Draft Environmental Impact Statement

Corporate Average Fuel Economy Standards,

Passenger Cars and Light Trucks, 

Model Years 2012-2016

September 2009

National HighwayTraffic 

Safety Administration







DRAFT ENVIRONMENTAL IMPACT STATEMENT

CORPORATE AVERAGE FUEL ECONOMY STANDARDS,

PASSENGER CARS AND LIGHT TRUCKS, MY 2012-2016 

SEPTEMBER 2009 

LEAD AGENCY: 

NATIONAL HIGHWAY TRAFFIC SAFETY ADMINISTRATION

COOPERATING AGENCY: 

U.S. ENVIRONMENTAL PROTECTION AGENCY

i 

Table of Contents 

List of Acronyms and Abbreviations ........................................................................................................x 

Glossary ..................................................................................................................................................xiv 

Summary ................................................................................................................................................. S-1 

S.1 Foreword................................................................................................................................... S-1 

S.2 Background............................................................................................................................... S-1 

S.3 Purpose and need for the Proposed Action............................................................................... S-3 

S.4 Alternatives............................................................................................................................... S-4 

S.5 Potential Environmental Consequences ................................................................................... S-8 

S.5.1 Direct and Indirect Effects ....................................................................................... S-10

S.5.2 Cumulative Effects................................................................................................... S-24

S.5.3 Mitigation................................................................................................................. S-41

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........................................................................1-4

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 ..............................................................................1-11

1.5.3 Next Steps in the NEPA Process and CAFE Rulemaking ........................................1-17

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..........................................................................................2-13

2.3.2 Alternative 2: 3-Percent Alternative ........................................................................2-13

2.3.3 Alternative 3: 4-Percent Alternative ........................................................................2-13

2.3.4 Alternative 4: Preferred Alternative.........................................................................2-13

2.3.5 Alternative 5: 5-Percent Alternative ........................................................................2-14

2.3.6 Alternative 6: MNB Alternative ..............................................................................2-14

2.3.7 Alternative 7: 6-Percent Alternative ........................................................................2-14

2.3.8 Alternative 8: 7-Percent Alternative ........................................................................2-14

2.3.9 Alternative 9: TCTB Alternative .............................................................................2-14

2.3.10 Fuel Economy Levels for Each Alternative..............................................................2-15

2.3.11 Greenhouse Gas Emission Standards for Light-Duty Vehicles ................................2-17

2.4 Sensitivity Analysis .................................................................................................................2-18

2.5 Alternatives Considered But Not Analyzed in Detail..............................................................2-20
Table of Contents 

ii 

2.6 Comparison of Alternatives.....................................................................................................2-22

2.6.1 Direct and Indirect Effects ........................................................................................2-22

2.6.2 Cumulative Effects....................................................................................................2-35

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

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

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...................................................................................3-35

3.4 Climate.....................................................................................................................................3-59

3.4.1 Introduction – Greenhouse Gases and Climate Change............................................3-59

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

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

3.4.4 Environmental Consequences...................................................................................3-83

3.5 Other Potentially Affected Resource Areas...........................................................................3-107

3.5.1 Water Resources .....................................................................................................3-107

3.5.2 Biological Resources ..............................................................................................3-110

3.5.3 Land Use and Development....................................................................................3-113

3.5.4 Safety and Other Impacts to Human Health ...........................................................3-114

3.5.5 Hazardous Materials and Regulated Wastes...........................................................3-115

3.5.6 Land Uses Protected under U.S. Department of Transportation 

Act Section 4(f).......................................................................................................3-117

3.5.7 Historic and Cultural Resources .............................................................................3-118

3.5.8 Noise .......................................................................................................................3-118

3.5.9 Environmental Justice.............................................................................................3-119

3.6 Unavoidable Impacts and Irreversible and Irretrievable Resource Commitment..................3-121

3.6.1 Unavoidable Adverse Impacts ................................................................................3-121

3.6.2 Short-term Uses and Long-term Productivity.........................................................3-121

3.6.3 Irreversible and Irretrievable Commitment of Resources.......................................3-122

3.7 EPA Action and Analysis ......................................................................................................3-123

3.7.1 Overview.................................................................................................................3-123

3.7.2 Summary of EPA Impact Analysis .........................................................................3-124

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........................................................................................................................................4-7 

4.2.1 Affected Environment.................................................................................................4-7
Table of Contents 

iii 

4.2.2 Methodology...............................................................................................................4-7 

4.2.3 Environmental Consequences.....................................................................................4-8 

4.3 Air Quality...............................................................................................................................4-11 

4.3.1 Affected Environment...............................................................................................4-11 

4.3.2 Methodology.............................................................................................................4-11 

4.3.3 Environmental Consequences...................................................................................4-12 

4.4 Climate.....................................................................................................................................4-33 

4.4.1 Introduction – Greenhouse Gases and Climate Change............................................4-33 

4.4.2 Affected Environment...............................................................................................4-34 

4.4.3 Methodology.............................................................................................................4-34 

4.4.4 Environmental Consequences...................................................................................4-48 

4.5 Health, Societal, and Environmental Impacts of Climate Change...........................................4-71

4.5.1 Introduction...............................................................................................................4-71

4.5.2 Methodology.............................................................................................................4-72

4.5.3 Freshwater Resources ...............................................................................................4-75

4.5.4 Terrestrial and Freshwater Ecosystems.....................................................................4-90

4.5.5 Marine, Coastal Systems, and Low-lying Areas.....................................................4-111

4.5.6 Food, Fiber, and Forest Products ............................................................................4-124

4.5.7 Industries, Settlements, and Society .......................................................................4-135

4.5.8 Human Health .........................................................................................................4-151

4.5.9 Tipping Points and Abrupt Climate Change ...........................................................4-161

4.6 Environmental Justice............................................................................................................4-173 

4.6.1 Affected Environment.............................................................................................4-173 

4.6.2 Environmental Consequences.................................................................................4-173 

4.7 Non-Climate Cumulative Impacts of Carbon Dioxide ..........................................................4-177 

4.7.1 Affected Environment.............................................................................................4-177 

4.7.2 Environmental Consequences.................................................................................4-178 

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 .....................................................................................................7-7 

7.3.5 Other Potentially Affected Resource References......................................................7-15 

7.3.6 Unavoidable Impacts and Irreversible and Irretrievable Resource 

References.................................................................................................................7-21

7.3.7 EPA Action and Analysis References.......................................................................7-21 
Table of Contents 

iv 

7.4 Cumulative Impacts References ..............................................................................................7-22 

7.4.1 Introduction References ............................................................................................7-22 

7.4.2 Energy References ....................................................................................................7-22 

7.4.3 Air Quality References .............................................................................................7-22 

7.4.4 Climate Change References......................................................................................7-23 

7.4.5 Resources Impact of Climate Change References ....................................................7-28 

7.4.6 Environmental Justice References ..........................................................................7-114 

7.4.7 Non-Climate Cumulative Impacts of CO2 References ...........................................7-115 

7.4.8 Unavoidable Impacts and Irreversible and Irretrievable Resource 

References...............................................................................................................7-121 

7.5 Mitigation References............................................................................................................7-121 

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

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

8.2 State And Local Government Organizations.............................................................................8-4 

8.3 Elected Officials ........................................................................................................................8-5 

8.4 Native American Tribes.............................................................................................................8-6 

8.5 Stakeholders...............................................................................................................................8-6 

 

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

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 

Appendix B Agency Consultation Letters 

Appendix C Air Quality Modeling Data 

Appendix D NHTSA Preliminary Regulatory Impact Assessment 

Appendix E EPA Draft Regulatory Impact Assessment 
Table of Contents 

v 

List of Tables 

Table S-1 Required MPG by Alternative ........................................................................................ S-6 

Table S-2 Achieved MPG by Alternative........................................................................................ S-7 

Table S-3 Passenger Car Annual Fuel Consumption and Fuel Savings (billion 

gallons gasoline equivalent) by Alternative.................................................................. S-11 

Table S-4 Light Truck Annual Fuel Consumption and Fuel Savings (billion 

gallons gasoline equivalent) by Alternative.................................................................. S-11 

Table S-5 Nationwide Criteria Pollutant Emissions and Toxic Air Pollutant Emissions 

from Passenger Cars and Light Trucks (tons/year, Calendar Year 2030) 

by Alternative ............................................................................................................... S-12 

Table S-6 Nationwide Changes in Health Outcomes from Criteria Pollutant 

Emissions (cases/year) from Passenger Cars and Light Trucks 

by Alternative ............................................................................................................... S-13 

Table S-7 Nationwide Changes in Health Costs (U.S. million dollars/year) from 

Criteria Pollutant Emissions from Passenger Cars and Light Trucks 

by Alternative ............................................................................................................... S-13 

Table S-8 Emissions and Emissions Reductions (MMTCO2) from 2012-2100 

by Alternative ............................................................................................................... S-15 

Table S-9 CO2 Concentration, Global Mean Surface Temperature Increase, and 

Sea-level Rise by Alternative........................................................................................ S-17 

Table S-10 Global Mean Precipitation (percent change) ................................................................ S-22 

Table S-11 CO2 Concentration, Temperature, and Sea-level Rise for Varying 

Climate Sensitivities for Selected Alternatives............................................................. S-23 

Table S-12 Cumulative Effects of Passenger Car Annual Fuel Consumption and 

Fuel Savings (billion gallons gasoline equivalent) by Alternative ............................... S-26 

Table S-13 Cumulative Effects of Light Truck Annual Fuel Consumption and 

Fuel Savings (billion gallons gasoline equivalent) by Alternative ............................... S-26 

Table S-14 Cumulative Effects of Nationwide Criteria Pollutant Emissions (tons/year) 

from Passenger Cars and Light Trucks by Alternative................................................. S-27 

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

Criteria Air Pollutant Emissions from Passenger Cars and Light Trucks 

by Alternative ............................................................................................................... S-28 

Table S-16 Cumulative Nationwide Changes in Health Costs (U.S. million dollars/year) 

from Criteria Air Pollutant Emissions from Passenger Cars and Light Trucks 

by Alternative ............................................................................................................... S-29 

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

from 2012-2100 by Alternative .................................................................................... S-31 

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

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

by Alternative ............................................................................................................... S-32 

Table S-19 Cumulative Effects on Global Mean Precipitation (percent change)............................ S-37 

Table S-20 Cumulative Effects on CO2 Concentration, Temperature, and Sea-level 

Rise for Varying Climate Sensitivities for Selected Alternatives................................. S-39 
Table of Contents 

vi 

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 .......................................................................................2-15 

Table 2.3-2 Achieved MPG by Alternative.......................................................................................2-16 

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

Footprint-Based CO2 Standards (g/mi) ..........................................................................2-17 

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

Footprint-Based CO2 Standards (g/mi) ..........................................................................2-18 

Table 2.4-1 Sensitivity Analysis of Fuel Consumption (2012-60; billion gallons) 

under Expected Value Model Input Assumptions versus other Model Input 

Assumptions for Selected Alternatives..........................................................................2-19 

Table 2.6-1 Passenger Car Annual Fuel Consumption and Fuel Savings (billion gallons 

gasoline equivalent) by Alternative ...............................................................................2-23 

Table 2.6-2 Light Truck Annual Fuel Consumption and Fuel Savings (billion gallons 

gasoline equivalent) by Alternative ...............................................................................2-23 

Table 2.6-3 Nationwide Criteria Pollutant Emissions and Toxic Air Pollutant Emissions 

from Passenger Cars and Light Trucks (tons/year, Calendar Year 2030) 

by Alternative ................................................................................................................2-24 

Table 2.6-4 Nationwide Changes in Health Outcomes from Criteria Pollutant Emissions 

(cases/year) from Passenger Cars and Light Trucks by Alternative..............................2-25 

Table 2.6-6 Emissions and Emissions Reductions (MMTCO2) from 2012-2100 

by Alternative ................................................................................................................2-26 

Table 2.6-7 CO2 Concentration, Global Mean Surface Temperature Increase, and 

Sea-level Rise by Alternative.........................................................................................2-28 

Table 2.6-8 Global Mean Precipitation (percent change) .................................................................2-33 

Table 2.6-12 Cumulative Nationwide Criteria Pollutant Emissions (tons/year) from 

Passenger Cars and Light Trucks by Alternative...........................................................2-37 

Table 2.6-15 Cumulative Effects of Emissions and Emissions Reductions (MMTCO2) 

from 2012-2100 by Alternative .....................................................................................2-40 

Table 2.6-16 Cumulative Effects on CO2 Concentrations, Global Mean Surface Temperature 

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

by Alternative ................................................................................................................2-41 

Table 2.6-17 Cumulative Effects on Global Mean Precipitation (percent change).............................2-46 

Table 2.6-18 Cumulative Effects on CO2 Concentration, Temperature, and Sea-level 

Rise for Varying Climate Sensitivities for Selected Alternatives..................................2-48 

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 gasoline 

equivalent) by Alternative..............................................................................................3-13 

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

equivalent) by Alternative..............................................................................................3-13 

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 and a 3% Discount Rate ..............................................................3-33 
Table of Contents 

vii 

Table 3.3.2-4 Incidence-per-Ton Values Premature Mortality ............................................................3-34 

Table 3.3.3-1 Nationwide Criteria Pollutant Emissions from Passenger Cars and Light Trucks by 

Alternative (tons/year) ...................................................................................................3-37 

Table 3.3.3-2 Nationwide Criteria Pollutant Emissions in 2030 from Passenger Cars and Light Trucks, 

by Vehicle Type by Alternative (tons/year)...................................................................3-39 

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

Light Trucks by Alternative...........................................................................................3-40 

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

Trucks by Alternative ...................................................................................................3-41 

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 ............................................................3-43 

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

and Light Trucks by Alternative ...................................................................................3-45 

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

by Nonattainment Area by Alternative ..........................................................................3-47 

Table 3.3.3-8 Nationwide Changes in Health Outcomes from Criteria Pollutant Emissions (cases/year) 

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

Table 3.3.3-9 Nationwide Changes in Health Costs (U.S. million dollars/year) from Criteria Pollutant 

Emissions from Passenger Cars and Light Trucks by Alternative ................................3-48 

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

Maximum Changes by Nonattainment Area by Alternative..........................................3-50 

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...........................................................3-87 

Table 3.4.4-3 Comparison of MAGICC Modeling Results and Reported IPCC Results ....................3-91 

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

Sea-Level Rise Using MAGICC (RCP MiniCAM Reference) by Alternative..............3-92 

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

Extracted from the IPCC Fourth Assessment Report ....................................................3-97 

Table 3.4.4-6 Global Mean Precipitation Change (scaled, % per °C)..................................................3-99 

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

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

Fourth Assessment Report ...........................................................................................3-102 

Table 3.4.4-9 CO2 concentration (ppm), Temperature (degrees C) and Sea-level 

Rise (cm) for Varying Climate Sensitivities for Selected Alternatives .......................3-105 

Table 3.7.2-1 Impacts of Proposed Standards on Fuel Savings .........................................................3-126 

Table 3.7.2-2 Impacts of Proposed Standards on Non-GHG Emissions 

(Short Tons Per Year) ..................................................................................................3-127 

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 gasoline equivalent) by Alternative ..........................................4-8 
Table of Contents 

viii 

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

Savings (billion gallons gasoline equivalent) by Alternative ..........................................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 4.3.3-3 Cumulative Nationwide Toxic Air Pollutant Emissions (tons/year) from 

Passenger Cars and Light Trucks by Alternative...........................................................4-16 

Table 4.3.3-4 Cumulative Nationwide Changes in Toxic Air Pollutant Emissions (tons/year) 

from Passenger Cars and Light Trucks by Alternative Compared to No Action 

Alternative .....................................................................................................................4-17 

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

from 2012 to 2100 by Alternative..................................................................................4-49 

Table 4.4.4-2 Cumulative Effects of Nationwide Emissions of Greenhouse Gases 

(MMT per year) from Passenger Cars and Light Trucks by Alternative.......................4-51 

Table 4.4.4-3 Comparison of MAGICC Results and Reported IPCC Results ....................................4-54 

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 ................................................................................................................4-56 

Table 4.4.4-5 Summary of Regional Changes to Warming and Seasonal Temperatures 

Extracted from the IPCC Fourth Assessment Report ....................................................4-61 

Table 4.4.4-6 Global Mean Precipitation Change (scaled, % per °C)..................................................4-63 

Table 4.4.4-7 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 4.4.4-8 Summary of Regional Changes to Precipitation Extracted from the IPCC 

Fourth Assessment.........................................................................................................4-65 

Table 4.4.4-9 Cumulative Effects on CO2 concentration, Temperature, and Sea-level 

Rise for Varying Climate Sensitivities for Selected Alternatives..................................4-68 

Table 4.5.5-1 Common Coastal Ecosystem .......................................................................................4-113 

Table 4.5.5-2 Common Marine Ecosystem Zones.............................................................................4-114 

List of Figures 

Figure S-1 Projected Annual Emissions (MMTCO2) by Alternative ............................................. S-16 

Figure S-2 CO2 Concentrations (ppm)............................................................................................ S-18 

Figure S-3 Global Mean Surface Temperature Increase (°C)......................................................... S-19 

Figure S-4 Reduction in CO2 Concentrations (ppm) Compared to the 

no Action Alternative.................................................................................................... S-20 

Figure S-5 Reduction in Global Mean Temperature Compared to the 

No Action Alternative................................................................................................... S-21 

Figure S-6 Cumulative Effects on CO2 Concentrations Using MAGICC ...................................... S-33 

Figure S-7 Cumulative Effects on the Global Mean Surface Temperature Increase 

Using MAGICC by Alternative.................................................................................... S-34 

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

No Action Alternative) ................................................................................................. S-35 
Table of Contents 

ix 

Figure S-9 Cumulative Effects on Global Mean Temperature (Reduction Compared 

to the No Action Alternative) ....................................................................................... S-36 

Figure 2.6-1 Projected Annual Emissions (MMTCO2) by Alternative ..............................................2-27 

Figure 2.6-2 CO2 Concentrations (ppm).............................................................................................2-29 

Figure 2.6-3 Global Mean Surface Temperature Increase (°C)..........................................................2-30 

Figure 2.6-4 Reduction in CO2 Concentrations (ppm) Compared to the 

No Action Alternative....................................................................................................2-31 

Figure 2.6-5 Reduction in Global Mean Temperature Compared to the 

No Action Alternative....................................................................................................2-32 

Figure 2.6-6 Cumulative Effects on CO2 Concentrations Using MAGICC .......................................2-42 

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

Using MAGICC by Alternative.....................................................................................2-43 

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

to the No Action Alternative) ........................................................................................2-44 

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

to the No Action Alternative) ........................................................................................2-45 

Figure 3.3.1-1 Vehicle Miles Traveled (VMT) vs. Vehicle Emissions.................................................3-22 

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

Cars and Light Trucks for 2030 by Alternative .............................................................3-38 

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

 Cars and Light Trucks for 2030 by Alternative ............................................................3-42 

Figure 3.4.1-1 Changes in Temperature, Sea Level, and Northern Hemisphere Snow Cover ..............3-61 

Figure 3.4.1-2 The Greenhouse Effect ..................................................................................................3-61 

Figure 3.4.3-1 Cascade of Uncertainty in Climate Change Simulations...............................................3-74 

Figure 3.4.3-2 Average GDP Growth Rates (1990 to 2030) .................................................................3-80 

Figure 3.4.3-3 Global CO2 Emissions from Fossil Fuel Use.................................................................3-80 

Figure 3.4.3-4 U.S. CO2 Emissions from Fossil Fuel Use.....................................................................3-81 

Figure 3.4.3-5 World Primary Energy Use Forecast .............................................................................3-81 

Figure 3.4.3-6 U.S. Primary Energy Use Forecast ................................................................................3-82 

Figure 3.4.4-1 Emissions and Emissions Reductions (MMTCO2) from 2010 to 2100 

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

Figure 3.4.4-2 Projected Annual Emissions (MMTCO2) by Alternative ..............................................3-86 

Figure 3.4.4-3 Historical Carbon Emissions with Two Potential Pathways for the Future...................3-89 

Figure 3.4.4-4 Stabilization Wedges .....................................................................................................3-89 

Figure 3.4.4-5 CO2 Concentrations (ppm).............................................................................................3-93 

Figure 3.4.4-6 Global Mean Surface Temperature Increase (°C)..........................................................3-94 

Figure 3.4.4-7 Reduction in CO2 Concentrations (ppm) Compared to the 

No Action Alternative....................................................................................................3-95 

Figure 3.4.4-8 Reduction in Global Mean Temperature Compared to the 

No Action Alternative....................................................................................................3-96 

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

from Baseline for Climate Sensitivities Ranging from 1.5–6 °C.................................3-128 

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) ........................................3-128 
Table of Contents 

x 

Figure 4.4.3-1 Cascade of Uncertainty in Climate Change Simulations...............................................4-35 

Figure 4.4.3-2 Average GDP Growth Rates (1990 to 2030) .................................................................4-44 

Figure 4.4.3-3 Global Annual CO2 Emissions from Fossil Fuel Use ....................................................4-45 

Figure 4.4.3-4 U.S. Annual CO2 Emissions from Fossil Fuel Use........................................................4-45 

Figure 4.4.3-5 World Primary Energy Use Forecast .............................................................................4-46 

Figure 4.4.3-6 U.S. Primary Energy Use Forecast ................................................................................4-46 

Figure 4.4.4-1 Cumulative Annual Emissions Under the MY 2012-2016 Standards 

and Other Reasonably Foreseeable Future Actions (MMTCO2) ...................................4-50 

Figure 4.4.4-2 Cumulative Effects on CO2 Concentrations...................................................................4-57 

Figure 4.4.4-3 Cumulative Effects on Global Mean Surface Temperature Increase.............................4-58 

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

to the No Action Alternative) ........................................................................................4-59 

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

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

Figure 4.5.3-1 Global Allocation of Water............................................................................................4-75 

Figure 4.5.4-1 Terrestrial Ecozones and Biomes of the World .............................................................4-91 

Figure 4.5.4-2 Freshwater Major Habitat Types (MHTs) .....................................................................4-94 

Figure 4.5.4-3 Level I Ecoregions in the North America ......................................................................4-97 
xi 

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 
List of Acronyms and Abbreviations 

xii 

FMCSA Federal Motor Carrier Safety Administration 

FR Federal Register 

FRIA Final Regulatory Impact Analysis 

FTA Federal Transit Administration 

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 

LDV light-duty vehicle 

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 
List of Acronyms and Abbreviations 

xiii 

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 
List of Acronyms and Abbreviations 

xiv 

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 
xv 

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. 
Glossary 

xvi 

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 

xvii 

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 

xviii 

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. 
 S-1 

1 Summary 

2 S.1 FOREWORD 

3 The National Highway Traffic Safety Administration (NHTSA) prepared this Environmental 

4 Impact Statement (EIS) to analyze and disclose the potential environmental impacts of the proposed 

5 model year (MY) 2012-2016 Corporate Average Fuel Economy (CAFE) standards for the total fleet of 

6 passenger and non-passenger automobiles (later referred to as passenger cars and light trucks, 

7 respectively) and reasonable alternative standards for the NHTSA CAFE Program pursuant to Council on 

8 Environmental Quality (CEQ) regulations implementing the National Environmental Policy Act (NEPA), 

U.S. Department of Transportation (DOT) Order 5610.1C, and NHTSA regulations.1 9 This EIS compares 

10 the potential environmental impacts of alternative mile-per-gallon (mpg) levels NHTSA will consider for 

11 the final rule, including the Preferred Alternative (i.e., the proposed standards) and a No Action 

12 Alternative. It also analyzes direct, indirect, and cumulative impacts and analyzes impacts in proportion 

13 to their significance. 

14 S.2 BACKGROUND 

15 The Energy Policy and Conservation Act of 1975 (EPCA) established a program to regulate 

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

passenger cars and separate standards for light trucks.2 17 As part of that Act, the CAFE Program was 

18 established to reduce national energy consumption by increasing the fuel economy of passenger cars and 

19 light trucks. The Act directs the Secretary of Transportation to set and implement fuel economy standards 

20 for passenger cars and light trucks sold in the United States. NHTSA is delegated responsibility for 

implementing the EPCA fuel economy requirements assigned to the Secretary of Transportation.3 21 

In December 2007, the Energy Independence and Security Act of 2007 (EISA)4 22 amended the 

23 EPCA CAFE Program requirements, providing DOT additional rulemaking authority and responsibilities. 

24 Pursuant to EISA, on April 22, 2008, NHTSA proposed CAFE standards for MY 2011-2015 passenger 

cars and light trucks in a Notice of Proposed Rulemaking (NPRM).5 25 On March 28, 2008, NHTSA issued 

a Notice of Intent (NOI) to prepare an EIS for proposed MY 2011-2015 CAFE standards.6 26 On October 

27 10, 2008, NHTSA submitted to the U.S. Environmental Protection Agency (EPA) its Final Environmental 

28 Impact Statement, Corporate Average Fuel Economy Standards, Passenger Cars and Light Trucks, Model 

29 Years 2011–2015. EPA published a Notice of Availability of the Final Environmental Impact Statement 

(FEIS) in the Federal Register on October 17, 2008.7 30 On January 7, 2009, the DOT announced that the 

 

1

 NEPA is codified at 42 United States Code (U.S.C.) §§ 4321-4347. CEQ NEPA implementing regulations are 

codified at 40 Code of Federal Regulations (CFR) Parts 1500-1508. NHTSA NEPA implementing regulations are 

codified at 49 CFR Part 520. 

2

 49 U.S.C. § 32901-32919

3

 Accordingly, the Secretary of Transportation, DOT, and NHTSA are used interchangeably in this Summary. 4

 EISA amends and builds on EPCA 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). 

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

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

Standards, 73 FR 16615 (Mar. 28, 2008). 7

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

 S-2 

Bush Administration would not issue the final rule.8 1 President Obama issued a memorandum on January 

2 26, 2009, to the Secretary of Transportation and the NHTSA Administrator requesting that NHTSA issue 

3 a final rule adopting CAFE standards for MY 2011 only, and to reconsider the standards for years after 

2011.9 4 In accordance with President Obama’s memorandum, on March 30, 2009, NHTSA issued a final 

rule adopting CAFE standards for MY 2011.10 5 On April 1, 2009, NHTSA published an NOI to prepare 

an EIS for proposed MY 2012-2016 CAFE standards.11 6 The NOI described the statutory requirements for 

7 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.12 8 

9 On May 19, 2009 President Obama announced a National Fuel Efficiency Policy aimed at both 

10 increasing fuel economy and reducing greenhouse gas pollution for all new cars and trucks sold in the 

11 United States, while also providing a predictable regulatory framework for the automotive industry. The 

12 policy seeks to set harmonized federal standards to regulate both fuel economy and greenhouse gas 

13 emissions while preserving the legal authorities of the Department of Transportation, the Environmental 

14 Protection Agency and the State of California. The program covers model year 2012 to model year 2016 

15 and ultimately requires the equivalent of an average fuel economy of 35.5 mpg in 2016, if all CO2

16 reduction were achieved through fuel economy improvements. In conjunction with the President’s 

17 announcement, the Department of Transportation and the Environmental Protection Agency issued on 

18 May 19, 2009, a Notice of Upcoming Joint Rulemaking to propose a strong and coordinated fuel 

19 economy and greenhouse gas National Program for Model Year (MY) 2012-2016 light duty vehicles. 

20 Today, concurrent with this DEIS, NHTSA and EPA are each announcing joint proposed rules 

21 whose benefits would address the urgent and closely intertwined challenges of energy independence and 

22 security and global warming. These proposed rules call for a strong and coordinated federal greenhouse 

23 gas and fuel economy program for passenger cars, light-duty-trucks, and medium-duty passenger vehicles 

24 (hereafter light-duty vehicles), referred to as the National Program. The proposed rules can achieve 

25 substantial improvements in fuel economy and reductions of greenhouse gas (GHG) emissions from the 

26 light-duty vehicle part of the transportation sector, based on technology that is already being 

27 commercially applied in most cases and that can be incorporated at a reasonable cost. 

28 Consistent, harmonized, and streamlined requirements under the National Program hold out the 

29 promise of delivering environmental and energy benefits, cost savings, and administrative efficiencies on 

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

31 Program makes it possible for the standards of two different federal agencies and the standards of 

32 California and other states to act in a unified fashion in providing these benefits. Establishing a 

33 harmonized approach to regulating light-duty vehicle greenhouse gas (GHG) emissions and fuel economy 

34 is critically important given the interdependent goals of addressing climate change and ensuring energy 

35 independence and security. Additionally, establishing a harmonized approach may help to mitigate the 

36 cost to manufacturers of having to comply with multiple sets of federal and state standards 

 

8

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

9, 2009). 

9

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

Administration, 74 FR 4907 (Jan. 26, 2009). 10 Final Rule, Average Fuel Economy Standards Passenger Cars and Light Trucks Model Year 2011, 74 FR 14196 

(Mar. 30, 2009). 

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

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

12 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. 
Summary 

 S-3 

1 Under NEPA, a federal agency must analyze environmental impacts if the agency implements a 

2 proposed action, provides funding for an action, or issues a permit for that action. Specifically, NEPA 

3 directs that “to the fullest extent possible,” federal agencies proposing “major federal actions significantly 

4 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).13 5 To inform 

6 its development of the new MY 2012-2016 CAFE standards required under EPCA, as amended by EISA, 

7 NHTSA prepared this EIS to analyze and disclose the potential environmental impacts of a proposed 

8 Preferred Alternative and other proposed alternative standards. 

9 Section 1501.6 of CEQ regulations emphasize agency cooperation early in the NEPA process, 

10 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.14 11 NHTSA invited 

12 EPA to be a cooperating agency, pursuant to CEQ regulations, because of its special expertise in the areas 

13 of climate change and air quality. On May 12, 2009, EPA accepted the NHTSA invitation and agreed to 

14 become a cooperating agency. EPA’s environmental analysis of its proposed rulemaking is summarized 

and referenced in the appropriate sections of this EIS.15 15 

16 S.3 PURPOSE AND NEED FOR THE PROPOSED ACTION 

17 For this EIS, the NHTSA Proposed Action is to set passenger car and light truck CAFE standards 

18 for MY 2012-2016 in accordance with EPCA, as amended by EISA. As mentioned above, in the 

19 NHTSA-EPA joint NPRM, NHTSA and EPA propose coordinated and harmonized CAFE standards and 

20 vehicle GHG emissions standards for passenger cars, light-duty trucks, and medium-duty passenger 

21 vehicles built in MY 2012-2016. NEPA requires that a proposed action’s alternatives be developed based 

22 on the action’s purpose and need. 

23 EPCA/EISA set forth extensive requirements for the rulemaking, and those requirements form the 

24 purpose of and need for the standards. The requirements also were the basis for establishing the range of 

25 alternatives considered in this EIS. Specifically, the statute requires the Secretary of Transportation to 

26 establish average fuel economy standards for each model year at least 18 months before the beginning of 

27 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.”16 28 When setting maximum feasible fuel 

29 economy standards, the Secretary is required to “consider technological feasibility, economic 

30 practicability, the effect of other motor vehicle standards of the Government on fuel economy, and the 

need of the United States to conserve energy.”17 31 NHTSA interprets the statutory factors as including 

 

13 42 U.S.C. § 4332. 

14 40 CFR § 1501.6. 

15 Consistent with the National Fuel Efficiency Policy that the President announced 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 the EPA proposed rule on GHG emissions could be considered a “connected action” 

under the CEQ regulation at 40 CFR Section 1508.25. For purposes of this EIS, however, NHTSA has decided to 

treat the EPA 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 expressly exempts from NEPA requirements EPA action taken under the 

CAA. See 15 U.S.C. § 793(c)(1). The NHTSA discussion of the EPA 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. 

16 49 U.S.C. § 32902(a). 

17 49 U.S.C. § 32902(f). 
Summary 

 S-4 

environmental issues and permitting the consideration of other relevant societal issues, such as safety.18 1 

2 The purpose of this EIS is to analyze and disclose the potential environmental impacts of the standards 

3 and alternatives for consideration by NHTSA decisionmakers. 

4 EPCA/EISA further direct the Secretary of Transportation, after consultation with the Secretary 

5 of Energy and the Administrator of EPA, to establish separate average fuel economy standards for 

6 passenger cars and for light trucks manufactured in each model year beginning with MY 2011 “to achieve 

7 a combined fuel economy average for MY 2020 of at least 35 miles per gallon for the total fleet of 

8 passenger and non-passenger automobiles manufactured for sale in the United States for that model 

year.”19 9 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 5 model years.20 10 

11 NHTSA also is guided by President Obama’s memorandum to DOT on January 26, 2009, as described in 

12 Section S.2 and Chapter 1. 

13 S.4 ALTERNATIVES 

14 NEPA requires an agency to compare the potential environmental impacts of its proposed action 

15 and a reasonable range of alternatives. The EPCA fuel economy requirements, including the four factors 

16 NHTSA must consider in determining maximum feasible CAFE levels – technological feasibility, 

17 economic practicability, the need to conserve energy, and the effect of other standards of the Government 

18 on fuel economy – form the purpose of and need for the MY 2012-2016 CAFE standards and, therefore, 

19 inform the range of alternatives for consideration in this NEPA analysis. The NHTSA decision process 

20 balances the four EPCA factors and must also be informed by the environmental considerations of NEPA. 

21 In developing its reasonable range of alternatives, NHTSA identified alternative stringencies that 

22 represent the full spectrum of potential environmental impacts and safety considerations. This EIS 

23 analyzes the impacts of eight “action” alternatives and the impacts that would be expected if NHTSA 

24 imposed no new requirements (the No Action Alternative). 

25 A large number of alternatives can be defined along a continuum from the least to the most 

26 stringent levels of potential CAFE standards. The specific alternatives NHTSA examined, described 

27 below, encompass a reasonable range to evaluate the potential environmental impacts of the CAFE 

28 standards and alternatives under NEPA, in view of EPCA requirements. At one end of this range is the 

29 No Action Alternative (Alternative 1), which assumes no action would occur under the National 

Program.21 30 The No Action Alternative assumes that average fuel economy levels in the absence of CAFE 

31 standards beyond MY 2011 would equal the higher of the agencies’ collective market forecast or the 

32 manufacturer’s required level of average fuel economy for MY 2011. The MY 2011 fuel economy level 

33 represents the standard NHTSA believes manufacturers would continue to abide by, assuming NHTSA 

34 does not issue a rule. NHTSA is also proposing to consider eight action alternatives, including NHTSA’s 

35 Preferred Alternative (Alternative 4), which requires approximately a 4.3-percent average annual increase 

36 in mpg from 2012 to 2016. This alternative and the EPA proposed rulemaking together comprise the 

37 National Program described in the NPRM. 

 

18 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). 

19 49 U.S.C. § 32902(b)(2)(A). 

20 49 U.S.C. §§ 32902(b)(2)(C), 32902(b)(3)(B). 

21 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). 
Summary 

 S-5 

1 Alternative 2 (3-Percent Alternative), Alternative 3 (4-Percent Alternative), Alternative 5 (5-

2 Percent Alternative), Alternative 7 (6-Percent Alternative), and Alternative 8 (7-Percent Alternative), 

3 require average annual increases in mpg of 3 percent to 7 percent from 2012 to 2016. Because the 

4 percentage increases in stringency are “average” increases, they can be constant throughout the period or 

5 can vary from year to year. 

6 NHTSA also added three alternatives to the list of alternatives first proposed in the NOI to 

7 prepare an EIS – the agency’s Preferred Alternative (Alternative 4), an alternative that maximizes net 

8 benefits (MNB) (Alternative 6), and an alternative under which total cost equals total benefits (TCTB) 

9 (Alternative 9). The agency’s Preferred Alternative represents the required fuel economy level that 

10 NHTSA has tentatively determined to be the maximum feasible under EPCA, based on balancing 

11 statutory and other relevant considerations. See Section S.3. The other two alternatives, the MNB and 

12 TCTB, represent fuel economy levels that depend on the agency’s best estimate of relevant economic 

13 variables (e.g., gasoline prices, social cost of carbon, the discount rate, and rebound effect). For further 

14 discussion of the economic assumptions, see Section 2.2.4. The MNB Alternative and TCTB Alternative 

15 provide the decisionmaker and the public with useful information about where the standards would be set 

16 if costs and benefits were balanced in two different ways. The 6-percent Alternative results in required 

17 mpg in 2016 that is slightly higher than required mpg under the MNB Alternative, but required mpg in 

18 2012 through 2015 under the 6-percent Alternative is actually slightly lower than under the MNB 

19 Alternative. In general, the net result is that there is very little substantive difference in required mpg 

20 under the 6-percent and MNB Alternatives. The TCTB Alternative results in required mpg in 2016 that is 

21 just slightly lower than required mpg under the 7-percent Alternative, but required mpg in 2012 through 

22 2015 under the TCTB Alternative is slightly higher than under the 7-percent Alternative. In general, the 

23 net result is that there is very little substantive difference in required mpg under the 7-percent and TCTB 

24 Alternatives. 

25 Table S-1 shows the required fuel economy levels for each alternative. For additional detail and 

26 discussion of how NHTSA considers the EPCA statutory and other factors that guide the agency’s 

27 determination of “maximum feasible” standards, and inform an evaluation of the alternatives, see Section 

28 IV.F of the NPRM. For detailed calculations and discussions of manufacturer cost impacts and estimated 

29 benefits for each of the alternatives, see Sections VII and VIII of the NHTSA Preliminary Regulatory 

30 Impact Analysis. 

Table S-2 shows the estimated22 31 achieved fuel economy levels for each alternative. Comparing 

32 Table S-2 with Table S-1 shows that estimated achieved combined mpg in 2016 would actually exceed 

33 required mpg under the No Action Alternative, indicating that some manufacturers would exceed the no 

34 action required mpg. Achieved combined mpg would equal required combined mpg under Alternative 2. 

 

22 As discussed above, the CAFE level required under an attribute-based standard depends on the mix of vehicles 

produced for sale in the U .S. 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. 
Summary 

 S-6 

Table S-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

~5.9%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.7%/year 

Increase 

 TCTB 

2012 

Passenger 

Cars 30.5 31.5 32.1 33.6 32.7 33.4 33.0 33.3 33.8

Light Trucks 24.3 24.3 24.3 25.0 24.4 26.4 24.6 24.8 26.7

Combined 27.9 28.4 28.7 29.8 29.0 30.4 29.2 29.5 30.8

2013 

Passenger 

Cars 30.5 32.9 33.6 34.4 34.2 36.0 34.9 35.5 36.7

Light Trucks 24.2 24.5 25.0 25.6 25.5 27.7 26.0 26.5 28.0

Combined 27.9 29.3 29.9 30.6 30.4 32.5 31.0 31.6 33.0

2014 

Passenger 

Cars 30.5 33.8 34.8 35.2 35.8 38.1 36.9 37.9 39.0

Light Trucks 24.2 25.2 26.0 26.2 26.7 28.8 27.5 28.3 29.2

Combined 27.9 30.2 31.0 31.4 31.9 34.2 32.9 33.8 34.8

2015 

Passenger 

Cars 30.5 34.7 36.1 36.4 37.5 39.5 38.9 40.4 40.8

Light Trucks 24.1 25.9 26.9 27.1 28.0 30.1 29.0 30.1 30.9

Combined 28.0 31.1 32.3 32.6 33.5 35.6 34.8 36.2 36.8

2016 

Passenger 

Cars 30.5 35.6 37.4 38.0 39.3 40.9 41.1 43.1 42.7

Light Trucks 24.1 26.6 27.9 28.3 29.3 30.6 30.7 32.2 31.5

Combined 28.0 32.0 33.6 34.1 35.2 36.8 36.9 38.7 38.1

1 
Summary 

 S-7 

Table S-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

~5.9%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.7%/year 

Increase 

TCTB 

2012 

Passenger 

Cars 32.4 32.7 33.0 33.3 33.2 33.5 33.4 33.5 33.7

Light Trucks 24.2 24.5 24.7 25.0 24.8 25.5 24.9 25.1 25.5

Combined 28.6 29.0 29.2 29.5 29.3 29.9 29.5 29.7 30.0

2013 

Passenger 

Cars 32.4 34.0 34.5 34.9 35.1 36.0 35.7 36.1 36.3

Light Trucks 24.3 25.0 25.5 25.9 25.9 27.2 26.3 26.7 27.3

Combined 28.7 29.9 30.4 30.9 30.9 32.1 31.5 31.8 32.3

2014 

Passenger 

Cars 32.4 34.6 35.5 35.9 36.5 37.8 37.4 38.0 38.2

Light Trucks 24.2 25.5 26.3 26.7 27.1 28.6 27.8 28.3 28.8

Combined 28.8 30.5 31.5 31.8 32.3 33.8 33.2 33.7 34.1

2015 

Passenger 

Cars 32.5 35.2 36.5 36.8 37.5 39.1 38.8 39.4 39.6

Light Trucks 24.1 26.0 27.1 27.4 28.2 29.7 29.2 29.9 30.1

Combined 28.9 31.3 32.5 32.8 33.6 35.1 34.7 35.4 35.6

2016 

Passenger 

Cars 32.5 36.0 37.5 37.9 39.1 40.4 40.5 41.4 41.4

Light Trucks 24.2 26.5 27.7 28.1 29.0 30.3 30.3 31.0 30.8

Combined 29.0 32.0 33.4 33.8 34.9 36.2 36.2 37.1 37.0

1 

2 Under other action alternatives, the estimated achieved mpg in 2016 would be somewhat lower 

3 than the required mpg levels because some manufacturers are not expected to comply fully with 

4 passenger car or light truck standards under some alternatives. Estimated achieved and required fuel 
Summary 

 S-8 

economy levels differ because manufacturers will, on average, undercomply23 1 in some model years and 

overcomply24 in others.25 2 

3 S.5 POTENTIAL ENVIRONMENTAL CONSEQUENCES 

4 This EIS describes potential environmental impacts to a variety of resources. Resources that the 

5 proposed action and alternative could affect include water resources, biological resources, land use and 

6 development, safety, hazardous materials and regulated wastes, noise, socioeconomics, and 

environmental justice. NHTSA assesses these resource areas qualitatively.26 7 This section focuses on the 

8 resources for which NHTSA performed a quantitative assessment  energy, air quality, and climate. 

9 Tables and figures in this section summarize the direct, indirect, and cumulative effects of the 

10 alternatives on energy, air quality, and climate. NHTSA recognizes the national interest in addressing 

11 global climate change issues and the role that transportation plays. “Global climate change” refers to 

12 long-term fluctuations in global surface temperatures, precipitation, sea level, cloud cover, ocean 

13 temperatures and currents, and other climatic conditions. Scientific research has shown that in the past 

14 century, Earth’s surface temperature has risen by an average of about 0.74 degree Celsius (°C) (1.3 

15 degrees Fahrenheit [°F]) and sea levels have risen 6.7 inches (0.17 meter), with a maximum rate of about 

16 0.08 inch (2 millimeters) per year over the past 50 years on the northeastern coast of the United States. 

17 Most scientists now agree that climate change is very likely due to GHG emissions from human 

18 activities. Most GHGs are naturally occurring, including carbon dioxide (CO2), methane (CH4), nitrous 

19 oxide (N2O), water vapor, and ozone. Human activities, such as the combustion of fossil fuel, the 

20 production of agricultural commodities, and the harvesting of trees, can contribute to increased 

21 concentrations of these gases in the atmosphere. 

 

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. 26 See 42 United States Code (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). 
Summary 

 S-9 

1 Levels of atmospheric CO2 have been rising rapidly. For about 10,000 years prior to the 

2 Industrial Revolution, atmospheric CO2 levels were 280 parts per million (ppm) (+/- 20 ppm). Since the 

3 Industrial Revolution, CO2 levels have risen to 386 ppm (+/- 20 ppm) in 2008. 

4 Contributions to the build-up of GHG in the atmosphere vary greatly from country to country and 

5 depend heavily on the level of industrial and economic activity. Emissions from the United States 

6 comprise about 15 to 20 percent of total global emissions. The U.S. transportation sector contributed 35.7 

7 percent of total U.S. CO2 emissions in 2007, with passenger cars and light trucks accounting for 60.8 

8 percent of total U.S. CO2 emissions from transportation. Thus, 21.7 percent of total U.S. CO2 emissions 

9 comes from passenger cars and light trucks. With the United States accounting for 17.2 percent of global 

10 CO2 emissions, passenger cars and light trucks in the United States account for roughly 3.7 percent of 

11 global CO2 emissions. 

12 Throughout this EIS, NHTSA has relied extensively on findings of the United Nations 

13 Intergovernmental Panel on Climate Change (IPCC), the U.S. Climate Change Science Program (CCSP), 

14 and EPA. Our discussion relies heavily on the most recent, thoroughly peer reviewed, and credible 

15 assessments of global and U.S. climate change  the IPCC Fourth Assessment Report (Climate Change 

16 2007), the EPA proposed Endangerment and Cause or Contribute Findings for Greenhouse Gases under 

17 Section 202(a) of the Clean Air Act and the accompanying Technical Support Document (TSD), and 

18 CCSP and National Science and Technology Council reports that include Scientific Assessment of the 

19 Effects of Global Change on the United States and Synthesis and Assessment Products. This EIS 

20 frequently cites these sources and the studies they review. 

21 Because of the link between the transportation sector and GHG emissions, NHTSA recognizes 

22 the need to consider possible impacts on climate and global climate change in the analysis of the effects 

23 of these fuel economy standards. NHTSA also recognizes the difficulties and uncertainties involved in 

24 such an impacts analysis. Accordingly, consistent with CEQ regulations on addressing incomplete or 

25 unavailable information in environmental impact analyses, NHTSA has reviewed existing credible 

26 scientific evidence relevant to this analysis and summarized it in this EIS. NHTSA has also employed 

27 and summarized the results of research models generally accepted in the scientific community. 

28 NHTSA emphasizes that the action of setting fuel economy standards does not directly regulate 

29 emissions from passenger cars and light trucks. NHTSA’s authority to promulgate new fuel economy 

30 standards is a limited authority and does not allow NHTSA to regulate other factors affecting emissions, 

31 including society’s driving habits. Specifically, NHTSA notes that under all of the alternatives analyzed, 

32 growth in the number of passenger cars and light trucks in use throughout the United States, combined 

33 with assumed increases in their average use (annual vehicle miles traveled per vehicle), is projected to 

34 result in growth in total passenger car and light truck travel. This growth in travel overwhelms 

35 improvements in fuel economy for each of the alternatives, resulting in projected increases in total fuel 

36 consumption by U.S. passenger cars and light trucks. Because CO2 emissions are a direct consequence of 

37 total fuel consumption, the same result is projected for total CO2 emissions from passenger cars and light 

38 trucks. NHTSA estimates that the CAFE standards will reduce fuel consumption and CO2 emissions from 

39 what they otherwise are estimated to be in the absence of the CAFE program. 

40 The proposed action before NHTSA is to establish the CAFE standards for MY 2012-2016 

41 passenger cars and light trucks, which has a primary goal of energy conservation. At the same time, the 

42 reduction of CO2 emissions is a substantial by-product of that conservation. Further, the stringency of 

43 fuel economy standards is based on the valuation of both direct (fuel savings) and indirect (e.g., the 

44 reduction of CO2 emissions) benefits. To the extent the CAFE standards reduce fuel consumption, they 

45 play a role in reducing vehicle emissions that would have occurred absent such conservation. 
Summary 

 S-10 

1 Consequently, as discussed in this EIS, the proposed action will indirectly contribute to reducing impacts 

2 on and associated with the ongoing process of global climate change. 

3 Although the alternatives have the potential to decrease GHG emissions substantially, they do not 

4 prevent climate change, but only result in reductions in the anticipated increases in CO2 concentrations, 

5 temperature, precipitation, and sea level. They would also, to a small degree, reduce the impacts and risks 

6 of climate change. As discussed below, NHTSA presumes that these reductions in climate effects will be 

7 reflected in reduced impacts on affected resources. 

8 NHTSA informed the public through notice in the Federal Register of its intent to prepare a EIS 

for this proposed action.27 9 The purpose of this notice was to request from the public its views and 

10 comments on the scope of the NEPA analysis, including the impacts and alternatives the EIS should 

11 address, and to inform NHTSA of any available studies that would assist in the impact analysis for global 

12 climate-change issues. NHTSA reviewed and considered the public scoping comments and the studies 

13 commenters suggested. The predominant request by commenters during the scoping process was that 

14 NHTSA focus the EIS on the possible impact of the standards on both air quality and global climate 

15 change. 

16 NHTSA consulted with various federal agencies in the development of this EIS, including EPA, 

17 the Bureau of Land Management, the Centers for Disease Control and Prevention, the Minerals 

18 Management Service, the National Park Service, the U.S. Army Corps of Engineers, the U.S. Forest 

19 Service, and the Advisory Council on Historic Preservation. NHTSA is also exploring its Section 7 

20 obligations under the Endangered Species Act with the U.S. Fish and Wildlife Service and the National 

21 Oceanic and Atmospheric Administration Fisheries Service. 

22 S.5.1 Direct and Indirect Effects 

23 Under NEPA, direct effects “are caused by the action and occur at the same time and place.” 40 

24 CFR § 1508.8. CEQ regulations define indirect effects as those that “are caused by the action and are 

25 later in time or farther removed in distance but are still reasonably foreseeable. Indirect effects may 

26 include...effects on air and water and other natural systems, including ecosystems.” 40 CFR § 1508.8. 

27 Sections S.5.1.1 through S.5.1.3 summarize the direct and indirect effects of the proposed action and 

28 alternatives on energy, air quality, and climate. 

29 S.5.1.1 Energy 

30 Tables S-3 and S-4 show the impact on annual fuel consumption for passenger cars and light 

31 trucks from 2020 through 2060, when the entire passenger-car and light-truck fleet is likely to be 

32 composed of MY 2016 or later passenger cars. Table S-3 shows annual total fuel consumption (both 

33 gasoline and diesel gasoline equivalent) under the No Action Alternative and the eight action alternatives. 

34 For passenger cars, fuel consumption under the No Action Alternative (Alternative 1) is 173.5 billion 

35 gallons in 2060. Fuel consumption ranges from 156.1 billion gallons under Alternative 2 (3-Percent 

36 Alternative) to 139.7 billion gallons under Alternative 9 (TCTB). Fuel consumption is 150.9 billion 

37 gallons under the Preferred Alternative (Alternative 4). 

 

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

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

 S-11 

Table S-3 

Passenger Car Annual Fuel Consumption and Fuel Savings (billion gallons gasoline equivalent) by 

Alternative 

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 

~5.9%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.7%/year 

Increase 

TCTB 

Fuel Consumption 

2020 69.4 65.7 64.3 63.9 63.0 61.8 61.9 61.2 61.1

2030 97.9 89.5 86.4 85.5 83.5 81.0 80.9 79.4 79.4

2040 121.7 110.9 106.9 105.9 103.2 100.1 99.9 98.0 98.1

2050 145.7 132.8 128.0 126.7 123.5 119.8 119.6 117.3 117.3

2060 173.5 158.2 152.4 150.9 147.1 142.7 142.4 139.7 139.7

Fuel Savings Compared to No Action 

2020 -- 3.7 5.1 5.5 6.4 7.6 7.6 8.2 8.3

2030 -- 8.4 11.5 12.3 14.4 16.8 17.0 18.4 18.4

2040 -- 10.8 14.8 15.9 18.5 21.6 21.8 23.7 23.7

2050 -- 12.9 17.7 19.0 22.2 25.9 26.2 28.4 28.4

2060 -- 15.4 21.1 22.6 26.5 30.9 31.2 33.9 33.8

1 

Table S-4 

Light Truck Annual Fuel Consumption and Fuel Savings (billion gallons gasoline equivalent) by Alternative

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 

~5.9%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.7%/year 

Increase 

TCTB 

Fuel Consumption 

2020 68.6 66.4 65.2 64.9 64.2 63.0 63.3 62.7 62.6

2030 66.0 61.6 59.6 59.0 57.6 55.8 55.9 55.0 55.1

2040 73.0 67.4 64.9 64.2 62.4 60.3 60.3 59.1 59.3

2050 85.5 78.7 75.7 74.8 72.7 70.2 70.1 68.7 69.0

2060 101.4 93.3 89.7 88.7 86.1 83.1 83.1 81.3 81.7

Fuel Savings Compared to No Action 

2020 -- 2.3 3.4 3.8 4.4 5.6 5.3 5.9 6.0

2030 -- 4.4 6.4 7.0 8.3 10.1 10.0 11.0 10.9

2040 -- 5.6 8.1 8.8 10.6 12.8 12.7 14.0 13.7

2050 -- 6.8 9.8 10.7 12.8 15.4 15.4 16.9 16.5

2060 -- 8.1 11.7 12.7 15.3 18.3 18.4 20.1 19.7

2 

3 For light trucks, fuel consumption under the No Action Alternative is 101.4 billion gallons in 

4 2060. Fuel consumption ranges from 93.3 billion gallons under Alternative 2 to 81.3 billion gallons 

5 under Alternative 8 (7-percent annual increase in mpg). Fuel consumption is 88.7 billion gallons under 

6 the Preferred Alternative. 

7 S.5.1.2 Air Quality 

8 Table S-5 summarizes the total annual national criteria and mobile source air toxic (MSAT) 

9 pollutant emissions in 2030 for the nine alternatives, left to right in order of generally increasing fuel 

10 economy requirements. Changes in overall emissions between the No Action Alternative (Alternative 1) 

11 and Alternatives 2 through 4 (3-Percent, 4-Percent, and Preferred Alternatives) are generally smaller than 
Summary 

 S-12 

1 those between the No Action Alternative and Alternatives 5 through 9. In the case of particulate matter 

2 with an aerodynamic diameter equal to or less than 2.5 microns (PM2.5), sulfur oxides (SOx), nitrogen 

3 oxides (NOx), and volatile organic compounds (VOCs), the No Action Alternative results in the highest 

4 emissions, and emissions generally decline as fuel economy standards increase across alternatives. 

5 Across Alternatives 4 through 9 (MNB, 6-Percent, 7-Percent, TCTB Alternatives) there are some 

6 emissions increases from one alternative to another, but emissions remain below the levels under the No 

7 Action Alternative. In the case of carbon monoxide (CO), emissions under Alternatives 2 through 4 are 

8 slightly higher than under the No Action Alternative. Emissions of CO decline as fuel economy standards 

9 increase across Alternatives 5 through 9. 

Table S-5 

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 

~5.9%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.7%/year 

Increase 

TCTB 

Criteria Pollutant Emissions 

Carbon

monoxide (CO) 17,766,186 17,875,841 17,857,900 17,830,426 17,374,361 16,933,532 16,692,592 16,584,083 16,544,125

Nitrogen oxides

(NOx) 1,467,596 1,453,694 1,445,588 1,443,013 1,416,117 1,390,714 1,379,863 1,370,822 1,368,895

Particulate 

matter (PM2.5) 76,589 74,147 73,316 73,321 73,122 73,349 73,725 73,362 73,382

Sulfur oxides 

(SOx) 201,502 186,242 180,661 179,415 178,313 176,493 178,441 176,043 176,396

Volatile organic

compounds

(VOCs) 1,668,085 1,596,544 1,564,323 1,553,482 1,514,436 1,469,438 1,456,616 1,439,159 1,438,649

Toxic Air Pollutant Emissions 

Acetaldehyde 6,631 6,665 6,683 6,678 6,710 6,721 6,733 6,748 6,751

Acrolein 342 345 348 351 366 385 393 398 399

Benzene 27,706 27,667 27,602 27,551 27,171 26,758 26,569 26,466 26,440

1,3-butadiene 3,610 3,631 3,637 3,638 3,615 3,597 3,584 3,581 3,579

Diesel 

particulate 

matter (DPM) 106,046 97,820 94,519 93,731 91,502 89,134 89,055 87,536 87,606

Formaldehyde 8,875 8,884 8,927 8,938 9,198 9,440 9,573 9,652 9,672

10 

11 The trend for toxic air pollutant emissions across the alternatives is mixed. Annual emissions of 

12 acetaldehyde in 2030 are lowest under Alternative 1, increase with each successive alternative (except for 

13 Alternative 4), and are highest under Alternative 9. Annual emissions of acrolein and formaldehyde 

14 increase under each successive alternative from Alternative 1 to Alternative 9. Annual emissions of 

15 benzene and DPM decrease under each successive alternative from Alternative 1 to Alternative 9. Annual 

16 emissions of 1,3-butadiene increase under each successive alternative from Alternative 1 to Alternative 4, 

17 and then decrease under each successive alternative from Alternative 5 to Alternative 9 in 2030. 

18 The reductions in emissions are expected to lead to reductions in adverse health effects. 

19 Table S-6 summarizes the national annual changes in health outcomes in 2030 for the nine alternatives, 

20 left to right in order of increasing fuel economy requirements. There would be reductions in adverse 

21 health effects nationwide under Alternatives 2 through 9 compared to the No Action Alternative. The No 
Summary 

 S-13 

1 Action Alternative results in no reductions in adverse health effects, and the reductions become larger as 

2 fuel economy standards increase and emissions decrease across alternatives. These reductions primarily 

3 reflect the projected PM2.5 reductions, and secondarily the reductions in SO2. 

Table S-6 

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 

~5.9%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.7%/year 

Increase 

TCTB 

Mortality (ages 30 and older), Pope et al.

2030 0 -153 -210 -217 -253 -276 -267 -296 -296

Mortality (ages 30 and older), Laden et al.

2030 0 -392 -537 -554 -648 -705 -683 -758 -758

Chronic bronchitis 

2030 0 -100 -138 -142 -167 -182 -177 -196 -196

Emergency Room Visits for Asthma 

2030 0 -140 -191 -198 -226 -244 -233 -258 -258

Work Loss Days 

2030 0 -18,031 -24,750 -25,522 -30,036 -32,758 -31,811 -35,301 -35,306

__________ 

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. 

4 

5 The economic value of health impacts would vary proportionally with changes in health 

6 outcomes. Table S-7 lists the corresponding reductions in annual health costs in 2030 under Alternatives 

7 2 through 9 compared to the No Action Alternative. Reductions in health costs are given for two 

8 alternative assumptions of the discount rate, 3 percent and 7 percent, consistent with EPA policy for 

9 presentation of future health costs. 

Table S-7 

Nationwide Changes in Health Costs (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 

~5.9%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.7%/year 

Increase 

TCTB 

3% Discount Rate

Pope et al.

2030 0 -1,361 -1,867 -1,926 -2,253 -2,452 -2,374 -2,635 -2,634

Laden et al.

2030 0 -3,334 -4,574 -4,720 -5,520 -6,007 -5,816 -6,454 -6,451

7% Discount Rate

Pope et al.

2030 0 -1,234 -1,693 -1,747 -2,044 -2,224 -2,154 -2,390 -2,389

Laden et al.

2030 0 -3,012 -4,131 -4,264 -4,987 -5,426 -5,254 -5,830 -5,827

__________ 

a/ Negative changes indicate economic benefit; positive changes indicate economic costs. 

b/ Changes in outcome under 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. 
Summary 

 S-14 

1 S.5.1.3 Climate Change 

2 This EIS uses a climate model to estimate the changes in CO2 concentrations, global mean 

3 surface temperature, and changes in sea level for each alternative CAFE standard. NHTSA used the 

4 publicly available modeling software, Model for Assessment of Greenhouse Gas-induced Climate Change 

5 (MAGICC) version 5.3.v2 to estimate changes in key direct and indirect effects. The application of 

6 MAGICC 5.3.v2 uses the emissions estimates for CO2, CH4, N2O, CO, NOx, SO2, and VOCs from the 

7 Volpe model. NHTSA performed a sensitivity analysis to examine the relationship among selected 

CAFE alternatives and likely climate sensitivities,28 8 and the associated direct and indirect effects for each 

9 combination. These relationships can be used to infer the effect of emissions associated with the action 

10 alternatives on direct and indirect climate effects. 

11 For the analysis using MAGICC, NHTSA assumed that global emissions consistent with the No 

12 Action Alternative (Alternative 1) follow the trajectory provided by the Representative Concentration 

Pathway (RCP) 4.5 MiniCAM (Mini Climate Assessment Model) reference scenario.29 13 The Synthesis 

14 and Assessment Product (SAP) 2.1 global emissions scenarios were created as part of the CCSP effort to 

15 develop a set of long-term (2000 to 2100) global emissions scenarios that incorporate an update of 

16 economic and technology data and utilize improved scenario development tools compared to the IPCC 

17 Special Report on Emissions Scenarios (SRES) developed more than a decade ago. 

18 The results rely primarily on the RCP 4.5 MiniCAM reference scenario to represent an emissions 

19 scenario; that is, future global emissions assuming no additional climate policy. Each alternative was 

20 simulated by calculating the difference in annual GHG emissions in relation to the No Action Alternative 

21 and subtracting this change from the RCP 4.5 MiniCAM reference scenario to generate modified global22 scale emissions scenarios, which each show the effect of the various regulatory alternatives on the global 

23 emissions path. 

24 To estimate changes in global precipitation, this EIS uses increases in global mean surface 

25 temperature combined with a scaling approach and coefficients from the IPCC Fourth Assessment Report. 

26 For all of the climate change analyses, the approaches focus on marginal changes in emissions 

27 that affect climate. Thus, the approaches result in a reasonable characterization of climate change for a 

28 given set of emissions reductions, regardless of the underlying details associated with those emissions 

29 reductions. The climate sensitivity analysis provides a basis for determining climate responses to varying 

30 climate sensitivities under the No Action Alternative and the Preferred Alternative (Alternative 4). 

31 Although the MAGICC model does not simulate abrupt climate change processes, some responses of the 

32 climate system represented in MAGICC are slightly non-linear, primarily due to carbon cycle feedbacks 

33 and the logarithmic response of equilibrium temperature to CO2 concentration. Therefore, by using a 

34 range of emissions cases and climate sensitivities, the effects of the alternatives in relation to different 

35 scenarios and sensitivities can be estimated. 

 

28 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. 

29 The reference scenario for global emissions assumes the absence of significant global GHG control policies. 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 emissions estimates for non-CO2 gases. 
Summary 

 S-15 

1 S.5.1.3.1 GHG Emissions 

2 Table S-8 shows total GHG emissions and emissions reductions from new passenger cars and 

3 light trucks, summed for the period 2012 through 2100 under each of the nine alternatives. Although 

4 GHG emissions from this sector will continue to rise over the period (absent other reduction efforts), the 

5 effect of the alternatives is to slow this increase by varying amounts. Emissions for the period range from 

6 201,200 million metric tons of CO2 (MMTCO2) under the 7%/year Increase (Alternative 8) to 243,600 

7 MMTCO2 under the No Action Alternative. Compared to the No Action Alternative, projections of 

8 emissions reductions over the period 2012 to 2100 due to the MY 2012-2016 CAFE standards range from 

9 19,300 to 42,400 MMTCO2. Compared to cumulative global emissions of 5,293,896 MMTCO2 over this 

10 period (projected by the RCP 4.5 MiniCAM reference scenario), this rulemaking is expected to reduce 

11 global CO2 emissions by about 0.4 to 0.8 percent. 

Table S-8 

Emissions and Emissions Reductions (MMTCO2) from 2012-2100 by Alternative 

Alternative Emissions 

Emissions Reductions 

Compared 

to the No Action Alternative 

1 No Action 243,600 0 

2 3%/year Increase 224,300 19,300 

3 4%/year Increase 216,700 26,900 

4 ~4.3%/year Increase, Preferred 214,700 29,000 

5 5%/year Increase 210,100 33,500 

6 ~5.9%/year Increase, MNB 204,500 39,100 

7 6%/year Increase 204,800 38,800 

8 7%/year Increase 201,200 42,400 

9 ~6.7%/year Increase, TCTB 201,500 42,100 

12 

13 To get a sense of the relative impact of these reductions, it can be helpful to consider the relative 

14 importance of emissions from passenger cars and light trucks as a whole and to compare them against 

15 emissions projections from the transportation sector. As mentioned earlier, U.S. passenger cars and light 

16 trucks account for significant CO2 emissions in the United States. With the action alternatives reducing 

17 U.S. passenger car and light truck CO2 emissions by 7.9 to 17.4 percent, the CAFE alternatives would 

18 have a noticeable impact on total U.S. CO2 emissions. Compared to total U.S. CO2 emissions in 2100 

19 projected by the MiniCAM reference scenario of 7,886 MMTCO2, the action alternatives would reduce 

20 annual U.S. CO2 emissions by 3.6 to 7.8 percent in 2100. As another comparison of the magnitude of 

21 these reductions, average annual CO2 emission reductions from the CAFE alternatives range from 217 to 

22 476 MMTCO2 over 2012-2100, equivalent to the annual CO2 emissions of 47 to 103 coal-fired power 

plants.30 23 Figure S-1 shows projected annual emissions from passenger cars and light trucks under the MY 

24 2012-2016 alternative CAFE standards. 

25 As explained above, under all of the alternatives analyzed, growth in the number of passenger 

26 cars and light trucks in use throughout the United States, combined with assumed increases in their 

27 average use, is projected to result in growth in total passenger car and light truck travel. This growth in 

28 travel overwhelms improvements in fuel economy for each of the alternatives, resulting in projected 

29 increases in total fuel consumption by U.S. passenger cars and light trucks over most of the period shown 

 

30 Estimated using EPA’s Greenhouse Gas Equivalencies Calculator (EPA 2009). 
Summary 

 S-16 

1 in the table. Because CO2 emissions are a direct consequence of total fuel consumption, the same result is 

2 projected for total CO2 emissions from passenger cars and light trucks. 

Figure S-1. Projected Annual Emissions (MMTCO2) by Alternative 

0

500

1000

1500

2000

2500

3000

3500

2010 2020 2030 2040 2050 2060

MMTCO2

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: ~5.9%/year Increase, MNB

Alt. 7: 6%/year Increase Alt. 8: 7%/year Increase

Alt. 9: ~6.7%/year Increase, TCTB

3 

4 Emissions of CO2, the primary gas that drives climate effects, from the U.S. passenger car and 

5 light truck fleets represented about 3.7 percent of total global emissions of CO2 in 2005. However, the 

6 relative contribution of CO2 emissions from U.S. passenger cars and light trucks is expected to decline in 

7 the future, due primarily to rapid growth of emissions from developing economies (which are due in part 

8 to growth in global transportation sector emissions). 

9 S.5.1.3.2 CO2 Concentration, Global Mean Surface Temperature, Sea-level Rise, and 

10 Precipitation 

11 Table S-9 shows estimated CO2 concentrations, increase in global mean surface temperature, and 

12 sea-level rise in 2030, 2050, and 2100 under the No Action Alternative and the eight action alternatives 

13 Figures S-2 through S-5 graphically illustrate estimated CO2 concentrations and reductions for the eight 

14 action alternatives. 

15 Table S-9 lists the impacts on sea-level rise under the alternatives and shows sea-level rise in 

16 2100 ranging from 38.00 centimeters (15.00 inches) under the No Action Alternative to 37.86 centimeters 

17 (14.9 inches) under the TCTB Alternative. Thus, the CAFE action alternatives will result in a maximum 
Summary 

 S-17 

1 reduction of sea level rise equal to 0.14 centimeters (0.10 inch) by 2100 under the No Action Alternative 

2 (i.e., from the levels that sea level is otherwise projected to rise). 

3 Estimated CO2 concentrations for 2100 range from 779.0 ppm under the most stringent 

4 alternative (TCTB) to 783.0 ppm under the No Action Alternative. For 2030 and 2050, the range is even 

5 smaller. Because CO2 concentration is the key driver of other climate effects (which in turn act as drivers 

6 on the resource impacts described in Section 4.5), this leads to small differences in these effects. While 

7 these effects are small, they occur on a global scale and are long-lived. Under the No Action Alternative, 

8 the temperature increase from 1990 is 0.92 °C (1.7 °F) for 2030, 1.56 °C (2.8 °F) for 2050, and 3.14 °C 

9 (3.1 °F) for 2100. The differences among alternatives are small, as shown in Figures S-2 through S-5. 

10 For 2100, the reduction in temperature increase, in relation to the No Action Alternative, ranges from 

11 0.007 °C (0.01 °F) to 0.015 °C (0.03 °F). 

12 

Table S-9 

CO2 Concentration, 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 441.6 514.3 781.2 0.922 1.554 3.129 8.38 15.16 37.94

3 4%/year Increase 441.6 514.1 780.4 0.922 1.553 3.126 8.38 15.15 37.92

4 ~4.3%/year Increase, Preferred 441.5 514.0 780.3 0.922 1.553 3.125 8.38 15.15 37.91

5 5%/year Increase 441.5 513.9 779.8 0.922 1.553 3.124 8.38 15.15 37.89

6 ~5.9%/year Increase, MNB 441.4 513.8 779.3 0.921 1.552 3.122 8.38 15.14 37.87

7 6%/year Increase 441.4 513.8 779.3 0.921 1.552 3.122 8.38 15.14 37.87

8 7%/year Increase 441.4 513.7 779.0 0.921 1.551 3.120 8.38 15.14 37.86

9 ~6.7%/year Increase, TCTB 441.4 513.7 779.0 0.921 1.551 3.120 8.38 15.14 37.86

Reductions under Alternative CAFE Standards

2 3%/year Increase 0.2 0.5 1.8 0.001 0.002 0.007 0.00 0.01 0.06

3 4%/year Increase 0.2 0.7 2.6 0.001 0.003 0.010 0.00 0.02 0.08

4 ~4.3%/year Increase, Preferred 0.3 0.8 2.7 0.001 0.004 0.010 0.00 0.02 0.09

5 5%/year Increase 0.3 0.9 3.2 0.001 0.004 0.012 0.00 0.02 0.11

6 ~5.9%/year Increase, MNB 0.4 1.0 3.7 0.002 0.005 0.014 0.00 0.03 0.13

7 6%/year Increase 0.4 1.0 3.7 0.002 0.005 0.014 0.00 0.03 0.13

8 7%/year Increase 0.4 1.1 4.0 0.002 0.006 0.015 0.00 0.03 0.14

9 ~6.7%/year Increase, TCTB 0.4 1.1 4.0 0.002 0.006 0.015 0.00 0.03 0.14

___________

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. 

13 
Summary 

 S-18 

Figure S-2. CO2 Concentrations (ppm) 

1 
Summary 

 S-19 

Figure S-3. Global Mean Surface Temperature Increase (°C) 

1 
Summary 

 S-20 

Figure S-4. Reduction in CO2 Concentrations (ppm) Compared to the 

No Action Alternative 

1 
Summary 

 S-21 

Figure S-5. Reduction in Global Mean Temperature Compared to the 

No Action Alternative 

1 

2 Given that all the action alternatives reduce temperature increases slightly in relation to the No 

3 Action Alternative, they also slightly reduce predicted increases in precipitation, as shown in Table S-10. 

4 In summary, the impacts of the proposed action and alternatives on global mean surface 

5 temperature, precipitation, or sea-level rise are small in absolute terms. This is because the action 

6 alternatives have a small proportional change in the emissions trajectories in the RCP 4.5 MiniCAM 

reference scenario.31 7 This is due primarily to the global and multi-sectoral nature of the climate problem. 

8 Although these effects are small, they occur on a global scale and are long-lived. 

9 NHTSA examined the sensitivity of climate effects to key assumptions used in the analysis. The 

10 sensitivity analysis is based on the results provided for two CAFE alternatives – the No Action 

11 Alternative (Alternative 1) and the Preferred Alternative (Alternative 4) – using climate sensitivities of 

12 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. 

13 NHTSA performed the sensitivity analysis for only two CAFE alternatives because this was deemed 

14 sufficient to assess the effect of various climate sensitivities on the results. 

 

31 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. 
Summary 

 S-22 

Table S-10 

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 2.810 

3 4%/year Increase 0.648 1.712 2.807 

4 ~4.3%/year Increase, Preferred 0.648 1.712 2.807 

5 5%/year Increase 0.648 1.711 2.805 

6 ~5.9%/year Increase, MNB 0.648 1.710 2.803 

7 6%/year Increase 0.648 1.710 2.803 

8 7%/year Increase 0.648 1.709 2.802 

9 ~6.7%/year Increase, TCTB 0.648 1.709 2.802 

Reduction in Global Temperature (oC) for Alternative CAFE Standards, Mid-level Results (Compared to the 

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 0.009 

5 5%/year Increase 0.000 0.005 0.011 

6 ~5.9%/year Increase, MNB 0.000 0.006 0.013 

7 6%/year Increase 0.000 0.006 0.013 

8 7%/year Increase 0.000 0.007 0.014 

9 ~6.7%/year Increase, TCTB 0.000 0.007 0.014 

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% 2.59% 4.58% 

4 ~4.3%/year Increase, Preferred 0.94% 2.58% 4.57% 

5 5%/year Increase 0.94% 2.58% 4.57% 

6 ~5.9%/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% 4.57% 

9 ~6.7%/year Increase, TCTB 0.94% 2.58% 4.57% 

Reduction in Global Mean Precipitation Change for Alternative CAFE Standards (% Compared to the No 

Action Alternative) 

2 3%/year Increase 0.00% 0.00% 0.01% 

3 4%/year Increase 0.00% 0.01% 0.01% 

4 ~4.3%/year Increase, Preferred 0.00% 0.01% 0.01% 

5 5%/year Increase 0.00% 0.01% 0.02% 

6 ~5.9%/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% 0.02% 

9 ~6.7%/year Increase, TCTB 0.00% 0.01% 0.02% 

_________________ 

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. 

1 

2 The use of different climate sensitivities (the equilibrium warming that occurs at a doubling of 

3 CO2 from pre-industrial levels) not only directly affects warming, it also indirectly affects CO2

4 concentration (through feedbacks on the solubility of CO2 in the oceans) and sea-level rise (through 

5 effects on thermal expansion and melting of land-based ice). 
Summary 

 S-23 

1 As shown in Table S-11, the sensitivity of the simulated CO2 emissions in 2030, 2050, and 2100 

2 to changes in climate sensitivity is low; the reduction of CO2 concentrations from the No Action 

3 Alternative to the Preferred Alternative in 2100 is from 2.7 to 2.8 ppm. 

Table S-11 

CO2 Concentration, Temperature, and Sea-level Rise for Varying Climate Sensitivities for Selected 

Alternatives a/ 

CAFE 

Alternative 

Climate 

Sensitivity 

(°C for 2  CO2) CO2 Concentration (ppm) 

Global Mean Surface 

Temperature Increase (°C) 

Sealevel 

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 

 2.0 439.9 510.0 762.4 0.698 1.166 2.284 28.61

 3.0 441.5 514.0 780.3 0.922 1.553 3.125 37.91

 4.5 443.3 518.7 802.5 1.166 1.987 4.119 48.55

Reduction compared to No Action 

 2.0 0.3 0.7 2.7 0.001 0.003 0.008 0.07

 3.0 0.3 0.8 2.7 0.001 0.004 0.010 0.09

 4.5 0.3 0.8 2.8 0.001 0.004 0.013 0.12

_________________

a/ Values in this table are rounded. 

4 

5 The sensitivity of the simulated global mean surface temperatures for 2030, 2050, and 2100 

6 varies, as also shown in Table S-11. In 2030, the impact is low, due primarily to the slow rate at which 

global mean surface temperature increases in response to increases in radiative forcing.32 7 The relatively 

8 slow response in the climate system explains the observation that even by 2100, when CO2 concentrations 

9 more than double in comparison to pre-industrial levels, the temperature increase is below the equilibrium 

10 sensitivity levels (i.e., the climate system has not had enough time to equilibrate to the new CO2

11 concentrations). Nonetheless, as of 2100 there is a larger range in temperatures across the different values 

12 of climate sensitivity: the reduction in global mean surface temperature from the No Action Alternative to 

13 the Preferred Alternative ranges from 0.008 °C (0.014 °F) for the 2.0 °C (3.6 °F) climate sensitivity to 

14 0.013 °C (0.02 °F) for the 4.5 °C (8.1 °F) climate sensitivity. 

15 The sensitivity of the simulated sea-level rise to change in climate sensitivity and global GHG 

16 emissions mirrors that of global temperature, as shown in Table S-11. Scenarios with lower climate 

17 sensitivities have lower increases in sea-level rise. The greater the climate sensitivity, the greater the 

18 decrement in sea-level rise under the Preferred Alternative compared to the No Action Alternative. 

 

32 As defined by the IPCC, “radiative forcing” is a measure of how the energy balance of the Earth-atmosphere 

system is influenced when factors that affect climate are altered. Positive forcing tends to warm the surface while 

negative forcing tends to cool it. 
Summary 

 S-24 

1 S.5.2 Cumulative Effects 

2 CEQ identifies the impacts federal agencies must address and consider to satisfy NEPA 

3 requirements. These include permanent, temporary, direct, indirect, and cumulative impacts. CEQ 

4 regulations define cumulative impacts as “the impact on the environment which results from the 

5 incremental impact of the action when added to other past, present, and reasonably foreseeable future 

6 actions regardless of what agency or person undertakes such other actions.” 40 CFR § 1508.7. Sections 

7 S.5.2.1 through S.5.2.3 describe the cumulative effects of the proposed action and alternatives on energy, 

8 air quality, and climate. 

9 The methodology for evaluating cumulative effects includes the reasonably foreseeable projected 

10 average annual passenger car and light truck mpg estimates from 2016 through 2030 that differ from mpg 

11 estimates reflected in the Chapter 3 analysis, as described in Section S.5.1. The Chapter 3 analysis 

12 reflects the direct and indirect impacts of MY 2012-2016 fuel economy requirements under each of the 

13 action alternatives, assuming no further increases in average new passenger car or light truck mpg after 

14 2016. The Chapter 4 evaluation of cumulative effects projects ongoing gains in average new passenger 

15 car and light truck mpg consistent with further increases in CAFE standards to an EISA-mandated 

16 minimum level of 35 mpg combined for passenger car and light trucks by the year 2020, along with 

17 Annual Energy Outlook (AEO) April 2009 (updated) Reference Case projections of annual percentage 

gains of 0.51 percent in passenger-car mpg and 0.86 percent in light-truck mpg through 2030.33 18 Both the 

19 public and private sectors regard AEO Reference Case projections as the official U.S. Government energy 

20 projections. 

21 The assumption that all action alternatives reach the EISA 35 mpg target by 2020, with mpg 

22 growth at the AEO forecast rate from 2020 to 2030, results in estimated cumulative impacts for 

23 Alternatives 2, 3, and 4 (3-Percent, 4-Percent, and Preferred Alternatives) that are substantially 

24 equivalent, with any minor variation in cumulative impacts across these alternatives due to the specific 

25 modeling assumptions used to ensure that each alternative achieves at least 35 mpg by 2020. Therefore, 

26 the cumulative impacts analysis in Chapter 4 adds substantively to the analysis of direct and indirect 

27 impacts in Chapter 3 when comparing cumulative impacts among Alternatives 4 through 9 (Preferred, 5-

28 Percent, MNB, 6-Percent, 7-Percent, and TCTB Alternatives), but not when comparing cumulative 

29 impacts among Alternatives 2 through 4. 

30 Another important difference in the methodology for evaluating cumulative effects is that the No 

31 Action Alternative also reflects the AEO Reference Case projected annual percentage gains of 0.51 

32 percent in passenger car mpg and 0.86 percent in light truck mpg for 2016 through 2030, whereas the 

33 Chapter 3 analysis assumed no increases in average new passenger car or light truck mpg after 2016 

34 under any alternative, including the No Action Alternative. The No Action Alternative assumes there is 

35 no action under the National Program, so average fuel economy levels in the absence of CAFE standards 

36 beyond MY 2011 would equal the higher of the agencies’ collective market forecast or the manufacturers’ 

37 required level of average fuel economy for MY 2011. The No Action Alternative, by definition, would 

38 not satisfy the EPCA requirement to set standards such that the passenger car and light truck fleet 

39 achieves a combined average fuel economy of at least 35 mpg for MY 2020 (nor would it satisfy the 

 

33 NHTSA considers these AEO projected mpg increases to be reasonably foreseeable future actions 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. Because the AEO forecasts do not extend beyond the year 2030, the mpg estimates for MY 2030 

through MY 2060 remain constant. 
Summary 

 S-25 

EPCA requirement to adopt annual fuel economy standard increases).34 1 The revised No Action 

2 Alternative in Chapter 4 is consistent with the concept of a No Action Alternative, because the projected 

3 annual percentage gains of 0.51 percent in passenger car mpg and 0.86 percent in light truck mpg for 

4 2016 through 2030 under the No Action Alternative still do not reflect any action under the National 

5 Program, but only the annual AEO projected gain in mpg through 2030 due to consumer demand and 

6 technology advances associated with ongoing increases in fuel prices. 

7 Even with this projected annual percentage gain in mpg for 2016 through 2030, the No Action 

8 Alternative would still not achieve the EISA requirement of 35 mpg in 2020. The annual AEO projected 

9 gain in mpg through 2030 due to consumer demand and technology advances is applied to the No Action 

10 Alternative and to each of the action alternatives so that the difference between fuel use, emissions, and 

11 other projections under the No Action Alternative and the action alternatives can be meaningfully 

12 compared (e.g., by calculating fuel saved by any action alternative in relation to the No Action 

13 Alternative). 

14 NHTSA also considered other reasonably foreseeable actions that would affect GHG emissions, 

15 such as regional, national, and international initiatives and programs to reduce GHG emissions. For a 

16 more detailed description of these initiatives, see Section S.5.2.3. 

17 S.5.2.1 Energy 

18 The nine alternatives evaluated in this EIS will result in different future levels of fuel use, total 

19 energy, and petroleum consumption, which will in turn have an impact on emissions of GHGs and criteria 

20 air pollutants. Table S-12 lists the cumulative annual fuel consumption and fuel savings of passenger cars 

21 from the onset of the proposed new CAFE standards. By 2060, annual fuel consumption reaches 162.8 

22 billion gallons under the No Action Alternative (Alternative 1). Consumption falls across the alternatives, 

23 from 140.7 billion gallons under Alternative 2 (3-percent annual increase in mpg) to 131.3 billion gallons 

24 under the TCTB Alternative (Alternative 9), representing an annual fuel savings of 22.1 to 31.5 billion 

25 gallons in 2060 compared to fuel consumption projected under the No Action Alternative. 

26 Table S-13 lists the cumulative annual fuel consumption and fuel savings for light trucks from the 

27 onset of the proposed new CAFE standards. Fuel consumption by 2060 reaches 91.2 billion gallons per 

28 year under the No Action Alternative. Consumption declines across the alternatives, from 80.1 billion 

29 gallons per year under the 3-Percent Alternative to 73.3 billion gallons per year under Alternative8. This 

30 represents an annual fuel savings of 11.1 to 17.9 billion gallons in 2060 compared to fuel consumption 

31 projected under the No Action Alternative. 

32 

 

34 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. 
Summary 

 S-26 

Table S-12 

Cumulative Effects of Passenger Car Annual Fuel Consumption and Fuel Savings (billion gallons gasoline 

equivalent) by Alternative 

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

~5.9%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.7%/year 

Increase 

TCTB 

Fuel Consumption

2020 69.1 64.7 63.8 63.6 62.8 61.6 61.6 61.0 60.9

2030 94.5 82.6 82.2 82.3 80.7 78.3 78.2 76.8 76.8

2040 114.7 99.1 99.1 99.3 97.3 94.5 94.2 92.5 92.5

2050 136.7 118.1 118.2 118.4 116.0 112.6 112.4 110.3 110.3

2060 162.8 140.7 140.7 141.0 138.2 134.1 133.8 131.3 131.3

Fuel Savings Compared to No Action

2020 0 4.4 5.3 5.6 6.3 7.5 7.5 8.1 8.2

2030 0 11.9 12.2 12.2 13.8 16.2 16.3 17.7 17.7

2040 0 15.6 15.5 15.4 17.3 20.2 20.4 22.2 22.2

2050 0 18.6 18.5 18.3 20.7 24.1 24.4 26.5 26.4

2060 0 22.1 22.1 21.8 24.6 28.7 29.0 31.5 31.5

1 

Table S-13 

Cumulative Effects of Light Truck Annual Fuel Consumption and Fuel Savings (billion gallons gasoline 

equivalent) by Alternative 

Calendar Year 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

~5.9%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.7%/year 

Increase 

TCTB 

Fuel Consumption

2020 68.3 65.6 64.9 64.6 64.0 62.8 63.1 62.5 62.4

2030 62.8 56.8 56.5 56.3 55.0 53.3 53.4 52.5 52.6

2040 66.7 58.9 58.9 58.7 57.1 55.2 55.2 54.1 54.3

2050 77.1 67.8 67.8 67.6 65.7 63.4 63.4 62.1 62.4

2060 91.2 80.1 80.1 79.9 77.6 74.9 74.9 73.3 73.7

Fuel Savings Compared to No Action

2020 0 2.7 3.4 3.7 4.4 5.6 5.3 5.8 5.9

2030 0 6.0 6.3 6.6 7.8 9.5 9.4 10.3 10.2

2040 0 7.7 7.8 8.0 9.5 11.5 11.5 12.6 12.3

2050 0 9.3 9.3 9.5 11.4 13.7 13.7 15.0 14.7

2060 0 11.1 11.1 11.3 13.6 16.3 16.3 17.9 17.5

2 

3 S.5.2.2 Air Quality 

Table S-14 summarizes the cumulative impacts for national toxic and criteria pollutants in 2050.35 4 

5 The table lists the action alternatives (Alternatives 2 through 9) left to right in order of increasing fuel 

 

35 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 
Summary 

 S-27 

1 economy requirements. In the case of PM2.5, SOx, NOx, and VOCs, the No Action Alternative results in 

2 the highest annual emissions, and emissions generally decline as fuel economy standards increase across 

3 alternatives. Exceptions to this declining trend are PM2.5 under Alternatives 3 and 4 and Alternatives 6 

4 and 8; and SOx under Alternatives 3 through 5, and Alternatives 7 and 9. Despite these individual 

5 increases, emissions of PM2.5, SOx, NOx, and VOCs remain below the levels under the No Action 

6 Alternative. In the case of CO, emissions under Alternatives 2 through 4 are slightly higher than under 

7 the No Action Alternative, and are lower than under the No Action Alternative under Alternatives 5 

8 through 9. Emissions of CO decline, though not consistently, as fuel economy standards increase across 

9 Alternatives 2 through 9. 

Table S-14 

Cumulative Effects of 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

~5.9%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.7%/year

Increase 

TCTB 

Criteria Pollutant Emissions (Calendar Year 2050) 

Carbon 

monoxide (CO) 24,155,097 24,530,976 24,385,367 24,315,810 23,541,753 22,770,712 22,314,840 22,130,779 22,061,720

Nitrogen oxides 

(NOx) 1,809,786 1,786,720 1,780,335 1,778,462 1,733,908 1,690,190 1,667,885 1,653,446 1,650,090

Particulate 

matter (PM2.5) 107,387 102,210 102,469 102,885 102,501 102,698 103,025 102,490 102,512

Sulfur oxides 

(SOx) 262,948 229,228 230,352 231,083 230,124 227,819 230,366 227,019 227,650

Volatile organic 

compounds 

(VOC) 1,803,222 1,652,075 1,645,210 1,640,518 1,587,401 1,522,744 1,501,494 1,476,771 1,476,595

Toxic Air Pollutant Emissions (Calendar Year 2050) 

Acetaldehyde 7,953 8,070 8,064 8,048 8,074 8,068 8,068 8,088 8,088

Acrolein 411 418 422 426 449 478 490 498 478

Benzene 28,048 28,111 27,984 27,901 27,253 26,534 26,164 25,993 25,945

1,3-butadiene 4,180 4,249 4,239 4,235 4,189 4,148 4,117 4,111 4,106

Diesel 

particulate 

matter (DPM) 138,391 120,407 120,494 120,706 118,016 114,922 114,724 112,629 112,810

Formaldehyde 10,901 10,966 11,022 11,036 11,416 11,775 11,970 12,092 12,118

10 The trend for toxic air pollutant emissions across the alternatives is mixed. Annual cumulative 

11 emissions of acetaldehyde in 2050 are lowest under Alternative 1 and increase, though not consistently 

12 across the alternatives, and are highest under Alternative 9. Annual emissions of acrolein and 

13 formaldehyde increase under each successive alternative from Alternative 1 to Alternative 9. Annual 

14 emissions of benzene and DPM decrease, though not consistently across the alternatives, and are lowest 

15 under Alternative 9 for benzene and Alternative 8 for DPM. Annual emissions of 1,3-butadiene increase 

16 from Alternative 1 to Alternative 2, and then decrease under each successive alternative from Alternative 

17 5 to Alternative 9. 

 

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 vehicle miles 

traveled (VMT) these vehicles account for would be even higher – 99 percent for passenger cars and 94 percent for 

light trucks. 
Summary 

 S-28 

1 As with criteria pollutants, annual cumulative emissions of most toxic air pollutants would 

2 decrease from one alternative to the next more stringent alternative. The exceptions are acrolein under 

3 Alternative 9; benzene under Alternatives 3 through 9; 1,3-butadiene under Alternatives 3 through 9; and 

4 formaldehyde under Alternatives 3 through 6. The changes in toxic air pollutant emissions, whether 

5 positive or negative, generally would be small in relation to Alternative 1 emissions levels. 

6 Cumulative emissions generally would be less than noncumulative emissions for the same 

7 combination of pollutant, year (excluding 2016, which is equivalent to the noncumulative emissions in all 

8 cases), and alternative because of differing changes in VMT and fuel consumption under the cumulative 

9 case compared to the noncumulative case. The exceptions are acrolein for all alternatives except 

10 Alternative 9, 1,3-butadiene for all alternatives except Alternative 2, and CO for all alternatives. 

11 The reductions in emissions are expected to lead to reductions in cumulative adverse health 

12 effects. Table S-15 summarizes the national annual changes in health outcomes in 2050 for the nine 

13 alternatives, left to right in order of increasing fuel economy requirements. There would be reductions in 

14 adverse health effects nationwide under all the action alternatives compared to the No Action Alternative. 

15 Reductions in adverse health effects decrease from Alternative 2 through Alternative 4, and then increase 

16 under Alternatives 5 through Alternative 9. These reductions primarily reflect the projected PM2.5

17 reductions, and secondarily the reductions in SO2. 

Table S-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 

~5.9%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.7%/year 

Increase 

TCTB 

Mortality (ages 30 and older) 

Pope et al. 2002 

2050 0 -364 -356 -339 -406 -453 -455 -504 -504

Laden et al. 2006 

2050 0 -930 -911 -867 -1,037 -1,157 -1,162 -1,287 -1,288

Chronic bronchitis 

2050 0 -230 -226 -215 -259 -290 -292 -323 -323

Emergency Room Visits for Asthma 

2050 0 -323 -315 -300 -347 -382 -377 -417 -416

Work Loss Days 

2050 0 -39,749 -38,969 -37,043 -44,648 -49,958 -50,334 -55,754 -55,808

__________ 

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. 
Summary 

 S-29 

1 The economic value of health impacts would vary proportionally with changes in health 

2 outcomes. Table S-16 lists the corresponding annual reductions in health costs in 2050 under the action 

3 alternatives compared to the No Action Alternative. Reductions in health costs are given for two 

4 alternative assumptions of the discount rate, 3 percent and 7 percent, consistent with EPA policy for 

5 presentation of future health costs. 

Table S-16 

Cumulative Nationwide Changes in Health Costs (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 

Discount 

and 

Year 

No 

Action b/ 

3%/year 

Increase 

4%/year 

Increase 

~4.3%/year

Increase 

Preferred 

5%/year 

Increase 

~5.9%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.7%/year 

Increase 

TCTB 

3-% Discount Rate

Pope et al. 2002 

2050 0 -3,292 -3,225 -3,067 -3,672 -4,097 -4,116 -4,558 -4,560

Laden et al. 2006 

2050 0 -8,069 -7,903 -7,518 -8,999 -10,040 -10,083 -11,167 -11,171

7-% Discount Rate

Pope et al. 2002 

2050 0 -2,985 -2,924 -2,782 -3,331 -3,716 -3,733 -4,134 -4,136

Laden et al. 2006 

2050 0 -7,287 -7,138 -6,790 -8,128 -9,068 -9,107 -10,087 -10,090

__________ 

a/ Negative changes indicate economic benefit; positive changes indicate economic costs. 

b/ Changes in outcome under 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. 

6 

7 S.5.2.3 Climate Change 

8 As with the analysis of the direct and indirect effects of the proposed action and alternatives on 

9 climate change, for the cumulative impacts analysis this EIS uses MAGICC version 5.3.v2 to estimate the 

10 changes in CO2 concentrations, global mean surface temperature, and changes in sea level for each 

11 alternative CAFE standard. To estimate changes in global precipitation, NHTSA uses increases in global 

12 mean surface temperature combined with a scaling approach and coefficients from the IPCC Fourth 

13 Assessment Report. NHTSA performed a sensitivity analysis to examine the relationship among the 

14 alternatives and likely climate sensitivities, and the associated direct and indirect effects for each 

15 combination. These relationships can be used to infer the effect of emissions associated with the 

16 regulatory alternatives on direct and indirect climate effects. 

17 One of the key categories of inputs to MAGICC is a time series of global GHG emissions. In 

18 assessing the cumulative effects on climate, NHTSA used the CCSP SAP 2.1 MiniCAM Level 3 scenario 

19 to represent a Reference Case global emissions scenario; that is, future global emissions assuming 

20 significant global actions to address climate change. This Reference Case global emissions scenario 

21 serves as a baseline against which the climate benefits of the various alternatives can be measured. 

22 The Reference Case global emissions scenario used in the cumulative impacts analysis (and 

23 described in Chapter 4 of this EIS) differs from the global emissions scenario used for the climate change 

24 modeling presented in Chapter 3. In Chapter 4, the Reference Case global emissions scenario reflects 

25 reasonably foreseeable actions in global climate change policy; in Chapter 3, the global emissions 
Summary 

 S-30 

1 scenario used for the analysis assumes that there are no significant global controls. Given that the climate 

2 system is non-linear, the choice of a global emissions scenario could produce different estimates of the 

3 benefits of the proposed action and alternatives, if the emissions reductions under the alternatives were 

4 held constant. 

5 The SAP 2.1 MiniCAM Level 3 scenario assumes a moderate level of global GHG reductions, 

6 resulting in a global atmospheric CO2 concentration of roughly 650 parts per million by volume (ppmv) 

7 as of 2100. The following regional, national, and international initiatives and programs are reasonably 

8 foreseeable actions to reduce GHG emissions: Regional Greenhouse Gas Initiative (RGGI); Western 

9 Climate Initiative (WCI); Midwestern Greenhouse Gas Reduction Accord; the EPA Proposed GHG 

10 Emissions Standards (H.R. 2454, American Clean Energy and Security Act [“Waxman-Markey Bill”]; 

11 Renewable Fuel Standard (RFS2); Program Activities of DOE’s Office of Fossil Energy; Program 

12 Activities of DOE’s Office of Nuclear Energy; United Nation’s Framework Convention on Climate 

13 Change (UNFCCC) – The Kyoto Protocol and upcoming Conference of the Parties (COP) 15 in 

14 Copenhagen, Denmark; G8 Declaration – Summit 2009; and the Asia Pacific Partnership on Clean 

Development and Climate.36 15 

16 The SAP 2.1 MiniCAM Level 3 scenario provides a global context for emissions of a full suite of 

17 GHGs and ozone precursors for a Reference Case harmonious with implementation of the above policies 

18 and initiatives. Each of the action alternatives was simulated by calculating the difference in annual GHG 

19 emissions in relation to the No Action Alternative, and subtracting this change in the MiniCAM Level 3 

20 scenario to generate modified global-scale emissions scenarios, which each show the effect of the various 

21 regulatory alternatives on the global emissions path. 

22 NHTSA used the MiniCAM Level 3 scenario as the primary global emissions scenario for 

23 evaluating climate effects, and used the MiniCAM Level 2 scenario and the RCP 4.5 MiniCAM reference 

24 emissions scenario to evaluate the sensitivity of the results to alternative emissions scenarios. The 

25 sensitivity analysis provides a basis for determining climate responses to varying levels of climate 

26 sensitivities and global emissions and under the No Action Alternative (Alternative 1) and the Preferred 

27 Alternative (Alternative 4). Some responses of the climate system are believed to be non-linear; by using 

28 a range of emissions cases and climate sensitivities, it is possible to estimate the effects of the alternatives 

29 in relation to different reference cases. 

30 S.5.2.3.1 Cumulative GHG Emissions 

31 Table S-17 shows total GHG emissions and emissions reductions from new passenger cars and 

32 light trucks from 2012 through 2100 under each of the nine alternatives. Projections of emissions 

33 reductions over the 2012 through 2100 period due to the MY 2012-2016 CAFE standards and other 

34 reasonably foreseeable future actions (i.e., forecasted AEO fuel economy increases resulting from 

35 projected demand for fuel economy) ranged from 27,300 to 39,100 MMTCO2. Compared to global 

36 emissions of 3,919,462 MMTCO2 over this period (projected by the SAP 2.1 MiniCAM Level 3 

37 scenario), the incremental impact of this rulemaking is expected to reduce global CO2 emissions by about 

38 0.7 to 1.0 percent from their projected levels under the No Action Alternative. 

 

36 These regional, national, and international initiatives and programs are those NHTSA has tentatively concluded 

are reasonably foreseeable past, present, 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 

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. 
Summary 

 S-31 

Table S-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 227,600 0 

2 3%/year Increase 200,300 27,300 

3 4%/year Increase 200,200 27,300 

4 ~4.3%/year Increase, Preferred 200,300 27,300 

5 5%/year Increase 196,700 30,900 

6 ~5.9%/year Increase, MNB 191,600 36,000 

7 6%/year Increase 191,800 35,800 

8 7%/year Increase 188,500 39,100 

9 ~6.7%/year Increase, TCTB 188,790 38,791 

1 

2 Emissions of CO2, the primary gas that drives climate effects, from the U.S. passenger-car and 

3 light-truck fleet represented about 3.7 percent of total global emissions of CO2 in 2005. Although 

4 substantial, this source is a still small percentage of global emissions. The relative contribution of CO2

5 emissions from U.S. passenger cars and light trucks is expected to decline in the future, due primarily to 

6 rapid growth of emissions from developing economies (which are due in part to growth in global 

7 transportation sector emissions). 

8 S.5.2.3.2 CO2 Concentration, Global Mean Surface Temperature, Sea-level Rise, and 

9 Precipitation 

10 Table S-18 and Figures S-6 through S-9 provide the mid-range results of MAGICC model 

11 simulations for the No Action Alternative and the eight action alternatives in terms of CO2 concentrations 

12 and increase in global mean surface temperature in 2030, 2050, and 2100. As Figures S-8 and S-9 show, 

13 the impact on the growth in CO2 concentrations and temperature is just a fraction of the total growth in 

14 CO2 concentrations and global mean surface temperature. However, the relative impact of the action 

15 alternatives is illustrated by the reduction in growth of both CO2 concentrations and temperature under the 

16 TCTB Alternative (Alternative 9). 

17 As shown in the table and figures, there is a fairly narrow band of estimated CO2 concentrations 

18 as of 2100, from 654 ppm under the TCTB Alternative to 657.5 ppm under the No Action Alternative. 

19 For 2030 and 2050, the range is even smaller. Because CO2 concentrations are the key driver of all other 

20 climate effects, this leads to small differences in these effects. While these effects are small, they occur 

21 on a global scale and are long-lived. 

22 Table S-18 also shows the MAGICC simulations of mean global surface air temperature 

23 increases. For all alternatives, the cumulative global mean surface temperature increase is about 0.80 to 

24 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 2100.37 The differences among alternatives are small.38 25 For 2100, the reduction in 

26 temperature increase for the action alternatives in relation to the No Action Alternative is about 0.01 to 

27 0.02 °C (0.02 to 0.04°F). 

 

37 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. 38 While these effects are small, they occur on a global scale and are long-lived. 
Summary 

 S-32 

Table S-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 438.7 498.0 657.5 0.805 1.327 2.611 7.83 13.67 32.84

2 3%/year Increase 438.5 497.3 655.1 0.805 1.323 2.600 7.83 13.65 32.75

3 4%/year Increase 438.5 497.3 655.1 0.805 1.323 2.600 7.83 13.65 32.75

4 ~4.3%/year Increase, Preferred 438.5 497.3 655.1 0.804 1.323 2.600 7.83 13.65 32.75

5 5%/year Increase 438.4 497.2 654.7 0.804 1.323 2.599 7.83 13.65 32.73

6 ~5.9%/year Increase, MNB 438.4 497.0 654.3 0.804 1.322 2.596 7.83 13.64 32.71

7 6%/year Increase 438.4 497.0 654.3 0.804 1.322 2.596 7.83 13.64 32.71

8 7%/year Increase 438.4 496.9 654.0 0.804 1.321 2.595 7.83 13.64 32.70

9 ~6.7%/year Increase, TCTB 438.4 496.9 654.0 0.804 1.321 2.595 7.83 13.64 32.70

Reductions Under Alternative CAFE Standards

2 3%/year Increase 0.2 0.7 2.4 0.001 0.003 0.011 0.00 0.02 0.09 

3 4%/year Increase 0.2 0.7 2.4 0.001 0.003 0.011 0.00 0.02 0.09 

4 ~4.3%/year Increase, Preferred 0.2 0.7 2.4 0.001 0.004 0.011 0.00 0.02 0.09 

5 5%/year Increase 0.3 0.8 2.8 0.001 0.004 0.012 0.00 0.02 0.11 

6 ~5.9%/year Increase, MNB 0.3 1.0 3.2 0.001 0.005 0.015 0.00 0.03 0.13 

7 6%/year Increase 0.3 1.0 3.2 0.001 0.005 0.015 0.00 0.03 0.13 

8 7%/year Increase 0.3 1.1 3.5 0.002 0.005 0.016 0.00 0.03 0.14 

9 ~6.7%/year Increase, TCTB 0.3 1.1 3.5 0.002 0.005 0.016 0.00 0.03 0.14 

_________________

a/ Values in this table are rounded. 

1 
Summary 

 S-33 

Figure S-6. Cumulative Effects on CO2 Concentrations 

Using MAGICC 

1 
Summary 

 S-34 

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

MAGICC by Alternative 

1 
Summary 

 S-35 

Figure S-8. Cumulative Effects on CO2 Concentrations 

(Reduction Compared to the No Action Alternative) 

1 
Summary 

 S-36 

Figure S-9. Cumulative Effects on Global Mean Temperature 

(Reduction Compared to the No Action Alternative) 

1 

2 Table S-18 lists the impact on sea-level rise from the scenarios and shows sea-level rise in 2100 

3 ranging from 32.84 centimeters (12.93 inches) under the No Action Alternative (Alternative 1) to 32.70 

4 centimeters (12.87 inches) under the TCTB Alternative (Alternative 9). Thus, the CAFE action 

5 alternatives will result in a maximum reduction of sea level rise equal to 0.14 centimeters by 2100 from 

6 the No Action Alternative (i.e., from the levels that sea level is otherwise projected to rise). 

7 Given that the action alternatives would reduce temperature increases slightly in relation to the 

8 No Action Alternative, they also would reduce predicted increases in precipitation slightly, as shown in 

9 Table S-19. 
Summary 

 S-37 

Table S-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 2.406 

3 4%/year Increase 0.586 1.462 2.406 

4 ~4.3%/year Increase, Preferred 0.586 1.462 2.406 

5 5%/year Increase 0.586 1.461 2.405 

6 ~5.9%/year Increase, MNB 0.586 1.460 2.403 

7 6%/year Increase 0.586 1.460 2.403 

8 7%/year Increase 0.586 1.459 2.401 

9 ~6.7%/year Increase, TCTB 0.586 1.459 2.402 

Reduction in Global Temperature (°C) for Alternative CAFE Standards, Mid-level Results (Compared to the 

No Action Alternative) 

2 3%/year Increase 0.000 0.004 0.009 

3 4%/year Increase 0.000 0.004 0.009 

4 ~4.3%/year Increase, Preferred 0.000 0.004 0.009 

5 5%/year Increase 0.000 0.005 0.011 

6 ~5.9%/year Increase, MNB 0.000 0.006 0.013 

7 6%/year Increase 0.000 0.006 0.013 

8 7%/year Increase 0.000 0.006 0.014 

9 ~6.7%/year Increase, TCTB 0.000 0.006 0.014 

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 ~5.9%/year Increase, MNB 0.85% 2.20% 3.92% 

7 6%/year Increase 0.85% 2.20% 3.92% 

8 7%/year Increase 0.85% 2.20% 3.91% 

9 ~6.7%/year Increase, TCTB 0.85% 2.20% 3.91% 

Reduction in Global Mean Precipitation Change for Alternative CAFE Standards (% Compared to 

the No Action Alternative)

2 3%/year Increase 0.00% 0.01% 0.01% 

3 4%/year Increase 0.00% 0.01% 0.01% 

4 ~4.3%/year Increase, Preferred 0.00% 0.01% 0.02% 

5 5%/year Increase 0.00% 0.01% 0.02% 

6 ~5.9%/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% 0.02% 

9 ~6.7%/year Increase, TCTB 0.00% 0.01% 0.02% 

_________________

a/ Values in this table are rounded. 

1 

2 In summary, the impacts of the proposed action and alternatives and other reasonably foreseeable 

3 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.39 4 

5 This is due primarily to the global and multi-sectoral nature of the climate problem. While these effects 

6 are small, they occur on a global scale and are long-lived. 

 

39 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. 
Summary 

 S-38 

1 NHTSA examined the sensitivity of climate effects on key assumptions used in the analysis. The 

2 two variables for which assumptions were varied were climate sensitivity and global emissions. Climate 

3 sensitivities used included 2.0, 3.0, and 4.5 °C (3.6, 5.4, and 8.1 °F) for a doubling of CO2 concentrations 

4 in the atmosphere. Global emissions scenarios used included the SAP 2.1 MiniCAM Level 3 (650 ppm as 

5 of 2100), the SAP 2.1 MiniCAM Level 2 (550 ppm as of 2100), and RCP 4.5 MiniCAM reference 

6 scenario (783 ppm as of 2100). The sensitivity analysis is based on the results provided for two 

7 alternatives – the No Action Alternative (Alternative 1) and the Preferred Alternative (Alternative 4). 

8 NHTSA performed the sensitivity analysis only for two alternatives because this was deemed sufficient to 

9 assess the effect of various climate sensitivities on the results. 

10 The results of these simulations illustrate the uncertainty due to factors influencing future global 

11 emissions of GHGs (factors other than the CAFE rulemaking). 

12 The use of different climate sensitivities (the equilibrium warming that occurs at a doubling of 

13 CO2 from pre-industrial levels) can affect not only warming but also indirectly affect sea-level rise and 

14 CO2 concentration. The use of alternative global emissions scenarios can influence the results in several 

15 ways. Emissions reductions can lead to larger reductions in the CO2 concentrations in later years because 

16 more anthropogenic emissions can be expected to stay in the atmosphere. 

17 As shown in Table S-20, the sensitivity of the simulated CO2 emissions in 2030, 2050, and 2100 

18 to assumptions of global emissions and climate sensitivity is low; stated simply, CO2 emissions do not 

19 change much with changes in global emissions and climate sensitivity. For 2030 and 2050, the choice of 

20 global emissions scenario has little impact on the results. By 2100, the Preferred Alternative (Alternative 

21 4) has the greatest impact in the global emissions scenario with the highest CO2 emissions (MiniCAM 

22 Reference Case) and the least impact in the scenario with the lowest CO2 emissions (MiniCAM Level 2). 

23 The total range of the impact of the Preferred Alternative on CO2 concentrations in 2100 is from 2.2 to 

24 2.7 ppm. The Reference Case using the MiniCAM Level 3 scenario and a 3.0 °C (5.4 °F) climate 

25 sensitivity has an impact of 2.4 ppm. 

26 Table S-20 also shows the sensitivity of the simulated global mean surface temperatures for 2030, 

27 2050, and 2100. In 2030, the impact is low due primarily to the slow rate at which the global mean 

28 surface temperature increases in response to increases in radiative forcing. The relatively slow response 

29 in the climate system explains the observation that even by 2100, when CO2 concentrations more than 

30 double in comparison to pre-industrial levels, the temperature increase is below the equilibrium sensitivity 

31 levels (i.e., the climate system has not had enough time to equilibrate to the new CO2 concentrations). 

32 Nonetheless, as of 2100 there is a larger range in temperatures across the different values of climate 

33 sensitivity: the reduction in global mean surface temperature from the No Action Alternative to the 

34 Preferred Alternative ranges from 0.008 °C (0.014 °F) for the 2.0 °C (3.6 °F) climate sensitivity to 0.012 

35 °C (0.022 °F) for the 4.5 °C (8.2 °F) climate sensitivity for the MiniCAM Level 3 emissions scenario. 

36 The impact on global mean surface temperature due to assumptions concerning global emissions 

37 of GHGs is also important. The scenario with the higher global emissions of GHGs (viz., the MiniCAM 

38 Reference) has a slightly lower reduction in global mean surface temperature, and the scenario with lower 

39 global emissions (viz., the MiniCAM Level 2) has a slightly higher reduction. This is largely due to the 

40 non-linear and near-logarithmic relationship between radiative forcing and CO2 concentrations. At high 

41 emissions levels, CO2 concentrations are higher and, as a result, a fixed reduction in emissions yields a 

42 lower reduction in radiative forcing and global mean surface temperature. 
Summary 

 S-39 

Table S-20 

Cumulative Effects on CO2 Concentration, Temperature, and Sea-level Rise for 

Varying Climate Sensitivities for Selected Alternatives a/ 

Emissions 

Scenario 

CAFE 

Alternative 

Climate 

Sensitivity 

(°C for 2  CO2) 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 2.0 434.3 483.0 551.3 0.612 0.986 1.546 22.32 

 3.0 435.7 486.5 563.5 0.812 1.324 2.177 29.92 

 4.5 437.4 490.5 578.8 1.034 1.705 2.948 38.76 

 Reduction compared to No Action 

 2.0 0.2 0.8 2.2 0.001 0.003 0.009 0.08 

 3.0 0.3 0.8 2.4 0.001 0.004 0.012 0.11 

 4.5 0.2 0.8 2.5 0.001 0.004 0.015 0.12 

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 2.0 437.0 493.8 641.0 0.606 0.987 1.880 24.60 

 3.0 438.5 497.3 655.1 0.804 1.323 2.600 32.75 

 4.5 440.1 501.3 672.6 1.023 1.702 3.461 42.12 

 Reduction compared to No Action 

 2.0 0.3 0.7 2.4 0.001 0.003 0.008 0.08 

 3.0 0.2 0.7 2.4 0.001 0.004 0.011 0.09 

 4.5 0.2 0.7 2.6 0.001 0.004 0.014 0.12 

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 2.0 439.9 510.0 762.6 0.699 1.166 2.285 28.61 

 3.0 441.5 514.1 780.4 0.922 1.553 3.126 37.91 

 4.5 443.3 518.8 802.6 1.166 1.987 4.120 48.55 

 Reduction compared to No Action 

 2.0 0.3 0.7 2.5 0.001 0.003 0.007 0.07 

 3.0 0.3 0.7 2.6 0.001 0.003 0.010 0.09 

 4.5 0.3 0.8 2.7 0.001 0.004 0.012 0.12 

_________________

a/ Values in this table are rounded. 

1 

2 The sensitivity of the simulated sea-level rise to changes in climate sensitivity and global GHG 

3 emissions mirrors that of global temperature, as shown in Table S-20. Scenarios with lower climate 

4 sensitivities have lower increases in sea-level rise. The greater the climate sensitivity, the greater the 

5 decrement in sea-level rise under the Preferred Alternative compared to the No Action Alternative. 
Summary 

 S-40 

1 S.5.2.4 Health, Societal, and Environmental Impacts of Climate Change 

2 The effects of the alternatives on climate – CO2 concentrations, temperature, precipitation, and 

3 sea-level rise – can translate into impacts on key resources, including terrestrial and freshwater 

4 ecosystems; marine, coastal systems, and low-lying areas; food, fiber, and forest products; industries, 

5 settlements, and society; and human health. Although the alternatives have the potential to substantially 

6 decrease GHG emissions, alone they would not prevent climate change. The magnitude of the changes in 

7 climate effects that the alternatives would produce – 2 to 5 ppm of CO2, a few hundredths of a degree 

8 Celsius difference in temperature, a small percentage change in the rate of precipitation increase, and 1 or 

9 2 millimeters of sea-level rise – are too small to address quantitatively in terms of their impacts on 

10 resources. Given the enormous resource values at stake, these distinctions could be important – very 

11 small percentages of huge numbers can still yield substantial results – but they are too small for current 

12 quantitative techniques to resolve. Consequently, the discussion of resource impacts does not distinguish 

13 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.40 14 

15 NHTSA examined the impacts resulting from global climate change due to all global emissions 

16 on the U.S. and global scales. Impacts to freshwater resources could include changes in precipitation 

17 patterns; decreasing aquifer recharge in some locations; changes in snowpack and timing of snowmelt; 

18 salt-water intrusion from sea-level changes; changes in weather patterns resulting in flooding or drought 

19 in certain regions; increased water temperature; and numerous other changes to freshwater systems that 

20 disrupt human use and natural aquatic habitats. Impacts to terrestrial ecosystems could include shifts in 

21 species range and migration patterns, potential extinctions of sensitive species unable to adapt to changing 

22 conditions, increases in the occurrence of forest fires and pest infestation, and changes in habitat 

23 productivity because of increased atmospheric CO2. Impacts to coastal ecosystems, primarily from 

24 predicted sea-level rise, could include the loss of coastal areas due to submersion and erosion, additional 

25 impacts from severe weather and storm surges, and increased salinization of estuaries and freshwater 

26 aquifers. Impacts to land use and several key economic sectors could include flooding and severe27 weather impacts to coastal, floodplain, and island settlements; extreme heat and cold waves; increases in 

28 drought in some locations; and weather- or sea-level-related disruptions of the service, agricultural, and 

29 transportation sectors. Impacts to human health could include increased mortality and morbidity due to 

30 excessive heat, increases in respiratory conditions due to poor air quality, increases in water and food31 borne diseases, changes to the seasonal patterns of vector-borne diseases, and increases in malnutrition. 

32 S.5.2.5 Non-climate Cumulative Impacts of CO2 Emissions 

33 In addition to its role as a GHG in the atmosphere, CO2 is transferred from the atmosphere to 

34 water, plants, and soil. In water, CO2 combines with water molecules to form carbonic acid. When CO2 

35 dissolves in seawater, a series of well-known chemical reactions begin that increase the concentration of 

36 hydrogen ions and make seawater more acidic, which has adverse effects on corals and some other marine 

37 life. 

38 Increased concentrations of CO2 in the atmosphere can also stimulate plant growth to some 

39 degree, a phenomenon known as the CO2 fertilization effect. This effect could have positive 

 

40 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).
Summary 

 S-41 

1 ramifications for agricultural productivity and forest growth. The available evidence indicates that 

2 different plants respond in different ways to enhanced CO2 concentrations. 

3 As with the climate effects of CO2, the changes in non-climate impacts associated with the 

4 alternatives are difficult to assess quantitatively. Whether the distinction in concentrations is substantial 

5 across alternatives is not clear because the damage functions and potential existence of thresholds for CO2

6 concentration are not known. However, what is clear is that a reduction in the rate of increase in 

7 atmospheric CO2, which all the action alternatives would provide to some extent, would reduce the ocean 

8 acidification effect and the CO2 fertilization effect. 

9 S.5.3 Mitigation 

10 CEQ regulations for implementing the procedural requirements of NEPA implicitly require that 

11 the discussion of alternatives in an EIS “[i]nclude appropriate mitigation measures not already included in 

12 the proposed action or alternatives.” 40 CFR § 1502.14(f). In particular, an EIS should discuss the 

13 “[m]eans to mitigate adverse environmental impacts.” 40 CFR § 1502.16(h). 

14 Under NEPA, an EIS should contain “a reasonably complete discussion of possible mitigation 

measures.”41 15 Essentially, “[t]he mitigation must ‘be discussed in sufficient detail to ensure that 

environmental consequences have been fairly evaluated.’”42 16 Under NEPA, an agency does not have to 

formulate and adopt a complete mitigation plan,43 17 but should analyze possible measures that could be 

18 adopted. An agency should state in its Record of Decision whether all practicable means to avoid or 

19 reduce environmental harm have been adopted into the selected alternative. 40 CFR § 1505.2(c). 

20 Generally, emissions from criteria pollutants and MSATs are anticipated to decline, although 

21 emissions of CO, acrolein, and 1,3-butadiene could increase under certain alternatives and analysis years, 

22 compared to the No Action Alternative (Alternative 1). NHTSA notes that the analysis for acrolein 

23 emissions is incomplete because upstream emissions factors are not available. Upstream emissions 

24 decrease due to fuel savings and reduced emissions from fuel refining and transportation. If upstream 

25 emissions of acrolein were included in the analysis, total acrolein emissions would show smaller increases 

26 or might decrease. Thus, the acrolein emissions reported in this EIS represent an upper bound. 

27 It should be noted that even if CO emissions show some level of increase, the associated harm 

28 might not increase concomitantly. After a long downward trend, there have been fewer than three 

29 violations of the CO standards per year since 2002, owing to the success of regulations governing fuel 

30 composition and vehicle emissions. Also, vehicle manufacturers can choose which technologies to 

31 employ to reach the new CAFE standards. Some of their choices regarding which technologies to use 

32 result in higher or lower impacts for these emissions. Nevertheless, there is the potential that some air 

33 pollutant emissions will increase in some years under some alternatives. 

34 Beyond these considerations, at the national level there could also be increases in criteria and 

35 toxic air pollutant emissions in some nonattainment areas as a result of implementation of the CAFE 

36 standards under the action alternatives. These increases would represent a slight decline in the rate of 

37 reductions being achieved by implementation of CAA standards. 

 

41 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)). 42 Id. (citing City of Carmel-By-The-Sea v. U.S. Dept. of Transp., 123 F.3d 1142, 1154 (9th Cir. 1997)). 43Id. (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). 
Summary 

 S-42 

1 Regarding air quality, federal transportation funds administered by the Federal Highway 

2 Administration (FHWA) could be available to assist in funding projects to reduce increases in emissions. 

3 FHWA provides funding to states and localities specifically to improve air quality under the Congestion 

4 Mitigation and Air Quality Improvement (CMAQ) Program. The FHWA and the Federal Transit 

5 Administration (FTA) also provide funding to states and localities under other programs that have 

6 multiple objectives, including air quality improvement. Specifically, the Surface Transportation Program 

7 provides flexible funding that states may use for projects on any federal aid. As state and local agencies 

8 recognize the need to reduce emissions of CO, acrolein, and 1,3-butadiene (or other emissions eligible 

9 under the CMAQ Program, including the criteria pollutants and MSATs analyzed in this EIS), they have 

10 the ability to apply CMAQ funding to reduce impacts in most areas. Further, under the CAA, EPA has 

11 the authority to continue to improve vehicle emissions standards, which could result in future reductions 

12 as EPA promulgates new regulations. 

13 Each of the action alternatives would reduce energy consumption and GHG emissions compared 

14 to the No Action Alternative (Alternative 1), resulting in a net beneficial effect. Regardless of these 

15 reductions, passenger cars and light trucks are a major contributor to energy consumption and GHG 

16 emissions in the United States. Although an agency typically does not propose mitigation measures for 

17 an action resulting in a net beneficial effect, NHTSA would like to call attention to several other federal 

18 programs, which in conjunction with NHTSA CAFE standards, can make significant contributions in 

19 further reducing energy consumption and GHG emissions. 

20 The programs described below are ongoing and at various stages of completing their goals. All 

21 these programs present the potential for future developments and advances that could further increase the 

22 net beneficial effect of the environmental impacts identified in the EIS. The programs are also indicative 

23 of the types of programs that might be available in the future at all government levels for even further 

24 mitigation. 

25  EPA administers Renewable Fuel Standards under Section 211(o) of the CAA. EPA 

26 estimates that the greater volumes of biofuel mandated by proposed standards would reduce 

27 GHG emissions from transportation by approximately 160 MMTCO2 equivalent per year. 

28  DOT, in coordination with EPA and the U.S. Department of Housing and Urban 

29 Development, announced six livability principles around which the agencies will coordinate 

30 agency policies. One of the principles is focused on increasing transportation options, which 

31 aims to decrease energy consumption, improve air quality, and reduce GHG emissions. The 

32 livability principles are an extension of ongoing national awareness and interest in Smart 

33 Growth. 

34  DOT is one of more than a dozen agency members of the U.S. Climate Change Technology 

35 Program, led by DOE, which is aimed at the development and adoption of technologies 

designed to reduce the U.S. carbon footprint.44 36 

37  DOE administers programs that provide mitigating effects, such as the Section 1605b 

38 Voluntary Reporting of Greenhouse Gases. Section 1605b reporting provides a forum for 

39 recording strategies and reductions in GHGs; it is a voluntary program that facilitates 

information sharing.45 40 

 

44 Office of Policy and International Affairs, Department of Energy, Climate Overview, 

http://www.pi.energy.gov/climateoverview.html (last visited on Jul. 15, 2009). 45 Id. 
Summary 

 S-43 

1  DOE’s Clean Cities Program develops government-industry partnerships designed to reduce 

petroleum consumption.46 2 

3  DOE administers the Vehicle Technologies Program, which creates public-private 

4 partnerships that enhance energy efficiency and productivity and can bring clean technologies 

to the marketplace.47 5 

 

46 Office of Energy Efficiency and Renewable Energy, U.S. Department of Energy, Clean Cities: Fact Sheet (2009). 47 Office of Energy Efficiency and Renewable Energy, U.S. Department of Energy, About the Program, 

http://www1.eere.energy.gov/vehiclesandfuels/about/index.html (last visited on Jul. 15, 2009). 
Summary 

 S-44 

1 
 1-1 

1 Chapter 1 Purpose and Need for the Proposed Action 

2 1.1 INTRODUCTION 

The Energy Policy and Conservation Act of 19751 3 (EPCA) established a program to regulate 

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

passenger cars and light trucks.2 5 As part of that Act, the Corporate Average Fuel Economy (CAFE) 

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

7 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 8 The National Highway 

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

economy requirements assigned to the Secretary of Transportation.4 10 

In December 2007, the Energy Independence and Security Act of 2007 (EISA)5 11 amended EPCA’s 

12 CAFE Program requirements, providing the U.S. Department of Transportation (DOT) additional 

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

14 standards for model year (MY) 2011-2015 passenger cars and light trucks in a Notice of Proposed 

Rulemaking (NPRM).6 15 On March 21, 2008, NHTSA issued a Notice of Intent to prepare an EIS for the 

MY 2011-2015 CAFE standards.7 16 On October 10, 2008, NHTSA submitted to the U.S. Environmental 

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

18 Standards, Passenger Cars and Light Trucks, MY 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 19 On 

20 January 7, 2009, the Department of Transportation announced that the Bush Administration would not 

issue the final rule.9 21 

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

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

24 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 United States Code (U.S.C.) § 32901 et seq. 2

 49 U.S.C. § 32901-32919. 3

 49 Code of Federal Regulations (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 1 The memorandum requested that NHTSA 

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

3 2012 and beyond.

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

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

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

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

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

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

10 concerning the model years after model year 2011, NHTSA

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

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

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

14 Academy of Sciences mandated under section 107 of EISA. 

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

16 are appropriate under applicable law and policy. 

17 1.2 JOINT RULEMAKING AND NEPA PROCESS 

18 Concurrent with this DEIS, NHTSA and EPA are each announcing joint proposed rules whose 

19 benefits would address the urgent and closely intertwined challenges of energy independence and security 

20 and global warming. These proposed rules call for a strong and coordinated federal greenhouse gas and 

21 fuel economy program for passenger cars, light-duty-trucks, and medium-duty passenger vehicles 

22 (hereafter light-duty vehicles), referred to as the National Program. The proposed rules can achieve 

23 substantial improvements in fuel economy and reductions of greenhouse gas (GHG) emissions from the 

24 light-duty vehicle part of the transportation sector, based on technology that is already being 

25 commercially applied in most cases and that can be incorporated at a reasonable cost. 

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

27 2009 of a National Fuel Efficiency Policy of establishing consistent, harmonized, and streamlined 

28 requirements that would improve fuel economy and reduce greenhouse gas emissions for all new 

passenger cars and light trucks sold in the United States.11 29 The National Program holds out the promise 

30 of delivering additional environmental and energy benefits, cost savings, and administrative efficiencies 

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

32 National Program also offers the prospect of regulatory convergence by making it possible for the 

33 standards of two different federal agencies and the standards of California and other states to act in a 

34 unified fashion in providing these benefits. This would allow automakers to produce and sell a single 

35 fleet nationally. Thus, it may also help to mitigate the additional costs that manufacturers would 

36 otherwise face in having to comply with multiple sets of federal and state standards. This joint notice is 

 

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

Administration, 74 FR 4907 (Jan. 26, 2009). 11 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 

also consistent with the Notice of Upcoming Joint Rulemaking signed by DOT and EPA on May 1912 1 and 

2 responds to the President’s January 26, 2009 memorandum on CAFE standards for model years 2011 and 

beyond.13 3 

4 1.2.1 Building Blocks of the National Program 

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

6 fuel economy and reducing CO2 tailpipe emissions is a very direct and close one. The amount of those 

7 CO2 emissions is essentially constant per gallon combusted of a given type of fuel. Thus, the more fuel 

8 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.14 9 While there are emission control technologies that reduce the pollutants 

10 (e.g., carbon monoxide) produced by imperfect combustion of fuel by capturing or destroying them, there 

11 is no such technology for CO2. Further, while some of those pollutants can also be reduced by achieving 

12 a more complete combustion of fuel, doing so only increases the tailpipe emissions of CO2. Thus, there is 

13 a single pool of technologies for addressing these twin problems, i.e., those that reduce fuel consumption 

14 and thereby reduce CO2 emissions as well. 

15 1.2.1.1 DOT’s CAFE Program 

16 In 1975, Congress enacted the Energy Policy and Conservation Act (EPCA), mandating that 

17 NHTSA establish and implement a regulatory program for motor vehicle fuel economy to meet the 

18 various facets of the need to conserve energy, including ones having energy independence and security, 

19 environmental and foreign policy implications. Fuel economy gains since 1975, due both to the standards 

20 and market factors, have resulted in saving billions of barrels of oil and avoiding billions of metric tons of 

21 CO2 emissions. In December 2007, Congress enacted the Energy Independence and Securities Act 

22 (EISA), amending EPCA to require substantial, continuing increases in fuel economy standards. 

23 The CAFE standards address most, but not all, of the real-world CO2 emissions because EPCA 

24 requires the use of 1975 passenger car test procedures under which vehicle air conditioners are not turned 

on during fuel economy testing.15 25 Fuel economy is determined by measuring the amount of CO2 and 

26 other carbon compounds emitted from the tailpipe, not by attempting to measure directly the amount of 

27 fuel consumed during a vehicle test, a difficult task to accomplish with precision. The carbon content of 

the test fuel16 28 is then used to calculate the amount of fuel that had to be consumed per mile in order to 

29 produce that amount of CO2. Finally, that fuel consumption figure is converted into a miles-per-gallon 

30 figure. CAFE standards also do not address the 5-8 percent of GHG emissions that are not CO2, i.e., 

31 nitrous oxide (N2O), and methane (CH4) as well as emissions of CO2 and hydrofluorocarbons (HFCs) 

32 related to operation of the air conditioning system. 

 

12 74 FR 24007 (May 22, 2009). 

13 Available at: http://www.whitehouse.gov/the_press_office/Presidential_Memorandum_Fuel_Economy/ (last 

accessed on August 18, 2009) 

14 Panel on Policy Implications of Greenhouse Warming, National Academy of Sciences, National Academy of 

Engineering, Institute of Medicine, “Policy Implications of Greenhouse Warming: Mitigation, Adaptation, and the 

Science Base,” National Academies Press, 1992. p. 287. 

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 1.2.1.2 EPA’s Greenhouse Gas Standards for Light-duty Vehicles 

2 Under the Clean Air Act 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 3 a case involving 

4 a 2003 order of the Environmental Protection Agency (EPA) denying a petition for rulemaking to regulate 

greenhouse gas emissions from motor vehicles under section 202(a) of the Clean Air Act (CAA).18 5 The 

6 Court held that greenhouse gases were air pollutants for purposes of the Clean Air Act and further held 

7 that the Administrator must determine whether or not emissions from new motor vehicles cause or 

8 contribute to air pollution which may reasonably be anticipated to endanger public health or welfare, or 

9 whether the science is too uncertain to make a reasoned decision. The Court further ruled that, in making 

10 these decisions, the EPA Administrator is required to follow the language of section 202(a) of the CAA. 

11 The Court rejected the argument that EPA cannot regulate CO2 from motor vehicles because to do so 

12 would de facto tighten fuel economy standards, authority over which has been assigned by Congress to 

13 DOT. The Court stated that “[b]ut that DOT sets mileage standards in no way licenses EPA to shirk its 

14 environmental responsibilities. EPA has been charged with protecting the public‘s ‘health’ and ‘welfare’, 

15 a statutory obligation wholly independent of DOT’s mandate to promote energy efficiency.” The Court 

16 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 17 The Court remanded the case back to 

the Agency for reconsideration in light of its findings. 20 18 

19 EPA has since proposed to find that emissions of GHGs from new motor vehicles and motor 

20 vehicle engines cause or contribute to air pollution that may reasonably be anticipated to endanger public 

health and welfare.21 21 Today’s proposal represents the second phase of EPA’s response to the Supreme 

22 Court’s decision. 

23 1.2.1.3 California Air Resources Board Greenhouse Gas Program 

24 In 2004, the California Air Resources Board approved standards for new light-duty vehicles, 

25 which regulate the emission of not only CO2, but also other GHGs. Since then, thirteen states and the 

26 District of Columbia, comprising approximately 40 percent of the light-duty vehicle market, have adopted 

27 California’s standards. These standards apply to model years 2009 through 2016 and require reductions 

28 in CO2 emissions for passenger cars and some light trucks of 323 g/mil in 2009 up to 205 g/mi in 2016 

29 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 30 The granting of the waiver permits 

31 California and the other states to proceed with implementing the California emission standards. 

32 1.2.2 Joint Proposal for a National Program 

33 On May 19, 2009, the Department of Transportation and the Environmental Protection Agency 

34 issued a Notice of Upcoming Joint Rulemaking to propose a strong and coordinated fuel economy and 

35 greenhouse gas National Program for Model Year (MY) 2012-2016 light duty vehicles. 

 

17 549 U.S. 497 (2007). 

18 68 FR 52922 (Sept. 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. There is a comprehensive 

discussion of the litigation’s history, the Supreme Court’s findings, and subsequent actions undertaken by the Bush 

Administration and the EPA from 2007-2008 in response to the Supreme Court remand. 

21 74 FR 18886 (Apr. 24, 2009). 

22 74 FR 32744 (July 8, 2009). 
Chapter 1 Purpose and Need for the Proposed Action 

 1-5 

1 NHTSA and EPA are proposing a harmonized and coordinated National Program with the 

2 following key elements: 

3 1.2.2.1 Level of the Standards 

4 NHTSA and EPA are proposing two separate sets of standards, each under its respective statutory 

5 authorities. NHTSA is proposing CAFE standards for passenger cars and light trucks under 49 U.S.C. § 

6 32902. These standards would require them to meet an estimated combined average fuel economy level 

7 of 34.1 mpg in model year 2016. EPA is proposing national CO2 emissions standards for light-duty 

8 vehicles under section 202 (a) of the Clean Air Act. These standards would require these vehicles to meet 

9 an estimated combined average emissions level of 250 grams/mile of CO2 in model year 2016. The 

10 proposed standards for both agencies begin with the 2012 model year, with standards increasing in 

11 stringency through model year 2016. They represent a harmonized approach that will allow industry to 

12 build a single national fleet that will satisfy both the GHG requirements under the CAA and CAFE 

13 requirements under EPCA/EISA.

14 Given differences in their respective statutory authorities, however, the agencies’ proposed 

15 standards include some important differences. Under the CO2 fleet average standard proposed under 

16 CAA section 202(a), EPA expects manufacturers to take advantage of the option to generate CO2-

17 equivalent credits by reducing emissions of hydrofluorocarbons (HFCs) and CO2 through improvements 

18 in their air conditioner systems. EPA accounted for these reductions in developing its proposed CO2

19 standard. EPCA does not allow vehicle manufacturers to use air conditioning credits in complying with 

CAFE standards for passenger cars.23 20 CO2 emissions due to air conditioning operation are not measured 

21 by the test procedure mandated by statute for use in establishing and enforcing CAFE standards for 

22 passenger cars. As a result, improvements in the efficiency of passenger car air conditioners would not be 

23 considered as a possible control technology for purposes of CAFE. 

24 These differences regarding the treatment of air conditioning improvements (related to CO2 and 

25 HFC reductions) affect the relative stringency of the EPA standard and NHTSA standard. The 250 grams 

per mile of CO2 equivalent emissions limit is equivalent to 35.5 mpg24 26 if the automotive industry were to 

27 meet this CO2 level all through fuel economy improvements. As a consequence of the prohibition against 

28 NHTSA’s allowing credits for air conditioning improvements for purposes of passenger car CAFE 

29 compliance, NHTSA is proposing fuel economy standards that are estimated to require a combined 

30 (passenger car and light truck) average fuel economy level of 34.1 mpg by MY 2016. 

31 1.2.2.2 Form of the Standards 

32 In this rule, NHTSA and EPA are proposing attribute-based standards for passenger cars and light 

33 trucks. NHTSA adopted an attribute standard based on vehicle footprint in its Reformed CAFE program 

for light trucks for model years 2008-2011,25 34 and recently extended this approach to passenger cars in the 

CAFE rule for MY 2011 as required by EISA.26 35 Under an attribute-based standard, every vehicle model 

36 has a performance target (fuel economy for the CAFE standards, and CO2 g/mile for the GHG emissions 

37 standards), the level of which depends on the vehicle’s attribute (for today’s proposal, footprint). The 

 

23 There is no such statutory limitation with respect to light trucks. 

24 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. 

25 71 FR 17566 (Apr. 6, 2006). 

26 74 FR 14196 (Mar. 30, 2009). 
Chapter 1 Purpose and Need for the Proposed Action 

 1-6 

manufacturers’ fleet average performance is determined by the production-weighed27 1 average (for CAFE, 

2 harmonic average) of those targets. 

3 NHTSA and EPA are proposing vehicle footprint as the attribute for the CAFE and GHG 

4 standards. Footprint is defined as a vehicle’s wheelbase multiplied by its track width – in other words, 

5 the area enclosed by the points at which the wheels meet the ground. The agencies believe that the 

6 footprint attribute is the most appropriate attribute on which to base the standards under consideration, as 

7 discussed in the NPRM and in Chapter 2 of the draft joint TSD. 

8 Under the proposed footprint-based standards, each manufacturer would have a CAFE and GHG 

9 target unique to its fleet, depending on the footprints of the vehicle models produced by that 

10 manufacturer. A manufacturer would have separate footprint-based standards for cars and for trucks. 

11 Generally, larger vehicles (i.e., vehicles with larger footprints) would be subject to less stringent standards 

12 (i.e., higher CO2 grams/mile standards and lower CAFE standards) than smaller vehicles. This is because, 

13 generally speaking, smaller vehicles are more capable of achieving higher standards than larger vehicles. 

14 While a manufacturer’s fleet average standard could be estimated throughout the model year based on 

15 projected production volume of its vehicle fleet, the standard to which the manufacturer must comply 

16 would be based on its final model year production figures. A manufacturer’s calculation of fleet average 

17 emissions at the end of the model year would thus be based on the production-weighted average 

18 emissions of each model in its fleet. 

19 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 2011.28 20 NHTSA and EPA worked 

21 together to design car and truck footprint curves that followed from logistic curves used in that rule. The 

22 agencies started by addressing two main concerns regarding the car curve. The first concern was that the 

23 2011 car curve was relatively steep near the inflection point thus causing concern that small variations in 

24 footprint could produce relatively large changes in fuel economy targets. A curve that was directionally 

25 less steep would reduce the potential for gaming. The second issue was that the inflection point of the 

26 logistic curve was not centered on the distribution of vehicle footprints across the industries’ fleet, thus 

27 resulting in a flat (universal or unreformed) standard for over half the fleet. The proposed car curve has 

28 been shifted and made less steep compared to the car curve adopted by NHTSA for 2011, such that it 

29 better aligns the sloped region with higher production volume vehicle models. Finally, both the car and 

30 truck curves are defined in terms of a constrained linear function for fuel consumption and, equivalently, 

31 a piece-wise linear function for CO2. NHTSA and EPA include a full discussion of the development of 

32 these curves in the joint TSD. In addition, a full discussion of the equations and coefficients that define 

33 the curves proposed by each agency is included in section III of the NPRM for the CO2 curves and section 

34 IV of the NPRM for the mpg curves. 

35 1.2.2.3 Program Flexibilities for Achieving Compliance 

36 NHTSA and EPA are proposing standards that are intended to provide compliance flexibility to 

37 manufacturers, especially in the early years of the program. This flexibility would be expected to provide 

38 sufficient lead time to make necessary technological improvements and additions, and to reduce the 

39 overall cost of the program without compromising overall environmental and fuel economy objectives. 

40 The broad goal of harmonizing the NHTSA and EPA standards would include providing manufacturer 

41 flexibilities in meeting the standards. The flexibility provisions the agencies jointly and separately 

42 contemplated in developing the program include CAFE/CO2 Credits Earned Based on Fleet Average 

 

27 Production for sale in the United States. 

28 74 FR 14407-14409 (Mar. 30, 2009). 
Chapter 1 Purpose and Need for the Proposed Action 

 1-7 

1 Performance, Air Conditioning Credits, Flex-Fuel and Alternative Fuel Vehicle Credits, Temporary Lead2 Time Allowance Alternative Standards (TLAAS), and Additional Potential Credit Opportunities. Some 

3 of these flexibilities will be available to manufacturers in aiding compliance under both sets of standards, 

4 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.29 5 

6 1.2.2.4 Compliance 

7 NHTSA and EPA propose a program that recognizes and replicates as closely as possible the 

8 compliance protocols associated with the existing CAFE standards and CAA Tier 2 vehicle emission 

9 standards. The certification, testing, reporting, and associated compliance activities could closely track 

10 current practice and thus be familiar to manufacturers. EPA already oversees testing, collects and 

11 processes test data, and performs calculations to determine compliance with both CAFE and CAA 

12 standards. NHTSA determines compliance with the CAFE program, manages credits, issues letters of 

13 noncompliance, and collects civil penalties from the manufacturers. In a coordinated approach, 

14 compliance mechanisms for both programs would be consistent and non-duplicative. 

15 Under NEPA a federal agency must analyze environmental impacts if the agency implements a 

16 proposed action, provides funding for an action, or issues a permit for that action. Specifically, NEPA 

17 directs that “to the fullest extent possible,” federal agencies proposing “major federal actions significantly 

18 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). 30 19 To 

20 inform its development of the new MY 2012-2016 CAFE standards required under EPCA, as amended by 

21 EISA, NHTSA prepared this draft EIS to analyze and disclose the potential environmental impacts of a 

22 proposed preferred alternative and other proposed alternative standards pursuant to CEQ NEPA 

implementing regulations, DOT Order 5610.1C, and NHTSA regulations.31 23 This EIS compares the 

24 potential environmental impacts among alternatives, including a no action alternative. It also analyzes 

25 direct, indirect, and cumulative impacts and discusses impacts in proportion to their significance. 

26 Section 1501.6 of CEQ regulations emphasize agency cooperation early in the NEPA process and 

27 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. 32 28 NHTSA invited 

29 EPA to be a cooperating agency, pursuant to CEQ regulations, because of its special expertise in the areas 

30 of climate change and air quality. On May 12, 2009, the EPA accepted NHTSA’s invitation and agreed 

31 to become a cooperating agency. 

32 EPA leads the nation's environmental science, research, education, and assessment efforts. The 

33 mission of the EPA is to protect human health and the environment. EPA is legally required to comply 

34 with the procedural requirements of NEPA for its research and development activities, facilities 

35 construction, wastewater treatment construction grants under Title II of the Clean Water Act (CWA), 

36 EPA-issued National Pollutant Discharge Elimination System permits for new sources, and for certain 

37 projects funded through EPA annual Appropriations Acts. However, EPA actions under the Clean Air 

38 Act (CAA), including the EPA proposed vehicle greenhouse gas emission standards under the Joint 

39 Rulemaking, are not subject to the requirements of NEPA. Pursuant to the National Fuel Efficiency 

40 Policy announced by the President on May 19, 2009, NHTSA and EPA published their Notice of 

 

29 See the discussion of compliance flexibilities in Section 3.1.4.1 of the joint NHTSA-EPA NPRM. 30 42 U.S.C. § 4332. 

31 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. 

32 40 CFR § 1501.6. 
Chapter 1 Purpose and Need for the Proposed Action 

 1-8 

1 Upcoming Joint Rulemaking to ensure a coordinated Federal Program on fuel economy and GHG 

2 emissions for passenger cars, light duty trucks, and medium-duty passenger vehicles. In order to improve 

3 the usefulness of the EIS for NHTSA decision makers and the public, EPA’s environmental analysis of its 

proposed rulemaking is summarized and referenced within the appropriate sections of this EIS. 33 4 

5 1.3 PROPOSED ACTION 

6 For this EIS, NHTSA’s Proposed Action is setting passenger car and light truck CAFE standards 

7 for MY 2012 through 2016, in accordance with EPCA, as amended by EISA. 

8 

9 As mentioned above, in the joint NHTSA-EPA NPRM issued concurrently with this Draft EIS, 

10 NHTSA and EPA are proposing coordinated and harmonized CAFE standards and vehicle greenhouse 

11 gas emissions for passenger cars, light-duty trucks, and medium-duty passenger vehicles built in MY 

12 2012 through 2016. 

13 

14 1.4 PURPOSE AND NEED 

15 NEPA requires that a proposed action’s alternatives be developed based on the action’s purpose 

16 and need. The purpose and need statement explains why the action is needed and the action’s intended 

17 purpose, and serves as the basis for developing the range of alternatives to be considered in the NEPA 

analysis. 34 18 In accordance with EPCA, as amended by EISA, one of the purposes of the Joint Rulemaking 

19 action is to establish MY 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.”35 20 

21 The implication of this requirement is that it calls for exceeding the minimum requirement if the agency 

22 determines that the manufacturers can achieve a higher level. When determining the level achievable by 

23 the manufacturers, EPCA requires that the agency consider the four statutory factors of technological 

24 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.36 25 In addition, the agency has the 

26 authority to and traditionally does consider other relevant factors, such as the effect of the CAFE 

standards on motor vehicle safety.37 27 

 

33 Pursuant to the National Program announced by the President on May 19, 2009, EPA and NHTSA published their 

Notice of Upcoming Joint Rulemaking to ensure a coordinated Federal 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 Council on 

Environmental Quality’s regulation at 40 CFR Section 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 decision makers 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 Clean Air Act 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 

Clean Air Act and places no obligation on EPA to comply with NEPA in promulgating its rule or taking any other 

action covered by the exemption. 

34 40 CFR § 1502.13. 

35 49 U.S.C. § 32902(a). 

36 49 U.S.C. §§ 32902(a), 32902(f). 

37 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). 
Chapter 1 Purpose and Need for the Proposed Action 

 1-9 

NHTSA has historically defined the aforementioned considerations as follows:38 1 

2  “Technological feasibility” refers to whether a particular method of improving fuel economy 

3 can be available for commercial application in the model year for which a standard is being 

4 established. 

5  “Economic practicability” refers to whether a standard is one within the financial capability 

6 of the industry, but not so stringent as to lead to adverse economic consequences, such as 

7 significant job losses or unreasonable elimination of consumer choice. 

8  “The effect of other motor vehicle standards of the Government on fuel economy,” involves 

an analysis of the effects of compliance with emission,39 9 safety, noise, or damageability 

10 standards on fuel economy capability and thus on average fuel economy. 

11  “The need of the United States to conserve energy” means the consumer cost, national 

12 balance of payments, environmental, and foreign policy implications of the Nation’s need for 

13 large quantities of petroleum, especially imported petroleum. 

14 NHTSA must establish separate standards for MY 2011-2020 passenger cars and light trucks, 

subject to two principal requirements.40 15 First, the standards are subject to a minimum requirement 

16 regarding stringency: they must be set at levels high enough to ensure that the combined US passenger 

17 car and light truck fleet achieves an average fuel economy level of not less than 35 mpg not later than MY 

2020.41 18 Second, as discussed above and at length in the March 2009 final rule establishing the MY 2011 

19 CAFE standards, EPCA requires that the agency establish standards for all new passenger cars and light 

20 trucks at the maximum feasible average fuel economy level that the Secretary decides the manufacturers 

can achieve in that model year.42 21 

22 Additionally, EPCA, as amended by EISA, requires that the CAFE standards for passenger cars 

23 and light trucks increase ratably in each model year between MY 2011 and MY 2020. Standards must be 

24 “based on one or more vehicle attributes related to fuel economy,” and “expressed in the form of a 

mathematical function.”43 25 In any single rulemaking, standards may be established for not more than five 

model years.44 26 

27 NHTSA is also guided by President Obama’s memorandum to the Department of Transportation 

28 (DOT) on January 26, 2009, as described in Section 1.1. 

 

38 74 FR 14196 (Mar. 30, 2009). 

39 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 Clean Air Act allows States to adopt and 

enforce State standards different from the Federal ones. 

40 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. 41 49 U.S.C. § 32902(b)(2)(A). 

42 49 U.S.C. § 32902(a). 

43 49 U.S.C. § 32902(a)(3)(A). 

44 49 U.S.C. §§ 32902(b)(3)(A), 32902(b)(3)(B). 
Chapter 1 Purpose and Need for the Proposed Action 

 1-10 

1 1.5 PUBLIC REVIEW AND COMMENT 

2 On April 1, 2009, NHTSA published a Notice of Intent (NOI) to prepare an EIS for the MY 

3 2012-2016 CAFE standards. The NOI described the statutory requirements for the standards, provided 

initial information about the NEPA process, and initiated scoping45 4 by requesting public input on the 

scope of the environmental analysis to be conducted.46 5 Two important purposes of scoping are 

6 identifying the substantial environmental issues that merit in-depth analysis in the EIS and identifying and 

7 eliminating from detailed analysis the environmental issues that are not substantial and therefore require 

only a brief discussion in the EIS.47 8 Scoping should “deemphasize insignificant issues, narrowing the 

scope of the environmental impact statement process accordingly.”48 9 Consistent with NEPA and its 

10 implementing regulations, on April 2, 2009, NHTSA mailed the April 1 NOI to: 

11  109 contacts at federal agencies having jurisdiction by law or special expertise with respect to 

12 the environmental impacts involved, or authorized to develop and enforce environmental 

13 standards, including other modes within DOT; 

14  The Governors of every state and U.S. territory; 

15  65 organizations representing state and local governments; 

16  599 Native American tribal organizations and academic centers that had issued reports on 

17 climate change and tribal communities; and 

18  265 contacts at other stakeholder organizations that NHTSA reasonably expected to be 

19 interested in the NEPA analysis for the MY 2012-2016 CAFE standards, including auto 

20 industry organizations, environmental organizations, and other organizations that had 

21 expressed interest in prior CAFE rules. 

22 NHTSA used its letters transmitting the April 1 NOI to develop a contact list for future notices 

23 about the NEPA process for the MY 2012-2016 CAFE standards. For instance, NHTSA asked each 

24 Governor to, “share [the] letter and the enclosed [NOI] with the appropriate environmental agencies and 

25 other offices within your administration and with interested local jurisdictions and government 

26 organizations within your State.” NHTSA further requested that each Governor ask their representative 

27 to provide contact information for the state’s lead office on the CAFE EIS by returning a contact list form 

28 to NHTSA or by sending NHTSA an e-mail containing the information requested on the form. NHTSA 

29 asked federal agency contacts to share the NOI with other interested parties within their organizations and 

30 to complete the contact list form. NHTSA asked contacts at other stakeholder organizations to let 

31 NHTSA know whether they wished to remain on the agency’s NEPA contact list for the CAFE EIS by 

32 returning a contact list form or sending NHTSA an e-mail containing the information requested on the 

33 form. NHTSA indicated that organizations that did not return the form would be removed from the 

34 NEPA contact list.

 

45 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.

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

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

47 40 CFR §§ 1500.4(g), 1501.7(a).

48 40 CFR § 1500.4(g).
Chapter 1 Purpose and Need for the Proposed Action 

 1-11 

1 1.5.1 Agency Consultation 

2 On May 5, 2009, NHTSA invited the EPA to become a cooperating agency with NHTSA in the 

3 development of the EIS for the CAFE rulemaking for MY 2012-2016 passenger cars and light trucks in 

4 accordance with 40 CFR § 1501.6 of the NEPA implanting regulations issued by CEQ. Under 40 CFR § 

5 1501.6, a federal agency which has special expertise with respect to any environmental issue which 

6 should be addressed in the statement may be a cooperating agency upon request of the lead agency. In its 

7 invitation letter, NHTSA suggested that EPA’s role in the development of the EIS could include the 

8 following, as they relate to EPA’s areas of expertise: 

9  The significant issues to be analyzed in the EIS from a climate change and air quality 

10 perspective. 

11  Assist NHTSA to “identify and eliminate from detailed study the issues which are not 

12 significant or which have been covered by prior environmental review, (§ 1506.3), narrowing 

13 the discussion of these issues in the statement to a brief presentation of why they will not 

14 have a significant effect on the human environment or providing a reference to their coverage 

15 elsewhere.” 40 CFR § 1501.7(a) (3). 

16  Participate in coordination meetings, as appropriate. 

17  Review and comment on the draft EIS and final EIS prior to publication. 

18 On May 12, 2009 EPA accepted NHTSA’s invitation and agreed to become a cooperating 

19 agency. EPA staff participated in technical discussions and reviewed and commented on draft sections 

20 and the draft final version of the DEIS. 

21 To comply with NEPA's requirements for agency consultation, on July 10, 2009, NHTSA mailed 

22 consultation letters to the following federal agencies: Bureau of Land Management, Centers for Disease 

23 Control and Prevention, Minerals Management Service, National Park Service, Advisory Council on 

24 Historic Preservation, U.S. Forest Service, and U.S. Army Corps of Engineers. NHTSA is also currently 

25 exploring its obligations under Section 7 of the Endangered Species Act with U.S. Fish and Wildlife 

26 Service and National Oceanic and Atmospheric Administration Fisheries Service. 

27 On July 30, 2009, NHTSA received a response from the Centers for Disease Control and 

28 Prevention indicating that they are interested in consulting on this EIS. 

29 1.5.2 Summary of Scoping Comments 

30 NHTSA received seven responses to its scoping notice. Comments were provided by federal and 

31 state agencies, one automobile trade association, one environmental advocacy group, and three 

32 individuals. This section summarizes these scoping comments. 

33 1.5.2.1 Federal Agencies 

34 The United States Environmental Protection Agency (EPA) was the only federal agency that 

35 provided scoping comments (Docket No. NHTSA-2009-0059-0005). EPA suggested that NHTSA 

36 incorporate material from the October, 10 2008 Final EIS in a judicious manner, recommending that 

37 NHTSA take into account areas where the earlier analysis is no longer applicable, including key baseline 

38 assumptions, the social cost of carbon, and the predicted cost of fuel. Refer to Section 2 of this EIS for a 

39 discussion of NHTSA’s current approach and assumptions. NHTSA notes that while some material from 
Chapter 1 Purpose and Need for the Proposed Action 

 1-12 

1 the October 10, 2008 Final EIS may still be relevant and applicable to the current EIS, the present 

2 document stands alone as a new analysis with a new consideration of all issues and impacts. EPA further 

3 suggested that NHTSA be cautious when trying to incorporate future promulgated actions into the 

4 cumulative impacts assessment, as this could prove to be highly speculative and not appropriate in the 

5 current rapid flux of potential related legislative and regulatory action. Refer to Section 4.4.3 

6 (Cumulative Climate Methodology) of this EIS for a discussion of the methodology used to analyze 

7 cumulative impacts to climate. NHTSA notes that EPA’s scoping comment was submitted before EPA 

8 received NHTSA’s letter inviting EPA to become a cooperating agency on the EIS. 

9 1.5.2.2 States 

10 NHTSA received a letter from the Attorneys General of the States of California, Connecticut, 

11 Massachusetts, New Mexico, and Oregon, the Secretary of the New Mexico Environment Department, 

12 the Secretary of the Commonwealth of Pennsylvania Department of Environmental Protection, and the 

13 Corporation Counsel of the City of New York (Docket No. NHTSA-2009-0059-0006). 

14 The Attorneys General emphasized that rather than focusing on the effects of the rulemaking on 

15 global climate change, NHTSA should explain how this rule is consistent with, and essential to, the 

16 Nation’s efforts to address global warming. In this regard, they suggested that the 2008 EIS minimizes 

17 the effects of the CAFE program on global climate change and does not analyze cumulative impacts 

18 appropriately. Quoting the Ninth Circuit Court of Appeals, which stated in a 2007 ruling that “[a]ny 

19 given rule setting a CAFE standard might have an ‘individually minor’ effect on the environment but 

20 these rules are ‘collectively significant actions taking place over a period of time,’” they suggested that 

21 the 2008 EIS failed to meet this standard, and instead, minimized the effect of the rulemaking by stating 

22 that one set of CAFE rules by itself would have a negligible effect on global warming and public health 

23 and welfare. Refer to Sections 4.1.2 (Temporal and Geographic Boundaries) and 4.4.4 (Climate 

24 Cumulative Impacts) of this EIS, which discuss the temporal and geographic boundaries used for the 

25 analysis and the cumulative impacts to climate analysis, respectively. NHTSA notes that the agency is 

26 taking a fresh approach to placing its analysis in context of global climate change in this EIS.

27 The letter cites the EPA “Proposed Endangerment and Cause or Contribute Findings for 

Greenhouse Gases Under Section 202(a) of the Clean Air Act,”49 28 which states that while no single 

29 greenhouse gas source category dominates on the global scale, many could be very significant 

30 contributors. In particular, EPA states that motor vehicle source categories contribute 24 percent of total 

31 U.S. greenhouse gas emissions, and that total U.S. greenhouse gas emissions make up about 18 percent of 

32 the world’s greenhouse gas emissions. The Attorneys General concluded by stating that NHTSA should 

33 put the CAFE rules in context by demonstrating their importance for reducing greenhouse gas emissions 

34 and reducing global warming. The Attorneys General listed some ways to provide the proper context, 

35 including: comparing carbon dioxide emission reductions with the overall emission reduction goals that 

36 the President has endorsed (80 percent reduction by 2050); evaluating whether the automobile 

37 manufacturing industry is doing its fair share to address global warming; and evaluating whether the rules 

38 will help prevent us from reaching a “tipping point” beyond which cataclysmic damages occur due to 

39 non-linear changes in the climate. Refer to Section 3.4 and 4.4 of this EIS, which discusses climate 

40 change due to direct or indirect and cumulative impacts. The Attorneys General also suggested 

41 evaluating whether new CAFE rules could constitute a “stabilization wedge.” Refer to Section 2.5 

42 (Alternatives Considered but Not Analyzed in Detail) of this EIS for a discussion of alternatives not 

43 included in the analysis and the reasons for their exclusion. 

