# Report to Congressional Committees 

# GAO United States Government Accountabilit y Office



# AVIATION AND CLIMATE CHANGE

Aircraft Emissions Expected to Grow, but Technological and Operational Improvements and Government Policies Can Help Control Emissions June 2009

GAO-09-554

## What GAO Found

**United States Government Accountability Office** 

## Why GAO Did This Study 

# H ighlights **Accountability Integrity Reliability June 2009**  

# AVIATION AND CLIMATE CHANGE

**Aircraft Emi ss**  **ion s**  **Expected to Grow, but Technolo**  **g ical and Operational Improvement**  **s and**  **Government Policie s**  **Can Help Control Emi ss**  **ion s**  Highlights of GAO-09-554 , a report to congressional committees



### A ircraft emit greenhouse gases and other emissions, contributing to increasing concentrations of such gases in the atmosphere. Many scientists and the Intergovernmental Panel on Climate Change (IPCC)—a United Nations organization that assesses scientific, technical, and economic information on climate change— believe these gases may negatively affect the earth’s climate. Given forecasts of growth in aviation emissions, some governments are taking steps to reduce emissions. In response to a congressional request, GAO reviewed (1) estimates of aviation’s current and future contribution to greenhouse gas and other emissions that may affect climate change; (2) existing and potential technological and operational improvements that can reduce aircraft emissions; and (3) policy options for governments to help address commercial aircraft emissions.

GAO conducted a literature review; interviewed representatives of government agencies, industry and environmental organizations, airlines, and manufacturers, and interviewed and surveyed 18 experts in economics and aviation on improvements for reducing emissions from aircraft.

GAO is not making recommendations. Relevant agencies provided technical comments which we incorporated as appropriate and EPA said emissions standards can have a positive benefit to cost ratio and be an important part of policy options to control emissions. 

### A ccording to IPCC, aviation currently ac counts for about 2 percent of humangenerated global carbon dioxide emissi ons, the most significant greenhouse gas—and about 3 percent of the potential warming effect of global emissions that can affect the earth’s climate, including carbon dioxide . IPCC’s mediumrange estimate forecasts that by 2050 the global aviation industry, including aircraft emissions, will emit about 3 percent of global carbon dioxide emissions and about 5 percent of the pot ential warming effect of all global human-generated emissions . Gross domestic product growth is the primary driver in IPCC’s forecasts. IPCC also made other assump tions about future aircraft fuel efficiency, improvements in air traffic management, and airport and runway capacity. IPCC’s 2050 fore casts for aviation’s contribution to global emissions assumed that emissions from other sectors will continue to grow. If other sectors make progress in reducing emissions and aviation emissions continue to grow, aviation’s relative contribution may be greater than IPCC estimated; on the other hand, if other sectors do not make progress, aviation’s relative c ontribution may be smal ler than estimated.

While airlines currently rely on a range of improvements, such as fuel-efficient engines, to reduce emissions, some of which may have limited potential to generate future reductions, experts we su rveyed expect a number of additional technological, operati onal, and alternative fuel im provements to help reduce aircraft emissions in the future. However, according to experts we interviewed, some technologies, such as advanced airframes, have potential, but may be years away from being ava ilable, and developing and a dopting them is likely to be costly. In addition, according to so me experts we interviewed, incentives for industry to research and adopt low-emissions technologies will be dependent to some extent on the level and stability of fuel prices. Finally, given expected growth of commercial aviation as forecasted by IPCC, even if many of these improvements are adopted, it appears unlikely they would greatly reduce emissions by 2050.

A number of policy options to address aircraft emissions are available to governments and can be part of broade r policies to address emissions from many sources including airc raft. Market-based measures can establish a price for emissions and provide incentives to airlines and consumers to reduce emissions. These measures can be prefer able to other options because they would generally be more economically e fficient. Such measures include a capand-trade program, in which governmen t places a limit on emissions from regulated sources, provides them wi th allowances for emissions, and establishes a market for them to trade emissions allowances with one another, and a tax on emissions. Governments can establish emissions standards for aircraft or engines. In addition, government could increase government research and development to encour age development of low-emissions improvements. To view the full product, including the scope and methodology, click on GAO-09-554

. For more information, contact Susan Fleming at (202) 512-2834 or flemings@gao.gov

.Page i GAO-09-554 

# Contents

Letter 1
Background 3 Aviation Emissions Represent a Small but Growing Share of All Emissions 10 Experts Believe Future Technological and Operational Improvements Are Likely to Help Reduce Emissions from Commercial Aircraft, but Likely Not by Enough to Fully Offset Estimated Market Growth 22 Governments Can Use a Variety of Policy Options to Help Reduce Commercial Aircraft Emissions, but the Costs and Benefits of Each Vary 35 Agency Comments and Our Evaluation 49



## Appendix I Legal Implications of European Union Emissions Trading Scheme 53



## Appendix II List of Experts 70



## Appendix III Detail ed Survey Results 71
Part 1: Technology Options 72 Part 2: Operational Options 76 Part 3: Alternative Fuel Options 83



## Appendix IV Scope and Methodology 87



## Appendix V Comments from the National Aeronautics and Space Administration 90



## Appendix VI Comments from th e Environmental Protection Agency 91

Aviation and Climate Change

## Appendix VII GAO Contact and Staff Acknowledgments 94



## Tables
Table 1: Types of Aviation Emissions and Their Effects at Cruising Altitude 13 Table 2: Selected Potential Aircraft Engine Improvements to Reduce Emissions 23 Table 3: Selected Aircraft Impr ovements to Reduce Emissions 25 Table 4: Selected Operational Improvements to Reduce Emissions 27 Table 5: Selected Air Traffic Management Improvements to Reduce Emissions 29 Table 6: NASA’s Subsonic Fixed-Wing Research Fuel-Reduction Goals 48



