. We recommend the following procedure, by example. 

Use an Environmental Economics measure of the total value of a local environment (the total economic 

services provided by the local environment) divided by the total number of people in that local 

environment to form a "total value of the local environment per person" value. For example in the Puget 

Sound region Earth Economics estimates this value is about one million dollars per person. Then pick a 

reasonable estimate of the elapsed time until C02 levels corresponding to what scientists consider 

irreversible damage is reached, for example 50 years. Take the ratio of these two numbers to arrive at a 

linearized C02 environmental damage per year: $20,000 C02 damage per citizen per year. Divide this by 

the amount of C02 emissions per citizen: 12.6 tons per citizen in WA state or $1,587 SCC per ton C02 

emitted. Average these calculations across all citizens of the US to find a US-wide average SCC based on 

Environmental Economics -- if identical to Puget Sound results in a SCC of $1,587 per ton. 

* * * * * 

DEIS does not describe how the EPA SCC of $40-$68/ton in 2011 suddenly became $20/ton in 2012, nor 

how the US with 24 percent of Global GDP somehow only receives 6 percent of global warming 

economic damage! . . . this appears to be a "pulling a rabbit out of a hat" value determined simply by take 

the ratio of US land mass to total World land mass = 6 percent. More than this needs to be done to derive 

a credible number. For example by comparison the US represents 24 percent of World GDP - implying 

that perhaps the US has 4X more to lose than the NHTSA 6 percent magic number. 

* * * * * 

The Tol meta analysis of SCC is not nearly a credible reference given that MANY of the SCC estimates 

used in the meta analysis come from Tol! A more reasoned meta analysis would only accept the most 

recent ONE estimate from each author - and NONE from the author of the meta analysis itself! Please 

completely discard the Tol meta analysis as a rational source of SCC estimates! 

* * * * * 

In general consumers with differing projections of the "true" future cost of SCC and fuel prices will make 

differing estimates of the utility of the purchase of a particular vehicle. Analysis that assumes one 

particular "US-wide" value of SCC or fuel costs will thus reach erroneous conclusions about vehicles 

Mfgs should be offering consumers . . . . 

* * * * * 

We believe CAFE needs to be responsive to SCC as set by future cap and trade regulation. It would be 

inappropriate, for example, if carbon is trading at $40 a ton but NHTSA has set an assumption of $20 a 

ton. 
Chapter 10 Responses to Public Comments 10.2 The Proposed Action and Alternatives 

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Response 

Federal government agencies are working toward, but do not yet have, an agreed-upon estimate for the 

social cost of carbon (SCC) to support federal regulatory activities where reducing emissions of CO2 is 

an important potential outcome. Nevertheless, NHTSA is obligated under EPCA to issue a CAFE rule 

regardless of whether there is a uniform federal government view on the SCC. For the analysis in the 

FEIS, the agency modeled a primary SCC value of $56, and conducted a sensitivity analysis using $10 

(see Sections 2.2.4 footnote 9 and 2.4 of this FEIS). However, this is not necessarily the estimate of the 

SCC that the agency will ultimately select for valuing reductions in CO2 emissions in the final rule. The 

FEIS uses a high SCC in the Volpe model so that the stringency of the CAFE standards for the MNB 

Alternative and the TCTB Alternative are higher than they would be for a lower valuation of SCC. This 

results in higher fuel savings and greater changes in environmental impacts for these alternatives than 

would result from using a lower SCC value in the model. The intent of this is to demonstrate the 

maximum differences in environmental impacts between the alternatives. The environmental impacts of 

the action alternatives other than the MNB Alternative and the TCTB Alternative are not significantly 

affected by the valuation of social cost of carbon in the model, as shown in Table 2.4-1. 

With regard to the comment that CAFE should be responsive to SCC as set by future cap and trade 

regulations, NHTSA does not believe it is appropriate to speculate on a market clearing price of carbon 

in a nationwide trading system. In addition, the market price for CO2 emission permits would reflect the 

number of such permits that have been made available and the costs of achieving further reductions in 

CO2 emissions, rather than the economic benefits from doing so. Thus the permit price would not 

necessarily provide reliable guidance about the economic benefits from increasing fuel economy, or for 

establishing the stringency of CAFE standards. 

10.2.3.4.3 Military Costs 

Comments 

Docket Number: 0049 

Organization: Individual 

Commenter: James Adcock 

We ask that NHTSA become more honest in their analysis of the role of oil in US involvement in Middle 

East Wars. . . . If the US didn't import any oil then the Middle East would not be of Strategic Importance. 

We suggest then that military costs have to be apportioned according to percent of oil imports; it cannot 

be independent of oil consumption as assumed by NHTSA. . . . Assumed 0 percent military cost 

assignment to maintaining the security of Middle East oil supplies is not reasonable. 

* * * * * 

We suggest military spending be modeled as linearly proportional to oil imports. Thus a portion of 

Middle East military activities should properly be apportioned to the cost of oil imports - we suggest that 

50 percent of military costs in the Middle East. 

We believe that the cost of Middle East War can be more appropriately assigned than NHTSA current 0 

percent similar to the following: $920,000,000,000 Cost of Iraq and Afghanistan Wars the last eight 

years, or $ 115,000,000,000 a year. 6,736,961,000 Barrels of Refined Petroleum a year equals 

208,845,791,000 gallons, or an apportionment of $0.55 war costs per gallon. If we assign 50 percent to 

the "strategic oil value" and the other 50 percent) to the terrorist aspects, then we find $0,275 a gallon of 

gasoline should be added for military costs. . . . When monosopy costs are passed on to nations that 
10.2 The Proposed Action and Alternatives Chapter 10 Responses to Public Comments 

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represent military and terrorist threats to the US, how can it be that NHTSA assumes such monetary 

transfers are "neutral" to US interests??? This is not rational. 

Docket Number: TRANS03 

Organization: Consumer Federation of America 

Commenter: Mark Cooper 

On the national security front, we believe the agency must assign a significant national security value to 

the benefit of reducing oil consumption. You don't have to look far to find politicians telling us how 

important our national security reducing our dependence on imported oil is. The fact that the governing 

statute, the most recently enacted amendments to the governing statute, had the title the Energy 

Independence and Security Act, should have alerted NHTSA to the fact that Congress considers the 

military and strategic value of oil to be important. In the floor statement, the manager of the bill, Mr. 

Markey, went to great lengths pointing out all of the military types who had helped finally get this 

improvement in increase in the CAFE level enacted. There's a substantial public policy in academic 

literature that believes oil has a military value. NHTSA has to stop putting a zero on the military value of 

reduced oil consumption. 

Response 

One possible component of the external economic costs of importing oil into the United States includes 

government outlays for maintaining a military presence to secure the supply of oil imports from 

potentially unstable regions of the world. In the NPRM, NHTSA tentatively concluded that: 

“NHTSA’s analysis does not include savings in budgetary outlays to support U.S. military 

activities among the benefits of higher fuel economy and the resulting fuel savings... This 

view concurs with that of the recent ORNL study of economic costs from U.S. oil imports, 

which concludes that savings in government outlays for these purposes are unlikely to result 

from reductions in consumption of petroleum products and oil imports on the scale of those 

resulting from higher CAFE standards.” See 74 FR 49674. 

NHTSA disagrees with the two commenters who took issue with this tentative conclusion and 

recommended that NHTSA assign a value to the reduction in military spending or other costs related to 

energy security that are likely to result from lower U.S. petroleum imports. NHTSA believes that there is 

no specific and measurable relationship that can be derived from the current literature, among higher 

CAFE standards, U.S. petroleum imports, and energy security costs. 

Although it is conceivable that by reducing fuel consumption and U.S. petroleum imports from the 

Persian Gulf region, higher CAFE standards might reduce military and political risks in the Persian 

Gulf, the agency does not believe there is convincing evidence that this would reduce U.S. military 

expenditures. No commenter has presented any convincing evidence that this would occur, nor do any of 

the references commenters included provide such evidence. There is no support for the commenter’s 

suggestion that military spending be modeled as proportional to oil imports. 

Although one recent economic analysis cited by commenters estimates the value of U.S. military spending 

attributable to securing oil imports from the Persian Gulf region, this study does not estimate the extent 

to which U.S. military spending is likely to vary in response to changes in U.S. imports of Persian Gulf 

oil. Thus, the reported values are clearly intended as estimates of the total and average per-gallon costs 

of U.S. military activities in the Persian Gulf that might reasonably be related to petroleum consumption 

by U.S. motor vehicles, and not as estimates of the extent to which those costs might be reduced as a 

consequence of lower fuel consumption by U.S. motor vehicles. 
Chapter 10 Responses to Public Comments 10.2 The Proposed Action and Alternatives 

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We also note that any reduction in U.S. military spending would require a specific decision of the 

Administration and act of Congress and would not necessarily result simply from lower U.S. oil imports. 

10.2.3.4.4 Fuel Prices 

Comments 

Docket Number: 0049 

Organization: Individual 

Commenter: James Adcock 

We believe it is not rational to estimate future fuel prices 2012-2016 lower than current at the pump fuel 

prices. 

Response 

We disagree that current pump prices can be used to derive a more accurate forecast than the most 

recent federal government forecast for future gasoline prices. Pump prices for gasoline have been 

volatile in the past several years. The agency calculated and analyzed mpg standards and environmental 

impacts associated with each alternative under both the “Reference Case” for key model inputs, which 

uses the U.S. Energy Information Administration’s (EIA’s) Reference Case fuel price forecast, a domestic 

social cost of carbon, and a 7-percent discount rate; and under a “High Scenario” set of input 

assumptions, which uses the EIA “High Case” for fuel price forecast, a global social cost of carbon, and 

a 3-percent discount rate. This FEIS also analyzes the impacts of various other combinations of economic 

assumptions inputs. 

In the DEIS, NHTSA relied on the EIA Annual Energy Outlook 2009 (AEO 2009) forecasts for the 

estimate of fuel price during the period covered by the agency’s action (EIA 2009). In the analyses 

reported in the FEIS, NHTSA utilizes the recently updated forecast of future fuel prices presented in the 

EIA Annual Energy Outlook 2010 Early Release. The agency notes that the forecast of retail fuel prices 

for 2012-2016 presented in AEO 2010 averages slightly under $3.00 per gallon (in today’s dollars). 

Federal government agencies generally use the EIA projections in their assessment of energy-related 

policies. In the DEIS and NPRM, the agency selected the EIA Reference Case fuel price forecast in 

performing the analysis. AEO 2009 also included “High Price Cases” and “Low Price Cases,” which 

reflected uncertainties regarding future levels of oil production and alternative strategic responses to 

market conditions by petroleum suppliers. The commenter has not provided adequate grounds for NHTSA 

to depart from its use of the EIA forecast. 

10.2.3.4.5 Consumer Demand 

Comments 

Docket Number: 0049 

Organization: Individual 

Commenter: James Adcock 

We believe NHTSA continues to misunderstand the oil shock 1973: It was high gas prices, NOT CAFE 

which lead consumers to downsize their choice of vehicles. Higher CAFE standards allow the consumer 

to be able to afford to buy a larger more safe vehicle than in the absence of CAFE. Consumer preference 

in vehicles HAS changed as indicated by Mfgs advertising MPG NOT HP in their TV ads. That offered 

MPG is not what consumers desire can be implied by the universal Mfg practice of touting HWY MPG 
10.2 The Proposed Action and Alternatives Chapter 10 Responses to Public Comments 

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NOT "Combined" MPG in their TV ads. . . . Assuming one set of beliefs or valuation of MPG among US 

citizens is false. 

* * * * * 

We believe the fundamental lack of understanding is that 15 percent of consumers (according to the Yale 

study) STRONGLY want higher fuel efficiency vehicles as a primary attribute of vehicle choice and that 

two thirds of consumers think that SOMETHING needs to be done about global warming. . . . 

Fixed assumptions of depreciation for all vehicles (1/3 residual value after 5 years) are belied by looking 

up any source of resale values: High Fuel Efficiency Vehicles maintain their value much better than 

NHTSA is assuming. 

* * * * * 

Price pass-through to consumers: the huge price premiums being charged in practice to purchasers of 

strong hybrids belies NHTSA assumptions that consumers are unwilling to pay for fuel efficiency. 

Docket Number: TRANS03 

Organization: Consumer Federation of America 

Commenter: Mark Cooper 

Our surveys show that consumers were out ahead of the auto makers in wanting more fuel efficient cars. 

We did a survey in which we asked people, "How much mileage do you want to get in your next car?" 

And they said, "We want to get 30 miles per gallon." Only two percent of the models in the showrooms 

get 30 miles per gallon or more. 

So as we go forward, we have to recognize that there was a massive market failure here, and the auto 

makers are at least as much to blame as the consumers were. Either way, there is a sound basis for doing 

the math, for calculating the benefits, and setting the standards at a high level. 

* * * * * 

We believe the analysis must recognize the higher resale value of more fuel efficient vehicles. 

* * * * * 

The agencies must recognize the willingness of consumers to change their demand for vehicles. We've 

had a dramatic demonstration of that in the past five years. 

Response 

The agency recognizes that increased fuel efficiency may result in increased residual value (resale 

amount) at the end of an ownership period. The NPRM for MYs 2012-2016 discussed this concept with 

regard to resultant price impacts due to technology application. The agency notes, however, that fuel 

efficiency is but one factor relevant to the determination of vehicle residual values. Additional factors that 

affect residual value include records of safety and durability, vehicle brand, and vehicle type. A fleetwide residual value was taken into account in this rulemaking with the premise that the fuel efficiency of 

all vehicles will increase over the timeframe of this rule and that residual values will increase 

proportionally. The attribute-based stringency levels in the proposed rule are intended to retain a degree 
Chapter 10 Responses to Public Comments 10.2 The Proposed Action and Alternatives 

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of consumer choice. At the same time, the agency recognizes that the year-over-year stringency increases 

may also result in increases to vehicle residual value. 

In response to the comment regarding consumer demand for high fuel efficiency vehicles, the agency 

agrees that consumers value increased fuel economy. Vehicles with increased fuel economy are less 

costly to run. Without knowing the context or details of the survey cited by the commenter, the agency 

cannot opine on its findings. However, as described, the survey does not appear to take into account 

factors other than fuel economy that impact consumer demand for vehicles, such as vehicle type (e.g., 

passenger cars for small families, mini-vans for large families, pickup trucks for load-carrying). The 

agency does not believe that all consumers would make identical trade-offs between increased fuel 

economy and all other vehicle attributes. 

In mandating that NHTSA set CAFE standards, Congress specifically directed that the agency set 

standards based on vehicle attributes, thereby recognizing that manufacturers have a mix of products to 

meet varying consumer demand. Pursuant to statute, NHTSA cannot mandate a single fuel economy for 

all vehicles; rather CAFE standards represent a fleet-wide average. 

10.2.3.4.6 Consumer Welfare 

Docket Number: TRANS03 

Organization: Consumer Federation of America 

Commenter: Mark Cooper 

If you look at the economic analysis, the societal benefit, the total societal benefit is made up primarily of 

the consumer welfare benefit. It accounts for about two-thirds of the net present value. The agencies must 

adopt and affirm an analytic framework that recognizes fuel economy standards and enhances consumer 

welfare. The billions of dollars of consumer welfare gains estimated in the economic analysis are 

substantial and real. The final rule must not only assert that the empirical estimates are gains for 

consumers, it should also conclude that there is a theoretical justification for incorporating those 

consumer welfare gains. 

In the proposed rule the agencies identify an argument which says that consumers buy the cars they want 

and the government can't possibly improve on that outcome. Now, there are some people who believe 

that. There is no support for that in the academic or empirical literature. The agency also recognizes the 

argument that consumers because of their behavioral patterns, their motivations, their perceptions, their 

calculations, may not have perfect information, perfect foresight, the ability to calculate the life cycle cost 

of the automobile. And they identify that as a possible basis for concluding that a standard might help 

consumers get better products, that if they were smart enough they would be able to figure out they really 

need it. 

Ironically, there is no discussion of the frailties of the auto industry. Automakers are people, too. They 

have the same problems of motivation, perception, and calculation. They make mistakes. We actually 

own two of them in the United States because they made mistakes. And there's solid evidence that it was 

management mistakes that contributed to the demise of the industry. 

Docket Number: 0046 

Organization: Tennessee Department of Transportation 

Commenter: Gerald Nicely 

Two arguments are often used in criticizing tighter CAFE standards. Some argue that the costs are too 

high, while others believe that they will make vehicles less safe. The standards will cost up to $1,300 per 
10.2 The Proposed Action and Alternatives Chapter 10 Responses to Public Comments 

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vehicle by 2016 but would save the average driver $3,000 in fuel costs over the life of the vehicle. Future 

increases in fuel prices will mean even greater savings at the pump. After a five-year vehicle loan is paid 

off, the additional fuel savings from a more efficient vehicle will continue to benefit vehicle owners. 

Response 

NHTSA considers the potential effects of this rulemaking on consumer welfare as one part of the agency’s 

evaluation of the costs and benefits of its proposal. From the societal perspective, the economic benefits 

and costs of establishing higher CAFE standards include not only private benefits and costs, but also 

changes in the value of environmental and economic externalities that result from fuel consumption and 

vehicle use. These include the reduction in potential climate-related economic damages resulting from 

lower CO2 emissions, reduced damages to human health from lower emissions of criteria air pollutants, 

reductions in economic externalities associated with U.S. petroleum imports, and increases in traffic 

congestion, vehicle noise, and accidents caused by the increased driving that results from the fuel 

economy rebound effect. 

A complete analysis of the potential effects of this rulemaking on consumer welfare will be published 

along with the forthcoming joint NHTSA-EPA Final Rule. For additional discussion of NHTSA’s 

consideration of consumer welfare, see section IV.G of the PRIA. 

10.2.3.4.7 Discount Rate 

Docket Number: 0098 

Organization: New York Department of Transportation 

Commenter: Stanley Gee 

It is not clear if the same discount rate that is applied to future benefits is applied to future costs in the 

proposal. For example, several tables (e.g. Tables IV.G.4-10 through IV.G.4-14) present various cost and 

benefit values. The titles of these tables imply that a discount rate is applied equally to costs and benefits. 