 

49 74 FR 18886, 18907 (Apr. 24, 2009). 
Chapter 1 Purpose and Need for the Proposed Action 

 1-13 

1 The Attorneys General letter also incorporated by reference previous comments submitted to the 

2 2008 EIS docket, including their 2008 scoping comments (Docket No. NHTSA-2008-0060-0007), 2008 

3 DEIS comments (Docket No. NHTSA-2008-0060-0585), and 2008 Notice of Proposed Rulemaking 

4 comments (Docket Nos. NHTSA-2008-0060-0585 (as an attachment to the 2008 DEIS comments) and 

5 NHTSA-2008-0089-0524). Comments received on the MY 2011 rulemaking and MY 2011–2015 CAFE 

6 EIS have been addressed in previous documents. NHTSA has re-examined all of these comments and has 

7 taken them into consideration in the development of this EIS. NHTSA is taking a fresh approach to this 

8 EIS. Thus, refer to the relevant sections of this EIS and the NPRM for MY 2012-2016 CAFE standards 

9 for new discussions of these issues. 

10 1.5.2.3 Automobile Trade Associations 

11 NHTSA received a letter from the Alliance of Automobile Manufacturers (AAM) that provided 

12 scoping comments (Docket No. NHTSA-2009-0059-0007). AAM commented that the rate of fuel 

13 efficiency increase proposed by NHTSA – a 3- to 7-percent annual increase depending on the alternative 

14 – is substantially greater than historical fuel efficiency increases of approximately 1 percent annually and 

15 too stringent for manufacturers undergoing difficult economic times. AAM noted that achieving the 

16 EISA mandated minimum fuel efficiency increases, which equate to an increase in fuel efficiency of 3 

17 percent per year, represents a substantial challenge for manufacturers. Furthermore, AAM stated that the 

18 most aggressive standards suggested by NHTSA would require an average annual light duty vehicle fuel 

19 economy of over 50 mpg in approximately 10 years, which no individual vehicle produced on a large 

20 scale can now achieve. These aggressive alternatives, AAM asserted, ignore the “economic 

21 practicability” provisions of EPCA and its case law. AAM suggested that NHTSA should keep historical 

22 rates of fuel efficiency change in mind when developing the alternatives in order to achieve a realistic 

23 increase in fuel efficiency. Refer to Section 2 (Alternatives) of this EIS for a discussion of the different 

24 alternatives selected for the analysis. 

25 AAM further suggested that more reasonable alternatives can be constructed by focusing on 

26 realistic variations of the 2020 MY endpoint under EISA, rather than incremental increases in average 

27 annual fuel economy improvement. Specifically, AAM suggests that Alternative 2 (as described in 

28 NHTSA’s April 1, 2009 NOI), could be redefined as improving fuel economy at a rate necessary to 

29 achieve 35 mpg fleet average fuel economy in MY 2020; Alternative 3 could be defined as improving 

30 fuel economy at a rate necessary to achieve a 36.75 mpg fleet average fuel economy in MY 2020; and 

31 Alternative 4 could be defined as improving fuel economy at the rate necessary to achieve a 38.5 mpg 

32 fuel economy in MY 2020. AAM noted that establishing a NEPA alternative based on a level of 

33 stringency tied to a “least capable manufacturer” analysis would provide important information to 

34 policymakers, especially for evaluating the effects of proposed standards on companies, which they 

35 contended are least likely to succeed under the new standards. AAM also suggested using increases 

36 based on only the reductions necessary to reach the MY 2020 endpoint under EISA. Refer to Section 2.5 

37 (Alternatives Considered but Not Analyzed in Detail) of this EIS for a discussion of alternatives not 

38 included in the analysis and the reasons for their exclusion. 

39 AAM highlighted that NHTSA’s NEPA regulations require the agency to apply a “systematic, 

interdisciplinary approach,”50 40 and that pursuant to this approach, NHTSA should consider a number of 

41 factors resulting from CAFE increases, including the effects of the CAFE increases on local air quality – 

42 specifically due to fleet turnover and rebound effects; the socioeconomic consequences of CAFE 

43 increases, such as impacts on the quality of life for workers at companies, which would be adversely 

44 affected by the regulations; and the effect of CAFE standards on ground-level ozone concentrations. 

 

50 49 CFR § 520.23(a).
Chapter 1 Purpose and Need for the Proposed Action 

 1-14 

1 Lastly, AAM suggested that regulation of motor vehicle greenhouse gases will increase the price of 

2 vehicles, thereby reducing fleet turnover and leading to increases in criteria pollutant emissions. They 

3 recommended that the EIS should fully explore the relationship between fleet turnover, vehicle prices, 

4 and the continued air quality improvements that are expected to result from an increase in CAFE 

5 standards. Refer to Section 3.3.3 (Air Quality Impacts) for a discussion of the air quality impacts of 

6 climate change. Refer to the NPRM for MY 2012-2016 CAFE standards for new discussions of the 

7 updated Volpe model. 

8 AAM also suggested that the EIS should only use studies that have undergone “rigorous scientific 

9 peer review” and suggested that NHTSA should coordinate with EPA in choosing criteria to determine 

10 which scientific studies to rely upon. NHTSA recognizes the importance of peer review in the validation 

of scientific studies and analytic methods.51 11 Refer to Section 4.1 for an explanation of the unique expert 

12 and panel review process of climate change research in the scientific community. We also note above 

13 that NHTSA is coordinating with EPA via the EPA’s role as a cooperating agency. 

14 AAM incorporated by reference its comments submitted during the 2008 scoping period. In this 

15 letter, AAM raised questions regarding the requirement for and appropriate scope of an EIS for the CAFE 

16 rulemaking, the appropriate definition of the alternatives, and the scope of the cumulative effects analysis. 

17 Refer to Chapter 1, Section 1.3.3, Summary of Scoping Comments and NHTSA’s Responses, in the 2008 

18 FEIS for an explanation of how NHTSA addressed these concerns in the 2008 FEIS. NHTSA is taking a 

19 fresh approach to this EIS. In this EIS, these comments are addressed in Chapters 1, 2, and 4. 

20 AAM incorporated by reference its comments on the 2008 DEIS. These comments addressed the 

21 requirement for and appropriate scope of an EIS for the CAFE rulemaking. AAM raised questions about 

22 the Volpe model, and pointed out that the fleet turnover effect may result in an increase in air pollutant 

23 emissions. Please refer to Chapter 10, Responses to Public Comments, of the 2008 FEIS for complete 

24 responses as to how NHTSA addressed AAM’s concerns in the 2008 FEIS. Refer to Chapters 1 and 2 in 

25 this EIS for a new discussion of these issues. 

26 1.5.2.4 Environmental Advocacy Groups 

27 The Center for Biological Diversity (CBD) was the only environmental advocacy group to 

28 provide scoping comments on the NOI to prepare an EIS (Docket No. NHTSA-2009-0059-0009). 

29 In general, CBD stated that there is a need for fundamental changes to the process by which the 

30 CAFE standards are developed in issuing a final rule that complies with EISA and EPCA. One such 

31 change CBD recommended was to eliminate the use of the Volpe model. CBD suggested that NHTSA: 

32 revise the definition of light trucks to more appropriately address their use as passenger cars; revise the 

33 Volpe model to accurately incorporate the benefits of lower vehicle weight for vehicle safety and fuel 

34 efficiency; revise the economic assumptions of the Volpe model to more accurately reflect the feasibility 

35 of setting more aggressive standards; and develop an independent process to derive technology and 

36 capacity estimates. Refer to Sections 2.2.1 (Volpe Model), Section 2.2.3 (Technology Assumptions), and 

37 Section 2.2.4 (Economic Assumptions) of this EIS for a discussion of the Volpe Model and the 

38 technology and economic assumptions used in the model. Refer to the NPRM for MY 2012-2016 CAFE 

39 standards for more detailed discussions of the updated Volpe model and the new assumptions. 

 

51 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 

 1-15 

1 CBD maintained that limiting technology implementation to manufacturer “redesign” and 

2 “refresh” cycles as done in previous EISs goes against the technology-forcing principle mandated by 

3 EPCA. By not including a technology-forcing alternative, they contend that NHTSA artificially 

4 constrains the range of alternatives analyzed in the EIS. In CBD’s opinion, these development cycles 

5 should have no bearing on the considerations of technology implementation within the cost-benefit 

6 analysis. On a similar note, CBD suggested that NHTSA’s “technology exhaustion” alternative, defined 

7 by the criteria “whether a particular method of improving fuel economy can be available for commercial 

8 application in the MY for which the standard is being established,” cannot substitute for consideration of 

9 a technology-forcing alternative, because it does not include standards that may appear impossible today, 

10 but which would force innovation as industry strives to meet a more challenging standard. NHTSA notes 

11 that this EIS does not consider a technology exhaustion alternative. Refer to Section 2.5 (Alternatives 

12 Considered but Not Analyzed in Detail) of this EIS for a discussion of other alternatives not included in 

13 the analysis and the reasons for their exclusion. We again refer the reader to Sections 2.2.1 (Volpe 

14 Model) and Section 2.2.3 (Technology Assumptions) of this EIS, and to the NPRM for MY 2012-2016 

15 CAFE standards for discussions of the updated Volpe model. 

16 CBD suggested that the EIS must include a reasonable analysis of the combined impact of 

17 NHTSA’s rulemaking on U.S. transportation sector emissions overall, as well as U.S. emissions overall. 

18 CBD recommended that NHTSA use the EIS to determine if the impact of the proposed rulemaking is 

19 sufficient to ensure that the necessary emissions reductions from the U.S. transportation sector overall 

20 will be achievable. CBD cited recent published reports that contend that it will be necessary to limit CO2 

21 concentrations to 350 ppm to avoid climate catastrophe, CBD requested that a maximum 350 ppm 

22 scenario should be included as an upper limit for defining the range of alternatives. CBD suggests using 

23 the function in MAGGIC that controls future emissions so that atmospheric CO2 concentrations do not 

24 exceed values ranging from 350 to 750 ppm. Refer to Section 3.4.2 (Affected Environment – Climate) of 

25 this EIS for a discussion of U.S. and global GHG emissions trends. Refer to Section 3.4.4.1 

26 (Environmental Consequences – Greenhouse Gas Emissions) for a discussion of the effect of the 

27 proposed CAFE standards and the alternatives on GHG emissions. Refer to Section 4.4.3.3 (Global 

28 Emissions Scenarios) for a discussion of reasonably foreseeable global emissions scenarios in the 

29 cumulative effects analysis. 

30 Lastly, CBD contended that NHTSA must initiate consultation with the U.S. Fish and Wildlife 

31 Service and National Marine Fisheries Service on the impact of the greenhouse gas and other air 

32 pollutants on listed species. Specifically, CBD stated that NHTSA must further examine the impact of its 

33 action on species listed as threatened or endangered under the Endangered Species Act (ESA) pursuant to 

34 both Section 7 of that law and the National Environmental Policy Act. NHTSA is taking a fresh look at 

35 Section 7 consultations under the ESA for the MY 2012-2016 CAFE rulemaking. We are currently 

36 exploring our obligations under the ESA and welcome comments from the public regarding this issue. 

37 1.5.2.5 Individuals 

38 Three individuals provided scoping comments on the proposed rulemaking: Jean Public 

39 (NHTSA-2009-0059-0002), Michael Gordon (NHTSA-2009-0059-0003), and James Adcock (NHTSA40 2009-0059-0004). 

41 Jean Public suggested that NHTSA raise standards to 100 mpg. Refer to Section 2.5 

42 (Alternatives Considered but Not Analyzed in Detail) of this EIS for a discussion of other alternatives not 

43 included in the analysis and the reasons for their exclusion. 
Chapter 1 Purpose and Need for the Proposed Action 

 1-16 

1 Michael Gordon stated his strong opposition to increasing CAFE standards, suggesting that 

2 CAFE standards should be controlled by consumer demand alone. Refer to Section 1.3 (Purpose and 

3 Need) of this EIS for a discussion of why CAFE standards must be increased. 

4 James Adcock suggested that due to the rapidly changing world and unknown future events, 

5 NHTSA should consider issuing standards fewer years at a time to allow itself flexibility to readdress fuel 

6 economy standards. Refer to Section 1.3 (Purpose and Need) of this EIS for a discussion of why the 

7 specific timescale implemented was chosen. He also suggested that NHTSA increase its fuel economy 

8 projections based on the leverage that the current Administration has to impress change upon automobile 

9 manufacturers. Refer to the NPRM for a discussion of the current vehicle market. 

10 Mr. Adcock stated that the Volpe Model source code and output results should be published so 

11 that the public can determine if any errors exist. NHTSA published the Volpe Model source code and 

12 output results. Refer to NHTSA’s website (www.nhtsa.gov) or the docket (NHTSA-2009-0059) for a 

13 publication of the Volpe Model source code and output results. 

14 Mr. Adcock contended that, contrary to the “footprint” model used by NHTSA, safety can be 

15 assured largely independent of fuel economy. He further highlighted techniques like sobriety checkpoints 

16 and enhanced traffic enforcement that can achieve safety improvements and help eliminate the perceived 

17 “size-based safety need” for large vehicles. Refer to Section 3.5.4 (Safety and Other Impacts to Human 

18 Health) of this EIS and Section IV.G.6 of the NPRM for MY 2012-2016 CAFE standards for a discussion 

19 of the safety impacts of the proposed action and alternatives. 

20 Mr. Adcock commented on a number of the assumptions used in the 2008 EIS. He recommended 

21 that NHTSA indicate what discount rate is being utilized and why. Regarding gas price estimates, Mr. 

22 Adcock suggested that NHTSA use futures markets for oil and gas and up-to-date prices rather than 

23 relying on EIA estimates of future gas prices. Mr. Adcock also stated that a backstop may be necessary to 

24 combat large fluctuations in fuel economy year to year due to changes in fuel costs and individuals 

25 involved in the auto market. Furthermore, he recommended that NHTSA consider the global costs of 

26 carbon dioxide externalities instead of just the domestic costs. Similarly, he claimed that NHTSA should 

27 assume that carbon dioxide reductions in the United States will be matched by carbon dioxide reductions 

28 in other nations. Refer to Sections 2.2.1 (Volpe Model), Section 2.2.3 (Technology Assumptions), and 

29 Section 2.2.4 (Economic Assumptions) of this EIS for a discussion of the Volpe Model and the 

30 technology and economic assumptions used in the model. 

31 Mr. Adcock also suggested that NHTSA allow an alternative certification path for vehicles in the 

32 U.S., accept European Community vehicle certification standards, and permit the importation of higher 

33 fuel efficiency European cars. The Vehicle Safety Act that mandates NHTSA set motor vehicle safety 

standards that are practicable, meet the need for motor vehicle safety, and are stated in objective terms.52 34 

35 NHTSA has done so. While NHTSA appreciates the commenter’s suggestion, it is unable, pursuant to its 

36 statutory authority, to accept imported vehicles that do not comply with applicable federal motor vehicle 

safety standards.53 37 NHTSA believes that the federal motor vehicle safety standards incorporate the 

38 appropriate balance between the codified statutory considerations and that adoption of the European 

39 Community standards would be in contravention of Congressional mandate. 

 

52 49 U.S.C. 30111. The Secretary has delegated authority for these standards to the National Highway Traffic 

Safety Administration (NHTSA). See 49 CFR 1.50. 53 See 49 U.S.C. 30112 (prohibiting the importation of vehicles that do not comply with applicable standards). 
Chapter 1 Purpose and Need for the Proposed Action 

 1-17 

1 Mr. Adcock also suggested that NHTSA change its current approach and consider use of a de2 powered "environmental" mode to increase fuel efficiency. He stated that NHTSA should also 

3 acknowledge that U.S. demand has shifted to smaller, more efficient vehicles. Refer to the NPRM for a 

4 discussion of the market demand for fuel efficient vehicles. 

5 1.5.3 Next Steps in the NEPA Process and CAFE Rulemaking 

6 This draft EIS is being published concurrently with the notice of Proposed Rulemaking to 

7 Establish Light-Duty Vehicle Greenhouse Gas Emission Standards and Corporate Average Fuel Economy 

8 Standards issued jointly by NHTSA and EPA. The draft EIS is being circulated for public review and 

9 will have a public comment period. Public hearings, where interested parties can present oral testimony, 

10 will be announced in the Federal Register and through NHTSA’s contact list for the EIS. Individuals 

11 may also submit their written comments, identified by the docket number, NHTSA-2009-0059, by any of 

12 the following methods: 

13  Federal eRulemaking Portal: Go to http://www.regulations.gov. Follow the instructions for 

14 submitting comments on the electronic docket site by clicking on “Help” or “FAQ.” 

15  Mail: Docket Management Facility, M-30, U.S. Department of Transportation, 1200 New 

16 Jersey Avenue SE, West Building, Ground Floor, Room W12-140, Washington, D.C. 20590. 

17  Hand Delivery: 1200 New Jersey Avenue SE, West Building Ground Floor, Room W12-140, 

18 between 9 a.m. and 5 p.m. Eastern Time, Monday through Friday, except federal holidays. 

19  Fax: 202-493-2251. 

20 The FEIS is expected to be released in early 2010. The FEIS will address comments received on 

21 the draft EIS. No sooner than 30 days after the availability of the FEIS is announced in the Federal 

22 Register by EPA, NHTSA will publish a final rulemaking by NHTSA and EPA and a Record of Decision. 

23 The Record of Decision will state and explain NHTSA’s decision. 
Chapter 1 Purpose and Need for the Proposed Action 

 1-18 

1 
2-1

1 Chapter 2 Proposed Action and Alternatives 

2 2.1 INTRODUCTION 

The National Environmental Policy Act1 3 (NEPA) requires an agency to compare the 

4 environmental impacts of its proposed action and alternatives. An agency must rigorously explore and 

5 objectively evaluate all reasonable alternatives, including a No Action Alternative. For alternatives an 

6 agency eliminates from detailed study, the agency must “briefly discuss the reasons for their having been 

eliminated.”2 7 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 8 

9 For this EIS, the National Highway Traffic Safety Administration (NHTSA) Proposed Action is 

10 to set passenger-car and light-truck Corporate Average Fuel Economy (CAFE) standards for model years 

11 (MY) 2012-2016 in accordance with the Energy Policy and Conservation Act (EPCA), as amended by the 

12 Energy Independence and Security Act (EISA). In developing the new proposed MY 2012-2016 CAFE 

13 standards and possible alternatives, NHTSA considered the four EPCA factors that guide the agency’s 

14 determination of “maximum feasible” standards: 

15 • Technological feasibility; 

16 • Economic practicability; 

17 • The effect of other standards of the Government on fuel economy; and 

• The need of the Nation to conserve energy.4 18 

In addition, NHTSA considered relevant environmental and safety factors. 5 19 For instance, 

20 NHTSA has placed monetary values on environmental externalities, including the benefits of reductions 

21 in carbon dioxide (CO2) emissions. The NEPA analysis presented in the Environmental Impact Statement 

22 (EIS) informs the agency’s action in setting CAFE standards. During the standard-setting process, 

23 NHTSA consults with the U.S. Department of Energy (DOE) and the Environmental Protection Agency 

24 (EPA) regarding a variety of matters as required by EPCA. NHTSA also is guided by President Obama’s 

25 memorandum to the U.S. Department of Transportation (DOT) on January 26, 2009, and the 

26 NHTSA/EPA Joint Rulemaking announced on May 19, 2009, as described in Chapter 1. 

27 2.2 STANDARDS-SETTING 

28 In developing the proposed MY 2012-16 standards, the agency developed and considered a wide 

29 variety of alternatives. NHTSA took a new approach to defining alternatives as compared to the most 

30 recent prior CAFE rulemaking. In the NOI, in response to comments received in the last round of 

31 rulemaking, NHTSA selected a range of candidate stringencies that increased annually, on average, 3 

32 percent to 7 percent. That same approach was carried over to this DEIS, to the NPRM, and to the 

 

1 42 United States Code (U.S.C.) § 4332(2)(C). NEPA is codified at 42 U.S.C. § 4321, et seq. 2 40 Code of Federal Regulations (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 FR 24352, 24364 (May 2, 2008). 
Chapter 2 Proposed Action and Alternatives 

 2-2 

1 accompanying PRIA. The majority of the alternatives considered by the agency are defined as average 

2 percentage increases in stringency – 3 percent per year, 4 percent per year, 5 percent per year, and so on. 

3 NHTSA believes that this approach more clearly communicates the level of stringency of each alternative 

4 and is more intuitive than alternatives defined in terms of different cost-benefit ratios, and still allows us 

5 to identify alternatives that represent different ways to balance NHTSA’s statutory requirements under 

6 EPCA/EISA. 

7 In the NOI, we noted that each of the listed alternatives represents, in part, a different way in 

8 which NHTSA could conceivably balance conflicting policies and considerations in setting the standards. 

9 We were mindful that the agency would need to weigh and balance many factors, such as the 

10 technological feasibility, economic practicability, including lead-time considerations for the introduction 

11 of technologies and impacts on the auto industry, the impacts of the standards on fuel savings and CO2

12 emissions, fuel savings by consumers; as well as other relevant factors such as safety. For example, the 

13 7-Percent Alternative, the most stringent alternative, weighs energy conservation and climate change 

14 considerations more heavily and technological feasibility and economic practicability less heavily. In 

15 contrast, the 3-Percent Alternative, the least stringent alternative, places more weight on technological 

16 feasibility and economic practicability. We recognized that the “feasibility” of the alternatives also may 

17 reflect differences and uncertainties in the way in which key economic (e.g., the price of fuel and the 

18 social cost of carbon) and technological inputs could be assessed and estimated or valued. 

19 After working with EPA in thoroughly reviewing and in some cases reassessing the effectiveness 

20 and costs of technologies, most of which are already being incorporated in at least some vehicles, market 

21 forecasts and economic assumptions, we used the Volpe model extensively to assess the technologies that 

22 the manufacturers could apply in order to comply with each of the alternatives. This permitted us to 

23 assess the variety, amount and cost of the technologies that could be needed to enable the manufacturers 

24 to comply with each of the alternatives. NHTSA estimated how the application of these and other 

25 technologies could increase vehicle costs. The following sections describe the Volpe model and the 

26 inputs to the Volpe model, to help the reader gain an overview of the analytical pieces and tools used in 

27 the agency’s analysis of alternatives. 

28 2.2.1 Volpe Model 

29 Since 2002, NHTSA has employed, as part of its analysis, a modeling system developed 

30 specifically to assist NHTSA with applying technologies to thousands of vehicles and developing 

31 estimates of the costs and benefits of potential CAFE standards. The CAFE Compliance and Effects 

32 Modeling System, developed by the DOT Volpe National Transportation Systems Center and commonly 

33 referred to as “the Volpe model,” enables the agency to efficiently, systematically, and reproducibly 

34 evaluate many more regulatory options, including attribute-based CAFE standards required by EISA, than 

35 were previously possible, and to do so much more quickly. Generally speaking, the model assumes that 

36 manufacturers apply the most cost-effective technologies first, and as more stringent fuel economy 

37 standards are evaluated, the model recognizes that manufacturers must apply less cost-effective 

38 technologies. The model then compares the discounted present value of costs and benefits for any 

39 specific CAFE standard. 

40 Model documentation, publicly available in the rulemaking docket and on NHTSA’s website, 

41 explains how the model is installed, how the model inputs and outputs are structured, and how the model 

42 is used. The model can be used on any Windows-based personal computer with Microsoft Office 2003 

43 and the Microsoft .NET framework installed (the latter available without charge from Microsoft). The 

44 executable version of the model, with all of its codes and accompanying demonstration files, is also 

45 available on NHTSA’s website for public download. The current version of the model was developed 
 Chapter 2 Proposed Action and Alternatives 

 2-3 

using Microsoft Development Environment 2003, and every line of computer code (primarily in C# 1 .NET) 

2 has been made available to individuals who have requested the code. 

3 The Volpe model requires the following types of input information: (1) a forecast of the future 

4 vehicle market; (2) estimates of the availability, applicability, and incremental effectiveness and cost of 

5 fuel-saving technologies; (3) estimates of vehicle survival and mileage accumulation patterns, the 

6 rebound effect, future fuel prices, the “social cost of carbon,” and many other economic factors; (4) fuel 

7 characteristics and vehicular emissions rates; and (5) coefficients defining the shape and level of CAFE 

8 curves to be examined. The model is a tool that the agency uses for analysis: it makes no a priori

9 assumptions regarding inputs such as fuel prices and available technology, and does not dictate the form 

10 or stringency of the CAFE standards to be examined. The agency makes those selections based on the 

11 best available information and data. 

12 Using inputs selected by the agency, NHTSA projects a set of technologies each manufacturer 

13 could apply in attempting to comply with the various levels of potential CAFE standards to be examined. 

14 The model then estimates the costs associated with this additional technology utilization, as well as 

15 accompanying changes in travel demand, fuel consumption, fuel outlays, emissions, and economic 

16 externalities related to petroleum consumption and other factors. 

17 Normally, the Volpe model uses technologies available on vehicles in the current year. For 

18 example, when modeling MY 2014, only vehicles with technologies “enabled” in MY 2014 would be 

19 candidates for technology application. One of the updates to the model for the current rulemaking is the 

20 addition of a “multi-year planning” capability, developed in response to comments to prior CAFE 

21 rulemakings. When run in multi-year mode, the model is allowed to “look back” to earlier years when a 

22 technology was enabled on any vehicles but not used, and consider “back-dating” the application of that 

23 technology when calculating the effective cost. Thus, if the model did not apply an enabled technology in 

24 either MY 2012 or MY 2013, then that technology remains available for multi-year application in MY 

25 2014. Multi-year mode is anticipated to be most useful in situations where the model finds that a 

26 manufacturer is able to reach compliance in earlier years of the modeling period (e.g., MY 2012) but is 

27 challenged to reach compliance in later years (e.g., MY 2014). In these cases, the model can go back to 

28 the earlier year and over-comply in order to make compliance in the later year easier to achieve. 

29 Recognizing the uncertainty inherent in many of the underlying estimates in the model, NHTSA 

30 has used the Volpe model to conduct both sensitivity analyses, by changing one factor at a time, and a 

31 probabilistic uncertainty analysis (a Monte Carlo analysis that allows simultaneous variation in these 

32 factors) to examine how key measures (e.g., mpg levels of the standard, total costs, and total benefits) 

33 vary in response to change in these factors. This type of analysis is used to estimate the uncertainty of the 

34 costs and benefits of a given set of CAFE standards. 

35 The model can also be used to fit coefficients defining an attribute-based standard, and to 

36 estimate the stringency that (a) generates a specified average required CAFE level, (b) maximizes net 

37 benefits to society, (c) achieves a specified stringency at which total costs equal total benefits, or (d) 

38 results in a specified total incremental cost, etc. The agency uses this information from the Volpe model 

39 as a tool to assist in setting standards. For additional discussions of the Volpe model and its inputs, see 

40 the accompanying Notice of Proposed Rulemaking (NPRM) for MY 2012-2016 CAFE standards 

41 (included in the docket for this DEIS), NHTSA’s Preliminary Regulatory Impact Analysis (PRIA) (see

42 Appendix D), and the NHTSA-U.S. Environmental Protection Agency (EPA) joint technical support 

43 document (included in the docket for this DEIS). 

44 Although NHTSA has used the Volpe model as a tool to inform its consideration of potential 

45 CAFE standards, the Volpe model, alone, does not determine the CAFE standards NHTSA will propose 
Chapter 2 Proposed Action and Alternatives 

 2-4 

1 or promulgate as final regulations. NHTSA considers the results of analyses conducted using the Volpe 

2 model and external analyses, including assessments of greenhouse gases and air pollution emissions, and 

3 technologies that may be available in the long term. NHTSA also considers whether the standards could 

4 expedite the introduction of new technologies into the market, and the extent to which changes in vehicle 

5 prices and fuel economy might affect vehicle production and sales. Using all of this information, the 

6 agency considers the governing statutory factors, along with environmental issues and other relevant 

7 societal issues, such as safety, and promulgates the maximum feasible standards based on its best 

8 judgment on how to balance these factors. 

9 2.2.2 Vehicle Market Forecast 

10 To determine what levels of stringency are feasible in future model years, the agencies must 

11 project what vehicles and technologies will exist in those model years, and then evaluate what 

12 technologies can feasibly be applied to those vehicles to raise their fuel economy and lower their CO2

13 emissions. The agencies, therefore, establish a baseline vehicle fleet representing those vehicles, based on 

14 the best available information and a reasonable balancing of various policy concerns, against which they 

15 can analyze potential future levels of stringency and their costs and benefits. 

16 NHTSA has historically based its analysis of potential new CAFE standards on detailed product 

17 plans the agency has requested from manufacturers planning to produce light vehicles for sale in the 

18 United States. For this rulemaking, and as explained in the Technical Support Document (TSD) prepared 

19 jointly by NHTSA and EPA, both agencies used a baseline vehicle fleet constructed beginning with 

20 CAFE certification data for the 2008 model year, the most recent for which final data is currently 

21 available from manufacturers. This data was used as the source for MY 2008 production volumes and 

22 some vehicle engineering characteristics, such fuel economy ratings, engine sizes, numbers of cylinders, 

23 and transmission types. 

24 Some information important for analyzing new CAFE standards is not contained in the CAFE 

25 certification data. EPA staff, in consultation with NHTSA staff, estimated vehicle wheelbase and track 

26 widths using data from Motortrend.com and Edmunds.com. This information is necessary for estimating 

27 vehicle footprint, which is required for the analysis of footprint-based standards. Considerable additional 

28 information regarding vehicle engineering characteristics is also important for estimating the potential to 

29 add new technologies in response to new CAFE standards. In general, such information helps to avoid 

30 “adding” technologies to vehicles that already have the same or a more advanced technology. Examples 

31 include valvetrain configuration (e.g., overhead valve configuration [OHV], single overhead cam 

32 [SOHC], double overhead cam [DOHC]), presence of cylinder deactivation, and fuel delivery (e.g., 

33 stoichiometric gasoline direct injection [SGDI]). To the extent that such engineering characteristics were 

34 not available in certification data, EPA staff relied on data published by Ward’s Automotive, 

35 supplementing this with information from internet sites such as Motortrend.com and Edmunds.com. 

36 NHTSA staff also added some more detailed engineering characteristics (e.g., type of variable valve 

37 timing) using data available from ALLDATA® Online. Combined with the certification data, all of this 

38 information yielded a MY 2008 baseline vehicle fleet. 

39 After the baseline was created the next step was to project the sales volumes for 2011-2016 model 

40 years. The agencies used projected-car and truck-volumes for this period from the Energy Information 

Administration (EIA) 2009 Annual Energy Outlook (AEO) (EIA 2009).6 41 However, AEO projects sales 

 

6

 The agencies have also used fuel price forecasts from AEO 2009. Both agencies regard AEO a credible source not 

only of such forecasts, but also of many underlying forecasts, including forecasts of the size the future light vehicle 

market. 
 Chapter 2 Proposed Action and Alternatives 

 2-5 

1 only at the car and truck level, not at the manufacturer and model-specific level, which are needed in 

2 order to estimate the effects new standards will have on individual manufacturers. Therefore, EPA 

3 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 4 This provided the year-by5 year percentages of cars and trucks sold by each manufacturer as well as the percentages of each vehicle 

6 segment. Although it was, therefore, necessary to assume the same manufacturer and segment shares in 

7 2016 as in 2015, 2016 estimates from CSM should be available for the final rule. Using these 

8 percentages normalized to the AEO projected volumes then provided the manufacturer-specific market 

9 share and model-specific sales for model years 2011-2016. 

10 The processes for constructing the MY 2008 baseline vehicle fleet and subsequently adjusting 

11 sales volumes to construct the MY 2011-2016 baseline vehicle fleet are presented in detail in the 

12 Technical Support Document. For a detailed discussion of this issue, see Chapter 1 of the TSD prepared 

13 jointly by NHTSA and EPA. For a detailed discussion of NHTSA’s historical prior product plan 

14 approach and the current baseline vehicle fleet approach used by NHTSA and EPA for this rulemaking, 

15 including, but not limited to, the differences, advantages and disadvantages between the two approaches, 

16 see Section II.B.3 of the NPRM.

17 2.2.3 Technology Assumptions 

18 The analysis of costs and benefits employed in the Volpe model reflects NHTSA’s assessment of 

19 a broad range of technologies that can be applied to passenger cars and light trucks. In the agency’s 

20 rulemakings covering light truck CAFE standards for MY 2005-2007 and MY 2008-2011, the agency 

21 relied on the 2002 National Academy of Sciences’ report Effectiveness and Impact of Corporate Average 

22 Fuel Economy Standards for estimating potential fuel economy benefits and associated retail costs of 

23 applying combinations of technologies (NRC 2002). In developing its final rule adopting CAFE 

24 standards for MY 2011, NHTSA reviewed manufacturers’ technology data and comments it received on 

25 its fuel saving technologies, and conducted its own independent analysis which involved hiring an 

26 international engineering consulting firm that specializes in automotive engineering, and that was used by 

27 EPA in developing its advance NPRM to regulate greenhouse gas emissions under the Clean Air Act 

(CAA).8 28 

29 In the MY 2011 CAFE final rule, as requested by the President in his January 2009 

30 memorandum, NHTSA also stated that it would continue to review these technology assumptions and the 

31 methodologies used to derive the costs and effectiveness values, in order to improve its assumptions. For 

32 the MY 2012-2016 rulemaking, NHTSA worked with EPA to revise and update a common list of fuel33 saving technology cost and effectiveness numbers. EPA is also using this list of fuel-saving technologies 

34 in its model for development of proposed CO2 standards in the joint NPRM. The revised technology 

35 assumptions – that is, estimates of the availability, applicability, cost, and effectiveness of fuel-saving 

36 technologies, and the order in which the technologies are applied – are described in greater detail in the 

37 NHTSA-EPA joint technical support document (available in the docket for this DEIS) and in NHTSA’s 

38 Regulatory Impact Analysis (RIA) (see Appendix D). 

 

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 

 2-6 

1 The technologies considered by the model are briefly described below, under the five broad 

2 categories of engine, transmission, vehicle, electrification/accessory, and hybrid technologies. 

3 Types of engine technologies that were considered under the benefit-cost analysis include the 

4 following:

5 • Low-friction lubricants – low viscosity and advanced low friction lubricants oils are now 

6 available with improved performance and better lubrication. 

7 • Reduction of engine friction losses – can be achieved through low-tension piston rings, roller 

8 cam followers, improved material coatings, more optimal thermal management, piston 

9 surface treatments, and other improvements in the design of engine components and 

10 subsystems that improve engine operation. 

11 • Conversion to dual overhead cam with dual cam phasing – as applied to overhead valves 

12 designed to increase the air flow with more than two valves per cylinder and reduce pumping 

13 losses.

14 • Cylinder deactivation – deactivates the intake and exhaust valves and prevents fuel injection 

15 into some cylinders during light-load operation. The engine runs temporarily as though it 

16 were a smaller engine, which substantially reduces pumping losses.

17 • Variable valve timing – alters the timing of the intake valve, exhaust valve, or both, primarily 

18 to reduce pumping losses, increase specific power, and control residual gases.

19 • Discrete variable valve lift – increases efficiency by optimizing air flow over a broader range 

20 of engine operation, which reduces pumping losses. Accomplished by controlled switching 

21 between two or more cam profile lobe heights. 

22 • Continuous variable valve lift – is an electromechanically controlled system in which valve 

23 timing is changed as lift height is controlled. This yields a wide range of performance 

24 optimization and volumetric efficiency, including enabling the engine to be valve throttled. 

25 • Stoichiometric gasoline direct-injection technology – injects fuel at high pressure directly into 

26 the combustion chamber to improve cooling of the air/fuel charge within the cylinder, which 

27 allows for higher compression ratios and increased thermodynamic efficiency. 

28 • Combustion restart – can be used in conjunction with gasoline direct-injection systems to 

29 enable idle-off or start-stop functionality. Similar to other start-stop technologies, additional 

30 enablers, such as electric power steering, accessory drive components, and auxiliary oil 

31 pump, might be required. 

32 • Turbocharging and downsizing – increases the available airflow and specific power level, 

33 allowing a reduced engine size while maintaining performance. This reduces pumping losses 

34 at lighter loads in comparison to a larger engine.

35 • Exhaust-gas recirculation boost – increases the exhaust-gas recirculation used in the 

36 combustion process to increase thermal efficiency and reduce pumping losses. 

37 • Diesel engines – have several characteristics that give superior fuel efficiency, including 

38 reduced pumping losses due to lack of (or greatly reduced) throttling, and a combustion cycle 
 Chapter 2 Proposed Action and Alternatives 

 2-7 

1 that operates at a higher compression ratio, with a very lean air/fuel mixture, relative to an 

2 equivalent-performance gasoline engine. This technology requires additional enablers, such 

3 as NOx trap catalyst after-treatment or selective catalytic reduction NOx after-treatment.

4 Types of transmission technologies considered include: 

5 • Improved automatic transmission controls – optimizes shift schedule to maximize fuel 

6 efficiency under wide ranging conditions, and minimizes losses associated with torque 

7 converter slip through lock-up or modulation. 

8 • Six-, seven-, and eight-speed automatic transmissions – the gear ratio spacing and 

9 transmission ratio are optimized for a broader range of engine operating conditions. 

10 • Dual clutch or automated shift manual transmissions – are similar to manual transmissions, 

11 but the vehicle controls shifting and launch functions. A dual-clutch automated shift manual 

12 transmission uses separate clutches for even-numbered and odd-numbered gears, so the next 

13 expected gear is pre-selected, which allows for faster and smoother shifting.

14 • Continuously variable transmission – commonly uses V-shaped pulleys connected by a metal 

15 belt rather than gears to provide ratios for operation. Unlike manual and automatic 

16 transmissions with fixed transmission ratios, continuously variable transmissions can provide 

17 fully variable transmission ratios with an infinite number of gears, enabling finer optimization 

18 of transmission torque multiplication under different operating conditions so that the engine 

19 can operate at higher efficiency. 

20 • Manual 6-speed transmission –offers an additional gear ratio, often with a higher overdrive 

21 gear ratio, than a 5-speed manual transmission. 

22 Types of vehicle technologies considered include: 

23 • Low-rolling-resistance tires – have characteristics that reduce frictional losses associated 

24 with the energy dissipated in the deformation of the tires under load, therefore improving fuel 

25 economy and reducing CO2 emissions. 

26 • Low-drag brakes – reduce the sliding friction of disc brake pads on rotors when the brakes 

27 are not engaged because the brake pads are pulled away from the rotors. 

28 • Front or secondary axle disconnect for four-wheel drive systems – provides a torque 

29 distribution disconnect between front and rear axles when torque is not required for the non30 driving axle. This results in the reduction of associated parasitic energy losses. 

31 • Aerodynamic drag reduction – is achieved by changing vehicle shape or reducing frontal 

32 area, including skirts, air dams, underbody covers, and more aerodynamic side view mirrors. 

33 • Mass reduction and material substitution – Mass reduction encompasses a variety of 

34 techniques ranging from improved design and better component integration to application of 

35 lighter and higher-strength materials. Mass reduction is further compounded by reductions in 

36 engine power and ancillary systems (transmission, steering, brakes, suspension, etc.).
Chapter 2 Proposed Action and Alternatives 

 2-8 

1 Types of electrification/accessory and hybrid technologies considered include: 

2 • Electric power steering (EPS) – is an electrically assisted steering system that has advantages 

3 over traditional hydraulic power steering because it replaces a continuously operated 

4 hydraulic pump, thereby reducing parasitic losses from the accessory drive.

5 • Improved accessories (IACC) – may include high efficiency alternators, electrically driven 

6 (i.e., on-demand) water pumps and cooling fans. This excludes other electrical accessories 

7 such as electric oil pumps and electrically driven air conditioner compressors.

8 • Air Conditioner Systems – These technologies include improved hoses, connectors and seals 

9 for leakage control. They also include improved compressors, expansion valves, heat 

10 exchangers and the control of these components for the purposes of improving tailpipe CO2

11 emissions as a result of air conditioning use. These technologies are covered separately in 

12 the EPA RIA. 

13 • 12-volt micro-hybrid (MHEV) – also known as idle-stop or start stop and commonly 

14 implemented as a 12-volt belt-driven integrated starter-generator, this is the most basic hybrid 

15 system that facilitates idle-stop capability. Along with other enablers, this system replaces a 

16 common alternator with a belt-driven enhanced power starter-alternator, and a revised 

17 accessory drive system.

18 • Higher Voltage Stop-Start/Belt Integrated Starter Generator (BISG) – provides idle-stop 

19 capability and uses a high voltage battery with increased energy capacity over typical 

20 automotive batteries. The higher system voltage allows the use of a smaller, more powerful 

21 electric motor. This system replaces a standard alternator with an enhanced power, higher 

22 voltage, higher efficiency starter-alternator, that is belt driven and that can recover braking 

23 energy while the vehicle slows down (regenerative braking).

24 • Integrated Motor Assist (IMA)/Crank integrated starter generator (CISG)– provides idle-stop 

25 capability and uses a high voltage battery with increased energy capacity over typical 

26 automotive batteries. The higher system voltage allows the use of a smaller, more powerful 

27 electric motor and reduces the weight of the wiring harness. This system replaces a standard 

28 alternator with an enhanced power, higher voltage, higher efficiency starter-alternator that is 

29 crankshaft mounted and can recover braking energy while the vehicle slows down 

30 (regenerative braking). 

31 • 2-mode hybrid (2MHEV) – is a hybrid electric drive system that uses an adaptation of a 

32 conventional stepped-ratio automatic transmission by replacing some of the transmission 

33 clutches with two electric motors that control the ratio of engine speed to vehicle speed, while 

34 clutches allow the motors to be bypassed. This improves both the transmission torque 

35 capacity for heavy-duty applications and reduces fuel consumption and CO2 emissions at 

36 highway speeds relative to other types of hybrid electric drive systems.

37 • Power-split hybrid (PSHEV)–a hybrid electric drive system that replaces the traditional 

38 transmission with a single planetary gearset and a motor/generator. This motor/generator 

39 uses the engine to either charge the battery or supply additional power to the drive motor. A 

40 second, more powerful motor/generator is permanently connected to the vehicle’s final drive 

41 and always turns with the wheels. The planetary gear splits engine power between the first 

42 motor/generator and the drive motor to either charge the battery or supply power to the 

43 wheels.
 Chapter 2 Proposed Action and Alternatives 

 2-9 

1 • Plug-in hybrid electric vehicles (PHEV) – are hybrid electric vehicles with the means to 

2 charge their battery packs from an outside source of electricity (usually the electric grid). 

3 These vehicles have larger battery packs with more energy storage and a greater capability to 

4 be discharged. They also use a control system that allows the battery pack to be substantially 

5 depleted under electric-only or blended mechanical/electric operation.

6 • Electric vehicles (EV) – are vehicles with all-electric drive and with vehicle systems powered 

7 by energy-optimized batteries charged primarily from grid electricity. 

8 2.2.4 Economic Assumptions 

9 The NHTSA analysis of the energy savings, emission reductions, and environmental impacts 

10 likely to result from alternative CAFE standards relies on a range of forecast, economic assumptions, and 

11 estimates of parameters used by the Volpe CAFE model. These proposed economic values play a 

12 significant role in determining the reductions in fuel consumption, changes in emissions of criteria air 

13 pollutants and GHGs, and economic benefits of alternative increases in CAFE standards. Under 

14 alternatives where standards would be established, in part, by reference to their costs and benefits (i.e., the 

15 Maximum Net Benefits Alternative, and the Total Cost Equals Total Benefit Alternative), these economic 

16 values also affect the levels of the CAFE standards themselves. 

17 The economic assumptions information includes the following: 

18 • Forecasts of sales of passenger cars and light trucks for MY 2012-2016. 

19 • Assumptions about the fraction of these vehicles that remain in service at different ages and 

20 how rapidly their use declines with increasing age. 

21 • Forecasts of fuel prices over the expected lifetimes of MY 2012-2016 passenger cars and 

22 light trucks. 

23 • Forecasts of expected future growth in total passenger-car and light-truck use, including 

24 vehicles of all model years comprising the U.S. vehicle fleet. 

25 • The size of the gap between test and actual on-road fuel economy. 

26 • The magnitude of the fuel economy rebound effect, or the increase in vehicle use that results 

27 from improved fuel economy. 

28 • Economic costs associated with U.S. consumption and imports of petroleum and refined 

29 petroleum products, over and above their market prices. 

30 • Changes in emissions of criteria air pollutants and GHGs that result from saving each gallon 

31 of fuel and from each added mile of driving. 

32 • The economic values of reductions in emissions of each criteria air pollutant and GHGs. 

33 • The value of increased driving range and less frequent refueling that results from increases in 

34 fuel economy. 
Chapter 2 Proposed Action and Alternatives 

 2-10 

1 • The costs of increased congestion, traffic accidents, and noise caused by added passenger-car 

2 and light-truck use. 

3 • The discount rate applied to future benefits. 

4 Table 2.2-1 presents many of the specific forecasts, assumptions, and parameter values used to 

5 calculate the energy savings, environmental impacts, and economic benefits of each alternative. Detailed 

6 descriptions of the proposed sources of forecast information, the rationale underlying each economic 

7 assumption, and the agency’s preliminary choices of specific parameter values are presented in Section 

8 IV.C.3 of the NPRM and Chapter VIII of NHTSA’s Preliminary Regulatory Impact Assessment 

9 accompanying this DEIS, as well as in Chapter IV of the joint EPA-NHTSA Technical Support 

10 Document for fuel economy and motor vehicle CO2 emission standards. 

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 1.1%

Fuel Prices (2012-50 average, $/gallon) 

Retail gasoline price $ 3.77

Pre-tax gasoline price $ 3.40

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) and CO2 equivalents of other GHGs $5,10,20,34,56

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

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%, 7%

11 

12 NHTSA’s main analysis of energy use and emissions resulting from alternative CAFE standards 

13 uses the forecasts, assumptions, and parameters reported in Table 2.2-1. The agency also analyzed the 

14 sensitivity of its estimates when using plausible variations in the values of many of these variables. The 
 Chapter 2 Proposed Action and Alternatives 

 2-11 

1 specific alternative values of these variables that were used in the agency’s sensitivity analysis and their 

2 effects on its estimates of fuel consumption and GHG emissions are reported and discussed in Section 2.4 

3 of this EIS. 

4 2.3 ALTERNATIVES 

5 EPCA, as amended by EISA, requires NHTSA to adopt attribute-based fuel economy standards 

6 for passenger cars and light trucks. NHTSA first employed this approach (then called “Reformed 

CAFE”) in establishing standards for MY 2008-2011 light trucks.9 7 In May 2008, NHTSA proposed 

separate standards for MY 2011-2015 passenger cars and light trucks, again using this approach.10 8 On 

9 March 30, 2009, NHTSA issued a final rule for MY 2011 passenger cars and light trucks, again using this 

approach.11 10 

11 Under the standards, fuel economy targets are established for vehicles of different sizes. Each 

12 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 13 The fuel economy 

14 target for each footprint reflects the technological and economic capabilities of the industry. These 

15 targets are the same for all manufacturers, regardless of the differences in their overall fleet mix. 

16 Compliance is determined by comparing a manufacturer’s harmonically averaged fleet fuel economy 

17 levels in a model year with an average required fuel economy level calculated using the manufacturer’s 

18 actual production levels and the targets for each footprint of the vehicles that it produces. 

19 A large number of alternatives can be defined along a continuum from the least to the most 

20 stringent levels of potential CAFE standards. The specific alternatives NHTSA examined, described 

21 below, encompass a reasonable range to evaluate the potential environmental impacts of the CAFE 

22 standards and alternatives under NEPA, in view of EPCA requirements. 

23 At one end of this range is the No Action Alternative (Alternative 1), which assumes no action 

24 would occur under the National Program. Under that alternative, neither NHTSA nor EPA would issue a 

25 rule regarding the CAFE standard or GHG emissions for MY 2012-2016. The No Action Alternative 

26 assumes that average fuel economy levels in the absence of CAFE standards beyond MY 2011 would 

27 equal the higher of the agencies’ collective market forecast or the manufacturer’s required level of 

28 average fuel economy for MY 2011. The MY 2011 fuel economy level represents the standard NHTSA 

29 believes manufacturers would continue to abide by, assuming NHTSA does not issue a rule. Costs and 

30 benefits of other alternatives are calculated relative to the baseline of the No Action Alternative. The No 

31 Action Alternative, by definition, would yield no incremental costs or benefits (and thus it would not 

32 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 that 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. 
Chapter 2 Proposed Action and Alternatives 

 2-12 

1 fuel economy of at least 35 mpg for MY 2020; nor would it satisfy the EPCA requirement to adopt annual 

fuel economy standard increases).13 2 

3 NHTSA is also proposing to consider eight action alternatives. Alternative 2 (3-Percent 

4 Alternative), Alternative 3 (4-Percent Alternative), Alternative 5 (5-Percent Alternative), Alternative 7 (6-

5 Percent Alternative), and Alternative 8 (7-Percent Alternative), require the average fuel economy for the 

6 industry-wide combined passenger-car and light-truck fleet to increase, on average, by a specified 

7 percentage for each model year from 2012-2016. Because the percentage increases in stringency are 

8 “average” increases, they may either be constant throughout the period or may vary from year to year. 

9 For a variety of reasons, the annual rates of increase in achieved mpg levels for passenger cars and light 

10 trucks separately will not exactly equal the rates of increase in combined passenger-car and light-truck 

11 required average mpg levels under each alternative. These include the fact that under some alternatives, 

12 separate required mpg levels for passenger cars and light trucks might not necessarily increase at annual 

13 rates that are identical to those for the combined standard. 

14 NHTSA also added three alternatives to the list of alternatives first proposed in the NOI – the 

15 agency’s Preferred Alternative (Alternative 4), an alternative that maximizes net benefits (MNB) 

16 (Alternative 6), and an alternative under which total cost equals total benefit (TCTB) (Alternative 9). The 

17 agency’s Preferred Alternative represents the required fuel economy level that we have tentatively 

18 determined to be maximum feasible under EPCA, based on our balancing of statutory considerations. See 

19 Section 2.1. The other two alternatives, MNB and TCTB, represent fuel economy levels that are 

20 dependent on the agency’s best estimate of relevant economic variables (e.g., gasoline prices, social cost 

21 of carbon, the discount rate, and rebound effect). See Section 2.2.4. The MNB Alternative and TCTB 

22 Alternative provide the decisionmaker and the public with useful information about where the standards 

23 would be set if costs and benefits were balanced in two different ways. All three alternatives (Preferred 

24 Alternative, MNB Alternative, and TCTB Alternative) are placed in context by identifying 

25 the approximate, on average annual percentage fuel economy increase, so that the public is able to see 

26 where they fall on the continuum of alternatives. 

27 Each of the alternatives considered by NHTSA represent, in part, a different way in which 

28 NHTSA conceivably could weigh EPCA’s statutory requirements and account for NEPA’s policies. For 

29 example, the 7-Percent Alternative weighs energy conservation and climate change considerations more 

30 heavily and technological feasibility and economic practicability less heavily. In contrast, the 3-Percent 

31 Alternative, the least stringent action alternative evaluated here, places more weight on technological 

32 feasibility and economic practicability. The “feasibility” of the alternatives also may reflect differences 

33 and uncertainties in the way in which key economic (e.g., the price of fuel and the social cost of carbon) 

34 and technological inputs could be assessed and estimated or valued. For additional detail and discussion 

35 of how NHTSA considers the EPCA statutory and other factors that guide the agency’s determination of 

36 “maximum feasible” standards, and inform an evaluation of the alternatives, we refer the reader to section 

37 IV.F of the NPRM. For detailed calculations and discussions of manufacturer cost impacts and estimated 

38 benefits for each of the alternatives, see Sections VII and VIII of NHTSA’s PRIA. 

 

13 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 

 2-13 

1 2.3.1 Alternative 1: No Action 

2 The No Action Alternative assumes that no action would occur under CAFE (or under the 

3 National Program). Under this alternative, NHTSA would not issue a rule regarding CAFE standards for 

4 MY 2012-2016. As explained above, the No Action Alternative assumes that average fuel economy 

5 levels in the absence of CAFE standards beyond MY 2011 would equal the higher of the agencies’ 

6 collective market forecast or the manufacturer’s required level of average fuel economy for MY 2011. 

7 The No Action MY 2016 achieved mpg forecast represents the market forecast for mpg, assuming that 

NHTSA does not issue a rule.14 8 

NEPA requires agencies to consider a No Action Alternative in their NEPA analyses,15 9 although 

10 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. 16 11 In the NPRM, NHTSA refers to the No Action Alternative as the no 

12 increase or baseline alternative. 

13 2.3.2 Alternative 2: 3-Percent Alternative 

14 The 3-Percent Alternative requires a 3-percent average annual increase in mpg, resulting in a 

15 required MY 2016 fleetwide 35.6 mpg for passenger cars and 26.6 mpg for light trucks. The 3-Percent 

16 Alternative also results in a combined required fleetwide 32.0 mpg in MY 2016. 

17 2.3.3 Alternative 3: 4-Percent Alternative 

18 The 4-Percent Alternative requires a 4-percent average annual increase in mpg, resulting in a 

19 required MY 2016 fleetwide 37.4 mpg for passenger cars and 27.9 mpg for light trucks. The 4-Percent 

20 Alternative also results in a combined required fleetwide 33.6 mpg in MY 2016. 

21 2.3.4 Alternative 4: Preferred Alternative 

22 The Preferred Alternative requires approximately a 4.3-percent average annual increase in mpg, 

23 resulting in an estimated required MY 2016 fleetwide 38.0 mpg for passenger cars and 28.3 mpg for light 

24 trucks. The Preferred Alternative also results in a combined estimated required fleetwide 34.1 mpg in 

25 MY 2016. The agency’s Preferred Alternative represents the required fuel economy level that we have 

26 tentatively determined to be the maximum feasible under EPCA, based on our balancing of statutory 

27 considerations. A full discussion regarding the agency’s tentative conclusion that Alternative 4 represents 

28 the “maximum feasible” average fuel economy level that the Secretary decides the manufacturers can 

29 achieve, considering the statutory and other relevant factors and is therefore the agency’s Preferred 

30 Alternative can be found in Section IV.F of the joint preamble of Notice of Proposed Rulemaking. 

31 

32 This alternative, along with EPA’s proposed standards, form the National Program and are 

33 consistent with the National Fuel Efficiency Policy announced by President Obama on May 19, 2009. 

34 Under the National Program, the overall light-duty vehicle fleet would reach 35.5 mpg in MY 2016, if all 

35 reductions were made through fuel economy improvements. 

36 

 

14 See 40 CFR §§ 1502.2(e) and 1502.14(d). 15 See 40 CFR § 1502.14(d). 16 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 

1 2.3.5 Alternative 5: 5-Percent Alternative 

2 The 5-Percent Alternative requires a 5-percent average annual increase in mpg, resulting in a 

3 required MY 2016 fleetwide 39.3 mpg for passenger cars and 29.3 mpg for light trucks. The 5-Percent 

4 Alternative also results in a required achieved fleetwide 35.2 mpg in MY 2016. 

5 2.3.6 Alternative 6: MNB Alternative 

6 In the MNB Alternative, the Volpe model applies technologies to the vehicle market forecast 

7 until marginal benefits are estimated to equal marginal costs and net benefits are maximized. In this case, 

8 the model continues to include technologies until the marginal cost of adding the next technology exceeds 

9 the marginal benefit. This alternative requires approximately a 5.9-percent average annual increase in 

10 mpg, resulting in a required MY 2016 fleetwide 40.9 mpg for passenger cars and 30.6 mpg for light 

11 trucks. The MNB Alternative also results in a combined required fleetwide 36.8 mpg in MY 2016. 

12 2.3.7 Alternative 7: 6-Percent Alternative 

13 The 6-Percent Alternative requires a 6-percent average annual increase in mpg, resulting in a 

14 required MY 2016 fleetwide 41.1 mpg for passenger cars and 30.7 mpg for light trucks. The 6-Percent 

15 Alternative also results in a combined required fleetwide 36.9 mpg in MY 2016. 

16 The 6-Percent Alternative results in required mpg in 2016 that is slightly higher than required 

17 mpg under the MNB Alternative, but required mpg in 2012 through 2015 under the 6-percent Alternative 

18 is actually slightly lower than under the MNB Alternative. In general, the net result is that there is very 

19 little substantive difference in required mpg under the 6-percent and MNB Alternatives. 

20 2.3.8 Alternative 8: 7-Percent Alternative 

21 The 7-Percent Alternative requires a 7-percent average annual increase, resulting in a required 

22 MY 2016 fleetwide 43.1 mpg for passenger cars and 32.2 mpg for light trucks. The 7-Percent Alternative 

23 also results in a combined required fleetwide 38.7 mpg in MY 2016. 

24 2.3.9 Alternative 9: TCTB Alternative 

25 In the TCTB Alternative, the Volpe model applies technologies to the vehicle market forecast 

26 until total costs equal total benefits. In this case, the model increases the standard to a point where 

27 essentially total costs of the technologies added together over the baseline equals total benefits added over 

28 the baseline. This alternative requires approximately a 6.7-percent on average annual increase in mpg, 

29 resulting in a required MY 2016 fleetwide 42.7 mpg for passenger cars and 31.5 mpg for light trucks. 

30 The TCTB Alternative also results in a combined required fleetwide 38.1 mpg in MY 2016. 

31 The TCTB Alternative results in required mpg in 2016 that is just slightly lower than required 

32 mpg under the 7-Percent Alternative, but required mpg in 2012 through 2015 under the TCTB Alternative 

33 is slightly higher than under the 7-Percent Alternative. In general, the net result is that there is very little 

34 substantive difference in required mpg under the 7-Percent and TCTB Alternatives. 
 Chapter 2 Proposed Action and Alternatives 

 2-15 

1 2.3.10 Fuel Economy Levels for Each Alternatives 

2 Table 2.3-1 shows the required fuel economy levels for each alternative. 

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

~5.9%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.7%/year 

Increase 

 TCTB 

2012 

Passenger 

Cars 30.5 31.5 32.1 33.6 32.7 33.4 33.0 33.3 33.8

Light Trucks 24.3 24.3 24.3 25.0 24.4 26.4 24.6 24.8 26.7

Combined 27.9 28.4 28.7 29.8 29.0 30.4 29.2 29.5 30.8

2013 

Passenger 

Cars 30.5 32.9 33.6 34.4 34.2 36.0 34.9 35.5 36.7

Light Trucks 24.2 24.5 25.0 25.6 25.5 27.7 26.0 26.5 28.0

Combined 27.9 29.3 29.9 30.6 30.4 32.5 31.0 31.6 33.0

2014 

Passenger 

Cars 30.5 33.8 34.8 35.2 35.8 38.1 36.9 37.9 39.0

Light Trucks 24.2 25.2 26.0 26.2 26.7 28.8 27.5 28.3 29.2

Combined 27.9 30.2 31.0 31.4 31.9 34.2 32.9 33.8 34.8

2015 

Passenger 

Cars 30.5 34.7 36.1 36.4 37.5 39.5 38.9 40.4 40.8

Light Trucks 24.1 25.9 26.9 27.1 28.0 30.1 29.0 30.1 30.9

Combined 28.0 31.1 32.3 32.6 33.5 35.6 34.8 36.2 36.8

2016 

Passenger 

Cars 30.5 35.6 37.4 38.0 39.3 40.9 41.1 43.1 42.7

Light Trucks 24.1 26.6 27.9 28.3 29.3 30.6 30.7 32.2 31.5

Combined 28.0 32.0 33.6 34.1 35.2 36.8 36.9 38.7 38.1

3 Analyzing the environmental impacts of these alternatives provides information on the full 

4 spectrum of CAFE choices reasonably available to the decisionmaker. Although NEPA requires – and 

5 this EIS analyzes – a full spectrum of alternatives, NHTSA is obligated by EPCA to consider additional 

6 requirements and factors in setting “maximum feasible” CAFE standards: (1) technological feasibility, 

7 (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. 17 8 

 

17 49 U.S.C. § 32902(f). 
Chapter 2 Proposed Action and Alternatives 

 2-16 

Table 2.3-2 shows the estimated18 1 achieved fuel economy levels for each alternative. Comparing 

2 Table 2.3-1 with Table 2.3-2 shows that estimated achieved combined mpg in 2016 would actually 

3 exceed required mpg under the No Action Alternative, indicating that some manufacturers would exceed 

4 the no action required mpg. Achieved combined mpg would equal required combined mpg under 

5 Alternative 2. Under other action alternatives, the estimated achieved mpg in 2016 would be somewhat 

6 lower than the required mpg levels because some manufacturers are not expected to comply fully with 

7 passenger-car or light-truck standards under some alternatives. Estimated achieved and required fuel 

economy levels differ because manufacturers will, on average, undercomply19 8 in some model years and 

overcomply20 in others.21 9 

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

~5.9%/year 

Increase 

MNB 

6%/year 

Increase

7%/year 

Increase 

~6.7%/year 

Increase 

TCTB 

2012 

Passenger 

Cars 32.4 32.7 33.0 33.3 33.2 33.5 33.4 33.5 33.7

Light Trucks 24.2 24.5 24.7 25.0 24.8 25.5 24.9 25.1 25.5

Combined 28.6 29.0 29.2 29.5 29.3 29.9 29.5 29.7 30.0

2013 

Passenger 

Cars 32.4 34.0 34.5 34.9 35.1 36.0 35.7 36.1 36.3

Light Trucks 24.3 25.0 25.5 25.9 25.9 27.2 26.3 26.7 27.3

Combined 28.7 29.9 30.4 30.9 30.9 32.1 31.5 31.8 32.3

2014 

Passenger 

Cars 32.4 34.6 35.5 35.9 36.5 37.8 37.4 38.0 38.2

Light Trucks 24.2 25.5 26.3 26.7 27.1 28.6 27.8 28.3 28.8

Combined 28.8 30.5 31.5 31.8 32.3 33.8 33.2 33.7 34.1

 

18 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. 

19 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. 

20 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). 21 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 

 2-17 

Table 2.3-2 (continued) 

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

~5.9%/year 

Increase 

MNB 

6%/year 

Increase

7%/year 

Increase 

~6.7%/year 

Increase 

TCTB 

2015 

Passenger 

Cars 32.5 35.2 36.5 36.8 37.5 39.1 38.8 39.4 39.6

Light Trucks 24.1 26.0 27.1 27.4 28.2 29.7 29.2 29.9 30.1

Combined 28.9 31.3 32.5 32.8 33.6 35.1 34.7 35.4 35.6

2016 

Passenger 

Cars 32.5 36.0 37.5 37.9 39.1 40.4 40.5 41.4 41.4

Light Trucks 24.2 26.5 27.7 28.1 29.0 30.3 30.3 31.0 30.8

Combined 29.0 32.0 33.4 33.8 34.9 36.2 36.2 37.1 37.0

1 

2 2.3.11 Greenhouse Gas Emission Standards for Light-Duty Vehicles 

3 As explained above, NHTSA’s proposed action is one part of a National Program consisting of 

4 new standards for light-duty vehicles that will improve fuel economy and reduced GHG emissions. EPA 

5 is proposing greenhouse gas emissions standards under Section 202(a) of the Clean Air Act, and NHTSA 

6 is proposing Corporate Average Fuel Economy standards under the Energy Policy and Conservation Act, 

7 as amended. EPA’s proposed standards would require light-duty vehicles to meet an estimated combined 

8 average emissions level of 250 grams per mile (g/mi) of CO2 in model year 2016. The proposed 

9 standards for both agencies begin with the 2012 model year, with standards increasing in stringency 

10 through model year 2016. They represent a harmonized approach that will allow industry to build a 

11 single national fleet that will satisfy both the GHG requirements under the CAA and CAFE requirements 

12 under EPCA/EISA. Given differences in their respective statutory authorities, however, the agencies’ 

13 proposed standards include some important differences. Refer to Section 3.7 for a discussion of these 

14 differences. 

15 EPA is proposing GHG emissions standards, and Table 2.3-3 provides EPA’s estimates of their 

projected overall fleet-wide CO2 equivalent emission levels.22 16 The g/mi values are CO2 equivalent values 

17 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 

18 

19 As shown in Table 2.3-3, fleet-wide CO2 emission level requirements for cars under the proposed 

20 approach are projected to increase in stringency from 261 to 224 grams per mile between MY 2012 and 

 

22 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 

 2-18 

1 MY 2016. Similarly, fleet-wide CO2 equivalent emission level requirements for trucks are projected to 

2 increase in stringency from 352 to 302 g/mi. As shown, the overall fleet average CO2 level requirements 

3 are projected to be 250 g/mi in 2016. 

4 EPA anticipates that manufacturers will take advantage of program flexibilities such as flex 

5 fueled vehicle credits, and car/truck credit trading. Due to the credit trading between cars and trucks, the 

6 estimated improvements in CO2 emissions are distributed differently than shown in Table 2.3-3, where 

7 full manufacturer compliance is assumed. Table 2.3-4 shows EPA projection of the achieved emission 

8 levels of the fleet for MY 2012 through 2016, which does consider the increase in emissions due to 

9 program flexibilities such as the flex fueled vehicle credits, as well as the impact of car/truck trading and 

10 optional air conditioning credits. As can be seen in Table 2.3-4, the projected achieved levels are slightly 

11 higher for MY 2012-2015 due to the projected use of the proposed flexibilities, but in MY 2016 the 

12 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 

13 

14 2.4 SENSITIVITY ANALYSIS 

15 There are many combinations of economic assumptions that can be used to estimate the costs and 

16 benefits of the alternatives, including future fuel prices, the value of CO2 emissions reductions(referred to 

17 as the social cost of carbon or SCC), the discount rate, the magnitude of the rebound effect, and the value 

18 of oil import externalities. Different combinations of economic assumptions can also affect the 

19 calculation of environmental impacts of the various action alternatives. This occurs partly because some 

20 economic inputs to the Volpe model – notably fuel prices and the size of the rebound effect – influence its 

21 estimates of vehicle use and fuel consumption, the main factors that determine emissions of GHGs, 

22 criteria air pollutants, and airborne toxics. In addition, changes in economic assumptions may affect the 

23 fuel economy levels required under the action alternatives established on the basis of economic benefits 

24 and costs (i.e., Alternative 6 (MNB) and Alternative 9 (TCTB)). 

25 The direct, indirect, and cumulative environmental impacts of the proposed CAFE Alternatives 

26 examined in this EIS reflect the following combination of economic inputs to the Volpe model, referred 

27 to as the “Expected Value” model inputs: 

28 • American Energy Outlook (AEO)April 2009 Reference Case fuel price forecast; 

29 • 3-percent discount rate used to determine present value of future costs and benefits; 

30 • 10-percent rebound effect (the estimated increase in driving due to higher fuel economy 

31 standards that reduce the cost per mile travelled); 

32 • $20 SCC (dollar value of per metric ton of CO2 emission reductions); 

33 • $0.17 reduction in oil import externalities per gallon of fuel saved (reduction in 

34 macroeconomic costs of oil price shocks only; includes no reduction in monopsony payments 

35 to oil producers or in military security outlays associated with oil imports). 
 Chapter 2 Proposed Action and Alternatives 

 2-19 

1 NHTSA selected these values based on the best available information and data, but the agency 

2 recognizes that the forecasts and assumptions they reflect are subject to considerable uncertainty, and that, 

3 with respect to Alternatives 6 and 9, both the achieved fuel economy standards and their resulting 

4 environmental impacts depend, in part, on the choice of inputs utilized by the Volpe model. Table 2.4-1 

5 presents a sensitivity analysis of how changes in key economic variables, including fuel price projections, 

6 the value of CO2, oil import externalities, and the rebound effect influence the estimates of fuel 

7 consumption over the period from 2012 to 2060 under each Alternative. The change in projected 2012-

8 2060 fuel consumption associated with different economic inputs to the Volpe model also indicates the 

9 magnitude of related changes in emissions and associated environmental impacts. Table 2.4-1 shows that 

10 fuel consumption (and thus related emissions and other environmental impacts) are relatively sensitive to 

11 fuel price projections, and somewhat sensitive to the estimated rebound effect, but relatively insensitive to 

12 changes in model input values for the discount rate, SCC, and oil import externalities. 

Table 2.4-1 

Sensitivity Analysis of Fuel Consumption (2012-60; 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 

~5.9%/year 

Increase 

MNB 

~6.7%/year 

Increase 

TCTB 

Expected Value Model Inputs 9,260 8,593 8,250 7,878 7,339

High AEO Fuel Price Forecast 8,499 7,878 7,549 7,202 6,745

Low AEO Fuel Price Forecast 11,444 10,656 10,211 9,920 9,088

7% Discount Rate 9,260 8,593 8,250 7,933 7,339

5% Rebound Effect 9,908 9,152 8,763 8,343 7,739

15% Rebound Effect 8,612 8,029 7,727 7,396 6,924

$56/ton CO2 Value 9,260 8,593 8,250 7,872 7,343

$34/ton CO2 9,260 8,593 8,250 7,875 7,343

$10/ton CO2 9,260 8,593 8,250 7,875 7,339

$5/ton CO2 9,260 8,593 8,250 7,875 7,339

5¢/gal Oil Import Externality 9,260 8,593 8,250 7,878 7,339

13 

14 The Expected Value model inputs result in 9,260 billion gallons of fuel consumption from 2012 

15 to 2060 under the No Action Alternative, and 7,339 billion gallons under the TCTB Alternative, with fuel 

16 consumption under other action alternatives falling within this range. Changing the projected fuel price 

17 input to the AEO High Fuel Price Forecast (while leaving other model inputs the same) reduces projected 

18 2012-2060 fuel consumption under each alternative by 8.1 percent to 8.6 percent from its estimated level 

19 under the same alternative with the Expected Value model inputs (including the AEO Reference Case fuel 

20 price forecast). In contrast, changing the projected fuel price input to the AEO Low Fuel Price Forecast 

21 (while leaving other model inputs values the same) increases projected 2012-2060 fuel consumption for 

22 each alternative by 23 percent to 26 percent from its level under the same alternative using the Expected 

23 Value model inputs (including the AEO Reference Case fuel price forecast). 

24 Changing the rebound effect input to 5 percent (while leaving other model inputs values the same, 

25 including the Reference Case fuel price forecast) increases projected 2012-2060 fuel consumption for 

26 each alternative by 5 percent to 7 percent from its level under the same alternative with a 10 percent 

27 rebound effect (the Expected Value model input). Increasing the rebound effect input to 15 percent 

28 reduces projected 2012-2060 fuel consumption for each alternative by 5 percent to 7 percent. The 

29 sensitivity analysis in Table 2.4-1 shows that changes in the input values for the discount rate, SCC, and 
Chapter 2 Proposed Action and Alternatives 

 2-20 

1 oil import externalities result in less than a 1-percent change in projected 2012-2060 fuel consumption 

2 under each alternative (and less than 0.01-percent for most alternatives). 

3 These results occur because variation in fuel prices and the magnitude of the rebound effect 

4 influence total vehicle use (as measured by the number of vehicle-miles traveled, or VMT), one of the 

5 two determinants of fuel consumption, under each alternative. This reflects the response of average 

6 vehicle use to changes in fuel cost per mile; variation in fuel prices directly affects fuel cost per mile, 

7 while the rebound effect expresses the sensitivity of average vehicle use to the resulting change in fuel 

cost per mile.23 8 In addition, changes in fuel prices and the rebound effect significantly change the 

9 stringency of CAFE standards under alternatives that would establish standards on the basis of benefits 

10 and costs (Alternatives 6 and 9), which reinforces the effect of changes in vehicle use on total fuel 

11 consumption under those alternatives. 

12 In contrast, variation in other economic assumptions, including the discount rate, the value of 

13 reducing CO2 emissions, and the value of petroleum import externalities has no effect on vehicle use 

14 under any alternative. At the same time, changes in these variables have only modest effects on the 

15 stringency of CAFE standards under alternatives that would establish standards on the basis of the 

16 resulting economic costs and benefits. As a consequence, changes in assumptions about these variables 

17 have little effect on total fuel consumption, as Table 2.4-1 illustrates, although these variables do have 

18 significant effects on the economic benefits resulting from the different Action Alternatives. 

19 2.5 ALTERNATIVES CONSIDERED BUT NOT ANALYZED IN DETAIL 

20 As a result of the scoping process, several suggestions were made to NHTSA regarding 

21 alternatives that should be examined in this EIS. NHTSA considered these alternatives and discusses 

22 them below along with the reasons why we believe these alternatives do not warrant further analysis in 

23 this EIS. 

24 • 100 mpg 

25 One commenter suggested NHTSA examine an alternative of setting standards to achieve 100 

26 mpg within 5 years. NHTSA did not pursue this suggested alternative for two reasons. First, a 

27 fleet-wide 100-mpg average would require the production of vehicles equipped with advanced 

28 technologies at a rate that is not possible in 5 years, as well as the elimination of some lower mpg 

29 vehicles for which there is some consumer demand and for which manufacturers currently have 

30 supply contracts established to build in the near future. Second, the suggested approach would 

31 not be an appropriate balancing of the statutory factors listed in EPCA since the measures are not 

32 economically practicable based on manufacturers’ limitations concerning retooling and 

established supply contracts.24 33 Indeed, the suggested approach would result in a level that is 

34 substantially higher than the “maximum feasible” CAFE standard, as required by EPCA. 

35 • Wedge Approach 

36 The Attorneys General commented that NHTSA’s EIS should show how the MY 2012-2016 

37 CAFE rules contribute to reducing greenhouse gas emissions and addressing global warming by 

 

23 Mathematically, the rebound effect is equal 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. 

24 49 U.S.C. § 32902(f) (establishing the considerations for decisions on maximum feasibility are: technological 

feasibility, economic practicability, the effect of other motor vehicle standards on fuel economy, and the need of the 

United States to conserve energy). 
 Chapter 2 Proposed Action and Alternatives 

 2-21 

1 evaluating whether the new CAFE rules could constitute a stabilization wedge. While NHTSA 

2 agrees that this is one possible approach, the agency declines to pursue a wedge analysis to fulfill 

3 its requirements under NEPA. CEQ regulations require NHTSA to rigorously explore all 

reasonable alternatives and examine their direct and indirect effects on climate change.25 4 

5 NHTSA’s current approach demonstrates changes in CO2 concentration, global mean surface 

6 temperature, regional temperature and precipitation, and sea level for each alternative. Analysis 

7 of stabilization wedges and framing the alternatives in terms of fractions of a stabilization edge, 

8 would only allow for a conceptual analysis of CO2 reductions. NHTSA believes that framing the 

9 alternatives as average annual percentage increase over current fuel economy levels is more 

10 intuitive to the public and to decisionmakers than framing the alternatives as suggested by the 

11 commenter. Therefore, NHTSA believes its chosen approach for addressing global warming is 

12 best able to describe the direct and indirect effects of climate change on all reasonable 

13 alternatives in accordance with NEPA. NHTSA has added a discussion of the wedge theory and 

14 how NHTSA’s proposed action generally looks in terms of a stabilization wedge in Section 

15 3.4.4.1. 

16 • Least Capable Manufacturer

17 In their scoping comments the Alliance of Automobile Manufacturers (“AAM”) suggested an 

18 alternative of NHTSA setting standards tailored to the “least capable manufacturer.” As NHTSA 

19 explained in the FEIS for MY2011 CAFE standards, the agency chose not to pursue the suggested 

20 approach for two reasons. First, the approach would not result in the EISA mandated fuel 

21 economy increases – namely, 35 mpg by MY 2020. Second, tailoring to the least capable 

22 manufacturer is unnecessary in Reformed CAFE, which was codified when EISA required all 

CAFE standards be based on one or more vehicle attributes.26 23 Reformed CAFE standards specify 

24 variable levels of CAFE depending on the production mix of each manufacturer, making it 

25 unnecessary to tailor to the least capable manufacturer. 

26 • Variations based on increases from EISA MY 2020 endpoint 

27 The AAM also suggested that NHTSA “consider crafting a couple of alternatives that would 

28 model increased CAFE stringency levels over the baseline level for MY 2020 as required by 

29 EISA. For instance: Alternative (2) could be redefined as improving fuel economy at the rate 

30 necessary to achieve 35 mpg fleet average fuel economy in MY 2020...Alternative (3) could be 

31 defined as improving fuel economy at the rate necessary to achieve a 36.75 mpg fleet average 

32 fuel economy in MY 2020, an increase of 5 [percent] above EISA’s baseline level in MY 2020.” 

33 Docket No. NHTSA-2009-0059-0007. NHTSA recognizes that this is one possible approach to 

34 creating regulatory alternatives, but instead prefers to establish regulatory alternatives by 

35 specifying average annual percentage increases over MY 2011 CAFE standards because the 

36 agency believes alternatives expressed this way are more intuitive and understandable to the 

37 public. We believe this approach best fulfills the goals of NEPA to inform both decisionmakers 

38 and the general public. CEQ regulations instruct agencies to write an EIS using plain language to 

39 enable understandability of complex environmental analyses for both decisionmakers and the 

public.27 40 CEQ regulations also indicate that a major purpose of an EIS is to facilitate public 

 

25 See 40 CFR § 1502.14-16. 26 49 U.S.C. § 32902(b)(3)(A); see 73 FR 24352, 24354-24355 (May 2, 2008). 27 40 CFR § 1502.8. 
Chapter 2 Proposed Action and Alternatives 

 2-22 

involvement in and knowledge of the NEPA process.28 1 NHTSA believes the approach chosen for 

2 generating alternatives best presents understandable regulatory approaches to CAFE increases. 

3 • Technology Exhaustion 

4 In the 2008 EIS, NHTSA analyzed a “technology exhaustion” alternative, which was 

5 developed by using the Volpe model to progressively increase the stringency of the standard in 

6 each model year until every manufacturer (among those without a history of paying civil 

7 penalties) exhausted technologies estimated to be available during the relevant model years. In 

8 its scoping comments, the Center for Biological Diversity stated that NHTSA should include one 

9 or more “technology forcing” alternatives, which would include standards that may appear 

10 impossible today, but which would force innovation as industry strives to meet a challenging 

11 standard. We consider the upper range of alternatives presented in this EIS to be technology 

12 forcing because at these higher average annual percentage increases some manufacturers run out 

13 of technologies before reaching the required CAFE standard and, therefore, these standards will 

14 be theoretically impossible to meet for some manufacturers. Since these higher average annual 

15 percentage increase regulatory alternatives force manufacturers to do something they would not 

16 otherwise be required to do, they are in that sense “technology forcing” as well. We consider our 

17 range of alternatives to represent a reasonable range of possible agency actions. 

18 2.6 COMPARISON OF ALTERNATIVES 

The CEQ NEPA regulations29 19 direct federal agencies to use the NEPA process to identify and 

20 assess the reasonable alternatives to proposed actions that would avoid or minimize adverse effects of 

these actions upon the quality of the human environment. CEQ regulations30 21 state: 

22 Based on the information and analysis presented in the sections on the Affected 

23 Environment (Sec. 1502.15) and the Environmental Consequences (Sec. 1502.16), [an 

24 EIS] should present the environmental impacts of the proposal and the alternatives in 

25 comparative form, thus sharply defining the issues and providing a clear basis for choice 

26 among options by the decisionmaker and the public. 

27 This section summarizes the direct, indirect, and cumulative effects of the proposed action and 

28 alternatives on energy resources, air quality, and climate. No quantifiable, alternative-specific effects 

29 were identified for the other resources discussed in Chapters 3 and 4 of this EIS. Refer to the text in 

30 Chapter 3 and 4 for qualitative discussions of the potential direct and indirect effects of the alternatives on 

31 these other resources. 

32 2.6.1 Direct and Indirect Effects 

33 Under NEPA, direct effects “are caused by the action and occur at the same time and place.” 40 

34 CFR 1508.8. CEQ regulations define indirect effects as those that “are caused by the action and are later 

35 in time or father removed in distance but are still reasonably foreseeable. Indirect effects may include ... 

36 effects on air and water and other natural systems, including ecosystems.” 40 CFR 1508.8. Below is a 

37 description of the direct and indirect effects of the CAFE alternatives on energy, air quality, and climate. 

 

28 See 40 CFR § 1500.1(b). 

29 See 40 CFR Part 1500.2(e). 30 See 40 CFR 1502.14. 
 Chapter 2 Proposed Action and Alternatives 

 2-23 

1 2.6.1.1 Energy 

2 Tables 2.6-1 and 2.6-2 show the impact on annual fuel consumption for passenger cars and light 

3 trucks from 2020 through 2060, when the entire passenger-car and light-truck fleet is likely to be 

4 composed of MY 2016 or later passenger cars. Table 2.6-1 shows annual total fuel consumption (both 

5 gasoline and diesel gasoline equivalent) under the No Action Alternative and the eight action alternatives. 

6 For passenger cars, fuel consumption under the No Action Alternative is 173.5 billion gallons in 2060. 

7 Fuel consumption ranges from 158.2 billion gallons under Alternative 2 (3-Percent Alternative) to 139.7 

8 billion gallons under Alternative 9 (TCTB). Fuel consumption is 150.9 billion gallons under the 

9 Preferred Alternative. 

Table 2.6-1 

Passenger Car Annual Fuel Consumption and Fuel Savings (billion gallons gasoline equivalent) by 

Alternative 

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 

~5.9%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.7%/year 

Increase 

TCTB 

Fuel Consumption 

2020 69.4 65.7 64.3 63.9 63.0 61.8 61.9 61.2 61.1

2030 97.9 89.5 86.4 85.5 83.5 81.0 80.9 79.4 79.4

2040 121.7 110.9 106.9 105.9 103.2 100.1 99.9 98.0 98.1

2050 145.7 132.8 128.0 126.7 123.5 119.8 119.6 117.3 117.3

2060 173.5 158.2 152.4 150.9 147.1 142.7 142.4 139.7 139.7

Fuel Savings Compared to No Action 

2020 -- 3.7 5.1 5.5 6.4 7.6 7.6 8.2 8.3

2030 -- 8.4 11.5 12.3 14.4 16.8 17.0 18.4 18.4

2040 -- 10.8 14.8 15.9 18.5 21.6 21.8 23.7 23.7

2050 -- 12.9 17.7 19.0 22.2 25.9 26.2 28.4 28.4

2060 -- 15.4 21.1 22.6 26.5 30.9 31.2 33.9 33.8

10 

Table 2.6-2 

Light Truck Annual Fuel Consumption and Fuel Savings (billion gallons gasoline equivalent) by Alternative

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 

~5.9%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.7%/year 

Increase 

TCTB 

Fuel Consumption 

2020 68.6 66.4 65.2 64.9 64.2 63.0 63.3 62.7 62.6

2030 66.0 61.6 59.6 59.0 57.6 55.8 55.9 55.0 55.1

2040 73.0 67.4 64.9 64.2 62.4 60.3 60.3 59.1 59.3

2050 85.5 78.7 75.7 74.8 72.7 70.2 70.1 68.7 69.0

2060 101.4 93.3 89.7 88.7 86.1 83.1 83.1 81.3 81.7

Fuel Savings Compared to No Action 

2020 -- 2.3 3.4 3.8 4.4 5.6 5.3 5.9 6.0

2030 -- 4.4 6.4 7.0 8.3 10.1 10.0 11.0 10.9

2040 -- 5.6 8.1 8.8 10.6 12.8 12.7 14.0 13.7

2050 -- 6.8 9.8 10.7 12.8 15.4 15.4 16.9 16.5

2060 -- 8.1 11.7 12.7 15.3 18.3 18.4 20.1 19.7

11 
Chapter 2 Proposed Action and Alternatives 

 2-24 

1 For light trucks, fuel consumption under the No Action Alternative is 101.4 billion gallons in 

2 2060. Fuel consumption ranges from 93.3 billion gallons under Alternative 2 (3-Percent Alternative) to 

3 81.3 billion gallons under Alternative 8 (7-percent annual increase in mpg). Fuel consumption is 88.7 

4 billion gallons under the Preferred Alternative (Alternative 4). 

5 2.6.1.2 Air Quality 

6 Table 2.6-3 summarizes the total national criteria and air toxic pollutant emissions in 2030 for the 

7 nine alternatives, left to right in order of increasing fuel economy requirements. Changes in overall 

8 emissions between the No Action Alternative and Alternatives 2 through 4 are generally smaller than 

9 those between the No Action Alternative and Alternatives 5 through 9. In the case of particulate matter 

10 (PM2.5), sulfur oxides (SOx), nitrogen oxides (NOx), and volatile organic compounds (VOCs), the No 

11 Action Alternative results in the highest emissions, and emissions generally decline as fuel economy 

12 standards increase across alternatives. Across Alternatives 4 through 9 some emissions increase from one 

13 alternative to another, but emissions remain below the levels under the No Action Alternative. In the case 

14 of carbon monoxide (CO), emissions under Alternatives 2 through 4 are slightly higher than under the No 

15 Action Alternative. Emissions of CO decline as fuel economy standards increase across Alternatives 5 

16 through 9. 

Table 2.6-3 

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

~5.9%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.7%/year

Increase 

TCTB 

Criteria Pollutant Emissions 

Carbon 

monoxide 

(CO) 17,766,186 17,875,841 17,857,900 17,830,426 17,374,361 16,933,532 16,692,592 16,584,083 16,544,125

Nitrogen 

oxides (NOx) 1,467,596 1,453,694 1,445,588 1,443,013 1,416,117 1,390,714 1,379,863 1,370,822 1,368,895

Particulate 

matter (PM2.5) 76,589 74,147 73,316 73,321 73,122 73,349 73,725 73,362 73,382

Sulfur oxides 

(SOx) 201,502 186,242 180,661 179,415 178,313 176,493 178,441 176,043 176,396

Volatile 

organic 

compounds 

(VOCs) 1,668,085 1,596,544 1,564,323 1,553,482 1,514,436 1,469,438 1,456,616 1,439,159 1,438,649

Toxic Air Pollutant Emissions 

Acetaldehyde 6,631 6,665 6,683 6,678 6,710 6,721 6,733 6,748 6,751

Acrolein 342 345 348 351 366 385 393 398 399

Benzene 27,706 27,667 27,602 27,551 27,171 26,758 26,569 26,466 26,440

1,3-butadiene 3,610 3,631 3,637 3,638 3,615 3,597 3,584 3,581 3,579

Diesel 

particulate 

matter (DPM) 106,046 97,820 94,519 93,731 91,502 89,134 89,055 87,536 87,606

Formaldehyde 8,875 8,884 8,927 8,938 9,198 9,440 9,573 9,652 9,672

17 
 Chapter 2 Proposed Action and Alternatives 

 2-25 

1 The trends for toxic air pollutant emissions across the alternatives are mixed. Annual emissions 

2 of nearly all toxic air pollutants are highest under the No Action Alternative, except for those of acrolein, 

3 which increases with each successive alternative and are highest under Alternative 9. The acrolein 

4 emissions in Table 2.6-3 are an upper-bound estimate and actual emissions might be less. Annual 

5 emissions in 2030 of acetaldehyde increase under each successive alternative from Alternative 1 to 

6 Alternative 9, except for Alternative 4. Annual emissions in 2030 of benzene and formaldehyde decrease 

7 under each successive alternative from Alternative 1 to Alternative 9. Annual emissions of 1,3-butadiene 

8 in 2030 increase under each successive alternative from Alternative 1 to Alternative 4, and then decrease 

9 under each successive alternative from Alternative 5 to Alternative 9 in 2030. Annual emissions of DPM 

10 in 2030 decrease with successive alternatives from Alternative 1 to Alternative 8 and decrease in 

11 Alternative 9. 

12 The reductions in emissions are expected to lead to reductions in adverse health effects. 

13 Table 2.6-4 summarizes the national changes in health outcomes in 2030 for the nine alternatives, left to 

14 right in order of increasing fuel economy requirements. There would be reductions in adverse health 

15 effects nationwide under Alternatives 2 (3-Percent Alternative) through 9 (TCTB) compared to the No 

16 Action Alternative. The No Action Alternative results in no reductions in adverse health effects, and the 

17 reductions become larger as fuel economy standards increase and emissions decrease across alternatives. 

18 These reductions primarily reflect the projected PM2.5 reductions, and secondarily the reductions in SO2. 

Table 2.6-4 

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 

~5.9%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.7%/year 

Increase 

TCTB 

Mortality (ages 30 and older), Pope et al. 

2030 0 -153 -210 -217 -253 -276 -267 -296 -296

Mortality (ages 30 and older), Laden et al. 

2030 0 -392 -537 -554 -648 -705 -683 -758 -758

Chronic bronchitis 

2030 0 -100 -138 -142 -167 -182 -177 -196 -196

Emergency Room Visits for Asthma 

2030 0 -140 -191 -198 -226 -244 -233 -258 -258

Work Loss Days 

2030 0 -18,031 -24,750 -25,522 -30,036 -32,758 -31,811 -35,301 -35,306

__________ 

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. 

19 

20 The economic value of health impacts would vary proportionally with changes in health 

21 outcomes. Table 2.6-5 lists the corresponding annual reductions in health costs in 2030 under 

22 Alternatives 2 (3-Percent Alternative) through 9 (TCTB) compared to the No Action Alternative. 

23 Reductions in health costs are given for two alternative assumptions of the discount rate, 3 percent and 7 

24 percent, consistent with EPA policy for presentation of future health costs. 

25 
Chapter 2 Proposed Action and Alternatives 

 2-26 

Table 2.6-5 

Nationwide Changes in Health Costs (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 

~5.9%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.7%/year 

Increase 

TCTB 

3% Discount Rate

Pope et al. 

2030 0 -1,361 -1,867 -1,926 -2,253 -2,452 -2,374 -2,635 -2,634

Laden et al. 

2030 0 -3,334 -4,574 -4,720 -5,520 -6,007 -5,816 -6,454 -6,451

7% Discount Rate

Pope et al. 

2030 0 -1,234 -1,693 -1,747 -2,044 -2,224 -2,154 -2,390 -2,389

Laden et al. 

2030 0 -3,012 -4,131 -4,264 -4,987 -5,426 -5,254 -5,830 -5,827

__________ 

a/ Negative changes indicate economic benefit; positive emissions changes indicate economic costs. 

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. 

1 2.6.1.3 Climate Change 

2 This EIS uses a climate model to estimate the changes in CO2 concentrations, global mean 

3 surface temperature, and changes in sea level for each alternative. NHTSA also estimated changes in 

4 global precipitation. 

5 2.6.1.3.1 GHG Emissions 

6 Table 2.6-6 shows total GHG emissions and emissions reductions from new passenger cars and light 

7 trucks, summed for the period 2012 through 2100 under each of the nine alternatives. Although GHG 

8 emissions from this sector will continue to rise over the period (absent other reduction efforts), the effect 

9 of the alternatives is to slow this increase by varying amounts. Emissions for the period range from 

Table 2.6-6 

Emissions and Emissions Reductions (MMTCO2) from 2012-2100 by Alternative 

Alternative Emissions 

Emissions Reductions 

Compared 

to No Action Alternative 

1 No Action 243,600 0 

2 3%/year Increase 224,300 19,300 

3 4%/year Increase 216,700 26,900 

4 ~4.3%/year Increase, Preferred 214,700 29,000 

5 5%/year Increase 210,100 33,500 

6 ~5.9%/year Increase, MNB 204,500 39,100 

7 6%/year Increase 204,800 38,800 

8 7%/year Increase 201,200 42,400 

9 ~6.7%/year Increase, TCTB 201,500 42,100 

10 
 Chapter 2 Proposed Action and Alternatives 

 2-27 

1 201,200 million metric tons of CO2 (MMTCO2) for the 7%/year Increase (Alternative 8) to 243,600 

2 MMTCO2 for the No Action Alternative (Alternative 1). Compared to the No Action Alternative, 

3 projections of emissions reductions over the period 2012 to 2100 due to the MY 2012-2016 CAFE 

4 standards range from 19,300 to 42,400 MMTCO2. Compared to cumulative global emissions of 

5 5,293,896 MMTCO2 over this period (projected by the RCP 4.5 MiniCAM reference scenario), this 

6 rulemaking is expected to reduce global CO2 emissions by about 0.4 to 0.8 percent. 

7 To get a sense of the relative impact of these reductions, it can be helpful to consider the relative 

8 importance of emissions from passenger cars and light trucks as a whole and to compare them against 

9 emissions projections from the transportation sector. As mentioned earlier, U.S. passenger cars and light 

10 trucks currently account for significant CO2 emissions in the United States. With the action alternatives 

11 reducing U.S. passenger car and light truck CO2 emissions by 7.9 to 17.4 percent of cumulative emissions 

12 from 2012 to 2100, the CAFE alternatives would have a noticeable impact on total U.S. CO2 emissions. 

13 Compared to total U.S. CO2 emissions in 2100 projected by the MiniCAM reference scenario of 7,886 

MMTCO2 14 , the action alternatives would reduce annual U.S. CO2 emissions by 3.6 to 7.8 percent in 2100. 

15 As another comparison of the magnitude of these reductions, average annual CO2 emission reductions 

16 from the CAFE alternatives range from 217 to 476 MMTCO2 over 2012 to 2100, equivalent to the annual 

CO2 emissions of 47 to 103 coal-fired power plants.31 17 Figure 2.6-1 shows projected annual emissions 

18 from passenger cars and light trucks under the MY 2012-2016 alternative CAFE standards. 

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

0

500

1000

1500

2000

2500

3000

3500

2010 2020 2030 2040 2050 2060

MMTCO2

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: ~5.9%/year Increase, MNB

Alt. 7: 6%/year Increase Alt. 8: 7%/year Increase

Alt. 9: ~6.7%/year Increase, TCTB

19 

 

31 Estimated using EPA’s Greenhouse Gas Equivalencies Calculator (EPA 2009). 
Chapter 2 Proposed Action and Alternatives 

 2-28 

1 Under all of the alternatives analyzed, growth in the number of passenger cars and light trucks in 

2 use throughout the United States, combined with assumed increases in their average use, is projected to 

3 result in growth in total passenger-car and light-truck travel. This growth in travel overwhelms 

4 improvements in fuel economy for each of the alternatives, resulting in projected increases in total fuel 

5 consumption by U.S. passenger cars and light trucks over most of the period shown in the table. Because 

6 CO2 emissions are a direct consequence of total fuel consumption, the same result is projected for total 

7 CO2 emissions from passenger cars and light trucks. 

8 Emissions of CO2, the primary gas that drives climate effects, from the U.S. passenger-car and 

light-truck fleet represented about 3.7 percent of total global emissions of CO2 in 2005.32 9 Although 

10 substantial, this source is a still small percentage of global emissions. The relative contribution of CO2

11 emissions from the U.S. passenger cars and light trucks is expected to decline in the future, due primarily 

12 to rapid growth of emissions from developing economies (which are due in part to growth in global 

13 transportation sector emissions). 

14 2.6.1.3.2 CO2 Concentration, Global Mean Surface Temperature, Sea-level Rise, 

15 and Precipitation 

16 Table 2.6-7 shows estimated CO2 concentrations, increase in global mean surface temperature, 

17 and sea-level rise in 2030, 2050, and 2100 under the No Action Alternative and the eight action 

18 alternatives Figures 2.6-2 through 2.6-5 graphically illustrate estimated CO2 concentrations and 

19 reductions for the eight action alternatives. 

20 Table 2.6-7 lists the impacts on sea-level rise under the scenarios and shows sea-level rise in 2100 

21 ranging from 38.00 centimeters under the No Action Alternative to 37.86 centimeters under the TCTB 

22 Alternative (Alternative 9), for a maximum reduction of 0.14 centimeters by 2100 from the No Action 

23 Alternative. 

Table 2.6-7 

CO2 Concentration, 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 441.6 514.3 781.2 0.922 1.554 3.129 8.38 15.16 37.94

3 4%/year Increase 441.6 514.1 780.4 0.922 1.553 3.126 8.38 15.15 37.92

4 ~4.3%/year Increase, Preferred 441.5 514.0 780.3 0.922 1.553 3.125 8.38 15.15 37.91

5 5%/year Increase 441.5 513.9 779.8 0.922 1.553 3.124 8.38 15.15 37.89

6 ~5.9%/year Increase, MNB 441.4 513.8 779.3 0.921 1.552 3.122 8.38 15.14 37.87

7 6%/year Increase 441.4 513.8 779.3 0.921 1.552 3.122 8.38 15.14 37.87

8 7%/year Increase 441.4 513.7 779.0 0.921 1.551 3.120 8.38 15.14 37.86

9 ~6.7%/year Increase, TCTB 441.4 513.7 779.0 0.921 1.551 3.120 8.38 15.14 37.86

 

32 Includes land-use change and forestry, and excludes international bunker fuels. 
 Chapter 2 Proposed Action and Alternatives 

 2-29 

Table 2.6-7 (continued) 

CO2 Concentration, 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 

Reductions under Alternative CAFE Standards

2 3%/year Increase 0.2 0.5 1.8 0.001 0.002 0.007 0.00 0.01 0.06

3 4%/year Increase 0.2 0.7 2.6 0.001 0.003 0.010 0.00 0.02 0.08

4 ~4.3%/year Increase, Preferred 0.3 0.8 2.7 0.001 0.004 0.010 0.00 0.02 0.09

5 5%/year Increase 0.3 0.9 3.2 0.001 0.004 0.012 0.00 0.02 0.11

6 ~5.9%/year Increase, MNB 0.4 1.0 3.7 0.002 0.005 0.014 0.00 0.03 0.13

7 6%/year Increase 0.4 1.0 3.7 0.002 0.005 0.014 0.00 0.03 0.13

8 7%/year Increase 0.4 1.1 4.0 0.002 0.006 0.015 0.00 0.03 0.14

9 ~6.7%/year Increase, TCTB 0.4 1.1 4.0 0.002 0.006 0.015 0.00 0.03 0.14

__________

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. 

1 

Figure 2.6-2. CO2 Concentrations (ppm) 
Chapter 2 Proposed Action and Alternatives 

 2-30 

Figure 2.6-3. Global Mean Surface Temperature Increase (°C) 
 Chapter 2 Proposed Action and Alternatives 

 2-31 

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

Alternative 

1 
Chapter 2 Proposed Action and Alternatives 

 2-32 

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

Alternative 

1 

2 Estimated CO2 concentrations for 2100 range from 779.0 ppm under the most stringent 

3 alternative (TCTB) to 783.0 ppm under the No Action Alternative. For 2030 and 2050, the range is even 

4 smaller. Because CO2 concentration is the key driver of other climate effects (which in turn act as drivers 

5 on the resource impacts discussed in Section 4.5), this leads to small differences in these effects. For the 

6 No Action alternative, the temperature increase from 1990 is 0.92 °C for 2030, 1.56 °C for 2050, and 

7 3.14 °C for 2100. The differences among alternatives are small, as shown in Figures 2.6-2 through 2.6-5. 

8 For 2100, the reduction in temperature increase, in relation to the No Action Alternative, ranges from 

9 0.007 °C to 0.015 °C. 

10 Given that all the action alternatives reduce temperature increases slightly in relation to the No 

11 Action Alternative, they also slightly reduce predicted increases in precipitation, as shown in Table 2.6-8. 

12 In summary, the impacts of the proposed action and alternatives on global mean surface 

13 temperature, precipitation, or sea-level rise are small in absolute terms. This is because the action 

14 alternatives have a small proportional change in the emissions trajectories in the RCP 4.5 MiniCAM 

reference scenario.33 15 This is due primarily to the global and multi-sectoral nature of the climate problem. 

16 Although these effects are small, they occur on a global scale and are long-lived. 

 

33 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 

(continued on bottom of next page) 
 Chapter 2 Proposed Action and Alternatives 

 2-33 

Table 2.6-8 

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 2.810 

3 4%/year Increase 0.648 1.712 2.807 

4 ~4.3%/year Increase, Preferred 0.648 1.712 2.807 

5 5%/year Increase 0.648 1.711 2.805 

6 ~5.9%/year Increase, MNB 0.648 1.710 2.803 

7 6%/year Increase 0.648 1.710 2.803 

8 7%/year Increase 0.648 1.709 2.802 

9 ~6.7%/year Increase, TCTB 0.648 1.709 2.802 

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 0.009 

5 5%/year Increase 0.000 0.005 0.011 

6 ~5.9%/year Increase, MNB 0.000 0.006 0.013 

7 6%/year Increase 0.000 0.006 0.013 

8 7%/year Increase 0.000 0.007 0.014 

9 ~6.7%/year Increase, TCTB 0.000 0.007 0.014

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% 2.59% 4.58% 

4 ~4.3%/year Increase, Preferred 0.94% 2.58% 4.57% 

5 5%/year Increase 0.94% 2.58% 4.57% 

6 ~5.9%/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% 4.57% 

9 ~6.7%/year Increase, TCTB 0.94% 2.58% 4.57% 

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% 0.01% 

4 ~4.3%/year Increase, Preferred 0.00% 0.01% 0.01% 

5 5%/year Increase 0.00% 0.01% 0.02% 

6 ~5.9%/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% 0.02% 

9 ~6.7%/year Increase, TCTB 0.00% 0.01% 0.02% 

__________________ 

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. 

 

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 

 2-34 

1 NHTSA examined the sensitivity of climate effects to key assumptions used in the analysis. The 

2 sensitivity analysis is based on the results provided for two CAFE alternatives – the No Action 

3 Alternative (Alternative 1) and the Preferred Alternative (Alternative 4) – using climate sensitivities of 

4 2.0, 3.0, and 4.5 °C for a doubling of CO2 concentrations in the atmosphere. The sensitivity analysis was 

5 conducted for only two CAFE alternatives, as this was deemed sufficient to assess the effect of various 

6 climate sensitivities on the results. 

7 The use of different climate sensitivities (the equilibrium warming that occurs at a doubling of 

8 CO2 from pre-industrial levels) not only directly affects warming, it also indirectly affects CO2

9 concentration (through feedbacks on the solubility of CO2 in the oceans) and sea-level rise (through 

10 effects on thermal expansion and melting of land-based ice). 

11 As shown in Table 2.6-9, the sensitivity of the simulated CO2 emissions in 2030, 2050, and 2100 

12 to changes in climate sensitivity is low; the reduction of CO2 concentrations from the No Action 

13 Alternative to the Preferred Alternative in 2100 is from 2.7 to 2.8 ppm. 

14 The sensitivity of the simulated global mean surface temperatures for 2030, 2050, and 2100 

15 varies, is also shown in Table 2.6-9. In 2030, the impact is low, due primarily to the slow rate at which 

16 the global mean surface temperature increases in response to increases in radiative forcing. The relatively 

17 slow response in the climate system explains the observation that even by 2100, when CO2 concentrations 

18 more than double in comparison to pre-industrial levels, the temperature increase is below the equilibrium 

19 sensitivity levels, i.e., the climate system has not had enough time to equilibrate to the new CO2

20 concentrations. Nonetheless, as of 2100 there is a larger range in temperatures across the different values 

21 of climate sensitivity: the reduction in global mean surface temperature from the No Action Alternative to 

22 the Preferred Alternative ranges from 0.008 °C for the 2.0 °C climate sensitivity to 0.013 °C for the 4.5 

23 °C climate sensitivity. 

Table 2.6-9 

CO2 concentration (ppm), Temperature (degrees C) 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 

 2.0 439.9 510.0 762.4 0.698 1.166 2.284 28.61

 3.0 441.5 514.0 780.3 0.922 1.553 3.125 37.91

 4.5 443.3 518.7 802.5 1.166 1.987 4.119 48.55

Reduction compared to No Action 

 2.0 0.3 0.7 2.7 0.001 0.003 0.008 0.07

 3.0 0.3 0.8 2.7 0.001 0.004 0.010 0.09

 4.5 0.3 0.8 2.8 0.001 0.004 0.013 0.12

a/ Values in this table are rounded.

24 
 Chapter 2 Proposed Action and Alternatives 

 2-35 

1 The sensitivity of the simulated sea-level rise to change in climate sensitivity and global GHG 

2 emissions mirrors that of global temperature, as shown in Table 2.6-9. Scenarios with lower climate 

3 sensitivities have lower increases in sea-level rise. The greater the climate sensitivity, the greater the 

4 decrement in sea-level rise for the Preferred Alternative as compared to the No Action Alternative. 

5 2.6.2 Cumulative Effects 

6 CEQ identifies the impacts that must be addressed and considered by federal agencies in 

7 satisfying the requirements of NEPA. These include permanent, temporary, direct, indirect, and 

8 cumulative impacts. CEQ regulations implementing the procedural provisions of NEPA define 

9 cumulative impacts as “the impact on the environment which results from the incremental impact of the 

10 action when added to other past, present, and reasonably foreseeable future actions regardless of what 

11 agency or person undertakes such other actions.” 40 CFR § 1508.7. Following is a description of the 

12 cumulative effects of the proposed action and alternatives on energy, air quality, and climate. 

13 The cumulative effects evaluation assumes ongoing gains in average new passenger-car and light14 truck mpg consistent with further increases in CAFE standards to an EISA-mandated minimum level of 

15 35 mpg combined for passenger car and light trucks by the year 2020. After 2020, all alternative continue 

16 to increase in fuel economy consistent with AEO April 2009 (updated) Reference Case projections of 

17 annual percentage gains of 0.51 percent in passenger-car mpg and 0.86 percent in light-truck mpg through 

2030.34 18 AEO Reference Case projections are regarded as the official U.S. government energy projections 

19 by both the public and private sector. 

20 2.6.2.1 Energy 

21 The nine alternatives examined in this EIS will result in different future levels of fuel use, total 

22 energy, and petroleum consumption, which will in turn have an impact on emissions of GHG and criteria 

23 air pollutants. Table 2.6-10 presents the cumulative fuel consumption and fuel savings of passenger cars 

24 from the onset of the proposed new CAFE standards. By 2060, fuel consumption reaches 162.8 billion 

25 gallons under the No Action Alternative (Alternative 1). Consumption falls across the alternatives, from 

26 140.7 billion gallons under Alternative 2 (3-percent annual increase in mpg) to 131.3 billion gallons under 

27 the TCTB Alternative (Alternative 9) representing a fuel savings of 22.1 to 31.5 billion gallons in 2060, 

28 as compared to fuel consumption projected under the No Action Alternative. 

29 Table 2.6-11 presents the cumulative fuel consumption and fuel savings for light trucks from the 

30 onset of the proposed new CAFE standards. Fuel consumption by 2060 reaches 91.2 billion gallons 

31 under the No Action Alternative (Alternative 1). Consumption declines across the alternatives, from 80.1 

32 billion gallons under the 3-Percent Alternative (Alternative 2) to 73.3 billion gallons under Alternative 8 

33 (7-percent annual increase in mpg). This represents a fuel savings of 11.1 to 17.9 billion gallons in 2060, 

34 as compared to fuel consumption projected under the No Action Alternative. 

35 

 

34 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. Since the AEO forecasts do not extend beyond the year 2030, the mpg estimates for MY 2030 

through MY 2060 remain constant. 
Chapter 2 Proposed Action and Alternatives 

 2-36 

Table 2.6-10 

Cumulative Effects of Passenger Car Annual Fuel Consumption and Fuel Savings (billion gallons gasoline 

equivalent) by Alternative 

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

~5.9%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.7%/year 

Increase 

TCTB 

Fuel Consumption

2020 69.1 64.7 63.8 63.6 62.8 61.6 61.6 61.0 60.9

2030 94.5 82.6 82.2 82.3 80.7 78.3 78.2 76.8 76.8

2040 114.7 99.1 99.1 99.3 97.3 94.5 94.2 92.5 92.5

2050 136.7 118.1 118.2 118.4 116.0 112.6 112.4 110.3 110.3

2060 162.8 140.7 140.7 141.0 138.2 134.1 133.8 131.3 131.3

Fuel Savings Compared to No Action

2020 -- 4.4 5.3 5.6 6.3 7.5 7.5 8.1 8.2

2030 -- 11.9 12.2 12.2 13.8 16.2 16.3 17.7 17.7

2040 -- 15.6 15.5 15.4 17.3 20.2 20.4 22.2 22.2

2050 -- 18.6 18.5 18.3 20.7 24.1 24.4 26.5 26.4

2060 -- 22.1 22.1 21.8 24.6 28.7 29.0 31.5 31.5

1 

Table 2.6-11 

Cumulative Effects of Light Truck Annual Fuel Consumption and Fuel Savings (billion gallons gasoline 

equivalent) by Alternative 

Calendar Year 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

~5.9%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.7%/year 

Increase 

TCTB 

Fuel Consumption

2020 68.3 65.6 64.9 64.6 64.0 62.8 63.1 62.5 62.4

2030 62.8 56.8 56.5 56.3 55.0 53.3 53.4 52.5 52.6

2040 66.7 58.9 58.9 58.7 57.1 55.2 55.2 54.1 54.3

2050 77.1 67.8 67.8 67.6 65.7 63.4 63.4 62.1 62.4

2060 91.2 80.1 80.1 79.9 77.6 74.9 74.9 73.3 73.7

Fuel Savings Compared to No Action

2020 -- 2.7 3.4 3.7 4.4 5.6 5.3 5.8 5.9

2030 -- 6.0 6.3 6.6 7.8 9.5 9.4 10.3 10.2

2040 -- 7.7 7.8 8.0 9.5 11.5 11.5 12.6 12.3

2050 -- 9.3 9.3 9.5 11.4 13.7 13.7 15.0 14.7

2060 -- 11.1 11.1 11.3 13.6 16.3 16.3 17.9 17.5

2 
 Chapter 2 Proposed Action and Alternatives 

 2-37 

1 2.6.2.2 Air Quality 

2 Table 2.6-12 summarizes the cumulative impacts for national toxic and criteria pollutants in 

2050.35 3 The table lists the action alternatives (Alternatives 2 through 9) left to right in order of increasing 

4 fuel economy requirements. In the case of PM2.5, SOx, NOx, and VOCs, the No Action Alternative results 

5 in the highest annual emissions, and emissions generally decline as fuel economy standards increase 

6 across alternatives. Exceptions to this declining trend are NOx under Alternative 7; PM2.5 under 

7 Alternatives 3 and 4, and Alternatives 8 and 9; SOx under Alternatives 3 through 5, and Alternatives 7 and 

8 9; and VOCs under Alternative 7. Despite these individual increases, emissions of PM2.5, SOx, NOx, and 

9 VOCs remain below the levels under the No Action Alternative. In the case of CO, emissions under 

10 Alternatives 2 through 4 are slightly higher than under the No Action Alternative and are lower than 

11 under the No Action Alternative under Alternatives 5 through 9. Emissions of CO decline as fuel 

12 economy standards increase across Alternatives 2 through 9. 

Table 2.6-12 

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

~5.9%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.7%/year

Increase 

TCTB 

Criteria Pollutant Emissions (Calendar Year 2050) 

Carbon 

monoxide 

(CO) 24,155,097 24,530,976 24,385,367 24,315,810 23,541,753 22,770,712 22,314,840 22,130,779 22,061,720

Nitrogen 

oxides (NOx) 1,809,786 1,786,720 1,780,335 1,778,462 1,733,908 1,690,190 1,667,885 1,653,446 1,650,090

Particulate 

matter (PM2.5) 107,387 102,210 102,469 102,885 102,501 102,698 103,025 102,490 102,512

Sulfur oxides 

(SOx) 262,948 229,228 230,352 231,083 230,124 227,819 230,366 227,019 227,650

Volatile 

organic compounds (VOC) 1,803,222 1,652,075 1,645,210 1,640,518 1,587,401 1,522,744 1,501,494 1,476,771 1,476,595

Toxic Air Pollutant Emissions (Calendar Year 2050) 

Acetaldehyde 7,953 8,070 8,064 8,048 8,074 8,068 8,068 8,088 8,088

Acrolein 411 418 422 426 449 478 490 498 478

Benzene 28,048 28,111 27,984 27,901 27,253 26,534 26,164 25,993 25,945

1,3-butadiene 4,180 4,249 4,239 4,235 4,189 4,148 4,117 4,111 4,106

Diesel 

particulate 

matter (DPM) 138,391 120,407 120,494 120,706 118,016 114,922 114,724 112,629 112,810

Formaldehyde 10,901 10,966 11,022 11,036 11,416 11,775 11,970 12,092 12,118

 

35 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 

 2-38 

1 As with criteria pollutants, annual emissions of most toxic air pollutants would decrease from one 

2 alternative to the next more stringent alternative. The exceptions are acrolein under Alternative 9; 

3 benzene under Alternatives 3 through 9; 1,3-butadiene under Alternatives 3 through 9; and formaldehyde 

4 under Alternatives 3 through 6. The changes in toxic air pollutant emissions, whether positive or 

5 negative, generally would be small in relation to Alternative 1 emissions levels. 

6 Cumulative emissions generally would be less than noncumulative emissions for the same 

7 combination of pollutant, year (excluding 2016 which is equivalent to the noncumulative emissions in all 

8 cases), and alternative because of differing changes in VMT and fuel consumption under the cumulative 

9 case compared to the noncumulative case. The exceptions are acrolein for all alternatives except 

10 Alternative 9, 1,3-butadiene for all alternatives except Alternative 2, and CO for all alternatives. 

11 The reductions in emissions are expected to lead to reductions in cumulative adverse health 

12 effects. Table 2.6-13 summarizes the national annual changes in health outcomes in 2050 for the nine 

13 alternatives, left to right in order of increasing fuel economy requirements. There would be reductions in 

14 adverse health effects nationwide under all the action alternatives compared to the No Action Alternative. 

15 Reductions in adverse health effects decrease from Alternative 2 through Alternative 3, with mixed 

16 results under Alternatives 4 through 7, and decreasing again under Alternatives 8 and 9. These reductions 

17 primarily reflect the projected PM2.5 reductions, and secondarily the reductions in SO2. 

Table 2.6-13 

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 

~5.9%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.7%/year 

Increase 

TCTB 

Mortality (ages 30 and older) 

Pope et al. 2002 

2050 0 -364 -356 -339 -406 -453 -455 -504 -504

Laden et al. 2006 

2050 0 -930 -911 -867 -1,037 -1,157 -1,162 -1,287 -1,288

Chronic bronchitis 

2050 0 -230 -226 -215 -259 -290 -292 -323 -323

Emergency Room Visits for Asthma 

2050 0 -323 -315 -300 -347 -382 -377 -417 -416

Work Loss Days 

2050 0 -39,749 -38,969 -37,043 -44,648 -49,958 -50,334 -55,754 -55,808

__________ 

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. 

18 The economic value of health impacts would vary proportionally with changes in health 

19 outcomes. Table 2.6-14 lists the corresponding annual reductions in health costs in 2050 under the action 

20 alternatives compared to the No Action Alternative. Reductions in health costs are given for two 

21 alternative assumptions of the discount rate, 3 percent and 7 percent, consistent with EPA policy for 

22 presentation of future health costs. 
 Chapter 2 Proposed Action and Alternatives 

 2-39 

Table 2.6-14 

Cumulative Nationwide Changes in Health Costs (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 

~5.9%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.7%/year 

Increase 

TCTB 

3-% Discount Rate

Pope et al. 2002 

2050 0 -3,292 -3,225 -3,067 -3,672 -4,097 -4,116 -4,558 -4,560

Laden et al. 2006 

2050 0 -8,069 -7,903 -7,518 -8,999 -10,040 -10,083 -11,167 -11,171

7-% Discount Rate

Pope et al. 2002 

2050 0 -2,985 -2,924 -2,782 -3,331 -3,716 -3,733 -4,134 -4,136

Laden et al. 2006 

2050 0 -7,287 -7,138 -6,790 -8,128 -9,068 -9,107 -10,087 -10,090

__________ 

a/ Negative changes indicate economic benefit; positive emissions changes indicate economic costs. 

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. 

1 

2 Climate Change 

3 The Reference Case global emissions scenario used in the cumulative impacts analysis (and 

4 described in Chapter 4 of this EIS) differs from the global emissions scenario used for the climate change 

5 modeling presented in Chapter 3. In Chapter 4, the Reference Case global emission scenario reflects 

6 reasonably foreseeable actions in global climate change policy; in Chapter 3, the global emissions 

7 scenario used for the analysis assumes that there are no significant global controls. Given that the climate 

8 system is non-linear, the choice of a global emissions scenario could produce different estimates of the 

9 benefits of the proposed action and alternatives, if the emission reductions of the alternatives were held 

10 constant. 

11 The SAP 2.1 MiniCAM Level 3 scenario assumes a moderate level of global GHG reductions, 

12 resulting in a global atmospheric CO2 concentration of roughly 650 parts per million by volume (ppmv) 

13 as of 2100. The following regional, national, and international initiatives and programs are reasonably 

14 foreseeable actions to reduce GHG emissions: Regional Greenhouse Gas Initiative (RGGI); Western 

15 Climate Initiative (WCI); Midwestern Greenhouse Gas Reduction Accord; EPA’s Proposed GHG 

16 Emissions Standards; H.R. 2454: American Clean Energy and Security Act (“Waxman-Markey Bill”); 

17 Renewable Fuel Standard (RFS2); Program Activities of DOE’s Office of Fossil Energy; Program 

18 Activities of DOE’s Office of Nuclear Energy; United Nation’s Framework Convention on Climate 

19 Change (UNFCCC) – The Kyoto Protocol and upcoming Conference of the Parties (COP) 15 in 

20 Copenhagen, Denmark; G8 Declaration – Summit 2009; and the Asia Pacific Partnership on Clean 

Development and Climate.36 21 

 

36 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 

(continued on bottom of next page) 
Chapter 2 Proposed Action and Alternatives 

 2-40 

1 NHTSA used the MiniCAM Level 3 scenario as the primary global emissions scenario for 

2 evaluating climate effects, and used the MiniCAM Level 2 scenario and the RCP 4.5 MiniCAM reference 

3 emissions scenario to evaluate the sensitivity of the results to alternative emission scenarios. The 

4 sensitivity analysis provides a basis for determining climate responses to varying levels of climate 

5 sensitivities and global emissions and under the No Action Alternative (Alternative 1) and the Preferred 

6 Alternative (Alternative 4). Some responses of the climate system are believed to be non-linear; by using 

7 a range of emissions cases and climate sensitivities, it is possible to estimate the effects of the alternatives 

8 in relation to different reference cases. 

9 2.6.2.2.1 Cumulative GHG Emissions 

10 Table 2.6-15 shows total GHG emissions and emissions reductions from new passenger cars and 

11 light trucks from 2012-2100 under each of the nine alternatives. Projections of emissions reductions over 

12 the 2012 to 2100 period due to the MY 2012-2016 CAFE standards and other reasonably foreseeable 

13 future actions ranged from 27,300 to 39,100 MMTCO2. Compared to global emissions of 3,919,462 

14 MMTCO2 over this period (projected by the SAP 2.1 MiniCAM Level 3 scenario), the incremental 

15 impact of this rulemaking is expected to reduce global CO2 emissions by about 0.7 to 1.0 percent from 

16 their projected levels under the No Action Alternative. 

Table 2.6-15 

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 227,600 0 

2 3%/year Increase 200,300 27,300 

3 4%/year Increase 200,200 27,300 

4 ~4.3%/year Increase, Preferred 200,300 27,300 

5 5%/year Increase 196,700 30,900 

6 ~5.9%/year Increase, MNB 191,600 36,000 

7 6%/year Increase 191,800 35,800 

8 7%/year Increase 188,500 39,100 

9 ~6.7%/year Increase, TCTB 188,790 38,791 

17 

18 Emissions of CO2, the primary gas that drives climate effects, from the U.S. passenger-car and 

light-truck fleet represented about 3.7 percent of total global emissions of CO2 in 2005.37 19 Although 

20 substantial, this source is a still small percentage of global emissions. The relative contribution of CO2

21 emissions from the U.S. passenger cars and light trucks is expected to decline in the future, due primarily 

22 to rapid growth of emissions from developing economies (which are due in part to growth in global 

23 transportation sector emissions). 

 

towards significant GHG reductions. Together they imply that future commitments for reductions are probable and, 

therefore, reasonably foreseeable under NEPA. 

37 Includes land-use change and forestry, and excludes international bunker fuels. 
 Chapter 2 Proposed Action and Alternatives 

 2-41 

1 2.6.2.2.2 CO2 Concentration, Global Mean Surface Temperature, Sea-level Rise, 

2 and Precipitation 

3 The mid-range results of MAGICC model simulations for the No Action Alternative and the eight 

4 action alternatives in terms of CO2 concentrations and increase in global mean surface temperature in 

5 2030, 2050, and 2100 are presented in Table 2.6-16 and Figures 2.6-6 through 2.6-9. As Figures 2.6-8 

6 and 2.6-9 show, the impact on the growth in CO2 concentrations and temperature is just a fraction of the 

7 total growth in CO2 concentrations and global mean surface temperature. However, the relative impact of 

8 the action alternatives is illustrated by the reduction in growth of both CO2 concentrations and 

9 temperature in the TCTB Alternative (Alternative 9). 

10 As shown in the table and figures, there is a fairly narrow band of estimated CO2 concentrations 

11 as of 2100, from 654.0 ppm for the TCTB Alternative (Alternative 9) to 657.5 ppm for the No Action 

12 Alternative (Alternative 1). For 2030 and 2050, the range is even smaller. Because CO2 concentrations 

13 are the key driver of all other climate effects, this leads to small differences in these effects. Although 

14 these effects are small, they occur on a global scale and are long-lived. 

15 The MAGICC simulations of mean global surface air temperature increases are also shown in 

16 Table 2.6-16. For all alternatives, the cumulative global mean surface temperature increase is about 

0.80 °C to 0.81 °C as of 2030; 1.32 to 1.33 °C as of 2050; and 2.60 to 2.61 °C as of 2100.38 17 The 

18 differences among alternatives are small. For 2100, the reduction in temperature increase for the action 

19 alternatives in relation to the No Action Alternative is about 0.01 to 0.02 °C. 

20 The impact on sea-level rise from the scenarios is presented in Table 2.6-16, showing sea-level rise in 

21 2100 ranging from 32.84 centimeters under the No Action Alternative (Alternative 1) to 32.70 

22 centimeters under the TCTB Alternative (Alternative 9), for a maximum reduction of 0.14 centimeters by 

23 2100 from the action alternatives. 

Table 2.6-16 

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 438.7 498.0 657.5 0.805 1.327 2.611 7.83 13.67 32.84

2 3%/year Increase 438.5 497.3 655.1 0.805 1.323 2.600 7.83 13.65 32.75

3 4%/year Increase 438.5 497.3 655.1 0.805 1.323 2.600 7.83 13.65 32.75

4 ~4.3%/year Increase, Preferred 438.5 497.3 655.1 0.804 1.323 2.600 7.83 13.65 32.75

5 5%/year Increase 438.4 497.2 654.7 0.804 1.323 2.599 7.83 13.65 32.73

6 ~5.9%/year Increase, MNB 438.4 497.0 654.3 0.804 1.322 2.596 7.83 13.64 32.71

7 6%/year Increase 438.4 497.0 654.3 0.804 1.322 2.596 7.83 13.64 32.71

8 7%/year Increase 438.4 496.9 654.0 0.804 1.321 2.595 7.83 13.64 32.70

9 ~6.7%/year Increase, TCTB 438.4 496.9 654.0 0.804 1.321 2.595 7.83 13.64 32.70

 

38 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. 
Chapter 2 Proposed Action and Alternatives 

 2-42 

Table 2.6-16 (continued) 

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 

Reductions Under Alternative CAFE Standards

2 3%/year Increase 0.2 0.7 2.4 0.001 0.003 0.011 0.00 0.02 0.09 

3 4%/year Increase 0.2 0.7 2.4 0.001 0.003 0.011 0.00 0.02 0.09 

4 ~4.3%/year Increase, Preferred 0.2 0.7 2.4 0.001 0.004 0.011 0.00 0.02 0.09 

5 5%/year Increase 0.3 0.8 2.8 0.001 0.004 0.012 0.00 0.02 0.11 

6 ~5.9%/year Increase, MNB 0.3 1.0 3.2 0.001 0.005 0.015 0.00 0.03 0.13 

7 6%/year Increase 0.3 1.0 3.2 0.001 0.005 0.015 0.00 0.03 0.13 

8 7%/year Increase 0.3 1.1 3.5 0.002 0.005 0.016 0.00 0.03 0.14 

9 ~6.7%/year Increase, TCTB 0.3 1.1 3.5 0.002 0.005 0.016 0.00 0.03 0.14 

a/ Values in this table are rounded. 

1 

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

2 
 Chapter 2 Proposed Action and Alternatives 

 2-43 

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

Using MAGICC by Alternative 

1 
Chapter 2 Proposed Action and Alternatives 

 2-44 

Figure 2.6-8. Cumulative Effects on CO2 Concentrations (Reduction Compared to the No 

Action Alternative) 

1 
 Chapter 2 Proposed Action and Alternatives 

 2-45 

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

Compared to the No Action Alternative) 

1 

2 Given that the action alternatives would reduce temperature increases slightly in relation to the 

3 No Action Alternative (Alternative 1), they also would reduce predicted increases in precipitation 

4 slightly, as shown in Table 2.6-17. 

5 In summary, the impacts of the proposed action and alternatives and other reasonably foreseeable 

6 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.39 7 

8 This is due primarily to the global and multi-sectoral nature of the climate problem. Although these 

9 effects are small, they occur on a global scale and are long-lived. 

 

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 

 2-46 

Table 2.6-17 

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 2.406 

3 4%/year Increase 0.586 1.462 2.406 

4 ~4.3%/year Increase, Preferred 0.586 1.462 2.406 

5 5%/year Increase 0.586 1.461 2.405 

6 ~5.9%/year Increase, MNB 0.586 1.460 2.403 

7 6%/year Increase 0.586 1.460 2.403 

8 7%/year Increase 0.586 1.459 2.401 

9 ~6.7%/year Increase, TCTB 0.586 1.459 2.402 

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 0.009 

3 4%/year Increase 0.000 0.004 0.009 

4 ~4.3%/year Increase, Preferred 0.000 0.004 0.009 

5 5%/year Increase 0.000 0.005 0.011 

6 ~5.9%/year Increase, MNB 0.000 0.006 0.013 

7 6%/year Increase 0.000 0.006 0.013 

8 7%/year Increase 0.000 0.006 0.014 

9 ~6.7%/year Increase, TCTB 0.000 0.006 0.014 

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 ~5.9%/year Increase, MNB 0.85% 2.20% 3.92% 

7 6%/year Increase 0.85% 2.20% 3.92% 

8 7%/year Increase 0.85% 2.20% 3.91% 

9 ~6.7%/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% 0.01% 

3 4%/year Increase 0.00% 0.01% 0.01% 

4 ~4.3%/year Increase, Preferred 0.00% 0.01% 0.02% 

5 5%/year Increase 0.00% 0.01% 0.02% 

6 ~5.9%/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% 0.02% 

9 ~6.7%/year Increase, TCTB 0.00% 0.01% 0.02% 

a/ Values in this table are rounded. 

1 

2 NHTSA examined the sensitivity of climate effects on key assumptions used in the analysis. The 

3 two variables for which assumptions were varied were climate sensitivity and global emissions. 

4 Climate sensitivities used included 2.0, 3.0, and 4.5 °C for a doubling of CO2 concentrations in 

5 the atmosphere. Global emissions scenarios used included the SAP 2.1 MiniCAM Level 3 (650 ppm as 

6 of 2100), the SAP 2.1 MiniCAM Level 2 (550 ppm as of 2100), and RCP 4.5 MiniCAM reference 
 Chapter 2 Proposed Action and Alternatives 

 2-47 

1 scenario (783 ppm as of 2100). The sensitivity analysis is based on the results provided for two 

2 alternatives – the No Action Alternative (Alternative 1) and the Preferred Alternative (Alternative 4). The 

3 sensitivity analysis was conducted only for two alternatives, as this was deemed sufficient to assess the 

4 effect of various climate sensitivities on the results. 

5 The results of these simulations illustrate the uncertainty due to factors influencing future global 

6 emissions of GHGs (factors other than the CAFE rulemaking). 

The use of different climate sensitivities40 7 (the equilibrium warming that occurs at a doubling of 

8 CO2 from pre-industrial levels) can affect not only warming but also indirectly affect sea-level rise and 

9 CO2 concentration. The use of alternative global emissions scenarios can influence the results in several 

10 ways. Emissions reductions can lead to larger reductions in the CO2 concentrations in later years because 

11 more anthropogenic emissions can be expected to stay in the atmosphere. 

12 As shown in Table 2.6-18, the sensitivity of the simulated CO2 emissions in 2030, 2050, and 2100 

13 to assumptions of global emissions and climate sensitivity is low; stated simply, CO2 emissions do not 

14 change much with changes in global emissions and climate sensitivity. For 2030 and 2050, the choice of 

15 global emissions scenario has little impact on the results. By 2100, the Preferred Alternative (Alternative 

16 4) has the greatest impact in the global emissions scenario with the highest CO2 emissions (MiniCAM 

17 Reference) and the least impact in the scenario with the lowest CO2 emissions (MiniCAM Level 2). The 

18 total range of the impact of the Preferred Alternative on CO2 concentrations in 2100 is from 2.2 to 2.7 

19 ppm. The Reference Case using the MiniCAM Level 3 scenario and a 3.0 °C climate sensitivity has an 

20 impact of 2.4 ppm. 

21 The sensitivity of the simulated global mean surface temperatures for 2030, 2050, and 2100 is 

22 also shown in Table 2.6-18. In 2030, the impact is low due primarily to the slow rate at which the global 

23 mean surface temperature increases in response to increases in radiative forcing. The relatively slow 

24 response in the climate system explains the observation that even by 2100, when CO2 concentrations 

25 more than double in comparison to pre-industrial levels, the temperature increase is below the equilibrium 

26 sensitivity levels, i.e., the climate system has not had enough time to equilibrate to the new CO2

27 concentrations. Nonetheless, as of 2100 there is a larger range in temperatures across the different values 

28 of climate sensitivity: the reduction in global mean surface temperature from the No Action Alternative to 

29 the Preferred Alternative ranges from 0.008 °C for the 2.0 °C climate sensitivity to 0.014 °C for the 4.5 

30 °C climate sensitivity, for the MiniCAM Level 3 emissions scenario. 

31 The impact on global mean surface temperature due to assumptions concerning global emissions 

32 of GHGs is also important. The scenario with the higher global emissions of GHGs (viz., the MiniCAM 

33 Reference) has a slightly lower reduction in global mean surface temperature, and the scenario with lower 

34 global emissions (viz., the MiniCAM Level 2) has a slightly higher reduction. This is in large part due to 

35 the non-linear and near-logarithmic relationship between radiative forcing and CO2 concentrations. At 

36 high emissions levels, CO2 concentrations are higher and, as a result, a fixed reduction in emissions yields 

37 a lower reduction in radiative forcing and global mean surface temperature. 

38 

 

40 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 

 2-48 

Table 2.6-18 

Cumulative Effects on CO2 Concentration, Temperature, 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 2.0 434.3 483.0 551.3 0.612 0.986 1.546 22.32 

 3.0 435.7 486.5 563.5 0.812 1.324 2.177 29.92 

 4.5 437.4 490.5 578.8 1.034 1.705 2.948 38.76 

 Reduction compared to No Action 

 2.0 0.2 0.8 2.2 0.001 0.003 0.009 0.08 

 3.0 0.3 0.8 2.4 0.001 0.004 0.012 0.11 

 4.5 0.2 0.8 2.5 0.001 0.004 0.015 0.12 

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 2.0 437.0 493.8 641.0 0.606 0.987 1.880 24.60 

 3.0 438.5 497.3 655.1 0.804 1.323 2.600 32.75 

 4.5 440.1 501.3 672.6 1.023 1.702 3.461 42.12 

 Reduction compared to No Action 

 2.0 0.3 0.7 2.4 0.001 0.003 0.008 0.08 

 3.0 0.2 0.7 2.4 0.001 0.004 0.011 0.09 

 4.5 0.2 0.7 2.6 0.001 0.004 0.014 0.12 

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 2.0 439.9 510.0 762.6 0.699 1.166 2.285 28.61 

 3.0 441.5 514.1 780.4 0.922 1.553 3.126 37.91 

 4.5 443.3 518.8 802.6 1.166 1.987 4.120 48.55 

 Reduction compared to No Action 

 2.0 0.3 0.7 2.5 0.001 0.003 0.007 0.07 

 3.0 0.3 0.7 2.6 0.001 0.003 0.010 0.09 

 4.5 0.3 0.8 2.7 0.001 0.004 0.012 0.12 

a/ Values in this table are rounded. 

1 

2 The sensitivity of the simulated sea-level rise to changes in climate sensitivity and global GHG emissions 

3 mirrors that of global temperature, as shown in Table 2.6-18. Scenarios with lower climate sensitivities 

4 have lower increases in sea-level rise. The greater the climate sensitivity, the greater the decrement in 

5 sea-level rise for the Preferred Alternative as compared to the No Action Alternative. 
3-1 

1 Chapter 3 Affected Environment and Environmental 

2 Consequences 

3 3.1 INTRODUCTION 

4 Council on Environmental Quality (CEQ) regulations for implementing the National 

5 Environmental Policy Act (NEPA) suggest a standard format for an environmental impact statement 

6 (EIS) that includes a section to describe the affected environment (existing conditions) and a section to 

7 describe the potential environmental consequences (impacts) of a proposed action and alternatives. In 

8 this EIS, the National Highway Traffic Safety Administration (NHTSA) describes the affected 

9 environment and potential environmental consequences of the proposed action and alternatives in sections 

10 under the heading for each resource area – energy (Section 3.2), air quality (Section 3.3), climate (Section 

11 3.4), and various other potentially affected resource areas (Section 3.5). This structure enables the reader 

12 to readily learn about existing environmental conditions and potential environmental consequences 

13 related to each resource area. Section 3.6 identifies unavoidable impacts and irreversible and irretrievable 

14 commitments of resources associated with the implementation of the Corporate Average Fuel Economy 

15 (CAFE) standards evaluated in this EIS. 

16 The following table lists topics addressed in a typical EIS and the section(s) in this chapter that 

17 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 

18 
3.1 Introduction Chapter 3 Affected Environment and Environmental Consequences 

 3-2 

1 3.1.1 Direct and Indirect Impacts 

2 CEQ regulations state that an EIS “shall succinctly describe” the environment to be affected by 

3 the alternatives under consideration and to provide data and analyses “commensurate with the importance 

4 of the impact[s].” 40 Code of Federal Regulations (CFR) §§ 1502.15, 1502.16. This chapter provides the 

5 analysis to determine and compare the significance of the direct and indirect effects of the proposed 

6 action and alternatives. Under NEPA, direct effects “are caused by the action and occur at the same time 

7 and place.” 40 CFR § 1508.8. CEQ regulations define indirect effects as those that “are caused by the 

8 action and are later in time or farther removed in distance but are still reasonably foreseeable. Indirect 

9 effects may include...effects on air and water and other natural systems, including ecosystems.” 40 CFR 

10 § 1508.8. Sections 3.2, 3.3, and 3.4 provide a quantitative analysis of the direct and indirect effects of the 

11 proposed action and alternatives on energy, air, and climate, respectively. Section 3.5 qualitatively 

12 describes impacts to other resource areas typically addressed in an EIS and the areas required by U.S. 

13 Department of Transportation (DOT) Order 5610, such as biological resources, water resources, noise, 

14 land use, and environmental justice, because there were not enough data available in the literature for a 

15 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 16 

17 3.1.2 Areas Not Affected 

18 DOT NEPA procedures describe various areas that should be considered in an EIS. Many of 

19 these areas are addressed Sections 3.2 through 3.6. NHTSA has considered the impact of the proposed 

20 action and alternatives on all areas outlined in the procedures and has determined that the action 

21 alternatives would not directly or indirectly affect the human environment in relation to disruption and 

22 relocation, and considerations related to pedestrians and bicyclists, floodplain management, and 

23 construction impacts. However, the cumulative impacts of the proposed action and alternatives in 

24 combination with other foreseeable actions could affect some of these areas of the human environment 

25 (see Chapter 4). 

26 3.1.3 Approach to Scientific Uncertainty and Incomplete Information 

27 3.1.3.1 CEQ Regulations 

28 CEQ regulations recognize that many federal agencies encounter limited information and 

29 substantial uncertainties when they analyze the potential environmental impacts of their actions. 

30 Accordingly, the regulations provide agencies with a means of formally acknowledging incomplete or 

31 unavailable information in NEPA documents. Where “information relevant to reasonably foreseeable 

32 significant adverse impacts cannot be obtained because the overall costs of obtaining it are exorbitant or 

33 the means to obtain it are not known,” the regulations require an agency to include in its NEPA 

34 document: 

35 1. A statement that such information is incomplete or unavailable; 

36 2. A statement of the relevance of the incomplete or unavailable information to evaluating 

37 reasonably foreseeable significant adverse impacts on the human environment; 

 

1 See 42 United States Code (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 

DELIBERATIVE 3-3 

1 3. A summary of existing credible scientific evidence relevant to evaluating the reasonably 

2 foreseeable significant adverse impacts on the human environment; and 

3 4. The agency’s evaluation of such impacts based on theoretical approaches or research methods 

4 generally accepted in the scientific community. 

5 40 CFR § 1502.22(b). 

6 Relying on these provisions is appropriate when an agency is performing a NEPA analysis that 

7 involves potential environmental impacts due to carbon dioxide (CO2) emissions. See, e.g., Mayo Found. 

8 v. Surface Transp. Bd., 472 F.3d 545, 555 (8th Cir. 2006). CEQ regulations also authorize agencies to 

9 incorporate material into a NEPA document by reference to “cut down on bulk without impeding agency 

10 and public review of the action.” 40 CFR § 1502.21. 

11 Throughout this EIS, NHTSA uses these two mechanisms – acknowledging incomplete or 

12 unavailable information and incorporation by reference – to address areas for which NHTSA cannot 

13 develop a credible estimate of the potential environmental impacts of the proposed action and 

14 alternatives. In particular, NHTSA recognizes that information about the potential environmental impacts 

15 of changes in emissions of CO2 and other greenhouse gases (GHGs) and associated changes in 

16 temperature, including those expected to result from the proposed rule, is incomplete. NHTSA often 

17 relies on the Intergovernmental Panel on Climate Change (IPCC) 2007 Fourth Assessment Report (IPCC 

18 2007a, 2007b, 2007c)as a recent “summary of existing credible scientific evidence which is relevant to 

19 evaluating the reasonably foreseeable significant adverse impacts on the human environment.” 40 CFR § 

20 1502.22(b)(3). 

21 3.1.4 Common Methodologies 

22 The CAFE Compliance and Effects Modeling System (referred to herein as the Volpe model) is a 

23 peer-reviewed modeling system developed by the DOT Volpe National Transportation Systems Center 

24 (Volpe Center). The Volpe model enables NHTSA to efficiently, systematically, and reproducibly 

25 evaluate many regulatory options by projecting technologies each manufacturer could apply in a given 

26 year to comply with a specific set of standards and by calculating the costs and effects of manufacturers’ 

27 application of technologies, including changes in fuel use and therefore CO2 emissions. The Volpe model 

28 provides outputs NHTSA used to analyze potential impacts to energy, air, and climate. 

29 The Volpe model begins with an initial state of the domestic vehicle market, which in this case is 

30 the market for passenger cars and light trucks. The model is designed to calculate incremental costs, 

31 effects, and benefits of alternative scenarios (i.e., regulatory alternatives) relative to a specified baseline 

32 scenario (i.e., a no-action alternative) and based on a specified market forecast. The market forecast, the 

33 baseline scenario, and all alternative scenarios are specified in model inputs. The model does not 

34 determine these inputs. For this analysis, the market forecast through model year (MY) 2016 specified as 

35 an input to the Volpe model is based on the MY 2008 fleet, with adjustments to sales volumes of specific 

36 vehicle models. NHTSA used the Volpe model to estimate the extent to which manufacturers could add 

37 technology under the baseline scenario, under which manufacturers are assumed to continue to comply 

38 with the MY2011 CAFE standards. This baseline scenario forms NHTSA's no-action alternative. All 

39 environmental effects attributable to technologies added under this scenario are subtracted from those 

40 attributable to all the other scenarios (i.e., regulatory alternatives). 

41 For the model years covered under the current proposal, the combined passenger-car and light42 truck market forecast developed by NHTSA and the U.S. Environmental Protection Agency (EPA) staff 

43 using MY 2008 CAFE compliance data includes about 1,100 vehicle models, about 400 specific engines, 

44 and about 200 specific transmissions. This level of detail in the representation of the vehicle market is 
3.1 Introduction Chapter 3 Affected Environment and Environmental Consequences 

 3-4 

1 similar to that NHTSA used in recent CAFE analyses. Within the limitations of information that can be 

2 made available to the public, it provides the foundation for a realistic analysis of manufacturer-specific 

3 costs and the analysis of footprint-based CAFE standards, and this level of detail is much greater than the 

4 level of detail used by many other models and analyses relevant to combined passenger-car and lighttruck fuel economy.2 5 

6 The Volpe model also uses several additional categories of data and estimates provided in various 

7 external input files for all 12 vehicle subclasses (sub-compact, sub-compact performance, compact, 

8 compact performance, midsize, midsize performance, large, and large performance cars; small sport 

9 utility vehicles [SUVs]/pickup trucks/vans, midsize SUVs/pickup trucks/vans, large SUVs/pickup 

10 trucks/vans, and minivans) including: 

11  Fuel-saving technology characteristics 

12  Commercialization year; 

13  Effectiveness and cost; 

14  “Learning effect” cost coefficients; 

15  “Technology path” inclusion/exclusion; 

16  “Phase-in caps” on penetration rates; and 

17  “Synergy” effects. 

18  Vehicular emissions rates for criteria air pollutants and their chemical precursors, including 

19 carbon monoxide (CO), volatile organic compounds (VOCs), nitrogen oxides (NOx), 

20 particulate matter (PM), and sulfur dioxide (SO2); these emission rates are functions of either 

21 vehicle use, as measured by the number of vehicle miles traveled (VMT), or fuel 

22 consumption, economic, and other data and estimates, such as: 

23  Vehicle survival (percent of vehicles of a given vintage that remain in service); 

24  Mileage accumulation (annual travel by vehicles of a given vintage); 

25  Price/fuel taxation rates for seven fuels (such as gasoline and diesel); 

26  Pump prices (including taxes) for vehicle fuel savings/retail price; 

27  Rebound effect coefficient (the elasticity of VMT in relation to per-mile cost of fuel); 

28  Discount rate; “payback period” (the number of years purchasers consider when taking 

29 into account fuel savings); 

30  Fuel economy “gap” (for example, laboratory versus actual); 

31  Per-vehicle value of travel time (in dollars per hour); 

32  The economic costs (in dollars per gallon) of petroleum consumption; 

33  Various external costs (all in dollars per mile) associated with changes in vehicle use; 

34  Damage costs (all on a dollar-per-ton basis) for each of the above-mentioned criteria 

35 pollutants; and 

36  The civil-penalties rate for noncompliance. 

37  Properties of different fuels 

38  Upstream CO2 and criteria pollutant emissions rates (that is, U.S. emissions resulting 

39 from the production and distribution of each fuel); 

 

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 fleets 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 

DELIBERATIVE 3-5 

1  Density (pounds per gallon); energy density (British thermal unit per gallon); 

2  Carbon content; 

3  Shares of fuel savings leading to reduced domestic refining; and 

4  Relative shares of different gasoline blends. 

5  Sensitivity analysis coefficients; high and low fuel price forecasts. 

6  CAFE scenarios 

7  Baseline (no action or business-as-usual); and 

8  Alternative scenarios defining coverage, structure, and stringency of CAFE standards. 

9 NHTSA estimates and specifies all of the input data, then uses the modeling system to project a 

10 set of technologies that each manufacturer could apply to its individual vehicle models in attempting to 

11 comply with the various levels of potential CAFE standards to be examined. The Volpe model then 

12 estimates the costs associated with this additional technology utilization, and accompanying changes in 

13 travel demand; fuel consumption; fuel outlays; emissions of criteria air pollutants; toxic air pollutants; 

14 and GHGs, and economic externalities related to petroleum consumption and other factors. 

15 One of the updates to the model for the current rulemaking is the addition of a “multiyear 

16 planning” capability, developed in response to comments on prior CAFE rulemakings. The version of the 

17 Volpe model used in the previous EIS did not have that capability. For example, when modeling MY 

18 2014, only vehicles with technologies “enabled” in MY 2014 would be candidates for technology 

19 application. When run in multi-year mode, the model “looks back” to earlier years when a technology 

20 was enabled on any vehicles but not used, and considers “back-dating” the application of that technology 

21 when calculating the effective cost. Thus, if the model did not apply an enabled technology in MYs 2012 

22 or 2013, then that technology remains available for multi-year application in MY 2014. 

23 The Volpe model’s multi-year analysis mode is anticipated to be most useful in situations where 

24 the model finds that a manufacturer is able to reach compliance in earlier years of the modeling period 

25 (e.g., MY 2012) but is challenged to reach compliance in later years (e.g., MY 2014). In these cases, the 

26 model can go back to the earlier year and over-comply to make compliance in the later year easier to 

27 achieve. Although this capability is computationally implemented in this “backward-looking” fashion, 

28 the approach simulates a given manufacturer’s ability to apply foresight, adding “extra” technology to a 

29 given model year to facilitate compliance in later model years. 

30 The Volpe model completes this compliance simulation for all manufacturers and all model years 

31 and produces various outputs from the effects of changes in fuel economy. The outputs include: 

32  Total cost (TC) of all applied technologies; 

33  Year-by-year mileage accumulation, including increased vehicle use due to the rebound 

34 effect; 

35  Year-by-year fuel consumption; 

36  Benefits from additional travel due to the fuel economy rebound effect, as measured by 

consumer surplus;3 37 

 

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). 
3.1 Introduction Chapter 3 Affected Environment and Environmental Consequences 

 3-6 

1  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 2 

3 and the economic value of resulting damages to human health; 

4  Total discounted/undiscounted national societal costs of year-to-year fuel consumption; 

5  Economic externalities caused by increased vehicle use (congestion, accidents, noise); 

6  Value of refueling time saved; and 

7  Total discounted/undiscounted societal benefits, including net social benefits and benefit-cost 

8 ratio (EIA 2008). 

9 The specific outputs associated with each action alternative examined in this EIS reflect the 

10 assumed values for key inputs to the Volpe model. The outputs of the Volpe model provide data used to 

11 analyze impacts to energy, air, and climate, so these environmental impacts also reflect the inputs into the 

12 Volpe model. Recognizing the uncertainty inherent in many of the underlying estimates in the model, 

13 NHTSA has used the Volpe model to conduct both sensitivity analyses (by changing the assumed value 

14 of one input at a time), and a probabilistic uncertainty analysis (a Monte Carlo analysis that allows 

15 simultaneous variation in these factors) to examine how key measures (e.g., miles-per-gallon [mpg] levels 

16 of the standard, total costs, and total benefits) vary in response to changes in these factors. This type of 

17 analysis is used to estimate the uncertainty surrounding the model’s estimates of the costs and benefits of 

18 a given set of CAFE standards. Chapter 2 describes the results of the sensitivity analysis. 

19 The model can also be used to fit coefficients defining the shape and level of attribute-based 

20 CAFE-standard curves, and to estimate the stringency at which various criteria are satisfied, such as (a) a 

21 specified average required CAFE level, (b) maximum net benefits to society, (c) total costs equal to total 

22 benefits to society, or (d) a specified total incremental cost. The agency uses such information from the 

23 Volpe model, and analysis performed outside the model, to assist in setting standards. 

24 Although NHTSA has used the Volpe model as a tool to inform its consideration of potential 

25 CAFE standards, the Volpe model, alone, does not determine the CAFE standards NHTSA will propose 

26 or promulgate as final regulations. NHTSA considers the results of analyses conducted using the Volpe 

27 model and external analyses, including assessments of GHGs and air pollutant emissions, and 

28 technologies that might be available in the long term. NHTSA also considers whether the standards could 

29 expedite the introduction of new technologies into the market, and the extent to which changes in vehicle 

30 prices and fuel economy might affect vehicle production and sales. Using all of this information, the 

31 agency considers the governing statutory factors, along with environmental issues and other relevant 

32 societal issues, such as safety, and promulgates the maximum feasible standards based on its best 

33 judgment on how to balance these factors. 

34 For additional detail on how the Volpe model works and the outputs it produces (and which 

35 outputs NHTSA uses to estimate environmental impacts), see the joint NHTSA-EPA Notice of Proposed 

36 Rulemaking (NPRM) (Sections II.A, II.B, and II.C) and the accompanying joint Technical Support 

37 Document. 

38 3.1.4.1 Effect of Credit Flexibility on Emissions 

39 Consistent with the Energy Independence and Security Act (EISA), NHTSA’s March 30, 2009 

40 MY 2011 CAFE final rule not only set MY 2011 CAFE standards for passenger cars and light trucks, but 

 

4

 Domestic full-fuel-cycle emissions include the emissions associated with production, transportation, and refining 

operations, and the CO2 emissions from fuel combustion. 
Chapter 3 Affected Environment and Environmental Consequences 3.1 Introduction 

DELIBERATIVE 3-7 

1 also revised provisions regarding the creation and application of CAFE credits. CAFE credits are earned 

2 when a manufacturer exceeds an applicable CAFE standard. Manufacturers can then use those credits to 

3 achieve compliance in years in which their measured average fuel economy falls below the standards. In 

4 this context, CAFE credits refer to flexibilities allowed under the Energy Policy and Conservation Act 

5 (EPCA) provisions governing use of Alternative Motor Fuels Act (AMFA) credits, allowable banked 

6 credits, and transfers of credits between the passenger-car and light-truck fleets allowed under EISA. 

7 AMFA credits allow manufacturers to increase their CAFE levels through MY 2019 by producing 

8 alternative fuel vehicles. The AMFA amended EPCA to provide an incentive for producing these 

9 vehicles by specifying that their fuel economy is to be determined using a special calculation procedure 

10 that results in those vehicles being assigned a high fuel economy level. The additional flexibility to 

11 transfer credits between manufacturing companies is addressed separately below. Because EPCA 

12 prohibits NHTSA from considering these flexibilities when determining the stringency of CAFE 

13 standards, NHTSA did not attempt to do so when it developed standards it has considered for this action. 

14 Under the EISA, AMFA credits are being phased out. The allowable credits are reduced so that, 

15 by law, by 2020 such credits will no longer be allowed. 

16 However, notwithstanding the EPCA constraints regarding the context for establishing CAFE 

17 standards, NHTSA could attempt to account for the creation and application of CAFE credits when 

18 evaluating the environmental impacts of new CAFE standards under NEPA. 

19 NHTSA believes that manufacturers are likely to take advantage of these flexibility mechanisms, 

20 thereby reducing benefits and costs. Manufacturers building dual-fuel vehicles are entitled to a CAFE 

21 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 

22 estimates that the impact of the use of AMFA credits could result in an average reduction of 

23 approximately 0.9 mpg in achieved average fuel economy in 2012-2016, and a related increase in CO2

24 emissions. Regarding credits other than AMFA credits (e.g., CAFE credits earned through over25 compliance, credits transferred between fleets, and credits acquired from other manufacturers), NHTSA 

26 does not have a sound basis to predict the extent to which manufacturers might use them, particularly 

27 because the credit-transfer and credit-trading programs have been only recently authorized, and credit 

transfers could involve complex interactions and multiyear planning.5 28 

29 3.1.4.2 Difficulties in Quantifying Emissions Implications of Credits 

30 Questions NHTSA might need to address in performing an analysis of potential credit use and the 

31 resulting emissions include the following: 

32  Would manufacturers that have never used CAFE flexibilities do so in the future? 

33  Would flexibility-induced increases in the sale of flexible-fuel vehicles (FFVs) lead to 

34 increases in the use of alternative fuels? 

35  Having earned CAFE credits in a given model year, in what model year would a given 

36 manufacturer most likely apply those credits, and how might that affect technologies added 

37 through multiyear planning? 

38  Having earned CAFE credits in one fleet (i.e., passenger or nonpassenger), to which fleet 

39 would a given manufacturer most likely apply those credits? 

 

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 

1 Such questions are similar to, though possibly less tractable than, the behavioral and strategic 

2 questions that were entailed in representing manufacturers’ ability to “pull ahead” the implementation of 

3 some technologies, and that would be involved in attempting to estimate CAFE-induced changes in 

4 market shares. Although the Volpe model has been modified to account for multiyear planning effects, 

5 substantial concerns remain about how to develop a credible market-share model for integration into the 

6 modeling system NHTSA has used to analyze the costs and effects of CAFE standards. 

7 3.1.4.3 Market Behavior 

8 Some manufacturers make substantial use of current flexibilities. Other manufacturers regularly 

9 exceed CAFE standards applicable to one or both fleets, and allow the corresponding excess CAFE 

10 credits to expire. Some manufacturers transfer earned CAFE credits to future (or past) model years, but 

11 do not produce FFVs and create corresponding CAFE credits. Finally, still other manufacturers regularly 

12 pay civil penalties for noncompliance, even when producing FFVs would substantially reduce the 

13 magnitude of those penalties. 

14 Notwithstanding these uncertainties, NHTSA anticipates that manufacturers would make varied 

15 use of the flexibilities provided by EPCA, as amended by EISA. These flexibilities could result in 

16 somewhat lower benefits (that is, CO2 emissions reductions) than estimated here, because manufacturers’ 

17 actions would cause VMT levels, fuel consumption, and emissions to be higher than reported here. 

18 NHTSA expects that the nine alternatives evaluated in this EIS, including the No Action Alternative in 

19 relation to which NHTSA measures the effects of the eight action alternatives, would be affected. Insofar 

20 as the No Action Alternative would be affected, it is even less certain how the net effects of each of the 

21 eight action alternatives would change. 

22 NHTSA expects that use of flexibilities would tend to be greater under more stringent standards. 

23 As stringency increases, the potential for manufacturers to face greater cost increases, and for some, 

24 depending on their level of technological implementation, costs could rise substantially. The economic 

25 advantage of employing allowed flexibilities increases could affect manufacturer behavior in this regard. 

26 A critical factor in addressing the fuel and emissions impacts of such flexibilities is that the likely extent 

27 of utilization cannot be assumed constant across the alternatives. 