## Figures
Figure 1: Selected Greenhouse Gas and Other Emissions from Aircraft at Cruising Altitude 4 Figure 2: Total Fuel Consumption and Fuel Efficiency of U.S. Airlines 5 Figure 3: Energy use per Passenger-mile, by Mode of Transportation 6 Figure 4: Forecasted Fuel C onsumption by U.S. Airlines 7 Figure 5: Global Transportation’s and Global Aviation’s Contributions to Carbon Dioxide Emissions, 2004 12 Figure 6: Estimated Relative Contribution of Aviation Emissions to Positive Radiative Forcing 15 Figure 7: Changes in Global and U.S. Aviation Passenger Traffic, 1978 through 2008 16 Figure 8: IPCC’s Scenarios for Global Aviation Carbon Dioxide Emissions 18 Figure 9: A Potential Cap-and-Trade Program Regulating Airlines and Other Emissions Sources 38

Page ii GAO-09-554 Aviation and Climate Change

### Abbreviations

ACARE Advisory Council for Aeronautics Research in Europe ADS-B Automatic Dependent Surveillance-Broadcast ATA Air Transport Association CDA Continuous Descent Arrival CER certified emissions reduction CO 2 

### carbon dioxide DG Environment Directorate-General of the Environment EEC European Economic Community EPA Environmental Protection Agency ERU emission reduction unit EU European Union EU ETS European Union Emissions Trading Scheme FAA Federal Aviation Administration GDP gross domestic product GIACC Group on International Aviation and Climate Change ICAO International Civil Aviation Organization IETA International Emissions Trading Association IPCC Intergovernmental Panel on Climate Change NASA National Aeronautics and Space Administration NextGen Next Generation Air Transportation System NOx nitrogen oxides RNAV area navigation RNP Required Navigation Performance SESAR Single European Sky Air Traffic Management Research Program UNFCCC United Nations Framew ork Convention on Climate Change

This is a work of the U.S. government and is not subject to copyright protection in the United States. The published product may be r eproduced and distributed in its entirety without further permission from GAO. Howe ver, because this work may contain copyrighted images or other material, permission from the copyright holder may be necessary if you wish to reproduce this material separately.

Page iii GAO-09-554 Aviation and Climate ChangePage 1 GAO-09-554 

### United States Government Accountability Office Washington, DC 20548



### June 8, 2009

Congressional Requesters

Many sources, including manufacturing, residential, and transportation sources, emit greenhouse gas es that contribute to the accumulation of these gases in the earth’s atmosphere . Greenhouse gases disperse and trap heat in the earth’s atmosphere. This heat-trapping effect, known as the greenhouse effect, moderates atmospheric and surface temperatures, keeping the earth warm enough to support life. However, according to the Intergovernmental Panel on Climate Change (IPCC)—a United Nations organization that assesses scientific, technical, and economic information on the effects of climate change—global atmospheric concentrations of these greenhouse gases have increased markedly as a result of human activities over the past 200 years, contributing to a warming of the earth’s climate. These trends, if unchecked, could have serious negative effects, such as rising sea levels and coastal flooding worldwide.

Aircraft emit a variety of greenhouse and other gases, including carbon dioxide—the most significant greenhouse gas emitted by aircraft—and nitrogen oxides, as well as other subs tances such as soot and water vapor that are believed to negatively affect the earth’s climate. Airlines have a financial incentive to reduce carbon dioxide emissions, as those emissions are a direct result of fuel burn, whic h represents a large portion of their operating costs—about 30 percent for U.S. airlines in 2008. Some experts expect aviation to grow at a fast rate until 2021, when the Federal Aviation Administration (FAA) forecasts that U.S. domestic commercial aviation will serve over 1 billion passengers a year. While the current economic downturn could delay this growth somewhat, experts believe that growth in the aviation sector means greater productivity and mobility, but is also likely to increase emissions. To c ounteract expected increases in emissions, many governments and international organizations have set goals for future emissions reductions. For example, a number of developed countries have set a goal to reduce carbon dioxide emissions by 50 percent by 2050. In addition, the Kyoto Protocol, an international agreement to minimize the adverse effects of climate change, set binding targets for the reduction of greenhouse gases for 37 industrialized countries and the European Econom ic Community (EEC) to achieve

Aviation and Climate Change

### during the 2008 through 2012 commitment period. 1 

### Although the United States is a signatory to the Kyoto Protocol, it is not bound by its terms or emissions target because it has not ratified the Protocol. The Protocol also requires industrialized nations and the EEC to pursue “limitations or reduction of emissions of greenhouses gases... from aviation... working through the International Civil Aviation Organization.” 2 

### Finally, some governments have taken actions designed to control aviation emissions.For example, in 2003, the European Union (EU) established a cap-andtrade program known as the EU Emissi ons Trading Scheme (EU ETS) to control carbon dioxide emissions from various energy and industrial sectors. The EU ETS was first impl emented in 2005 and was amended in 2008 to include aviation. Beginning in 2012, the ETS will include all covered flights into or out of an EU airport. 3



### You asked us to provide informati on on aviation emissions of greenhouse gases and other emissions that may affect climate change. To do so, we identified (1) aviation’s current and estimated future contribution to the emissions of greenhouse gases and other emissions that may affect climate change, (2) existing and potential future technological and operational improvements that the commercial aviation industry can use to reduce commercial aircraft emissions, and (3) policy options for the U.S. government and other governments to help reduce commercial aviation emissions and the potential costs and benefits of each option. You also asked that we describe the EU’s plans to add the aviation industry to its existing ETS and the potential legal implications of doing so. (See app. I for this description.) To address th ese objectives, we reviewed studies on the impact of aviation on climate change. We also collaborated with the National Academy of Sciences to identify and recruit experts with experience in climate change and the aviation industry. We interviewed 18 such experts (see app. II for a list of the experts). After these interviews,

1 Kyoto Protocol to the United Nations Framework Convention on Climate Change (hereinafter the Kyoto Protocol). The Kyoto Protocol was adopted in December 1997 and was open for signature between Mar. 16, 1998, and Mar. 15, 1999. As of Jan. 14, 2009, 183 countries and the EEC had ratified the Kyoto Protocol. The binding emissions targets varies by country and is generally higher for more highly developed countries. For instance, the EEC has agreed to reduce their aggregate em issions by 8 percent from 1990 emissions levels.