However, the NPRM defines the discount rate as follows: 'The Reference Case uses a discount rate of 3 

percent to discount future benefits." Although the sensitivity analyses in the DEIS and NPRM indicate 

that the only economic factors of importance are industry compliance costs, the cost of fuel, and the 

magnitude of the rebound effect, the DEIS and NPRM should more clearly define how discount rates are 

applied to both costs and benefits. As noted in our comments to NHTSA dated September 8, 2008, 

discount rates should be applied to both benefits and costs. 

Response 

One of the most complex issues in estimating benefits associated with the mitigation of climate change 

involves selecting the appropriate discount rate. Discounting future benefits and costs is intended to 

account for the reduction in their value to society when they are deferred until some future date, rather 

than received immediately. The discount rate expresses the percent decline in the value of these benefits – 

as viewed from today’s perspective – for each year they are deferred into the future. In evaluating the 

non-climate-related benefits of the proposed standards, NHTSA has employed discount rates of both 3 

percent and 7 percent as guided by the Office of Management and Budget. See 74 FR 49454, 49506; 

PRIA § VIII. NHTSA agrees that the discount rate should be applied to all benefits and costs that occur 

in the future. The discount rate, as applied to technology costs, the cost of fuel, and the magnitude of the 

rebound effect is described below. 

NHTSA treats technology costs as occurring in the present, which is the model year in which future 

vehicles will be produced and sold. Thus, technology costs are not discounted in the proposal. 
Chapter 10 Responses to Public Comments 10.2 The Proposed Action and Alternatives 

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Additionally, NHTSA defines future savings in fuel costs as benefits, thereby discounting them as the 

commenter recommends. Future costs resulting from increased rebound-effect driving (including 

increased costs of congestion, accidents, and noise) are treated as ‘dis-benefits’ (i.e., negative benefits 

which are subtracted from positive benefits such as fuel savings). These future costs are also discounted 

as the commenter recommends. For additional details on the application of discount rates in the 

proposal, NHTSA refers readers to Section VIII of the PRIA.

10.2.4 Alternatives 

Note to Reader 

Where there is a federal action requiring an EIS, NEPA requires an agency to develop “alternatives to 

the proposed action.” 42 U.S.C. § 4332(2)(C)(iii). CEQ regulations state that consideration of 

alternatives is the “heart” of an EIS. 40 CFR § 1502.14. However, under CEQ regulations and 

applicable case law, NHTSA is not required to include every conceivable “alternative” in an EIS, nor 

necessarily other hypothetical “alternatives” submitted by commenters. Rather, an agency is to consider 

“reasonable” alternatives. The purpose of and need for the action determines the range of reasonable 

alternatives under NEPA. NHTSA believes its analysis of alternatives satisfies NEPA. 

The CEQ regulations state that the alternatives “should present the environmental impacts of the 

proposal and the alternatives in comparative form, thus sharply defining the issues and providing a clear 

basis for choice among options by the decisionmaker and the public.” 40 CFR § 1502.14. CEQ 

guidance also instructs that “[w]hen there are potentially a very large number of alternatives, only a 

reasonable number of examples, covering the full spectrum of alternatives, must be analyzed and 

compared in the EIS.” Forty Most Asked Questions Concerning CEQ’s National Environmental Policy 

Act Regulations, 46 FR 18026, 18027 (Mar. 23, 1981). The CEQ regulations for EISs further provide 

that the alternatives section must: 

(a) Rigorously explore and objectively evaluate all reasonable alternatives, and for alternatives 

which were eliminated from detailed study, briefly discuss the reasons for their having been 

eliminated. 

(b) Devote substantial treatment to each alternative considered in detail including the proposed 

action so that reviewers may evaluate their comparative merits. 

(c) Include reasonable alternatives not within the jurisdiction of the lead agency. 

(d) Include the alternative of no action. 

(e) Identify the agency’s preferred alternative or alternatives, if one or more exists, in the draft 

statement and identify such alternative in the final statement unless another law prohibits the 

expression of such a preference. 

(f) Include appropriate mitigation measures not already included in the proposed action or 

alternatives. 

40 CFR § 1502.14. 

Agencies are required to examine reasonable alternatives, and not those that are a “worst case 

scenario.” Robertson v. Methow Valley Citizens Council, 490 U.S. 332, 354-55 (1989). An agency is not 

required to consider alternatives “whose effect cannot be reasonably ascertained, and whose 
10.2 The Proposed Action and Alternatives Chapter 10 Responses to Public Comments 

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implementation is deemed remote and speculative.” Headwaters, Inc. v. Bureau of Land Mgmt., Medford 

Dist, 914 F.2d 1174, 1180 (9th Cir. 1990) (quoting Life of the Land v. Brinegar, 485 F.2d 460 (9th Cir. 

1973), cert. denied, 416 U.S. 961 (1974)). An agency is also not required to consider alternatives that 

are “infeasible, ineffective, or inconsistent with the basic policy objectives” of the proposal. Id. (citing 

California v. Block, 690 F.2d 753, 767 (9th Cir. 1982)). 

CEQ guidance on this point is similar. “Reasonable alternatives include those that are practical or 

feasible from the technical and economic standpoint and using common sense, rather than simply 

desirable from the standpoint of the applicant.” Forty Most Asked Questions Concerning CEQ's 

National Environmental Policy Act Regulations, 46 FR 18026, 18027 (Mar. 23, 1981) (emphasis added). 

The “rule of reason” also guides the choice of alternatives and the extent to which the EIS must discuss 

each alternative. See, e.g., City of Carmel-by-the-Sea v. U.S. Dep’t of Transp., 123 F.3d 1142, 1155 (9th 

Cir. 1997). See also American Rivers v. FERC, 201 F.3d 1186, 1200 (9th Cir. 2000) (same, quoting City 

of Carmel-by-the-Sea, 123 F.3d at 1155). Under the rule of reason, an agency “need not consider an 

infinite range of alternatives, only reasonable or feasible ones.” Id. (citing 40 CFR § 1502.14(a)-(c), as 

set forth above). “[F]or alternatives which were eliminated from detailed study, [an EIS must] briefly 

discuss the reasons for their having been eliminated.” American Rivers v. FERC, 201 F.3d at 1200 

(citing 40 CFR § 1502.14(a)) (emphasis in original). 

With this understanding, and as explained in the NPRM and the DEIS, EPCA requires the Secretary of 

Transportation to establish average fuel economy standards for each model year at least 18 months 

before the beginning of that model year and to set them at “the maximum feasible average fuel economy 

level that the Secretary decides the manufacturers can achieve in that model year.” When setting 

“maximum feasible” fuel economy standards, the Secretary is required to “consider technological 

feasibility, economic practicability, the effect of other motor vehicle standards of the Government on fuel 

economy, and the need of the United States to conserve energy.” NHTSA has always taken passenger 

safety into account in adopting CAFE standards. NHTSA has also considered environmental issues and 

other relevant societal issues, such as safety. “Congress did not prescribe a precise formula by which 

NHTSA should determine the maximally-feasible fuel economy standard, but instead gave it broad 

guidelines within which to exercise its discretion.” Competitive Enterprise. Inst. v. NHTSA, 901 F.2d 

107, 121 (D.C. Cir. 1990) (citing Public Citizen v. NHTSA, 848 F.2d 256, 265 (D.C. Cir. 1988)). See 

also Ctr. for Auto Safety v. NHTSA, 793 F.2d 1322, 1340 (D.C. Cir. 1986) (same). Thus, EPCA does not 

require the agency to establish fuel-economy standards at any chosen level, but instead confers on 

NHTSA broad discretion to balance these factors when setting an appropriate standard. 

This FEIS informs decisionmakers and the public of the reasonable alternatives and the environmental 

impacts associated with each alternative. Consistent with EPCA’s overall purpose – energy conservation 

– NHTSA sought to balance the EPCA statutory factors when articulating its Preferred Alternative in the 

DEIS. After careful consideration of all comments, NHTSA concludes that Alternative 4 remains the 

agency’s Preferred Alternative. Alternative 4 represents the required fuel economy level that NHTSA has 

determined to be the “maximum feasible” under EPCA, based on balancing statutory and other relevant 

considerations. 

With this understanding of the applicable standards for NEPA alternatives in the context of this 

rulemaking under EPCA, NHTSA turns now to the comments the agency received regarding specific 

alternatives. The comments fell into several subcategories, which are set forth below along with 

NHTSA’s response.
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10.2.4.1 Environmentally Preferred Alternative 

Docket Number: 0049 

Organization: Individual 

Commenter: James Adcock

The DEIS fails to identify the "environmentally preferred alternative." 

Response 

The agency’s preferred alternative was identified in the DEIS, in accordance with NEPA requirements. 

However, different requirements apply to the alternative that is considered to be environmentally 

preferable. The CEQ Regulations require that the alternative that is considered to be environmentally 

preferable be identified in the Record of Decision (ROD) for the agency action, not in the DEIS or FEIS. 

See 40 CFR § 1505.2. In accordance with 40 CFR § 1505.2(b) NHTSA will identify and discuss the 

alternative that is considered to be environmentally preferable in the ROD, which will be issued a 

minimum of 30 days after release of the FEIS. See 40 CFR § 1506.10(b). 

10.2.4.2 No Action Alternative 

Comments 

Docket Number: 0053.1 

Organization: Center for Biological Diversity, Public Citizen, and the Sierra Club 

Commenter: Brian Nowicki 

The No Action alternative presumes no federal action to raise fuel economy, not even actions necessary to 

achieve the 35 mpg standards mandated in the EISA. NHTSA claims that this is a requirement from CEQ. 

However, NHTSA cannot presume away implementation of California’s (Pavley) standards that apply to 

greenhouse gas emissions from motor vehicles sold in California, representing approximately 40% of the 

U.S. new vehicle market. In addition, California has been granted the federal Clean Air Act waiver to 

implement the greenhouse gas standards; California and 16 other states are expected to implement these 

standards. The No Action scenario should have accounted for this. 

Docket Number: TRANS01 

Organization: Sierra Club 

Commenter: Ann Mensikoff 

NHTSA's no action scenario fails to account for California's implementation of its standards . . . . 40 

percent of the market covered by those standards, a no action scenario which may be required by CEQ 

and should assume no national governmental action, that CAFE will not be implemented, that an energy 

bill will not be implemented, that NHTSA would do nothing, it cannot ignore the action that the agency 

cannot control . And I think in that case it's a failure to account for California's implementation and 40 

percent of the vehicle market being covered by those standards that would affect how the different 

scenarios measure up and compare to each other in the DEIS. And I think it skews the analysis and should 

be reconciled in the final DEIS. 
10.2 The Proposed Action and Alternatives Chapter 10 Responses to Public Comments 

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Docket Number: TRANS02 

Organization: Public Citizen 

Commenter: Lena Pons 

Again, NHTSA has sensibly identified the problem that you cannot regulate greenhouse gas emissions for 

motor vehicles by regulating fuel economy alone. But the agency does not consider actions outside the 

jurisdiction as required by NEPA. These actions that have not been considered include continued 

regulation of greenhouse gases by California and the states and policies to reduce vehicle miles traveled. 

It is reasonably foreseeable that California will continue to extend regulations for greenhouse gas 

emissions for motor vehicles and intend to do so beyond 2017. NHTSA makes no attempt to consider the 

impacts of these standards for a substantial share of the U.S. light duty vehicle market. 

Docket Number: TRANS01 

Organization: Sierra Club 

Commenter: Ann Mensikoff 

NHTSA cannot ignore again California's implementation of its standards in its no action scenario. 

Response 

NEPA provides that, where a federal action requires an EIS, an agency must develop “alternatives to the 

proposed action.” 42 U.S.C. § 4332(2)(C)(iii). Pursuant to CEQ regulations, the alternatives must be 

compared against a “no action” alternative. 40 CFR § 1502.14. CEQ guidance instructs that where the 

agency’s choice of no action “would result in predictable actions by others, this consequence of the ‘no 

action’ alternative should be included in the analysis.” Forty Most Asked Questions Concerning CEQ’s 

National Environmental Policy Act Regulations (“Forty Questions”), 46 FR 18026, 18027 (Mar. 23, 

1981). For example, “if denial of a permission to build a railroad to a facility would lead to construction 

of a road and increased truck traffic, the EIS should analyze this consequence of the ‘no action’ 

alternative.” Id. 

NHTSA’s No Action Alternative (Alternative 1) assumes no action would occur under the National 

Program. Under that alternative, neither NHTSA nor EPA would issue a rule regarding the CAFE 

standard or GHG emissions for MYs 2012-2016. The No Action Alternative assumes that average fuel 

economy levels in the absence of CAFE standards beyond MY 2011 would equal the higher of the 

agencies’ collective market forecast or the manufacturer’s required level of average fuel economy for MY 

2011. 

Several commenters suggested that NHTSA’s No Action Alternative should account for implementation of 

motor vehicle GHG standards by California and other states, which would directly affect the fuel 

economy of new passenger cars and light trucks sold in those states. Pursuant to the Clean Air Act 

(CAA), 42 U.S.C. § 7401 et seq., federal emission standards set by EPA generally preempt state and local 

government emission standards for new motor vehicles. California, however, may be granted a waiver to 

set emission standards under certain circumstances. See 42 U.S.C. § 7543; CAA § 209. In addition, 

pursuant to section 177 of the CAA, any other state may adopt a plan for regulating vehicle emissions if 

its plan is identical to one for which California was granted a waiver. See 42 U.S.C. § 7507. 
Chapter 10 Responses to Public Comments 10.2 The Proposed Action and Alternatives 

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On June 30, 2009, EPA granted a waiver to California, allowing the State to set GHG standards for 

motor vehicles starting with MY 2009. 74 FR 32744 (Jul. 8, 2009).4

 California has adopted regulations 

implementing such standards,5 and, in addition, 13 other states and the District of Columbia have 

adopted California’s standards pursuant to section 177 of the CAA.6

 

If NHTSA were not to implement CAFE standards for MYs 2012-2016,7

 it is likely that California, as well 

as those jurisdictions that have adopted the California standards, would enforce California state motor 

vehicle GHG standards pursuant to section 177 of the CAA (42 U.S.C. § 7507).8

 Assuming that most or 

all of these state regulations would be effective for MY 2012 vehicles,9

 one conceivable result of states 

enforcing California motor vehicle GHG standards in the absence of new CAFE standards is that the 

average fuel economy of new passenger cars and light trucks produced and sold in the United States 

would rise. However, while action by California and other states is likely in the absence of action by 

NHTSA, numerous factors (further detailed below), make the actual impact of such action – and therefore 

the impact of such action on the baseline analyzed by NHTSA – especially uncertain. In particular, the 

range of potential actions by numerous state actors, taken together with the complex economic and 

political considerations that may influence the automobile market in the absence of new CAFE standards, 

injects uncertainty into the determination of a modified No Action Alternative. 

A no action alternative must take into account predictable actions of others. Forty Questions, 46 FR at 

18027. At the same time, however, CEQ guidance indicates that the purpose of including a no action 

alternative in the EIS is to provide “a benchmark, enabling decisionmakers to compare the magnitude of 

environmental effects of the action alternatives.” Id. As one court noted regarding the no action 

 

4

 EPA’s decision granting the California Air Resources Board’s (CARB’s) request for a waiver noted that CARB 

could “fully implement and enforce its regulations . . . for 2009 model year families issued both before and after the 

date of today’s waiver . . . .” 74 FR at 32778. 

5 See 13 Cal. Code Regs. 1961.1.

6 New York (6 N.Y. Code, R. & Regs., 218-8.3); Massachusetts (310 Code of Mass. Regs. 7.40(2)(a)(6)); Maryland 

(Code of Md. Regs. § 26.11.34); Vermont (Vt. Air Poll. Ctrl. Regs., subch. XI, 5-1106(a)(5)); Maine (06 Code of 

Maine Rules § 127); Connecticut (Conn. Admin. Code § 22a-174-36b); Arizona (Ariz. Admin. Code 18-2-1802); 

New Jersey (N.J. Admin. Code § 7:27); New Mexico (N.M. Admin. Code § 20-2-88); Oregon (Or. Admin. Rules § 

340-257); Pennsylvania (36 Pa.B. 7424); Rhode Island (R.I. Air Poll. Ctrl. Reg. 37.2.3); Washington (Wash. 

Admin. Code § 173-423-090(2)); and Washington, D.C. (D.C. Law 17-0151). In addition, several other states 

appear to have completed steps necessary for the adoption of standards, including Florida and Colorado. 

7

 Although EISA’s recent amendments to EPCA direct NHTSA to increase CAFE standards and do not permit the 

agency to take no action on fuel economy, CEQ regulations mandate analysis of a no action alternative. See 40 

CFR § 1502.14(d). CEQ has explained that: “[T]he regulations require the analysis of the no action alternative 

even if the agency is under a court order or legislative command to act.” Forty Most Asked Questions Concerning 

CEQ’s National Environmental Policy Act Regulations, 46 FR 18026 (1981) (emphasis added). 

8 In a May 18, 2009 letter to EPA Administrator Lisa P. Jackson and Secretary of Transportation Ray LaHood, 

Mary D. Nichols, Chairman of the California Air Resources Board, stated that California committed “to revise its 

standards on GHG emissions from new motor vehicles for MY 2012 through 2016, such that compliance with the 

GHG emissions standards adopted by EPA shall be deemed compliance with the California GHG emissions 

standards. . . .” California’s commitment contemplated that a number of actions would occur, including that EPA 

would propose and adopt national GHG standards “substantially as described in the May, 2009 Joint Notice of 

Intent to conduct rulemaking.” 

9

 State regulations implementing the California standards appear to have varying enforcement dates. While 

California and a number of states’ regulations become effective for MY 2012 vehicles, other states begin to enforce 

the standards in 2011 or 2012. See e.g., N.M. Admin. Code 20-2-88; Code of Md. Regs. § 26.11.34; Ariz. Admin. 

Code 18-2-1802. 
10.2 The Proposed Action and Alternatives Chapter 10 Responses to Public Comments 

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alternative, “the [CEQ] intended that agencies compare the potential impacts of the proposed major 

federal action to the known impacts of maintaining the status quo.” Custer County Action Assoc. v. 

Garvey, 256 F.3d 1024, 1040 (10th Cir. 2001) (citing Ass’n of Pub. Agency Customers v. Bonneville 

Power Admin., 126 F.3d 1158, 1188 (9th Cir. 1997), and 46 FR 18,026, 18,027 (1981)). As explained 

below, NHTSA believes the No Action Alternative as described in the DEIS effectively serves its purpose 

as a benchmarking and comparison tool for the decisionmaker. 