28 3.1.4.4 Trading Between Companies 

29 The allowable trading between manufacturers is categorically different from the case discussed 

30 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 31 Therefore, there would not be an 

32 environmental impact of any such trades because any increases in fuel use or emissions would have to be 

33 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 

1 3.2 ENERGY 

2 Energy intensity in the United States (energy use per dollar of gross domestic product [GDP]) has 

3 declined steadily at about 2 percent per year since 1973, when the U.S. Department of Energy (DOE) 

4 began tracking the statistic (EIA 2009a). Since 2000, energy intensity in the U.S. economy has fallen 

5 from 10.08 million British thermal units per dollar of “real” or inflation-adjusted GDP, measured in year 

6 2000 dollars to 8.52 million British thermal units per dollar of GDP (in year 2000 dollars), and DOE 

7 projections show a further steady decline through 2030, with energy intensity reaching 5.58 million 

8 British thermal units per dollar of GDP (in year 2000 dollars) in the latter year (EIA 2009b). Although 

9 U.S. population and economic activity have grown steadily, energy intensity has fallen due to a 

10 combination of increased efficiency and a structural shift in the economy toward less energy-intensive 

11 industries. Despite this continuing improvement in economy-wide energy efficiency, however, 

12 transportation fuel consumption has grown steadily, and now represents the major use of petroleum in the 

13 U.S. economy. 

14 3.2.1 Affected Environment 

15 The energy projections NHTSA uses in this section are from the DOE Energy Information 

16 Administration (EIA), which collects and provides the official energy statistics for the United States. EIA 

17 is the primary source of data used by government agencies and private firms to analyze and model energy 

18 systems. Every year EIA issues projections of energy consumption and supply for both the United States 

19 (Annual Energy Outlook [AEO]) and for the world (International Energy Outlook [IEO]). EIA reports 

20 and projects energy consumption by energy mode, by sector, and by geographic region. The modeling 

21 used to formulate the EIA’s projections incorporates all laws and regulations that are in force at the time 

22 of the modeling. 

23 In the case of the AEO 2009, EIA issued an updated Reference Case in April 2009 to incorporate 

the impacts of the American Recovery and Reinvestment Act of 2009,1 24 the MY 2011 CAFE standards, 

25 and an update of the macroeconomic assumptions (EIA 2009b). Table 3.2.1-1 shows U.S. and global 

26 energy consumption by sector. Actual energy-consumption data show a steady increase in energy use in 

27 all U.S. sectors. By 2004, the transportation sector was the second largest consumer of energy after the 

28 industrial sector, and comprised 27.8 and 17.3 percent of U.S. and global (less U.S.) energy use, 

29 respectively. Over half of U.S. energy consumption in the transportation sector can be attributed to 

30 passenger cars and light trucks, ranging from 58 percent in 2010 to 53 percent by 2030. Going forward in 

31 time, transportation energy consumption is expected to continue to be the largest component after the 

32 industrial sector, but in the forecasted outer years in the United States the gap between energy 

33 consumption in the two sectors narrows. As a percentage of total economy-wide energy consumption, 

34 projected energy use in the U.S. transportation sector remains fairly constant throughout the projection 

35 years. 

36 The EIA projections include all forms of energy, including renewable fuels and biofuels. Despite 

37 efforts to increase the use of non-fossil fuels in transportation, fuel use remains largely petroleum based. 

38 In 2007, finished motor gasoline and on-road diesel constituted 66 percent of all finished petroleum 

39 products consumed in the United States. If other transportation fuels (aviation fuels, marine and 

40 locomotive diesel, and bunkers) are included, transportation fuels constitute approximately 79 percent of 

41 the finished petroleum products used. In the same year, the biofuel component of the total U.S. 

42 transportation sector energy consumption was slightly more than 2 percent. According to AEO 

43 projections, the biofuels share of energy consumption in the transportation sector will rise to 10 percent 

44 by 2030. 

 

1

 Pub. L. No. 111-5, 123 Stat. 115 (Feb. 17, 2009). 
3.2 Energy Chapter 3 Affected Environment and Environmental Consequences 

 3-10 

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), http://www.eia.doe.gov/aer/pdf/pages/sec2_4.pdf 

 Actual World data: EIA (2009d), http://www.eia.doe.gov/pub/international/iealf/tablee1.xls 

b/ Forecasted United States data: EIA (2009c), http://www.eia.doe.gov/oiaf/aeo/supplement/arra/excel/

suptab_10.xls 

 Forecasted World data: EIA (2009d), http://www.eia.doe.gov/oiaf/ieo/excel/ieoendusetab_1.xls 

c/ Btu = British thermal unit. 

1 

2 The analysis of fuel consumption and energy use conducted for this EIS assumes that fuel 

3 consumed by U.S. passenger cars and light trucks will consist predominantly of gasoline or diesel fuel 

4 derived from petroleum. Implicitly, ethanol FFVs are assumed to operate exclusively on gasoline, while 

5 diesel vehicles are assumed to operate exclusively on petroleum-based diesel rather than on biodiesel. 

6 The estimates of gasoline consumption reported in this analysis include ethanol used as a gasoline 

7 additive to increase its oxygen content, while the estimates of diesel fuel consumption include biodiesel 

used as a blending agent.2 8 The analysis makes no other assumption about the use of renewable fuels or 

9 biofuels. 

10 Most U.S. gasoline and diesel is produced domestically (EIA 2009a). In 2007, 4 percent of 

11 finished motor gasoline and 6 percent of on-road diesel were imported. However, increasing volumes of 

12 crude oil are imported for processing in U.S. refineries because domestic production is steadily declining. 

13 By 2006, petroleum imports equaled 60 percent of total liquids supplied and by 2007, crude oil imports 

 

2

 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 (April 2009 release), Reference Case, Table 17 

and Supplemental Table 46. 
Chapter 3 Affected Environment and Environmental Consequences 3.2 Energy 

3-11 

1 had surpassed 10 million barrels per day (EIA 2009a), a high proportion of it coming from volatile and 

2 unstable regions. 

3 A fall in the demand for transportation fuels likely would affect imports of crude oil more than 

4 motor gasoline. Over the last decade there has been a shift in product imports, with volumes of finished 

5 gasoline stabilizing and declining slightly. However, volumes of motor gasoline blending components 

6 have been rapidly increasing, so that by 2007, the imports of blending components were twice that of 

7 finished gasoline. 

8 According to EIA, net imports of crude oil – in part due to improvements in fuel efficiency 

9 required by the changes in CAFE standards, in part due to substitution of biofuels, and in part due to high 

10 prices – will fall to 48 percent of liquid fuel supply in 2020 and then decline further to 40 percent in 2030. 

11 The further decrease in 2030 is due in part due to a projected surge in domestic crude oil production. The 

12 impact of these anticipated developments on the petroleum industry is likely to be felt largely by overseas 

13 producers (EIA 2009c), although the net impact on petroleum production levels of overseas suppliers and 

14 the associated change in their emissions of air pollutants and GHGs will ultimately depend on whether 

15 demand for motor fuel in developing nations rises sufficiently to replace declining U.S. demand. 

16 3.2.2 Methodology 

17 The methodology for examining the impact of higher CAFE standards on gasoline and diesel 

18 consumption relies on outputs from the Volpe model. The Volpe model, as described in Section 3.1.4, 

19 requires the following types of input information: (1) a forecast of the future vehicle market; (2) 

20 estimates of the availability, applicability, and incremental effectiveness and cost of fuel-saving 

21 technologies; (3) estimates of vehicle survival and mileage accumulation patterns, the rebound effect, 

22 future fuel prices, the “social cost of carbon,” and many other economic factors; (4) fuel characteristics 

23 and vehicular emissions rates; and (5) coefficients defining the shape and level of CAFE curves to be 

24 examined. 

25 Using NHTSA-selected inputs, the agency projects a set of technologies each manufacturer could 

26 apply in attempting to comply with the various levels of potential CAFE standards to be examined. The 

27 model then estimates the costs associated with this additional technology utilization, and accompanying 

28 changes in travel demand, fuel consumption, fuel outlays, emissions, and economic externalities related to 

29 petroleum consumption and other factors. 

30 The analysis of costs and benefits employed in the Volpe model reflects the NHTSA assessment 

31 of a broad range of technologies that can be applied to passenger cars and light trucks. In the agency’s 

32 rulemakings covering light-truck CAFE standards for MY 2005-2007 and MY 2008-2011, the agency 

33 relied on the 2002 National Academy of Sciences report, Effectiveness and Impact of Corporate Average 

34 Fuel Economy Standards for estimating potential fuel economy benefits and associated retail costs of 

35 applying combinations of technologies. In developing its final rule adopting CAFE standards for MY 

36 2011, NHTSA reviewed manufacturers’ technology data and comments it received on its fuel-saving 

37 technologies, and conducted its own independent analysis, which involved hiring an international 

38 engineering consulting firm that specializes in automotive engineering, the same firm EPA used in 

39 developing its advance notice of proposed rulemaking to regulate GHG emissions under the Clean Air 

40 Act (CAA). Since then, NHTSA and EPA have collaborated on further updates to estimates of the cost, 

41 effectiveness, and availability of fuel-saving technologies the agencies expect to be available during MY 

42 2012-2016. The revised technology assumptions – that is, estimates of the availability, applicability, cost, 

43 and effectiveness of fuel-saving technologies, and the order in which the technologies are applied – are 

44 described in greater detail in the NHTSA-EPA joint technical support document and in NHTSA’s RIA, 
3.2 Energy Chapter 3 Affected Environment and Environmental Consequences 

 3-12 

1 which can be found in the docket for this action. See Section 3.1.4 for further information on the Volpe 

2 model. 

3 The Volpe model produces various outputs, including its estimates of year-by-year fuel 

4 consumption by U.S. passenger-car and light-truck fleets. The Volpe model estimates annual fuel 

5 consumption and fuel savings for each calendar year from 2012, when the CAFE standards considered in 

6 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 2016.3 7 Therefore, the 

8 estimated fuel savings during 2060 represents the maximum annual fuel savings resulting from the CAFE 

9 standards established by this rulemaking. 

10 To calculate fuel savings for each action alternative, NHTSA subtracted fuel consumption under 

11 that alternative from its level under the No Action Alternative. The Volpe model estimated fuel savings 

12 using the following mpg assumptions: for MY 2012-2016, the fuel economy of new passenger cars and 

13 light trucks under each action alternative increases annually in accordance with the CAFE standards 

specified in that particular alternative.4 14 For MY 2017-2060, all new vehicles were assumed to meet the 

15 MY 2016 CAFE standards that would be established under each action alternative. In effect, this means 

16 that fuel economy achieved by passenger cars and light trucks produced in MY 2017-2060 remains 

constant at their levels estimated for MY 2016 under each action alternative.5 17 

18 3.2.3 Environmental Consequences 

19 Table 3.2.3-1, which lists the impact on fuel consumption for passenger cars from 2020 through 

20 2060, shows the increasing impact of alternative CAFE standards over time. The table reports total fuel 

21 consumption for passenger cars, both gasoline and diesel, under the No Action Alternative (Alternative 1) 

22 and each of the eight action alternatives, as described in Section 2.3. By 2060, when the entire passenger23 car and light-truck fleet is likely to be composed of MY 2016 or later passenger cars and light trucks, fuel 

24 consumption reaches 173.5 billion gallons under the No Action Alternative. Fuel consumption is less 

25 than that projected under the No Action alternative for all the action alternatives, ranging from 158.2 

26 billion gallons under Alternative 2 (3-percent annual increase in mpg) to 139.7 billion gallons under 

27 Alternatives 8 and 9 (TCTB). In 2060, fuel consumption under the TCTB Alternative amounts to 9.1 

28 million barrels of fuel per day, while under Alternative 4 (the Preferred Alternative), daily fuel 

consumption amounts to 9.8 million barrels per day.6 29 As a point of reference, NHTSA projects that fuel 

30 consumption under the No Action Alternative would be 11.3 million barrels per day in 2060. In 2007, the 

31 United States consumed 9.3 million barrels of fuel per day (EIA 2009a). 

 

3

 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. 

4

 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. 

5

 See footnote 2 in this chapter. 

6

 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 

3-13 

Table 3.2.3-1 

Passenger Car Annual Fuel Consumption and Fuel Savings (billion gallons gasoline equivalent) by 

Alternative 

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 

~5.9%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.7%/year 

Increase 

TCTB 

Fuel Consumption 

2020 69.4 65.7 64.3 63.9 63.0 61.8 61.9 61.2 61.1

2030 97.9 89.5 86.4 85.5 83.5 81.0 80.9 79.4 79.4

2040 121.7 110.9 106.9 105.9 103.2 100.1 99.9 98.0 98.1

2050 145.7 132.8 128.0 126.7 123.5 119.8 119.6 117.3 117.3

2060 173.5 158.2 152.4 150.9 147.1 142.7 142.4 139.7 139.7

Fuel Savings Compared to No Action 

2020 -- 3.7 5.1 5.5 6.4 7.6 7.6 8.2 8.3

2030 -- 8.4 11.5 12.3 14.4 16.8 17.0 18.4 18.4

2040 -- 10.8 14.8 15.9 18.5 21.6 21.8 23.7 23.7

2050 -- 12.9 17.7 19.0 22.2 25.9 26.2 28.4 28.4

2060 -- 15.4 21.1 22.6 26.5 30.9 31.2 33.9 33.8

1 

2 Table 3.2.3-2 lists comparable results for light trucks for the same period and for the same 

3 alternative CAFE standards. As in the previous table, reported fuel consumption includes light-truck 

4 diesel and gasoline consumption. Fuel consumption under the No Action Alternative is estimated to total 

5 101.4 billion gallons in 2060, and to decline progressively under the action alternatives, from 93.3 billion 

6 gallons under Alternative 2 to 81.3 billion gallons under Alternative 8. These represent fuel savings 

7 compared to the No Action Alternative that range from 8.1 billion gallons annually under Alternative 2 to 

8 20.1 billion gallons annually under Alternative 8, or from 0.5 million to 1.3 million barrels of petroleum 

9 per day. 

Table 3.2.3-2 

Light Truck Annual Fuel Consumption and Fuel Savings (billion gallons gasoline equivalent) by Alternative

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 

~5.9%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.7%/year 

Increase 

TCTB 

Fuel Consumption 

2020 68.6 66.4 65.2 64.9 64.2 63.0 63.3 62.7 62.6

2030 66.0 61.6 59.6 59.0 57.6 55.8 55.9 55.0 55.1

2040 73.0 67.4 64.9 64.2 62.4 60.3 60.3 59.1 59.3

2050 85.5 78.7 75.7 74.8 72.7 70.2 70.1 68.7 69.0

2060 101.4 93.3 89.7 88.7 86.1 83.1 83.1 81.3 81.7

Fuel Savings Compared to No Action 

2020 -- 2.3 3.4 3.8 4.4 5.6 5.3 5.9 6.0

2030 -- 4.4 6.4 7.0 8.3 10.1 10.0 11.0 10.9

2040 -- 5.6 8.1 8.8 10.6 12.8 12.7 14.0 13.7

2050 -- 6.8 9.8 10.7 12.8 15.4 15.4 16.9 16.5

2060 -- 8.1 11.7 12.7 15.3 18.3 18.4 20.1 19.7

10 
3.2 Energy Chapter 3 Affected Environment and Environmental Consequences 

 3-14 

1 
Chapter 3 Affected Environment and Environmental Consequences 3.3 Air Quality 

3-15 

1 3.3 AIR QUALITY 

2 3.3.1 Affected Environment 

3 3.3.1.1 Relevant Pollutants and Standards 

4 The proposed CAFE standards would affect air pollution and air quality, which in turn, have the 

5 potential to affect public health and welfare and the environment. The CAA is the primary federal 

6 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 pollutants1 7 (relatively 

8 commonplace pollutants that can accumulate in the atmosphere as a result of normal levels of human 

9 activity). This EIS air quality analysis assesses the impacts of the action alternatives in relation to criteria 

10 pollutants and some hazardous air pollutants from mobile sources. 

11 The criteria pollutants are CO, nitrogen dioxide (NO2) (one of several oxides of nitrogen), ozone, 

12 SO2, PM with an aerodynamic diameter equal to or less than 10 microns (PM10) and 2.5 microns (PM2.5), 

13 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.2 14 

15 The U.S. transportation sector is a major source of emissions of certain criteria pollutants or their 

16 chemical precursors. Total emissions from on-road mobile sources (passenger cars and light trucks) have 

17 declined dramatically since 1970 as a result of pollution controls on vehicles and regulation of the 

18 chemical content of fuels, despite continuing increases in the amount of vehicle travel. From 1970 to 

19 2008, the most recent year for which data are available, emissions from on-road mobile sources declined 

20 76 percent for CO, 59 percent for NOx, 64 percent for PM10, 77 percent for SO2, and 80 percent for 

21 VOCs. Emissions of PM2.5 from on-road mobile sources declined 66 percent from 1990, the earliest year 

22 for which data are available, to 2008 (EPA 2009i). 

23 On-road mobile sources are responsible for 50 percent of total U.S. emissions of CO, 4 percent of 

24 PM2.5 emissions, and 1 percent of PM10 emissions (EPA 2009i). Almost all of the PM in motor-vehicle 

25 exhaust is PM2.5; therefore, this analysis focuses on PM2.5 rather than PM10. On-road mobile sources also 

26 contribute 21 percent of total nationwide emissions of VOCs and 32 percent of NOx, which are chemical 

27 precursors of ozone. In addition, NOx is a PM2.5 precursor and VOCs can be PM2.5 precursors. On-road 

28 mobile sources contribute only 1 percent of SO2, but SO2 and other oxides of sulfur (SOx) are important 

29 because they contribute to the formation of PM2.5 in the atmosphere; however, on-road mobile sources 

30 contribute only 1 percent of SO2. With the elimination of lead in gasoline, lead is no longer emitted from 

31 motor vehicles in more than negligible quantities. Lead is not assessed further in this analysis. 

32 Table 3.3.1-1 lists the primary and secondary NAAQS for each criteria pollutant. Primary 

33 standards are set at levels intended to protect against adverse effects on human health; secondary 

34 standards are intended to protect against adverse effects on public welfare, such as damage to agricultural 

35 crops or vegetation, and damage to buildings or other property. Because each criteria pollutant has 

 

1

 “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 pollutants,” by contrast, refer to substances defined as hazardous by the 1990 CAA 

amendments. These substances include certain VOCs, pesticides, herbicides, and radionuclides that present tangible 

hazards, based on scientific studies of exposure to humans and other mammals. 2

 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 

 3-16 

1 different potential effects on human health and public welfare, the NAAQS specify different permissible 

2 levels for each pollutant. NAAQS for some pollutants include standards for both short- and long-term 

3 average levels. Short-term standards, which typically specify higher levels of a pollutant, are intended to 

4 protect against acute health effects from short-term exposure to higher levels of a pollutant; long-term 

5 standards are established to protect against chronic health effects resulting from long-term exposure to 

6 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 

Nitrogen dioxide 0.053 ppm 

(100 μg/m3

) 

Annual 

(Arithmetic Mean) 

Same as Primary 

Particulate matter (PM10) 150 μg/m3 24 hours c/ Same as Primary 

15.0 μg/m3 Annual d/ 

(Arithmetic Mean) 

Particulate matter (PM2.5) Same as Primary 

35 μg/m3 24 hours e/ Same as Primary 

0.075 ppm 

(2008 std.) 

Ozone 8 hours f/ Same as Primary 

0.08 ppm 

(1997 std.) 

8 hours g/ h/ 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/ Not to be exceeded more than once per year on average over 3 years. 

d/ 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

. 

e/ 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). 

f/ 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). 

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 0.08 ppm. 

h/ 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 2009f. 

7 

8 Under the CAA, EPA is required to review NAAQS every 5 years and to change the levels of the 

9 standards if warranted by new scientific information. NAAQS formerly included an annual PM10

10 standard, but EPA revoked the annual PM10 standard in 2006 based on an absence of evidence of health 

11 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 12 . In March 2008, EPA tightened the 
Chapter 3 Affected Environment and Environmental Consequences 3.3 Air Quality 

3-17 

1 8-hour ozone standard from 0.08 part per million (ppm) to 0.075 ppm. At present, EPA is considering 

2 further changes to the PM2.5 standards and changes to the NO2 standard. 

3 The air quality of a geographic region is usually assessed by comparing the levels of criteria air 

4 pollutants found in the atmosphere to the levels established by NAAQS. Concentrations of criteria 

5 pollutants within the air mass of a region are measured in parts of a pollutant per million parts of air or in 

6 micrograms of a pollutant per cubic meter of air present in repeated air samples taken at designated 

7 monitoring locations. These ambient concentrations of each criteria pollutant are compared to the 

8 permissible levels specified by NAAQS to assess whether the region’s air quality could be unhealthful. 

9 When the measured concentrations of a criteria pollutant within a geographic region are below 

10 those permitted by NAAQS, EPA designates the region as an attainment area for that pollutant; regions 

11 where concentrations of criteria pollutants exceed federal standards are called nonattainment areas. 

12 Former nonattainment areas that have attained NAAQS are designated as maintenance areas. Each 

13 nonattainment area is required to develop and implement a State Implementation Plan (SIP), which 

14 documents how the region will reach attainment levels within periods specified in the CAA. In 

15 maintenance areas, the SIP documents how the state intends to maintain compliance with NAAQS. When 

16 EPA changes a NAAQS, states must revise their SIPs to address how they will attain the new standard. 

17 Compounds emitted from vehicles, which are known or suspected to cause cancer or other serious 

18 health and environmental effects, are known as mobile source air toxics (MSATs). The MSATs included 

19 in this analysis are acetaldehyde, acrolein, benzene, 1,3-butadiene, diesel particulate matter (DPM), and 

20 formaldehyde. EPA and the Federal Highway Administration (FHWA) have identified these air toxics as 

21 the MSATs of concern for impacts of highway vehicles (EPA 2007, FHWA 2006). DPM is a component 

22 of exhaust from diesel-fueled vehicles and falls almost entirely within the PM2.5 particle-size class. 

23 Section 3.4 addresses the major GHGs – CO2, methane (CH4), and nitrous oxides (N2O); these 

24 GHGs are not included in this air quality analysis, except the evaluation of NOx includes N2O because it 

25 is one of the oxides of nitrogen. 

26 3.3.1.2 Health Effects of Criteria Pollutants 

27 The following paragraphs briefly describe the health effects of the six federal criteria pollutants. 

28 This information is adapted from the EPA Green Book, Criteria Pollutants (EPA 2008b). EPA’s most 

29 recent technical reports and Federal Register notices for NAAQS reviews contain more information on 

30 the health effects of criteria pollutants (see http://www.epa.gov/ttn/naaqs/). 

31 Ozone is a photochemical oxidant and the major component of smog. Ozone is not emitted 

32 directly into the air, but is formed through complex chemical reactions between precursor emissions of 

33 VOCs and NOx in the presence of the ultraviolet component of sunlight. Ground-level ozone causes 

34 health problems because it irritates the mucous membranes, damages lung tissue, reduces lung function, 

35 and sensitizes the lungs to other irritants. Exposure to ozone for several hours at relatively low 

36 concentrations has been found to substantially reduce lung function and induce respiratory inflammation 

37 in normal, healthy people during exercise. There is also evidence that short-term exposure to ozone 

38 directly or indirectly contributes to non-accidental and cardiopulmonary-related mortality. 

39 PM is a generic term for a broad class of chemically and physically diverse substances that exist 

40 as discrete particles. PM includes dust, dirt, soot, smoke, and liquid droplets directly emitted into the air, 

41 and particles formed in the atmosphere by condensation or by the transformation of emitted gases such as 

42 NOx, SOx and VOCs. The definition of PM also includes particles composed of elemental carbon (carbon 

43 black or black carbon). Both gasoline-fueled and diesel-fueled vehicles emit PM. In general, the smaller 
3.3 Air Quality Chapter 3 Affected Environment and Environmental Consequences 

 3-18 

1 the PM, the deeper it can penetrate into the respiratory system and the more damage it can cause. 

2 Depending on its size and composition, PM can damage lung tissue, aggravate existing respiratory and 

3 cardiovascular diseases, alter the body’s defense systems against foreign materials, and cause cancer and 

4 premature death. As noted above, EPA regulates PM according to two particle size classifications, PM10

5 and PM2.5. This analysis only considers PM2.5 because almost all of the PM emitted in exhaust from 

6 passenger cars and light trucks is PM2.5. 

7 CO is a colorless, odorless, poisonous gas produced by incomplete combustion of carbon in fuels. 

8 Motor vehicles are the largest source of CO emissions nationally. When CO enters the bloodstream, it 

9 acts as an asphyxiant by reducing the delivery of oxygen to the body’s organs and tissues. It can impair 

10 the brain’s ability to function properly. Health threats are most serious for those who suffer from 

11 cardiovascular disease, particularly those with angina or peripheral vascular disease. 

12 Lead is a toxic heavy metal used in industry, such as in battery manufacturing, and formerly in 

13 widespread use as an additive in paints. Lead gasoline additives (in piston-engine powered aircraft), non14 ferrous smelters, and battery plants are the most significant contributors to atmospheric lead emissions. 

15 Lead exposure can occur through multiple pathways, including inhalation of air and ingestion of lead in 

16 food, water, soil, or dust. Excessive lead exposure can cause seizures, mental retardation, behavioral 

17 disorders, severe and permanent brain damage, and death. Even low doses of lead can lead to central 

18 nervous system damage. Because of the prohibition of lead as an additive in motor vehicle liquid fuels, 

19 light-duty gasoline onroad vehicles are no longer a major source of lead pollution. 

20 SO2, one of various oxides of sulfur (SO), is a gas formed from combustion of fuels containing 

21 sulfur. Most SO2 emissions are produced by stationary sources such as power plants. SO2 is also formed 

22 when gasoline is extracted from crude oil in petroleum refineries, and in other industrial processes. High 

23 concentrations of SO2 cause severe respiratory distress (difficulty breathing), irritate the upper respiratory 

24 tract, and can aggravate existing respiratory and cardiovascular disease. SO2 also is a primary contributor 

25 to acid deposition, or acid rain, which causes acidification of lakes and streams and can damage trees, 

26 crops, historic buildings, and statues. 

27 NO2 is a reddish-brown, highly reactive gas, one of the oxides of nitrogen formed by 

28 high-temperature combustion (as in vehicle engines) of nitrogen and oxygen. Most NOx created in the 

29 combustion reaction consists of nitric oxide (NO), which oxidizes to NO2 in the atmosphere. NO2 can 

30 irritate the lungs and mucous membranes, cause bronchitis and pneumonia, and lower resistance to 

31 respiratory infections. Oxides of nitrogen are an important precursor both to ozone and acid rain, and can 

32 affect both terrestrial and aquatic ecosystems. 

33 3.3.1.3 Health Effects of Mobile Source Air Toxics (adapted from EPA 2009d) 

34 Motor vehicle emissions contribute to ambient levels of air toxics known or suspected as human 

35 or animal carcinogens, or that have noncancer health effects. The population experiences an elevated risk 

36 of cancer and other noncancer health effects from exposure to air toxics (EPA 1999a). These compounds 

37 include, but are not limited to, acetaldehyde, acrolein, benzene, 1,3-butadiene, and formaldehyde. These 

38 five air toxics, plus DPM, comprise the six priority MSATs analyzed in this EIS. These compounds, 

39 except acetaldehyde, plus polycyclic organic matter (POM) and naphthalene, were identified as national 

40 or regional risk drivers in the EPA 2002 National-scale Air Toxics Assessment (NATA) and have 

41 significant inventory contributions from mobile sources (EPA 2009a). This EIS does not analyze POM 

42 separately, but it can occur as a component of DPM and is addressed under DPM below. Naphthalene is 

43 not analyzed separately in this EIS; however, naphthalene is a member of the POM class of compounds 

44 discussed under DPM. 
Chapter 3 Affected Environment and Environmental Consequences 3.3 Air Quality 

3-19 

1 Acetaldehyde is classified in EPA’s Integrated Risk Information System (IRIS) database as a 

2 probable human carcinogen, based on nasal tumors in rats, and is considered toxic by the inhalation, oral, 

3 and intravenous routes (EPA 1991). Acetaldehyde is reasonably anticipated to be a human carcinogen by 

4 the U.S. Department of Health and Human Services (DHHS) in the 11th Report on Carcinogens and is 

5 classified as possibly carcinogenic to humans (Group 2B) by the International Agency for Research on 

6 Cancer (IARC) (NTP 2005, IARC 1999). EPA is reassessing cancer risk from inhalation exposure to 

7 acetaldehyde. 

8 The primary noncancer effects of exposure to acetaldehyde vapors include eye, skin, and 

9 respiratory-tract irritation (EPA 1991). In short-term (4-week) rat studies, degeneration of olfactory 

10 epithelium was observed at various concentration levels of acetaldehyde exposure (Appleman et al. 1982, 

11 1986). EPA used data from these studies to develop an inhalation reference concentration. Some 

12 asthmatics have been shown to be a sensitive subpopulation to decrements in functional expiratory 

13 volume (FEV1 test) and bronchoconstriction upon acetaldehyde inhalation (Myou et al. 1993). EPA is 

14 reassessing the health hazards from inhalation exposure to acetaldehyde. 

15 Acrolein is extremely acrid and irritating to humans when inhaled, with acute exposure resulting 

16 in upper respiratory tract irritation, mucus hypersecretion, and congestion. Levels considerably lower 

than 1 ppm (2.3 mg/m3 17 ) elicit subjective complaints of eye and nasal irritation and a decrease in the 

18 respiratory rate (Weber-Tschopp et al. 1977, Sim and Pattle 1957). Lesions to the lungs and upper 

19 respiratory tracts of rats, rabbits, and hamsters have been observed after subchronic exposure to acrolein. 

20 Based on animal data, individuals with compromised respiratory function (e.g., emphysema, asthma) are 

21 expected to be at increased risk of developing adverse responses to strong respiratory irritants such as 

22 acrolein. This was demonstrated in mice with allergic-airway disease by comparison to non-diseased 

23 mice in a study of the acute respiratory irritant effects of acrolein (Morris et al. 2003). The intense 

24 irritancy of this carbonyl has been demonstrated during controlled tests in human subjects, who suffer 

25 intolerable eye and nasal mucosal sensory reactions within minutes of exposure (Sim and Pattle 1957). 

26 EPA determined in 2003 that the human carcinogenic potential of acrolein could not be 

27 determined because the available data were inadequate. No information was available on the 

28 carcinogenic effects of acrolein in humans and the animal data provided inadequate evidence of 

29 carcinogenicity (EPA 2003). IARC determined in 1995 that acrolein was not classifiable as to its 

30 carcinogenicity in humans (IARC 1995). 

31 The EPA IRIS database lists benzene as a known human carcinogen (causing leukemia) by all 

32 routes of exposure, and concludes that exposure is associated with additional health effects, including 

33 genetic changes in both humans and animals and increased proliferation of bone marrow cells in mice 

34 (EPA 2000a, IARC 1982, Irons et al 1992). EPA states in its IRIS database that data indicate a causal 

35 relationship between benzene exposure and acute lymphocytic leukemia and suggest a relationship 

36 between benzene exposure and chronic non-lymphocytic leukemia and chronic lymphocytic leukemia. 

37 IARC has determined that benzene is a human carcinogen and DHHS has characterized benzene as a 

38 known human carcinogen (IARC 1987, NTP 2005). 

39 A number of adverse noncancer health effects, including blood disorders such as preleukemia and 

40 aplastic anemia, have also been associated with long-term exposure to benzene (Askoy 1989, Goldstein 

41 1988). The most sensitive noncancer effect observed in humans, based on current data, is the depression 

42 of the absolute lymphocyte count in blood (Rothman et al 1996, EPA 2002a). In addition, recent work, 

43 including studies sponsored by the Health Effects Institute, provides evidence that biochemical responses 

44 are occurring at lower levels of benzene exposure than previously known (Qu et al. 2002, 2003; Lan et al.

45 2004; Turtletaub and Mani 2003) The EPA IRIS program has not yet evaluated these new data. 
3.3 Air Quality Chapter 3 Affected Environment and Environmental Consequences 

 3-20 

1 EPA has characterized 1,3-butadiene as carcinogenic to humans by inhalation (EPA 2002b, 

2 2002c). IARC has determined that 1,3-butadiene is a human carcinogen, and DHHS has characterized 

3 1,3-butadiene as a known human carcinogen (IARC 1999, NTP 2005). There are numerous studies 

4 consistently demonstrating that animals and humans in experiments metabolize 1,3-butadiene into 

5 genotoxic metabolites. The specific mechanisms of 1,3-butadiene-induced carcinogenesis are not known; 

6 however, scientific evidence strongly suggests that the carcinogenic effects are mediated by genotoxic 

7 metabolites. Animal data suggest that females could be more sensitive than males for cancer effects 

8 associated with 1,3-butadiene exposure; there are insufficient data in humans from which to draw 

9 conclusions about sensitive subpopulations. 1,3-butadiene also causes a variety of reproductive and 

10 developmental effects in mice; no human data on these effects are available. The most sensitive effect 

11 was ovarian atrophy observed in a lifetime bioassay of female mice (Bevan et al. 1996). 

12 DPM is a component, along with diesel exhaust organic gases, of diesel exhaust. DPM particles 

13 are very fine, with most particles smaller than 1 micron, and their small size allows inhaled DPM to reach 

14 the lungs. Particles typically have a carbon core coated by condensed organic compounds such as POM, 

15 which include mutagens and carcinogens. DPM also includes elemental carbon (carbon black or black 

16 carbon) particles emitted from diesel engines. Diesel exhaust is likely to be carcinogenic to humans by 

17 inhalation from environmental exposure. 

18 DPM can contain POM, which is generally defined as a large class of organic compounds that 

19 have multiple benzene rings and a boiling point greater than 100 degrees Celsius (oC). EPA classifies 

20 many of the compounds included in the POM class as probable human carcinogens based on animal data. 

21 Polycyclic aromatic hydrocarbons (PAHs) are a subset of POM that contains only hydrogen and carbon 

22 atoms. A number of PAHs are known or suspected carcinogens. Recent studies have found that maternal 

23 exposures to PAHs in a population of pregnant women were associated with several adverse birth 

24 outcomes, including low birth weight and reduced length at birth, and impaired cognitive development at 

25 age 3 (Perera et al. 2002, 2006). EPA has not yet evaluated these recent studies. 

26 Since 1987, EPA has classified formaldehyde as a probable human carcinogen based on evidence 

27 in humans and in rats, mice, hamsters, and monkeys (EPA 1987). EPA is reviewing recently published 

28 epidemiological data. For example, National Cancer Institute (NCI) research found an increased risk of 

29 nasopharyngeal cancer and lymphohematopoietic malignancies such as leukemia among workers exposed 

30 to formaldehyde (Hauptmann et al. 2003, 2004). In an analysis of the lymphohematopoietic cancer 

31 mortality from an extended followup of these workers, NCI confirmed an association between 

32 lymphohematopoietic cancer risk and peak exposures to formaldehyde (Beane Freeman et al. 2009). A 

33 recent National Institute of Occupational Safety and Health study of garment workers also found 

34 increased risk of death due to leukemia among workers exposed to formaldehyde (Pinkerton 2004). 

35 Extended followup of a cohort of British chemical workers did not find evidence of an increase in 

36 nasopharyngeal or lymphohematopoietic cancers, but did report a continuing statistically significant 

37 excess in lung cancers (Coggon et al. 2003). Recently, IARC reclassified formaldehyde as a human 

38 carcinogen (Group 1) (IARC 2006). 

39 Formaldehyde exposure also causes a range of noncancer health effects, including irritation of the 

40 eyes (burning and watering), nose, and throat. Effects in humans from repeated exposure include 

41 respiratory-tract irritation, chronic bronchitis, and nasal epithelial lesions such as metaplasia and loss of 

42 cilia. Animal studies suggest that formaldehyde might also cause airway inflammation, including 

43 eosinophil infiltration into the airways. There are several studies suggesting that formaldehyde might 

44 increase the risk of asthma, particularly in the young (ATSDR 1999, WHO 2002). 
Chapter 3 Affected Environment and Environmental Consequences 3.3 Air Quality 

3-21 

1 3.3.1.4 Clean Air Act and Conformity Regulations 

2 3.3.1.4.1 Vehicle Emission Standards 

3 Under the CAA, EPA has established emission standards for vehicles. EPA has tightened the 

4 emission standards over time as more effective emission-control technologies have become available. 

5 These reductions in the levels of the standards are responsible for the declines in total emissions from 

6 motor vehicles, as discussed above. The EPA Tier 2 Vehicle & Gasoline Sulfur Program, which went 

7 into effect in 2004 established the CAA emissions standards that will apply to MY 2012-2016 passenger 

8 cars and light trucks (EPA 1999b). Under the Tier 2 standards, emissions from passenger cars and light 

9 trucks will continue to decline. In 2004, the Nation’s refiners and importers of gasoline began to 

10 manufacture gasoline with sulfur levels capped at 300 ppm, approximately a 15-percent reduction from 

11 the previous industry average of 347 ppm. By 2006, refiners met a 30-ppm average sulfur level with a 

12 cap of 80 ppm. These fuels enable post-2006 model year vehicles to use emissions controls that reduce 

13 tailpipe emissions of NOx by 77 percent for passenger cars and by as much as 95 percent for pickup 

14 trucks, vans, and SUVs, compared to 2003 levels. Figure 3.3.1-1 shows that cleaner vehicles and fuels 

15 will result in continued reductions in emissions from passenger cars and light trucks, despite increases in 

16 travel. Figure 3.3.1-1 illustrates current trends in travel and emissions from passenger cars and light 

17 trucks under the existing CAFE standards. Figure 3.3.1-1 does not show the effects of the proposed 

18 action and alternatives; see Section 3.3.3. 

19 From 1970 to 1999, aggregate emissions traditionally associated with vehicles substantially 

20 decreased (with the exception of NOx) even as VMT has increased by approximately 149 percent. NOx

21 emissions increased 16 percent between 1970 and 1999, due mainly to emissions from light-duty trucks 

22 and heavy-duty vehicles. However, as future trends show, vehicle travel is having a smaller and smaller 

23 impact on emissions as a result of stricter EPA standards for vehicle emissions and the chemical 

24 composition of fuels, even with additional growth in VMT (Smith 2002). This general trend will 

25 continue, to a greater or lesser degree, with implementation of any of the proposed alternative CAFE 

26 standards. 

27 EPA is addressing air toxics through its MSAT rules (EPA 2007). These rules limit the benzene 

28 content of gasoline beginning in 2011. They also limit exhaust emissions of hydrocarbons (many VOCs 

29 and MSATs are hydrocarbons) from passenger cars and light trucks when they are operated at cold 

30 temperatures. The cold-temperature standard will be phased in from 2010 to 2015. The MSAT rules also 

31 adopt nationally the California evaporative emissions standards. EPA projects that these controls will 

32 substantially reduce emissions of acetaldehyde, acrolein, benzene, 1,3-butadiene, and formaldehyde. 

33 3.3.1.4.2 Conformity Regulations 

34 Section 176(c) of the CAA prohibits federal agencies from taking actions in nonattainment or 

35 maintenance areas that do not “conform” to the SIP. The purpose of this conformity requirement is to 

36 ensure that general activities do not interfere with meeting the emissions targets in SIPs, do not cause or 

37 contribute to new violations of NAAQS, and do not impede the ability to attain or maintain NAAQS. 

38 EPA has issued two sets of regulations to implement CAA Section 176(c), as follows: 

39  The Transportation Conformity Rules (40 CFR Part 93, Subpart A), which apply to 

40 transportation plans, programs, and projects funded under U.S.C. Title 23 or the Federal 

41 Transit Act. Highway and transit infrastructure projects funded by FHWA or the Federal 

42 Transit Administration (FTA) usually are subject to transportation conformity. 
3.3 Air Quality Chapter 3 Affected Environment and Environmental Consequences 

 3-22 

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

1 

2  The General Conformity Rule (40 CFR Part 51, Subpart W) apply to all other federal actions 

3 not covered under transportation conformity. The General Conformity Rule established 

4 emissions thresholds, or de minimis levels, for use in evaluating the conformity of a project. 

5 If the net emissions increases due to the project are less than these thresholds, then the project 

6 is presumed to conform and no further conformity evaluation is required. If the emissions 

7 increases exceed any of these thresholds, then a conformity determination is required. The 

8 conformity determination can entail air quality modeling studies, consultation with EPA and 

9 state air quality agencies, and commitments to revise the SIP or to implement measures to 

10 mitigate air quality impacts. 

11 The CAFE standards and associated program activities are not funded under U.S.C. Title 23 or 

12 the Federal Transit Act. Further, NHTSA establishes CAFE standards, not FHWA or FTA. Accordingly, 

13 the CAFE standards and associated rulemakings are not subject to transportation conformity. 

14 The General Conformity Rule contains several exemptions applicable to federal actions, which 

15 the conformity regulations define as “any activity engaged in by a department, agency, or instrumentality 

16 of the Federal Government, or any activity that a department, agency or instrumentality of the Federal 

17 Government supports in any way, provides financial assistance for, licenses, permits, or approves, other 

18 than activities [subject to transportation conformity].” 40 CFR 51.852. “Rulemaking and policy 

19 development and issuance” are exempted at 40 CFR 51.853(c)(2)(iii). Because NHTSA’s CAFE 

20 standards involve a rulemaking process, NHTSA’s action is exempt from general conformity. Also, 

21 emissions for which a federal agency does not have a “continuing program responsibility” are not 

22 considered “indirect emissions” subject to general conformity under 40 CFR 51.852. “Emissions that a 

23 Federal agency has a continuing program responsibility for means emissions that are specifically caused 

24 by an agency carrying out its authorities, and does not include emissions that occur due to subsequent 

25 activities, unless such activities are required by the Federal agency.” 40 CFR 51.852. Emissions that 

26 occur as a result of the CAFE standards are not caused by NHTSA carrying out its statutory authorities 

27 and clearly occur due to subsequent activities, including vehicle manufacturers’ production of passenger28 car and light-truck fleets and consumer purchases and driving behavior. Thus, changes in any emissions 

29 that result from NHTSA’s new CAFE standards are not those for which the agency has a “continuing 
Chapter 3 Affected Environment and Environmental Consequences 3.3 Air Quality 

3-23 

1 program responsibility”; therefore, a general conformity determination is not required. Nonetheless, 

2 NHTSA is evaluating the potential impacts of air emissions for the purposes of NEPA. 

3 3.3.2 Methodology 

4 3.3.2.1 Overview 

5 To analyze impacts to air quality, NHTSA calculated the emissions of criteria pollutants and 

6 MSATs from passenger cars and light trucks that would occur under each alternative and assessed the 

7 changes in emissions in relation to the No Action Alternative (Alternative 1). 

8 For purposes of analyzing potential direct and indirect impacts (environmental consequences), the 

9 No Action Alternative in this EIS consists of the existing CAFE standards with no changes in the future. 

10 That is, the No Action Alternative assumes that average fuel economy levels in the absence of CAFE 

11 standards beyond MY 2011 would equal the higher of the agencies’ collective market forecast or the 

12 manufacturer’s required level of average fuel economy for MY 2011. See Section 2.3.2. The basic 

13 method used to estimate emissions entails multiplying activity levels of passenger cars and light trucks, 

14 expressed as the total number VMT, by emission factors measured in grams of pollutant emitted per 

15 VMT. National emissions estimates for all passenger cars and light trucks projected to be in use during 

16 future years were developed using the Volpe model. The Volpe model utilizes emission factors 

17 developed using EPA’s draft MOVES2009 emission model (EPA 2009j) for light-duty gasoline vehicles, 

18 and MOBILE6.2 (EPA 2004) for light-duty diesel vehicles. MOVES reflects EPA’s updated estimates 

19 of real-world emissions from passenger cars and trucks, and accounts for emission control requirements 

20 on exhaust (tailpipe) emissions and evaporative emissions, including the Tier 2 Vehicle & Gasoline 

21 Sulfur Program and Mobile Source Air Toxics (MSAT) rule. 

22 Impacts on upstream emissions (oil refining as well as fuel transport, storage, and distribution) 

23 were estimated using emission factors provided by EPA. These were based on the Greenhouse Gas, 

24 Regulated Emissions, and Energy Use in Transportation model (GREET, version 1.8) developed by DOE 

25 Argonne National Laboratory (Argonne 2002). EPA modified GREET for use in analyzing its 

Renewable Fuel Standard rulemaking3 26 analysis to account for recent EPA emission standards for gasoline 

27 transport and the addition of air toxics emission factors. 

28 By reducing the cost of fuel consumed per mile driven, setting future CAFE standards that require 

29 higher mpg levels would create an incentive for additional driving. The resulting increase in driving 

30 offsets part of the fuel savings that would otherwise result from requiring higher fuel economy; this 

31 phenomenon is known as the fuel economy “rebound effect.” The total amount of passenger car and light 

32 truck VMT would increase slightly due to the rebound effect, and emissions from these vehicles would 

33 increase in proportion to the increased VMT. Although higher CAFE standards would decrease the total 

34 amount of fuel consumed from its level under the No Action Alternative despite the rebound effect, the 

35 reduction in fuel usage cannot be linked directly to any decrease in emissions resulting directly from 

36 vehicle use. 

37 The NHTSA CAFE standards and the EPA emissions standards impose separate requirements on 

38 motor-vehicle manufacturers. Although manufacturers must meet both the CAFE standards and the EPA 

39 emissions standards simultaneously, neither NHTSA nor EPA dictates the design and technology choices 

40 manufacturers must make to comply. For example, a manufacturer could use a technique that increases 

41 fuel economy but also increases emissions, as long as the manufacturer’s production still meets both the 

42 CAFE standards and the EPA emissions standards. For this reason, the air quality analysis methodology 

 

3

 74 FR 24904, May 26, 2009 
3.3 Air Quality Chapter 3 Affected Environment and Environmental Consequences 

 3-24 

1 does not assume any reduction in direct emissions from motor vehicle use solely due to improvements in 

2 fuel economy. 

3 However, the proposed CAFE standards would lead to reductions in “upstream” emissions, which 

4 are emissions associated with petroleum extraction, refining, storage, and distribution of transportation 

5 fuels. Upstream emissions would decrease as a consequence of the proposed CAFE standards because the 

6 total amount of fuel used by passenger cars and light trucks would decrease. 

7 Although the rebound effect is assumed to result in identical percentage increases in VMT and 

8 emissions from vehicle use in all regions of the Nation, the associated changes in upstream emissions are 

9 expected to vary among regions because fuel refining and storage facilities are not uniformly distributed 

10 across the Country. Thus, an individual region could experience either a net increase or a net decrease in 

11 emissions of each pollutant due to the proposed CAFE standards, depending on the relative magnitudes of 

12 the increase in emissions from vehicle use and the regional reduction in emissions from fuel production 

13 and distribution. 

14 To assess regional differences in the effects of the alternatives, NHTSA estimated net emissions 

15 changes for individual nonattainment areas. NHTSA used nonattainment areas because these are the 

16 regions in which air quality problems have been greatest. All nonattainment areas assessed were in 

17 nonattainment for ozone or PM2.5 because these are the pollutants for which emissions from passenger 

18 cars and light trucks are of greatest concern. NHTSA did not quantify PM10 emissions separately from 

19 PM2.5 because almost all the PM in the exhaust from passenger cars and light trucks is PM2.5. The road20 dust component of PM10 concentrations from passenger cars and light trucks would increase in proportion 

21 to the rebound effect. There are no longer any nonattainment areas for annual PM10 because EPA 

22 revoked the annual PM10 standard. Currently there are no NO2 nonattainment areas, and only one area 

23 remains designated nonattainment for CO.

24 The air quality analysis is nationwide and regional and does not address the specific geographic 

25 locations of increases in emissions because emissions increases due to the rebound effect consist of higher 

26 emissions from passenger cars and light trucks operating on regional roadway networks. Thus, any 

27 emissions increases due to the VMT rebound effect would be distributed along a region’s entire road 

28 network. At any one location the increase would be small compared to total emissions near the source 

29 (i.e., existing emissions from traffic on the road), so the localized impacts on ambient concentrations and 

30 health should also be small. The aggregate of such small near-source impacts on ambient concentrations 

31 and health nationwide might be larger, but is not feasible to quantify. 

32 3.3.2.2 Time Frames for Analysis 

33 Ground-level concentrations of criteria and toxic air pollutants generally respond quickly to 

34 changes in emission rates. The longest averaging period for measuring whether ambient concentrations 

of a pollutant comply with the NAAQS is 1 year.4 35 The air quality analysis considers the emissions that 

36 would occur over annual periods, consistent with NAAQS. NHTSA selected calendar years that are 

37 meaningful for the timing of likely effects of the alternatives. 

38 Passenger cars and light trucks remain in use for many years, so the change in emissions due to 

39 any change in the CAFE standards for MY 2012-2016 would also continue for many years. The influence 

 

4

 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 

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. 
Chapter 3 Affected Environment and Environmental Consequences 3.3 Air Quality 

3-25 

1 of vehicles produced during a particular model year declines over time as those vehicles are gradually 

2 retired from service as they age, while those that remain in use are driven progressively less. The Volpe 

3 model defines vehicle lifetime as the point at which less than 2 percent of the vehicles originally produced 

4 in a model year remain in service. Under this definition, passenger cars survive in the fleet for as long as 

5 26 years, while light trucks can survive for up to 37 years. Of course, any individual vehicle might not 

6 necessarily survive to these maximum ages; the typical or “expected” lifetimes for passenger cars and 

7 light trucks are approximately half of their respective maximum lifetimes. 

8 The survival of vehicles and the amount they are driven can be forecast with reasonable accuracy 

9 for a decade or two, while the influences of fuel prices and general economic conditions are less certain. 

10 To evaluate impacts to air quality, specific years must be selected for which emissions will be estimated 

11 and their effects on air quality calculated. NHTSA performed the air quality analysis in two ways that 

12 affect the choice of analysis years. For the NEPA direct and indirect impacts analysis, NHTSA assumed 

13 that the CAFE standards for MY 2012-2016 would remain in force indefinitely at the 2016 level; NHTSA 

14 did not include potential CAFE standards for MY 2017-2020 because they are not within the scope of this 

15 rulemaking. 

16 The paragraphs below describe the analysis years NHTSA used in this EIS and the rationales for each. 

17  2016 – First year of complete implementation of the MY 2012-2016 CAFE standards; year of 

18 highest overall emissions from passenger cars and light trucks following complete 

19 implementation. 

20  2020 – Latest required attainment date for 8-hour ozone nonattainment areas (2020 is latest 

21 full year, because the last attainment date is June 2021 for South Coast Air Basin, 

California5 22 ); by this point a large proportion of passenger-car and light-truck VMT would be 

23 accounted for by vehicles that meet the MY 2012-2016 standards; first year of complete 

24 implementation of potential MY 2017-2020 CAFE standards (see Section 4.3). 

25  2030 – By 2030, almost all passenger cars and light trucks in operation would meet at least 

26 the MY 2012-2016 standards, and the impact of these standards would be determined 

27 primarily by VMT growth rather than further tightening of the standards. The year-by-year 

28 impacts of the CAFE standards for MY 2012-2016 and the EPA standards by 2030 will 

29 change little from model year turnover, and most changes in emissions from year to year will 

30 come from added driving due to the fuel economy rebound effect. 

31 3.3.2.3 Treatment of Incomplete or Unavailable Information 

32 As noted throughout this methodology section, the estimates of emissions rely on models and 

33 forecasts that contain numerous assumptions and data that are uncertain. Examples of areas in which 

34 information is incomplete or unavailable include future emissions rates, vehicle manufacturers’ decisions 

35 on vehicle technology and design, the mix of vehicle types and model years comprising the passenger-car 

36 and light-truck fleet, VMT projections, emissions from fuel refining and distribution, and economic 

37 factors. To approximate the health benefits associated with each alternative, NHTSA used screening38 level estimates of health outcomes in the form of cases per ton of criteria pollutant emissions reduced, and 

39 of monetized health benefits in the form of dollars per ton of criteria pollutant emissions reduced. The 

40 use of such dollars-per-ton numbers, however, does not account for all potential health and environmental 

 

5

 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 

 3-26 

1 benefits, because the information necessary to monetize all potential health and environmental benefits is 

2 unavailable. As a result, NHTSA has probably underestimated the total criteria pollutant benefits. 

3 Reductions in emissions of toxic air pollutants should result in health benefits as well, but scientific data 

4 that would support quantification and monetization of these benefits are not available. 

5 Where information in the analysis included in the EIS is incomplete or unavailable, NHTSA has 

6 relied on CEQ regulations regarding incomplete or unavailable information. See 40 CFR § 1502.22(b). 

7 NHTSA has used the best available models and supporting data. The models used for the EIS were 

8 subjected to scientific review and have received the approval of the agencies that sponsored their 

9 development. NHTSA believes that the EIS assumptions regarding uncertain conditions reflect the best 

10 available information and are valid and sufficient for this analysis. 

11 3.3.2.4 Allocation of Exhaust Emissions to Nonattainment Areas 

12 For each alternative, the Volpe model provided national emissions estimates for each criteria air 

13 pollutant (or its chemical precursors) and MSAT. National emissions were allocated to the county level 

14 using VMT data for each county. EPA provided passenger-car and light-truck VMT data for all counties 

15 in the United States for 2014, 2020, and 2030 and consistent with the EPA National Emissions Inventory 

16 (NEI) (EPA 2006 as cited in EPA 2009g). Data for 2014, 2020, and 2030 were based on growth from 

17 economic modeling and EIA (2006). The VMT data used in the NEI were projected from traffic counts 

18 taken by counties and states on major roadways, and therefore are subject to some uncertainty. NHTSA 

19 used the VMT data from the NEI only to allocate nationwide total emissions to counties, and not to 

20 calculate the emissions. The estimates of nationwide total emissions are based on the national VMT data 

21 used in the Volpe model. 

22 NHTSA used the county-level VMT allocations, expressed as fractions of national VMT for each 

23 county, to derive the county-level emissions from the estimates of nationwide total emissions. Emissions 

24 for each nonattainment area were derived by summing the emissions for the counties included in each 

25 nonattainment area. Most nonattainment areas comprise one or more counties, and because county-level 

26 emissions are aggregated for each nonattainment area, uncertainties in the country-level emissions 

27 estimates carry over to NHTSA’s estimates of emissions within each nonattainment area. Over time, 

28 some counties will grow faster than others, and VMT growth rates will also vary. EPA provided the 

29 VMT data which includes forecasts of the county allocation only as far as 2030. The EPA forecasts of 

30 county-level VMT allocation introduce some uncertainty into the nonattainment-area-level VMT 

31 estimates. Additional uncertainties that affect county-level exhaust emissions estimates arise 

32 from differences between counties or nonattainment areas other than VMT, such as ambient temperatures, 

33 vehicle age distributions, vehicle speed distributions, vehicle inspection and maintenance programs, and 

34 fuel composition requirements. This uncertainty increases as the projection period lengthens, such as 

35 analysis year 2030 compared to 2016. 

36 The geographic definitions of ozone and PM2.5 nonattainment areas came from the current EPA 

37 Greenbook list (EPA 2009e). For nonattainment areas that include portions of counties, NHTSA 

38 calculated the proportion of county population that falls within the nonattainment area boundary as a 

39 proxy for the proportion of county VMT within the nonattainment area boundary. This method assumes 

40 that per-capita VMT is constant within each county, so that the proportion of county population in the 

41 partial county area reflects the VMT in that area. This assumption introduces some uncertainty into the 

42 allocation of VMT to partial counties, because actual VMT per capita can vary according to the 

43 characteristics of land use and urban development. For example, VMT per capita can be lower than 

44 average in urban centers with mass transit and higher than average in suburban and rural areas where 

45 people tend to drive more (Cook et al. 2006). 
Chapter 3 Affected Environment and Environmental Consequences 3.3 Air Quality 

3-27 

1 Partial county boundaries were taken from geographic information system files based on 2006 

2 nonattainment area definitions. In some cases, partial counties within nonattainment areas as currently 

3 defined were not included in the 2006 nonattainment areas. In those cases, NHTSA did not add any part 

4 of the missing counties’ VMT to the nonattainment area totals, on the basis that partial counties added to 

5 nonattainment areas between 2006 and 2009 are likely to represent relatively small additions to total 

6 nonattainment area VMT. Several urban areas are in nonattainment for both ozone and PM2.5. Where 

7 boundary areas differ between the two pollutants, NHTSA used the larger boundary. This approach is 

8 conservative (tending to overestimate emissions within the nonattainment area for the pollutant having the 

9 smaller boundary) because it assigns the larger area’s VMT (and thus, its emissions) to the smaller area. 

10 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 Moderate Nonattainment 100 100 

Columbus, OH Subpart 1 Nonattainment 100 100 

Dallas-Fort Worth, TX Moderate - 100 - 

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 
3.3 Air Quality Chapter 3 Affected Environment and Environmental Consequences 

 3-28 

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

Houston-Galveston-Brazoria, TX Moderate - 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 Subpart 1 - 100 100 

Providence (All RI), RI Moderate - 100 - 

Reading, PA - Nonattainment - 100 

Riverside Co., CA (Coachella Valley) Serious - 50 - 

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 
Chapter 3 Affected Environment and Environmental Consequences 3.3 Air Quality 

3-29 

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

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 2008, 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. 

1 

2 3.3.2.4.1 Allocation of Upstream Emissions to Nonattainment Areas 

3 Upstream emissions associated with the production and distribution of fuels used by motor 

4 vehicles are generated when fuel products are produced, processed, and transported. Upstream emissions 

5 are typically divided into four categories: 

6  Feedstock recovery (mainly petroleum extraction); 

7  Feedstock transportation; 

8  Fuel refining; and 

9  Fuel transportation, storage, and distribution (TS&D). 

10 Feedstock recovery refers to the extraction or production of fuel feedstocks. In the case of 

11 petroleum, this is the stage of crude-oil extraction. During the next stage, feedstock transportation, crude 

12 oil, or other feedstocks are shipped to fuel refineries. Fuel refining refers to the processing of crude oil 

13 into gasoline and diesel fuel. TS&D refers to the movement of gasoline and diesel from refineries to bulk 

14 terminals, storage at bulk terminals, and transportation of fuel from bulk terminals to retail outlets. 

15 Emissions of pollutants at each stage are associated with expenditure of energy, as well as with leakage or 

16 spillage and evaporation of fuel products. 

17 To analyze the impact of the alternatives on individual nonattainment areas, NHTSA allocated 

18 emissions reductions to geographic areas according to the following methodology:

19  Feedstock recovery – NHTSA assumed that little to no extraction of crude oil occurs in 

20 nonattainment areas. Of the top 50 highest producing oil fields in the United States, only 

21 nine are in nonattainment areas. These nine fields account for just 10 percent of domestic 

22 production, or 3 percent of total crude-oil imports plus domestic production (EIA 2006, EIA 

23 2008). Therefore, because relatively little extraction occurs in nonattainment areas, NHTSA 

24 ignored emissions reductions from feedstock recovery in nonattainment areas. As a result of 

25 not quantifying the upstream emissions reductions associated with feedstock recovery, this 

26 part of the analysis is conservative (tending to underestimate the emission reduction benefits 

27 of the proposed CAFE standards). 
3.3 Air Quality Chapter 3 Affected Environment and Environmental Consequences 

 3-30 

1  Feedstock transportation – NHTSA assumed that little to no crude oil is transported through 

2 nonattainment areas. Most refineries are outside of, or on the outskirts of, urban areas. 

3 Crude oil is typically transported hundreds of miles from extraction points and ports to reach 

4 refineries. Most transportation is by ocean tanker and pipeline. Probably only a very small 

5 proportion of criteria pollutants emitted in the transport of crude oil occurs in nonattainment 

6 areas. Therefore, NHTSA ignored emissions reductions from feedstock transportation within 

7 nonattainment areas. 

8 Because NHTSA ignores emissions changes from the first two upstream stages, our assumptions 

9 produce conservative estimates of emission reductions in nonattainment areas (i.e., the estimates slightly 

10 underestimate the emissions benefits reductions associated with lower fuel production and use). 

11  Fuel refining – Fuel refining is the largest source of upstream emissions of criteria pollutants. 

12 Depending on the specific fuel and pollutant, fuel refining accounts for between one third and 

13 three quarters of all upstream emissions (based on outputs of the Volpe model). NHTSA 

14 used projected emissions data for 2022 from EPA’s 2005-based air quality modeling platform 

15 (EPA 2009h) to allocate fuel refining emission reductions to nonattainment areas. The NEI 

16 estimates emissions of criteria and toxic pollutants by county and by source category code 

17 (SCC). Because there are specific SCCs for fuel refining processes, it is possible to 

18 determine the share of national fuel refining emissions allocated to each nonattainment area. 

19 It is assumed that the share of fuel refining emissions allocated to each nonattainment area 

20 does not change over time, and that fuel refining emissions will change uniformly across all 

21 refineries nationwide as a result of the alternatives. 

22  TS&D – NHTSA used data from the EPA modeling platform (EPA 2009h) to allocate TS&D 

23 emissions to nonattainment areas in the same way as for fuel refining emissions. It is 

24 assumed that the share of TS&D emissions allocated to each nonattainment area does not 

25 change over time, and that TS&D emissions will change uniformly nationwide as a result of 

26 the alternatives. 

27 The data provided by EPA was missing county-level data for acetaldehyde, benzene, and 

28 formaldehyde. Therefore, for these three pollutants, NHTSA allocated national emissions based on the 

29 allocation of the pollutant that is believed to behave most similarly to the pollutant in question, as 

30 follows: 

31  For acetaldehyde, the data provided by EPA did not report TS&D emissions at the national or 

32 county level, so NHTSA assumed there are no acetaldehyde emissions associated with TS&D 

33 (i.e., that 100 percent of upstream acetaldehyde emissions come from refining). The EPA 

34 data included national fuel-refining emissions of acetaldehyde, but data by county are not 

35 available. To allocate acetaldehyde emissions to counties, NHTSA used the county 

36 allocation of acrolein, because acrolein is the toxic air pollutant which has, among those for 

37 which county-level data were available, the highest proportion of its emissions coming from 

38 refining. Thus, the use of acrolein data for allocation of acetaldehyde emissions to counties is 

39 most consistent with the assumption that 100 percent of acetaldehyde emissions come from 

40 refining 

41  For benzene, the EPA data included nationwide fuel refining and TS&D emissions, and 

42 TS&D emissions at the county level, but not refining emissions at the county level. To 

43 allocate fuel refining emissions of benzene to counties, NHTSA used the same county 

44 allocation as butadiene because, among toxic air pollutants for which county-level data were 
Chapter 3 Affected Environment and Environmental Consequences 3.3 Air Quality 

3-31 

1 available, butadiene has the ratio of fuel refining and TS&D emissions that is closest to the 

2 ratio for benzene emissions. 

3  For formaldehyde, the EPA data included national fuel refining and TS&D emissions, but 

4 county-level data were not available. To allocate formaldehyde emissions to counties, 

5 NHTSA used the same county allocation as for butadiene because, among toxic air pollutants 

6 for which county-level data were available, butadiene has the ratio of fuel refining and TS&D 

7 emissions that is closest to the ratio for formaldehyde emissions. 

8 For the final EIS, NHTSA will use a complete set of EPA county-level data for these pollutants to 

9 allocate the emission reductions from GREET. 

10 

11 3.3.2.4.2 Health Outcomes and Costs 

12 Overview

13 This section describes the NHTSA approach to addressing public comments on the need to 

14 provide more quantitative estimates of adverse health effects of conventional air pollutants associated 

15 with each alternative. 

16 In this analysis, NHTSA quantified and monetized impacts to human health for each alternative. 

17 The agency evaluated the health impacts of CAFE alternatives for four health outcomes – premature 

18 mortality, chronic bronchitis, respiratory emergency-room visits, and work-loss days. For each analysis 

19 year, this methodology estimates the health impacts of each alternative, expressed as the number of 

20 additional or avoided outcomes per year. The general approach to calculating health outcomes associated 

21 with each alternative is to multiply the pollutant-specific incidence-per-ton value (number of annual 

22 outcomes avoided per ton of pollutant emissions reduced) by the emissions of the pollutant (tons per 

23 year), summed across all pollutants. Similarly, the general approach to calculating the monetary value of 

24 the health outcomes for each alternative is to multiply the pollutant-specific benefits-per-ton value (dollar 

25 value of human health benefits per ton of pollutant emissions reduced) by the emissions of the pollutant 

26 (tons per year), summed across all pollutants. The impact of a CAFE action alternative is calculated as 

27 the difference in the dollar value of benefits or the number of health outcomes between that alternative 

28 and the No Action Alternative. 

29 NHTSA estimated only the PM2.5-related human health impacts that are expected to result from 

30 reduced population exposure to atmospheric concentrations of PM2.5. The estimates are derived from 

31 PM2.5-related dollar-per-ton estimates that include only quantifiable reductions in health impacts likely 

32 to result from reduced population exposure to particular matter (PM). Three other pollutants - NOx, SO2, 

33 and VOCs - are included in the analysis as precursor emissions that contribute to PM2.5 not emitted 

34 directly from a source, but instead formed by chemical reactions in the atmosphere (secondary PM2.5). 

35 The dollar-per-ton estimates do not include all health impacts related to reduced exposure to PM, nor do 

36 they include any reductions in health impacts resulting from lower population exposure to other criteria 

37 air pollutants (particularly ozone) and air toxics. The agency is using PM-related benefits-per-ton values 

38 as an interim approach to estimating the PM-related benefits of the proposal. To model the ozone and PM 

39 air quality benefits of the final rule, the analysis will utilize ambient concentration data derived from full40 scale photochemical air quality modeling. 

41 Monetized Health Impacts

42 The PM2.5 benefit-per-ton estimates provide the total monetized human health benefits (the sum 

43 of premature mortality and premature morbidity) of reducing one ton of directly emitted PM2.5, or its 
3.3 Air Quality Chapter 3 Affected Environment and Environmental Consequences 

 3-32 

1 precursors (such as NOx, SO2, and VOCs), from a specified source. NHTSA followed the benefit-per-ton 

2 technique used in the EPA recent Ozone NAAQS Regulatory Impact Analysis (RIA) (EPA 2008a), 

3 Portland Cement National Emission Standards for Hazardous Air Pollutants (NESHAP) RIA (EPA 

4 2009b), and NO2 NAAQS (EPA 2009c). Table 3.3.2-2 lists the quantified and unquantified PM2.5-related 

5 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 

6 

7 The benefits estimates utilize the concentration-response functions as reported in the 

8 epidemiology literature. Readers interested in reviewing the complete methodology for creating the 

9 benefit-per-ton estimates used in this analysis can consult the EPA Technical Support Document 

10 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.6 11 

12 As described in the documentation for the benefit-per-ton estimates cited above, national per-ton 

13 estimates are developed for selected pollutant/source category combinations. The per-ton values 

14 calculated therefore apply only to tons reduced from those specific pollutant/source combinations (e.g., 

15 NO2 emitted from mobile sources; direct PM emitted from stationary sources). The NHTSA estimate of 

16 PM2.5 benefits is therefore based on the total direct PM2.5 and PM2.5-related precursor emissions controlled 

17 by sector and multiplied by this per-ton value. 

18 The benefit-per-ton coefficients were derived using modified versions of the health impact 

19 functions used in the EPA PM NAAQS RIA. Specifically, this analysis incorporated functions directly 

20 from the epidemiology studies without an adjustment for an assumed threshold. 

21 PM-related mortality provides most of the monetized value in each benefit-per-ton estimate. 

22 NHTSA calculated the premature-mortality-related effect coefficients that underlie the benefits-per-ton 

23 estimates from epidemiology studies that examined two large population cohorts – the American Cancer 

24 Society cohort (Pope et al. 2002) and the Harvard Six Cities cohort (Laden et al. 2006). These are logical 

25 choices for anchor points when presenting PM-related benefits because, while both studies are well 

26 designed and peer reviewed, there are strengths and weaknesses inherent in each, which argues for using 

 

6

 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 

1 both studies to generate benefits estimates. However, due to the analytical limitations associated with this 

2 analysis, NHTSA chose to use the benefit-per-ton value derived from the American Cancer Society study 

3 and note that benefits would be approximately 145 percent (or almost two-and-a-half times) larger if the 

4 agency used the Harvard Six Cities values. 

5 The benefits-per-ton estimates used in this analysis are based on a value of statistical life (VSL) 

6 estimate that was vetted and endorsed by EPA’s Science Advisory Board (SAB) in the Guidelines for 

Preparing Economic Analyses (EPA 2000b).7 7 This approach calculates a mean value across VSL 

8 estimates derived from 26 labor market and contingent valuation studies published between 1974 and 

9 1991. The mean VSL across these studies is $6.3 million (in 2000 dollars). The dollar-per-ton estimates 

10 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% 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). 

11 

12 Quantified Health Impacts

13 Table 3.3.2-4 lists the incidence-per-ton estimates for select PM-related endpoints (derived by the 

14 same process as described above for the dollar-per-ton estimates). 

15 For the analysis of direct and indirect impacts (see Section 3.4), NHTSA used the values for 

16 2016, 2020, and 2030 (see Section 3.3.2.2). For the analysis of cumulative impacts (see Section 4.3), 

17 which also includes estimated impacts for 2050, NHTSA used the same values and used the values for 

18 2040 for the 2050 analysis. 

 

7

 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 

 3-34 

Table 3.3.2-4 

Incidence-per-Ton Values Premature Mortality – 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).

1 

2 Assumptions and Uncertainties

3 The benefit-per-ton estimates are subject to a number of assumptions and uncertainties, as 

4 follows: 

5  They do not reflect local variability in population density, meteorology, exposure, baseline 

6 health incidence rates, or other local factors that might lead to an overestimate or 

7 underestimate of the actual benefits of controlling fine particulates. Emissions changes and 

8 benefits-per-ton estimates alone are not a good indication of local or regional air quality and 

9 health impacts, because there could be localized impacts associated with the proposed action. 

10 Because the atmospheric chemistry related to ambient concentrations of PM2.5, ozone, and air 

11 toxics is very complex, full-scale photochemical air quality modeling would be necessary to 

12 control for local variability. Full-scale photochemical modeling would provide the needed 

13 spatial and temporal detail to more completely and accurately estimate changes in ambient 

14 levels of these pollutants and their associated health and welfare impacts. EPA is conducting 

15 full-scale photochemical modeling for its rulemaking on vehicle GHG standards, which is an 
Chapter 3 Affected Environment and Environmental Consequences 3.3 Air Quality 

3-35 

1 element of the joint NHTSA-EPA rulemaking for CAFE (NHTSA) and GHG (EPA) 

2 standards for MY 2012-2016 passenger cars and light trucks. Due to the unique nature of the 

3 joint NHTSA-EPA rulemaking, and as a component of the National Program, EPA’s air 

4 quality modeling analysis of its GHG standards will provide insight into the uncertainties 

5 associated with the use of monetary benefits-per-ton estimates. 

6  NHTSA assumed that all fine particles, regardless of their chemical composition, are equally 

7 potent in causing premature mortality. This is an important assumption, because PM2.5

8 produced via transported precursors emitted from stationary sources might differ significantly 

9 from direct PM2.5 released from diesel engines and other industrial sources, but there are no 

10 clear scientific grounds to support estimating differential effects by particle type. 

11  NHTSA assumed that the health impact function for fine particles is linear within the range of 

12 ambient concentrations under consideration. Thus, the estimates include health benefits from 

13 reducing fine particles in areas with varied concentrations of PM2.5, including both regions 

14 that are in attainment with the fine-particle standard and those that do not meet the standard 

15 down to the lowest modeled concentrations. 

16  There are several health-benefits categories NHTSA was unable to quantify due to limitations 

17 associated with using benefits-per-ton estimates, several of which could be substantial. 

18 Because NOx and VOCs are also precursors to ozone, reductions in NOx and VOC emissions 

19 would also reduce ozone formation and the health effects associated with ozone exposure. 

20 Unfortunately, there are no benefits-per-ton estimates because of issues associated with the 

21 complexity of the atmospheric air chemistry and nonlinearities associated with ozone 

22 formation. The PM-related benefits-per-ton estimates also do not include any human welfare 

23 or ecological benefits. 

24 3.3.3 Environmental Consequences 

25 3.3.3.1 Results of the Emissions Analysis 

26 The CAA has been a success in reducing emissions from on-road mobile sources. As discussed 

27 in Section 3.3.1, pollutant emissions from vehicles have been declining since 1970 and EPA projects that 

28 they will continue to decline. However, as future trends show, vehicle travel is having a smaller and 

29 smaller impact on emissions as a result of stricter EPA standards for vehicle emissions and the chemical 

30 composition of fuels, even with additional growth in VMT (Smith 2002). This general trend will 

31 continue, to a greater or lesser degree, with implementation of any of the alternative CAFE standards. 

32 The analysis by alternative in this section shows that the CAFE action alternatives will lead to both 

33 reductions and increases in emissions from passenger cars and light trucks, compared to current trends 

34 without the proposed CAFE standards. The amounts of the reductions and increases would vary by 

35 pollutant, calendar year, and action alternative. The more restrictive action alternatives generally would 

36 result in greater emissions reductions compared to the No Action Alternative. 

37 Sections 3.3.3.2 through 3.3.3.10 describe the results of the emissions analysis for Alternatives 1 

38 through 9. 

39 3.3.3.2 Alternative 1: No Action 

40 3.3.3.2.1 Criteria Pollutants 

41 Under the No Action Alternative, average fuel economy levels in the absence of CAFE standards 

42 beyond MY 2011 would equal the higher of the agencies’ collective market forecast or the manufacturer’s 

43 required level of average fuel economy for MY 2011. Current trends in the levels of emissions from 
3.3 Air Quality Chapter 3 Affected Environment and Environmental Consequences 

 3-36 

1 vehicles would continue, with emissions continuing to decline due to the EPA emissions standards, 

2 despite a growth in total VMT. The EPA vehicle emissions standards regulate all criteria pollutants 

3 except SO2, which is regulated through fuel sulfur content. The No Action Alternative would not result in 

4 any change in criteria pollutant emissions, other than current trends, in nonattainment and maintenance 

5 areas throughout the United States. 

6 Table 3.3.3-1 summarizes the total national emissions from passenger cars and light trucks by 

7 alternative for each of the criteria pollutants and analysis years. The table presents the action alternatives 

8 (Alternatives 2 through 9) left to right in order of increasing fuel economy requirements. Figure 3.3.3-1 

9 illustrates this information. Table 3.3.3-1 and Figure 3.3.3-1 show that changes in overall emissions 

10 between the No Action Alternative and Alternatives 2 through 4 are generally smaller than those between 

11 the No Action Alternative and Alternatives 5 through 9. In the case of NOx, PM2.5, SOx, and VOCs, the 

12 No Action Alternative results in the highest emissions, and emissions generally decline as fuel economy 

13 standards increase across alternatives. Across Alternatives 4 through 9 there are some emissions 

14 increases from one alternative to another, but emissions remain below the levels under the No Action 

15 Alternative. In the case of CO, emissions under Alternatives 2 through 4 are slightly higher than under 

16 the No Action Alternative. Emissions of CO decline as fuel economy standards increase across 

17 Alternatives 5 through 9. 

18 Total emissions are composed of four components: tailpipe emissions and upstream emissions 

19 for passenger cars, and tailpipe emissions and upstream emissions for light trucks. To show the 

20 relationship among these four components for criteria pollutants, Table 3.3.3-2 breaks down the total 

21 emissions of criteria pollutants by component for calendar year 2030. 

22 Table 3.3.3-3 lists the net change in nationwide emissions from passenger cars and light trucks 

23 compared to the No Action Alternative for each of the criteria pollutants and analysis years. The table 

24 lists the action alternatives (Alternatives 2 through 9) left to right in order of increasing fuel economy 

25 requirements. In Table 3.3.3-3, the nationwide emissions reductions generally become greater from left 

26 to right, reflecting the increasing fuel economy requirements assumed under successive alternatives, 

27 although the decreases are smaller for some pollutants and years under Alternatives 4 through 9 due to the 

28 interaction of VMT, fuel economy, and the share of VMT accrued by diesel vehicles. Emissions of CO 

29 under Alternatives 2 through 4 are exceptions, showing increases compared to the No Action Alternative, 

30 because increases in VMT more than offset increases in fuel efficiency and declines in CO emission rates 

31 per vehicle. 

32 3.3.3.2.2 Toxic Air Pollutants 

33 Under Alternative 1 (No Action), the average fuel economy would remain at the MY 2011 level 

34 in future years. As with the criteria pollutants, current trends in the levels of toxic air pollutant emissions 

35 from vehicles would continue, with emissions continuing to decline due to the EPA emissions standards, 

36 despite a growth in total VMT. An exception to this general trend is DPM, for which emissions are 

37 projected to increase over time under the No Action Alternative due to increasing use of diesel vehicles 

38 and increasing VMT. EPA regulates toxic air pollutants from motor vehicles through vehicle emissions 

39 standards and fuel quality standards, as discussed in Section 3.3.1. The No Action Alternative would not 

40 change the current CAFE standards and therefore would not result in any change in toxic air pollutant 

41 emissions, other than current trends in emissions and VMT, in nonattainment and maintenance areas 

42 throughout the United States. 
Chapter 3 Affected Environment and Environmental Consequences 

3-37 

Table 3.3.3-1 

Nationwide Criteria Pollutant Emissions from Passenger Cars and Light Trucks by Alternative (tons/yea

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 

~5.9%/year 

Increase 

MNB 

6%/year 

Increase 

7%

In

Carbon monoxide (CO) 

2016 18,046,737 18,055,567 18,054,219 18,049,276 17,990,071 17,954,866 17,943,080 12020 15,996,845 16,026,834 16,022,019 16,011,136 15,852,005 15,731,014 15,677,635 12030 17,766,186 17,875,841 17,857,900 17,830,426 17,374,361 16,933,532 16,692,592 1

Nitrogen oxides (NOx) 

2016 2,043,669 2,040,386 2,038,801 2,038,077 2,035,890 2,033,211 2,033,658 2020 1,612,106 1,604,439 1,600,822 1,599,457 1,591,815 1,584,855 1,584,110 2030 1,467,596 1,453,694 1,445,588 1,443,013 1,416,117 1,390,714 1,379,863 

Particulate matter (PM2.5) 

2016 63,686 63,201 63,010 62,991 63,145 63,149 63,315 2020 62,698 61,520 61,109 61,096 61,212 61,368 61,681 2030 76,589 74,147 73,316 73,321 73,122 73,349 73,725 

Sulfur Oxides (SOx) 

2016 164,406 161,493 160,246 159,818 160,089 159,031 159,855 2020 169,832 162,689 159,941 159,199 159,114 157,754 159,065 2030 201,502 186,242 180,661 179,415 178,313 176,493 178,441 

Volatile organic compounds (VOCs) 

2016 2,307,062 2,293,122 2,286,048 2,282,711 2,275,408 2,264,296 2,265,703 2020 1,943,639 1,909,647 1,893,787 1,887,837 1,869,970 1,847,814 1,845,130 2030 1,668,085 1,596,544 1,564,323 1,553,482 1,514,436 1,469,438 1,456,616 
3.3 Air Quality Chapter 3 Affected Environment an

3-38 

Figure 3.3.3-1. Nationwide Criteria Pollutant Emissions (tons/year) 

from Passenger Cars and Light Trucks for 2030 by Alternative 

0

300,000600,000900,000

1,200,0001,500,0001,800,000

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 

~5.9%/year

Increase

MNB

Alt. 7 

6%/year

Increase

Alt. 8 

7%/year

Increase

~6

In

Alternative

Tons/Year (NOx, PM, SOx, VOC) 

Nitrogen Oxides (NOx) Particulate Matter (PM) Sulfur Oxides (SOx) Volatile Organic Compounds (VOC) Carbon Mon
Chapter 3 Affected Environment and Environmental Consequences 

3-39 

Table 3.3.3-2 

Nationwide Criteria Pollutant Emissions in 2030 from Passenger Cars and Light Trucks, by Vehicle Type by Alternat

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 

~5.9%/year 

Increase 

MNB 

6%/year 

Increase 

7%/

Incr

Carbon monoxide (CO) 

Car Tail 7,878,750 7,937,359 7,955,806 7,918,203 7,943,240 7,855,275 7,853,156 7,8Car Up 53,101 48,746 47,151 47,013 45,909 45,327 45,282 Truck Tail 9,798,206 9,855,973 9,821,999 9,832,640 9,351,783 8,999,460 8,759,619 8,6Truck Up 36,129 33,762 32,944 32,569 33,429 33,470 34,535 Total 17,766,186 17,875,841 17,857,900 17,830,426 17,374,361 16,933,532 16,692,592 16,5

Nitrogen oxides (NOx)

Car Tail 356,847 359,498 360,336 358,668 359,796 355,896 355,804 3Car Up 166,236 152,516 147,473 146,902 143,439 141,283 141,128 1Truck Tail 831,560 836,147 834,927 835,741 809,211 790,193 776,714 7Truck Up 112,953 105,533 102,852 101,702 103,672 103,342 106,217 1Total 1,467,596 1,453,694 1,445,588 1,443,013 1,416,117 1,390,714 1,379,863 1,3

Particulate matter (PM2.5) 

Car Tail 20,921 21,211 21,364 21,562 21,627 22,147 22,165 Car Up 22,635 20,783 20,106 20,055 19,585 19,355 19,337 Truck Tail 17,624 17,752 17,788 17,807 17,607 17,501 17,398 Truck Up 15,409 14,400 14,058 13,897 14,303 14,346 14,825 Total 76,589 74,147 73,316 73,321 73,122 73,349 73,725 

Sulfur Oxides (SOx) 

Car Tail 18,336 16,737 16,130 15,922 15,533 14,954 14,922 Car Up 101,646 93,341 90,306 90,097 87,987 86,998 86,918 Truck Tail 12,306 11,477 11,056 10,956 10,432 9,926 9,774 Truck Up 69,215 64,688 63,168 62,440 64,362 64,616 66,828 Total 201,502 186,242 180,661 179,415 178,313 176,493 178,441 1

Volatile organic compounds (VOCs)  Car Tail 235,488 237,323 238,032 237,683 238,339 237,644 237,637 2 Car Up 554,868 505,473 486,552 478,608 466,733 445,352 444,215 4 Truck Tail 507,103 508,318 508,451 508,635 505,087 502,838 501,083 5 Truck Up 370,625 345,430 331,288 328,556 304,277 283,605 273,681 2 Total 1,668,085 1,596,544 1,564,323 1,553,482 1,514,436 1,469,438 1,456,616 1,4
3.3 Air Quality Chapter 3 Affected Environment an

3-40 

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 

~5.9%/year 

Increase 

MNB 

6%/year 

Increase 

7%/

Incr

Carbon monoxide (CO) 

2016 0 8,829 7,482 2,539 -56,666 -91,872 -103,657 2020 0 29,989 25,174 14,291 -144,840 -265,831 -319,210 2030 0 109,654 91,714 64,239 -391,826 -832,654 -1,073,594 -1

Nitrogen oxides (NOx) 

2016 0 -3,283 -4,868 -5,592 -7,779 -10,458 -10,011 2020 0 -7,667 -11,284 -12,649 -20,291 -27,251 -27,996 2030 0 -13,902 -22,008 -24,583 -51,479 -76,882 -87,733 

Particulate matter (PM2.5) 

2016 0 -486 -677 -696 -541 -538 -371 2020 0 -1,178 -1,589 -1,602 -1,486 -1,330 -1,017 2030 0 -2,442 -3,273 -3,268 -3,467 -3,240 -2,864 

Sulfur Oxides (SOx) 

2016 0 -2,912 -4,160 -4,588 -4,316 -5,375 -4,551 2020 0 -7,143 -9,891 -10,633 -10,718 -12,078 -10,767 2030 0 -15,261 -20,842 -22,087 -23,189 -25,009 -23,061 

Volatile organic compounds (VOCs) 

2016 0 -13,941 -21,014 -24,352 -31,654 -42,766 -41,359 2020 0 -33,992 -49,852 -55,802 -73,669 -95,825 -98,509 2030 0 -71,541 -103,762 -114,603 -153,648 -198,646 -211,468 

__________ 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.
Chapter 3 Affected Environment and Environmental Consequences 3.3 Air Quality 

3-41 

1 Table 3.3.3-4 summarizes the total national emissions of toxic air pollutants from passenger cars 

2 and light trucks by alternative for each of the pollutants and analysis years. Figure 3.3.2-2 lists the total 

3 national emissions of toxic air pollutants from passenger cars and light trucks by alternative. Emissions 

4 of benzene and DPM are highest under the No Action Alternative, and emissions of acetaldehyde, 

5 acrolein, and formaldehyde are highest under Alternative 9. Emissions of 1,3-butadiene are highest under 

6 Alternative 9 in 2016 and 2020, but highest under Alternative 4 in 2030. 

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 

~5.9%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.7%/year 

Increase 

TCTB 

Acetaldehyde 

2016 10,039 10,041 10,045 10,047 10,071 10,087 10,090 10,097 10,100

2020 7,928 7,938 7,947 7,947 7,986 8,017 8,033 8,046 8,051

2030 6,631 6,665 6,683 6,678 6,710 6,721 6,733 6,748 6,751

Acrolein 

2016 521 521 522 522 527 531 531 533 533

2020 410 411 412 413 423 432 435 438 439

2030 342 345 348 351 366 385 393 398 399

Benzene 

2016 52,316 52,296 52,283 52,272 52,222 52,177 52,171 52,157 52,151

2020 39,693 39,653 39,623 39,601 39,466 39,340 39,302 39,265 39,256

2030 27,706 27,667 27,602 27,551 27,171 26,758 26,569 26,466 26,440

1,3-Butadiene 

2016 5,704 5,706 5,707 5,708 5,709 5,711 5,711 5,712 5,712

2020 4,504 4,510 4,513 4,514 4,512 4,514 4,514 4,515 4,515

2030 3,610 3,631 3,637 3,638 3,615 3,597 3,584 3,581 3,579

Diesel particulate matter (DPM) 

2016 86,700 85,133 84,397 84,123 83,788 82,953 83,249 82,892 82,695

2020 89,445 85,599 83,968 83,503 82,523 81,119 81,313 80,551 80,431

2030 106,046 97,820 94,519 93,731 91,502 89,134 89,055 87,536 87,606

Formaldehyde 

2016 12,851 12,848 12,856 12,863 12,954 13,014 13,028 13,051 13,062

2020 10,204 10,198 10,219 10,226 10,398 10,539 10,608 10,656 10,672

2030 8,875 8,884 8,927 8,938 9,198 9,440 9,573 9,652 9,672

7 

8 
3.3 Air Quality Chapter 3 Affected Environment and Environmental Consequences 

 3-42 

Figure 3.3.3-2. Nationwide Toxic Air Pollutant Emissions (tons/year) 

from Passenger Cars and Light Trucks for 2030 by Alternative 

0

2,000

4,000

6,000

8,000

10,000

12,000

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 

~5.9%/year

Increase

MNB

Alt. 7 

6%/year

Increase

Alt. 8 

7%/year

Increase

Alt 9 

~6.7%/year

Increase

TCTB

Alternative

Tons/Year (Acetaldehyde, Acrolein, 1,3-Butadiene, 

Formaldehyde) 

0

20,000

40,000

60,000

80,000

100,000

120,000 Tons/Year (Benzene, Diesel Particulate Matter)

Acetaldehyde Acrolein 1,3-Butadiene Formaldehyde Benzene Diesel Particulate Matter (DPM) .

1 

2 The trends for toxic air pollutant emissions across the alternatives are mixed. Table 3.3.3-4 

3 shows that emissions of acetaldehyde increase under each successive alternative from Alternative 1 to 

4 Alternative 9, except for Alternative 4 in 2020 and 2030. Emissions of acrolein increase under each 

5 successive alternative from Alternative 1 to Alternative 9. Emissions of benzene decrease under each 

6 successive alternative from Alternative 1 to Alternative 9. Emissions of 1,3-butadiene in 2016 increase 

7 under each successive alternative from Alternative 1 to Alternative 9, except under Alternative 7; 

8 emissions of 1,3-butadiene in 2020 increase under each successive alternative from Alternative 1 to 

9 Alternative 9, except under Alternatives 5 and 7; emissions of 1,3-butadiene in 2030 increase under each 

10 successive alternative from Alternative 1 to Alternative 4, and then decrease under each successive 

11 alternative from Alternative 5 to Alternative 9. Emissions of DPM decrease under each successive 

12 alternative from Alternative 1 to Alternative 9, except for Alternative 7 in 2016 and 2020 and Alternative 

13 9 in 2030. Emissions of formaldehyde in 2016 and 2020 decrease from Alternative 1 to Alternative 2, 

14 and then increase under each successive alternative from Alternative 3 through Alternative 9; in 2030 

15 emissions of formaldehyde increase under each successive alternative from Alternative 1 through 

16 Alternative 9. These trends are accounted for by the interaction between the share of VMT accrued by 

17 diesel vehicles, which increases across successive years as well as successive alternatives in the Volpe 

18 model, and fuel economy, which increases across successive alternatives except for Alternative 9. 

19 Total emissions are composed of four components: tailpipe emissions and upstream emissions 

20 for passenger cars, and tailpipe emissions and upstream emissions for light trucks. To show the 

21 relationship among these four components for air toxic pollutants, Table 3.3.3-5 breaks down the total 

22 emissions of air toxic pollutants by component for calendar year 2030. 
Chapter 3 Affected Environment and Environmental Consequences 

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 

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 

~5.9%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

Acetaldehyde Car Tail 2,851 2,875 2,884 2,878 2,887 2,875 2,874 2,88Car Up 59 54 52 52 50 49 49 4Truck Tail 3,681 3,699 3,710 3,713 3,737 3,763 3,775 3,78Truck Up 40 37 36 36 35 34 34 3Total 6,631 6,665 6,683 6,678 6,710 6,721 6,733 6,74Acrolein Car Tail 141 143 144 147 147 154 154 15Car Up 8 7 7 7 7 7 7 Truck Tail 188 189 192 192 207 220 227 23Truck Up 5 5 5 5 5 5 5 Total 342 345 348 351 366 385 393 39Benzene Car Tail 9,584 9,654 9,677 9,638 9,667 9,578 9,576 9,59Car Up 1,201 1,095 1,055 1,041 1,015 975 972 95Truck Tail 16,117 16,168 16,148 16,157 15,813 15,566 15,395 15,31Truck Up 805 750 722 716 676 639 625 61Total 27,706 27,667 27,602 27,551 27,171 26,758 26,569 26,461,3-Butadiene Car Tail 1,526 1,540 1,546 1,545 1,550 1,549 1,549 1,55Car Up 13 12 12 12 11 11 11 1Truck Tail 2,062 2,071 2,072 2,073 2,046 2,028 2,015 2,00Truck Up 9 8 8 8 8 8 9 Total 3,610 3,631 3,637 3,638 3,615 3,597 3,584 3,58Diesel particulate matter (DPM) Car Tail 11 98 166 361 360 854 869 90Car Up 63,320 57,856 55,797 55,180 53,840 52,080 51,980 51,01Truck Tail 113 119 174 173 577 897 1,098 1,21Truck Up 42,601 39,747 38,382 38,017 36,725 35,304 35,108 34,40Total 106,046 97,820 94,519 93,731 91,502 89,134 89,055 87,53
3.3 Air Quality Chapter 3 Affected Environment an

3-44 

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 

~5.9%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

Formaldehyde  Car Tail 3,535 3,575 3,594 3,610 3,621 3,662 3,664 3,67 Car Up 444 407 393 389 380 370 370 36 Truck Tail 4,595 4,622 4,668 4,670 4,933 5,149 5,279 5,35 Truck Up 300 280 271 269 265 259 261 25 Total 8,875 8,884 8,927 8,938 9,198 9,440 9,573 9,65
Chapter 3 Affected Environment and Environmental Consequences 3.3 Air Quality 

 3-45

1 Table 3.3.3-6 lists the net change in nationwide emissions from passenger cars and light trucks 

2 for each of the toxic air pollutants and analysis years. After the No Action Alternative (Alternative 1), the 

3 table presents the action alternatives (Alternatives 2 through 9) left to right; this corresponds to the order 

4 of increasing fuel economy except for Alternative 9. In Table 3.3.3-6, the nationwide emissions changes 

5 are uneven in relation to pollutant and alternative, although some demonstrate reductions, reflecting the 

6 changes in VMT and emissions by passenger cars versus light trucks and gasoline versus diesel engines 

7 projected to occur with the increasing fuel economy requirements assumed under successive alternatives. 

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 

~5.9%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.7%/year 

Increase 

TCTB 

Acetaldehyde 

2016 0 3 7 8 32 48 51 58 61

2020 0 9 19 18 58 88 104 118 122

2030 0 34 52 48 79 91 103 118 120

Acrolein 

2016 0 0 1 1 6 10 10 12 12

2020 0 1 2 3 13 22 25 28 29

2030 0 3 6 8 24 43 50 55 56

Benzene 

2016 0 -19 -33 -43 -93 -139 -144 -159 -164

2020 0 -40 -70 -92 -227 -353 -390 -427 -437

2030 0 -39 -104 -154 -534 -948 -1,137 -1,240 -1,266

1,3-Butadiene 

2016 0 2 3 3 5 7 6 7 8

2020 0 6 9 9 8 10 10 11 11

2030 0 21 27 28 5 -13 -26 -29 -31

Diesel particulate matter (DPM) 

2010 0 -1,567 -2,302 -2,577 -2,911 -3,747 -3,451 -3,807 -4,005

2020 0 -3,846 -5,477 -5,942 -6,922 -8,327 -8,132 -8,894 -9,015

2030 0 -8,225 -11,527 -12,315 -14,544 -16,912 -16,991 -18,510 -18,439

Formaldehyde 

2010 0 -4 5 11 103 163 177 200 210

2020 0 -6 16 23 194 336 404 452 469

2030 0 9 52 63 324 565 698 778 798

__________ 

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. 

8 

9 3.3.3.2.3 Health Outcomes and Costs 

10 Under Alternative 1 (No Action), average fuel economy would remain at the MY 2011 level in 

11 future years. Current trends in the levels of criteria pollutants and toxic air pollutants emissions from 
3.3 Air Quality Chapter 3 Affected Environment and Environmental Consequences 

 3-46 

1 vehicles would continue, with emissions continuing to decline due to the EPA emissions standards, 

2 despite a growth in total VMT. The human health effects and health-related costs that occur under current 

3 trends would continue. The No Action Alternative would not result in any other increase or decrease in 

4 human health effects and health-related costs throughout the United States. 

5 3.3.3.3 Alternative 2: 3-Percent Annual Increase 

6 3.3.3.3.1 Criteria Pollutants 

7 Under the 3-Percent Alternative (Alternative 2), generally the CAFE standards would require 

8 increased fuel economy compared to the No Action Alternative (Alternative 1). Alternative 2 would 

9 increase fuel economy less than would Alternatives 3 through 9. There would be reductions in 

10 nationwide emissions of NOx, PM2.5, SOx, and VOCs under Alternative 2 compared to the No Action 

11 Alternative. Depending on the year, NOx emissions would be reduced 0.2 to 0.9 percent, PM2.5 emissions 

12 would be reduced 0.8 to 3.2 percent, SOx emissions would be reduced 1.8 to 7.6 percent, and VOC 

13 emissions would be reduced 0.6 to 4.3 percent. There would be increases of CO emissions. CO 

14 emissions would increase 0.05 to 0.6 percent under Alternative 2, depending on the year. 

15 At the national level, the reduction in upstream emissions of criteria air pollutants tends to offset 

16 the increase in VMT and emissions due to the rebound effect. However, the reductions in upstream 

17 emissions are not uniformly distributed to individual nonattainment areas. For example, a nonattainment 

18 area that contains petroleum-refining facilities, such as Houston-Galveston-Brazoria, Texas, would 

19 experience more reductions in upstream emissions than an area that has none. There can be net emissions 

20 reductions if the reduction in upstream emissions in the nonattainment area more than offsets the increase 

21 within the area due to the rebound effect. Under Alternative 2, all nonattainment areas would experience 

22 reductions in emissions of SOx and VOCs. Some nonattainment areas would experience increases of CO, 

23 NOx, and PM2.5 emissions. The increases in CO, NOx, and PM2.5 emissions are the result of increased 

24 tailpipe emissions due to the rebound effect, particularly for CO emissions, which are dominated by 

25 tailpipe emissions rather than upstream emissions. Although NOx and PM2.5 emissions would increase in 

26 some nonattainment areas, the increase in each area is generally quite small. The decreases in nationwide 

27 NOx and PM2.5 emissions are the result of the decreases in upstream emissions and do not occur in all 

28 nonattainment areas. Although NOx and PM2.5 emissions would decrease in fewer nonattainment areas, 

29 the decreases in each area are much larger. The net result is decreased NOx and PM2.5 emissions 

30 nationwide. 

31 Tables in Appendix C list the emissions reductions for each nonattainment area. Table 3.3.3-7 

32 summarizes the criteria air pollutant results by nonattainment area. 

33 3.3.3.3.2 Toxic Air Pollutants 

34 There would be reductions in nationwide emissions of benzene and DPM in all analysis years, 

35 and formaldehyde in 2030, under Alternative 2 compared to the No Action Alternative. Emissions for the 

36 other toxic air pollutants and years are higher under Alternative 2 than under Alternative 1. 

37 Compared to Alternatives 3 through 9, Alternative 2 would have higher emissions of benzene and 

38 DPM, but lower emissions of acetaldehyde, acrolein, and formaldehyde. For 1,3-butadiene, Alternative 2 

39 would have lower emissions than Alternatives 3 through 9 in 2016 and 2020, lower emissions than 

40 Alternatives 3 and 4 in 2030, and higher emissions than Alternatives 5 through 9 in 2030. 
Chapter 3 Affected Environment and Environmental Consequences 3.3 Air Quality 

 3-47

Table 3.3.3-7 

Criteria Pollutant Emissions from Passenger Cars and Light Trucks, Maximum Changes 

by Nonattainment Area by 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. 

1 

2 At the national level, the reduction in upstream emissions of toxic air pollutants tends to offset the 

3 increase in VMT and emissions due to the rebound effect. However, as noted above, the reductions in 

4 upstream emissions are not uniformly distributed to individual nonattainment areas. For example, a 

5 nonattainment area that contains petroleum-refining facilities, such as Houston-Galveston-Brazoria, 

6 Texas, would experience more reductions in upstream emissions than an area that has none. There can be 

7 net emissions reductions if the reduction in upstream emissions in the nonattainment area more than 

8 offsets the increase within the area due to the rebound effect. 

9 Under Alternative 2, many nonattainment areas would experience net increases in emissions of 

10 one or more toxic air pollutants in at least one of the analysis years (see Appendix C). However, the sizes 

11 of the emissions increases would be quite small, as shown in Appendix C, and emissions increases would 

12 be distributed throughout each nonattainment area. 

13 3.3.3.3.3 Health Outcomes and Costs 

14 There would be reductions in adverse health effects nationwide under Alternative 2 compared to 

15 the No Action Alternative (see Table 3.3.3-8). These reductions primarily reflect the projected PM2.5

16 reductions, and secondarily the reductions in SOx (while the magnitude of PM2.5 reductions under this 

17 alternative is smaller than that of SOx, the pollutant is the largest contributor to adverse health effects on a 

18 per-ton basis). Compared to the No Action Alternative, Alternative 2 would reduce cases of premature 

19 mortality by 153 (under Pope et al.; reductions would be 156 percent greater under Laden et al.) in year 

20 2030. In the same year, the number of work-loss days would be reduced by 18,031. 

21 Table 3.3.3-9 lists the corresponding reductions in health costs under Alternative 2 compared to 

22 the No Action Alternative. Alternative 2 would reduce health costs by $1.36 billion in 2030, using a 3-

23 percent discount rate and estimates from Pope et al. Under Laden et al., economic benefits would be 145 

24 percent greater. Using a 7-percent discount rate, economic benefits would be 9.3 to 9.5 percent less. 
3.3 Air Quality Chapter 3 Affected Environment and Environmental Consequences 

 3-48 

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 

~5.9%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.7%/year 

Increase 

TCTB 

Mortality (ages 30 and older), Pope et al.

2016 0 a/ -26 b/ -36 -39 -36 -41 -34 -38 -41

2020 0 -64 -89 -93 -97 -102 -90 -101 -103

2030 0 -153 -210 -217 -253 -276 -267 -296 -296

Mortality (ages 30 and older), Laden et al.

2016 0 -66 -93 -99 -92 -106 -87 -98 -105

2020 0 -165 -227 -237 -248 -263 -231 -259 -263

2030 0 -392 -537 -554 -648 -705 -683 -758 -758

Chronic bronchitis 

2016 0 -17 -25 -26 -24 -28 -23 -26 -28

2020 0 -44 -61 -63 -66 -70 -62 -69 -71

2030 0 -100 -138 -142 -167 -182 -177 -196 -196

Emergency Room Visits for Asthma 

2016 0 -24 -34 -37 -34 -39 -32 -37 -39

2020 0 -62 -85 -89 -91 -97 -85 -95 -97

2030 0 -140 -191 -198 -226 -244 -233 -258 -258

Work Loss Days 

2010 0 -3,365 -4,776 -5,093 -4,713 -5,423 -4,444 -5,045 -5,390

2020 0 -8,308 -11,439 -11,925 -12,494 -13,231 -11,672 -13,077 -13,277

2030 0 -18,031 -24,750 -25,522 -30,036 -32,758 -31,811 -35,301 -35,306

__________ 

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. 

1 

2 

Table 3.3.3-9 

Nationwide Changes in Health Costs (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 

~5.9%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.7%/year 

Increase 

TCTB 

3% Discount Rate

Pope et al.

2016 0 a/ -215 b/ -306 -326 -302 -348 -285 -324 -346

2020 0 -560 -771 -805 -840 -890 -785 -879 -892

2030 0 -1,361 -1,867 -1,926 -2,253 -2,452 -2,374 -2,635 -2,634

Laden et al.

2016 0 -528 -749 -800 -739 -853 -699 -793 -847

2020 0 -1,372 -1,889 -1,972 -2,057 -2,181 -1,922 -2,153 -2,185

2030 0 -3,334 -4,574 -4,720 -5,520 -6,007 -5,816 -6,454 -6,451
Chapter 3 Affected Environment and Environmental Consequences 3.3 Air Quality 

 3-49

Table 3.3.3-9 (cont’d) 

Nationwide Changes in Health Costs (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 

~5.9%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.7%/year 

Increase 

TCTB 

7% Discount Rate

Pope et al.

2016 0 -196 -277 -296 -274 -316 -259 -294 -314

2020 0 -508 -700 -730 -762 -808 -712 -797 -809

2030 0 -1,234 -1,693 -1,747 -2,044 -2,224 -2,154 -2,390 -2,389

Laden et al.

2010 0 -477 -677 -723 -668 -770 -631 -716 -765

2020 0 -1,240 -1,707 -1,781 -1,859 -1,970 -1,736 -1,945 -1,974

2030 0 -3,012 -4,131 -4,264 -4,987 -5,426 -5,254 -5,830 -5,827

__________ 

a/ Negative changes indicate economic benefit; positive emissions changes indicate economic costs. 

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. 

1 

2 3.3.3.4 Alternative 3: 4-Percent Annual Increase 

3 3.3.3.4.1 Criteria Pollutants 

4 Under the 4-Percent Alternative (Alternative 3), generally the CAFE standards would increase 

5 fuel economy more than would Alternative 2 but less than would Alternatives 4 through 9. There would 

6 be reductions in nationwide emissions of NOx, PM2.5, SOx, and VOCs under Alternative 3 compared to 

7 the No Action Alternative. Depending on the year, NOx emissions would be reduced 0.2 to 1.5 percent, 

8 PM2.5 emissions would be reduced 1.1 to 4.3 percent, SOx emissions would be reduced 2.5 to 10.3 

9 percent, and VOC emissions would be reduced 0.9 to 6.2 percent. These emissions reductions are 

10 generally greater than would occur under Alternative 2 but less than would occur under Alternatives 4 

11 through 9. There would be increases of CO emissions from 0.04 to 0.5 percent, depending on the year. 

12 Under Alternative 3, all nonattainment areas would experience reductions in emissions of SOx and VOCs. 

13 Most nonattainment areas would experience increases of CO, NOx, and PM2.5 emissions compared to the 

14 No Action Alternative. The increases in CO, NOx, and PM2.5 emissions are the result of increased tailpipe 

15 emissions due to the rebound effect. Although NOx and PM2.5 emissions would increase in many 

16 nonattainment areas, the increase in each area is quite small. The decreases in nationwide NOx and PM2.5

17 emissions are the result of the decreases in upstream emissions and do not occur in all nonattainment 

18 areas. There would be fewer nonattainment areas with decreases in NOx and PM2.5 emissions than with 

19 increases, but the decreases would be much larger than the increases. The net result is decreased NOx

20 and PM2.5 emissions nationwide. Tables in Appendix C list the emissions reductions for each 

21 nonattainment area. Table 3.3.3-10 summarizes the criteria air pollutant results by nonattainment area. 

22 3.3.3.4.2 Toxic Air Pollutants 

23 Alternative 3 would reduce emissions of toxic air pollutants compared to the No Action 

24 Alternative for all pollutants (except acrolein). Aside from acrolein, Alternative 3 would have higher or 

25 equal emissions of all pollutants compared to Alternatives 4 through 9, except for benzene under 

26 Alternatives 5 through 7, 1,3-butadiene under Alternative 9 in 2016 and Alternative 4 in 2030, and 

27 formaldehyde under Alternatives 8 and 9 in all years. 
3.3 Air Quality Chapter 3 Affected Environment and Environmental Consequences 

 3-50 

Table 3.3.3-10 

Changes in Toxic Air Pollutant Emissions from Passenger Cars and Light Trucks, 

Maximum Changes by Nonattainment Area by Alternative a/

Hazardous Air 

Pollutant 

Increase/ 

Decrease 

Change 

(tons/year) Year Alt. No. Nonattainment Area 

Maximum 

Increase 6.4 2030 9 New York-N. New Jersey-Long Island, NY-NJ-CT 

Acetaldehyde Maximum 

Decrease 4.6 2030 8 Beaumont/Port Arthur, TX

Maximum 

Increase 2.7 2030 9 New York-N. New Jersey-Long Island, NY-NJ-CT 

Acrolein Maximum 

Decrease 0.47 2030 8 Beaumont/Port Arthur, TX 

Maximum 

Increase 4.8 2030 2 Los Angeles South Coast Air Basin, CA 

Benzene Maximum 

Decrease 52 2030 9 Houston-Galveston-Brazoria, TX

Maximum 

Increase 1.40 2030 4 New York-N. New Jersey-Long Island, NY-NJ-CT 

1,3-Butadiene Maximum 

Decrease 1.4 2030 9 Houston-Galveston-Brazoria, TX

Maximum 

Increase 41 2030 9 Atlanta, GA Diesel particulate 

matter Maximum 

Decrease 1,953 2030 8 Houston-Galveston-Brazoria, TX 

Maximum 

Increase 43 2030 9 New York-N. New Jersey-Long Island, NY-NJ-CT 

Formaldehyde Maximum 

Decrease 45 2030 8 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. 

1 

2 At the national level, emissions of toxic air pollutants could decrease because the reduction in 

3 upstream emissions more than offsets the increase in VMT and emissions due to the rebound effect. 

4 However, as with Alternative 2, the reductions in upstream emissions would not be uniformly distributed 

5 to individual nonattainment areas. Under Alternative 3, most nonattainment areas would experience net 

6 increases in emissions of one or more toxic air pollutants in at least one of the analysis years (see

7 Appendix C). However, the sizes of the emissions increases would be quite small, as shown in Appendix 

8 C, and emissions increases would be distributed throughout each nonattainment area. 

9 3.3.3.4.3 Health Outcomes and Costs 

10 There would be reductions in adverse health effects nationwide under Alternative 3 compared to 

11 the No Action Alternative, as shown in Table 3.3.3-8. These reductions primarily reflect the projected 

12 PM2.5 reductions, and secondarily the reductions in SOx (while the magnitude of PM2.5 reductions under 

13 this alternative is smaller than that of SOx, the pollutant is the largest contributor to adverse health effects 

14 on a per-ton basis). Compared to the No Action Alternative, Alternative 3 would reduce cases of 

15 mortality by 210 (under Pope et al.; reductions would be 156 percent greater under Laden et al.) and the 

16 number of work-loss days by 24,750 in 2030. 

17 Table 3.3.3-9 lists the corresponding reductions in health costs under Alternative 3 compared to 

18 the No Action Alternative. Alternative 3 would reduce health costs by $1.87 billion in 2030, using a 3-
Chapter 3 Affected Environment and Environmental Consequences 3.3 Air Quality 

 3-51

1 percent discount rate and estimates from Pope et al. Under Laden et al., economic benefits would be 145 

2 percent greater. Using a 7-percent discount rate, economic benefits would be 9.3 to 9.5 percent less. 

3 3.3.3.5 Alternative 4: Preferred Alternative 

4 3.3.3.5.1 Criteria Pollutants 

5 Under the Preferred Alternative (Alternative 4), the CAFE standards would increase fuel 

6 economy more than would Alternatives 1 through 3 but less than would Alternatives 5 through 9. There 

7 would be reductions in nationwide emissions of NOx, PM2.5, SOx, and VOCs under Alternative 4 

8 compared to the No Action Alternative. Depending on the year, NOx emissions would be reduced 0.3 to 

9 1.7 percent, PM2.5 emissions would be reduced 1.1 to 4.3 percent, SOx emissions would be reduced 2.8 to 

10 11.0 percent, and VOC emissions would be reduced 1.1 to 6.9 percent. These emissions reductions are 

11 greater than would occur under Alternative 3 (except for PM2.5 in 2030) but less than would occur under 

12 Alternatives 5 through 9. There would be increases of CO emissions of 0.01 to 0.4 percent, depending on 

13 the year. 

14 Under Alternative 4, all nonattainment areas would experience reductions in emissions of SOx

15 and VOCs. Most nonattainment areas would experience increases of CO, NOx, and PM2.5 emissions 

16 compared to the No Action Alternative. The increases in CO, NOx, and PM2.5 emissions are the result of 

17 increased tailpipe emissions due to the rebound effect. Although NOx and PM2.5 emissions would 

18 increase in some nonattainment areas, the increase in each area is quite small. The decreases in 

19 nationwide NOx and PM2.5 emissions are the result of the decreases in upstream emissions and do not 

20 occur in all nonattainment areas. Although NOx and PM2.5 emissions would decrease in fewer 

21 nonattainment areas, the decreases in each area are much larger. The net result is decreased NOx and 

22 PM2.5 emissions nationwide. Tables in Appendix C list the emissions reductions for each nonattainment 

23 area. 

24 3.3.3.5.2 Toxic Air Pollutants 

25 Alternative 4 would result in reduced emissions of benzene and DPM, and increased emissions of 

26 acetaldehyde, acrolein, 1,3-butadiene, and formaldehyde, compared to the No Action Alternative. 

27 Compared to Alternatives 5 through 9, Alternative 4 would have lower emissions of acetaldehyde, 

28 acrolein, and formaldehyde, and higher emissions of benzene and DPM. Results would be mixed for 1,3-

29 butadiene, depending on the year and alternative. 

30 At the national level, emissions of toxic air pollutants might decrease because the reduction in 

31 upstream emissions more than offsets the increase in VMT and emissions due to the rebound effect. 

32 However, as with prior alternatives, the reductions in upstream emissions would not be uniformly 

33 distributed to individual nonattainment areas. Under Alternative 4, most nonattainment areas would 

34 experience net increases in emissions of one or more toxic air pollutants in at least one of the analysis 

35 years (see Appendix C). However, the sizes of the emissions increases would be quite small, as shown in 

36 Appendix C. Potential air quality impacts from these increases would be minor, because the VMT and 

37 emissions increases would be distributed throughout each nonattainment area. 

38 3.3.3.5.3 Health Outcomes and Costs 

39 There would be reductions in adverse health effects nationwide under Alternative 4 compared to 

40 the No Action Alternative, as shown in Table 3.3.3-8. These reductions primarily reflect the projected 

41 PM2.5 reductions, and secondarily the reductions in SOx (while the magnitude of PM2.5 reductions under 

42 this alternative is smaller than that of SOx, the pollutant is the largest contributor to adverse health effects 
3.3 Air Quality Chapter 3 Affected Environment and Environmental Consequences 

 3-52 

1 on a per-ton basis). Compared to the No Action Alternative, Alternative 4 would reduce cases of 

2 premature mortality by 217 (under Pope et al.; reductions would be 156 percent greater under Laden et 

3 al.) in year 2030. In the same year, the number of work-loss days would be reduced by 25,222. 

4 Table 3.3.3-9 lists the corresponding reductions in health costs under Alternative 4 compared to 

5 the No Action Alternative. Alternative 4 would reduce health costs by $1.93 billion in 2030, using a 3-

6 percent discount rate and estimates from Pope et al. Under Laden et al., economic benefits would be 145 

7 percent greater. Using a 7-percent discount rate, economic benefits would be 9.3 to 9.5 percent less. 

8 3.3.3.6 Alternative 5: 5-Percent Annual Increase 

9 3.3.3.6.1 Criteria Pollutants 

10 Under the 5-Percent Alternative (Alternative 5), the CAFE standards would increase fuel 

11 economy more than would Alternatives 1 through 4 but less than would Alternatives 6 through 9. There 

12 would be reductions in nationwide emissions of all criteria pollutants under Alternative 5 compared to the 

13 No Action Alternative. Reductions would be greater than under Alternative 4 (except for PM2.5 in 2016 

14 and 2020 and SOx in 2016), but less than under Alternatives 6 through 9. Depending on the year, CO 

15 emissions would be reduced 0.3 to 2.2 percent, NOx emissions would be reduced 0.4 to 3.5 percent, PM2.5

16 emissions would be reduced 0.8 to 4.5 percent, SOx emissions would be reduced 2.6 to 11.5 percent, and 

17 VOC emissions would be reduced 1.4 to 9.2 percent. All individual nonattainment areas would 

18 experience reductions in emissions of CO, NOx, SOx, and VOCs. PM2.5 emissions would increase in 

19 some nonattainment areas and would decrease in others compared to the No Action Alternative. Tables 

20 in Appendix C list the emissions reductions for each nonattainment area. 

21 3.3.3.6.2 Toxic Air Pollutants 

22 Alternative 5 would result in reduced emissions of benzene and DPM, and increased emissions of 

23 acetaldehyde, acrolein, 1,3-butadiene, and formaldehyde, compared to the No Action Alternative. 

24 Compared to Alternatives 6 through 9, Alternative 5 would have lower emissions of acetaldehyde, 

25 acrolein, formaldehyde, and 1,3-butadiene (in 2016 and 2020), and higher emissions of benzene, DPM, 

26 and 1,3-butadiene (in 2030). 

27 At the national level, emissions of toxic air pollutants could decrease because the reduction in 

28 upstream emissions more than offsets the increase in VMT and emissions due to the rebound effect. 

29 However, as with prior alternatives, the reductions in upstream emissions would not be uniformly 

30 distributed to individual nonattainment areas. Under Alternative 5, most nonattainment areas would 

31 experience net increases in emissions of one or more toxic air pollutants in at least one of the analysis 

32 years (see Appendix C). However, the sizes of the emissions increases would be quite small, as shown in 

33 Appendix C, and emissions increases would be distributed throughout each nonattainment area. 

34 3.3.3.6.3 Health Outcomes and Costs 

35 There would be reductions in adverse health effects nationwide under Alternative 5 compared to 

36 the No Action Alternative, as shown in Table 3.3.3-8. These reductions primarily reflect the projected 

37 PM2.5 reductions, and secondarily the reductions in SOx (while the magnitude of PM2.5 reductions under 

38 this alternative is smaller than that of SOx, the pollutant is the largest contributor to adverse health effects 

39 on a per-ton basis). Compared to the No Action Alternative, Alternative 5 would reduce cases of 

40 premature mortality by 253 (under Pope et al.; reductions would be 156 percent greater under Laden et 

41 al.) in year 2030. In the same year, the number of work-loss days would be reduced by 30,036. 
Chapter 3 Affected Environment and Environmental Consequences 3.3 Air Quality 

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1 Table 3.3.3-9 lists the corresponding reductions in health costs under Alternative 5 compared to 

2 the No Action Alternative. Alternative 5 would reduce health costs by $2.25 billion in 2030, using a 3-

3 percent discount rate and estimates from Pope et al. Under Laden et al., economic benefits would be 145 

4 percent greater. Using a 7-percent discount rate, economic benefits would be 9.3 to 9.5 percent less. 

5 3.3.3.7 Alternative 6: MNB 

6 3.3.3.7.1 Criteria Pollutants 

7 Under the MNB (Alternative 6), the CAFE standards would increase fuel economy more than 

8 would Alternatives 1 through 5 but less than would Alternatives 7 through 9. There would be reductions 

9 in nationwide emissions of all criteria pollutants under Alternative 6 compared to the No Action 

10 Alternative. Reductions in CO, NOx, and VOC emissions would be greater than under Alternative 5, but 

11 less than under Alternatives 7 through 9 (except for NOx and VOC in 2016 under Alternative 7). For 

12 PM2.5 and SOx, the emissions would be similar for Alternatives 5 through 9; the reductions under 

13 Alternative 6 are slightly greater or less than the reductions under Alternatives 5 and 7 through 9, 

14 depending on the year and alternative. Depending on the year, CO emissions would be reduced 0.5 to 

15 4.7 percent, NOx emissions would be reduced 0.5 to 5.2 percent, PM2.5 emissions would be reduced 0.8 to 

16 4.2 percent, SOx emissions would be reduced 3.3 to 12.4 percent, and VOC emissions would be reduced 

17 1.9 to 11.9 percent. All individual nonattainment areas would experience reductions in emissions of CO, 

18 NOx, SOx, and VOCs. PM2.5 emissions would increase in some nonattainment areas and would decrease 

19 in others compared to the No Action Alternative. Tables in Appendix C list the emissions reductions for 

20 each nonattainment area. 

21 3.3.3.7.2 Toxic Air Pollutants 

22 Alternative 6 would result in reduced emissions of benzene, DPM, and 1,3-butadiene (in 2030), 

23 and increased emissions of acetaldehyde, acrolein, 1,3-butadiene (in 2016 and 2020), and formaldehyde, 

24 compared to the No Action Alternative. Compared to Alternatives 7 through 9, Alternative 6 would have 

25 equal or lower emissions of acetaldehyde, acrolein, formaldehyde, and 1,3-butadiene (in 2016 and 2020), 

26 and higher emissions of benzene, DPM, and 1,3-butadiene (in 2030). At the national level, emissions of 

27 toxic air pollutants could decrease for many combinations of pollutant, year, and alternative because the 

28 reduction in upstream emissions more than offsets the increase in VMT and emissions due to the rebound 

29 effect. However, as with prior alternatives, the reductions in upstream emissions would not be uniformly 

30 distributed to individual nonattainment areas. Under Alternative 6, most nonattainment areas would 

31 experience net increases in emissions of one or more toxic air pollutants in at least one of the analysis 

32 years (see Appendix C). However, the sizes of the emissions increases would be quite small, as shown in 

33 Appendix C, and emissions increases would be distributed throughout each nonattainment area. 

34 3.3.3.7.3 Health Outcomes and Costs 

35 There would be reductions in adverse health effects nationwide under Alternative 6 compared to 

36 the No Action Alternative, as shown in Table 3.3.3-8. The reductions in mortality, chronic bronchitis, 

37 and work loss days primarily reflect the projected PM2.5 reductions, and secondarily the reductions in 

38 SOx. The reductions in emergency room visits for asthma primarily reflect the projected SOx reductions, 

39 and secondarily the reductions in PM2.5. Compared to the No Action Alternative, Alternative 6 would 

40 reduce cases of premature mortality by 276 (under Pope et al.; reductions would be 156 percent greater 

41 under Laden et al.) in year 2030. In the same year, the number of work-loss days would be reduced by 

42 32,758. 
3.3 Air Quality Chapter 3 Affected Environment and Environmental Consequences 

 3-54 

1 Table 3.3.3-9 lists the corresponding reductions in health costs under Alternative 6 compared to 

2 the No Action Alternative. Alternative 6 would reduce health costs by $2.45 billion in 2030, using a 3-

3 percent discount rate and estimates from Pope et al. Under Laden et al., economic benefits would be 145 

4 percent greater. Using a 7-percent discount rate, economic benefits would be 9.3 to 9.5 percent less. 

5 3.3.3.8 Alternative 7: 6-Percent Annual Increase 

6 3.3.3.8.1 Criteria Pollutants 

7 Under the 6-Percent Alternative (Alternative 7), the CAFE standards would increase fuel 

8 economy more than would Alternatives 1 through 6 but less than would Alternatives 8 and 9. There 

9 would be reductions in nationwide emissions of all criteria pollutants under Alternative 7 compared to the 

10 No Action Alternative. Reductions in CO, NOx, and VOC emissions would be greater than under 

11 Alternative 6 (except for NOx and VOC in 2016), but less than under Alternatives 8 and 9. For PM2.5 and 

12 SOx the emission reductions under Alternative 7 would be less than under Alternative 6, 8, and 9. 

13 Depending on the year, CO emissions would be reduced 0.6 to 6.0 percent, NOx emissions would be 

14 reduced 0.5 to 6.0 percent, PM2.5 emissions would be reduced 0.6 to 3.7 percent, SOx emissions would be 

15 reduced 2.8 to 11.4 percent, and VOC emissions would be reduced 1.8 to 12.7 percent. All individual 

16 nonattainment areas would experience reductions in emissions of CO, NOx, SOx, and VOCs under 

17 Alternative 7. PM2.5 emissions would increase in some nonattainment areas and would decrease in others 

18 compared to the No Action Alternative. Tables in Appendix C list the emissions reductions for each 

19 nonattainment area. 

20 3.3.3.8.2 Toxic Air Pollutants 

21 Alternative 7 would result in reduced emissions of benzene, DPM and 1,3-butadiene (in 2030), 

22 and increased emissions of acetaldehyde, acrolein, 1,3-butadiene (in 2016 and 2020), and formaldehyde, 

23 compared to the No Action Alternative. Compared to Alternatives 8 and 9, Alternative 7 would have 

24 lower emissions of acetaldehyde, acrolein, formaldehyde, and 1,3-butadiene (in 2016 and 2020), and 

25 higher emissions of benzene, DPM, and 1,3-butadiene (in 2030). 

26 At the national level, emissions of toxic air pollutants could decrease because the reduction in 

27 upstream emissions more than offsets the increase in VMT and emissions due to the rebound effect. 

28 However, as with previous alternatives, the reductions in upstream emissions would not be uniformly 

29 distributed to individual nonattainment areas. Under Alternative 7, most nonattainment areas would 

30 experience net increases in emissions of one or more toxic air pollutants in at least one of the analysis 

31 years (see Appendix C). However, the sizes of the emissions increases would be quite small, as shown in 

32 Appendix C, and emissions increases would be distributed throughout each nonattainment area. 

33 3.3.3.8.3 Health Outcomes and Costs 

34 There would be reductions in adverse health effects nationwide under Alternative 7 compared to 

35 the No Action Alternative, as shown in Table 3.3.3-8. The reductions in mortality, chronic bronchitis, 

36 and work loss days primarily reflect the projected PM2.5 reductions, and secondarily the reductions in 

37 SOx. The reductions in emergency room visits for asthma primarily reflect the projected SOx reductions, 

38 and secondarily the reductions in PM2.5. Compared to the No Action Alternative, Alternative 7 would 

39 reduce cases of premature mortality by 267 (under Pope et al.; reductions would be 156 percent greater 

40 under Laden et al.) in year 2030. In the same year, the number of work-loss days would be reduced by 

41 31,811. 
Chapter 3 Affected Environment and Environmental Consequences 3.3 Air Quality 

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1 Table 3.3.3-9 lists the corresponding reductions in health costs under Alternative 7 compared to 

2 the No Action Alternative. Alternative 7 would reduce health costs by $2.37 billion in 2030, using a 3-

3 percent discount rate and estimates from Pope et al. Under Laden et al., economic benefits would be 145 

4 percent greater. Using a 7-percent discount rate, economic benefits would be 9.3 to 9.5 percent less. 

5 3.3.3.9 Alternative 8: 7-Percent Annual Increase 

6 3.3.3.9.1 Criteria Pollutants 

7 Under the 7-Percent Alternative (Alternative 8), the CAFE standards would increase fuel 

8 economy more than all the other alternatives. There would be reductions in nationwide emissions of all 

9 criteria pollutants under Alternative 8 compared to the No Action Alternative. Reductions would be 

10 greater than under Alternative 7 but less than under Alternative 9 (except for PM2.5 and SOx in 2030). CO 

11 emissions would be reduced 0.6 to 6.7 percent, NOx emissions would be reduced 0.5 to 6.6 percent, PM2.5

12 emissions would be reduced 0.7 to 4.2 percent, SOx emissions would be reduced 3.1 to 12.6 percent, and 

13 VOC emissions would be reduced 2.0 to 13.7 percent compared to the No Action Alternative, depending 

14 on the year. All individual nonattainment areas would experience reductions in emissions of CO, NOx, 

15 SOx, and VOCs. PM2.5 emissions would increase in some nonattainment areas and would decrease in 

16 others compared to the No Action Alternative. Tables in Appendix C list the emissions reductions for 

17 each nonattainment area. 

18 3.3.3.9.2 Toxic Air Pollutants 

19 Alternative 8 would result in reduced emissions of benzene, DPM and 1,3-butadiene (in 2030), 

20 and increased emissions of acetaldehyde, acrolein, 1,3-butadiene (in 2016 and 2020), and formaldehyde, 

21 compared to the No Action Alternative. Compared to Alternative 9, Alternative 8 would have equal or 

22 lower emissions of acetaldehyde, acrolein, 1,3-butadiene (in 2016 and 2020), DPM (in 2030), and 

23 formaldehyde, and higher emissions of benzene, 1,3-butadiene (in 2030), and DPM (in 2016 and 2020). 

24 At the national level, emissions of toxic air pollutants could decrease because the reduction in 

25 upstream emissions more than offsets the increase in VMT and emissions due to the rebound effect. 

26 However, as with prior alternatives, the reductions in upstream emissions would not be uniformly 

27 distributed to individual nonattainment areas. Under Alternative 8, most nonattainment areas would 

28 experience net increases in emissions of one or more toxic air pollutants in at least one of the analysis 

29 years (see Appendix C). However, the sizes of the emissions increases would be quite small, as shown in 

30 Appendix C, and emissions increases would be distributed throughout each nonattainment area. 

31 3.3.3.9.3 Health Outcomes and Costs 

32 There would be reductions in adverse health effects nationwide under Alternative 8 compared to 

33 the No Action Alternative, as shown in Table 3.3.3-8. The reductions in mortality, chronic bronchitis, 

34 and work loss days primarily reflect the projected PM2.5 reductions, and secondarily the reductions in 

35 SOx. The reductions in emergency room visits for asthma primarily reflect the projected SOx reductions, 

36 and secondarily the reductions in PM2.5. In comparison to the No Action Alternative, Alternative 8 would 

37 reduce cases of premature mortality by 296 (under Pope et al.; reductions would be 156 percent greater 

38 under Laden et al.) in year 2030. In the same year, the number of work-loss days would be reduced by 

39 35,301. 

40 Table 3.3.3-9 lists the corresponding reductions in health costs under Alternative 8 compared to 

41 the No Action Alternative. Alternative 8 would reduce health costs by $2.64 billion in 2030, using a 3-
3.3 Air Quality Chapter 3 Affected Environment and Environmental Consequences 

 3-56 

1 percent discount rate and estimates from Pope et al. Under Laden et al., economic benefits would be 145 

2 percent greater. Using a 7-percent discount rate, economic benefits would be 9.3 to 9.5 percent less. 

3 3.3.3.10 Alternative 9: TCTB 

4 3.3.3.10.1 Criteria Pollutants 

5 Under the TCTB Alternative (Alternative 9), the CAFE standards would increase fuel economy 

6 more than would Alternatives 1 through 7 but less than would Alternative 8. There would be reductions 

7 in nationwide emissions of all criteria pollutants under Alternative 9 compared to the No Action 

8 Alternative. Emissions reductions of CO, NOx, and VOC under Alternative 9 would be greater than with 

9 any other alternative. Emissions of PM2.5 under Alternative 9 would be lower than under Alternatives 1 

10 and 7, Alternative 2 in 2016, and Alternative 8 in 2016 and 2020; however, PM2.5 emissions under 

11 Alternative 9 would be higher than under Alternatives 3 through 6, Alternative 2 in 2020, and Alternative 

12 8 in 2030. Emissions of SOx under Alternative 9 would be less than with any other alternative (except for 

13 Alternative 6 in 2020 and Alternative 8 in 2030). Depending on the year, CO emissions would be 

14 reduced 0.7 to 6.9 percent, NOx emissions would be reduced 0.6 to 6.7 percent, PM2.5 emissions would be 

15 reduced 0.8 to 4.2 percent, SOx emissions would be reduced 3.3 to 12.5 percent, and VOC emissions 

16 would be reduced 2.0 to 13.8 percent compared to the No Action Alternative. All individual 

17 nonattainment areas would experience reductions in emissions of CO, NOx, SOx, and VOCs. PM2.5

18 emissions would increase in some nonattainment areas and would decrease in others compared to the No 

19 Action Alternative. Tables in Appendix C list the emissions reductions for each nonattainment area. 

20 3.3.3.10.2 Toxic Air Pollutants 

21 Alternative 9 would result in reduced emissions of benzene, 1,3-butadiene (in 2030), and DPM, 

22 and increased emissions of acetaldehyde, acrolein, 1,3-butadiene (in 2016 and 2020), and formaldehyde, 

23 compared to the No Action Alternative. Emissions reductions of benzene, 1,3-butadiene (in 2030), and 

24 DPM (in 2016 and 2020) under Alternative 9 would be greater than with any other alternative. 

25 At the nationwide level, emissions of toxic air pollutants could decrease because the reduction in 

26 upstream emissions more than offsets the increase in VMT and emissions due to the rebound effect. 

27 However, as with prior alternatives, the reductions in upstream emissions would not be uniformly 

28 distributed to individual nonattainment areas. Under Alternative 9, most nonattainment areas would 

29 experience net increases in emissions of one or more toxic air pollutants in at least one of the analysis 

30 years (see Appendix C). Under Alternative 9, most nonattainment areas would experience net increases 

31 in emissions of one or more toxic air pollutants in at least one of the analysis years (see Appendix C). 

32 However, the sizes of the emissions increases would be quite small, as shown in Appendix C, and 

33 emissions increases would be distributed throughout each nonattainment area. 

34 3.3.3.10.3 Health Outcomes and Costs 

35 There would be reductions in adverse health effects nationwide under Alternative 9 compared to 

36 the No Action Alternative, as shown in Table 3.3.3-8. The reductions in mortality, chronic bronchitis, 

37 and work loss days primarily reflect the projected PM2.5 reductions, and secondarily the reductions in 

38 SOx. The reductions in emergency room visits for asthma primarily reflect the projected SOx reductions, 

39 and secondarily the reductions in PM2.5. Compared to the No Action Alternative, Alternative 9 would 

40 reduce cases of premature mortality by 296 (under Pope et al.; reductions would be 156 percent greater 

41 under Laden et al.) in year 2030. In the same year, the number of work-loss days would be reduced by 

42 35,306 days. 
Chapter 3 Affected Environment and Environmental Consequences 3.3 Air Quality 

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1 Table 3.3.3-9 lists the corresponding reductions in health costs under Alternative 9 compared to 

2 the No Action Alternative. Alternative 9 would reduce health costs by $2.63 billion in 2030, using a 3-

3 percent discount rate and estimates from Pope et al. Under Laden et al., economic benefits would be 145 

4 percent greater. Using a 7-percent discount rate, economic benefits would be 9.3 to 9.5 percent less. 
3.3 Air Quality Chapter 3 Affected Environment and Environmental Consequences 

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1 
Chapter 3 Affected Environment and Environmental Consequences 3.4 Climate 

 3-59 

1 3.4 CLIMATE 

2 This section describes how the MY 2012-2016 CAFE standards would affect the anticipated pace 

3 and extent of future changes in the global climate. Because there is little precedent for addressing climate 

4 change within the structure of an EIS, several reasonable judgments were required to distinguish the 

5 direct and indirect effects of alternative CAFE standards (Chapter 3) from the cumulative impacts 

6 associated with those same alternatives (Chapter 4). 

7 NHTSA determined that the scope of climate change issues covered in Chapter 3 would be 

8 narrower than the scope of those addressed in Chapter 4 in two respects: (1) the discussion in Chapter 3 

9 focuses on impacts associated with reductions in GHG emissions due exclusively to the MY 2012-2016 

10 CAFE standards (which are then assumed to remain in place at the MY 2016 levels from 2016 through 

11 2060) and (2) the Chapter 3 discussion of consequences focuses on GHG emissions and their effects on 

12 the climate system, for example, atmospheric CO2 concentrations, temperature, sea level, and 

13 precipitation. The analysis presented in Chapter 4 is more comprehensive in that (1) it addresses the

14 effects of the MY 2012-2016 standards together with those of reasonably foreseeable future actions, 

15 including the continuing increases in CAFE standards for MY 2017-2020 that are necessary under some 

16 alternatives to reach the EISA-mandated target of a combined 35 mpg; and (2) continuing market-driven 

17 increases in fuel economy based on AEO projections through 2030 as a reasonably foreseeable future 

18 action (since the AEO forecasted fuel economy increases result from projections of rising future demand 

19 for fuel economy, as opposed to future increases in CAFE standards). These reasonably foreseeable 

20 future actions would affect fuel consumption and emissions attributable to passenger cars and light trucks 

21 through 2060. The climate modeling in Chapter 4 applies different assumptions about the effect of 

22 broader global GHG policies on emissions outside the U.S. transportation sector, and it extends the 

23 discussion of consequences to include not only the immediate effects of emissions on the climate system, 

24 but also the impacts of changes in the climate system on key resources (such as freshwater resources, 

25 terrestrial ecosystems, and coastal ecosystems). Thus, the reader is encouraged to explore the cumulative 

26 impacts discussion in Chapter 4 to fully understand NHTSA’s approach to climate change in this EIS. 

27 Section 3.4.1 introduces key topics on GHGs and climate change, while Section 3.4.2 outlines the 

28 methodology NHTSA used to evaluate climate effects. Section 3.4.3 describes the affected environment,

29 and Section 3.4.4 describes the direct and indirect environmental consequences of the proposed action and 

30 alternative actions that were considered by NHTSA. 

31 3.4.1 Introduction – Greenhouse Gases and Climate Change 

32 This document primarily draws upon panel-reviewed synthesis and assessment reports from the 

33 IPCC and U.S. Global Change Research Program (USGCRP). It also cites EPA’s Technical Support 

34 Document for its proposed Endangerment and Cause or Contribute Findings for GHGs under the Clean 

35 Air Act – which heavily relied on these panel reports. NHTSA similarly relies on panel reports because 

36 they have assessed numerous individual studies to draw general conclusions about the state of science;

37 have been reviewed and formally accepted by, commissioned by, or in some cases authored by, U.S. 

38 government agencies and individual government scientists and provide NHTSA with assurances that this 

39 material has been well vetted by both the climate change research community and by the U.S. 

40 government; and in many cases, they reflect and convey the consensus conclusions of expert authors. 

41 These reports therefore provide the overall scientific foundation for U.S. climate policy at this time. 

42 This document also refers to new peer-reviewed literature that has not been assessed or 

43 synthesized by an expert panel. This new literature supplements but does not supersede the findings of 

44 the panel-reviewed reports. 
3.4 Climate Chapter 3 Affected Environment and Environmental Consequences 

3-60 

1 NHTSA’s consideration of newer studies and highlighting of particular issues responds to 

2 previous public comments received on the scoping document and the prior EIS for the MY 2011 CAFE 

3 standard, as well as the Ninth Circuit’s decision in CBD v. NHTSA, 538 F.3d 1172 (9th Cir. 2008). The 

4 level of detail regarding the science of climate change in this draft EIS, and NHTSA’s consideration of 

5 other studies that show illustrative research findings pertaining to the potential impacts of climate change 

6 on health, society, and the environment, are provided to help inform the public and the decisionmaker,

7 consistent with the agency’s approach in the prior EIS for the MY 2011 CAFE standards. 

8 3.4.1.1 Uncertainty within the IPCC Framework 

9 The IPCC reports communicate uncertainty and confidence bounds using descriptive words in 

10 italics, such as likely and very likely, to represent likelihood of occurrence. The IPCC Fourth Assessment 

11 Synthesis Report and the IPCC Fourth Assessment Report Summary for Policymakers (IPCC 2007c, 

12 IPCC 2007b) briefly explain this convention. The IPCC Guidance Notes for Lead Authors of the IPCC 

13 Fourth Assessment Report on Addressing Uncertainties (IPCC 2005) provides a more detailed discussion 

14 of the IPCC treatment of uncertainty. 

15 This EIS uses the IPCC uncertainty language (always noted in italics) throughout Chapters 3 

16 and 4 when discussing qualitative environmental impacts on certain resources. The reader should refer to 

17 the referenced IPCC documents to gain a full understanding of the meaning of those uncertainty terms, 

18 because they might be used differently than similar language describing uncertainty in the EIS, as 

19 required by the CEQ regulations described in Section 3.1.3.1. Section 4.5.2.2 of this EIS summarizes the 

20 IPCC treatment of uncertainty. 

21 3.4.1.2 What is Climate Change? 

22 Global climate change refers to long-term (i.e., multi-decadal) trends in global average surface 

23 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 24 century, Earth’s global-average 

25 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 26 

27 Century (IPCC 2007b) with a maximum rate of about 2 millimeters (0.08 inch) per year over the last 50 

28 years on the northeastern coast of the United States (EPA 2009b); Arctic sea ice cover has been 

29 decreasing at a rate of about 2.7 percent per decade, with faster decreases of 7.4 percent per decade in 

30 summer; and the extent and volume of mountain glaciers and snow cover have also been decreasing (EPA 

31 2009b, IPCC 2007b) (see Figure 3.4.1-1). 

32 3.4.1.3 What Causes Climate Change? 

33 Earth absorbs heat energy from the sun and returns most of this heat to space as terrestrial 

34 infrared radiation. Accumulated GHGs trap heat in the troposphere (the layer of the atmosphere that 

35 extends from Earth’s surface up to about 8 miles above the surface), absorb heat energy emitted by 

36 Earth’s surface and lower atmosphere, and reradiate much of it back to Earth’s surface, thereby causing 

37 warming. This process, known as the “greenhouse effect,” is responsible for maintaining surface 

38 temperatures warm enough to sustain life (see Figure 3.4.1-2). Human activities, particularly fossil-fuel 

39 combustion, lead to the presence of increased concentrations of GHGs in the atmosphere; this buildup of 

40 GHGs in the atmosphere is upsetting Earth’s energy balance. 
Chapter 3 Affected Environment and Environmental Consequences 3.4 Climate 

 3-61 

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

Hemisphere Snow Cover (Source: IPCC 2007b) 

1 

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

2 
3.4 Climate Chapter 3 Affected Environment and Environmental Consequences 

3-62 

1 The observed changes in the global climate described in Section 3.4.1.2 are largely a result of 

2 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 3 Century is very likely due to the 

4 observed increase in anthropogenic [human-caused] greenhouse gas concentrations” (EPA 2009b, IPCC 

2007b).1

5 

6 Most GHGs, including CO2, methane (CH4), nitrous oxide (N2O), water vapor, and ozone, occur 

7 naturally. Human activities such as the combustion of fossil fuel for transportation and electric power, the 

8 production of agricultural and industrial commodities, and the loss of soil fertility and the harvesting of 

9 trees can contribute to very significant increases in the concentrations of these gases in the atmosphere. 

10 In addition, several very potent anthropogenic GHGs, including hydrofluorocarbons (HFCs), 

11 perfluorocarbons (PFCs), and sulfur hexafluoride (SF6), are created and emitted through industrial 

12 processes and emitted as a result, for example, of leaks in refrigeration and air-conditioning systems. 

13 3.4.1.4 What are the Anthropogenic Sources of Greenhouse Gases? 

14 Human activities that emit GHGs to the atmosphere include the combustion of fossil fuels, 

15 industrial processes, solvent use, land-use change and forestry, agricultural production, and waste 

16 management. Atmospheric concentrations of CO2, CH4, and N2O − the most important anthropogenic 

GHGs, comprising over 99 percent of anthropogenic emissions (WRI 2009)2

17 − have increased 

18 approximately 38, 149, and 23 percent, respectively, since the beginning of the Industrial Revolution in 

19 the mid-1700s. During this time, the atmospheric CO2 concentration has increased from 280 ppm to 386 

20 ppm in 2008 (EPA 2009b). Isotopic and inventory-based studies make clear that this rise in the CO2

21 concentration is largely a result of combustion of fossil fuels (coal, petroleum, and gas) used to produce 

22 electricity, heat buildings, and run motor vehicles and airplanes, among other uses. 

23 Contributions to the build up of GHGs in the atmosphere vary greatly from country to country, 

24 and depend heavily on the level of industrial and economic activity, the population, the standard of living, 

25 the character of a country’s buildings and transportation system, energy options that are available, and the 

26 climate. The U.S. transportation sector contributed 35.7 percent of total U.S. CO2 emissions in 2007 

27 (EPA 2009a), with passenger cars and light trucks accounting for 60.8 percent of total U.S. CO2

28 emissions from transportation (EPA 2009a). Thus, 21.7 percent (equal to 35.7 percent of 60.8 percent) of 

29 total U.S. CO2 emissions is attributable to the use of passenger cars and light trucks. With the United 

30 States accounting for 17.2 percent of global CO2 emissions (WRI 2009), passenger cars and light trucks in 

31 the United States account for roughly 3.7 percent (equal to 21.7 percent of 17.2 percent) of global CO2

emissions.3

32 

33 3.4.1.5 Evidence of Climate Change 

34 Observations and studies across the globe are reporting evidence that Earth is undergoing climatic 

35 change much more quickly than would be expected from natural variations. The global average 

36 temperature is rising, with 8 of the 10 warmest years on record occurring since 2001 (EPA 2009b). Cold37 dependent habitats are shifting to higher altitudes and latitudes and growing seasons are becoming longer 

 

1

 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. 

2

 This calculation is weighted by global warming potential. 

3

 Percentages include land-use change and forestry, and exclude international bunker fuels (i.e., international marine 

and aviation travel). 
Chapter 3 Affected Environment and Environmental Consequences 3.4 Climate 

 3-63 

1 (EPA 2009b). Sea level is rising, caused by thermal expansion of the ocean and melting of snow and ice. 

2 More frequent weather extremes such as droughts, floods, severe storms, and heat waves have also been 

3 observed (EPA 2009b, IPCC 2007b). Oceans are becoming more acidic as a result of increasing 

4 absorption of CO2, driven by higher atmospheric concentration of CO2, (EPA 2009b). Statistically 

5 significant indicators of climate change have been observed on every continent (Rosenzweig et al. 2008). 

6 Additional evidence of climate change is discussed throughout this section. 

7 3.4.1.6 Future Climatic Trends and Expected Impacts 

8 As the world population grows and developing countries industrialize and bring their populations 

9 out of poverty, fossil-fuel use and resulting GHG emissions are expected to grow substantially over the 

21st 10 century unless there is a significant shift away from deriving energy from fossil fuels. Based on the 

11 current trajectory, the IPCC projects that the atmospheric CO2 concentration could rise to more than three 

12 times the pre-industrial level by 2100 (EPA 2009b, IPCC 2007b). 

13 If there is an unchecked rise in the atmospheric CO2 concentration out to 2100, the average global 

14 surface temperature is likely to rise by 2.0 to 11.5 °F by that time (EPA 2009b). In addition, EPA (2009b) 

15 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 

16 expansion and the melting of glaciers and small ice caps; even greater rise is projected if ice streams 

17 draining the Greenland and Antarctic ice sheets accelerate. If this happens, and satellite observation 

18 suggest such changes are beginning, recent studies indicate that sea-level rise could be even higher, and 

19 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 

20 4.6 feet) (Rahmstorf 2007) by 2100. In addition to increases in global-average temperature and sea level, 

21 climate change is expected to have many environmental, human health, and economic consequences. 

22 For a more in-depth analysis of the future impacts of climate change on various sectors, see 

23 Section 4.5 of this EIS. 

24 3.4.1.7 Black Carbon 

This EIS does not model the climatic impacts of black carbon.4

25 Therefore, the direct effects (the 

26 radiative properties) and indirect effects (the impacts on clouds and surface snow/ice) of black carbon are 

27 qualitatively discussed here. 

28 Black carbon is an aerosol that forms during incomplete combustion of certain fossil fuels 

29 (primarily coal and diesel) and biomass (primarily fuel wood and crop waste). Developing countries are 

30 the primary emitters of black carbon because they depend more heavily on biomass-based fuel sources for 

31 cooking and heating and on diesel vehicles for transport, and have less stringent air emission control

32 standards and technologies. The United States contributes about 7 percent of the world’s black carbon 

 

4

 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. 
3.4 Climate Chapter 3 Affected Environment and Environmental Consequences 

3-64 

1 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)5

2 . 

3 While black carbon has been an air pollutant of concern for years due to its direct human health 

4 effects, climate change experts are now paying attention to it for its influence on climate change (EPA 

5 2009b). Black carbon has a warming effect on the climate by (1) absorbing solar radiation, (2) reducing 

the albedo6

6 of clouds while suspended in the air, and (3) reducing the albedo of snow and ice when it falls 

7 onto snow and ice fields. 

8 The scientific literature is far from conclusive as to what effect black carbon has on the climate. 

9 In the IPCC Fourth Assessment Report (IPCC 2007b), the scientific knowledge level of black carbon’s 

10 effect on the climate was classified as medium to low (CCSP 2008e). Another study estimates that there 

11 is a 50-percent uncertainty in global emissions estimates, while the regional uncertainty in emissions can 

12 range from factors of two to five (Ramanathan and Carmichael 2008). Although emission estimates are 

13 uncertain, recent studies suggest that black carbon might be a major contributor to climate change. 

14 In a recent study, black carbon was estimated to have more than half of the positive radiative 

15 forcing effect of CO2 (EPA 2009b); it might be a more important driver of climate change than the 

16 increase in the concentrations of CH4 or N2O (Ramanathan and Carmichael 2008). Another study found 

17 that black carbon in the atmosphere might cause approximately 30 percent or more of warming in the 

18 Arctic (Shindell and Faluvegi 2009 in Pew 2009). Recent research indicates that black carbon has 

19 contributed approximately 0.5 to 1.4 °C (0.9 to 2.52 °F) to Arctic warming since 1980 (Shindell and 

20 Faluvegi 2009), and 0.25 °C (0.45 °F) to overall global warming (Tollefson 2009). Other research 

21 suggests that black carbon might have a played a role in droughts in the northern part of China and floods 

22 in the southern part of China (Menon et al. 2002 in Tollefson 2009), and caused roughly one-third of the 

23 glacial retreat in the past 2 decades (Tollefson 2009). 

24 Because aerosols, including black carbon, play a role in cloud formation, scientists are 

25 investigating how black carbon affects clouds, which in turn affect Earth’s temperature. Lower clouds

26 reflect substantial amounts of solar radiation back into space, which results in a cooling effect through 

27 cloud albedo. Conversely, higher clouds reflect relatively little solar radiation back into space but trap 

28 higher amounts of infrared radiation, which leads to a warming effect. Thus, the way black carbon affects 

29 cloud formation, and which types of clouds it generally impacts, is important. In warm low-level clouds, 

30 water vapor attaches to cloud nuclei and grow as larger cloud drops fall and combine with smaller cloud 

31 drops. The cloud drops might eventually grow to the size of a rain drop and fall from the cloud as rain. 

32 Some aerosols prevent this combining of drops, thereby extending the life of the cloud and reducing 

33 precipitation. 

34 Black carbon, on the other hand, radiatively warms the surrounding air, which leads to 

35 evaporation of cloud drops and reduces cloud cover. An important issue, which can vary by region, is 

36 whether the non-black carbon aerosols or the black carbon aerosols dominate in cloud effects 

37 (Ramanathan and Carmichael 2008). Meanwhile, it is also believed that black carbon-related warming 

 

5

 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.) 

6

 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. 
Chapter 3 Affected Environment and Environmental Consequences 3.4 Climate 

 3-65 

1 might cause convection patterns that ultimately lead to cloud formation (Rudich et al. 2003 in 

2 Ramanathan and Carmichael 2008). The ultimate climate effect of changes in cloud formation depends 

3 partly on the types of clouds affected; however, studies often focus on lower-lying clouds, in which case 

4 the greater the cloud cover, the greater the cooling effect. 

5 Given the potential for the effect to be substantial, the U.S. Congress is (as of July 2009) 

6 considering legislation (proposed Senate bill S.849) that would direct EPA to do a 1-year study on the

7 climate impacts of black carbon and cost-effective technologies and strategies for black carbon 

reduction.7

8 

9 Two characteristics of black carbon are unique compared to GHGs − its short lifetime in the 

10 atmosphere and, in most situations, the concentration of its climate effects near its emission source. First, 

11 black carbon has a much shorter atmospheric lifespan than GHGs. CCSP (2009) estimates the lifetime of

12 black carbon in the atmosphere as being between 5.3 and 15 days, generally depending on the 

13 meteorological situation. Because the atmospheric loading of black carbon depends on being continually 

14 replenished, reductions in black-carbon emissions can have an almost immediate effect on radiative 

15 forcing. Meanwhile, the lifespan of CO2 in the atmosphere is hundreds of years. Therefore, due to the 

16 long lifespan of CO2, mitigation of its emissions in the short-term will have long-lasting impacts. 

17 Second, while GHGs are considered to be global pollutants (because their impact on climate is 

18 the same regardless of where they are emitted), black carbon has greater impacts in the region where it is 

19 emitted. Although black carbon can travel great distances in the atmosphere, its concentrations decrease 

20 as distance from the emission source increases. Black carbon increases temperatures locally, unlike 

21 GHGs, which affect the climate by trapping radiation on a global scale. Thus, increases or decreases in 

22 black carbon emissions will have the greatest impact on the area where the black carbon is concentrated, 

23 which is typically near the emission sources. 

24 The impact that the new CAFE standards will have on black carbon emissions is uncertain. 

25 Historically, diesel vehicles have emitted more black carbon than gasoline vehicles on a per-mile basis. 

26 Thus, a shift to diesel vehicles could increase black carbon emissions, resulting in increased warming. 

27 Widespread deployment of recent, more effective control technologies for particulate-matter emissions 

28 from diesel vehicles could minimize any increase in warming due to this shift. NHTSA estimates that the 

29 fraction of new passenger cars that are diesel-powered would rise from zero under the No Action 

30 Alternative to 1 to 2 percent under the Preferred Alternative, and would reach 3 to 4 percent under 

31 alternatives that would establish the most stringent CAFE standards. At the same time, the agency 

32 projects that the diesel fraction of light trucks would rise from less than 2 percent under the No Action 

33 Alternative to almost 3 percent under the Preferred Alternative, and would range as high as 15 to 20 

34 percent under alternatives that would establish the highest CAFE standards. 

35 Using estimates of U.S. on-road emissions of black carbon in fine particles (PM 2.5) (Battye et al.

36 2002) and global emissions of black carbon in PM 2.5 (Bond et al. 2004), U.S. motor vehicles contribute 

37 just over 1 percent of global black carbon emissions. As noted above, the effects of the alternative CAFE 

38 standards considered in this analysis on U.S. and global black carbon emissions have not been 

39 established. The precise amount by which CAFE standards will increase black carbon emissions depends

40 on the increase in the presence of diesel vehicles in the future U.S. vehicle fleet that results from 

41 manufacturers’ efforts to comply with higher CAFE standards, particularly under those alternatives that 

42 would impose the most stringent standards. It also depends on future improvements in the effectiveness 

43 of emissions control technology for diesel vehicles, including both light-duty diesel vehicles and the

44 heavy-duty diesel trucks that are used extensively for fuel distribution to retail stations. 

 

7

 S. 849, 111th Cong. (2009). 
3.4 Climate Chapter 3 Affected Environment and Environmental Consequences 

3-66 

1 3.4.2 Affected Environment 

2 This section describes the affected environment in terms of current and anticipated trends in GHG 

3 emissions and climate. Effects of emissions and the corresponding processes that affect climate involve 

4 very complex processes with considerable variability, which complicates the measurement and detection 

5 of change. Recent advances in the state of the science, however, are contributing to an increasing body of 

6 evidence that anthropogenic GHG emissions are affecting climate in detectable and quantifiable ways. 

7 This section begins with a discussion of emissions, and then turns to climate. Both discussions 

8 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.8

9 

10 3.4.2.1 Greenhouse Gas Emissions (Historic and Current) 

11 3.4.2.1.1 U.S. Emissions 

GHG emissions for the United States in 20079

12 were estimated at 7,150.1 million metric tons of 

carbon dioxide (MMTCO2)

10 13 (EPA 2009a), and, as noted earlier, contributes about 18 percent of total 

global emissions11 14 (WRI 2009). Annual U.S. emissions, which have increased 17 percent since 1990 and 

15 typically increase each year, are heavily influenced by “general economic conditions, energy prices, 

16 weather, and the availability of non-fossil alternatives” (EPA 2009a). 

17 CO2 is by far the primary GHG emitted in the United States, representing almost 85.4 percent of 

18 all U.S. GHG emissions in 2007 (EPA 2009a). The other gases include CH4, N2O, and a variety of 

19 fluorinated gases, including HFCs, PFCs, and SF6. The fluorinated gases are collectively referred to as 

20 high global warming potential (GWP) gases. CH4 accounts for 8.2 percent of the remaining GHGs on a 

21 GWP-weighted basis, followed by N2O (4.4 percent), and the high-GWP gases (2.1 percent) (EPA 

22 2009a). 

23 GHGs are emitted from a wide variety of sectors, including energy, industrial processes, waste, 

24 agriculture, and forestry. Most U.S. emissions are from the energy sector, largely due to CO2 emissions 

25 from the combustion of fossil fuels, which alone account for 80 percent of total U.S. emissions (EPA 

26 2009a). These CO2 emissions are due to fuels consumed in the electric power (42 percent of fossil fuel 

27 emissions), transportation (33 percent), industry (15 percent), residential (6 percent), and commercial (4 

28 percent) sectors (EPA 2009a). However, when U.S. CO2 emissions are apportioned by end use, 

29 transportation is the single leading source of U.S. emissions from fossil fuels, causing approximately one30 third of total CO2 emissions from fossil fuels (EPA 2009a). 

31 As noted earlier, the U.S. transportation sector contributed 35.7 percent of total U.S. CO2

32 emissions in 2007, with passenger cars and light trucks accounting for 60.8 percent of total U.S. CO2

33 emissions from transportation. Thus, 21.7 percent of total U.S. CO2 emissions comes from passenger cars 

 

8

 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”). 

9

 Most recent year for which an official EPA estimate is available. 

10 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). 

11 Based on 2005 data and excludes carbon sinks from forestry and agriculture. 
Chapter 3 Affected Environment and Environmental Consequences 3.4 Climate 

 3-67 

1 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 3.7 percent of global CO2 emissions.12 2 

3 Passenger cars and light trucks, which include SUVs, pickup trucks, and minivans, account for 

4 more than half of U.S. transportation emissions, and emissions from these vehicles have increased by 21 

5 percent since 1990 (EPA 2009a). This increase was driven by two factors − (1) an increase in use of 

6 passenger cars and light trucks and (2) relatively little improvement in their average fuel economy. 

7 Population growth and expansion, economic growth, and low fuel prices led to more VMT, while the 

8 rising popularity of SUVs and other light trucks kept the average combined fuel economy of new 

9 passenger cars and light trucks relatively constant (EPA 2009a). 