2 Kyoto Protocol, art. 2(2).

3 This would also include those airports in non -EU countries currently participating in the EU ETS—Norway, Iceland, and Liechtenstein. S ee app. I for further explanation of the EU ETS.

Page 2 GAO-09-554 Aviation and Climate Change

### we asked the experts to complete a survey in which they assessed a list of options to reduce emissions on a variety of predetermined factors, such as potential for emissions reductions and costs (see app. III for complete results). In addition, we spoke with government, airline, and interest group officials in the United States, the EU, and the United Kingdom, focusing on commercial aviation. (See app. IV for a more detailed description of our scope and methodology.) We conducted our work from March 2008 through June 2009 in accordance with generally accepted government auditing standards. Those standards require that we plan and perform the audit to obtain sufficient, appropriate evidence to provide a reasonable basis for our findings and conclusions based on our audit objectives. We believe that the evidence obtained provides a reasonable basis for our findings and conclusions based on our audit objectives.

Emissions from a variety of human-generated sources, including commercial aircraft, trap heat in the atmosphere and contribute to climate change. During flight operations, ai rcraft emit a number of greenhouse gas and other emissions, including carbon dioxide, nitrogen oxides (NOx), soot, and water vapor. Figure 1 s hows the primary emissions from commercial aircraft. Carbon dioxide emissions from aircraft are a direct result of fuel burn. For every gallon of jet fuel burned, about 21 pounds of carbon dioxide are emitted. Reducing the amount of fuel burned, therefore, also reduces the amount of carbon dioxide emitted. Water vapor emissions and certain atmospheric temperature and humidity conditions can lead to the formation of contrails, a cloudlike trail of condensed water vapor, and can induce the creation of cirrus clouds. Both contrails and cirrus clouds are believed to have a warming effect on the earth’s atmosphere. Aircraft also emit other pollutants that affect local air quality. Finally, airport operations are sour ces of greenhouse gas and other emissions, which we are not examining in this report. 

# Background

Page 3 GAO-09-554 Aviation and Climate Change**Figure 1: Selected Greenhouse Gas and Other Emissions from Aircraft at Cruising Altitude** 

**Air Exhau**  **s t**  **Jet en g**  **ine**
C a r b on dioxide Nitrogen oxide s

W a ter v a por

Su lph a te

S oot

S o u rce: GAO. **Fuel**

**Combu s**  **tion**



### Historically, the commercial aviation industry has grown substantially in the United States and worldwide and is a contributor to economic growth. Between 1981 and 2008, passenger traffic increased 226 percent in the United States on a revenue passenger mile basis and 257 percent globally on a revenue passenger kilometer basis. 4 

### According to the FAA, in 2006 the civil aviation industry in the United States directly and indirec contributed 11 million jobs and 5.6 percent of total gross domestic product (GDP) to the U.S. economy. Globally, the International Air Transport Association estimated that in 2007 the aviation industry had a global economic impact of over $3.5 trillion, equivalent to about 7.5 percent of worldwide GDP. Recently, however, the airline industry has experienced declining traffic and financial losses as the result of the current recession. tly

The fuel efficiency of commercial jet aircraft has improved over time. According to IPCC, aircraft today are about 70 percent more fuel efficient on a per passenger kilometer basis than they were 40 years ago because of improvements in engines and airframe design. 5 

### The cost of jet fuel is a large cost for airlines. In the 2008, when global fuel prices were high, jet fuel accounted for about 30 percent of U.S. airlines’ total operating expenses, compared with 23 percent during 2007. Fuel efficiency (measured by available seat-miles per gallon consumed) for U.S. carriers increased about 17 percent between 1990 and 2008, as shown in figure 2. Internationally, according to the International Air Transport Association,

4 Fuel consumption of U.S.-based airlines roughly doubled during that same period.

5 However, some aircraft available in the 1950s were about equally as fuel efficient as jets currently available today.

Page 4 GAO-09-554 Aviation and Climate Change

### fuel efficiency (measured by revenue passenger kilometers) improved 16.5 percent between 2001 and 2007. According to FAA, between 2000 and early 2008 U.S. airlines reduced fuel burn and emissions while transporting more passengers and cargo.

**Figure 2: Total Fuel Consumption and Fuel Efficiency of U.S. Airlines**

**Gallon s**  **con s**  **umed** (in b illion s ) **Available s**  **eat mile s**  **per g**  **allon**

S o u rce: U. S . Dep a rtment of Tr a n s port a tion. **Year**

G a llon s of f u el per a v a il ab le s e a t mile

G a llon s of f u el con su med **0 2**  **4 6**  **8 10**  **12 14**  **16 18**  **20**

**2008200720062005200420032002200120001999199819971996199519941993199219911990198919881987198619851984198319821981 0**  **44 46**  **48 50**  **52 54**  **56 58**  **60**



### In addition, commercial aviation has become less energy intensive over time—that is, to transport a single passe nger a single mile uses less energy than it previously did, measured in British thermal units. See figure 3 showing energy intensity over time of aviation and other modes of transportation.

Page 5 GAO-09-554 Aviation and Climate Change**Figure 3**  **: Energy use per Passenger-mile , by Mode of**  **Transportation**

**0 1000**  **2000 3000**  **4000 5000**  **6000 7000**  **8000 9000** 

**2005 2002**  **1999 1996**  **1993 1990**  **1987 1984**  **1981 1978**  **1975 BTU**  **s /pa**  **ss en**  **g er mile** 

**Year**

Air
C a r s Intercity r a il
B us e s
Tr a n s it r a il

S o u rce: Dep a rtment of Energy.



### However, despite these efficiency im provements, overall fuel burn and emissions of U.S. airlines are expected to grow in the future. FAA forecasts that between 2008 and 2025 fuel consumption of U.S.-based airlines will increase an average of 1.6 percent per year while revenue passenger miles will increase an average of 3.1 percent per year over the same period. As seen in figure 4, FAA forecasts that between 2008 and 2025 fuel consumption of U.S.-based airlines will increase an average of 1.6 percent per year.