In the absence of federal action, it is unclear how manufacturers would react to the two sets of standards 

that applied in different states – the California standard in California and in other states adopting the 

California standard, and no CAFE standard in all other states.10 For example, in the absence of federal 

action, rather than marketing different vehicle fleets in states that adopted the California standard and 

those that did not, some manufacturers might opt to produce and sell vehicles that met a uniform 

California standard nationwide. Alternately, in the current economic climate, it is plausible that a 

number of manufacturers might simply shift the availability and sale of more fuel-efficient existing models 

to those states that had adopted the California standards, while selling vehicles with lower fuel economy 

elsewhere. Manufacturers’ product decisions in this regard are likely to depend in part on the number of 

states that adopt California standards and the timeline over which they are adopted. 

Hypothetically, the No Action Alternative could be affected in the following ways. If manufacturers 

complied with the California standard by shifting distribution networks to sell only higher mpg vehicles in 

those states that adopted and were enforcing California GHG emissions standards and to sell lower mpg 

vehicles in states that were not enforcing California GHG emissions standards, the agency’s No Action 

Alternative would not change at all, because with this seemingly least-cost compliance strategy, the 

average fuel economy of these manufacturers’ fleets would not change. At the other extreme, if 

manufacturers modified their fleets to meet California standards on average, the No Action Alternative 

would result in the same emissions reductions as the agency’s Preferred Alternative. A manufacturer 

might choose this latter course of action to maximize flexibility in the distribution of vehicles across the 

country while simultaneously ensuring that it met GHG emissions limits in the states that were enforcing 

California’s GHG emission standards. Different manufacturers might choose different strategies or 

combinations of strategies. 

NHTSA believes that the likely reaction across all vehicle manufacturers would fall somewhere in 

between these two boundaries but cannot ascertain with any reasonable confidence the combination of 

shifts in vehicle distribution patterns and application of fuel-economy-increasing technologies that would 

occur. Due to these uncertainties, determining an appropriate and reasonable way to adjust the agency’s 

No Action Alternative is problematic at best. 

The broad geographical impacts of this action, as well as the numerous potential actors involved, make it 

distinguishable from most actions requiring the issuance of an EIS. Indeed, cases in which the No Action 

Alternative has been examined with regard to actions by others have generally been limited to those in 

 

10 If NHTSA failed to take action to set CAFE standards for a given model year, no CAFE standard would apply for 

that model year. 
Chapter 10 Responses to Public Comments 10.2 The Proposed Action and Alternatives 

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 which an agency’s action will be confined to a specific, identifiable locale and the actions expected by 

others in the absence of a federal agency’s action are relatively certain.11 

Aside from the uncertainty in determining the baseline for a modified No Action Alternative, as a 

practical matter, the agency does not understand how such a modification would change the 

decisionmaker’s task. One commenter suggests that consideration of the California standards would 

affect how the alternatives “measure up and compare to each other in the DEIS” and that failure to 

consider them “skews the analysis.” We believe that the practicable effect of taking the California 

standards into account would be to decrease the measured difference in environmental impacts between 

the No Action Alternative and the other alternatives under consideration. While the effects of the action 

alternatives would be measured from a different reference point, the difference between the action 

alternatives would not change. Thus, the fact that states might act in the absence of Federal action does 

not change the calculus before the federal decisionmaker in setting CAFE standards. 

In NHTSA’s view, given the uncertainty of determining the effect of state GHG standards on overall 

emissions in the absence of federal action, a modified No Action Alternative is not required here under 

CEQ guidance and applicable law. Because the effects of the action alternatives would simply be 

measured from a different, if possibly higher, reference point, such a modified No Action Alternative 

would not aid the decisionmaker or the public in understanding the relative environmental impacts of the 

alternatives. 

10.2.4.3 Suggestions for New Alternatives 

Comments 

Docket Number: 0050.1 

Organization: Environmental Consultants of Michigan 

Commenter: 

Low Carbon Fuel Standards are an emerging greenhouse gas control strategy employed around the world. 

Using the most recent GHG lifecycle models published by the Department of Energy's Argonne National 

Lab. Converting 100% of the ENTIRE ON ROAD FLEET of motor vehicles (not just new motor 

vehicles) to achieve over 100 mpg would be insufficient to achieve an 80% reduction in sector GHGs. On 

the other hand, changing less than half of the fuel to a second generation Fischer-Tropsch (or Mobil 

Process) gasoline and/or diesel would achieve this substantial reduction without changing the on road 

fleet. Thus Low Carbon Fuel Standards are: 

1. Inevitable 

2. Necessary to achieve any meaningful reduction in GHG emissions 

3. Not in conflict with common law, the Fifth Amendment or the decision in Massachusetts vs. EPA 

Given the refinery industry investment in hydrocarbon based fuels, it is reasonable to assume that if a 

National Low Carbon Fuel Standard is implemented, the industry will find ways to produce renewable 

 

11 See, e.g., Nashvillians Against I-440 v. Lewis, 524 F.Supp. 962, 988-89 (M.D. Tenn, 1981) (upholding agency’s 

determination that “no action” alternative should include anticipated improvements to a city’s surface streets in the 

absence of building the proposed highway); Ctr. for Biological Diversity v. Dep’t of the Interior, 581 F.3d 1063 (9th 

Cir. 2009) (finding agency’s definition of “no action” alternative arbitrary and capricious where the agency had 

detailed knowledge of the plans of a potential land owner with regard to specific land proposed to be exchanged); 

Young v. Gen. Serv. Admin., 99 F.Supp.2d 59 (D.D.C. 2000) (finding government’s inclusion of foreseeable private 

development of a specific site in the “no action” alternative reasonable). 
10.2 The Proposed Action and Alternatives Chapter 10 Responses to Public Comments 

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diesel and gasoline. Royal Dutch Shell is currently partnering with German based Choren Industries to 

build a biomass to biodiesel plant. Choren believes Bio-to-Liquid fuels could meet 10 percent of 

Germany's transport fuel needs by 2015. Its 'Carbo-V' process turns wood and other biomass into 

'SunDiesel', capturing the attention of major corporations such as Volkswagen, Renault, Ford and 

Daimler. Choren estimates that global biomass production exceeds oil consumption by five-fold. 

[Citations omitted]. 

Choren and other biofuel innovators, such as Canadian ethanol developer Iogen (also partnered with 

Shell), work with biomass -- organic leftovers such as sawdust -- which are as abundant as they are cheap. 

A Canadian study revealed that the biodiesel produced from just 10 percent of the country's agricultural 

wastes would satisfy 16.7 percent of its appetite for diesel. 

The key to achieving sustainability target in the transportation sector (and most other sectors) is the 

switch to low carbon and carbon-free fuels that can be used in existing vehicles. 

Docket Number: 0053.1 

Organization: Center for Biological Diversity, Public Citizen, and the Sierra Club 

Commenter: Brian Nowicki 

The EPCA is a “technology-forcing” statute, whereby a challenging standard encourages technological 

innovation. As part of the statutory balancing, NHTSA must necessarily determine what is 

“technologically feasible.” While NHTSA has discretion to set standards somewhere below that level 

based on its consideration of the three other statutory factors, if it is reasonable to do so, NHTSA violates 

both EPCA and NEPA by failing to even consider or disclose what is truly “technologically feasible.” An 

essential component of the EIS must be disclosure of the maximum “technologically feasible” fuel 

economy level, along with the environmental impact of choosing this level of fuel economy as compared 

to NHTSA’s preferred alternative and a reasonable range of additional alternatives. The DEIS fails to 

provide both the basic starting point for this analysis and the proper analysis that must follow. [Citations 

omitted]. 

In the DEIS, NHTSA rejects calls for analysis of a technologically feasible level. “We consider the upper 

range of alternatives presented in this EIS to be technology forcing because at these higher average annual 

percentage increases some manufacturers run out of technologies before reaching the required CAFE 

standard and, therefore, these standards will be theoretically impossible to meet for some manufacturers. 

Since these higher average annual percentage increase regulatory alternatives force manufacturers to do 

something they would not otherwise be required to do, they are in that sense “technology forcing” as 

well.” DEIS at 2-22. That is, NHTSA appears to define “technology forcing” as any standard that is 

beyond the capacity of “some” manufacturers, utilizing the technologies currently in use in those product 

lines. 

In their proposed joint rulemaking, NHTSA and EPA recognize that this approach is incorrect: “At the 

same time, the law does not preclude a CAFE standard that poses considerable challenges to any 

individual manufacturer. The Conference Report for EPCA, as enacted in 1975, makes clear, and the case 

law affirms, ‘a determination of maximum feasible average fuel economy should not be keyed to the 

single manufacturer which might have the most difficulty achieving a given level of average fuel 

economy.’ Instead, NHTSA is compelled ‘to weigh the benefits to the nation of a higher fuel economy 

standard against the difficulties of individual automobile manufacturers.’ 

Id. The law permits CAFE standards exceeding the projected capability of any particular manufacturer as 

long as the standard is economically practicable for the industry as a whole. Thus, while a particular 

CAFE standard may pose difficulties for one manufacturer, it may also present opportunities for another. 
Chapter 10 Responses to Public Comments 10.2 The Proposed Action and Alternatives 

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The CAFE program is not necessarily intended to maintain the competitive positioning of each particular 

company. Rather, it is intended to enhance fuel economy of the vehicle fleet on American roads, while 

protecting motor vehicle safety and being mindful of the risk of harm to the overall United States 

economy.” Proposed Rulemaking to Establish Light-Duty Vehicle Greenhouse Gas Emission Standards 

and Corporate Average Fuel Economy Standards; Proposed Rule, 74 FR 49461 (Sept. 28, 2008). 

Furthermore, NHTSA’s position directly contradicts the “technology forcing” intention of the EPCA, 

which is meant to encourage technological innovation in the field, not just the wider adoption of existing 

technologies. As the court in Center for Auto Safety v. Thomas noted, “[t]he experience of a decade 

leaves little doubt that the congressional scheme in fact induced manufacturers to achieve major 

technological breakthroughs as they advanced towards the mandated goal.” 847 F.2d 843, 870 (D.C. Cir. 

1988) (overruled on other grounds); see also Green Mt. Chrysler Plymouth Dodge Jeep v. Crombie, 508 

F. Supp. 2d 295, 358-359 (D. Vt. 2007) (discussing technology-forcing character of EPCA and the use of 

increased fuel efficiency to augment performance rather than mileage). As explained by the court in 

Kennecott Greens Creek Min. Co. v. Mine Safety and Health Admin., “when a statute is technology 

forcing, the agency can impose a standard which only the most technologically advanced plants in an 

industry have been able to achieve-even if only in some of their operations some of the time.” 476 F.3d 

946, 957 (D.C. Cir. 2007) (quoting United Steel Workers of America, AFL-CIO-CLC v. Marshall, 647 

F.2d 1189, 1246 (D.C. Cir. 1980). With regard to a similarly technology-forcing statute, the Clean Air 

Act, legislative history indicates that the primary purpose of the Act was not “to be limited by what is or 

appears to be technologically or economically feasible,” which may mean that “industries will be asked to 

do what seems impossible at the present time.” 116 Cong. Rec. 32901-32902 (1970), Legislative History 

of the Clean Air Amendments of 1970 (Committee Print compiled for the Senate Committee on Public 

Works by the Library of Congress), Ser. No. 93-18, p. 227 (1974); see also Whitman v. American 

Trucking Associations, 531 U.S. 457, 491 (2001). 

* * * * * 

Due to the technology-forcing nature of the statutory scheme, NHTSA was required to include one or 

more technology-forcing alternatives in the DEIS. Such an alternative would include standards that may 

appear difficult to achieve today, but that would force innovation as industry strives to meet such a 

standard. Having failed to include such an alternative, NHTSA then failed to analyze the environmental 

impacts of a technology-forcing standard. This omission is particularly significant because such a 

technology forcing standard would have environmental benefits that not only amplify the ability of 

automakers to meet higher standards in later years, but that also create benefits throughout the economy 

through new investment, the creation of green jobs, and the potential for technological development in 

one field to spur innovation in another sector. NHTSA’s failure to consider this important aspect of the 

analysis renders the DEIS inadequate. 

Docket Number: 0098 

Organization: New York Department of Transportation 

Commenter: Stanley Gee 

NYSDOT recommends that NHTSA establish a more aggressive standard and achievement timetable for 

the new CAFE standards. In our comments to NHTSA on the DEIS for the MY 2011-2015 standards 

dated August 18, 2008, NYSDOT recommended that NHTSA establish a hybrid of alternatives that 

would be equivalent to the ''Total Costs Equal Total Benefits (TCTB)” alternative for passenger vehicles 

and the "Technology Exhaustion" alternative for light duty trucks. Such a standard would result in a 

required fuel economy of 43.3 mpg for passenger vehicles and 34.7 miles per gallon for light duty trucks. 
10.2 The Proposed Action and Alternatives Chapter 10 Responses to Public Comments 

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Response 

One commenter suggests that NHTSA’s analysis should have taken into account “low carbon fuel 

standards.” The commenter states that changing a portion of the fuel to a second generation gasoline 

and/or diesel would achieve a greater reduction in GHG emissions. 

Under EPCA, NHTSA prescribes average fuel economy standards. Thus NHTSA does not have the 

statutory authority to require the reductions in GHGs emitted by vehicles driven; nor does it have the 

statutory authority to regulate the content or type of vehicle fuel. As a practical matter, however, as 

NHTSA’s fuel economy standards are made more stringent, emissions of CO2 per mile driven decrease. 

EPA’s formula for calculating fuel economy (mpg) is controlled by and directly related CO2 emissions. 

 

In response to the comment that NHTSA did not include a technology-forcing alternative, the agency 

expects that, other than the No Action Alternative, all of the analyzed alternatives will induce 

manufacturers to implement additional technologies. Further, for the higher average annual percentage 

increases considered in this EIS some manufacturers run out of available technologies before reaching 

the required CAFE standard and, therefore, these standards will be theoretically impossible to meet for 

some manufacturers. Since these higher average annual percentage increase regulatory alternatives 

would tend to force manufacturers to do something they could not do with available technologies, they 

are in that sense “technology forcing” as well. Also, for most fuel efficiency technologies that NHTSA 

took into account in its analysis, the agency applied phase-in constraints that made less limited 

assumptions than in previous rulemaking analyses, while continuing to recognize that most technologies 

must still be applied as part of a vehicle freshening or redesign. 

Further, NHTSA notes that, under CEQ regulations and applicable case law, NHTSA is not required to 

include every conceivable alternative in an EIS, nor necessarily other hypothetical alternatives submitted 

by commenters. Rather, an agency is to consider “reasonable” alternatives. The purpose of and need 

for the rulemaking determines the range of reasonable alternatives under NEPA. We consider our range 

of alternatives to represent a reasonable range of possible agency actions. For a discussion of the 

alternatives, see Section 2.3 of the DEIS and this FEIS, Chapter III of the PRIA. 

10.2.4.4 Adoption of More Aggressive Alternatives 

Comments 

Docket Number: TRANS03 

Organization: Consumer Federation of America 

Commenter: Mark Cooper 

The transitional nature of this proceeding has led the agencies to set the standard at the level agreed upon 

by federal and state authorities through negotiation. But the subsequent analysis shows that the chosen 

levels leave a large quantity of consumer, economic, national security and environmental gains 

unrealized. If the standards were set at the level of maximum economic or maximum practicable 

environmental benefits, we would observe the following additional gains: 

Gasoline consumption would be lower than the proposed standard by 28 to 34 billion gallons, pushing the 

total savings to about 90 billion gallons. 

The net present value of societal savings would be 20 to 25 billion higher, pushing it to a total of over 120 

billion. The consumer pocketbook savings would be about 80 billion, 10 billion more than the proposed 

standards. 
Chapter 10 Responses to Public Comments 10.2 The Proposed Action and Alternatives 

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Perhaps the most interesting, the average cost of conserved energy under a more rigorous standard would 

be less than $1.30 a gallon. The marginal cost would be $1.80 per gallon. That is compared to a projected 

average cost of gasoline over the life of the vehicles of $3.00 per gallon. 

The American consumer would benefit mightily if we captured the efficiency, the much lower cost 

efficiency, and stopped spending it on gasoline. So setting the standards to maximize economic benefit or 

maximum practicable environmental benefit is a win-win-win for consumers, the nation, and the 

environment. That is why EPA and NHTSA as they reconcile their statutes must not let the transition 

extend past the 2016 model year. Each year of delay in moving to the proper level of the standard results 

in severe loss to consumers and the nation. 

Response 

Congress has stated that when setting maximum feasible CAFE standards, NHTSA must consider and 

balance the four EPCA statutory factors (i.e., technological feasibility, economic practicability, the effect 

of other motor vehicle standards of the Government on fuel economy, and the need of the United States to 

conserve energy). 49 U.S.C. § 32902(f). NHTSA has balanced those factors in a way that achieves 

substantial fuel economy gains – on average 4.3 percent per year over five years. NHTSA notes that 

electing to impose more aggressive standards would impose substantial additional costs on the industry 

at a time when the industry and economy are both facing difficult conditions, and could result in part in 

more penalties rather than achieving higher levels of fuel economy. Overly aggressive standards would 

not achieve the result intended by EPCA, i.e., meeting EPCA’s overarching goal of energy conservation 

while also weighing economic practicability and technological feasibility. 

We disagree that consumer gains will be unrealized under the National Program. Consumers will be 

able to purchase a range of vehicles. This will include small, fuel-efficient vehicles.

One commenter noted that setting standards at the maximum economic or maximum practicable 

environmental benefit would result in additional gains, and appeared to urge the agency to take this into 

account in future rulemakings. By statute, the determination of the appropriate standards is based, not 

on maximum economic or environmental benefit, but on a balancing of the four factors identified above. 

The agency is mindful that there are lead time and other restraints that manufacturers face that limit 

acceleration of technologies. NHTSA has carefully balanced the statutory factors and believes that the 

Preferred Alternative reasonably accommodates these competing interests. For a discussion on NHTSA’s 

balancing of the factors, see Section IV.F of the NPRM. 

In response to comments urging NHTSA and EPA to look beyond MY 2016, we note that while this 

proposal covers MYs 2012-2016, EPA and NHTSA anticipate seeking a strong, coordinated national 

program for light-duty vehicles in model years beyond 2016 in a future rulemaking. 