10 3.4.2.1.2 Global Emissions 

11 Although humans have always contributed to some level of GHG emissions to the atmosphere 

12 through activities like farming and land clearing, substantial contributions did not begin until the mid13 1700s, with the onset of the Industrial Revolution. People began burning coal, oil, and natural gas to light 

14 their homes, power trains and cars, and run factories and industrial operations. Today the burning of

15 fossil fuels is still the predominant source of GHG emissions. 

16 Levels of atmospheric CO2 have been rising rapidly. For about 10,000 years before the Industrial 

17 Revolution, atmospheric CO2 levels were 280 ppm (+/- 20 ppm). Since the Industrial Revolution, CO2

18 levels have risen to 386 ppm in 2008 (EPA 2009b). In addition, the concentrations of CH4 and N2O in the 

19 atmosphere have increased 149 and 23 percent, respectively (EPA 2009b). 

20 In 2000, gross global GHG emissions were calculated to be 41,638.5 MMTCO2 equivalent, an 8-

percent increase since 199013 21 (WRI 2009). In general, global GHG emissions have increased regularly, 

22 though annual increases vary according to a variety of factors (weather, energy prices, and economic 

23 factors). 

24 As in the United States, the primary GHGs emitted globally are CO2, CH4, N2O, and the 

25 fluorinated gases HFCs, PFCs, and SF6. In 2000, CO2 emissions comprised 77 percent of global 

26 emissions on a GWP-weighted basis, followed by CH4 (14.5 percent) and N2O (7.5 percent). 

27 Collectively, fluorinated gases represented 1.1 percent of global emissions (WRI 2009). 

28 Various sectors contribute to global GHG emissions, including energy, industrial processes, 

29 waste, agriculture, and land-use change and forestry. The energy sector is the largest contributor of

30 global GHG emissions, accounting for 59 percent of global emissions in 2000. In this sector, the 

31 generation of electricity and heat accounts for 25 percent of total global emissions. The next highest 

32 contributors to emissions are land-use change and forestry (18 percent), agriculture (14 percent), and

33 transportation (12 percent, which is included in the 59 percent for the energy sector) (WRI 2009). 

34 Emissions from transportation are primarily due to the combustion of petroleum-based fuels to 

35 power vehicles such as cars, trucks, trains, airplanes, and ships. In 2005, transportation represented 14 

36 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).14 37 

 

12 Percentages include land-use change and forestry, and exclude international bunker fuels. 

13 All GHG estimates cited in this section include contributions from land-use change and forestry, unless noted 

otherwise. 

14 Values in this paragraph exclude land-use change and forestry. 
3.4 Climate Chapter 3 Affected Environment and Environmental Consequences 

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1 3.4.2.2 Climate Change Effects and Impacts (Historic and Current) 

2 3.4.2.2.1 U.S. Climate Change Effects 

3 This section describes observed historical and current climate change effects and impacts for the 

4 United States. Much of the material that follows is drawn from the following sources, including the 

5 citations therein: Technical Support Document for Endangerment and Cause or Contribute Findings for 

6 Greenhouse Gases under Section 202(a) of the Clean Air Act (EPA 2009b), Scientific Assessment of the 

7 Effects of Global Change on the United States (National Science and Technology Council 2008), and

8 Global Climate Change Impacts in the United States (GCRP 2009). 

9 Increased Temperatures

10 The past decade has been the warmest in more than a century of direct observations, with average 

11 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 12 

13 Century with an average warming of 0.13 °F per decade over 1895-2008, and the rate of warming is 

14 increasing (EPA 2009b). 

15 Since 1950, the frequency of heat waves has increased, although those recorded in the 1930s 

16 remain the most severe. There were also fewer unusually cold days in the past few decades with fewer 

17 severe cold waves for the most recent 10-year period in the record (National Science and Technology 

18 Council 2008). 

19 Sea-level Rise

20 Relative sea level is rising 0.8 to 1.2 inches per decade along most of the Atlantic and Gulf 

21 Coasts, and a few inches per decade along the Louisiana Coast (due to land subsidence); sea level is 

22 falling (due to land uplift) at the rate of a few inches per decade in parts of Alaska (National Science and 

23 Technology Council 2008, EPA 2009b). Sea level does not rise uniformly across the globe, and, as a 

24 result of gravitational and centrifugal considerations, parts of the Pacific, Atlantic, and Gulf coasts of the 

25 United States would be expected to be subjected in the future to greater sea-level rise compared to global 

26 averages (Bamber et al. 2009 and Yin et al. 2009, both in Pew 2009). 

27 Sea-level rise extends the zone of impact from storm surge and waves from tropical and other 

28 storms farther inland, causing coastal erosion and other damage. Resulting shoreline erosion is well 

29 documented. Since the 1970s, half of the coastal area in Mississippi and Texas has been eroding by an

30 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 

31 been eroding at an average rate of more than 12.0 meters (39 feet) per year (Nicholls et al. 2007 in EPA 

32 2009). 

33 Changes in Precipitation Patterns

34 Higher temperatures cause higher rates of evaporation and plant transpiration, meaning that more 

35 water vapor is available in the atmosphere for precipitation events. Depending on atmospheric 

36 conditions, increased evaporation means that some areas experience increases in precipitation events, 

37 while other areas are left more susceptible to droughts. 

38 Over the contiguous United States, total annual precipitation increased about 6 percent from 1901 

39 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 40 Century, and mainly over eastern regions 
Chapter 3 Affected Environment and Environmental Consequences 3.4 Climate 

 3-69 

1 (National Science and Technology Council 2008). Most regions experienced decreases in drought 

severity and duration during the second half of the 20th 2 Century, although there was severe drought in the 

3 Southwest from 1999 to 2008 (EPA 2009b); the Southeast has also recently experienced severe drought 

4 (National Science and Technology Council 2008). 

5 Increased Incidence of Severe Weather Events

6 It is likely that the numbers of tropical storms, hurricanes, and major hurricanes each year in the 

7 North Atlantic have increased during the past 100 years (CCSP 2008c in National Science and 

8 Technology Council 2008) and that Atlantic sea-surface temperatures have increased over the same 

9 period. However, these trends are complicated by multi-decadal variability and data-quality issues. In 

10 addition, there is evidence of an increase in extreme wave-height characteristics over the past 2 decades, 

11 associated with more frequent and more intense hurricanes (CCSP 2008a). 

12 Changes in Water Resources

13 Melting snow and ice, increased evaporation, and changes in precipitation patterns all affect 

14 surface water. Stream flow decreased about 2 percent per decade over the past century in the central 

15 Rocky Mountain region (Rood et al. 2005 in Field et al. 2007), while in the eastern United States it 

16 increased 25 percent in the past 60 years (Groisman et al. 2004 in Field et al. 2007). Annual peak stream 

17 flow (dominated by snowmelt) in western mountains is occurring at least a week earlier than in the 

middle of the 20th 18 Century. Winter stream flow is increasing in seasonal snow-covered basins and the 

19 fraction of annual precipitation falling as rain (rather than snow) has increased in the past half century 

20 (National Science and Technology Council 2008). 

21 Changes in temperature and precipitation are also affecting frozen surface water. Spring and 

22 summer snow cover has decreased in the West. In mountainous regions of the western United States, 

23 April snow water equivalent has declined 15 to 30 percent since 1950, particularly at lower elevations and 

24 primarily due to warming (Field et al. 2007 in National Science and Technology Council 2008). 

25 However, total snow-cover area in the United States increased in the November-to-January season from 

26 1915 to 2004 (National Science and Technology Council 2008). 

27 Barnett et al. (2008) found that human-induced climate change was responsible for 60 percent of 

28 the observed changes in river flows, winter air temperature, and snow pack in the western United States. 

29 Annual average Arctic sea ice extent decreased 2.7 (+/- 0.6) percent per decade from 1978 to 

30 2005. In 2007, sea ice extent was approximately 23 percent less than the previous all-time minimum 

31 observed in 2005. Average sea ice thickness in the central Arctic very likely has decreased by 

32 approximately 3 feet from 1987 to 1997. These area and thickness reductions allow winds to generate 

33 stronger waves, which have increased shoreline erosion along the Alaskan coast. Alaska has also 

34 experienced increased thawing of the permafrost base of up to 1.6 inches per year since 1992 (EPA 

35 2009b, National Science and Technology Council 2008). 

36 Rivers and lakes are freezing over later, at an average rate change of 5.8 (+/- 1.6) days per 

37 century, with ice breakup taking place earlier, at an average rate of 6.5 (+/- 1.2) days per century. Loss of 

38 glacier mass is occurring in the mountainous regions of the Pacific Northwest and has been especially 

39 rapid in Alaska since the mid-1990s (National Science and Technology Council 2008). 

40 Snowpack is also changing. At high elevations that remain below freezing in winter, 

41 precipitation increases have resulted in increased snowpack. Warmer temperatures at mid-elevations 

42 have decreased snowpack and led to earlier snowmelt, even with precipitation increases (Kundzewicz et 
3.4 Climate Chapter 3 Affected Environment and Environmental Consequences 

3-70 

1 al. 2007). An empirical analysis of available data indicated that temperature and precipitation impact 

2 mountain snowpack simultaneously, with the nature of the impact strongly dependent on factors such as 

3 geographic location, latitude, and elevation (Stewart 2009). 

4 3.4.2.2.2 Global Climate Change Effects 

5 In their most recent assessment of climate change, the IPCC states that, “Warming of the climate 

6 system is unequivocal, as is now evident from observations of increases in global average air and ocean 

7 temperatures, widespread melting of snow and ice and rising global average sea level” (IPCC 2007b). 

8 The IPCC concludes that, “At continental, regional and ocean basin scales, numerous long-term changes 

9 in climate have been observed. These include changes in arctic temperatures and ice, widespread changes 

10 in precipitation amounts, ocean salinity, wind patterns and aspects of extreme weather including droughts, 

11 heavy precipitation, heat waves and the intensity of tropical cyclones” (IPCC 2007b). 

12 This section describes observed historical and current climate-change effects and impacts at a 

13 global scale. As with the discussion of effects for the United States, much of the material that follows is 

14 drawn from the following studies, including the citations therein: Summary for Policymakers (IPCC 

15 2007b), Technical Support Document for Endangerment and Cause or Contribute Findings for 

16 Greenhouse Gases under Section 202(a) of the Clean Air Act (EPA 2009b), Scientific Assessment of the 

17 Effects of Global Change on the United States (National Science and Technology Council 2008), and

18 Global Climate Change Impacts in the United States (GCRP 2009). 

19 Increased Temperatures

20 The IPCC states that scientific evidence shows with very high confidence that the increase in 

21 GHGs since 1750 has led to a global positive radiative forcing of 1.6 watts per meter (EPA 2009b). The 

22 radiative forcing from increased CO2 concentrations alone increased by 20 percent between 1995 and 

23 2005, which is the largest increase in the past 200 years (IPCC 2007b). 

24 This increase in radiative forcing results in higher temperatures, which are already being 

25 observed. Global temperature has been increasing over the past century. In the past 100 years, global 

26 mean surface temperatures have risen by 0.74 +/- 0.18 °C (1.3 +/- 0.32 °F) (EPA 2009b). Temperatures 

27 are rising at an increasing rate. The average rate of increase over the past century was 0.07 +/- 0.02 °C 

28 (0.13 +/- 0.04 °F) per decade. Over the past 50 years, temperatures have been rising at nearly twice that 

29 average rate, or 0.13 +/- 0.03 °C (0.23 +/- 0.05 °F) per decade (EPA 2009b). Over the past 30 years, 

30 average global temperatures have risen even faster, for an average of 0.29 °F per decade (NOAA 2009 in

31 EPA 2009b). Average Arctic temperatures have increased at almost twice the global average rate in the

32 past 100 years. Temperature increases are more pronounced over land, because air temperatures over 

33 oceans are warming at about half the rate as air over land (EPA 2009b). 

34 Extreme temperatures have changed significantly over the past 50 years. Hot days, hot nights, 

35 and heat waves have become more frequent; cold days, cold nights, and frost have become less frequent 

36 (EPA 2009b). 

37 Weather balloons, and now satellites, have directly recorded increases in temperatures since the 

38 1940s (GCRP 2009). In addition, higher temperatures are also independently confirmed by other global 

39 observations. For example, scientists have documented shifts to higher latitudes and elevations of certain 

40 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 41 Century (EPA 2009b), and plant flowering and animal spring 

42 migration patterns are occurring earlier (EPA 2009b). Permafrost top layer temperatures have generally 

43 increased since the 1980s (about 3 °C [5 °F] in the Arctic), while the maximum area covered by seasonal 
Chapter 3 Affected Environment and Environmental Consequences 3.4 Climate 

 3-71 

1 frozen ground has decreased since 1900 by about 7 percent in the Northern Hemisphere, with a decrease 

2 in spring of up to 15 percent (EPA 2009b). 

3 Some temperature-related climate variables are not changing. The diurnal temperature range has 

not changed from 1979 to 2004; 15 4 day- and night-time temperatures have risen at similar rates. Antarctic 

5 sea-ice extent shows no substantial average trends, despite inter-annual variability and localized changes, 

6 consistent with the lack of warming across the region from average atmospheric temperatures (GCRP 

7 2009). 

8 Sea-level Rise

9 Higher temperatures cause sea level to rise due to both thermal expansion of water and to an 

10 increased volume of ocean water from melting glaciers and ice sheets. EPA estimates that between 1993

11 and 2003, thermal expansion and melting ice were roughly equal in their effect on sea-level rise (EPA 

12 2009b). 

13 Between 1961 and 2003, observations of global ocean temperature indicate that it warmed by 

14 about 0.18 °F from the surface to a depth of 700 meters (0.43 mile). This warming contributed an 

15 average of 0.4 +/- 0.1 millimeter (0.016 +/- 0.0039 inch) per year to sea-level rise (EPA 2009b), because 

16 seawater expands as it warms. Mountain glaciers, ice caps, and snow cover have declined on average, 

17 contributing further to sea-level rise. Losses from the Greenland and Antarctic ice sheets have very likely 

18 contributed to sea-level rise from 1993 to 2003 and satellite observations indicate that they have 

19 contributed to sea-level rise in the years since (Shepherd and Wingham 2007). Dynamical ice loss 

20 explains most of the Antarctic net mass loss and about half of the Greenland net mass loss; the other half 

21 occurred because melting has exceeded snowfall accumulation (IPCC 2007b). 

22 Global average sea level rose at an average rate of 1.8 +/- 0.5 millimeters (0.07 +/- 0.019 inch) 

23 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 24 -Century rise is estimated at 0.17 +/- 0.05 meter 

25 (0.56 +/- 0.16 foot) (EPA 2009b). However, since the IPCC Fourth Assessment Report was published in 

26 2007, a recent study improved the historical estimates of upper-ocean (300 meters to 700 meters [0.19 to 

27 0.43 mile]) warming from 1950 to 2003 (by correcting for expendable bathy-thermographs instrument 

28 bias). Domingues et al. (2008) found the improved estimates demonstrate clear agreement with the 

29 decadal variability of the climate models that included volcanic forcing. Furthermore, this study 

30 estimated the globally averaged sea-level trend from 1961 to 2003 to be 1.5 +/- 0.4 millimeters (0.063 +/- 

31 0.01 inch) per year with a rise of 2.4 millimeters (0.094 inch) per year evident from 1993 to 2003, 

32 consistent with the estimated trend of 2.3 millimeters (0.091 inch) per year from tide gauges after taking 

33 into account thermal expansion in the upper ocean and deep ocean, variations in the Antarctica and 

34 Greenland ice sheets, glaciers and ice caps, and terrestrial storage. 

35 Sea-level rise is not uniform across the globe. The largest increases since 1992 have been in the 

36 western Pacific and eastern Indian Oceans; meanwhile, sea level in the eastern Pacific and western Indian 

Oceans has actually been falling (EPA 2009b)16 37 . 

 

15 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. 

16 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. 
3.4 Climate Chapter 3 Affected Environment and Environmental Consequences 

3-72 

1 Changes in Precipitation Patterns

2 Average atmospheric water vapor content has increased since at least the 1980s over land and the 

3 oceans, and in the upper troposphere, largely consistent with air temperature increases. As a result, heavy 

4 precipitation events have increased in frequency over most land areas (National Science and Technology

5 Council 2008). 

6 Long-term trends in global precipitation amounts have been observed since 1900. Precipitation 

7 has substantially increased in eastern parts of North and South America, northern Europe, and northern

8 and central Asia. Drying has been observed in the Sahel, the Mediterranean, southern Africa, and parts of 

9 southern Asia. Spatial and temporal variability for precipitation is high, and data are limited for some 

10 regions (EPA 2009b). 

11 Droughts that are more intense and longer have been observed since the 1970s, particularly in the 

12 tropics and subtropics, and were caused by higher temperatures and decreased precipitation. Changes in 

13 sea-surface temperatures, wind patterns, and decreased snowpack and snow cover have also been linked 

14 to droughts (EPA 2009b). 

15 Increased Incidence of Severe Weather Events

16 Long-term trends in tropical cyclone activity have been reported, but there is no clear trend in the 

17 number of tropical cyclones each year. There is observational evidence of an increase in intense tropical 

18 cyclone activity in the North Atlantic since about 1970, correlated with increases of tropical sea surface 

19 temperatures. However, concerns about data quality and multi-decadal variability persist (EPA 2009b). 

20 The World Meteorological Organization (WMO) Sixth International Workshop on Tropical Cyclones in 

21 2006 agreed that “no firm conclusion can be made” on anthropogenic influence on tropical cyclone 

22 activity because “there is evidence both for and against the existence of a detectable anthropogenic signal 

23 in the tropical cyclone climate record” (WMO 2006).

24 There is also insufficient evidence to determine whether there are trends in large-scale 

25 phenomena such as the meridional overturning circulation (MOC) (a mechanism for heat transport in the 

26 North Atlantic Ocean, where warm waters are carried north and cold waters are carried toward the 

27 equator) or in small-scale phenomena such as tornadoes, hail, lightning, and dust storms (IPCC 2007b).

28 Changes in Ice Cover

29 Changes in air and ocean temperatures, precipitation onto the ice mass, and water salinity are 

30 affecting glaciers and ice sheets. Numerous studies have confirmed that glaciers and ice sheets have 

31 significantly shrunk in the past half century. Satellite images have documented the shrinking of the 

32 Greenland ice sheet and the West Antarctic ice sheet (NASA 2009), and summertime sea ice has declined 

33 34 percent since 1979 (EPA 2009b). Additionally, some Arctic ice that previously was thick enough to 

34 last through summer has now thinned enough that it melts completely in summer. In 2003, 62 percent of

35 the Arctic’s total ice volume was stored in multi-year ice; in 2008, only 32 percent was stored in multi36 year ice (NASA 2009). 

37 Acidification of Oceans

38 Oceans have absorbed some of the increase in atmospheric CO2, which lowers the pH of the 

39 water. When CO2 dissolves in seawater, there is an increase in the hydrogen ion concentration of the 

40 water, measured as a decline in pH. Relative to the pre-industrial period, the pH of the world’s oceans has 

41 dropped 0.1 pH units (Royal Society 2005 and EPA 2009b). Because pH is measured on a logarithmic 
Chapter 3 Affected Environment and Environmental Consequences 3.4 Climate 

 3-73 

1 scale, this represents a 30% increase in the hydrogen ion concentration of seawater, a significant 

2 acidification of the oceans. Although research on the ultimate impacts of ocean acidification is limited, 

3 scientists believe that the acidification is likely to interfere with the calcification of coral reefs and thus 

4 inhibit the growth and survival of coral reef ecosystems (EPA 2009b). 

5 3.4.3 Methodology 

6 The methodology NHTSA used to characterize the effects of the alternatives on climate has two 

7 key elements, as follows: 

8 1. Analyzing the effects of the proposed action and alternatives on GHG emissions; and 

9 2. Analyzing how GHG emissions affect the climate system (climate effects). 

10 For both effects on GHG emissions and effects on the climate system, this EIS expresses results – 

11 for each alternative – in terms of the environmental attribute being characterized (emissions, CO2

12 concentrations, temperature, precipitation, and sea level). Comparisons between the No Action 

13 Alternative (Alternative 1) and each action alternative (Alternatives 2 through 9) are also presented to 

14 illustrate the differences in environmental effects among the alternative CAFE standards. The impact of 

15 each action alternative on these results is measured by the difference in its value under the No Action 

16 Alternative and its value under that action alternative. For example, the reduction in CO2 emissions 

17 attributable to an action alternative is measured by the difference in emissions under that alternative and 

18 emissions under the No Action Alternative. 

19 The methods used to characterize emissions and climate effects involve considerable uncertainty. 

20 Sources of uncertainty include the pace and effects of technology change in the transportation sector and 

21 other sectors that emit GHGs; changes in the future fuel supply and fuel characteristics that could affect 

22 emissions; sensitivity of climate to increased GHG concentrations; rate of change in the climate system in 

23 response to changing GHG concentrations; potential existence of thresholds in the climate system (which 

24 cannot be predicted or simulated); regional differences in the magnitude and rate of climate changes; and 

25 many other factors. 

26 Moss and Schneider (2000) characterize the “cascade of uncertainty” in climate change 

27 simulations (Figure 3.4.3-1). As indicated in the figure, the emissions estimates used in this EIS have 

28 narrower bands of uncertainty than the global climate effects, which are less uncertain than the regional 

29 climate change effects. The effects on climate are, in turn, less uncertain than the impacts of climate 

30 changes on affected resources (such as terrestrial and coastal ecosystems, human health, and other 

31 resources discussed in Section 4.5). Although the uncertainty bands get broader with each successive step 

32 in the analytic chain, this is not to say that all values within the bands are equally likely – it is still the 

33 case that the mid-range values have the highest likelihood. 

34 Where information in the analysis in this EIS is incomplete or unavailable, NHTSA has relied on 

35 the CEQ regulations regarding incomplete or unavailable information (see 40 CFR § 1502.22(b)). The 

36 scientific understanding of the climate system is incomplete; like any analysis of complex, long-term 

37 changes to support decisionmaking, evaluating reasonably foreseeable significant adverse impacts on the 

38 human environment involves many assumptions and uncertainties. This EIS uses methods and data that 

39 represent the best and most up-to-date information available on this topic, and have been subjected to

40 peer-review and scrutiny. In fact, the information cited throughout this section that is extracted from the 

41 most recent EPA, IPCC, and CCSP reports on climate change has endured a more thorough and 

42 systematic review process than information on virtually any other topic in environmental science and 

43 policy. The tools used to perform the climate change impacts analysis in this EIS, including MAGICC 

44 (Model for the Assessment of Greenhouse-gas Induced Climate Change) and the Representative 
3.4 Climate Chapter 3 Affected Environment and Environmental Consequences 

3-74 

1 Concentration Pathway (RCP) and CCSP Final Report of Synthesis and Assessment Product (SAP) 2.1 

2 emissions scenarios described below, are widely available and generally accepted in the scientific 

3 community. 

Figure 3.4.3-1. Cascade of Uncertainty in Climate Change Simulations a/ 

4 

5 CCSP SAP 3.1 on the strengths and limitations of climate models (CCSP 2008d) provides a 

6 thorough discussion of the methodological limitations regarding modeling. Readers interested in a 

7 detailed treatment of this topic can find the SAP 3.1 report useful in understanding the issues that 

8 underpin the modeling of environmental impacts of the proposed action and the range of alternatives on

9 climate change. 

10 3.4.3.1 Methodology for Modeling Greenhouse Gas Emissions 

11 GHG emissions were estimated using the Volpe model, as described in Section 3.1.4. The 

12 emissions estimates include global CO2, CH4, and N2O emissions resulting from direct fuel combustion 

13 and from the production and distribution of fuel (upstream emissions). The Volpe model also accounted

14 for and estimated the following non-GHGs: SO2, NOx, CO, and VOCs. 

15 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.17 16 There is a direct relationship 

17 among fuel economy, fuel consumption, and CO2 emissions. Lower fuel consumption reduces CO2

18 emissions directly because the primary source of vehicle-related CO2 emissions is fuel combustion in 

19 internal-combustion engines. Therefore, fuel consumption is directly related to CO2 emissions and CO2

20 emissions are directly related to fuel economy. NHTSA estimates reductions in CO2 emissions resulting 

21 from fuel savings by assuming that the carbon content of gasoline, diesel, and other fuels is converted 

 

17 For this rulemaking, NHTSA estimated emissions of vehicular CO2, CH4, and N2O emissions, but did not estimate 

vehicular emissions of HFCs. CH4 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 non-tailpipe) 

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.) 

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.”
Chapter 3 Affected Environment and Environmental Consequences 3.4 Climate 

 3-75 

entirely to CO2 during the combustion process.18 1 Specifically, NHTSA estimates CO2 emissions from 

2 fuel combustion as the product of the volume of each type of fuel consumed (in gallons), its mass density 

3 (in grams per gallon), the fraction of its total mass represented by carbon (measured as a proportion), and 

4 CO2 emissions per gram of fuel carbon (the ratio of the molecular weights of CO2 and elemental carbon). 

5 Reduced fuel consumption also lowers CO2 emissions that result from the use of carbon-based 

6 energy sources during fuel production and distribution. NHTSA currently estimates the global reductions 

7 in CO2 emissions during each phase of fuel production and distribution using CO2 emissions rates 

8 obtained from the Greenhouse Gases, Regulated Emissions, and Energy Use in Transportation (GREET) 

9 version 1.8b model using the previous assumptions about how fuel savings are reflected in reductions in 

10 activity during each phase of fuel production and distribution. The total reduction in CO2 emissions from 

11 improving fuel economy under each CAFE alternative is the sum of the reductions in motor vehicle 

12 emissions from reduced fuel combustion, plus the reduction in upstream emissions from a lower volume 

13 of fuel production and distribution. 

14 3.4.3.2 Methodology for Estimating Climate Effects

15 This EIS estimates and reports on four direct and indirect effects of climate change, driven by 

16 alternative scenarios of GHG emissions, as follows:

17 1. Changes in CO2 concentrations; 

18 2. Changes in global mean surface temperature; 

19 3. Changes in regional temperature and precipitation; and 

20 4. Changes in sea level. 

21 The change in CO2 concentration is a direct effect of the changes in GHG emissions and 

22 influences each of the other factors. 

23 This EIS uses a simple climate model to estimate the changes in CO2 concentrations, global mean 

24 surface temperature, and changes in sea level for each CAFE alternative and uses increases in global 

25 mean surface temperature combined with an approach and coefficients from the IPCC Fourth Assessment 

26 Report (IPCC 2007a) to estimate changes in global precipitation. NHTSA used the publicly available 

27 modeling software MAGICC 5.3.v2 (Wigley 2008) to estimate changes in key direct and indirect effects. 

28 The application of MAGICC 5.3.v2 uses the estimated reductions in emissions of CO2, CH4, N2O, CO, 

29 NOx, SO2, and VOCs produced by the Volpe model. A sensitivity analysis was completed to examine the 

30 relationship among selected CAFE alternatives and likely climate sensitivities, and the associated direct 

31 and indirect effects for each combination. These relationships can be used to infer the effect of emissions 

32 associated with the CAFE alternatives on direct and indirect climate effects. 

33 This section describes MAGICC, the climate sensitivity analysis, and the emissions scenario used 

34 in the analysis. 

 

18 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 

3-76 

1 3.4.3.2.1 MAGICC Version 5.3.v2 

2 The selection of MAGICC for this analysis was driven by a number of factors, as follows: 

3 • MAGICC has been used in the peer-reviewed literature to evaluate changes in global mean 

4 surface temperature and sea-level rise, including the IPCC Fourth Assessment Report for 

5 Working Group I (WGI) (IPCC 2007a) in which it was used to scale the results from the 

atmospheric-ocean general circulation models (AOGCMs)19 6 to estimate the global mean 

7 surface temperature and the sea-level rise for global emissions scenarios that the AOGCMs 

8 did not run. 

9 • MAGICC is publicly available and was designed for the type of analysis performed in this 

10 EIS. 

11 • More complex AOGCMs are not designed for the type of sensitivity analysis performed here 

12 and are best used to provide results for groups of scenarios with much greater differences in 

13 emissions. 

14 • MAGICC has been updated to version 5.3.v2 to incorporate the science from the IPCC 

15 Fourth Assessment Report (Wigley 2008). 

16 • EPA is also using MAGICC 5.3.v2 for their vehicle GHG emissions standards Regulatory 

17 Impact Analysis (RIA), which accompanies the joint NHTSA and EPA NPRM. 

18 NHTSA assumed that global emissions under the No Action Alternative (Alternative 1) follow 

19 the trajectory provided by the RCP 4.5 MiniCAM (Mini Climate Assessment Model) reference scenario. 

20 This scenario represents a reference case, in which future global emissions continue to rise unchecked

21 assuming no additional climate policy. It is based on the CCSP SAP 2.1 MiniCAM reference scenario, 

22 and has been revised by the Joint Global Change Research Institute to update emission estimates of non23 CO2 gases. Section 3.4.3.3 describes the RCP 4.5 MiniCAM reference scenario. 

24 3.4.3.2.2 Reference Case Modeling Runs 

25 The modeling runs and sensitivity analysis are designed to use information on CAFE alternatives, 

26 climate sensitivities, and the RCP 4.5 MiniCAM reference emissions scenario (Clarke et al. 2007, Smith 

and Wigley 2006)20 27 to model relative changes in atmospheric concentrations, global mean surface 

28 temperature, precipitation, and sea-level rise likely to result under each alternative. 

29 The modeling runs are based on the results provided for the nine CAFE alternatives, a climate 

30 sensitivity of 3 °C (5.4 °F) for a doubling of CO2 concentrations in the atmosphere, and the RCP 4.5 

31 MiniCAM reference scenario. 

32 The approach uses the following steps to estimate these changes: 

33 1. NHTSA assumed that global emissions under the No Action Alternative follow the trajectory 

34 provided by the RCP 4.5 MiniCAM reference scenario.

35 2. NHTSA assumed that global emissions for the CAFE alternatives are equal to the global 

36 emissions from the No Action Alternative minus the emissions reductions from the Volpe 

37 model for CO2, CH4, N2O, SO2, NOx, CO, and VOCs. (For example, the global emissions 

 

19 For a discussion of AOGCMs, see WGI, Chapter 8 in IPCC (2007a). 

20 The use of different emissions scenarios provides insight into the impact of alternative global emissions scenarios 

on the effect of the CAFE alternatives. 
Chapter 3 Affected Environment and Environmental Consequences 3.4 Climate 

 3-77 

1 scenario under Alternative 2 equaled the RCP 4.5 MiniCAM reference scenario minus the 

2 emission reductions from that Alternative). All SO2 reductions were applied to the Aerosol 

3 region 1 of MAGICC, which includes North America. 

4 3. NHTSA used MAGICC 5.3.v2 to estimate the changes in global CO2 concentrations, global 

5 mean surface temperature, and sea-level rise through 2100 using the global emissions 

6 scenario under each CAFE alternative, developed in Steps 1 and 2 above. 

7 4. NHTSA used the increase in global mean surface temperature, along with factors relating 

8 increase in global average precipitation to this increase in global mean surface temperature, to 

9 estimate the increase in global averaged precipitation for each CAFE alternative using the 

10 RCP 4.5 MiniCAM reference scenario. 

11 Section 3.4.4 presents the results of the model runs for the alternatives. 

12 3.4.3.2.3 Sensitivity Analysis 

13 NHTSA conducted a sensitivity analysis to examine the effect of various equilibrium climate 

sensitivities on the results. Equilibrium climate sensitivity21 14 (or climate sensitivity) is the projected 

15 responsiveness of Earth’s global climate system to forcing from GHG drivers, and is often expressed in

16 terms of changes to global surface temperature resulting from a doubling of CO2 in relation to pre17 industrial atmospheric concentrations (280 ppm CO2) (NRC 2001 in EPA 2009b). In the past 8 years, 

18 confidence in climate sensitivity projections has increased significantly (Meehl et al. 2007b in EPA 

19 2009). According to IPCC, with a doubling of the concentration of atmospheric CO2, there is a 66- to 90-

20 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 

21 the single most likely surface temperature increase (EPA 2009b, Meehl et al. 2007a). 

22 Climate sensitivities of 2.0, 3.0, and 4.5 °C (3.6, 5.4, and 8.1 °F) for a doubling of CO2

23 concentrations in the atmosphere were assessed. NHTSA conducted the sensitivity analysis around two of

24 the CAFE alternatives, the No Action Alternative (Alternative 1) and the Preferred Alternative 

25 (Alternative 4), as this was deemed sufficient to assess the effect of various climate sensitivities on the 

26 results. 

27 The approach uses the following steps to estimate the sensitivity of the results to alternate 

28 estimates of the climate sensitivity: 

29 1. NHTSA used the RCP 4.5 MiniCAM reference scenario to represent emissions from the No 

30 Action Alternative. 

31 2. Starting with the RCP 4.5 MiniCAM reference scenario from step 1, NHTSA assumed that 

32 the reductions in global emissions of CO2, CH4, N2O, SO2, NOx, CO, and VOCs resulting 

33 from the Preferred Alternative are equal to the global emissions of each pollutant under the 

34 No Action Alternative, minus emissions of each pollutant under the Preferred Alternative. 

35 All SO2 reductions were applied to Aerosol region 1 of MAGICC, which includes North 

36 America. 

37 3. NHTSA assumed climate sensitivity values consistent with the likely range from the IPCC 

38 Fourth Assessment Report (IPCC 2007a) of 2.0, 3.0, and 4.5 °C (3.6, 5.4, and 8.1 °F). 

39 4. For each climate sensitivity in step 3, NHTSA used MAGICC 5.3.v2 to estimate the resulting 

40 changes in CO2 concentrations, global mean surface temperature, and sea-level rise through 

41 2100 for the global emissions scenarios in step 1 and 2. 

 

21 In this document, the term “climate sensitivity” refers to “equilibrium climate sensitivity.” 
3.4 Climate Chapter 3 Affected Environment and Environmental Consequences 

3-78 

1 Section 3.4.4.2.5 presents the results of the model runs for the alternatives. 

2 3.4.3.3 Global Emissions Scenarios 

3 As described above, MAGICC uses long-term emissions scenarios representing different 

4 assumptions about key drivers of GHG emissions. The RCP 4.5 MiniCAM reference scenario is based on 

5 the MiniCAM reference scenario developed for the SAP 2.1 report. This scenario was created as part of

6 the CCSP effort to develop a set of long-term (2000 to 2100) global emissions scenarios that incorporate 

7 an update of economic and technology data and utilize improved scenario-development tools compared to 

8 the IPCC Special Report on Emissions Scenarios (SRES) (IPCC 2000) developed more than a decade 

9 ago. 

10 The Strategic Plan for the U.S. Climate Change Science Program (CCSP 2003) called for the 

11 preparation of 21 synthesis and assessment products and noted that emissions scenarios are essential for 

12 comparative analysis of future climate change and for analyzing options for mitigating and adapting to

13 climate change. The Plan includes Product 2.1, Scenarios of Greenhouse Gas Emissions and 

14 Atmospheric Concentrations and Review of Integrated Scenario Development and Application (Clarke et 

15 al. 2007), which presents 15 scenarios, five from each of the three modeling groups (IGSM, MiniCAM, 

and MERGE).22 16 

17 Each climate modeling group independently produced a unique emissions reference scenario 

18 based on the assumption that no climate policy would be implemented beyond the current set of policies

19 in place using a set of assumptions about drivers such as population changes, economic growth, land and 

20 labor productivity growth, technological options, and resource endowments. In addition, each group 

21 produced four additional stabilization scenarios, which are defined in terms of the total long-term 

22 radiative impact of the suite of GHGs that includes CO2, N2O, CH4, HFCs, PFCs, and SF6. These 

23 stabilization scenarios represent various levels of implementation of global GHG emissions reduction 

24 policies. 

25 The results rely primarily on the RCP 4.5 MiniCAM reference scenario (which is based on the 

26 MiniCAM reference scenario developed for SAP 2.1) to represent a reference case emissions scenario; 

27 that is, future global emissions assuming no additional climate policy. NHTSA chose the RCP 4.5 

28 MiniCAM reference scenario based on the following factors: 

29 • The RCP 4.5 MiniCAM reference scenario is a slightly updated version of the scenario 

30 developed by the MiniCAM Model of the Joint Global Change Research Institute, which is a 

31 partnership between the Pacific Northwest National Laboratory and the University of 

32 Maryland, and is one of three reference climate scenarios described in the SAP 2.1. The 

33 MiniCAM reference scenario is based on a set of assumptions about drivers such as 

34 population, technology, and socioeconomic changes in the absence of global action to 

35 mitigate climate change. 

36 • In terms of global emissions of CO2 from fossil fuels and industrial sources, the MiniCAM 

37 reference scenario illustrates a pathway of emissions between the IGSM and MERGE 

reference scenarios for most of the 21st 38 Century. In essence, out of the three SAP 2.1 

39 reference case scenarios, the MiniCAM reference scenario is the “middle ground” scenario. 

 

22 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. 
Chapter 3 Affected Environment and Environmental Consequences 3.4 Climate 

 3-79 

1 • CCSP SAP 2.1 is more than a decade newer than the IPCC SRES, and therefore has updated 

2 economic and technology data and assumptions and uses improved integrated assessment 

3 models that account for advances in economics and science over the past 10 years. 

4 • EPA is also using the RCP 4.5 MiniCAM reference scenario for their vehicle GHG emissions 

5 standards RIA, which accompanies the joint NHTSA and EPA NPRM. 

6 The RCP 4.5 MiniCAM reference scenario provides a global context for emissions of a full suite 

7 of GHGs and ozone precursors. There are some inconsistencies between the overall assumptions that 

8 SAP 2.1 and the Joint Global Change Research Institute used to develop the global emissions scenario 

9 and the assumptions used in the Volpe model in terms of economic growth, energy prices, energy supply,

10 and energy demand. However, these inconsistencies affect the characterization of each CAFE alternative 

11 in equal proportion, so the relative estimates provide a reasonable approximation of the differences in 

12 environmental impacts among the alternatives. 

13 Each of the alternatives was simulated by calculating the difference between annual GHG 

14 emissions under that alternative and emissions under the No Action Alternative, and subtracting this 

15 change from the RCP 4.5 MiniCAM reference scenario to generate modified global-scale emissions 

16 scenarios, which show the effects of the various regulatory alternatives on the global emissions path. For 

17 example, CO2 emissions from U.S. passenger cars and light trucks in 2020 under Alternative 1, No 

18 Action, are 1,660 MMTCO2; the emissions in 2020 under the Alternative 4 (Preferred) are 1,550 

19 MMTCO2 (see Table 3.4.4-2). The difference of 110 MMTCO2 represents the reduction in emissions 

20 projected to result from adopting the Preferred Alternative. Global emissions for the RCP 4.5 MiniCAM

21 reference scenario in 2020 are 38,020 MMTCO2, which are assumed to incorporate the level of emissions 

22 from U.S. passenger cars and light trucks under the No Action Alternative. Global emissions under the

23 Preferred Alternative are thus estimated to be 110 MMTCO2 less than this reference level, or 37,910 

MMTCO2 24 in 2020. 

25 Many of the economic assumptions used in the Volpe model (such as fuel price, VMT, U.S. 

26 GDP) are based on EIA’s Annual Energy Outlook (AEO) 2009 (EIA 2009a) and International Energy 

27 Outlook (IEO) 2009 (EIA 2009b), which forecast energy supply and demand in the U.S. and globally to 

28 2030. Figures 3.4.3-2 to 3.4.3-6 show how the EIA forecasts of global and U.S. GDP, CO2 emissions 

29 from energy use, and primary energy use compare against the assumptions used to develop the SAP 2.1 

MiniCAM reference scenario.23,24 30 Both forecasts presented here are for reference scenarios. 

31 The GDP growth assumptions for the IEO reference scenario are slightly higher than those in 

32 SAP scenarios by about 0.6 percent annually for the world and 0.9 percent annually for the United States 

33 (see Figure 3.4.3-2). 

 

23 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. 

24 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). 
3.4 Climate Chapter 3 Affected Environment and Environmental Consequences 

3-80 

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

1 

2 

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 
Chapter 3 Affected Environment and Environmental Consequences 3.4 Climate 

 3-81 

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

1 

2 

Figure 3.4.3-5. World Primary Energy Use Forecast 

3 
3.4 Climate Chapter 3 Affected Environment and Environmental Consequences 

3-82 

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

1 

2 Despite this IEO assumption of higher economic growth, the growth in primary energy use is 

3 similar between the IEO and MiniCAM with the total primary energy use in MiniCAM slightly lower 

4 than that of the IEO, as shown in Figure 3.4.3-5. Thus, the global primary liquids energy use in SAP 2.1 

5 and the IEO 2009 compare well. Much of the difference in energy use in the IEO forecast is due to 

6 assumptions of higher coal use, which results in higher CO2 emissions, as shown in Figure 3.4.3-4. 

7 Additionally, the IEO reference scenario estimates have a lower share of “other” fuels, which include 

8 biomass and renewable fuels, and is likely due to different treatments of non-commercial fuels in the two 

9 sets of forecasts. 

10 The primary energy use projections for the United States show a different trend than the global 

numbers. The AEO 2009 (EIA 2009b)25 11 projection shows an increase in total primary energy use in the 

12 United States, but much of the increase is from the use of coal. On the other hand, the MiniCAM 

13 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 fuels26 14 than the MiniCAM reference scenario, resulting in lower CO2

15 emissions (see Figure 3.4.3-4). 

16 Where information in the analysis included in this EIS is incomplete or unavailable, NHTSA has 

17 relied on the CEQ regulations regarding incomplete or unavailable information (see 40 CFR § 

18 1502.22(b)). In this case, despite the inconsistencies between the MiniCAM assumptions on global trends 

19 across all GHG-emitting sectors (and the drivers that affect them) and the particularities of the emissions 

20 estimates for the U.S. transportation sector provided by the Volpe model, the approach used is valid for 

21 this analysis. These inconsistencies affect all alternatives equally; therefore, they do not hinder a

22 comparison of the alternatives in terms of their relative effects on climate. 

23 The approaches focus on marginal changes in emissions that affect climate. Thus, the approaches 

24 result in a reasonable characterization of climate change for a given set of emissions reductions, 

25 regardless of the underlying details associated with those emissions reductions. Section 3.4.4 

26 characterizes projected climate change under the No Action Alternative (Alternative 1) and the action 

27 alternatives (Alternatives 2 through 9). 

 

25 AEO 2009 revised estimates were used for U.S. primary energy consumption and form the basis for the IEO 2009 

forecast. 

26 For AEO reference scenario, “other” includes biomass, hydropower, and other renewable fuels. 
Chapter 3 Affected Environment and Environmental Consequences 3.4 Climate 

 3-83 

1 The climate sensitivity analysis provides a basis for determining climate responses to varying 

2 climate sensitivities under the No Action Alternative (Alternative 1) and the Preferred Alternative 

3 (Alternative 4). Section 3.4.3.2.2 discusses the methodology for the sensitivity analysis. Though the 

4 MAGICC model does not simulate abrupt climate change processes, some responses of the climate 

5 system represented in MAGICC are slightly non-linear, primarily due to carbon cycle feedbacks and the 

6 logarithmic response of equilibrium temperature to CO2 concentration. Therefore, by using a range of 

7 emissions cases and climate sensitivities, the effects of the alternatives in relation to different scenarios 

8 and sensitivities can be estimated 

9 3.4.3.3.1 Tipping Points and Abrupt Climate Change

10 The phrase “tipping point” is most typically used, in the context of climate change and its 

11 consequences, to describe situations in which the climate system (the atmosphere, oceans, land, 

cryosphere,27 12 and biosphere) reaches a point at which there is a disproportionally large or singular 

13 response in a climate-affected system as a result of only a moderate additional change in the inputs to that 

14 system (such as an increase in the CO2 concentration). Exceeding one or more tipping points, which 

15 “occur when the climate system is forced to cross some threshold, triggering a transition to a new state at 

16 a rate determined by the climate system itself and faster than the cause” (National Research Council 2002 

17 in EPA 2009b), could result in abrupt changes in the climate or any part of the climate system. These

18 changes would likely produce impacts at a rate and intensity far greater than the slower, steady changes 

19 currently being observed (and in some cases, planned for) in the climate system (EPA 2009b). 

20 The methodology used to address tipping points is based on an analysis of climate change science 

21 synthesis reports – including the Technical Support Document for EPA’s Endangerment Finding for 

22 GHGs (EPA 2009b), the IPCC WGI report (Meehl et al. 2007a) and CCSP SAP 3.4: Abrupt Climate 

23 Change – and recent literature on the issue of tipping points and abrupt climate change. The analysis 

24 identifies vulnerable systems, possible temperature thresholds, and estimates of the likelihood, timing, 

25 and impacts of abrupt climate events. While there are methodological approaches to estimate 

26 temperatures resulting from a reduction in GHG emissions and associated radiative forcing, the present

27 state of the art does not allow for quantification of how emission reductions from a specific policy or 

28 action might affect the probability and timing of abrupt climate change. This is one of the most complex 

29 and scientifically challenging areas of climate science, and given the difficulty of simulating the large30 scale processes involved in these tipping points – or inferring their characteristics from paleoclimatology 

31 – considerable uncertainties remain as to the tipping points and rate of change. Despite the lack of a 

32 precise quantitative methodological approach, Section 4.5.9 presents a qualitative and comparative 

analysis of tipping points and abrupt climate change.28 33 

34 3.4.4 Environmental Consequences 

35 This section describes the environmental consequences of the proposed action and alternatives in 

36 relation to GHG emissions and climate effects. 

 

27 The cryosphere describes the portion of Earth’s surface that is frozen water, such as snow, permafrost, floating 

ice, and glaciers. 

28 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). 
3.4 Climate Chapter 3 Affected Environment and Environmental Consequences 

3-84 

1 3.4.4.1 Greenhouse Gas Emissions 

2 To estimate the emissions resulting from changes in passenger-car and light-truck CAFE 

3 standards, NHTSA uses the Volpe model (see Sections 2.2.1 through 2.2.4 and Section 3.1.4 for

4 descriptions of the model). The change in fuel use projected to result from each alternative CAFE 

5 standard determines the resulting impacts on total and petroleum energy use, which in turn affects the

6 amount of CO2 emissions. Reducing fuel use also lowers CO2 emissions from the use of fossil carbon7 based energy during crude-oil extraction, transportation, and refining, and in the transportation, storage, 

8 and distribution of refined fuel. Because CO2 accounts for such a large fraction of total GHGs emitted 

9 during fuel production and use – more than 95 percent, even after accounting for the higher global 

10 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.29 11 

12 NHTSA estimated GHG emissions for each alternative using the economic assumptions 

13 described in Section 2.2.4. In the discussion and table that follows, emissions reductions represent the 

14 differences in total annual emissions by all passenger cars or light trucks in use between their estimated 

15 future levels under the No Action Alternative (Alternative 1) and each action alternative (Alternatives 2 

16 through 9). Emissions reductions resulting from the proposed action and alternatives for MY 2012-2016

17 passenger cars and light trucks were estimated from 2012 to 2100. For each alternative, all vehicles after 

18 MY 2016 were assumed to meet the MY 2016 CAFE standards. Emissions were estimated for all 

19 alternatives through 2060, and emissions from 2061 through 2100 were assumed to remain constant at 

their levels estimated for 2060.30 20 Emissions under each action alternative were then compared against 

21 those under the No Action Alternative to determine its impact on emissions. 

22 Table 3.4.4-1 and Figure 3.4.4-1 show total emissions and emissions reductions resulting from 

23 applying the nine alternative CAFE standards to new passenger cars and light trucks from 2012 to 2100. 

24 Emissions for this period range from a low of 201,200 MMTCO2 under the 7%/year Increase (Alternative 

25 8) to 243,600 MMTCO2 under the No Action Alternative (Alternative 1). Compared to the No Action 

26 Alternative, projections of emissions reductions over the period 2012 to 2100 due to the MY 2012-2016 

27 CAFE standards ranged from 19,300 to 42,400 MMTCO2. Compared to cumulative global emissions of 

28 5,293,896 MMTCO2 over this period (projected by the RCP 4.5 MiniCAM reference scenario), this 

29 rulemaking is expected to reduce global CO2 emissions by about 0.4 to 0.8 percent from their projected 

30 levels under the No Action Alternative. 

31 To get a sense of the relative impact of these reductions, it can be helpful to consider the relative 

32 importance of emissions from passenger cars and light trucks as a whole and to compare them against 

33 emissions projections from the transportation sector, and expected or stated goals from existing programs 

34 designed to reduce CO2 emissions. As mentioned earlier, U.S. passenger cars and light trucks currently 

35 account for a significant amount of CO2 emissions in the United States. With the action alternatives 

36 reducing U.S. passenger car and light truck CO2 emissions by 7.9 to 17.4 percent of cumulative emissions 

37 from 2012-2100, they will have a noticeable impact on total U.S. CO2 emissions. Compared to total U.S. 

38 CO2 emissions in 2100 of 7,886 MMTCO2 projected by the MiniCAM reference scenario (Clarke et al.

39 2007), the action alternatives would reduce total U.S. CO2 emissions by 3.6 to 7.8 percent in 2100. 

40 Figure 3.4.4-2 shows projected annual emissions from passenger cars and light trucks under the MY 

41 2012-2016 alternative CAFE standards. 

 

29 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. 

30 See Section 3.1.3 for a summary of the scope and parameters of the Volpe model. 
Chapter 3 Affected Environment and Environmental Consequences 3.4 Climate 

 3-85 

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 243,600 0 

2 3%/year Increase 224,300 19,300 

3 4%/year Increase 216,700 26,900 

4 ~4.3%/year Increase, Preferred 214,700 29,000 

5 5%/year Increase 210,100 33,500 

6 ~5.9%/year Increase, MNB 204,500 39,100 

7 6%/year Increase 204,800 38,800 

8 7%/year Increase 201,200 42,400 

9 ~6.7%/year Increase, TCTB 201,500 42,100 

__________

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. 

1 

Figure 3.4.4-1. Emissions and Emissions Reductions (MMTCO2) 

from 2010 to 2100 by Alternative 

-

50,000 

100,000 

150,000 

200,000 

250,000 

300,000 

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: 

~5.9%/year 

Increase, MNB

Alt. 7: 

6%/year Increase

Alt. 8: 

7%/year Increase

Alt. 9: 

~6.7%/year 

Increase, TCTB

2 
3.4 Climate Chapter 3 Affected Environment and Environmental Consequences 

3-86 

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

0

500

1000

1500

2000

2500

3000

3500

2010 2020 2030 2040 2050 2060

MMTCO2

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: ~5.9%/year Increase, MNB

Alt. 7: 6%/year Increase Alt. 8: 7%/year Increase

Alt. 9: ~6.7%/year Increase, TCTB

1 

2 As Table 3.4.4-2 shows, total CO2 emissions accounted for by the U.S. passenger-car and light3 truck fleets are projected to increase substantially after 2020 under the No Action Alternative, which

4 assumes average full economy would remain at the 2011 level for all future model years. The table also 

5 shows that each of the action alternatives would reduce total passenger car and light-truck CO2 emissions 

6 in future years significantly from their projected levels under the No Action Alternative. Progressively 

7 larger reductions in CO2 emissions from their levels under the No Action Alternative are projected to 

8 occur during each future year because the action alternatives require successively higher fuel economy

9 levels for MY 2012-2016 and later passenger cars and light trucks. 

10 Under all of the alternatives analyzed, growth in the number of passenger cars and light trucks in 

11 use throughout the United States, combined with assumed increases in their average use, is projected to 

12 result in growth in total passenger car and light truck travel. This growth in travel overwhelms 

13 improvements in fuel economy for each of the alternatives, resulting in projected increases in total fuel 

14 consumption by U.S. passenger cars and light trucks over most of the period shown in the table. Because 

15 CO2 emissions are a direct consequence of total fuel consumption, the same result is projected for total 

16 CO2 emissions from passenger cars and light trucks. 
Chapter 3 Affected Environment and Environmental Consequences 3.4 Climate 

 3-87 

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

~5.9%/year 

Increase

MNB 

6%/year 

Increase 

7%/year 

Increase

~6.7%/year 

Increase 

TCTB 

Carbon dioxide (CO2) 

2010 1,700 1,700 1,700 1,700 1,700 1,700 1,700 1,700 1,700 

2020 1,660 1,590 1,560 1,550 1,540 1,510 1,520 1,500 1,500 

2030 1,970 1,820 1,760 1,740 1,710 1,660 1,670 1,640 1,640 

2040 2,350 2,150 2,073 2,050 2,010 1,950 1,950 1,920 1,920 

2050 2,790 2,550 2,460 2,430 2,380 2,310 2,310 2,270 2,270 

2060 3,310 3,030 2,920 2,890 2,825 2,750 2,750 2,670 2,700 

Methane (CH4) 

2010 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 

2020 1.94 1.86 1.82 1.81 1.79 1.76 1.77 1.75 1.75 

2030 2.31 2.13 2.06 2.04 2.00 1.94 1.94 1.91 1.91 

2040 2.74 2.52 2.43 2.40 2.35 2.28 2.28 2.23 2.24 

2050 3.25 2.98 2.88 2.85 2.78 2.70 2.70 2.65 2.65 

2060 3.87 3.55 3.42 3.39 3.30 3.21 3.20 3.14 3.15 

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 0.03 0.03 

2030 0.04 0.04 0.04 0.04 0.04 0.03 0.03 0.03 0.03 

2040 0.05 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 

2050 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 

2060 0.06 0.06 0.06 0.06 0.06 0.06 0.05 0.05 0.05 

1 

2 Emissions of CO2, the primary gas that drives climate effects, from the U.S. passenger-car and 

3 light-truck fleet represented about 3.7 percent of total global emissions of all CO2 emissions in 2005 

(EPA 2009a, WRI 2009).31 4 Although substantial, this source contributes a small percentage of global 

5 emissions, and the relative contribution of CO2 emissions from the U.S. combined passenger-car and

6 light-truck fleet is expected to decline in the future. This expected decline is due primarily to rapid 

7 growth of emissions from developing economies (which result in part from growth in global 

8 transportation sector emissions). In the CCSP SAP 2.1 MiniCAM reference scenario, the share of liquid

9 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 2100.32 10 

11 In its updated Annual Energy Outlook 2009, EIA projects U.S. transportation CO2 emissions to 

increase from 1,905 MMTCO2 in 2010 to 2,045 MMTCO2 in 2030,33 12 with cumulative U.S. emissions 

 

31 Includes land-use change and forestry, and excludes international bunker fuels. 

32 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. 

33 AEO provides projections through 2030, not through 2100 (the relevant period for climate modeling). 
3.4 Climate Chapter 3 Affected Environment and Environmental Consequences 

3-88 

1 from transportation over this period at 41,093 MMTCO2 (EIA 2009a). Over this same period, the 

2 cumulative emissions reductions over the range of the CAFE action alternatives are projected to be 1,490 

3 to 3,350 MMTCO2, which would yield a 4- to 8-percent reduction in CO2 emissions from the 

4 transportation sector. The environmental impact from increasing fuel economy standards grows as new 

5 vehicles meeting the higher CAFE standards that each action alternative would establish enter the fleet, 

6 while older vehicles are retired. For example, in 2030, projected emissions reductions are 150 to 340

7 MMTCO2, a 7- to 16-percent decrease from projected U.S. transportation emissions of 2,045 MMTCO2 in 

8 2030. 

9 As another measure of the relative environmental impact of this rulemaking, these emissions 

10 reductions can be compared to existing programs designed to reduce GHG emissions in the United States. 

11 In 2007, Arizona, California, New Mexico, Oregon, and Washington formed the Western Climate 

12 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).34 13 If this goal is achieved, 

14 emissions levels in 2020 would be 33-percent lower than under the No Action Alternative, and 15-percent 

15 lower than those at the beginning of the WCI action (WCI 2007b). By comparison, the proposed CAFE 

16 rulemaking is expected to reduce CO2 emissions by 290 to 690 MMTCO2 over the same period, with 

17 emissions levels in 2020 representing a 4- to 10-percent reduction from the future baseline emissions for 

18 passenger cars and light trucks. 

19 Nine northeast and mid-Atlantic states have formed the Regional Greenhouse Gas Initiative 

20 (RGGI) to reduce CO2 emissions from power plants in the northeast. Emissions reductions from 2006 to 

2024 were estimated at 268 MMTCO2 (RGGI 2006).35 21 This represents a 23-percent reduction from the 

22 future baseline and a 10-percent reduction in 2024 emissions from their levels at the beginning of the

23 action (RGGI 2006). By comparison, NHTSA forecasts that the proposed CAFE rulemaking would 

24 reduce CO2 emissions by 670 to 1,540 MMTCO2 over this period (depending on alternative), with 

25 emissions levels in 2024 representing a 6- to 14-percent reduction from the future baseline emissions for 

26 passenger cars and light trucks. 

27 Two features of these comparisons are extremely important to emphasize. First, emissions from 

28 the sources addressed in the WCI and RGGI plans are projected to decrease compared to the beginning of

29 the action, while emissions from passenger cars and light trucks are projected to increase under all 

30 alternatives for this proposed rulemaking due to increases in vehicle ownership and use. Second, these 

31 projections are only estimates, and the scope of these climate programs differs from that in the scope of 

32 the proposed rulemaking in terms of geography, sector, and purpose. 

33 In 2004, Robert Socolow and Stephen Pacala first introduced the concept of stabilization 

34 “wedges” − idealizing a new scheme to prevent atmospheric CO2 levels from doubling in the next 50 

35 years (Pacala and Socolow 2004). In 2004, the concentration of atmospheric CO2 was about 375 ppm. 

36 Socolow and Pacala proposed to stabilize atmospheric CO2 at a maximum concentration of approximately 

37 500 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 carbon36 38 per year 

 

34 Since this goal was 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 July 14, 2009. 

35 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. 

36 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. 
Chapter 3 Affected Environment and Environmental Consequences 3.4 Climate 

 3-89 

1 (GtC/year) for the next 50 years. Socolow and Pacala depicted the necessary reductions in emissions 

2 from their projected increase over the next 50 years as a triangle, with progressively larger reductions in 

3 emissions from their projected level required during each successive future year (see Figure 3.4.4-3). 

Figure 3.4.4-3. Historical Carbon Emissions with Two Potential 

Pathways for the Future (Source: Socolow et al. 2004) 

4 

5 Socolow and Pacala divided the stabilization triangle into wedges, with each wedge representing 

6 an activity that reduces projected growth in carbon emissions by progressively larger amounts each year 

7 over a 50-year period ending in 2055, with the reduction reaching 1 billion tons annually in 2055. 

8 Socolow and Pacala estimated that approximately seven wedges of this size would be needed to fill the 

9 stabilization triangle (see Figure 3.4.4-4). 

Figure 3.4.4-4. Stabilization Wedges (Source: Socolow et al. 2004) 

10 
3.4 Climate Chapter 3 Affected Environment and Environmental Consequences 

3-90 

1 Wedges can be achieved from improvements in energy efficiency, decarbonization of energy 

2 sources, decarbonization of fuels, and from forests and agricultural soils. For example, approximately 

3 one wedge could be achieved from improvements in either fuel efficiency, reduced reliance on passenger

4 cars, storing CO2 from power and hydrogen plants, or reduced deforestation. 

5 Socolow and Pacala estimate that improving the average fuel economy of the world’s combined 

6 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.37 7 Their estimate is based on a global fleet of approximately 2 

8 billion passenger cars and light trucks, averaging 10,000 miles per year. 

9 By comparison, NHTSA estimates that the number of passenger cars and light trucks in use 

10 throughout the United States will increase to almost 320 million by 2055, the same year Socolow and 

11 Pacala analyzed, and that under the No Action alternative these vehicles will be driven an average of 

12 almost 19,000 miles. Thus, in total, NHTSA projects that passenger cars and light trucks in the United 

13 States will be driven a almost 6.1 trillion miles during 2055 under the No Action Alternative. NHTSA 

14 estimates that the progressively higher fuel economy levels required by the under the eight action 

15 alternatives considered in this EIS (allowing for the accompanying increases in average vehicle use) 

16 would reduce total passenger car and light truck fuel consumption during 2055 by 22 billion gallons 

17 (under Alternative 2) to as much as 49 billion gallons (under Alternative 8). As a consequence, CO2

18 emissions attributable to U.S. passenger-car and light-truck use through 2055 would decline by the 

equivalent of 8 percent (Alternative 2) to 17 percent (Alternative 9) of one “stabilization wedge.”38 19 

20 NHTSA emphasizes that the action of setting fuel economy standards does not directly regulate 

21 emissions from passenger cars and light trucks. NHTSA’s authority to promulgate new fuel economy 

22 standards does not allow it to regulate other factors affecting emissions, including society’s driving

23 habits. NHTSA does not have the authority to control the increase of vehicles on the road or the amount 

24 of miles people drive. NHTSA’s authority is to establish average fuel economy standards for each model 

25 year at “the maximum feasible average fuel economy that the Secretary decides the manufacturers can 

26 achieve in that model year.” 49 U.S.C. § 32902(a). NHTSA estimates that the various alternatives being 

27 considered will decrease emissions from what they otherwise would be if the agency did not increase 

28 CAFE standards. However, due to the continued growth of VMT that the government forecasts, 

29 increased efficiency of internal combustion engines will not decrease total emissions from passenger cars 

30 and light trucks, although it will significantly slow the rate at which emissions from these vehicles 

31 increase, as mentioned above and as illustrated in Figure 3.4.4-2. 

32 Where information in the analysis included in this EIS is incomplete or unavailable, NHTSA has 

33 relied on the CEQ regulations regarding incomplete or unavailable information (see 40 CFR § 

34 1502.22(b)). In this case, the comparison of emissions reductions from the alternative CAFE standards to 

35 emissions reductions associated with other programs is intended to benefit decisionmakers by providing

36 relative benchmarks, rather than absolute metrics, for selecting among alternatives. In summary, the 

37 alternatives analyzed herein deliver GHG emissions reductions that are on the same scale as many of the 

38 most progressive and ambitious GHG emissions reduction programs underway in the United States. 

 

37 Id.; see also http://www.princeton.edu/~cmi/resources/wedgesumtb.htm (listing 15 examples of potential wedges). 

38 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, slightly later than the 2005 initial year for 

emissions reductions assumed in the Socolow Pacala analysis. 
Chapter 3 Affected Environment and Environmental Consequences 3.4 Climate 

 3-91 

1 3.4.4.2 Direct and Indirect Effects on Climate Change 

2 Sections 3.4.4.2.1 through 3.4.4.2.5 describe the direct and indirect effects of the alternatives on 

3 four relevant climate change indicators: atmospheric CO2 concentrations, temperature, precipitation, and 

4 sea-level rise. 

5 3.4.4.2.1 Atmospheric CO2 Concentrations 

6 MAGICC 5.3.v2 is a simple climate model that is well calibrated to the mean of the multi-model 

7 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 3.4.4-3.39 8 As the table indicates, the 

9 results of the model runs developed for this analysis agree relatively well with IPCC estimates for both 

10 CO2 concentrations and surface temperature. 

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. 

11 

12 A comparison of sea-level rise from MAGICC 5.3.v2 and the IPCC Fourth Assessment Report is 

13 presented in the release documentation for MAGICC 5.3.v2 (Wigley 2008). In Table 3 of the 

14 documentation, Wigley presents the results for six SRES scenarios, which show that the comparable value 

15 for sea-level rise from MAGICC 5.3.v2 (total sea-level rise minus estimates for contributions from non16 melt sources such as warming of the permafrost) within 0.01 centimeter in 2095. 

17 As discussed in Section 3.4.3, NHTSA used the RCP 4.5 MiniCAM reference scenario to 

18 represent the No Action Alternative in the MAGICC modeling runs. Table 3.4.4-4 and Figures 3.4.4-5 

19 through 3.4.4-8 present the results of MAGICC simulations for the No Action Alternative and the eight 

20 action alternatives in terms of CO2 concentrations and increases in global mean surface temperature in 

21 2030, 2050, and 2100. As Figures 3.4.4-7 and 3.4.4-8 show, the reduction in the increases in projected 

22 CO2 concentrations and temperature from each of the action alternatives amounts to a small fraction of 

23 the total increases in CO2 concentrations and global mean surface temperature. However, the relative 

24 impact of the action alternatives is shown by the reduction in increases of both CO2 concentrations and 

25 temperature under Alternative 9. As shown in Figures 3.4.4-7 and 3.4.4-8, the reduction in increase of 

26 CO2 concentrations by 2100 under Alternative 9 is two and a half times that of Alternative 2. Similarly,

27 the reduction in increase of temperature under Alternative 9 is two and a half times that of Alternative 2. 

 

39 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 

3-92 

1 As shown in Table 3.4.4-4 and Figures 3.4.4-5 through 3.4.4-8, estimated CO2 concentrations for 

2 2100 range from 779.0 ppm under the most stringent alternative (TCTB) to 783.0 ppm under the No 

3 Action Alternative. For 2030 and 2050, the corresponding range is even smaller. Because CO2

4 concentrations are the key driver of other climate effects (which in turn act as drivers on the resource 

5 impacts discussed in Section 4.5), this leads to small differences in these effects. While these effects are 

6 small, they occur on a global scale and are long-lived. 

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 441.6 514.3 781.2 0.922 1.554 3.129 8.38 15.16 37.94 

3 4%/year Increase 441.6 514.1 780.4 0.922 1.553 3.126 8.38 15.15 37.92 

4 ~4.3%/year 

Increase, Preferred 441.5 514.0 780.3 0.922 1.553 3.125 8.38 15.15 37.91 

5 5%/year Increase 441.5 513.9 779.8 0.922 1.553 3.124 8.38 15.15 37.89 

6 ~5.9%/year 

Increase, MNB 441.4 513.8 779.3 0.921 1.552 3.122 8.38 15.14 37.87 

7 6%/year Increase 441.4 513.8 779.3 0.921 1.552 3.122 8.38 15.14 37.87 

8 7%/year Increase 441.4 513.7 779.0 0.921 1.551 3.120 8.38 15.14 37.86 

9 ~6.7%/year 

Increase, TCTB 441.4 513.7 779.0 0.921 1.551 3.120 8.38 15.14 37.86 

Reductions Under Alternative CAFE Standards

2 3%/year Increase 0.2 0.5 1.8 0.001 0.002 0.007 0.00 0.01 0.06 

3 4%/year Increase 0.2 0.7 2.6 0.001 0.003 0.010 0.00 0.02 0.08 

4 ~4.3%/year 

Increase, Preferred 0.3 0.8 2.7 0.001 0.004 0.010 0.00 0.02 0.09 

5 5%/year Increase 0.3 0.9 3.2 0.001 0.004 0.012 0.00 0.02 0.11 

6 ~5.9%/year 

Increase, MNB 0.4 1.0 3.7 0.002 0.005 0.014 0.00 0.03 0.13 

7 6%/year Increase 0.4 1.0 3.7 0.002 0.005 0.014 0.00 0.03 0.13 

8 7%/year Increase 0.4 1.1 4.0 0.002 0.006 0.015 0.00 0.03 0.14 

9 ~6.7%/year 

Increase, TCTB 0.4 1.1 4.0 0.002 0.006 0.015 0.00 0.03 0.14 

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. 

7 
Chapter 3 Affected Environment and Environmental Consequences 3.4 Climate 

 3-93 

Figure 3.4.4-5. CO2 Concentrations (ppm) 

1 
3.4 Climate Chapter 3 Affected Environment and Environmental Consequences 

3-94 

Figure 3.4.4-6. Global Mean Surface Temperature Increase (°C) 

1 
Chapter 3 Affected Environment and Environmental Consequences 3.4 Climate 

 3-95 

Figure 3.4.4-7. Reduction in CO2 Concentrations (ppm) Compared to the No Action 

Alternative 
3.4 Climate Chapter 3 Affected Environment and Environmental Consequences 

3-96 

Figure 3.4.4-8. Reduction in Global Mean Temperature Compared to the No Action 

Alternative 

1 

2 3.4.4.2.2 Temperature 

3 Table 3.4.4.4 lists MAGICC simulations of mean global surface air temperature increases. Under 

4 the No Action Alternative, the temperature increase from 1990 is 0.92 °C (1.65 °F) for 2030, 1.56 °C 

5 (2.80 °F) for 2050, and 3.14 °C (5.65 °F) for 2100. The differences among alternatives are small. For 

6 2100, the reduction in temperature increase in relation to the No Action Alternative ranges from 0.007 °C 

7 (0.013 °F) to 0.015 °C (0.027 °F). 

8 Table 3.4.4-5 summarizes the regional changes in warming and seasonal temperatures presented 

9 in the IPCC Fourth Assessment Report. At this time, quantifying the changes to regional climate from the 

10 CAFE alternatives is not possible due to the limitations of existing climate models, but the alternatives 

11 would be expected to reduce the impacts in proportion to the amount of reduction in global mean surface 

12 temperature. 
Chapter 3 Affected Environment and Environmental Consequences 3.4 Climate 

 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) 

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 

 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 

 
3.4 Climate Chapter 3 Affected Environment and Environmental Consequences 

3-98 

1 

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 

Australia and New 

Zealand 

Southern Australia Likely comparable to the 

global mean but less than in 

the rest of Australia 

 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 

Increased frequency of extreme high 

daily temperatures and decreased 

frequency of cold extremes are very 

likely

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 

2 

3 MAGICC 5.3.v2 estimates radiative forcing from black carbon, a primary aerosol emitted 

4 through the incomplete combustion of fossil fuel and biomass burning. However, emissions trends for 

5 black carbon are “hard-wired” in the model to follow emissions of SO2 and cannot be specified as 

separate inputs to the model.40 6 The radiative forcing of black carbon is difficult to accurately quantify 

7 because it is a function of microphysical properties of the geographic and vertical placement, and lifetime 

8 of the aerosol; however, it is not clear that black carbon contributes substantially to global warming

9 (Jacobson 2001). Total global black carbon emissions are estimated to be approximately 8 Teragrams of

10 carbon per year (Tg C/yr) (Bond et al. 2004 in Forster et al. 2007) with estimates of fossil fuel 

11 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)41 12 . In summary, the climate modeling accounts for the

13 effects of black carbon on climate variables. 

14 3.4.4.2.3 Precipitation 

15 In some areas, higher temperatures might increase precipitation. Increases in precipitation are a 

16 result of higher temperatures causing greater water evaporation, which causes more water vapor to be 

17 available for precipitation (EPA 2009b). Increased evaporation leads to increased precipitation in areas 

18 where there is sufficient surface water, such as over oceans and lakes. In drier areas, the increased

19 evaporation can actually accelerate surface drying, which can lead to drought conditions (EPA 2009b). 

 

40 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. 

41 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. 
Chapter 3 Affected Environment and Environmental Consequences 3.4 Climate 

 3-99 

1 Overall, according to IPCC (Meehl et al. 2007a), global mean precipitation is expected to increase under 

2 all scenarios. However, there will be considerable spatial and seasonal variations. Generally, 

3 precipitation increases are very likely to occur in high latitudes, and decreases are likely to occur in the 

4 sub-tropics (EPA 2009b). 

5 Where information in the analysis included in this EIS is incomplete or unavailable, NHTSA has 

6 relied on the CEQ regulations regarding incomplete or unavailable information (see 40 CFR § 

7 1502.22(b)). As noted earlier in the methodology section, MAGICC does not directly simulate changes 

8 in precipitation, and it was not feasible to undertake precipitation modeling with a full Atmospheric9 Ocean General Circulation Model within the time and resources available for this EIS. In this case, the 

10 IPCC (Meehl et al. 2007a) summary of precipitation represents the most thoroughly reviewed, credible 

11 means of producing an assessment of this highly uncertain factor. NHTSA expects that the proposed 

12 action and alternatives would reduce anticipated changes in precipitation (i.e., in a reference case with no 

13 GHG emission reduction policies) in proportion to the alternatives’ effects on temperature. 

14 The global mean change in precipitation provided by the IPCC for the A2 (high), A1B (medium), 

15 and B1 (low) scenarios (Meehl et al. 2007a) is given as the scaled change in precipitation (as a percentage 

16 change from 1980 to 1999 averages) divided by the increase in global mean surface warming for the same

17 period (per °C) as shown in Table 3.4.4-6. The IPCC provides scaling factors in the year ranges of 2011 

18 to 2030, 2046 to 2065, 2080 to 2099, and 2180 to 2199. NHTSA used the scaling factors for the RCP 4.5

19 MiniCAM reference scenario in this analysis because MAGICC does not directly estimate changes in 

global mean precipitation.42 20 

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 

21 

22 Applying these scaling factors to the reductions in global mean surface warming provides 

23 estimates of changes in global mean precipitation. Given that the CAFE action alternatives reduce 

24 temperature increases slightly in relation to the No Action Alternative, they also slightly reduce predicted 

25 increases in precipitation, as shown in Table 3.4.4-7 (again based on the A1B [medium] scenario). 

26 In addition to changes in mean annual precipitation, climate change is anticipated to affect the 

27 intensity of precipitation, as described below (Meehl et al. 2007a): 

28 Intensity of precipitation events is projected to increase, particularly in tropical and high 

29 latitude areas that experience increases in mean precipitation. Even in areas where mean 

30 precipitation decreases (most subtropical and mid-latitude regions), precipitation intensity 

31 is projected to increase but there would be longer periods between rainfall events. There 

32 is a tendency for drying of the mid-continental areas during summer, indicating a greater 

33 risk of droughts in those regions. Precipitation extremes increase more than does the 

34 mean in most tropical and mid- and high-latitude areas. 

 

42 Although MAGICC does not estimate changes in precipitation, SCENGEN does. 
3.4 Climate Chapter 3 Affected Environment and Environmental Consequences 

3-100 

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 2.810 

3 4%/year Increase 0.648 1.712 2.807 

4 ~4.3%/year Increase, Preferred 0.648 1.712 2.807 

5 5%/year Increase 0.648 1.711 2.805 

6 ~5.9%/year Increase, MNB 0.648 1.710 2.803 

7 6%/year Increase 0.648 1.710 2.803 

8 7%/year Increase 0.648 1.709 2.802 

9 ~6.7%/year Increase, TCTB 0.648 1.709 2.802 

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 0.009 

5 5%/year Increase 0.000 0.005 0.011 

6 ~5.9%/year Increase, MNB 0.000 0.006 0.013 

7 6%/year Increase 0.000 0.006 0.013 

8 7%/year Increase 0.000 0.007 0.014 

9 ~6.7%/year Increase, TCTB 0.000 0.007 0.014 

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% 2.59% 4.58% 

4 ~4.3%/year Increase, Preferred 0.94% 2.58% 4.57% 

5 5%/year Increase 0.94% 2.58% 4.57% 

6 ~5.9%/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% 4.57% 

9 ~6.7%/year Increase, TCTB 0.94% 2.58% 4.57% 
Chapter 3 Affected Environment and Environmental Consequences 3.4 Climate 

 3-101 

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% 0.01% 

4 ~4.3%/year Increase, Preferred 0.00% 0.01% 0.01% 

5 5%/year Increase 0.00% 0.01% 0.02% 

6 ~5.9%/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% 0.02% 

9 ~6.7%/year Increase, TCTB 0.00% 0.01% 0.02% 

____________________

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. 

1 Regional variations and changes in the intensity of precipitation events cannot be quantified 

2 further, primarily due to the unavailability of AOGCMs required to estimate these changes. These 

3 models are typically used to provide results among scenarios with very large changes in emissions, such 

4 as the SRES B1 (low), A1B (medium), and A2 (high) scenarios; very small changes in emissions profiles 

5 would produce results that would be difficult to resolve among scenarios with small changes in emissions. 

6 Also, the multiple AOGCMs produce results that are regionally consistent in some cases but inconsistent 

7 for other areas. 

8 Table 3.4.4-8 summarizes the regional changes in precipitation from the IPCC Fourth Assessment 

9 Report. Quantifying the changes in regional climate from the alternative CAFE standards is not possible 

10 at present, but they would be expected to reduce the changes in relation to the reduction in global mean 

11 surface temperature. 

12 3.4.4.2.4 Sea-level Rise 

13 IPCC identifies four primary components of sea-level rise: (1) thermal expansion of ocean water, (2) 

14 melting of glaciers and ice caps, (3) loss of land-based ice in Antarctica, and (4) loss of land-based ice in 

15 Greenland (IPCC 2007b). Ice-sheet discharge is an additional factor that could influence sea level over 

16 the long term. Ocean circulation, changes in atmospheric pressure, and geological processes can also 

17 influence sea-level rise at a regional scale (EPA 2009b). MAGICC calculates the oceanic thermal 

18 expansion component of global mean sea-level rise using a nonlinear temperature- and pressure19 dependent expansion coefficient (Wigley 2008). It also addresses the other three primary components 

20 through ice-melt models for small glaciers and the Greenland and Antarctic ice sheets, and excludes non21 melt sources, which the IPCC Fourth Assessment Report also excluded. Neither MAGICC 5.3.v2 nor the 

22 IPCC Fourth Assessment Report includes more recent information, suggesting that ice flow from 

23 Greenland and Antarctica will be accelerated. The Fourth Assessment Report estimates the ice flow to be 

24 between 9 and 17 centimeters (3.5 and 6.7 inches) by 2100 (Wigley 2008). 
3.4 Climate Chapter 3 Affected Environment and Environmental Consequences 

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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 
Chapter 3 Affected Environment and Environmental Consequences 3.4 Climate 

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1 

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 

2 

3 The state of the science reflected as of the publication of the IPCC Fourth Assessment Report 

4 projects a sea-level rise of 18 to 59 centimeters (0.6 to 1.9 feet) by 2090 to 2099 (EPA 2009b). This

5 projection does not include all changes in ice-sheet flow or the potential for rapid acceleration in ice loss 

6 (Alley et al. 2005, Gregory and Huybrechts 2006, and Hansen 2005, all in Pew 2007). Several recent 

7 studies have found the IPCC estimates of potential sea-level rise might be underestimated regarding ice 

8 loss from the Greenland and Antarctic ice sheets (Shepherd and Wignham 2007, Csatho et al. 2008) and 

9 ice loss from mountain glaciers (Meier et al. 2007). Further, IPCC results for sea-level projections might 

10 underestimate sea-level rise due to changes in global precipitation (Wentz et al. 2007, Zhang et al. 2007). 

11 Rahmstorf (2007) used a semi-empirical approach to project future sea-level rise. The approach yielded a 

12 proportionality coefficient of 3.4 millimeters per year per degree Centigrade of warming, and a projected 

13 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 

14 Assessment Report warming scenarios. Rahmstorf (2007) concludes that “[a] rise over 1 meter (3.3 feet) 

15 by 2100 for strong warming scenarios cannot be ruled out.” None of these studies takes into account the 

16 potential complex changes in ocean circulation that might further influence sea-level rise. Section 4.5.5 

17 discusses sea-level rise in more detail. 

18 Table 3.4.4-4 lists the impacts on sea-level rise under the scenarios and shows sea-level rise in 

19 2100 ranging from 38.00 centimeters (14.96 inches) under the No Action Alternative to 37.86 centimeters 
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1 (14.91 inches) under the TCTB (Alternative 9), for a maximum reduction of 0.14 centimeters (0.055 

2 inches) by 2100 under the No Action Alternative. 

3 In summary, the impacts of the proposed action and alternatives on global mean surface 

4 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.43 5 This is due primarily to the 

6 global and multi-sectoral nature of the climate problem. Although these effects are small, they occur on a 

7 global scale and are long-lived. 

8 3.4.4.2.5 Climate Sensitivity Variations 

9 NHTSA examined the sensitivity of projected climate effects to key technical or scientific 

10 assumptions used in the analysis. This examination included reviewing the impact of various climate 

11 sensitivities on the climate effects due to the No Action Alternative (Alternative 1) and the Preferred 

12 Alternative (Alternative 4) with the RCP 4.5 MiniCAM reference scenario. Table 3.4.4-9 lists the results 

13 from the sensitivity analysis (3.0 °C [5.4 °F] for a doubling of CO2 climate sensitivity). 

14 The use of different climate sensitivities (the equilibrium warming that occurs at a doubling of 

15 CO2 from pre-industrial levels) can affect not only warming but also sea-level rise and CO2 concentration 

16 indirectly. 

17 As shown in Table 3.4.4-9, the sensitivity of the simulated CO2 emissions in 2030, 2050, and 

18 2100 to changes in climate sensitivity is low; the reduction of CO2 concentrations from the No Action 

19 Alternative to the Preferred Alternative in 2100 is from 2.7 to 2.8 ppm. 

20 The sensitivity of the simulated global mean surface temperatures for 2030, 2050, and 2100 

21 varies, as shown in Table 3.4.4-9. In 2030, the impact is low due primarily to the rate at which the global 

22 mean surface temperature increases in response to increases in radiative forcing. In 2100, the impact is 

23 larger due not only to the climate sensitivity but also to the change in emissions. In 2100, the reduction in 

24 global mean surface temperature from the No Action Alternative to the Preferred Alternative in 2100 

25 ranges from 0.008 oC (0.014 °F) for the 2.0 °C (3.6 °F) climate sensitivity to 0.013 oC (0.023 °F) for the 

26 4.5 °C (8.1 °F) climate sensitivity, as listed in Table 3.4.4-9. The impact on global mean surface 

27 temperature due to assumptions concerning global emissions of GHG is also important. 

28 The sensitivity of the simulated sea-level rise to change in climate sensitivity and global GHG emissions 

29 mirrors that of global temperature, as shown in Table 3.4.4-9. Scenarios with lower climate sensitivities 

30 have lower increases in sea-level rise. Also, the reduction in the increase in sea-level rise is lower under 

31 the Preferred Alternative compared to the No Action Alternative. Conversely, scenarios with higher 

32 climate sensitivities have higher sea-level rise. The reduction in the increase of sea-level rise is greater 

33 under the Preferred Alternative compared to the No Action Alternative. The range in reduction of sea34 level rise under the Preferred Alternative compared to the No Action Alternative is 0.07 to 0.12 

35 centimeters (0.03 to 0.05 inch), depending on the climate sensitivity. 

 

43 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 3 Affected Environment and Environmental Consequences 3.4 Climate 

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Table 3.4.4-9 

CO2 concentration (ppm), Temperature (degrees C) 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) 

Sealevel 

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 

 2.0 439.9 510.0 762.4 0.698 1.166 2.284 28.61

 3.0 441.5 514.0 780.3 0.922 1.553 3.125 37.91

 4.5 443.3 518.7 802.5 1.166 1.987 4.119 48.55

Reduction compared to No Action 

 2.0 0.3 0.7 2.7 0.001 0.003 0.008 0.07

 3.0 0.3 0.8 2.7 0.001 0.004 0.010 0.09

 4.5 0.3 0.8 2.8 0.001 0.004 0.013 0.12

__________

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. 

1 
3.4 Climate Chapter 3 Affected Environment and Environmental Consequences 

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1 
Chapter 3 Affected Environment and Environmental Consequences 3.5 Other Potentially Affected Resource Areas 

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1 3.5 OTHER POTENTIALLY AFFECTED RESOURCE AREAS 

2 This section describes the affected environment and environmental consequences of the proposed 

3 action and alternatives on water resources (Section 3.5.1), biological resources (Section 3.5.2), land use 

4 and development (Section 3.5.3), safety and other impacts to human health (Section 3.5.4), hazardous 

5 materials and regulated wastes (Section 3.5.5), land uses protected under U.S. Department of 

6 Transportation Act Section 4(f) (Section 3.5.6), historic and cultural resources (Section 3.5.7), noise 

7 (Section 3.5.8), and environmental justice (Section 3.5.9). These sections describe the current and 

8 projected future threats to those resources from non-global climate change impacts relevant to the CAFE 

9 alternatives and provide primarily qualitative assessments of any potential consequences of the 

10 alternatives, positive or negative, on these resources. 

11 This section does not describe the affected environment in relation to, or address potential 

12 environmental consequences resulting from, global climate change. For a description of potential impacts 

13 resulting from global climate change, see Chapter 4. 

14 3.5.1 Water Resources 

15 3.5.1.1 Affected Environment 

16 Water resources include surface water and groundwater. Surface waters are water bodies open to 

17 the atmosphere, such as rivers, streams, lakes, oceans, and wetlands; surface waters can contain either 

18 fresh or salt water. Groundwater is found in natural reservoirs or aquifers below Earth’s surface. Sources 

19 of groundwater include rainfall and surface water, which penetrate the ground and recharge the water 

20 table. Sections 3.5.1.1.1 through 3.5.1.1.3 describe existing and projected future threats to these resources 

21 from non-global climate change impacts related to the proposed action. The production and combustion 

22 of fossil fuels, the production of biofuels, and shifts in the location of mining activities are the identified 

23 relevant sources of impact. Section 3.5.2 describes relevant aspects of surface water resources from a 

24 habitat perspective. For a discussion of the effects of global climate change on freshwater and coastal 

25 systems, see Sections 4.5.3 and 4.5.5. 

26 Impacts to water resources during recent decades have come from a number of sources, including 

27 increased water demand for human and agricultural use, pollution from point and non-point sources, and 

28 climatic changes. One of the major human-caused impacts to water quality has been the extraction, 

29 refining, and combustion of petroleum products, or oil. 

30 3.5.1.1.1 Oil Extraction and Refining 

31 Oil refineries, which produce gasoline and diesel fuel, and the motor vehicles that combust 

32 petroleum-based fuels, are major sources of VOCs, SO2, NOx, CO, and other air pollutants (EPA 1995a, 

33 EPA 1997a). In the atmosphere, SO2 and NOx contribute to the formation of acid rain (the wet, dry, or 

34 fog deposition of SO2 and NOx), which enters water bodies either directly or as runoff from terrestrial 

35 systems (see Section 3.3 for more information on air quality). Once in surface waters, these pollutants 

36 can cause acidification of the water body, changing the acidity or alkalinity (commonly called pH) of the 

37 system and affecting the function of freshwater ecosystems (Van Dam 1996, Baum 2001, EPA 2007). An 

38 EPA survey of sensitive freshwater lakes and streams (those with a low capacity to neutralize or buffer 

39 against decreases in pH) found that 75 percent of the lakes and 50 percent of the streams had experienced 

40 acidification as a result of acid rain (EPA 2007). EPA has identified the areas of the United States most 

41 sensitive to acid rain as the Adirondacks and Catskill Mountains in New York State, the mid-Appalachian 

42 highlands along the east coast, the upper Midwest, and mountainous areas of the western United States 

43 (EPA 2007). 
3.5 Other Potentially Affected Resource Areas Chapter 3 Affected Environment and Environmental Consequences 

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1 Water quality might also be affected by petroleum products released during the refining and 

2 distribution process. Oil spills can lead to contamination of surface water and groundwater and can result 

3 in impacts to drinking water and marine and freshwater ecosystems (see Section 3.5.2.1.1). EPA 

4 estimates that, of the volume of oil spilled in “harmful quantities,” as defined under the CAA, 83.8 

5 percent was deposited in internal/headland waters and within 3 miles of shore, with 17.5 percent spilled 

6 from pipelines, often in inland areas (EPA 2004). The environmental impacts to and recovery time for 

7 individual waterbodies vary based on several factors (e.g., salinity, water movement, wind, temperature), 

8 with locations of faster-moving and warm water recovering more quickly (EPA 2008c). 

9 During oil extraction, the primary waste product is highly saline liquid called “produced water,” 

10 which can contain metals and other potentially toxic components (see Section 3.5.5.1.1 for more on 

11 produced water). Produced water and other oil extraction wastes are most commonly disposed of by 

12 reinjecting them to the well, which increases pressure and can force out more oil. Potential impacts from 

13 these wastes generally occur when large amounts are spilled and they enter surface waters, when 

14 decommissioned wells are improperly sealed, or when saline water from the wells intrudes into fresh 

15 surface water or groundwater (Kharaka and Otton 2003). 

16 Water quality impacts also occur as a result of contamination by VOCs. A nationwide USGS 

17 study of groundwater aquifers found VOCs in 90 of 98 major aquifers sampled (Zogorski et al. 2006). 

18 The study concluded that “...[t]he widespread occurrence of VOCs indicates the ubiquitous nature of 

19 VOC sources and the vulnerability of many of the Nation’s aquifers to low-level VOC contamination.” 

20 Several of the most commonly identified VOCs were a gasoline additive (gasoline oxygenate – methyl 

21 tertiary butyl ether [MTBE]) and a gasoline hydrocarbon (toluene). USGS notes, however, that only 1 to 

22 2 percent of the well samples had concentrations of VOCs at levels that would be of potential concern to 

23 human health; none of the VOCs found in potentially hazardous quantities were primarily used in the 

24 manufacture of fuels or as fuel additives (Zogorski et al. 2006). Section 3.5.5 describes toxic chemicals 

25 released during fuel production and combustion. 

26 3.5.1.1.2 CO2 Emissions 

27 Oceanic concentrations of CO2 from anthropogenic (human-made) sources, primarily the 

28 combustion of fossil fuels, have increased since the Industrial Revolution and will likely continue to 

29 increase. In addition to its role as a GHG, atmospheric CO2 plays a key role in the biogeochemical cycle 

30 of carbon. Atmospheric CO2 concentrations influence the chemistry of natural waters. 

31 Atmospheric concentrations of CO2 are in equilibrium with aqueous (dissolved in water) carbonic 

32 acid, which in turn influences the aqueous concentrations of bicarbonate ion and carbonate ion. In natural 

33 waters, the carbonate system controls pH, which in turn controls the availability of some nutrients and 

34 toxic materials in freshwater and marine systems. 

35 One of the large-scale non-climatic effects of an increase in CO2 emissions is the potential for 

36 ocean acidification. The ocean exchanges huge quantities of CO2 with the atmosphere, and when 

37 atmospheric concentrations rise (due to anthropogenic emissions), there is a net flux from the atmosphere 

38 into the oceans. This decreases the pH of the oceans, reducing the availability of calcium. According to 

39 Richardson and Poloczanska (2008), “declines in ocean pH may impact calcifying organisms, from corals 

40 in the tropics to pteropods (winged snails) in polar ecosystems, and will take tens of thousands of years to 

41 reequilibrate to preindustrial conditions.” Section 4.7 provides more information on the non-climate 

42 effects of CO2 on plant and animal communities. 
Chapter 3 Affected Environment and Environmental Consequences 3.5 Other Potentially Affected Resource Areas 

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1 3.5.1.1.3 Biofuel Cultivation and Mining Activity 

2 The need to supply agricultural products for a growing population will continue to affect water 

3 resources; future irrigation needs are likely to include increased production of both food and biofuel crops 

4 (Simpson et al 2008). Global demand for water is increasing as a result of population growth and 

5 economic development and irrigation currently accounts for around 70 percent of global water 

6 withdrawals (Shiklomanov and Rodda 2003 in Kundzewicz et al. 2007). EPA states that “[d]emand for 

7 biofuels is also likely to have impacts on water including increasing land in agricultural production, 

8 resulting in increased risk of runoff of sediments, nutrients, and pesticides...[p]roduction of biofuels also 

9 uses significant amounts of water” (EPA 2008b). Runoff from agricultural sources often contains 

10 nitrogen, phosphorus, and other fertilizers and chemicals that harm water quality and can lead to 

11 eutrophication (the enrichment of a water body with plant-essential nutrients that can ultimately lead to 

12 oxygen depletion) (Vitousek et al. 1997, as in Fischlin et al. 2007). If biofuel production in the United 

13 States continues to be based on input-intensive crops like corn and soybeans, projected expansions to 

14 meet demand likely will result in significantly increased runoff of fertilizer and sediment (Simpson 2008). 

15 Shifts toward fuel-saving lighter vehicles, either as a result of consumer preference for fuel16 efficient vehicles or downweighting-design decisions by manufacturers, might result in changes in mining 

17 land-use patterns with resulting impacts to water quality (see Section 3.5.3.1.1). Metal mining results in 

18 impacts to water resources via run-off sedimentation from cleared mining sites and degradation of 

19 groundwater quality or quantity due to excavation and extraction activities (EPA 1995a). Shifts in 

20 demand for lighter vehicles could mean that areas with iron deposits would experience less mining 

21 activity, while areas where commonly used light-weight metals (such as aluminum or magnesium) might 

22 experience an increase in mining and related water impacts. 

23 3.5.1.2 Environmental Consequences 

24 As discussed in Section 3.3, each action alternative is generally expected to decrease the amount 

of VOCs, SO2, 25 NOx, and other air pollutants in relation to No Action Alternative (Alternative 1) levels. 

26 Reductions in these pollutant levels would be the result of lower petroleum fuel consumption by 

27 passenger cars and light trucks, and a potential for reduced extraction, transportation, and refining of 

28 crude oil. NHTSA expects that lower pollutant emissions would decrease the formation of acid rain in the 

29 atmosphere compared to the No Action Alternative, which in turn would have a beneficial impact on the 

quality of freshwater by decreasing eutrophication1 30 and acidification. As discussed in Section 3.4, the 

31 impact of the alternative CAFE standards on CO2 is relatively small compared to global emissions of 

32 CO2. The U.S. passenger-car and light-truck fleet represents less than 4 percent of the global emissions of 

33 CO2 from passenger cars and light trucks, and this contribution is projected to decline in the future, due 

34 primarily to rapid growth of emissions from developing countries. 

35 Each alternative could lead to an indirect increase in the production of biofuels and the use of 

36 more light-weight materials in vehicles, depending on the mix of methods manufacturers use to meet the 

37 increased CAFE standards, economic demand, and technological capabilities. If biofuel production 

38 increased, agricultural runoff could increase. If manufacturers opted for increased production of 

39 downweighted vehicles, shifts in the location of metal extraction could alternatively benefit water quality 

40 in locations of decreased activity, while negatively affecting it in areas of increased activity. However, 

41 due to uncertainty about how manufacturers would meet the new requirements, and the fact that none of 

 

1

 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 

 3-110 

1 the alternative CAFE standards prescribe increased biofuel use or vehicle downweighting, these potential 

2 impacts are not quantifiable. Section 3.5.4 provides additional information on vehicle downweighting.

3 3.5.2 Biological Resources 

4 3.5.2.1 Affected Environment 

5 Biological resources include vegetation, wildlife, and special status species (those classified as 

6 “threatened” or “endangered” under the Endangered Species Act). The U.S. Fish and Wildlife Service 

7 has jurisdiction over terrestrial and freshwater special status species and the National Marine Fisheries 

8 Service has jurisdiction over marine special status species. States and federal agencies, such as the 

9 Department of the Interior’s Bureau of Land Management, also have species of concern to which they 

10 have assigned additional protections. Sections 3.5.2.1.1 through 3.5.2.1.3 describe the existing and 

11 projected future threats to these biological resources from non-global climate change impacts related to 

12 the proposed action and alternatives. As discussed below, the production and combustion of fossil fuels, 

13 the cultivation and production of biofuels from agricultural crops, and shifts in the location of mining 

14 activities are the identified relevant sources of impacts to biological resources. Section 4.5 describes the 

15 effects of global climate change on ecosystems. 

16 3.5.2.1.1 Petroleum Extraction and Refining 

17 Oil extraction activities could impact biological resources through habitat destruction and 

18 encroachment, raising concerns about their effects on the preservation of animal and plant populations 

19 and their habitats. Oil exploration and extraction result in intrusions into onshore and offshore natural 

20 habitats and can involve construction within natural habitats. “The general environmental effects of 

21 encroachment into natural habitats and the chronic effects of drilling and generating mud and discharge 

22 water on benthic (bottom-dwelling) populations, migratory bird populations, and marine mammals 

23 constitute serious environmental concerns for these ecosystems” (Borasin et al. 2002, in O’Rourke and 

24 Connolly 2003). 

25 Oil extraction and transportation can also result in spills of oil and hazardous materials. Oil 

26 contamination of aquatic and coastal habitats can directly smother small species and is dangerous to 

27 animals and fish if ingested or coated on their fur, skin, or scales. Oil refining and related activities result 

28 in chemical and thermal pollution of water, both of which can be harmful to animal and plant populations 

29 (Borasin et al. 2002, in O’Rourke and Connolly 2003). Offshore and onshore drilling and oil transport 

30 can lead to spills, vessel or pipeline breakage, and other accidents that release petroleum, toxic chemicals, 

31 and highly saline water into the environment and affect plant and animal communities. 

32 Oil extraction, refining, and transport activities, and the combustion of fuel during motor-vehicle 

33 operation, result in air emissions that affect air quality and can contribute to the production of acid rain. 

34 These effects can result in negative impacts to plants and animals. Once present in surface waters, air 

35 pollutants can cause acidification of waterbodies, changing the pH of the system and affecting the 

36 function of freshwater ecosystems. EPA (2008a) states: 

37 ...plants and animals living within an ecosystem are highly interdependent...Because of 

38 the connections between the many fish, plants, and other organisms living in an aquatic 

39 ecosystem, changes in pH or aluminum levels affect biodiversity as well. Thus, as lakes 

40 and streams become more acidic, the numbers and types of fish and other aquatic plants 

41 and animals that live in these waters decrease. 
Chapter 3 Affected Environment and Environmental Consequences 3.5 Other Potentially Affected Resource Areas 

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1 Acid rain has also been shown to affect forest ecosystems negatively, both directly and indirectly. 

2 These impacts include stunted tree growth and increased mortality, primarily as a result of the leaching of 

3 calcium and other soil nutrients (Driscoll et al. 2001, DeHayes et al. 1999, Baum 2001). Declines in 

4 biodiversity of aquatic species and changes in terrestrial habitats likely have ripple effects on other 

5 wildlife that depend on these resources. 

6 The combustion of fossil fuels and certain agricultural practices have lead to a disruption in the 

7 nitrogen cycle (the process by which gaseous nitrogen from the atmosphere is used and recycled by 

8 organisms) with serious repercussions for biological resources. Nitrogen-cycle disruption has occurred 

9 through the introduction of large amounts of anthropogenic nitrogen in the form of ammonium and 

10 nitrogen oxides to aquatic and terrestrial systems (Vitousek 1994). Increased availability of nitrogen in 

11 these systems is a major cause of eutrophication in freshwater and marine waterbodies. Eutrophic 

12 systems typically contain communities dominated by phytoplankton (free-floating microscopic plants). 

13 Eutrophication can ultimately result in the death of fish and other aquatic animals, as well as harmful 

14 algal blooms. Acid rain enhances eutrophication of aquatic systems through the deposition of additional 

15 nitrogen (Lindberg 2007). Introduction of large quantities of nitrogen to certain terrestrial systems has 

16 also been predicted to lead to an increase in decomposing soil bacteria and subsequent increase in the 

17 release of CO2 into the atmosphere as these bacteria consume organic matter (Black 2008). 

18 3.5.2.1.2 CO2 Emissions 

19 Ocean acidification as a result of increasing concentrations of atmospheric CO2, primarily from 

20 the combustion of fossil fuels, is expected to affect calciferous marine organisms. In conjunction with 

21 rapid climate change, ocean acidification could pose severe threats to coral reef ecosystems. Hoegh22 Guldberg et al. (2007) state that “[u]nder conditions expected in the 21st century, global warming and 

23 ocean acidification will compromise carbonate accretion, with corals becoming increasingly rare on reef 

24 systems. The result will be less diverse reef communities and carbonate reef structures that fail to be 

25 maintained.” 

26 In contrast to its potential adverse effect on the productivity of marine ecosystems, higher CO2

27 concentrations in the atmosphere could increase the productivity of terrestrial systems, because plants use 

28 CO2 as an input to photosynthesis. The IPCC Fourth Assessment Report states that “[o]n physiological 

29 grounds, almost all models predict stimulation of carbon assimilation and sequestration in response to 

30 rising CO2, called CO2 fertilization” (Denman et al. 2007). 

31 Under bench-scale and field-scale experimental conditions, several investigators have found that 

32 higher concentrations have a “fertilizer” effect on plant growth (e.g., Long et al. 2006, Schimel et al.

33 2000). IPCC reviewed and synthesized field and chamber studies, finding that: 

34 There is a large range of responses, with woody plants consistently showing NPP [net 

35 primary productivity] increases of 23 to 25 percent (Norby et al. 2005), but much smaller 

36 increases for grain crops (Ainsworth and Long 2005)...Overall, about two-thirds of the 

37 experiments show positive response to increased CO2 (Ainsworth and Long 2005, 

38 Denman et al. 2007). Since saturation of CO2 stimulation due to nutrient or other 

39 limitations is common (Dukes et al. 2005, Körner et al. 2005, both in Denman et al.

40 2007), it is not yet clear how strong the CO2 fertilization effect actually is. 

41 The CO2 fertilization effect could mitigate some of the increase in atmospheric CO2

42 concentrations by resulting in more storage of carbon in vegetation. 
3.5 Other Potentially Affected Resource Areas Chapter 3 Affected Environment and Environmental Consequences 

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1 Increased atmospheric CO2, in conjunction with other environmental factors and changes in plant 

2 communities, could alter growth, abundance, and respiration rates of some soil microbes (Lipson et al.

3 2005, Chung et al. 2007, Lesaulnier et al. 2008). Section 4.7 provides more information on the non4 climate effects of CO2 on plant and animal communities. 

5 3.5.2.1.3 Land Disturbances Due to Biofuel Production and Mining 

6 Future demands for biofuel production are predicted to require increased commitments of land to 

7 agricultural production (EPA 2008b). Placing additional land into agricultural production or returning 

8 marginal agricultural land to production to grow perennial grass or trees for use in cellulosic ethanol 

9 production would decrease the area available as natural habitat. A decrease in habitat and potential 

10 habitat for plants and animal species would likely result in negative impacts to certain species. Increased 

11 agriculture production would also likely result in increased surface runoff of sediments and fertilizers. 

12 Additional fertilizer inputs to water could increase eutrophication and associated impacts. Sediment 

13 runoff can settle to the bottom of waterbodies and degrade essential habitat for some species of aquatic 

14 organisms, bury food sources and areas used for spawning, and kill benthic organisms (EPA 2000a). 

15 As stated in Section 3.5.1.1.3, a shift toward lighter vehicles would likely result in changes to 

16 mining land-use patterns and impacts to water quality; such changes could affect aquatic and terrestrial 

17 ecosystems. EPA notes that mining activities could result in the destruction of terrestrial habitat, loss of 

18 fish populations due to water-quality impacts, and a loss of plants due to increased dust (EPA 1995a). As 

19 previously stated, such a shift would likely be beneficial in areas of decreased activity and detrimental in 

20 areas of increased activity. 

21 3.5.2.1.4 Endangered Species 

22 Off-shore drilling, on-shore oil and gas drilling, and roads created to access remote extraction 

23 sites through habitats used by threatened or endangered species might also affect these plants and animals 

24 both directly, through loss of individual animals or habitat, and indirectly, through water-quality 

25 degradation or cumulative impacts with other projects. Loss of potential habitat to the production of 

26 biofuels could also result in negative impacts to some species (e.g., diminished potential for habitat 

27 expansion, increased runoff-related impacts). 

28 Increased anthropogenic inputs of nitrogen to terrestrial, aquatic, and microbial communities 

29 containing rare plants and animals could also affect threatened and endangered species. In ecosystems 

30 with certain vegetation and soil types, this increased nitrogen availability can result in reduced 

31 biodiversity or the exclusion of certain endemic species in favor of those adapted to make use of these 

32 nutrients to their competitive advantage (Bobbink et al. 1998, Fenn et al. 2003, Weiss 1999). For 

33 example, the decline of certain nutrient-poor native grasslands in California, which serve as critical 

34 habitat for the Bay checkerspot butterfly, is likely partially due to an increase in invasive grass species 

35 made possible by such nutrient inputs (Weiss 1999). 

36 3.5.2.2 Environmental Consequences 

37 The decrease in overall fuel consumption by passenger cars and light trucks, anticipated under all 

38 of the alternatives except the No Action Alternative, could lead to reductions in oil exploration, 

39 extraction, transportation, and refining. NHTSA expects that a reduction in these activities would result 

40 in decreased impacts to on- and off-shore habitat and plant and animal species. This decrease could have 

41 a small overall benefit to plants and animals, primarily through decreased levels of direct ground 

42 disturbance and releases of oil and hazardous materials. Reductions in the rate of fuel consumption 

43 increase under all of the alternatives compared to the No Action Alternative would lead to overall 
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1 decreases in the release of SO2 and NOx. Reductions in acid rain and anthropogenic nutrient deposition 

2 could lower levels of eutrophication in surface waters and could slow direct impacts to ecosystems and to 

3 soil leaching. 

4 Reductions in the rate of fuel consumption increase would also lead to a decrease in the release of 

5 CO2 compared to the No Action Alternative. Lower levels of atmospheric CO2 could slow projected 

6 effects to terrestrial plant growth, calciferous marine organisms, and microorganisms. However, as 

7 discussed in Section 3.5.1.2, the reduction in CO2 as a result of the proposed action and alternatives 

8 would be relatively small compared to current and projected global CO2 releases (see Chapter 2 and 

9 Section 3.3). 

10 The alternatives could lead to an increase in the production of biofuels and mining for light11 weight raw materials, depending on the mix of methods manufacturers use to meet the new CAFE 

12 standards, economic demands from consumers and manufacturers, and technological developments. 

13 Depending on these factors, increased production of biofuels could result in the conversion of existing 

14 food-agricultural lands and non-agricultural areas to biofuel crop production. This change in land use 

15 would have implications for environmental issues associated with fertilizer runoff, water-body 

16 eutrophication, and sediment runoff effects to aquatic-organism food and spawning habitat. Similarly, 

17 increased mining land-disturbance activities could affect aquatic health due to increased sedimentation. 

18 However, due to the uncertainty surrounding how manufacturers would meet the new requirements and 

19 the fact that none of the alternatives analyzed prescribe increased biofuel use or vehicle downweighting, 

20 these potential effects are not quantifiable. 

21 NHTSA is exploring its Section 7 obligations under the Endangered Species Act. 

22 3.5.3 Land Use and Development 

23 3.5.3.1 Affected Environment 

24 Land use and development refers to human activities that alter land (e.g., industrial and 

25 residential construction in urban and rural settings, clearing of natural habitat for agricultural or industrial 

26 use) and could affect the amount of carbon or biomass in existing forest or soil stocks in the affected 

27 areas. For purposes of this analysis, shifts in agricultural and mining production and changes to 

28 manufacturing plants that produce passenger cars and light trucks are the identified relevant sources of 

29 impact. 

30 3.5.3.1.1 Changes in Agricultural Production and Mining 

31 Biofuel production is predicted to require increased devotion of land to agricultural production 

32 (EPA 2008b, Keeney and Hertel 2008). Converting areas into cropland would decrease the overall land 

33 area kept in a natural state and the potential area available for other uses (such as commercial 

34 development or pastureland) (Keeney and Hertel 2008). There is uncertainty regarding how much 

35 additional land could be required to meet projected biofuel needs in the United States, and how an 

36 increase in biofuel production could affect other land uses (Keeney and Hertel 2008). 

37 Shifts toward fuel-saving lighter vehicles, either as a result of consumer preference for fuel38 efficient vehicles or downweighting design decisions by manufacturers, might result in changes in mining 

39 land-use patterns. Mining for the minerals needed to construct these lighter vehicles (primarily aluminum 

40 and magnesium) could shift some metal-extraction activities to areas rich in these resources. 

41 Schexnayder et al. (2001) noted that such a shift in materials “could reduce mining for iron ore in the 

42 United States, but increase the mining of bauxite for aluminum, magnesium, titanium, and other materials 
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1 in such major countries as Canada, China, and Russia and in many small, developing countries, such as 

2 Guinea, Jamaica, and Sierra Leone.” 

3 3.5.3.1.2 Manufacturing Changes 

4 Recent shifts in consumer demand in the United States away from less-fuel-efficient vehicles 

5 have begun to change the types of vehicles produced and the manufacturing plants where they are made. 

6 Sharp decreases in demand for trucks and SUVs have recently resulted in plant closures and production 

7 shifts to plants where small cars and gas-electric hybrid vehicles are made (WWJ News Radio 2008, 

8 Keenan and Mckenna 2008, Bunkley 2008). 

9 3.5.3.2 Environmental Consequences 

10 The CAFE alternatives could lead to an increase in the production of biofuels and lighter 

11 vehicles, depending on the mix of methods manufacturers use to meet the new CAFE standards, 

12 economic demands from consumers and manufacturers, and technological developments. Depending on 

13 these factors, increased production of biofuels could result in the conversion of existing food-agricultural 

14 lands and natural areas to the production of these fuel crops. Depending on how manufacturers achieve 

15 reductions in vehicle weight, downweighted vehicles could result in shifts in mining from areas 

16 containing iron to those containing aluminum and magnesium, and shifts from facilities that process iron 

17 ore (for iron and steel) to those that process bauxite (for aluminum) and brine (for magnesium). These 

18 changes would have implications for environmental issues associated with land use and development, and 

19 material processing. However, due to the uncertainty surrounding how manufacturers would meet the 

20 new requirements and the fact that none of the analyzed alternatives prescribe increased biofuel use or 

21 vehicle downweighting (much less specific engineering and materials shifts to reduce vehicle mass), these 

22 potential environmental impacts are not quantifiable. See Section 3.5.4 for more information on vehicle 

23 downweighting. 

24 Major changes to manufacturing facilities, such as those occurring with the apparent shift in 

25 consumer demand toward more fuel-efficient vehicles, might have implications for environmental issues 

26 associated with land use and development. However, NHTSA’s review of existing and available 

27 technologies and capabilities shows that the CAFE standards under all the action alternatives can be met 

28 by existing and planned manufacturing facilities. Because of the availability of sufficient existing and 

29 planned capacity, and because none of the alternatives prescribe particular technologies for meeting these 

30 standards, the various alternatives are not projected to force changes in product mixes that would result in 

31 plant changes. 

32 3.5.4 Safety and Other Impacts to Human Health 

33 NHTSA has analyzed how future improvements in fuel economy might affect human health and 

34 welfare through vehicle safety performance and the rate of traffic fatalities. The agency also considered 

35 how the new standards might affect energy concerns, which could have ramifications for family health 

36 and welfare. For more details on this analysis, see Section IV of the joint preamble and Chapter 9 of the 

37 RIA. 

38 
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1 3.5.5 Hazardous Materials and Regulated Wastes 

2 3.5.5.1 Affected Environment 

3 Hazardous wastes are defined here as solid wastes, which also include certain liquid or gaseous 

4 materials, that because of their quantity and concentration, or their physical, chemical, or infectious 

5 characteristics, could cause or contribute to an increase in mortality or an increase in serious irreversible 

6 or incapacitating reversible illness or could pose a substantial hazard to human health or the environment 

7 when improperly treated, stored, used, transported, disposed of, or otherwise managed. Hazardous wastes 

8 are generally designated as such by individual states or EPA under the Resource Conservation and 

9 Recovery Act of 1976. Additional federal and state legislation and regulations, such as the Federal 

10 Insecticide, Fungicide, and Rodenticide Act, determine handling and notification standards for other 

11 potentially toxic substances. For purposes of this analysis, hazardous materials and wastes generated 

12 during the oil-extraction and refining processes and by agricultural production and mining activities are 

13 the identified relevant sources of impact. 

14 3.5.5.1.1 Wastes Produced during the Extraction Phase of Oil Production 

15 The primary waste created during the extraction of oil is “produced water,” highly saline water 

16 pumped from oil and gas wells during mining (American Petroleum Institute 2000, EPA 2000b). In 1995, 

17 the onshore oil and gas industry produced approximately 15 billion barrels of produced water (American 

18 Petroleum Institute 2000). Produced water is generally “highly saline (total dissolved solids may exceed 

19 350,000 milligrams per liter [mg/L]), may contain toxic metals, organic and inorganic components, and 

20 radium-226/228 and other naturally occurring radioactive materials” (Kharaka and Otton 2003). Drilling 

21 wastes, primarily mud and rock cuttings, account for 149 million barrels of extraction wastes. 

22 “Associated wastes,” generally the most hazardous wastes produced during extraction (often containing 

23 benzenes, arsenic, and toxic metals), account for another 22 million barrels (The American Petroleum 

24 Institute 2000, EPA 2000b). 

25 Wastes produced during oil and gas extraction have been known to have serious environmental 

26 effects on soil, water, and ecosystems (Kharaka and Otton 2003, O’Rourke and Connolly 2003). Onshore 

27 environmental effects result “primarily from the improper disposal of large volumes of saline water 

28 produced with oil and gas, from accidental hydrocarbon and produced water releases, and from 

29 abandoned oil wells that were not correctly sealed” (Kharaka and Otton 2003). Offshore effects result 

30 from improperly treated produced water released into the waters surrounding the oil platform (EPA 

31 2000b). 

32 3.5.5.1.2 Wastes Produced during the Refining Phase of Oil Production 

33 Wastes produced during the petroleum-refining process are primarily released to the air and 

34 water, accounting for 75 percent (air emissions) and 24 percent (wastewater discharges) of the total (EPA 

35 1995a). EPA defines a release as the “on-site discharge of a toxic chemical to the environment... 

36 emissions to the air, discharges to bodies of water, releases at the facility to land, as well as contained 

37 disposal into underground injection wells” (EPA 1995a). EPA reports that nine of the 10 most common 

38 toxic substances released by the petroleum-refining industry are volatile chemicals, highly reactive 

39 substances prone to state changes or combustion, that include benzene, toluene, ethylbenzene, xylene, 

40 cyclohexane, 1,2,4-trimethylbenzene and ethylbenze (EPA 1995a). These substances are present in crude 

41 oil and in finished petroleum products. Other potentially dangerous substances commonly released 

42 during the refining process include ammonia, gasoline additives (methanol, ethanol, and MTBE), and 

43 chemical feedstocks (propylene, ethylene, and napthalene) (EPA 1995a). Spent sulfuric acid is by far the 
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1 most commonly produced toxic substance; however, it is generally reclaimed instead of released or 

2 transferred for disposal (EPA 1995a). 

3 Wastes released during the oil-refining process can cause environmental impacts to water quality, 

4 air quality, and human health. The volatile chemicals released during the refining process are known to 

5 react in the atmosphere and contribute to ground-level ozone and smog (EPA 1995a). Several of the 

6 produced volatile chemicals are also known or suspected carcinogens and many others are known to 

7 cause respiratory problems and impair internal-organ functions, particularly in the liver and kidneys (EPA 

8 1995a). Ammonia is a form of nitrogen and can contribute to eutrophication in surface waters. 

9 3.5.5.1.3 Agricultural Materials 

10 Agricultural production, especially of the type required to grow the corn and soybeans most 

11 commonly used to produce biofuels in the United States, also results in the release of potentially 

12 hazardous materials and wastes. Wastes from agricultural production can include pesticide (insecticides, 

13 rodenticides, fungicides, and herbicides) and fertilizer runoff and leaching, wastes used in the 

14 maintenance and operation of agricultural machinery (used oil, fuel spills, organic solvents, metal 

15 machining wastes, spent batteries), and other assorted process wastes (EPA 2000c). 

16 Agricultural wastes in the form of runoff from agricultural fields can cause environmental 

17 impacts to water and human health. Fertilizers can run off into surface waters and cause eutrophication, 

18 while pesticides can directly affect beneficial insects and wildlife (EPA 2000c). A National Renewable 

19 Energy Lab report concludes that the negative environmental impacts on soil and water due to impacts of 

20 increased biofuel production are likely to occur disproportionately in the Midwest, where most of these 

21 crops are grown (Powers 2005). Human health can also be affected by improperly handled or applied 

22 pesticides, with potential effects ranging from minor respiratory or skin inflammation to death (EPA 

23 2000c). Nitrogen fertilizer runoff to drinking-water sources can lead to methemoglobinemia, the 

24 potentially fatal binding of a form of nitrogen to hemoglobin in infants (Powers 2005). 

25 Ethanol, as a biofuel additive to gasoline, is suspected of enhancing the plume size after a 

26 gasoline-blended ethanol spill and might decrease degradation of the spilled hydrocarbon and related 

27 compounds, such as benzene (Powers et al. 2001, Deeb et al. 2002, Williams et al. 2003). 

28 3.5.5.1.4 Automobile Production and Assembly 

29 Motor vehicles and the motor vehicle equipment industry, and businesses engaged in the 

30 manufacture and assembly of cars, trucks, and buses produce hazardous materials and toxic substances. 

31 EPA reports that solvents (xylene, methyl ethyl ketone, acetone, etc.) are the most commonly released 

32 toxic substances it tracks for this industry (EPA 1995a). These solvents are used to clean metal and in the 

33 vehicle-finishing process during assembly and painting (EPA 1995a). Other industry wastes include 

34 metal paint and component-part scrap. 

35 In addition, studies have suggested that the substitution of lighter-weight materials (such as 

36 aluminum, magnesium, titanium, or plastic) for steel and iron to increase fuel efficiency could increase 

37 the total waste stream resulting from automobile manufacturing (Schexnayder et al. 2001). Mining 

38 wastes generated during the extraction of these lighter raw materials would likely increase substantially, 

39 primarily due to aluminum mining, and other production wastes (e.g., from refining of aluminum and 

40 plastic manufacturing) could also increase (Schexnayder et al. 2001, Dhingra et al. 1999). The extraction 

41 and processing of these metals and the production of manmade fibers and plastics also generate various 

42 hazardous wastes (EPA 1995b, EPA 1997b). An assessment of the solid and hazardous wastes generated 

43 during the production of three light-weight concept cars concluded the net generation of waste would 
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1 increase versus conventional vehicles; however, the study also noted that the generation of most 

2 hazardous materials of particular concern to human health (e.g., cadmium, chlorine, lead) emitted during 

3 the production of vehicles appeared to decrease in the vehicle models analyzed (Schexnayder et al. 2001). 

4 Recycling of vehicles at the end of the vehicle life could help to offset some of the projected net increase 

5 in waste production versus primarily steel/iron construction vehicles. 

6 3.5.5.1.5 CO2 Emissions 

7 CO2 is not classified as a hazardous material or regulated waste. For a discussion of the release 

8 of CO2 relevant to the proposed action and alternatives and its impacts on climate change, see Section 3.4. 

9 For a discussion of the impacts of CO2 on water resources, see Section 3.5.1.1.2. For a discussion of the 

10 impacts of CO2 on biological resources, see Section 3.5.2.1.2. 

11 3.5.5.2 Environmental Consequences 

12 The projected reduction in fuel production and consumption as a result of the proposed action and 

13 alternatives could lead to a reduction in the amount of hazardous materials and wastes created by the oil14 extraction and refining industries. NHTSA expects corresponding decreases in the associated 

15 environmental and health impacts of these substances. However, these effects would likely be small if 

16 they occurred, because of the limited overall effect of the proposed action and alternatives on these areas. 

17 All of the alternatives could lead to an increase in the production of biofuels and the use of more 

18 light-weight materials in vehicles, depending on the mix of methods manufacturers use to meet the new 

19 CAFE standards, economic demands from consumers and manufacturers, and technological 

20 developments. If biofuel production increased, these could be additional runoff of agricultural fertilizers 

21 and pesticides; if manufacturers pursued vehicle downweighting, these could be a net increase in the 

22 waste stream. However, due to the uncertainty surrounding how manufacturers would meet the new 

23 requirements and the fact that none of the alternatives analyzed prescribes increased biofuel use or vehicle 

24 downweighting (or specific means of vehicle downweighting), these potential impacts are not 

25 quantifiable. See Section 3.5.4 for additional information on vehicle downweighting. 

26 3.5.6 Land Uses Protected under U.S. Department of Transportation Act Section 4(f) 

27 3.5.6.1 Affected Environment 

28 Section 4(f) resources are publicly owned parks, recreational areas, wildlife and waterfowl 

29 refuges, or public and private historical sites to which the DOT gives special consideration. Originally 

30 included as part of the Department of Transportation Act of 1966, Section 4(f) stipulates that DOT 

31 agencies cannot approve the use of land from publicly owned parks, recreational areas, wildlife and 

32 waterfowl refuges, or public and private historical sites unless “(1) there is no feasible and prudent 

33 alternative to the use of such land, and (2) such program includes all possible planning to minimize harm 

34 to such park, recreational area, wildlife and waterfowl refuge, or historic site resulting from such use.” 49 

35 U.S.C. 303. 

36 3.5.6.2 Environmental Consequences 

37 “Section 4(f) only applies where land is permanently incorporated into a transportation facility 

38 and when the primary purpose of the activity on the 4(f) resource is for transportation” (FHWA 2005). 

39 Because the proposed action in this EIS does not meet these criteria, Section 4(f) does not apply. 
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1 3.5.7 Historic and Cultural Resources 

2 3.5.7.1 Affected Environment 

3 The National Historic Preservation Act of 1966 (16 U.S.C. 470 et seq.), Section 106, states that 

4 agencies of the Federal Government must take into account the impacts of their action to historic 

5 properties; the regulations to meet this requirement can be found at 36 CFR Part 800. This process, 

6 known as the “Section 106 process,” is intended to support historic preservation and mitigate impacts to 

7 significant historical or archeological properties through the coordination of federal agencies, states, and 

8 other affected parties. Historic properties are generally identified through the National Register of 

9 Historic Places, which lists properties of significance to the United States or a particular locale because of 

10 their setting or location, contribution to or association with history, or unique craftsmanship or materials. 

11 National Register-eligible properties must also be sites “A. That are associated with events that have 

12 made a significant contribution to the broad patterns of our history; or B. That are associated with the 

13 lives of persons significant in our past; or C. That embody the distinctive characteristics of a type, period, 

14 or method of construction, or that represent the work of a master, or that possess high artistic values, or 

15 that represent a significant and distinguishable entity whose components may lack individual distinction; 

16 or D. That have yielded, or may be likely to yield, information important in prehistory or history.” 36 

17 CFR 60.4. Acid rain as a result of the processing of petroleum products and the combustion of 

18 petroleum-based fuels is the identified relevant source of impact to historic and cultural resources for this 

19 analysis. 

20 Acid rain, the primary source of which is the combustion of fossil fuels, is one cause of 

21 degradation to exposed cultural resources and historic sites. EPA states that “[a]cid rain and the dry 

22 deposition of acidic particles contribute to the corrosion of metals (such as bronze) and the deterioration 

23 of paint and stone (such as marble and limestone). These effects substantially reduce the societal value of 

24 buildings, bridges, cultural objects (such as statues, monuments, and tombstones), and cars” (EPA 2007). 

25 3.5.7.2 Environmental Consequences 

26 The projected reduction in fuel production and combustion as a result of the proposed action and 

27 alternatives could lead to a minor reduction in the amount of pollutants that cause acid rain. A decrease in 

28 the production of such pollutants could result in a corresponding decrease in the amount of damage to 

29 historic and other structures caused by acid rain. However, such effects are not quantifiable. 

30 3.5.8 Noise 

31 3.5.8.1 Affected Environment 

32 Excessive amounts of noise, which is measured in decibels, can present a disturbance and a 

33 hazard to human health at certain levels. Potential health hazards from noise range from annoyance 

34 (sleep disturbance, lack of concentration, and stress) to hearing loss at high levels (Delucchi and Hsu 

35 1998, Geary 1998, Fleming et al. 2005). Motor-vehicle noise also affects property values. A study of the 

36 impacts of roadway noise on property values estimated this cost to be roughly 3 billion dollars in 1991 

37 dollars (Delucchi and Hsu 1998). The noise from motor vehicles has been shown to be one of the primary 

38 causes of noise disturbance in homes (OECD 1988, in Delucchi and Hsu 1998, and Geary 1998). Noise 

39 generated by vehicles causes inconvenience, irritation, and potentially even discomfort to occupants of 

40 other vehicles, to pedestrians and other bystanders, and to residents or occupants of surrounding property. 
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1 3.5.8.2 Environmental Consequences 

2 As a result of the rebound effect (the increase in VMT as the cost per mile for fuel decreases), 

3 NHTSA predicts that there will be increased vehicle use under all of the alternatives; higher overall VMT 

4 would result in increases in vehicle road noise. However, determining if there will be noise impacts is not 

5 possible based on available data. Noise levels are location specific, meaning factors such as the time of 

6 day at which increases in traffic occur, existing ambient noise levels, the presence or absence of noise 

7 abatement structures, and the location of schools, residences, and other sensitive noise receptors all 

8 influence whether there will be noise impacts. 

9 All of the alternatives could lead to an increase in use of hybrid vehicles, depending on the mix of 

10 methods manufacturers use to meet the new CAFE standards, economic demands from consumers and 

11 manufacturers, and technological developments. An increased percentage of hybrid vehicles could result 

12 in reduced road noise, potentially offsetting some of the increase in road noise predicted to result from 

13 increased VMT. However, due to the uncertainty surrounding how manufacturers would meet the new 

14 requirements, the fact that none of the alternatives prescribes increased production of hybrid vehicles, and 

15 the location-specific nature of noise impacts, these potential impacts are not quantifiable. 

16 3.5.9 Environmental Justice 

17 3.5.9.1 Affected Environment 

18 Federal agencies must identify and address disproportionately high and adverse impacts to 

19 minority and low-income populations in the United States (Executive Order 12898, Federal Actions to 

20 Address Environmental Justice in Minority Populations and Low-Income Populations). DOT Order 

21 5610.2 establishes the process the Department uses to “incorporate environmental justice principles (as 

22 embodied in the Executive Order) into existing programs, policies, and activities.” The production and 

23 use of fossil fuels and the production of biofuels are the identified relevant sources of impact to 

24 environmental populations for this analysis. For a discussion of the effects of climate change on 

25 environmental justice populations, see Section 4.6. 

26 Numerous studies have noted that there appears to be a historic and ongoing relationship between 

27 the environmental impacts of petroleum extraction, processing, and use and environmental justice 

28 populations (Pastor et al. 2001, O’Rourke and Connolly 2003, Lynch et al. 2004, Hymel 2007, Srinivasan 

29 et al. 2003). 

30 Potential impacts of the oil exploration and extraction process on environmental justice 

31 communities include “human health and safety risks for neighboring communities and oil industry 

32 workers, and displacement of indigenous communities” (O’Rourke and Connolly 2003). Subsistence-use 

33 activities (collecting plants or animals to fulfill basic needs for food, clothing, or shelter) can also be 

34 affected by extraction and exploration through the direct loss of subsistence-use areas or impacts to 

35 culturally/economically important plants and animals as a result of a spill or hazardous-material release 

36 (O’Rourke and Connolly 2003, Kharaka and Otton 2003). 

37 It has been shown that minority and low income populations often disproportionately reside near 

38 high-risk polluting facilities, such as oil refineries (Pastor et al. 2001, Graham et al. 1999, O’Rourke and 

39 Connolly 2003), and “mobile” sources of air toxins and pollutants, as in the case of populations residing 

40 near highways (Morello-Frosch 2002, Jerrett et al. 2001, O’Neill et al. 2003). Populations near refineries 

41 could be disproportionately affected by exposure to potentially dangerous petroleum and by-products of 

42 the refining process, such as benzene (Borasin et. al 2002). Exposure to the toxic chemicals associated 

43 with refineries, primarily by refinery workers, has been shown to be related to increases in certain 

44 diseases and types of cancer (Pukkala 1998, Chan et al. 2006); the precise nature and severity of these 
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1 health impacts are still under debate. Pollutants from transportation sources, such as NO2 and CO from 

2 roadway traffic, are often unevenly distributed and tend to remain near their release locations (O’Neill et 

3 al. 2003). A correlation between this uneven distribution of some pollutants and minority and low 

4 income populations has been documented, demonstrating the potential for a disproportionate allocation of 

5 the health impacts of these air pollutants to environmental justice populations (Jerret et al. 2001, Morello6 Frosch 2002). Recent reviews by health and medical researchers indicate a general consensus that 

7 proximity to high-traffic roadways could result in health effects in the areas of cardiovascular health 

8 (Adar and Kaufman 2007), and asthma and respiratory health (Heinrich and Wichmann 2004, Salam et al.

9 2008). The exact nature of the relationship between these health impacts, traffic-related emissions, and 

10 the influence of confounding factors such as traffic noise are not known at this time (Samet 2007). 

11 The production of biofuels could, depending on the mix of agricultural crops or crop residues 

12 used in its production, affect food prices. The International Food Policy Research Institute states, “An 

13 aggressive biofuel scenario that assumes that current plans for expansion of the sector in Africa, Asia, 

14 Europe, and North and South America are actually realized could lead to substantial price increases for 

15 some food crops by 2020 – about 80 percent for oilseeds and about 40 percent for maize – unless new 

16 technologies are developed that increase efficiency and productivity in both crop production and biofuel 

17 processing” (von Braun and Pachauri 2006). Such an increase in food prices would disproportionately 

18 affect low income populations, because these groups typically spend a larger share of their incomes on 

19 food. 

20 3.5.9.2 Environmental Consequences 

21 The projected reduction in fuel production and consumption as a result of the action alternatives 

22 could lead to a minor reduction in the amount of direct land disturbance as a result of oil exploration and 

23 extraction, and the amount of air pollution produced by the oil refineries. There could be corresponding 

24 decreases in impacts on environmental justice populations as a result of the alternatives, but the effects of 

25 any such decreases are not quantifiable and would likely be minor, if they occurred. 

26 As discussed in Section 3.3, the overall decrease in emissions predicted to occur as a result of the 

27 proposed new CAFE standards is not evenly distributed due to the increase in VMT from the rebound 

28 effect and regional changes in upstream emissions. As a result, some criteria and toxic air pollutants are 

29 predicted to increase in some air quality nonattainment areas. The large size of each nonattainment area 

30 and the minor emissions increases in affected nonattainment and other areas make it unlikely that there 

31 would be disproportionate effects to environmental justice populations. 

32 All of the alternatives could lead to an increase in the production of biofuels, depending on the 

33 mix of methods manufacturers use to meet the increased CAFE standards, economic demands from 

34 consumers and manufacturers, and technological developments. If grain-based biofuel production 

35 increases, there could be effects on food prices. However, because of the uncertainty surrounding how 

36 manufacturers would meet the new requirements, and the fact that none of the alternatives prescribes 

37 increased biofuel use, these potential impacts are not quantifiable. 

38 
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1 3.6 UNAVOIDABLE IMPACTS AND IRREVERSIBLE AND IRRETRIEVABLE RESOURCE 

2 COMMITMENT 

3 3.6.1 Unavoidable Adverse Impacts 

4 The National Highway Traffic Safety Administration (NHTSA) proposed action is to implement 

5 new Corporate Average Fuel Economy (CAFE) standards for model years (MY) 2012-2016. Under 

6 Alternative 1 (No Action), neither NHTSA nor EPA would issue a rule regarding fuel economy or GHG 

7 emissions for MY 2012-2016. Each of the eight action alternatives (Alternatives 2 through 9) would 

8 result in a decrease in carbon dioxide (CO2) emissions and associated climate change effects and a 

9 decrease in energy consumption as compared to the No Action Alternative. However, total energy 

10 consumption and CO2 emissions by U.S. passenger cars and light trucks are projected to continue to 

11 increase under all of the alternatives as a result of projected increases in the number of these vehicles in 

12 use and the total number of miles they are driven each year (as measured by vehicle miles traveled, or 

13 VMT). 

14 Based on NHTSA’s current understanding of global climate change, certain effects are likely to 

15 occur as a consequence of accumulated total greenhouse gas (GHG) emissions in Earth’s atmosphere. 

16 Neither the proposed action nor its alternatives would prevent these effects. As described in Section 

17 3.4.4.2, each of the action alternatives could contribute to reductions in global GHG emissions from the 

18 levels that would occur if average fuel economy were to continue at its current levels, thus diminishing 

19 these anticipated changes in the global climate. 

20 Oxides of nitrogen (NOx), particulate matter (PM2.5), oxides of sulfur (SOx), volatile organic 

21 compounds (VOCs), benzene, 1,3-butadiene, and diesel particulate matter (DPM) exhibit decreases in 

22 emissions for all action alternatives and analysis years as compared to their levels under the No Action 

23 Alternative. Any negative health impacts associated with these emissions are expected to be similarly 

24 reduced, and there would be no unavoidable negative impacts of these emissions. 

25 According to NHTSA’s analysis, emissions of carbon monoxide (CO) and acrolein could increase 

26 under certain alternatives from the levels that are projected under the No Action Alternative. Thus, the 

27 potential for unavoidable impacts depends on the selection of the final standards. The CO increases occur 

28 only under Alternatives 2 through 4 and are approximately 0.7 percent or less over the No Action 

29 Alternative. In addition, as noted in Section 3.3.3, the acrolein emissions reported in the EIS represent an 

30 upper bound, and thus potential unavoidable impacts of acrolein emissions might be less. 

31 Increases in criteria and toxic air pollutant emissions could occur in some nonattainment areas as 

32 a result of implementation of the CAFE standards under the action alternatives, largely due to increases in 

33 vehicle miles traveled. These increases represent a slight decline in the rate of reductions being achieved 

34 by implementation of Clean Air Act standards. 

35 3.6.2 Short-term Uses and Long-term Productivity 

36 The eight action alternatives (Alternatives 2 through 9) would result in a decrease in energy 

37 (crude oil) consumption and reductions in CO2 emissions and associated climate change impacts 

38 compared to those of Alternative 1, No Action. Manufacturers would need to apply various technologies 

39 to the production of passenger cars and light trucks to meet the MY 2012-2016 CAFE standards under the 

40 eight action alternatives. NHTSA cannot predict which specific technologies manufacturers would apply 

41 to meet the CAFE standards under any of the eight action alternatives; however, NHTSA estimates that 

42 existing technologies and existing vehicle production facilities can be applied to meet the standards under 

43 the eight action alternatives. Some vehicle manufacturers might need to commit additional resources to 
3.6 Unavoidable Impacts Chapter 3 Affected Environment and Environmental Consequences 

 3-122 

1 existing, redeveloped, or new production facilities to meet the CAFE standards. Such short-term uses of 

2 resources by vehicle manufacturers to meet the CAFE standards would enable the long-term reduction of 

3 national energy consumption and would enhance long-term national productivity. 

4 3.6.3 Irreversible and Irretrievable Commitment of Resources 

5 Energy consumption in the United States would decrease under all the action alternatives 

6 compared to the No Action Alternative. Tables 3.2.3-1 and 3.2.3-2 (see Section 3.2 of this EIS) 

7 summarize fuel consumption under each alternative for passenger cars and light trucks, respectively. For 

the Preferred Alternative (Alternative 4) the fuel savings1 8 over the No Action Alternative in 2060 would 

9 be 21.9 billion gallons for passenger cars and another 13.1 billion gallons for light trucks. 

10 As discussed in Section 3.6.2, manufacturers would need to apply various technologies to the 

11 production of passenger cars and light trucks to meet the MY 2012-2016 CAFE standards under the eight 

12 action alternatives. NHTSA cannot predict which specific technologies manufacturers would apply to 

13 meet the CAFE standards under any of the eight action alternatives. Existing technologies and existing 

14 vehicle production facilities can be applied to meet the CAFE standards under the eight action 

15 alternatives. However, some vehicle manufacturers might need to commit additional resources to 

16 existing, redeveloped, or new production facilities to meet the standards. The specific amounts and types 

17 of irretrievable resources (such as electricity and other energy consumption) manufacturers would expend 

18 in meeting the CAFE standards would depend on the specific methods and technologies manufacturers 

19 choose to implement. Commitment of resources for manufacturers to comply with the CAFE standards 

20 would tend to be offset by the fuel savings from implementing the standards. 

21 

 

1

 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 Action and Analysis 

3-123 

1 3.7 EPA ACTION AND ANALYSIS 

2 3.7.1 Overview 

3 As explained in Chapter 1, in a joint rulemaking being issued in parallel with this EIS, NHTSA 

4 and EPA are proposing a strong and coordinated federal greenhouse gas and fuel economy program for 

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

6 National Program. This rule proposes to increase vehicle fuel economy and reduce vehicle GHG 

7 emissions. NHTSA is proposing CAFE standards under EPCA, as amended by EISA 2007, and EPA is 

8 proposing its first-ever GHG emissions standards under the CAA. This joint proposal is consistent with 

9 the President’s announcement on May 19, 2009 of a National Fuel Efficiency Policy that will improve 

10 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.1 11 

12 This section of the EIS presents EPA’s analysis of its proposed action under the CAA, and 

13 attempts to place EPA’s proposed action in context of NHTSA’s proposed action (setting CAFE 

14 standards) and the National Program. Section 1501.6 of CEQ regulations emphasize agency cooperation 

15 early in the NEPA process and allow a lead agency (in this case, NHTSA) to request the assistance of 

16 other agencies that either have jurisdiction by law or have special expertise regarding issues considered in 

17 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.2 18 On May 12, 2009, the EPA accepted 

19 NHTSA’s invitation and agreed to become a cooperating agency.

20 In developing their respective proposals, NHTSA and EPA considered many of the same issues. 

21 Given differences in their respective statutory authorities, however, the agencies’ proposals include some 

22 important differences. Significantly, under the CO2 fleet average standard proposed under CAA section 

23 202(a), EPA expects manufacturers to take advantage of the option to generate CO2-equivalent credits by 

24 reducing emissions of hydrofluorocarbon (HFC) refrigerant and CO2 through improvements to their air 

25 conditioner systems. EPA accounted for these reductions in developing its proposed CO2 standard. 

26 However, EPCA does not permit NHTSA to consider air conditioning credits in developing a proposed 

27 CAFE standard for passenger cars. CO2 emissions due to air conditioning operation are not measured by 

28 the test procedure mandated by statute for use in establishing and enforcing CAFE standards for 

29 passenger cars. As a result, improvements in the efficiency of passenger car air conditioners would not be 

30 considered as a possible control technology for the purposes of CAFE. 

31 In addition, in its analysis of the impacts of the program, EPA took into consideration three 

32 compliance flexibilities that are proposed with the program: full transfer of credits between car and truck 

 

1 See Notice of Upcoming Joint Rulemaking To Establish Vehicle GHG Emissions and CAFE Standards, 74 FR 

24007 (May 22, 2009). 

2

 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 Action and Analysis Chapter 3 Affected Environment and Environmental Consequences 

 3-124 

1 fleets; flex fueled vehicle credits; and the Temporary Lead-time Allowance Alternative Standards 

2 program. NHTSA’s CAFE program has its own compliance flexibilities. However, because EPCA 

3 prohibits NHTSA from considering compliance flexibilities when determining the stringency of CAFE 

4 standards, NHTSA did not attempt to do so when it developed standards it has considered for this action. 

5 Finally, under the proposed EPA GHG emissions standards, there is no ability for a manufacturer 

6 to intentionally plan to pay a set fine in lieu of meeting the standard. However, under EPCA, automotive 

7 manufacturers are allowed to pay a fine for every 0.1 mpg they fall short of meeting the CAFE standard 

8 as a method of compliance. In NHTSA’s analysis prepared for this EIS, there is some level of voluntary 

9 fine payment reflected in the impacts which reduce the estimated benefits of the alternative CAFE 

10 standards analyzed. Since intentional noncompliance is not permitted under the CAA, this consideration 

11 justifies proposing more stringent GHG emissions standards, and is not reflected in EPA’s impacts 

12 analysis. 

13 For the above reasons, the proposed CAFE standards (under the Preferred Alternative) are 

14 somewhat lower than the proposed EPA GHG standard. However, together, NHTSA’s proposed CAFE 

15 standards and EPA’s GHG emissions standards would represent a harmonized and consistent National 

16 Program under each agency’s respective statutory framework. They require vehicles to meet an estimated 

17 combined average emissions level of 250 grams of CO2 per mile in MY 2016 under EPA’s GHG 

18 program, and 34.1 mpg in MY 2016 under NHTSA’s CAFE program. Under the National Program, the 

19 overall light-duty vehicle fleet would reach 35.5 mpg in MY 2016, if all reductions were made through 

20 fuel economy improvements and result in significant reductions in both greenhouse gas emissions and oil 

21 consumption. For more details, see NHTSA and EPA’s joint preamble and the EPA and NHTSA Draft 

22 Regulatory Impact Analysis (DRIA) associated with the joint proposal. 

23 3.7.2 Summary of EPA Impact Analysis 

24 The action EPA is proposing as a part of the National Program would reduce GHG emissions 

25 emitted directly from vehicles due primarily to reduced fuel use and secondarily to improved air 

26 conditioning systems. In addition to these “downstream” emissions, reducing CO2 emissions through 

27 reducing fuel use translates directly to reductions in the emissions associated with the processes involved 

28 in getting petroleum to the pump, including the extraction and transportation of crude oil, and the 

29 production and distribution of finished gasoline (termed “upstream” emissions). Reductions from tailpipe 

30 GHG standards grow over time as the fleet turns over to vehicles affected by these standards, meaning the 

31 benefit of the standards will continue as long as the oldest vehicles in the fleet are replaced by newer, 

32 lower CO2 emitting vehicles. 

33 As detailed in the EPA DRIA (see Appendix E), EPA estimated calendar year tailpipe CO2

34 reductions based on pre- and post-control CO2 gram per mile levels from EPA’s vehicle technology and 

35 cost model (which relates manufacturer technology choices and GHG emission reductions) and VMT 

projections described in the draft Joint Technical Support Document.3 36 These estimates reflect the CO2

37 emissions reductions projected for the entire U.S. vehicle fleet in a specified calendar year. 

38 As in NHTSA’s analysis, EPA projected expected changes in both “downstream” (vehicle 

39 tailpipe) and “upstream” (fuel production and distribution) emissions, including the effects of additional 

 

3

 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. 
Chapter 3 Affected Environment and Environmental Consequences 3.7 EPA Action and Analysis 

3-125 

1 driving (“VMT rebound”). EPA analyzed the expected effects of the standards on emissions of the 

2 vehicle-related greenhouse gases: CO2, air conditioning related emissions of HFC refrigerant and CO2, 

3 N2O, andCH4. EPA also analyzed the effect of the proposed program on “criteria” air pollutants and 

4 precursors (including CO, PM2.5, SOx, VOC, NOx); and air toxics (including benzene, 1,3-butadiene, 

5 formaldehyde, acetaldehyde, and acrolein). 

6 EPA developed downstream emission impacts using a spreadsheet analysis based on data from 

7 two EPA models. EPA derived computation algorithms and achieved CO2 levels from EPA’s vehicle 

8 model, coupled with non-CO2 emission rates from EPA’s MOVES. 

9 EPA calculated upstream emission changes resulting from the decreased fuel consumption using 

10 a spreadsheet model based on emission factors from Argonne National Laboratory’s GREET Model. 

11 EPA and NHTSA shared common data inputs for their parallel analyses, as described in the Joint 

12 Technical Support Document associated with the proposed National Program. For full details of EPA’s 

13 subsequent analyses and results, please refer to Chapter 5 of EPA’s DRIA, also associated with the 

14 proposed National Program. 

15 In addition, EPA estimated changes in projected global mean surface temperature and sea-level 

16 rise to 2100 using the MiniCAM integrated assessment model coupled with the MAGICC, version 5.3 

17 climate model. MiniCAM was used to create the globally and temporally consistent set of emission 

18 scenarios required for running MAGICC. MAGICC was then used to estimate the change in the global 

19 mean surface temperature and sea-level rise over time (at five-year time steps). Given the magnitude of 

20 the estimated emissions reductions associated with the proposal, a simple climate model such as 

21 MAGICC is reasonable for estimating the climate response. 

22 To capture some key uncertainties in the climate system with the MAGICC model, the changes in 

23 projected temperatures and sea level were estimated across the most current IPCC range of climate 

sensitivities, 1.5 °C to 6.0 °C.4 24 To compute the change in temperature and sea-level rise attributable to 

25 the proposal, the output from the proposal’s emissions scenario were subtracted from an existing 

26 MiniCAM emission scenario. Details about the models used, reference case scenario, and how the 

27 emissions reductions were applied to generate the proposal scenario can be found in chapter 7.4 of EPA’s 

28 DRIA (see Appendix E). 

29 3.7.2.1 Energy 

30 EPA anticipates its proposal would create significant fuel savings as compared to the baseline. 

31 Projected fuel savings are shown in Table 3.7.2-1. 

32 In calendar year 2030, EPA analysis projects its proposal to reduce light duty fuel consumption 

33 approximately 17 percent relative to the reference scenario. 

 

4

 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 Action and Analysis Chapter 3 Affected Environment and Environmental Consequences 

 3-126 

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 

1 

2 3.7.2.2 Air Quality 

3 EPA estimates that its proposed standards would result in emission reductions of NOx, VOC, 

4 PM2.5 and SOx, but would increase CO emissions. The overall impact of its proposal would be relatively 

5 small compared to total U.S. inventories across all sectors for these pollutants. In 2030, its proposed 

6 standards would reduce these total NOx, PM and SOx inventories by 0.2 to 0.3 percent and reduce the 

7 VOC inventory by 1.2 percent, while increasing the total national CO inventory by 0.4 percent. 

8 EPA estimates that the proposed GHG standards would result in mixed impacts on air toxic 

9 emissions. Again, the overall impact of the proposal would be relatively small for these pollutants 

10 compared to total U.S. inventories across all sectors. In 2030, EPA estimates that its standards would 

11 reduce total acrolein, benzene, and formaldehyde emissions by less than 0.1 percent. Total 1,3-butadiene 

12 and acetaldehyde emissions would increase by 0.1 to 0.2 percent. 

13 Table 3.7.2-2 presents the impacts of the proposed standards on each of the non-GHG pollutants 

14 that EPA analyzed. 

15 For its final rule, EPA will perform a national-scale air quality modeling analysis to analyze the 

16 impacts of the proposed vehicle GHG standards on PM2.5, ozone, and selected air toxics (i.e., benzene, 

17 formaldehyde, acetaldehyde, acrolein and 1,3-butadiene). The length of time needed to prepare the 

18 necessary emissions inventories, in addition to the processing time associated with the modeling itself, 

19 has precluded EPA from performing air quality modeling for the proposed rule. 

20 The atmospheric chemistry related to ambient concentrations of PM2.5, ozone and air toxics is 

21 very complex, and making predictions based solely on emissions changes is extremely difficult. 

22 However, based on the magnitude of the emissions changes predicted to result from the proposed vehicle 

23 GHG standards, EPA expects that there will be an improvement in ambient air quality, pending a more 

24 comprehensive analysis for the final rule. 

25 
Chapter 3 Affected Environment and Environmental Consequences 3.7 EPA Action and Analysis 

3-127 

TABLE 3.7.2-2 

Impacts of Proposed Standards on Non-GHG Emissions (Short Tons Per Year) 

Pollutant 

Calendar Year 

2020 

% Change vs. 

2020 Reference 

Calendar Year 

2030 

% Change vs. 

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%

1 

2 3.7.2.3 Climate Change 

3 The results, in both Figures 3.7.2-1 and 3.7.2-2, of EPA’s climate change modeling analysis show 

4 a small, but quantifiable, reduction in projected global mean surface temperature and sea level as a result 

5 of this proposal across all climate sensitivities. Global mean temperature is projected to be reduced by 

6 approximately 0.007–0.016 °C by 2100 and global mean sea-level rise is projected to be reduced by 

7 approximately 0.06–0.15 cm by 2100. The reductions are small relative to the IPCC’s 2100 “best 

8 estimates” for global mean temperature increases (1.8–4.0 oC) and sea-level rise (0.20–0.59 m) for all 

9 global GHG emissions sources for a range of emissions scenarios. These projected reductions are 

10 proportionally representative of changes to U.S. GHG emissions in the transportation sector. 

11 As a substantial portion of CO2 emitted into the atmosphere is not removed by natural processes 

12 for millennia, each unit of CO2 not emitted into the atmosphere avoids essentially permanent climate 

13 change on centennial time scales. While not formally estimated for the joint proposed rule, a reduction in 

14 projected global mean temperature and sea-level rise implies a reduction in the adverse risks associated 

15 with climate change. Both figures illustrate that the distribution for projected global mean temperature 

16 and sea-level rise increases has shifted downward as a result of the proposal. 
3.7 EPA Action and Analysis Chapter 3 Affected Environment and Environmental Consequences 

 3-128 

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

1 

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

2 
4-1 

1 Chapter 4 Cumulative Impacts 

2 4.1 INTRODUCTION 

3 The Council on Environmental Quality (CEQ) identifies the impacts federal agencies must 

4 address and consider in satisfying the requirements of the National Environmental Policy Act (NEPA). 

5 This includes permanent, short-term and long-term direct, indirect, and cumulative impacts. 

6 CEQ NEPA implementing regulations at 40 Code of Federal Regulations (CFR) § 1508.7 define 

7 cumulative impact as “the impact on the environment which results from the incremental impact of the 

8 action when added to other past, present, and reasonably foreseeable future actions regardless of what 

9 agency (Federal or non-Federal) or person undertakes such other actions.” Cumulative impacts should be 

10 evaluated along with the overall impacts of each alternative. The range of alternatives considered should 

11 include a No Action Alternative as a baseline against which to evaluate cumulative effects. The range of 

12 actions to be considered includes not only the proposed action but all connected and similar actions that 

13 could contribute to cumulative effects. Connected actions should be addressed in the same analysis. 

14 CEQ recommends that an agency’s analysis accomplish the following: 

15  Focus on the effects and resources within the context of the proposed action. 

16  Present a concise list of issues that have relevance to the anticipated effects of the proposed 

17 action or eventual decision. 

18  Reach conclusions based on the best available data at the time of the analysis. 

19  Rely on information from other agencies and organizations on reasonably foreseeable 

20 projects or activities that are beyond the scope of the analyzing agency’s purview. 

21  Relate to the geographic scope of the proposed project. 

22  Relate to the temporal period of the proposed project. 

23 A cumulative impacts analysis involves assumptions and uncertainties. Monitoring programs and 

24 research can be identified to supplement the available information and thus enhance analyses for the 

25 future. The absence of an ideal database should not prevent the completion of a cumulative effects 

26 analysis. 

27 Chapter 4 addresses areas of the quantitative analyses presented in Chapter 3, with particular 

28 attention to energy, air, and climate, and describes the indirect cumulative effects of climate change on a 

29 global scale. This chapter is organized according to the conventions of the climate change literature 

30 rather than the conventions of an Environmental Impact Statement (EIS) format. To assist the reader, the 

31 table on the following page maps topics found in U.S. Department of Transportation (DOT) NEPA 

32 documents (DOT Order 5610.1C) to the sections in this EIS. 
4.1 Introduction Chapter 4 Cumulative Impacts 

 4-2 

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 

1 

2 4.1.1 Approach to Scientific Uncertainty and Incomplete Information 

3 4.1.1.1 CEQ Regulations 

4 CEQ regulations recognize that many federal agencies confront limited information and 

5 substantial uncertainties when analyzing the potential environmental impacts of their actions under 

6 NEPA. 40 CFR § 1502.22. Accordingly, the regulations provide agencies with a means to formally 

7 acknowledge incomplete or unavailable information in NEPA documents. Where “information relevant 

8 to reasonably foreseeable significant adverse impacts cannot be obtained because the overall costs of 

9 obtaining it are exorbitant or the means to obtain it are not known,” the regulations require an agency to 

10 include in its NEPA document: 

11 1. A statement that such information is incomplete or unavailable; 

12 2. A statement of the relevance of the incomplete or unavailable information to evaluating 

13 reasonably foreseeable significant adverse impacts on the human environment; 
Chapter 4 Cumulative Impacts 4.1 Introduction 

4-3 

1 3. A summary of existing credible scientific evidence that is relevant to evaluating the 

2 reasonably foreseeable significant adverse impacts on the human environment; and 

3 4. The agency’s evaluation of such impacts based on theoretical approaches or research methods 

4 generally accepted in the scientific community. 

5 Relying on these provisions is appropriate when an agency is performing a NEPA analysis that 

6 involves potential environmental impacts resulting from carbon dioxide (CO2) emissions (e.g., Mayo 

7 Found. v. Surface Transp. Bd., 472 F.3d 545, 555 (8th Cir. 2006). CEQ regulations at 40 CFR § 1502.21 

8 also authorize agencies to incorporate material into a NEPA document by reference to “cut down on bulk 

9 without impeding agency and public review of the action.” 

10 Throughout this EIS, the National Highway Transportation Safety Administration (NHTSA) uses 

11 these two mechanisms – acknowledging incomplete or unavailable information and incorporation by 

12 reference – to address areas for which the agency cannot develop a credible estimate of the potential 

13 environmental impacts of the standards or reasonable alternatives. In particular, NHTSA recognizes that 

14 information about the potential environmental impacts of changes in emissions of CO2 and other 

15 greenhouse gases (GHGs) and associated changes in temperature, including those expected to result from 

16 the proposed rule, is incomplete. In this EIS, NHTSA often relies on the EPA Technical Support 

17 Document entitled Endangerment and Cause or Contribution Findings for Greenhouse Gases under 

18 Section 202(a) of the Clean Air Act (EPA 2009), the Intergovernmental Panel on Climate Change (IPCC) 

19 Fourth Assessment Report by Working Group II (WGII) entitled Climate Change 2007 – Impacts, 

20 Adaptation, and Vulnerability (IPCC 2007), and the U.S. Climate Change Science Program (CCSP) 

21 Synthesis and Assessment Product (SAP) reports as a recent “summary of existing credible scientific 

22 evidence which is relevant to evaluating the reasonably foreseeable significant adverse impacts on the 

23 human environment.” See 40 CFR § 1502.22(b)(3). 

24 4.1.2 Temporal and Geographic Boundaries 

25 When evaluating cumulative effects, the analysis must consider expanding the geographic study 

26 area beyond that of the proposed action, and expanding the temporal (time) limits to consider past, 

27 present, and reasonably foreseeable future actions that might affect the environmental resources of 

28 concern. The timeframe for this cumulative impacts analysis extends through 2050 for the air quality 

29 analysis and through 2100 for energy and climate change. The analysis considers potential cumulative 

30 impacts on a national and global basis. 

31 4.1.3 Reasonably Foreseeable Future Actions 

32 The methodology for evaluating cumulative effects includes the reasonably foreseeable future 

33 actions of projected average annual passenger-car and light-truck mile-per-gallon (mpg) estimates from 

34 2016 through 2030 that differ from mpg estimates reflected in the Chapter 3 analysis. The Chapter 3 

35 analysis reflects the direct impacts of fuel economy requirements for model years (MY) 2012 through 

36 2016 under each of the action alternatives, assuming no further increases in average new passenger-car or 

37 light-truck mpg after 2016. For Chapter 3, this is a reasonable assumption because Chapter 3 is intended 

38 to show the direct and indirect effects of the proposed action. The Chapter 3 analysis does not show the 

39 environmental effects of fuel economy improvements beyond those made under the proposed action by 

40 MY 2016. 

41 However, the Chapter 4 evaluation of cumulative effects projects ongoing gains in average new 

42 passenger-car and light-truck mpg consistent with Annual Energy Outlook (AEO) April 2009 (updated) 

43 Reference Case projections because those projected gains are reasonably foreseeable future actions. AEO 
4.1 Introduction Chapter 4 Cumulative Impacts 

 4-4 

1 Reference Case projections are regarded as the official U.S. Government energy projections by both the 

2 public and private sector. Chapter 3, Section 3.2.1 provides an expanded description of the AEO. In 

3 general, the AEO Reference Case projections tend to fall in the middle of similar publicly available 

4 projections. The April 2009 Reference Case reflected in this EIS incorporates effects of the American 

5 Recovery and Reinvestment Act, and updated economic projections. The AEO projections for average 

6 new passenger-car and light-truck mpg assume that combined new passenger cars and light trucks surpass 

7 an average of 35 mpg in 2019, and reach 35.5 mpg in 2020, slightly exceeding the Energy Independence 

8 and Security Act (EISA) 2007 requirement of 35 mpg in 2020. The AEO Reference Case projections also 

9 anticipate an average annual percentage gain of 0.51 percent in passenger-car mpg and 0.86 percent in 

10 light-truck mpg from 2019 through 2030, due to consumer demand and technology advances associated 

11 with ongoing increases in fuel prices through 2030. The analysis of cumulative effects in this chapter 

12 reflects these AEO mpg projections as reasonably foreseeable future actions, associated with future 

13 government actions as needed to achieve the EISA 2007 requirement of 35 mpg in 2020, and future 

14 consumer and industry actions that result in ongoing mpg gains through 2030. Because the AEO 

15 forecasts do not extend beyond 2030, the mpg estimates for MY 2030 through MY 2060 remain constant. 