Page 6 GAO-09-554 Aviation and Climate Change**Figure 4: Forecasted Fuel Consumption by U.S. Airlines**

**0 5**  **10 15**  **20 25**  **30**

**2025 2024**  **2023 2022**  **2021 2020**  **2019 2018**  **2017 2016**  **2015 2014**  **2013 2012**  **2011 2010**  **2009 Gallon**  **s con**  **s umed (billion**  **s )** 

S o u rce: FAA Aero s p a ce Forec as t, FY 2009-2005. **Fi s**  **cal year**



### To develop a better understanding of the effects of human-induced climate change and identify options for adaptation 6 

### and mitigation, 7 

### two United Nations organizations established IPCC in 1988 to assess scientific, technical, and socio-economic information on the effects of climate change. IPCC releases and periodically updates estimates of future greenhouse gas emissions from human activities under different economic development scenarios. In 1999, IPCC released its report, Aviation and the Global Atmosphere, conducted at the request of the International Civil Aviation Organization (ICAO)—a United Nations organization that aims to promote the establishment of inte rnational civilian aviation standards and recommended practices and procedures. In 2007, IPCC released an

6 According to IPCC, adaptation is an adjustment that occurs in resp onse to expected or actual climatic stimuli or effects in order to moderate damages or exploit beneficial opportunities.

7 IPCC defines mitigation as t echnological change and substitution that reduce resource inputs, such as energy use, and emissions per unit of output. Al though several social, economic, and technological policies would pr oduce an emissions reduction, with respect to climate change, mitigation means implem enting policies to reduce greenhouse gas emissions.

Page 7 GAO-09-554 Aviation and Climate Change

### update on emissions from transportation and other sectors called the Fourth Assessment Report of the Intergovernmental Panel on Climate Change . These reports were developed with input from over 300 experts worldwide and are internationally accepted and used for policy-making.

A variety of federal agencies have roles in addressing aviation emissions. In 2004, FAA and other organizations including the National Aeronautics and Space Administration (NASA) released a report, Aviation and the Environment: A National Vision Statement, Framework for Goals and Recommended Actions , through the collaborative PARTNER program, 8 

### stating a general goal to reduce overall levels of emissions from commercial aviation and proposing actions to deal with aviation emissions. FAA also is involved in a number of emissions-reduction initiatives—including work on low-emissions technologies and low-carbon alternative fuels; the implementation of a new air traffic management system, the Next Generation Air Transportation System (NextGen); 9 

### and climate research to better understa nd the impact of emissions from aviation. NASA has been involved in research that has led to the development of technologies that reduce aircraft emissions. Currently, NASA’s Subsonic Fixed-Wing project, part of its Fundamental Aeronautics program, aims to help develop technologies to reduce fuel burn, noise, and emissions in the future. Both FAA and NASA are involved in the Aviation Climate Change Research Initiative, whose goals include improving the scientific understanding of aviation’s impact on climate change. Also, as mandated under Title II of the Clean Air Act, the Environmental Protection Agency (EPA) promulgates certain emissions standards for aircraft and aircraft engines 10 

### and has adopted emission standards matching those for aircraft set by ICAO. 11 

### While neither ICAO nor EPA has established standards for aircraft engine emissions of carbon dioxide, ICAO is

8 The PARTNER program—the Partnership for AiR Transportation Noise and Emissions Reduction—is a cooperative research organization sponsored by FAA, NASA, and Transport Canada, with members including un iversities and other organizations with expertise.

9 NextGen is a new, satellite-based air traffic management system that is expected to increase the safety and enhan ce the capacity of the air transport system. NextGen will transform the current radar-based air traffic control system.

10 42 U.S.C. § 7571.

11 However, EPA has the authority to set emissi ons standards. As th e technical agency with responsibility for international civil aviation in the United States, FAA, in consultation with EPA, works with representatives of other ICAO member countries to formulate the standards.

Page 8 GAO-09-554 Aviation and Climate Change

### currently discussing proposals for carbon dioxide emissions standards and considering a global goal for fuel efficiency. 12 

### In addition, in 2007 a coalition of environmental interest groups filed a petition with EPA asking the agency, pursuant to the Clean Air Act, to make a finding that “greenhouse gas emissions from ai rcraft engines may be reasonably anticipated to endanger the public health and welfare” and, after making this endangerment finding, promul gate regulations for greenhouse gas emissions from aircraft engines. 13



### International concerns about the contri bution of human activities to global climate change have led to several efforts to reduce their impact. In 1992, the United Nations Framework Convention on Climate Change (UNFCCC)—a multilateral treaty whose objective is to stabilize greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous human interference with the climate system—was signed. 14 

### By 1995, the parties to the UNFCCC, including the United States, realized that progress toward this goal was not sufficient. In December 1997, the parties reconvened in Kyoto, Japan, to adopt binding measures to reduce greenhouse gas emissions. Under the resulting Kyoto Protocol, which the United States has not ratified, industrialized nations committed to reduce or limit their emissions of carbon dioxide and other greenhouse gases during the 2008 through 2012 commitment period. 15 

### The Protocol

12 In addition, H.R. 2454, the Am erican Clean Energy and Secu rity Act of 2009, § 221(b), 111th Cong. (2009), would requ ire EPA to issue standards for greenhouse gas emissions from new aircraft and new engines used in aircraft by Dec. 31, 2012.