10.2.4.5 Sensitivity Analysis 

Comments 

Docket Number: 0053.1 

Organization: Center for Biological Diversity, Public Citizen, and the Sierra Club 

Commenter: Brian Nowicki 

The sensitivity analysis of economic inputs to the Volpe model fails to describe the limitations and 

inherent problems of the model’s cost-benefit analysis. 
10.2 The Proposed Action and Alternatives Chapter 10 Responses to Public Comments 

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The sensitivity analysis of economic inputs to the Volpe model indicated relative insensitivity to a 

number of controversial factors. “Table 2.4-1 shows that fuel consumption (and thus related emissions 

and other environmental impacts) are relatively sensitive to fuel price projections, and somewhat sensitive 

to the estimated rebound effect, but relatively insensitive to changes in model input values for the 

discount rate, SCC, and oil import externalities.” DEIS at 2-19. 

It is disappointing that NHTSA continues to rely on the outdated methods and assumptions of the Volpe 

model, even if the role of the Volpe model was greatly reduced in the development of the current rule. 

The fact that the model is relatively sensitive to the rebound effect raises serious concerns about the use of 

the Volpe model when NHTSA has failed to adequately consider other agency actions, policies, and 

social changes that may affect vehicle miles traveled much more significantly than does the rebound 

effect. In addition, the insensitivity of the model to the social cost of carbon indicates that the Volpe 

model is an inappropriate tool in this context. The Volpe model, like the DEIS as a whole, fails to 

adequately incorporate and respond to the enormous real-world impacts and costs at stake as a result of 

the impacts of climate change. 

Response

The commenter does not appear to understand the agency’s use of the Volpe model. Although NHTSA 

uses the Volpe model as a tool to inform its consideration of potential CAFE standards, the results it 

produces are dependent on inputs selected by NHTSA. In addition to identifying the input assumptions 

underlying its decisions, NHTSA provides the rationale and justification for selecting those inputs, and is 

guided by the statutory requirements of EPCA in the ultimate selection of a CAFE standard. The agency 

recognizes that many of these variables (e.g., fuel price) are subject to change based on differing 

economic circumstances, making the assessment process difficult.. 

Recognizing the uncertainty inherent in many of the underlying estimates in the model, NHTSA uses the 

Volpe model to conduct both a sensitivity analysis, by changing one factor at a time, and a probabilistic 

uncertainty analysis (a Monte Carlo analysis that allows simultaneous variation in the factors), to 

examine how key measures vary in response to changes in these factors. This type of analysis is used to 

estimate the uncertainty of the costs and benefits of a given set of CAFE standards. Specifically, NHTSA 

examines the sensitivity of fuel savings and other benefits from adopting higher CAFE standards to 

variation in four economic parameters (specifically, the price of gasoline, the magnitude of the fuel 

economy rebound effect, the value of reducing CO2 emissions, and whether to include non-zero values for 

the reductions in monopsony payments to foreign petroleum suppliers and in outlays for maintaining the 

U.S. military presence in the Persian Gulf). In addition, the agency separately examines the sensitivity of 

total benefits to variation in the value of health benefits stemming from reducing emissions of criteria 

pollutants and reductions in fatalities resulting from improved vehicle safety. For additional information 

and preliminary results of NHTSA’s sensitivity analyses the agency refers readers to Section XII of the 

PRIA which addresses Net Benefits and Sensitivity Analyses. The sensitivity analysis results under 

consideration for the final rule are discussed in Section 2.4. 

NHTSA disagrees with the commenter’s assessment that the methods and assumptions of the Volpe model 

are outdated. The agency believes that the inputs it has selected and the range of alternatives considered 

in the DEIS and this FEIS fully inform the decisionmaker and the public about the environmental impacts 

of the Preferred Alternative, including impacts related to climate change. 

NHTSA further disagrees with the commenter’s assertion that the Volpe model is unduly insensitive to 

inputs specifying some economic estimates, including SCC. The manner in which the Volpe model 

applies these inputs to calculate economic benefits is the same as would apply outside the Volpe model. 

For example, applying the estimated SCC involves simply multiplying the SCC by the quantity of carbon 
Chapter 10 Responses to Public Comments 10.2 The Proposed Action and Alternatives 

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dioxide emissions avoided. Therefore, calculations performed outside the model should be similar in 

their relative sensitivity to changes in different economic inputs. The range of SCC values examined 

spanned $5–$56 per ton of carbon dioxide – a range equivalent to approximately $0.044–$0.498 per 

gallon of gasoline. By comparison, the range of gasoline prices examined spanned $2.04-$5.47 (by 

calendar year 2030), a range nearly eight times larger than the SCC range. It is only natural, therefore, 

that economic calculations – whether implemented using the Volpe model, some other tool, or hand 

calculations – would be far less sensitive to these SCC variations than to these fuel price variations.

10.2.4.6 Comparison of Alternatives and Context of Analysis 

Comments

Docket Number: 0046 

Organization: Tennessee Department of Transportation 

Commenter: Gerald Nicely 

Cut global warming emissions by 215 million metric tons in 2020, the equivalent of taking nearly 32 

million of today's cars and light trucks off the road that year. These standards are the single biggest step 

the U.S. can take to reduce energy consumption and greenhouse gas emissions. The draft EIS is much too 

negative about the significance of these reductions. 

Docket Number: 0053.1 

Organization: Center for Biological Diversity, Public Citizen, and the Sierra Club 

Commenter: Brian Nowicki 

The DEIS artificially minimizes climate change impacts by analyzing them only as a proportion of global 

greenhouse gas emissions. 

The DEIS itself points out that by analyzing the climate impacts of the rule solely as proportions of global 

greenhouse gas emissions, these obviously enormous impacts are artificially reduced to the point that 

quantitative analysis is made exceedingly difficult. “Although the alternatives have the potential to 

substantially decrease GHG emissions, alone they would not prevent climate change. The magnitude of 

the changes in climate effects that the alternatives would produce – 2 to 5 ppm of CO2, a few hundredths 

of a degree Celsius difference in temperature, a small percentage change in the rate of precipitation 

increase, and 1 or 2 millimeters of sea-level rise – are too small to address quantitatively in terms of their 

impacts on resources. Given the enormous resource values at stake, these distinctions could be important 

– very small percentages of huge numbers can still yield substantial results – but they are too small for 

current quantitative techniques to resolve. Consequently, the discussion of resource impacts does not 

distinguish among the CAFE alternatives; rather, it provides a qualitative review of the benefits of 

reducing GHG emissions and the magnitude of the risks involved in climate change.” DEIS at S-40. 

However, there are significant quantifiable differences among alternatives. For the DEIS to be meaningful 

and useful in making a decision, the agency must place impacts in a context that provides a basis for 

comparison between them. Rather than being compared only to overall global concentrations, alternatives 

should be analyzed for their effect on emissions from motor vehicles in particular and the U.S. 

transportation sector in general. For example, NHTSA estimates in the DEIS that in 2100 the 2012-2016 

standards would reduce global greenhouse gas emissions by 0.4 to 0.8 percent, but this reduction is more 

meaningful as a percent reduction in emissions from the U.S. light duty transportation sector. The U.S. 

transportation sector is the second largest contributor to this nation’s greenhouse gas emissions behind 

only the electricity sector. Understanding how the various alternatives begin to curb this key sector’s 
10.2 The Proposed Action and Alternatives Chapter 10 Responses to Public Comments 

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emissions is crucial to understanding what impact NHTSA’s first-ever efforts (in its joint rulemaking with 

EPA) to affect the U.S. contribution to global warming can and should make. 

NHTSA should also present alternatives analyzed for their effect on emissions from, and their capacity to 

contribute to, a cross-sectoral and national effort to reduce greenhouse gas emissions and avoid some of 

the most severe and imminent impacts of climate change. For example, NHTSA should consider the 

alternatives in terms of reducing greenhouse gas emissions to 1990 levels by 2020 – data that can be 

relatively reliably estimated, and that is highly relevant to decision makers and the public. The EPA’s 

inventory of greenhouse gas sources and sinks provides an estimate for 1990 greenhouse gas emissions 

and 2020 projected greenhouse gas emissions, assuming recent trends remain. Assuming reductions from 

light duty transportation that are proportional to reductions that must be contributed by other sectors to 

reach this goal, reductions of 423 million metric tons of carbon dioxide from the light vehicle sector alone 

are needed in 2020. NHTSA has estimated emissions reductions annually ranging between 217 million 

metric tons of CO2 and 479 million metric tons of CO2, with Alternatives 1-5 falling short of the 423 

million metric tons threshold and Alternatives 6-9 meeting or exceeding the threshold. In this context, 

there are dramatic differences among alternatives. Other important contexts for assessing the emissions 

and reductions proposed in the rule are President Obama’s commitment at the G8 summit in July 2009, to 

curtail climate change at 2 degrees Celsius above the historic average, and the need to reduce atmospheric 

concentrations to 350 ppm 

Docket Number: TRANS01 

Organization: Sierra Club 

Commenter: Ann Mensikoff 

Cars and light trucks emit 20 percent of U.S. C02 pollution. And CAFE standards can only reduce the 

emissions from that sector of the economy from those vehicles and should be evaluated, therefore, in a 

narrower context. NHTSA, and now EPA, has the administrative capacity to make a significant reduction 

in U.S. C02 emissions. NHTSA continues to minimize the impact of the different options it has control 

over rather than assessing them in an appropriate context or giving them meaning within a reasonably 

understandable context. And it therefore diminishes the differences between the different scenarios, the 

difference between getting to 35 in 2015 as we had urged based on the economic analysis in the prior rule 

and getting to 35 in 2016 here, leaving the door open for greater standards beyond that. 

And also there is a significant difference between those in terms of nearer term oil savings, nearer term 

consumer savings and environmental benefits that are not adequately presented through the analysis done 

in this DEIS. 

* * * * * 

I would urge the agency to focus the DEIS on how CAFE standards affect emissions for vehicles, and 

perhaps within the context of transportation, confining that analysis to nearer term will show greater 

impact and greater variation on the options presented by the agencies in this document. 

* * * * * 

If you go out to 2100 and 779 parts per billion of carbon in the atmosphere and then you're looking at 

small changes in rainfall and weather, that's beyond the tipping point. At that point you are sort of saying 

that what you have control over really makes no difference in climate change and really will make no 

difference and, therefore, maybe we should do nothing in this context, because it becomes meaningless 

that far out and I think meaningless to the public and I would assume meaningless to other folks who 

would look at this and say what is the impact of the different options that the agency considered. You've 
Chapter 10 Responses to Public Comments 10.2 The Proposed Action and Alternatives 

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got to either narrow your focus or account for other foreseeable changes that will complement fuel 

economy and give it meaning within that longer term context. But in my view, 2100 takes you too far out. 

* * * * * 

The DEIS should inform the agency of its options and not diminish the differences between them or 

trivialize their importance. 

Docket Number: TRANS02 

Organization: Public Citizen 

Commenter: Lena Pons 

The agency has not placed the impacts of the range of alternatives in a context that allows for meaningful 

comparison. The purpose of the Draft Environmental Impact Statement is to support an action based on a 

range of alternatives considered and the impacts of that range. The document fails to achieve this purpose 

because it has not placed the impacts of the range of alternatives in a context that allows for meaningful 

comparison among the alternatives. The EPA estimates that the United States contributes 18 percent of 

global greenhouse gas emissions and that motor vehicles contribute 24 percent of U.S. greenhouse gas 

emissions. Therefore, motor vehicles are responsible for about four percent of global greenhouse gas 

emissions. Consistent with EPA's assessment in its proposed endangerment finding on carbon dioxide, no 

single source or category of sources dominates global initiatives but some sources may be significant. 

NHTSA estimates in the DEIS that in 2100 the 2012 through 2016 standards would reduce global 

greenhouse gas emissions by 0.4 to 0.8 percent. Considering that if all motor vehicle sources of 

greenhouse gas emissions were shut down the reduction would be just four percent of global emissions, 

the impacts of proposed standards is significant with respect to reductions in the light duty transportation 

sector. 

For the DEIS to be meaningful and useful in making a decision, the agency must place impacts in a 

context that provides a basis for comparison between them. One example of such a context would be to 

consider the alternatives in terms of reducing greenhouse gas emissions to 1990 levels by 2020, 

something which can relatively reliably be estimated as relevant and foreseeable to decision-makers and 

the public. 

The EPA's inventory of greenhouse gas emissions provides us with an estimate for 1993 greenhouse gas 

emissions and projected greenhouse gas emissions in 2020, assuming recent trends. Considering 

reductions proportional to the contribution from the light duty transportation sector, reductions of 423 

million metric tons of carbon dioxide are needed in 2020. Based on the DEIS, we can break out the 

alternatives and their annual reductions in greenhouse gas emissions in the light duty transportation 

sector. And considered in this context, Alternatives 1 through 5 would fall short of the reductions needed 

as estimated by EPA, while Alternatives 6 through 9 would meet or exceed those needed reductions. 

Considered in this context, you can make a confident decision about what action is supported by the 

DEIS. 

* * * * * 

The Draft EIS does not serve the function of informing decision-makers about relative impacts of a range 

of alternatives. The document does not place impacts in a meaningful context to compare the alternatives 

and it does not provide a basis for decision-makers and the public to make a reasoned decision about the 

relative impacts of the proposed alternatives. Climate change is a problem that goes beyond just the 
10.2 The Proposed Action and Alternatives Chapter 10 Responses to Public Comments 

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transportation sector. It is unreasonable for the DEIS to judge fuel economy standards solely on its impact 

to global greenhouse gas emissions. 

Transportation emissions are particularly complicated because they're dependent on the efficiency of the 

vehicle, the carbon content of the fuel used to propel it, and the number of miles a vehicle is driven. There 

is no one policy that can solve the problem, but fuel economy standards are a critical policy. 

Transportation emissions account for a third of greenhouse gas emissions in the United States, so actions 

to reduce these emissions has a significant impact. However, since the agency cannot resolve the 

difference between alternatives considered on a global scale for the period considered, it must place the 

alternatives in a context that allows for differentiation between the options. 

It is also important to remember that although the impact of this single policy is not sufficient to combat 

climate change, it does have a significant and measurable impact. 

* * * * * 

NHTSA should place the alternatives in a context that allows for comparison and is relevant to the reader. 

For example, NHTSA discusses annual carbon dioxide reductions in terms of emissions of coal-fired 

power plants, but does not discuss whether the impact of eliminating emissions from those power plants 

would be significant or greater than reductions from the transportation sector. 

We suggest that making a similar comparison readily available through the same EPA calculator that 

NHTSA used that presenting the impacts as equivalent to removing a number of cars from the road would 

be a better context for understanding. The agency could also devote more prose to discussing the 

relevance of light duty transportation to greenhouse gas emissions in the United States and globally which 

would help put into perspective the role of these regulations in reducing greenhouse gas emissions from 

the light duty transportation sector. 

We urge that NHTSA revise the Draft Environmental Impact Statement to make it more informative to 

decision-makers and the public. This is an opportunity to set an example for how such a document can be 

used to communicate the value of source and sector specific policies for reducing greenhouse gas 

emissions. 

Docket Number: TRANS03 

Organization: Consumer Federation of America 

Commenter: Mark Cooper 

It's quite clear that fuel economy improvements cannot solve the national security problem. They cannot 

solve the climate change problem. And because they cannot solve it, there's a tendency to diminish the 

value of it, to say, "Well, it's not big enough to matter. We have not used a framework that you can really 

see it." 

Docket Number: 0098 

Organization: New York Department of Transportation 

Commenter: Stanley Gee 

NYSDOT agrees that the CAFE standards should not be based on speculative scenarios. However, a 

multitude of states and municipalities around the nation are committing to achieve an 80% reduction in 

greenhouse gas emissions by the year 2050. Indeed, this goal is the hallmark of the Waxman-Markey Bill 

and the majority of carbon emissions reduction initiatives at the local, state, and international level. In 
Chapter 10 Responses to Public Comments 10.2 The Proposed Action and Alternatives 

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light of the growing consensus to achieve this magnitude of carbon emissions reductions, NYSDOT 

recommends that NHTSA and EPA consider the contribution of the transportation sector to achieving 

progress to attain the "80 by 50" goal. 

Response 

Climate change is a global phenomenon. GHGs can persist in the atmosphere for decades to centuries, 

and the effects of a given level of emissions in one location can occur over large scales such as globally. 

NHTSA has presented emissions data in a number of contexts but believes that it is appropriate to 

evaluate the effects of this rulemaking in terms of its relation to global emissions and global climate 

conditions using year 2100 as an endpoint. This is a common approach for climate modeling. While 

Sections 3.4 and 4.4 of the FEIS show small differences in climate effects (CO2 concentration, 

temperature, sea-level rise, precipitation) when expressed in terms of climate endpoints, i.e., the results at 

the end of an analysis period, NHTSA believes that this is likely true for any given GHG emission 

mitigation strategy when taken alone. A suite of many GHG emission reduction policies in many 

countries and environmental sectors would need to be implemented to mitigate climate change 

substantially. NHTSA’s analysis of the rule’s effect on global climate conditions is not intended to 

downplay the effectiveness or importance of the regulatory options in reducing CO2 emissions and global 

warming impacts, but to quantify these potential reductions in the proper context for climate change. 

NHTSA recognizes the importance of the climate change problem. The agency is acting within its 

statutory authority to increase average fuel economy and in so doing to reduce annual U.S. vehicle 

emissions of CO2. Under EPCA, as amended by EISA, NHTSA has the authority to set fuel economy 

standards for passenger cars and light trucks. Emissions from these vehicles constitute about 60.6 

percent of total U.S. transportation sector emissions. U.S. transportation sector emissions are about 31.5 

percent of total annual U.S. CO2 emissions. Because U.S. emissions constitute 17.2 percent of global 

CO2 emissions, U.S. light duty vehicle emissions (those that NHTSA has the authority to regulate under 

EPCA) account for roughly 3.7 percent of global annual CO2 emissions. NHTSA recognizes the 

important role that transportation plays in addressing global climate change issues. 