16 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 5.75 0.51 

New Light Truck 9.94 0.86 

17 

18 The specific manner in which the AEO mpg projections are applied varies across the action 

19 alternatives to ensure that all action alternatives achieve the EISA 2007 requirement of 35 mpg in 2020. 

20 The increase in fuel economy from 2016 to 2030 is expected to be at least equal to a gain of 0.51 percent 

21 in passenger-car mpg and 0.86 percent in light-truck mpg under all action alternatives. Also, an even 

22 faster rate of mpg gain is expected from 2016 to 2020 for two action alternatives that would have to 

23 increase mpg at a faster rate after 2016 to achieve the EISA 2007 requirement of 35 mpg in 2020. 

24 Alternatives 4 through 9 would exceed the EISA requirement of 35 mpg in 2020, with an average annual 

25 percentage gain of 0.51 percent in passenger-car mpg and 0.86 percent in light-truck mpg after 2016. 

26 Therefore, the analysis of cumulative impacts projects annual percentage gains of 0.51 percent in 

27 passenger-car mpg and 0.86 percent in light-truck mpg for 2016 through 2030 under Alternatives 4 

28 through 9. Alternatives 2 and 3 would require larger percentage gains in mpg from 2016 to 2020 to 

29 achieve the EISA requirement of 35 mpg in 2020. Therefore, the analysis of cumulative impacts projects 

30 annual gains in mpg from 2016 to 2020 under Alternatives 2 and 3 that are large enough to achieve the 

31 EISA requirement of 35 mpg in 2020. The projected actual achieved mpg in 2020 (fleet-wide average) 

32 actually slightly exceeds 35 mpg in 2020 (consistent with the AEO projection) under Alternatives 2 and 3 

33 (and under other action alternatives) because some manufacturers would exceed the EISA requirement of 

34 35 mpg in 2020. The analysis of cumulative impacts also projects annual percentage gains of 0.51 

35 percent in passenger-car mpg and 0.86 percent in light-truck mpg under Alternatives 2 and 3 from 2020 

36 through 2030. 

37 The assumption that all Action Alternatives reach the EISA 35 mpg target by 2020, with mpg 

38 growth at the AEO forecast rate from 2020 to 2030, results in estimated cumulative impacts for 

39 Alternatives 2, 3, and 4 that are substantially equivalent, with any minor variation in cumulative impacts 

40 across these Alternatives due to the specific modeling assumptions used to ensure that each Alternative 

41 achieves at least 35 mpg by 2020. Therefore, the cumulative impacts analysis in Chapter 4 adds 
Chapter 4 Cumulative Impacts 4.1 Introduction 

4-5 

1 substantively to the analysis of direct impacts in Chapter 3 when comparing cumulative impacts between 

2 Alternatives 4 through 9, but not when comparing cumulative impacts between Alternatives 2 through 4. 

3 Another important difference in the methodology for evaluating cumulative effects is that the No 

4 Action Alternative (Alternative 1) also reflects projected annual percentage gains of 0.51 percent in 

5 passenger-car mpg and 0.86 percent in light-truck mpg for 2016 through 2030, whereas the Chapter 3 

6 analysis assumed no increases in average new passenger-car or light-truck mpg after 2016 under any 

7 alternative, including the No Action Alternative. Chapter 2 explained that the No Action Alternative 

8 (Alternative 1) assumes no action occurs under the National Program (i.e., NHTSA and EPA do not act, 

9 and in the absence of standards, manufacturers continue to meet the NHTSA MY 2011Corporate Average 

10 Fuel Economy (CAFE) standards), so average fuel economy levels in the absence of CAFE standards 

11 beyond MY 2011 would equal the higher of the agencies’ collective market forecast or the manufacturer’s 

12 required level of average fuel economy for MY 2011. The No Action Alternative, by definition, would 

13 not satisfy the Energy Conservation and Policy Act (EPCA) (as updated by EISA) requirement to set 

14 standards such that the combined fleet of passenger cars and light trucks achieves a combined average 

15 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 16 The evaluation of cumulative effects in 

17 this chapter is consistent in that the projected annual percentage gains of 0.51 percent in passenger-car 

18 mpg and 0.86 percent in light-truck mpg for 2016 through 2030 under the No Action Alternative still do 

19 not reflect any action under the National Program, but only the annual AEO projected gain in mpg 

20 through 2030 due to consumer demand and technology advances associated with ongoing increases in 

21 fuel prices. 

22 Even with this projected annual percentage gain in mpg for 2016 through 2030, the No Action 

23 Alternative would still not achieve the EISA requirement of 35 mpg in 2020. The annual AEO projected 

24 gain in mpg through 2030 due to consumer demand and technology advances is applied to the No Action 

25 Alternative and to each of the action alternatives so that the difference between fuel use, emissions, and 

26 other projections under the No Action Alternative and the action alternatives can be meaningfully 

27 compared (e.g., by calculating fuel saved by any action alternative in relation to the No Action 

28 Alternative). 

29 NHTSA also considered other reasonably foreseeable actions that would affect greenhouse gas 

30 emissions (GHGs). Section 4.4.3.3 discusses these actions and their incorporation into the analysis. 

31 

 

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. 
4.1 Introduction Chapter 4 Cumulative Impacts 

 4-6 

1 
Chapter 4 Cumulative Impacts 4.2 Energy 

4-7 

1 4.2 ENERGY 

2 A NEPA analysis must consider the cumulative impacts of the proposed action. For this EIS, 

3 such considerations involve evaluating the cumulative fuel consumption of the vehicle fleet from the 

4 onset of the proposed new CAFE standards. 

5 4.2.1 Affected Environment 

6 According to the Energy Information Administration (EIA), net imports of total liquid fuels, 

7 including crude oil, refined products, and biofuels, which in 2007 amounted to 58 percent of total 

8 consumption, will fall to 48 percent of total consumption in 2020 and then fall further to 40 percent of 

9 consumption in 2030 (EIA 2009a). This change is attributed in part to expected changes in the CAFE 

10 standards and to the increased use of biofuels. The steep decline in imports by 2030 is also driven by the 

11 surge in U.S. domestic crude-oil production in the decade before 2030. The shift in crude oil imports in 

12 the period leading up to 2030 could have some effect on the global price of crude oil, but the United 

13 States is a price taker not a price maker when it comes to petroleum. In addition, over time the U.S. share 

14 of global demand for liquid fuels will decline due to rapid increases in demand in developing economies, 

15 including China and India, reducing the relative impact of the CAFE standards on global markets. EIA 

16 projections show that U.S. consumption of petroleum liquids amounted to 24 percent of global liquid 

17 consumption in 2007 and falls to 20 percent by 2030 (EIA 2009a). 

18 Over time, a larger share of liquid fuels is expected to be produced from unconventional sources 

19 such as biofuels, shale oil, coal-to-liquids, and gas-to-liquids. These alternative sources would affect CO2

20 and other emissions reductions from the CAFE alternatives. This shift would be driven by changes to the 

21 Renewable Fuels Standard (RFS) in EISA, which forecasts that 36 billion gallons of renewable fuels will 

22 be required by 2022 for use primarily in the transportation sector. The EIA AEO 2009 forecasts that 

23 domestic production of non-hydro renewable energy (biomass, landfill gas, biogenic municipal waste, 

24 wind, photovoltaic, and solar thermal sources) will increase from just over 4 quadrillion British thermal 

25 units in 2007 to almost 12 quadrillion British thermal units in 2030 (EIA 2009b). In the United States, 

26 liquid fuels from gas, coal, and biomass are projected to increase from 0.00 quadrillion British thermal 

27 units in 2007 to 2.21 quadrillion British thermal units by 2030. 

28 Changes to the CAFE standards are unlikely to affect domestic production, given the level of 

29 crude oil imports. Impacts on production would occur outside of the United States, and would be 

30 determined by the balance between the decline in U.S. imports and the increase in demand from 

31 developing countries. Impacts on petroleum products would be mixed. U.S. imports of petroleum 

32 products are often targeted for specific product requirements, for logistical reasons, or to optimize the 

33 inputs and outputs from refineries. Petroleum imports depend on specific product demands and the mix 

34 of crudes processed in the refineries, which are projected to change considerably over time. 

35 Consequently, any decline in demand for petroleum products is likely to have some effect on both 

36 overseas and domestic refineries. 

37 4.2.2 Methodology 

38 As explained in Section 4.1.3, AEO mpg projections through 2030 are reflected in the analysis of 

39 cumulative impacts. In particular, this analysis projects annual gains in mpg from 2016 to 2020 under 

40 Alternatives 2 and 3 large enough to achieve the EISA requirement of 35 mpg combined for passenger 

41 cars and light trucks in 2020. Additionally, the analysis projects annual percentage gains of 0.51 percent 

42 in passenger-car mpg and 0.86 percent in light-truck mpg from 2020 through 2030 under Alternatives 2 

43 and 3, and from 2016 through 2030 under the No Action Alternative and Alternatives 4 through 9. The 

44 compound annual gains of 0.51 percent in passenger-car mpg and 0.86 percent in light-truck mpg through 
4.2 Energy Chapter 4 Cumulative Impacts 

 4-8 

1 2030 reflect the total percentage gains projected by AEO from 2019 through 2030 (see Table 4.1.3-1 in 

2 Section 4.1.3). 

3 4.2.3 Environmental Consequences 

4 Implementing alternative CAFE standards would result in different future levels of fuel use, total 

5 energy, and petroleum consumption, which in turn would have an impact on emissions of GHGs and 

6 criteria air pollutants. An important measure of the impact of alternative CAFE standards is the impact on 

7 the fuel consumption of the vehicle fleet from the onset of the new standards. Passenger cars and light 

8 trucks are considered separately; total fuel consumption encompasses gasoline and diesel. CAFE 

9 standards for MY 2012-2020 are assumed to apply to all subsequent additions to the vehicle fleet. 

10 Table 4.2.3-1 shows the fuel consumption of passenger cars under the No Action Alternative 

11 (Alternative 1) and the eight action alternatives (Alternatives 2 through 9), as described in Section 2.3. 

12 By 2060, fuel consumption reaches 162.8 billion gallons under the No Action Alternative. Consumption 

13 falls across the alternatives,from 140.7 billion gallons under Alternatives 3 and 4 to 131.3 billion gallons 

14 under Alternatives 8 and 9 representing a fuel savings of 21.8 to 31.5 billion gallons in 2060. 

15 Table 4.2.3-2 shows the fuel consumption of light trucks under the CAFE alternatives examined. 

16 Fuel consumption by 2060 reaches 91.2 billion gallons under the No Action Alternative. Consumption 

17 declines across the alternatives, from 80.1 billion gallons under Alternative 2 to 73.3 billion gallons under 

18 Alternative 8. This represents a fuel savings of 11.1 to 17.9 billion gallons in 2060. 

Table 4.2.3-1 

Cumulative Effects of Passenger Car Annual Fuel Consumption and Fuel Savings (billion gallons gasoline 

equivalent) by Alternative 

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

~5.9%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.7%/year 

Increase 

TCTB 

Fuel Consumption 

2020 69.1 64.7 63.8 63.6 62.8 61.6 61.6 61.0 60.9

2030 94.5 82.6 82.2 82.3 80.7 78.3 78.2 76.8 76.8

2040 114.7 99.1 99.1 99.3 97.3 94.5 94.2 92.5 92.5

2050 136.7 118.1 118.2 118.4 116.0 112.6 112.4 110.3 110.3

2060 162.8 140.7 140.7 141.0 138.2 134.1 133.8 131.3 131.3

Fuel Savings Compared to No Action 

2020 -- 4.4 5.3 5.6 6.3 7.5 7.5 8.1 8.2

2030 -- 11.9 12.2 12.2 13.8 16.2 16.3 17.7 17.7

2040 -- 15.6 15.5 15.4 17.3 20.2 20.4 22.2 22.2

2050 -- 18.6 18.5 18.3 20.7 24.1 24.4 26.5 26.4

2060 -- 22.1 22.1 21.8 24.6 28.7 29.0 31.5 31.5

19 

20 
Chapter 4 Cumulative Impacts 4.2 Energy 

4-9 

Table 4.2.3-2 

Cumulative Effects of Light Truck Annual Fuel Consumption and Fuel Savings (billion gallons gasoline 

equivalent) by Alternative 

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

~5.9%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.7%/year 

Increase 

TCTB 

Fuel Consumption 

2020 68.3 65.6 64.9 64.6 64.0 62.8 63.1 62.5 62.4

2030 62.8 56.8 56.5 56.3 55.0 53.3 53.4 52.5 52.6

2040 66.7 58.9 58.9 58.7 57.1 55.2 55.2 54.1 54.3

2050 77.1 67.8 67.8 67.6 65.7 63.4 63.4 62.1 62.4

2060 91.2 80.1 80.1 79.9 77.6 74.9 74.9 73.3 73.7

Fuel Savings Compared to No Action 

2020 -- 2.7 3.4 3.7 4.4 5.6 5.3 5.8 5.9

2030 -- 6.0 6.3 6.6 7.8 9.5 9.4 10.3 10.2

2040 -- 7.7 7.8 8.0 9.5 11.5 11.5 12.6 12.3

2050 -- 9.3 9.3 9.5 11.4 13.7 13.7 15.0 14.7

2060 -- 11.1 11.1 11.3 13.6 16.3 16.3 17.9 17.5

1 
4.2 Energy Chapter 4 Cumulative Impacts 

 4-10 

1 
Chapter 4 Cumulative Impacts 4.3 Air Quality 

 4-11 

1 4.3 AIR QUALITY 

2 4.3.1 Affected Environment 

3 Section 3.3.1 describes the air quality affected environment. 

4 4.3.2 Methodology 

5 4.3.2.1 Overview 

6 The analysis methodology for air quality cumulative impacts and consequent health outcomes is 

7 the same as described in Section 3.3.2, except that the cumulative impacts analysis assumes annual 

8 average percentage gains in average fuel economy from 2016 through 2030 consistent with the AEO 2009 

9 updated Reference Case projections, with all action alternatives exceeding the combined EISA target of 

10 35 mpg in 2020 (see Section 4.1.3). These AEO mpg projections reflect reasonably foreseeable future 

11 government actions as needed to achieve the EISA 2007 requirement, and future consumer and industry 

12 actions that result in ongoing mpg gains through 2030. Because there are no valid projections that go past 

13 calendar year 2030, the average fuel economy estimates for MY 2030-MY 2050 remain constant. 

14 NHTSA analyzed the cumulative air quality impacts of the action alternatives by calculating the 

15 emissions from passenger cars and light trucks that would occur under each alternative, including the 

16 effects of percentage gains in mpg from 2016 through 2030 consistent with AEO projections, and 

17 assessing the changes in emissions in relation to the No Action Alternative, to which the AEO forecasted 

18 fuel economy increases were also applied. 

19 This analysis considers the following cumulative impacts of alternative CAFE standards for MY 

20 2012-2016 and other reasonably foreseeable actions projected to affect fuel economy through 2030, as 

21 described in Section 4.1.3. Because CAFE standards and ongoing mpg gains apply to new vehicles, this 

22 assumption results in emissions reductions and fuel savings that continue to grow as new vehicles with 

23 higher average mpg are added to the fleet in each subsequent year, reaching their maximum values when 

24 all passenger cars and light trucks in the U.S. fleet meet the mpg projection for new passenger cars and 

25 light trucks in 2030. To account for these effects on emissions beyond calendar year 2030, NHTSA 

26 analyzed cumulative impacts through 2050. Because the cumulative impacts analysis assumes that new 

27 vehicles in model years beyond MY 2016 have a higher fleet average fuel economy based on AEO fuel 

28 economy projections, these assumptions result in emissions reductions and fuel savings that continue to 

29 grow as these new, more fuel efficient vehicles are added to the fleet in each subsequent year, reaching 

30 their maximum values when all passenger cars and light trucks in the U.S. fleet have these higher mpg 

31 levels. Because of this, NHTSA analyzed the air emissions through 2050, when most of the fleet would 

32 achieve the average fuel economy levels the agency projects in 2030 (based on AEO fuel economy 

forecasts).1 33 For comparison, the Chapter 3 analysis only examines the direct and indirect effects of the 

34 proposed MY 2012-2016 standards and analyzes the effect of this rule through 2030. 

35 4.3.2.2 Treatment of Incomplete or Unavailable Information 

36 As noted in Section 3.3.2, the estimates of emissions rely on models and forecasts that contain 

37 numerous assumptions and data that are uncertain. Examples of areas in which information is incomplete 

38 or unavailable include future emission rates, vehicle manufacturers’ decisions on vehicle technology and 

39 design, the mix of vehicle types and model years, projections of vehicle miles traveled (VMT), emissions 

 

1

 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. 
4.3 Air Quality Chapter 4 Cumulative Impacts 

 4-12 

1 from fuel refining and distribution, and economic factors. NHTSA used screening-level estimates of 

2 health outcomes in the form of cases per ton of criteria pollutant emissions reduced, and of monetized 

3 health benefits in the form of dollars per ton of criteria pollutant emissions reduced, to approximate the 

4 health benefits associated with each alternative. The use of such dollar-per-ton numbers, however, does 

5 not account for all potential health and environmental benefits because the information necessary to 

6 monetize all potential health and environmental benefits is unavailable (e.g., health effects per ton of 

7 emissions of pollutants other than PM, values of property damage, and effects on vegetation), which leads 

8 to an underestimate of total criteria pollutant benefits. Reductions in emissions of toxic air pollutants 

9 should result in health benefits as well, but scientific data are not available that would allow 

10 quantification and monetization of these benefits. 

11 Where information in the analysis included in this EIS is incomplete or unavailable, the agency 

12 has relied on CEQ regulations regarding incomplete or unavailable information. 40 CFR § 1502.22(b). 

13 NHTSA used the best available models and supporting data in preparing this EIS. The models used have 

14 been scientifically reviewed and have been approved by the agencies that sponsored their development. 

15 NHTSA believes that the assumptions in this EIS regarding uncertain conditions reflect the best available 

16 information and are valid and sufficient for this analysis. 

17 4.3.3 Environmental Consequences 

18 4.3.3.1 Results of Emissions Analysis 

19 The Clean Air Act (CAA) has been a success in reducing emissions from on-road mobile sources. 

20 As discussed in Section 3.3.1, pollutant emissions from vehicles have been declining since 1970 and the 

21 U.S. Environmental Protection Agency (EPA) projects that they will continue to decline. However, as 

22 future trends show, vehicle travel is having a smaller and smaller impact on emissions as a result of 

23 stricter EPA standards for vehicle emissions and the chemical composition of fuels, even with additional 

24 growth in VMT (Smith 2002). This general trend will continue, to a greater or lesser degree, with 

25 implementation of any of the alternative CAFE standards. The analysis by alternative in this section 

26 shows that the alternative CAFE standards will lead to both reductions and increases in emissions from 

27 passenger cars and light trucks (depending on the pollutant), compared to current trends (i.e., the No 

28 Action Alternative). The amounts of the reductions and increases would vary by pollutant, calendar year, 

29 and alternative. The more restrictive alternatives generally would result in greater emissions reductions 

30 compared to the No Action Alternative. This trend is shown in the analysis of the MY 2012-2016 CAFE 

31 standards in Section 3.3.3. 

32 4.3.3.2 Alternative 1: No Action 

33 4.3.3.2.1 Criteria Pollutants 

34 Under the No Action Alternative, average fuel economy levels in the absence of CAFE standards 

35 beyond MY 2011 would equal the higher of the agencies’ collective market forecast or the manufacturer’s 

36 required level of average fuel economy for MY 2011. Average fuel economy is assumed to increase from 

37 2012 through 2030 due to projected rising demand for fuel economy, consistent with AEO projections 

38 (see Section 4.1.3). Current trends in the levels of emissions from vehicles would continue through 2030, 

39 with emissions continuing to decline due to the EPA emissions standards, despite a growth in total VMT. 

40 By 2050, however, VMT growth more than offsets decreases due to emission standards and total 

41 emissions increase. The EPA vehicle emissions standards regulate all criteria pollutants except sulfur 

42 dioxide (SO2), which is regulated through the fuel sulfur content. The No Action Alternative would not 

43 change the MY 2011 CAFE standards; therefore, any change in criteria pollutant emissions in 

44 nonattainment and maintenance areas throughout the United States would be attributable to current 
Chapter 4 Cumulative Impacts 4.3 Air Quality 

 4-13 

1 emissions regulatory programs and the assumed future trends in fuel economy increases in accordance 

2 with the AEO projections. 

3 Table 4.3.3-1 summarizes the total national emissions of criteria pollutants from passenger cars 

4 and light trucks under the No Action Alternative. Table 4.3.3-1 lists the action alternatives (Alternatives 

5 2 through 9) left to right in order of generally increasing fuel economy requirements. In the case of 

6 particulate matter with an aerodynamic diameter equal to or greater than 2.5 microns (PM2.5), sulfur 

7 oxides (SOx), nitrogen oxides (NOx), and volatile organic compounds (VOCs), the No Action Alternative 

8 results in the highest emissions, and emissions generally decline as fuel economy standards increase 

9 across alternatives. Due to the interaction of VMT, fuel economy, and the share of VMT accrued by 

10 diesel vehicles, there are some exceptions to this declining trend (emissions increase from one individual 

11 alternative to the next higher fuel economy alternative), although emissions of these pollutants would 

12 remain below the levels under the No Action Alternative. These exceptions are NOx under Alternative 7 

13 in 2016; PM2.5 under Alternative 3 in 2030 and 2050, Alternative 4 in 2020, 2030, and 2050, Alternative 5 

14 in 2016 and 2020, Alternatives 6 and 7 in all years, and Alternative 9 in 2030 and 2050; SOx under 

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 

~5.9%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.7%/year 

Increase 

TCTB 

Carbon monoxide (CO) 

2016 18,046,737 18,055,567 18,054,219 18,049,276 17,990,071 17,954,866 17,943,080 17,930,498 17,927,150

2020 15,999,485 16,036,418 16,026,843 16,014,641 15,855,097 15,734,079 15,680,630 15,645,538 15,633,337

2030 17,816,418 18,001,706 17,934,568 17,893,423 17,432,546 16,991,218 16,749,111 16,641,134 16,600,732

2050 24,155,097 24,530,976 24,385,367 24,315,810 23,541,753 22,770,712 22,314,840 22,130,779 22,061,720

Nitrogen oxides (NOx) 

2016 2,043,669 2,040,386 2,038,801 2,038,077 2,035,890 2,033,211 2,033,658 2,032,473 2,031,999

2020 1,611,302 1,602,178 1,599,759 1,598,716 1,591,187 1,584,242 1,583,478 1,580,423 1,579,736

2030 1,460,039 1,441,960 1,438,364 1,437,032 1,410,643 1,385,381 1,374,322 1,365,493 1,363,497

2050 1,809,786 1,786,720 1,780,335 1,778,462 1,733,908 1,690,190 1,667,885 1,653,446 1,650,090

Particulate matter (PM2.5) 

2016 63,686 63,201 63,010 62,991 63,145 63,149 63,315 63,249 63,205

2020 62,568 61,146 60,931 60,970 61,102 61,259 61,570 61,420 61,400

2030 75,214 71,757 71,840 72,092 71,975 72,220 72,570 72,232 72,245

2050 107,387 102,210 102,469 102,885 102,501 102,698 103,025 102,490 102,512

Sulfur oxides (SOx) 

2016 164,406 161,493 160,246 159,818 160,089 159,031 159,855 159,312 159,006

2020 169,092 160,530 158,908 158,466 158,475 157,123 158,423 157,254 157,156

2030 193,480 171,806 171,744 171,993 171,402 169,671 171,512 169,231 169,555

2050 262,948 229,228 230,352 231,083 230,124 227,819 230,366 227,019 227,650

Volatile organic compounds (VOCs) 

2016 2,307,062 2,293,122 2,286,048 2,282,711 2,275,408 2,264,296 2,265,703 2,261,824 2,259,827

2020 1,940,313 1,900,024 1,889,242 1,884,635 1,867,354 1,845,387 1,842,769 1,834,396 1,832,809

2030 1,632,483 1,533,652 1,525,914 1,521,679 1,486,550 1,443,565 1,431,412 1,414,818 1,414,284

2050 1,803,222 1,652,075 1,645,210 1,640,518 1,587,401 1,522,744 1,501,494 1,476,771 1,476,595

15 
4.3 Air Quality Chapter 4 Cumulative Impacts 

 4-14 

1 Alternatives 3 in 2050, Alternative 4 in 2030 and 2050, Alternative 5 in 2016 and 2020, Alternative 7 in 

2 all years, and Alternative 9 in 2030 and 2050; and VOCs under Alternative 7 in 2016. Despite these 

3 individual increases, emissions of PM2.5, SOx, NOx, and VOCs remain below the levels under the No 

4 Action Alternative. In the case of CO, emissions under Alternatives 2 through 4 are slightly higher than 

5 under the No Action Alternative, and are lower than under the No Action Alternative for Alternatives 5 

6 through 9. Appendix C presents cumulative emissions of criteria pollutants for each nonattainment area. 

7 Table 4.3.3-2 lists the net changes in nationwide cumulative emissions from passenger cars and 

8 light trucks for the No Action Alternative for each criteria pollutant and analysis year. The table lists 

9 Alternatives 2 through 9 from left to right in order of generally increasing fuel economy requirements. 

10 The reductions in nationwide cumulative emissions generally increase from left to right, though unevenly, 

11 as noted above, due to the interaction of VMT, fuel economy, and the share of VMT accrued by diesel 

12 vehicles. There are some increases in CO emissions under Alternatives 2 through 4, as noted above, 

13 because increases in VMT more than offset declines in CO emission rates and increases in fuel economy. 

Table 4.3.3-2 

 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 

~5.9%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.7%/year 

Increase 

TCTB 

Carbon monoxide (CO) 

2016 0 8,829 7,482 2,539 -56,666 -91,872 -103,657 -116,240 -119,587

2020 0 36,933 27,358 15,156 -144,388 -265,407 -318,855 -353,947 -366,148

2030 0 185,288 118,150 77,005 -383,872 -825,200 -1,067,306 -1,175,284 -1,215,686

2050 0 375,879 230,270 160,713 -613,344 -1,384,385 -1,840,257 -2,024,318 -2,093,377

Nitrogen oxides (NOx) 

2016 0 -3,283 -4,868 -5,592 -7,779 -10,458 -10,011 -11,196 -11,670

2020 0 -9,124 -11,543 -12,586 -20,115 -27,061 -27,824 -30,879 -31,566

2030 0 -18,079 -21,675 -23,008 -49,396 -74,658 -85,717 -94,546 -96,543

2050 0 -23,066 -29,451 -31,324 -75,878 -119,596 -141,901 -156,340 -159,696

Particulate matter (PM2.5) 

2016 0 -486 -677 -696 -541 -538 -371 -438 -482

2020 0 -1,422 -1,637 -1,598 -1,466 -1,308 -998 -1,148 -1,167

2030 0 -3,456 -3,373 -3,122 -3,239 -2,994 -2,644 -2,982 -2,969

2050 0 -5,177 -4,918 -4,502 -4,886 -4,689 -4,362 -4,897 -4,875

Sulfur oxides (SOx) 

2016 0 -2,912 -4,160 -4,588 -4,316 -5,375 -4,551 -5,094 -5,400

2020 0 -8,562 -10,184 -10,626 -10,617 -11,969 -10,669 -11,838 -11,936

2030 0 -21,674 -21,735 -21,487 -22,078 -23,809 -21,968 -24,249 -23,925

2050 0 -33,720 -32,596 -31,865 -32,824 -35,129 -32,582 -35,928 -35,298

Volatile organic compounds (VOCs) 

2016 0 -13,941 -21,014 -24,352 -31,654 -42,766 -41,359 -45,238 -47,235

2020 0 -40,289 -51,071 -55,678 -72,959 -94,926 -97,544 -105,917 -107,504

2030 0 -98,830 -106,569 -110,804 -145,932 -188,917 -201,070 -217,665 -218,198

2050 0 -151,146 -158,012 -162,704 -215,820 -280,477 -301,727 -326,450 -326,627

__________ 

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. 

14 
Chapter 4 Cumulative Impacts 4.3 Air Quality 

 4-15 

1 Cumulative emissions in 2016 would be equivalent to the noncumulative emissions in all cases. 

2 Cumulative emissions of NOx, PM2.5, SO2, and VOCs in 2020 and 2030 would be less than 

3 noncumulative emissions for the same combination of pollutant, year, and alternative because of differing 

4 changes in VMT and fuel consumption under the cumulative case compared to the noncumulative case 

5 (i.e., because of the impact of projected higher average fuel economy in the cumulative analysis). 

6 Cumulative emissions of CO in 2020 and 2030 would be greater than the corresponding noncumulative 

7 emissions. 

8 4.3.3.2.2 Toxic Air Pollutants 

9 As with the criteria pollutants, current trends in the levels of toxic air pollutant emissions from 

10 vehicles would continue, with emissions of most toxic air pollutants continuing to decline, despite a 

11 growth in total VMT, as a result of the EPA emission standards. With current trends, emissions of diesel 

12 particulate matter (DPM) would increase in 2020, 2030, and 2050 over 2016 levels under the No Action 

13 Alternative. Alternative 1 (No Action) would result in no other increase or decrease in cumulative toxic 

14 air pollutant emissions in nonattainment and maintenance areas throughout the United States. 

15 Table 4.3.3-3 summarizes the cumulative national toxic air pollutant emissions from passenger 

16 cars and light trucks under the No Action Alternative for each toxic air pollutant and analysis year. The 

17 table lists Alternatives 2 through 9 from left to right in order of generally increasing fuel economy 

18 requirements. As with criteria pollutants, emissions of most toxic air pollutants would increase from one 

19 alternative to the next more stringent alternative. The exceptions are acetaldehyde emissions, which 

20 would decrease under Alternative 3 in 2050, Alternative 4 in 2020, 2030 and 2050, and Alternative 6 in 

21 2050; acrolein emissions, which would decrease under Alternative 9 in 2020, 2030 and 2050; benzene 

22 emissions, which would decrease under all alternatives and years except Alternative 2 in 2050; 1,3-

23 butadiene emissions, which would decrease under Alternatives 3 through 9 in 2030 and 2050, Alternative 

24 5 in 2020, and Alternative 7 in 2016 and 2020; DPM emissions, which would decrease under Alternatives 

25 2, 5, 6, and 8 in all years, Alternative 3 in 2016, 2020, and 2030, Alternative 4 in 2016 and 2020, 

26 Alternative 7 in 2030 and 2050, and Alternative 9 in 2016 and 2020; and formaldehyde emissions, which 

27 would decrease under Alternative 2 in 2016 and 2020. The changes in toxic air pollutant emissions, 

28 positive or negative, would generally be small in relation to the No Action Alternative emissions levels. 

29 The exceptions are acrolein emissions, which would increase by more than 10 percent under Alternatives 

30 6 through 9 in 2030 and 2050; DPM emissions, which would decrease by more than 10 percent under all 

31 action alternatives in 2030 and 2050, and Alternative 9 in 2020; and formaldehyde emissions, which 

32 would increase by more than 10 percent under Alternatives 8 and 9 in 2050. Appendix C presents the 

33 cumulative emissions of toxic air pollutants for each nonattainment area for the No Action Alternative. 

34 Cumulative emissions after 2016 would generally be greater than noncumulative emissions for 

35 the same combination of pollutant, year, and alternative because of differing changes in VMT and fuel 

36 consumption under the cumulative case compared to the noncumulative case (i.e., because of the impact 

37 of projected higher fuel economy in the cumulative analysis). The exceptions are acrolein under 

38 Alternative 9 in 2030 and 2050; benzene under all alternatives in 2020, and Alternatives 1 through 5 in 

39 2030; DPM under all alternatives in 2020 and 2030; and formaldehyde under Alternatives 1 through 4 in 

40 2020, and Alternative 1 in 2030. 

41 Emissions changes with the cumulative analysis (compared to the No Action Alternative) would 

42 be greater than the corresponding emissions changes with the noncumulative analysis for most toxic air 

43 pollutants. The exceptions are acrolein under Alternative 9 in all years; benzene under Alternatives 6 

44 through 9 in 2020, and Alternatives 3 through 9 in 2030; 1,3-butadiene under Alternatives 6 through 9 in 

45 2020 and 2030, and formaldehyde under Alternatives 3 through 6 in 2016. 
4.3 Air Quality Chapter 4 Cumulative Impacts 

 4-16 

Table 4.3.3-3 

 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 

~5.9%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.7%/year 

Increase 

TCTB 

Acetaldehyde 

2016 10,039 10,041 10,045 10,047 10,071 10,087 10,090 10,097 10,100

2020 7,929 7,940 7,948 7,948 7,987 8,018 8,034 8,047 8,052

2030 6,644 6,700 6,705 6,696 6,727 6,740 6,752 6,768 6,770

2050 7,953 8,070 8,064 8,048 8,074 8,068 8,068 8,088 8,088

Acrolein 

2016 521 521 522 522 527 531 531 533 533

2020 410 411 412 413 423 432 435 438 432

2030 343 346 349 352 367 386 394 399 386

2050 411 418 422 426 449 478 490 498 478

Benzene 

2016 52,316 52,296 52,283 52,272 52,222 52,177 52,171 52,157 52,151

2020 39,689 39,643 39,619 39,598 39,464 39,338 39,301 39,264 39,254

2030 27,680 27,659 27,597 27,546 27,169 26,760 26,571 26,471 26,444

2050 28,048 28,111 27,984 27,901 27,253 26,534 26,164 25,993 25,945

1,3-Butadiene 

2016 5,704 5,706 5,707 5,708 5,709 5,711 5,711 5,712 5,712

2020 4,505 4,512 4,514 4,514 4,513 4,515 4,514 4,516 4,516

2030 3,618 3,652 3,650 3,648 3,625 3,607 3,594 3,592 3,589

2050 4,180 4,249 4,239 4,235 4,189 4,148 4,117 4,111 4,106

Diesel particulate matter (DPM) 

2010 86,700 85,133 84,397 84,123 83,788 82,953 83,249 82,892 82,695

2020 89,057 84,468 83,431 83,124 82,204 80,814 81,010 80,256 80,135

2030 101,834 90,261 89,882 89,885 88,037 85,824 85,767 84,330 84,393

2050 138,391 120,407 120,494 120,706 118,016 114,922 114,724 112,629 112,810

Formaldehyde 

2010 12,851 12,848 12,856 12,863 12,954 13,014 13,028 13,051 13,062

2020 10,202 10,195 10,218 10,225 10,398 10,539 10,608 10,656 10,673

2030 8,867 8,885 8,927 8,939 9,203 9,448 9,582 9,664 9,684

2050 10,901 10,966 11,022 11,036 11,416 11,775 11,970 12,092 12,118

1 

2 Table 4.3.3-4 lists the net changes in nationwide cumulative emissions from passenger cars and 

3 light trucks compared to Alternative 1 (No Action) for each toxic air pollutant and analysis year. The 

4 table lists Alternatives 2 through 9 left to right in order of generally increasing fuel economy 

5 requirements. 

6 
Chapter 4 Cumulative Impacts 4.3 Air Quality 

 4-17 

Table 4.3.3-4 

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 

~5.9%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.7%/year 

Increase 

TCTB 

Acetaldehyde 

2016 0 3 7 8 32 48 51 58 61

2020 0 11 19 19 58 89 105 118 123

2030 0 57 61 53 84 97 109 125 127

2050 0 118 112 95 121 115 116 135 135

Acrolein 

2016 0 0 1 1 6 10 10 12 12

2020 0 1 2 3 13 22 25 28 22

2030 0 3 6 9 24 43 51 56 43

2050 0 7 11 15 38 67 79 87 67

Benzene 

2016 0 -19 -33 -43 -93 -139 -144 -159 -164

2020 0 -45 -70 -91 -225 -350 -388 -425 -435

2030 0 -21 -83 -134 -511 -920 -1,109 -1,209 -1,236

2050 0 62 -64 -147 -795 -1,514 -1,884 -2,055 -2,103

1,3-Butadiene 

2016 0 2 3 3 5 7 6 7 8

2020 0 7 9 10 8 10 10 11 11

2030 0 34 32 30 7 -11 -24 -26 -29

2050 0 69 58 54 8 -32 -64 -69 -75

Diesel particulate matter (DPM) 

2010 0 -1,567 -2,302 -2,577 -2,911 -3,747 -3,451 -3,807 -4,005

2020 0 -4,589 -5,626 -5,933 -6,853 -8,243 -8,047 -8,801 -8,922

2030 0 -11,572 -11,952 -11,949 -13,797 -16,010 -16,067 -17,504 -17,441

2050 0 -17,984 -17,897 -17,685 -20,375 -23,469 -23,667 -25,762 -25,581

Formaldehyde 

2010 0 -4 5 11 103 163 177 200 210

2020 0 -7 16 23 195 337 406 454 470

2030 0 18 61 72 336 581 715 797 817

2050 0 66 121 135 516 874 1,070 1,192 1,218

__________ 

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. 

1 

2 4.3.3.2.3 Health Outcomes and Costs 

3 Under Alternative 1 (No Action), average fuel economy would remain at the 2011 level until 

4 2016, increase as projected by AEO until 2030, and then remain at the 2030 level through 2050. 

5 Emissions of criteria pollutants and toxic air pollutants would change as described above. Human health 

6 effects of emissions are tied to specific pollutants, and will vary as emissions of these pollutants vary. 
4.3 Air Quality Chapter 4 Cumulative Impacts 

 4-18 

1 The No Action Alternative would result in no other increase or decrease in human health effects 

2 throughout the United States compared to current trends because the No Action Alternative represents 

3 maintaining the status quo (i.e., no action by either NHTSA or the EPA). 

4 Table 4.3.3-5 lists the net changes in health outcomes due to nationwide cumulative emissions in 

5 each analysis year. The table lists Alternatives 1 through 9 left to right in order of generally increasing 

6 fuel economy requirements. The health impacts of vehicle emissions decrease successively (i.e., the 

7 benefits increase) in each analysis year, and generally decrease across more stringent alternatives through 

8 Alternative 3, with mixed results under Alternatives 4 through 7, and decreasing again under Alternatives 

9 8 and 9. 

Table 4.3.3-5 

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 

~5.9%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.7%/year 

Increase 

TCTB 

Mortality (ages 30 and older) 

Pope et al. 2002 

2016 0 -26 -36 -39 -36 -41 -34 -38 -41

2020 0 -77 -91 -92 -95 -101 -89 -100 -101

2030 0 -215 -216 -208 -239 -260 -252 -280 -280

2050 0 -364 -356 -339 -406 -453 -455 -504 -504

Laden et al. 2006 

2016 0 -66 -93 -99 -92 -106 -87 -98 -105

2020 0 -199 -234 -237 -245 -259 -229 -256 -260

2030 0 -551 -553 -532 -612 -665 -646 -717 -718

2050 0 -930 -911 -867 -1,037 -1,157 -1,162 -1,287 -1,288

Chronic Bronchitis 

2016 0 -17 -25 -26 -24 -28 -23 -26 -28

2020 0 -53 -63 -63 -66 -69 -61 -69 -70

2030 0 -141 -142 -136 -158 -172 -167 -186 -186

2050 0 -230 -226 -215 -259 -290 -292 -323 -323

Emergency Room Visits for Asthma 

2016 0 -24 -34 -37 -34 -39 -32 -37 -39

2020 0 -74 -87 -89 -90 -96 -84 -94 -96

2030 0 -197 -198 -191 -213 -230 -220 -245 -244

2050 0 -323 -315 -300 -347 -382 -377 -417 -416

Work Loss Days 

2010 0 -3,365 -4,776 -5,093 -4,713 -5,423 -4,444 -5,045 -5,390

2020 0 -9,983 -11,769 -11,896 -12,350 -13,073 -11,527 -12,916 -13,120

2030 0 -25,339 -25,475 -24,466 -28,335 -30,890 -30,088 -33,394 -33,445

2050 0 -39,749 -38,969 -37,043 -44,648 -49,958 -50,334 -55,754 -55,808

__________ 

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. 

10 
Chapter 4 Cumulative Impacts 4.3 Air Quality 

 4-19 

1 In Table 4.3.3-5 the health impacts of each alternative are expressed in terms of changes in health 

2 outcomes compared to the No Action Alternative. The health impacts of each alternative represent 

3 predicted changes from the baseline incidence (or prevalence) rates. To provide context for the estimated 

4 health impacts given in Table 4.3.3-5, it is helpful to compare the impacts to sample baseline incidence 

5 rates. These sample baseline incidence rates provide an estimate of the typical prevalence rates of each 

6 outcome nationwide under the No Action Alternative. The EPA Report to Congress on The Benefits and 

7 Costs of the Clean Air Act 1990 to 2010 (EPA 1999) estimated baseline rates for particulate matter (PM)-

8 related mortality and morbidity for 2010. Generally, the EPA extrapolated these baseline rates from the 

9 health effect concentration-response function, or estimated them using hospital admissions rates for 

10 respiratory and cardiovascular conditions. The EPA analysis estimated the following mean baseline 

11 incidence rates (cases per year) for PM-related effects nationwide in 2010: 2.3 million cases of premature 

12 mortality, 640,000 cases of chronic bronchitis, 870,000 hospital emergency room visits for asthma, and 

13 440 million work loss days. 

14 The economic value of health impacts would vary proportionally with changes in health 

15 outcomes under the methodology defined in Section 3.3.2.4.2. The economic impacts analyzed here are 

16 the result of changes in ambient PM concentrations caused by changes in the precursor criteria pollutants 

17 NOx, VOCs, SO2, and PM2.5. Alternative 1 (No Action) would result in no other change in health-related 

18 costs throughout the United States, compared to current trends because the No Action Alternative 

19 represents maintaining the status quo (i.e., no action by either NHTSA or the EPA). 

20 Table 4.3.3-6 lists the nationwide changes in health costs from cumulative emissions from 

21 passenger cars and light trucks. Results for each analysis year are shown for the No Action Alternative in 

22 the left column, and for the other alternatives from left to right in order of generally increasing fuel 

23 economy requirements. Economic impacts follow the trends established with health outcomes above, 

24 generally decreasing (i.e., benefits increasing) across more stringent alternatives through Alternative 3, 

25 with mixed results under Alternatives 4 through 7, and decreasing again under Alternatives 8 and 9. 

Table 4.3.3-6 

Cumulative Nationwide Changes in Health Costs (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 

~5.9%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.7%/year 

Increase 

TCTB 

3-% Discount Rate

Pope et al. 2002 

2016 0 a/ -215 -306 -326 -302 -348 -285 -324 -346

2020 0 -673 -794 -803 -830 -880 -775 -868 -882

2030 0 -1,913 -1,922 -1,848 -2,126 -2,313 -2,246 -2,492 -2,495

2050 0 -3,292 -3,225 -3,067 -3,672 -4,097 -4,116 -4,558 -4,560

Laden et al. 2006 

2016 0 -528 -749 -800 -739 -853 -699 -793 -847

2020 0 -1,649 -1,944 -1,967 -2,034 -2,155 -1,898 -2,126 -2,159

2030 0 -4,688 -4,711 -4,528 -5,209 -5,665 -5,501 -6,105 -6,110

2050 0 -8,069 -7,903 -7,518 -8,999 -10,040 -10,083 -11,167 -11,171
4.3 Air Quality Chapter 4 Cumulative Impacts 

 4-20 

Table 4.3.3-6 (cont’d) 

Cumulative Nationwide Changes in Health Costs (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 

~5.9%/year 

Increase 

MNB 

6%/year 

Increase 

7%/year 

Increase 

~6.7%/year 

Increase 

TCTB 

7-% Discount Rate

Pope et al. 2002 

2016 0 -196 -277 -296 -274 -316 -259 -294 -314

2020 0 -611 -720 -729 -753 -798 -703 -788 -800

2030 0 -1,735 -1,744 -1,676 -1,929 -2,098 -2,037 -2,261 -2,263

2050 0 -2,985 -2,924 -2,782 -3,331 -3,716 -3,733 -4,134 -4,136

Laden et al. 2006 

2010 0 -477 -677 -723 -668 -770 -631 -716 -765

2020 0 -1,490 -1,756 -1,777 -1,837 -1,947 -1,715 -1,921 -1,950

2030 0 -4,235 -4,255 -4,090 -4,705 -5,117 -4,969 -5,515 -5,519

2050 0 -7,287 -7,138 -6,790 -8,128 -9,068 -9,107 -10,087 -10,090

__________ 

a/ Negative changes indicate economic benefit; positive emissions changes indicate economic costs. 

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. 

1 

2 4.3.3.3 Alternative 2: 3-Percent Annual Increase 

3 4.3.3.3.1 Criteria Pollutants 

4 Under the 3-Percent Alternative (Alternative 2), generally the CAFE standards would require 

5 increased fuel economy compared to the No Action Alternative (Alternative 1). Alternative 2 would 

6 increase fuel economy less than Alternatives 3 through 9. There would be reductions in nationwide 

7 emissions of NOx, PM2.5, SOx, and VOCs under Alternative 2 compared to the No Action Alternative. 

8 Depending on the year, NOx emissions would be reduced 0.2 to 1.3 percent, PM2.5 emissions would be 

9 reduced 0.8 to 4.8 percent, SOx emissions would be reduced 1.8 to 12.8 percent, and VOC emissions 

10 would be reduced 0.6 to 8.4 percent, compared to emissions projected under the No Action Alternative. 

11 There would be increases of CO emissions. CO emissions would increase 0.05 to 1.6 percent under 

12 Alternative 2, depending on the year, compared to emissions projected under the No Action Alternative. 

13 Emissions in individual nonattainment areas might follow different patterns from nationwide 

14 emissions. Emissions of criteria pollutants vary due to interrelations among upstream emissions, VMT 

15 increases, and diesel share of VMT and fuel usage. Compared to Alternative 1, cumulative emissions of 

16 SOx and VOCs under Alternative 2 would decrease in all nonattainment areas. In contrast, CO emissions 

17 would increase in almost all nonattainment areas, while NOx and PM emissions would decrease in some 

18 nonattainment areas and increase in others. Tables in Appendix C list emissions reductions for each 

19 nonattainment area. 

20 Cumulative fuel economy standards would lead to lower emissions of most pollutants compared 

21 to noncumulative standards, due to the impact of higher projected average fuel economy in the cumulative 

22 case. Under Alternative 2, cumulative emissions of NOx, PM2.5, SOx, and VOCs are lower than 

23 noncumulative emissions. However, emissions of CO are higher under the cumulative case than the 

24 noncumulative case, because increases in VMT more than offset declines in CO emission rates and 

25 increases in fuel economy. 
Chapter 4 Cumulative Impacts 4.3 Air Quality 

 4-21 

1 Emissions reductions (compared to the No Action Alternative) under the Alternative 2 

2 cumulative analysis would be greater than the corresponding emissions reductions under the Alternative 2 

3 noncumulative analysis for NOx, PM2.5, SO2, and VOCs. For CO, emissions increases under Alternative 2 

4 cumulative analysis would be greater than the corresponding emissions increases under Alternative 2 

5 noncumulative analysis. 

6 4.3.3.3.2 Toxic Air Pollutants 

7 Under Alternative 2, cumulative emissions of acetaldehyde, acrolein, 1,3-butadiene, and 

8 formaldehyde (in 2030) would be greater than noncumulative emissions for the same combinations of 

9 pollutant and year. Cumulative emissions of benzene, DPM, and formaldehyde (in 2020) would generally 

10 be less than noncumulative emissions for the same combinations of pollutant and year. 

11 Alternative 2 would reduce toxic air pollutant emissions compared to the No Action Alternative 

12 for benzene (except in 2050), DPM, and formaldehyde (in 2016 and 2020), and would increase emissions 

13 of acetaldehyde, acrolein, benzene (in 2050), 1,3-butadiene, and formaldehyde (in 2030 and 2050). 

14 Compared to Alternatives 3 through 9, Alternative 2 would result in lower emissions of acetaldehyde 

15 (except Alternative 4 in 2030, and Alternatives 3, 4, 6, and 7 in 2050), acrolein (in all years), 1,3-

16 butadiene (in 2030 and 2050), DPM (under Alternatives 3 and 4 in 2050), and formaldehyde. 

17 Emissions changes (compared to the No Action Alternative) under the Alternative 2 cumulative 

18 analysis would be greater than the corresponding emissions changes under the Alternative 2 

19 noncumulative analysis for all toxic air pollutants. 

20 Nationwide, the reduction in upstream emissions of toxic air pollutants tends to offset the 

21 increase in VMT and emissions due to the rebound effect. However, as noted above, the reductions in 

22 upstream emissions are not uniformly distributed to individual nonattainment areas. There can be net 

23 emission reductions if the reduction in upstream emissions in the nonattainment area more than offsets the 

24 increase within the area due to the rebound effect. Under Alternative 2, most nonattainment areas would 

25 experience net increases in emissions of one or more toxic air pollutant in at least one of the analysis 

26 years (see Appendix C). However, the emissions increases would be quite small, as shown in 

27 Appendix C, and emissions increases would be distributed throughout each nonattainment area. 

28 4.3.3.3.3 Health Outcomes and Costs 

29 Compared to Alternative 1 (No Action), the cumulative impact of Alternative 2 would result in 

30 364 fewer mortalities and 39,749 fewer work-loss days in 2050. Mortality benefits are measured 

31 according to Pope et al. (2002); reductions would be 156 percent greater using the Laden et al. (2006) 

32 benefit-per-ton values. 

33 Table 4.3.3-6 lists the corresponding reductions in health costs under Alternative 2 compared to 

34 the No Action Alternative. In 2050, Alternative 2 would reduce health costs by $3.3 billion annually 

35 using a 3-percent discount rate and estimates from Pope et al. (2002). With the Laden et al. (2006) 

36 method, economic benefits would be 145 percent greater. Using a 7-percent discount rate, economic 

37 benefits would be 9.3 to 9.5 percent less. Alternative 2 would result in less health and economic benefit 

38 than other more stringent alternatives. 
4.3 Air Quality Chapter 4 Cumulative Impacts 

 4-22 

1 4.3.3.4 Alternative 3: 4-Percent Annual Increase 

2 4.3.3.4.1 Criteria Pollutants 

3 Under the 4-Percent Alternative (Alternative 3), the CAFE standards generally would increase 

4 fuel economy more than Alternative 2 but less than Alternatives 4 through 9. There would be reductions 

5 in nationwide emissions of NOx, PM2.5, SOx, and VOCs under Alternative 3 compared to the No Action 

6 Alternative. Depending on the year, NOx emissions would be reduced 0.2 to 1.6 percent, PM2.5 emissions 

7 would be reduced 1.1 to 4.6 percent, SOx emissions would be reduced 2.5 to 12.4 percent, and VOC 

8 emissions would be reduced 0.9 to 8.8 percent, compared to emissions projected under the No Action 

9 Alternative. Except for emissions of PM2.5 in 2030 and 2050, and SOx in 2050, these emissions 

10 reductions are generally greater than would occur under Alternative 2. Except for emissions of PM2.5 in 

11 all years and SOx in 2030 and 2050, these emissions reductions are generally greater than would occur 

12 under Alternatives 4 through 9. There would be increases of CO emissions from 0.04 to 1.0 percent, 

13 depending on the year, compared to emissions projected under the No Action Alternative. 

14 Emissions in individual nonattainment areas might follow different patterns from nationwide 

15 emissions. Emissions of criteria pollutants vary due to interrelations among upstream emissions, VMT 

16 increases, and diesel share of fuel consumption. Compared to Alternative 1, cumulative emissions of SOx

17 and VOCs under Alternative 3 would decrease in all nonattainment areas. In contrast, CO emissions 

18 would increase in almost all nonattainment areas, while NOx and PM2.5 emissions would would decrease 

19 in some nonattainment areas and increase in others. Tables in Appendix C list the emissions reductions 

20 for each nonattainment area. 

21 Cumulative fuel economy standards would lead to lower emissions of most pollutants compared 

22 to noncumulative standards, due to the impact of higher projected average fuel economy in the cumulative 

23 case. Under Alternative 3, cumulative emissions of NOx, PM2.5, SOx, and VOCs would be lower than 

24 noncumulative emissions. However, emissions of CO are higher under the cumulative case than the 

25 noncumulative case, because increases in VMT more than offset declines in CO emission rates and 

26 increases in fuel economy. 

27 Emissions reductions (compared to the No Action Alternative) under the Alternative 3 cumulative 

28 analysis would be less than the corresponding emissions reductions under the Alternative 3 

29 noncumulative analysis for NOx, PM2.5, SO2, and VOCs, except for NOx in 2020, PM2.5 and VOCs in 

30 2020 and 2030, and SO2 in all years. For CO, emissions increases under the Alternative 3 cumulative 

31 analysis would be greater than the corresponding emissions increases under the Alternative 3 

32 noncumulative analysis. For CO, emissions reductions under the Alternative 3 cumulative analysis would 

33 be less than the corresponding emissions reductions under the Alternative 3 noncumulative analysis. 

34 4.3.3.4.2 Toxic Air Pollutants 

35 Under Alternative 3, cumulative emissions would be less than noncumulative emissions for some 

36 combinations of pollutant and year and greater than noncumulative emissions for other combinations of 

37 pollutant and year. 

38 Alternative 3 would reduce toxic air pollutant emissions compared to the No Action Alternative 

39 for benzene and DPM, and would increase emissions of acetaldehyde, acrolein, 1,3-butadiene, and 

40 formaldehyde compared to the No Action Alternative. Compared to Alternatives 4 through 9, Alternative 

41 3 would result in higher emissions of benzene and DPM (except under Alternative 4 in 2030 and 2050), 

42 and lower emissions of acetaldehyde (except under Alternative 4 in 2030 and 2050), acrolein, 1,3-

43 butadiene (except in 2030 and 2050), and formaldehyde. 
Chapter 4 Cumulative Impacts 4.3 Air Quality 

 4-23 

1 Emissions changes (compared to the No Action Alternative) under the Alternative 3 cumulative 

2 analysis would be greater than the corresponding emissions changes under the Alternative 3 

3 noncumulative analysis for all toxic air pollutants except benzene (in 2030) and formaldehyde (in 2016). 

4 For benzene (in 2030) and formaldehyde (in 2016), emissions changes under the Alternative 3 cumulative 

5 analysis would be less than the corresponding emissions changes under the Alternative 3 noncumulative 

6 analysis. 

7 Nationwide, emissions of toxic air pollutants can decrease because the reduction in upstream 

8 emissions more than offsets the increase in VMT and emissions due to the rebound effect. However, the 

9 reductions in upstream emissions are not uniformly distributed to individual nonattainment areas. Under 

10 Alternative 3, most nonattainment areas would experience net increases in emissions of one or more toxic 

11 air pollutant in at least one of the analysis years (see Appendix C). However, the emissions increases 

12 would be quite small, as shown in Appendix C, and emissions increases would be distributed throughout 

13 each nonattainment area. 

14 4.3.3.4.3 Health Outcomes and Costs 

15 Compared to Alternative 1 (No Action), the cumulative impact of Alternative 3 would result in 

16 356 fewer mortalities and 38,969 fewer work-loss days in 2050. Mortality benefits are measured 

17 according to Pope et al.(2002); reductions would be 156 percent greater under the Laden et al. (2006) 

18 methodology. 

19 Table 4.3.3-6 lists the corresponding reductions in health costs under Alternative 3 compared to 

20 the No Action Alternative. In 2050, Alternative 3 would reduce health costs by $3.2 billion annually, 

21 using a 3-percent discount rate and estimates from Pope et al. (2002). With the Laden et al. (2006) 

22 method, economic benefits would be 145 percent greater. Using a 7-percent discount rate, economic 

23 benefits would be 9.3 to 9.5 percent less. 

24 4.3.3.5 Alternative 4: Preferred Alternative 

25 4.3.3.5.1 Criteria Pollutants 

26 Under the Preferred Alternative (Alternative 4), the CAFE standards would increase fuel 

27 economy more than Alternatives 1 through 3 but less than Alternatives 5 through 9. There would be 

28 reductions in nationwide emissions of NOx, PM2.5, SOx, and VOCs under Alternative 4 compared to the 

29 No Action Alternative. Depending on the year, NOx emissions would be reduced 0.3 to 1.7 percent, 

30 PM2.5 emissions would be reduced 1.1 to 4.2 percent, SOx emissions would be reduced 2.8 to 12.1 

31 percent, and VOC emissions would be reduced 1.1 to 9.0 percent, compared to emissions projected under 

32 the No Action Alternative. The emissions reductions for these pollutants are generally greater than would 

33 occur under Alternative 3, except for PM2.5 in 2020, 2030, and 2050, and SOx in 2030 and 2050. 

34 Emissions reductions of these four pollutants under Alternative 4 would be less than would occur under 

35 Alternatives 5 through 9, except for PM2,5 in 2016, 2020, and 2030, and SOx in 2016 and 2020 (as 

36 compared to Alternative 5). There would be increases of CO emissions of 0.1 to 0.7 percent, depending 

37 on the year, compared to emissions projected under the No Action Alternative. 

38 Emissions in individual nonattainment areas might follow different patterns from nationwide 

39 emissions. Emissions of criteria pollutants vary due to interrelations among upstream emissions, VMT 

40 increases, and diesel share of fuel consumption. Compared to Alternative 1, cumulative emissions of SOx

41 and VOCs under Alternative 4 would decrease in all nonattainment areas. In contrast, CO emissions 

42 would increase in almost all nonattainment areas, while NOx and PM emissions would decrease in some 
4.3 Air Quality Chapter 4 Cumulative Impacts 

 4-24 

1 nonattainment areas and increase in others. Tables in Appendix C list the emissions reductions for each 

2 nonattainment area. 

3 Cumulative fuel economy standards would lead to lower emissions of most pollutants compared 

4 to noncumulative standards, due to the impact of higher projected average fuel economy in the cumulative 

5 case. Under Alternative 4, cumulative emissions of NOx, PM2.5, SOx, and VOCs are lower than 

6 noncumulative emissions. However, emissions of CO are higher under the cumulative case than the 

7 noncumulative case, because increases in VMT more than offset declines in CO emission rates and 

8 increases in fuel economy. 

9 Emissions reductions (compared to the No Action Alternative) under the Alternative 4 cumulative 

10 analysis would be less than the corresponding emissions reductions under the Alternative 4 

11 noncumulative analysis for NOx, PM2.5, SO2, and VOCs. For CO, emissions increases under the 

12 Alternative 4 cumulative analysis would be greater than the corresponding emissions increases under the 

13 Alternative 4 noncumulative analysis. 

14 4.3.3.5.2 Toxic Air Pollutants 

15 Under Alternative 4, cumulative emissions would be less than noncumulative emissions for some 

16 combinations of pollutant and year and greater than noncumulative emissions for other combinations of 

17 pollutant and year. 

18 Alternative 4 would reduce toxic air pollutant emissions compared to the No Action Alternative 

19 for benzene and DPM, and would increase emissions of acetaldehyde, acrolein, 1,3-butadiene, and 

20 formaldehyde compared to the No Action Alternative. Compared to Alternatives 5 through 9, Alternative 

21 4 would result in higher emissions of benzene (in 2030 and 2050) and DPM, and lower emissions of 

22 acetaldehyde, acrolein, 1,3-butadiene (in 2016 and 2020), and formaldehyde. 

23 Emissions changes (compared to the No Action Alternative) under the Alternative 4 cumulative 

24 analysis would be greater than the corresponding emissions changes under the Alternative 4 

25 noncumulative analysis for all toxic air pollutants except benzene (in 2030) and formaldehyde (in 2016). 

26 For benzene (in 2030) and formaldehyde (in 2016), emissions changes under the Alternative 4 cumulative 

27 analysis would be less than the corresponding emissions changes under the Alternative 4 noncumulative 

28 analysis. 

29 Nationwide, emissions of toxic air pollutants can decrease because the reduction in upstream 

30 emissions more than offsets the increase in VMT and emissions due to the rebound effect. However, the 

31 reductions in upstream emissions would not occur uniformly in all nonattainment areas. Under 

32 Alternative 4, most nonattainment areas would experience net increases in emissions of one or more toxic 

33 air pollutant in at least one of the analysis years (see Appendix C). However, the emissions increases 

34 would be quite small, as shown in Appendix C, and emissions increases would be distributed throughout 

35 each nonattainment area. 

36 4.3.3.5.3 Health Outcomes and Costs 

37 Compared to Alternative 1 (No Action), the cumulative impact of Alternative 4 would result in 

38 339 fewer mortalities and 37,043 fewer work-loss days in 2050. Mortality benefits are measured 

39 according to Pope et al. (2002); reductions would be 156 percent greater using the Laden et al. (2006) 

40 methodology. 
Chapter 4 Cumulative Impacts 4.3 Air Quality 

 4-25 

1 Table 4.3.3-6 lists the corresponding reductions in health costs under Alternative 4 compared to 

2 the No Action Alternative. In 2050, Alternative 4 would reduce health costs by $3.1 billion annually, 

3 using a 3-percent discount rate and estimates from Pope et al. (2002). With the Laden et al. (2006)

4 method, economic benefits would be 145 percent greater. Using a 7-percent discount rate, economic 

5 benefits would be 9.3 to 9.5 percent less. 

6 Compared to more stringent alternatives, health and economic benefits are less than for all 

7 successive alternatives. 

8 4.3.3.6 Alternative 5: Five Percent Annual Increase 

9 4.3.3.6.1 Criteria Pollutants 

10 Under the 5-Percent Alternative (Alternative 5), the CAFE standards would increase fuel 

11 economy more than Alternatives 1 through 4 but less than Alternatives 6 through 9. There would be 

12 reductions in nationwide emissions of all criteria pollutants under Alternative 5 compared to the No 

13 Action Alternative. Reductions under Alternative 5 would be greater than under Alternative 4 (except for 

14 PM2.5 and SOx in 2016 and 2020), and less than under Alternative 6 through 9 (except for PM2.5 for all 

15 years and alternatives but Alternatives 8 and 9 in 2050, and for SOx for Alternative 7 in 2030 and 2050). 

16 Depending on the year, CO emissions would be reduced 0.3 to 2.5 percent, NOx emissions would be 

17 reduced 0.4 to 4.2 percent, PM2.5 emissions would be reduced 0.8 to 4.6 percent, SOx emissions would be 

18 reduced 2.6 to 12.5 percent, and VOC emissions would be reduced 1.4 to 12.0 percent, compared to 

19 emissions projected under the No Action Alternative. 

20 Emissions in individual nonattainment areas could follow different patterns from nationwide 

21 emissions. Emissions of criteria pollutants vary due to interrelations among upstream emissions, VMT 

22 increases, and diesel share of fuel. Compared to Alternative 1, cumulative emissions of CO, NOx, SOx, 

23 and VOCs under Alternative 5 would decrease in all nonattainment areas. PM2.5 results would be mixed, 

24 with emissions increasing in some nonattainment areas and decreasing in others. Tables in Appendix C 

25 list the emissions reductions for each nonattainment area. 

26 Cumulative fuel economy standards would lead to lower emissions of most pollutants compared 

27 to noncumulative standards, due to the impact of higher projected average fuel economy in the cumulative 

28 case. Under Alternative 5, cumulative emissions of NOx, PM2.5, SOx, and VOCs are lower than 

29 noncumulative emissions. However, emissions of CO are higher under the cumulative case than the 

30 noncumulative case, because increases in VMT more than offset declines in CO emission rates and 

31 increases in fuel economy. 

32 Emissions reductions (compared to the No Action Alternative) under the Alternative 5 cumulative 

33 analysis would be greater than the corresponding emissions reductions under the Alternative 5 

34 noncumulative analysis for NOx, PM2.5, SO2, and VOCs. For CO, emissions reductions under the 

35 Alternative 5 cumulative analysis would be less than the corresponding emissions reductions under the 

36 Alternative 5 noncumulative analysis. 

37 4.3.3.6.2 Toxic Air Pollutants 

38 Under Alternative 5, cumulative emissions would be less than noncumulative emissions for some 

39 combinations of pollutant and year and greater than noncumulative emissions for other combinations of 

40 pollutant and year. 
4.3 Air Quality Chapter 4 Cumulative Impacts 

 4-26 

1 Alternative 5 would reduce toxic air pollutant emissions compared to the No Action Alternative 

2 for benzene and DPM, and would increase emissions of acetaldehyde, acrolein, 1,3-butadiene, and 

3 formaldehyde compared to the No Action Alternative. Compared to Alternatives 6 through 9, Alternative 

4 5 would result in higher emissions of benzene, 1,3-butadiene (in 2030 and 2050), and DPM, and lower 

5 emissions of acetaldehyde, acrolein, 1,3-butadiene (in 2016 and 2020), and formaldehyde. 

6 Emissions changes (compared to the No Action Alternative) under the Alternative 5 cumulative 

7 analysis would be greater than the corresponding emissions changes under the Alternative 4 

8 noncumulative analysis for all toxic air pollutants except benzene (in 2030). For benzene (in 2030) 

9 emissions changes under the Alternative 5 cumulative analysis would be less than the corresponding 

10 emissions changes under the Alternative 5 noncumulative analysis. 

11 Nationwide, emissions of toxic air pollutants can decrease because the reduction in upstream 

12 emissions more than offsets the increase in VMT and emissions due to the rebound effect. However, the 

13 reductions in upstream emissions are not uniformly distributed to individual nonattainment areas. Under 

14 Alternative 5, most nonattainment areas would experience net increases in emissions of one or more toxic 

15 air pollutant in at least one of the analysis years (see Appendix C). However, the emissions increases 

16 would be quite small, as shown in Appendix C, and emissions increases would be distributed throughout 

17 each nonattainment area. 

18 4.3.3.6.3 Health Outcomes and Costs 

19 Compared to Alternative 1 (No Action), the cumulative impact of Alternative 5 would result in 

20 406 fewer mortalities and 44,648 fewer work-loss days in 2050. Mortality benefits are measured 

21 according to Pope et al.(2002); reductions would be 156 percent greater using the Laden et al. (2006) 

22 methodology. 

23 Table 4.3.3-6 lists the corresponding reductions in health costs under Alternative 5 compared to 

24 the No Action Alternative. In 2050, Alternative 5 would reduce health costs by $3.7 billion annually, 

25 using a 3-percent discount rate and estimates from Pope et al. (2002). With the Laden et al. (2006) 

26 method, economic benefits would be 145 percent greater. Using a 7-percent discount rate, economic 

27 benefits would be 9.3 to 9.5 percent less. 

28 Compared to Alternative 5, health and economic benefits would be greater under Alternatives 6, 

29 8, and 9, and Alternative 7 in 2050, but less under Alternative 7 in 2016, 2020, and 2030. 

30 4.3.3.7 Alternative 6: MNB 

31 4.3.3.7.1 Criteria Pollutants 

32 Under the MNB (Alternative 6), the CAFE standards would increase fuel economy more than 

33 Alternatives 1 through 4 but less than Alternatives 7 through 9. There would be reductions in nationwide 

34 emissions of all criteria pollutants under Alternative 6 compared to the No Action Alternative. 

35 Reductions under Alternative 6 would be greater than under Alternative 5 (except for PM2.5 for all years), 

36 less than under Alternative 7 (except in for NOx and VOCs in 2016 and PM2.5 and SOx in all years), less 

37 than under Alternative 8 (except for PM2.5 in 2016, 2020, and 2030 and SOx in 2016 and 2020), and less 

38 than under Alternative 9 (except for PM2.5 in 2016, 2020, and 2030 and SOx in 2020). Depending on the 

39 year, CO emissions would be reduced 0.5 to 5.7 percent, NOx emissions would be reduced 0.5 to 6.6 

40 percent, PM2.5 emissions would be reduced 0.8 to 4.4 percent, SOx emissions would be reduced 3.3 to 

41 13.4 percent, and VOC emissions would be reduced 1.9 to 15.6 percent, compared to emissions projected 

42 under the No Action Alternative. 
Chapter 4 Cumulative Impacts 4.3 Air Quality 

 4-27 

1 Emissions in individual nonattainment areas could follow different patterns from nationwide 

2 emissions. Emissions of criteria pollutants vary due to interrelations among upstream emissions, VMT 

3 increases, and diesel share of fuel consumption. Compared to Alternative 1, cumulative emissions of CO, 

4 NOx, SOx, and VOCs under Alternative 6 would decrease in all nonattainment areas. PM2.5 results are 

5 mixed, with emissions increasing in some nonattainment areas and decreasing in others. Tables in 

6 Appendix C list the emissions reductions for each nonattainment area. 

7 Cumulative fuel economy standards would lead to lower emissions of most pollutants compared 

8 to noncumulative standards, due to the impact of higher projected average fuel economy in the cumulative 

9 case. Under Alternative 6, cumulative emissions of NOx, PM2.5, SOx, and VOCs would be lower than 

10 noncumulative emissions. However, emissions of CO would be higher under the cumulative case than 

11 the noncumulative case, because increases in VMT more than offset declines in CO emission rates and 

12 increases in fuel economy. 

13 Emissions reductions (compared to the No Action Alternative) under the Alternative 6 cumulative 

14 analysis would be less than the corresponding emissions reductions under the Alternative 6 

15 noncumulative analysis for all pollutants. 

16 4.3.3.7.2 Toxic Air Pollutants 

17 Under Alternative 6, cumulative emissions would be less than noncumulative emissions for some 

18 combinations of pollutant and year and greater than noncumulative emissions for other combinations of 

19 pollutant and year. Alternative 6 would reduce toxic air pollutant emissions compared to the No Action 

20 Alternative for benzene, 1,3-butadiene (in 2030 and 2050), and DPM, and would increase emissions of 

21 acetaldehyde, acrolein, 1,3-butadiene (in 2016 and 2020), and formaldehyde compared to the No Action 

22 Alternative. Compared to Alternatives 7 through 9, Alternative 6 would result in higher emissions of 

23 benzene, 1,3-butadiene (in 2030 and 2050), and DPM (except under Alternative 7 in 2016 and 2020), and 

24 lower emissions of acetaldehyde, acrolein, 1,3-butadiene (in 2016 and 2020), and formaldehyde. 

25 Emissions changes (compared to the No Action Alternative) under the Alternative 6 cumulative 

26 analysis would be greater than the corresponding emissions changes under the Alternative 6 

27 noncumulative analysis for all toxic air pollutants except benzene (in 2020 and 2030), 1,3-butadiene (in 

28 2020 and 2030), and formaldehyde (in 2016). For benzene (in 2020 and 2030), 1,3-butadiene (in 2020 

29 and 2030), and formaldehyde (in 2016) the emissions changes under the Alternative 6 cumulative analysis 

30 would be less than the corresponding emissions changes under the Alternative 6 noncumulative analysis. 

31 Nationwide, emissions of toxic air pollutants can decrease because the reduction in upstream 

32 emissions more than offsets the increase in VMT and emissions due to the rebound effect. However, the 

33 reductions in upstream emissions are not uniformly distributed to individual nonattainment areas. Under 

34 Alternative 6, most nonattainment areas would experience net increases in emissions of one or more toxic 

35 air pollutant in at least one of the analysis years (see Appendix C). However, the emissions increases 

36 would be quite small, as shown in Appendix C, and emissions increases would be distributed throughout 

37 each nonattainment area. 

38 4.3.3.7.3 Health Outcomes and Costs 

39 Compared to Alternative 1 (No Action), the cumulative impact of Alternative 6 would result in 

40 453 fewer mortalities and 49,958 fewer work-loss days in 2050. Mortality benefits are measured 

41 according to Pope et al.; reductions would be 156 percent greater using the Laden et al. methodology 
4.3 Air Quality Chapter 4 Cumulative Impacts 

 4-28 

1 Table 4.3.3-6 lists the corresponding reductions in health costs under Alternative 6 compared to 

2 the No Action Alternative. In 2050, Alternative 6 would reduce health costs by $4.1 billion annually, 

3 using a 3-percent discount rate and estimates from Pope et al. (2002). With the Laden et al. (2006) 

4 method, economic benefits would be 145 percent greater. Using a 7-percent discount rate, economic 

5 benefits would be 9.3 to 9.5 percent less. 

6 Compared to Alternative 6, health and economic benefits would be greater under Alternatives 8 

7 and 9, and Alternative 7 in 2050, but less under Alternative 7 in 2016, 2020, and 2030. 

8 4.3.3.8 Alternative 7: 6-Percent Annual Increase 

9 4.3.3.8.1 Criteria Pollutants 

10 Under the 6-Percent Alternative (Alternative 7), the CAFE standards would increase fuel 

11 economy more than Alternatives 1 through 6 but less than Alternatives 8 and 9. There would be 

12 reductions in nationwide emissions of all criteria pollutants under Alternative 7 compared to the No 

13 Action Alternative. Reductions would be greater than under Alternative 6 (except for NOx and VOCs in 

14 2016, PM2.5 and SOx in all years) but less than under Alternatives 8 and 9. Depending on the year, CO 

15 emissions would be reduced 0.6 to 7.6 percent, NOx emissions would be reduced 0.5 to 7.8 percent, PM2.5

16 emissions would be reduced 0.6 to 4.1 percent, SOx emissions would be reduced 2.8 to 12.4 percent, and 

17 VOC emissions would be reduced 1.8 to 16.7 percent, compared to emissions projected under the No 

18 Action Alternative. 

19 Emissions in individual nonattainment areas could follow different patterns from nationwide 

20 emissions. Emissions of criteria pollutants vary due to interrelations among upstream emissions, VMT 

21 increases, and diesel share of fuel consumption. Compared to Alternative 1, cumulative emissions of CO, 

22 NOx, SOx, and VOCs under Alternative 7 would decrease in all nonattainment areas. PM2.5 results are 

23 mixed, with emissions increasing in some nonattainment areas and decreasing in others. Tables in 

24 Appendix C list the emissions reductions for each nonattainment area. 

25 Cumulative fuel economy standards would lead to lower emissions of most pollutants compared 

26 to noncumulative standards, due to the impact of higher projected average fuel economy in the cumulative 

27 case. Under Alternative 7, cumulative emissions of NOx, PM2.5, SOx, and VOCs are lower than 

28 noncumulative emissions. However, emissions of CO are higher under the cumulative case than the 

29 noncumulative case, because increases in VMT more than offset declines in CO emission rates and 

30 increases in fuel economy. 

31 Emissions reductions (compared to the No Action Alternative) under the Alternative 7 cumulative 

32 analysis would be greater than the corresponding emissions reductions under the Alternative 7 

33 noncumulative analysis for all pollutants. 

34 4.3.3.8.2 Toxic Air Pollutants 

35 Under Alternative 7, cumulative emissions would be less than noncumulative emissions for some 

36 combinations of pollutant and year and greater than noncumulative emissions for other combinations of 

37 pollutant and year. 

38 Alternative 7 would reduce toxic air pollutant emissions compared to the No Action Alternative 

39 for benzene, 1,3-butadiene (in 2030 and 2050), and DPM, and would increase emissions of acetaldehyde, 

40 acrolein, 1,3-butadiene (in 2016 and 2020), and formaldehyde compared to the No Action Alternative. 

41 Compared to Alternatives 8 and 9, Alternative 7 would result in higher emissions of acrolein (under 
Chapter 4 Cumulative Impacts 4.3 Air Quality 

 4-29 

1 Alternative 9 in 2020, 2030, and 2050), benzene, 1,3-butadiene (in 2030 and 2050), and DPM, and lower 

2 emissions of acetaldehyde, acrolein (under Alternative 9 in 2016), 1,3-butadiene (in 2016 and 2020), and 

3 formaldehyde. 

4 Emissions changes (compared to the No Action Alternative) under the Alternative 7 cumulative 

5 analysis would be greater than the corresponding emissions changes under the Alternative 7 

6 noncumulative analysis for all toxic air pollutants except benzene (in 2020 and 2030) and 1,3-butadiene 

7 (in 2020 and 2030). For benzene (in 2020 and 2030) and 1,3-butadiene (in 2020 and 2030) the emissions 

8 changes under the Alternative 7 cumulative analysis would be less than the corresponding emissions 

9 changes under the Alternative 7 noncumulative analysis. 

10 Nationwide, emissions of toxic air pollutants can decrease because the reduction in upstream 

11 emissions more than offsets the increase in VMT and emissions due to the rebound effect. However, the 

12 reductions in upstream emissions are not uniformly distributed to individual nonattainment areas. Under 

13 Alternative 7, most nonattainment areas would experience net increases in emissions of one or more toxic 

14 air pollutant in at least one of the analysis years (see Appendix C). However, the emissions increases 

15 would be quite small, as shown in Appendix C, and emissions increases would be distributed throughout 

16 each nonattainment area. 

17 4.3.3.8.3 Health Outcomes and Costs 

18 Compared to Alternative 1 (No Action), the cumulative impact of Alternative 7 would result in 

19 455 fewer mortalities and 50,334 fewer work-loss days in 2050. Mortality benefits are measured 

20 according to Pope et al.(2002); reductions would be 156 percent greater using the Laden et al. (2006) 

21 methodology. 

22 Table 4.3.3-6 lists the corresponding reductions in health costs under Alternative 7 compared to 

23 the No Action Alternative. In 2050, Alternative 7 would reduce health costs by $4.1 billion annually, 

24 using a 3-percent discount rate and estimates from Pope et al. With the Laden et al. method, economic 

25 benefits would be 145 percent greater. Using a 7-percent discount rate, economic benefits would be 9.3 

26 to 9.5 percent less. 

27 Compared to Alternative 7, health and economic benefits would be greater under Alternatives 8 

28 and 9. 

29 4.3.3.9 Alternative 8: 7-Percent Annual Increase 

30 4.3.3.9.1 Criteria Pollutants 

31 Under the 7-Percent Alternative (Alternative 8), the CAFE standards would increase fuel 

32 economy more than Alternatives 1 through 7 and also more than Alternative 9. There would be 

33 reductions in nationwide emissions of all criteria pollutants under Alternative 8 compared to the No 

34 Action Alternative. Reductions would be greater than under Alternative 7 but less than under Alternative 

35 9 (except for PM2.5 and SOx in 2030 and 2050). Depending on the year, CO emissions would be reduced 

36 0.6 to 8.4 percent, NOx emissions would be reduced 0.5 to 8.6 percent, PM2.5 emissions would be reduced 

37 0.7 to 4.6 percent, SOx emissions would be reduced 3.1 to 13.7 percent, and VOC emissions would be 

38 reduced 2.0 to 18.1 percent, compared to emissions projected under the No Action Alternative. 

39 Emissions in individual nonattainment areas could follow different patterns from nationwide 

40 emissions. Emissions of criteria pollutants vary due to interrelations among upstream emissions, VMT 

41 increases, and diesel share of fuel. Compared to Alternative 1, cumulative emissions of CO, NOx, SOx, 
4.3 Air Quality Chapter 4 Cumulative Impacts 

 4-30 

1 and VOCs under Alternative 8 would decrease in all nonattainment areas. PM2.5 results are mixed, with 

2 emissions increasing in some nonattainment areas and decreasing in others. Tables in Appendix C list the 

3 emissions reductions for each nonattainment area. 

4 Cumulative fuel economy standards would lead to lower emissions of most pollutants compared 

5 to noncumulative standards, due to the impact of higher projected fuel economy in the cumulative case. 

6 Under Alternative 8, cumulative emissions of NOx, PM2.5, SOx, and VOCs would be lower than 

7 noncumulative emissions. However, emissions of CO would be higher under the cumulative case than 

8 the noncumulative case, because increases in VMT more than offset declines in CO emission rates and 

9 increases in fuel economy. 

10 Emissions reductions (compared to the No Action Alternative) under the Alternative 8 cumulative 

11 analysis would be greater than the corresponding emissions reductions under the Alternative 8 

12 noncumulative analysis for all pollutants. 

13 4.3.3.9.2 Toxic Air Pollutants 

14 Under Alternative 8, cumulative emissions would be less than noncumulative emissions for some 

15 combinations of pollutant and year and greater than noncumulative emissions for other combinations of 

16 pollutant and year. 

17 Alternative 8 would reduce toxic air pollutant emissions compared to the No Action Alternative 

18 for benzene, 1,3-butadiene (in 2030 and 2050), and DPM, and would increase emissions of acetaldehyde, 

19 acrolein, 1,3-butadiene (in 2016 and 2020), and formaldehyde compared to the No Action Alternative. 

20 Compared to Alternative 9, Alternative 8 would result in higher emissions of acrolein (in 2020, 2030, and 

21 2050), benzene, 1,3-butadiene (in 2030 and 2050), and DPM, and lower emissions of acetaldehyde, 

22 acrolein (in 2016), 1,3-butadiene (in 2016 and 2020), and formaldehyde. 

23 Emissions changes (compared to the No Action Alternative) under the Alternative 8 cumulative 

24 analysis would be greater than the corresponding emissions changes under the Alternative 8 

25 noncumulative analysis for all toxic air pollutants except benzene (in 2020 and 2030) and 1,3-butadiene 

26 (in 2020 and 2030). For benzene (in 2020 and 2030) and 1,3-butadiene (in 2020 and 2030) the emissions 

27 changes under the Alternative 7 cumulative analysis would be less than the corresponding emissions 

28 changes under the Alternative 7 noncumulative analysis. 

29 Nationwide, emissions of toxic air pollutants can decrease because the reduction in upstream 

30 emissions more than offsets the increase in VMT and emissions due to the rebound effect. However, the 

31 reductions in upstream emissions are not uniformly distributed to individual nonattainment areas. Under 

32 Alternative 8, most nonattainment areas would experience net increases in emissions of one or more toxic 

33 air pollutant in at least one of the analysis years (see Appendix C). However, the emissions increases 

34 would be quite small, as shown in Appendix C, and emissions increases would be distributed throughout 

35 each nonattainment area. 

36 4.3.3.9.3 Health Outcomes and Costs 

37 Compared to Alternative 1 (No Action), the cumulative impact of Alternative 8 would result in 

38 504 fewer mortalities and 55,754 fewer work-loss days in 2050. Mortality benefits are measured 

39 according to Pope et al.; reductions would be 156 percent greater using the Laden et al. methodology. 

40 Table 4.3.3-6 lists the corresponding reductions in health costs under Alternative 8 compared to 

41 the No Action Alternative. In 2050, Alternative 8 would reduce health costs by $4.6 billion annually, 
Chapter 4 Cumulative Impacts 4.3 Air Quality 

 4-31 

1 using a 3-percent discount rate and estimates from Pope et al. (2002). With the Laden et al. (2006) 

2 method, economic benefits would be 145 percent greater. Using a 7-percent discount rate, economic 

3 benefits would be 9.3 to 9.5 percent less. Compared to Alternative 9, health and economic benefits would 

4 be smaller under Alternative 8. 

5 4.3.3.10 Alternative 9: TCTB 

6 4.3.3.10.1 Criteria Pollutants 

7 Under the TCTB Alternative (Alternative 9), the CAFE standards would increase fuel economy 

8 more than Alternatives 1 through 7, but less than Alternative 8. There would be reductions in nationwide 

9 emissions of all criteria pollutants under Alternative 9 compared to the No Action Alternative. Emission 

10 reductions of all criteria pollutants under Alternative 9 would be greater than with any other alternative 

11 (except for PM2.5 in all analysis years and SOx in 2020, 2030, and 2050). Depending on the year, CO 

12 emissions would be reduced 0.7 to 8.7 percent, NOx emissions would be reduced 0.6 to 8.8 percent, PM2.5

13 emissions would be reduced 0.8 to 4.5 percent, SOx emissions would be reduced 3.3 to 13.4 percent, and 

14 VOC emissions would be reduced 2.0 to 18.1 percent, compared to emissions projected under the No 

15 Action Alternative. 

16 Emissions in individual nonattainment areas could follow different patterns from nationwide 

17 emissions. Emissions of criteria pollutants vary due to interrelations among upstream emissions, VMT 

18 increases, and diesel share of fuel. Compared to Alternative 1, cumulative emissions of CO, NOx, SOx, 

19 and VOCs under Alternative 9 decrease in all nonattainment areas. PM2.5 results are mixed, with 

20 emissions increasing in some nonattainment areas and decreasing in others. Tables in Appendix C list the 

21 emissions reductions for each nonattainment area. 

22 Cumulative fuel economy standards would lead to lower emissions of most pollutants compared 

23 to noncumulative standards, due to the impact of higher projected average fuel economy in the cumulative 

24 case. Under Alternative 9, cumulative emissions of NOx, PM2.5, SOx, and VOCs are lower than 

25 noncumulative emissions. However, emissions of CO are higher under the cumulative case than the 

26 noncumulative case, because increases in VMT more than offset declines in CO emission rates and 

27 increases in fuel economy. 

28 Emissions reductions (compared to the No Action Alternative) under the Alternative 9 cumulative 

29 analysis would be greater than the corresponding emissions reductions under the Alternative 9 

30 noncumulative analysis for all pollutants. 

31 4.3.3.10.2 Toxic Air Pollutants 

32 Under Alternative 9, cumulative emissions would be less than noncumulative emissions for some 

33 combinations of pollutant and year and greater than noncumulative emissions for other combinations of 

34 pollutant and year. 

35 Alternative 9 would reduce toxic air pollutant emissions compared to the No Action Alternative 

36 for benzene, 1,3-butadiene (in 2030 and 2050), and DPM, and would increase emissions of acetaldehyde, 

37 acrolein, 1,3-butadiene (in 2016 and 2020), and formaldehyde compared to the No Action Alternative. 

38 Emissions changes (compared to the No Action Alternative) under the Alternative 9 cumulative 

39 analysis would be greater than the corresponding emissions changes under the Alternative 9 

40 noncumulative analysis for all toxic air pollutants except acrolein, benzene (in 2020 and 2030) and 1,3-

41 butadiene (in 2020 and 2030). For acrolein, benzene (in 2020 and 2030), and 1,3-butadiene (in 2020 and 
4.3 Air Quality Chapter 4 Cumulative Impacts 

 4-32 

1 2030), the emissions changes under the Alternative 7 cumulative analysis would be less than the 

2 corresponding emissions changes under the Alternative 7 noncumulative analysis. 

3 Nationwide, emissions of toxic air pollutants can decrease because the reduction in upstream 

4 emissions more than offsets the increase in VMT and emissions due to the rebound effect. However, the 

5 reductions in upstream emissions are not uniformly distributed to individual nonattainment areas. Under 

6 Alternative 9, most nonattainment areas would experience net increases in emissions of one or more toxic 

7 air pollutant in at least one of the analysis years (see Appendix C). However, the emissions increases 

8 would be quite small, as shown in Appendix C, and emissions increases would be distributed throughout 

9 each nonattainment area. 

10 4.3.3.10.3 Health Outcomes and Costs 

11 Compared to Alternative 1 (No Action), the cumulative impact of Alternative 9 would result in 

12 504 fewer mortalities and 55,808 fewer work-loss days in 2050. Mortality benefits are measured 

13 according to Pope et al.(2002); reductions would be 156 percent greater using the Laden et al. (2006) 

14 methodology. 

15 Table 4.3.3-6 lists the corresponding reductions in health costs under Alternative 8 compared to 

16 the No Action Alternative. In 2050, Alternative 8 would reduce health costs by $4.6 billion annually, 

17 using a 3-percent discount rate and estimates from Pope et al. (2002). With the Laden et al. (2006) 

18 method, economic benefits would be 145 percent greater. Using a 7-percent discount rate, economic 

19 benefits would be 9.3 to 9.5 percent less. 
Chapter 4 Cumulative Impact 4.4 Climate 

4-33 

1 4.4 CLIMATE 

2 As noted earlier, a cumulative impact is defined as “the impact on the environment which results 

3 from the incremental impact of the action when added to other past, present, and reasonably foreseeable 

4 future actions regardless of what agency or person undertakes such other actions. Cumulative impacts 

5 can result from individually minor but collectively significant actions taking place over a period of time.” 

6 40 CFR § 1508.70. 

7 This section on the cumulative impacts of the proposed action and alternatives on climate covers 

8 many of the same topics as Section 3.4. However, the analysis in Chapter 4 is broader than the analysis in 

9 Chapter 3 because it addresses (1) the effects of the MY 2012-2016 standards together with those of

10 reasonably foreseeable future actions, including the continuing increases in CAFE standards for MY 

11 2017-2020 that are necessary under some alternatives to reach the EISA-mandated target of a combined 

12 mpg of 35 mpg (see Section 4.1.3), and (2) continuing market-driven annual average percentage gains in 

13 mpg from 2016 through 2030 consistent with the AEO projections as a reasonably foreseeable future 

14 action. These reasonably foreseeable future actions would affect fuel consumption and emissions 

15 attributable to passenger cars and light trucks through 2060. Because these mpg projections apply to new 

16 vehicles, this assumption results in emissions reductions and fuel savings that continue to grow as new 

17 vehicles are added to the fleet in each subsequent year, and as VMT continue to grow. This is the case 

18 under the No Action Alternative and each of the action alternatives. Like Chapter 3, Chapter 4 addresses 

19 the consequences of emissions and effects on the climate system. However, Chapter 4 goes beyond this 

20 to discuss the impacts of changes in the climate system on key resources (e.g., freshwater resources, 

21 terrestrial ecosystems, and coastal ecosystems). 

22 Understanding that many readers do not read through an EIS in linear fashion, but instead focus 

23 on the sections of most interest, this section repeats some of the information in Section 3.4 with only 

24 minor modifications to reflect the slightly different scope (cumulative impacts versus the direct and 

25 indirect effects of the proposed action and alternatives). 

26 4.4.1 Introduction – Greenhouse Gases and Climate Change 

27 This document primarily draws upon panel-reviewed synthesis and assessment reports from the 

28 IPCC and U.S. Global Change Research Program (USGCRP). It also cites EPA’s Technical Support 

29 Document for its proposed Endangerment and Cause or Contribute Findings for GHGs under the Clean 

30 Air Act – which heavily relied on these panel reports. NHTSA similarly relies on panel reports because 

31 they have assessed numerous individual studies to draw general conclusions about the state of science;

32 have been reviewed and formally accepted by, commissioned by, or in some cases authored by, U.S. 

33 government agencies and individual government scientists and provide NHTSA with assurances that this 

34 material has been well vetted by both the climate change research community and by the U.S. 

35 government; and in many cases, they reflect and convey the consensus conclusions of expert authors. 

36 These reports therefore provide the overall scientific foundation for U.S. climate policy at this time. 

37 This document also refers to new peer-reviewed literature that has not been assessed or 

38 synthesized by an expert panel. This new literature supplements but does not supersede the findings of 

39 the panel-reviewed reports. 

40 NHTSA’s consideration of newer studies and highlighting of particular issues responds to 

41 previous public comments received on the scoping document and the prior EIS for the MY 2011 CAFE 

42 standard, as well as the Ninth Circuit’s decision in CBD v. NHTSA, 538 F.3d 1172 (9th Cir. 2008). The 

43 level of detail regarding the science of climate change in this draft EIS, and NHTSA’s consideration of 

44 other studies that show illustrative research findings pertaining to the potential impacts of climate change 
4.4 Climate Chapter 4 Cumulative Impacts 

4-34 

1 on health, society, and the environment, are provided to help inform the public and the decisionmaker,

2 consistent with the agency’s approach in the prior EIS for the MY 2011 CAFE standards. 

3 Global climate change refers to long-term trends in global terrestrial surface temperatures, 

4 precipitation, ice cover, sea levels, cloud cover, sea-surface temperatures and currents, and other climatic 

5 conditions. Scientific research has shown that, in the past century Earth’s surface temperature and sea 

6 levels have risen, and most scientists attribute this to GHGs released by human activities, primarily the 

7 combustion of fossil fuels. Both EPA and IPCC have recently found that “Most of the observed increase

8 in global average temperatures since the mid-20th century is very likely due to the observed increase in 

9 anthropogenic greenhouse gas concentrations” (EPA 2009b, IPCC 2007b). 

10 The primary GHGs – CO2, methane (CH4), and nitrous oxide (N2O) – are created by both natural 

11 and human activities. Human activities that emit GHGs to the atmosphere include the combustion of 

12 fossil fuels, industrial processes, solvent use, land-use change and forestry, agricultural production, and 

13 waste management. These accumulated gases trap heat in Earth’s atmosphere, changing the climate, 

14 which then impacts resources such as ecosystems, water resources, agriculture, forests, and human health. 

15 As the world population grows and developing countries industrialize, fossil fuel use and resulting GHG 

16 emissions and their concentrations in the atmosphere are expected to grow substantially over the next 

17 century. For a more in-depth discussion of the science of climate change, see Section 3.4.1. 

18 4.4.1.1 Uncertainty within the IPCC Framework 

19 IPCC reports communicate uncertainty and confidence bounds using descriptive words in italics, 

20 such as likely and very likely, to represent levels of confidence in conclusions. This is briefly explained in 

21 the IPCC Fourth Assessment Synthesis Report and the IPCC Fourth Assessment Report Summary for 

22 Policy Makers (IPCC 2007c, IPCC 2007b). A more detailed discussion of the IPCC treatment of 

23 uncertainty can be found in the Guidance Notes for Lead Authors of the IPCC Fourth Assessment Report 

24 on Addressing Uncertainties (IPCC 2005). This EIS uses the IPCC uncertainty language (always noted in

25 italics) when discussing qualitative environmental impacts on certain resources. Section 4.5.2.2 

26 summarizes the IPCC treatment of uncertainty. 

27 4.4.2 Affected Environment 

28 The affected environment can be characterized in terms of GHG emissions and climate. Section 

29 3.4.2 provides a discussion of both topics, including a description of conditions in both the United States 

30 and the global environment. Because there is no distinction between the affected environment for 

31 purposes of the analysis of direct and indirect effects and the analysis of cumulative impacts, NHTSA 

32 refers readers to Section 3.4.1 for a discussion of this topic. 

33 4.4.3 Methodology 

34 The methodology NHTSA used to characterize the effects of the proposed action and alternatives 

35 on climate has two key elements: (1) analyzing the effects of the proposed action and alternatives on

36 GHG emissions and (2) analyzing how GHG emissions affect the climate system (climate effects). 

37 This cumulative impacts analysis of each alternative includes the effects of the proposed CAFE 

38 standards for MY 2012-2016 and other reasonably foreseeable actions, including ongoing gains in mpg 

39 through 2030 consistent with AEO projections (see Section 4.1.3). This EIS expresses results for each 

40 alternative in terms of the environmental attribute being characterized (emissions, CO2 concentrations, 

41 temperature, precipitation, and sea level). Comparisons between the No Action Alternative (Alternative 

42 1) and each action alternative (Alternatives 2 through 9) illustrate the differences in environmental effects 
Chapter 4 Cumulative Impact 4.4 Climate 

4-35 

1 among the alternative CAFE standards. The impact of each action alternative on these results is measured 

2 by the difference in its value under the No Action Alternative and its value under that action alternative. 

3 For example, the reduction in CO2 emissions attributable to an action alternative is measured by the 

4 difference in emissions under that alternative and emissions under the No Action Alternative. 

5 The methods NHTSA used to characterize emissions and climate-change impacts involve 

6 considerable uncertainty. Sources of uncertainty include the pace and effects of technology change in the 

7 transportation sector and other sectors that emit GHGs; changes in the future fuel supply and fuel 

8 characteristics that could affect emissions; the sensitivity of climate to increased GHG concentrations; the 

9 rate of change in the climate system in response to changing GHG concentrations; the potential existence 

10 of thresholds in the climate system (which could be difficult to predict and simulate); regional differences 

11 in the magnitude and rate of climate changes; and many other factors. 

12 Moss and Schneider (2000) characterize the “cascade of uncertainty” in climate change 

13 simulations (Figure 4.4.3-1). As shown in the figure, emissions estimates NHTSA used in this EIS are 

14 less uncertain than the global climate effects (as illustrated by the heights of the bars), which in turn are 

15 less uncertain than regional climate-change effects. The effects on climate are in turn less uncertain than 

16 the impacts of climate change on affected resources (terrestrial and coastal ecosystems, human health, and 

17 other resources, as discussed in Section 4.5). 

Figure 4.4.3-1. Cascade of Uncertainty in Climate Change Simulations a/ 

18 

19 Where information in the analysis included in this EIS is incomplete or unavailable, NHTSA has 

20 relied on CEQ regulations regarding incomplete or unavailable information (see 40 CFR § 1502.22(b)). 

21 The scientific understanding of the climate system is incomplete. Like any analysis of complex, long22 term changes to support decisionmaking, the analysis described below involves many assumptions and 

23 uncertainties in the course of evaluating reasonably foreseeable significant adverse impacts on the human 

24 environment. This EIS uses methods and data that represent the best and most current information 

25 available on this topic, and that have been subjected to peer review and scrutiny. The information cited 

26 throughout this section that is extracted from recent EPA, IPCC, and CCSP reports on climate change has 

27 endured a more thorough and systematic review process than information on virtually any other topic in

28 environmental science and policy. The tools used to perform the climate-change impacts analysis in this 

29 EIS, including the Model for Assessment of Greenhouse Gas-Induced Climate Change (MAGICC) and 

30 the CCSP Final Report of SAP 2.1 (CCSP 2007), and Representative Concentration Pathway (RCP) 

31 emissions scenarios described below, are generally accepted in the scientific community. 

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.”
4.4 Climate Chapter 4 Cumulative Impacts 

4-36 

1 The CCSP SAP 3.1 report on the strengths and limitations of climate models (CCSP 2008a) 

2 provides a thorough discussion of the methodological limitations regarding modeling. Readers interested 

3 in a detailed treatment of this topic might find the SAP 3.1 report useful in understanding the issues that 

4 underpin the modeling of environmental impacts of the proposed action and the range of alternatives on

5 climate change. 

6 4.4.3.1 Methodology for Modeling Greenhouse Gas Emissions 

7 GHG emissions were estimated using the Volpe model, which is described in Section 3.1.4. The 

8 estimates include global CO2, CH4, and N2O emissions resulting from direct fuel consumption and from 

9 the production and distribution of fuel (“upstream emissions”). The Volpe model also estimated the 

10 following non-GHGs, and accounted for in the climate modeling: SO2, NOx, CO, and VOCs. 

11 Fuel savings from CAFE standards for MY 2012-2016 and other reasonably foreseeable actions 

12 result in lower emissions of CO2, the primary GHG emitted as a result of refining, distribution, and use of 

transportation fuels.1

13 There is a direct relationship among fuel economy, fuel consumption, and CO2

14 emissions. Lower fuel consumption reduces CO2 emissions directly, because the primary source of 

15 transportation-related CO2 emissions is fuel combustion in internal combustion engines. NHTSA 

16 estimated reductions in CO2 emissions resulting from fuel savings by assuming that the entire carbon 

content of gasoline, diesel, and other fuels is converted to CO2 during the combustion process.2

17 

18 Specifically, NHTSA estimated CO2 emissions from fuel combustion as the product of the volume of 

19 each type of fuel consumed (in gallons), its mass density (in grams per gallon), the fraction of its total 

20 mass represented by carbon (measured as a proportion), and CO2 emissions per gram of fuel carbon (the 

21 ratio of the molecular weights of CO2 and elemental carbon). 

22 Reduced fuel consumption also lowers CO2 emissions that result from the use of carbon-based 

23 energy sources during fuel production and distribution. NHTSA estimated the global reductions in CO2

24 emissions during each phase of fuel production and distribution using CO2 emissions rates obtained from 

25 the Greenhouse Gases Regulated Emissions and Energy Use in Transportation (GREET version 1.8b) 

26 model (Argonne 2002). The total reduction in CO2 emissions from the improvement in fuel economy 

27 under each alternative CAFE standard and other reasonably foreseeable actions is the sum of the 

28 reductions in motor-vehicle emissions from reduced fuel combustion, plus the reduction in upstream 

29 emissions from a lower volume of fuel production and distribution. 

30 4.4.3.2 Methodology for Estimating Climate Effects 

31 This EIS estimates and reports four direct and indirect effects of climate change driven by 

32 alternative scenarios of GHG emissions – changes in CO2 concentrations, changes in global temperature, 

33 changes in regional temperature and precipitation, and changes in sea level. 

 

1

 In estimating vehicular GHG emissions (i.e., not including the full life-cycle emissions) for this rulemaking, 

NHTSA estimated CO2, CH4, and N2O emissions, but not HFCs (hydrofluorocarbons). Of the total vehicular 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.) 

2

 This assumption results in a slight overestimate of CO2 emissions, because a small fraction of the carbon content of 

gasoline is emitted as carbon monoxide and unburned hydrocarbons. However, the magnitude of this overestimation 

is likely to be extremely small, and in any case, most of the carbon monoxide and unburned hydrocarbons are likely 

to be oxidized in the atmosphere to CO2. This approach is consistent with the IPCC recommendation for “Tier 1” 

national GHG emissions inventories (IPCC 2006). 
Chapter 4 Cumulative Impact 4.4 Climate 

4-37 

1 The change in CO2 concentration is a direct effect of the changes in GHG emissions, and 

2 influences each of the other factors. 

3 This EIS uses a climate model to estimate the changes in CO2 concentrations, global mean 

4 surface temperature, and changes in sea level for each alternative CAFE standard and uses increases in

5 global mean surface temperature combined with an approach and coefficients from the IPCC Fourth 

6 Assessment Report (IPCC 2007a) to estimate changes in global precipitation. NHTSA used the publicly 

7 available modeling software MAGICC version 5.3.v2 (Wigley 2008) to estimate changes in key direct 

8 and indirect effects. MAGICC 5.3.v2 uses the estimated reductions in emissions of CO2, CH4, N2O, CO, 

9 NOx, SO2, and VOCs produced by the Volpe model. Sensitivity analyses examined the relationship 

10 among various CAFE alternatives, likely climate sensitivities, and scenarios of global emissions paths and 

11 the associated direct and indirect effects for each combination. These relationships can be used to infer 

12 the effect of the emissions associated with the regulatory alternatives on direct and indirect climate

13 effects. 

14 Sections 4.4.3.2.1, 4.4.3.2.2, and 4.4.3.2.3 describe MAGICC, the reference case modeling runs, 

15 the sensitivity analysis, and the emissions scenarios NHTSA used in the analysis. 

16 4.4.3.2.1 MAGICC Version 5.3.v2 

17 The selection of MAGICC for this analysis was driven by a number of factors, as follows: 

18 • MAGICC has been used in the peer-reviewed literature to evaluate changes in global mean 

19 surface temperature and sea-level rise. In the IPCC Fourth Assessment Report for Working 

20 Group I (WGI) (IPCC 2007a), it was used to scale the results from the atmospheric-ocean 

general circulation models (AOGCMs)321 to estimate the global mean surface temperature and 

22 the sea-level rise for global emissions scenarios that the AOGCMs did not run. 

23 • MAGICC is publicly available and was designed for the type of analysis performed in this 

24 EIS. 

25 • More complex AOGCMs are not designed for the type of sensitivity analysis performed here 

26 and are best used to provide results for groups of scenarios with much greater differences in 

27 emissions. 

28 • MAGICC has been updated to version 5.3.v2 to incorporate the science from the IPCC 

29 Fourth Assessment Report (Wigley 2008). 

30 • EPA is also using MAGICC 5.3.v2 for their vehicle GHG emissions standards Regulatory 

31 Impact Analysis (RIA), which accompanies the joint NPRM between NHTSA and EPA. 

32 NHTSA assumed that global emissions consistent under the No Action Alternative (Alternative 

33 1) would follow the trajectory provided by the CCSP SAP 2.1 MiniCAM Level 3 scenario. This scenario 

34 represents a Reference Case where future global emissions assume significant global actions to address

35 climate change. Section 4.4.3.2.2 describes the CCSP SAP 2.1 scenarios. 

36 4.4.3.2.2 Reference Case Modeling Runs 

37 The modeling runs and sensitivity analysis are designed to use information on the alternatives, 

38 climate sensitivities, and CCSP SAP 2.1 emissions scenarios (Clarke et al. 2007) to model relative 

39 changes in atmospheric concentrations, global mean surface temperature, precipitation, and sea-level rise 

40 likely to result under each alternative. 

 

3

 For a discussion of AOGCMs, see Chapter 8 in IPCC (2007a). 
4.4 Climate Chapter 4 Cumulative Impacts 

4-38 

1 The primary modeling runs are based on the results provided for the nine CAFE alternatives, a 

2 climate sensitivity of 3.0 °C for a doubling of CO2 concentrations in the atmosphere, and the CCSP SAP

3 2.1 MiniCAM Level 3 scenario. These are referred to as the Reference Case results below, in contrast to 

4 various sensitivity runs that test high and low values for the climate sensitivity and the global emissions 

5 scenario. 

6 The approach uses the following steps to estimate these changes: 

7 1. NHTSA assumed that global emissions under the No Action Alternative (Alternative 1) 

8 follow the trajectories provided by the CCSP SAP 2.1 MiniCAM Level 3 scenario. 

9 2. NHTSA assumed that global emissions for the action alternatives (Alternatives 2 through 9) 

10 are equal to the global emissions from the No Action Alternative minus the emissions 

11 reductions from the Volpe model for CO2, CH4, N2O, SO2, NOx, CO, and VOCs. (For 

12 example, the global emissions scenario under Alternative 2 equaled the RCP 4.5 MiniCAM 

13 reference scenario minus the emission reductions from that Alternative). All SO2 reductions 

14 were applied to Aerosol Region 1 of MAGICC, which includes North America. 

15 3. MAGICC 5.3.v2 was used to estimate the changes in global CO2 concentrations, global mean 

16 surface temperature, and sea-level rise through 2100 using the global emissions scenario 

17 under each CAFE alternative developed in Steps 1 and 2 above for a climate sensitivity of 3.0 

18 °C. 

19 4. The increase in global mean surface temperature was used along with factors that relate 

20 increase in global average precipitation to this increase in global mean surface temperature to 

21 estimate the increase in global averaged precipitation for each alternative for the CCSP SAP 

22 2.1 MiniCAM Level 3 scenario. 

23 Section 4.4.4 presents the results of the reference case modeling runs. 

24 4.4.3.2.3 Sensitivity Analysis 

25 The sensitivity analysis is based on the results provided for: 

26 1. The No Action Alternative (Alternative 1) and the Preferred Alternative (Alternative 4). The 

27 sensitivity analysis was only performed for two CAFE alternatives because NHTSA deemed 

28 this sufficient to assess the effect of various climate sensitivities on the results. 

29 2. Climate sensitivities, for a doubling of CO2 concentrations in the atmosphere, of 2.0, 3.0, and 

4.5 °C (3.6, 5.4, and 8.1 °F).4

30 

31 3. Global emissions scenarios that include the SAP 2.1 MiniCAM Level 3 (650 ppm as of 

32 2100), the SAP 2.1 MiniCAM Level 2 (550 ppm as of 2100), and RCP 4.5 MiniCAM 

33 reference scenario (783 ppm as of 2100). These global emissions scenarios represent various 

34 levels of implementation of global GHG emissions reduction policies. 

 

4

 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 (280 ppm CO2) (NRC 2001 

in EPA 2009). In the past 8 years, confidence in climate sensitivity projections has increased significantly (Meehl et 

al. 2007 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. 2007). 
Chapter 4 Cumulative Impact 4.4 Climate 

4-39 

1 The results of these simulations illustrate the uncertainty due to factors influencing future global 

2 emissions of GHGs (factors other than the CAFE rulemaking). 

3 The approach uses the following steps to estimate the sensitivity of the results to alternative 

4 estimates of the climate sensitivity and global emissions scenarios: 

5 1. NHTSA assumed global emissions scenarios that include the SAP 2.1 MiniCAM Level 3 

6 (650 ppm as of 2100), the SAP 2.1 MiniCAM Level 2 (550 ppm as of 2100), and RCP 4.5 

7 MiniCAM reference scenario (783 ppm as of 2100). These global emissions scenarios 

8 represent various levels of implementation of global GHG emissions reduction policies. 

9 2. For each global emissions scenario from Step 1, NHTSA assumed that the reductions in 

10 global emissions of CO2, CH4, N2O, SO2, NOx, CO, and VOCs under the Preferred 

11 Alternative (Alternative 4) are equal to the global emissions of each pollutant under the No 

12 Action Alternative (Alternative 1), minus emissions of each pollutant under the Preferred 

13 Alternative. All SO2 reductions were applied to the Aerosol region 1 of MAGICC, which 

14 includes North America. 

15 3. NHTSA assumed climate sensitivity values of 2.0, 3.0, and 4.5 °C (3.6, 5.4, and 8.1 °F), 

16 consistent with the likely range from the IPCC Fourth Assessment Report (IPCC 2007a). 

17 4. NHTSA used MAGICC 5.3.v2 to estimate the resulting changes in CO2 concentrations, 

18 global mean surface temperature, and sea-level rise through 2100 for each global emissions 

19 scenario in Step 2, and climate sensitivity in Step 3. 

20 Section 4.4.4.2.5 presents the results of the sensitivity analysis. 

21 4.4.3.3 Global Emissions Scenarios 

22 As described above, MAGICC uses long-term emissions scenarios representing different 

23 assumptions about key drivers of GHG emissions. All scenarios used are based on the CCSP effort to 

24 develop a set of long-term (2000 to 2100) emissions scenarios that incorporate an update of economic and 

25 technology data and utilize improved scenario development tools compared to the IPCC Special Report 

26 on Emissions Scenarios (SRES) (IPCC 2000) developed more than a decade ago. 

27 The Strategic Plan for the U.S. Climate Change Science Program (CCSP 2003) called for the 

28 preparation of 21 synthesis and assessment products and noted that emissions scenarios are essential for 

29 comparative analysis of future climate change and for analyzing options for mitigating and adapting to

30 climate change. The Plan includes Product 2.1, Scenarios of Greenhouse Gas Emissions and 

31 Atmospheric Concentrations and Review of Integrated Scenario Development and Application (Clarke et 

32 al. 2007), which presents 15 scenarios, five from each of the three modeling groups (IGSM, MiniCAM, 

33 and MERGE). 

34 Each climate modeling group independently produced a unique emissions reference scenario 

35 based on the assumption that no climate policy would be implemented beyond the current set of policies

36 in place using a set of assumptions about drivers such as population changes, economic growth, land and 

37 labor productivity growth, technological options, and resource endowments. Each group produced four 

38 additional stabilization scenarios, which are defined in terms of the total long-term radiative impact of the 

39 suite of GHGs that includes CO2, N2O, CH4, HFCs, perfluorocarbons (PFCs), and sulfur hexafluoride 

40 (SF6). These stabilization scenarios represent various levels of implementation of global GHG emissions 

41 reduction policies. 
4.4 Climate Chapter 4 Cumulative Impacts 

4-40 

1 The results in this chapter rely primarily on the CCSP SAP 2.1 MiniCAM Level 3 scenario to 

2 represent a Reference Case global emissions scenario, that is, future global emissions assuming 

3 significant global actions to address climate change. This Reference Case global emissions scenario 

4 serves as a baseline against which the climate benefits of the various CAFE alternatives can be 

measured.5

5 NHTSA chose the SAP 2.1 MiniCAM Level 3 scenario to represent reasonably foreseeable 

6 actions based on the following factors: 

7 • The SAP 2.1 MiniCAM Level 3 scenario was developed by the MiniCAM Model of the Joint 

8 Global Change Research Institute (which is a partnership between the Pacific Northwest 

9 National Laboratory and the University of Maryland) and is one of three Level 3 climate 

10 scenarios described in the SAP 2.1. MiniCAM Level 3 is based on a set of assumptions about 

11 drivers such as population, technology, and socioeconomic changes, and global climate 

12 policies that correspond to total radiative forcing stabilization by 2100 and associated CO2

13 concentrations at roughly 650 parts per million by volume (ppmv), after accounting for the 

14 contributions to radiative forcing from the non-CO2 GHGs. It therefore represents an 

15 illustration of a plausible future pathway of global emissions in response to significant global 

16 action to mitigate climate change. 

17 • CCSP SAP 2.1 is more than a decade newer than the IPCC SRES, and therefore has updated 

18 economic and technology data/assumptions and uses improved integrated assessment models 

19 that account for advances in economics and science over the past 10 years. 

20 The SAP 2.1 MiniCAM Level 3 scenario assumes a moderate level of global GHG reductions, 

21 resulting in a global atmospheric CO2 concentration of roughly 650 ppmv by 2100. The regional, 

22 national, and international initiatives and programs discussed below are those NHTSA has tentatively 

23 concluded are reasonably foreseeable past, current, or future actions to reduce GHG emissions. Although 

24 many of these actions, policies, or programs are not associated with precise GHG reduction commitments, 

25 collectively they illustrate an existing and continuing trend of U.S. and global awareness, emphasis, and 

26 efforts toward significant GHG reductions. Together they imply that future commitments for reductions

27 are probable and, therefore, reasonably foreseeable under NEPA. 

United States: Regional Actions6

28 

29 • Regional Greenhouse Gas Initiative (RGGI). Beginning January 1, 2009, RGGI is the first 

30 mandatory, market-based effort in the United States to reduce GHG emissions (RGGI 2009a). 

31 Ten Northeastern and Mid-Atlantic states (Connecticut, Delaware, Maine, Maryland, 

32 Massachusetts, New Hampshire, New Jersey, New York, Rhode Island, and Vermont) have 

33 capped annual emissions from power plants in the region at 188 million tons of CO2 (RGGI 

34 2009b). Beginning in 2015, this cap will be reduced 2.5 percent each year through 2019, for 

35 a total of a 10-percent emissions reduction from the 2015 cap from the power sector by 2018 

36 (RGGI 2009c, Department of Environmental Conservation, New York State 2009). Thus, the 

37 cap is comprised of two phases: the first is a stabilization phase from 2009 to 2014, and the 

38 second is a reduction phase from 2015 through 2018. 

 

5

 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. 

6

 Two of the three regional actions include Canadian provinces as participants and observers. 
Chapter 4 Cumulative Impact 4.4 Climate 

4-41 

1 • Western Climate Initiative (WCI) – The WCI includes seven states (Arizona, California, 

2 Montana, New Mexico, Oregon, Utah, and Washington) and four Canadian provinces (British 

3 Columbia, Manitoba, Ontario, and Quebec). Set to begin on January 1, 2012, the WCI cap4 and-trade program will cover emissions of the six main greenhouse gases (CO2, CH4, N2O, 

5 HFC’s, PFC’s, and SF6) from the following sectors of the economy: electricity generation, 

6 including imported electricity; industrial and commercial fossil fuel combustion; industrial 

7 process emissions; gas and diesel consumption for transportation; and residential fuel use. 

8 Covered entities and facilities will be required to surrender enough allowances to cover 

9 emissions that occur within each 3-year “compliance period.” This multi-sector program is 

10 the most comprehensive carbon-reduction strategy designed to date in the United States. This 

11 program is an important component of the WCI comprehensive regional effort to reduce 

12 GHG emissions to 15 percent below 2005 levels by 2020. The program will be rolled out in 

13 two phases. The first phase will begin on January 1, 2012, and will cover emissions from 

14 electricity, including imported electricity, industrial combustion at large sources, and 

15 industrial process emissions for which adequate measurement methods exist. The second 

16 phase begins in 2015, when the program expands to include transportation fuels and 

17 residential, commercial, and industrial fuels not otherwise covered (WCI 2009). When fully 

18 implemented in 2015, the program will cover nearly 90 percent of greenhouse gas emissions 

19 in the 11 WCI Partner states and provinces. 

20 • Midwestern Greenhouse Gas Reduction Accord – The Accord includes six states (Illinois, 

21 Iowa, Kansas, Michigan, Minnesota, and Wisconsin) and one Canadian province (Manitoba). 

22 Signed on November 15, 2007, the Midwestern Greenhouse Gas Reduction Accord serves as 

23 a regional strategy to achieve energy security and reduce GHG emissions (Midwestern 

24 Governors Association 2009). The Accord will establish GHG-reduction targets and time 

25 frames consistent with member states’ targets; develop a market-based and multi-sector cap26 and-trade mechanism to help achieve those reduction targets; establish a system to enable 

27 tracking, management, and crediting for entities that reduce GHG emissions; and develop and 

28 implement additional steps as needed to achieve the reduction targets, such as low-carbon 

29 fuel standards and regional incentives and funding mechanisms (Midwestern Greenhouse Gas 

30 Reduction Accord 2009). 

31 United States: Federal Actions 

32 • EPA Proposed GHG Emissions Standards. In a joint NHTSA and EPA notice of proposed 

33 rulemaking published concurrently with this Draft EIS, EPA will propose a national CO2

34 vehicle emissions standard under Section 202(a) of the Clean Air Act, which will be 

coordinated and harmonized with NHTSA proposed CAFE standards. 35 These standards 

36 would apply to passenger cars, light-duty trucks, and medium-duty passenger vehicles (light37 duty vehicles) built in MY 2012-2016. These vehicle categories are responsible for almost 60 

38 percent of all U.S. transportation-related GHG emissions. EPA is considering proposing 

39 standards that would, if made final, achieve an average of 250 grams per mile of CO2 in MY 

40 2016. The standards would begin with the 2012 model year and the program is intended to 

41 reduce GHG emissions from the U.S. light-duty vehicle fleet by 19 percent by 2030 (EPA 

42 2009d).

43 • H.R. 2454: American Clean Energy and Security Act (“Waxman-Markey Bill”) 

44 (Congressional Research Service 2009). The bill, as introduced on May 15, 2009, would 

45 amend the Clean Air Act to require the EPA Administrator to promulgate regulations to (1) 

46 cap and reduce GHG emissions, annually, so that GHG emissions from capped sources would 

47 be reduced to 97 percent of 2005 levels by 2012, 83 percent by 2020, 58 percent by 2030, and 

48 17 percent by 2050; and (2) establish a federal GHG registry. The bill designates CO2, CH4, 
4.4 Climate Chapter 4 Cumulative Impacts 

4-42 

1 N2O, SF6, PFCs, and nitrogen trifluoride (NF3) as GHGs and establishes a CO2 equivalent 

2 value for each gas. The release of these gases would be regulated for sources including 

3 electricity sources, fuel producers and importers, industrial gas producers and importers, 

4 geological sequestration sites, industrial stationary sources, industrial fossil fuel-fired 

5 combustion devices, natural gas local distribution companies, NF3 sources, algae-based fuels, 

6 and fugitive emissions. In addition, the bill would establish a combined efficiency and 

7 renewable electricity standard that requires utilities to supply an increasing percentage of 

8 their demand from a combination of energy efficiency savings and renewable energy (6 

9 percent in 2012, 9.5 percent in 2014, 13 percent in 2016, 16.5 percent in 2018, and 20 percent 

10 in 2021 through 2039). The bill has passed in the House of Representatives, and at this 

11 writing is under consideration in the Senate. 

12 • Renewable Fuel Standard (RFS2). Section 211(o) of the Clean Air Act requires that a 

13 renewable fuel standard be determined annually that is applicable to refiners, importers, and 

14 certain blenders of gasoline (73 FR 70643). On the basis of this standard, each obligated 

15 party determines the volume of renewable fuel that it must ensure is consumed as motor 

16 vehicle fuel. RFS2 will increase the volume of renewable fuel required to be blended into 

17 gasoline from 9 billion gallons in 2008 to 36 billion gallons by 2022 (EPA 2009e), and the 

18 renewable fuel standard for 2009 is 10.21 percent (73 FR 70643). EPA estimates that the 

19 greater volumes of biofuel mandated by RFS2 will reduce life-cycle GHG emissions by an 

20 annual average of 150 million tons CO2 equivalent (EPA 2009c). 

21 International Actions 

22 • United Nation’s Framework Convention on Climate Change (UNFCCC) – The Kyoto 

23 Protocol, and upcoming Conference of the Parties (COP)-15 in Copenhagen, Denmark. 

24 UNFCCC is an international treaty signed by many countries around the world (including the 

United States7

25 ), which entered into force on March 21, 1994, and sets an overall framework 

26 for intergovernmental efforts to tackle the challenge posed by climate change (UNFCCC 

27 2002). The Kyoto Protocol is an international agreement linked to the United Nations 

28 Framework Convention on Climate Change. The major feature of the Kyoto Protocol is that 

29 it sets binding targets for 37 industrialized countries and the European community for 

30 reducing GHG emissions, which covers more than half of the world’s GHG emissions. These 

31 amount to an average of 5 percent of 1990 levels over the 5-year period 2008 through 2012 

32 (UNFCCC 2005). It was recognized in December of 2007 at the COP-13 meeting in Bali, 

33 Indonesia, that the upcoming December 2009 COP-15 meeting in Copenhagen represents 

34 more or less the last chance to achieve an agreement under the UNFCCC, if this agreement is 

35 to be approved and ratified in time for it to come into force immediately after the Kyoto 

36 Protocol expires in 2012 (United Nations Climate Change Conference 2008). 

37 • The European Union Greenhouse Gas Emission Trading System (EU ETS) - In January 

38 2005 the EU ETS commenced operation as the largest multi-country, multi-sector 

39 Greenhouse Gas Emission Trading System world-wide (European Union 2009). The aim of 

40 the EU ETS is to help European Union Member States achieve compliance with their 

41 commitments under the Kyoto Protocol (European Union 2005). This trading system does 

 

7

 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 

4-43 

1 not entail new environmental targets; instead, it allows for less expensive compliance with 

2 existing targets under the Kyoto Protocol. 

3 

4 The scheme is based on Directive 2003/87/EC, which entered into force on October 25, 2003 

5 (European Union 2009), and covers over 11,500 energy-intensive installations across the 

6 European Union, which represent almost half of Europe’s emissions of CO2. These 

7 installations include combustion plants, oil refineries, coke ovens, iron and steel plants, and 

8 factories making cement, glass, lime, brick, ceramics, pulp and paper (European Union 

9 2005). 

10 • G8 Declaration – Summit 2009. During the July 2009 G8 Summit in Italy, the group

11 officially recognized the importance of the outcome of COP-15, issuing the following 

12 statement regarding GHG emissions reductions: “We recognize the broad scientific view that 

13 the increase in global average temperature above pre-industrial levels ought not to exceed 

14 2 °C. Because this global challenge can only be met by a global response, we reiterate our 

15 willingness to share with all countries the goal of achieving at least a 50 percent reduction of 

16 global emissions by 2050, [recognizing] that this implies that global emissions need to peak 

17 as soon as possible and decline thereafter. As part of this, we also support a goal of 

18 developed countries reducing emissions of greenhouse gases in aggregate by 80 percent or 

19 more by 2050 compared to 1990 or more recent years” (G8 Summit 2009, page 19). 

20 • Asia Pacific Partnership on Clean Development and Climate. The Asia-Pacific 

21 Partnership on Clean Development and Climate is an effort to accelerate the development and 

22 deployment of clean energy technologies. The Asia-Pacific Partnership partners (Australia, 

23 Canada, China, India, Japan, Korea, and the United States) have agreed to work together and 

24 with private-sector partners to meet goals for energy security, national air pollution reduction, 

25 and climate change in ways that promote sustainable economic growth and poverty reduction. 

26 These seven partner countries collectively account for more than half of the world's economy, 

27 population, and energy use, and they produce about 65 percent of the world's coal, 62 percent 

28 of the world's cement, 52 percent of world's aluminum, and more than 60 percent of the 

29 world's steel (APP 2009a). The Partnership aims to be consistent with and contribute to the 

30 members’ efforts under the UNFCCC and will complement, but not replace, the Kyoto 

31 Protocol (APP 2009b). 

32 The SAP 2.1 MiniCAM Level 3 scenario provides a global context for emissions of a full suite of 

33 GHGs and ozone precursors for a Reference Case harmonious with implementation of the above policies 

34 and initiatives. There are some inconsistencies between the overall assumptions used by CCSP in SAP 

35 2.1 (Clarke et al. 2007) to develop global emissions scenarios and the assumptions used in the Volpe 

36 model in terms of economic growth, energy prices, energy supply, and energy demand. However, these 

37 inconsistencies affect the characterization of each CAFE alternative in equal proportion, so the relative 

38 estimates provide a reasonable approximation of the differences in environmental impacts among the 

39 alternatives. 

40 NHTSA used the MiniCAM Level 3 scenario as the primary global emissions scenario for 

41 evaluating climate effects in the Chapter 4 analysis, but used the MiniCAM Level 2 scenario and the RCP 

42 4.5 MiniCAM reference emissions scenario to evaluate the sensitivity of the results to alternative 

43 emissions scenarios. The RCP 4.5 MiniCAM reference emissions scenario assumes that no climate 

44 policy would be implemented beyond the current set of policies in place, whereasthe SAP 2.1 MiniCAM 

45 Level 2 and 3 scenarios correspond to total radiative forcing stabilization by 2100 and associated CO2

46 concentrations at roughly 550 ppmv and 650 ppmv, respectively, after accounting for the contributions to 

47 radiative forcing from the non-CO2 GHGs. 
4.4 Climate Chapter 4 Cumulative Impacts 

4-44 

1 Separately, each of the other alternatives was simulated by calculating the difference between 

2 annual GHG emissions under that alternative and emissions under the No Action Alternative (Alternative

3 1), and subtracting this change in the MiniCAM Level 3 scenario to generate modified global-scale 

4 emissions scenarios, which show the effect of the various CAFE alternatives on the global emissions path. 

5 For example, emissions from U.S. passenger cars and light trucks in 2020 under the No Action 

6 Alternative are 1,660million metric tons of CO2 (MMTCO2); emissions in 2020 under the Preferred 

7 Alternative (Alternative 4) are 1,550 MMTCO2 (see Table 4.4.4-2). The difference of 110 MMTCO2 

8 represents the reduction in emissions projected to result from adopting the Preferred Alternative. Global 

9 emissions for the MiniCAM Level 3 scenario in 2020 are 34,060 MMTCO2, which are assumed to 

10 incorporate the level of emissions from U.S. passenger cars and light trucks under the No Action 

11 Alternative. Global emissions under the Preferred Alternative are thus estimated to be 110 MMTCO2 less 

than this reference level, or 33,950 MMTCO2 12 in 2020. 

13 Many of the economic assumptions used in the Volpe model (such as fuel price, VMT, U.S. gross 

14 domestic product [GDP]) are based on the EIA AEO 2009 (EIA 2009a) and International Energy Outlook 

15 (IEO) 2009 (EIA 2009b), which forecast energy supply and demand in the United States and globally to 

16 2030. Figures 4.4.3-2 through 4.4.3-6 show how the EIA forecasts of global and U.S. GDP, CO2

17 emissions from energy use, and primary energy use compare against the assumptions used to develop the 

SAP 2.1 MiniCAM scenarios.8,9 18 The IEO forecast is for a reference case, while the SAP 2.1 forecasts are 

19 for a reference case and two climate policy cases. 

Figure 4.4.3-2. 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 

20 

 

8

 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. 

9

 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. All IEO energy-use estimates were converted to 

exajoules. 
Chapter 4 Cumulative Impact 4.4 Climate 

4-45 

Figure 4.4.3-3. Global Annual CO2 Emissions from Fossil Fuel Use 

1 

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

2 
4.4 Climate Chapter 4 Cumulative Impacts 

4-46 

Figure 4.4.3-5. World Primary Energy Use Forecast 

1 

Figure 4.4.3-6. U.S. Primary Energy Use Forecast 

2 

3 The GDP growth assumptions for the IEO reference scenario are slightly higher than those in the 

4 SAP scenarios, by about 0.6 percent annually for the world and 0.9 percent annually for the United States 

5 (see Figure 4.4.3-2). 

6 Despite this IEO assumption of higher economic growth, the growth in primary energy use is 

7 similar between the IEO and MiniCAM, with the primary energy use in MiniCAM slightly lower than 

8 that of the IEO, as shown in Figure 4.4.3-5. The global primary liquids energy use in SAP 2.1 and the

9 IEO 2009 compare well. Much of the difference in energy use in the IEO forecast is due to assumptions

10 of higher coal use that result in higher CO2 emissions, as shown in Figure 4.4.3-3. Additionally, the IEO 

11 reference scenario estimates have a particularly low share of “other” fuels, which includes biomass and 

12 renewable fuels, and is likely due to different treatments of non-commercial fuels in the two sets of 

13 forecasts. 
Chapter 4 Cumulative Impact 4.4 Climate 

4-47 

1 The primary energy use projections for the United States show a different trend than the global 

numbers. The AEO 2009 (EIA 2009a)10 2 projection shows an increase in total primary energy use in the 

3 United States, but much of the increase is from the use of coal. On the other hand, the SAP MiniCAM 

4 scenarios have a higher share of natural gas (Figure 4.4.3-6). However, the AEO reference scenario has a 

larger share of other fuels11 5 than the SAP MiniCAM scenarios, resulting in lower CO2 emissions 

6 (Figure 4.4.3-4). 

7 The approaches focus on the marginal climate effects of marginal changes in emissions. Thus, 

8 they generate a reasonable characterization of climate changes for a given set of emissions reductions, 

9 regardless of the underlying details associated with those emissions reductions. The discussion in Section 

10 4.4.4 characterizes projected climate change under the No Action Alternative and the changes associated 

11 with each action alternative.

12 The climate sensitivity analysis (see Section 4.4.3.2.3) also uses the MiniCAM Level 2 emissions 

13 scenario (Clarke et al. 2007) and the RCP 4.5 MiniCAM reference emissions scenario as possible global 

14 emissions scenarios. This provides a basis for determining climate responses to varying levels of global 

15 emissions and climate sensitivities under the No Action Alternative (Alternative 1) and the Preferred 

16 Alternative (Alternative 4). Some responses of the climate system are believed to be non-linear; by using 

17 a range of emissions cases and climate sensitivities, it is possible to estimate the effects of the alternatives 

18 in relation to different scenarios and sensitivities. 

19 Where information in the analysis included in this EIS is incomplete or unavailable, NHTSA has 

20 relied on CEQ regulations regarding incomplete or unavailable information (see 40 CFR § 1502.22(b)). 

21 For this analysis, despite the inconsistencies between the MiniCAM assumptions on global trends across

22 all GHG-emitting sectors (and the drivers that affect them) and the particularities of the emissions 

23 estimates for the U.S. transportation sector provided by the Volpe model, the approach used is valid; these 

24 inconsistencies affect all alternatives equally, and thus do not hinder a comparison of the alternatives in 

25 terms of their relative effects on climate. 

26 4.4.3.3.1 Tipping Points and Abrupt Climate Change 

27 The phrase “tipping point” is most typically used in the context of climate change and its 

28 consequences to describe situations in which the climate system (the atmosphere, oceans, land, 

cryosphere,12 29 and biosphere) reaches a point at which there is a disproportionally large or singular 

30 response in a climate-affected system as a result of only a moderate additional change in the inputs to that 

31 system (such as an increase in the CO2 concentration). Exceeding one or more tipping points, which 

32 “occur when the climate system is forced to cross some threshold, triggering a transition to a new state at 

33 a rate determined by the climate system itself and faster than the cause” (National Research Council 2002 

34 in EPA 2009), could result in abrupt changes in the climate or any part of the climate system. These 

35 changes would likely produce impacts at a rate and intensity far greater than the slower, steady changes 

36 currently being observed (and in some cases, planned for) in the climate system (EPA 2009b). 

37 The methodology used to address tipping points is based on an analysis of climate change science 

38 synthesis reports – including the Technical Support Document for EPA’s Endangerment Finding for 

39 GHGs (EPA 2009b), the IPCC WGI report (Meehl et al. 2007), and CCSP SAP 3.4: Abrupt Climate 

 

10 AEO 2009 revised estimates were used for U.S. primary energy consumption and form the basis for the IEO 2009 

forecast. 

11 For the AEO reference scenario, “other” includes biomass, hydropower, and other renewable fuels. 

12 The cryosphere describes the portion of Earth’s surface that is frozen water, such as snow, permafrost, floating 

ice, and glaciers. 
4.4 Climate Chapter 4 Cumulative Impacts 

4-48 

1 Change (CCSP 2008c) – and recent literature on the issue of tipping points and abrupt climate change. 

2 The analysis identifies vulnerable systems, possible temperature thresholds, and estimates of the 

3 likelihood, timing, and impacts of abrupt climate events. While there are methodological approaches to 

4 estimate temperatures resulting from a reduction in GHG emissions and associated radiative forcing, the 

5 present state of the art does not allow for quantification of how emission reductions from a specific policy 

6 or action might affect the probability and timing of abrupt climate change. This is one of the most 

7 complex and scientifically challenging areas of climate science, and given the difficulty of simulating the 

8 large-scale processes involved in these tipping points – or inferring their characteristics from 

9 paleoclimatology – considerable uncertainties remain as to the tipping points and rate of change. Despite 

10 the lack of a precise quantitative methodological approach, Section 4.5.9 presents a qualitative survey of 

11 the current state of climate science on tipping points and abrupt climate change and provides a summary 

12 of existing credible scientific evidence. 

13 4.4.4 Environmental Consequences 

14 This section describes the consequences of the proposed action and alternatives and other 

15 reasonably foreseeable future actions in relation to GHG emissions and global climate change 

16 consequences. 

17 4.4.4.1 Greenhouse Gas Emissions 

18 To estimate the emissions resulting from changes in passenger car and light truck CAFE 

19 standards, NHTSA uses the Volpe model (see Sections 2.2.1 through 2.2.4 and Section 3.1.4 for

20 descriptions of the model). The change in fuel use projected to result from each alternative CAFE 

21 standard determines the resulting impacts on total energy and petroleum energy use, which in turn affects 

22 the amount of CO2 emissions. These CO2 emissions estimates also include upstream emissions, which 

23 occur from the use of carbon-based energy during crude oil extraction, transportation, and refining, and in 

24 the transportation, storage, and distribution of refined fuel. Because CO2 accounts for such a large 

25 fraction of total GHG emitted during fuel production and use – more than 95 percent, even after 

26 accounting for the higher global warming potentials (GWPs) of other GHGs – NHTSA’s consideration of 

27 GHG impacts focuses on reductions in CO2 emissions resulting from the savings in fuel use that 

accompany higher fuel economy.13 28 

29 NHTSA considers the following measures of the cumulative impact of alternative CAFE 

30 standards for MY 2012-2016 and other reasonably foreseeable actions affecting CO2 emissions: 

31 • CO2 emissions from MY 2012-2016 passenger cars and light trucks, which are directly 

32 affected by the new CAFE standards; 

33 • CO2 emissions from MY 2017-2030 passenger cars and light trucks, assuming annual average 

34 percentage gains in mpg consistent with the AEO 2009 updated Reference Case projections, 

35 with all action alternatives exceeding the combined EISA target of 35 mpg in 2020 (see

36 Section 4.1.3); 

37 • CO2 emissions from MY 2031-2060 passenger cars and light trucks, for which the overall 

38 fuel economy of the fleet continues to improve as new vehicles enter the fleet with an average 

fuel economy equivalent to MY 2030 vehicles,14 39 and older vehicles leave the fleet; and 

 

13 Although this section includes only a discussion of CO2 emissions, 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. 

14 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. 
Chapter 4 Cumulative Impact 4.4 Climate 

4-49 

1 • CO2 emissions from MY 2061-2100 passenger cars and light trucks, for which emissions are 

held constant.15 2 

3 Cumulative emissions reductions from each action alternative increase across alternatives, with 

4 Alternative 2 having the lowest cumulative emissions reductions and Alternative 9 having the highest 

5 cumulative emissions reductions. Emissions reductions represent the differences in total annual 

6 emissions by all passenger cars or light trucksin use between their estimated future levels under the No 

7 Action Alternative (baseline), and with each alternative CAFE standard in effect. 

8 Emissions reductions resulting from applying the reasonably foreseeable future actions to the 

9 proposed CAFE standards for MY 2012-2016 passenger cars and light trucks and the eight action 

10 alternatives were estimated from 2012 to 2060. Emissions were estimated for all alternatives through 

11 2060, and these emissions were compared against the No Action Alternative (which assumes post-MY 

12 2011 fuel economy levels grow at the rates projected by the AEO fuel economy forecasts) to estimate 

13 emissions reductions. Annual emissions reductions from 2061 to 2100 were held constant at 2060 levels. 

14 Emissions under each action alternative were then compared against those under the No Action 

15 Alternative to determine its impact on emissions. 

16 Table 4.4.4-1 shows total GHG emissions and emissions reductions from new passenger cars and light 

17 trucks from 2012-2100 under each of the nine alternatives. Projections of emissions reductions over the 

18 2012 to 2100 period due to the MY 2012-2016 CAFE standards and other reasonably foreseeable future 

19 actions ranged from 27,300 to 39,100 MMTCO2. Compared to cumulative global emissions of 3,919,462 

20 MMTCO2 over this period (projected by the projected by the SAP 2.1 MiniCAM Level 3 scenario), the 

21 incremental impact of this rulemaking is expected to reduce global CO2 emissions by about 0.7 to 1.0 

22 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 

Alternative Emissions 

Emissions Reductions 

Compared to No 

Action Alternative 

1 No Action 227,600 0 

2 3%/year Increase 200,300 27,300 

3 4%/year Increase 200,200 27,300 

4 ~4.3%/year Increase, Preferred 200,300 27,300 

5 5%/year Increase 196,700 30,900 

6 ~5.9%/year Increase, MNB 191,600 36,000 

7 6%/year Increase 191,800 35,800 

8 7%/year Increase 188,500 39,100 

9 ~6.7%/year Increase, TCTB 188,790 38,791 

23 

24 To get a sense of the relative impact of these reductions, it can be helpful to consider the relative 

25 importance of emissions from passenger cars and light trucks as a whole and to compare them against 

26 emissions projections from the United States, and expected or stated goals from existing programs 

 

15 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. 
4.4 Climate Chapter 4 Cumulative Impacts 

4-50 

1 designed to reduce CO2 emissions. As mentioned earlier, U.S. passenger cars and light trucks currently 

2 account for approximately 21.7 percent of CO2 emissions in the United States. With the action 

3 alternatives reducing U.S. passenger car and light truck CO2 emissions by 11.2 to 16.0 percent, the CAFE 

4 alternatives will have a noticeable impact on total U.S. CO2 emissions. Compared to total U.S. CO2

5 emissions in 2100 projected by the MiniCAM reference scenario of 7,886 MMTCO2 (Clarke et al. 2007), 

6 the action alternatives would reduce total U.S. CO2 emissions by 5.1 to 7.2 percent in 2100. 

7 Figure 4.4.4-1 shows projected annual emissions from passenger cars and light trucks under MY 2012-

8 2016 standards and other reasonably foreseeable future actions. 

Figure 4.4.4-1. Cumulative Annual Emissions Under the MY 2012-2016 Standards 

and Other Reasonably Foreseeable Future Actions (MMTCO2) 

0

500

1000

1500

2000

2500

3000

3500

2010 2020 2030 2040 2050 2060

MMTCO2

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: ~5.9%/year Increase, MNB

Alt. 7: 6%/year Increase Alt. 8: 7%/year Increase

Alt. 9: ~6.7%/year Increase, TCTB

9 

10 As Table 4.4.4-2 shows, total CO2 emissions accounted for by the U.S. passenger car and light 

11 truck fleets are projected to increase substantially from their level in 2011 under the No Action 

12 Alternative, which would assume that passenger cars and light trucks continue to achieve the level of fuel 

13 economy required by MY 2011 CAFE standards. The table also shows that each of the action alternatives

14 would reduce total passenger-car and light-truck CO2 emissions in future years significantly from their

15 projected levels under the No Action Alternative. Progressively larger reductions in CO2 emissions from 

16 their levels under the No Action Alternative are projected to occur during each future year because the 

17 action alternatives require successively higher fuel economy levels for MY 2012-2016 and later passenger 

18 cars and light trucks. For example, Alternative 9 (which results in 37.0 mpg in 2016) will get much larger 

19 by 2030 growing at 0.51 percent a year than Alternative 2 (which results in 32 mpg in 2016) will get by 

20 2030 growing at 0.51 percent a year. 
Chapter 4 Cumulative Impacts 

4-51 

1 2 

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 

~5.9%/year 

Increase 

MNB 

6%/year 

Increase 

7%/y

Incre

Carbon dioxide (CO2) 

2010 1,700 1,700 1,700 1,700 1,700 1,700 1,700 1,72020 1,660 1,570 1,550 1,550 1,530 1,500 1,510 1,52030 1,900 1,680 1,670 1,670 1,640 1,600 1,600 1,52040 2,190 1,900 1,900 1,910 1,870 1,820 1,820 1,72050 2,580 2,240 2,240 2,250 2,200 2,140 2,140 2,12060 3,060 2,660 2,660 2,670 2,610 2,540 2,540 2,5

Methane (CH4) 

2010 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.02020 1.93 1.84 1.81 1.81 1.79 1.76 1.76 1.72030 2.22 1.97 1.96 1.96 1.92 1.87 1.87 1.82040 2.56 2.24 2.24 2.24 2.19 2.13 2.13 2.02050 3.01 2.63 2.63 2.63 2.58 2.50 2.50 2.42060 3.58 3.12 3.13 3.13 3.06 2.97 2.97 2.9

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 0.03 0.02030 0.04 0.04 0.04 0.04 0.03 0.03 0.03 0.02040 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.02050 0.05 0.05 0.05 0.05 0.05 0.05 0.04 0.02060 0.06 0.06 0.06 0.06 0.06 0.05 0.05 0.0

3 
4.4 Climate Chapter 4 Cumulative Impacts 

4-52 

1 Under all of the alternatives, projected growth in the number of passenger cars and light trucks in 

2 use throughout the United States, combined with assumed increases in their average use (VMT per 

3 vehicle), is projected to result in growth in total passenger car and light truck travel (VMT). As shown in 

4 Figure 4.4.4-1, despite increases in fuel economy, total fuel consumption by U.S. passenger cars and light 

5 trucks is projected to increase over most of the period shown in the table under each of the action 

6 alternatives. Because CO2 emissions are a direct consequence of total fuel consumption, the same result 

7 is projected for total CO2 emissions from passenger cars and light trucks. 

8 Emissions of CO2, the primary gas that drives climate effects, from the U.S. passenger-car and 

9 light-truck fleet represented about 3.7 percent of total global emissions of CO2 in 2005 (EPA 2009a, WRI 

2009).16 10 Although substantial, this source is still a small percentage of global emissions. The relative 

11 contribution of CO2 emissions from U.S. passenger cars and light trucks is expected to decline in the 

12 future, due primarily to rapid growth of emissions from developing economies (which are due in part to

13 growth in global transportation sector emissions). These conclusions are not meant to be interpreted as 

14 expressing NHTSA views that the U.S. vehicle fleet’s contribution to global CO2 emissions is not an area 

15 of concern for policymakers. Under NEPA, the agency is obligated to discuss “the environmental 

16 impact[s] of the proposed action.” 42 U.S.C. § 4332(2)(C)(i) (emphasis added). The analysis in this EIS 

17 fulfills NHTSA obligations in this regard. 

18 In its updated AEO 2009, EIA projects U.S. transportation-derived CO2 emissions will increase 

19 from 1,905 MMTCO2 in 2010 to 2,045 MMTCO2 in 2030, with cumulative emissions from transportation 

20 over this period reaching 41,093 MMTCO2 (EIA 2009a). Over this same period, the cumulative 

21 emissions reductions from this rulemaking and other reasonably foreseeable actions are projected to be

22 1,950 to 3,260 MMTCO2 compared to emissions projected under the No Action Alternative, which would 

23 yield a 5- to 8-percent reduction in CO2 emissions from the transportation sector. The emissions 

24 reductions as a result of increasing fuel economy of new passenger cars and light trucks would be 

25 expected to increase further as new vehicles, meeting the higher CAFE standards that each action 

26 alternative would establish, enter the fleet and older vehicles are retired. For example, in 2030, projected 

27 emissions reductions would be 220to 320 MMTCO2 depending on the alternative, a 11- to 16-percent 

28 decrease from projected U.S. transportation emissions of 2,045 MMTCO2 in 2030 (i.e., under the No 

29 Action Alternative). 

30 As another measure of the relative environmental impact of this rulemaking, these emissions 

31 reductions can be compared to existing programs designed to reduce GHG emissions in the United States. 

32 In 2007, Arizona, California, New Mexico, Oregon, and Washington formed the WCI to develop regional 

33 strategies to address climate change. WCI has a stated goal of reducing 350 MMTCO2 equivalent over 

the period from 2009 to 2020 (WCI 2007a).17 34 If this goal is achieved, emissions levels in 2020 would be 

35 33-percent less than the future baseline (the No Action Alternative), and 15-percent lower than those at 

36 the beginning of the WCI action (WCI 2007b). By comparison, this rulemaking is expected to reduce 

37 CO2 emissions by 310 to 680 MMTCO2 over the same period, with emissions levels in 2020 representing 

38 a 5- to 10-percent reduction from the future baseline emissions for passenger cars and light trucks. 

39 In the Northeast and Mid-Atlantic, nine states have formed the RGGI to reduce CO2 emissions 

40 from power plants. Emissions reductions from 2006 to 2024 are estimated at 268 MMTCO2 from what 

they were otherwise projected to be (RGGI 2006).18 41 This represents a 23-percent reduction from the 

 

16 Includes land-use change and forestry, and excludes international bunker fuels. 

17 Since this goal was stated, Montana, Quebec, and Ontario joined the WCI. Thus, the total emissions reduction is 

likely to be more than 350 MMTCO2. A revised estimate was not available as of July 14, 2009. 

18 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 

4-53 

1 future baseline and a 10-percent reduction in 2024 emissions from their levels at the beginning of the

2 action (RGGI 2006). By comparison, NHTSA forecasts that this rulemaking will reduce CO2 emissions 

3 by 810 to 1,530 MMTCO2 over this period, with emissions levels in 2024 representing an 8- to 13-percent 

4 reduction from the future baseline emissions for passenger cars and light trucks. 

5 Two features of these comparisons are extremely important to emphasize. First, emissions from 

6 the sources addressed in the WCI and RGGI plans are projected to decrease compared to the beginning of

7 the action, while emissions from passenger cars and light trucks are projected to increase under all 

8 alternatives for this rulemaking due to increases in vehicle ownership and use. Second, these projections 

9 are only estimates, and the scope of these climate programs differs from that in this rulemaking in terms 

10 of geography, sector, and purpose. 

11 Where information in the analysis included in this EIS is incomplete or unavailable, NHTSA has 

12 relied on CEQ regulations regarding incomplete or unavailable information (see 40 CFR § 1502.22(b)). 

13 In this case, the comparison of emissions reductions from the action alternatives to emissions reductions 

14 associated with other programs is intended to aid decisionmakers by providing relative benchmarks, 

15 rather than absolute metrics, for selecting among alternatives. In summary, the alternatives analyzed here 

16 deliver GHG emissions reductions that are on a scale similar to many of the most progressive and 

17 ambitious GHG emissions reduction programs underway in the United States. However, due to projected 

18 increases in VMT, increases in CAFE standards are not projected to provide absolute emissions 

19 reductions from today’s levels of passenger-car and light-truck emissions, whereas some regional 

20 programs do predict such absolute reductions. 

21 4.4.4.2 Cumulative Effects on Climate Change 

22 The approach to estimating the cumulative effects of climate change from the MY 2012-2016 

23 CAFE standards combined with other reasonably foreseeable future actions mirrors that used to estimate

24 the direct and indirect effects of the MY 2012-2016 CAFE standards. 

25 Again, because EISA directs NHTSA to increase CAFE standards to reach a combined fleet 

26 average CAFE level of at least 35 mpg by MY 2020, MY 2017-2020 CAFE standards are reasonably 

27 foreseeable and must be accounted for when analyzing the cumulative impacts of the MY 2012-2016 

28 CAFE standards. Many of the action alternatives surpass the target of 35 mpg in 2016. For action 

29 alternatives that do not reach 35 mpg by MY 2016 (Alternative 2 and Alternative 3), the Chapter 4 

30 cumulative impacts mpg is expected to continue to rise from 2017 to 2020 so that the MY 2020 EISA 

31 target 35 mpg is at least met. Once the 35 mpg target is met or exceeded, NHTSA assumes that the 

32 overall fuel economy of the fleet continues to improve until 2030 at a pace consistent with the AEO 2009 

33 updated Reference Case projections (see Section 4.1.3). NHTSA also assumes fuel economy increases 

34 consistent with the AEO projections under the No Action Alternative. 

35 Because the CAFE standards apply to new vehicles, this assumption results in emissions 

36 reductions and fuel savings that continue to grow after 2030 as new vehicles meeting the 2030 mpg 

37 average are added to the fleet in each subsequent year, reaching their maximum values when all passenger 

38 cars and light trucks in the U.S. fleet meet the 2030 average mpg. Overall, the emissions reductions for 

39 the MY 2012-2016 CAFE standards have a small impact on climate change. The emissions reductions 

40 and resulting climate impacts for the MY 2012-2016 CAFE standards and other reasonably foreseeable 

41 future actions are larger, although they are still relatively small in absolute terms. While these effects are 

42 small, they occur on a global scale and are long-lived. These conclusions are not meant to be interpreted 

43 as expressing NHTSA views that anthropogenic climate change is not an area of concern for 

44 policymakers. Under NEPA, the agency is obligated to discuss “the environmental impact[s] of the 
4.4 Climate Chapter 4 Cumulative Impacts 

4-54 

1 proposed action.” 42 U.S.C. § 4332(2)(C)(i) (emphasis added). The analysis in this EIS fulfills NHTSA 

2 obligations in this regard. 

3 Sections 4.4.4.2.1 through 4.4.4.2.4 describe cumulative effects of the alternatives on climate 

4 change in terms of atmospheric CO2 concentrations, temperature, precipitation, and sea-level rise. 

5 4.4.4.2.1 Atmospheric Carbon Dioxide Concentrations

6 MAGICC is a simple climate model that is well calibrated to the mean of the multi-model 

7 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 4.4.4-3.19 8 As the table indicates, the 

9 model runs developed for this analysis achieve relatively good agreement with IPCC WGI estimates in 

10 terms of both CO2 concentrations and surface temperature. 

Table 4.4.4-3 

Comparison of MAGICC Results and Reported IPCC Results (IPCC 2007a) 

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.

11 

12 A comparison of sea-level rise from MAGICC 5.3.v2 and the IPCC Fourth Assessment Report 

13 can be found in the release documentation for MAGICC 5.3.v2 (Wigley 2008). In Table 3 of the 

14 documentation, Wigley (2008) presents the results for six SRES scenarios that show the comparable value 

15 for sea-level rise from MAGICC 5.3.v2 (total sea-level rise minus estimates for contributions from non16 melt sources such as warming of the permafrost) within 0.01 centimeters (0.04 inch) in 2095. 

17 The MiniCAM Level 3 scenario, which is a radiative forcing stabilization scenario with a 

18 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.20 19 Table 4.4.4-4 and Figures 4.4.4-2 

20 through 4.4.4-5 show the mid-range results of MAGICC model simulations for Alternative 1 and the eight

21 action alternatives for CO2 concentrations and increase in global mean surface temperature in 2030, 2050, 

22 and 2100. As Figures 4.4.4-2 and 4.4.4-3 show, the reduction impact on the growth in projected CO2

23 concentrations and temperature amounts to a small fraction of the total growth in CO2 concentrations and 

24 global mean surface temperature. However, the relative impact of the action alternatives is illustrated by 

25 the reduction in growth of both CO2 concentrations and temperature under the TCTB Alternative 

26 (Alternative 9). 

 

19 NHTSA used the default climate sensitivity in MAGICC of 3.0 °C (5.4 °F) 

20 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. 
Chapter 4 Cumulative Impacts 4.4 Climate 

4-55 

1 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 

2 of estimated CO2 concentrations as of 2100, from 654.0 ppm under the TCTB Alternative (Alternative 9) 

3 to 657.5 ppm under the No Action Alternative (Alternative 1). For 2030 and 2050, the corresponding 

4 range is even smaller. Because CO2 concentrations are the key driver of all other climate effects, this 

5 leads to small differences in these effects. Although these effects are small, they occur on a global scale 

6 and are long-lived. 

7 4.4.4.2.2 Temperature 

8 MAGICC simulations of mean global surface air temperature increases are shown above in Table 

9 4.4.4-4. For all alternatives, the cumulative global mean surface temperature increase is about 0.80 °C to 

10 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 2.60 to 2.61 °C 

(4.68 to 4.70 °F) as of 2100.21 11 The differences among alternatives are small. For 2100, the reduction in 

12 temperature increase under the action alternatives in relation to the No Action Alternative is about 0.01 to 

13 0.02 °C (0.02 to 0.04 °F). Although these effects are small, they occur on a global scale and are long14 lived. 

15 Table 4.4.4-5 summarizes the regional changes to warming and seasonal temperatures from the 

16 IPCC Fourth Assessment Report. Quantifying the changes to regional climate from the CAFE 

17 alternatives is not possible at this point due to the limitations of existing climate models, but it is expected 

18 that the alternatives would reduce the changes in relation to the reduction in global mean surface 

19 temperature. 

20 MAGICC 5.3.v2 estimates radiative forcing from black carbon, a primary aerosol emitted 

21 through the incomplete combustion of fossil fuel and biomass burning. However, emissions trends for 

22 black carbon are “hard-wired” in the model to follow emissions of SO2, which means they cannot be 

specified separately in the model.22 23 The radiative forcing of black carbon is difficult to quantify 

24 accurately because it is a function of microphysical properties, the geographic and vertical placement, and 

25 lifetime of the aerosol. However, black carbon clearly contributes substantially to global warming 

26 (Jacobson 2001). Total global black carbon emissions are estimated to be approximately 8 teragrams 

(1012 27 grams) of carbon per year (Bond et al. 2004 in Forster et al. 2007), with estimates of fossil fuel 

28 contributions ranging from 2.8 teragrams of carbon per year (Ito and Penner 2005 in Forster et al. 2007) 

29 to 8.0 teragrams of carbon per year (Haywood and Boucher 2000 in Forster et al. 2007). In summary, 

30 climate modeling does account for the effects of black carbon on climate variables. 

 

21 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. 