13 In addition, in 2007, the Supreme Court rule d that greenhouse gases meet the Clean Air Act’s definition of an air pollutant and that EPA has the statutory authority to regulate greenhouse gas emissions from new motor vehicles under the Act. Massachusetts v. Environmental Protection Agency , 549 U.S. 497 (2007). As a re sult of the opinion, EPA must take one of three actions: 1) issue a finding that greenhouse gas emissions cause or contribute to air pollution that may endanger pub lic heath or welfare; 2) issue a finding that greenhouse gases do not endanger public health or welfare; or 3) provide a reasonable explanation as to why it cannot or will not exercise its disc retion to issue a finding. In response to this case, EPA issued an Advance Notice of Proposed Rulemaking, “Regulating Greenhouse Gas Emissions Unde r the Clean Air Act,” 73 Fed. Reg. 44354 (July 30, 2008). EPA subsequently issued a pro posed finding that carbon dioxide, methane, nitrous oxide, and hydrofluorocarbon emissions from new mo tor vehicles are contributing to air pollution which is endangering public health and welf are. 74 Fed. Reg. 18886 (Apr. 24, 2009). EPA is moving forward with the proposed finding while it develops proposed standards for regulating greenhouse gas emi ssions from motor vehicles.

14 To date, 192 countries have ratified the UNFCCC.

15 The emissions reduction goal varies by country and is generally higher for more highly developed countries. Some Euro pean countries, for example, agreed to reduce emissions by 8 percent compared to 1990 levels.

Page 9 GAO-09-554 Aviation and Climate Change

### directed the industrialized nations to work through ICAO to reduce or limit emissions from aviation, but inte rnational aviation emissions are not explicitly included in Kyoto’s targets. In 2004, ICAO endorsed the further development of an open emissions trading system for international aviation, and in 2007 called for mutual agreement between contracting states before implementation of an emissions trading scheme. In part to meet its Kyoto Protocol requiremen ts, the EU implemented its ETS in 2005, which sets a cap on carbon dioxid e emissions and allows regulated entities to buy and sell emissions allowances with one another. In 2008, the European Parliament and the Council of the European Union passed a directive, or law, to include aviation in the ETS. Under the directive, beginning in 2012 a cap will be pl aced on total carbon dioxide emissions from all covered flights by aircraft operators into or out of an EU airport. 16 

### Many stakeholders and countries have stated objections to the EU’s plans and legal challenges are possible. (See app. I for a discussion of the ETS’s inclusion of aviation.) In December 2009, the parties to the UNFCCC will convene in Copenhagen, Denmark, to discuss and negotiate a post-Kyoto framework for addressing global climate change.

IPCC estimates that aviation emissions currently account for about 2 percent of global human-generated carbon dioxide emissions and about 3 percent of the radiative forcing 17 

### of all global human-generated emissions (including carbon dioxide) that contribute to climate change. On the basis of available data and assumptions about future conditions, IPCC forecasted emissions to 2015 and forecasted three scenarios—low, medium, and high—for growth in gl obal aviation carbon dioxide emissions from 2015 to 2050. These scenarios are driven primarily by assumption about economic growth—the factor most closely linked historically to the aviation industry’s growth—but they also reflect other aviation-related assumptions. Because IPCC’s forecasts depend in large part on assumptions, they, like all forecasts, are inherently uncertain. Nevertheless, as previously noted, IPCC’s work reflects the input of over 

# Aviation Emissions Represent a Small but Growing Share of All Emissions

16 In addition to the current 27 EU member states, other European countries not part of the EU, such as Norway, Iceland, and Liechtenstein , participate in the ETS. These airports are included in the amended ETS.

17 Radiative forcing is a measure for the chan ge of the Earth’s energy balance due to a change in concentrations of greenhouse gases and other em issions that contribute to climate change.

Page 10 GAO-09-554 Aviation and Climate Change

### 300 leading and contributing authors and experts worldwide and is internationally accepted and used for policy making. 18



# Aviation Contributes about 2 Percent of Global Carbon Dioxide Emissions According to IPCC, global aviation contributes about 2 percent of the global carbon dioxide emissions caused by human activities. 19 

### This 2 percent estimate includes emissions from all global aviation, including both commercial and military. Global commercial aviation, including cargo, accounted for over 80 percent of this estimate. 20 

### In the United States, domestic aviation contributes about 3 percent of total carbon dioxide emissions, according to EPA data. 21



### Many industry sectors, such as the electricity-generating and manufacturing sectors, contribute to global carbon dioxide emissions, as do residential and commercial buildings that use fuel and power. The transportation sector also contribut es substantially to global carbon dioxide emissions. Specifically, it accounts for about 20 percent of total global carbon dioxide emissions. 22 

### Road transportation accounts for the largest share of carbon dioxide emissions—74 percent—from the transportation sector; aviation acco unts for about 13 percent of carbon

18 According to IPCC, the report was compiled by 107 lead authors from 18 countries. Successive drafts of the report were circulated for review by experts, followed by review of governments and experts. Over 100 contribu ting authors submitted draft text and information to the lead authors and o ver 150 reviewers subm itted suggestions for improvement during the review process.

19 According to IPCC, global aviation’s global carb on dioxide emissions totaled an estimated 480 million tons in 2000.

20 According to EPA, in 2007 commercial aviat ion represented about 82 percent of all aviation emissions, and about 2.5 percent of U. S. carbon dioxide emi ssions. In the United States, military aviation represents less than 10 percent of total aviation emissions.

21 EPA, Draft Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2007 , (March 2009). The aviation estimates do not include fuel consumed for international air transport per UNFCCC’s reporting guidelines; accordin g to the EPA, in 2006, when those international fuels were included, domestic and internationa l commercial, military, and general aviation flights represented about 3.4 percent of U.S. carbon dioxide emissions.

22 In the United States according to EPA, carbon dioxide emissions from fossil fuel combustion in the transportation sector acco unt for an estimated 31 percent of carbon dioxide emissions (in carbon dioxide equivalents not including fuels used for international flights). Carbon dioxide equivalents prov ide a common standard for measuring the warming potential of different greenhouse gas es and are calculated by multiplying the emissions of the non-carbon-dioxide gas by it s global warming potential, a factor that measures its heat-trapping ability re lative to that of carbon dioxide.