To get a sense of the relative impact of these emissions reductions resulting from CAFE standards, it can 

be helpful to consider the relative importance of emissions from passenger cars and light trucks as a 

whole, as discussed above. In fact, throughout the DEIS, NHTSA did indicate the important role that 

transportation plays in addressing global climate change issues, and attempted to put the impacts of the 

alternative CAFE standards in the context of passenger car and light truck emissions. See DEIS Sections 

S.5, 2.6.1.3.1, 3.4.2, and 3.4.4.1. However, NHTSA has added additional graphs and figures to place the 

impacts of the agency’s action in the context of total U.S. GHG emissions, and in the context of total U.S. 

transportation sector emissions. See FEIS Summary p. S-23. 

NHTSA recognizes that such comparisons present the proposed action and the impacts of the alternatives 

under consideration in perspective for the public and decisionmakers. The agency has emphasized the 

context discussions in the EIS Summary so that they are more prominent in the document. NHTSA has 

revised the Summary to focus on communicating the importance of the impacts of the agency’s action in a 

non-technical, and average-reader-friendly way. This summary contains (1) a general discussion of the 

greenhouse effect and climate change, (2) a summary of impacts expected with climate change, (3) a brief 

discussion of the direct, indirect, and cumulative effects of alternatives on GHG emissions as well as 

atmospheric CO2 concentration, global mean surface temperature, sea-level rise, and precipitation, (4) 

graphical depictions of impacts of the agency action on U.S. passenger car and light truck emissions, and 

(5) additional context to help decisionmakers and the public understand the differences among the 

alternatives and how this action fits into larger U.S. GHG reduction goals (see below). NHTSA will 

enable for download a separate file containing only the Summary, in full color, on the agency’s website 
10.2 The Proposed Action and Alternatives Chapter 10 Responses to Public Comments 

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alongside the full EIS. This separate file will provide interested members of the public with easy access 

to a summary of the environmental impacts of NHTSA’s action of setting CAFE standards. 

NHTSA has also added an analysis in the FEIS showing the differences in CO2 emissions among the 

alternatives in 2016 (the final year of the rulemaking) expressed as the equivalent number of passenger 

cars and light trucks removed from the road in those years. NHTSA has also added a brief discussion of 

the magnitude of CO2 emission reductions under this action in terms of the relative contribution of 

passenger cars and light trucks towards the recently stated White House goal of reducing U.S. GHG 

emissions in the range of 17% below 2005 levels by 2020. These discussions of impacts and comparisons 

of alternatives have been added to the Summary of the EIS, in an effort to differentiate among the 

alternatives in a way that is more relevant to the decisionmaker and the public. 

NHTSA believes that comparing the differences among alternatives against the transportation sector’s 

contribution to a near-term goal for 2020 provides a more meaningful context for this rulemaking than 

comparisons against longer term goals (e.g., 2050). The 17% by 2020 goal is an estimate of the 

reductions that could be achieved with existing technologies, and assumes continued widespread use of 

fossil fuels. The 80% by 2050 goal, which one commenter suggested NHTSA use as a basis for 

comparison, is in a legislative proposal that has not been adopted. However, the greater level of 

reductions targeted by such a goal by 2050 would require substantial increases in technology innovation 

from today’s levels, and would require an economy and vehicle fleet that has largely moved away from 

the use of fossil fuels. That goal does not provide context that is as useful for the reader as a nearer term 

goal because NHTSA’s action of setting CAFE standards through MY 2016 cannot make such giant 

leaps.
Chapter 10 Responses to Public Comments 10.3 Affected Environment and Environmental Consequences 

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10.3 AFFECTED ENVIRONMENT AND ENVIRONMENTAL CONSEQUENCES 

10.3.1 Common Methodologies 

Comments 

Docket Number: 0019 

Organization: Individual 

Commenter: Gail Gilbert 

I worry that loopholes will creep in as they have in the past. For example, one new provision could 

underestimate the heat-trapping emissions of "zero-emission" vehicle technologies such as plug-in 

hybrids and electric vehicles. The rules do not count heat-trapping emissions associated with generating 

the electricity that charges those vehicles. 

Docket Number: 

Organization: Individual 

Commenter: James Adcock 

The assumption that PHEVs will be charged from a dirty electricity source doesn't make sense given that 

owners have the option to purchase "green electricity" and green electricity reduces carbon footprint 

much less expensively than PHEVs. . . . Thus emissions due to PHEV charging should be assumed to be 

zero.

Response 

NHTSA believes that these comments refer to one of EPA’s proposed credits, which is designed to 

encourage the commercialization of advanced technology vehicles, including electric vehicles (EVs), 

plug-in hybrid electric vehicles (PHEVs), and fuel cell vehicles. EPA proposed to assign a value of 0 

grams per mile CO2 for EVs and the electric portion of PHEVs, since traditionally mobile source tailpipe 

standards do not consider upstream emissions. However, EPA did request public comment on the issue 

of whether upstream emissions should be considered. A number of similar comments were received on 

the joint NHTSA-EPA NPRM, and EPA will address these issues in the forthcoming joint NHTSA-EPA 

Final Rule. For purposes of NHTSA’s environmental analysis, however, including estimates of emissions 

from generation of electricity consumed by plug-in hybrid and electric vehicles would not significantly 

affect the environmental impacts projected to result from increased CAFE standards for MYs 2012-2016 

passenger cars and light trucks, because the agency’s modeling analysis does not require significant 

penetration levels for these technologies in the rulemaking timeframe. 

10.3.2 Air Quality 

10.3.2.1 Methodology 

Comments

Docket Number: 0051.1 

Organization: Missouri Department of Natural Resources 

Commenter: Dru Buntin 

Compared to the no action alternative, any of the alternatives that will increase the CAFE standard would 

result in lower levels of most criteria pollutants, including nitrogen oxides (NOx), sulfur oxides (SOx), 
10.3 Affected Environment and Environmental Consequences Chapter 10 Responses to Public Comments 

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and particulate matter (PM). According to the report, ozone levels are more difficult to determine since it 

is a secondary pollutant, formed by combining NOx with volatile organic compounds (VOCs). However, 

the study does project that VOC levels will also be reduced by increasing the CAFE standard. The final 

report on the revised CAFE standards is expected to contain modeling that will better determine the 

results of ozone levels resulting from the increase in CAFE values. 

Response 

In response to concerns raised by commenters to the current EIS and the agency’s 2008 EIS, this FEIS 

includes a photochemical air quality modeling analysis that estimates the changes in ambient air quality 

and serves as an input to the analysis of associated health outcomes and health-related costs due to the 

alternative CAFE standards. Emissions estimates from the analysis conducted in the DEIS alone do not 

account for the complex chemical transformations that nitrogen oxides (NOx), particulate matter (PM), 

sulfur oxides (SOx), and volatile organic compounds (VOC) emissions undergo while being dispersed and 

transported in the atmosphere. These transformations include reactions of NOx and VOCs that lead to 

formation of ozone. The photochemical air quality modeling and health impacts analysis accounts for 

this atmospheric chemistry as well as local variability in meteorology, population density, exposure, and 

baseline health incidence rates, all of which may lead to differing localized pollutant concentrations and 

related human health impacts. By accounting for these factors the photochemical air quality modeling 

analysis in the FEIS provides additional spatial and temporal detail to more completely and accurately 

estimate changes in ambient levels of these pollutants and their associated health and welfare impacts. 

The photochemical air quality modeling analysis is included as Appendix F in this FEIS. 

10.3.2.2 Consequences 

Comments 

Docket Number: 0051.1 

Organization: Missouri Department of Natural Resources 

Commenter: Dru Buntin 

For a number of the toxics that appear in gasoline, all of the proposed alternatives result in a number of 

toxics at higher levels than taking no action. This is again attributed to the rebound effect, increasing 

emissions more than would be compensated for by the reduction in the total number of gallons used. 

Again, the study's baseline calculation is based on the belief that the rebound effect will result in an 

increase in VMTs that will negate the decrease in gallons of fuel used that results from higher CAFE 

standards. By using the report methodology, emission reductions would be very conservative in regards to 

actual emissions reductions attributed to vehicle miles traveled. 

Localized Calculation of Emissions Reductions 

The study also examined the effects of the proposed alternative CAFE standards on nonattainment and 

maintenance areas. Because the majority of these areas do not have petroleum production or refining 

within their boundaries, and the study assumed that petroleum was not transported through urban areas, 

the localized results showed that very little emissions reductions would result in nonattainment or 

maintenance areas from any of the alternative CAFE standards. In fact, it was projected that some urban 

areas may have an increased level of criteria and toxic emissions resulting from the rebound effect. These 

results for nonattainment and maintenance areas are of particular concern because of the air quality status 

of the two largest urban areas in Missouri. St. Louis is currently designated as nonattainment for ozone 

and PM. Kansas City is designated as a maintenance area for ozone. The specific criteria pollutants of 

concern in Kansas City and St. Louis are outlined below: 
Chapter 10 Responses to Public Comments 10.3 Affected Environment and Environmental Consequences 

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Ozone - Kansas City 

The Kansas City Metropolitan Area is a maintenance area under the previous one-hour ozone standard, 

and was designated attainment for the 8-hour ozone standard. As such, the area is required to have a 

maintenance plan under the current 8-hour ozone standard. Also, the area has numerous local controls 

implemented as a result of the previous ozone violations under the one-hour ozone standard. These 

controls are found in the Kansas City Ozone portion of the Missouri State Implementation Plan, and in 

Title 10, Division 10, Chapter 2 of the Missouri Code of State Regulations. Finally, the new 8-hour ozone 

maintenance plan for the Kansas City Maintenance Area was approved by EPA in 2007. This plan 

includes additional local control measures that are required to be implemented in two phases when 

triggered. The first phase was triggered by the quality assured violation of the 8-hour ozone standard 

during the 2007 ozone season. This phase includes a heavy-duty diesel idle reduction measure and 

emissions reductions from sources that fall under the Clean Air Interstate Rule. 

It is also anticipated that the Kansas City area will be designated as a nonattainment area for ozone under 

the recently revised 2008 ozone standard, which may require additional emission controls for the area. 

Ozone - St. Louis 

The St. Louis area counties of Jefferson, Franklin, St. Charles, and St Louis and St. Louis City are an 

ozone nonattainment area under the 1997, 8-hour ozone standard. As such, the area is required to have 

emission reduction plans to achieve attainment. The area also has numerous local emissions controls on 

various types of emission sources, which are found in the St. Louis portion of the Missouri State 

Implementation Plan. 

It is also anticipated that the St. Louis area will continue to be designated as a nonattainment area for 

ozone under the recently revised 2008 ozone standard, which may require additional emission controls for 

the area. 

Particulate Matter - St. Louis 

The St. Louis area contains the only part of the state designated as nonattainment for particulate matter 

under the 1997 PM 2.5 Standard. The St. Louis particulate matter nonattainment area includes the City of 

St. Louis and the counties of St. Louis, St. Charles, Franklin, and Jefferson. 

Response 

Toxics Pollutant Emissions 

The commenter notes correctly that the additional tailpipe emissions due to the VMT rebound effect 

would tend to offset the decreases in upstream emissions due to lower fuel consumption. If the actual 

VMT rebound effect were less than was assumed in the DEIS, then total emissions would be lower and the 

emission reductions would be greater than were estimated in the DEIS. The same is true of the FEIS. 

For a discussion of NHTSA’s and EPA’s assumptions regarding the rebound effect, see FEIS Section 

10.2.3.4.1; NPRM, 74 FR 49454, 49608, 49671-49672 (Sep. 28, 2009); Draft Joint Technical Support 

Document, Proposed Rulemaking to Establish Light-Duty Vehicle Greenhouse Gas Emission Standards 

and Corporate Average Fuel Economy Standards, Docket No. NHTSA-2009-0059-0029, § 4.2.5; NHTSA 

PRIA, Corporate Average Fuel Economy for MY 2012 – MY 2016 Passenger Cars and Light Trucks, 

Docket No. NHTSA-2009-0059-0016.1, 355-361. 
10.3 Affected Environment and Environmental Consequences Chapter 10 Responses to Public Comments 

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Localized Calculation of Emissions Reductions 

The commenter noted that the DEIS projected that some areas including nonattainment and maintenance 

areas may have an increased level of criteria pollutants and toxic emissions resulting from the rebound 

effect. The commenter states that these results are of particular concern because of the air quality status 

of the two largest urban areas in Missouri. The commenter also states that the St. Louis area is currently 

designated as a nonattainment area for ozone and PM. Kansas City is designated as a maintenance area 

for ozone. Table 3.3.3-7 of the FEIS shows that the maximum increase in NOx emissions in any 

nonattainment area is estimated to be 149 tons per year, and the maximum increase in PM of 2.5 microns 

diameter or less (PM2.5) emissions in any nonattainment area is estimated to be 23 tons per year. By 

comparison, in 2002 (the most recent data available from the EPA National Emissions Inventory) the 

total emissions of NOx and PM2.5 in the St. Louis nonattainment area were 185,870 tons and 29,684 tons, 

respectively. The total 2002 emissions of NOx and PM2.5 in the Kansas City maintenance area 

were104,748 tons and 13,552 tons, respectively.12 The maximum increase in emissions predicted in the 

FEIS for any nonattainment area are small in the context of the total emissions inventories in the St. 

Louis nonattainment area and the Kansas City maintenance area. No VOC emissions increases were 

predicted for any nonattainment area. 

Ozone – Kansas City 

The Kansas City Metropolitan Area was not analyzed individually in the DEIS because the area is 

currently designated as an attainment area for the 8-hour ozone standard. The maximum emissions 

increases given in Table 3.3.3-7 suggest that if the Kansas City Metropolitan Area had been included in 

the analysis, and if any increases in NOx or VOC emissions were predicted to occur in the Kansas City 

Metropolitan Area, then such increases would likely be small. 

Ozone – St. Louis 

The data given in Appendix C of the FEIS show that emissions of NOx and VOC in the St. Louis ozone 

nonattainment area are predicted to decrease under every action alternative for all analysis years. 

Particulate Matter – St. Louis 

The data given in Appendix C of the FEIS show that emissions of PM2.5 in the St. Louis PM2.5

nonattainment area are predicted to decrease under every action alternative for all analysis years. 

Accordingly, the proposed CAFE standards would not jeopardize the area’s progress toward attainment 

of the PM2.5 standard. 

Air quality chemistry is complex, and projected changes in emissions do not account for meteorology, 

pollutant transport, pollutant formation in the atmosphere, and other local factors. Nevertheless, the 

projected changes in emissions under the action alternatives provide an indication that there would be no 

adverse impacts on attainment in the St. Louis and Kansas City nonattainment areas. Conclusions about 

localized attainment/nonattainment impacts should not be based upon information gleaned from emission 

inventory estimates alone. Instead, potential attainment impacts should be evaluated based upon fullscale photochemical air quality modeling data that are consistent with guidelines for determining 

attainment status (see U.S. EPA (2007) Guidance on the Use of Models and Other Analyses For 

Demonstrating Attainment of Air Quality Goals for Ozone, PM2.5, and Regional Haze; EPA-454/B-07-

002; Research Triangle Park, NC; April 2007). EPA is conducting full-scale air quality modeling for the 

 

12 EPA (U.S. Environmental Protection Agency). 2009. Emissions by Category Report – Criteria Air Pollutants. Last 

Revised: November 6, 2009. Available: http://www.epa.gov/oar/data/emcatrep.html. Accessed December 30, 2009.
Chapter 10 Responses to Public Comments 10.3 Affected Environment and Environmental Consequences 

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forthcoming joint NHTSA-EPA Final Rule to Establish Light-Duty Vehicle Greenhouse Gas Emission 

Standards and Corporate Average Fuel Economy Standards and will provide a description of the PM and 

ozone attainment impacts of the EPA GHG rule in the final regulatory impact analysis. 

10.3.3 Climate Tipping Points 

Comments 

Docket Number: 0053.1 

Organization: Center for Biological Diversity, Public Citizen, and the Sierra Club 

Commenter: Brian Nowicki 

The DEIS fails to adequately address climate change tipping points. 

The DEIS acknowledges the risk that continued petroleum consumption and the subsequent emission of 

greenhouse gases can exceed “tipping point” thresholds, resulting in abrupt and irreversible climate 

change. “Exceeding one or more tipping points, which ‘occur when the climate system is forced to cross 

some threshold, triggering a transition to a new state at a rate determined by the climate system itself and 

faster than the cause’ (National Research Council 2002 in EPA 2009b), could result in abrupt changes in 

the climate or any part of the climate system. These changes would likely produce impacts at a rate and 

intensity far greater than the slower, steady changes currently being observed (and in some cases, planned 

for) in the climate system (EPA 2009b).” DEIS at 3-83. “The CCSP report summarizes scientific studies 

suggesting that there are several ‘triggers’ of abrupt climate change and that ‘anthropogenic forcing could 

increase the risk of abrupt climate change...’” DEIS at 4-163. 

* * * * * 

Nearly every piece of information in any EIS contains levels of uncertainty, yet an agency is expected to 

make a good faith effort to consider impacts that are reasonably certain to occur. In this case, it is now 

certain that tipping points will be reached if global warming remains unchecked, and there is more than 

sufficient knowledge of climate tipping points and the potential for a stringent CAFE rule to be one of the 

most significant components of a national greenhouse gas emissions reduction program that would 

significantly decrease the likelihood of surpassing them. The threat of climate tipping points is well 

established and understood. A recent analysis of “tipping elements” indicates that contrary to the IPCC’s 

conservative projections, there is a strong chance that tipping points will be crossed within this century. 

Furthermore, NHTSA does not need to identify times or atmospheric conditions leading to tipping points 

with specificity in order to quantify the benefits and priority for greater, earlier reductions in greenhouse 

gas emissions. What NHTSA must do is analyze alternative outcomes with reasonable detail to arrive at 

reasonable conclusions concerning how best to avoid disastrous consequences. 

Under all scenarios considered in the DEIS, the atmospheric CO2 concentrations would reach 550 ppm or 

greater. This is well above the threshold for abrupt and catastrophic climate change caused by crossing 

tipping points. As a result, no alternatives adequately address the need for deep reductions in CO2 

emissions. 

We acknowledge the obvious point that action by the U.S. alone cannot avert catastrophic results. In its 

proposed Endangerment Finding, however, EPA has finally publicly debunked the legally erroneous and 

morally repugnant position that the U.S. therefore either cannot or should not take the amount of action 

necessary to contribute its share of needed greenhouse gas emission reductions. Unfortunately, that 

laudatory reversal of position is not reflected in the analysis of the DEIS, which remains fatally flawed. 