22 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 PM mass 

that is then incorporated into the Volpe model. This PM is based on tailpipe emissions and therefore includes 

carbon emissions from the combustion process. Because the carbon emissions are lumped into the PM and not 

treated independently, the Volpe model does not provide direct results of the impact of the carbon emissions. 
4.4 Climate Chapter 4 Cumulative Impacts 

4-56 

1 

2 

Table 4.4.4-4 

Cumulative Effects on CO2 Concentrations, Global Mean Surface Temperature Increase, and Sea-level Rise Using MAGICC 

Alternative a/ 

CO2 Concentration 

(ppm) 

Global Mean Surface 

Temperature Increase 

(°C) 

Totals by Alternative 2030 2050 2100 2030 2050 2100 203

1 No Action 438.7 498.0 657.5 0.805 1.327 2.611 7.82 3%/year Increase 438.5 497.3 655.1 0.805 1.323 2.600 7.83 4%/year Increase 438.5 497.3 655.1 0.805 1.323 2.600 7.84 ~4.3%/year Increase, Preferred 438.5 497.3 655.1 0.804 1.323 2.600 7.85 5%/year Increase 438.4 497.2 654.7 0.804 1.323 2.599 7.86 ~5.9%/year Increase, MNB 438.4 497.0 654.3 0.804 1.322 2.596 7.87 6%/year Increase 438.4 497.0 654.3 0.804 1.322 2.596 7.88 7%/year Increase 438.4 496.9 654.0 0.804 1.321 2.595 7.89 ~6.7%/year Increase, TCTB 438.4 496.9 654.0 0.804 1.321 2.595 7.8Reductions Under Alternative CAFE Standards2 3%/year Increase 0.2 0.7 2.4 0.001 0.003 0.011 0.03 4%/year Increase 0.2 0.7 2.4 0.001 0.003 0.011 0.04 ~4.3%/year Increase, Preferred 0.2 0.7 2.4 0.001 0.004 0.011 0.05 5%/year Increase 0.3 0.8 2.8 0.001 0.004 0.012 0.06 ~5.9%/year Increase, MNB 0.3 1.0 3.2 0.001 0.005 0.015 0.07 6%/year Increase 0.3 1.0 3.2 0.001 0.005 0.015 0.08 7%/year Increase 0.3 1.1 3.5 0.002 0.005 0.016 0.09 ~6.7%/year Increase, TCTB 0.3 1.1 3.5 0.002 0.005 0.016 0.0

_______________ 

a/ The numbers in this table have been rounded for presentation purposes. Therefore, the reductions might not reflect the exact differe

cases. 

3 
Chapter 4 Cumulative Impacts 4.4 Climate 

4-57 

Figure 4.4.4-2. Cumulative Effects on CO2 Concentrations 

1 
4.4 Climate Chapter 4 Cumulative Impacts 

4-58 

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

1 
Chapter 4 Cumulative Impacts 4.4 Climate 

4-59 

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

No Action Alternative) 

1 
4.4 Climate Chapter 4 Cumulative Impacts 

4-60 

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

the No Action Alternative) 

1 
Chapter 4 Cumulative Impacts 4.4 Climate 

4-61 

Table 4.4.4-5 

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 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 of longer duration, 

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 

Warming likely to be largest 

in winter 

Minimum winter temperatures 

likely to increase more than 

the average 

 Southwest Warming likely to be largest 

in summer 

Maximum summer 

temperatures likely to 

increase more than the 

average 

 Northeast USA 

 Southern Canada 

 Canada 

Likely to exceed the global mean 

 Northernmost part of 

Canada 

Central and South 

America 

Southern South 

America 

Likely to be similar to the global mean 

 Central America 

 Southern Andes 

 Tierra del Fuego 

 Southeastern South 

America 

 Northern South 

America 

Likely to be larger than global mean 
4.4 Climate Chapter 4 Cumulative Impacts 

4-62 

Table 4.4.4-5 (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 

Australia and New 

Zealand 

Southern Australia Likely comparable to the global mean 

but less than in the rest of Australia 

 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 

Increased frequency of 

extreme high daily 

temperatures and a decrease 

in the frequency of cold 

extremes very likely

Polar Regions Arctic Very likely to warm during this century 

more than the global mean 

Warming largest in winter and 

smallest in summer 

 Antarctic Likely to warm 

Small Islands Likely to be smaller than the global 

annual mean 

1 

2 4.4.4.2.3 Precipitation 

3 In some areas, higher temperatures can increase precipitation. Increases in precipitation are a 

4 result of higher temperatures causing more water evaporation, which causes more water vapor to be 

5 available for precipitation (EPA 2009b). Increased evaporation leads to increased precipitation in areas 

6 where there is sufficient surface water, such as over oceans and lakes. In drier areas, the increased

7 evaporation can actually accelerate surface drying, which can lead to drought conditions (EPA 2009b). 

8 Overall, according to IPCC (Meehl et al. 2007), global mean precipitation is expected to increase under 

9 all scenarios. However, there will be considerable spatial and seasonal variations. Generally, 

10 precipitation increases are very likely to occur in high latitudes, and decreases are likely to occur in the 

11 sub-tropics (EPA 2009b). 

12 Where information in the analysis included in this EIS is incomplete or unavailable, NHTSA has 

13 relied on CEQ regulations regarding incomplete or unavailable information (see 40 CFR § 1502.22(b)). 

14 In this case, the IPCC (Meehl et al. 2007) summary of precipitation represents the most thoroughly 

15 reviewed, credible assessment of this highly uncertain factor. NHTSA expects that the CAFE alternatives 

16 would reduce the changes in precipitation in proportion to their effects on temperature. 

17 The global mean change in precipitation provided by the IPCC for the A2 (high), A1B (medium), 

18 and B1 (low) scenarios (Meehl et al. 2007) is given as the scaled change in precipitation (as a percentage 

19 change from 1980 through 1999 averages) divided by the increase in global mean surface warming for the

20 same period (per °C), as shown in Table 4.4.4-6. IPCC provided scaling factors in the year ranges 2011 

21 through 2030, 2046 through 2065, 2080 through 2099, and 2180 through 2199. NHTSA used the scaling 

22 factors for the A1B (medium) scenario in this EIS analysis because MAGICC does not directly estimate 

23 changes in global mean precipitation. 

24 Applying these scaling factors to the reductions in global mean surface warming provides 

25 estimates of changes in global mean precipitation. Given that the action alternatives would reduce 

26 temperature increases slightly in relation to the No Action Alternative, they also would reduce predicted 

27 increases in precipitation slightly, as shown in Table 4.4.4-7 (again, based on the A1B [medium] 

28 scenario). 
Chapter 4 Cumulative Impacts 4.4 Climate 

4-63 

Table 4.4.4-6 

Global Mean Precipitation Change (scaled, % per °C) (Meehl et al. 2007) a/ 

Scenario 2011-2030 2046-2065 2080-2099 2180-2199 

A2 1.38 1.33 1.45 NA 

A1B 1.45 1.51 1.63 1.68 

B1 1.62 1.65 1.88 1.89 

_______________ 

a/ These years do not correspond exactly to the years for which results are being reported. 

1 

Table 4.4.4-7 

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 2.406 

3 4%/year Increase 0.586 1.462 2.406 

4 ~4.3%/year Increase, Preferred 0.586 1.462 2.406 

5 5%/year Increase 0.586 1.461 2.405 

6 ~5.9%/year Increase, MNB 0.586 1.460 2.403 

7 6%/year Increase 0.586 1.460 2.403 

8 7%/year Increase 0.586 1.459 2.401 

9 ~6.7%/year Increase, TCTB 0.586 1.459 2.402 

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 0.009 

3 4%/year Increase 0.000 0.004 0.009 

4 ~4.3%/year Increase, Preferred 0.000 0.004 0.009 

5 5%/year Increase 0.000 0.005 0.011 

6 ~5.9%/year Increase, MNB 0.000 0.006 0.013 

7 6%/year Increase 0.000 0.006 0.013 

8 7%/year Increase 0.000 0.006 0.014 

9 ~6.7%/year Increase, TCTB 0.000 0.006 0.014 

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 ~5.9%/year Increase, MNB 0.85% 2.20% 3.92% 

7 6%/year Increase 0.85% 2.20% 3.92% 

8 7%/year Increase 0.85% 2.20% 3.91% 

9 ~6.7%/year Increase, TCTB 0.85% 2.20% 3.91% 
4.4 Climate Chapter 4 Cumulative Impacts 

4-64 

Table 4.4.4-7 (cont’d) 

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 

Reduction in Global Mean Precipitation Change for Alternative CAFE Standards (% Compared to 

No Action Alternative)

2 3%/year Increase 0.00% 0.01% 0.01% 

3 4%/year Increase 0.00% 0.01% 0.01% 

4 ~4.3%/year Increase, Preferred 0.00% 0.01% 0.02%

5 5%/year Increase 0.00% 0.01% 0.02% 

6 ~5.9%/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% 0.02% 

9 ~6.7%/year Increase, TCTB 0.00% 0.01% 0.02% 

_______________ 

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. 

1 

2 In addition to changes in mean annual precipitation, climate change is anticipated to affect the 

3 intensity of precipitation, as described in Meehl et al. (2007, page 750): 

4 Intensity of precipitation events is projected to increase, particularly in tropical and high 

5 latitude areas that experience increases in mean precipitation. Even in areas where mean 

6 precipitation decreases (most subtropical and mid-latitude regions), precipitation intensity 

7 is projected to increase but there would be longer periods between rainfall events. There 

8 is a tendency for drying of the mid-continental areas during summer, indicating a greater 

9 risk of droughts in those regions. Precipitation extremes increase more than does the 

10 mean in most tropical and mid- and high-latitude areas. 

11 Regional variations and changes in the intensity of precipitation events cannot be quantified 

12 further. This inability is due primarily to the lack of availability of AOGCMS required to estimate these 

13 changes. AOGCMS are typically used to provide results among scenarios having very large changes in 

14 emissions such as the SRES B1 (low), A1B (medium), and A2 (high) scenarios; very small changes in 

15 emissions profiles produce results that would be difficult to resolve among scenarios having relatively 

16 small changes in emissions. Also, the multiple AOGCMs produce results that are regionally consistent in 

17 some cases but are inconsistent in others. 

18 Table 4.4.4-8 summarizes the regional changes to precipitation from the IPCC Fourth Assessment 

19 Report. Quantifying the changes to regional climate from the action alternatives is not possible at this 

20 point, but the action alternatives would reduce the changes in relation to the reduction in global mean 

surface temperature.23 21 

 

23 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 4.4 Climate 

4-65 

Table 4.4.4-8 

Summary of Regional Changes to Precipitation Extracted from the IPCC Fourth Assessment 

(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 Annual mean precipitation likely to 

increase 

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 very likely to decrease 

Likely to decrease 

Asia Central Asia Precipitation in summer likely to 

decrease 

 Tibetan Plateau Precipitation in boreal winter very likely 

to increase 

 Northern Asia Precipitation in boreal winter very likely 

to increase 

Precipitation in summer likely to 

increase 

 Eastern Asia Precipitation in boreal winter likely to 

increase 

Precipitation in summer likely to 

increase 

Very likely to be an increase in the 

frequency of intense precipitation 

Extreme precipitation and winds 

associated with tropical cyclones likely 

to increase 

 South Asia Precipitation in summer likely to 

increase 

Very likely to be an increase in the 

frequency of intense precipitation 

Extreme precipitation and winds 

associated with tropical cyclones likely 

to increase 

 Southeast Asia Precipitation in boreal winter likely to 

increase in southern parts 

Precipitation in summer likely to 

increase in most parts of southeast Asia

Extreme precipitation and winds 

associated with tropical cyclones likely 

to increase 
4.4 Climate Chapter 4 Cumulative Impacts 

4-66 

Table 4.4.4-8 (cont’d) 

Summary of Regional Changes to Precipitation Extracted from the IPCC Fourth Assessment 

(Christensen et al. 2007)

Land Area Sub-region Precipitation 

Snow Season and 

Snow Depth 

North America Northern 

regions/Northern 

North America 

Snow season length and 

snow depth very likely to 

decrease 

 Southwest Annual mean precipitation is likely to 

decrease 

 Northeast USA Annual mean precipitation very 

likely to increase 

 Southern Canada 

 Canada Annual mean precipitation very 

likely to increase 

 Northernmost part of 

Canada 

Snow season length and 

snow depth likely to increase 

Central and South 

America 

Southern South 

America 

 Central America Annual precipitation likely to decrease 

 Southern Andes Annual precipitation likely to decrease 

 Tierra del Fuego Winter precipitation likely to increase 

 Southeastern South 

America 

Summer precipitation likely to increase 

 Northern South 

America 

Uncertain how precipitation will change 

Australia and New 

Zealand 

Southern Australia Precipitation likely to decrease in winter 

and spring 

 Southwestern 

Australia 

Precipitation very likely to decrease in 

winter 

 Rest of Australia 

 New Zealand, South 

Island 

Precipitation likely to increase in the 

west 

 Rest of New Zealand 

Polar Regions Arctic Annual precipitation very likely to 

increase; Very likely that the relative 

precipitation increase will be largest in 

winter and smallest in summer 

 Antarctic Precipitation likely to increase 

Small Islands Mixed, depending on the region 

1 

2 4.4.4.2.4 Sea-level Rise 

3 IPCC identifies four primary components of sea-level rise: (1) thermal expansion of ocean water, 

4 (2) melting of glaciers and ice caps, (3) loss of land-based ice in Antarctica, and (4) and loss of land5 based ice in Greenland (IPCC 2007b). Ice-sheet discharge is an additional factor that could influence sea 
Chapter 4 Cumulative Impacts 4.4 Climate 

4-67 

1 level over the long term. Ocean circulation, changes in atmospheric pressure, and geological processes 

2 can also influence sea-level rise at a regional scale (EPA 2009b). MAGICC calculates the oceanic 

3 thermal expansion component of global-mean sea-level rise using a nonlinear temperature- and pressure4 dependent expansion coefficient (Wigley 2008). It also addresses the other three primary components 

5 through ice-melt models for small glaciers and the Greenland and Antarctic ice sheets, and excludes non6 melt sources, which the IPCC Fourth Assessment Report also excluded. Neither MAGICC 5.3.v2 nor the 

7 IPCC Fourth Assessment Report includes more recent information, suggesting that ice flow from 

8 Greenland and Antarctica will be accelerated. The Fourth Assessment Report estimates the ice flow to be 

9 between 9 and 17 centimeters (3.5 and 6.7 inches) by 2100 (Wigley 2008).

10 The state of the science reflected as of the publication of the IPCC Fourth Assessment Report 

11 projects a sea-level rise of 18 to 59 centimeters (0.6 to 1.9 feet) by 2090 to 2099 (EPA 2009b). This

12 projection does not include all changes in ice-sheet flow or the potential for rapid acceleration in ice loss 

13 (Alley et al. 2005, Gregory and Huybrechts 2006, and Hansen 2005, all in Pew 2007). Several recent 

14 studies have found the IPCC estimates of potential sea-level rise might be underestimated regarding ice 

15 loss from the Greenland and Antarctic ice sheets (Shepherd and Wignham 2007, Csatho et al. 2008) and 

16 ice loss from mountain glaciers (Meier et al. 2007). Further, IPCC results for sea-level projections might 

17 underestimate sea-level rise due to changes in global precipitation (Wentz et al. 2007, Zhang et al. 2007). 

18 Rahmstorf (2007) used a semi-empirical approach to project future sea-level rise. The approach yielded a 

19 proportionality coefficient of 3.4 millimeters per year per degree Centigrade of warming, and a projected 

20 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 

21 Assessment Report warming scenarios. Rahmstorf (2007) concludes that “[a] rise over 1 meter by 2100 

22 for strong warming scenarios cannot be ruled out.” Section 4.5.5.1 discusses sea-level rise in more detail. 

23 Table 4.4.4-4 presents the impact on sea-level rise from the scenarios and show sea-level rise in 

24 2100 ranging from 32.84 centimeters (12.93 inches) under the No Action Alternative (Alternative 1) to 

25 32.70 centimeters (12.87 inches) under the TCTB Alternative (Alternative 9), for a maximum reduction 

26 of 0.14 centimeter (0.06 inch) by 2100 under the No Action Alternative. 

27 In summary, the impacts of the proposed action and alternatives and other reasonably foreseeable 

28 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.24 29 

30 This is due primarily to the global and multi-sectoral nature of the climate problem. Although these 

31 effects are small, they occur on a global scale and are long-lived. 

32 4.4.4.2.5 Climate Sensitivity Variations 

33 NHTSA examined the sensitivity of climate effects on key assumptions used in the analysis. This 

34 examination included reviewing the impact of various climate sensitivities and global emissions scenarios 

35 on the climate effects under the No Action Alternative (Alternative 1) and the Preferred Alternative 

36 (Alternative 4). Table 4.4.4-9 presents the results from the sensitivity analysis. 

 

24 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. 
4.4 Climate Chapter 4 Cumulative Impacts 

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Table 4.4.4-9 

Cumulative Effects on CO2 concentration, Temperature, 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 2.0 434.3 483.0 551.3 0.612 0.986 1.546 22.32 

 3.0 435.7 486.5 563.5 0.812 1.324 2.177 29.92 

4.5 437.4 490.5 578.8 1.034 1.705 2.948 38.76 

 Reduction compared to No Action 

 2.0 0.2 0.8 2.2 0.001 0.003 0.009 0.08 

 3.0 0.3 0.8 2.4 0.001 0.004 0.012 0.11 

 4.5 0.2 0.8 2.5 0.001 0.004 0.015 0.12 

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 2.0 437.0 493.8 641.0 0.606 0.987 1.880 24.60 

 3.0 438.5 497.3 655.1 0.804 1.323 2.600 32.75 

4.5 440.1 501.3 672.6 1.023 1.702 3.461 42.12 

 Reduction compared to No Action 

 2.0 0.3 0.7 2.4 0.001 0.003 0.008 0.08 

 3.0 0.2 0.7 2.4 0.001 0.004 0.011 0.09 

 4.5 0.2 0.7 2.6 0.001 0.004 0.014 0.12 

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 2.0 439.9 510.0 762.6 0.699 1.166 2.285 28.61 

 3.0 441.5 514.1 780.4 0.922 1.553 3.126 37.91 

4.5 443.3 518.8 802.6 1.166 1.987 4.120 48.55 

 Reduction compared to No Action 

 2.0 0.3 0.7 2.5 0.001 0.003 0.007 0.07 

 3.0 0.3 0.7 2.6 0.001 0.003 0.010 0.09 

 4.5 0.3 0.8 2.7 0.001 0.004 0.012 0.12 

_______________ 

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. 

1 
Chapter 4 Cumulative Impacts 4.4 Climate 

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1 The use of alternative global emissions scenarios can influence the results in several ways. 

2 Emissions reductions can lead to larger reductions in the CO2 concentrations in later years because more 

3 of the anthropogenic emissions can be expected to stay in the atmosphere. The use of different climate 

4 sensitivities (the equilibrium warming that occurs at a doubling of CO2 from pre-industrial levels) can 

5 affect not only warming but also indirectly affect sea-level rise and CO2 concentration. 

6 As shown in Table 4.4.4-9, the sensitivity of simulated CO2 emissions in 2030, 2050, and 2100 to 

7 assumptions of global emissions and climate sensitivity is low; stated simply, CO2 emissions do not 

8 change much with changes in global emissions and climate sensitivity. For 2030 and 2050, the choice of 

9 global emissions scenario has little impact on the results. By 2100, the Preferred Alternative (Alternative 

10 4) has the greatest impact in the global emissions scenario with the highest CO2 emissions (MiniCAM 

11 Reference) and the least impact in the scenario with the lowest CO2 emissions (MiniCAM Level 2). The 

12 total range of the impact of the Preferred Alternative on CO2 concentrations in 2100 is from 2.2 to 2.7 

13 ppm. The Reference Case using the MiniCAM Level 3 scenario and a 3.0 °C (5.4 °F) climate sensitivity 

14 has an impact of 2.4 ppm. 

15 The sensitivity of the simulated global mean surface temperatures for 2030, 2050, and 2100 

16 varies, as shown in Table 4.4.4-9. In 2030, the impact is low due primarily to the rate at which global 

17 mean surface temperature increases in response to increases in radiative forcing. In 2100, the impact is 

18 large due not only to the climate sensitivity but also to the change in emissions. In 2030, the reduction in 

19 global mean surface temperature from the No Action Alternative to the Preferred Alternative is 

20 consistently 0.001 °C (0.002 °F) for 2.0 °C (3.6 °F) climate sensitivity to the 4.5 °C (8.1 °F) climate 

21 sensitivity across each of the global emissions scenarios, as shown in Table 3.4.4-9. The impact on global 

22 mean surface temperature due to assumptions concerning global emissions of GHG is also important. 

23 The scenarios with the higher global emissions of GHGs, such as the MiniCAM Reference, have a lower 

24 reduction in global mean surface temperature and the scenarios with lower global emissions have a higher 

25 reduction. This is in large part due to the non-linear and near-logarithmic relationship between radiative 

26 forcing and CO2 concentrations. At high emissions levels, CO2 concentrations are high; therefore, a fixed 

27 reduction in emissions yields a lower reduction in radiative forcing and global mean surface temperature. 

28 The sensitivity of simulated sea-level rise to change in climate sensitivity and global GHG 

29 emissions mirrors that of global temperature, as shown in Table 4.4.4-9. Scenarios with lower climate

30 sensitivities have lower increases in sea-level rise; the increase in sea-level rise is lower under the 

31 Preferred Alternative (Alternative 4) than it would be under scenarios with higher climate sensitivities. 

32 Conversely, scenarios with higher climate sensitivities have higher sea-level rise; the increase of sea-level 

33 rise is higher under the Preferred Alternative than it would be under scenarios with lower climate 

34 sensitivities. Higher global GHG emissions have higher sea-level rise, but the impact of the Preferred 

35 Alternative is less than in scenarios with lower global emissions. Conversely, scenarios with lower global 

36 GHG emissions have lower sea-level rise, though the impact of the Preferred Alternative is greater than in 

37 scenarios with higher global emissions. 

38 
4.4 Climate Chapter 4 Cumulative Impacts 

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1 
Chapter 4 Cumulative Impacts 4.5 Health, Societal, and Environmental Impacts of Climate Change 

4-71 

1 4.5 HEALTH, SOCIETAL, AND ENVIRONMENTAL IMPACTS OF CLIMATE CHANGE 

2 4.5.1 Introduction 

3 The effects of the proposed action and alternatives on climate as described in Section 4.4 – CO2

4 concentrations, temperature, precipitation, and sea-level rise – can translate to impacts to key natural and 

5 human resources. Section 4.5.2 describes the methodology NHTSA used to evaluate the cumulative 

6 impacts stemming from climate change on key natural and human resources. Sections 4.5.3 through 4.5.8

7 address cumulative impacts to the following key natural and human resources: 

8 • Freshwater resources (the availability, practices, and vulnerabilities of freshwater as a 

9 function of climate); 

10 • Terrestrial and freshwater ecosystems (existing and potential vulnerabilities and benefits of 

11 the respective species and communities in response to climate change); 

12 • Marine, coastal systems, and low-lying areas (the interplay between climate, environment, 

13 species, and communities within coastal and open-ocean waters, including coastal wetlands 

14 and coastal human settlements); 

15 • Food, fiber, and forest products (the environmental vulnerabilities of farming, forestry, and 

16 fisheries that could be affected by climate change); 

17 • Industries, settlements, and society (covers a broad range of human institutions and systems, 

18 including industrial and service sectors; large and small urban areas and rural communities; 

19 transportation systems; energy production; and financial, cultural, and social institutions in 

20 the context of how these elements might be affected by climate change; and 

21 • Human health (how a changing climate might affect human mortality and morbidity). 

22 Each section discusses the affected environment, provides an overview of the resource within the 

23 U.S. and globally, and addresses the consequences and observed changes of climate change on that 

24 resource. The section also includes a discussion of both the beneficial and adverse consequences of 

25 climate change, as they are represented in the literature. Although the approach is systematic, these topics 

26 do not exist in isolation and there is some overlap between discussions. 

27 The sections generally follow the organization of topic areas in the climate literature, notably by 

28 IPCC, which is a key source for much of the information presented in this section, and by EPA and 

29 CCSP. These categories do not follow the classification of resources typically found in an EIS. See the 

30 chart in Section 4.1 to find where specific NEPA topics are covered. 

31 As shown in Section 4.4, although the alternatives could substantially decrease GHG emissions, 

32 they would not prevent climate change; instead they would result in reductions to the anticipated 

33 increases of global CO2 concentrations, temperature, precipitation, and sea level. NHTSA’s assumption 

34 is that these reductions in climate effects would be reflected in reduced impacts to affected resources. 

35 However, the magnitude of the changes in climate effects that the alternatives would produce – a few ppm 

36 of CO2, a hundredth of a degree Centigrade difference in temperature, a small percentage change in the 

37 rate of precipitation increase, and 1 or 2 millimeters of sea-level rise, see Section 4.4.4 – are too small to 

38 address quantitatively in terms of their impacts on resources. Given the enormous resource values at 

39 stake, these distinctions could be important – very small percentages of huge numbers can yield 

40 substantial results – but they are too small for current quantitative techniques to resolve. Consequently, 

41 the discussion of resource impacts does not distinguish among the CAFE alternatives; rather it provides a 
4.5 Health, Societal, and Environmental Impacts of Climate Change Chapter 4 Cumulative Impacts 

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1 qualitative review of the benefits of reducing GHG emissions and the magnitude of the risks involved in 

climate change. 1 2 

3 4.5.2 Methodology 

4 This document primarily draws upon panel-reviewed synthesis and assessment reports from the 

5 IPCC and U.S. Global Change Research Program (USGCRP). It also cites EPA’s Technical Support 

6 Document for its proposed Endangerment and Cause or Contribute Findings for GHGs under the Clean 

7 Air Act – which heavily relied on these panel reports. NHTSA similarly relies on panel reports because 

8 they have assessed numerous individual studies in order to draw general conclusions about the state of

9 science; have been reviewed and formally accepted by, commissioned by, or in some cases authored by, 

10 U.S. government agencies and individual government scientists and provide NHTSA with assurances that 

11 this material has been well vetted by both the climate change research community and by the U.S. 

12 government; and in many cases, they reflect and convey the consensus conclusions of expert authors. 

13 These reports therefore provide the overall scientific foundation for U.S. climate policy at this time. 

14 This document also refers to new peer-reviewed literature that has not been assessed or 

15 synthesized by an expert panel. This new literature supplements but does not supersede the findings of 

16 the panel-reviewed reports. 

17 NHTSA’s consideration of newer studies and highlighting of particular issues responds to 

18 previous public comments received on the scoping document and the prior EIS for the MY 2011 CAFE 

19 standard, as well as the Ninth Circuit’s decision in CBD v. NHTSA, 538 F.3d 1172 (9th Cir. 2008). The 

20 level of detail regarding the science of climate change in this draft EIS, and NHTSA’s consideration of 

21 other studies that show illustrative research findings pertaining to the potential impacts of climate change 

22 on health, society, and the environment, are provided to help inform the public and the decisionmaker,

23 consistent with the agency’s approach in the prior EIS for the MY 2011 CAFE standards. 

24 NHTSA compiled research on freshwater resources; terrestrial and freshwater ecosystems and 

25 biodiversity; marine, coastal, and low-lying areas; industry, settlement, and society; food, fiber, and forest 

26 products; and human health. Each section includes an introduction and addresses the impacts anticipated 

27 for both the United States and the global environment. 

28 To accurately reflect the likelihood of climate-change impacts for each sector, NHTSA 

29 referenced the IPCC uncertainty guidelines (see Section 4.4.1.1 and Section 4.5.2.2). This approach 

30 provided a consistent methodology to define confidence levels and percent probability of a predicted 

31 outcome or impact. More information on the uncertainty guidelines is provided in the Treatment of 

32 Uncertainties in the IPCC’s Working Group II Assessment in Solomon et al. (2007). Section 4.5.2.2 

33 summarizes the IPCC treatment of uncertainty. 

34 4.5.2.1 Cumulative Climate-Change Impacts 

35 As described in Chapter 3, the proposed action and alternatives result in different periods of CO2

36 emissions associated with the operation of U.S. vehicles. These emissions, in combination with U.S. 

37 GHG emissions from other sources (such as power plants, natural gas use, and agricultural production) 

 

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 4 Cumulative Impacts 4.5 Health, Societal, and Environmental Impacts of Climate Change 

4-73 

1 and with emissions of all GHGs globally, would alter atmospheric concentrations of GHGs. As the 

2 modeling results presented in Section 4.4 show, different atmospheric concentrations of GHGs will be 

3 associated with long-term changes in global climate variables, including global average temperature, 

4 precipitation, and rising sea level. In turn, these climate changes would result in changes to a range of 

5 natural and human resources and systems, including water supplies, human health, the built environment, 

6 and a host of others. 

7 The most common approach to assessing the impacts of climate change is to construct future 

8 scenarios that represent combinations of changes in levels, and sometimes patterns or variability, of 

9 temperature, precipitation, sea-level rise, and other relevant climatic and related variables (IPCC 2007b). 

10 In some cases these scenarios will represent the results of specific climate modeling (the output of 

11 General Circulation Models), often downscaled to provide results at a finer level of geographic resolution. 

12 In other cases, scenarios might be designed to be representative of the types and ranges of effects 

13 expected to occur under climate change, and not the results of specific models (Parson et al. 2007). 

14 Impacts associated with these scenarios are then estimated using a variety of techniques, including models 

15 of individual systems (specific ecosystems or geographic areas, such as a park) and examination of 

16 performance under similar historical conditions. 

17 Climate impacts literature suggests that some regions and sectors will likely experience positive 

18 effects of future climate change, particularly at lower levels of temperature change (less than 1 to 3 °C 

19 [1.8 to 5.4 degrees Fahrenheit {°F} above 1990 levels), while others will experience negative effects 

20 (IPCC 2007b). The IPCC WGII for the Fourth Assessment Report found that, at higher levels of 

21 temperature, on balance the net global effects are expected to be negative: “while developing countries 

22 are expected to experience larger percentage losses, global mean losses could be 1 to 5 percent GDP for 4 

23 °C [7.2 °F] of warming” (IPCC 2007b). The modeling results presented in Section 4.4 suggest that, for

24 the CAFE alternatives, the cumulative climate effects in terms of temperature rise under a moderate 

25 emissions scenario lie in the range of 2.59 to 2.61 °C (4.66 to 4.70 °F) as of 2100. 

26 NHTSA’s presumption, consistent with the general literature cited above and reviewed for 

27 Section 4.5, is that reducing emissions and concomitant climate effects will reduce the net negative 

28 long-term effects that have been projected for climate change. NHTSA has not, however, performed a 

29 quantitative comparison of the climate impacts of the alternative CAFE standards on individual resource 

30 areas, for several reasons. 

31 First, as indicated above, analyses of impacts often focus on discrete climate scenarios, rather 

32 than a continuum of climate outcomes; the information to analyze small changes in climate variables is

33 not, therefore, generally available in the literature. Moreover, as the global climate changes, so will 

34 regional and local climates. Changes in global climate variables will be reflected in regional and local 

35 changes in average climate variables, and in the variability and patterns of climate, such as seasonal and 

36 annual variations, the frequency and intensity of extreme events, and other physical changes, such as the 

37 timing and amount of snowmelt. Impacts assessments often rely on highly localized data for both climate 

38 and other conditions and circumstances (CCSP 2008d). Thus, changes in impacts due to changes in 

39 global average climate, as projected in this analysis, likely will not be adequately represented by a simple 

40 scaling of results. Where information in the analysis included in the EIS is incomplete or unavailable, the 

41 agency has relied on CEQ regulations regarding incomplete or unavailable information (see 40 CFR § 

42 1502.22(b)). Information on the effect of very small changes in temperature, precipitation, and sea-level 

43 rise (at the scale of the distinctions among the alternative CAFE standards) is not currently available. 

44 Nevertheless, NHTSA’s qualitative characterization – that the greater the reductions in GHG emissions,

45 the lower the environmental impact – is consistent with theoretical approaches and research methods 

46 generally accepted in the scientific community. 
4.5 Health, Societal, and Environmental Impacts of Climate Change Chapter 4 Cumulative Impacts 

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1 Second, there is considerable debate about the likely shape of a global climate impacts damage 

2 function. Although many believe the function to be upwardly sloped (so that marginal net damages 

3 increase with increasing levels of climate change), fewer agree on its shape, that is, how rapidly net 

4 climate damages increase as temperature and other variables increase (IPCC 2007b). There is also the 

5 important question of whether there are thresholds, that is, stress points at which ecosystems collapse or 

6 the negative impacts rapidly accelerate – a topic important enough to warrant attention in a SAP Report 

7 for which the USGS is the lead agency (CCSP 2009c). Finally, much of the work on impacts – both 

8 global and more localized – is, in and of itself, qualitative and so does not lend itself to further 

9 quantification. 

10 4.5.2.2 Treatment of Uncertainties in the Working Group I Assessment 

11 Uncertainties can be classified in several different ways. “Value uncertainties” and “structural 

12 uncertainties” are two primary types of uncertainties. When data are inaccurate or do not fully represent 

13 the phenomenon of interest, value uncertainties arise. These types of uncertainties are typically estimated 

14 with statistical techniques, and then expressed probabilistically. An incomplete understanding of the

15 process that controls particular values or results generates structural uncertainties. These types of

16 uncertainties are described by presenting the authors’ collective judgment of their confidence in the 

17 correctness of a result. As stated in the WGI assessment, a “careful distinction between levels of 

18 confidence in scientific understanding and the likelihoods of specific results” are drawn in the uncertainty 

19 guidance provided for the Fourth Assessment Report.

20 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 

21 

22 The standard terms used to define the likelihood of an outcome or result where the outcome or 

23 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 

24 
Chapter 4 Cumulative Impacts 4.5 Health, Societal, and Environmental Impacts of Climate Change 

4-75 

1 4.5.3 Freshwater Resources 

2 In 2008, IPCC concluded that “Observational records and climate projections provide abundant 

3 evidence that freshwater resources are vulnerable and have the potential to be strongly impacted by 

4 climate change, with wide-ranging consequences for human societies and ecosystems” (Bates et al. 2008). 

5 In the United States, according to EPA (2009b), the vulnerability of these resources varies regionally. 

6 This section summarizes current global and U.S. observations of freshwater resources and the most recent 

7 projections of future changes. 

8 4.5.3.1 Affected Environment 

9 4.5.3.1.1 Freshwater Systems and Storage 

10 Without water, there would be no life on Earth. Climate change implications for water resources 

11 are therefore of fundamental interest. As seen in Figure 4.5.3-1, water covers about 70 percent of Earth’s 

12 surface, and most of this water (97.5 percent) is contained in the oceans. The remaining 2.5 percent is 

13 fresh water, most of which (68.7 percent) is ice and permanent snow cover in the Antarctic, the Arctic, 

14 and mountainous regions. Another 29.9 percent is fresh groundwater. Only 0.26 percent of the total 

15 amount of fresh water is contained in lakes, reservoirs, and river systems (UNESCO 2003). 

Figure 4.5.3-1. Global Allocation of Water 

16 

17 The largest volume of fresh water is stored in the cryosphere, and consists of snow, glaciers, ice, 

18 and frozen ground. Most glaciers and ice sheets are found in Antarctica (almost 90 percent), with the

19 remainder found in Greenland (almost 10 percent) and in mountain glaciers. Permafrost extends over 

20 northeastern Europe and the northern and northeastern parts of Asia, including the Arctic islands, northern 

21 Canada, the fringes of Greenland and Antarctica, and the high-altitude areas of South America (UNESCO 

22 2003). 

23 Groundwater occurs in the pores of soils and fractures of rocks and is the second largest source of 

24 fresh water. Groundwater feeds springs, streams, and lakes; supports wetlands; and is a critical source of 

25 water for human consumption. Groundwater also includes aquifers, underground strata of water-bearing 

26 permeable rock or unconsolidated materials (sand, gravel, and some silts and clays) from which water is 

27 extracted by well systems (UNESCO 2003). 
4.5 Health, Societal, and Environmental Impacts of Climate Change Chapter 4 Cumulative Impacts 

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1 Lakes, which can be broadly defined as bodies of water collected in depressions in Earth’s 

2 surface, are widespread and numerous (there are approximately 15 million) and store the largest volume

3 of fresh surface waters. Reservoirs – human-made lakes – are constructed for the storage of water, and 

4 are typically created by damming a river channel in a valley (UNESCO 2003). 

5 Rivers are bodies of flowing water that drain surface runoff from land to the seas and oceans. 

6 They begin in higher elevations such as mountains and hills where rainwater and snowmelt collect, 

7 forming small tributary streams that flow into larger streams and rivers (UNESCO 2003). 

8 4.5.3.1.2 Non-climate Threats to Freshwater Resources 

9 Freshwater resources during recent decades are threatened by non-climatic and climatic drivers. 

10 The non-climate threats include population growth and economic development, which create increasing 

11 demands for water from the residential, industrial, municipal, and agricultural sectors. In particular, 

12 irrigation of agricultural lands accounts for nearly 70 percent of global freshwater withdrawals and for 

13 more than 90 percent of global consumptive use (Bates et al. 2008). The extent of irrigated areas, which 

14 is expected to expand in areas that are already water-stressed, will determine the effect that this use will 

15 have on global water use in the future (EPA 2009b, Bates et al. 2008, Kundzewicz et al. 2007a). 

16 Other pressures on freshwater resources include infrastructure development (dams, dikes, levees, 

17 and river diversions); poor land use (urbanization, conversion to crop or grazing lands, wetland removal 

18 or reduction, and deforestation); overexploitation (groundwater aquifer depletion and reduced water levels 

19 in lakes, rivers, and wetlands); water pollution from industrial, municipal, and agricultural sources 

20 (pathogens and microbial contaminants, pesticides, phosphorus and nitrogen from fertilizers, heavy 

21 metals, toxic organic compounds and microorganic pollutants); silt and suspended particles (from soil 

22 erosion); acidification (from air pollution); and thermal pollution (from industrial discharges and slow 

23 flows caused by dams and reservoirs) (EPA 2009b, Bates et al. 2008, Kundzewicz et al. 2007a). 

24 4.5.3.2 Environmental Consequences 

25 Although there will be water-supply increases in some areas and decreases in others, there will be 

26 an overall net negative impact of climate change on water resources and freshwater ecosystems 

27 worldwide. The effects of climate change on freshwater resources will exacerbate the impacts of other

28 stressors, such as increases in population growth, economic activity, land-use change, and urbanization. 

29 In some areas, including regions as diverse as the Rhine basin, southeastern Michigan, Pennsylvania, and 

30 central Ethiopia, models project that land-use change will have a small effect compared to climate change 

31 (Kundzewicz et al. 2007a). 

32 Areas in which runoff is projected to decline are likely to face a reduction in the value of the 

33 services provided by freshwater resources. The beneficial impacts of increased annual runoff in other

34 areas will be offset to some extent by the negative effects of increased precipitation variability and

35 seasonal runoff shifts on water supply, water quality, and flood risks (EPA 2009b). 

36 Chemical and microbial inputs, biogeochemical processes, water temperature, and water levels 

37 control water quality. Climate changes can affect water quality from increases in temperature or through 

38 changes in precipitation and water quantity. Negative impacts from water temperature increases include 

39 algal blooms, increased microbial concentrations, and out-gassing of volatile and semi-volatile 

40 compounds like ammonia, mercury, dioxins, and pesticides (EPA 2009b). Negative impacts on water 

41 quality from changes in water quantity include resuspension of bottom sediments, increased turbidity 

42 (suspended solids), pollutant introduction, and reduced dilution. Increased stream flow can dilute 
Chapter 4 Cumulative Impacts 4.5 Health, Societal, and Environmental Impacts of Climate Change 

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1 pollutant concentrations or transport additional pollutants into surface-water sources, while extreme 

2 events – floods and droughts – generally exacerbate water quality problems (EPA 2009b). 

3 In general, consequences of changes in snow, ice, and frozen ground (including permafrost) 

4 include (Rosenzweig et al. 2007): 

5 • Ground instability in permafrost regions; 

6 • A shorter travel season for vehicles over frozen roads in the Arctic; 

7 • Increase in the number and size of glacial lakes in mountain regions; 

8 • Destabilization of moraines damming glacial lakes; 

9 • Changes in Arctic and Antarctic Peninsula flora and fauna; 

10 • Limitations on mountain sports in lower-elevation alpine areas; and 

11 • Changes in indigenous livelihoods in the Arctic. 

12 4.5.3.2.1 Observed Impacts of Climate Change on Freshwater Resources in the 

13 United States 

14 Precipitation and Stream Flow

15 Conditions across the United States tend to be increasingly dry from east to west. Upslope areas 

16 in the Cascade and coastal mountain ranges are more humid, with relatively low precipitation variability. 

17 The Intermountain West and Southwest are driest, and the greatest precipitation variability is in the arid 

18 and semi-arid West (EPA 2009b, Lettenmaier et al. 2008a). Stream gauge data show increases in stream 

19 flow from 1939 through 1998 in the eastern United States (Mauget 2003 in Lettenmeier et al 2008) and a

20 more or less reverse pattern in the western United States (Lettenmaier et al. 2008a, National Science and 

21 Technology Council 2008). Stream flow in the eastern United States has increased 25 percent in the past 

22 60 years, and has decreased by about 2 percent per decade in the central Rocky Mountain region over the 

23 past century (EPA 2009b). Since 1950, stream discharge in both the Colorado and Columbia River 

24 Basins has decreased, while over the same period annual evapotranspiration from the conterminous 

25 United States increased by 55m (2.2 inches) (Walter et al. 2004). 

26 The observed impacts to precipitation and streamflow also include: 

27 • In regions with winter snow, warming has shifted the magnitude and timing of hydrologic 

28 events (Mote et al. 2005, Regonda et al. 2005, Stewart et al. 2005 in National Science and 

29 Technology Council 2008). From 1949 to 2004, the fraction of annual precipitation falling as 

30 rain (rather than snow) increased at 74 percent of the weather stations studied in the western 

31 mountains of the United States (EPA 2009b). 

32 • Streamflow peaks in the snowmelt-dominated western mountains of the United States 

33 occurred 1 to 4 weeks earlier in 2002 than in 1948 (Stewart et al. 2005 in National Science 

34 and Technology Council 2008). 

35 • Precipitation in the Arctic has increased 8 percent on average over the past century. Much of 

36 that increase has occurred as rain (EPA 2009b). 

37 Precipitation variability and subsequent surface-water availability vary regionally across the 

38 United States depending on a catchment’s (watershed) physical, hydrological, and geological 

39 characteristics (National Science and Technology Council 2008). EPA has identified the Great Lakes, 

40 Chesapeake Bay, Gulf of Mexico, and Columbia River Basin as large water bodies for which climate 

41 change is a particular concern (EPA 2009b). 
4.5 Health, Societal, and Environmental Impacts of Climate Change Chapter 4 Cumulative Impacts 

4-78 

1 The IPCC Fourth Assessment Report summarized the current precipitation and water supply 

2 trends in the United States as follows (EPA 2009b): 

3 • Annual precipitation has increased throughout most of North America. 

4 • Stream flow has increased in the eastern United States in the last 60 years, but has decreased 

5 in the central Rocky Mountain region over the last century. 

6 • Since 1950, stream discharge in both the Colorado and Columbia River basins has decreased. 

7 • In regions with winter snow, warming has shifted the magnitude and timing of hydrologic 

8 events. 

9 • The fraction of annual precipitation falling as rain (rather than snow) increased at 74 percent 

10 of the weather stations studied in the western mountains of the United States from 1949 

11 through 2004. 

12 Snow Cover

13 There is a trend toward reduced mountain snowpack and earlier spring snowmelt runoff peaks 

14 across much of the western United States. Evidence suggests this trend is very likely attributable, at least 

15 in part, to long-term warming, although decadal-scale variability, including a shift in Pacific Decadal 

16 Oscillation (PDO) in the 1970s, might have played some part. Where shifts to earlier snowmelt peaks and 

17 reduced summer and fall low flows have already been detected, continuing shifts in this direction are 

18 expected and could have substantial impacts on the performance of reservoir systems (EPA 2009b). 

19 Snowpack in the mountainous headwater regions of the western United States generally declined 

over the second half of the 20th 20 Century, especially at lower elevations and in locations where average 

winter temperatures are close to or above 0o

21 C (32 °F). These trends toward reduced winter snow

22 accumulation and earlier spring melt are also reflected in a tendency toward earlier runoff peaks in spring, 

23 a shift that has not occurred in rainfall-dominated watersheds in the same region (Lettenmaier et al. 2008b 

24 in National Science and Technology Council 2008). 

25 Spring and summer snow cover has decreased in the western United States (Groisman et al.

26 2004). April snow water equivalent has declined 15 to 30 percent since 1950 in the western mountains of 

27 North America, particularly at lower elevations and primarily due to warming rather than changes in 

28 precipitation (Mote et al. 2003, 2005 and Lemke et al. 2007b, all in National Science and Technology 

29 Council). Additionally, the break-up of river and lake ice in North America is now occurring earlier, with 

30 an advance of 0.2 to 12.9 days over the last century (EPA 2009b). 

31 Groundwater

32 The effects of climate on groundwater – especially groundwater recharge – is a topic that requires 

33 further research to determine current effects from climate change. The available literature (Vaccaro 1992, 

34 Loaiciga et al. 2000, Hanson and Dettinger 2005, Scibek and Allen 2006, Gurdak et al. 2007, all in 

35 Lettenmaier et al. 2008a) implies that groundwater systems generally respond more slowly to climate 

36 change than do surface-water. However, a 2.5 °C (4.5 °F) or greater warming scenario is projected to 

37 decrease the recharge of the Ogallala aquifer region by 20 percent (EPA 2009b). 

38 Groundwater levels correlate most strongly with precipitation. Temperature is a more important 

39 factor for shallow aquifers during warm periods (National Science and Technology Council 2008). 
Chapter 4 Cumulative Impacts 4.5 Health, Societal, and Environmental Impacts of Climate Change 

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1 Groundwater and surface water might also be affected by sea-level rise. Saltwater intrusion into 

2 aquifers might occur in coastal areas, and increased salinity of ground and estuary water might reduce

3 freshwater availability. 

4 Water Quality

5 Chemical and microbial inputs, biogeochemical processes, water temperature, and water levels 

6 control water quality. Water temperature and water quantity are sensitive to climate change. However, 

7 pollution from land use – especially agricultural runoff, urban runoff, and thermal pollution from energy 

8 production – have caused most of the observed changes in water quality (National Science and 

9 Technology Council 2008). 

10 Rising water temperatures negatively affect aquatic biota, especially certain fish species such as 

11 salmon (Bartholow 2005, Crozier and Zabel 2006, both in Lettenmaier et al. 2008). Rising temperatures 

12 also affect dissolved oxygen, oxidation/reduction potentials, lake stratification, and mixing rates. 

13 However, the direction of climate change effects associated with water quantity on water quality is not as 

14 evident. Increased streamflow can dilute pollutant concentrations or transport additional pollutants into 

15 surface water sources. Extreme events – floods and droughts – generally exacerbate water quality 

16 problems. 

17 Extreme Events – Floods and Drought

18 Extreme events such as floods and drought affect freshwater resources. Climatic phenomena 

19 (intense/long-lasting precipitation, snowmelt, ice jams) and non-climatic phenomena (dam failure, 

20 landslides) can exacerbate floods and drought. 

21 As previously mentioned, research to date has not provided clear evidence for a climate-related 

22 trend in floods during past decades. However, evidence suggests that the observed increase in 

23 precipitation intensity and other observed climate changes could have affected floods (National Science 

24 and Technology Council 2008). 

25 There is some evidence of long-term drying and increase in drought severity and duration in the 

26 West and Southwest (National Science and Technology Council 2008) that is probably a result of 

27 decadal-scale climate variability and long-term change (EPA 2009b). 

28 Over-allocation and continuing competition for freshwater resources for agriculture, cities, and 

29 industry increases vulnerability to extended drought in North America (EPA 2009b), despite the fact that 

30 per-capita water consumption has declined over the past 2 decades in the United States (Lettenmaier et al.

31 2008a). 

32 4.5.3.2.2 Globally Observed Impacts of Climate Change on Freshwater Resources 

33 Trends associated with climate change have already been observed in various inputs, throughputs, 

34 and outputs to the global freshwater system, including (Kundzewicz et al. 2007a): 

35 • Precipitation – increasing over northern (30 degrees north) latitudes, decreasing over middle 

36 (10 degrees south to 30 degrees north) latitudes, increasing in intensity; 

37 • Stream flow – increasing in Eurasian Arctic, measurable increases or decreases in some river 

38 basins, earlier spring peak flows and increased winter-based flows in North America and 

39 Eurasia; 
4.5 Health, Societal, and Environmental Impacts of Climate Change Chapter 4 Cumulative Impacts 

4-80 

1 • Evapotranspiration – increased actual evapotranspiration in some areas; 

2 • Lakes – warming, substantial increases and decreases in some lake levels, and reduction in 

3 ice cover; 

4 • Snow cover – decreasing in most regions; 

5 • Glaciers – decreasing almost everywhere; and 

6 • Permafrost – thawing between 0.08 inch per year (Alaska) and 1.8 inches per year (Tibetan 

7 plateau). 

8 For other anticipated changes in the freshwater system, data are often insufficient to observe a 

9 climate trend, especially when compared to the non-climatic pressures mentioned previously. The lack of 

10 an observed trend does not necessarily indicate a lack of sensitivity to climate change. The current 

11 hydrologic observing system was not designed specifically for detecting the effects of climate change on 

12 water resources (Lettenmaier et al. 2008a). In addition, there are large-scale climate variations, such as 

13 ENSO events, occurring at the same time as global and regional climate changes. For these reasons, it

14 can be difficult to detect a climate change signal within the climate variability without observations of a 

15 decade or longer (Rosenzweig et al. 2007). 

16 Snow Cover and Frozen Regions

17 Temperature increases lead to declines in snow cover, and where most of winter precipitation 

18 currently falls as snow, hydrologic impact studies have shown that warming leads to changes in the 

19 seasonality of river flows. Areas vulnerable to these changes include the European Alps, the Himalayas, 

20 western North America, central North America, eastern North America, the Russian territory, 

21 Scandinavia, and Baltic regions (Kundzewicz et al. 2007a). 

22 Precipitation is also an important driver of changes in snow cover. At high elevations that remain 

23 below freezing in winter, precipitation increases have resulted in increased snowpack. Warmer 

24 temperatures at mid-elevations have decreased snowpack and led to earlier snowmelt, even with 

25 precipitation increases (Kundzewicz et al. 2007a). An empirical analysis of available data indicated that 

26 both temperature and precipitation impact mountain snowpack simultaneously, with the nature of the 

27 impact strongly dependent on factors such as geographic location, latitude, and elevation (Stewart 2009). 

28 Global warming is increasing glacier melt worldwide and decreasing snow cover in most regions. 

29 More than one-sixth of the world’s population lives in glacier- or snowmelt-fed river basins and will be 

30 affected by a seasonal shift in stream flow, an increase in the ratio of winter to annual flows, and a

31 reduction in low flows caused by decreased glacier extent or snow water storage (Kundzewicz et al.

32 2007a). 

33 Glacier melt sustains many rivers during summer in the Hindu Kush Himalaya and the South 

34 American Andes (Singh and Kumar 1997, Mark and Seltzer 2003, Singh 2003, Barnett et al. 2005 in 

35 Kundzewicz et al 2007,). The mass of some northern hemisphere glaciers is projected to decrease up to

36 60 percent by 2050 (Schneeberger et al. 2003 in Kundzewicz et al 2007). Glaciers throughout the Arctic 

37 are melting, with a particularly rapid retreat of Alaska’s glaciers, representing about half of the loss of 

38 glacial mass worldwide (ACIA 2004). 

39 From 2010 to 2015, the ice cover on Siberian rivers is expected to melt 15 to 27 days sooner than 

40 it did from 1950 to 1979. The maximum ice cover is also expected to be 20 to 40 percent thinner 

41 (Vuglinsky and Gronskaya 2005 in Kundzewicz et al 2007). 
Chapter 4 Cumulative Impacts 4.5 Health, Societal, and Environmental Impacts of Climate Change 

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1 Permafrost is thawing in many regions, with variations among regions in the degree of thawing. 

2 In Alaska, permafrost is declining 0.08 inch per year, while permafrost melting is 1.8 inches per year on 

3 the Tibetan plateau (Kundzewicz et al. 2007a). 

4 Surface Waters

5 A recent analysis of streamflow records for 925 of the world’s largest ocean-discharging rivers 

6 from 1948 through 2004 indicated significant trends for about one-third of the top 200 rivers. There were 

7 significant downward trends in annual streamflow in low- and mid-altitude regions, consistent with the

8 general drying trend over global lands for the past half-century, whereas there was a large upward trend 

9 for annual discharge into the Arctic Ocean. The data also indicated that ENSO events are important for 

10 rivers discharging into the Atlantic, Pacific, Indian and global oceans as a whole, but not for the Arctic 

11 Ocean and the Mediterranean and Black Seas. Significantly, the effect of human activities on annual 

12 stream flow and streamflow trends was found to be small for most of the world’s large rivers compared to 

13 the influence of climate change (Dai et al. 2009). 

14 Climate models consistently project precipitation increases in high latitudes and parts of the 

15 tropics, and decreases in lower mid-latitude regions (Milly et al. 2005c, Nohara et al. 2006 in Ebi et al.

16 2008). Projections for the area in between remain highly uncertain (Kundzewicz et al. 2007a). Data from 

17 24 climate model runs generated by 12 different general circulation models generally agreed that by 2050 

18 annual average river runoff and water availability will increase by 10 to 40 percent at high latitudes

19 (North America, Eurasia) and in some wet tropical areas, and decrease by 10 to 30 percent over some dry 

20 regions at mid-latitudes and in the dry tropics (Milly et al. 2005a). 

21 Semi-arid and arid areas are particularly vulnerable to precipitation declines. Many of these areas 

22 are water stressed, including the Mediterranean, southern Africa, and northeastern Brazil. In southeastern 

23 Australia and southern India, climate change has the potential to exacerbate reductions in runoff caused 

24 by forestation (Bates et al. 2008, Kundzewicz et al. 2007a). 

25 In snow-dominated basins, where most precipitation occurs in winter in the form of snow, it is 

26 projected that winter snows will be reduced and snowmelt will occur earlier, resulting in reduced spring 

27 runoff and summer flows (Bates et al. 2008). Projections for rain-fed basins describe higher flows in the 

28 peak-flow season, with either lower flows in low-flow seasons or extended dry periods (Kundzewicz et 

29 al. 2007a). 

30 Water Quality

31 A brief overview of the effects of climate change on the availability and quality of drinking water 

32 is provided by Epstein et al. (2006). Many countries are experiencing water-quality issues in their water 

33 and wastewater treatment plants. Increased filtration is required in drinking water plants to address

34 microorganism outbreaks following intense rain, thus increasing some operating costs by 20 to 30 percent 

35 (AWWA 2006 in Kundzewicz 2007). Other stressors on water quality noted by the IPCC include 

36 (Kundzewicz et al. 2007a): 

37 • More water impoundments for hydropower (Kennish 2002 in Kundzewicz et al 2007, 

38 Environment Canada 2004 in Fischlin et al 2007); 

39 • Stormwater drainage operation and sewage disposal disturbances in coastal areas resulting 

40 from sea-level rise (Haines et al. 2000); 

41 • Increasing water withdrawals from low-quality sources; 
4.5 Health, Societal, and Environmental Impacts of Climate Change Chapter 4 Cumulative Impacts 

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1 • Greater pollutant loads resulting from increased infiltration rates to aquifers or higher runoff 

2 to surface waters (resulting from high precipitation); 

3 • Water infrastructure malfunctioning during floods (GEO-LAC 2003, DFID 2004); 

4 • Overloading the capacity of water and wastewater treatment plants during extreme rainfall 

5 (Environment Canada 2001); and 

6 • Increased amounts of polluted storm water. 

7 Higher water temperatures, increased precipitation intensity, and longer periods of low flows 

8 exacerbate existing water pollution, with impacts on ecosystems, human health, water system reliability, 

9 and operating costs. Pollutants include sediments, nutrients, dissolved organic carbon, pathogens, 

10 pesticides, salt, and thermal pollution. Rising temperatures also have adverse effects on dissolved oxygen 

11 levels, oxidation/reduction potentials, and lake stratification and mixing rates (EPA 2009b, Kundzewicz 

12 et al. 2007a). 

13 4.5.3.2.3 Projected Impacts of Climate Change on Freshwater Resources in the 

14 United States 

15 Most freshwater resource analyses are keyed either to climate scenarios (what happens if 

16 temperature increases by 6 °F and precipitation declines by 10 percent) or to global climate model outputs 

17 pegged to IPCC-reported emission scenarios. This section summarizes the projected impacts resulting 

18 from such analyses, current sensitivities, and potential vulnerabilities (including extreme events). 

19 The climate-change impacts on freshwater resources in the United States are described by 

20 National Science and Technology Council (2008), Lettenmaier et al. (2008a), and Field et al. (2007a). 

21 “In regards to the hydrologic observing systems on which these sections are based, Lettenmaier et al.

22 (2008a) found that the current hydrologic observing system was not designed specifically for the purpose 

23 of detecting the effects of climate change on water resources. In many cases, the resulting data are unable 

24 to meet the predictive challenges of a rapidly changing climate” (National Science and Technology 

25 Council 2008). 

26 Precipitation

27 Recent climate model simulations reported by the IPCC indicate that, in general, current patterns 

28 will continue, with increases in runoff over the eastern United States, gradually transitioning to little 

29 change in the Missouri and lower Mississippi, to substantial decreases in annual runoff in the interior 

30 West (Colorado and Great Basin) (Bates et al. 2008, Kundzewicz et al. 2007a). Many areas in the 

31 western and southwestern United States already stressed are expected to suffer from additional decreases 

32 in precipitation and runoff from future climate changes (EPA 2009b). In eastern North America, 

33 meanwhile, precipitation may increase. Under a mid-range scenario, daily precipitation so heavy that it 

34 now occurs only every 20 years is likely to occur every 8 years by 2100 (EPA 2009b). 

35 Additionally, several recent state and regional studies have examined specific climate-change 

36 impacts on freshwater resources. For example, many impacts on freshwater resources described above 

37 have been projected for New Mexico (D’Antonio 2006), New Jersey (EPA 1997), and the West (Saunders 

38 et al. 2008). “Projections for the western mountains of the United States suggest that warming, and 

39 changes in the form, timing, and amount of precipitation will very likely lead to earlier melting and 

40 significant reductions in snowpack by the middle of the 21st Century (high confidence). In mountainous 

41 snowmelt-dominated watersheds, projections suggest advances in the timing of snowmelt runoff, 

42 increases in winter and early spring flows (raising flooding potential), and substantially decreased 

43 summer flows. Heavily utilized water systems of the western United States that rely on capturing 
Chapter 4 Cumulative Impacts 4.5 Health, Societal, and Environmental Impacts of Climate Change 

4-83 

1 snowmelt runoff, such as the Columbia River system, will be especially vulnerable” (Field et al. 2007b in 

2 National Science and Technology Council 2008). 

3 Although uncertainties in climate model projections of precipitation changes make future 

4 projections of stream flow uncertain, watersheds dominated by spring and summer snowmelt are an 

5 exception. In mountainous snowmelt-dominated watersheds, projections suggest advances in the timing 

6 of snowmelt runoff, increases in winter and early spring flows (raising flooding potential), and 

7 substantially decreased summer flows (Stewart 2009). 

8 Snowpack

9 Trends in declining snowpack are perhaps best illustrated from studies conducted for California. 

10 Reduced snowpack has been identified as a major concern for the State (California Energy Commission 

11 2006b in National Science and Technology Council 2008). Several authors anticipate a coming crisis in

12 water supply for the western United States (Barnett et al. 2008), and have projected that Lake Mead (on 

13 the Colorado River system) might go dry (Barnett and Pierce 2008 in CCSP 2008b While these studies 

14 focus on issues already identified in the literature, their findings suggest that freshwater resources might 

15 be more sensitive to climate change than previously projected. A recent article by Rauscher et al. (2008) 

16 used a high-resolution nested climate model to investigate future changes in snowmelt-driven runoff over 

17 the western United States and modeled increases in seasonal temperature of approximately 3 to 5 °C (5.4 

18 to 9 °F) by 2100, which could cause snowmelt-driven runoff to occur as much as 2 months earlier than at 

19 present – twice as early as other projections – affecting reservoir water storage and hydroelectric 

20 generation, and impacting land use, agriculture, and water management. 

21 In the western United States, where water supplies are already strained, continuing shifts toward 

22 drier conditions will have significant implications for water supplies and water management (Brekke et 

23 al. 2009, Lettenmaier et al. 2008a). Projections for the western mountains of the United States suggest 

24 that warming, and changes in the form, timing, and amount of precipitation will very likely lead to earlier 

25 melting and significant reductions in snowpack by the middle of the 21st Century. Heavily utilized water 

26 systems of the western United States that rely on capturing snowmelt runoff, such as the Columbia River 

27 system, will be especially vulnerable (EPA 2009b). 

28 Snowpack is also decreasing in Alaska. Snow cover in that area is expected to decrease 10 to 20 

29 percent by the 2070s (EPA 2009b). 

30 Groundwater

31 Future groundwater supplies will depend on both climate-related changes in recharge rates and 

32 withdrawals for human uses. Many parts of the United States depend on groundwater supplies for 

33 drinking water, irrigating agriculture, and a variety of residential uses, and increased demands due to 

34 population growth, increased temperature, and reduced precipitation could draw down groundwater 

35 supplies faster than it can be recharged (GCRP et al. 2009). In arid and semi-arid regions, groundwater 

36 supplies are more vulnerable than elsewhere, and in some areas it might not be possible to rely on 

37 groundwater to make up declines in surface-water supplies resulting from climate change and other 

38 stressors. Projections for the Ogallala aquifer, for example, indicate a 20 percent decrease in groundwater 

39 recharge based on simulations of future warming using a number of different climate models (EPA 

40 2009b). 
4.5 Health, Societal, and Environmental Impacts of Climate Change Chapter 4 Cumulative Impacts 

4-84 

1 Water Quality

2 Climate change will make achieving existing water quality goals more difficult. Historically, 

3 agricultural runoff, urban runoff, and thermal pollution from energy production have caused most of the 

4 observed changes in water quality in the United States (Kundzewicz et al. 2007a, The National Science 

5 and Technology Council 2008). EPA cites siltation, excess nutrients, and metals (e.g., mercury) as the 

6 main pollutants in U.S. waters, primarily because of nonpoint source pollution from runoff from urban 

7 and agricultural lands (EPA 2000, EPA 2007). 

8 Restoration of beneficial uses (to address habitat loss, eutrophication, beach closures) under the 

9 Great Lakes Water Quality Agreement will likely be vulnerable to declines in water levels, warmer water 

10 temperatures, and more intense precipitation (Mortsch et al. 2003). Based on simulations, phosphorus 

11 remediation targets for the Bay of Quinte (Lake Ontario) and the surrounding watershed could be 

12 compromised as 5.4 to 7.2 °F warmer water temperatures contribute to 77 to 98 percent increases in 

13 summer phosphorus concentrations in the Bay (Nicholls 1999, in National Science and Technology 

14 Council 2008), and as changes in precipitation, streamflow, and erosion lead to increases in average 

15 phosphorus concentrations in streams of 25 to 35 percent (Walker 2001 in Field et al 2007). 

16 Projected impacts on water quality also include (National Science and Technology Council 

17 2008): 

18 • Changes in precipitation could increase nitrogen loads from rivers in the Chesapeake and 

19 Delaware Bay regions by up to 50 percent by 2030 (Kundzewicz et al. 2007a). 

20 • Decreases in snow cover and increases in winter rain on bare soil will likely lengthen the 

21 erosion season and enhance erosion intensity. This will increase the potential for sediment22 related water quality impacts in agricultural areas (Field et al. 2007a). 

23 • Increased precipitation amounts and intensities will lead to greater rates of erosion in the 

24 United States and in other regions unless protection measures are taken (Kundzewicz et al.

25 2007a). Soil-management practices (crop residue, no-till) in some regions (e.g., the Corn 

26 Belt) might not provide sufficient erosion protection against future intense precipitation and 

27 associated runoff (Field et al. 2007a). 

28 • For the Midwest, simulations project that the low flows used to develop pollutant discharge 

29 limits (Total Maximum Daily Loads) would decrease by more than 60 percent were there to 

30 be a 25 percent decrease in mean precipitation; adding on irrigation demand, the effective 

31 decline is projected to reach 100 percent (Eheart et al. 1999 in National Science and 

32 Technology Council 2008). 

33 • Restoration of beneficial uses (to address habitat loss, eutrophication, beach closures) under 

34 the Great Lakes Water Quality Agreement will likely be vulnerable to declines in water 

35 levels, warmer water temperatures, and more intense precipitation (Mortsch et al. 2003). 

36 • Based on simulations, phosphorus remediation targets for the Bay of Quinte (Lake Ontario) 

37 and the surrounding watershed could be compromised as 5.4 to 7.2 °F warmer water 

38 temperatures contribute to 77 to 98 percent increases in summer phosphorus concentrations in 

39 the Bay (Nicholls 1999 in National Science and Technology Council 2008), and as changes in 

40 precipitation, streamflow, and erosion lead to increases in average phosphorus concentrations 

41 in streams of 25 to 35 percent (Walker 2001 in Field et al. 2007). 

42 Kundzewicz et al. (2007a) also concluded (high confidence) that climate change is likely to make 

43 achieving existing water quality goals for North America more difficult (National Science and 

44 Technology Council 2008). 
Chapter 4 Cumulative Impacts 4.5 Health, Societal, and Environmental Impacts of Climate Change 

4-85 

1 Extreme Events – Floods and Drought

2 Climate change is expected to increase the frequency and intensity of extreme events such as 

3 floods and drought. Research to date has not provided clear evidence for a climate-related trend in floods 

4 in the United States during past decades. However, evidence suggests that the observed increase in 

5 precipitation intensity and other observed climate changes could have affected floods (National Science 

6 and Technology Council 2008). Climatic phenomena (intense/long-lasting precipitation, snowmelt, ice 

7 jams) and non-climatic phenomena (dam failure, landslides) can exacerbate floods and droughts. In the

8 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 9 Century (Field et al. 2007a). 

10 Because the intensity and mean amount of precipitation is projected to increase across the United 

11 States at middle and high latitudes, the risk of flash flooding and urban flooding will increase in these 

12 areas (EPA 2009b). At the same time, greater temporal variability in precipitation increases the risk of 

13 drought (Christensen et al. 2007a). There is some evidence of long-term drying and increase in drought 

14 severity and duration in the West and Southwest (National Science and Technology Council 2008) that is

15 probably a result of decadal-scale climate variability and long-term change (EPA 2009b). 

16 Water Availability and Water Use

17 Regionally, the IPCC concluded that large changes in irrigation water demand are likely due to 

18 climate change (Kundzewicz et al. 2007a). Irrigation continues to be the largest use of water, accounting 

19 for 70 percent of global water use and 90 percent of consumptive use. Over-allocation and continuing 

20 competition for freshwater resources for agriculture, cities, and industry increases vulnerability to climate 

21 changes. Federal agencies have identified a number of areas, mostly in the western half of the United

22 States, where there could be conflicts over growing water shortages in a changing climate (U.S. DOI 

23 2005, Brekke et al. 2009). For example, in southern California, 41 percent of the water supply will be 

24 vulnerable by the 2020s due to loss of snowpack in the Sierra Nevada and Colorado River Basin (EPA 

25 2009b). 

26 4.5.3.2.4 Projected Impacts of Climate Change on Global Freshwater Resources 

27 The IPCC report is the most recent, comprehensive, and peer-reviewed summary of impacts on 

28 global freshwater resources available. Kundzewicz et al. (2007a) summarized the conclusions from the 

29 freshwater resources and management chapter as follows: 

30 • The impacts of climate change on freshwater systems and their management are mainly due 

31 to the observed and projected increases in temperature, sea level, and precipitation variability 

32 (very high confidence). 

33 • More than one-sixth of the world’s population lives in glacier- or snowmelt-fed river basins 

34 and will be affected by the seasonal shift in streamflow, an increase in the ratio of winter to 

35 annual flows, and possibly the reduction in low flows caused by decreased glacier extent or 

36 snow-water storage (high confidence). 

37 • Sea-level rise will extend areas of salinization of groundwater and estuaries, resulting in a 

38 decrease in freshwater availability for humans and ecosystems in coastal areas (very high 

39 confidence). 

40 • Increased precipitation intensity and variability is projected to increase the risks of flooding 

41 and drought in many areas (high confidence). 
4.5 Health, Societal, and Environmental Impacts of Climate Change Chapter 4 Cumulative Impacts 

4-86 

1 • Semi-arid and arid areas are particularly exposed to the impacts of climate change on 

2 freshwater (high confidence). 

3 • Many of these areas (Mediterranean basin, western United States, southern Africa, and 

4 northeastern Brazil) will suffer a decrease in water resources due to climate change (very high 

5 confidence). 

6 • Efforts to offset declining surface-water availability due to increasing precipitation variability 

7 will be hampered by the fact that groundwater recharge will decrease considerably in some 

8 already water-stressed regions (high confidence), where vulnerability is often exacerbated by 

9 the rapid increase in population and water demand (very high confidence). 

10 • Higher water temperatures, increased precipitation intensity, and longer periods of low flows 

11 exacerbate many forms of water pollution, with impacts on ecosystems, human health, water12 system reliability, and operating costs (high confidence). 

13 • These pollutants include sediments, nutrients, dissolved organic carbon, pathogens, 

14 pesticides, salt, and thermal pollution. 

15 • Climate change affects the function and operation of existing water infrastructure and water 

16 management practices (very high confidence). 

17 • Adverse effects of climate on freshwater systems aggravate the impacts of other stresses, 

18 such as population growth, changing economic activity, land use change, and urbanization 

19 (very high confidence). 

20 • Globally, water demand will grow in the coming decades, primarily due to population growth 

21 and increased affluence; regionally, large changes in irrigation water demand as a result of 

22 climate change are likely (high confidence). 

23 • Current water management practices are very likely to be inadequate to reduce the negative 

24 impacts of climate change on water supply reliability, flood risk, health, energy, and aquatic 

25 ecosystems (very high confidence). 

26 • Improved incorporation of current climate variability into water-related management would 

27 make adaptation to future climate change easier (very high confidence). 

28 • Adaptation procedures and risk management practices for the water sector are being 

29 developed in some countries and regions (the Caribbean, Canada, Australia, Netherlands, 

30 United Kingdom, United States, and Germany) that have recognized projected hydrological 

31 changes with related uncertainties (very high confidence). 

32 • Since the IPCC Third Assessment, uncertainties have been evaluated, their interpretation has 

33 improved, and new methods (e.g., ensemble-based approaches) are being developed for their 

34 characterization (very high confidence). 

35 • Nevertheless, quantitative projections of changes in precipitation, river flows, and water 

36 levels at the river-basin scale remain uncertain (very high confidence). 

37 • The negative impacts of climate change on freshwater systems outweigh its benefits (high 

38 confidence). 

39 • All IPCC regions (see Chapters 3 through 16 of the IPCC report) show an overall net 

40 negative impact of climate change on water resources and freshwater ecosystems (high 

41 confidence). 

42 • Areas in which runoff is projected to decline are likely to face a reduction in the value of the 

43 services provided by water resources (very high confidence). 
Chapter 4 Cumulative Impacts 4.5 Health, Societal, and Environmental Impacts of Climate Change 

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1 • The beneficial impacts of increased annual runoff in other areas will be tempered by the 

2 negative effects of increased precipitation variability and seasonal runoff shifts on water 

3 supply, water quality, and flood risks (high confidence). 

4 Observed global climate-related trends affecting freshwater resources were identified previously. 

5 The following discussion identifies key projected impacts to surface waters, groundwater, extreme events, 

6 and water quality. 

7 Surface Water

8 Data from 24 climate model runs generated by 12 different general circulation models (Milly et 

9 al. 2005b in Kundzewicz et al. 2007) generally agreed that by 2050: 

10 • Annual average river runoff and water availability will increase by 10 to 40 percent at high 

11 latitudes (North America, Eurasia) and in some wet tropical areas. 

12 • Annual average river runoff and water availability will decrease by 10 to 30 percent over 

13 some dry regions at mid-latitudes and in the dry tropics, some of which are presently water14 stressed areas (Mediterranean, southern Africa, and western United States/northern Mexico). 

15 Hydrological impact studies have shown that warming leads to changes in the seasonality of river 

16 flows where much winter precipitation currently falls as snow, including the European Alps, the 

17 Himalayas, western North America, central North America, eastern North America, the Russian territory,

18 Scandinavia, and Baltic regions. Winter flows will increase, summer flows will decrease, and peak flow 

19 will occur at least 1 month earlier in many cases (Kundzewicz et al. 2007a). 

20 Higher temperatures increase glacier melt. Glacier melt sustains many rivers during summer in 

21 the Hindu Kush Himalaya and the South American Andes (Singh and Kumar 1997, Mark and Seltzer 

22 2003 in Kundzewicz et al 2007, Singh 2003, Barnett et al. 2005, all in Kundzewicz et al. 2007). The 

23 mass of some northern hemisphere glaciers is projected to decrease up to 60 percent by 2050 

24 (Schneeberger et al. 2003 in Kundzewicz et al. 2007). 

25 Projections for rain-fed basins describe higher flows in peak-flow season with either lower flows 

26 in low-flow season or extended dry periods (Kundzewicz et al. 2007a). 

27 Lake levels are determined by river and rain water inputs and evaporation outputs. By the end of 

the 21st 28 Century, water levels are projected to change between −4.5 feet and +1.15 feet in the Great Lakes 

29 (Lofgren et al. 2002, Schwartz et al. 2004, both in Kundzewicz et al. 2007) and to drop about 29.5 feet in 

30 the Caspian Sea (Elguindi and Giorgi 2006 in Kundzewicz et al. 2007). 

31 From 2010 to 2015, the ice cover on Siberian rivers is expected to melt 15 to 27 days sooner than 

32 it did from 1950 to 1979. The maximum ice cover is also expected to be 20 to 40 percent thinner 

33 (Vuglinsky and Gronskaya 2005 in Kundzewicz et al. 2007). 

34 A combination of land-use changes and climate change could affect annual runoff. Land-use 

35 changes are projected by model studies to have a small effect compared to climate change in the Rhine 

36 basin, southeastern Michigan, Pennsylvania, and central Ethiopia. In southeastern Australia and southern 

37 India, projections are comparable, with climate change having the potential to exacerbate reductions in 

38 runoff caused by afforestation (Kundzewicz et al. 2007a). 

39 Evapotranspiration (water loss from plant leaves) responds to increases in carbon dioxide in two 

40 distinct ways. First, higher CO2 concentrations cause leaf stomata to close, reducing evapotranspiration. 
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1 Second, CO2 fertilization encourages plant growth, increasing total leaf area and subsequent 

2 evapotranspiration. Considering these vegetation effects, global mean runoff has been projected to 

3 increase by 5 percent for a doubling of CO2 concentration (Betts et al. 2007, Leipprand and Gerten 2006, 

4 both in Kundzewicz et al. 2007) compared to a 5 to 17 percent increase under climate change alone 

5 (Kundzewicz et al. 2007a). 

6 Small islands are especially vulnerable to future change in water availability. Most small islands 

7 already have limited availability of freshwater, and changes in their hydrologic cycle can pose serious 

8 threats for their water supply (EPA 2009b). 

9 Groundwater

10 Climate change will mainly affect groundwater recharge rates, although very little research has 

11 been done on the issue. Groundwater levels could change as a result of thawing permafrost, vegetation

12 changes, changes in river level (where hydraulic connection is adequate), and changes in floods. Global 

13 hydrological models project that globally averaged groundwater recharge will increase less (2 percent)

14 than total runoff (9 percent) in the 2050s compared to recharge and runoff rates from 1961 to 1990. In 

15 northeastern Brazil and southwestern Africa, and along the southern Mediterranean coast, groundwater 

16 recharge is projected to decrease by more than 70 percent. In contrast, recharge is projected to increase 

17 by more than 30 percent in the Sahel, Near East, northern China, Siberia, and the western United States 

18 (Döll and Flörke 2005 in Kundzewicz et al. 2007). Projected impacts on individual aquifers return very 

19 site-specific results. 

20 Any decrease in groundwater recharge will exacerbate the effect of saltwater intrusion. Saltwater 

21 intrusion has been projected for a sea-level rise of 0.33 foot on two coral islands off the Indian coast – the 

22 thickness of the freshwater lens decreasing from 82 feet to 32 feet and from 118 feet to 92 feet (Bobba et 

23 al. 2000 in Kundzewicz et al. 2007). Saltwater intrusion from sea-level rise might also affect 

24 groundwater/aquifer water supplies on similar small islands. 

25 Some areas might try to offset decreases in surface water availability by increasing withdrawals 

26 of groundwater. However, decreases in groundwater discharge will hamper such efforts (EPA 2009b). 

27 Extreme Events – Floods and Droughts

28 Increased precipitation intensity and variability are projected to increase the risks of flooding and 

29 drought in many areas, and extreme floods and extreme droughts are projected to become more frequent 

30 (EPA 2009b). The proportion of total rainfall from heavy precipitation events is likely to increase over 

31 most areas, particularly in tropical and high-latitude regions, while droughts are expected to increase in 

32 subtropical and mid-latitude regions. Precipitation changes between these regions are uncertain (Bates et 

33 al. 2008). More floods are projected for northern and northeastern Europe, while more drought is 

34 projected for southern and southeastern Europe (Lehner et al. 2005 in Kundzewicz et al 2007). 

35 Projections of climate-change impacts on flood magnitude and frequency can be both positive 

36 and negative, depending on the global climate model used, snowmelt contributions, catchment 

37 characteristics, and location (Reynard et al. 2004 in Kundzewicz et al 2007). Up to 20 percent of the 

38 world’s population lives in river basins at risk from increased flooding (Kleinen and Petschel-Held 2007 

39 in Kundzewicz et al 2007). The area flooded in Bangladesh is projected to increase by 23 to 29 percent 

40 with a global temperature rise of 3.6 °F (Mirza 2003 in Kundzewicz et al 2007). 

41 A recent study by Allen and Soden (2008) using a combination of satellite observations and 

42 model simulations showed a link between rainfall extremes and temperature. The observed amplification
Chapter 4 Cumulative Impacts 4.5 Health, Societal, and Environmental Impacts of Climate Change 

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1 of rainfall extremes was larger than other model projections, leading the authors to infer that “projections 

2 of future changes in rainfall extremes due to anthropogenic global warming may be underestimated.” 

3 Globally, it is projected that by the 2090s, there will be an increase in drought-affected areas, 

4 with the land area in extreme drought at a given time expected to be ten times what it is today (Bates et al. 

5 2008, Kundzewicz et al. 2007a). By the 2090s, the proportion of the total land surface in extreme drought 

6 is projected to increase ten-fold, from the current rate of 1 to 3 percent to 30 percent; extreme drought 

7 events per 100 years are projected to double; and mean drought duration is projected to increase by a 

8 factor of six (Burke et al. 2006a in Kundzewicz et al 2007). 

9 Water Quality

10 Higher water temperatures and runoff variations are likely to affect water quality negatively (Patz 

11 2001, Lehman 2002, O’Reilly et al. 2003, Hurd et al. 2004, all in Kundzewicz et al. 2007). Negative 

12 impacts on water quality from changes in water quantity include resuspension of bottom sediments, 

13 increased turbidity (suspended solids), pollutant introduction, and reduced dilution. Negative impacts 

14 from water temperature include algal blooms, increased microbial concentrations, and out-gassing of 

15 volatile and semi-volatile compounds like ammonia, mercury, dioxins, and pesticides (Kundzewicz et al.

16 2007a). 

17 Acidic atmospheric deposition is projected to increase acidification in rivers and lakes (Ferrier 

18 and Edwards 2002, Gilvear et al. 2002, Soulsby et al. 2002, all in Kundzewicz et al. 2007a). 

19 Salt concentration is expected to increase in estuaries and inland reaches under decreasing 

20 streamflows. For example, salinity is projected to increase in the tributary rivers above irrigation areas in 

21 Australia’s Murray-Darling Basin by 13 to 19 percent by 2050 and by 21 to 72 percent by 2100 

22 (Kundzewicz et al. 2007a). 

23 No quantitative studies projecting the impact of climate change on microbiological water quality 

24 for developing countries are cited by the IPCC. However, climate change will be an additional stressor 

25 affecting water quality and public health. Potential impacts include increased waterborne disease with 

26 increases in extreme rainfall, and great incidence of diarrheal and water-related diseases in regions with 

27 increased drought (Kundzewicz et al. 2007a). A brief overview of the effects of climate change on the 

28 availability and quality of drinking water is provided by Epstein et al. (2006). 

29 Developed countries are also experiencing water-quality issues in their water and wastewater 

30 treatment plants. Increased filtration is required in drinking water plants to address microorganism 

31 outbreaks following intense rain, thus increasing some operating costs by 20 to 30 percent (AWWA 2006 

32 in Kundzewicz et al. 2007a). Other stressors on water quality include (Kundzewicz et al. 2007a): 

33 • More water impoundments for hydropower (Kennish 2002 in Kundzewicz et al 2007, 

34 Environment Canada 2004 in Fischlin et al 2007); 

35 • Stormwater drainage operation and sewage disposal disturbances in coastal areas resulting 

36 from sea-level rise (Haines et al. 2000); 

37 • Increasing water withdrawals from low-quality sources; 

38 • Greater pollutant loads resulting from increased infiltration rates to aquifers or higher runoff 

39 to surface waters (resulting from high precipitation); 

40 • Water infrastructure malfunctioning during floods (GEO-LAC 2003, DFID 2004); 
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1 • Overloading the capacity of water and wastewater treatment plants during extreme rainfall 

2 (Environment Canada 2001); and 

3 • Increased amounts of polluted storm water. 

4 In many regions, there is no alternative supply even as water quality declines, and reusing 

5 wastewater (e.g., to irrigate crops) can introduce other public health problems. 

6 4.5.4 Terrestrial and Freshwater Ecosystems 

7 This section addresses climate-related impacts on terrestrial and freshwater ecosystems, including 

8 non-coastal wetlands. An ecosystem is defined as a complex of biological communities (plants, animals, 

9 and microorganisms) and their non-living environments, which act together as a unit (MA 2005c in 

10 Lettenmeier et al 2008 and MA 2005b in Fischlin et al. 2007). By definition, relationships within an 

11 ecosystem are strong, while relationships with components outside the ecosystem boundaries are weak 

12 (MA 2005b in Fischlin et al. 2007). Ecosystems are critical, in part, because they supply humans with 

13 services that sustain life and are beneficial to the functioning of society (Fischlin et al. 2007). 

14 In addition to anthropogenic stressors, such as extraction of natural resources and changes in land 

15 use (Bush et al. 2004 in Fischlin et al. 2007), climate change poses a threat to the wellbeing of 

16 ecosystems. Many terrestrial and freshwater ecosystems have demonstrated resilience to historical 

17 changes in climate; however, their ability to maintain resilience in response to more rapid and profound 

18 changes in climate, such as those expected to occur over the next century, is uncertain (Chapin et al. 

19 2004, Jump and Peñuelas 2005, both in Fischlin et al. 2007). Projected climate change and other 

20 ecosystem stressors generated by humans in the next century are “virtually certain to be unprecedented” 

21 (Forster et al. 2007 in Fischlin et al. 2007). While some climate-change impacts are expected to 

22 exacerbate existing ecosystem stressors, others represent entirely new stressors. For example, increasing 

23 surface temperatures or changes in snow cover will sometimes result in a mismatch in timing between 

24 predators and their prey, constraining the ability of populations to sustain themselves via a limited food 

25 supply (EPA 2009b, UNEP 2006). Impacts projected for species biodiversity “are significant and of key

26 relevance, since global losses in biodiversity are irreversible (very high confidence)” (EPA 2009b). 

27 4.5.4.1 Affected Environment 

28 Earth’s biosphere is an interconnected network of individuals, populations, and interacting natural 

29 systems, referred to as ecosystems. Ecosystems provide society benefits such as supporting services, 

30 such as biodiversity, “a resource that...sustain[s] many of the goods and services that humans enjoy from 

31 ecosystems”; provisioning services, such as food and building/clothing materials; regulating services, 

32 such as the sequestration of carbon, regulation of climate and water, and protection from natural hazards 

33 (floods, landslides, pest regulation); and cultural services, which allow humans the opportunity to 

34 appreciate the aesthetics of ecosystems components (Hassan et al. 2005b in Fischlin et al. 2007). The 

35 focus of this section is on non-marine ecosystems only. Section 4.5.5 addresses marine and coastal 

36 ecosystems. 

37 Ecosystems addressed in this section include (EPA 2009b, EPA 2001)terrestrial communities, 

38 such as forests, grasslands, shrublands, savanna, and tundra; aquatic communities, such as rivers, lakes, 

39 and ponds; and freshwater wetlands, such as marshes, swamps, and bogs. 
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1 4.5.4.1.1 Global Ecoregions and Ecozones 

2 Terrestrial Communities

3 The World Wildlife Fund (WWF) has developed a widely accepted classification scheme for 

4 global terrestrial ecosystems; the classification includes ecozones, biomes, and ecoregions. Similar to the 

5 classification of Miklos Udvary’s (1975) biogeographical realm, the ecozone is the biogeographic 

6 division of Earth's surface at the largest scale. Terrestrial ecozones follow the floral and faunal 

7 boundaries that separate the world's major plant and animal communities. The WWF has identified eight

8 terrestrial ecozones, as indicated in Figure 4.5.4-1. 

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

Lettenmeier et al 2008)

9 

10 Biomes are climatically and geographically defined areas of ecologically similar communities of 

11 plants, animals, and microorganisms. These habitat types are defined by factors such as plant structures, 

12 leaf types, plant spacing, and climate. The land classification system developed by WWF identifies 14

13 major terrestrial habitat types, which can be further divided into 825 smaller, more distinct terrestrial 

14 ecoregions (WWF 2008a). 

15 The 14 primary terrestrial habitats recognized by WWF are as follows: 

16 • Tundra is a treeless polar desert found at high latitudes in the Polar Regions, primarily in 

17 Alaska, Canada, Russia, Greenland, Iceland, and Scandinavia, and sub-Antarctic islands. 

18 These regions are characterized by long, dry winters, months of total darkness, and extremely 
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1 frigid temperatures. The vegetation is composed of dwarf shrubs, sedges and grasses, 

2 mosses, and lichens. A wide variety of animals thrive in the tundra, including herbivorous 

3 and carnivorous mammals and migratory birds. 

4 • Boreal Forests and Taiga are forests found at northerly latitudes in inland Alaska, Canada, 

5 Sweden, Finland, Norway, and Russia, and parts of the extreme northern continental United 

6 States, northern Kazakhstan, and Japan. Annual temperatures are low and precipitation 

7 ranges from 15 to 40 inches per year and can fall mainly as snow. Vegetation includes 

8 coniferous and deciduous trees, lichens, and mosses. Herbivorous mammals and small 

9 rodents are the predominant animal species; however, predatory birds and mammals also 

10 occupy this habitat type. 

11 • Temperate coniferous forests are found predominantly in areas with warm summers and cool 

12 winters. Plant life varies greatly across temperate coniferous forests. In some forests, 

13 needleleaf trees dominate, while others consist of broadleaf evergreen trees or a mix of both 

14 tree types. Typically, there are two vegetation layers in a temperate coniferous forest: an 

15 understory dominated by grasses and shrubs and an overstory of large tree species. 

16 • Temperate broadleaf and mixed forests experience a wide range of variability in temperature 

17 and precipitation. In regions where rainfall is distributed throughout the year, deciduous trees 

18 are mixed with evergreens. Species such as oak, beech, birch, and maple typify the tree 

19 composition of this habitat type. Diversity is high for plants, invertebrates, and small 

20 vertebrates. 

21 • Mediterranean forests, woodlands, and shrub ecoregions are characterized by hot and dry 

22 summers, while winters tend to be cool and moist. Most precipitation arrives during winter. 

23 Only five regions in the world experience these conditions: the Mediterranean, south-central 

24 and southwestern Australia, the fynbos of southern Africa, the Chilean matorral, and the 

25 Mediterranean ecoregions of California. These regions support a tremendous diversity of 

26 habitats and species. 

27 • Tropical and subtropical coniferous forests are found predominantly in North and Central 

28 America and experience low levels of precipitation and moderate variability in temperature. 

29 These forests are characterized by diverse species of conifers, whose needles are adapted to 

30 deal with the variable climate conditions. These forests are wintering ground for a variety of 

31 migratory birds and butterflies. 

32 • Tropical and subtropical moist broadleaf forests are generally found in large, discontinuous 

33 patches centered on the equatorial belt and between the Tropics of Cancer and Capricorn. 

34 They are characterized by low variability in annual temperature and high levels of rainfall. 

35 Forest composition is dominated by semi-evergreen and evergreen deciduous tree species. 

36 These forests are home to more species than any other terrestrial ecosystem. A square 

37 kilometer can support more than 1,000 tree species. Invertebrate diversity is extremely high, 

38 and dominant vertebrates include primates, snakes, large cats, amphibians, and deer. 

39 • Tropical and subtropical dry broadleaf forests are found in southern Mexico, southeastern 

40 Africa, the Lesser Sundas, central India, Indochina, Madagascar, New Caledonia, eastern 

41 Bolivia, central Brazil, the Caribbean, valleys of the northern Andes, and along the coasts of 

42 Ecuador and Peru. Deciduous trees predominate in most of these forests and they are home 

43 to a wide variety of wildlife, including monkeys, large cats, parrots, various rodents, and 

44 ground-dwelling birds. 
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1 • Temperate grasslands, savannas, and shrublands are known as prairies in North America, 

2 pampas in South America, veld in southern Africa, and steppe in Asia. They differ from 

3 tropical grasslands in species composition and the annual temperature regime under which 

4 they thrive. These regions are devoid of trees, except for riparian or gallery forests associated 

5 with streams and rivers. Biodiversity in these habitats includes a number of large grazing 

6 mammals and associated predators, burrowing mammals, numerous bird species, and a 

7 diversity of insects. 

8 • Tropical and subtropical grasslands, savannas, and shrublands are found in the large 

9 expanses of land in the tropics that do not receive enough rainfall to support extensive tree 

10 cover. However, there could be great variability in soil moisture throughout the year. 

11 Grasses dominate the species composition of these ecoregions, although scattered trees can be 

12 common. Large mammals that have evolved to take advantage of the ample forage typify the 

13 biodiversity associated with these habitats. 

14 • Montane grasslands and shrublands include high-elevation grasslands and shrublands, such 

15 as the puna and paramo in South America, subalpine heath in New Guinea and East Africa, 

16 steppes of the Tibetan plateaus, and other similar subalpine habitats around the world. 

17 Montane grasslands and shrublands are tropical, subtropical, and temperate. Mountain 

18 ecosystem services such as water purification and climate regulation extend beyond the 

19 geographical boundaries of the grasslands and shrublands and affect all continental mainlands 

20 (Woodwell 2004). Characteristic plants of these habitats display features such as rosette 

21 structures, waxy surfaces, and abundant pilosity (WWF 2008b). 

22 • Deserts and xeric shrublands across the world vary greatly with respect to precipitation and 

23 temperature. Generally, rainfall is less than 10 inches annually and evaporation exceeds 

24 precipitation. Temperature variability is also extremely diverse in these remarkable lands. 

25 Many deserts, such as the Sahara, are hot year-round, but others, such as Asia’s Gobi, 

26 become quite cold in winter. Woody-stemmed shrubs and plants evolved to minimize water 

27 loss characterize vegetation in these regions. Animal species are equally well-adapted to the 

28 dry conditions, and species are quite diverse. 

29 • Mangroves occur in the waterlogged, salty soils of sheltered tropical and subtropical shores, 

30 where they stretch from the intertidal zone to the high tide mark. Associated with these tree 

31 species is a whole host of aquatic and salt-tolerant plants. Mangroves provide important 

32 nursery habitats for a vast array of aquatic animal species. 

33 • Flooded grasslands and savannas are common to four continents. These vast areas support 

34 numerous plants and animals adapted to the unique hydrologic regimes and soil conditions. 

35 Large congregations of migratory and resident water birds can be found in these regions. 

36 Ecosystem services include breeding habitat and the buffering of inland areas from the effects 

37 of wave action and storms (MA 2005c in Lettenmeier et al 2008). 

38 Freshwater Aquatic Communities

39 According to the Freshwater Ecoregions of the World (FEOW) project, although freshwater 

40 biodiversity is more imperiled overall than terrestrial biodiversity, conservation efforts have largely 

41 focused on terrestrial ecosystems. This is due, in large part, to a lack of comprehensive data on 

42 freshwater species distribution (FEOW 2009). FEOW has worked to identify and classify Earth’s many 

43 freshwater habitats into larger, more manageable groupings. From the 426 freshwater ecoregions 

44 identified in Abell et al. (2008), FEOW has defined 12 Major Habitat Types (MHTs), which represent 
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1 groups of “ecoregions with similar biological, chemical, and physical characteristics and are roughly 

2 equivalent to biomes for terrestrial systems” (FEOW 2009). These are presented in Figure 4.5.4-2 and are 

3 described below. 

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

4 

5 The 12 MHTs recognized by FEOW are as follows (FEOW 2009): 

6 • Large lakes are dominated and defined by lentic (still or standing water) systems. 

7 Ecosystems in this MHT include areas of in-flow and out-flow from rivers and adjacent 

8 wetlands in addition to the lakes themselves. These regions include large tropical, temperate, 

9 and polar lakes. 

10 • Large river deltas contain deltaic features such as those from tidal influences and their 

11 associated fish species, which are different from those found upstream. Regions containing 

12 deltaic features, but that aren’t defined by specific fish species, are not included in these 

13 ecoregions.

14 • Montane freshwaters are composed on streams, rivers, lakes or wetlands at higher elevations. 

15 Included are high gradient, fast-flowing streams, and complexes of higher elevation wetlands 

16 and lakes.

17 • Xeric freshwaters and endorheic (closed) basins contain freshwater systems found in arid, 

18 semi-arid, or sub-humid environments. They usually contain plant and animal species that 

19 are adapted to ephemeral regimes, intermittent flooding, or lower levels of water periodically 

20 throughout the year.
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1 • Temperate coastal rivers usually contain small to medium coastal basins at middle latitudes. 

2 While characterized by river systems, they can also include wetlands, small lakes, and 

3 lagoons. Migratory animal species that live in both fresh and marine ecosystems may be 

4 present. Island ecoregions with these characteristics are included here.

5 • Temperate upland rivers include non-floodplain rivers at middle latitudes, along with 

6 headwater drainages and tributaries of large rivers. These rivers typically flow over moderate 

7 gradients and do not flood cyclically.

8 • Temperate floodplain rivers and wetland complexes each contain a single large river system 

9 at a middle latitude, including its associated sub-basins, which are or have historically been 

10 cyclically flooded. These regions can contain wetland complexes with deltas, swamps, and 

11 marshes.

12 • Tropical and subtropical coastal river ecoregions contain several tropical small or medium 

13 coastal basins that drain into the ocean. The areas are characterized by river systems but can 

14 also contain lakes, lagoons, and wetlands. Islands with these characteristics are included 

15 here.

16 • Tropical and subtropical upland rivers contain non-floodplain rivers in the tropics, including 

17 headwater drainages and tributaries of larger rivers. These rivers flow over moderate 

18 gradients.

19 • Tropical and subtropical floodplain rivers and wetland complexes are characterized by a 

20 single tropical large river and include that river’s main stem drainage and its sub-basins, 

21 which are or have historically been cyclically flooded. Internal deltas, marshes, and swamps 

22 may be included in these areas.

23 • Polar freshwaters are high-latitude ecoregions that contain the entire drainage from the 

24 headwaters to the mouth of the system. The Yukon in Alaska is one example of this MHT.

25 • Oceanic islands include the ecoregions of one or more islands, and above high tide. The 

26 plant and animal species found here are freshwater, but have evolved from marine ancestors. 

27 Freshwater Wetlands

28 As the barriers between terrain and water, wetlands are typically not only rich sources of 

29 biodiversity, but also provide services critical to humans, such as mitigation of flooding and storm runoff, 

30 erosion control, and filtration of pollutants from water and sediments. The roles of particular wetlands 

31 vary depending on the location and main water source of the wetland. Those that are dominated by 

32 precipitation supply water to streams and replenish groundwater reservoirs while riparian wetlands are

33 dominated by surface flow and may remove, store, or release water, nutrients, and sediments. Types of

34 wetlands, excluding those associated with marine systems or estuaries (which are addressed in Section 

35 4.5.5), are as follows (EPA 2001): 

36 • Precipitation-dominated Wetlands 

37 − Bogs form where peat accumulates at a faster rate than it decomposes. These receive 

38 little to no surface water in-flow due to their elevation above surrounding areas due to the 

39 peat accumulation. Due to this lack of in-flow, they have low rates of primary 

40 productivity. The dominant plant matter in bogs, Sphagnum moss, releases organic acids, 
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1 usually resulting in acidification of the bogs, with a pH as low as 3.0. Also found in bogs 

2 are evergreen trees and shrubs. This environment has produced unique plants that 

3 evolved to thrive in conditions that are acidic and lacks nutrients. 

4 − Vernal pools are low-lying areas in grasslands and forests that are underlain by clay or 

5 bedrock, which acts to pool the water, rather than allowing any accumulated water to 

6 drain away. While covered by shallow water during some periods, they can be 

7 completely dry during some months of the summer and fall. 

8 − Playas are small, low-lying marshlike ponds that collect rainfall and storm runoff from 

9 surrounding areas. These form in arid regions such as the Southern Great Plains in the 

10 United States. 

11 − Prairie potholes are holes generated by past glacial events in northern North America 

12 that subsequently fill up with rainwater and snowmelt. The potholes contribute to 

13 groundwater recharge, at times. 

14 − Wet meadows are grasslands formed in poorly drained areas that get waterlogged after 

15 precipitation events, such as basins and depressions, between marshes and upland areas. 

16 They are often dry during summer months. 

17 − Wet prairies are similar to wet meadows but remain waterlogged longer than do wet 

18 meadows. Additionally, they receive water not only from precipitation but also from 

19 groundwater and intermittent streams. 

20 • Groundwater-dominated Wetlands 

21 − Fens form in low-lying areas or near slopes where groundwater meets the soil surface. 

22 These wetlands accumulate peat, similar to bogs, but are supplied with groundwater, 

23 rather than precipitation and, as such, are provided with a year-round water supply. Fens 

24 are typically found at higher latitudes and in previously-glaciated locations. 

25 • Surface Water-dominated Wetlands 

26 − Freshwater marshes are formed in depressions around lakes and rivers and can contain 

27 permanent or periodic shallow water with little or no accumulation of peat. They usually 

28 have the greatest biodiversity of the types of wetlands (along with tidal marshes). Much 

29 of a marsh’s water is from surface sources, but some is from groundwater. They are 

30 dominated by floating-leaf plants, such as lilies, and soft-stemmed plants like cattails. 

31 − Riparian forested wetlands (swamps) are linear systems formed along rivers and lakes. 

32 They are typically saturated during the winter while plants are dormant and 

33 evapotranspiration is low. During the summer, they are usually dry, except during 

34 periods of flooding. The pH and nutrient load of riparian wetlands vary, depending on 

35 the inputs, but they are almost always very productive ecosystems. Many bird and fish 

36 species are known to be solely dependent on riparian wetlands. 

37 − Tidal freshwater marshes are influenced by tides only in terms of water levels, and 

38 receive little, if any, saline water from the ocean. These are found upstream from 

39 estuarine systems and receive most water from upstream sources, with some additional 

40 input from storm runoff and precipitation. These marshes have very high primary 
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1 productivity and are known for their rich biodiversity. A key function performed by tidal 

2 freshwater marshes is the prevention of nitrogen entering in to estuaries; they can filter 

3 out as much of 50 percent of the nitrogen that enters the marsh.

4 4.5.4.1.2 Ecosystems in the United States 

5 Published in 1976, Ecoregions of the United States represented one of the first attempts to 

6 systematically divide the Country’s terrestrial ecosystems into more manageable regions. Subsequently, 

7 Bailey (1980) provided, for each region, a brief description of the dominant physical and biological 

8 characteristics based on land-surface form, climate, vegetation, soils, and fauna. Bailey defined four 

9 major domains, 12 divisions, and 30 provinces. Since then, the terrestrial ecoregions of North America 

10 have been further refined by the international working group of the Commission of Environmental 

11 Cooperation (CEC 1997). Their system divides the continent into 15 broad level I ecoregions, 52 level II 

12 ecoregions, and approximately 200 level III ecoregions. The level I terrestrial ecoregions present in the 

13 United States include tundra, taiga, northern forests, northwestern forested mountains, marine west coast 

14 forests, eastern temperate forests, great plains, North American deserts, Mediterranean California, 

15 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) 

16 
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1 There are 50 freshwater ecoregions in the United States. These ecoregions are divided among 

2 eight of the 12 MHTs recognized in the FEOW project − polar freshwaters (two), temperate coastal rivers 

3 (12), temperate upland rivers (12), large lakes (two), temperate floodplain rivers and wetlands (seven), 

4 xeric freshwaters and endorheic basins (11), tropical and subtropical coastal rivers (three), and oceanic 

5 islands (one) (FEOW 2009). One of the most ecologically valuable freshwater resources in the United 

6 States is the Prairie Pothole Region (PPR) of the Great Plains, which falls primarily within the temperate 

7 floodplain rivers and wetlands MHT. This region contains as many as eight million acres of wetlands, 

8 providing crucial ecosystem services to the Country in addition to habitat critical to waterfowl (EPA 

9 2009b, CCSP 2009c). Almost 90 percent of variation in the mallard duck reproductive variability 

10 depends on breeding activities within the PPR (Johnson et al. 2005a). Historically, the climate of this 

11 area has fluctuated, sometimes between extremes such as devastating droughts and periodic flooding. 

12 Both ends of the climate spectrum resulted in widespread tree and grassland mortality (CCSP 2009c). 

13 More than 90 percent of the eastern PPR wetlands have been drained for agricultural purposes and, 

14 although restoration activities have been underway for more than 20 years, less than 1 percent of drained 

15 basins have been restored (Johnson et al. 2005a). 

16 The Great Lakes region is an ecologically and economically significant area that spreads across 

17 the northern United States and southern Canada in eastern North America. The lakes (Erie, Huron, 

18 Michigan, Ontario, and Superior) contain 18 percent of the world’s fresh water. They not only supply 

19 water to millions of people, but also are home to some of the richest ecosystems on the continent (Kling et 

20 al. 2003). The lakes themselves provide habitat for large populations of trout, salmon, and other popular 

21 game fish, while the surrounding marsh and coniferous forests sustain grey wolves, moose, peregrine 

22 falcons, bald eagles, and black bears. The Upper Peninsula of Michigan has a 1,700-mile shoreline and

23 16,500 square miles of largely intact forests. The Peninsula contains rich populations of both aquatic and 

24 terrestrial species, including 300 bird species, of which 25 to 30 percent are year-round residents; the rest 

25 are migratory (Kling et al. 2003). 

26 Ecosystems are dynamic and can change naturally over time as a result of drivers such as climate 

27 change (natural or anthropogenic), geological processes (volcanic eruptions, earthquakes, landslides, 

28 erosion, stream migration), fire, disease or pest outbreaks, and evolution. All organisms modify their 

29 environment to some extent; however, in the past century and especially in the past 50 years, human 

30 population growth and technological innovations have affected ecosystems drastically (Vitousek et al.

31 1997). In fact, the structure of the world’s ecosystems have changed more rapidly in the second half of 

the 20th 32 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 33 Century, the resilience of many ecosystems is likely to be 

34 exceeded by anthropogenic pressures (Fischlin et al. 2007). 

35 4.5.4.2 Environmental Consequences 

36 This section discusses existing climate and non-climate related impacts that have already been 

37 observed, and projected impacts. Climate-change impacts are discussed globally, and with specific 

38 attention to impacts in the United States. The EPA Technical Support Document Endangerment and 

39 Cause or Contribute Findings for Greenhouse Gases Under Section 202(a) of the Clean Air Act was 

40 released in 2009 (EPA 2009b), the IPCC WGI Fourth Assessment Report (Fischlin et al. 2007) was 

41 released in 2007, the CCSP report on climate sensitive ecosystems was released in 2008 (CCSP 2008a). 

42 The 2009 EPA findings and the 2007 IPCC report are the most comprehensive recent summaries of 

43 projected impacts of climate change. Many of the impacts discussed in this section were gathered from

44 these reports, which provide analyses and discussions on both global and U.S. scales. Information about 

45 impacts specific to ecosystems in the United States was obtained from the EPA findings and the 2008 

46 CCSP report, along with information from several other recent reports. The projected impacts described 
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1 in Sections 4.5.4.2.1 through 4.5.4.2.5 were forecast with varying degrees of certainty. Where relevant, 

2 the descriptions include the level of certainty as defined by IPCC. 

3 4.5.4.2.1 Non-climate Threats to Terrestrial and Freshwater Ecosystems 

4 The Millennium Ecosystem Assessment (MA), a United Nations research project, focuses on 

5 identifying the current inventory and conditions of 10 categories of global ecosystems and projecting 

6 changes and trends into the future. 

7 In 2005, the MA released five technical volumes and six synthesis reports, providing a scientific 

8 appraisal of the condition and trends in the world’s ecosystems (terrestrial, marine, and freshwater) and 

9 the services they provide. From 2001 to 2005, the MA involved the work of more than 1,360 experts 

10 worldwide. The MA included the following conclusions regarding the current state of global ecosystems

11 (MA 2005c in Lettenmeier et al 2008): 

12 • Cultivated systems now cover one quarter of Earth’s terrestrial surface. More than two thirds 

13 of the area of two of the world’s 14 major terrestrial biomes and more than half of the area of 

14 four other biomes had been converted by 1990, primarily to agriculture. 

15 • Across a range of taxonomic groups, for most species, either the population size or range or 

16 both is currently declining. 

17 • The distribution of species on Earth is becoming more homogenous; in other words, the set of 

18 species in any one region of the world is becoming more similar to the set in other regions 

19 primarily as a result of introductions of species, both intentionally and inadvertently in 

20 association with increased travel and shipping. 

21 • The number of species on the planet is declining. Over the past few hundred years, humans 

22 have increased the species extinction rate by as much as 1,000 times over background rates 

23 typical over Earth’s history. Some 10 to 30 percent of mammal, bird, and amphibian species 

24 are currently threatened with extinction. 

25 • Only four of the 24 ecosystem services examined in this assessment have been enhanced, 

26 while 15 have been degraded (Hassan et al. 2005a). 

27 The MA concluded that biodiversity changes due to human activities were more rapid in the past 

28 50 years than at any time in human history. Moreover, the forces causing biodiversity loss and leading to 

29 changes in ecosystem services are either steady, show no evidence of declining over time, or are 

30 increasing in intensity. The MA examined four plausible future scenarios and projected that the rates of 

31 biodiversity change will continue or accelerate (MA 2005c in Lettenmeier et al 2008). The changes in 

32 ecosystems identified in the MA can have impacts on ecological processes, species composition, and 

33 genetic diversity. Ecosystem processes, which include water, nitrogen, carbon, and phosphorous cycling, 

have all changed more rapidly in the second half of the 20th 34 Century than at any time in recorded human 

35 history (MA 2005c in Lettenmeier et al 2008). Human actions have not only changed the structure of 

36 ecosystems, but also the processes as functions of the ecosystems. 

37 A change in ecosystem structure also affects the species within the system and vice versa. 

38 Historically, the natural processes of evolution and the combination of natural barriers to species 

39 migration and local adaptation resulted in substantial phenotypic differences in plant and animal species 

40 of different ecosystems. These regional differences are now becoming rare. 

41 Some ecosystem changes have been the inadvertent result of activities unrelated to the use of 

42 ecosystem services, such as the construction of roads, ports, and cities and the discharge of pollutants. 
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1 However, most ecosystem changes were the direct or indirect result of changes made to meet growing 

2 demands for food, water, timber, fiber, and fuel (MA 2005c in Lettenmeier et al. 2008). In addition to 

3 climate change, ecosystem dynamics can be affected by a variety of human and natural drivers, including, 

4 land use change, hydrologic modification, wildfires, insect outbreaks, species decline and extinctions, and 

5 pollution. These drivers can act independently or in concert with each other (EPA 2009b, Lepers et al.

6 2004), and are summarized below.

7 Land-use Change

8 Land-use change represents the anthropogenic replacement of one land use type by another, such 

9 as forest converted to cultivated land (or the reverse), and subtle changes of management practices within 

10 a given land use type, such as intensification of agricultural practices. Both forms of land-use change are 

11 affecting 40 percent of the terrestrial surface (Foley et al. 2005 in Easterling et al. 2007). Land-use 

12 change can lead to habitat loss and fragmentation and is an important driver in ecosystem change 

13 (Heywood and Watson 1995 in Fischlin et al. 2007, Fahrig 2003 in Fischlin et al. 2007). Overall, land 

14 transformation represents the primary driving force in the loss of biological diversity (Vitousek et al.

15 1997). In nine of the 14 terrestrial biomes studied by the MA, more than half the area has been 

16 transformed, largely by agricultural cultivation (Hassan et al. 2005a). Only the biomes that are less 

17 suitable for agriculture, such as deserts, boreal forests, and tundra, have remained largely untransformed 

18 by human activity. 

19 Virtually all of Earth’s ecosystems have now been substantially transformed through human 

20 actions (MA 2005c in Lettenmeier et al 2008). Approximately 70 percent of original temperate 

21 grasslands and forests and Mediterranean forests were lost by 1950, primarily from conversion to 

22 agricultural lands. More land was converted to cropland in the 30 years after 1950 than in the 150 years 

23 between 1700 and 1850 (MA 2005a in Kundzewicz et al 2007, Hassan et al. 2005a). 

24 Historically, terrestrial ecosystems that have been most substantially altered by human activity 

25 include temperate broadleaf forests, temperate grasslands, Mediterranean forests, and tropical dry forests 

26 (Hassan et al. 2005a). Of these, more than two thirds of the temperate grasslands and Mediterranean 

27 forests, and more than half of tropical dry forests, temperate broadleaf forests, and tropical grasslands 

28 have been converted to agriculture (Hassan et al. 2005a). Forest systems in general have been reduced by 

29 half over the past 3 centuries, and have effectively disappeared in 25 countries. Another 29 countries 

30 have lost 90 percent or more of their forest cover (Hassan et al. 2005a). 

31 Globally, the rate of ecosystem conversion has begun to decelerate, mainly because the rate of 

32 expansion of cultivated land has declined. Ecosystems are beginning to return to conditions and species 

33 compositions similar to their pre-conversion states. However, rates of ecosystem conversion remain high 

34 or are increasing for specific ecosystems and ecoregions (MA 2005c in Lettenmeier et al 2008). Land-use 

35 changes and land degradation are important drivers of ecosystem change globally and in the United 

36 States. For example, “between 1982 and 1997, 11 million acres of nonfederal grasslands and shrublands

37 were converted to other uses” (The H. John Heinz III Center for Science 2002). 

38 The increase in cultivated land, especially for the purpose of grazing, has led to an increase in 

39 desertification. Desertification involves the expansion of deserts into semi-arid and subhumid regions, 

40 and the loss of productivity in arid zones. Desertification is characterized by loss of groundcover and 

41 soils, replacement of palatable, mesophytic grasses by unpalatable xerophytic shrubs, or both (EPA 

42 2009b, Ryan et al. 2008a). Desertification affects the livelihoods of millions of people, including a large 

43 portion of the poor residents of drylands (Hassan et al. 2005a). While desertification can certainly be 

44 exacerbated by changes in climate, there has been long-standing controversy over the relative 
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1 contributions of climatic and anthropogenic factors as drivers of desertification (National Science and 

2 Technology Council 2008). 

3 Hydrologic Modification

4 An ongoing and significant threat to freshwater ecosystems is the practice of hydrologic 

5 modification, including the damming of lakes and rivers for hydroelectric power and re-routing stream 

6 systems for the purposes of agricultural irrigation. At present, there are 45,000 large dams (more than 

7 about 50 feet high) and as many as 800,000 smaller dams around the world (MA 2005a in Kundzewicz et 

8 al 2007). These practices can negatively impact migratory patterns of aquatic species, interfering with 

9 reproductive patterns, for example. The tight control of waterways through damming, though partially 

10 intended to help prevent the damages from periodic flooding, has also worked to prevent the positive 

11 impacts of flooding, such as the replacement of soil nutrients to agricultural lands and terrestrial 

12 ecosystems (Heino et al. 2008, MA 2005a in Kundzewicz et al 2007). In recent years, decisionmakers in 

13 the United States have realized the damages to aquatic ecosystems and the surrounding landscape caused

14 by such modifications. Therefore, fewer dams are being constructed and some are being dismantled. 

15 However, most remain intact. 

16 Wildfires

17 Fire influences ecosystem structure by promoting species that tolerate fire or even enhance the 

18 spread of fire, resulting in a relationship between the relative flammability of a species and its relative 

19 abundance in a particular community (Bond and Keeley 2005). Intensified and increasing wildfire 

20 occurrences appear to be changing vegetation structure and composition in some ecoregions (Kasischke 

21 and Turetsky 2006). 

22 Insect Outbreaks

23 Invasive alien species represent a major threat to endemic or native biodiversity in terrestrial and 

24 aquatic systems. Invasions of alien species also interact with other drivers, sometimes resulting in 

25 unexpected outcomes. The impact of insect damage is substantial and can exceed the impacts of fire in

26 some ecosystems, but especially in boreal forests (EPA 2009b, Logan et al. 2003). For example, spruce 

27 budworm defoliated more than 20 times the area burned in eastern Ontario between 1941 and 1996 

28 (Fleming et al. 2002). Fires tended to occur 3 to 9 years after a spruce budworm outbreak (Fleming et al.

29 2002), suggesting that insect outbreaks can be a driver of increased fire events. 

30 Species Decline and Extinction

31 Although extinction is a natural part of Earth’s history, observed modern rates of extinction are 

32 not part of natural cycles. Over the past few hundred years, humans have increased the extinction rate by 

33 as much as 1,000 times over the rate expected based on natural history (Hassan et al. 2005a). A decrease 

34 in global genetic diversity is linked to extinction. The loss of unique populations has resulted in the loss 

35 of genetic diversity. The loss of genetic diversity among terrestrial species has also declined among

36 cultivated species as farmers have shifted from locally adapted crop populations to more widely adapted 

37 varieties produced through formal breeding practices. For most species across a wide range of taxonomic 

38 groups, either the population size, population range, or both is in decline (MA 2005c in Lettenmeier et al 

39 2008). 
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1 Pollution

2 Pollution is another substantial threat to ecosystems. Over the past 4 decades, excessive nutrient 

3 loading has emerged as one of the most important direct drivers of ecosystem change in terrestrial, 

4 freshwater, and marine systems. A known cause is the use of increasing amounts of synthetic nitrogen 

5 and phosphorous fertilizers, which can be lost to the environment after application (EPA 2009b). 

6 Consumption of nitrogen fertilizer grew almost 800 percent between 1960 and 2003 (MA 2005c in 

7 Lettenmeier et al 2008). In terrestrial ecosystems, excessive nitrogen flows contribute to acidification. 

8 Nitrogen also plays a role in ground-level ozone, which can lead to a loss of forest and agricultural 

9 productivity ( EPA 2009b, MA 2005c in Lettenmeier et al 2008). In aquatic systems, excessive nitrogen

10 and phosphorus loads often result in eutrophication of both surface and deeper waters (Poff et al. 2002). 

11 As the nutrient enrichment encourages growth of aquatic vegetation in the surface layers of water bodies, 

12 the result is that natural processes that occur as the plants die, sink to the lower layers of water, and decay 

13 lead to depleted oxygen. The depletion of oxygen makes it more difficult for many species to thrive and 

14 sometimes results in large areas of “dead zones,” in which no species are able to thrive. In one example, 

15 in the 1960s, Lake Erie experienced such significant phosphorus pollution that algal bloom decay used up 

16 almost all of the dissolved oxygen in the lake and the lake was almost entirely unable to support any fish 

17 and other aquatic life (Kling et al. 2003). 

18 4.5.4.2.2 Observed Impacts on Terrestrial and Freshwater Ecosystems in the 

19 United States 

20 Changes and impacts on ecosystems in the United States are similar to those occurring globally. 

During the 20th 21 Century, the United States already had begun to experience the effects of climate change. 

22 Precipitation over the contiguous United States increased 6.5 percent over long-term averages (EPA 

23 2009b), while a sea-level rise of 0.08 to 0.12 inch per year has occurred at most of the country’s 

24 coastlines; the Louisiana coast has experienced an even greater rise in sea level at a rate of 0.36 inches per 

25 year (EPA 2009b). It should be noted that while global sea level rise is relatively smooth across the 

26 globe, the amount at any particular location can be affected by many factors. 

27 Examples of observed changes to non-marine ecosystems in the United States attributable to 

28 anthropogenic climate change include: 

29 • Many plant species are expanding leaves or flowering earlier, for example: earlier flowering 

30 in lilac, 1.8 days per decade (Schwartz and Reiter 2000) and honeysuckle, 3.8 days per 

31 decade (Cayan et al. 2001). 

32 • Warmer springs have led to earlier nesting for 28 migrating bird species on the east coast of 

33 the United States and to earlier egg laying for Mexican jays and tree swallows (EPA 2009b). 

34 • Several frog species now initiate breeding calls 10 to 13 days earlier than a century ago (EPA 

35 2009b). 

36 • In lowland California, 70 percent of 23 butterfly species advanced the date of first spring 

37 flights by an average of 24 days over 31 years (Forister and Shapiro 2003 in Easterling et al 

38 2007). 

39 • Many North American plant and animal species have shifted their ranges, typically to the 

40 north or to higher elevations (EPA 2009b, Parmesan and Yohe 2003a). 

41 • Edith’s checkerspot butterfly has become locally extinct in the southern, low-elevation 

42 portion of its western North American range but has extended its range 56 miles north and 

43 394 feet higher in elevation (EPA 2009b, Parmesan 1996, Crozier 2003, and Parmesan and 
Chapter 4 Cumulative Impacts 4.5 Health, Societal, and Environmental Impacts of Climate Change 

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1 Galbraith 2004). Forty percent of the populations below 2,400 feet elevation are now extinct 

2 (GCRP et al. 2009). 

3 • The frequency of large forest fires and the length of the fire season in the western United 

4 States have increased substantially since 1985. These phenomena are related to the advances 

5 in the timing of spring snowmelt and increases in spring and summer air temperatures (EPA 

6 2009b, Westerling et al. 2006 as cited in CCSP 2008b). 

7 • The vegetation growing season has increased on average by about 2 days per decade since 

8 1948, with the largest increase happening in the West (Easterling 2002, Feng and Hu 2004 in 

9 Rosenzweig et al 2007). 

10 • Recently, spruce budworm in Alaska has completed its lifecycle in 1 year, rather than the 2 

11 years previously (EPA 2009b). This allows many more individuals to survive the 

12 overwintering period with impacts on the boreal forests of North America. 

13 • Over the past 3 to 5 decades, all the major continental mountain chains exhibited upward 

14 shifts in the height of the freezing level (Diaz et al. 2003). 

15 • Populations of the American pika, a mountain-dwelling relative of the rabbit, are in decline 

16 (EPA 2009b). The pika might be the first North American mammal to become extinct as a 

17 result of anthropogenic climate change. Several populations of the pika, in the Rocky 

18 Mountain region, appear to have been extirpated as of the 1990s, compared to those that 

existed in the early 20th 19 Century. One of the important factors in this occurrence is climate 

20 change that affected food supply and habitat availability (Janetos et al. 2008). 

21 • Reproductive success in polar bears has declined as a result of melting Arctic Sea ice. 

22 Without ice, polar bears cannot hunt seals, their preferred prey (Derocher et al. 2004). On 

23 May 15, 2008, the U.S. Fish and Wildlife Service listed the polar bear as a threatened species 

24 (EPA 2009b), reflecting the loss of sea ice habitat that once encompassed more than 90 

25 percent of the polar bear’s habitat range (Federal Register 73, 28212-28303, May 15, 2008). 

26 • Between 1970 and 2000, much of Alaska has experienced approximately 10 additional snow27 free days. The response to this is variable throughout the state. In northern Alaska, above28 ground vegetation is increasing on the tundra while decreasing in the boreal forest regions in 

29 the interior of the state (CCSP 2009c). 

30 • Permafrost in Alaska is warming and thawing in some areas and large areas of thermokarst 

31 terrain (subsidence from thawing) are observed. Estimates of the surface warming thus far 

32 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 

33 as 6 meters in some locations (CCSP 2009c). 

34 • In northern Alaska, shrub cover has increased by 16 percent since 1950. In 200 Arctic 

35 locations, there has been a 70 percent increase in shrub cover (EPA 2009b). This is already 

36 resulting in decreased surface albedo, reinforcing the warming trend (CCSP 2009c). The 

37 northward-shifting tree line into the tundra is encroaching on habitat for a number of 

38 migratory birds and land mammals, such as caribou (GCRP et al. 2009). 

39 • Northeastern birds that winter in the southern United States arrive home 13 days earlier than 

they did in the early 20th 40 Century. Those that migrate to South America arrive home 4 days 

41 earlier, on average (GCRP et al. 2009). 

42 • In the past decade, the percentage of Rocky Mountain wildflower buds that are exposed to 

43 frost has doubled, hindering their reproductive ability (GCRP et al. 2009). 

44 • Since 1906, climate in the PPR has been generally been warmer and wetter. Minimum daily 

45 temperatures have been increasing in winter while maximum daily temperatures in the 
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1 summer have been decreasing. Average annual precipitation over the same time period 

2 increased by 9 percent. The moisture gradient (wet in the east, dry in the west) steepened, as 

3 well. This trend is threatening the productive are of wetlands (Millett et al. 2009). 

4 • There have been major changes in plant species abundance in Thoreau’s Walden Woods in 

5 Concord, MA. Meticulous records of species have been kept for 150 years. Much of the 

6 change is thought due to changes in climate. The mean annual temperature in the Concord 

7 area has risen 2.4 °C (4.3 °F) in the last 100 years. Species in the area are now flowering 7 

8 days earlier than they were during Thoreau’s record-keeping days (Willis et al. 2008). 

9 4.5.4.2.3 Observed Impacts of Climate Change on Terrestrial and Freshwater 

10 Ecosystems Globally 

11 Because all ecosystems are defined by the interactions of biotic factors (plants, animals, and 

12 microorganisms) and abiotic factors (geology, hydrology, weather), climate is a key factor in determining 

13 the different characteristics and distributions of natural systems. 

14 Studies have noted the response of biological and chemical characteristics of ecosystems to 

15 climate conditions, especially temperature change. Substantial research has examined the effects of 

16 climate change on vegetation and wildlife, leading to the conclusion that the changing climate is already 

17 having a real and demonstrable effect on a variety of ecosystem types (EPA 2009b, CCSP 2008b). As 

18 noted in the IPCC report, plants and animals can reproduce, grow, and survive only within specific ranges 

19 of climate and environmental conditions (EPA 2009b, Fischlin et al. 2007). Changes in climate can affect 

20 terrestrial ecosystems in any of the following ways (EPA 2009b): 

21 • Shifting the timing of life cycle events such as blooming or migration; 

22 • Shifting range boundaries or densities of individuals within their ranges; 

23 • Changing species morphology (body size, egg size), reproduction, or genetics; and 

24 • Causing extirpation or extinction. 

25 These changes are a result of many factors. Phenology – the timing of seasonal activities of 

26 animals and plants – is perhaps the simplest process by which to track changes in the ecology of species 

27 in response to climate change (EPA 2009b, Rosenzweig et al. 2007). Observed phenological events 

28 include spring leaf unfolding, flowering, fruit ripening, autumn leaf coloring, leaf fall of plants, bird 

29 migration, chorusing of amphibians, and appearance or emergence of butterflies. Global daily satellite 

30 data, available since 1981, indicate an earlier onset of spring by 10 to 14 days over 19 years, particularly 

31 across temperate latitudes of the northern hemisphere (EPA 2009b, Lucht et al. 2002). Leaf unfolding 

32 and flowering in spring and summer have, on average, advanced by 1 to 3 days per decade in Europe, 

33 North America, and Japan over the last 30 to 50 years (Fischlin et al. 2007). The seasonal timing of bird 

34 migration and egg-laying has also changed, associated with the increase of temperature in breeding 

35 grounds and migration routes (EPA 2009b). According to IPCC (Rosenzweig et al. 2007), “Many small 

36 mammals have been observed to come out of hibernation and to breed earlier in the spring than they did a 

37 decade ago (Inouye et al. 2000, Franken and Hik 2004) and even larger mammals such as reindeer are 

38 showing phenological changes (Post and Forchhammer 2002), as are butterflies, crickets, aphids, and 

39 hoverflies (Forister and Shapiro 2003 in Easterling et al 2007, Stefanescu et al. 2003, Hickling et al.

40 2005, and Newman 2005). Increasing regional temperatures are also associated with earlier calling and

41 mating and shorter time to maturity of amphibians (Gibbs and Breisch 2001, Reading 2003, and 

42 Tryjanowski et al. 2003).” Frogs have been documented initiating mating calls as many as 10 to 13 days 

43 earlier then they were a century ago in some areas (EPA 2009b). 

44 Rapid global warming can directly affect the size of a species’ range, the density of individuals 

45 within the range, and the abundance of preferred habitat within the range. Climate changes have affected 
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1 the location of suitable habitat for several species of plants and animals. Changes in the distribution of 

2 species have occurred across a wide range of taxonomic groups and geographical locations (Rosenzweig 

3 et al. 2007). Several different bird species no longer migrate out of Europe in the winter as the 

4 temperature continues to warm (Rosenzweig et al. 2007). Over the past decades, a poleward extension of 

5 various species has been observed, which is probably attributable to increases in temperature (Parmesan 

6 and Yohe 2003b in Rosenzweig et al. 2007). Many Arctic and tundra communities are affected and have 

7 been replaced by trees and dwarf shrubs (Kullman 2002 and ACIA 2005b, both in Rosenzweig et al.

8 2007, and EPA 2009b). In some mountainous areas of the northern hemisphere, including in Alaska, tree

9 lines have shifted to higher altitudes over the past century (Sturm et al. 2001 in Rosenzweig et al. 2007). 

10 Decreases in the size of a species’ range, the density of individuals within the range, and the 

11 abundance of its preferred habitat factors can lower species population size (Wilson et al. 2004 in 

12 Rosenzweig et al. 2007) and can increase the risk of extinction. Examples of declines in populations and 

13 subsequent extinction or extirpation are found in amphibians around the world (Alexander and Eischeid 

14 2001, Middleton et al. 2001, Ron et al. 2003, and Burrowes et al. 2004, all in Rosenzweig et al. 2007). 

15 Increased toad mortality in freshwater systems in recent years has been attributed, in part, to exposure of 

16 their eggs to ultraviolet B radiation, which increases susceptibility to certain fungal parasites (EPA

17 2009b). 

18 Changes in morphology and reproduction rates have been attributed to climate change. For 

19 example, the egg sizes of many bird species are changing with increasing regional temperatures (Jarvinen 

20 1996 and Tryjanowski et al. 2003). Several studies conducted in Asia and Europe found that some birds 

21 and mammals are experiencing increases in body size as temperatures increase, on a regional scale, most 

22 likely due to the increasing availability of food (Nowakowski 2002, Yom-Tov 2003, Kanuscak et al.

23 2004, and Yom-Tov and Yom-Tov 2004 in Rosenzweig et al. 2007). Many northern insects have a 2-

24 year life cycle, and warmer winter temperatures allow a larger fraction of overwintering larvae to survive. 

25 The mountain pine beetle has expanded its range in British Columbia into areas previously considered too 

26 cold (Carroll et al. 2004) for its survival. 

27 Examples of observed changes to non-marine ecosystems attributable to changes in climate also 

28 include: 

29 • In lakes around the world, disruptions of trophic interactions among phytoplankton and 

30 zooplankton species with different temperature requirements have been observed (Winder 

31 and Schindler, 2004). 

32 • Forest growth has increased over the last several decades due to increasing CO2 in the 

33 atmosphere, an earlier onset of the growing season, and increased atmospheric nitrogen 

34 deposition (GCRP et al. 2009). 

35 • Changes in the relative timing of caterpillar food supplies for European woodland birds, 

36 including the Great Tit and the Pied Flycatcher, are impacting the reproductive success for 

37 those that cannot adjust their phenological timing, accordingly (UNEP 2006). 

38 • In Northern Scotland, some populations of seabirds have had failures of close to 100 percent 

39 in recent years, due primarily to warmer waters becoming more hostile to phytoplankton, 

40 providing less food to the fish, which are the seabirds’ food source (UNEP 2006). 

41 • New species of fish, such as pacific salmon, have been identified in aquatic systems of the 

42 Canadian Arctic in recent years as a result of expanded ranges from warming waters (UNEP 

43 2006). 
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1 4.5.4.2.4 Projected Impacts of Climate Change on Terrestrial and Freshwater 

2 Ecosystems in the United States 

3 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 4 Century. Although 

5 the entire Country is projected to experience some degree of change, particular regions of the United 

6 States could experience changes of a greater-than-average magnitude. For example, the greatest changes 

7 in temperature are projected for Alaska and the western continental United States (EPA 2009b, CCSP 

8 2008a). In northern Alaska, the average temperatures are projected to increase 5.0 °C (9.0 °F) by the end 

of the 21st 9 Century. Areas near coasts are projected to witness an increase of approximately 2.0 °C 

10 (3.6 °F) over the same period; summer temperatures nationwide could increase 3.0 to 5.0 °C (5.4 to 9.0

11 °F); and winter temperatures are projected to increase 7.0 to 10.0 °C (12.6 to 18.0 °F) (CCSP 2008a). 

12 Additionally, the northeastern United States is expected to experience a rise in sea level that is 0.3 to 0.51 

13 meter (1.0 to 1.6 feet) greater than the projected global average of 0.8 to 2.0 meters (2.6 to 6.6 feet) (EPA 

14 2009b, Pfeffer et al. 2008). 

15 Additional expected changes in United States climate include: 

16 • More frequent hot days and hot nights (EPA 2009b); 

17 • Heavier precipitation events, primarily in the form of rain rather than snow (EPA 2009b). 

18 Annual precipitation in the northeastern United States is projected to increase while 

19 precipitation in the Southwest is expected to decrease (EPA 2009b, Christensen et al. 2007a); 

20 and 

21 • A decline in spring snow cover, leading to decreased availability of water in reservoirs (EPA 

22 2009b). 

23 Ecosystems across the United States are projected to experience both positive and negative 

24 impacts from climate change over the next century. The degree of impacts will vary by region. Wildlife 

25 species have already responded to climate change and its effects on migration patterns, reproduction, and 

26 geographic ranges (EPA 2009b). Future, more substantial changes in climate are projected to affect many 

27 ecosystem services negatively (EPA 2009b, CCSP 2008a). The IPCC WGII has projected, with a high 

28 level of confidence, “that recent regional changes in temperature have had discernible impacts on many 

29 physical and biological systems” (National Science and Technology Council 2008). 

30 The IPCC has determined that areas of the United States that experience temperature increases of 

31 1.5 to 2.5 °C (2.7 to 4.5 °F) are at highest risk for modifications to ecosystem structure and composition 

32 (IPCC 2007c in CCSP 2008). Over the next century, it is projected that species could move northward 

33 and to higher elevations (Field et al. 2007b in National Science and Technology Council, 2008). In one 

34 example of possible future threats to ecosystem vegetation, the upward move in elevation of species as

35 the snow and tree line advances suggests that alpine ecosystems could be endangered by the introduction 

36 of invasive species (National Science and Technology Council 2008). 

37 Rather than experiencing impacts of climate change directly, most animals could experience the 

38 effects of climate change indirectly through changes to their habitat, food sources, and predators 

39 (Schneider and Root 1996 in National Science and Technology Council 2008). A changing climate 

40 facilitates migration of certain species into non-native habitats, potentially affecting current goods and 

41 services (EPA 2009b, CCSP 2008a). 
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1 Ecosystems in the United States are projected to experience a variety of climate-change impacts. 

2 For example: 

3 • The area of drought-limited ecosystems is projected to expand in the U.S. 11 percent for 

4 every 1.0 °C (1.8 °F) (EPA 2009b). 

5 • Changes in hydrology as a result of changes in precipitation patterns could interrupt the 

6 breeding cycles of amphibians, which depend on the ability to migrate to breeding ponds. 

7 The production of their eggs is also highly dependent on temperature and moisture 

8 availability (Fischlin et al. 2007 in National Science and Technology Council 2008). 

9 • Changes in climate that occur over at least several years are likely to affect the reproductive 

10 success of migratory birds and their ability to survive. A mismatch in timing between the 

11 migration and reproduction periods and peak food availability is the potential pathway for 

12 such impacts (EPA 2009b). 

13 • The migration of butterflies is highly dependent on spring temperatures, and anthropogenic 

14 climate change is likely to lead to earlier spring arrivals. As with migratory birds, an earlier 

15 butterfly migration could result in a mismatch with food supply, thus threatening 

16 reproduction and survival (Forister and Shapiro 2003 in National Science and Technology 

17 Council, 2008). 

18 • Shifts in migration ranges could result in disease entering new areas, for example, avian 

19 malaria in Hawaii could move upslope as climate changes (CCSP 2008a). 

20 In one well-publicized example of mammals experiencing the effects of a warming climate, the 

21 polar bear is specifically adapted to conditions in a narrow ecological slot niche (an environment with 

22 cold temperatures and access to snow, ice, and open water) and depends on this sea ice environment to 

23 hunt ice-breeding seals (EPA 2009b). As the climate warms and sea ice melts, the polar bear loses much 

24 of its natural habitat. If current trends in sea-ice loss continue, the polar bear could become extirpated 

25 from most of its range within 100 years (IUCN 2008). Two thirds of polar bears could be gone from 

26 Alaska by the middle of this century (GCRP et al. 2009). Polar bears were listed as threatened under the 

27 Endangered Species Act on May 15, 2008, due to the ongoing and projected loss of their sea-ice habitat

28 from global warming (EPA 2009b). 

29 The vegetation of terrestrial ecosystems in the United States is projected to experience a variety 

30 of direct impacts from climate change. For example, national forests, which harbor much of the Nation’s 

31 biodiversity, and national grasslands are expected to experience an exacerbation of preexisting stressors, 

32 such as wildfires, invasive species, extreme weather events, and air pollution (CCSP 2008a). 

33 Warmer, drier climates weaken resistance of trees to insect infestation, as they are more likely to 

34 be wilted and weakened under those conditions. In a healthy state, trees can typically fight off beetle 

35 infestation by drowning them with resin (sap) as they bore through the bark. Drought reduces the flow of 

36 resin and beetles that are able to penetrate the bark introduce decay-causing fungus. This problem has 

37 already been documented. Since 1994, winter mortality of beetle larvae in Wyoming has been cut due to

38 mild winters (from 80 percent to less than 10 percent mortality). As a result, the beetles have been able to 

39 strip four million acres of Wyoming forests (Egan 2002 in Epstein et al. 2006). In the southwestern 

40 United States, high temperatures, drought, and the piñon ips bark beetle have had the cumulative effect of 

41 causing a mass die-back of piñon trees. From 2002 to 2003 alone, piñon mortality in Mesa Verde 

42 National Park in Colorado and Bandelier National Monument in New Mexico exceeded 90 percent. 

43 Researchers determined that climate factors drove the die-off (Saunders et al. 2008). The U.S. Forest 

44 Service reports that bark beetles have now impacted over 1.5 million acres in northern Colorado and 
4.5 Health, Societal, and Environmental Impacts of Climate Change Chapter 4 Cumulative Impacts 

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1 southern Wyoming, killing lodgepole pines and affecting watersheds, timber production, and wildlife 

2 habitats, along with other human activities (USFS 2008). 

3 Additional impacts on vegetation in ecosystems in the United States could include: 

4 • Water management in the West would be complicated by increases in temperatures and 

5 changes in precipitation patterns, which lead to reduced snow pack, earlier snowmelt, and 

6 modified hydrology (EPA 2009b). 

7 • High latitudes would experience increased vegetation productivity. Regions in the mid8 latitudes would experience either increased or decreased productivity, depending on whether 

9 the primary impact is more precipitation or higher temperatures (increasing evaporation and 

10 dryness) (Bachelet et al. 2001b, Berthelot et al. 2002, Gerber et al. 2004, Woodward and 

11 Lomas 2004, all in National Science and Technology Council 2008, EPA 2009b). 

12 • Terrestrial ecosystems in the East would be statistically “likely to become carbon sources, 

13 while those in the west would be likely to remain carbon sinks” (Bachelet et al. 2004 in 

14 National Science and Technology Council 2008). 

15 • The jet stream would move northward with increasing atmospheric temperatures. The 

16 consequence of this shift is a drying of the Southeast. Closed-canopy forest ecosystems could 

17 be converted to savanna ecosystems, woodlands, or grasslands, measurably increasing the 

18 threat of fire occurrence (CCSP 2008a). 

19 • Growing seasons would lengthen, according to several predictive models; this would 

20 beneficially act to sustain carbon sinks (EPA 2009b). 

21 • In the Olympic Range, a temperature increase of 2 °C (3.6 °F) would move tree species 

22 upwards 0.20 to 0.38 mile. Temperate species would replace subalpine species over 300 to 

23 500 years (Zolbrod and Peterson 1999). 

24 Stefan et al. (2001) in Kling et al. 2003 simulated the effects of a doubling of CO2 on U.S. lakes 

25 and projected that suitable habitat for coldwater and cool water fishes would decline by 45 and 30 

26 percent, respectively. By 2050, coldwater stream fish habitat is projected to decline by 20 percent in the 

27 U.S. as a whole and 50 percent in the Rocky Mountain Region (Preston 2006). More than half of the wild 

28 trout populations of the southern Appalachian Mountains are projected to disappear as streams warm. 

29 Some studies project that losses of western trout populations could exceed 60 percent (Keleher and Rahel 

30 1996 in Poff et al. 2002; Rahel et al. 1996 in Mohseni et al. 2003; Rahel 2002 in Battin et al. 2007). In 

31 the desert Southwest and the southern Great Plains, where rivers drain to the east and west, fish species 

32 will have no opportunity for northward migration, and it is expected that many native fish species in these 

33 regions could become extinct with only a few degrees of warming (Poff et al. 2002). Models of Pacific 

34 Northwest salmon populations project losses of 20 to 40 percent by 2050 (Battin et al. 2007). 

35 The millions of wetlands in the North American Prairie Pothole region, which provide essential 

36 breeding habitat to waterfowl, are considered particularly vulnerable to a warmer and drier climate. The 

37 wetlands of this region are considered the most productive habitat for waterfowl in the world, and it is 

38 estimated that the wetlands in the area support up to 80 percent of North American ducks. Simulations

39 suggest that under a drier climate, the most productive habitat for breeding waterfowl would shift from 

40 the center of the region in the Dakotas and southeastern Saskatchewan to the wetter eastern and northern 

41 fringes, areas that are less productive or where most wetlands have been drained, resulting in significant 

42 declines in productivity (Johnson et al. 2005a). 

43 Seasonal migrations of wetland species will be disrupted, with reduced survival and possible 

44 extinctions of some species. Boreal peatlands are considered particularly vulnerable (Wrona et al. 2006; 
Chapter 4 Cumulative Impacts 4.5 Health, Societal, and Environmental Impacts of Climate Change 

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1 Heino et al. 2008). Declines in abundance and local and global extinctions of arctic fish species are 

2 projected for this century. Species vulnerable to declines include arctic char, broad whitefish, and Arctic 

3 cisco, which are important components of the diets of indigenous peoples (ACIA 2004). 

4 4.5.4.2.5 Projected Impacts of Climate Change on Global Terrestrial and 

5 Freshwater Ecosystems 

6 The IPCC concludes (very high confidence) that anthropogenic temperature rises have visibly

7 altered ecosystems (Parry et al. 2007). The exact impacts of climate changes are difficult to discern, 

8 however, because they are mediated by other stressors and the capabilities of natural systems to adapt to 

9 changing climates to some degree (Parry et al. 2007). 

10 Some regions of the world are more vulnerable to changes in climate than others. Regions of 

11 snow, ice, and tundra have been visibly altered by changes in global temperature. Observations of frozen 

12 regions already show larger glacial lakes and the destabilization of glacial debris that dam these lakes; 

13 changes in ecosystems at both poles; and increased melting of ice sheets, glaciers, and ice caps (Parry et 

14 al. 2007). 

15 Ecosystems in all regions of the world are expected to respond to climate-change impacts with 

16 poleward and upward shifts of plants and animals; earlier onset of migration of terrestrial species such as 

17 birds and butterflies; and localized disappearance of particular species (EPA 2009b). 

18 Additional factors, such as projected growth in human populations, are expected to exacerbate the 

19 effects of climate change. For example, river basin ecosystems that are already experiencing high levels 

20 of stress are projected, with medium confidence, to witness growth in human populations from 

21 approximately 1.4 to 1.6 billion in 1995 to roughly 4.3 to 6.9 billion by 2050 (Parry et al. 2007). River 

22 basins experience the stress of increasing human populations as manifested in increasing demands for 

23 water (CCSP 2008b) and more inputs of pollutants. A warmer, drier climate could increase these 

24 stressors and reduce access to other water sources (EPA 2009b). 

25 Other projected global impacts of climate change include: 

26 • The hardiness of the world’s ecosystems is expected (high confidence) to be challenged over 

the 21st 27 Century with “an unprecedented combination of climate change, associated 

28 disturbances (e.g., flooding, drought, wildfire, insects, and ocean acidification), and other 

29 global change drivers (especially land use, pollution, and over-exploitation of resources) 

30 (Fischlin et al. 2007). 

31 • Declines in keystone species populations are projected to be the primary factor in causing 

32 ecological cascades, which are “sequential chains of ecological effects, including starvation 

33 and death, beginning at the bottom levels of the food chain and ascending to higher levels, 

34 including apex predators” (EPA 2009b). 

35 • CO2 levels are projected to be much higher than any in the past 650,000 years, and 

36 temperatures are projected to be as high as any in the past 740,000 years. Both increases are 

37 very likely to impact ecosystems (very likely) (EPA 2009b). 

38 • Eighty-four percent of the species listed in the Convention on Migratory Species could be 

39 impacted in some way by climate change: 53 percent are susceptible to changes in water 

40 regime, 24 percent to mismatched water supply, 18 percent to sea-level rise, 17 percent to 

41 changes in prey range, 17 percent to habitat shifts, and seven percent to increased storm 

42 severity. The number of species threatened due to climate change is greater than the total 

43 number that are threatened by all other anthropogenic effects (UNEP 2006). 
4.5 Health, Societal, and Environmental Impacts of Climate Change Chapter 4 Cumulative Impacts 

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1 • By 2050, the Amazon forest is likely committed to losing 50 percent of its area. Even if all 

2 further forcing were to discontinue, projections indicate that almost all of the Amazon forest 

3 would be committed to loss (Jones et al. 2009). 

4 • Fifty to 70 percent of the global climate models utilized by IPCC in 2007 project a 20-percent 

5 reduction in dry season precipitation in the eastern Amazon region, 40 percent in the central 

6 region, and 20 percent in the west. The Amazon forest seems resilient short-term droughts 

7 but large tree mortality begins after 3 years of drought (Betts et al. 2008). 

8 • Global average temperature increases in excess of 1.5 to 2.5 °C (2.7 to 4.5 °F) are statistically 

9 likely to threaten 20 to 30 percent of plant and animal species with extinction by 2100 (EPA 

10 2009b, GCRP et al. 2009). 

11 • Thirty-five percent of known bird species (3,438 of 9,856) are potentially susceptible to 

12 climate change, as are 52 percent of global amphibian species. Seventy to 80 percent of birds 

13 that are already considered threatened are also climate-change susceptible (IUCN 2008). 

14 • Carbon uptake by ecosystems such as forests and grasslands is statistically likely to peak 

during the 21st 15 Century and might ultimately even reverse (forests and grasslands would emit 

16 carbon, rather than taking it in), which would amplify climate change due to increased 

17 atmospheric CO2 (Fischlin et al. 2007 in National Science and Technology Council 2008). 

18 In addition to other anthropogenic stressors, “such as extractive use of goods, and increasing 

19 fragmentation and degradation of natural habitats” (Bush et al. 2004 in Fischlin et al. 2007), climate 

20 change poses a threat to the wellbeing of ecosystems. Although many ecosystems have been resilient to

21 historical changes in climate, it is not clear whether their resilience is enough to withstand the more rapid 

22 and profound changes that are projected given the buildup of GHGs in the atmosphere (Chapin et al.

23 2004, Jump and Peñuelas 2005 in Fischlin et al. 2007). Projected climate change and other anthropogenic 

24 stressors are “virtually certain to be unprecedented” (Forster et al. 2007 in Fischlin et al. 2007). While 

25 some of the impacts expected with climate change serve to exacerbate existing stressors on ecosystems,

26 other expected impacts could be altogether new. For example, increasing temperatures could cause some

27 current sinks for GHGs, such as forest vegetation, to actually become sources for these gases (including 

28 CO2 and methane) (Fischlin et al. 2007). 

29 Effects of anthropogenic climate change on ecosystems are anticipated at different levels of 

30 severity and over varying time scales (decades to centuries) (Lischke et al. 2002 in Fischlin et al. 2007). 

31 Some of the broad impacts on ecosystems associated with climate change are expected to include species

32 extinctions, loss of habitat due to more severe tropical storms (Wiley and Wunderle 1994 in Fischlin et al.

33 2007), changes in the types and abundance of vegetation present in an ecosystem (Schröter et al. 2005, 

34 Metzger et al. 2006, both in Fischlin et al. 2007), and increased susceptibility of land to desertification 

35 (Burke et al. 2006b in Fischlin et al. 2007). 

36 Aquatic species will be vulnerable to changes in precipitation, hydrologic regimes, and water 

37 temperatures that alter or reduce habitat. Coldwater fishes, aquatic invertebrates, and waterfowl are

38 among the species groups expected to move north as the climate warms (Poff et al. 2002; Wrona et al. 

39 2006), with the potential for some extinctions of fishes that are already at the northern limits of their 

40 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), 

41 there would be a shift in thermal regimes northward by about 422 miles (Sweeney et al. 1992 in Heino et 

42 al. 2008). Eaton and Scheller (1996) in Mohseni et al. 2003 estimated that with this degree of warming, 

43 thermally suitable habitat for 57 stream fishes requiring cold or cool water would decline by 50 percent. 
Chapter 4 Cumulative Impacts 4.5 Health, Societal, and Environmental Impacts of Climate Change 

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1 Foreseeable pathways of climate change-induced impacts on ecosystems include: 

2 • CO2 fertilization effects on vegetation (EPA 2009b). 

3 • Higher atmospheric temperatures that could lead to more frequent insect and disease 

4 outbreaks (EPA 2009b). 

5 • Increased radiation due to a projected decrease in tropical cloud cover (Nemani et al. 2003 in 

6 Fischlin et al. 2007). This is linked to warming, which can directly affect ecosystems and 

7 increase the frequency and severity of storms originating in the tropics. 

8 Increased water temperatures in freshwater systems sometimes make aquatic species more 

9 susceptible to pathogens. Increasing evaporation of lakes and stream systems can also increase 

10 concentrations of pollutants in water bodies. 

11 Ecological Thresholds

12 Ecosystems have thresholds, similar to climatic or oceanic system tipping points, over which any 

13 small stressors on an ecosystem could result in abrupt changes in the quality or properties of the whole 

14 system. “Threshold phenomena are particular nonlinear behaviors that involve a rapid shift from one 

15 ecosystem state (or dynamic regime) to another that is the result of, or provokes, instability in any 

16 ecosystem” attribute (CCSP 2009c). This kind of instability is associated with some type of positive,

17 runaway feedback, which differentiates a threshold from other types of changes in the ecosystem that are 

18 the result of environmental modifications. 

19 Crossing over a threshold, an ecosystem makes a well defined break from previous trends in the 

20 system’s behaviors and overall characteristics (CCSP 2009c). An example cited in CCSP (2009a) that 

21 illustrates this is the observed impact to grasslands that was the result of interactions between drought and 

22 livestock overgrazing. As soon as a component critical to the wellbeing of the grassland ecosystem 

23 failed, that failure triggered “runaway desertification...a domino-like cascade of instability that 

24 substantially alter[ed] the rest of the system” (Groffman et al. 2006 in CCSP 2009c). Another example is 

25 that of the previously cited rapid die-off of forests in the southwestern United States. The primary trigger 

26 to runaway changes, sudden tree mortality from the drought-bark beetle stressors, led to other nonlinear 

27 changes in the ecosystem, such as erosion and the increased incidence of forest fires. Similarly, in the 

28 1990s, southern Alaska experienced a world-record-breaking onslaught of spruce bark beetles, which was

29 linked to a threshold response to observed changes in climate, primarily milder winter seasons that 

30 reduced the beetles’ winter mortality and allowed the beetles to complete their life cycles in 1 year, rather 

31 than the historical 2 years. The beetle outbreak occurred on top of a 9-year drought that had already

32 pushed spruce trees to the limits of their resilience; the trees were unable to protect themselves from 

33 insect pests at that time, leading to widespread tree mortality (CCSP 2009c). 

34 In the future, facing changes in precipitation, temperature, and sea level, it might not be possible 

35 for ecosystems to meet historic benchmarks. Therefore, managers of ecosystem resources will likely have 

36 to modify their goals to accommodate these changes. For example, it could be necessary to foster the 

37 growth of more resilient components of ecosystems, such as those with only a few strong connections 

38 between them, which would build a “fire-break” into the systems and help to protect them from collapse

39 (CCSP 2009c). 

40 4.5.5 Marine, Coastal Systems, and Low-lying Areas 

41 This section addresses climate-related impacts to marine and coastal ecosystems and low-lying 

42 areas. Coastal zones, commonly included as part of the marine intertidal and neritic zones, are unique 
4.5 Health, Societal, and Environmental Impacts of Climate Change Chapter 4 Cumulative Impacts 

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1 environments where land and water meet. Though there is no single definition for coastal zones, all 

2 coastal zones include an area of land with a portion covered by saltwater. Burke et al. (2001) defines 

3 coastal zones as the “intertidal and subtidal areas on and above the continental shelf (to a depth of about 

4 200m (650 feet)) – areas routinely inundated by saltwater – and immediately adjacent lands.” Marine 

5 zones are also varied, often categorized according to both water depth and distance from land. In general, 

6 most geographic categorizations make clear delineations among shallow zones near the coast, open ocean

7 areas, and the deepest areas of the sea; however, there is no one universal definition applicable to 

8 establishing the different subboundaries of marine zones. Alternatively, marine zones can also be defined 

9 by the ecosystems they support; NOAA has identified 64 Large Marine Ecosystems that each represent 

10 vast marine areas with distinct physical characteristics and where plant and animal populations are 

11 inextricably linked in the food chain (NOAA 2009a).

12 This section introduces the marine and coastal environments and discusses the observed and 

13 projected impacts of climate change. These environments are particularly vulnerable to warming water 

14 temperatures, sea-level rise, melting of freshwater ice, storm events, and water acidification (see Section 

15 4.7.2. for discussion of water acidification). 

16 4.5.5.1 Affected Environment 

17 The world’s coastal length is estimated to be 1,015,756 miles, with North America having the 

18 longest coastal length of all continents (Pruett and Cimino 2000 in Burke et al. 2001). Canada has the 

19 longest coastal length of any country in the world and the United States has the second longest, at 

20 265,523 km (164,988 miles) and 133,312 km (82,836 miles), respectively (Pruett and Cimino 2000 in 

21 Burke et al. 2001). Important ecosystems found in coastal zones can include estuaries, coral reefs, coastal 

22 lagoons, mangroves, seagrass meadows, upwelling areas, salt marshes, beaches, bays, deltas, kelp forests, 

23 and barrier islands. A variety of terminology exists for describing coastal zone ecosystems. Table 4.5.5-1 

24 lists some of the more commonly described ecosystems found in coastal zones. 

25 Coastal zones are areas of substantial biological productivity that provide food, shelter, spawning 

26 grounds, and nurseries for fish, shellfish, birds, and other wildlife. The interaction between aquatic and 

27 terrestrial components of coastal ecosystems creates a unique environment that is critical to the life cycles 

28 of many plant and animal species. In the United States, 85 percent of commercially harvested fish depend 

29 on estuaries and coastal waters at some stage in their life cycle (Summers et al. 2004), while as much as 

30 95 percent of the world’s marine fish harvest is caught or reared in coastal waters (Sherman 1993 in 

31 Burke et al. 2001). Most historical information available on coastal ecosystems focuses on data related to 

32 fisheries (see Section 4.5.6, Food, Fiber, and Forests, for a detailed discussion on fisheries). As more 

33 research is conducted on other increasingly important coastal ecosystems, new data and information are

34 becoming available. For example, coral reefs alone, while representing only 0.2 percent of the total area 

35 of oceans (Bryant et al. 1998), harbor more than 25 percent of all known marine fish (Tibbetts 2004). In 

36 addition, the species in some coral reefs can reach densities of 1,000 per square meter (Tibbetts 2004). In 

37 the United States, coastal ecosystems provide the Country’s essential nesting, feeding, and breeding 

38 habitat for 85% of the waterfowl and other migratory birds (Summers et al. 2004). Coastal zones have 

39 also been found to support a much higher percentage of the world’s threatened and endangered species. 

40 
Chapter 4 Cumulative Impacts 4.5 Health, Societal, and Environmental Impacts of Climate Change 

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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)

1 

2 Because a disproportionate percentage of the world’s population lives in coastal zones, the 

3 activities of humans have created environmental pressures that threaten the very resources that make the 

4 coastal zones desirable (Summers et al. 2004). The impact of these activities varies from place to place 

5 and depends on the types and sensitivity of coastal ecosystems involved. A wide range of pressures has 

6 been identified as causing adverse changes in coastal ecosystems, but the leading causes of coastal 

7 ecosystem degradation include physical alteration, habitat degradation and destruction, water withdrawal, 

8 overexploitation, pollution, and the introduction of non-native species (UNESCO and WWAP 2006). In 

9 addition, climate change might compound these pressures through the effects of higher sea levels, warmer 

10 seawater, altered ocean circulation patterns, increased and extreme storm events, and increased carbon

11 dioxide concentrations (UNESCO and WWAP 2006, Burke et al. 2001). 
4.5 Health, Societal, and Environmental Impacts of Climate Change Chapter 4 Cumulative Impacts 

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1 There are numerous ways to define marine zones. Table 4.5.5-2 illustrates some commonly used 

2 zones (note that many of zones are similar in definition or overlap with other zones). Zonal 

3 characteristics include their proximity to land and their depth. Water zones close to land tend to be

4 shallower, warmer, and have greater exposure to sunlight compared to deeper waters; thus, these different 

5 zones support very distinct ecosystems. Note the intertidal and neritic zones can also be defined as 

6 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.

7 

8 Marine ecosystems play critical roles in global ecology. Marine ecosystems support almost half 

9 of all known species on Earth, and contribute 5 percent of the protein in the human diet (NOAA 2009b). 

10 Plankton and seaweed growing in shallower waters are the primary resource for many marine and coastal 

11 food chains/webs. Marine zones also play an important role in climate change through absorption of CO2. 