Page 11 GAO-09-554 Aviation and Climate Change

### dioxide emissions from all transportation sources; and other transportation sources, such as rail, account for the remaining 13 percent. Figure 5 shows the relative contributions of industry, transportation, and all other sources to global carbon dioxide emissions and breaks down transportation’s share to illustrate the re lative contributions of road traffic, aviation, and other transportation sources.

**Figure 5: Global Transportation’s and Gl obal Aviation’s Contributions to Carbon**  **Dioxide Emissions, 2004**



### 8% **13%**

**20% 18%** 

**41%**

S o u rce s : GAO pre s ent a tion of Intern a tion a l Energy Agency a nd IPCC d a t a

. Other s o u rce s Re s identi a l a nd s ervice s Ind us try

Power gener a tion Tr a n s port a tion

Ro a d



### 74% 

### 13% Avi a tion 

### 13% R a il a nd other

s o u rce s



# Aviation Contributes about3 Percent of All HumanGenerated Emissions When other aviation emissions—such as nitrogen oxides, sulfate aerosols, and water vapor—are combined with carbon dioxide, aviation’s estimated share of global emissions increases fr om 2 percent to 3 percent, according to IPCC. However, the impact of these other emissions on climate change is less well understood than the impact of carbon dioxide, making IPCC’s combined estimate more uncertain than its estimate for carbon dioxide alone.

Aviation emissions may contribute directly or indirectly to climate change. Although most aviation emissions have a warming effect, sulfate aerosols and a chemical reaction involving methane have a cooling effect. The warming effect is termed “positive radiative forcing” and the cooling effect “negative radiative forcing.” Aviation emissions also may contribute to the formation of cirrus clouds, which can cause atmospheric warming, but the

Page 12 GAO-09-554 Aviation and Climate Change

### scientific community does not yet understand this process well enough to quantify the warming effect of aviation-induced cirrus clouds. Table 1 describes the direct or indirect effects of aviation emissions on climate change.

**Table 1: Types of Aviation Emissions a nd Their Effects at Cruising Altitude** 

**Direct greenhouse gases and emissions**
Carbon dioxide Carbon dioxide has a warming effect on the climate and remains in the atmosphere for hundreds of years. Carbon dioxide emissions from aviation have the same effect as those from other industry sectors because the carbon dioxide emitted from aircraft remains in the atmosphere long enough to be well mixed with the carbon dioxide emitted from ground-based sources. Water vapor Water vapor has a warming effect on the climate and is generat ed from the hydrogen contained in aviation fuel. It remains for only a short period in the troposphere (the lowest portion of the earth’s atmosphere), where most emissions from aviation occur. The quantity of water vapor emitted by avia tion is small compared with the quantities emitted from natural atmospheric sources. Soot particles Soot particles are produced du ring combustion and have a small warming (positive radiative forcing a ) effect on the climate as they abs orb incoming sunlight and heat the atmosphere. **Indirect greenhouse gases and emissions** Ozone (from NOx) Nitrogen emissions do not contribute to global warming directly, but the ozone generated from increased nitrogen oxides (NOx) is a greenhouse gas that produces a warming effect on the climate. The effect is higher at cruising altitude than on the ground because of longer lifetimes and greater radiative forcing in the higher levels of the atmosphere. Methane (NOx related) Very little or no methane is emitted by aircraft, but NO x emissions initiate a destruction of methane molecules, which generates an overa ll cooling effect on t he climate. Overall, the warming effect of NOx emissions due to ozone formation is estimated to be higher than the cooling that results from methane destruction.
Sulfate aerosols Sulfate aerosols, whic h arise from sulfur in jet fuel, scatter incoming sunlight back to the atmosphere and have a relatively sm all cooling effect on the climate.
**Cloud formation**
Contrails Contrails are formed through emissions of water and particles under certain atmospheric conditions such as temperature and humidity. They mainly consist of water already contained in the atmosphere, and aircraft operations only trigger their formation in these areas. Contrails cool the climate through increas ed reflection of solar radiation, but also trap heat on the earth, which contributes to global warming. Overall, contrails have a warming effect, although uncertainties about the magnitude of this effect remain.
Cirrus clouds Cirrus cloud formation might be augmented through aviation-induced contrails and cloud seeding from emission particles. Cirrus clouds have a warming effect, but exact quantifications are not yet pos sible. Consequently, IPCC did not include the impact of cirrus cloud formation in its estimates of aviation’s contribution to human-generated emissions. b

Source: IPCC, the Aviation Climate Change Research Initiative, and the European Topic Center on Air and Climate Change.

Page 13 GAO-09-554 Aviation and Climate Changea According to the IPCC, radiativ e forcing has advantages over global warming potential (GWP) for estimating aviation’s impact from short-lived aviation emissions and aerosols and contrails. GWP is used to measure the heat-absorbing ability of long-lived gases using carbon dioxide as a reference. Each measure has limits and several other impact measures including a modified GWP are under consideration to address some of the limitations.

b University and government organizations, including NASA, are conducting research on them to better understand their effects.



### According to IPCC, when the positive radiative forcing effects of carbon dioxide and the positive and negative radiative forcing effects of other aviation emissions are combined, global aviation contributes about 3 percent 23 

### of human-generated positive radiative forcing. When the radiative forcing effects of the various aviation emissions are considered carbon dioxide, nitrogen oxides, and c ontrails have the greatest poten to contribute to climate change , tial

.
The level of scientific understanding about the impact of particular aviation emissions on radiative forcing varies, making estimates of their impact on climate change uncertain to varying degrees. A recent report that described levels of scientific understanding of aviation emissions found that the levels for carbon dioxide were high; the levels for nitrogen oxides, water vapor, sulfates, and soot were medium; and the levels for contrails and aviation-induced cirrus clouds were low. 24 

### Aviation’s contribution to total emissions, estimated at 3 percent, could be as low as 2 percent or as high as 8 percent, according to IPCC. Figure 6 shows IPCC’s estimate of the relative positive radiative forcing effects of each type of aviation emission for the year 2000. The overall radiative forcing

23 This 3 percent radiative forcing estimate for aviation is based on more recent research, included in IPCC’s 2007 Fourth Assessment Report . Originally, IPCC calculated a 3.5 percent estimate for 1992, which it published in its 1999 special report, Aviation and the Global Atmosphere

.