(Some citations omitted.) 
10.3 Affected Environment and Environmental Consequences Chapter 10 Responses to Public Comments 

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Response

While many scientists assert that if thresholds relating to the climate system are exceeded, this may result 

in severe and abrupt climate changes and impacts, there remains substantial uncertainty surrounding the 

existence of a single tipping point, and, if there is a single level, whether it corresponds to a specific CO2

concentration (e.g., 450 parts per million (ppm)) or increase in annual average temperature (e.g., 2 oC 

over pre-industrial levels). For example, there are indicators of multiple tipping points within various 

global systems, as noted in scientific observations, peer-reviewed scientific literature, and paleoclimatic 

data. See FEIS Section 4.5.9; DEIS Section 4.5.9. These points might occur when CO2 concentrations 

are lower or higher than 450 ppm and would have varying direct and indirect impacts. 

The EIS discusses the impacts on various climate systems of reaching or passing various climate tipping 

points. See FEIS Section 4.5.9.2; DEIS Section 4.5.9.2. That section contains discussions of potential 

impacts resulting from tipping points being reached for glaciers and ice sheets, the likelihood and 

persistence of drought, potential impacts on Amazon rainforests, and potential impacts on other climate 

systems.

NHTSA does not believe that examining the alternatives in relation to reaching tipping points triggered 

by CO2 emissions is practicable. In the context of this EIS, due to the uncertainty surrounding the precise 

global temperature change or CO2 concentration level that would constitute a tipping point, it is not 

currently practicable to attempt to estimate how this action could delay or mitigate the triggering of 

tipping points in any quantitative manner. Thus, it would not be possible for NHTSA to relate the 

reductions in CO2 emissions, sea-level rise, precipitation changes, and temperatures to tipping-point 

thresholds or to determine to what extent the different alternatives would affect tipping points. This 

federal action alone, even as analyzed under the most stringent alternative, is not likely to produce 

enough reductions in CO2 emissions to avert CO2 levels that some have identified as corresponding to 

abrupt and severe climate change. In fact, CO2 emissions of passenger cars and light trucks account for 

roughly 3.3 percent of global annual CO2 emissions. Even if NHTSA could set standards that reduced 

emissions from this sector to zero, tipping-point thresholds (whether they occur at 550 ppm or any other 

level of that general order of magnitude) would not likely be avoided without other significant global 

actions. To the degree that the action in this rulemaking reduces the rate of CO2 emissions growth, the 

rule contributes to the general reduction or delay of reaching these tipping-point thresholds. Moreover, 

while NHTSA’s action alone does not produce sufficient CO2 emissions reductions, it is one of several 

federal programs, that, together, could make substantial contributions in averting levels of abrupt and 

severe climate change. 

These conclusions are not meant to express the view that tipping points in climate-related systems are not 

areas of concern for policymakers. Addressing abrupt and severe climate-change tipping points 

(whatever they may be) requires a global effort, including CO2-reduction initiatives beyond the scope of 

the current rulemaking. Due to the largely incomplete and unavailable state of information surrounding 

this issue, the only conclusion NHTSA can reach at this time is that the reduction in CO2 emissions 

expected under this rulemaking to a limited degree will lower the risk of abrupt climate change. 

However, NHTSA recognizes the potential severity of the consequences and the desire for unified national 

and international action to avert the possible impacts associated with abrupt climate change. The EIS 

discussions of tipping points and abrupt climate change, thus, include discussions of potential impacts 

and possible severity of those impacts. See FEIS Section 4.5.9.2.
Chapter 10 Responses to Public Comments 10.3 Affected Environment and Environmental Consequences 

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10.3.4 Other Potentially Affected Resource Areas 

10.3.4.1 Safety and Other Human Health Impacts 

Comments 

Docket Number: 0042 

Organization: Centers for Disease Control 

Commenter: Andrew Dannenberg 

Fleet Design Changes and Human Health: 

As the DEIS acknowledges in Appendix D, we agree that vehicle and transportation safety is a common 

and legitimate public health concern. Decreasing vehicle fleet disparities in size and weight can act to 

decrease crash-related injury to those driving lighter-weight automobiles and trucks as well as other 

modes of transportation such as bicycles, motorcycles, and scooters. Changing CAFE Standards will 

affect fleet design and therefore have the potential to increase or decrease crash-related injury. For 

example, to comply with new CAFE Standards, size/weight disparities in the new fleet might increase, 

potentially leading to increased injury, or decrease, causing a potential reduction in crash-related injuries. 

To adequately promote and protect human health assuming shifts in the US automobile fleet make-up: 

Potential fleet design and composition by which vehicle manufacturers will comply with new CAFE 

Standards warrants further analysis. Modeling these projections is critical to an adequate analysis of the 

impact that new CAFE Standards will have on the human environment. 

* * * * * 

Fuel Consumption Changes and Human Health: 

Additional consideration of the effects of increasing demand and consumption of fossil fuel in an era of 

decreased availability on human health and well-being is needed. Decreasing the dependence, demand, 

and consumption of motor vehicle fuels in the United States may benefit mental health, reduce stress, and 

increase economic stability. These health determinants and/or direct health outcomes are critical elements 

of a stable society and should be considered as factors affected by CAFE Standards, Therefore: 

The health-related consequences of concurrent factors, such as increasing demand and decreased 

availability of fossil fuels, ought to be included in the scope of analysis pursuant to NEPA. 

Collaboration with public health professionals is suggested. 

Docket Number: 0046 

Organization: Tennessee Department of Transportation 

Commenter: Gerald Nicely 

Other critics argue that the new CAFE standards will compromise safety because auto makers will be 

forced to make their vehicles smaller and lighter. Others counter that technology will again intervene to 

reduce the significance of this concern. Stronger, lighter materials are available that can reduce a car's 

weight while still increasing its overall ability to withstand impacts. In addition, today's new vehicles are 

much more maneuverable than in the past. 
10.3 Affected Environment and Environmental Consequences Chapter 10 Responses to Public Comments 

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Docket Number: 0049 

Organization: Individual 

Commenter: James Adcock 

ESC, Side Air bags, and the introduction of the Crossover segment so changes the market and the safety 

aspects of the market as to moot the results of Kahane—parts of which are based on car and truck designs 

which are now almost 20 years old. 

We find based on the IIHS 2007 “Driver Deaths” report that it is moderate sized SUVs which are most 

likely to roll over, not small cars. In any case the HUGE safety record disparities in similarly sized 

vehicles show that it is the quality of the engineering design NOT size which is the ultimate determinant 

of vehicle safety. 

In fact, based on Kahane, we see no “safety” rationale for using wheelbase as a factor in the CAFE metric 

at all. 

By not including ESC in the safety studies NHTSA forces consumers to pay for this degree of safety 

twice, once for the ESC which is not included in the safety studies, and secondly by requiring a larger 

footprint than would be required if the positive benefits of ESC had been properly accounted for. Same 

arguments goes for side air bags—NHTSA is making consumers pay for the same degree of safety 

“twice.” 

...Witness for example the wide variation in fatality rates within class. Also the cab design failure of a 

well-known pickup. Also consider all the well-known as-yet unresolved design issues and 

incompatibilities: Poor SSF, roof crush, sill height incompatibility, bumper height incompatibility, etc. 

We find it disingenuous that NHTSA blame MPG when so much unrelated regulatory improvements are 

possible! 

We note that just the reduced air pollution fatalities due to reducing fuel consumption alone may offset 

the Kahane assumed fatalities due to potential downsizing. Even the excess highway deaths due to 

extreme weather events caused by global warming exceed the downsizing risks. 

Given 1,300 million metric tons CO2 from LDVs. EIA estimates 31,000 million metric tons CO2 

worldwide emissions. 150,000 global warming deaths a year (World Health Org.) Or about 6,300 global 

warming deaths a year can be attributed to US LDV GHG emissions—which is 10X as large as Kahane 

assumed risk of deaths due to downsizing. Kahane page 20 car to truck collisions cause 4X more 

fatalities in the car. This goes to the issue of “freedom of choice” and Environmental Justice where some 

vehicle choices are effectively denied to consumers due to risk of being crushed by a large truck. This is 

unacceptable, and NHTSA must work harder to reduce these car/truck incompatibilities—which in turn 

keep consumer from being able to choose smaller more fuel efficient vehicles. 

Kahane’s statistics DO NOT in fact show that large cars are safer than middle sized cars. What the 

statistics do show is that small cars are more dangerous. 

Response 

Several commenters raised concerns that NHTSA’s proposed rule must appropriately take into account 

the impacts of setting CAFE standards on safety. In particular, one commenter suggested specific factors 

that NHTSA should take into account when considering safety. As outlined below, NHTSA has 

considered impacts to safety in analyzing the consequences of the agency’s action. NHTSA believes that 

under any analysis of the potential downweighting associated with attribute-based standards, the overall 
Chapter 10 Responses to Public Comments 10.3 Affected Environment and Environmental Consequences 

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societal benefits of the Preferred Alternative CAFE standards far outweigh projected costs, supporting 

the reasonableness of the agency’s Preferred Alternative. 

As explained in detail in the NPRM, NHTSA has long considered the potential for adverse safety 

consequences when establishing CAFE standards. See, e.g., 74 FR 49454, 49462. This practice is 

recognized approvingly in case law.13 Under the universal or “flat” CAFE standards that NHTSA was 

previously authorized to establish, the primary risk to safety came from the possibility that manufacturers 

would respond to higher standards by building smaller, less safe vehicles in order to “balance out” the 

larger, safer vehicles that the public generally preferred to buy. Under the attribute-based standards of 

the current rulemaking, that risk is reduced because building smaller vehicles tends to raise a 

manufacturer’s overall CAFE obligation, rather than only raising its fleet average CAFE. 

In the 2002 congressionally-mandated report entitled “Effectiveness and Impact of Corporate Average 

Fuel Economy (CAFE) Standards,”14 a committee of the National Academy of Sciences (NAS) (“2002 

NAS Report”) concluded that the then-existing form of passenger car and light truck CAFE standards 

permitted vehicle manufacturers to comply in part by downweighting and even downsizing their vehicles 

and that these actions had led to additional fatalities. The committee explained that this safety problem 

arose because, at that time, the CAFE standards subjected all passenger cars to the same fuel economy 

target and all light trucks to the same target, regardless of their weight, size, or load-carrying capacity.15

The committee said that this experience suggests that consideration should be given to developing a new 

system of fuel economy targets that reflects differences in such vehicle attributes. Without a thoughtful 

restructuring of the program, there would be trade-offs that must be made if CAFE standards were 

increased by any significant amount.16

As outlined in the NPRM, attribute-based standards reduce the incentive for manufacturers to respond to 

CAFE in ways harmful to safety.17 74 FR 49454, 49685. Because each vehicle model has its own target 

(based on the attribute chosen), attribute-based standards provide no incentive to build smaller vehicles 

simply to meet a fleet-wide average. Id. Since smaller vehicles are subject to more stringent fuel 

economy targets, a manufacturer's increasing its proportion of smaller vehicles would simply cause its 

compliance obligation to increase. Id. 

In response to the conclusions of the 2002 NAS Report, NHTSA issued attribute-based CAFE standards 

for light trucks and sought legislative authority to issue attribute-based CAFE standards for passenger 

cars. Congress went a step further in enacting EISA, not simply authorizing the issuance of attributebased standards, but mandating them. See 49 U.S.C. § 32902(b)(3)(A) (requiring the agency to prescribe 

 

13 As the United States Court of Appeals pointed out in upholding NHTSA’s exercise of judgment in setting the 

1987-1989 passenger car standards, “NHTSA has always examined the safety consequences of the CAFE standards 

in its overall consideration of relevant factors since its earliest rulemaking under the CAFE program.”Competitive 

Enterprise Institute v. NHTSA (CEI I), 901 F.2d 107, 120 at n.11 (D.C. Cir. 1990).

14 National Research Council, “Effectiveness and Impact of Corporate Average Fuel Economy (CAFE) Standards,” 

National Academy Press, Washington, DC (2002). Available at 

http://www.nap.edu/openbook.php?isbn=0309076013 (last accessed August 9, 2009). The conference committee 

report for the Department of Transportation and Related Agencies Appropriations Act for FY 2001 (Pub. L. 106-

346) directed NHTSA to fund a study by NAS to evaluate the effectiveness and impacts of CAFE standards (H. Rep. 

No. 106-940, p. 117-118). In response to the direction from Congress, NAS published this lengthy report.

15 NHTSA formerly used this approach for CAFE standards. EISA prohibits its use after MY 2010.

16 NAS, p. 9.

17 The 2002 NAS Report described at length and quantified the potential safety problem with average fuel economy 

standards that specify a single numerical requirement for the entire industry. See NAS Report at 5, finding 12.
10.3 Affected Environment and Environmental Consequences Chapter 10 Responses to Public Comments 

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fuel economy standards “based on 1 or more vehicle attributes related to fuel economy and express each 

standard in the form of a mathematical function”). 

In this joint rulemaking, NHTSA and EPA reconsidered the appropriate attribute for setting CAFE and 

CO2 standards, and concluded that footprint best provides the ability to address safety concerns without 

creating undue risk that program benefits will be lost to induced mix shifting. See 74 FR 49454, 49635. 

There are several policy reasons why NHTSA and EPA both believe that footprint is the most appropriate 

attribute on which to base the standards, as discussed below. 

As discussed in the NPRM, in NHTSA’s judgment, it is important that the CAFE standards be set in a way 

that does not encourage manufacturers to respond by selling vehicles that are less safe. See 74 FR

49454, 49685. Footprint-based standards provide an incentive to use advanced lightweight materials 

and structures that would be discouraged by weight-based standards, because manufacturers can use 

them to improve a vehicle’s fuel economy without necessarily causing a change in the vehicle’s target 

level of fuel economy. Id. 

Even under attribute-based standards, there is still concern that manufacturers might rely on 

downweighting to improve their fuel economy (for a given vehicle at a given footprint target) in ways that 

may reduce safety. NHTSA has reviewed recent research in this area, and has given full consideration to 

the comments on both the DEIS and the joint NPRM concerning safety, and will fully discuss its 

consideration of safety in the agencies’ forthcoming joint NHTSA-EPA Final Rule. In sum, NHTSA 

believes that even taking the most pessimistic prediction of manufacturer downweighting (for a given 

vehicle at a given footprint target), the overall societal benefits of the Preferred Alternative CAFE 

standards far outweigh the projected costs, supporting the reasonableness of the agency’s Preferred 

Alternative. 

A commenter suggested that “[d]ecreasing the dependence, demand, and consumption of motor vehicle 

fuels in the United States may benefit mental health, reduce stress, and increase economic stability” and 

that therefore, “[t]he health-related consequences of . . . increasing demand and decreased availability of 

fossil fuels, ought to be included in the scope of analysis pursuant to NEPA.” The Supreme Court has 

held that NEPA does not require an agency to consider potential mental health effects caused by risk 

related to the agency’s actions. See Metropolitan Edison Company v. People Against Nuclear Energy, 

460 U.S. 766, 778-79 (1983). This is because a mental health effect related to risk is “not an effect on the 

physical environment.” Id. at 775. 

NHTSA notes, however, that the cumulative impacts of this action include direct impacts on human 

health. As detailed in the FEIS in Section 4.5, the effects of the Preferred Alternative and other 

alternatives on climate – CO2 concentrations, temperature, precipitation, and sea-level rise—can 

translate to impacts to key natural and human resources. The Preferred Alternative and other 

alternatives result in different periods of CO2 emissions associated with the operation of U.S. vehicles. 

These emissions, in combination with U.S. GHG emissions from other sources (power plants, natural gas 

use, and agricultural production) and with emissions of all GHGs globally, would alter atmospheric 

concentrations of GHGs. Different atmospheric concentrations of GHGs will be associated with longterm changes in global climate variables. These climate changes would result in changes to a range of 

natural and human resources and systems, including human health. Specifically, climate change has 

contributed to human mortality and morbidity, and could increase the risk of flooding; increase the 

incidence of heat waves; change the severity, duration, and location of extreme weather; increase surface 

temperature; and alter precipitation intensity and frequency. These events can affect human health either 

directly through temperature and weather or indirectly through changes in water, air, food quality, vector 

ecology, ecosystems, agriculture, industry, and settlements. For additional discussion, see FEIS Section 

4.5. 
Chapter 10 Responses to Public Comments 10.3 Affected Environment and Environmental Consequences 

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10.3.4.2 Environmental Justice 

Comments 

Docket Number: 0049 

Organization: Individual 

Commenter: James Adcock 

Choosing a footprint model which does not meaningfully discourage the sale of large trucks represents an 

environmental injustice because less wealthy Americans are more likely to own smaller cars which emit a 

smaller share of CO2 pollution yet are more likely to be killed in a collision with the likely more wealthy 

owner of the large truck. Further, as Kahane discusses, the owner of the small car is more likely to be a 

female killed in a collision with a male driving a large truck, going to the issue of gender equity. 

Mfgs “opting out” and just paying penalties goes to the issue of Environmental Justice since these are 

mostly luxury or premium sports car Mfgs. Thus wealthy Americans purchasing these vehicles are not 

doing their part towards protecting fellow Americans from the dangers of global warming. We suggest 

the “opt out” penalties need to be maximized in the interest of Environmental Justice. It is inappropriate 

that the wealthy owners of vehicles failing to meet CAFE standards strike and kill the less wealthy 

owners of small vehicles which did meet the CAFE standards! 

We suggest that both the truck and car upper cutoff be set to a footprint equivalent to approx. 4000 lbs. 

and that the lower cutoffs be set equivalent to approx. 2000 lbs. To do otherwise belies the issue of 

Environmental Justice. 

Response 

Section 3.5.9 of this EIS discusses all reasonably foreseeable potential impacts to environmental justice 

populations, including those stemming from the consequences of global climate change. CEQ has 

provided guidance on how federal agencies should identify and address environmental justice concerns in 

a NEPA analysis.18 That guidance describes environmental justice issues as “disproportionately high 

and adverse human health or environmental effects” of federal actions, programs or policies on minority 

populations and low-income populations. We believe the commenter misapplies the concept of 

environmental justice impacts to the agency’s action. The purported relationship between small vehicles 

and lower-income populations described by the commenter is unsubstantiated. To the extent that such a 

relationship exists, however, it is not a causal effect of this rulemaking action. The setting of CAFE 

standards will not change the fact that vehicles of varying sizes and weights will be marketed to 

consumers. There is no evidence that this rulemaking will alter the purchasing preferences of consumers, 

including low-income populations. 