12 Plankton absorb CO2 as they grow, and ultimately will sequester some of that carbon when they die and 

13 fall to the ocean bottom. Additionally, ocean water itself absorbs some of the CO2 in the atmosphere, 

14 increasing water acidity and contributing to reduced concentrations of dissolved oxygen, both of which

15 can harm marine ecosystems (see Section 4.7.2 for more information on ocean acidification) (EPA 

16 2009b). 
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1 4.5.5.2 Environmental Consequences 

2 4.5.5.2.1 Observed Trends and Impacts of Climate Change 

3 Many marine and coastal ecosystems around the globe have been substantially degraded, and 

4 many have been lost altogether. Quantifying the changes in coastal ecosystems is difficult because 

5 historical data describing the previous extent of these ecosystems are very limited. More and higher6 quality data characterizing the world’s marine and coastal zones are needed (Burke et al. 2001). 

7 Ecosystem Conditions

8 A warming climate is already affecting the ocean. Increasing water temperatures have caused a 

9 rapid poleward shift in fish and plankton populations in the North East Atlantic (EPA 2009b). As ice 

10 melts and precipitation increases at varying degrees around the globe, freshwater enters the ocean system, 

11 decreasing salinity and increasing the temperatures. Boyer et al. (2005) found that salinity levels of the 

12 oceans have changed when comparing 5 year periods from 1955-1959 and 1994-1998 (investigating the 

13 ocean surface vertically down to a depth of 3 km), and found that some areas are experiencing freshening 

14 while others are experiencing increases in salinity; in some parts, it is reasoned that the increase in salinity 

15 is due to increased evaporation. This study concludes that some parts of the Atlantic and Pacific Oceans 

16 are decreasing in salinity, while other parts are increasing; in most areas of the Indian Ocean, the upper 

17 layers are increasing in salinity, while the subsurface layers are freshening. Hegerl et al. (2006 in Fischlin 

18 et al 2007) found that observed changes in salinity are consistent with simulations of warming and an 

19 increase of the hydrologic cycle. Less saline waters can inhibit the vertical mixing of ocean waters 

20 interfering with the distribution of nutrients, although the ultimate impact of this phenomenon remains 

21 unclear (Denman et al. 2007). 

22 Ocean ecosystems are being pressured by overfishing, pollution, and other human-induced 

23 stressors. The United Nations estimates that 75 percent of the world’s fish stocks are fully exploited, 

24 overexploited, or depleted (FAO 2004 in Easterling et al. 2007) (see Section 4.5.6). Even where fish 

25 populations are stable, fishing alters marine ecosystems by reducing the age, size, geographic diversity, 

26 and biodiversity of the populations. Brander (2007) finds that this decrease in diversity leaves the 

27 ecosystems more vulnerable to environmental stressors such as climate change. 

28 Recent studies using relatively new data collection methods link changes in temperature to the 

29 productivity in the world’s oceans. Based on a decade of data from National Aeronautics and Space 

30 Administration satellite ocean-color sensors launched in 1997, Behrenfeld et al. (2006) in Doney (2006) 

31 show that trends in chlorophyll productivity closely follow changes in temperature, and that in general, 

32 phytoplankton biomass and growth decline as surface waters warm. In addition, excess amounts of 

33 decaying plankton and elevated dissolved CO2 concentrations can cause and expand hypoxic (low34 oxygen) zones, or oceanic dead zones, which could physiologically stress marine animals (Brewer and 

35 Peltzer 2009 in Kundzewicz et al 2007). Additionally, as the oceans absorb CO2, they become more 

36 acidic, threatening coral reef ecosystems (EPA 2009b) (see Section 4.7.2. for more information on ocean 

37 acidification). A recent study found that one-third of the 704 zooxanthellate reef-building coral species 

38 assessed are at increased risk of extinction (Carpenter et al. 2008). This number has risen dramatically in 

39 recent decades due to bleaching and diseases driven by elevated sea-surface temperatures. 

40 The conditions of coastal ecosystems vary from place to place and depend on many factors. 

41 Attempts have been made to assess the global extent and distribution of aquatic habitats, but estimates 

42 vary considerably depending on the type and source of data (UNESCO and WWAP 2006). While 

43 inventories of coastal zones exist, no high-quality data sets or indicators are available at the global level 

44 that track changes in condition over time (UNESCO and WWAP 2006). Despite the lack of high-quality 
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1 data, it is safe to assume that coastal zones with substantial human populations are vulnerable to a range 

2 of human activities that can increase pressure and cause adverse changes to coastal ecosystems. As 

3 mentioned above, typical coastal ecosystem degradation would include physical alteration, habitat 

4 degradation and destruction, water withdrawal, overexploitation, pollution, and the introduction of non5 native species. The effects of sea-level rise from climate change could compound these potential impacts. 

6 EPA considers the current overall coastal condition of the United States to be fair (Summers et al.

7 2004). EPA evaluated six geographic coastal regions (Great Lakes Coastal Area, Northeast Coastal Area, 

8 Southeast Coastal Area, Gulf Coast Coastal Area, West Coastal Area, and Alaska, Hawaii, and Island 

9 Territories) using five ecological health indicators (water quality, sediment quality, benthic, coastal 

10 habitat, and fish tissue contaminants) to assess estuarine coastal conditions as good, fair, or poor. Of the 

11 five indicators, only the coastal habitat index received an overall poor rating. The benthic and sediment 

12 quality indices rated fair to poor, while the water quality and fish tissue contaminants indices received fair 

13 ratings. Of the six coastal regions, the Southeast Coastal Area ranked highest, with all indicators rating 

14 fair to good. The region with the worst coastal condition was the Northeast Coastal Area, with four of the 

15 five indicators rating poor or fair to poor. In terms of human and aquatic life use, 21 percent of the 

16 assessed coastal resources of the Country are considered unimpaired (good condition), whereas 35 percent 

17 are impaired (poor condition) and 44 percent threatened (fair condition). 

18 A number of marine wildlife species have been or could be adversely affected by environmental 

19 changes in temperature, availability of water and nutrients, runoff from land, wind patterns, and 

20 storminess that are associated with climate change (Kennedy et al. 2002). Burke et al. (2001) found the 

21 following trends in the conditions of marine and coastal ecosystems: 

22 • Many coastal habitats are disappearing at a fast pace, with extensive losses in the past 

23 50 years. 

24 • Although some industrial countries have improved coastal water quality, chemical pollutant 

25 discharges are increasing overall as agriculture intensifies and new synthetic compounds are 

26 developed. 

27 • Pollution-filtering capacities are lost as coastal ecosystems are lost. 

28 • Nutrient inputs to coastal waters appear to be increasing because of population increase and 

29 agricultural intensification. 

30 • The frequency of harmful algal blooms resulting in mass mortality of marine organisms has 

31 increased substantially over the past few decades. 

32 • More than 25 different coral reef diseases have been recorded since 1970, and reports of coral 

33 bleaching have increased measurably in recent years. 

34 • The capacity of coastal ecosystems to produce fish for human harvest has been highly 

35 degraded by overfishing, destructive trawling techniques, and loss of coastal nursery areas. 

36 • An increased number of invasive species is being reported throughout the world’s coastal 

37 ecosystems. 

38 • Increased occurrences of hypoxia (shortage of oxygen in water) have been reported. 

39 • Many commercial fish species and other marine wildlife have become threatened. 

40 • Large-scale marine oil spills have been declining, but oil discharges from land-based sources 

41 are believed to be increasing. 

42 • The number of protected marine and coastal areas has increased, indicating greater awareness 

43 of the need to protect these environments. 
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1 • Global marine fish production has increased six-fold since 1950. 

2 • Notable ecosystem changes have occurred over the last half-century in some fishery areas, 

3 such as the North Atlantic and Northeast Pacific. 

4 Marshes and mangroves are particularly susceptible to sea-level rise affecting the feeding or 

5 nesting grounds of black rail, clapper rail, some terns, and plovers (Kennedy et al. 2002). Over the short 

6 term, however, shrimp, menhaden, dabbling ducks, and some shorebirds would benefit from the release of

7 nutrients from the breakup of marshes (Kennedy et al. 2002). 

8 Sea-level Rise

9 There is strong evidence that temperature increases caused a rise in global sea level during the 

20th 10 Century (Parry et al. 2007). Because each coastal area has its own unique geographic and 

11 environmental characteristics, consequences from adaptations to climate change are expected to differ for 

12 each community. Areas of critical sensitivity on the global scale include Tokyo, Shanghai, London, 

13 Thailand, India, and Vietnam (Nicholls et al. 2007a in National Science and Technology Council 2008). 

14 These areas share the characteristics of coastal location, low elevation, large population, and stressed 

15 resources. Because of their proximity to the water’s edge and the high level of infrastructure typical of 

16 many coastal communities, these urban centers are sensitive to changes in sea-level rise (National Science 

17 and Technology Council 2008). 

18 Recent data suggest that the rise in global sea level has had an effect on some U.S. coastal zones. 

19 Sea-level rise is non-uniform around the world. In some regions, rates of rise have been as much as 

20 several times the global mean, while other regions have experienced falling sea level. This might be the 

21 result of variations in thermal expansion and exchanges of water between oceans and other reservoirs, 

22 ocean and atmospheric circulation, and geologic processes (EPA 2009b). Satellite measurements provide

23 unambiguous evidence of regional variability of sea-level change from 1993 to 2003, with the largest sea24 level rise occurring in the western Pacific and eastern Indian Oceans (EPA 2009b). 

25 Tide gauges have measured the average rate of sea-level rise to be 1.8 millimeters (0.07 inch) +/−

26 0.5 millimeter (0.019 inch) per year from 1961 to 2003 and 1.7 millimeters (0.07 inch) +/− 0.5 

27 millimeter (0.02 inch) per year over the past century (EPA 2009b). These changes are attributed to 

28 thermal expansion associated with rising global temperature, thawing of permafrost, and loss of sea ice 

29 (EPA 2009b). The global ocean temperature averaged from the surface to a depth of approximately 700 

30 meters (2,300 feet) has increased by 0.10 °C (0.18 °F) 1961 to 2003, contributing to an average increase 

31 in sea level of 0.4 millimeter (0.02 inch) +/− 0.1 millimeter (0.004 inch) per year (EPA 2009b). This 

32 contribution increased from 1993 to 2003, with a rate of sea-level rise of 1.6 millimeters (0.06 inch) +/−

33 0.5 millimeter (0.02 inch) per year (EPA 2009b). Melting of mountain glaciers, ice caps, and land ice

34 have also contributed to the measured sea-level rise. From 1961 to 2003, the melting of land ice has 

35 contributed approximately 0.7 millimeter (0.03 inch) +/− 0.5 millimeter (0.02 inch) per year to sea-level 

36 rise, with an accelerated rate of 1.2 millimeter (0.05 inch) +/− 0.4 millimeter (0.02 inch) per year between 

37 1993 and 2003 (EPA 2009b). Recent global sea-level data from satellite altimetry show an accelerated 

38 rate of sea-level rise of 2.4 millimeters (0.094 inch) per year evident from 1993 to 2003 (Domingues et al.

39 2008 in Epstein et al 2006), and a rate of 3.36 millimeters (0.13 inch) +/− 0.4 millimeter (0.02 inch) from 

40 1993 to 2007 (Beckley et al. 2007 in Chao et al. 2008), although it is uncertain whether this more recent 

41 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 the beginning of the 20th 42 Century 

43 along most of the Atlantic and Gulf Coasts in the United States (EPA 2009b), with the Gulf Coast 

44 experiencing a rise of a few inches per decade (primarily due to land subsidence) and Alaskan coasts 
4.5 Health, Societal, and Environmental Impacts of Climate Change Chapter 4 Cumulative Impacts 

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1 experiencing decreases in relative sea level (due to land rising) of a few inches per decade (National

2 Science and Technology Council 2008 and EPA 2009). Approximately one-sixth of U.S. land that is 

3 close to sea level is in the mid-Atlantic region; consequently, much of the reporting on effects focuses on 

4 that region (National Science and Technology Council 2008). Over the past century, the highest rate of 

5 sea-level rise has been observed in the mid-Atlantic region, in part resulting from subsidence of the land 

6 surface (Gutierrez et al. 2007). For example, Virginia has observed sea-level rise at 4.4 millimeters (0.17 

7 inch) per year compared to 1.8 millimeters (0.07 inch) per year in Maine (Zervas 2001 in Gutierrez et al.

8 2007). New Jersey, with 60 percent of its population living along the 127 miles of coastline, has 

9 experienced coastline subsidence and beach erosion, threatening communities and coastal wetlands 

10 (Union of Concerned Scientists 2007 in Kundzewicz et al 2007, Aucott and Caldarelli 2006, Jacob et al.

11 2000). Sea level on the California coast rose by almost 18 centimeters (7.1 inches) over the last century 

12 EPA 2009b)). 

13 Enhanced storm surge is an associated stressor directly related to sea-level rise. In one example, 

14 Frumhoff et al. (2007) discusses the impacts of surging waters during a coastal storm in December 1992, 

15 when strong winds and rising water levels disrupted the New York City public transit system and required 

16 the evacuation of communities in New Jersey and Long Island. Sea-level rise in the Chesapeake Bay has

17 accelerated erosion rates, resulting in wetland destruction (National Science and Technology Council 

18 2008). According to the Maryland Geological Survey, Tropical Storm Isabel resulted in the loss of an 

19 estimated 20 acres or more of land on the western shore of Chesapeake Bay, causing significant damages

20 to shoreline structures (EPA 2009b). 

21 Coastal wetland loss is occurring where ecosystems are squeezed between natural and artificial 

22 landward boundaries and rising sea levels (EPA 2009b). Rise in sea level could be contributing to coastal 

23 erosion across the eastern United States (Zhang et al. 2004 in Rosenzweig et al. 2007). In Mississippi 

24 and Texas, more than half of the shorelines have eroded at average rates of 2.6 meters (8.5 feet) to 3.1 

25 meters (10.2 feet) per year since the 1970s, while 90 percent of the Louisiana shoreline has eroded at a 

26 rate of 12.0 meters (39.4 feet) per year (EPA 2009b). Areas in Louisiana are experiencing barrier island 

27 erosion, resulting in an increased height of waves (Nicholls et al. 2007a in National Science and 

28 Technology Council 2008). Furthermore, regional sea-level rise has contributed to increased storm-surge 

29 impacts along the North American eastern coast (National Science and Technology Council 2008). 

30 Particularly because subsidence is occurring in parts of this area, areas such as the Louisiana and Gulf 

31 coasts are considered at high risk from erosion and storm surges, and any area along the coast with low 

32 elevation, large populations, and stressed resources could be expected to be at risk from any future sea33 level rise. Saltwater intrusion is a projected threat to estuarine and mangrove ecosystems. The decline of 

34 bald cypress forests in Louisiana and cabbage palm forests in Florida has already been linked with 

35 saltwater intrusion. (EPA 2009b) Low-lying areas of the United States Pacific coast are also at increasing 

36 risk of flooding as sea level rises. 

37 4.5.5.2.2 Projected Impacts of Climate Change for the United States 

38 Impacts to marine and coastal ecosystems are expected to continue due to climate and non39 climate stressors, particularly where coastal populations increase and demand more coastal space and 

40 resources. As of 2003, 153 million people (53 percent of the total population) lived in coastal counties of 

41 the United States, an increase of 33 million people since 1980. The U.S. coastal population was projected 

42 to rise to 160 million by 2008. It is also estimated that an additional 25 million people will live in the 

43 coastal United States in the next 25 years (EPA 2009b). This change in population is expected to 

44 compound the anticipated adverse effects of climate change on coastal communities, placing heavier 

45 demand on already stressed ecosystems (EPA 2009b). Nicholls et al. (2007b) in (EPA 2009b) suggests 

46 that “The major non-climate impacts for the U.S. and other world regions include drainage of coastal 

47 wetlands, resource extraction, deforestation, introductions of invasive species, shoreline protection, and 
Chapter 4 Cumulative Impacts 4.5 Health, Societal, and Environmental Impacts of Climate Change 

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1 the discharge of sewage, fertilizers, and contaminants into coastal waters,” and further notes “The 

2 cumulative effect of these non-climate, anthropogenic impacts increases the vulnerability of coastal 

3 systems to climate-related stressors.” 

4 Sea-level Rise

5 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 6 Century is expected to 

7 exceed that of past years, with potential adverse consequences for coastal communities and the 

8 infrastructures they support. Recent studies have shown that global sea level does not rise uniformly and 

9 that the coastal United States is expected to experience significantly higher sea levels than the global 

10 average (Bamber et al. 2009b, Yin et al. 2009, both in Pew Center on Global Climate Change 2009). 

11 Some general effects associated with rising sea levels include:

12 • Loss of land area due to submergence and erosion of lands in the coastal zone; 

13 • Changes to coastal environments; 

14 • More flooding due to storm surges; and 

15 • Salinization of estuaries and groundwater (National Science and Technology Council 2008). 

16 For islands such as those in Hawaii and other U.S. territories in the Pacific, outcomes could 

17 include a reduction in island size and the abandonment of inundated areas (National Science and 

18 Technology Council 2008, EPA 2009b). 

19 The effects of sea-level rise on some coastal communities could be devastating because of 

20 increased flooding and erosion. As much as 21 percent of the U.S. mid-Atlantic coastal wetlands are 

21 potentially at risk of inundation between 2000 and 2100 (EPA 2009b), and coastal wetlands already 

22 experiencing submergence are “virtually certain” to continue to shrink due to accelerated sea-level rise, 

23 among other climate- and non-climate-related factors (EPA 2009b). Additionally, the melting of the 

24 Greenland ice sheet could have an effect on ocean circulation and sea-level rise dynamics, which might

25 exacerbate sea-level rise experienced on the northeast North American coast (Hu et al. 2009). Extensive 

26 erosion has already been documented across the East Coast, as have notable decreases in the coastal 

27 wetlands of Louisiana, the mid-Atlantic region, New England, and New York (Rosenzweig et al. 2007 in 

28 National Science and Technology Council 2008). Erosion is expected to be worse in sandy environments 

29 along the mid-Atlantic coast, Mississippi, and Texas (National Science and Technology Council 2008, 

30 Nicholls et al. 2007a in National Science and Technology Council 2008). The IPCC notes that sandy 

31 shorelines are already retreating and that sea-level rise due to climate change is an underlying cause. 

32 Furthermore, areas in Louisiana are experiencing barrier-island erosion, resulting in increases in the

33 height of waves that make it to shore (EPA 2009b). A large storm can affect the shoreline position for 

34 weeks to a decade or longer (Morton 1994, Zhang et al. 2004, List et al. 2006, Riggs and Ames 2003, all 

35 in Gutierrez et al. 2007). Tidal wetlands, estuarine beaches, marshes, and deltas are expected to be 

36 inundated with water in areas such as the Mississippi River, Louisiana Delta, and the Blackwater River

37 marshes in Maryland (Titus et al. 2008 in National Science and Technology Council 2008). The “coastal 

38 squeeze” phenomenon, where wetlands are trapped between natural and human-made land boundaries, is 

39 causing wetland loss and habitat destruction (EPA 2009b). Freshwater resources are also at risk given the 

40 likely intrusion of saltwater into groundwater supplies, adversely affecting water quality and salinization 

41 rates (Kundzewicz et al. 2007b in National Science and Technology Council 2008). 

42 The most devastating impacts related to increased mean sea level are associated with impacts of 

43 storm surge (EPA 2009b). The height of storm surges will increase if sea level rises, regardless of storm 

44 frequency and intensity increases; thus, a storm of similar behavior will cause greater damage with rising 

45 sea level (Fisher et al. 2000 in Easterling et al 2007). One study suggests the 100-year flood might 
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1 actually occur every 25 to 30 years (Najjar et al. 1999 in Easterling et al 2007). By mid-century, Boston 

2 and Atlantic City could experience a 100-year flood event every 2 to 4 years and annually by the end of 

3 the century (Frumhoff et al. 2007). 

4 Sections of the California coastal ecosystems are at risk due to sea-level rise. The historic rate of

5 sea-level rise observed at San Francisco and San Diego during the past 100 years was 15 to 20 

6 centimeters (5.9 to 7.9 inches). Parts of the California coast are at risk for flood damage, which could 

7 further jeopardize levees in the City of Santa Cruz (California Environmental Protection Agency 2006). 

8 Santa Cruz is 20 feet above sea level and has levees built to contain the 100-year flood. If sea levels were 

9 to increase above 12 inches as projected for the medium warming range of temperatures, a flood 

10 associated with a storm surge event at the 100-year level might happen once every 10 years (California

11 Energy Commission 2006a). The ENSO events of 1982-1983 and 1997-1998 corresponded to high sea 

12 level episodes (Flick 1998 in Cayan et al. 2006). The most severe coastal impacts occur as a result of 

13 coinciding factors including (a) elevated storm surge during, (b) high astronomical tide with (c) higher sea 

14 levels due to monthly-to-annual sea-level fluctuations associated with ENSO events, and (d) higher mean 

15 sea levels (Cayan et al. 2008). 

16 In the San Francisco Bay Area, by 2050, 180,000 acres of shoreline will be vulnerable to 

17 inundation with a 16-inch rise in sea level, which is the lower of two sea-level rise scenarios considered 

18 by the Bay Area Conservation and Development Commission. Additionally, a 16-inch rise in sea level 

19 would impact 90 to 95 percent of existing tidal marshes and tidal flats, 20 percent of which would be 

20 vulnerable to permanent submersion and erosion. (Heberger et al. 2009 in BCDC 2009) 

21 Storm Events 

22 The frequency and intensity of storms are expected to increase at the same time sea levels rise 

23 and sea surface temperatures increase (Nicholls et al. 2007a in National Science and Technology Council 

24 2008). Some societal effects include (see Section 4.5.7 for more information on societal effects): 

25 • Infrastructure such as bulkheads, dams, and levees could be damaged by flooding and strong 

26 storms (Nicholls et al. 2007a in National Science and Technology Council 2008). 

27 • Coastal ports, roads, railways, and airports are at risk of disruption due to power outages, 

28 flooded routes, and poor travel conditions (Nicholls et al. 2007a in National Science and 

29 Technology Council 2008). 

30 • Industries that rely on coastal stability, such as travel and recreation, fishing and hunting, and 

31 trade, are expected to become increasingly sensitive to these temperature and precipitation 

32 changes in the coming decades (Nicholls et al. 2007a in National Science and Technology 

33 Council 2008). 

34 • The most at-risk state in the United States is expected to be Alaska because the indigenous 

35 communities depend on wildlife for hunting and fishing practices, reside within floodplains, 

36 and currently face water shortages (Field et al. 2007b in National Science and Technology 

37 Council 2008). 

38 One ecological effect of intense storms is the loss of coastal wetlands, which has been 

39 documented on many occasions. A prominent recent example is the loss of coastal lands as a result of 

40 Hurricane Katrina in 2005. In Louisiana alone, the loss of land during Hurricane Katrina was 

41 approximately 217 square miles. The Chandeleur Islands, which New Orleans relied on as a tropical 

42 storm buffer, lost 85 percent of their surface area (CCSP 2008b). Parts of New Orleans and surrounding 

43 areas are 1.5 to 3 meters (4.9 to 9.8 feet) below sea level. With a sea-level rise of 480 millimeters

44 (roughly 1.6 feet) and accounting for land subsidence, the region could be 2.5 to 4.0 meters (8.2 to 13.1 
Chapter 4 Cumulative Impacts 4.5 Health, Societal, and Environmental Impacts of Climate Change 

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1 feet) or more below mean sea level by 2100. Further, in this scenario, a storm surge of 3 to 4 meters (9.8 

2 to 13.1 feet) (an estimated storm surge from a Category 3 hurricane), without the effect of waves, could 

3 be 6 to 7 meters (19.7 to 23.0 feet) above areas that were heavily populated in 2004. (EPA 2009b) 

4 Severe storms and sea-level rise have had detrimental effects on coastal ecosystems in areas with 

5 sandy beaches. Many species rely on the wellbeing of, and accessibility to, beaches. Examples include: 

6 • Diamondback terrapins and horseshoe crabs rely on beach sands to bury their eggs. The eggs 

7 not only act to propagate the species, but some shorebirds, such as the piping plover, rely on 

8 these eggs as a food source (USFWS 1988 in CCSP 2009b ). 

9 • Horseshoe crabs rarely spawn unless sand is deep enough to nearly cover their bodies, about 

10 10 centimeters (4 inches) (Weber 2001). Shoreline protection structures designed to slow 

11 beach loss can also block horseshoe crab access to beaches and can trap or strand spawning 

12 crabs when wave energy is high (Doctor and Wazniak 2005). In this case, both the loss of 

13 beach and the adaptation strategy selected by the community can harm local species. 

14 • A rare firefly, Photuris bethaniensis, is found only in areas between dunes on Delaware’s 

15 barrier beaches. Its habitat is at risk due to beach stabilization and hardening of shorelines, 

16 which limits migration of dunes and the formation of the swales between dunes where the 

17 firefly is found (CCSP 2009b ). 

18 Because the distribution of marine fish and plankton is largely driven by climate-related factors, 

19 climate change is causing significant ecosystem alterations, including marine species shifts and effects on 

20 fisheries. The IPCC estimates that 20 to 30 percent of marine species studied would be in climate zones 

21 outside their current ranges with a temperature rise of 3.5 to 5.5 °F, and would likely be at risk of 

22 extinction (CCSP 2009a). Rising water temperatures and other climate-driven changes (e.g., salinity, 

23 dissolved oxygen levels, ocean circulation) have been associated with the movement of plankton by 10° 

24 latitude toward the poles over a period of 4 decades in the North Atlantic (EPA 2009b). Tuna stocks in 

25 the Pacific are expected to shift eastward due to climate change, and marine ecosystems in Alaska are 

26 already experiencing significant alterations (CCSP 2009a). The Bering Sea produces the largest 

27 commercial fishery harvests in the United States and supports subsistence economies of the indigenous 

28 peoples of Alaska (ACIA 2005a). Current observations indicate that continued climate-related changes in 

29 the north Bering Sea could result in major shifts in marine fish stocks, including commercially important 

30 species such as Pollock, upon which Alaskan Natives depend (Grebmeier et al. 2006). 

31 4.5.5.2.3 Projected Global Impacts of Climate Change 

32 Globally, coastal systems and low-lying areas are experiencing adverse effects related to climate 

33 change and sea-level rise, such as coastal inundation, erosion, ecosystem loss, coral bleaching and 

34 mortality at low latitudes, thawing of permafrost, and associated coastal retreat at high latitudes (very high 

35 confidence) (Nicholls et al. 2007c in Ebi et al 2008). To further exacerbate the stressors, human 

36 settlement and encroachment on coastal systems and low-lying areas have been increasing, with an 

37 estimated 23 percent of the world’s population living within about 60 to 65 miles of the coast and no 

38 more than about 330 feet above sea level (Small and Nicholls 2003 in National Science and Technology 

39 Council 2008). 

40 Sea-level Rise

41 Although non-uniform around the world, global sea level is estimated to have risen by 1.7 

42 millimeters (0.07 inch) +/− 0.5 millimeter (0.02 inch) per year over the past century, with the western 

43 Pacific Ocean and the eastern Indian Ocean experiencing the greatest rise (Nicholls et al. 2007c in Ebi et 
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1 al 2008). Sea-level rise, coupled with both projected sea surface temperatures increasing 1 oC (1.8 oF) to 

2 3 °C (5.4 °F) and intensified cyclonic activity, could lead to larger waves and storm surges, which would 

3 impact coastal systems and low-lying areas across the globe (Nicholls et al. 2007c in Ebi et al 2008). The 

4 loss or degradation of coastal ecosystems has a direct impact on societies that depend on coastal-related 

5 goods and services such as freshwater and fisheries and has the potential to impact hundreds of millions 

6 of people (Parry et al. 2007). 

7 There is variability in the projected effects from climate change and sea-level rise on an 

8 international scale. For instance, if the global mean annual temperature increases above 1980 to 1999

9 levels, coastal systems and low-lying areas are anticipated to sustain increased damage due to floods and 

10 storms; an additional increase of 2 °C (3.6 °F) would lead to an increase of millions of people that could 

11 experience coastal flooding each year; an increase of 3 °C (5.4 °F) is estimated to cause a loss of 

12 30 percent of the global coastal wetlands (high confidence; IPCC 2007d, Figure SPM.2). Coastal wetland 

13 ecosystems are at substantial risk from sea-level rise if they are sediment-starved or prevented from 

14 migrating inland. As sea water temperatures increase, it is likely that coral bleaching and mortality will 

15 rise unless corals demonstrate thermal adaptation (Nicholls et al. 2007c in Ebi et al 2008). These adverse 

16 impacts are expected to increase in severity as the global mean annual temperature increases. 

17 IPCC (2007) and EPA (2009b) state that sea level will likely rise 0.19 to 0.58 meter (0.6 to 1.9 

18 feet) by 2100. However, this estimate does not fully account for effects from loss of land-surface ice 

19 flowing into the ocean; it might also underestimate ice losses from the Greenland and Antarctic ice sheets 

20 (Pfeffer et al. 2008, Meier et al. 2007 in Kundzewicz et al 2007, Rahmstorf 2007, Shepherd and 

21 Wingham 2007); and it does not account for adjustments to water volume due to changes in global 

22 precipitation (Wentz et al. 2007, Zhang et al. 2007). Recent studies that account for some of these effects 

23 indicate that sea-level rise might be even higher. For example, Pfeffer et al. (2008) estimates sea level 

24 could rise 0.8 to 2.0 meters (2.6 to 6.6 feet) by 2100 compared to present day, while Rahmstorf (2007)

25 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 

26 to 1990 levels. None of these studies account for the potential complex changes in ocean circulation that 

27 could further influence sea-level rise. 

28 Complete melting of the Greenland ice sheet could occur from a sustained summertime warming 

29 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), 

30 which would exacerbate coastal sea-level rise (Hu et al. 2009). This scenario raises concern regarding the

31 viability of coastal communities, salt marshes, corals, and mangroves. A sea-level rise of about 36 

32 centimeters (14 inches) from 2000 to 2080 is projected to reduce coastal wetlands by 33 percent, with the 

33 largest impact on the Atlantic and Gulf of Mexico coasts of the Americas, on the Mediterranean, on the

34 Baltic, and on small-islands (Nicholls et al. 2007c in Ebi et al 2008). 

35 IPCC SRES estimated that the coastal population could grow from 1.2 billion people in 1990 to 

36 between 1.8 billion and 5.2 billion people by the 2080s, with this range dependent on coastal migration. 

37 Although the impact of sea-level rise on a specific region can be difficult to quantify given regional and 

38 local variations (Parry et al. 2007), the IPCC describes the following coastal regions as the most 

39 vulnerable to the impact of climate change: South Asia, Southeast Asia, East Asia, Africa, and small 

40 islands (Nicholls et al. 2007c in Ebi et al 2008). 

41 Many of the coastal cities that are most vulnerable to adverse impacts of climate change are at 

42 further risk due to human activities such as agriculture, aquaculture, silviculture, industrial uses, and 

43 residential uses that have degraded the natural protective qualities of the coastal systems (Nicholls et al.

44 2007c in Ebi et al 2008). Examples of coastal countries at risk for shoreline retreat and flooding due to 

45 degradation associated with human activity include Thailand (Durongdej 2001, Saito 2001, both in 

46 National Science and Technology Council 2008); India (Mohanti 2000 in National Science and 
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1 Technology Council 2008); Vietnam (Thanh et al. 2004 in National Science and Technology Council 

2 2008); and the United States (Scavia et al. 2002 in National Science and Technology Council 2008), with 

3 emphasis on the seven Asian megadeltas that have a combined population of more than 200 million 

4 (Nicholls et al. 2007c in Ebi et al 2008). Of particular concern are those highly populated coastal regions 

5 in countries with limited financial resources to protect or relocate its populations (Nicholls et al. 2007c in 

6 Ebi et al 2008). 

7 Small islands are particularly vulnerable to climate change and sea-level rise, especially those 

8 prone to subsidence (Parry et al. 2007). Beach erosion is projected to increase as sea level rises and sea 

9 water temperature increases. Arctic islands could experience increased erosion and volume loss as 

10 permafrost and ground ice warms in response to rising global temperatures (Mimura et al. 2007). Coastal 

11 stability in the Arctic is influenced by a combination of factors, including shoreline exposure, relative sea12 level change, local geology, temperatures, ground ice, and sea ice (EPA 2009b). Rising temperatures 

13 melt sea ice and create more open water, wind and waves thereby increasing shoreline erosion. This 

14 dynamic process is exacerbated by relative sea-level rise and thawing of permafrost (EPA 2009b). 

15 Changes in Sea Ice and Ocean Warming

16 Annual average temperature in the Arctic has increased at twice the rate of the rest of the world, 

17 and additional warming of 4 to 7 °F is expected over the next century. The stronger warming is primarily 

18 a result of the positive feedback due to decreased surface albedo as sea ice is lost (EPA 2009b). Annual 

19 average Arctic sea ice extent decreased 2.7 +/− 0.6 percent per decade from 1978 to 2005. In 2007, sea 

20 ice extent was approximately 23 percent less than the previous all-time minimum observed in 2005. 

21 Average sea ice thickness in the central Arctic very likely has decreased up to approximately 3 feet from 

22 1987 to 1997 (EPA 2009b). Recent results indicate that summer Arctic sea ice could be gone as early as 

23 2037 (Wang and Overland 2009). Sea ice dynamics are nonlinear and many thermodynamic processes 

24 will affect potential threshold behavior (Eisenman and Wettlaufer 2009). 

25 Ocean warming and sea-ice decline is leading to a change from arctic to subarctic conditions in 

26 the northern Bering Sea. This is having significant impacts on Arctic sea-ice ecosystems. Phytoplankton 

27 (algae) that form the base of the Arctic food web bloom on the underside of sea ice. The timing and 

28 distribution of plankton blooms are regulated by the ice edge in spring, and as the extent and location of 

29 the ice edge changes with warming sea surface temperatures, the timing of blooms change. This leads to 

30 more consumption at the surface by zooplankton and less organic material reaching the sea bed. As a 

31 result, there is a decline in benthic production of clams and other small mollusks and crustaceans, which 

32 are the food source for many bottom-feeding sea ducks and marine mammals, including walrus and gray 

33 whales. (Janetos et al. 2008) 

34 As a result of these dynamics, the trend toward more subarctic ecosystem conditions in the 

35 northern Bering Sea is contributing to declines in Arctic marine mammal and diving seabird populations, 

36 and in commercial and subsistence fisheries (Grebmeier et al. 2006). In other ocean basins, there is 

37 evidence of changes in important prey species of zooplankton, with resulting food-web changes. For 

38 example, in the North Atlantic the distribution of warm-water copepods (aquatic crustaceans) has shifted 

39 north by 10° latitude as a result of a change in the North Atlantic Oscillation and climate (Beaugrand et 

40 al. 2002a). In the southwest Atlantic, the distribution of emperor and Adelie penguins, which depend on 

41 ice habitat, has shifted to the north and contracted (Forcada and Trathan 2009 in Easterling et al 2007). 

42 Positive impacts anticipated to be experienced in high latitudes include a longer tourist season 

43 and better navigability (Mimura et al. 2007). 
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1 4.5.6 Food, Fiber, and Forest Products 

2 This section defines food, fiber, and forest product resources and the existing conditions and 

3 potential vulnerability of each to the impacts of climate change. The primary source of information in 

4 this section is the IPCC Fourth Assessment Report (Easterling et al. 2007), specifically, Chapter 5 for 

5 food, fiber, and forest products. 

6 The food, fiber, and forest sector is a substantial source of livelihood and food for large numbers 

7 of the world’s population and a major land cover type at a global level. Cropland, pasture, or natural 

8 forests account for approximately 70 percent of Earth’s land cover. The United Nations Food and 

9 Agriculture Organization (FAO) estimates that approximately 450 million of the world’s poorest people 

10 depend entirely on this sector for their livelihood (Easterling et al. 2007). 

11 According to IPCC, this sector includes agriculture, forestry, and fisheries and the IPCC describes 

12 the climate-change impacts to these systems and their capacity to provide food and sustenance for human 

13 consumption. This sector also includes subsistence and smallholder agriculture, defined as rural 

14 producers who farm or fish primarily with family labor and for whom this activity provides the primary

15 source of income (Easterling et al. 2007). 

16 4.5.6.1 Affected Environment 

17 An estimated 40 percent of Earth’s land surface is used for cropland and pasture (Foley et al.

18 2005 in Easterling et al. 2007). The FAO estimates that natural forests cover another 30 percent of the 

19 land surface, and that 5 percent of that natural forest area generates 35 percent of global timber production 

20 (FAO 2000 in Easterling et al. 2007). Almost 70 percent of people in lower-income countries around the 

21 world live in rural areas where agriculture is the primary source of livelihood. Growth in agricultural 

22 incomes in developing countries fuels the demand for non-basic goods and services fundamental to 

23 human development. The FAO estimates that the livelihoods of roughly 450 million of the world’s 

24 poorest people depend entirely on managed ecosystem services. Fish provide more than 2.6 billion 

25 people with at least 20 percent of their average per-capita animal protein intake, but 75 percent of global 

26 fisheries are fully exploited, overexploited, or depleted (FAO 2004 in Easterling et al. 2007). 

27 4.5.6.1.1 Terrestrial Systems 

28 The distribution of crop, pasture, and forest species between the polar and equatorial latitudes is a 

29 function of existing climatic and atmospheric conditions, and a function of photoperiod. Agricultural, 

30 pastoral, and forestry systems depend on total seasonal precipitation and its pattern of variability, and on 

31 wind and humidity. Crops exhibit threshold responses to their climatic environment, which affect their 

32 growth, development, and yield (Porter and Semenov 2005 in Easterling et al. 2007). Short-term natural 

33 extremes, such as storms and floods, interannual and decadal climate variations, and large-scale 

34 circulation changes, such as ENSO, all have important effects on crop, pasture, and forest production 

35 (Tubiello 2005 in Easterling et al. 2007). 

36 For example, Europe experienced a particularly extreme climate event during the summer of 

37 2003, with temperatures up to 6 °C (11 °F) above long-term means, and precipitation deficits up to 12 

38 inches (Trenberth et al. 2007 in Easterling et al. 2007). Associated with this extreme climate event was a 

39 decline in corn yield of 36 percent in the Po River valley in Italy and 30 percent in France. In addition, 

40 French fruit harvests declined by 25 percent, winter wheat yields declined by 21 percent, and hay and 

41 other forage production declined by an average of 30 percent (Ciais et al. 2005 in Easterling et al. 2007). 

42 The impacts to the terrestrial biosphere (e.g., increased tree death) could increase due to the lag effect of 

43 the heat wave in the years following an extreme event (Heimann and Reichstein 2008). African droughts
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1 between 1981 and 1999 caused livestock mortality from 20 percent to more than 60 percent in countries 

2 such as Botswana, Niger, Ethiopia, and Kenya (Easterling et al. 2007). 

3 Total forest productivity might rise modestly, with considerable global variation, due to extended 

4 growing seasons and elevated CO2 concentrations. Nitrogen deposition and warmer temperatures have 

5 likely increased forest growth in locations not water limited. For example, in regions that are historically 

6 limited by low temperatures and short growing seasons, forest growth seems to be slowly accelerating 

7 (less than 1 percent per decade). Conversely, growth is slowing in areas subject to drought. For example, 

8 in the southwestern United States, growth rates have decreased since 1895, correlating to drought caused 

9 by warming temperatures. Similarly, increased drought stress has lowered the growth of white spruce on 

10 Alaska’s dry south-facing slopes (EPA 2009b). 

11 Wildfires have been increasing in some areas, limiting forest productivity. The wildfire season in 

12 the western United States has increased by 78 days in the last 3 decades. Burn durations of large fires 

13 (more than 2,470 acres) has increased from 7.5 to 37.1 days due to an increase in spring and summer 

14 temperatures of 1.4 °F (EPA 2009b). 

15 Overall, climate change might benefit crop and pasture yields in mid- to high-latitude regions, 

16 while decreasing yields in dry and low-latitude regions. Local extinctions of fish species are expected, 

17 particularly at the edges of habitat ranges (Easterling et al. 2007). 

18 Agricultural and forest lands are experiencing multiple stresses that increase their vulnerability to 

19 climate-change impacts. Examples include soil erosion, salinization of irrigated areas, overgrazing, over20 extraction of groundwater, loss of biodiversity, and erosion of the genetic resource base in agricultural, 

21 forest, and pasture areas. Overfishing, loss of biodiversity, and water pollution in aquatic areas are 

22 stresses that increase the vulnerability of fishery resources to climate-change impacts(Easterling et al.

23 2007). 

24 The vulnerability of these resources depends on both the exposure to climate conditions and 

25 capacity to cope with changing conditions. Exposure to conditions highly depends on local geography 

26 and environment. Adaptive capacity is dynamic and depends on wealth, human capital, information and 

27 technology, material resources and infrastructure, and institutions and entitlements (Easterling et al.

28 2007). 

29 Sub-Saharan Africa offers one example of a region that is highly vulnerable to food insecurity 

30 (Vogel 2005 in Easterling et al. 2007). Drought conditions, flooding, and pest outbreaks are some of the 

31 existing stressors on food security that could be influenced by future climate change. Options for 

32 addressing food insecurity in this region (and overall development initiatives related to agriculture,

33 fisheries, and forestry) could be constrained by health status, lack of information, and ineffective 

34 institutional structures. These constraints could limit future adaptations to periods of heightened climate 

35 stress (Reid and Vogel 2006 in Easterling et al. 2007). 

36 4.5.6.1.2 Aquatic Systems 

37 Spatial adaptation of marine ecosystems to climate change is in some ways less geographically 

38 constrained than for terrestrial systems. The rates at which planktonic ecosystems have shifted their

39 distribution have been very rapid over the past 3 decades, which can be regarded as natural adaptation to a 

40 changing physical environment (Beaugrand et al. 2002b in Easterling et al. 2007). Most fishing 

41 communities use stocks that fluctuate due to interannual and decadal climate variability, and consequently 

42 have developed considerable coping capacity (King 2005 in Easterling et al. 2007). 
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1 Research on the relationship between water temperature and the health of freshwater fishes 

2 indicates different impacts in summer and winter. Although temperature increases might cause seasonal

3 increases in growth in winter, mortality risks to fish populations occur at the upper end of their thermal 

4 tolerance zone in summer. 

5 World capture production of finfish and shellfish in 2004 was more than twice that of 

6 aquaculture, but since 1997, capture production decreased by 1 percent whereas aquaculture increased by 

7 59 percent (Easterling et al. 2007). The increasingly important aquaculture sector allows for the 

8 application of similar types of management adaptations to climate change suggested for crop, livestock, 

9 and forestry sectors. This is not the case, however, for marine capture fisheries, which are shared 

10 resources subject to varying degrees of effective governance. Adaptation options for marine capture 

11 fisheries include altering catch size and effort. Three-quarters of world marine fish stocks are exploited at 

12 levels close to or above their productive capacity (Bruinsma 2003 in Easterling et al. 2007). Reductions 

13 in level of effort and harvest are required to sustain yields. Such a course of action might also benefit fish 

14 stocks that are sensitive to climate variability when their population age-structure and geographic 

15 substructure are reduced (Brander 2005 in Easterling et al. 2007). 

16 4.5.6.2 Environmental Consequences 

17 Earth’s land surface is composed mostly of managed cropland and pasture (40 percent) and 

18 natural forests (30 percent) (Foley et al. 2005 in Easterling et al. 2007). These sectors provide important 

19 commodities that are produced in a variety of geographic and climatic regions (CCSP 2008c). Continued

20 growth and productivity of the world’s agriculture and forests is necessary to sustain human economic 

21 and social development. 

22 The discussion below focuses on impacts to food and industrial crops, fisheries, agricultural 

23 pastures, commercial forestry, and subsistence farming (Easterling et al. 2007). The key drivers for 

24 climate impacts in this sector are higher temperatures, changed precipitation and transpiration dynamics, 

25 the effects of increased CO2 concentrations on vegetative growth and yield, greater frequency in extreme 

26 weather events, and increased stressors to forests and agriculture in the form of pests and weeds 

27 (Easterling et al. 2007). 

28 The world’s food crops, forests, and fisheries have evolved to be in tune with the present climatic 

29 environment. The productivity of these systems ultimately relies on the interaction of various climate 

30 factors, including temperature, radiation, precipitation, wind speed, and water vapor pressure (Easterling 

31 et al. 2007). Threshold climatic conditions for crops and forests affect their growth and yield, and 

32 climatic conditions and their interaction influence the global distribution of agricultural and forest species 

33 (Porter and Semenov 2005 in Easterling et al. 2007). Extreme weather events, including droughts and 

34 intense rainfall episodes, can adversely impact crop yields due to the increases and decreases of water 

35 associated with these events (CCSP 2008c). 

36 The sensitivity to climate change and exposure to various other stressors increases the 

37 vulnerability of the forest, food, and fiber systems (Easterling et al. 2007). Non-climate stressors such as 

38 soil erosion, overgrazing, loss of biodiversity, decreased availability of water resources, increased 

39 economic competition among regions, and the adaptive capacity of various species increase overall 

40 sensitivity to the climate and thus exacerbate the adverse effects of climate change (CCSP 2008c). 

41 Climate change could also benefit agriculture and silviculture through the CO2 fertilization effect. 

42 CO2 is essential for plant growth; some research suggests that higher atmospheric concentrations lead to 

43 higher productivity of some food, fiber, and forest crops. Milder winters and longer growing seasons 

44 could also increase productivity in some regions. 
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1 Important examples that highlight the link between large-scale climate changes and the sensitivity 

2 of the food, fiber, and forest systems include the effects of ENSO, a relatively well-known phenomenon, 

3 on crop yield. In Australia, during ENSO years there is increased probability of a decline in farmers’ 

4 incomes by as much as 75 percent below the median income compared to non-ENSO years (Tubiello 

5 2005 in Easterling et al. 2007). Another example is the extreme heat wave that occurred in Europe in 

6 2003, which lowered maize yield by 36 percent in Italy and 30 percent in France (Ciais et al. 2005 in 

7 Easterling et al. 2007). Uninsured losses for the entire European Union agriculture sector were estimated 

8 at 13 billion euros; 4 billion euros was lost in France alone (Sénat 2004 in Easterling et al. 2007). 

9 In the United States, particularly in the north, the average increase in temperature is expected to 

10 lead to a longer growing season. However, temperature increases could also lead to increased sensitivity 

11 to climate change in the southeast and the corn belt (Carbone et al. 2003 in National Science and 

12 Technology Council 2008). The Great Plains region is not expected to experience increased sensitivity to 

13 climate change (Mearns et al. 2003 in National Science and Technology Council 2008). 

14 The most recent comprehensive and peer-reviewed literature about global climate impacts on the 

15 food and forestry sectors is from the IPCC Fourth Assessment Report. The SAP 4.3 Report (CCSP 

16 2008c) provides an additional source of information on the impacts of climate change on agriculture, land 

17 resources, and biodiversity in the United States. Most of the evidence cited in this section focuses on the 

18 results of the IPCC Fourth Assessment Report and SAP 4.3 (CCSP 2008c). Additionally, this section 

19 includes information from EPA (EPA 2009b). However, because new evidence is continuously emerging 

20 on the subject of climate-change impacts on the agriculture and forest systems, the discussion below also 

21 draws on results reported in more recent studies. 

22 4.5.6.2.1 Projected Impacts of Climate Change for the United States 

23 Forests

24 In the United States, the combination of human management and temperate climate has resulted 

25 in a productive and healthy forest system, as exemplified by the southern pine plantations (CCSP 2000). 

26 Forests are generally considered the most productive of the terrestrial ecosystems and provide important 

27 commodities like timber products. They are also key biodiversity sanctuaries and providers of ecosystem 

28 services. Forests cover roughly one third of the land in the United States. Net growth of these forests 

29 (growth minus removals minus decomposition) accounts for removing about 910.7 MMTCO2 per year 

30 from the atmosphere, about 12.7 percent of gross national GHG emissions (EPA 2009a). Globally, 

31 forests account for the largest fraction of terrestrial ecosystem sequestered carbon, estimated to be 

32 roughly 1,640 petagrams (3,615 trillion pounds) of carbon (Sabine et al. 2004 in CCSP 2008c). Climate 

33 change could directly affect the ability of forests to provide key services and commodities in several

34 ways. 

35 Overall, forest productivity could increase through the CO2 fertilization effect, the warming of 

36 colder climates associated with increased CO2 concentrations, and increased precipitation, especially in 

37 arid regions (EPA 2009b). Forest growth in North America will likely increase between 10 and 20 

percent throughout the 21st 38 Century, but with noticeable variation both temporally and regionally (EPA 

39 2009b). The expected productivity benefits from increased CO2 concentrations can be counteracted by 

40 water shortages and drought, which in turn are affected by increased nitrogen deposition rates and ozone 

41 concentrations (Malmsheimer et al. 2008). Additionally, new studies indicate that the direct CO2

42 fertilization effect on tree growth is less than previously believed (EPA 2009b). 

43 One key impact of climate change is the extended risk and increased burn area of forest fires 

44 coupled with pathogenic stressors that damage fragile forest systems (EPA 2009b). It is projected that the 
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1 forest fire season (summer) could be extended by 10 to 30 percent as a result of warmer temperatures 

2 (Parry et al. 2007). In the western states, the anticipated warmer spring and summer temperatures are 

3 expected to reinforce longer fire seasons and increased frequency of large wildfires. In turn, the carbon 

4 pools within forests are expected to be affected by changes in forest composition and reduced tree 

5 densities (Westerling et al. 2006 as cited in CCSP 2008b). 

6 More specifically, the Hadley and Canadian climate and ecological models project an increase in 

the fire season hazard by 10 percent in the 21st 7 Century in the United States, with small regional decreases 

8 in the Great Plains and a 30-percent increase in Alaska and the Southeast (CCSP 2000). Highlighting the 

9 geographic differences even within a state, two climate models (the Geophysical Fluid Dynamics 

10 Laboratory model and the Parallel Climate Model) were run using “business as usual” (A2) and 

11 “transition to a low GHG emissions” (B1) IPCC SRES emissions scenarios. The results showed increases 

12 in fire risk in Northern California (15 to 90 percent), increasing with temperature, whereas, in Southern 

13 California, the change in fire risks ranged from a decrease of 29 percent to an increase of 28 percent. 

14 These results were largely driven by differences in precipitation between the different scenarios. In

15 Southern California the drier conditions simulated in both the Geophysical Fluid Dynamics Laboratory 

16 model scenarios led to reduced fire risks in large parts of southern California, with fire risks increased in 

17 parts of the San Bernardino Mountains (Westerling and Bryant 2006). 

18 Historical evidence indicates that the warmer periods in the past millennium correlated with 

19 increased frequency in wildfires, particularly in western forests (CCSP 2008c). General circulation 

20 models project increased wildfire activity in the western states, particularly from 2010 through 2029 

21 (Flannigan et al. 2000, Brown et al. 2004a, both in CCSP 2008c). In 2060, models have projected forest 

22 fire severity increases of 10 to 30 percent in southeastern states and 10 to 20 percent in northeastern states 

23 (Flannigan et al. 2000 in CCSP 2008c). Some models have projected even larger increases in wildfire 

24 activity, particularly in the southeastern region of the United States (Bachelet et al. 2001a in CCSP 

25 2008c). Potential losses to North American producers from increased disturbances (including wildfires, 

26 insects, and diseases) coupled with climate-change impacts have been estimated to range from $1 to $2 

billion per year averaged throughout the 21st 27 Century (Sohngen and Sedjo 2005 in Field et al. 2007). 

28 Ancillary consequences of the projected increase in wildfire frequency across the United States 

29 include an increase in GHG emissions and criteria air pollutant emissions. Although the GHGs released

30 through wildfires could eventually be sequestered by forest regrowth, this carbon release might not be

31 fully recovered in the short term and thus might be an important source of CO2 in the atmosphere 

32 (Kashian et al. 2006 in CCSP 2008c). Particularly in forests in the western United States, “If wildfire 

33 trends continue, at least initially this biomass burning will result in carbon release, suggesting that the 

34 forests of the western United States could become a source of increased atmospheric carbon dioxide 

35 rather than a sink, even under a relatively modest temperature increase scenario” (Westerling et al. 2006 

36 as cited in CCSP 2008b). 

37 Invasive Species 

38 The increasing occurrence of forest fires, which is likely to continue with projected warming 

39 temperatures, would impact ecosystem services, reduce the potential for carbon storage via forest 

40 management, and provide increased potential habitat for invasive species and insect outbreaks (Parry et 

41 al. 2007). 

42 Because invasive species and pests are not constrained by the need for pollinators or seed 

43 spreaders, these species are more adaptable to the warming climate (Vila et al. 2007 in CCSP 2008c). 

44 The northward movement of weed species, especially invasive weeds, is likely to be a result of higher 

45 projected temperatures and increased CO2 concentration. This movement northward could further be 
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1 accelerated, because some studies that have shown that the responsiveness of weeds to glyphosate, an 

2 important herbicide used in the United States, diminishes with increases in CO2 concentration levels 

3 (Ziska et al. 1999 in CCSP 2008c). 

4 Disease and Pathogens

5 Warming temperatures might be allowing for the migration of diseases and pathogens (CCSP 

6 2008c). More specifically, increases in temperature are influencing the development of insect lifecycles, 

7 reducing winter mortality rates (EPA 2009b) and “influence[ing] synchronization of mass attacks required 

8 to overcome tree defenses” (Ryan et al. 2008b in CCSP 2008). EPA (2009) states that the impacts of 

9 climate change on North American commercial forestry are likely to be sensitive to changes in 

10 disturbances from insects and diseases. 

11 Warming trends in the United States have already allowed for earlier spring insect activity and 

12 increased proliferation of certain species (CCSP 2008c). These warming trends have also allowed for an 

13 increase in the survival rates of diseases and pathogens that affect crops and plant and animal species. 

14 Recent research has linked rising temperatures to increased outbreaks of the mountain pine beetle, the

15 southern pine beetle, and the spruce beetle (EPA 2009b). Rising temperatures have also been correlated 

16 with the expansion of suitable range for the hemlock wooly adelgid and the gypsy moth (Ryan et al.

17 2008b in CCSP 2008). Not only are the boundaries of insects being shifted by climate change, but “tree 

18 physiology and tree defense mechanisms” are being altered (Kirilenko and Sedjo 2007). The damage to 

19 forests is expected to depend on seasonal warming − increases in winter and spring temperatures might 

20 increase losses to insects such as the southern pine beetle (Gan 2004 in Field et al. 2007). 

21 In the western United States, particularly in Colorado, a recent measurable decline in aspen trees 

22 has been linked to global warming. Unlike earlier episodes of aspen tree dieback, the current decline is 

23 occurring more rapidly and over larger areas. The dieback is caused by bark beetles that were not known 

24 to have existed in the area (Saunders et al. 2008). In effect, “the hotter, drier conditions recently present 

25 in Colorado’s mountains have enabled these unexpected agents to so quickly kill so many aspen” 

26 (Saunders et al. 2008). The forest disturbances such as insect outbreaks “are increasing and are likely to 

27 intensify in a warmer future with drier soils and longer growing seasons” (Field et al. 2007c in Saunders 

28 et al. 2008). The control of increased insect populations, especially in the projected warmer winters and 

29 in the southern regions, might require increased applications of insecticides. It is important to control 

30 these insect populations because of their ability to spread other pathogens, especially the flea beetle, 

31 which is known to be a conduit for the corn damaging bacterium Stewart’s Wilt (CCSP 2008c). 

32 Migration

33 Under future climate-warming scenarios, plant and animal species are expected to shift northward 

34 and to migrate to higher elevations, thus redistributing North American ecosystems (Parry et al. 2007). 

35 The projected increases in precipitation over dry regions might encourage forest growth and displace 

36 some grasslands (CCSP 2008c). Recent bioclimate modeling indicates that over the long term the 

37 diversity of tree species in the Northwest will increase while in the Southwest tree species richness will 

38 decrease. However, the benefit of increased diversity of species in the North over the long term might 

39 lead to decreases in the short term because migration of new species northward might be slower than the 

40 disappearance of species who have not adapted to local conditions (EPA 2009b). 

41 As an example of species migration as a result of climate change, the United States has 

42 experienced an incursion of perennial herbaceous species that limit the soil moisture available for other 

43 crops throughout the growing season (CCSP 2008c). The invasion of these non-native species could 

44 impact how these regions adapt to climate change and could lead to the potential for more frequent 
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1 wildfires by increasing vegetation density (Fenn et al. 2003 and Wisdom et al. 2005 both in CCSP 

2 2008c). As another example, aspen trees in Colorado have been encroaching on the more cold-tolerant 

3 spruce-fir forests over the past century (EPA 2009b). Additionally, certain habitats like the mountain 

4 forests are losing ground due to lowland encroachment and high-altitude habitat loss as a result of 

5 warming (EPA 2009b). 

6 A marked change in forest composition and distribution has been noted in Alaska, as indicated by 

7 a northward migration of the subarctic boundary tree line by 6 miles, and the displacement of 2 percent of 

8 the Alaskan tundra in the past 50 years (EPA 2009b). Also, as evidenced by remote sensing analysis, the 

9 growing season is increasing in length by roughly 3 days per decade (CCSP 2008c). Arctic vegetation is 

10 expected to shift northward and cause forests to overtake tundra (EPA 2009b). 

11 Crops and Agriculture 

12 The agriculture sector in the United States is vulnerable to climate change due to the many factors 

13 that affect crops and agriculture, including the availability of water resources, the adaptive capacity of the 

14 agricultural sector, technological improvements in farming practices, economic competition, and existing 

15 climate and soil conditions (EPA 2009b). 

16 In the early part of the 21st Century, moderate climate change could increase crop yields on 

17 agricultural land by 5 to 20 percent (Easterling et al. 2007). However, this increase would depend on 

18 crops that rely on already highly utilized water resources (Parry et al. 2007). Crops that are near the 

19 threshold of their productive temperature range (i.e., crops that are “near the warm end of their suitable 

20 range”), such as wine grapes in California, are expected to decrease in yield or quality based on moderate 

21 climate-change scenarios (EPA 2009b). The probability of the loss of popular and recognizable plants 

22 such as saguaro cacti and Joshua trees will increase because temperature increases will increasingly affect 

23 the reproductive development of various crops, particularly in arid regions (CCSP 2008c). 

24 Grain crops in the United States are likely to initially benefit from the increased temperature and 

25 CO2 levels. However, as temperatures continue to rise, sensitivity of these grain crops could increase. 

26 This sensitivity is expected to an even greater extent for horticultural crops such as tomatoes and onions, 

27 compromising their productive yield (CCSP 2008c). Various studies have found differing thresholds for

28 maize production in the United States, with one in particular showing a 17-percent reduction of maize 

29 yield per 1 °C (1.8 °F) increase in temperature (Lobell and Asner 2003 in CCSP 2008c). Other crops, 

30 such as wheat, are regionally and temporally dependent. Studies show that wheat yield in the Great 

31 Plains “is estimated to decline 7 percent per 1 °C increase in air temperature between 18 and 21 °C [50 

32 and 53 °F] and about 4 percent per 1 °C increase in air temperature above 21 °C” (Lobell and Field 2007 

33 in CCSP 2008c). Similarly, rice yields are projected to decline about 10 percent per 1 °C increase for 

34 temperature profiles that are above current summer mean air temperatures (CCSP 2008c). 

35 Using an assumed 1.2 °C (2.2 °F) warming over the next 30 years, maize, wheat, sorghum, and 

36 dry bean yields are projected to each decrease by 4.0 to 9.4 percent in their major production areas of the 

37 United States. Soybean yield, on the other hand, is projected to increase 2.5 percent in the Midwest. 

38 However, crop yields in the South will likely decrease. (EPA 2009b) 

39 In the Great Lakes region, fruit production might benefit from climate change, although there 

40 might be increased risk of winter thaws and spring frost (Bélanger et al. 2002, Winkler et al. 2002, both 

41 in Field et al. 2007). In New Jersey, higher summer temperatures are expected to depress the yields of a 

42 number of other economically important crops adapted to cooler conditions (e.g., spinach, lettuce) by 

43 mid-century, while rising winter temperatures are expected to drive the continued northward expansion of 

44 agricultural pests and weeds (such as kudzu) (Frumhoff et al. 2007). Cranberries are especially 
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1 susceptible because of their requirement to be subjected to long periods of cold winter temperatures for 

2 development (Frumhoff et al. 2007). 

3 Climate changes could result in significant impacts to irrigation needs. Decreased rainfall, 

4 increased evaporation from higher temperatures, and longer growing seasons can all increase irrigation

5 needs. Recent studies indicate that by 2030, changes in irrigation requirements could range from -1 to 

6 +451 percent for corn in the United States. Overall, irrigation requirements in the U.S. are projected to 

7 increase by 35 to 64 percent (EPA 2009b). 

8 Agriculture could also be affected by the impact of climate change on pests and weeds. Warming 

9 trends have in some cases led to earlier spring activity and proliferation of some species. Warmer winters 

10 also might allow for higher survival rates of pathogens and parasites. Further, weeds might respond more 

11 favorably to elevated CO2 levels than cash crops. However, further research is needed on this topic 

12 before conclusions can be drawn on the effects of elevated CO2 levels on pests and weeds (EPA 2009b). 

13 Extreme Weather Events 

14 The negative impacts of increased frequency of extreme weather events on crop yield might 

15 temper the beneficial effects of increased CO2 concentrations (CCSP 2008c). Extreme weather events, 

16 including droughts and intense rainfall episodes, might adversely impact crop yields due to the increases 

17 and decreases of water associated with these events (CCSP 2008c). 

18 Multi-year droughts, which could have been a result of increased temperature conditions in 

19 lower-elevation forests in the southwestern region, have had a large impact on forest mortality rates 

20 (Breshears et al. 2005 in CCSP 2008c). The mortality rate continued to increase even though growth at 

21 the forest tree line had been increasing previously (Swetnam and Betancourt 1998 in CCSP 2008c). 

22 Forest productivity has decreased from climate change-induced warming in drought-prone regions 

23 (McKenzie et al. 2001 in CCSP 2008c) and in subalpine regions (Monson et al. 2005, Sacks et al. 2007, 

24 both in CCSP 2008c). Droughts are more prevalent in the western U.S. but the East could also be 

25 affected by drought and the associated reductions in water supply (EPA 2009b). 

26 Intense rainfall events will also cause crop losses via soil compaction and increased susceptibility 

27 to root diseases. Intense rainfall also causes more runoff and leaching. In turn, this will delay spring 

28 planting for crops, which influences economic profits of the agriculture sector (EPA 2009b). Surface 

29 waters could be inundated by sediments, pathogens, and pesticides as increased runoff from crop fields

30 and animal agriculture operations result from intense rainfall events (EPA 2009b). 

31 Livestock

32 The livestock production infrastructure in the United States is likely to be influenced by the 

33 climate-change-induced distributional and productivity changes to plant species. Livestock production

34 during the summer season would very likely be reduced due to higher temperatures, but livestock 

35 production during winter months could increase, again due to the projected increase in temperatures 

36 (CCSP 2008c). 

37 The expected elevated CO2 concentrations could diminish the quality of grass feed. An increase 

38 in the carbon-to-nitrogen ratio would decrease the nutritional value of feed. In turn, grazing livestock that 

39 feed on lower-quality grasses might be affected in terms of decreased weight and health (EPA 2009b). 

40 For example, an experiment conducted on shortgrass prairie found that increased CO2 concentrations 

41 reduced the protein concentration, which in turn reduced the digestibility of forage by 14 percent in mid42 summer (CCSP 2008c). Expected future average climate-change conditions could have less effect on 
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1 livestock productivity and potential livestock loss than the effects of increased weather variability (e.g., 

2 droughts and temperature extremes) (EPA 2009b). 

3 Models of the impact of climate change on agriculture have projected decreases in livestock 

4 productivity in the United States simply due to projected temperature increases. In 2050, such a model 

5 projects an average decrease in swine, beef, and milk production of 0.9 to 1.2 percent, 0.7 to 2.0 percent, 

6 and 2.1 to 2.2 percent, respectively (Frank et al. 2001 in CCSP 2008c). Higher temperatures directly

7 affect animals’ abilities to maintain homeostasis; consequently, livestock must engage in altered 

8 metabolic thermoregulatory processes (Mader et al. 1997, Davis et al. 2003c, both in CCSP 2008c). The 

9 induced thermal stress on livestock often results in a reduction in physical activity and ultimately 

10 diminishes feed intake. Livestock production losses and associated economic losses might be attributed 

11 to increasing temperatures that are “beyond the ability of the animal to dissipate [and] result in reduced 

12 performance (i.e., production and reproduction), health, and well-being” (Hahn et al. 1992, Mader 2003, 

13 both in National Science and Technology Council 2008). However, EPA (2009b) points out that 

14 decreases in livestock production from hotter summers will likely be partly offset by increased production 

15 from warmer winters (EPA 2009b). 

16 The increased temperature expected as a result of climate change could allow for easier migration 

17 of animal pathogens and diseases, especially in the northward transition from the low to mid-latitudes, 

18 which would adversely affect livestock wellbeing in the United States (White et al. 2003, Anon 2006, van 

19 Wuijckhuise et al. 2006, all in CCSP 2008c). 

20 Fisheries

21 Freshwater fisheries are sensitive to changes in water temperature, and to changes in river flows 

22 and lake levels caused by changes in surface water (EPA 2009b). Although fisheries in cold freshwater

23 regions are expected to be adversely affected, fisheries in warm freshwater regions could benefit from

24 climate change (EPA 2009b). The effects of temperature increases have caused northward shifts of 

25 fisheries systems and this is expected to continue in the future (CCSP 2008c). According to IPCC, “many 

26 warm-water and cool-water species will shift their ranges northward or to higher altitudes” (Clark et al.

27 2001, Mohseni et al. 2003, both in Field et al. 2007). It has been observed that Pacific salmon species 

28 have been recently appearing in Arctic rivers (EPA 2009b). 

29 An example of negative impacts that result from large-scale species migration is the recent 

30 migration of two protozoan parasites from the Gulf of Mexico northward into Delaware Bay. This 

31 parasitic incursion, possibly as a result of climate change, has led to a substantially increased mortality 

32 rate of oysters in the region (Hofmann et al. 2001 in CCSP 2008c). 

33 According to IPCC, the survival of brook trout in the United States is directly correlated to the 

34 availability of its preferred cold-water habitat. As temperatures increase, mortality rates also increase for 

35 certain species of trout (EPA 2009b). Other cold-water salmonid species are likely to be negatively 

36 affected by rising temperatures (EPA 2009b). It is likely that other coldwater species could disappear 

37 from all but the deeper lakes; cool-water species will be lost mainly from shallow lakes; and warm-water 

38 species will thrive, except in the far south, where temperatures in shallow lakes will exceed survival

39 thresholds (EPA 2009b). Stocks of the river-spawning walleye will likely decline due to lower lake levels 

40 and climate-change impacts in Lake Erie (Jones et al. 2006 in Field et al. 2007). 

41 Coastal fisheries are also expected to experience the negative impacts of climate change, 

42 including coral reef bleaching, due to increased ocean temperatures (EPA 2009b). In Alaska, the 

43 spawning and migration behaviors of commercially fished species could be affected and increasing 
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1 temperatures might cause an increase in the cooling needs for storage and processing of catch (CIER 

2 2007). 

3 4.5.6.2.2 Projected Global Impacts of Climate Change 

4 Although the preceding section highlights anticipated impacts of climate change in the United 

5 States, there are additional impacts that could affect forest and agriculture systems elsewhere in the world. 

6 Crops

7 Globally, climate change will affect the agriculture and forest sectors. A recent Harvard report on 

8 Climate Change Futures states that a “changing climate will alter the hydrological regime, the timing of 

9 seasons, the arrival of pollinators and the prevalence, extent, and type of crop diseases and pests” (Epstein 

10 et al. 2006). Throughout the mid- to high-latitudinal regions, crop-specific productivity increases are 

11 projected for global mean temperature increases of 1 to 3 oC (1.8 to 5.4 oF). Beyond a 3-oC increase in 

12 global mean temperature, crop productivity is expected to decrease in some regions (Easterling et al.

13 2007). Depending on crop type, experiments on the effects of increased CO2 concentrations (namely, 550 

14 ppm as opposed to existing levels of roughly 380 ppm) suggest that crop yields could increase by 0 to 25 

15 percent (EPA 2009b). In the lower-latitude dry regions, cereal crop productivity is projected to decrease 

16 with temperature increases of 1 to 2 oC (1.8 to 3.6 oF), thereby exacerbating hunger issues for the 

17 population living in these regions (Parry et al. 2007). 

18 In a modest warming climate scenario, adaptive practices such as using various cultivars and 

19 altering planting and harvesting times might maintain cereal crop yields and possibly allow for an 

20 increase in productivity in the high latitudinal and temperate regions (Easterling et al. 2007). The 

21 adaptive practice in regions with 1 to 2 oC temperature increases corresponds to an avoidance of a 10- to 

22 15-percent reduction in yield for cereal crops (Parry et al. 2007). 

23 According to IPCC, the “projected changes in the frequency and severity of extreme climate 

24 events will have more serious consequences for food and forestry production, and food insecurity, than

25 will changes in projected means of temperature and precipitation” (Easterling et al. 2007). The low 

26 latitudinal regions might experience an increase in the frequency of extreme weather events like floods 

27 and droughts, which could adversely affect crop production, especially in subsistence farming regions 

28 (Easterling et al. 2007). Extreme weather events “reduce crop yield and livestock productivity beyond 

29 the impacts due to changes in mean variables alone, creating the possibility for surprises” (Parry et al.

30 2007). The reduced adaptive capacity of small-scale farmers such as subsistence and artisanal fisherfolk 

31 could result in increased vulnerability to extreme weather events, sea-level rise, and the spread of human 

32 disease, which could negatively affect agricultural and fish yields (Parry et al. 2007). Existing climate33 change models do not yet include recent findings on precipitation extremes that are expected to impact

34 agricultural production in areas such as southern Asia, northern Europe, and eastern Australia. These

35 areas are expected to experience an impact on agricultural productivity as a result of projected increased 

36 precipitation extremes such as floods and droughts (Christensen et al. 2007b in Easterling et al. 2007). 

37 Certain crops, such as wheat, are impacted by high precipitation events because wheat is “susceptible to 

38 insects and diseases (especially fungal diseases) under rainy conditions” (Rosenzweig and Hillel 1998 in 

39 Epstein et al. 2006). On the other hand, during droughts, certain fungi, such as Aspergillus flavus, are 

40 stimulated and will feed on drought-weakened crops (Epstein et al. 2006). 

41 Decreases in crop and forest yields in moderate warming scenarios for the low latitudes will 

42 likely result in increased dependence on food imports in these typically the developing countries. As

43 such, agricultural exports to lower latitude countries are likely to increase in the short term (Parry et al.

44 2007). 
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1 There could be a marginal increase in the population at risk of hunger due to climate change, but 

2 this would occur in the context of an overall decrease in the global population at risk of hunger as a result 

3 of anticipated economic development (Parry et al. 2007). 

4 Forests

5 Globally, commercially grown forests for use in timber production are expected to increase 

6 modestly in the short term, depending on geographic region (Easterling et al. 2007). Large regional and 

7 local differences are anticipated, as is a shift in terms of production increase from the lower latitudes to 

8 the higher latitudes (Parry et al. 2007). This poleward shift of forests and vegetation is estimated at 

9 roughly 500 kilometers (about 310 miles) or more for the boreal zones for climate scenarios with CO2

10 concentrations of double present levels (Kirilenko and Sedjo 2007). In terms of distributional production, 

11 net benefits will accrue to regions experiencing increased forest production, whereas regions with 

12 declining activity will likely face net losses (Kirilenko and Sedjo 2007). 

13 Due to increases in CO2 concentration, there is potential for a carbon fertilization effect on the 

14 growth of trees, with some experiments showing up to an 80-percent increase in wood production for 

15 orange trees (Kirilenko and Sedjo 2007). There is evidence to support elevated growth for young, 

16 immature forests in response to higher CO2 concentration levels (Parry et al. 2007). However, free-air 

17 CO2 enrichment experiments indicate that mature forests show no appreciable response to elevated CO2

18 concentrations. However, young, immature forests show elevated growth in response to higher CO2

19 concentrations (Parry et al. 2007). It should be noted that one study regarding forest free-air CO2

20 enrichment of 100-year-old tree stands found little to no enhanced stem growth, but this lack of growth 

21 might be explained by the relative difficulty of controlling for constant CO2 levels (Kirilenko and Sedjo 

22 2007). 

23 Many forest models have projected increases in forest production in certain geographic regions 

24 (with a few exceptions). For example, the Terrestrial Ecosystem Model and the Center for International 

25 Trade in Forest Products Global Trade Model have simulated a future harvest increase of 2 to 11 percent 

26 in western North America, a 10- to 12-percent increase in New Zealand, a 10- to 13-percent increase in

27 South America, and a harvest decrease in Canada (Kirilenko and Sedjo 2007). 

28 It is important to contrast these possible short-term benefits with the negative implications of a 

29 warming climate, because “continued warming favors more fungal and insect of forests, and more harsh 

30 weather will further weaken tree defenses against pests” (Epstein et al. 2006). For example, in Europe the 

31 spruce bark beetle will likely produce more broods more frequently than in the past due to the warmer 

32 climate (Schlyter et al. 2006 in Malmsheimer et al. 2008). The ability of forests to continue to function 

33 as providers of agriculture and energy and sequester carbon will be affected by climate change (Epstein et 

34 al. 2006). Overall, the “effects of future drought and decreased soil moisture on agriculture and natural 

35 vegetation (such as forests) are uncertain and may, at least in part, be temporarily offset by fertilization 

36 effects of higher atmospheric concentrations of CO2” (Triggs et al. 2004 in CIER 2007). These extreme 

37 weather events, in concert with increased damage from insect and pathogen outbreaks and wildfires, 

38 might result in large-scale deforestation, as evidenced by recent trends in the Amazon basin (Kirilenko 

39 and Sedjo 2007). Climate-vegetation models have indicated that at CO2 concentration levels of roughly 

40 three times present levels, the Amazon rainforests will eventually be lost due to climate change (Cox et 

41 al. 2004 in Kirilenko and Sedjo 2007). 

42 Fisheries

43 The aquaculture and fisheries sector is expected to experience negative impacts as a result of the 

44 regional changes in the distribution and proliferation of various marine species (Easterling et al. 2007). 
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1 As the distribution of certain fish species continues to be regionally rearranged, there is the potential for 

2 notable extinctions in the fisheries system, especially in freshwater species, in temperature ranges at the 

3 margin (Parry et al. 2007). Recent evidence indicates that the Meridional Overturning Circulation, which 

4 supplies nutrients to the upper layers of the Pacific and Atlantic Oceans, is slowing and therefore 

5 adversely affecting regional production of primary food supply for fisheries systems (McPhaden and 

6 Zhang 2002, Curry and Mauritzen 2005, Gregg et al. 2003, Lehodey et al. 2003b, all in Easterling et al.

7 2007). In the North Sea, a shift in the distribution of warm-water species such as zooplankton has 

8 resulted in a shift of fish species from whiting to sprat (Beaugrand 2004 in CCSP 2008c). 

9 The largest economic impacts associated with the fisheries sector as a result of climate change are 

10 expected to occur in coastal regions of Asia and South America (Allison et al. 2005 in CCSP 2008c). 

11 Specifically, regional climate change could most affect species such as tuna and Peruvian anchovy 

12 (Barber 2001, Lehodey et al. 2003a, both in CCSP 2008c). 

13 Earlier spring ice melts in the Arctic and diminishing sea ice are affecting the distribution and 

14 productivity of marine species, particularly the upper-level sea organisms. In turn, fish harvests in the 

15 Arctic region are expected to change in the warming future. Freshwater species in the Arctic region are 

16 expected to be most affected by increasing temperatures (Wrona et al. 2005 in Field et al. 2007). 

17 4.5.7 Industries, Settlements, and Society 

18 This section defines industries, settlements, and society resources and describes the existing 

19 conditions and potential vulnerability of each to climate-change impacts. In addition, this section briefly 

20 describes the potential vulnerability of cultural resources, including archaeological resources and 

21 buildings of historic significance, to climate-change impacts. The primary source for the information in 

22 this section is the IPCC Fourth Assessment Report (Wilbanks et al. 2007), specifically, Chapter 7 for 

23 industry, settlement, and society. 

24 The industries, settlements, and society sector encompasses resources and activities that describe 

25 how people produce and consume goods and services, deliver and receive public services, and live and 

26 relate to each other in society. 

27 As defined by IPCC, this sector includes: 

28 • Industry − manufacturing, transport, energy supply and demand, mining, construction, and 

29 related informal production activities (Wilbanks et al. 2007); 

30 • Services − trade, retail, and commercial services, tourism, risk financing/insurance (IPCC 

31 2007a); 

32 • Utilities/infrastructure − systems designed to meet relatively general human needs, often 

33 through largely or entirely public utility-type institutions (Wilbanks et al. 2007); 

34 • Human settlement − urbanization, urban design, planning, rural settlements (Wilbanks et al.

35 2007); and 

36 • Social issues − demography, migration, employment, livelihood, and culture (Wilbanks et al.

37 2007). 
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1 4.5.7.1 Affected Environment 

2 The industry, settlements, and society sector covers a very broad range of human institutions and 

3 systems, including the industrial and services sectors, large and small urban areas and rural communities, 

4 transportation systems, energy production, and financial, cultural, and social institutions. 

5 A principal objective of human societies is to reduce their sensitivity to weather and climate. 

6 Recent experience with storms such as Hurricane Katrina reveals the limits to human control over 

7 climate-related impacts on industries, settlements, and society. Systems that are sensitive to climate 

8 change include air and water quality, linkage systems (transportation and transmission networks), 

9 building structures, resource supplies, social networks, and economic systems (Wilbanks et al. 2007). 

10 This sector normally experiences and is generally resilient to variability in environmental 

11 conditions. Industries, settlements, and human society, however, can be vulnerable to extreme or 

12 persistent changes. Vulnerability increases when changes are unexpected or if resources or other factors 

13 inhibit the ability of this sector to respond to changes (EPA 2009b). 

14 Together, industry and economic services account for more than 95 percent of gross domestic 

15 product in highly developed economies and between 50 and 80 percent of gross domestic product in less16 developed economies (World Bank 2006 in Wilbanks et al. 2007). Industrial activities are vulnerable to 

17 temperature and precipitation changes. For example, in Canada, weather-related road accidents translate 

18 into annual losses of at least $1 billion Canadian annually, and more than a quarter of air travel delays in 

19 the United States are weather related (Andrey and Mills 2003 in Wilbanks et al. 2007). Buildings, linking 

20 systems, and other infrastructure are often in areas vulnerable to extreme weather events (flooding, 

21 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 22 Century using global and high23 resolution regional climate models. The analysis suggests a future increase in these conditions of 100 

24 percent or more in Atlanta, Georgia, and New York, New York. Such extreme events that can threaten 

25 linkage infrastructures such as bridges, roads, pipelines, or transportation networks could cause industry 

26 to experience substantial economic losses (Wilbanks et al. 2007). In one example of non-storm-related 

27 impacts of climate change to infrastructure, in Russia there have been documented structural failures due 

28 to unusual levels of permafrost thaw from warming trends (EPA 2009b). 

29 Institutional infrastructure is generally considered to be less vulnerable to weather and climate 

30 variation, as it embodies less fixed investment and is more readily adapted within the time scale of 

31 climate change. In some cases, experience with climatic variability can enhance the resilience of 

32 institutional infrastructure by triggering adaptive responses (Wilbanks et al. 2007). 

33 Vulnerability to climate-change impacts is determined by local geography and social context, 

34 rather than by large-scale or aggregate factors (Wilbanks et al. 2007). A trend toward urbanization can 

35 also increase the vulnerability of an area when that urbanization concentrates people in areas at risk for 

36 negative climate-change impacts. Sections 4.5.7.1.1 through 4.5.7.1.3 briefly describe risk factors 

37 associated with local geography, social context, and urbanization. 

38 4.5.7.1.1 Geography 

39 Extreme weather events are more likely to pose risks to industry, settlements, and society than 

40 gradual climate change (Wilbanks et al. 2007). Resources and activities in areas with higher 

41 susceptibility to extreme weather events (high temperatures, high winds, and flooding) are more 

42 vulnerable to the impacts of climate change. The most vulnerable areas are likely to be Alaska, coastal 

43 and river basins susceptible to flooding, arid areas, and areas where the economic bases are climate 
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1 sensitive (EPA 2009b). Extreme weather events can damage transportation routes and other 

2 infrastructure, damage property, dislocate settlement patterns, and disrupt economic activity (EPA 

3 2009b). Gradual climate change can change patterns of consumption, decrease or increase the availability 

4 of inputs for production, and affect public-health needs. Such impacts are experienced locally, but can be 

5 linked to impacts on national and global systems (Wilbanks et al. 2007). 

6 Archaeological resources and buildings of historic significance are fixed in location and are 

7 therefore vulnerable to the effects of extreme weather events and gradual changes associated with local 

8 geography. Extreme weather events can expose archaeological resources and damage structures. Over 

9 time, gradual changes to weather patterns can also erode protective cover around archaeological resources 

10 and increase the rate of deterioration of historic buildings. Vulnerability of these resources to climate11 change impacts is tied to the susceptibility of location and local geography to extreme and gradual 

12 changes to weather. 

13 4.5.7.1.2 Social Context 

14 Worldwide, many of the places where people live are under pressure from a combination of 

15 growth, social inequity, jurisdictional fragmentation, fiscal shortfalls, and aging infrastructure. These 

16 stresses can include scarcity of water, poor sanitation, inadequate governance structures, unmet resource 

17 requirements, economic inequities, and political instability. While these types of stresses vary greatly 

18 across localities, they can combine with climate-change impacts to result in substantial additional stress at 

19 local, national, and global levels (Wilbanks et al. 2007). 

20 The social impacts associated with climate change will be mainly determined by how the changes 

21 interact with economic, social, and institutional processes to minimize or magnify the stresses. From an 

22 environmental justice perspective, the most vulnerable populations include the poor, the very old and very 

23 young, the disabled, and other populations that have limited resources and ability to adapt to changes

24 (EPA 2009b). Environmental justice issues are made apparent as warmer temperatures in urban summers 

25 have more direct impact on those living and working without air conditioning (EPA 2009b). Section 4.6

26 addresses environmental justice. 

27 4.5.7.1.3 Urbanization 

28 It is estimated that one third of the world’s urban population (almost 1 billion people) lives in 

29 overcrowded and unserviced slums, and 43 percent of the urban population is in developing countries. 

30 More generally, human settlements are often situated in risk-prone regions such as steep slopes, ravines, 

31 and coastal areas. These risk-prone settlements are expected to experience an increase in population,

32 urbanized area, and economic activity. The population in the near-coastal zone (i.e., within 330 feet 

33 elevation and 60 to 65 miles distance from the coast) has been estimated to be between 600 million and

34 1.2 billion, or 10 to 23 percent of the world’s population (Adger et al. 2005a, McGranahan et al. 2006, 

35 both in Wilbanks et al. 2007). Migration from rural to urban areas is a common response to calamities 

36 such as floods and famines (Wilbanks et al. 2007). 

37 4.5.7.2 Environmental Consequences 

38 Key climate-change impacts on this set of human systems are likely to vary widely and depend on 

39 a range of location-specific characteristics and circumstances. Moreover, potential climate-change 

40 impacts on this sector could be particularly challenging to determine because effects tend to be indirect 

41 rather than direct. For example, changes in temperature, a direct effect of climate change, affect air 

42 pollution concentrations in urban areas, thereby affecting human health and health care systems. These 

43 are all indirect effects (Wilbanks et al. 2007). The significance of climate-change impacts on human 
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1 systems will largely be determined through its interaction with other processes, driving forces, and 

2 stresses (CCSP 2008d). This type of multi-stress perspective indicates that changes in climate extremes 

3 are very often of more concern than changes in climate averages (EPA 2009b). 

4 The human institutions and systems that comprise the industry, settlements, and society sector 

5 tend to be quite resilient to fluctuations in environmental conditions that are within the range of normal 

6 occurrence. However, when environmental changes are more extreme or persistent, these systems can 

7 exhibit a range of vulnerabilities “especially if the changes are not foreseen and/or if capacities for 

8 adaptation are limited” (Wilbanks et al. 2007). For this reason industry, settlements, and society in 

9 developing countries are expected to be more vulnerable to direct and indirect climate-change impacts 

10 than they are in industrialized countries (Wilbanks et al. 2007). 

11 Climate change is expected to affect industry, settlements, and society via a range of physical 

12 effects, including the frequency and intensity of tropical cyclones and storms, extreme rainfall and floods, 

13 heat and cold waves, drought, temperature extremes, precipitation, and sea-level rise. Following the 

14 approach in Wilbanks et al. (2007), the categories of human systems addressed in this section include 

15 industry, services, utilities and infrastructure, settlements, and social issues. The following paragraphs 

16 describe each category and potential climate impacts on each category. Subsequent sections describe in 

17 more detail key systems within these categories that are expected to experience impacts associated with 

18 climate change. 

19 Industry – This category includes manufacturing, transport, energy supply and demand, mining, 

20 construction, and related informal production activities (Wilbanks et al. 2007). These activities can be 

21 vulnerable to climate change when (a) facilities are in climate-sensitive areas such as coasts and 

22 floodplains, (b) the sector depends on climate-sensitive inputs such as food processing, or (c) the sector 

23 has long-lived capital assets (Ruth et al. 2004 in Wilbanks et al. 2007). For the energy sector, in addition 

24 to possible infrastructure damage or destruction from the effects of climate change (e.g., as could happen 

25 due to extreme weather events) effects could include climate-driven changes in demands for energy. For 

26 example, demand for heating could decline in winter months while demand for cooling could rise in 

27 summer months (CCSP 2008d). 

28 Services – This category includes trade, retail and commercial services, tourism, and risk 

29 financing or insurance (Wilbanks et al. 2007). Possible climate-change impacts on trade include impacts 

30 on transportation from extreme weather events like snow and ice storms that could impede the ability to 

31 transport goods, or impacts on comparative advantage of a region or country due to temperature shifts that 

32 affect production. Climate-change impacts on transportation could also affect retail and commercial 

33 services. Retail and commercial services could also be affected by climatic conditions that affect prices 

34 of raw materials and by potential damage to infrastructure, such as facilities in climate-sensitive areas like 

35 coastal regions. Extreme events such as hurricanes can also affect tourism infrastructure. Tourism 

36 services could also be affected by climate-change impacts through temperature shifts and changes that 

37 affect the natural landscape of tourist destinations. Potential indirect effects of climate change on tourism 

38 include changes in availability of water and energy prices. Regarding the insurance sector, climate39 change impacts could lead to increasing risk, which could trigger higher premiums and more conservative 

40 coverage. A reduction in availability of or ability to afford insurance could in turn lead to impacts on 

41 local and regional economies. 

42 Utilities and infrastructure – This category includes systems that are “designed to meet relatively 

43 general human needs, often through largely or entirely public utility-type institutions” (Wilbanks et al.

44 2007). This includes physical infrastructure such as water, transportation, energy, and communications 

45 systems, and institutional infrastructure such as shelters, public health-care systems, and police, fire, and 

46 emergency services. “These infrastructures are vulnerable to climate change in different ways and to 
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1 different degrees depending on their state of development, their resilience, and their adaptability” 

2 (Wilbanks et al. 2007). In general, institutional infrastructure tends to be less vulnerable to climate 

3 change than physical infrastructure because it typically involves less investment in fixed assets and is 

4 more flexible over timeframes that are relevant to climate change. There are numerous points where 

5 impacts on different infrastructures interact and the failure of one system can put pressure on others. At 

6 the same time, however, “this means that measures to protect one sector can also help to safeguard the

7 others” (Wilbanks et al. 2007). 

8 Human settlement – Climate change interacts with other stresses in its impact on human 

9 settlements (Wilbanks et al. 2007). Potential impacts on human settlements could be experienced through 

10 several pathways. Sea-level rise threatens populations in coastal areas by accelerating the inundation of 

11 coastal wetlands, threatening vital infrastructure and water supplies, augmenting summertime energy 

12 demand, and affecting public health (Wilbanks et al. 2007). Changes in precipitation patterns could alter 

13 the availability of potable water, while changes in temperature could affect air quality and contribute to an 

14 increase in incidents of heat stress and respiratory illnesses (Wilbanks et al. 2007). In urban areas, the 

15 Urban Heat Island effect (Wilbanks et al. 2007), which relates to the “degree to which built and paved 

16 areas are associated with higher temperatures than surrounding rural areas” (National Science and 

17 Technology Council 2008), might affect the manner in which climate change affects these areas. For 

18 example, imbalances in the urban metabolism could aggravate climate-change impacts such as the role of

19 the Urban Heat Index in the formation of smog in cities (CCSP 2008d). 

20 Social Issues – Within human settlements, society could also experience a variety of effects 

21 associated with climate change. For example, communities could experience increasing stress on 

22 management and budget requirements for public services if demands on public health care and disaster 

23 risk reduction grow (CCSP 2008d). There could be a loss of cultural and traditional groups of people,

24 e.g. “indigenous societies in polar regions” (Wilbanks et al. 2007). Societal concerns that might be 

25 affected by the impacts of climate change include socioeconomic issues relating to developed versus 

26 developing areas and rich versus poor. Because the developing countries and poorer populations tend to 

27 have weaker infrastructure in place to begin with, their vulnerability to climate-change impacts is 

28 expected to be higher and their capacity to cope or adapt are expected to be lower than developed 

29 countries and wealthier populations (EPA 2009b). 

30 4.5.7.2.1 Projected Impacts of Climate Change for the United States 

31 The research literature on climate-change impacts on U.S. industry, settlements, and society is 

32 relatively sparse. “At the current state of knowledge, vulnerabilities to possible impacts are easier to 

33 project than actual impacts because they estimate risks or opportunities associated with possible 

34 consequences rather than estimating the consequences themselves” (CCSP 2008d). In general, “climate 

35 change effects on human settlements in the United States are expected to occur as a result of interaction 

36 with other processes” (National Science and Technology Council 2008). These effects include those on 

37 health, water resources, physical infrastructure (notably transportation systems), energy systems, human 

38 settlements, and economic opportunities. 

39 Impacts on human health and human health care systems are expected to arise because of 

40 temperature-related stress. Increases in cases of respiratory illness associated with high concentrations of 

41 ground-level ozone; water-, food-, and vector-borne diseases; and allergies related to higher 

42 concentrations of plant species are expected. 

43 Effects on water are expected to include reductions in snowpack, river flows, and groundwater 

44 levels, saline intrusion in rivers and groundwater, an increase in water demand due to increasing 
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1 temperatures, and impacts on sanitation, transportation, food and energy, and communication 

2 infrastructures from severe weather events. 

3 The U.S. coastline, deltas, and coastal cities such as the Mississippi Delta and surrounding cities, 

4 are vulnerable to sea-level rise. “Rapid development, including an additional 25 million people in the 

5 coastal United States over the next 25 years will further reduce the resilience of coastal areas to rising sea 

6 levels and increase the economic resources and infrastructure vulnerable to impacts” (Field et al. 2007b in 

7 National Science and Technology Council 2008). 

8 Effects on other key human systems are discussed in greater detail below. Because this section 

9 deals with such a broad set of human systems, the potential impacts of climate change and potential 

10 adaptations available to key human systems are discussed together. Given the enormous range of human 

11 systems that could be affected by climate change, the discussion here is focused on a few key systems for 

12 which impacts can best be characterized or supported by sufficient information. 

13 Impacts on Transportation Infrastructure

14 Climate affects the design, construction, operation, safety, reliability, and maintenance of 

15 transportation infrastructure, services, and systems (EPA 2009b). The potential for climate change raises 

16 critical questions about how changes in temperature, precipitation, storm events, sea-level rise, and other 

17 climate variables could affect the system of roads, airports, rail, public transit, pipelines, ports, 

18 waterways, and other elements of the nation’s and the world’s complex transportation systems. 

19 Climate changes anticipated during the next 50 to 100 years include higher temperatures, changes 

20 in precipitation patterns, increased storm frequency and intensity, and rising sea levels globally, resulting 

21 from the warming of Earth’s oceans and decline in polar ice sheets. These changes could affect the 

22 transportation system in a wide variety of ways. The following paragraphs summarize those of greatest

23 relevance for the United States. 

24 • Increases in very hot days and heat waves. It is very likely that heat extremes and heat waves

25 will continue to become more frequent, more intense, and last longer in most regions during 

the 21st 26 Century. This could increase the cost of transportation construction, operations, and 

27 maintenance. 

28 • Increases in Arctic temperatures. Arctic warming is virtually certain because temperature 

29 increases are expected to be greatest over land and at most high northern latitudes. As much 

30 as 90 percent of the upper layer of permafrost could thaw under more pessimistic emissions 

31 scenarios. 

• Rising sea levels. It is virtually certain that sea levels will continue to rise in the 21st 32 Century 

33 as a result of thermal expansion and loss of mass from ice sheets. This could make much of 

34 the existing transportation infrastructure in coastal areas prone to frequent, severe, and/or 

35 permanent inundation. 

36 • Increases in intense precipitation events. It is very likely that intense precipitation events

37 will continue to become more frequent in widespread areas of the United States. 

38 Transportation networks, safety, and reliability could be disrupted by visibility problems for 

39 drivers, and by flooding, which could result in substantial damage to the transportation 

40 system. 

41 • Increases in hurricane intensity. Increased tropical storm intensities, with larger peak wind 

42 speeds and more intense precipitation, are likely. This could result in increased travel 

43 disruption, impacts on the safety and reliability of transportation services and facilities, and 
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1 increased costs for construction, maintenance, and repair (Transportation Research Board 

2 2008). 

3 Numerous studies have examined ways of mitigating the transportation sector’s contribution to 

4 global warming from GHG emissions. However, far less attention has been paid to the potential impacts

5 of climate change on U.S. transportation systems and on how transportation professionals can best adapt 

6 to climate changes that are already occurring, and will continue to occur into the foreseeable future even 

7 if drastic mitigation measures were taken today. Because GHGs have long life spans, they continue to 

8 impact global climate change for decades (Transportation Research Board 2008). 

9 Scientific evidence reports that climate change is already occurring, and that it will trigger new, 

10 extreme weather events and could lead to surprises, such as more rapid than expected rises in sea levels or 

11 temperature changes. Every mode of transportation will be affected as climate change poses new and 

12 often unfamiliar challenges to infrastructure providers (Transportation Research Board 2008). 

13 Consideration of climate-change-related factors in transportation planning and investment 

14 decisions should lead to a more resilient, reliable, and cost-effective transportation system in the coming 

15 decades. When decisionmakers better understand the risks associated with climate change, they can make 

16 better decisions about potential adaptation strategies and the tradeoffs involved in planning, designing, 

17 constructing, operating, and maintaining transportation systems (Transportation Research Board 2008). 

18 Projected climate changes have profound implications for transportation in the United States 

19 (Transportation Research Board 2008). Climate change is likely to increase costs for construction and

20 maintenance of transportation infrastructure; impact safety through reduced visibility during storms and 

21 destruction of elements of the transportation system during extreme weather events; disrupt transportation 

22 networks with flooding and visibility problems; inundate substantial portions of the transportation system 

23 in low-lying coastal areas; increase the length and frequency of disruptions in transportation service; 

24 cause substantial damage and incur costly repairs to transportation infrastructure; and impact the overall 

25 safety and reliability of the Nation’s transportation system (Transportation Research Board 2008). 

26 Transportation systems across the United States are projected to experience both positive and 

27 negative impacts from climate change over the next century; the degree of impacts will be determined, in 

28 part, by the geographic region (Transportation Research Board 2008). Coastal communities are 

29 especially vulnerable to impacts associated with sea-level rise, increased frequency or intensity of storms, 

30 and damage to the transportation system due to storm surges and flooding. The literature indicates that 

31 the intensity of major storms could increase by 10 percent or more, which could result in more frequent 

32 Category 3 (or higher) storms along the Gulf Coast and the Atlantic Coast (Transportation Research 

33 Board 2008). Warming temperatures might require changes in the kinds of materials used for 

34 construction of transportation facilities, and in the operation and maintenance of transportation facilities 

35 and services. Higher temperatures could require the development and use of more heat-tolerant materials 

36 (Transportation Research Board 2008). Restrictions on work rules could increase the time and costs for 

37 labor for construction and maintenance of transportation facilities. Rail lines could be affected by higher 

38 temperatures and more frequent rail buckling, which would affect service reliability, safety, and overall 

39 system costs and performance. Costs could increase for ports, maintenance facilities, and transportation 

40 terminals if higher temperatures require an increase in refrigeration and cooling (Transportation Research 

41 Board 2008); and higher temperatures could affect aircraft performance and the runway lengths required

42 for safe operation (Transportation Research Board 2008). In addition, due to the potential global nature 

43 of the changes in severe weather, climate change could profoundly affect the operational aspects of 

44 aviation and overall air traffic and air space management (CCSP 2008b). On the positive side, higher 

45 temperatures might open up northern transportation routes for longer periods and allow more direct 

46 routing for marine transportation (Transportation Research Board 2008). In addition, warmer or less 
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1 snowy winters could be beneficial by reducing delays, improving ground and air transportation reliability, 

2 and decreasing the need for winter road maintenance (EPA 2009b). 

3 Changes in precipitation patterns could increase short-term flooding, resulting in decreased 

4 safety, disruptions in transportation services, and costly damage to transportation infrastructure. Hotter 

5 climates could exhibit reduced soil moisture and average runoff, which might require changes in the 

6 management and maintenance of publicly owned rights-of-way. The potential increase in heavy rainfall 

7 might exceed the capacity of existing drainage systems, resulting in more frequent flooding and 

8 associated disruptions in transportation system reliability and service, increased costs for maintenance of 

9 existing facilities, and increased costs for construction of new facilities (Transportation Research Board 

10 2008). 

11 Relative sea-level rise might inundate existing transportation infrastructure and substantially 

12 increase the cost of providing new transportation facilities and services. Some portions of the 

13 transportation infrastructure in coastal areas, or in areas prone to flooding, might have to be protected 

14 with dikes or levees – increasing the cost for construction and maintenance, and the potential for more 

15 serious flooding incidents associated with the failure of such dikes and levees (Transportation Research 

16 Board 2008). 

17 Increased storm frequency and intensity might lead to more disruption to greater transportation 

18 services, and damage to transportation infrastructure in coastal and inland areas. Model results for the 

19 study of the Gulf Coast conservatively estimated a 22- to 24-foot potential surge for major hurricanes

20 (Transportation Research Board 2008). During Hurricane Katrina (a Category 3 storm at landfall) surges 

21 exceeded these heights in some locations (Transportation Research Board 2008). While the specific 

22 location and strength of storm surges are difficult to project due to the variation of the scale and trajectory 

23 of individual tropical storms, substantial portions of the coastal infrastructure across the United States are 

24 vulnerable to increased damage resulting from the impacts of climate change (Transportation Research 

25 Board 2008). The central Gulf Coast is particularly vulnerable because of the high frequency of 

26 hurricanes, its loss of natural protection (e.g., barrier islands and wetlands), and the fact that much of its 

27 land is sinking in relation to mean sea level (EPA 2009b). 

28 Disruptions in transportation-system availability could result in substantial economic impacts 

29 associated with increased costs to construct or repair transportation infrastructure, and costs associated 

30 with disruptions in transportation for goods and services. Increasing fuel costs and delays in 

31 transportation service result in increased transport costs, which are then passed on to consumers. A 

32 substantial disruption in transportation (e.g., destruction of a major transportation facility by hurricane, 

33 flood, or other extreme weather event) could affect the regional economy in many different ways. 

34 Communities are likely to require long periods of time to recover from these events, and some 

35 communities could be permanently affected (Transportation Research Board 2008). 

36 The analysis to date raises clear cause for concern regarding the vulnerability of transportation 

37 infrastructure and services in coastal areas, and across the United States. Addressing the risks associated 

38 with a changing climate in the planning and design of transportation facilities and services can help public 

39 agencies and private investors to minimize disruptions to the smooth and safe provision of transportation 

40 services; and can protect the substantial investments made in the Nation’s transportation infrastructure 

41 now and in the future (Transportation Research Board 2008). 

42 According to the CCSP Impacts of Climate Change and Variability on Transportation Systems 

43 and Infrastructure Report (Transportation Research Board 2008), four key factors are critical to 

44 understanding how climate change might affect transportation: 
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1 • Exposure. What is the magnitude of stress associated with a climate factor (sea-level rise, 

2 temperature change, severe storms, and precipitation) and the probability that this stress will 

3 affect a transportation segment or facility? 

4 • Vulnerability. Based on the structural strength and integrity of the infrastructure, what is the 

5 potential for damage and disruption in transportation services from this exposure? 

6 • Resilience. What is the capacity of a system to absorb disturbances and retain transportation 

7 performance? 

8 • Adaptation. What response(s) can be taken to increase resilience at both the facility (e.g., a 

9 specific bridge) and system levels? 

10 New approaches to address climate-change factors in transportation planning and decisionmaking 

11 could include: 

12 • Extending planning timeframes. To address the long time frame over which climate changes 

13 and environmental processes occur, planning time frames might need to be extended beyond 

14 the typical 20- to 30-year planning horizon. The fact that transportation infrastructure can 

15 last for many decades (or even more than 100 years) argues for planning for much longer 

16 time frames to examine the potential impacts of climate change and other elements of the 

17 natural environment on the location, construction techniques, and costs for transportation 

18 infrastructure investments that are expected to last for many decades (Transportation 

19 Research Board 2008). 

20 • Conducting risk assessment analysis for transportation investments. Transportation 

21 investments face many uncertainties, including the potential impacts of climate change on 

22 construction, operations, and maintenance. Planners and decisionmakers can use iterative 

23 risk management analysis to evaluate potential risks of all types, and to identify potential 

24 ways to minimize the risks and increase the resiliency of transportation infrastructure. 

25 Transportation structures and facilities can be hardened, raised, or even relocated if needed. 

26 Where it is critical to safety, reliability, and mobility, redundant systems might be necessary 

27 for the most critical elements of the transportation system (Transportation Research Board 

28 2008). 

29 Impacts on Energy Systems

30 Although the energy sector has been seen as a driver of climate change, the energy sector is also 

31 subject to the effects of climate change (Wilbanks et al. 2007, EPA 2009b). All major energy sources are 

32 subject to a variety of climate change effects, including temperature, wind, humidity, precipitation, and 

33 extreme weather events (Bhatt et al. 2007; EPA 2009b). The most direct climate-change impacts for 

34 fossil fuel and nuclear power plants, for example, are related to power-plant cooling and water availability 

35 (Bhatt et al. 2007). Each kilowatt of electricity generated by thermoelectric generation requires about 25 

36 gallons of water. Power plants rank only slightly behind irrigation in freshwater withdrawals in the 

37 United States (USGS 2004 in Bhatt et al. 2007). In addition, about 10 percent of all U.S. coal shipments 

38 were delivered by barge in 2003; consequently, low river flows can create shortfalls in coal supplies at 

39 power plants (Bhatt et al. 2007). 

40 CCSP identified potential effects of climate change on energy production and use in the United 

41 States, which are stated in terms of likelihood (Wilbanks et al. 2007). Principal impacts and their 

42 likelihood are as follows: 
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1 • Climate change will reduce total energy demand for space heating; effects will differ by 

2 region (virtually certain). 

3 • Climate change will increase total energy demand for space cooling; effects will differ by 

4 region (virtually certain). 

5 • Net effects on energy use will differ by region. Overall impacts will be affected by patterns 

6 of interregional migration – which are likely to be in the direction of net cooling load 

7 regions – and investments in new building stock (virtually certain). 

8 • Temperature increases will increase peak demands for electricity (very likely). 

9 • Changes in the distribution of water availability will affect power plants; in areas with 

10 decreased water availability, competition for water supplies between energy and other sectors 

11 will increase (virtually certain). 

12 • Temperature increases will reduce overall efficiency of thermoelectric power generation 

13 (virtually certain). 

14 • In some regions, energy resource production and delivery systems will be vulnerable to the 

15 effects of sea-level rise and extreme weather events, especially the Gulf Coast and the East 

16 Coast (virtually certain). 

17 • Hydropower production will be directly and substantially affected by climate change, 

18 especially in the West and Northwest (very likely). 

19 • Climate change concerns will affect perceptions and practices related to risk management 

20 behavior in investment by energy institutions (very likely). 

21 • Climate change concerns are almost certain to affect public and private sector energy 

22 technology research and development investments and energy resource and technology 

23 choices by energy institutions, along with associated emissions (virtually certain). 

24 CCSP concluded that there is very little literature on adaptation of the energy sector to effects of 

25 climate change, and its following discussion is therefore largely speculative (Wilbanks et al. 2007). Both 

26 energy users and providers are accustomed to changing conditions that affect their decisions. The energy 

27 sector is among the most resilient of all economic sectors in terms of responding to changes within the 

28 range of historical experience (Wilbanks et al. 2007). Adaptations to the effects of climate change on 

29 energy use could focus on increased demands and rising costs for space cooling; likely responses include 

30 investing in more efficient cooling equipment and building envelopes. Increased demands for both peak

31 and average electricity demands could lead to contingency planning for load leveling, more efficient and 

32 expanded generation capacity, expanded interties, and increased storage capacity (Wilbanks et al. 2007). 

33 In terms of energy production and supply, the most likely near-term adaptation is expected to be 

34 an increase in perceptions of uncertainty and risk in long-term strategic planning and investment, with 

35 investors seeking to reduce risks through such approaches as diversifying supply sources and 

36 technologies, and risk-sharing arrangements (Wilbanks et al. 2007). 

37 Impacts on Human Settlements

38 The impacts of climate change on human settlements are expected to be substantial in a number 

39 of ways. “Settlements are important because they are where most of the [U.S.] population lives, often in 

40 concentrations that imply vulnerabilities to location-specific events and processes” (Wilbanks et al.

41 2007). Among the general effects of climate change are increased stress on human settlements due to 

42 higher summer temperatures and decreased stress associated with warmer winter temperatures. Changes 

43 in precipitation and water availability, rising sea levels in coastal regions, and greater risks from extreme 
Chapter 4 Cumulative Impacts 4.5 Health, Societal, and Environmental Impacts of Climate Change 

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1 weather events such as storms, flooding, and droughts are also expected to affect human settlements to

2 various degrees (EPA 2009b). At the same time, stresses due to extreme cold weather events, such as 

3 blizzards and ice storms, are expected to decrease (Wilbanks et al. 2007). In addition to climate change 

4 itself, climate-change mitigation measures could affect human settlements. For example, policies related 

5 to energy sources and uses, environmental emissions, and land use could have direct and short-term 

6 effects on settlements in regions where the economies are closely related to the production and 

7 consumption of large quantities of fossil fuels (CCSP 2008d). 

8 Predicting climate-change impacts on U.S. settlements is difficult because climate change is not 

9 forecast on a scale that is appropriate for local decisionmaking, and because climate is not the only 

10 change that settlements are confronting. A key example is the continuing population shift, particularly 

11 among persons who have reached retirement, toward the Sun Belt and coastal areas. This means an ever 

12 larger elderly population could be at risk, especially from extreme weather events such as tropical storms, 

13 and some types of vector-borne diseases and heat-related illnesses (CCSP 2008d). 

14 Anticipated human impacts include: 

15 • Increased respiratory and cardiovascular problems (Patz and Baldus 2001 in National 

16 Research Council 2002a). 

17 • Changes in mortality rates caused by temperature extremes (Rozenzweig and Solecki 2001 in 

18 CCSP 2008d). 

19 • Increased water demands associated with warming accompanied by changes in precipitation 

20 that alters access to water (Gleick 2000, Kirshen 2002, Ruth et al. 2007, all in CCSP 2008d). 

21 • Damages or disruptions to services associated with urban infrastructure such as sanitation 

22 systems, electricity transmission networks, communication systems, and the like could occur 

23 as a result of storms, floods, and fires (CCSP 2008d). 

24 • Sea-level rise could jeopardize many of the 673 coastal counties and threaten population 

25 centers (Neumann et al. 2000, Kirshen et al. 2004, both in CCSP 2008d). 

26 • Vulnerable populations such as the poor, elderly, those in ill health, the disabled, persons 

27 living alone, and individuals with limited rights (e.g., recent migrants) are expected to be at 

28 greater risk from climate change (CCSP 2008d). 

29 As a specific example regarding urban infrastructure, the New York City Department of 

30 Environmental Protection assessed potential climate-change impacts on the City’s drainage and 

31 wastewater collection systems, noting that if rainfall becomes more intense, sewer-system capacities 

32 could be exceeded, leading to street and basement flooding (NY City DEP 2008). Additionally, extreme 

33 precipitation events could lead to an inundation of the Water Pollution Control Plants’ influent wells. 

34 Sea-level rise could threaten hydraulic capacity of Water Pollution Control Plants’ outfalls by making

35 peak flow discharges more difficult and increase the salinity of influent to the Water Pollution Control 

36 Plant, which would upset biological treatment processes and lead to corrosion of equipment (NY City 

37 DEP 2008). 

38 The vulnerability of human settlements and infrastructure in coastal areas to natural disasters such 

39 as hurricanes and tropical storms was demonstrated through the damages Hurricanes Katrina and Rita 

40 caused along the U.S. Gulf Coast. After Hurricane Katrina struck, a total of 90,000 square miles was 

41 declared a federal disaster area, 80 percent of New Orleans was flooded, more than 1,700 lives were lost, 

42 850,791 housing units were damaged, and 2,100 oil platforms and more than 15,000 miles of pipeline 

43 were damaged (Petterson et al. 2006 in CIER 2007). 
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1 There is considerable potential for adaptation through technological and institutional 

2 development, in addition to behavioral changes, in particular where such developments meet other 

3 sustainable development needs (CCSP 2008d). There are various possible adaptation strategies for 

4 human settlements including assuring effective governance; increasing the resilience of physical and 

5 linkage infrastructures; changing settlement locations over time; changing settlement form; reducing heat6 island effects; reducing emissions and industry effluents; improving waste handling; providing financial 

7 mechanisms for increasing resiliency; targeting assistance programs for especially impacted segments of 

8 the population; and adopting sustainable community development practices (Wilbanks et al. 2005 in 

9 Wilbanks et al. 2007). Land-use choices, specifically the discouragement of housing development in 

10 flood-prone areas, including areas below sea level and in deep flow plains, can help protect human 

11 settlements and preserve management flexibility for these areas (Isenberg et al. 2008). The choice of 

12 strategies and policies for adaptation depend on their relationships with other social and ecological 

13 processes and level of economic development (O’Brien and Leichenko 2000 in Wilbanks et al. 2007). 

14 Impacts on Economic Opportunities and Risks

15 Communities or regions that depend on climate-sensitive resources or goods or whose 

16 comparative advantage could be affected are expected to be particularly vulnerable to climate change. 

17 The insurance sector is an example of an industry that could be highly vulnerable to climate impacts. If 

18 increasing trends of adverse weather events continue, claims made to private and public insurers are 

19 expected to climb (NAST 2001 in CIER 2007). Overall risk exposure of insurers’ has grown 

20 considerably (e.g., the National Flood Insurance Program’s exposure increased four-fold since 1980 to $1 

21 trillion in 2005 and the Federal Crop Insurance Corporation’s exposure grew up to $44 billion) (U.S. 

22 GAO 2007 in CIER 2007). In the United States, of the $19 trillion in insured commercial and residential 

23 properties, 41 percent are in coastal communities. In Florida, this portion is 79 percent; in New York 63 

24 percent; and in Connecticut 61 percent (EPA 2009b). To the extent that climate change increases costs

25 for insurers or increases the difficulty of forecasting risks, the insurance sector might “withdraw (or make 

26 much more expensive) private insurance coverage from areas vulnerable to climate change impacts” 

27 (National Science and Technology Council 2008). 

28 Trade, retail, and commercial services, and tourism are other economic areas that are expected to 

29 be affected by climate-change impacts, largely as a result of impacts on the transportation and energy

30 sectors. For example, impacts on transportation will affect distribution and receipt of goods for retail 

31 services. This could have a particular effect on the Midwest, which is a heavy domestic freight and 

32 shipping route area. Approximately “$3.4 billion and 60,000 jobs rely on the movement of goods within

33 the Great Lakes-St. Lawrence shipping route annually” (Easterling and Karl 2001 in CIER 2007). A 

34 decline in water levels could jeopardize this mode of transporting manufacturing. Future low-flow 

35 conditions in some areas could affect the ability of ships to navigate waterways and use some ports (EPA 

36 2009b). In fact, “system connectivity is predicted to be come 25 percent impaired causing a loss of $850 

37 million annually” (Easterling and Karl 2001 in CIER 2007). Dredging 7.5 to 12.5 million cubic yards, 

38 which would cost $85 to $142 million, might be the only alternative to salvage this system if water levels 

39 decline substantially (Great Lakes Regional Assessment Group 2000 in CIER 2007). 

40 Tourism could be affected by “changes in the landscape of areas of tourist interest” and by 

41 changes in the availability of resources and energy costs (Wilbanks et al. 2007). In the United States, 

42 climate-change impacts could affect winter recreation and tourism in the Northeast. Warmer winters 

43 would “shorten the average ski and snowboard seasons, increase snow making requirements, and drive up 

44 operating costs,” possibly “prompting further closures and consolidation of ski areas northward toward

45 the Canadian border” (Frumhoff et al. 2007). 
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1 Historical and Cultural Resources

2 A variety of cultural and historical resources are at risk from climate change. According to a 

3 recent study by UNESCO, “The adverse impacts of climate change will have consequences for humanity 

4 as a whole including the products of human creativity...these consequences will be manifest in at least 

5 two principal ways: (1) the direct physical effects on the buildings or structures and (2) the effects on 

6 social structures and habitats” (Colette et al. 2007). 

7 Alaska is the region expected to be most affected by climate change, largely because of location 

8 (warming is more pronounced closer to the poles) and way of life (settlement and economic activities 

9 based around Arctic conditions) (CCSP 2008d). Indigenous communities in Alaska are facing major 

10 economic and cultural impacts because they depend for subsistence on various climate-sensitive animals

11 such as polar bears, walruses, seals, and caribou (National Science and Technology Council 2008). 

12 “Changes in species’ ranges and availability, access to these species, a perceived reduction in weather 

13 predictability, and travel safety in changing ice and weather conditions present serious challenges to

14 human health and food security, and possibly even the survival of some cultures” (EPA 2009b). 

15 In discussing the impacts of climate change on historic cities and settlements around the world, 

16 Colette et al. 2007 lists the following potential threats associated with climate change: 

17 • Increased salt mobilization with resulting damage to surfaces and decoration as a result of 

18 increasing rate of heavy rainfall. 

19 • Changes in the amplitude of temperature and humidity can cause splitting, cracking, flaking 

20 and other damage to exposed surfaces. 

21 • Organic building materials such as wood could be subject to increase infestation as a result of 

22 migration of pests. 

23 • An increase in flooding can directly damage structures and promote growth of damaging 

24 micro-organisms such as molds and fungi. 

25 • In arid regions, desertification, salt weathering and erosion could threaten cultural and 

26 historic sites. 

27 Climate change could also create pressures that result in migration of populations, which in turn 

28 could result in the breakdown of communities and the loss of “rituals and cultural memory” (Colette et al.

29 2007). 

30 4.5.7.2.2 Projected Global Impacts of Climate Change 

31 As the discussion above suggests, the three major ways in which industry, settlements, and 

32 society are vulnerable to climate change are through impacts on economics, infrastructure, and health. 

33 The magnitude of impacts on industry, settlements, and society largely depends on location and the level 

34 of development of the area or region. The following discussion highlights anticipated impacts on key 

35 human systems at the global level. 

36 Global Energy Sector Impacts

37 Regarding energy production and use, expected global impacts will likely be similar to those 

38 described above for the United States. When the climate warms, less heating will be needed for 

39 industrial, commercial, and residential buildings, with changes varying by region and by season 

40 (Wilbanks et al. 2007). Electricity is used in areas around the world for cooling; coal, oil, gas, biomass, 
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1 and electricity provide energy for heating. Regions with substantial requirements for both cooling and 

2 heating could see net increases in electricity demands while demands for other energy sources decline 

3 (Hadley et al. 2006 in Wilbanks et al. 2007). 

4 According to one study, by 2100 the benefits (reduced heating) will be about 0.75 percent of 

5 gross domestic product, and impacts (increased cooling) will be approximately 0.45 percent (Tol 2002a,

6 2002b, both in Wilbanks et al. 2007). These percentages could be affected by migration from heating7 intensive regions to cooling-intensive regions (Wilbanks et al. 2007). 

8 Climate change could also affect global energy production and distribution if extreme weather 

9 events become more frequent or intense (EPA 2009b); and in regions that depend on water supplies for 

10 hydropower or thermoelectric generation if there are substantial changes in rainfall/snowfall locations and 

11 seasonality. Reduced stream flows are expected to jeopardize hydropower production in some areas, but

12 higher precipitation rates resulting in greater or more sustained stream flows could be beneficial (Casola 

13 et al. 2005, Viosin et al. 2006, both in Wilbanks et al. 2007). More frequent or intense extreme weather 

14 events could threaten coastal energy infrastructures, including electricity transmission and distribution 

15 facilities (Bull et al. 2007). 

16 Warming temperatures resulting in melting of permafrost threaten petroleum production facilities 

17 and pipelines, electrical transmission towers, and nuclear power plants in the Arctic region (EPA 2009b). 

18 As with Alaska’s North Slope facilities, structural failures in transportation and industrial infrastructure 

19 are becoming more common in northern Russia due to melting permafrost (EPA 2009b). 

20 Global Transportation Sector Impacts

21 The IPCC concludes, with very high confidence, that data since 1970 have demonstrated 

22 anthropogenic temperature rises have visibly altered ecosystems (Parry et al. 2007). Other stressors on 

23 the built environment and the ability of cities and countries to adapt to a changing climate make it 

24 difficult to discern the exact impacts of climate change on transportation systems around the world. 

25 Additional factors, such as projected population growth, are expected to exacerbate the effects of climate 

26 change. Development typically occurs in coastal regions, especially in the newly developing third-world 

27 countries. These areas are particularly vulnerable to the impacts of projected increases in extreme 

28 weather events such as hurricanes, cyclones, unusually heavy precipitation, and flooding. In addition, 

29 these developing countries are less able to adapt to expected changes due to their limited resources and 

30 other pressing needs (Wilbanks et al. 2007). 

31 Transportation-system vulnerabilities in more-developed countries often focus on physical assets 

32 and infrastructures and their economic value and replacement costs, along with linkages to global 

33 markets. Vulnerabilities in less-developed countries often focus on human populations and institutions 

34 that are likely to have very different transportation needs and resources (Wilbanks et al. 2007). A 

35 warmer, drier climate could exacerbate many of the problems of developing countries, including drought

36 and decreases in food production in areas of Africa and Asia (Wilbanks et al. 2007). 

37 At a national scale, industrialized countries such as the United Kingdom and Norway can cope 

38 with most kinds of gradual climate change, but localized differences can show considerable variability in 

39 stresses and capacities to adapt (Environment Canada 1997, Kates and Wilbanks 2003 in National 

40 Science and Technology Council 2008, London Climate Change Partnership 2004, O’Brien et al. 2004, 

41 Kirshen et al. 2006). 
Chapter 4 Cumulative Impacts 4.5 Health, Societal, and Environmental Impacts of Climate Change 

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1 Impacts on the U.S. transportation systems described above apply in other countries as well. 

2 Based on information developed by the Transportation Research Board (2008) the potential impacts of 

3 climate change on transportation fall into the two major categories, as follows: 

4 • Climate change will affect transportation primarily through increases in several types of 

5 weather and climate extremes, such as very hot days, intense precipitation events, intense 

6 hurricanes, drought, and rising sea levels, coupled with storm surges and land subsidence. 

7 The impacts will vary by mode of transportation and region, but they will be widespread and 

8 costly in both human and economic terms and will require substantial changes in the 

9 planning, design, construction, operation, and maintenance of transportation systems. 

10 • Potentially, the greatest impact of climate change on global transportation systems will be 

11 flooding of coastal roads, railways, transit systems, and runways because of rising sea levels 

12 coupled with storm surges, and exacerbated in some locations by land subsidence (National 

13 Science and Technology Council 2008). 

14 Given the global nature of the impacts of climate change and the world economy, coordination 

15 within and among nations will become increasingly important (Wilbanks et al. 2007). Strong and 

16 complex global linkages and interactions occur throughout the world today and are likely to increase in 

17 the future. Climate-change effects cascade through interlinked systems for international trade, migration, 

18 and communication patterns, producing a variety of direct and indirect effects. Some of these impacts

19 might be anticipated. However, many might not, especially if the globalized economy becomes less 

20 resilient and more interdependent (Wilbanks et al. 2007). 

21 The impacts of an extreme weather event in one location (e.g., Hurricane Katrina in Louisiana) 

22 causes ripple effects throughout the transportation system in the United States and in areas around the 

23 world linked to the United States through the ports in the affected area (Transportation Research Board 

24 2008). 

25 There are now incidences in Europe, North America, and Japan of new transportation 

26 infrastructure being designed and constructed with potential climate change in mind. For example, 

27 designing bridges and other infrastructure at higher elevations in anticipation of sea-level rise over the life 

28 span of these transportation-system elements (Wilbanks et al. 2007). 

29 Global Human Settlements Impacts

30 Human settlements are vulnerable to the effects of climate change in three major ways: (1) 

31 through economic sectors affected by changes in input resource productivity or market demands for goods 

32 and services, (2) through impacts on certain physical infrastructure, and (3) through impacts of weather 

33 and extreme events on the health of populations. The degree of vulnerability tends to be a function of the 

34 location (coastal and riverine areas are most at risk), economy (economies most dependent on weather35 related sectors are at highest risk), and size (larger settlements are at greater aggregate risk, but they likely 

36 have greater resources to prevent the impacts of climate change and respond to events that result from

37 climate changes, such as hurricanes, floods, or other extreme weather events) (EPA 2009b). 

38 Shifts in precipitation patterns might affect already stressed environments. For example, mean 

39 precipitation in all four seasons has tended to decrease in all main arid and semi-arid regions of the world 

40 (northern Chile and northeast Brazil, West Africa, and Ethiopia, drier parts of southern Africa, and 

41 western China) (Folland et al. 2001 in Wilbanks et al. 2007). Increasing temperature could aggravate 

42 ozone pollution in many cities, which could affect quickly growing urban areas that are experiencing 

43 more air pollution problems, especially those in developing countries (Wilbanks et al. 2007). 
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1 Additionally, sea-level rise will threaten the habitability of island nations in the Caribbean and Pacific, 

2 where 50 percent of populations live within 0.93 mile of the shoreline (EPA 2009b). 

3 Extreme weather events affect settlements and society in developing countries just as they do 

4 developed countries − through damage and destruction of infrastructure and loss of human life − although 

5 perhaps in slightly different ways. For example, in some urban areas of developing countries, informal 

6 settlements develop. These informal settlements are especially vulnerable because they tend to be built 

7 on hazardous sites and be susceptible to floods, landslides, and other climate-related disasters (Cross 

8 2001, UN-Habitat 2003, both in Wilbanks et al. 2007). Another example is how “[i]n developing 

9 countries, a common cause of death associated with extreme weather events in urban areas is 

10 electrocution by fallen power cables” (Few et al. 2004 in Wilbanks et al. 2007). 

11 Generally, low-income and other vulnerable populations would experience the same impacts from 

12 climate change as populations in comparable geographic areas described in this section and Sections 

13 4.5.6, Food, Fiber, and Forest Products, and 4.5.8, Human Health. However, as with environmental 

14 justice populations in the United States, vulnerable populations would likely experience climate-change 

15 impacts differentially. The magnitude of climate-change impacts on residents of developing countries 

16 would be expected to be greater (EPA 2009b). For example, IPCC notes that the continent of Africa’s 

17 “major economic sectors are vulnerable to current climate sensitivity, with huge economic impacts, and

18 this vulnerability is exacerbated by existing developmental challenges such as endemic poverty, complex 

19 governance and institutional dimensions; limited access to capital, including markets, infrastructure and 

20 technology; ecosystem degradation; and complex disasters and conflicts. These in turn have contributed 

21 to Africa’s weak adaptive capacity, increasing the continent’s vulnerability to projected climate change” 

22 (Wilbanks et al. 2007). 

23 As discussed in this section, the danger to human health from climate change will affect 

24 developing countries differentially. The IPCC states that “Adverse health impacts will be greatest in low25 income countries. Those at greater risk include, in all countries, the urban poor, the elderly and children, 

26 traditional societies, subsistence farmers, and coastal populations” (Wilbanks et al. 2007). Section 4.5.8 

27 describes in detail the potential health effects from climate change on developing countries, which 

28 include: 

29 • Increases in malnutrition, and related health impacts, in developing regions of the world due 

30 to declining crop yields; 

31 • Potential increases in water-related diseases, such as diarrhea-causing pathogens, due to 

32 higher temperatures; 

33 • Potential for continuation of upward trends in certain vector-borne diseases, such as malaria 

34 in Africa, which have been attributed to temperature increases; and 

35 • Increases in temperature leading to increased ozone and air pollution levels in large cities 

36 with vulnerable populations. 

37 Section 4.5.6 and this section describe the effects of climate change on developing countries that 

38 would differ or be substantially more severe than similar effects experienced by developed nations. 

39 Because the developing world tends to depend more on small-scale farming and subsistence economic 

40 activities, individuals in these areas would be disproportionately affected by climate-change impacts on 

41 agricultural and subsistence resources. In particular, these impacts could include: 

42 • Decreases in precipitation in developing parts of the world, such as southern Africa and 

43 northern South America, leading to decreases in agricultural production and increased food 

44 insecurity; 
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1 • Substantial potential for impacts on small-scale subsistence farmers resulting from increases 

2 in extreme weather events projected under global climate change, reducing agricultural 

3 production in some areas of the globe; 

4 • Changes in the range of fish and animals and species extinctions, affecting populations in 

5 developing nations that depend economically on these resources; 

6 • Declines in tourism, especially to coastal and tropical areas heavily affected by sea-level rise, 

7 with severe economic consequences for smaller, developing nations; and 

8 • Sea-level rise and severe weather-related events affecting the long-term habitability of atolls 

9 (low coral reef-formed islands) (Barnet and Adger 2003). 

10 Global Impacts on Economic Opportunities and Risks

11 Impacts vary by region and locality and cannot be generalized for all nations. Although impacts 

12 are expected to vary, a factor that developed countries have in common is that their access to material and 

13 financial resources provides them opportunities to adapt to the effects of a changing climate. In contrast, 

14 developing countries are expected to be less able to adapt to climate change because they lack both the 

15 physical and financial resources needed to bolster their resilience to the same extent possible in 

16 industrialized countries (EPA 2009b). 

17 In developing countries “industry includes a greater proportion of enterprises that are small-scale, 

18 traditional, and informally organized...Impacts of climate change on these businesses are likely to depend 

19 on...location in vulnerable areas, dependence on inputs sensitive to climate, and access to resources to

20 support adaptive actions” (Wilbanks et al. 2007). One specific industry that could become more 

21 vulnerable to direct and indirect impacts of climate change is tourism. Impacts on this industry can be 

22 “especially significant for smaller, tourist-oriented countries often in the developing world” (Wilbanks et 

23 al. 2007). It seems “likely that tourism based on natural environments will see the most substantial 

24 changes due to climate change...Tropical island nations and low-lying coastal areas may be especially 

25 vulnerable as they may be affected by sea-level rise, changes in storm tracks and intensities, changes in 

26 perceived climate-related risks, and changes in transport costs...” (Wilbanks et al. 2007). The 

27 implications are most notable for areas in which tourism is a relatively large share of the local or regional 

28 economy, and those for which adaptation would represent a relatively substantial need and a relatively

29 substantial cost (Wilbanks et al. 2007). Trade is another industry that could be affected by extreme 

30 weather events that temporarily close ports or transportation routes and damage infrastructure critical to 

31 trade, both domestic and international. There could be “linkages between climate change scenarios and

32 international trade scenarios, such as a number of regional and sub-regional free trade agreements” 

33 (Wilbanks et al. 2007). However, research on this topic is lacking. 

34 4.5.8 Human Health 

35 4.5.8.1 Affected Environment 

36 Climate change has contributed to human mortality and morbidity (very high confidence; IPCC 

37 2007b) with further projected increases (EPA 2009b). Climate change could increase the risk of flooding; 

38 increase incidence of heat waves; change the severity, duration, and location of extreme weather; increase 

39 surface temperature; and alter precipitation intensity and frequency. These events can affect human 

40 health either directly through temperature and weather or indirectly though changes in water, air, food 

41 quality, vector ecology, ecosystems, agriculture, industry, and settlements. Climate change can also 

42 affect health through social and economic disruption. Malnutrition, death, and disease brought on by 

43 climate change are projected to affect millions of people (Confalonieri et al. 2007). 
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1 4.5.8.2 Environmental Consequences 

2 4.5.8.2.1 Observed Health Impacts and Vulnerabilities Associated with Climate 

3 Change 

4 Heat Waves

5 A heat wave is a period of abnormally high temperatures that can be accompanied by unusual 

6 humidity. This weather phenomenon is not formally specified by a time period or temperature reading. 

7 Conventionally, a heat wave lasts several days to several weeks, though a 1-day event can qualify as a

8 heat wave. The temperature to qualify as a heat wave depends on what is considered unusually hot for 

9 that region, because increases in mortality can occur below temperatures considered extremely hot (Ebi et 

10 al. 2008). IPCC has found the number of hot days, hot nights, and heat waves to have increased 

11 (Confalonieri et al. 2007). Global warming has increased the intensity of heat waves (Houghton et al.

12 2001 in Epstein et al. 2006), due in part to disproportionate warming at night (Easterling et al.1997 in 

13 Epstein et al. 2006). Heat waves can trigger poor air quality and forest fires, leading to further increases 

14 in human mortality and morbidity (Bates et al. 2005, Goodman et al. 2004, Keatinge and Donaldson 

15 2001, O’Neill et al. 2005, Ren et al. 2006, all in Ebi et al. 2008). 

16 The impact of a heat wave on the affected population depends on the population’s health and 

17 economic status. Globally, those most sensitive to heat waves include the rural population, the elderly, 

18 outdoor workers, the very young, city dwellers, those with less education, those who are socially isolated, 

19 medicated, or mentally ill, and those without available air conditioning (Chaudhury et al. 2000 in 

20 Confalonieri et al. 2007; Diaz et al. 2002, Klinenberg 2002, McGeehin and Mirabelli 2001, Semenza et 

21 al. 1996, Whitman et al. 1997, Basu et al. 2005, Gouveia et al. 2003, Greenberg et al. 1983, O’Neill et al.

22 2003, Schwartz 2005, Jones et al. 1982, Kovats et al. 2004, Schwartz et al. 2004, Semenza et al. 1999, 

23 Watkins et al. 2001, all in Ebi 2008; EPA 2009b). People in developed areas also can be impacted 

24 substantially by heat waves. Existing electricity grids in the United States would be severely stressed by 

25 a major heat wave, leading to brownouts and blackouts and further contributing to increased heat-related 

26 illnesses (Epstein et al. 2006). In addition, increased electricity demand during heat waves and summer 

27 months can compound health issues because air pollutant levels from electrical generating units increase 

28 (IPCC, 2007b). Populations identified to be vulnerable to heat waves in the United States include those 

29 with diabetes, mobility constraints, and cognitive constraints (Schwartz 2005 in Ebi et al. 2008; EPA 

30 2009a). 

31 The urban heat island effect could increase temperatures experienced in cities by 2 to 10 oF 

32 compared to neighboring rural and suburban areas (EPA 2005 in Ebi et al. 2008). This increase in 

33 temperature occurs, in part, as the city pavement and buildings absorb a greater amount of incoming solar 

34 radiation compared to vegetation and trees; in addition, heat is also emitted from buildings and 

35 transportation (EPA 2005, Pinho and Orgaz 2000, Vose et al. 2004, Xu and Chen 2004, all in Ebi et al.

36 2008). However, it has been demonstrated that during a heat wave, not all urban areas experience greater 

37 heat-related mortality than the surrounding rural and suburban areas (Sheridan and Dolney, 2003 in Ebi et 

38 al. 2008). In addition, a sociological analysis of a 1995 Chicago heat wave found populations were at 

39 higher risk in neighborhoods without public gathering places and active street life (Klinenberg 2002 in 

40 Ebi et al. 2008). Population growth over the next 50 years is projected to occur primarily in cities, 

41 thereby increasing the number of people exposed to heat waves (EPA 2009b). 

42 Cold Waves

43 Human mortality and morbidity can also be caused by cold waves. Cold waves affect human 

44 health through death, hypothermia, frostbite, damage to organs such as kidneys, pancreas, and liver, with 
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1 the greatest risk to infants and the elderly (NOAA 2001). Cold waves can cause further complications of 

2 heavy snow, ice, coastal flooding, and stranded motorists. As with a heat wave, the classification of a 

3 cold wave varies by region, with no formal definition for the minimum temperature reached, the rate of

4 temperature fall, or the duration of the event. Populations in temperate countries that do not traditionally 

5 experience cold waves tend to be more sensitive (Honda et al. 1998 in Confalonieri et al. 2007); however, 

6 populations in cold environments are considered vulnerable if electricity or heating systems fail (EPA

7 2009b). The human-health reaction of a population to a cold wave can vary depending on income, (Healy

8 2003 in Ebi et al. 2008), age, topography, climate (Curriero et al. 2002, Hajat 2006, both in Confalonieri 

9 et al. 2007), race (Fallico et al. 2005 in Ebi et al. 2008), sex (Wilkinson et al. 2004 in Ebi et al. 2008), 

10 health (Wilkinson et al. 2004 in Ebi et al. 2008), dress (Donaldson et al. 2001 in Ebi et al. 2008), and 

11 access to fuel (Healy 2003 in Ebi et al. 2008). Cold days, cold nights, and frost days have become less 

12 common (IPCC 2007b), with the winter season projected to continue to decrease in duration and intensity 

13 (IPCC 2007e in Ebi et al. 2008). This could lead to a decrease in cold-related health impacts, 

14 notwithstanding external factors, such as influenza outbreaks (Ebi et al. 2008, EPA 2009b). It has not 

15 been determined if the reduced mortality associated with cold waves will be more or less than the 

16 increased heat-related mortality projected to occur in response to climate change (CCSP 2008d, EPA 

17 2009b). 

18 Extreme Weather Events

19 Climate change is anticipated to affect the number, severity, and duration of extreme weather 

20 events (Fowler and Hennessey 1995 in Sussman et al. 2008). Extreme weather events include floods, 

21 tropical and extra-tropical cyclones, tornadoes, windstorms, and drought. Extreme weather can further

22 trigger additional extreme events such as wildfires, negatively affecting infrastructure, including 

23 sanitation, human mortality and morbidity, and mental health (Confalonieri et al. 2007). The loss of 

24 shelter, large-scale population displacement, damage to community sanitation and health care, and 

25 reduction in food availability can extend the level of mortality and morbidity beyond the actual event

26 (Curriero et al. 2001b in Sussman et al. 2008). Factors that influence population vulnerability to extreme 

27 weather include location, population density, land use, age, income, education, health, health-care 

28 response, and disaster preparedness (Blaikie et al. 1994, Menne 2000, Olmos 2001, Adger et al. 2005b, 

29 Few and Matthies 2006, all in Confalonieri et al. 2007; EPA 2009b). 

30 Adverse weather conditions create safety hazards and delays in the Nation’s transportation 

31 systems, especially on its highways. The Federal Highway Administration estimates that about 28 

32 percent of highway crashes occur during adverse weather, resulting in about 19 percent of highway 

33 fatalities (AMS, 2004), while the Federal Motor Carrier Safety Administration found that the factor 

“environmental conditions” was the critical reason2

34 for 3 percent of large truck crashes (FMCSA, 2007). 

35 Extreme weather events that increase adverse weather conditions on the Nation’s highways could affect 

36 highway safety. 

37 Floods occur with the greatest frequency compared to other extreme weather events (EM-DAT 

38 2006 in Confalonieri et al. 2007). The intensity of a flood depends on rainfall, surface runoff, 

39 evaporation, wind, sea level, and local topography (Confalonieri et al. 2007). Health impacts related to 

40 flood events include deaths and injuries sustained during a flood event; increased transmission and 

41 prevalence of infectious diseases; toxic contamination of supplies and food; and post-traumatic stress

42 disorders (EPA 2009b). Additional health impact stressors such as geographic displacement and damage 

 

2 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.
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1 to possessions and property can occur after the initial event, leading to continued disruption and anxiety 

2 regarding the recurrence of the event (Tapsell et al. 2002 in Ebi et al. 2008). Coastal storms can cause 

3 drowning by the associated storm surge particularly in regions of high-density populations living in low4 lying coastal sections, as evidenced in the U.S. Gulf Coast during 2005 Hurricane Katrina (EPA 2009b). 

5 Globally, if 40 percent of the increase in number of weather-related disasters from 1980 to present is

6 attributed to climate change and a “4 percent proportion of the total seriously affected by environmental 

7 degradation based on negative health outcomes,” it can be estimated that 325 million people are seriously 

8 affected annually by climate change (GHF 2009).

9 Drought is an abnormal period of dry weather that has led to substantial decrease in water 

10 availability for a given location (Huschke 1959). The health impacts associated with a drought include 

11 mortality, malnutrition, infectious diseases, and respiratory diseases (Menne and Bertollini 2000 in 

12 Confalonieri et al. 2007). Aggravating this situation, malnutrition increases the susceptibility of 

13 contracting an infectious disease (Confalonieri et al. 2007) and drought-related population displacement 

14 can reduce access to adequate and safe water, food, and shelter, leading to increased malnutrition and

15 infectious diseases. Further health impacts can spiral, such as a change in the transmission of mosquito16 borne diseases during and after the drought event (Confalonieri et al. 2007). Impacts on agricultural 

17 productivity affect health through risk of under- and malnutrition (Epstein et al. 2006), and increased dust 

18 storm activity and frequency of forest fires. Drought conditions weaken trees’ defenses against pests and 

19 can result in increased threats to human health from forest fires (Mattson and Haack 1987, Boyer 1995,

20 Holsten et al. 2000, all in Epstein et al. 2006). Health impacts associated with drought tend to be more 

21 prevalent in drier climates with poor populations and where there is human-induced water scarcity. 

22 Therefore, the most severe drought-related health impacts are likely to be in developing countries rather 

23 than in the United States (EPA 2009b). 

24 Air Quality

25 Climate change can affect air quality through altering local weather patterns and/or pollution 

26 concentrations. Ground-level ozone, PM, and airborne allergens contribute to poor air quality, leading to 

27 respiratory ailments and premature mortality. Increasing exposure to these pollutants would have 

28 substantial negative health impacts (Confalonieri et al. 2007). 

29 Ground-level ozone contributes to urban smog, and occurs both naturally and as a secondary 

pollutant formed through photochemical reactions of NOx and VOCs.3

30 These reactions are accelerated 

31 with increasing sunlight and temperatures. Ozone concentrations tend to peak around 3pm through 6pm 

32 depending and in the warmer season. EPA (2009b) states that ozone generally increases with higher 

33 temperatures. Studies have already found increasing levels of ground-level ozone in most regions (Wu 

34 and Chan 2001, Chen et al. 2004, both in Confalonieri et al. 2007). A recent study found increases in 

35 CO2 concentrations contribute to increased water vapor and temperatures and separately increase ozone 

36 more with higher ozone . (Jacobson 2008). These lead to an increase U.S. annual air pollution deaths by 

37 about 1,000 (350-1,800) where about 40% of the additional death may be due to ozone (the remaining 

38 60% to particles). The study further extrapolates the findings to a global scale estimating 21,600 (7,500-

39 39,000) excess CO2-caused annual pollution deaths 

40 Ozone exposure is associated with respiratory ailments such as pneumonia, chronic obstructive 

41 pulmonary disease, asthma, allergic rhinitis, chest pain and other respiratory diseases (Mudway and Kelly 

42 2000, Gryparis et al. 2004, Bell et al. 2005, 2006, Ito et al. 2005, Levy et al. 2005, all in Confalonieri et 

 

3 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.
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1 al. 2007). Asthmatics are considered a sensitive population (Ebi et al. 2008). Long-term exposure to 

2 elevated amounts of ozone has been shown to affect lung efficiency (Ebi et al. 2008). 

3 PM comprises solid and liquid particles suspended in the atmosphere varying in both chemical 

4 composition and origin. Concentrations of PM are affected by emission rates and local weather 

5 conditions such as atmospheric stability, wind, and topography. Some particulates display seasonal 

6 variability directly linked to seasonal weather patterns (Alvarez et al. 2000, Kassomenos et al. 2001, 

7 Hazenkamp-von Arx et al. 2003, Nagendra and Khare 2003, Eiguren-Fernandez et al. 2004, all in 

8 Confalonieri et al. 2007). In Mexico City and Los Angeles, local weather conditions can create a stagnant 

9 air mass, restricting dispersion of pollution. Seasonal weather patterns can further enhance the chemical 

10 reactions of emissions, thereby increasing secondary PM (Rappengluck et al. 2000, Kossmann and 

11 Sturman 2004, both in Confalonieri et al. 2007). 

12 Breathing PM can cause respiratory ailments, heart attack, and arrhythmias (Dockery et al. 1993, 

13 Samet et al. 2000, Pope et al. 1995, 2002, 2004, Pope and Dockery 2006, Dominici et al. 2006, Laden et 

14 al. 2006, all in Ebi et al. 2008). Populations at greatest risk could include children, the elderly, and those 

15 with heart and lung disease, diabetes (Ebi et al. 2008), and high blood pressure (Künzli et al. 2005 in Ebi 

16 et al. 2008). Chronic exposure to PM could decrease lifespan by 1 to 3 years (Pope 2000 in American 

17 Lung Association 2008). Increasing PM concentrations are expected to have a measurable adverse 

18 impact on human health (Confalonieri et al. 2007). 

19 Forest fires contribute to poor air quality conditions. During the fifth largest U.S. wildfire, in 

20 1999, medical visits at the Hoopa Valley National Indian Reservation increased by 52 percent, with 

21 symptoms affecting lower respiratory tract and preexisting cardiopulmonary conditions (Mott et al. 2002). 

22 Human-health ailments associated with forest fires include burns, smoke inhalation, mortality, eye 

23 illnesses, and respiratory illnesses (Confalonieri et al. 2007, Ebi et al. 2008). One study found there is an 

24 increase in the number of patients requesting emergency services for smoke and ash inhalation when there 

25 are large fires (EPA 2009b). Certain regions are anticipated to experience an increase in frequency and 

26 intensity of fire events with projected changes in temperature and precipitation. Pollutants from forest 

27 fires can affect air quality for thousands of miles (EPA 2009b). Pollution from forest fires along with 

28 other pollutants, such as carbon monoxide, ozone, desert dust, mould spores and pesticides, can be 

29 transported thousands of kilometers on time scales of 4 to 6 days and affecting populations far from the 

30 sources (Gangoiti et al. 2001, Stohl et al. 2001, Buchanan et al. 2002, Chan et al. 2002, Martin et al.

31 2002, Ryall et al. 2002, Ansmann et al. 2003, He et al. 2003, Helmis et al. 2003, Moore et al. 2003, 

32 Shinn et al. 2003, Unsworth et al. 2003, Kato et al. 2004, Liang et al. 2004, Tu et al. 2004, all in 

33 Confalonieri et al. 2007). 

34 Water-borne and Food-borne Diseases

35 Substantial morbidity and childhood mortality has been linked to water- and food-borne diseases. 

36 Climate change is projected to alter temperature and the hydrologic cycle through changes in 

37 precipitation, evaporation, transpiration, and water storage. These changes, in turn, potentially affect 

38 water-borne and food-borne diseases, such as salmonellosis, campylobacter, leptospirosis, and pathogenic 

39 species of vibrio. They also have a direct impact on surface-water availability and water quality. It has 

40 been estimated that more than 1 billion people in 2002 did not have access to adequate clean water 

41 (McMichael et al. 2003 in Epstein et al. 2006). Increased temperatures, greater evaporation, and heavy42 rain events have been associated with adverse impacts on drinking water through increased waterborne 

43 diseases, algal blooms, and toxins (Chorus and Bartram 1999, Levin et al. 2002, Johnson and Murphy 

44 2004, all in Epstein et al. 2006). A seasonal signature has been associated with waterborne disease 

45 outbreaks (EPA 2009b). In the United States, 68 percent of all waterborne diseases between 1948 and 

46 1994 were observed after heavy rainfall events (Curriero et al. 2001a in Epstein et al. 2006). 
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1 Climate change could further impact a pathogen by directly affecting its life cycle (Ebi et al.

2 2008). The global increase in the frequency, intensity, and duration of red tides could be linked to local 

3 impacts already associated with climate change (Harvell et al. 1999 in Epstein et al. 2006); toxins 

4 associated with red tide directly affect the nervous system (Epstein et al. 2006). 

5 Many people do not report or seek medical attention for their ailments of water-borne or food6 borne diseases; hence, the number of actual cases with these diseases is greater than clinical records

7 demonstrate (Mead et al. 1999 in Ebi et al. 2008). Many of the gastrointestinal diseases associated with 

8 water-borne and food-borne diseases can be self-limiting; however, vulnerable populations include young 

9 children, those with a compromised immune system, and the elderly. 

10 Vector-borne Diseases

11 Infections can be spread by the bite of an infected arthropod (termed vector-borne) such as 

12 mosquitoes, ticks, sandflies, and blackflies, or through non-human vertebrates such as rodents, canids, 

13 and other mammals. Such diseases include typhus, malaria, yellow fever, dengue fever, West Nile virus, 

14 Western Equine encephalitis, Eastern Equine encephalitis, Bluetongue virus, and Lyme disease. 

15 Increased insect density has been correlated with milder seasonal variability (Confalonieri et al. 2007) 

16 and tick distributions tend to expand with higher minimum temperatures (Ebi et al. 2008). In the United 

17 States, the greatest transmissions of West Nile virus occurred during the 2002 through 2004 summers 

18 associated with above average temperatures (EPA 2009b). In general, climate and weather are important

19 constraints on the range of transmission for vector-borne diseases. For example, temperature and 

20 flooding are key constraints on the range of mosquitoes, which serve as a primary vector for malaria and 

21 other diseases (Epstein et al. 2006). Changes in seasonal duration and increases in weather variability 

22 reduce or eliminate these constraints (Epstein et al. 2006). In southern Mozambique, the number of 

23 malaria cases increased four to five times over long-term averages in the days and weeks following a 

24 severe flooding event in 2000 (Epstein et al. 2006). Temperature and the availability of water can both 

25 play key roles in regulating population size. For the deer tick, the disease vector for Lyme disease, off26 host survival is strongly affected by these two variables; therefore, climate is the primary factor 

27 determining size and distribution of deer tick populations (Needham and Teel 1991, Bertrand and Wilson

28 1996, both in Epstein et al. 2006). Changes in land-use practices or to the habitat and behavior of wildlife 

29 hosts of the insect can also impact latitudinal or altitudinal shifts in the disease-carrying species 

30 (Confalonieri et al. 2007). 

31 4.5.8.2.2 Projected Health Impacts of Climate Change on the United States 

32 Human health is projected to be adversely affected by rising temperatures, increasing ground33 level ozone concentrations, changes in extreme weather events, and increasing food- and water-borne 

34 pathogens. The impact of the varying health-related event is dependent on location. The United States is 

35 anticipated to sustain fewer cases of illness and death associated with climate change compared with the 

36 developing world (CCSP 2008d). The existing health infrastructure Federal Government disaster 

37 planning and emergency response systems are key assets to enable the United States to meet changing 

38 health-effect demands associated with climate change. These health impacts will vary in scope across the 

39 United States. 

40 In the United States, there were 20,000 heat and solar-related deaths from 1936 to 1975, with the 

41 heat wave of 1980 accounting for more than 1,250 of these deaths (NOAA 2005 in Kundzewicz et al.

42 2007). There could be a rise in heat-related morbidity and mortality in the coming decades (CCSP 2008d) 

43 due, in part, to an aging population. By 2010, 13 percent of the population of the United States is 

44 projected to be over the age of 65 (Day 1996 in Ebi et al. 2008), and this proportion will grow 

45 dramatically as Baby Boomers age (EPA 2009b). Additionally, most population growth will occur in the 
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1 cities, where temperatures tend to be higher due to the urban heat island effect (EPA 2009b). This shift 

2 toward an older, and more urban population, could increase heat-related health risks. 

3 Studies have shown a decline in heat-related mortality over the past decades, possibly due to 

4 increased air conditioning usage and improved health care (Davis et al. 2002, Davis et al. 2003a, Davis et 

5 al. 2003b, Carson et al. 2006, all in Ebi et al. 2008). Heat waves are anticipated to increase in severity, 

6 frequency and duration, particularly in the Midwest and Northeast (CCSP 2008d). In U.S. regions where

7 severe heat waves already occur, these events are projected (high confidence) to intensify in magnitude 

8 and duration. Tor example, in 2080 through 2099, Chicago could experience a 25-percent increase in the 

9 annual frequency of heat waves under the business-as-usual (A1B) emissions scenario (EPA 2009b). 

10 The northern latitudes of the United States are likely to experience the greatest increases in 

11 average temperature and concentrations of many of the airborne pollutants (CCSP 2008d). A regional 

12 climate simulation projected air quality to worsen in Texas but to improve in the Midwest in 2045 to 2055 

13 compared to 1995 to 2005 (Leung and Gustafson 2005 in Ebi et al. 2008). In urban areas, ground-level 

14 ozone concentrations are anticipated to increase in response to higher temperatures and increases in water 

15 vapor concentration (CCSP 2008d, Jacobson 2008). Climate change could further cause stagnant air 

16 masses that increase pollution concentrations of ground-level ozone and PM in populated areas. For 

17 example, one study projected an increase in upper Midwest stagnant air between 2000 and 2052 (Mickley 

18 et al. 2004 in Ebi et al. 2008). An alternative study found an increase in evaporative losses from nitrate 

19 particles reduces PM levels (Aw and Kleeman 2003 in Ebi et al. 2008). A recent study concluded that 

20 continuous local outdoor CO2 emissions can increase the respective CO2 concentration for that area, 

21 thereby increasing ozone levels (Jacobson 2008). 

22 The spring pollen season has recently been shown to begin earlier than usual in the Northern 

23 Hemisphere (D’Amato et al. 2002, Weber 2002, Beggs 2004, all in Confalonieri et al. 2007). There is 

24 further evidence suggesting a lengthening of the pollen season for some plant species (Confalonieri et al.

25 2007). A recent study determined that the density of air-borne pollen for some species has increased,

26 however, it is not understood what the allergenic content of this additional pollen is (Huynen and Menne 

27 2003, Beggs and Bambrick 2005, both in Confalonieri et al. 2007). Additionally, climate change could 

28 alter the pollen concentration of a given plant species as the species reacts to increased concentrations of 

29 CO2. Current findings demonstrate that ragweed pollen production and the length of the ragweed pollen 

30 season increase with rising CO2 concentrations and temperatures (Wan et al. 2002, Wayne et al. 2002, 

31 Singer et al. 2005, Ziska et al. 2005, Rogers et al. 2006a, all in Confalonieri et al. 2007). Invasive plant 

32 species with high allergenic content, such as ragweed and poison ivy, have been found to be spreading in 

33 particular locations around the world, increasing potential health risks (Rybnicek and Jaeger 2001, 

34 Huynen and Menne 2003, Taramarcaz et al. 2005, Cecchi et al. 2006, all in Confalonieri et al. 2007). For 

35 example, a field study determined urban locations could experience an increase in ragweed pollen 

36 compared to rural locations due to the projected temperature and CO2 concentrations in these locations 

37 (EPA 2009b). Scientific findings are not conclusive about how climate change might impact allergenic 

38 illnesses in the United States, particularly in relation to other factors such as changes in land use, air 

39 pollution, and adaptation practices (EPA 2009b). 

40 Extreme weather events are likely to be altered by climate change, though there is uncertainty 

41 projecting the frequency and severity of events. Some regions in the United States might experience 

42 drought conditions due to the reduction in rainfall, while other sections of the Country are likely to

43 experience increased frequency of heavy rainfall events, leading to potential flood risk (GCRP 2009). It 

44 is considered very likely (greater than 90 percent certainty) that over the course of this century there will 

45 be an increase in the frequency of extreme precipitation (IPCC 2007a). The Southeast, Intermountain 

46 West, and West are likely to experience an increase in frequency, severity, and duration of forest fires 

47 (CCSP 2008d, Brown et al. 2004b, Fried et al. 2004, all in Ebi et al. 2008). Impacts to respective 
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1 vulnerable populations could change in the future as shifts occur in population, suburban development,

2 and community preparedness. It is very likely that a large portion of the projected growth of the United 

3 States population will occur in areas considered to be at risk for future extreme weather events (Ebi et al.

4 2008). Hence, even if the rate of health impacts decreased, the growth in population in risk areas would 

5 still cause an increase in the total number of people affected. Intense tropical cyclone activity is “likely” 

6 to intensify, increasing the risk of death, injuries, diseases, and mental health disorders (EPA 2009b). 

7 Pathogen transmission depends on many climate-related factors such as temperature, 

8 precipitation, humidity, water salinity, extreme weather events, and ecological shifts, and could display 

9 seasonal shifts (Ebi et al. 2008). Few studies have projected the health impact of vector-borne diseases. 

10 Vector-borne illnesses are likely to shift or expand northward and to higher elevations with the possible 

11 introduction of new vector-borne diseases (CCSP 2008d), while decreasing the range of tick-borne 

12 encephalitis in low latitudes and elevation (Randolph and Rogers 2000 in Ebi et al. 2008). For example, 

13 the northern range limit of Lyme disease could shift north by as much as 200 kilometers (about 124 

14 miles) by 2020 and 1,000 kilometers (about 621 miles) by 2080 (Field et al. 2007a; EPA 2009b). Malaria 

15 in the United States is unlikely to be affected by climate change variables given public intervention and 

16 vector control (EPA 2009b). 

17 Food- and water-borne pathogens might spread with a warmer climate. Increases in temperature, 

18 precipitation, and extreme events could spread these pathogens, depending on their survival, persistence, 

19 habitat range, and transmission under changing climate and environmental conditions. While the quality 

20 of the U.S. water supply is well maintained by the Safe Drinking Water Act and the Clean Water Act, 

21 individuals can still be exposed to these pathogens through other means (e.g., swimming) (EPA 2009b). 

22 Climate change is anticipated to increase ozone-related diseases (Sussman et al. 2008). However, 

23 it is important to note that the concentration of ground-level ozone for a particular location varies as a 

24 function of temperature, wind, solar radiation, atmospheric moisture, atmospheric mixing, and cloud 

25 cover. The impact climate change has on some of these variables could have a positive effect on ozone

26 concentrations, while simultaneously the impact of climate change on other variables could have a 

27 negative effect on ozone concentrations (EPA 2009b). Therefore, when estimating the impact climate 

28 change will have on ground-level ozone, it is necessary to account for all of these factors, and not just 

29 temperature (EPA 2009b). That said, climate change is projected to increase surface layer ozone 

30 concentrations in urban and polluted rural environments (EPA 2009b). 