24 See Aviation Climate Change Research Initiative: A Report on the Way Forward, (2008) citing Forster, P., et al. (2007), Changes in atmospheric constituen ts and in radiative forcing. In: IPCC, 2007: Climate Change 2007: Th e 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. Mann ing, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor and H.L. Miller (eds.)]. Cambridge Un iversity Press, Cambridge, United Kingdom and New York, NY, USA; and Sausen, R. et al., Aviation radiative forcing in 2000: An update on IPCC (1999), Meteorologische Zeitschrift, 14-4, 555–561, 2005.

Page 14 GAO-09-554 Aviation and Climate Change

### from aviation emissions is estimated to be approximately two times that of carbon dioxide alone. 25

**Figure 6: Estimated Relati ve Contribution of Aviation Emissions to Positive**  **Radiative Forcing**



### 20%

**22% 49%** 

S o u rce: GAO pre s ent a tion of IPCC reported s t u dy. 

### 4% W a ter v a por 

### 5% S oot

Contr a il s

Nitrogen oxide s

C a r b on dioxide

Note: This figure portrays the relative contributions of emissions that have a net positive radiative forcing effect. The effect of sulfate emissions, which have a negative radiativ e forcing, or cooling, effect, is not included. The result reported for nitro gen oxides is the net warming effect calculated by subtracting the cooling effect of methane from t he warming effect of ozone. The aviation radiative forcing impact estimates described by IPCC in 2007 are reported as (positive) warming and (negative) cooling in milliwatts per meter squared: carbon diox ide (+ 25.3), ozone production from nitrogen oxides (+21.9), reduction of atmospheric methane as a result of nitrogen oxides (-10.4), water vapor (+2.0), sulfate particles (-3.5), soot particles (+2.5), and contrails (+10.0). For cirrus clouds, IPCC had no best estimate due to uncertai nty, but a possible range of +10 to +80 was reported. The relative contributions of emissions in this chart are an approximation because of the uncertainty surrounding the non-carbon dioxide forcing estimates. IPCC, 2007: Climate Change 2007: The Physical Scienc e 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, Un ited Kingdom and New York, NY, USA.

25 The 1999 IPCC report originally estimated that aviation’s impact could be two to four times that of carbon dioxide alone. The use of a radiative forcing ratio of the forcing of all aviation emissions over carbon dioxide is an approximation and is an area for further research and understanding.

Page 15 GAO-09-554 Aviation and Climate Change

# Global Aviation Emissions Are Expected to Grow but Forecasts Vary, Primarily Reflecting Different Economic Growth Assumptions IPCC generated three scenarios that forecasted the growth of global aviation carbon dioxide emissions from the near-term (2015) to the longterm (2050) and described these scenarios in its 1999 report. These forecasts are generated by models that incorporate assumptions about future conditions, the most important of which are assumptions about global economic growth and related increases in air traffic. Other assumptions include improvements in aircraft fuel efficiency and air traffic management and increases in airport and runway capacity. Because the forecasts are based on assumptions, they are inherently uncertain.

Historically, global economic growth ha s served as a reliable indicator of air traffic levels. Aviation traffic has increased during periods of economic growth and slowed or decreased duri ng economic slowdowns. As figure 7 shows, U.S and global passenger tra ffic (including the U.S.) generally trended upward from 1978 through 2008, but leveled off or declined during economic recessions in the United States. 

## Forecasts of Global Economic Growth and Air Traffic Primarily Drive IPCC’s Emissions Estimates

**Figure 7: Changes in Global and U.S. Aviation Passenger Traffic, 197**  **8 through 200**  **8**

S o u rce s : U. S . Dep a rtment of Tr a n s port a tion d a t a a nd ICAO d a t a from the Air Tr a n s port A ss oci a tion. **Year**

Glo ba l p ass enger tr a ffic

U. S . p ass enger tr a ffic

Period s of rece ss ion **0 100**  **200 300**  **400 500**  **600 700**  **800 900**  **Global pa ss**  **en g**  **er traffic** (reven u e p ass enger kilometer s , in trillion s ) **U. S**  **. carrier pa ss**  **en g**  **er traffic** (reven u e p ass enger mile s , in b illion s )

**2008 2007**  **2006 2005**  **2004 2003**  **2002 2001**  **2000 1999**  **1998 1997**  **1996 1995**  **1994 1993**  **1992 1991**  **1990 1989**  **1988 1987**  **1986 1985**  **1984 1983**  **1982 1981**  **1980 1979**  **1978 0.0**  **1.0 2.0**  **3.0 4.0**  **5.0**

Page 16 GAO-09-554 Aviation and Climate Change

### Forecast models described in IPCC’s re port incorporate historical trends and the relationship between economic growth and air traffic to produce scenarios of global aviation’s potential future carbon dioxide emissions. IPCC used a NASA emissions forecast for carbon dioxide emissions until 2015. IPCC used an ICAO emissions forecasting model to forecast emissions from 2015 to 2050 using three different assumptions for global economic growth—low (2.0 percent), me dium (2.9 percent), and high (3.5 percent). As a result, IPCC produced three different potential scenarios for future air traffic and emissions. 26 

### The 2050 scenarios include a 40 percent to 50 percent increase in fuel efficiency by 2050 from improvements in aircraft engines and airframe technology and from deployment of an advanced air traffic management system (these are discussed in more detail below). Figure 8 shows IPCC’s low-, mid-, and high-range scenarios for carbon dioxide emissions for 2015, 2025, and 2050 as a ratio over 1990 emissions. IPCC used the medium ec onomic growth rate scenario to estimate aviation’s contribution to overall emissions in 2050.

26 IPCC assumed a maturing global market with the above economic growth rates from 1990 to 2025 and slightly lower economic growth rates thereafter.