Significantly, the commenter provided no studies that support the premise that environmental justice 

populations and women purchase smaller cars, and NHTSA is not aware of any data or studies that show 

that such populations are more likely than others to purchase or operate smaller vehicles. As a separate 

matter, NHTSA considered the potential safety concerns of making vehicles lighter (i.e., downweighting) 

in the NPRM (see Section IV.G.7). 

The commenter suggests that NHTSA increase compliance penalties in the interest of environmental 

justice. Through EPCA, Congress has mandated a fairly prescriptive penalty system for non-compliance 

 

18 See CEQ, Environmental Justice: Guidance Under the National Environmental Policy Act (1997), available at 

http://ceq.hss.doe.gov/nepa/regs/ej/justice.pdf (last accessed Jan. 19, 2009). 
10.3 Affected Environment and Environmental Consequences Chapter 10 Responses to Public Comments 

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with CAFE standards. See 49 U.S.C. § 32912. The penalty is standardized under the statute – $5.50 per 

tenth of an mpg by which a manufacturer misses the applicable standard, times the number of vehicles in 

the manufacturer’s fleet that misses the standard – NHTSA does not have the option of “maximizing” 

penalties for manufacturers that choose to pay fines. EPCA does have a provision for prescribing a 

higher penalty than the standardized penalty, but that provision requires NHTSA to show that the 

increase in penalty “will result in, or substantially further, substantial energy conservation for 

automobiles in model years for which the increased penalty may be imposed,” which is a specific and 

demanding requirement. 49 U.S.C. § 32912(c). NHTSA refers readers to Section IV of the NPRM for 

additional details on CAFE compliance and enforcement.

10.3.5 Unavoidable Impacts and Irreversible and Irretrievable Resource Commitment 

Comments 

Docket Number: 0049 

Organization: Individual 

Commenter: James Adcock 

"Unavoidable Adverse Impacts": We believe that Strong Hybrids, PHEVs and EVs - if NHTSA set 

stringency high enough to require them, reduce the UAI due to the reduced total running time of the 

combustion engine. Thus these adverse impacts are in fact "Avoidable." 

"Commitment of Resources": Actually, NHTSA analysis would lead one to believe that Mfgs 

commitment of these resources leads to a much greater nationwide reduction in the consumption of 

resources. 

Response 

Pursuant to the CEQ regulations implementing NEPA, NHTSA has included a summary of the 

Unavoidable Adverse Impacts of this rulemaking in the Environmental Consequences section of the EIS, 

see Section 3.6.1. (40 CFR Section 1502.10). For all alternatives, these include energy consumption, 

GHG emissions, and the effects of climate change. NHTSA has concluded that these adverse impacts will 

occur as a result of either the Preferred Alternative or those that require higher mpg levels. We note that 

even if manufacturers produce greater numbers of vehicles that reduce running time of combustion 

engines, vehicle emissions and their impact on global climate change will continue. 

As discussed in Section 3.6.3, Irreversible and Irretrievable Commitment of Resources, of the 

EIS, NHTSA cannot mandate or predict which specific technologies manufacturers would apply to meet 

the CAFE standards under any of the eight action alternatives. Existing, advanced technologies and 

existing vehicle production facilities can be applied to meet the CAFE standards under the eight action 

alternatives. However, some vehicle manufacturers might commit additional resources to existing, 

redeveloped, or new production facilities. The specific amounts and types of irretrievable resources (such 

as electricity and other energy consumption) manufacturers might expend in meeting the CAFE standards 

depends on the specific methods and technologies manufacturers choose to implement. Commitment of 

resources for manufacturers to comply with the CAFE standards tends to be offset by the fuel savings 

from implementing the standards. 
Chapter 10 Responses to Public Comments 10.4 Cumulative Impacts 

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10.4 CUMULATIVE IMPACTS 

10.4.1 Reasonably Foreseeable Future Actions 

Comments 

Docket Number: 0053.1 

Organization: Center for Biological Diversity, Public Citizen, and the Sierra Club 

Commenter: Brian Nowicki 

Furthermore, it is reasonably foreseeable that California will continue to extend regulations for 

greenhouse gas emissions from motor vehicles, and to implement more stringent standards beyond 2016. 

In fact, in late 2009, the California Air Resources Board initiated a rulemaking to develop such standards. 

However, NHTSA makes no attempt to consider the impact of these standards on approximately 40 

percent of the U.S. light duty vehicle market. Likewise, NHTSA does not consider reasonably foreseeable 

actions to reduce growth in VMT, a goal that has been cited as a priority of many transportation policy 

experts and agencies. For example, California is currently undertaking rulemaking that would develop 

regional plans to curb urban sprawl and reduce VMTs, pursuant to the requirements of California’s 

Global Warming Solutions Act (AB 32) and SB 375. In addition, NHTSA fails to consider the 

commitment by President Obama at the G8 summit this July to limit global warming to 2 degrees C 

above historic levels, a goal that will require drastic reductions in greenhouse gas emissions by the U.S. 

and others. Without comparative analysis, decision makers are without the tools necessary to assess the 

effect this rulemaking will have to accomplish this or any other alternative goal. 

* * * * * 

NHTSA failed to consider many reasonably foreseeable actions that would affect fuel efficiency 

standards and greenhouse gas emissions from the transportation sector. 

A cumulative impact is defined under NEPA as “the impact on the environment which results from the 

incremental impact of the action when added to other past, present, and reasonably foreseeable future 

actions regardless of what agency (Federal or non-Federal) or person undertakes such other actions.” 40 

C.F.R. § 1508.7. However, the DEIS fails to consider many reasonably foreseeable actions that are likely 

to affect greenhouse gas emissions, including actions by other agencies likely to affect greenhouse gas 

emissions from the transportation sector. These actions include continued regulation of greenhouse gases 

by California and the states, and policies to reduce vehicle miles traveled (VMT). 

Docket Number: TRANS01 

Organization: Sierra Club 

Commenter: Ann Mensikoff 

NHTSA fails to consider additional increases beyond 2016 aside from those nominal ones projected by 

AEO. It can foresee and models out massive VMT increases, changes in how many vehicles will be 

owned and what the fleet will look like. NHTSA should therefore have the capacity to model out 

reasonably foreseeable maximum feasible standards beyond 2016, beyond 2020, and into 2030, not 

prejudging what future standards that the agency will set but there has to be a way if you're going to go 

out to 2030, 50 and 2100 with certain assumptions about how many miles we're driving, you have to be 

able to then project what the fuel economy could be based upon the technology assessments that's fully 

within the agency's capacity. 
10.4 Cumulative Impacts Chapter 10 Responses to Public Comments 

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Docket Number: TRANS02 

Organization: Public Citizen 

Commenter: Lena Pons 

The range of alternatives does not consider all reasonably foreseeable actions. The National 

Environmental Policy Act states that NHTSA must consider reasonably foreseeable actions and their 

impacts. NHTSA has not considered all of the reasonably foreseeable actions, nor has it considered 

scenarios where other agencies regulate the other variables related to transportation emissions. 

NHTSA has sensibly identified the problem that you cannot regulate greenhouse gas emissions for motor 

vehicles by regulating fuel economy alone. But the agency does not consider actions outside the 

jurisdiction as required by NEPA. 

These actions that have not been considered include continued regulation of greenhouse gases by 

California and the states and policies to reduce vehicle miles traveled. It is reasonably foreseeable that 

California will continue to extend regulations for greenhouse gas emissions for motor vehicles and intend 

to do so for years beyond 2017. 

NHTSA makes no attempt to consider the impacts of these standards for a substantial share of the U.S. 

light duty vehicle market. Likewise, it does not consider a reasonably foreseeable action to reduce the 

(inaudible) growth, something that has been cited as a priority of many transportation policy experts and 

agencies and was cited as necessary to contain the costs of maintaining surface transportation 

infrastructure by the National Surface Transportation Infrastructure and Funding Commission. 

Response 

Commenters requested that NHTSA consider: (1) the impact of actions by California and other U.S. 

states to regulate fuel economy beyond 2016 which commenters consider to be reasonably foreseeable; 

(2) the impact of actions by states and local governments to enact policies to reduce VMT growth; (3) 

scenarios where other agencies regulate variables related to transportation emissions; and (4) President 

Obama’s commitment at the recent G8 summit. 

Pursuant to CEQ NEPA regulations, cumulative effects are “the impact on the environment which results 

from the incremental impact of the action when added to other past, present, and reasonably foreseeable 

future actions regardless of what agency (federal or non-federal) or person undertakes such other 

actions.” 40 CFR § 1508.7. Accordingly, under NHTSA’s cumulative effects analysis the FEIS needs to 

account for future emissions-reduction strategies if they are reasonably foreseeable. Because California, 

other states and local governments have not established in law or regulation improvements in CO2

emissions after 2016 or reductions in VMT growth, and other agencies have not established regulations 

related to transportation emissions, explicitly including these presumed actions would be uncertain in the 

context of NEPA. The uncertainty is compounded by the likelihood of litigation as was spawned by the 

initial California CO2 regulations that other states adopted. However, the EIS does implicitly consider 

various combinations of emissions reductions strategies as reasonably foreseeable in the form of 

modeling different global emissions scenarios as discussed in Section 4.4.3.3. 

Multilateral agreements and actions to limit global warming to 2 °C above historic levels are not 

concluded and therefore not reasonably foreseeable. The Congress has not yet taken any action to 

implement this commitment by the President, and has not yet established the regulatory structure or 

allocated the budget to do so. Therefore the timing of the impacts of this commitment is uncertain. In its 

analysis of cumulative impacts, NHTSA assumes a moderate level of global GHG reductions, resulting in 

a global atmospheric CO2 concentration of roughly 650 ppm by 2100. See FEIS Section 4.4.3.3. NHTSA 
Chapter 10 Responses to Public Comments 10.4 Cumulative Impacts 

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believes that the regional, national, and international initiatives and programs established to reduce 

GHG emissions and/or energy use illustrate an existing and continuing trend of U.S. and global 

awareness, emphasis, and efforts toward significant GHG reductions. Together they imply that future 

commitments for reductions are probable and, therefore, reasonably foreseeable under NEPA. 

Addressing climate change to limit global warming to 2 °C above historic levels would require much 

greater actions from the United States and the global community. 

In this rulemaking, NHTSA will establish CAFE standards through MY 2016; EPCA gives NHTSA 

authority to set CAFE standards for up to five model years at once. 49 U.S.C. § 32902(b)(3)(B). For 

MYs 2011-2020, EPCA requires that separate standards for passenger cars and for light trucks be set at 

levels high enough to ensure that the average fuel economy level of the industry-wide combined fleet of 

new passenger cars and light trucks reaches at least 35 mpg not later than MY 2020. 49 U.S.C. § 

32902(b)(2)(A). NHTSA’s analysis takes this into account as a reasonably foreseeable future action in 

the EIS’s cumulative effects analysis. See FEIS Section 4.1.3. Beyond MY 2016, the agency’s cumulative 

effects analysis uses the Annual Energy Outlook (AEO) fuel economy level forecasts through 2030 to 

estimate projected gains in fuel economy. Id. These projected gains are reasonably foreseeable because 

they are associated with future government actions as needed to achieve the EISA requirement of 35 mpg 

in 2020, and future consumer and industry actions that are projected to result in ongoing mpg gains 

through 2030. The AEO fuel economy projections are based on consumer demand and technology 

advances associated with ongoing projected increases in fuel price through 2030. The AEO reference 

case projections are regarded as the official U.S. Government energy projections by both the public and 

private sectors. 

10.4.2 Climate Methodology 

Comments 

Docket Number: 0053.1 

Organization: Center for Biological Diversity, Public Citizen, and the Sierra Club 

Commenter: Brian Nowicki 

The DEIS fails to consider the need to reduce atmospheric greenhouse gas concentrations to 350 ppm. 

The DEIS refers to previous comments regarding the need to reduce atmospheric greenhouse gas 

concentrations to 350 ppm. “The CBD cited recent published reports that contend that it will be necessary 

to limit CO2 concentrations to 350 ppm to avoid climate catastrophe, CBD requested that a maximum 

350 ppm scenario should be included as an upper limit for defining the range of alternatives. CBD 

suggests using the function in MAGGIC that controls future emissions so that atmospheric CO2 

concentrations do not exceed values ranging from 350 to 750 ppm.” DEIS at 1-15. However, the DEIS 

addresses this concern only once. “Hansen’s more recent publications have suggested a target 

atmospheric CO2 concentration of 350 ppm (Hansen et al. 2008) – lower than the CO2-equivalent 

concentration, including the offsetting effects of aerosols, is today.” DEIS at 4-167. 

Recent scientific evidence indicates that to avoid tipping points and climate catastrophe, it will be 

necessary to reduce atmospheric CO2 concentrations to 350 ppm [citing Hansen et al., Target 

Atmospheric CO2: Where Should Humanity Aim? The Open Atmospheric Science Journal, 2008, 2, 217-

231.]. This study uses the most comprehensive analysis to date of both slow and fast feedback loopson 

climate and reaches the conclusion that global CO2 concentrations must be capped and reduced to 350 

ppm to avoid dangerous and irreversible climate change. Much of the data is based on paleoclimate 

records, as opposed to computer modeling. The study provides evidence of large changes in sea level on 

decadal time scales as well as past rates of sea level rise in excess of 1 m/century, correlated to global 
10.4 Cumulative Impacts Chapter 10 Responses to Public Comments 

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CO2 concentration levels. Thus, a 350 ppm scenario to be reached over several alternative time intervals, 

along with a number of other CO2 concentration level alternatives, should be included as context for 

analysis of cumulative impacts. This analysis is entirely possible because MAGICC, the software used by 

the NHTSA to model the climate change impacts of each alternative, already includes various alternative 

scenarios in which future emissions are controlled so that atmospheric CO2 concentrations do not exceed 

values ranging from 350 to 750 ppm. 

Response 

As noted by the commenter, NHTSA disclosed in the DEIS that 350 ppm has been suggested as a target 

atmospheric CO2 concentration. While it may be technically possible to model global emissions 

trajectories needed to reach 350 ppm, NHTSA believes this analysis would be inconsistent with a 

cumulative effects analysis required under NEPA because it would not put the projected emissions from 

NHTSA’s proposal into the context of “reasonably foreseeable” future actions, as defined in the CEQ 

NEPA Regulations. See 40 CFR § 1508.7 and § 1508.8. NHTSA also believes that modeling this global 

emission trajectory for the cumulative effects analysis in the EIS would not help inform the public and 

decisionmakers of the differences among the alternatives. The differences in the climate change risks and 

impacts between alternatives are already disclosed in detail in the EIS, within a broad discussion of 

climate change. 

The regulatory alternatives evaluated by NHTSA predict continued increases in GHG emissions from 

passenger cars and light trucks over time for each alternative because growth in the number of passenger 

cars and light trucks in use throughout the United States, combined with assumed increases in their 

average use (annual vehicle-miles traveled), is projected to result in growth in total passenger car and 

light truck travel. This growth in travel overwhelms improvements in fuel economy for each of the 

alternatives, resulting in projected increases in total fuel consumption by U.S. passenger cars and light 

trucks. Because CO2 emissions are a direct consequence of total fuel consumption, the same result is 

projected for total CO2 emissions from passenger cars and light trucks. NHTSA estimates that the CAFE 

standards will reduce fuel consumption and CO2 emissions from what they otherwise are estimated to be 

in the absence of the CAFE program. 

Although NHTSA estimates that each of the alternative increases in CAFE standards analyzed in this EIS 

would reduce fuel consumption and CO2 emissions from their levels under the No Action Alternative, the 

agency projects that the consumption of petroleum-based fuels and resulting CO2 emissions by U.S. 

passenger cars and light trucks would continue to increase over the long-term future under even those 

action alternatives that would require the most rapid increases in CAFE standards. This result also 

reflects the fact that NHTSA’s and EPA’s models currently project that the U.S. light-duty vehicle fleet 

will continue to be powered primarily by fossil fuels through at least the next several decades. 

Because the current global atmospheric CO2 concentration is approximately 385 ppm19 and there is 

considerable “momentum” inherent in the global climate system, however, reaching the 350 ppm 

concentration target would require reversing the current upward trend in GHG emissions and ending the 

continued reliance on conventional vehicle technologies and petroleum-based fuels that it reflects. Thus, 

achieving the 350 ppm target appears inconsistent with the assumptions in the agency’s analysis (as well 

as in EIA’s forecasts of future energy consumption) on reasonably foreseeable global energy use and fuel 

sources. 

 

19 National Oceanic & Atmospheric Administration, Earth System Research Laboratory, Global Monitoring 

Division, http://www.esrl.noaa.gov/gmd/ccgg/trends/ (last accessed Dec. 28, 2009).
Chapter 10 Responses to Public Comments 10.4 Cumulative Impacts 

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As a consequence, NHTSA has elected not to employ an emissions scenario that is consistent with 

achieving the 350 ppm concentration target in the modeling of climate impacts the agency conducted for 

this EIS. The agency’s decision to not model the 350 ppm emissions scenario is not intended to convey a 

position regarding the prospects for achieving the 350 ppm concentration goal. However, for this 

rulemaking, the agency has concluded that the global emissions scenario that would achieve the 350 ppm 

target is inconsistent with the analyses of fuel use and GHG emissions conducted for each action 

alternative, and is thus beyond the scope of the GHG reduction programs identified in Section 4.4.3.3 as 

reasonably foreseeable. 

The Model for Assessment of Greenhouse Gas-Induced Climate Change (MAGICC) is capable of running 

using various long-term global emissions scenarios which each represent different assumptions about key 

drivers of GHG emissions, e.g., population changes, economic growth, land and labor productivity 

growth, technological options, and resource endowments. Different scenarios represent various levels of 

implementation of global GHG emissions reduction policies. See FEIS Section 4.4.3.3; DEIS Section 

4.4.3.3. While MAGICC 5.3 does include two scenarios of global emissions (the 350NFB and WRE350 

scenarios20) where global concentrations would decrease and stabilize at 350 ppm, these scenarios do 

not, in fact, attain the 350 ppm stabilization target by 2100 ( the endpoint of the EIS modeling analysis), 

but rather by about 2150 (WRE350) and 2200 (350NFB). Thus, to develop an analysis with the MAGICC 

model that would reduce concentrations to 350 ppm within the simulation period (i.e., by 2100), NHTSA 

would have to develop a new emission scenario that would not appear to disclose any additional 

information about the incremental impact of NHTSA’s rule on the risks and impacts of climate change. 