31 Climate change could also have opposing effects on PM. On the one hand, increased 

32 precipitation and humidity in some areas could lower PM concentrations. On the other hand, increased 

33 forest fires could increase PM concentrations. Preliminary modeling indicates an overall small decrease 

34 in PM concentrations due to climate change; however, there are significant regional variations. In the 

35 United States, the Midwest and Northeast, for example, could experience noteworthy increases in PM 

36 concentrations (EPA 2009b). 

37 Overall, populations within certain regions of the United States regions could experience climate 

38 change-induced health impacts from a number of pathways simultaneously. For instance, populations in 

39 coastal communities could experience an extreme weather event, such as a tropical cyclone and flooding, 

40 adding to health burdens associated with sea-level rise or coastal erosion. 

41 4.5.8.2.3 Projected Global Health Impacts of Climate Change 

42 Globally, climate change is anticipated to contribute to both adverse and beneficial health 

43 impacts. Projected adverse health impacts include malnutrition leading to disease susceptibility (high 

44 confidence); increased heat-wave-, flood-, storm- and fire-induced mortality (high confidence); decrease 
Chapter 4 Cumulative Impacts 4.5 Health, Societal, and Environmental Impacts of Climate Change 

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1 in cold-related deaths (high confidence); increased diarrheal disease burden (medium confidence); 

2 increased levels of ground-level ozone (high confidence); and altered geographic distribution of some 

3 infectious disease vectors (high confidence) (Confalonieri et al. 2007). A decrease in cold-related 

4 mortality and some pollutant-related mortality, increased crop yields in certain areas, and restriction of 

5 certain diseases in certain areas (if temperatures or precipitation rise above the critical threshold for vector 

6 or parasite survival) are examples of projected beneficial health impacts (Confalonieri et al. 2007). The 

7 adverse impacts, however, greatly outweigh the beneficial impacts, particularly after mid-century 

8 (Confalonieri et al. 2007). 

9 Regionally, the impact on human health will vary. Some Asian countries could experience 

10 increasing malnutrition by 2030, with crop yields decreasing later in the century, rendering the population 

11 in the region particularly vulnerable to malnutrition-associated diseases and disorders (Confalonieri et al.

12 2007). Certain coastal areas will experience flooding by 2030, impacting human mortality (Confalonieri 

13 et al. 2007). By 2080, Lyme disease is projected to have moved northward into Canada, due to a two- to 

14 four-fold increase in tick abundance (Confalonieri et al. 2007). By 2085, climate change is projected to 

15 increase the population at risk to dengue fever to a total of 3.5 billion people (Confalonieri et al. 2007). 

16 Heat waves have been experienced globally; thousands of deaths incurred in India over the 18 

17 heat waves recorded between 1980 and 1998 (De and Mukhopadhyay 1998, Mohanty and Panda 2003, 

18 De et al. 2004, all in Confalonieri et al. 2007). In August 2003, approximately 35,000 deaths were linked 

19 to a heat wave in Europe, with France alone incurring more than 14,800 deaths (Hemon and Jougla 2004, 

20 Martinez-Navarro et al. 2004, Michelozzi et al. 2004, Vandentorren et al. 2004, Conti et al. 2005, Grize 

21 et al. 2005, Johnson et al. 2005b, all in Confalonieri et al. 2007). About 60 percent of the heat-wave22 related deaths in France were people at or over 75 years of age (Hemon and Jougla 2004 in Confalonieri

23 et al. 2007). Overall, studies have linked high temperatures to about 0.5 to 2 percent of annual mortality 

24 in the elderly European population (Pattenden et al. 2003, Hajat et al. 2006, both in Confalonieri et al.

25 2007). 

26 In 2003, floods in China affected 130 million people (EM-DAT 2006 in Confalonieri et al.2007). 

27 In 1999, storms with floods and landslides in Venezuela killed 30,000 people (Confalonieri et al. 2007). 

28 The World Health Organization (WHO) estimates that a high proportion of those in dry regions 

29 (approximately 2 billion) experience malnutrition, infant mortality, and water-related diseases (WHO 

30 2005 in Confalonieri et al. 2007). Children in low-income countries are particularly vulnerable to loss of 

31 life due to diarrhea. The transmission of the enteric pathogen appears to increase during the rainy season 

32 for children in sub-Saharan Africa (Nchito et al. 1998, Kang et al. 2001, both in Confalonieri et al. 2007). 

33 In Peru, higher temperatures have been linked to periods of increased diarrhea incidence experienced by 

34 adults and children (Checkley et al. 2000, Speelmon et al. 2000, Checkley et al. 2004, Lama et al. 2004, 

35 all in Confalonieri et al. 2007). 

36 Cholera outbreaks associated with floods can occur in areas of poor sanitation. A study of sea37 surface temperatures in the Bay of Bengal demonstrated a bimodal seasonal pattern that translated to 

38 increased plankton activity and leading to increases in cholera in nearby Bangladesh (Colwell 1996, 

39 Bouma and Pascual 2001, both in Confalonieri et al. 2007). 

40 Dengue is considered the most important vector-borne viral disease (Confalonieri et al. 2007). 

41 There is a strong correlation between climate-based factors such as temperature, rainfall, and cloud cover 

42 with the observed disease distribution in Colombia, Haiti, Honduras, Indonesia, Thailand and Vietnam 

43 (Hopp and Foley 2003 in Confalonieri et al. 2007). About one-third of the world’s population lives in 

44 areas with climate conditions favorable for dengue (Hales et al. 2002, Rogers et al. 2006b, both in 

45 Confalonieri et al. 2007). 
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1 Malaria is a vector-borne disease spread by mosquitoes. Depending on location, malaria 

2 outbreaks could be influenced by rainfall amounts and sea-surface temperatures in southern Asia, 

3 Botswana, and South America (Kovats et al. 2003, Thomson et al. 2005, DaSilva et al. 2004, all in 

4 Confalonieri et al. 2007). A recent study of malaria in East Africa found that the measurable warming 

5 trend the area has experienced since the 1970s can be correlated with the potential of disease 

6 transmission. (Pascual et al. 2006 in Confalonieri et al. 2007). However, southern Africa was not shown 

7 to exhibit the same trend (Craig et al. 2004 in Confalonieri et al. 2007). External factors are also 

8 influencing the number of cases of the disease in Africa, such as drug-resistant malaria, and parasite and 

9 HIV infections. Studies did not provide clear evidence that malaria in South America or the continental 

10 regions of the Russian Federation have been affected by climate change (Benitez et al. 2004, Semenov et 

11 al. 2002, both in Confalonieri et al. 2007). In general, however, higher temperatures and more frequent 

12 extreme weather occurrences (such as floods and droughts) are projected to have a stronger influence on 

13 the wider spread of malaria with increasing climate change (McMichael et al. 1996 in Epstein et al.

14 2006). 

15 Temperature has been shown to affect food- and water-borne diseases (EPA 2009b). Several 

16 studies have found increases in salmonellosis cases (food poisoning) within 1 to 6 weeks of the high17 temperature peaks (controlled by season). This could be due in part to the processing of food products 

18 and the population varying its eating habits during warmer months (Fleury et al. 2006b, Naumova et al.

19 2006, Kovats et al. 2004, D’Souza et al. 2004a, all in Ebi et al. 2008). High temperatures have been 

20 shown to increase common types of food poisoning (D’Souza et al. 2004b, Kovats et al. 2004, Fleury et 

21 al. 2006a, all in Confalonieri et al. 2007). Increasing global temperatures could contribute to a rise in 

22 salmonellosis cases (Ebi et al. 2008). There is further concern that projected increasing temperatures 

23 from climate change will also increase leptospirosis cases, a disease that is resurging in the United States. 

24 The effects of climate change on air quality are expected to adversely impact people suffering 

25 from asthma and other respiratory ailments. Increases in temperature, humidity, the prevalence and 

26 frequency of wildfires, and other factors are expected to result in more smog, dust, and particulates that 

27 exacerbate asthma. Widespread respiratory distress throughout many regions of the world is a possible

28 result of climate change. Existing asthma treatment and management plans might be overwhelmed, 

29 leading to major increases in asthma-related morbidity and mortality (Epstein et al. 2006). 

30 Warm climates are more apt to support the growth of the pathogenic species of Vibrio, leading to 

31 shell-fish related death and morbidity that might affect the United States, Japan and Southeast Asia (Janda 

32 et al. 1988, Lipp et al. 2002, both in Ebi et al. 2008, 2-10; Wittmann and Flick 1995, Tuyet et al. 2002, 

33 both in Confalonieri et al. 2007). If temperatures increase, the geographic range and concentration of the 

34 Vibrio species could expand. For example, as the waters of the northern Atlantic have warmed, the 

35 concentration of Vibrio species has increased (Thompson et al. 2004 in Ebi et al. 2008). Future ocean 

36 warming might also lead to the proliferation of harmful algal blooms, releasing toxins that contaminate 

37 shellfish and lead to food-borne diseases (Confalonieri et al. 2007). 

38 In 2000, WHO estimated that climate change has caused the loss of more than 150,000 lives 

39 (Campbell-Lendrum et al. 2003, Ezzati et al. 2004, McMichael 2004, all in Confalonieri et al. 2007). The 

40 projected risks in 2030 described by WHO study vary by health outcome and region; most of the increase

41 in disease is due to diarrhea and malnutrition. More cases of malaria are projected in countries situated at 

42 the edge of the existing distribution. The projected health impact associated with malaria is mixed, with 

43 some regions demonstrating increased burden and others exhibiting decreased burden. 
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1 4.5.9 Tipping Points and Abrupt Climate Change 

2 This section starts by providing an overview of tipping points and abrupt climate change, then 

3 discusses specific climate systems that could be affected, and concludes with a summary. 

4 4.5.9.1 Overview 

5 The phrase “tipping point” is most typically used in the context of climate change and its 

6 consequences to describe situations in which the climate system (the atmosphere, oceans, land, 

cryosphere,4

7 and biosphere) reaches a point at which there is a disproportionately large or singular 

8 response in a climate-affected system as a result of only a moderate additional change in the inputs to that 

9 system (such as an increase in the CO2 concentration). Exceeding one or more tipping points, which 

10 “occurs when the climate system is forced to cross some threshold, triggering a transition to a new state at 

11 a rate determined by the climate system itself and faster than the cause” (National Research Council 

12 2002b in EPA 2009b), could result in abrupt changes in the climate or any part of the climate system. 

13 These changes would likely produce impacts at a rate and intensity far greater than the slower, steady

14 changes currently being observed (and in some cases, planned for) in the climate system (EPA 2009b). 

15 The phrase tipping point is also used outside the climate-modeling community. In addition to 

16 climate scientists, many others – including biologists, marine chemists, engineers, and policymakers – are 

17 concerned about tipping points because it is not just the climate that can change abruptly. The same type 

18 of non-linear responses exists in the physical, environmental, and societal systems that climate affects. 

19 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. 5 20 Consideration of possible tipping 

21 points could therefore encompass sharp changes in climate-affected resources and not be restricted to 

22 climatic parameters and processes. 

23 Using the broad definition of the term tipping point to include both climate change and its 

24 consequences, the scale of spatial responses can range from global (e.g., a “supergreenhouse” atmosphere 

25 with higher temperatures worldwide), to continental or subcontinental changes (such as dramatically 

26 altering the Asian monsoon), to regional (e.g., drying in the southwestern United States, leading to 

27 drought and increases in the frequency of fires), to local (such as loss of the Sierra Nevada snowpack). 

28 The definition of tipping point used by Lenton et al. (2008) (discussed below) specifically applies only to 

29 subcontinental or larger features, whereas public policy is concerned with a wider range of scales, as the 

30 IPCC analysis (discussed below) suggests. 

31 The temporal scales considered are also important. On crossing a tipping point, the evolution of 

32 the climate-affected system is no longer controlled by the time scale of the climate forcing (such as the 

33 heat absorption by GHGs), but rather is determined by its internal dynamics, which can either be much 

34 faster than the forcing, or substantially slower. The much faster case – abrupt climate change – might be 

35 said to occur when the: 

36 • Rate of change is sharply greater than (or a different sign than) what has prevailed over 

37 previous decades; 

38 • State of the system exceeds the range of variations experienced in the past; or 

 

4

 The cryosphere describes the portion of Earth’s surface that is frozen water, such as snow, permafrost, floating ice, 

and glaciers. 

5

 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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1 • Rate has accelerated to a pace that exceeds the resources and ability of nations to respond to 

2 it. 

3 Climate changes could occur in many ways as tipping points are reached. These mechanisms 

4 range from the appearance or unusual strengthening of positive feedbacks – self-reinforcing cycles – and 

5 reversible-phase transitions in climate-affected systems to irreversible-phase transitions – where a 

6 threshold has been crossed that could lead to either abrupt or unexpected changes in the rate or direction 

7 of change in climate-affected systems. Although climate models incorporate many positive (and 

8 negative, or dampening) feedback mechanisms, the magnitude of these effects and the threshold at which

9 the feedback-related tipping points are reached are only roughly known, especially regarding global 

10 impacts. In addition, models of climate and climate-affected systems do not contain all feedback 

11 processes. As subsequently shown in this section, substantial progress has been made in understanding

12 the qualitative processes associated with tipping points, although there are limits to the quantitative 

13 understanding of many of these systems. 

14 In recent years, the concept of a tipping point (or a set of tipping points) and abrupt change (or 

15 abrupt changes) in Earth’s climate system has been attracting increased attention among climate scientists 

16 and policymakers. For example, information on Abrupt Climate Change and High Impact Events was 

17 recently presented in the Technical Support Document for Endangerment and Cause or Contribute 

18 Findings for Greenhouse Gases under Section 202(a) of the Clean Air Act (EPA 2009b). The information 

19 that follows provides a brief survey of tipping points and abrupt climate change, drawing on perspectives 

20 from key analyses of the issue and other relevant research − IPCC, CCSP, Lenton et al. (2008), and 

paleoclimate6

21 evidence − and uses much of the same available literature as used in EPA (2009b) and 

22 recent peer-reviewed research. 

23 In its Fourth Assessment Report, the IPCC addresses the issue of tipping points in the discussion 

24 of “major or abrupt climate changes” (Meehl et al. 2007) and highlights three large systems: the 

25 meridional overturning circulation (MOC) system that drives Atlantic Ocean circulation, the collapse of 

26 the West Antarctic ice sheet, and the loss of the Greenland ice sheet. The IPCC states that there is 

27 uncertainty in the understanding of these systems but concludes that these systems are unlikely to reach 

28 their tipping points within the 21st Century (Meehl et al. 2007). The IPCC also mentions additional 

29 systems that might have tipping points (as noted below), but does not include estimates for them. 

30 The IPCC WGII report provides insight on the uncertainties surrounding tipping points, their 

31 systemic and impact thresholds, and the value judgments required to select a critical level of warming

32 (Carter et al. 2007). The presence of these thresholds can also present their own physical and ecological 

33 limits and informational and cognitive barriers to adaptation (Adger et al. 2007). In the case of this EIS, 

34 uncertainty prevents NHTSA from being able to quantify the impacts of the alternatives under 

35 consideration on specific tipping-point thresholds.

36 In the IPCC WGII report, certain thresholds are assumed and then used with analyses of 

37 emissions scenarios and stabilization targets to assess how certain impacts might be avoided (Schneider et 

38 al. 2007). For example, several authors hypothesize that a large-scale climatic event or other impacts (for 

39 example, widespread coral-reef bleaching; deglaciation of West Antarctica) would be likely if 

40 atmospheric CO2 concentrations stabilize at levels exceeding 450 ppm, although the location of the 

41 tipping points and thresholds is uncertain (O’Neill and Oppenheimer 2002, Lowe et al. 2006, and Corfee42 Morlot and Höhne 2003, all in Schneider et al. 2007). 

 

6

 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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1 The CCSP reaches similar conclusions in its report Scientific Assessment of the Effects of Global 

2 Change on the United States (National Science and Technology Council 2008). The CCSP report 

3 summarizes scientific studies suggesting that there are several “triggers” of abrupt climate change and 

4 that “anthropogenic forcing could increase the risk of abrupt climate change;” however, “future abrupt 

5 changes cannot be predicted with confidence” because of the insufficiencies of current climate models,

which reflect the limits of current understanding.7

6 However, the CCSP report does reiterate the 

7 conclusions of the Committee on Abrupt Climate Change (National Research Council 2002a) that 

8 anthropogenic forcing could increase the risk of abrupt climate change and that (1) “greenhouse warming 

9 and other human alterations of the Earth system may increase the possibility of large, abrupt, and 

10 unwelcome regional or global climatic events;” (2) “abrupt changes of the past are not fully explained yet, 

11 and climate models typically underestimate the size, speed, and extent of those changes;” and (3) “future 

12 abrupt changes cannot be predicted with confidence, and climate surprises are to be expected” (EPA 

13 2009b). 

14 The CCSP report (National Science and Technology Council 2008) considers the susceptibility of 

15 the same three systems to abrupt change as IPCC highlighted − the Atlantic MOC (AMOC) system that 

16 drives Atlantic Ocean circulation, the collapse of the West Antarctic ice sheet, and the loss of the 

17 Greenland ice sheet. The report also suggests that there are thresholds in non-climate systems influenced 

18 by CO2 emissions, such as ocean acidification, where there could be a threshold beyond which existing 

19 coral reef ecosystems cannot survive (National Science and Technology Council 2008). The CCSP report 

20 concludes that these impacts, including climate-related thresholds, could occur in groups as thresholds are 

21 crossed, but, due to the uncertainty, more research is needed to quantify the impacts of crossing particular 

22 thresholds and to determine when these thresholds would be reached (National Science and Technology 

23 Council 2008). 

24 The IPCC WGI report (Meehl et al. 2007) describes various climate and climate-affected systems 

25 that might undergo abrupt change, contribute to “climate surprises,” or experience irreversible impacts, as 

26 follows: AMOC and other ocean circulation changes, Arctic sea ice, glaciers, and ice caps, Greenland 

27 and West Antarctic ice sheets, vegetation cover, and atmospheric and ocean-atmosphere regimes. 

28 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.8

29 These reasons for concern 

include the risks of large-scale discontinuities (also referred to as singularities or tipping points).

9

30 

31 Recently, Smith et al. (2008), the authors of the reasons for concern, describe revised sensitivities to 

32 increases in global mean temperature for the reasons for concern, and present a more thorough 

33 understanding of the concept of vulnerability based on expert judgment about findings in the literature 

34 assessed in the Fourth Assessment Report and additional research published since. In the case of the 

35 likelihood of large-scale discontinuities, including partial or complete deglaciation of the Greenland ice 

36 sheet or the West Antarctic ice sheet and substantial reduction or collapse of the AMOC, the authors 

37 acknowledge that “no single metric could adequately describe the diversity of impacts and associated risk 

38 for any one [reason for concern], let alone aggregate across all of them into a single “dangerous” global 

39 temperature threshold.” However, based on “growing evidence that even modest increases in [global 

40 mean temperature] could commit the climate system to the risk of very large impacts on multiple-century 

 

7

See CCSP 2008d. 

8

 The “reasons for concern” were originally introduced and discussed in the IPCC Third Assessment Report. 

9

 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. 
4.5 Health, Societal, and Environmental Impacts of Climate Change Chapter 4 Cumulative Impacts 

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time scales,”10 1 the risks of large-scale discontinuities were expertly judged to begin being a source of 

2 substantial risk around 1 °C (around 2 °F). Smith et al. (2008) projected 2.5 °C (4.5 °F) – the midpoint of 

3 the warming range cited for partial deglaciation – to be the “possible trigger for commitment to large4 scale global impacts over multiple-century time scales.” 

5 Building on the IPCC and early CCSP research, at a workshop entitled “Tipping Points in the 

6 Earth System” experts identified several climate systems that have tipping points, and tested and refined a 

7 questionnaire subsequently distributed electronically to 193 international scientists. Fifty-two scientists 

8 (among them 16 workshop participants and 22 contributors to the IPCC Fourth Assessment Report) 

9 returned a completed questionnaire. Lenton et al. (2008) published the findings from this expert 

10 elicitation identifying nine systems facing separate tipping points due to increased CO2 and temperature 

11 levels that met four scientifically based criteria to be considered “policy-relevant potential future tipping 

12 elements in the climate system” (Lenton et al. 2008). Additional systems were identified, but insufficient 

13 information precluded these systems from meeting the definition of policy relevant. The systems at risk 

14 that the researchers identified are: Arctic sea ice, Greenland ice sheet, West Antarctic ice sheet, Atlantic 

15 thermohaline circulation (a component of the AMOC), El-Niño-Southern Oscillation, Indian summer 

16 monsoon, Sahara/Sahel and West African monsoon, Amazon rainforest, and boreal forest. 

The CCSP report SAP 3.4, Abrupt Climate Change 11 17 (CCSP 2008e), provides additional 

18 information on the topic of abrupt climate change, focusing on rapid change in glaciers, ice sheets, and 

19 hence sea level; widespread and sustained changes to the hydrologic cycle; abrupt change in the AMOC; 

20 and rapid release to the atmosphere of methane trapped in permafrost and on continental margins. 

21 The report updates “the state and strength of existing knowledge, both from the paleoclimate and 

22 historical records, and from model predictions for future change” and “reflects the significant progress in 

23 understanding abrupt climate change that has been made since” the report by the Committee on Abrupt 

24 Climate Change (National Research Council 2002a) and the IPCC WGI report (Meehl et al. 2007). 

25 4.5.9.2 Affected Climate Systems 

26 The list of affected climate systems covered by the key analyses and peer-reviewed research 

27 identified above includes: 

28 • Rapid changes in glaciers and ice sheets (including paleoclimate evidence on sea-level rise 

29 from previous ice-sheet melt); 

30 • Hydrologic variability and change; 

31 • Potential for abrupt change in the AMOC and Atlantic Thermohaline Circulation (a 

32 component of the AMOC); 

33 • Potential for abrupt changes in atmospheric methane; 

34 • El-Niño-Southern Oscillation; 

35 • Indian summer monsoon; 

36 • Sahara/Sahel and West African monsoon; 

 

10 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. 

11 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 

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1 • Amazon rainforest; and 

2 • Boreal forest. 

3 Each system is described below. 

4 Rapid Changes in Glaciers and Ice Sheets. Based on an assessment of the published scientific 

5 literature, Clark et al. (2008) found that “observations demonstrate that it is extremely likely that the GIS 

6 [Greenland ice sheet] is losing mass and that this has very likely been accelerating since the mid-1990s” 

7 (EPA 2009b). Another recent CCSP report, SAP 1.2, Past Climate Variability and Change in the Arctic 

8 and High Latitudes (CCSP 2009a), finds a threshold for ice-sheet removal from sustained summertime 

9 warming in relation to pre-industrial temperatures of 5 °C (9 °F) (with a range of uncertainty from 2 to 7 

10 °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) 

11 suggested by Meehl et al. (2007) for the complete melting of the Greenland ice sheet, albeit over many 

12 hundreds of years (see EPA 2009b). 

13 The surface of Arctic sea ice has a higher albedo (reflectivity) than the darker ocean surface. As 

14 sea ice melts from higher air and ocean temperatures, more of the ocean is exposed, which allows more 

15 radiation to be absorbed, amplifying the sea-ice melt. In summer, Arctic sea-ice loss could lead to the ice 

16 cap melting beyond a certain size/thickness, making it unstable and leading to an ice-free Arctic. Recent 

17 record ice losses and modeling studies have led some researchers to suggest that the summer Arctic will 

18 be ice-free within a decade or less, that there is a critical threshold for summer Arctic sea-ice loss, and 

19 that this threshold has already been crossed (Borenstein and Joling 2008 in Lenton et al. 2008). 

20 The USGS estimates that a complete disintegration of the neighboring, predominantly land-based 

21 Greenland ice sheet would raise sea level by 6.55 meters (21.5 feet; Williams and Hall 1993 in USGS 

22 2000). However, a recent paper by Pfeffer et al. (2008) studying Kinematic Constraints on Glacier 

23 Contributions to 21st-Century Sea-Level Rise and taking dynamic land ice loss into account, postulates 

24 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 

25 meters (0.6 to 1.9 feet) projected in the IPCC Fourth Assessment Report. Pfeffer et al. (2008) conclude 

26 that “increases in excess of 2 meters [6.6 feet] are physically untenable” by 2100. Rahmstorf (2007) 

27 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 

28 dynamic land ice-loss processes credited with accelerated ice loss include enhanced surface melt-water

29 production penetrating to the glacier base lubricating motion; and buttressing ice-shelf removal, ice-front 

30 retreat, and glacier un-grounding that reduce resistance to glacier flow. 

31 The Greenland ice sheet is also susceptible to positive feedbacks. Melting at the glacial margins 

32 lowers the edge of the ice sheet to elevations that are warmer and where more melting will occur. The

33 IPCC estimated the Greenland ice sheet threshold for negative surface mass at 1.9 to 4.6 °C (3.4 to 8.3 °F) 

34 above pre-industrial temperature, well within the predicted temperature range for this century. Dynamic 

35 ice-melting processes, regional temperatures, warming surrounding oceans, and recent observations 

36 indicating that both Greenland and Antarctica are now losing mass have led researchers to conclude that 

37 the timescale for Greenland ice sheet collapse is conceivably on a scale of hundreds rather than thousands 

38 of years (Lenton et al. 2008). 

39 The USGS (2005) estimates the collapse of the West Antarctic ice sheet would raise sea level by 

40 approximately 6 meters (approximately 20 feet) although the most recent reassessment by Bamber et al. 

41 (2009a) obtains a value of 3.3 meters (10.8 feet). The processes of surface melt and glacier un-grounding 

42 from melting at the base from a warmer ocean are implicated in the potential destabilization of the West 

43 Antarctic ice sheet (EPA 2009b). However, ice-sheet models do not include all the small-scale dynamical 

44 processes involving the glacier base and the ocean at the edge of the ice sheet (EPA 2009b, Meehl et al. 

45 2007) and dynamic ice loss was not represented in the models used by the IPCC to project sea-level rise 
4.5 Health, Societal, and Environmental Impacts of Climate Change Chapter 4 Cumulative Impacts 

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1 (EPA 2009b). Therefore, while these models suggest that Antarctica will gain in mass due to increased

2 snowfall, Clark et al. (2008) indicate that substantial ice losses from West Antarctica and the Antarctic 

3 Peninsula are very likely occurring, so that Antarctica is losing ice mass on balance despite ice thickening 

4 over some higher-elevation regions (EPA 2009b). Lemke et al. (2007a) have presented satellite and in 

5 situ observations of dynamic ice-sheet reactions behind disintegrating ice shelves, and found no 

6 significant continent-wide trends in snow accumulation over the past several decades (EPA 2009b). 

7 Because the present generation of models does not capture all these processes, Clark et al. (2008) 

8 state that “it is unclear whether [glacier accelerations of flow and thinning are] a short-term natural 

9 adjustment or a response to recent climate change,” however, “accelerations are enabled by warming, so

10 these adjustments will very likely become more frequent in a warmer climate.” 

11 Because the West Antarctic ice sheet is grounded below sea level, positive feedbacks could result 

12 from the loss of buttressing sea-ice shelves and the ingress of warmer ocean water. While centuries or 

13 millennia could pass before a collapse, the thresholds for ocean and surface atmospheric warming 

14 temperature are likely to be crossed this century (Lenton et al. 2008). A recent study of ice-core records 

15 suggests strong links between past West Antarctic climate, and potentially its ice sheet, to large-scale 

16 changes in global climate, particularly major El Niño events (Schneider and Steig 2008 in Lenton et al. 

17 2008). 

18 The paleoclimate record cited by IPCC, CCSP, and others gives an indication of sea-level rise 

19 from previous ice-sheet melt, and the corresponding temperature for these periods. For example, 

20 geological evidence showing the presence of elevated beaches suggests that global sea level was 4 to 6

21 meters (13 to 20 feet) higher during the most recent interglacial period about 125,000 years ago (Jansen et 

22 al. 2007). Paleoclimatic reconstructions suggest that global average temperature then was about 1 °C (1.8 

23 °F) warmer than during the present interglacial period (Hansen et al. 2007). Corings from the ice sheets 

24 to determine their ages, supplemented by simulations of ice-sheet extent, suggest that large-scale retreat 

25 of the southern half of the Greenland ice sheet and other Arctic ice fields likely contributed roughly 2 to 4 

26 meters (6.6 to 13.1 feet) of sea-level rise during the last interglacial period, with most of any remainder 

27 likely coming from the Antarctic ice sheet (Jansen et al. 2007). Schneider et al. (2007) assess similar 

28 paleoclimatic evidence for a sea-level rise of 4 to 6 meters (13.1 to 19.7 feet) during the last interglacial 

29 period, with polar temperatures 3 to 5 °C (5.4 to 9.0 °F) warmer than at present (and global mean 

30 temperature not notably warmer than at present) (EPA 2009b). Schneider et al. (2007) go on to conclude 

31 with medium confidence that partial melting of the Greenland ice sheet (and possibly the West Antarctic 

32 ice sheet) would occur over a timescale of centuries to millennia for a global average temperature increase 

33 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 

34 (EPA 2009b). 

35 Paleoclimatic reconstructions also indicate occurrences of abrupt changes in the terrestrial, ice, 

36 and oceanic climatic records. For example, ice-core records suggest that temperatures atop the Greenland 

37 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,12 38 which were likely caused by the North Atlantic Ocean being covered by 

39 catastrophic outflows of glacial meltwater from the North American ice sheet that was present during 

40 glacial times (Jansen et al. 2007). A more recent study (Steffensen et al. 2008) provides more detail, 

41 indicating that there was a sharp warming over 1 to 3 years (that is, “abrupt climate change happens in [a] 

42 few years”), followed by a more gradual warming over 50 years. 

 

12 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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1 For the future, Hansen et al. (2007) and Hansen et al. (2008) suggest that climate feedback 

2 processes not included in most climate models (e.g., slower surface albedo and ice-sheet feedbacks) have 

3 the potential to cause large and rapid shifts in climate and in factors like glacial melt and sea-level rise 

4 that are closely dependent on the climate. 

In a study utilizing model simulations and paleoclimatic data,13 5 Hansen et al. (2007) conclude 

6 that “...a CO2 level exceeding about 450 ppm is ‘dangerous,’” where “dangerous” is defined by the 

7 authors to be global warming of more than 1 oC (1.8 oF) above the level in 2000, potentially leading to 

8 highly disruptive effects. Although this 450-ppm estimate has limitations and uncertainties, Hansen’s

9 more recent publications have suggested a target atmospheric CO2 concentration of 350 ppm (Hansen et 

10 al. 2008) – lower than the CO2-equivalent concentration, including the offsetting effects of aerosols, is 

11 today. 

12 The range of views linking past and future sea-level rise is clearly broad, with uncertainty 

13 attributable to each view. 

14 Hydrologic Variability and Change. Clark et al. (2008) state that “there is no clear evidence to 

15 date of human-induced global climate change on North American precipitation amounts,” however, 

16 “further analysis [since the IPPC Fourth Assessment Report] of climate models scenarios of future 

17 hydrological change over North America and the global subtropics indicate that subtropical aridity is 

18 likely to intensify and persist due to future greenhouse gas warming.” The projected drying would extend 

19 into the southwest United States and potentially increase the likelihood of future severe and persistent 

20 drought in the region, and while model results indicate that this drying might have already begun, it 

21 cannot be definitively distinguished from the natural variability of hydro-climate for the region (EPA

22 2009b). 

23 A recent paper by Solomon et al. (2009) also demonstrates the potential for substantial – and 

24 irreversible – decreases in dry-season rainfall in a number of already-dry areas (including the southwest 

25 United States), and while these impacts are not expressly related to a specific tipping point or an 

26 associated abrupt climate change, the magnitude and irreversibility of these impacts makes them policy

27 relevant. The paper shows that the climate change resulting from an increase in atmospheric CO2 levels 

28 from near present-day values – 385 ppm – to a peak of 450 to 600 ppm over the coming century is largely 

29 irreversible. Solomon et al. (2009) used a suite of AOGCM projections to characterize precipitation 

30 changes. More than 80 to 90 percent of the models project increased drying of respective dry seasons for 

31 the regions of southern Europe, northern Africa, southern Africa, southwestern United States, eastern 

32 South America, and western Australia; and long-term irreversible warming and mean rainfall changes. 

33 For example, changes in dry-season precipitation in southwestern North America would be about 10 

34 percent for 2 °C (3.6 °F) of global mean warming, comparable to the American “dust bowl,” with average

35 rainfall decreases of around 10 percent over about 10 to 20 years. 

36 Potential for Abrupt Change in the Atlantic Meridional Overturning Circulation. The AMOC is 

37 the northward flow of warm, salty water in the upper layers of the Atlantic Ocean coupled to the 

38 southward flow of colder water in the deep layers, and transports oceanic heat from low to high latitudes. 

39 Clark et al. (2008) state, “it is very likely that the strength of the AMOC will decrease over the course of 

the 21st 40 Century in response to increasing greenhouse gases, with a best estimate decrease of 25–30 

 

13 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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1 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 2 Century, and is unlikely to collapse during this period, 

3 although they do not entirely exclude the possibility (EPA 2009b). 

4 The term thermohaline circulation (THC) refers to the physical driving mechanism of ocean 

5 circulation, resulting from fluxes of heat and fresh water across the sea surface, subsequent interior

6 mixing of heat and salt, and geothermal heat sources. The MOC, discussed in the IPCC and CCSP 

7 reports, is the observed response in an ocean basin to this type of ocean circulation coupled with wind8 driven currents. The Lenton et al. (2008) paper refers to risk to the Atlantic THC instead of the AMOC 

9 because they are discussing the influence of climate change on the underlying cooling or freshwater 

10 forcing of the Atlantic Ocean circulation, even though this in turn dramatically affects the AMOC. 

11 If enough fresh water enters the North Atlantic (such as from melting sea ice or the Greenland ice 

12 sheet), the density-driven sinking of North Atlantic waters might be reduced or even stopped, as 

13 apparently occurred during the last glacial cycle (Stocker and Wright 1991 in Lenton et al. 2008). This 

14 would likely reduce the northward flow of thermal energy in the Gulf Stream and result in less heat 

15 transport to the North Atlantic. At the same time, reduced formation of very cold water would likely slow 

16 the global ocean THC, leading to impacts on global climate and ocean currents. The IPCC review of the

17 results of model simulations suggests that an abrupt transition of the Atlantic Ocean’s component of the 

18 global THC is very unlikely this century. However, more recent modeling that includes increased 

19 freshwater inputs suggests there could be initial changes this century, with larger and more intense 

20 reductions in the overturning circulation persisting for many centuries (Mikolajewicz et al. 2007 in 

21 Lenton et al. 2008). 

22 Potential for Abrupt Changes in Atmospheric Methane. A “dramatic” release of CH4 to the 

atmosphere from clathrate hydrates14 23 in the sea bed and permafrost, and from northern high-latitude and 

24 tropical wetlands, has been identified as a potential cause of abrupt climate change (EPA 2009b). Clark 

25 et al. (2008) state that the size of the hydrate reservoir is uncertain (perhaps by up to a factor of 10), 

26 making judgments about risk difficult to assess (EPA 2009b). This uncertainty is borne out by a recent 

27 study by Tanocai et al. (2009) estimating soil organic carbon pools in the northern circumpolar 

28 permafrost regions. The study reports new estimates − including deeper layers and pools not previously 

29 accounted for − about double those reported in previous analyses for the first meter of soil.

30 Clark et al. (2008) conclude that despite suggestions in the literature of a possible dramatic abrupt 

31 release of CH4 to the atmosphere, modeling and isotopic fingerprinting of ice-core CH4 do not support 

32 such a release over the last 100,000 years or in the near future, and “the risk of catastrophic release of 

33 methane to the atmosphere in the next century appears very unlikely” (EPA 2009b). However, Clark et 

34 al. (2008) also state “it is very likely that climate change will accelerate the pace of persistent emissions 

35 from both hydrate sources and wetlands. Current models suggest wetland emissions could double in the 

36 next century. However, because these models do not realistically represent all of the processes thought to 

37 be relevant to future northern high-latitudes CH4 emissions, much larger (or smaller) increases cannot be 

38 discounted. Acceleration of persistent release from hydrate reservoirs is likely, but its magnitude is 

39 difficult to estimate” (EPA 2009b).

 

14 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).

15 1 The changes that might lead to increasingly persistent 

2 (and frequent) El Niño (or La Niña) conditions are particularly uncertain. Increases in ocean heat content 

3 could have an effect on ENSO conditions, but predictive and paleoclimate modeling studies do not agree

4 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).16 5 

6 Indian Summer Monsoon. The Indian summer monsoon is the result of land-to-ocean pressure 

7 gradients and advection of moisture from ocean to land. By warming the land more than the ocean, 

8 climate change generally strengthens the monsoon. However, reductions in the amount of solar radiation 

9 that is absorbed by the land surface, due to some types of land-use change, generally weaken it. An 

10 albedo greater than roughly 50 percent is necessary to simulate the collapse of the Indian summer 

11 monsoon in a simple model (Zickfield et al. 2005 in Lenton et al. 2008). IPCC projections do not project 

12 passing a threshold this century, although paleoclimatic reconstructions do indicate that the monsoon has 

13 changed substantially in the past (Lenton et al. 2008). 

14 West African Monsoon. Sahara/Sahel rainfall depends on the West African monsoon circulation, 

15 which is affected by sea-surface temperature. By warming the land more than the ocean and therefore 

16 causing greater upward movement of the air, GHG forcing is expected to draw more moist oceanic air 

17 inland and thereby increase rainfall in the region, which as simulated by some models. Other models, 

18 however, project a less productive monsoon. The reasons for this inconsistency are not clear (Lenton et 

19 al. 2008).

20 Amazon Rainforest. The recycling of precipitation in the Amazon rainforest implies that 

21 deforestation, reductions in precipitation, a longer dry season, and increased summer temperature could 

22 contribute to forest dieback. These conditions are thought to be linked to a more persistent El Niño and 

23 an increase of global average temperature by 3 to 4 °C (5.4 to 7.2 °F). Important additional stressors also 

24 present include forest fires and human activity (such as land clearing). A critical threshold might exist in 

25 canopy cover, which could be reached through changes in land use or regional precipitation, ENSO 

26 variability, and global forcing (Lenton et al. 2008). 

27 Boreal Forest. The dieback of boreal forest could result from a combination of increased heat 

28 stress and water stress, leading to decreased reproduction rates, increased disease vulnerability, and

29 subsequent fire. Although highly uncertain, studies suggest a global warming of 3 °C (5.4 °F) could be 

30 the threshold for loss of the boreal forest (Lenton et al. 2008).

31 4.5.9.3 Summary 

32 The IPCC, CCSP, and Lenton et al. (2008) conclude that the loss of the Greenland ice sheet, the 

33 collapse of the West Antarctic ice sheet, and the disruption of the Atlantic THC systems are not expected 

34 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 centuries17 35 ). Lenton et al. (2008) 

36 determined that several other systems (loss of Arctic sea ice, Indian summer monsoon disruption, 

 

15 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. 

16 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.). 

17 See Lenton et al. (2008). 
4.5 Health, Societal, and Environmental Impacts of Climate Change Chapter 4 Cumulative Impacts 

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1 Sahara/Sahel and West African monsoon changes, drying of the Amazon rainforest, and warming of the 

2 boreal forest) could reach a tipping threshold within the century, however. 

3 A factor that might accelerate climate change at rates faster than those currently observed is the 

4 possible shift of soil and vegetation-carbon feedbacks, causing the soil and vegetation to become carbon 

5 sources rather than carbon sinks. At present, soil and vegetation act as sinks, absorbing carbon from the 

6 atmosphere as plant material and storing carbon in the soil when the plants die. However, by mid-century 

7 (about the time the IPCC projects the global average temperature reaches 2.0 oC [3.6 oF] above pre8 industrial levels), increasing temperatures and precipitation could cause increased rates of transpiration, 

9 resulting in soil and vegetation becoming a potential source of carbon emissions (Cox et al. 2000 in 

10 Meehl et al. 2007). Warming could also thaw frozen Arctic soils (permafrost), causing the wet soils to 

11 emit more CH4, a GHG. This suggestion is supported by the findings of the most recent CCSP reports, 

12 with Clark et al. (2008) suggesting that it is very likely that climate change will accelerate the pace of 

13 persistent emissions from hydrate sources and wetlands (EPA 2009b). In fact, there is evidence that 

14 permafrost is already melting (Walter et al. 2007). 

15 Across all of the climate systems for which tipping points have been hypothesized or observed 

16 from the paleoclimatological record, uncertainties exist, especially for timing estimates, and the 

17 uncertainties are at least partly responsible for the broad spectrum of views regarding tipping points. 

18 Exactly where these tipping points exist, and the levels at which they occur, are still a matter in need of 

19 further scientific investigation before precise quantitative conclusions can be made. 

20 Where information in this EIS analysis is incomplete or unavailable, as here due to current 

21 climate modeling limitations, NHTSA has relied on the CEQ regulations regarding incomplete or 

22 unavailable information (see 40 CFR § 1502.22(b)). CEQ regulations state, in part, that when an agency 

23 is evaluating “reasonably foreseeable significant adverse impacts on the human environment and 

24 ...information relevant to...[the] impacts cannot be obtained because the overall costs of obtaining it are 

25 exorbitant or the means to obtain it are not known, the agency shall include within the [EIS]: 

26 (1) a statement that such information is incomplete or unavailable; 

27 (2) a statement of the relevance of the incomplete or unavailable information to evaluating 

28 reasonably foreseeable significant adverse impacts on the human environment; 

29 (3) a summary of existing credible scientific evidence which is relevant to evaluating the 

30 reasonably foreseeable significant adverse impacts on the human environment; and 

31 (4) the agency’s evaluation of such impacts based upon theoretical approaches or research 

32 methods generally accepted in the scientific community. For the purposes of this section, 

33 “reasonably foreseeable” includes impacts which have catastrophic consequences, even if 

34 their probability of occurrence is low, provided that the analysis of the impacts is supported 

35 by credible scientific evidence, is not based on pure conjecture, and is within the rule of 

36 reason.” 

37 40 CFR § 1502.22 (b). 

38 This EIS addresses the requirements of 40 CFR § 1502.22 appropriately. The above survey of the 

39 current state of climate science tipping points provides a “summary of existing credible scientific 

40 evidence which is relevant to evaluating the...adverse impacts of the CAFE standards.” In Colorado 

41 Environmental Coalition v. Dombeck, the Tenth Circuit found that the ultimate goal of the agency is to 

42 ensure that the EIS’s “form, content, and preparation foster both informed decision making and informed 

43 public participation” (185 F.3d 1162, 1172 [10th Cir. 1999] [quoting Oregon Envtl. Council v. Kunzman, 
Chapter 4 Cumulative Impacts 4.5 Health, Societal, and Environmental Impacts of Climate Change 

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1 817 F.2d 484, 492 (9th Cir. 1987)]). The Tenth Circuit held that 40 CFR § 1502.22 could not be read as 

2 imposing a “data gathering requirement under circumstances where no such data exists.” Id.

3 In this case, this EIS acknowledges that information on tipping points or abrupt climate change is 

4 incomplete, and the state of the science does not allow for a characterization of how the CAFE 

5 alternatives influence these risks, beyond emission levels serving as a reasonable proxy for the risks and 

6 impacts of climate change, including tipping point risks. This action alone, even as analyzed for the most 

7 stringent alternative, is very unlikely to produce sufficient CO2 emissions reductions to avert emission 

8 levels corresponding to abrupt and severe climate change. To the degree that the action in this 

9 rulemaking reduces the rate of CO2 emissions, the rule contributes to the general reduction or delay of 

10 reaching these tipping-point thresholds. Moreover, while NHTSA’s action alone does not produce 

11 sufficient CO2 emissions reductions, it is one of several other federal programs, which, in conjunction 

12 with NHTSA CAFE standards, could make substantial contributions in averting levels of abrupt and 

13 severe climate change. These conclusions are not meant to be read as expressing NHTSA views that 

14 tipping points in climate-related systems are not areas of concern for policymakers. Under NEPA, the 

15 agency is obligated to discuss “the environmental impact[s] of the proposed action.” 42 U.S.C. § 

16 4332(2)(C)(i) (emphasis added). The discussion above fulfills NHTSA’s NEPA obligations regarding 

17 this issue. 

18 
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1 
Chapter 4 Cumulative Impacts 4.6 Environmental Justice 

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1 4.6 ENVIRONMENTAL JUSTICE 

2 4.6.1 Affected Environment 

3 Executive Order (EO) 12898, Federal Actions to Address Environmental Justice in Minority 

4 Populations and Low Income Populations, directs federal agencies to “promote nondiscrimination in 

5 federal programs substantially affecting human health and the environment, and provide minority and low 

6 income communities access to public information on, and an opportunity for public participation in, 

7 matters relating to human health or the environment.” EO 12898 also directs agencies to identify and 

8 consider disproportionately high and adverse human health or environmental effects of their actions on 

9 minority and low-income communities, and provide opportunities for community input in the NEPA 

10 process, including input on potential effects and mitigation measures. CEQ, the entity responsible for 

11 compliance with EO 12898, has provided agencies with general guidance on how to meet the 

12 requirements of the EO as it relates to NEPA in Environmental Justice Guidance Under the National 

13 Environmental Policy Act (CEQ 1997). This guidance document also defines the terms “minority” and 

14 “low-income community” in the context of environmental justice analysis. Members of a minority are 

15 defined as: American Indians or Alaskan Natives, Asian or Pacific Islanders, Blacks, and Hispanics. 

16 Low-income communities are defined as those below the poverty thresholds from the U.S. Census 

17 Bureau. The term “environmental justice populations” refers to the group comprised of minorities and 

18 low-income communities as defined. 

19 In compliance with EO 12898, NHTSA provides in this EIS a qualitative analysis of the 

20 cumulative effects of the proposed action in regard to air pollutant discharges and climate change on these 

populations.1 21 

22 As described in Section 3.5.10, research studies have shown that minority and low-income 

23 populations often disproportionately reside near high-risk polluting facilities, such as oil refineries, and 

24 “mobile” sources of air toxins and pollutants, as in the case of populations residing near highways. 

25 Environmental justice populations also tend to be concentrated in areas with a higher risk of climate26 related impacts. CCSP notes that this geographic placement might put these communities at higher risk, 

27 “from climate variability and climate-related extreme events such as heat waves, hurricanes, and tropical 

28 and riverine flooding” (CCSP 2008). 

29 4.6.2 Environmental Consequences 

30 4.6.2.1 Air Quality 

31 NHTSA predicts that upstream emissions from oil refining would decrease, which could cause a 

32 local improvement in air quality for residents near oil refineries. This improvement could represent a 

33 small positive impact on environmental justice populations living or working near these facilities. 

34 Emissions of all but one of the criteria air pollutants analyzed and all but one of the MSATs 

35 analyzed would decrease overall with adoption of any of the action alternatives and the foreseeable fuel 

36 economy improvements (see Section 4.3). However, increases in VMT due to the rebound effect are still 

37 projected to cause increases in emissions of some criteria and toxic air pollutants in some air quality 

 

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). 
4.6 Environmental Justice Chapter 4 Cumulative Impacts 

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1 nonattainment areas. These emissions would be distributed throughout the roadway network. The large 

2 size of each nonattainment area and the minor emissions increases in affected nonattainment and other 

3 areas make it unlikely that there would be disproportionate effects to environmental justice populations. 

4 4.6.2.2 Effects of Climate Change in the United States 

5 Environmental justice populations in the United States, as defined by EO 12898, would 

6 experience the same general impacts as a result of global climate change felt by the U.S. population as a 

7 whole and described in Sections 4.5.6, Food, Fiber, and Forest Products; 4.5.7, Industries, Settlements, 

8 and Society; and 4.5.8, Human Health. However, the CCSP notes that the general climate change impacts 

9 to the U.S. population might be differentially experienced by environmental justice populations, 

10 explaining that “[e]conomic disadvantage, lower human capital, limited access to social and political 

11 resources, and residential choices are social and economic reasons that contribute to observed differences 

12 in disaster vulnerability by race/ethnicity and economic status” (CCSP 2008). These impacts are similar 

13 to those that would be experienced globally, although the severity of impacts experienced by developing 

14 countries would likely be disproportionately larger than those experienced in developed nations, such as 

15 the United States. 

16 Within the United States, some environmental justice populations are likely to be affected. The 

17 remainder of this section discusses, qualitatively, the most substantial areas of potential disproportionate 

18 impacts for these populations in the United States. 

19 4.6.2.2.1 Human Health 

20 Low-income and minority communities exposed to the direct effects of extremes in climatic 

21 conditions might also experience synergistic effects with preexisting health risk factors, such as limited 

22 availability of preventative medical care and inadequate nutrition (CCSP 2008). 

23 As described in Section 4.5.7, increases in heat-related morbidity and mortality as a result of 

24 higher overall and extreme temperatures is likely to disproportionately affect minority and low-income 

25 populations, partially as a result of limited access to air conditioning and a result of high energy costs 

26 (CCSP 2008, EPA 2009a, O’Neill et al. 2005). Urban areas, which often have relatively large 

27 environmental justice populations, would likely experience the most substantial temperature increase due 

28 to the urban “heat island” effect and could be particularly vulnerable to this type of health impact (CCSP 

29 2008, Knowlton et al. 2007). 

30 The IPCC notes that many human diseases are sensitive to weather. Increasing temperatures 

31 could lead to expanded ranges for a number of diseases (CCSP 2008). As described in Section 4.5.8, the 

32 number and severity of outbreaks for vector-borne illnesses, such as the West Nile Virus, could become 

33 more frequent and severe. Because the vectors of these diseases (such as mosquitoes) are more likely to 

34 come into contact with environmental justice populations, there could be disproportionate impacts. For 

35 example, an outbreak of the mosquito-borne dengue fever in Texas primarily affected low-income 

36 Mexican immigrants living in lower-quality housing without air conditioning, leading a team researching 

37 the outbreak to conclude that the low prevalence of dengue in the United States is primarily due to 

38 economic, rather than climatic, factors (Reiter et al. 2003). 

39 4.6.2.2.2 Land Use 

40 In the United States, two primary types of geographical environmental justice communities are 

41 likely to be affected by global climate change: urban areas, because of their relatively high 

42 concentrations of low-income and minority residents, and indigenous communities. Environmental 
Chapter 4 Cumulative Impacts 4.6 Environmental Justice 

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1 justice communities in urban areas, because of previously mentioned heat exposure and health issues, are 

2 likely to experience climate change impacts more acutely. Additionally, environmental justice 

3 populations in coastal urban areas (vulnerable to increases in flooding as a result of projected sea-level 

4 rise, larger storm surges, and human settlement in floodplains) are less likely to have the means to quickly 

5 evacuate in the event of a natural disaster (CCSP 2008, GCRP 2009). CCSP, as an example, notes that 

6 flooding in Louisiana following the 2005 Hurricane Katrina primarily killed poor and elderly residents 

7 having no means to flee (GCRP 2009). In Alaska, more than 100 Native American villages on the coast 

8 and in low-lying areas along rivers are subject to increased flooding and erosion due to climate change 

9 (GCRP 2009). These indigenous communities could face major impacts on their subsistence economies 

10 from climate change. These impacts would result from their partial reliance on arctic animals, such as 

11 seals and caribou, for food and the potential destruction of transportation infrastructure due to ground 

12 thaw. 

13 In coastal and floodplain areas prone to flooding because of larger storm surges and generally 

14 more extreme weather, increases in flood insurance premiums could disproportionately affect 

15 environmental justice populations unable to absorb the additional cost. Lack of sufficient insurance 

16 coverage might render these populations more financially vulnerable to severe weather events. 

17 Potential food insecurity as a result of global climate change, particularly among low-income 

18 populations in the United States and abroad, is an often mentioned concern (Wilbanks et al. 2007, CCSP 

19 2008). Climate change is likely to affect agriculture by changing the growing season, limiting rainfall and 

20 water availability, or increasing the prevalence of agricultural pests (see Section 4.5.6 for more 

21 information). In the United States, the most vulnerable segment of the population to food insecurity is 

22 likely to be low-income children (Cook and Frank 2008 in CCSP 2008). 

23 
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1 
Chapter 4 Cumulative Impacts 4.7 Non-Climate Cumulative Impacts of CO2

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1 4.7 NON-CLIMATE CUMULATIVE IMPACTS OF CARBON DIOXIDE 

2 4.7.1 Affected Environment 

3 In addition to its role as a GHG in the atmosphere, CO2 is exchanged from the atmosphere to 

4 water, plants, and soil. CO2 dissolves easily in water and more easily in salt water, such as oceans. In 

5 water, CO2 combines with water molecules to form carbonic acid. The amount of CO2 dissolved in the 

6 upper ocean is related to its concentration in the air. As the atmospheric concentration continues to 

7 increase, this process takes up about 30% of each year’s emissions (Canadell et al. 2007). This reduces 

8 the increase in the atmospheric concentration of CO2, but also increases the acidity of the ocean. Although 

9 ocean uptake is slowly decreasing, the increasing CO2 concentration will have a global effect on the 

10 oceans. It is estimated that by 2100, ocean pH could drop 0.3 to 0.5 units in relation to pre-industrial 

11 levels (Caldeira and Wickett 2005). 

12 Terrestrial plants remove CO2 from the atmosphere through photosynthesis and use the carbon for 

13 plant growth. This uptake by plants can influence annual fluctuations of CO2 on the order of 3 percent 

14 from growing season to non-growing season (Schneider and Londer 1984 in Perry 1994). Increased 

15 levels of CO2 essentially act as a fertilizer, influencing normal annual terrestrial plant growth. Over recent 

16 decades, terrestrial uptake has amounted to about 30% of each year’s emissions (Canadell et al. 2007). 

17 In addition, CO2 concentrations affect soil microorganisms. Only recently have the relationships 

18 between above-ground and below-ground components of ecosystems been considered significant; there is 

19 increasing awareness that feedbacks between the above-ground and below-ground components play a 

20 fundamental role in controlling ecosystem processes. For example, plants provide most of the organic 

21 carbon required for below-ground decomposition. Plants also provide the resources for root-associated 

22 microorganisms (Wardle et al. 2004). The “decomposer subsystem in turn breaks down dead plant 

23 material and indirectly regulates plant growth and community composition by determining the supply of 

24 available root nutrients” (Wardle et al. 2004). 

25 Specific plant species, depending on the quantity and quality of resources provided to below26 ground components, might have greater impacts on soil biota and the processes regulated by those biota 

27 than do other plants. Variation in the quality of forest litter produced by co-existing species of trees, for 

28 example, “explains the patchy distribution of soil organisms and process rates that result from ‘single 

29 tree’ effects” (Wardle et al. 2004). The composition of plant communities has a consistent and substantial 

30 impact on the composition of root-associated microbes; however, the effects of plant community 

31 composition on decomposer systems are apparently context-dependent. In one study, manipulating the 

32 composition of plant communities in five sites in Europe produced distinctive effects on decomposer 

33 microbes, while root-related soil microbes experienced no clear effect (Wardle et al. 2004). 

34 The amount of carbon stored in soils of temperate and boreal forests is about four times greater 

35 than the carbon that is stored by vegetation and is “33 percent higher than total carbon storage in tropical 

36 forests” (Heath et al. 2005). Terrestrial communities contain as much carbon as the atmosphere. Forest 

37 soils are also the longest lived carbon pools in terrestrial ecosystems (King et al. 2004). Several 

38 experiments involving increases of atmospheric CO2 resulted in increased carbon mass in trees, but a 

39 reduction of carbon sequestration in soils. This is associated with increasing soil microorganism 

40 respiration (Heath et al. 2005, Black 2008); respiration is associated with “root herbivory, predation, 

41 consumption of root exudates, and the decomposition of root and leaf litter” (King et al. 2004). 
4.7 Non-Climate Cumulative Impacts of CO2 Chapter 4 Cumulative Impacts 

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1 NHTSA provides in this EIS a qualitative analysis of the cumulative effects of the proposed 

action regarding to non-climate cumulative impacts of CO2.

1 2 

3 4.7.2 Environmental Consequences 

4 4.7.2.1 Ocean Acidification 

5 Ocean acidification occurs when CO2 dissolves in seawater, initiating a series of well-known 

6 chemical reactions that increases the concentration of hydrogen ions and makes seawater less basic (and 

7 therefore more acidic), measured as a decline in pH (Bindoff et al. 2007, Denham et al. 2007). An 

8 important consequence of this change in ocean chemistry is that the excess hydrogen ions bind with 

9 carbonate ions, making the carbonate ions unavailable to marine organisms for forming the calcium 

10 carbonate minerals (mostly aragonite or calcite) that make up their shells, skeletons, and other hard parts. 

11 Once formed, aragonite and calcite will dissolve back into the surrounding seawater, unless the water 

12 contains a sufficiently high concentration of carbonate ions (recent reviews by Doney 2009, Doney et al. 

13 2009, EPA 2009, Fabry et al. 2008, Fischlin et al. 2007, Guinotte and Fabry 2008, Raven et al. 2005). 

14 

15 For many millennia before present, there was little change in ocean pH. Even during the warm 

16 Cretaceous period, about a 100 million years ago, when atmospheric CO2 concentrations were between 

17 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 18 changed in the past was much slower 

19 than at present, and during slow natural changes, the carbon system in the oceans has time to reach a 

20 steady state with sediments. If the ocean starts to become more acidic, some carbonate will be dissolved 

21 from sediments, buffering the chemistry of the seawater so that pH changes are lessened (Raven et al. 

22 2005). 

23 

24 However, as anthropogenic emissions have increased there has been an accumulation of CO2 in 

25 the atmosphere and a net flux of CO2 from the atmosphere to the oceans. As a result, the pH and 

26 carbonate ion concentrations of the world’s oceans have declined and are now lower than at any time in 

27 the past 420,000 years (Hoegh-Guldberg et al. 2007). It is estimated that the pH of today’s oceans has 

28 declined in relation to the pre-industrial period by 0.1 pH units (on a log scale), representing a 30-percent 

29 increase in ocean acidity (Caldeira and Wickett 2003). Scientists predict that as early as 2050, ocean pH 

30 could be lower than at any time during the past 20 million years (Feely et al., 2004). This rate of change is 

31 at least a hundred times greater than during the past hundreds of millennia (Raven et al., 2005). By 2100, 

32 depending on the emissions scenario modeled, the average ocean pH could decline by 0.3 to 0.5 pH units 

33 in relation to pre-industrial levels (Caldeira and Wickett 2005). Atmospheric CO2 would need to be 

34 stabilized under 500 parts per million (ppm) for the decline in locally measured ocean pH to remain 

35 below the 0.2 pH unit limit established by EPA in 1976 for the protection of marine life (Caldeira et al. 

36 2007). 

37 

38 At present, ocean surface waters are super-saturated with respect to the two prevalent calcium 

39 carbonate forms – aragonite and calcite (Bindoff et al. 2007) – but the saturation horizon (the depth above 

40 which supersaturation occurs and within which, for example, all near surface reef systems were located in 

41 pre-industrial times) is becoming shallower (Feely et al. 2004). As the oceans absorb increasing amounts 

42 of CO2, the greatest pH decline in relation to the global average will occur in polar and subpolar regions. 

 

1 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). 
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1 CO2 dissolves more readily in cold water, which is naturally low in carbonate ion concentration and more 

2 acidic than surface waters (Meehl et al. 2007). Under the IPCC IS92a “business as usual” scenario 

3 (Pepper et al. 1992), the multi-model projection of 788 ppm of atmospheric CO2 by 2100 indicates that as 

4 early as 2050, Southern Ocean surface waters would begin to become undersaturated with respect to 

5 aragonite; by 2100 all of the Southern Ocean south of 60 degrees south and portions of the Subarctic 

6 North Pacific could become undersaturated (Orr et al. 2005). Simulation of the IPCC IS92a scenario 

7 predicted wintertime aragonite undersaturation in the Southern Ocean between 2030 and 2038 (McNeil 

8 and Matear 2008). Simulation of the SRES A2 scenario (IPCC 2000) predicts aragonite undersaturation in 

9 Arctic surface waters once the CO2 concentration increases above 450 ppm (Steinacher et al. 2009). 

10 Under this scenario, the ocean volume that is saturated with respect to aragonite, and therefore contains 

11 much of the ocean’s biodiversity, could decrease from about 42 percent today to 25 percent by 2100, 

12 resulting in a significant loss of marine life (Steinacher et al. 2009). 

13 

14 Recent observations indicate that ocean acidification is increasing in some areas faster than 

15 expected. Hydrographic surveys have found that this occurs when, for example, wind-induced upwelling 

16 of seawater that is undersaturated with respect to aragonite spreads out over the continental shelf; 

17 evidence of this is reported from western North America during unusual weather conditions, decades 

18 earlier than model predictions for average weather conditions (Feely et al. 2008). Measurements of ocean 

19 pH off the coast of Washington State over a period of 8 years, for example, found that acidity in the 

20 region has increased more than 10 times faster than other areas (Wootton et al. 2008). 

21 

22 4.7.2.1.1 Effects of Ocean Acidification on Marine Calcifiers 

23 Laboratory and observational studies make clear that, with few exceptions, the reduction in 

24 calcium carbonate resulting from ocean acidification reduces the calcification rates of marine organisms, 

25 a finding that holds over a wide range of taxa (reviewed by Doney 2009, Doney et al. 2009, EPA 2009, 

26 Fabry et al. 2008, Guinotte and Fabry 2008, Fischlin et al. 2007, Raven et al. 2005). Table 1 in Fabry et 

27 al. (2008) and Table 2 in Guinotte and Fabry (2008) provide citations for the available literature. Here we 

28 provide representative results, ranging from the individual to ecosystem level, for a variety of marine 

29 taxa. 

30 Warmwater Corals. Studies indicate that a doubling of the CO2 concentration from pre-industrial 

31 levels to 560 ppm will result in a 20- to 60-percent decrease in the calcification rates of tropical reef32 building corals, with the percent decrease depending on the species (Kleypas et al. 1999, Guinotte and 

33 Fabry 2008, Hoegh-Guldberg 2007). Langdon et al. (2000) and Leclerq et al. (2000) showed that 

34 saturation state was the primary factor determining calcification rates of coral reef ecosystems grown in a 

35 large mesocosm (i.e., an outdoor cage). Fine and Tchernov (2007) showed that two species of coral 

36 experienced complete dissolution of their shells in highly acidified water but were able to regrow their 

37 shells when returned to water of normal pH. Under the SRES A2 scenario, ocean waters with an 

38 aragonite saturation level considered suitable for coral growth are projected to disappear in the second 

39 half of this century; water considered optimal for coral growth, which covered about 16 percent of the 

40 ocean surface in pre-industrial times, could be gone within the next few years (Guinotte et al. 2006). 

41 As a result of the combined effects of increased CO2 and “bleaching” events resulting from 

42 elevated sea surface temperatures, tropical and subtropical corals could become rare by 2050 (Hoegh43 Guldberg 2007). Bleaching occurs when corals eject their symbiotic algae when the temperature of 

44 surface waters increase above a threshold near 30 °C. Increases in sea surface temperatures have 

45 contributed to major bleaching events of subtropical and tropical coral reefs (EPA 2009). The IPCC 

46 concluded that it is “very likely” that a projected future increase in sea surface temperature of 1 to 3 

47 degrees °C will result in more frequent bleaching events and widespread coral mortality, unless there is 

48 long-term thermal adaptation by corals and their algal symbionts (Nicholls et al. 2007; EPA 2009). A 
4.7 Non-Climate Cumulative Impacts of CO2 Chapter 4 Cumulative Impacts 

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1 group of 39 coral experts from around the world estimated that one-third of reef-building corals face 

2 elevated risk of extinction. A group of 39 coral experts from around the world estimated that one-third of 

3 reef-building corals face elevated extinction risk from climate change and local anthropogenic stressors 

4 (Carpenter et al. 2008). The vulnerability of these corals to thermal stress will also be dependent on the 

5 existence of additional adverse factors stressing the corals such as overfishing, pollution, invasive species, 

6 and available nutrients (EPA 2009). 

7 Coldwater Corals. As the saturation horizon becomes shallower, saturated waters are becoming 

8 limited to the warm surface layers of the world’s oceans. As a result, under the IPCC “business as usual” 

9 scenario, it is projected that by 2100, only 30 percent of coldwater corals will remain in saturated waters

10 (Guinotte et al. 2006). 

11 Marine Algae. Crustose coralline algae are critical for coral reefs because they cement together 

12 carbonate fragments. Under high CO2 conditions in an outdoor mesocosm experiment, the recruitment 

13 rate and percentage cover of crustose coralline algae decreased by 78 percent and 92 percent, 

14 respectively, whereas that of non-calcifying algae increased by only 52 percent (Kuffner et al. 2008). 

15 While some marine phytoplankton grow well over a wide range of pH, others have growth rates that vary 

16 greatly over a narrow 0.5 to 1.0 pH unit change (Hinga 2002). Eutrophication and ocean acidification 

17 might interact to increase the frequency of blooms of those species that tolerate extreme pH (Hinga 2002). 

18 Coccolithophores, planktonic microalgae that are the main calcifiers in the ocean, show a mix of 

19 responses. In one study, coccolithophores show reduced calcification when grown at 750 ppm CO2

20 (Riebesell et al. 2000), while in another study they showed no change (Langer et al., 2006). 

21 Molluscs. Gazeau et al. (2007) found that calcification in a mussel species and Pacific oyster 

22 declined by 25 percent and 10 percent, respectively, when grown in seawater at 740 ppm CO2, which is 

23 the concentration expected by 2100 under the IPCC IS92a scenario. Pteropods, small marine snails, show 

24 shell dissolution in seawater undersaturated with respect to aragonite (Feely et al. 2004, Orr et al. 2005). 

25 When live pteropods were collected in the Subarctic Pacific and exposed to a level of aragonite 

26 undersaturation similar to that projected for the Southern Ocean by 2100 under the IPCC IS92a emissions 

27 scenario, shell dissolution occurred within 48 hours (Orr et al. 2005). Declines in pteropods are a 

28 particular concern in high-latitude oceans, where they are a critical food source for marine animals 

29 ranging from krill (small shrimp-like organisms) to whales, and including highly valued fish such as 

30 salmon. Therefore, their loss could have significant effects on high-latitude food webs (Guinotte and 

31 Fabry 2008).

32 Echinoderms. Sea urchins show reduced early development (Kurihara and Shirayama 2004) and 

33 shell growth (Shirayama and Thornton 2005) in seawater with elevated CO2 concentrations. 

34 Field observations are limited but consistent with the results of laboratory and mesocosm studies, 

35 as follows: 

36  Shifts in community composition were observed in a mussel-dominated rocky intertidal 

37 community experiencing rapid declines in pH. Years of low pH were accompanied by 

38 declines in calcerous species (e.g., mussels, stalked barnacles) and increases in non-calcerous 

39 species (e.g., acorn barnacles, algae) (Wootton et al. 2008). 

40  Near-subsurface areas with natural, volcanic venting of CO2, stony corals are absent and the 

41 abundance of calcifying sea urchins, coralline algae, and gastropods is greatly reduced (Hall42 Spencer et al. 2008). 

43  Moy et al. (2009) provided direct evidence that ocean acidification is affecting shell 

44 formation, finding that the shells of foraminifera in the Southern Ocean are lighter than shells 
Chapter 4 Cumulative Impacts 4.7 Non-Climate Cumulative Impacts of CO2

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1 of the same species in core samples from ocean sediments that predate the industrial 

2 revolution. Modern shells were found to be 30 to 35 percent lighter than older shells of the 

3 same size. 

4  De’ath et al. (2009) examined growth patterns of 328 massive coral colonies from the Great 

5 Barrier Reef of Australia and found that their rates of calcification have declined by almost 

6 15 percent since 1990, to values lower than any seen for the past 400 years. The investigators 

7 believe that the main causes of this continuing decline are increasing sea surface temperatures 

8 and ocean acidification. 

9 4.7.2.1.2 Changes in the Effectiveness of the Ocean Sink 

10 In addition to its role in calcium carbonate formation, carbonate ion concentration also controls 

11 the uptake of CO2. As CO2 increases in surface waters and carbonate concentration declines, the 

12 effectiveness of the ocean as a “sink” for CO2 will decrease (Bindoff et al. 2007, Denham et al. 2007, 

13 Sabine et al. 2004). In addition, ocean warming decreases the solubility of CO2 in seawater (Binhoff et 

14 al. 2007, Denham et al. 2007). Observations and modeling studies indicate that the sinks in the North 

15 Atlantic (Lefèvre et al. 2004, Schuster and Watson 2009) and Southern Ocean (LeQuéré et al. 2007, 

16 Lovenduski et al. 2008) have declined in recent decades, consistent with expectations. From 2000 to 

17 2006, it is estimated that the oceans absorbed about 25 percent of anthropogenic CO2 emissions, 

18 representing a decline in the ocean sink from earlier decades (Canadell et al. 2007). 

19 4.7.2.1.3 IPCC Conclusions about Ocean Acidification 

20 The IPCC conclusions about ocean acidification are as follows (EPA 2009, Denman et al. 2007): 

21  The biological production of corals, and calcifying phytoplankton and zooplankton within the 

22 water column, could be inhibited or slowed down as a result of ocean acidification. 

23  Cold-water corals are likely to show large reductions in geographic range this century. 

24  The dissolution of calcium carbonate at the ocean floor will be enhanced, making it difficult 

25 for benthic calcifiers to develop protective structures. 

26  Acidification can influence the marine food web at higher trophic levels. 

27 4.7.2.2 Plant Growth and Soil Microorganisms 

28 In contrast to its potential adverse effect on the productivity of marine ecosystems, higher CO2

29 concentrations in the atmosphere could increase the productivity of terrestrial systems. CO2 can have a 

30 stimulatory or fertilization effect on plant growth (EPA 2009). Plants use CO2 as an input to 

31 photosynthesis. The IPCC Fourth Assessment Report states that “[o]n physiological grounds, almost all 

32 models predict stimulation of carbon assimilation and sequestration in response to rising CO2, referred to 

33 as ‘CO2 fertilization’” (Denman et al. 2007). IPCC projects with medium confidence that forest growth in 

34 North America will likely increase 10 to 20 percent, due to both CO2 fertilization and longer growing 

35 seasons, over this century (EPA 2009, Field et al. 2007). 

36 Under bench-scale and field-scale experimental conditions, several investigators have found that 

37 higher CO2 concentrations have a fertilizing effect on plant growth (e.g., Long et al. 2006, Schimel et al.

38 2000). Through free air CO2 Enrichment experiments, at an ambient atmospheric concentration of 550 

39 ppm CO2, unstressed C3 crops (e.g., wheat, soybeans, and rice) yielded 10 to 25 percent more than under 

40 current CO2 conditions, while C4 crops (e.g., maize) yielded up to 10 percent more (EPA 2009). In 

41 addition, IPCC reviewed and synthesized field and chamber studies, finding that: 
4.7 Non-Climate Cumulative Impacts of CO2 Chapter 4 Cumulative Impacts 

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1 There is a large range of responses, with woody plants consistently showing net primary 

2 productivity (NPP) increases of 23 to 25 percent (Norby et al. 2005), but much smaller 

3 increases for grain crops (Ainsworth and Long 2005). Overall, about two-thirds of the 

4 experiments show positive response to increased CO2 (Ainsworth and Long 2005; Luo et 

5 al. 2004). Since saturation of CO2 stimulation due to nutrient or other limitations is 

6 common (Dukes et al. 2005; Köerner et al. 2005), the magnitude, and effect of the CO2

7 fertilization is not yet clear. 

8 Forest productivity gains that might result through the CO2 fertilization effect can be reduced by 

9 other changing factors, but the magnitude of this effect remains uncertain over the long term (EPA 2009). 

10 Easterling et al. (2007) discussed studies suggesting that the CO2 fertilization effect might be lower than 

11 assumed previously, with the initial increases in growth potentially limited by competition, disturbance 

12 (e.g., storm damage, forest fires, and insect infestation), air pollutants (primarily tropospheric ozone), 

13 nutrient limitations, ecological processes, and other factors (EPA 2009). 

14 The CO2 fertilization effect could mitigate some of the increase in atmospheric CO2

15 concentrations by resulting in more storage of carbon in biota. It should also be noted that while CO2 

16 fertilization can result in a greater mass of available vegetation, it can also increase the carbon-to-nitrogen 

17 ratio in plants. In one study, such fertilization of forage grasses for livestock increased their abundance, 

18 but reduced their nutritional value, affecting livestock “weight and performance” (EPA 2009). 

19 Additionally, there is evidence that long-term exposure to elevated ambient CO2 levels, such as areas near 

20 volcano outgassing, will result in a die-off of some plants. Although, under typical atmospheric CO2

21 concentrations, soil gas is 0.2 to 0.4 percent CO2, while in areas of observed die-off, CO2 concentration 

22 comprised as much as 20 to 95 percent of soil gas. Any CO2 concentration above 5 percent is likely to 

23 adversely impact vegetation, and if concentrations reach 20 percent, CO2 is observed to have a phytotoxic 

24 effect (EPA 2009). 

25 The current annual exchange in CO2 between the atmosphere and terrestrial ecosystems is 

26 estimated at nine to 10 times greater than annual emissions produced as a result of burning fossil fuels. 

27 Even a small shift in the magnitude of this exchange could have a measurable impact on atmospheric CO2

28 concentration (Heath et al. 2005). The above-ground/below-ground processes and components in 

29 terrestrial ecosystems typically sequester carbon. Studies are now confirming that variations in 

30 atmospheric CO2 have impacts not only on the above-ground plant components, but also on the below31 ground microbial components of these systems. 

32 In one study, CO2 levels were artificially elevated in a forest for the purpose of studying the effect 

33 of atmospheric CO2 on soil communities. An indirect impact of the increased CO2 was that distinct 

34 changes in the composition of soil microbe communities occurred as a result of increased plant detritus 

35 (BNL 2007, Science Daily 2007). In another study, an increase in CO2 directly resulted in increased soil 

36 microbial respiration. However, after 4 to 5 years of increased exposure to CO2, “the degree of 

37 stimulation declined” to only a 10 to 20 percent increase in respiration over the base rate (King et al.

38 2004). Additionally, the degree of stimulation was linked to variability in seasonal and interannual 

39 weather (King et al. 2004). Ryan et al. (2008) suggest that for forest ecosystems, several unresolved 

40 questions prevent a definitive assessment of the effect of elevated CO2 on components of the carbon cycle 

41 other than carbon sequestration, mostly in wood (EPA 2009). 

42 The increase in microbe respiration could, therefore, diminish the carbon sequestration role of 

43 terrestrial ecosystems. Upon reaching a certain level of CO2 in the atmosphere, carbon sinks in soils 

44 could become net carbon emitters (Heath et al. 2005, Black 2008). Because of the number of factors 

45 involved in determining soil respiration and carbon sequestration, the threshold for substantial changes in 

46 these activities varies spatially and temporally (King et al. 2004). 
Chapter 4 Cumulative Impacts 4.7 Non-Climate Cumulative Impacts of CO2

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1 As with the climatic effects of CO2, the changes in non-climatic impacts associated with the 

2 alternatives is difficult to assess quantitatively. In the possible climate scenarios presented by IPCC, 

3 atmospheric CO2 concentrations increase from current levels of approximately 380 ppm to as much as 800 

4 ppm in 2100 (Kleypas et al. 2006). Whether the distinction in concentrations is substantial across 

5 alternatives is not clear because the damage functions and potential existence of thresholds for CO2

6 concentration are not known. However, what is clear is that a reduction in the rate of increase in 

7 atmospheric CO2, which all the action alternatives would provide to some extent, would reduce the ocean 

8 acidification effect and the CO2 fertilization effect. 
4.7 Non-Climate Cumulative Impacts of CO2 Chapter 4 Cumulative Impacts 

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1 
 5-1 

1 Chapter 5 Mitigation 

2 Council on Environmental Quality (CEQ) regulations for implementing the procedural 

3 requirements of the National Environmental Policy Act (NEPA) implicitly require that the discussion of 

4 alternatives in an Environmental Impact Statement (EIS) “[i]nclude appropriate mitigation measures not 

5 already included in the proposed action or alternatives.” 40 CFR § 1502.14(f). In particular, an EIS 

6 should discuss the “[m]eans to mitigate adverse environmental impacts.” 40 CFR § 1502.16(h). As 

7 defined in the CEQ regulations, mitigation includes: 

8 (a) Avoiding the impact altogether by not taking a certain action or parts of an action. 

9 (b) Minimizing impacts by limiting the degree or magnitude of the action and its implementation. 

10 (c) Rectifying the impact by repairing, rehabilitating, or restoring the affected environment. 

11 (d) Reducing or eliminating the impact over time by preservation and maintenance operations 

12 during the life of the action. 

13 (e) Compensating for the impact by replacing or providing substitute resources or environments. 

14 40 CFR § 1508.20. 

15 Under NEPA, an EIS should contain “a reasonably complete discussion of possible mitigation 

measures.”1 16 Essentially, “[t]he mitigation must ‘be discussed in sufficient detail to ensure that 

environmental consequences have been fairly evaluated.’”2 17 Under NEPA, an agency does not have to 

formulate and adopt a complete mitigation plan,3 18 but should analyze possible measures that could be 

19 adopted. An agency should state in its Record of Decision whether all practicable means to avoid or 

20 reduce environmental harm have been adopted into the selected alternative. 40 CFR § 1505.2(c). 

21 5.1 OVERVIEW OF IMPACTS 

22 The National Highway Traffic Safety Administration’s (NHTSA’s) proposed action is to 

23 implement Corporate Average Fuel Economy (CAFE) standards for model years (MY) 2012-2016, as 

24 required by the Energy Independence and Security Act of 2007 (EISA). The cumulative impacts analysis 

25 (see Chapter 4) considers the implementation of CAFE standards for MY 2012-2016 and for MY 2017-

2030.4 26 Under Alternative 1, No Action, there would be no action under the National Program, and thus 

27 NHTSA would take no action to implement the MY 2012-2016 CAFE standards. The No Action 

28 Alternative (Alternative 1) assumes that average fuel economy levels in the absence of CAFE standards 

29 beyond 2011 would equal the manufacturer’s required level of average fuel economy for MY 2011. 

30 Compared to the No Action Alternative, each of the eight action alternatives (Alternatives 2 through 9) 

31 would result in a decrease in energy consumption, carbon dioxide (CO2) emissions, and associated 

32 climate-change effects. 

 

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 MY 2017 and beyond in a future rulemaking, this NEPA analysis 

makes assumptions about the MY 2017-2030 standards based on the MY 2012-2016 standards, the EISA 

requirements, and the Annual Energy Outlook 2009 assumptions regarding projected vehicle fuel economy 

increases. 
Chapter 5 Mitigation 

 5-2 

1 As analyzed in this EIS, emissions from criteria air pollutants and mobile source air toxics 

2 (MSATs) are generally anticipated to decline. According to the analyses described in Sections 3.3 and 

3 4.3, some emissions would increase under some alternatives and for some analysis years, while most 

4 demonstrate declines compared to the No Action Alternative (Alternative 1). Health costs and impacts 

5 are estimated to be reduced under all alternatives. 

6 Nitrogen oxides (NOx), particulate matter (PM2.5), sulfur oxides (SOx), volatile organic 

7 compounds (VOCs), acetaldehyde, benzene, diesel particulate matter (DPM), and formaldehyde exhibit 

8 decreases in emissions under all action alternatives for all analysis years, compared to the No Action 

9 Alternative (Alternative 1). Therefore, any negative health impacts associated with these emissions are 

10 similarly expected to be reduced, and mitigation is not necessary. 

11 According to the NHTSA analysis, emissions of carbon monoxide (CO), acrolein, and 1,3-

12 butadiene could increase under certain alternatives and analysis years, which requires further examination 

13 regarding the need for mitigation. The potential for harm depends on the selection of the final standards, 

14 the magnitude of the increases, and other factors. In all cases except for acrolein, the increases are 

15 approximately 1.5 percent or less for CO and 0.02 percent for 1,3-butadiene, compared to those under the 

16 No Action Alternative (Alternative 1). 

17 5.2 MITIGATION MEASURES 

18 As noted above, NEPA does not obligate an agency to adopt a mitigation plan. Rather, NEPA 

merely requires an agency to discuss possible measures that could be adopted.5 19 In accordance with 

20 NEPA and CEQ regulations, the following is a discussion of possible measures that could mitigate the 

21 effects of NHTSA’s action. These include current and future actions that NHTSA or other federal 

22 agencies could take. Any of the proposed CAFE standards in conjunction with these actions would 

23 mitigate the environmental impacts and provide even greater environmental benefits. 

24 Generally emissions from criteria pollutants and MSATs are anticipated to decline, although 

25 emissions of CO, acrolein, and 1,3-butadiene could increase under certain alternatives and analysis years, 

26 compared to the No Action Alternative (Alternative 1). NHTSA notes that the analysis for acrolein 

27 emissions is incomplete because upstream emissions factors are not available. Upstream emissions 

28 decrease due to fuel savings and reduced emissions from fuel refining and transportation. If upstream 

29 emissions of acrolein were included in the analysis, total acrolein emissions would show smaller increases 

30 or might decrease. Thus, the acrolein emissions reported in this EIS represent an upper bound. 

31 It should be noted that even if CO emissions show some level of increase, the associated harm 

32 might not increase concomitantly. After a long downward trend, there have been fewer than three 

33 violations of the CO standards per year since 2002, owing to the success of regulations governing fuel 

34 composition and vehicle emissions (EPA 2009c). Also, vehicle manufacturers can choose which 

35 technologies to employ to reach the new CAFE standards. Some of their choices regarding which 

36 technologies to use have higher or lower impacts for these emissions. Nevertheless, there is the potential 

37 that some air pollutant emissions will increase in some years for some alternatives. 

38 Beyond these considerations, at the national level there could also be increases in criteria and 

39 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 

1 standards under the action alternatives. These increases would represent a slight decline in the rate of 

2 reductions being achieved by implementation of Clean Air Act (CAA) standards. 

3 In regard to air quality, federal transportation funds administered by the Federal Highway 

4 Administration (FHWA) could be available to assist in funding projects to reduce increases in emissions. 

5 FHWA provides funding to states and localities specifically to improve air quality under the Congestion 

6 Mitigation and Air Quality Improvement (CMAQ) Program. The FHWA and the Federal Transit 

7 Administration (FTA) also provide funding to states and localities under other programs that have 

8 multiple objectives including air quality improvement. Specifically, the Surface Transportation Program 

9 provides flexible funding that may be used by states for projects on any federal-aid highway (DOE 

10 2009a). As state and local agencies recognize the need to reduce emissions of CO, acrolein, and 1,3-

11 butadiene (or other emissions eligible under the CMAQ Program, including the criteria pollutants and 

12 MSATs analyzed in this EIS), they have the ability to apply CMAQ funding to reduce impacts in most 

13 areas. Further, the U.S. Environmental Protection Agency (EPA) has the authority to continue to improve 

14 vehicle emissions standards under CAA, which could result in future reductions as EPA promulgates new 

15 regulations. 

16 Each of the proposed alternatives would reduce energy consumption and greenhouse gas (GHG) 

17 emissions compared to the No Action Alternative (Alternative 1), resulting in a net beneficial effect. 

18 Regardless of these reductions, passenger cars and light trucks are a major contributor to energy 

19 consumption and GHG emissions in the United States. Although an agency typically does not propose 

20 mitigation measures for an action resulting in a net beneficial effect, NHTSA would like to call attention 

21 to several other federal programs, which in conjunction with NHTSA CAFE standards, can make 

22 significant contributions in further reducing energy consumption and GHG emissions. 

23 The programs discussed below are ongoing and at various stages of completing their goals. All 

24 these programs present the potential for future developments and advances that could further increase the 

25 net beneficial effect of the environmental impacts identified in this EIS. The programs are also indicative 

26 of the types of programs that might be available in the future at all government levels for even further 

27 mitigation. 

28 Regarding energy consumption, EPA administers Renewable Fuel Standards (RFS) under Section 

29 211(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 30 The 

31 current proposed standard would increase the volume of renewable fuel required to be blended into 

32 gasoline from 9 billion gallons in 2008 to 36 billion gallons by 2022 (EPA 2009a). EPA estimates that 

33 the greater volumes of biofuel mandated by proposed standards would reduce GHG emissions from 

34 transportation by a total of 6.8 billion tons CO2 equivalent when measured over a 100-year timeframe and 

35 discounted at 2 percent. This is equivalent to approximately 160 million tons CO2 equivalent per year. 

36 See Section 4.4.3.3 for further details. 

37 In addition, the U.S. Department of Transportation (DOT), in coordination with EPA and the U.S. 

38 Department of Housing and Urban Development, announced six livability principles around which the 

39 agencies will coordinate agency policies. One of the principles is focused on increasing transportation 

40 options, which aims to decrease energy consumption, improve air quality, and reduce GHG emissions 

41 (EPA 2009b). This agency coordination establishes the basis upon which DOT, with assistance from 

42 EPA and the Department of Housing and Urban Development, can embark on future projects and direct 

43 existing programs toward further achievements in the areas of energy consumption, air quality, and 

 

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 

1 climate change. Specifically, DOT has a Secretarial goal to lower the number of vehicle miles travelled 

2 (VMT). In support of this goal, Secretary LaHood testified before the Senate Committee on Environment 

3 and Public Works detailing a departmental policy of cooperation and community planning, aimed at 

4 developing livable communities and improving multi-modal transportation, which is anticipated to result 

5 in decreasing VMT (LaHood 2009). The livability principles are an extension of ongoing national 

6 awareness and interest in Smart Growth. The Smart Growth movement presents great potential for 

7 mitigating environmental effects caused by fuel consumption for transportation. EPA provides 

information and support for Smart Growth, further encouraging its growth.7 8 

9 DOT is also one of more than a dozen agency members of the U.S. Climate Change Technology 

10 Program, which the Department of Energy (DOE) leads, that is aimed at the development and adoption of 

11 technologies designed to reduce the U.S. carbon footprint (DOE 2009b). Additionally, DOE administers 

12 programs that provide mitigating effects, such as the Section 1605b Voluntary Reporting of Greenhouse 

13 Gases. Section 1605b reporting provides a forum for recording strategies and reductions in GHGs and is 

14 a voluntary program that facilitates information sharing (DOE 2009b). Such programs can provide a 

15 source of information and strategy for future programs. 

16 Regarding carbon emissions, DOE administers programs designed to give consumers and 

17 industries information required to make environmentally conscious decisions. Specifically, the DOE 

18 Clean Cities program develops government-industry partnerships designed to reduce petroleum 

19 consumption (DOE 2009a). The focus on urbanized areas overlaps with some of the nonattainment areas 

20 identified in Sections 3.3.2 and 4.3.2. Also, DOE administers the Vehicle Technologies Program, which 

21 creates public-private partnerships that enhance energy efficiency and productivity and bring clean 

22 technologies to the marketplace (DOE 2009c). 

 

7 See http://www.epa.gov/smartgrowth/index.htm (last accessed Jul. 27, 2009). 
 6-1 

1 Chapter 6 Preparers 

2 6.1 NATIONAL HIGHWAY TRAFFIC SAFETY ADMINISTRATION 

Name Qualifications/Experience 

PREPARERS 

Carol Hammel-Smith, Contracting Officer’s Technical Representative 

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 

J.D. Candidate, Georgetown University Law Center; B.A., Government (Honors), Philosophy, and 

History, Wesleyan University 

 1 year of legal experience 

Anita Ghosh 

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 

Angel Jackson 

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 

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 

Peter Prout 

M.B.A., University of Michigan- Dearborn; B.S., Eastern Michigan University

 25 years of automotive engineering and regulatory compliance experience 

Henrietta Spinner 

 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

 J.D., College of William & Mary; B.A., International Affairs, James Madison University 

 5 years of legal experience 
Chapter 6 Preparers 

 6-2 

Name Qualifications/Experience 

REVIEWERS 

Julie Abraham, Director, Office of International Policy, Fuel Economy and Consumer Programs 

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 

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 

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 

1 6.2 CONSULTANT TEAM 

2 ICF International supported the National Highway Traffic Safety Administration (NHTSA) in 

3 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 

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 
Chapter 6 Preparers 

 6-3 

Name/Role Qualifications/Experience 

TECHNICAL AND OTHER EXPERTISE (alphabetically) (continued) 

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 

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 
Chapter 6 Preparers 

 6-4 

Name/Role Qualifications/Experience 

TECHNICAL AND OTHER EXPERTISE (alphabetically) (continued) 

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 

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 
Chapter 6 Preparers 

 6-5 

Name/Role Qualifications/Experience 

TECHNICAL AND OTHER EXPERTISE (alphabetically) (continued) 

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 

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 
Chapter 6 Preparers 

 6-6 

Name/Role Qualifications/Experience 

TECHNICAL AND OTHER EXPERTISE (alphabetically) (continued) 

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; 15 years of experience in analysis of impacts of 

human stressors on water resources and aquatic ecosystems

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 

1 
 7-1 

Chapter 7 References 

7.1 PURPOSE AND NEED REFERENCES 

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

Sinks: 1990–2007. 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. 

7.2 PROPOSED ACTION AND ALTERNATIVES REFERENCES 

EIA (Energy Information Administration). 2009. 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. 56 pgs. 

EPA (U.S. Environmental Protection Agency). 2009. 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. 

EIA (Energy Information Administration). 2008. Annual Energy Outlook 2008. U.S. Department of 

Energy. June. DOE/EIA-0383(2008). 215 pgs. 

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. 
Chapter 7 References 

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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. 56 pgs. 

EIA (Energy Information Administration). 2009c. Annual Energy Outlook 2009. U.S. Department of 

Energy. Washington, District of Columbia. DOE/EIA-0383(2009). 221 pgs. 

EIA (Energy Information Administration). 2009d. International Energy Outlook 2009. Washington, 

District of Columbia. DOE/EIA-0484-(2009). 274 pgs. 

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. 

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 

Formaldehyde. U.S. Department of Health and Human Services, Atlanta, Georgia. Available: 

<http://www.atsdr.cdc.gov/toxprofiles/tp111.html>. Accessed: August 28, 2009. 

Beane Freeman, L.E., A. Blair, J.H. Lubin, P.A. Stewart, R.B. Hayes, R.N. Hoover, and M. Hauptmann. 

2009. Mortality from Lymphohematopoietic Malignancies among Workers in Formaldehyde 

Industries: The National Cancer Institute Cohort. Journal of the National Cancer Institute 

101:751–761. 

Bevan, C., J.C. Stadler, G.S. Elliot, S.R. Frame, J.K. Baldwin, H.W. Lueng, E. Moran, and A.S. 

Penepinto. 1996. Subchronic Toxicity of 4-Vinylcyclohexene in Rats and Mice by Inhalation. 

Toxicological Science 32(1):1–10. 
Chapter 7 References 

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Coggon, D., E.C. Harris, J. Poole, and K.T. Palmer. 2003. Extended Follow-up of a Cohort of British 

Chemical Workers Exposed to Formaldehyde. Journal of the National Cancer Institute 95:1608–

1615. 

Cook, R., J.S. Touma, A. Beidler, and M. Strum. 2006. Preparing Highway Emissions Inventories for 

Urban-scale Modeling: A Case Study in Philadelphia. Transportation Research Part D 

11(6):396–407. 

EIA (Energy Information Administration). 2006. Annual Energy Outlook. Washington, District of 

Columbia. DOE/EIA-0383(2006). 

EIA (Energy Information Administration). 2008. Petroleum Supply and Disposition Data. Energy 

Information Administration, U.S. Department of Energy. Released July 28. Available: 

<http://tonto.eia.doe.gov/dnav/pet/pet_sum_snd_d_nus_mbblpd_a_cur.htm>. Accessed: August 

29, 2009. 

EPA (U.S. Environmental Protection Agency). 1987. Assessment of Health Risks to Garment Workers 

and Certain Home Residents from Exposure to Formaldehyde. Office of Pesticides and Toxic 

Substances. 707 pgs. 

EPA (U.S. Environmental Protection Agency). 1991. Integrated Risk Information System File of 

Acetaldehyde. Last Revised: July 9, 2009. Available: <http://www.epa.gov/iris/subst/0290.htm>. 

Accessed: August 5, 2009. 

EPA (U.S. Environmental Protection Agency). 1999a. National-scale Air Toxics Assessment. 

Washington, District of Columbia. Last Revised: June 26, 2009. Available: 

<http://www.epa.gov/ttn/atw/nata1999/risksum.html>. Accessed: August 5, 2009. 

EPA (U.S. Environmental Protection Agency). 1999b. Cleaner Vehicles and Cleaner Gasoline Tier 

2/Gasoline Sulfur Rule. Last Revised: September 19, 2007. Available: 

<http:www.epa.gov/otaq/regs/ld-hwy/tier-2/index.htm>. Accessed: August 5, 2009. 

EPA , U.S. (U.S. Environmental Protection Agency). 2000a. Integrated Risk Information System File for 

Benzene. Last Revised: July 9, 2009. Available: <http://www.epa.gov/iris/subst/0276.htm>. 

Accessed: August 5, 2009. 

EPA (U.S. Environmental Protection Agency). 2000b. Guidelines for Preparing Economic Analyses. 

National Center for Environmental Economics, Office of Policy Economics and Innovation. EPA 

240-R-00-003. 180 pgs. 

EPA (U.S. Environmental Protection Agency). 2002a. Toxicological Review of Benzene (Noncancer 

Effects). Integrated Risk Information System (IRIS), Research and Development. EPA-635-R02-001F . Washington, District of Columbia. 180 pgs. 

EPA (U.S. Environmental Protection Agency). 2002b. Health Assessment of 1,3-Butadiene. National 

Center for Environmental Assessment; Washington, District of Columbia. EPA-600-P-98-001F. 

435 pgs. 

EPA (U.S. Environmental Protection Agency). 2004. Approved Final Version of MOBILE6.2. Office of 

Air Quality Planning and Standards: Office of Transportation and Air Quality, computer program 

released by memorandum Policy Guidance on the Use of MOBILE 6.2 and the December 2003 
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AP-42 Method for Re-entrained Road Dust for SIP Development and Transportation Conformity. 

Available: <http://www.epa.gov/otaq/m6.htm>. Accessed: August 29, 2009. 

EPA (U.S. Environmental Protection Agency). 2006. Vehicle Miles Traveled (VMT) Projection Methods 

Technical Memorandum. Durham, NC. Prepared for Emission Inventory Group Office of Air 

Quality Planning and Standards, Environmental Protection Agency. [As cited in EPA (U.S. 

Environmental Protection Agency). 2009. Personal communication between Harvey Michaels 

(EPA) and Carol Hammel-Smith (NHTSA) regarding CAFE.] 

EPA (U.S. Environmental Protection Agency). 2007. Control of Hazardous Air Pollutants From Mobile 

Sources, Final Rule (the 2007 “MSAT rules”). Office of Transportation and Air Quality. 

February. EPA420-F-07-017. 5 pgs. 

EPA (U.S. Environmental Protection Agency). 2008a. Final Ozone NAAQS Regulatory Impact Analysis. 

U.S. Environmental Protection Agency, Washington, District of Columbia. EPA-452/R-08-003. 

558 pgs. 

EPA (U.S. Environmental Protection Agency). 2008b. Green Book, Criteria Pollutants. Washington, 

District of Columbia. Last Revised: June 11, 2009. U.S. Environmental Protection Agency. 

Available: <http://www.epa.gov/air/oaqps/greenbk/o3co.html>. Accessed: August 5, 2009. 

EPA (U.S. Environmental Protection Agency). 2008c. Guidelines for Preparing Economic Analyses. 

External Review Draft. National Center for Environmental Economics, Office of Policy 

Economics and Innovation. 274 pgs. 

EPA (U.S. Environmental Protection Agency). 2009a. National-scale Air Toxics Assessment for 2002. 

Last Revised: June 26, 2009. Available: <http://www.epa.gov/nata2002/>. Accessed: August 5, 

2009. 

EPA (U.S. Environmental Protection Agency). 2009b. Regulatory Impact Analysis: National Emission 

Standards for Hazardous Air Pollutants from the Portland Cement Manufacturing Industry. 

Prepared by RTI International. Prepared for Office of Air Quality Planning and Standards. 

Research Triangle Park, North Carolina. RTI Report 0209897.003.067. 115 pgs. 

EPA (U.S. Environmental Protection Agency). 2009c. Proposed NO2 National Ambient Air Quality 

Standards (NAAQS) Regulatory Impact Analysis (RIA). Research Triangle Park, North Carolina. 

244 pgs. 

EPA (U.S. Environmental Protection Agency). 2009d. Preamble. In: Light-duty GHG Rule. U.S. 

Environmental Protection Agency, Washington, District of Columbia. Federal Register: 74(68): 

16447-16731. Apr 10, 2009. 

EPA (U.S. Environmental Protection Agency). 2009e. Currently Designated Nonattainment Areas for All 

Criteria Pollutants. Last Revised: June 5, 2009. Available: 

<http://www.epa.gov/air/oaqps/greenbk/ancl3.html>. Accessed: August 5, 2009. 

EPA (U.S. Environmental Protection Agency). 2009f. National Ambient Air Quality Standards. Last 

Revised: 7/14/2009. Available: <http://epa.gov/air/criteria.html>. Accessed: August 5, 2009. 

EPA (U.S. Environmental Protection Agency). 2009g. Personal communication between Harvey 

Michaels (EPA) and Carol Hammel-Smith (NHTSA) regarding CAFE. 
Chapter 7 References 

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EPA (U.S. Environmental Protection Agency). 2009h. Personal communication between Craig Harvey 

(EPA) and Carol Hammel-Smith regarding CAFE (NHTSA). 

EPA (U.S. Environmental Protection Agency). 2009i. National Emissions Inventory (NEI) Air Pollution 

Emissions Trends Data. Available: <http://www.epa.gov/ttn/chief/trends/index.html#tables>. 

Accessed: August 28, 2009. 

EPA (U.S. Environmental Protection Agency). 2009j. Draft MOVES2009 (Motor Vehicle Emission 

Simulator). April. Available. < http://www.epa.gov/otaq/models/moves/index.htm>. Accessed: 

August 17, 2009. 

EPA (U.S. Environmental Protection Agency), and NCEA (National Center for Environmental 

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7.4.5 Health, Societal, and Environmental Impacts of Climate Change 

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and Ecosystem Processes. Journal of Marine Science 65(3):414–432. 

Feely, R.A., C.L. Sabine, J.M. Hernandez-Ayon, D. Ianson, and B. Hales. 2008. Evidence of Upwelling 

of Corrosive “Acidified” Water onto the Continental Shelf. Science 320(5882):1490–1492. 

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Fine, M., and D. Tchernov. 2007. Scleractinian Coral Species Survive and Recover from Decalcification. 

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Gazeau, F., C. Quiblier, J.M. Jansen, J.P. Guttuso, J.J. Middleberg, and C.H.P. Heip. 2007. Impact of 

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Guinotte, J.M., and V.J. Fabry. 2008. Ocean Acidification and Its Potential Effects on Marine 

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Tedesco, and M.C. Buia. 2008. Volcanic Carbon Dioxide Vents Reveal Ecosystem Effects of 

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Heath, J., E. Ayres, M. Possell, R.S. Bardgett, H.I.J. Black, J. Grant, P. Ineson, and G. Kerstiens. 2005. 

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Hinga, K.R. 2002. Effects of pH on Coastal Marine Phytoplankton. Marine Ecology Progress Series 

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Hoegh-Guldberg, O., P.J. Mumby, A.J. Hooten, R.S. Steneck, P. Greenfield, E. Gomez, C.D. Harvell, 

P.F. Sale, A.J. Edwards, K. Caldeira, N. Knowlton, C.M. Eakin, R. Iglesias-Prieto, N. Muthiga, 

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Thornton, D. Ojima, W. Parton, R. Kelly, M. Sykes, R. Neilson, and B. Rizzo. 2000. Contribution 

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Acidification in the Arctic Projected with the NCAR Global Coupled Carbon Cycle-Climate 

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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. 

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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. 

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Press, Cambridge, United Kingdom. 976 pgs. 

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 

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7.4.8 Unavoidable Impacts and Irreversible and Irretrievable Resource References 

No citations appear in Section 4.8. 

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. 

DOE (U.S. Department of Energy). 2009b. Climate Overview. Available: 

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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. 

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August 5, 2009. 
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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. 
 8-1 

1 Chapter 8 Distribution List 

2 The Council on Environmental Quality (CEQ) regulation for implementing the National 

3 Environmental Policy Act (NEPA) (40 Code of Federal Regulations 1501.19) specify requirements for 

4 circulating an Environmental Impact Statement (EIS). In accordance with those requirements, NHTSA is 

5 mailing this EIS to the agencies, officials, and other interested persons listed in this chapter. 

6 8.1 FEDERAL AGENCIES 

7  Advisory Council on Historic Preservation 

8  Council on Environmental Quality 

9  Council on Environmental Quality, NEPA Oversight 

10  Delaware River Basin Commission 

11  Denali Commission 

12  Federal Energy Regulatory Commission, Division of Gas - Environmental and Engineering 

13  Federal Energy Regulatory Commission, Division of Hydropower, Environment and 

14 Engineering 

15  Federal Energy Regulatory Commission, Office of Energy Projects 

16  International Boundary and Water Commission 

17  International Boundary and Water Commission, Environmental Management Division 

18  Marine Mammal Commission 

19  National Capital Planning Commission, Office of Urban Design and Plan Review 

20  National Science Foundation, Office of the General Counsel 

21  Office of Science and Technology Policy, National Science and Technology Council, 

22 Executive Office of the President 

23  Presidio Trust, NEPA Compliance Division 

24  Susquehanna River Basin Commission 

25  Tennessee Valley Authority, NEPA Policy 

26  U.S. Agency for International Development, Bureau for Economic growth, Agriculture, and 

27 Trade 

28  U.S. Department of Agriculture, Agricultural Research Service 

29  U.S. Department of Agriculture, Animal and Plant Health Inspection Service, Environmental 

30 Services 

31  U.S. Department of Agriculture, Cooperative State Research, Education and Extension 

32 Service 

33  U.S. Department of Agriculture, Farm Service Agency 

34  U.S. Department of Agriculture, Natural Resources Conservation Service 

35  U.S. Department of Agriculture, Rural Business-Cooperative Service 

36  U.S. Department of Agriculture, Rural Housing Services, Technical Support Branch 
Chapter 8 Distribution List 

 8-2 

1  U.S. Department of Agriculture, Rural Utilities Service, Engineering and Environmental Staff 

2  U.S. Department of Agriculture, U.S. Forest Service 

3  U.S. Department of Commerce, Economic Development Administration, Legislative and 

4 Intergovernmental Affairs 

5  U.S. Department of Commerce, National Oceanic and Atmospheric Administration, National 

6 Marine Fisheries Service 

7  U.S. Department of Commerce, National Oceanic and Atmospheric Administration, National 

8 Climatic Data Center 

9  U.S. Department of Commerce, National Oceanic and Atmospheric Administration, Planning 

10 and Integration Office 

11  U.S. Department of Defense, Army Corps of Engineers, Office of Environmental Policy 

12  U.S. Department of Defense, Office of Deputy Undersecretary of Defense of Installations and 

13 Environment, Environmental Security 

14  U.S. Department of Energy, Office of Climate Change Policy (PI-63) 

15  U.S. Department of Energy, Office of NEPA Policy and Compliance (EH-42) 

16  U.S. Department of Energy, Western Energy and Waste Management Unit 

17  U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, 

18 Building and Facilities Office 

19  U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, 

20 National Center for Environmental Health, Agency for Toxic Substances and Disease 

21 Registry, Environmental Public Health Readiness Branch 

22  U.S. Department of Health and Human Services, Food and Drug Administration, Center for 

23 Food Safety and Applied Nutrition 

24  U.S. Department of Health and Human Services, Food and Drug Administration, Office of 

25 Commissioner 

26  U.S. Department of Health and Human Services, Health Resources and Services 

27 Administration 

28  U.S. Department of Health and Human Services, Indian Health Service, Division of 

29 Sanitation Facilities Construction 

30  U.S. Department of Health and Human Services, National Institutes of Health, Division of 

31 Environmental Protection, ORF, Environmental Quality Branch 

32  U.S. Department of Health and Human Services, Office of the Secretary, Office for Facilities 

33 Management and Policy, Division of Real Property 

34  U.S. Department of Homeland Security, Federal Emergency Management Agency 

35  U.S. Department of Homeland Security, Office of Safety and Environment 

36  U.S. Department of Homeland Security, U.S. Coast Guard, Environmental Management 

37 Division (G-SEC-3) 

38  U.S. Department of Housing and Urban Development, Office of Environment and Energy 

39  U.S. Department of Justice, Environment and Natural Resources Division 
Chapter 8 Distribution List 

 8-3 

1  U.S. Department of Labor, Mine Safety and Health Administration, Office of Standards, 

2 Regulations, and Variances 

3  U.S. Department of Labor, Occupational Safety and Health Administration, Office of the 

4 Assistant Secretary 

5  U.S. Department of State, Bureau of Oceans and International Environmental and Scientific 

6 Affairs 

7  U.S. Department of the Interior 

8  U.S. Department of the Interior, Bureau of Indian Affairs 

9  U.S. Department of the Interior, Bureau of Land Management, Renewable Resources 

10 Planning Division, Planning and Science Policy 

11  U.S. Department of the Interior, Bureau of Reclamation 

12  U.S. Department of the Interior, Main Interior 

13  U.S. Department of the Interior, Minerals Management Service, Environmental Assessment 

14 Branch 

15  U.S. Department of the Interior, National Park Service, Cultural Resources GIS Facility 

16  U.S. Department of the Interior, National Park Service, Environmental Quality Division 

17  U.S. Department of the Interior, Office of Environmental Policy and Compliance 

18  U.S. Department of the Interior, Office of Environmental Policy and Compliance, Natural 

19 Resources Management Team, Transportation Projects 

20  U.S. Department of the Interior, Office of Surface Mining 

21  U.S. Department of the Interior, U.S. Fish and Wildlife Service 

22  U.S. Department of the Interior, U.S. Geological Survey, Office of Environmental Affairs 

23 Program 

24  U.S. Department of Transportation, Federal Aviation Administration 

25  U.S. Department of Transportation, Federal Aviation Administration, Office of Environment 

26 & Energy (AEE-400) 

27  U.S. Department of Transportation, Federal Highway Administration 

28  U.S. Department of Transportation, Federal Highway Administration, Office of NEPA 

29 Facilitation 

30  U.S. Department of Transportation, Federal Motor Carrier Safety Administration 

31  U.S. Department of Transportation, Federal Railroad Administration 

32  U.S. Department of Transportation, Federal Railroad Administration, Office of Railroad 

33 Development 

34  U.S. Department of Transportation, Federal Transit Administration 

35  U.S. Department of Transportation, Maritime Administration, Office of Environmental 

36 Activities 

37  U.S. Department of Transportation, Office of the Assistant Secretary for Transportation 

38 Policy 
Chapter 8 Distribution List 

 8-4 

1  U.S. Department of Transportation, Office of the Secretary 

2  U.S. Department of Transportation, Pipeline & Hazardous Materials Safety Administration 

3  U.S. Department of Transportation, Research and Innovative Technology Administration 

4  U.S. Department of Transportation, Research and Innovative Technology Administration, 

5 Volpe Center, Environmental Engineering Division 

6  U.S. Department of Transportation, Saint Lawrence Seaway Development Corporation 

7  U.S. Department of Transportation, Surface Transportation Board, Section of Environmental 

8 Analysis 

9  U.S. Department. of State, Bureau of Oceans and International Environmental and Scientific 

10 Affairs 

11  U.S. Environmental Protection Agency 

12  U.S. Environmental Protection Agency, NEPA Compliance Division 

13  U.S. Environmental Protection Agency, Office of Federal Activities, EIS Filing Section 

14  U.S. Environmental Protection Agency, Office of Transportation and Air Quality 

15  U.S. Institute for Environmental Conflict Resolution, ECR Policy and Leadership 

16  U.S. Nuclear Regulatory Commission 

17  Valles Caldera Trust 

18 8.2 STATE AND LOCAL GOVERNMENT ORGANIZATIONS 

19  American Samoa Department of Public Safety 

20  Assistant Corporation Counsel of the City of New York, Environmental Law Division 

21  California Attorney General's Office 

22  Connecticut Office of the Attorney General 

23  Corporation Counsel of the City of New York 

24  Vermont Attorney General, Environmental Division 

25  Georgia Environmental Protection Division 

26  Massachusetts Attorney General's Office 

27  Montana Department of Environmental Quality 

28  New Mexico Department of Attorney General 

29  New Mexico Environment Department 

30  New York State Department of Transportation 

31  Oregon Department of Attorney General 

32  Pennsylvania Department of Environmental Protection 

33  Washington State Department of Ecology 
Chapter 8 Distribution List 

 8-5 

1 8.3 ELECTED OFFICIALS 

2  The Honorable Bob Riley, Governor of Alabama 

3  The Honorable Sean Parnell, Governor of Alaska 

4  The Honorable Togiola T.A. Tulafono, Governor of American Samoa 

5  The Honorable Janet Napolitano, Governor of Arizona 

6  The Honorable Mike Beebe, Governor of Arkansas 

7  The Honorable Arnold Schwarzenegger, Governor of California 

8  The Honorable Bill Ritter, Governor of Colorado 

9  The Honorable M. Jodi Rell, Governor of Connecticut 

10  The Honorable Ruth Ann Minner, Governor of Delaware 

11  The Honorable Adrian Fenty, Mayor of the District of Columbia 

12  The Honorable Charlie Crist, Governor of Florida 

13  The Honorable Sonny Perdue, Governor of Georgia 

14  The Honorable Felix P. Camacho, Governor of Guam 

15  The Honorable Linda Lingle, Governor of Hawaii 

16  The Honorable C.L. “Butch” Otter, Governor of Idaho 

17  The Honorable Pat Quinn, Governor of Illinois 

18  The Honorable Mitchell E. Daniels, Governor of Indiana 

19  The Honorable Chet Culver, Governor of Iowa 

20  The Honorable Kathleen Sebelius, Governor of Kansas 

21  The Honorable Steve Beshear, Governor of Kentucky 

22  The Honorable Bobby Jindal, Governor of Louisiana 

23  The Honorable John E. Baldacci, Governor of Maine 

24  The Honorable Martin O'Malley, Governor of Maryland 

25  The Honorable Deval Patrick, Governor of Massachusetts 

26  The Honorable Jennifer M. Granholm, Governor of Michigan 

27  The Honorable Tim Pawlenty, Governor of Minnesota 

28  The Honorable Haley Barbour, Governor of Mississippi 

29  The Honorable Jay Nixon, Governor of Missouri 

30  The Honorable Brian D. Schweitzer, Governor of Montana 

31  The Honorable Dave Heineman, Governor of Nebraska 

32  The Honorable Jim Gibbons, Governor of Nevada 

33  The Honorable John Lynch, Governor of New Hampshire 

34  The Honorable Jon S. Corzine, Governor of New Jersey 
Chapter 8 Distribution List 

 8-6 

1  The Honorable Bill Richardson, Governor of New Mexico 

2  The Honorable David A. Paterson, Governor of New York 

3  The Honorable Bev Perdue, Governor of North Carolina 

4  The Honorable John Hoeven, Governor of North Dakota 

5  The Honorable Benigno R. Fitial, Governor of the Commonwealth of the Northern Mariana 

6 Islands 

7  The Honorable Ted Strickland, Governor of Ohio 

8  The Honorable Brad Henry, Governor of Oklahoma 

9  The Honorable Ted Kulongoski, Governor of Oregon 

10  The Honorable Edward G. Rendell, Governor of Pennsylvania 

11  The Honorable Luis Fortuño, Governor of Puerto Rico 

12  The Honorable Donald L. Carcieri, Governor of Rhode Island 

13  The Honorable Mark Sanford, Governor of South Carolina 

14  The Honorable Mike Rounds, Governor of South Dakota 

15  The Honorable Phil Bredesen, Governor of Tennessee 

16  The Honorable Rick Perry, Governor of Texas 

17  The Honorable Jon Huntsman, Jr., Governor of Utah 

18  The Honorable Jim Douglas, Governor of Vermont 

19  The Honorable Timothy M. Kaine, Governor of Virginia 

20  The Honorable John P. deJongh, Jr., Governor of the United States Virgin Islands 

21  The Honorable Chris Gregoire, Governor of Washington 

22  The Honorable Joe Manchin, III, Governor of West Virginia 

23  The Honorable Jim Doyle, Governor of Wisconsin 

24  The Honorable Dave Freudenthal, Governor of Wyoming 

25 8.4 NATIVE AMERICAN TRIBES 

26  Cedarville Rancheria 

27  Leisnoi Village aka Woody Island Tribal Council 

28  Mille Lacs Band of Ojibwe 

29  Native Village of Point Hope 

30  Natives of Larsen Bay 

31  Table Mountain Rancheria 

32 8.5 STAKEHOLDERS 

33  Alliance of Automobile Manufacturers 

34  American Association of Blacks in Energy 
Chapter 8 Distribution List 

 8-7 

1  American Council for an Energy Efficient Economy 

2  American International Automobile Dealers Association 

3  American Jewish Committee 

4  American Jewish Committee, Washington Chapter, Office of Government and International 

5 Affairs 

6  BG Automotive Group, Ltd. 

7  BMW (US) Holding Corp. 

8  BMW of North America, LLC 

9  California Air Pollution Control Officers Association 

10  Cambridge Consumers’ Council 

11  Cambridge Consumers' Council, Massachusetts Consumers Council 

12  Center for Biological Diversity 

13  Chrysler LLC 

14  Conservation Law Foundation 

15  Conservation Law Foundation, Vermont Advocacy Center 

16  Consumer Action 

17  Consumer Federation of America 

18  Consumers for Auto Reliability and Safety 

19  Consumers Union 

20  Environment America 

21  Environmental Council of the States 

22  Environmental Defense Fund 

23  Evangelical Lutheran Church in America 

24  Ford Motor Company 

25  Ford Motor Company, Environmental and Safety Engineering 

26  Fred T. Teal, Jr. 

27  Friends Committee on National Legislation 

28  Fuji Heavy Industries USA/Subaru 

29  General Motors Corporation 

30  General Motors, Public Policy Center 

31  Gibson, Dunn & Crutcher LLP 

32  Insurance Institute for Highway Safety 

33  James L. Adcock 

34  Jean Public 

35  Jewish Community Relations Council of Greater Washington 
Chapter 8 Distribution List 

 8-8 

1  Kirkland & Ellis LLP 

2  Maryknoll Office of Global Concerns 

3  Michael Gordon 

4  Missionary Society of St. Columban 

5  Missionary Society of St. Columban, Columban Justice Peace and Integrity of Creation 

6 Office 

7  National Automobile Dealers Association 

8  National Council of Churches USA 

9  National Tribal Environmental Council 

10  Natural Resources Canada 

11  Natural Resources Defense Council 

12  Nissan North America, Inc. 

13  Northeast States for Coordinated Air Use Management 

14  Presbyterian Church (USA) 

15  Public Citizen 

16  Sierra Club 

17  Sierra Club Global Warming and Energy Program 

18  Sierra Club Legislative Office 

19  Stratacomm on behalf of Aluminum Association Auto & Light Truck Group 

20  The American Council for an Energy-Efficient Economy (ACEEE) 

21  The Consumer Alliance 

22  The Episcopal Church 

23  The United Methodist Church General Board of Church and Society 

24  U.S. PIRG 

25  U.S. PIRG, Illinois PIRG 

26  U.S. PIRG, MASSPIRG 

27  Union for Reform Judaism 

28  Union of Concerned Scientists 

29  Union of Concerned Scientists, Washington Office 

30  United Church of Christ 

31  University of Colorado School of Law 

32  Volkswagen Group of America 

33  Volkswagen of America, Industry-Government Relations 

34  Western Governors’ Association 

35  Western Regional Air Partnership 
 9-1 

Chapter 9 Index 

adaptation, 1-3, 2-8, 4-3, 4-86, 4-99, 4-121, 4-122, 4-125, 4-126, 4-138, 4-141, 4-143, 4-144, 4-146, 

4-151, 4-157, 4-162, 4-179 

afforestation, 4-87 

air pollutants, 1-4, 1-14, 1-15, 2-9, 2-18, 2-25, 2-35, 2-38, 3-4, 3-5, 3-6, 3-11, 3-15, 3-17, 3-24, 3-26, 

3-30, 3-31, 3-32, 3-36, 3-41, 3-42, 3-45, 3-46, 3-47, 3-49, 3-50, 3-51, 3-52, 3-53, 3-54, 3-55, 3-56, 

3-64, 3-107, 3-109, 3-110, 3-120, 3-121, 3-125, 4-8, 4-12, 4-15, 4-16, 4-17, 4-21, 4-22, 4-23, 4-24, 

4-26, 4-27, 4-28, 4-29, 4-30, 4-31, 4-32, 4-128, 4-152, 4-173, 4-182, 5-2 

albedo, 3-64, 4-103, 4-123, 4-165, 4-167, 4-169 

Alliance of Automobile Manufacturers, 1-13, 2-21 

Alternative 1, 2-1, 2-11, 2-13, 2-15, 2-16, 2-17, 2-19, 2-23, 2-24, 2-25, 2-26, 2-27, 2-28, 2-31, 2-32, 2-33, 

2-34, 2-35, 2-36, 2-37, 2-38, 2-39, 2-40, 2-41, 2-44, 2-45, 2-46, 2-47, 2-48, 3-8, 3-12, 3-13, 3-23, 3-31, 

3-35, 3-36, 3-37, 3-39, 3-40, 3-41, 3-42, 3-43, 3-44, 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, 3-65, 3-73, 3-76, 3-77, 3-79, 3-82, 3-83, 3-84, 3-85, 3-86, 3-87, 3-88, 

3-90, 3-91, 3-92, 3-95, 3-96, 3-99, 3-100, 3-101, 3-103, 3-104, 3-105, 3-109, 3-112, 3-113, 3-121, 

3-122, 3-126, 4-1, 4-5, 4-7, 4-8, 4-9, 4-11, 4-12, 4-13, 4-14, 4-15, 4-16, 4-17, 4-18, 4-19, 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, 4-37, 4-38, 4-39, 4-44, 

4-47, 4-49, 4-50, 4-51, 4-52, 4-53, 4-54, 4-55, 4-56, 4-59, 4-60, 4-62, 4-63, 4-64, 4-67, 4-68, 4-69, 5-1, 

5-2, 5-3 

Alternative 2, 1-13, 2-12, 2-13, 2-15, 2-16, 2-17, 2-19, 2-23, 2-24, 2-25, 2-26, 2-28, 2-29, 2-33, 2-35, 

2-36, 2-37, 2-38, 2-39, 2-40, 2-41, 2-42, 2-46, 3-12, 3-13, 3-37, 3-39, 3-40, 3-41, 3-42, 3-43, 3-44, 

3-45, 3-46, 3-47, 3-48, 3-49, 3-50, 3-56, 3-77, 3-85, 3-87, 3-90, 3-91, 3-92, 3-100, 3-101, 4-8, 4-9, 

4-13, 4-14, 4-15, 4-16, 4-17, 4-18, 4-19, 4-20, 4-21, 4-22, 4-38, 4-49, 4-50, 4-51, 4-53, 4-56, 4-63, 4-64 

Alternative 3, 1-13, 2-12, 2-13, 2-15, 2-16, 2-17, 2-23, 2-24, 2-25, 2-26, 2-28, 2-29, 2-33, 2-36, 2-37, 

2-38, 2-39, 2-40, 2-41, 2-42, 2-46, 3-13, 3-37, 3-39, 3-40, 3-41, 3-42, 3-43, 3-44, 3-45, 3-48, 3-49, 

3-50, 3-51, 3-85, 3-87, 3-92, 3-100, 3-101, 4-8, 4-9, 4-13, 4-14, 4-15, 4-16, 4-17, 4-18, 4-19, 4-20, 

4-22, 4-23, 4-49, 4-51, 4-53, 4-56, 4-63, 4-64 

Alternative 4, 1-13, 2-12, 2-13, 2-23, 2-24, 2-25, 2-34, 2-35, 2-40, 2-47, 2-48, 3-12, 3-41, 3-42, 3-49, 

3-51, 3-52, 3-65, 3-77, 3-79, 3-83, 3-104, 3-122, 3-124, 4-13, 4-14, 4-15, 4-21, 4-22, 4-23, 4-24, 4-25, 

4-26, 4-38, 4-39, 4-44, 4-47, 4-67, 4-69 

Alternative 5, 2-12, 2-14, 2-15, 2-16, 2-17, 2-23, 2-24, 2-25, 2-26, 2-28, 2-29, 2-33, 2-36, 2-37, 2-38, 

2-39, 2-40, 2-41, 2-42, 2-46, 3-13, 3-37, 3-39, 3-40, 3-41, 3-42, 3-43, 3-44, 3-45, 3-48, 3-49, 3-52, 

3-53, 3-85, 3-87, 3-92, 3-100, 3-101, 4-8, 4-9, 4-13, 4-14, 4-15, 4-16, 4-17, 4-18, 4-19, 4-20, 4-23, 

4-25, 4-26, 4-49, 4-51, 4-56, 4-63, 4-64 

Alternative 6, 2-12, 2-14, 2-18, 3-53, 3-54, 3-56, 4-15, 4-25, 4-26, 4-27, 4-28 

Alternative 7, 2-12, 2-14, 2-15, 2-16, 2-17, 2-23, 2-24, 2-25, 2-26, 2-28, 2-29, 2-33, 2-36, 2-37, 2-38, 

2-39, 2-40, 2-41, 2-42, 2-46, 3-13, 3-37, 3-39, 3-40, 3-41, 3-42, 3-43, 3-44, 3-45, 3-48, 3-49, 3-53, 

3-54, 3-55, 3-85, 3-87, 3-92, 3-100, 3-101, 4-8, 4-9, 4-13, 4-14, 4-15, 4-16, 4-17, 4-18, 4-19, 4-20, 

4-25, 4-26, 4-27, 4-28, 4-29, 4-30, 4-32, 4-49, 4-51, 4-56, 4-63, 4-64 
Chapter 9 Index 

 9-2 

Alternative 8, 2-2, 2-12, 2-14, 2-15, 2-16, 2-17, 2-19, 2-23, 2-24, 2-25, 2-26, 2-27, 2-28, 2-29, 2-33, 2-35, 

2-36, 2-37, 2-38, 2-39, 2-40, 2-41, 2-42, 2-46, 3-13, 3-37, 3-39, 3-40, 3-41, 3-43, 3-44, 3-45, 3-48, 

3-49, 3-55, 3-56, 3-84, 3-85, 3-87, 3-90, 3-92, 3-100, 3-101, 4-8, 4-9, 4-13, 4-14, 4-16, 4-17, 4-18, 

4-19, 4-20, 4-26, 4-29, 4-30, 4-31, 4-32, 4-49, 4-51, 4-56, 4-63, 4-64 

Alternative 9, 2-12, 2-14, 2-18, 2-19, 2-23, 2-25, 2-28, 2-35, 2-38, 2-41, 3-12, 3-41, 3-42, 3-45, 3-49, 

3-55, 3-56, 3-57, 3-90, 3-91, 3-104, 4-13, 4-14, 4-15, 4-26, 4-29, 4-30, 4-31, 4-32, 4-49, 4-50, 4-54, 

4-55, 4-67 

Alternative Motor Fuels Act (AMFA), 3-7 

Annual Energy Outlook (AEO), 2-4, 2-18, 2-19, 2-35, 2-37, 3-9, 3-10, 3-59, 3-79, 3-82, 3-87, 4-3, 4-4, 

4-5, 4-7, 4-11, 4-12, 4-17, 4-33, 4-34, 4-44, 4-47, 4-48, 4-49, 4-52, 4-53, 5-1 

anthropogenic, 2-47, 3-62, 3-66, 3-72, 3-108, 3-111, 3-112, 3-113, 4-34, 4-53, 4-69, 4-89, 4-90, 4-98, 

4-100, 4-101, 4-102, 4-103, 4-107, 4-109, 4-110, 4-119, 4-148, 4-163, 4-178, 4-180, 4-181 

aquaculture, 4-122, 4-126, 4-134 

atmospheric-ocean general circulation model (AOGCM), 3-76, 3-101, 4-37, 4-64, 4-167 

Attorney General, 1-12, 1-13, 2-20 

benthic, 3-110, 3-112, 4-114, 4-116, 4-123, 4-181 

biofuel, 3-9, 3-10, 3-11, 3-107, 3-109, 3-110, 3-112, 3-113, 3-114, 3-116, 3-117, 3-119, 3-120, 4-7, 4-42, 

5-3 

biosphere, 3-83, 4-47, 4-90, 4-124, 4-161 

carbon sink, 3-66, 4-108, 4-170, 4-182 

Center for Biological Diversity (CBC), 1-14, 2-22 

Centers for Disease Control and Prevention (CDC), 1-11 

Clean Air Act (CAA), 1-4, 1-5, 1-7, 1-8, 1-9, 1-12, 2-5, 2-17, 3-11, 3-15, 3-16, 3-17, 3-21, 3-22, 3-25, 

3-27, 3-28, 3-29, 3-35, 3-59, 3-68, 3-70, 3-108, 3-121, 3-123, 3-124, 4-3, 4-12, 4-19, 4-33, 4-41, 4-42, 

4-72, 4-98, 4-162, 5-3 

climate change, 1-1, 1-7, 1-10, 1-11, 1-12, 1-14, 2-2, 2-12, 2-21, 2-39, 3-59, 3-60, 3-63, 3-64, 3-68, 3-69, 

3-70, 3-73, 3-74, 3-75, 3-78, 3-82, 3-83, 3-88, 3-91, 3-99, 3-107, 3-110, 3-111, 3-117, 3-119, 3-121, 

3-123, 3-127, 4-1, 4-3, 4-33, 4-34, 4-35, 4-36, 4-37, 4-39, 4-40, 4-42, 4-43, 4-47, 4-48, 4-52, 4-53, 

4-54, 4-64, 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, 

4-86, 4-87, 4-88, 4-89, 4-90, 4-98, 4-100, 4-102, 4-103, 4-104, 4-105, 4-106, 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, 4-122, 4-123, 4-124, 4-125, 

4-126, 4-127, 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, 4-146, 4-147, 4-148, 4-149, 4-150, 4-151, 4-153, 4-154, 4-155, 

4-156, 4-157, 4-158, 4-159, 4-160, 4-161, 4-162, 4-163, 4-164, 4-166, 4-167, 4-168, 4-169, 4-170, 

4-171, 4-173, 4-174, 4-175, 4-180, 5-4 

coastal, 3-1, 3-107, 4-2, 4-71, 4-112, 4-113, 4-114, 4-115, 4-117, 4-119, 4-121, 4-122 
 Chapter 9 Index 

 9-3 

Code of Federal Regulations (CFR), 1-1, 1-7, 1-8, 1-10, 1-11, 1-13, 1-16, 2-1, 2-11, 2-12, 2-13, 2-21, 

2-22, 2-35, 3-2, 3-3, 3-21, 3-22, 3-26, 3-73, 3-82, 3-83, 3-90, 3-99, 3-118, 3-123, 4-1, 4-2, 4-3, 4-5, 

4-12, 4-33, 4-35, 4-47, 4-53, 4-62, 4-64, 4-72, 4-73, 4-170, 4-173, 4-178, 5-1 

cold wave, 3-68, 4-138, 4-152 

coral bleaching, 4-116, 4-121, 4-122 

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, 1-17, 2-1, 2-2, 2-3, 2-4, 2-5, 2-9, 2-10, 2-11, 2-12, 2-13, 2-15, 2-16, 2-17, 2-18, 2-20, 

2-21, 2-22, 2-27, 2-29, 2-33, 2-34, 2-35, 2-40, 2-42, 2-46, 2-47, 2-48, 3-1, 3-3, 3-4, 3-5, 3-6, 3-7, 3-8, 

3-9, 3-11, 3-12, 3-13, 3-15, 3-21, 3-22, 3-23, 3-24, 3-25, 3-29, 3-31, 3-35, 3-36, 3-46, 3-49, 3-51, 3-52, 

3-53, 3-54, 3-55, 3-56, 3-59, 3-60, 3-65, 3-73, 3-74, 3-75, 3-76, 3-77, 3-79, 3-84, 3-88, 3-90, 3-92, 

3-96, 3-99, 3-100, 3-101, 3-105, 3-107, 3-109, 3-113, 3-114, 3-117, 3-119, 3-120, 3-121, 3-122, 3-123, 

3-124, 4-5, 4-7, 4-8, 4-11, 4-12, 4-20, 4-22, 4-23, 4-25, 4-26, 4-28, 4-29, 4-31, 4-33, 4-34, 4-36, 4-37, 

4-38, 4-39, 4-40, 4-41, 4-43, 4-44, 4-48, 4-49, 4-50, 4-52, 4-53, 4-55, 4-56, 4-62, 4-63, 4-64, 4-68, 

4-71, 4-72, 4-73, 4-170, 4-171, 5-1, 5-2, 5-3 

Council on Environmental Quality (CEQ), 1-7, 1-8, 1-11, 2-12, 2-13, 2-21, 2-22, 2-35, 3-1, 3-2, 3-3, 3-26, 

3-60, 3-66, 3-73, 3-82, 3-83, 3-90, 3-99, 3-123, 4-1, 4-2, 4-3, 4-5, 4-12, 4-35, 4-47, 4-53, 4-62, 4-64, 

4-72, 4-73, 4-170, 4-173, 4-178, 5-1, 5-2 

criteria pollutants, 2-37, 2-38, 3-4, 3-15, 3-17, 3-23, 3-30, 3-36, 3-45, 3-52, 3-53, 3-54, 3-55, 3-56, 4-12, 

4-13, 4-14, 4-15, 4-17, 4-19, 4-20, 4-22, 4-23, 4-25, 4-26, 4-27, 4-28, 4-29, 4-31, 5-2, 5-3 

crude oil, 3-10, 3-11, 3-18, 3-29, 3-30, 3-109, 3-115, 3-121, 3-124, 4-7, 4-48 

cryosphere, 3-83, 4-47, 4-75, 4-161 

Department of Transportation Act of 1966, 3-117 

desertification, 4-100, 4-110, 4-111, 4-147 

diesel particulate matter, 2-24, 2-25, 2-37, 3-17, 3-18, 3-20, 3-36, 3-41, 3-42, 3-43, 3-45, 3-46, 3-50, 3-51, 

3-52, 3-53, 3-54, 3-55, 3-56, 3-121, 4-15, 4-16, 4-17, 4-21, 4-22, 4-24, 4-26, 4-27, 4-28, 4-30, 4-31, 5-2 

disease, 3-18, 3-19, 3-32, 3-119, 4-89, 4-98, 4-107, 4-111, 4-115, 4-116, 4-128, 4-129, 4-131, 4-132, 

4-133, 4-139, 4-145, 4-150, 4-151, 4-153, 4-154, 4-155, 4-156, 4-158, 4-159, 4-160, 4-169, 4-174 

downweighting of vehicles, 3-109, 3-110, 3-113, 3-114, 3-117 

drought, 3-63, 3-64, 3-68, 3-69, 3-70, 3-72, 3-98, 3-99, 4-62, 4-64, 4-77, 4-79, 4-85, 4-88, 4-89, 4-98, 

4-107, 4-109, 4-110, 4-111, 4-124, 4-125, 4-126, 4-127, 4-131, 4-132, 4-133, 4-134, 4-136, 4-138, 

4-145, 4-148, 4-149, 4-153, 4-154, 4-157, 4-160, 4-161, 4-167, 4-169 

ecosystem, 2-22, 3-1, 3-2, 3-18, 3-59, 3-73, 3-107, 3-108, 3-110, 3-111, 3-112, 3-113, 3-115, 4-2, 4-33, 

4-34, 4-35, 4-71, 4-72, 4-73, 4-74, 4-75, 4-76, 4-82, 4-85, 4-86, 4-90, 4-92, 4-93, 4-94, 4-95, 4-96, 

4-97, 4-98, 4-99, 4-100, 4-101, 4-102, 4-104, 4-105, 4-106, 4-107, 4-108, 4-109, 4-110, 4-111, 4-112, 

4-113, 4-114, 4-115, 4-116, 4-117, 4-118, 4-120, 4-121, 4-122, 4-123, 4-124, 4-125, 4-127, 4-128, 

4-129, 4-134, 4-148, 4-150, 4-151, 4-161, 4-163, 4-177, 4-179, 4-181, 4-182 
Chapter 9 Index 

 9-4 

El Nino Southern Oscillation, 4-80, 4-81, 4-120, 4-124, 4-127, 4-169 

electric vehicle, 2-9 

emission rates, 3-4, 3-24, 3-36, 3-125, 4-11, 4-14, 4-20, 4-22, 4-24, 4-25, 4-27, 4-28, 4-30, 4-31, 4-155 

Energy Independence and Security Act (EISA), 1-1, 1-2, 1-3, 1-5, 1-7, 1-8, 1-9, 1-13, 1-14, 2-1, 2-2, 2-11, 

2-12, 2-13, 2-17, 2-21, 2-35, 3-6, 3-7, 3-8, 3-59, 3-123, 4-4, 4-5, 4-7, 4-11, 4-33, 4-48, 4-53, 5-1 

Energy Information Administration (EIA), 1-16, 2-4, 3-6, 3-9, 3-10, 3-11, 3-12, 3-26, 3-29, 3-79, 3-82, 

3-87, 4-7, 4-44, 4-47, 4-52 

Energy Policy and Conservation Act (EPCA), 1-1, 1-3, 1-5, 1-7, 1-8, 1-9, 1-13, 1-14, 1-15, 2-1, 2-2, 2-11, 

2-12, 2-13, 2-15, 2-16, 2-17, 2-20, 3-7, 3-8, 3-12, 3-123, 3-124, 4-5 

environmental justice, 3-2, 3-107, 3-119, 3-120, 4-137, 4-150, 4-173, 4-174, 4-175 

eutrophication, 3-109, 3-111, 3-112, 3-113, 3-116, 4-84, 4-102 

Executive Order (EO), 2-4, 3-9, 3-79, 3-119, 4-44, 4-173, 4-174 

Federal Highway Administration (FHWA), 3-17, 3-21, 3-22, 3-117, 4-153, 5-3 

Federal Register (FR), 1-1, 1-2, 1-3, 1-4, 1-5, 1-6, 1-8, 1-9, 1-10, 1-12, 1-14, 1-17, 2-1, 2-5, 2-11, 2-12, 

2-13, 2-21, 3-17, 3-23, 3-123, 4-1, 4-5, 4-42, 4-103, 5-3 

Federal Transit Administration (FTA), 3-21, 3-22, 5-3 

feedstock recovery, 3-29, 3-30 

fisheries, 1-11, 1-15, 3-110, 4-71, 4-112, 4-117, 4-121, 4-122, 4-123, 4-124, 4-125, 4-126, 4-132, 4-134, 

4-135 

flexible fuel vehicle, 2-16 

flood, 3-63, 3-64, 4-76, 4-77, 4-79, 4-82, 4-85, 4-86, 4-87, 4-88, 4-89, 4-90, 4-95, 4-119, 4-120, 4-122, 

4-124, 4-133, 4-137, 4-138, 4-142, 4-145, 4-146, 4-149, 4-150, 4-153, 4-157, 4-158, 4-159, 4-160, 

4-175 

food production, 3-18, 3-109, 3-112, 3-113, 3-114, 3-119, 3-120, 4-2, 4-71, 4-72, 4-90, 4-100, 4-103, 

4-105, 4-106, 4-107, 4-109, 4-112, 4-114, 4-121, 4-123, 4-124, 4-125, 4-126, 4-127, 4-133, 4-135, 

4-138, 4-139, 4-140, 4-147, 4-148, 4-150, 4-151, 4-153, 4-154, 4-155, 4-156, 4-158, 4-160, 4-174, 

4-175, 4-180, 4-181 

forest products, 3-90, 4-34, 4-90, 4-92, 4-93, 4-96, 4-97, 4-98, 4-100, 4-101, 4-103, 4-107, 4-110, 4-111, 

4-112, 4-118, 4-124, 4-126, 4-127, 4-128, 4-129, 4-130, 4-131, 4-134, 4-177 

freshwater resources, 3-59, 3-107, 3-108, 3-109, 3-110, 3-111, 4-2, 4-33, 4-71, 4-72, 4-75, 4-76, 4-77, 

4-79, 4-80, 4-82, 4-83, 4-85, 4-86, 4-87, 4-88, 4-90, 4-93, 4-94, 4-95, 4-96, 4-98, 4-99, 4-101, 4-102, 

4-104, 4-105, 4-106, 4-109, 4-111, 4-112, 4-113, 4-115, 4-119, 4-122, 4-126, 4-132, 4-135, 4-143, 

4-168 
 Chapter 9 Index 

 9-5 

Fuel Transportation, Storage, and Distribution, 3-24, 3-25, 3-29, 3-30, 3-31, 4-12, 5-2 

glacier, 3-60, 3-63, 3-69, 3-71, 3-72, 3-83, 3-101, 3-103, 4-47, 4-66, 4-67, 4-75, 4-80, 4-85, 4-87, 4-109, 

4-117, 4-161, 4-163, 4-164, 4-165, 4-166 

global emissions, 1-15, 2-27, 2-28, 2-39, 2-40, 2-46, 2-47, 3-64, 3-65, 3-66, 3-67, 3-76, 3-77, 3-78, 3-79, 

3-84, 3-87, 3-104, 3-109, 4-37, 4-38, 4-39, 4-40, 4-43, 4-44, 4-47, 4-49, 4-52, 4-67, 4-69 

global warming potential, 3-62, 3-66, 3-67, 3-84, 4-48 

greenhouse gas, 1-2, 1-3, 1-4, 1-5, 1-6, 1-7, 1-8, 1-12, 1-14, 1-15, 2-4, 2-5, 2-9, 2-10, 2-11, 2-17, 2-18, 

2-20, 2-26, 2-35, 2-39, 2-40, 2-47, 2-48, 3-3, 3-5, 3-6, 3-8, 3-11, 3-17, 3-34, 3-59, 3-60, 3-62, 3-63, 

3-65, 3-66, 3-67, 3-70, 3-73, 3-74, 3-75, 3-76, 3-77, 3-78, 3-79, 3-82, 3-83, 3-84, 3-87, 3-88, 3-90, 

3-99, 3-104, 3-108, 3-121, 3-123, 3-124, 3-126, 3-127, 4-3, 4-5, 4-8, 4-33, 4-34, 4-35, 4-36, 4-37, 4-38, 

4-39, 4-40, 4-41, 4-42, 4-43, 4-44, 4-47, 4-48, 4-49, 4-51, 4-52, 4-53, 4-54, 4-69, 4-71, 4-72, 4-73, 

4-110, 4-127, 4-128, 4-141, 4-161, 4-167, 4-169, 4-170, 4-177, 5-3, 5-4 

Greenhouse Gases, Regulated Emissions, and Energy Use in Transportation Model (GREET), 3-23, 3-31, 

3-75, 3-125, 4-36 

groundwater, 3-107, 3-108, 3-109, 4-75, 4-76, 4-78, 4-79, 4-83, 4-85, 4-86, 4-87, 4-88, 4-95, 4-96, 4-119, 

4-125, 4-139 

heat wave, 3-63, 3-68, 3-70, 3-97, 4-61, 4-124, 4-127, 4-140, 4-151, 4-152, 4-153, 4-156, 4-157, 4-159, 

4-173 

human health, 1-7, 3-6, 3-15, 3-31, 3-46, 3-63, 3-64, 3-73, 3-107, 3-108, 3-114, 3-115, 3-116, 3-117, 

3-118, 3-119, 4-17, 4-34, 4-35, 4-71, 4-72, 4-73, 4-82, 4-86, 4-137, 4-139, 4-147, 4-150, 4-151, 4-152, 

4-154, 4-155, 4-156, 4-159, 4-173 

hybrid electric vehicle, 2-9 

hydrology, 4-104, 4-107, 4-108 

ice sheets, 3-63, 3-71, 3-72, 3-101, 3-103, 4-67, 4-75, 4-109, 4-119, 4-122, 4-140, 4-162, 4-163, 4-164, 

4-165, 4-166, 4-168, 4-169 

Intergovernmental Panel on Climate Change (IPCC), 2-47, 3-3, 3-59, 3-60, 3-61, 3-62, 3-63, 3-64, 3-70, 

3-71, 3-72, 3-73, 3-75, 3-76, 3-77, 3-78, 3-79, 3-83, 3-91, 3-96, 3-97, 3-98, 3-99, 3-101, 3-102, 3-103, 

3-111, 3-125, 3-127, 4-3, 4-33, 4-34, 4-35, 4-36, 4-37, 4-38, 4-39, 4-40, 4-47, 4-54, 4-55, 4-61, 4-62, 

4-64, 4-65, 4-66, 4-67, 4-71, 4-72, 4-73, 4-74, 4-75, 4-78, 4-81, 4-82, 4-85, 4-86, 4-89, 4-98, 4-104, 

4-106, 4-109, 4-110, 4-119, 4-121, 4-122, 4-124, 4-127, 4-128, 4-132, 4-133, 4-135, 4-148, 4-150, 

4-151, 4-152, 4-153, 4-157, 4-161, 4-162, 4-163, 4-164, 4-165, 4-166, 4-168, 4-169, 4-170, 4-174, 

4-179, 4-180, 4-181, 4-183 

International Energy Outlook (IEO), 3-9, 3-79, 3-82, 4-44, 4-46, 4-47 

land use, 3-1, 3-2, 3-26, 3-107, 3-113, 3-114, 4-2, 4-76, 4-79, 4-83, 4-86, 4-90, 4-100, 4-109, 4-145, 

4-153, 4-157, 4-169 

MAGICC model, 2-41, 2-42, 2-43, 3-73, 3-75, 3-76, 3-77, 3-78, 3-83, 3-91, 3-92, 3-96, 3-98, 3-99, 3-100, 

3-101, 3-125, 4-35, 4-37, 4-38, 4-39, 4-54, 4-55, 4-56, 4-62, 4-63, 4-64, 4-67 
Chapter 9 Index 

 9-6 

Millennium Ecosystems Assessment (MA), 3-27, 3-28, 4-90, 4-91, 4-93, 4-98, 4-99, 4-100, 4-101, 4-102, 

4-104 

mitigation, 1-3, 3-65, 4-95, 4-141, 4-145, 4-173, 5-1, 5-2, 5-3 

mobile source air toxics (MSATs), 3-17, 3-18, 3-21, 3-23, 3-26, 3-98, 4-55, 4-173, 5-2, 5-3 

National Ambient Air Quality Standards (NAAQS), 3-15, 3-16, 3-17, 3-21, 3-24, 3-31, 3-32 

National Environmental Policy Act of 1969 (NEPA), 1-2, 1-7, 1-8, 1-10, 1-11, 1-13, 1-15, 1-17, 2-1, 

2-11, 2-12, 2-13, 2-15, 2-21, 2-22, 2-32, 2-35, 2-39, 2-45, 3-1, 3-2, 3-3, 3-7, 3-23, 3-25, 3-66, 3-83, 

3-104, 3-123, 4-1, 4-2, 4-3, 4-5, 4-7, 4-40, 4-52, 4-53, 4-67, 4-71, 4-171, 4-173, 5-1, 5-2 

National Highway Traffic Safety Administration (NHTSA), 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, 1-17, 2-1, 2-2, 2-3, 2-4, 2-5, 2-9, 2-10, 2-11, 2-12, 2-13, 2-15, 2-16, 

2-17, 2-19, 2-20, 2-21, 2-22, 2-26, 2-32, 2-34, 2-35, 2-37, 2-39, 2-40, 2-45, 2-46, 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, 3-59, 3-60, 3-65, 3-66, 3-73, 3-74, 3-75, 3-76, 3-77, 3-78, 3-79, 3-82, 3-84, 3-88, 3-90, 3-91, 

3-99, 3-104, 3-109, 3-112, 3-113, 3-114, 3-117, 3-119, 3-121, 3-122, 3-123, 3-124, 3-125, 4-3, 4-5, 

4-11, 4-12, 4-18, 4-19, 4-33, 4-34, 4-35, 4-36, 4-37, 4-38, 4-39, 4-40, 4-41, 4-43, 4-47, 4-48, 4-52, 

4-53, 4-54, 4-62, 4-67, 4-71, 4-72, 4-73, 4-74, 4-162, 4-170, 4-171, 4-173, 4-178, 5-1, 5-2, 5-3 

National Household Transportation Survey (NHTS), 2-10, 3-118 

nonattainment, 3-17, 3-21, 3-24, 3-25, 3-26, 3-27, 3-28, 3-29, 3-30, 3-36, 3-46, 3-47, 3-49, 3-50, 3-51, 

3-52, 3-53, 3-54, 3-55, 3-56, 3-120, 3-121, 4-12, 4-14, 4-15, 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, 4-174, 5-2, 5-4 

nonattainment area (NAA), 3-17, 3-24, 3-25, 3-26, 3-27, 3-29, 3-30, 3-46, 3-47, 3-49, 3-50, 3-51, 3-52, 

3-53, 3-54, 3-55, 3-56, 3-120, 3-121, 4-14, 4-15, 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, 4-174, 5-2, 5-4 

Notice of Intent (NOI), 1-1, 1-10, 1-13, 1-14, 2-1, 2-2, 2-12 

Notice of Proposed Rulemaking (NPRM), 1-1, 1-2, 1-4, 1-6, 1-7, 1-8, 1-13, 1-14, 1-15, 1-16, 1-17, 2-1, 

2-3, 2-5, 2-10, 2-11, 2-12, 2-13, 3-6, 3-76, 3-79, 4-37 

ocean acidification, 3-73, 3-108, 3-111, 4-109, 4-114, 4-115, 4-163, 4-178, 4-179, 4-180, 4-181, 4-183 

ocean circulation, 3-72, 3-101, 3-103, 4-67, 4-113, 4-119, 4-121, 4-122, 4-135, 4-162, 4-163, 4-167, 

4-168 

Organization for Economic Cooperation and Development (OECD), 3-118 

permafrost, 3-69, 3-70, 3-83, 3-91, 4-47, 4-54, 4-75, 4-77, 4-80, 4-81, 4-88, 4-103, 4-117, 4-121, 4-123, 

4-136, 4-140, 4-148, 4-161, 4-164, 4-168, 4-170 

polar bear, 4-103, 4-107, 4-147 

polar regions, 3-60, 3-63, 3-64, 3-69, 3-70, 3-71, 3-72, 3-98, 3-101, 3-103, 4-62, 4-66, 4-67, 4-75, 4-77, 

4-79, 4-80, 4-81, 4-91, 4-103, 4-105, 4-109, 4-122, 4-123, 4-130, 4-132, 4-135, 4-139, 4-140, 4-147, 

4-148, 4-162, 4-163, 4-164, 4-165, 4-166, 4-169, 4-170, 4-179 
 Chapter 9 Index 

 9-7 

precipitation, change in, 2-21, 2-26, 2-28, 2-32, 2-33, 2-41, 2-45, 2-46, 3-59, 3-60, 3-64, 3-68, 3-69, 3-70, 

3-72, 3-73, 3-75, 3-76, 3-77, 3-91, 3-98, 3-99, 3-100, 3-101, 3-102, 3-103, 3-104, 4-34, 4-36, 4-37, 

4-38, 4-54, 4-62, 4-63, 4-64, 4-65, 4-66, 4-67, 4-71, 4-73, 4-76, 4-77, 4-78, 4-79, 4-80, 4-81, 4-82, 

4-83, 4-84, 4-85, 4-86, 4-87, 4-88, 4-89, 4-92, 4-93, 4-95, 4-96, 4-102, 4-104, 4-106, 4-107, 4-108, 

4-110, 4-111, 4-115, 4-120, 4-122, 4-124, 4-126, 4-127, 4-128, 4-129, 4-133, 4-136, 4-138, 4-139, 

4-140, 4-142, 4-143, 4-144, 4-145, 4-148, 4-149, 4-150, 4-151, 4-155, 4-157, 4-158, 4-159, 4-162, 

4-167, 4-169, 4-170 

preferred alternative, 1-17 

Preliminary Regulatory Impact Analysis (PRIA), 2-2, 2-3, 2-12 

rebound effect, 1-13, 2-3, 2-9, 2-12, 2-18, 2-19, 2-20, 3-4, 3-5, 3-11, 3-23, 3-24, 3-25, 3-46, 3-47, 3-49, 

3-50, 3-51, 3-52, 3-53, 3-54, 3-55, 3-56, 3-119, 3-120, 4-21, 4-23, 4-24, 4-26, 4-27, 4-29, 4-30, 4-32, 

4-173 

Reference Case, 2-18, 2-19, 2-35, 2-39, 2-47, 3-9, 3-10, 3-76, 4-3, 4-11, 4-37, 4-38, 4-40, 4-43, 4-48, 

4-52, 4-53, 4-69 

Reformed CAFE Program, 1-5, 2-11, 2-21 

safety, 1-8, 1-9, 1-14, 1-16, 2-1, 2-2, 2-4, 3-20 

saltwater intrusion, 4-79, 4-88, 4-118 

sea level rise, 4-102, 4-118, 4-119, 4-123 

Secretary of Transportation, 1-1, 1-2, 1-8, 3-8 

sensitivity analyses, 2-3, 3-5, 3-6, 4-37 

Social Cost of Carbon (SCC), 1-11, 2-2, 2-3, 2-12, 2-18, 2-19, 3-11, 3-30 

Special Report on Emission Scenarios (SRES), 2-45, 3-78, 3-79, 3-91, 3-101, 4-39, 4-40, 4-54, 4-64, 

4-67, 4-122, 4-128, 4-179, 4-129, 4-131 

State Implementation Plan (SIP), 3-17, 3-21, 3-22 

Synthesis and Assessment Product (SAP), 2-39, 2-40, 2-46, 3-74, 3-76, 3-78, 3-79, 3-82, 3-83, 3-87, 4-3, 

4-35, 4-36, 4-37, 4-38, 4-39, 4-40, 4-43, 4-44, 4-46, 4-47, 4-49, 4-74, 4-127, 4-161, 4-164, 4-165 

temperature, change in, 2-21, 2-26, 2-28, 2-29, 2-30, 2-32, 2-33, 2-34, 2-35, 2-41, 2-42, 2-43, 2-45, 2-46, 

2-47, 2-48, 3-3, 3-18, 3-21, 3-59, 3-60, 3-61, 3-62, 3-63, 3-64, 3-69, 3-70, 3-71, 3-72, 3-73, 3-75, 3-76, 

3-77, 3-83, 3-91, 3-92, 3-94, 3-96, 3-99, 3-100, 3-101, 3-104, 3-105, 3-108, 3-125, 3-127, 4-3, 4-34, 

4-36, 4-37, 4-38, 4-39, 4-43, 4-48, 4-54, 4-55, 4-56, 4-58, 4-60, 4-62, 4-63, 4-64, 4-67, 4-68, 4-69, 

4-71, 4-73, 4-74, 4-76, 4-78, 4-79, 4-80, 4-82, 4-83, 4-85, 4-88, 4-89, 4-92, 4-93, 4-104, 4-105, 4-106, 

4-107, 4-108, 4-109, 4-110, 4-111, 4-115, 4-116, 4-117, 4-120, 4-121, 4-122, 4-123, 4-126, 4-127, 

4-128, 4-129, 4-130, 4-131, 4-132, 4-133, 4-135, 4-136, 4-137, 4-138, 4-139, 4-140, 4-141, 4-143, 

4-144, 4-145, 4-147, 4-148, 4-149, 4-150, 4-151, 4-152, 4-153, 4-155, 4-156, 4-157, 4-158, 4-159, 

4-160, 4-162, 4-163, 4-164, 4-165, 4-166, 4-167, 4-168, 4-169, 4-170, 4-174, 4-179 
Chapter 9 Index 

 9-8 

terrestrial ecosystems, 3-59, 3-112, 4-33, 4-91, 4-93, 4-97, 4-100, 4-101, 4-102, 4-104, 4-107, 4-108, 

4-127, 4-177, 4-182 

tipping point, 1-12, 3-83, 4-47, 4-111, 4-161, 4-162, 4-163, 4-164, 4-167, 4-170, 4-171 

U.S. Department of Energy (DOE), 2-1, 2-39, 3-9, 3-23, 5-3, 5-4 

U.S. Department of Transportation (DOT), 1-1, 1-3, 1-4, 1-7, 1-9, 1-10, 1-17, 2-1, 2-2, 3-2, 3-3, 3-107, 

3-117, 3-119, 3-123, 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, 1-14, 

1-17, 2-1, 2-2, 2-3, 2-4, 2-5, 2-8, 2-10, 2-11, 2-13, 2-16, 2-17, 2-18, 2-25, 2-27, 2-38, 2-39, 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, 3-34, 3-35, 3-36, 3-46, 3-59, 3-60, 3-62, 3-63, 3-64, 3-65, 3-66, 3-67, 3-68, 3-69, 3-70, 3-71, 

3-72, 3-73, 3-74, 3-76, 3-77, 3-79, 3-83, 3-87, 3-98, 3-99, 3-101, 3-103, 3-107, 3-108, 3-109, 3-110, 

3-112, 3-113, 3-115, 3-116, 3-118, 3-121, 3-123, 3-124, 3-125, 3-126, 3-127, 4-1, 4-3, 4-5, 4-12, 4-15, 

4-18, 4-19, 4-33, 4-34, 4-35, 4-36, 4-37, 4-38, 4-41, 4-42, 4-47, 4-52, 4-62, 4-67, 4-71, 4-72, 4-75, 

4-76, 4-77, 4-78, 4-79, 4-82, 4-83, 4-84, 4-85, 4-88, 4-90, 4-95, 4-98, 4-100, 4-101, 4-102, 4-103, 

4-104, 4-105, 4-106, 4-107, 4-108, 4-109, 4-110, 4-111, 4-113, 4-114, 4-115, 4-116, 4-117, 4-118, 

4-119, 4-121, 4-122, 4-123, 4-125, 4-127, 4-129, 4-130, 4-131, 4-132, 4-133, 4-136, 4-137, 4-138, 

4-139, 4-140, 4-142, 4-143, 4-145, 4-146, 4-147, 4-148, 4-149, 4-150, 4-151, 4-152, 4-153, 4-154, 

4-155, 4-156, 4-157, 4-158, 4-160, 4-161, 4-162, 4-163, 4-165, 4-166, 4-167, 4-168, 4-170, 4-174, 

4-178, 4-179, 4-181, 4-182, 5-2, 5-3 

United States emissions, 1-15, 3-4, 3-15, 3-66, 3-87 

Volpe model, 1-14, 1-15, 1-16, 2-2, 2-3, 2-5, 2-9, 2-14, 2-18, 2-19, 2-22, 3-3, 3-4, 3-5, 3-6, 3-8, 3-11, 

3-12, 3-23, 3-25, 3-26, 3-30, 3-42, 3-74, 3-75, 3-76, 3-79, 3-82, 3-84, 3-98, 3-100, 4-36, 4-37, 4-38, 

4-43, 4-44, 4-47, 4-48, 4-49, 4-55, 4-63 

World Meteorological Organization (WMO), 3-72