Further, given NHTSA’s reliance on peer-reviewed emission scenarios for the EIS, it would be 

inconsistent to develop new scenarios for this purpose. To do so would be outside the range of scenarios 

that have been used for previous climate change modeling, and outside the range of scenarios that are 

well accepted in the scientific community. 

Finally, although 350 ppm has been discussed as a concentration target to avoid adverse impacts of 

climate change, several other concentration targets have been identified (e.g., 450 ppm; 550 ppm), and 

there is not widespread acceptance that 350 ppm is more appropriate than these other targets (or that 

concentration targets are more meaningful than increases in annual average global temperature or other 

measures). NHTSA’s decision not to model the 350 ppm emissions scenario is not intended to convey a 

position regarding the 350 ppm concentration goal. However, for this rulemaking, the 350 ppm global 

emissions scenario would not be consistent with other assumptions used by NHTSA and EPA to project 

environmental impacts of NHTSA’s and EPA’s standards. Therefore, NHTSA does not believe it is 

reasonable or necessary to model the 350 ppm global emissions concentration scenario. 

 

20 The 350NFB scenario is a 350 ppm atmospheric CO2 concentration scenario with no climate feedbacks, as 

described by Tom Wigley (Wigley, T. 2004. Overshoot Pathways to CO2 Concentration Stabilization. National 

Center for Atmospheric Research. Workshop on GHG Stabilization Scenarios. Tsukuba, Japan. Pgs. 37). The 

WRE350 scenario is a 350 ppm scenario that refers to the three authors who developed it – Wigley, Richels, and 

Edmonds (Wigley, T.M.L; R. Richels and J.A. Edmonds. 1996. Economic and Environmental Choices in the 

Stabilization of Atmospheric CO2 Concentrations. Nature. Vol. 379. January 18. Pgs. 240-243). 
10.5 Mitigation Chapter 10 Responses to Public Comments 

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10.5 MITIGATION 

Comments 

Docket Number: 0098 

Organization: New York Department of Transportation 

Commenter: Stanley Gee 

In light of the growing consensus to achieve this magnitude of carbon emissions reductions, NYSDOT 

recommends that NHTSA and EPA consider the contribution of the transportation sector to achieving 

progress to attain the “80 by 50” goal. As appropriate, the DEIS should be revised to discuss the 

mitigation strategies needed to offset the significant increases in future emissions. 

Response

Pursuant to CEQ regulations, which require an EIS to discuss the “[m]eans to mitigate adverse 

environmental impacts,” Chapter 5 of the EIS discusses mitigation measures for impacts related to 

NHTSA’s action of setting CAFE standards. 40 CFR § 1502.16(h). As explained in Chapter 5, NEPA 

does not obligate an agency to adopt a mitigation plan. However, NEPA requires an agency to discuss 

measures that could be adopted. Chapter 5 accordingly discusses possible measures that could mitigate 

the effects of NHTSA’s action. These include current and future actions that NHTSA or other federal 

agencies could take. 

As the commenter implies, and as NHTSA explains throughout the EIS, annual passenger car and light 

truck GHG emissions will continue to increase regardless of what level NHTSA sets CAFE standards. 

NHTSA’s setting of CAFE standards will reduce the rate at which these emissions will increase. See

Figure 2.6-1. We agree with the commenter that mitigation of this sector’s emissions is desirable. 

Emissions mitigation in this sector can only be discussed in the context of larger national emissions 

reductions policies and strategies. GHG emission reductions of the order of magnitude necessary to 

mitigate climate change will require concurrent efforts from many different international actors, from 

both the public and private sectors. For this reason, mitigation of global GHG emissions presents a 

unique set of challenges reaching far beyond this rulemaking. That said, in the light duty vehicle sector, 

some policies that could be explored to contribute towards this sector’s GHG mitigation include 

expanding and improving mass transit, raising gas taxes or other driving-associated fees to deter VMT 

growth, and setting lower speed limits. NHTSA has supplemented the existing discussion by adding a 

discussion of these strategies in Chapter 5 of the EIS.
Chapter 10 Responses to Public Comments 10.6 Rulemaking 

 10-73 

10.6 RULEMAKING 

10.6.1 Alternative Fuel Credits 

Comments 

Docket Number: 0049 

Organization: Individual 

Commenter: James Adcock

We suggest NHTSA ask Congress for authority that Alt Fuel Vehicles only get the credit when sold in 

states where at least one in three gas stations actually carry that Alt Fuel for sale to the general public. 

* * * * * 

We suggest that NHTSA and EPA should phase-out FFV benefits as quickly as possible, since recent 

scientific studies have found no environmental benefits for FFV - only rising food prices and 

environmental damage. Current FFV rules lack a rational basis. 

Response 

EPCA provides manufacturers an incentive under the CAFE program for production of duel-fueled or 

flexible-fuel vehicles (FFV) and dedicated alternative fuel vehicles by specifying that their fuel economy 

is determined using a special calculation procedure that results in those vehicles being assigned a higher 

fuel economy level than would otherwise occur. This is typically referred to as an FFV credit. See 74 FR 

49454. However, as the commenter indicates, EPCA does not premise the availability of FFV credits on 

actual use of alternative fuel. Id. We recognize that under NHTSA’s current EPCA authority, FFV credits 

are independent of actual use of alternative fuel, and that this potentially undermines the purpose of 

credits if a FFV uses less alternative fuel than anticipated – because alternative fueling stations are not 

available, or for other reasons. However, for this rulemaking, the agency must implement CAFE credits 

as Congress has directed. We note, that EISA amended EPCA to phase out FFV credits by MY 2019. 49 

U.S.C. § 32906(a). The commenter’s suggestion has been noted for consideration in future actions. For 

additional details on Flex-Fuel and Alternative Fuel Vehicle Credits, the agency refers readers to 

Sections I and IV of the NPRM. 

10.6.2 Regulatory Compliance Penalties 

Comments 

Docket Number: 0049 

Organization: Individual 

Commenter: James Adcock

Regulatory Compliance Penalties: We believe these penalties should be consistent with NHTSA estimates 

of the social costs of the fuel not saved - excluding the retail cost of the fuel itself- and that NHTSA 

should seek Congressional authority to set fines at this level. 

Response 

NHTSA’s CAFE enforcement program and the compliance flexibilities available to manufacturers are 

largely established by statute, and EPCA and EISA are prescriptive. See 49 U.S.C. § 32912. In the event 
10.6 Rulemaking Chapter 10 Responses to Public Comments 

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that a manufacturer does not comply with a CAFE standard, even after the consideration of credits, 

EPCA provides for the assessment of civil penalties. The Act specifies a precise formula for determining 

the amount of civil penalties for such noncompliance. The penalty, as adjusted for inflation by law, is 

$5.50 for each tenth of an mpg that a manufacturer’s average fuel economy falls short of the standard for 

a given model year multiplied by the total volume of those vehicles in the affected fleet (i.e., import or 

domestic passenger car, or light truck), manufactured for that model year. The amount of the penalty 

may not be reduced except under the unusual or extreme circumstances specified in the statute. For 

additional details of CAFE compliance and enforcement, the agency refers readers to Section IV of the 

NPRM. 

10.6.3 Vehicle Performance Characteristics 

Comments 

Docket Number: 0049 

Organization: Individual 

Commenter: James Adcock 

"Compromising Performance" is only a compromise to the extent that consumers WANT their 

"performance" measured on a "0 to 60" basis. To the extent consumers want their "performance" 

measured on an "MPG" basis then downsizing engines cost the Mfgs "Less than Nothing" - thus NHTSA 

standards based on an assumed "no change in performance" [meaning no change in "0 to 60"] are in fact 

being set too low - because at least some consumers measure "performance" on an MPG basis, not on a "0 

to 60" basis. 

Response 

For purposes of this rulemaking and this FEIS, NHTSA refers to “performance” in this context as 

reductions in horsepower, torque, towing and hauling capacity, etc., and not as fuel economy 

performance, or how far the vehicle can go on a gallon of fuel. Thus, when NHTSA describes the 

agency’s attempt to “hold performance constant” in the analysis of which technologies can feasibly be 

applied to vehicles in order to achieve compliance with the standards, NHTSA is referring to maintaining 

a performance-neutral position in the analysis, as the agency believes that manufacturers could meet the 

standards adopted as part of this rulemaking at the estimated compliance costs without noticeably 

affecting vehicle performance or utility. However, we do not require manufacturers to pursue the 

technology path that we model in our analysis as their way of achieving compliance with the standards – 

manufacturers are free to choose any technologies or technological solutions, some of which may include 

reducing “performance” as the agency defines it. For example, at the time of this rulemaking, the agency 

notes that some manufacturers have announced downsized engines for the U.S. market as a strategy to 

improve fuel economy in their model lineups. These pre-production announcements indicate that future, 

more advanced downsized engines will mostly maintain, or have slightly reduced, power output levels in 

comparison with the larger optional engines previously or concurrently offered by the manufacturer in 

the same vehicle. 

Nevertheless, while NHTSA recognizes that there may be specific situations where performance reduction 

may be a cost-effective compliance strategy for certain manufacturers, the agency believes that the net 

cost of reducing performance must generally be comparable to or higher than that of technological 

approaches to fuel economy improvement. Thus the outcome of this rulemaking process is not 

significantly affected by omission of performance reduction as an explicit compliance strategy. 
Chapter 10 Responses to Public Comments 10.6 Rulemaking 

 10-75 

NHTSA continues to monitor the U.S. vehicle market sales and, specifically, the penetration of smaller 

displacement and/or reduced cylinder count engines. For future rulemakings, NHTSA may assess the 

market acceptance of downsized engines with potentially reduced performance yielding possible 

modification of the agency’s modeling analysis along with other potential changes driven by the evolution 

of technology application and vehicle market mix. 

10.6.4 Cost and Benefits of the Proposed Rule 

Comments 

Docket Number: 0050.1

Organization: Environmental Consultants of Michigan 

Commenter: 

The Agency incorrectly calculated the costs and benefits of their GHG rule. The Agency should have 

calculated the incremental cost above the cost of compliance with the NHTSA fuel economy standard and 

compared this with only the incremental benefits. The current EPA method double counts the benefits of 

the duplicative rule. 

Response 

The cost-benefit analyses are one of the important factors that the agencies consider when making a 

judgment as to the appropriate standards to propose. While EPCA neither requires nor precludes the use 

of any type of cost-benefit analysis as a tool to help inform the balancing process required to set 

maximum feasible fuel economy standards, considerations relating to costs and benefits remain an 

important part of CAFE standard setting. In drafting the joint proposal, both agencies considered the 

overall costs and benefits of their respective proposed standards in relation to a baseline scenario where 

the proposed standards are not in place. This method accounts for the incremental costs and benefits of 

the proposed standards alone if they were enacted. Had we summed the results of the separate NHTSA 

and EPA analyses, the claim that the method double counts the costs and benefits of the rule would be 

valid. However, this was not the case in the proposal, nor will it be the case in the final analysis. For 

additional details on each agency’s method of calculating the associated costs and benefits of the joint 

rule, refer to Sections III and IV of the NPRM which discuss the EPA Proposal for Greenhouse Gas 

Vehicle Standards and NHTSA Proposal for Passenger Car and Light Truck CAFE Standards for MYs 

2012–2016 respectively.

10.6.5 Vehicle Classification 

Comments 

Docket Number: 0046 

Organization: Tennessee Department of Transportation 

Commenter: Gerald Nicely 

In the past, loopholes in fuel economy rules, such as allowing automakers to reclassify cars as "light 

trucks" to decrease fuel economy requirements and incorporating weight thresholds that allowed vehicles 

like the Hummer to evade fuel economy regulations, seriously weakened CAFE requirements. The 

current NHTSA proposal calls for strong new standards and closes certain loopholes that have long been 

used by the automobile industry. The final standards must guard against potential loopholes or other 

efforts to weaken the effectiveness of the program. 
10.6 Rulemaking Chapter 10 Responses to Public Comments 

 10-76 

Docket Number: 0049 

Organization: Individual 

Commenter: James Adcock

 Reformed CAFE DOES offer an advantage to Mfgs to upsize vehicles—specifically to jack up 4x4 

station wagons in order to qualify them as “trucks.”... In general we are concerned about gaming the car 

vs. truck designation in order to gain four years of regulatory leniency simply by increasing clearance 

height—while simultaneously increasing clearance height—while simultaneously increasing rollover 

fatalities by raising CG and thereby reducing SSF. Thus, in practice, NHTSA car vs. truck classification 

rules increase fatalities it does not reduce them. 

We are concerned about the possibility of footprint “gaming” by adding wheel-well flares and/or 4 wheel 

rear axles on pickup trucks. We suggest that base model design—without flares nor 4 wheel read axles be 

used as the measure of track widths in these situations—and that mere name changes not be sufficient to 

determine a new model. 

We suggest that to the extent possible by law “off-road capable” should be defined by an actual NHTSA 

off-road obstacle course.. Many of NHTSA’s “off-road capable” vehicles have no nexus to off-roading. 

We believe Congress intended “off-road capable” to allow enthusiasts to drive their Jeeps on highway to 

the back country NOT to allow Mfgs to jack up station wagons and thereby receive an additional four 

year of regulatory leniency. 

Luxury vehicles should be excluded from the “truck” classification because they are in practice being 

used as passenger vehicles not work vehicles. 

We are concerned that “wide tire” performance options “gaming” will not in practice improve safety 

while actually decreasing MPG [while increasing measured track width.] 

In general we believe EPA and NHTSA are offering way too many loopholes, credits, and footprint 

"gaming" opportunities to make for an effective regulation actually reducing fuel consumption. 

Response 

Commenters suggested that the standards do not reflect the fact that many light trucks are used as 

passenger vehicles. As NHTSA discussed in the joint NPRM, the fact that vehicles are used for personal 

transportation does not make them passenger vehicles for purposes of CAFE. This is because the 

statutory definition of “passenger automobile” is “an automobile that the Secretary decides by regulation 

is manufactured primarily for transporting not more than 10 individuals . . . .” 42 U.S.C. § 32901(a)(18). 

Notably, the statute does not employ the phrase “used primarily.” 

Under EPCA, NHTSA has the discretion to further define a “passenger automobile” for the purposes of 

setting CAFE standards based on particular vehicle characteristics (e.g., gross vehicle weight). 49 

U.S.C. § 32901(a)(18). For additional information on this issue, NHTSA refers readers to the discussion 

in the 2012-2016 CAFE NPRM at 74 FR 49454, 49732-49734 (Sep. 28, 2009) and the discussion of 

EPCA’s legislative history in the proposal and final rule establishing NHTSA’s vehicle definition 

regulation. EPCA 501(2), 89 Stat. 901. 41 FR 55368, 55369-71 (Dec. 20, 1976); 42 FR 38362, 38365-67 

(Jul. 28, 1977). 

Starting with MY 2011 vehicles, NHTSA tightened its regulatory definition of “light truck” to ensure that 

vehicles are properly classified under the CFR Part 523 – Vehicle Classification. As defined under 49 

CFR § 523.5(b), in order to be properly classifiable as a light truck, a two-wheel drive SUV must either 
Chapter 10 Responses to Public Comments 10.6 Rulemaking 

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be over 6,000 lbs GVWR and meet 4 out of 5 ground clearance characteristics to make it off-highway 

capable, or it must meet one of the functional characteristics under § 523.5(a) (e.g., cargo carrying 

capacity that is greater than passenger carrying capacity). This amendment resulted in the 

reclassification of an average of 1,400,000 two-wheel drive SUVs from light trucks to passenger cars in 

each of the five model years covered by the standards. The result of this reclassification would be an 

average increase of 0.8 mpg in the combined passenger car and light truck standards over MYs 2012-

2016, resulting in substantial fuel savings and reduction in CO2 emissions during the useful life of 

vehicles sold during these model years. All of the alternatives and scenarios analyzed in this FEIS reflect 

this re-classification. 

One commenter suggested that manufacturers can “game” vehicle definitions. However, the current 

definitions are tighter than the commenter suggests. With regard to the commenter’s argument that the 

standards allow manufacturers to “game” the definitions by making minor changes to vehicles to obtain 

a light truck classification and thus, a lower fuel economy target, NHTSA notes that fairly major changes 

would be required to redesign a vehicle classified as a passenger car so it is classified as a light truck. 

To make a two-wheel drive SUV a light truck, for example, manufacturers would need either to add a 

third row of seats, convert it to four-wheel drive, or raise its GVWR over 6,000 lbs and ensure that it 

meets the specified ground clearance requirements to be deemed off-road capable. See 49 CFR § 

523.5(b). These changes are not minor, and likely can be made only every several years at the time of a 

periodic vehicle redesign. Additionally, the minor benefit to be gained by a manufacturer in terms of a 

lower target must be balanced against consumer demand. 

With regard to the comment that the existing definitions do not ensure that “vehicles that more closely 

resemble large cars and station wagons” (which NHTSA takes to refer to crossovers) are classified as 

passenger cars, we note that as a result of the tightened implementation of our vehicle definitions, many 

crossovers are in fact now properly classified as passenger cars. To the extent that crossovers are not 

classified as passenger cars, it is, we believe, only because they either (1) have four-wheel drive and meet 

4 out of 5 ground clearance characteristics; (2) are over 6,000 lbs GVWR and meet 4 out of 5 ground 

clearance characteristics; or (3) have three rows of seats, enabling the passenger-carrying capabilities 

normally associated with light trucks. In addition, NHTSA has sought comment in the 2012-2016 CAFE 

program NPRM regarding vehicle classification. NHTSA will be assessing this feedback in future 

rulemaking development. In conclusion, we believe that NHTSA’s recent revisions to the vehicle 

classification regulations address the commenter’s concern. See 49 CFR Part 523. NHTSA will continue 

to monitor the effectiveness of current vehicle classifications through CAFE compliance to ensure that 

manufacturer classification of vehicles occurs as NHTSA and Congress intended.