Page 17 GAO-09-554 Aviation and Climate Change**Figure 8**  **: IPCC’s Scenarios for Global Av iation Carbon Dioxide Emissions** 

**0.0 0.5**  **1.0 1.5**  **2.0 2.5**  **3.0 3.5**  **4.0 4.5**  **5.0**

**2050 2025**  **2015 2000**  **1990 Ratio of e**  **s timate over 1990 level** 

S o u rce: IPCC. **Year s** 

Low GDP s cen a rio
Medi u m GDP s cen a rio High GDP s cen a rio

Note: Includes advanced air traffic management and 40 percent to 50 percent f uel efficiency gain by 2050.



### IPCC compared aviation and overall emissions for the future and found that global aviation carbon dioxide emissions could increase at a greater rate than carbon dioxide emissions fr om all other sources of fossil fuel combustion. For example, for the me dium GDP growth rate scenario, IPCC assumed a 2.9 percent annual average increase in global GDP, which translated into almost a tripling (a 2.8 times increase) of aviation’s global carbon dioxide emissions from 1990 to 2050. For the same medium GDP growth scenario, IPCC also estima ted a 2.2 times increase of carbon dioxide emissions from all other sources of fossil fuel consumption worldwide during this period. Over al l, using the midrange scenario for global carbon dioxide emissions and projections for emissions from other sources, IPCC estimated that in 2050, carbon dioxide emissions from aviation could be about 3 percent of global carbon dioxide emissions, up from 2 percent. IPCC further estimated that, when other aviation

Page 18 GAO-09-554 Aviation and Climate Change

### emissions were combined with carbon dioxide emissions, aviation would account for about 5 percent of global human-generated positive radiative forcing, up from 3 percent. 27 

### IPCC concluded that the aviation traffic estimates for the low-range scenario, though plausible, were less likely given aviation traffic trends at the time the report was published in 1999. IPCC’s 2007 Fourth Assessment Report included two additional forecasts of global aviation carbon dioxide emissions for 2050 developed through other studies. 28 

### Both of these studies forecasted mid- and high-range aviation carbon dioxide emissions for 2050 that were within roughly the same range as the 1999 IPCC report’s forecasts. 29 

### For example, one study using average GDP growth assumptions that were similar to IPCC’s showed mid- and high-range estimates that were close to IPCC’s estimates.

In 2005, FAA forecasted a 60 percen t growth in aviation carbon dioxide and nitrogen oxide emissions from 2001 to 2025. However, FAA officials recently noted that this estimate did not take into account anticipated aircraft fleet replacements, advances in aircraft and engine technology, and improvements to the air transpor tation system, nor did it reflect the recent declines in air traffic due to the current recession. After taking these factors into account, FAA reduced its estimate in half and now estimates about a 30 percent increase in U.S. aviation emissions from 2001 to 2025. 30 

### To account for some uncertainties in FAA’s emissions forecasting, FAA officials said they are working on creating future

27 This 5 percent estimate of aviation’s contribu tion to 2050 global radiative forcing is based on IPCC’s midrange estimate. IPCC did not prov ide this estimate for the 2050 high- and low-range scenarios.

28 B. Owen and D.S. Lee, Allocation of International Avia tion Emissions from Scheduled Air Traffic—Future Cases, 2005 to 2050 , Manchester Metropolitan University (Manchester, UK, March 2006) and Ralf Berghof, Alf Schmitt et al., CONSAVE 2050 Final Technical Report (July 2005).

29 The 1999 IPCC report included a high-growth emissions scenario for 2050 from an environmental organization that showed aviat ion contributing 9.8 percent of global carbon dioxide emissions. This estimate assumed air traffic levels for 2050 that were more than double those used in th e highest IPCC estimate. IPCC concluded that such an estimate for 2050, though not impossible, was unlikely because it would require countries to build more than 1,300 new airports with 15 gates each, or the equivalent of 2 new airports per month for 60 years, which would be unprecedented co mpared with historical increases in global airport capacity.

30 This estimate is based on emissions of carbon dioxide and nitrogen oxides. In terms of fuel consumption, FAA estima tes a 28 percent increase in US carriers commercial aviation jet fuel from 2001 to 2025 (see FAA Aerospace Forecast, Fiscal Years 2009-2025 , table 22).

Page 19 GAO-09-554 Aviation and Climate Change

### scenarios for the U.S. aviation sector to assess the influence of a range of technology and market assumptions on future emissions levels.

While recent aviation forecasts are generally consistent with IPCC’s expectation for long-term global eco nomic growth, the current economic slowdown has led to downward revi sions in growth forecasts. For example, in 2008, Boeing’s annual forecast for the aviation market projected a 3.2 percent annual global GDP growth rate from 2007 to 2027. However, this estimate was made before the onset of negative global economic growth in 2009 and could be revised downward in Boeing’s 2009 forecast. According to FAA’s March 2009 Aerospace Forecast, global GDP, which averaged 3 percent annual growth from 2000 to 2008, will be 0.8 percent from 2008 to 2010 before recovering to an estimated average annual growth rate of 3.4 percent from 2010 to 2020. 31 

### The International Air Transport Association has predicted that global air traffic will decrease by 3 percent in 2009 with the econom ic downturn. Moreover, according to the association, even if air traffic growth resumes in 2010, passenger air traffic levels will be 12 percent lower in the first few years after the slowdown and 9 percent lower in 2016 than the association forecasted in late 2007. To the extent that air traffic declines, emissions also will 

## Other Forecasts Show Continued Long-term Growth, but Emissions Could Fall below Estimated Levels during the Current Economic Downturn

decline.

ecast results, as IPCC itself,

of e fuel efficiency by 40 percent to 50 percent

32



### ould be in place worldwide by 2050, 33 

### reducing congestion and delays. In developing its forecasts, IPCC made assumptions about factors other than economic growth that also affected its for 

## A ssumptions about Other Factors Co uld Affect IPCC’s Forecasts e xperts we interviewed, and FAA have noted:

• 

### IPCC assumed that advances in aircraft technology and the introduction new aircraft would increas f rom 1997 through 2050.

• 

### IPCC assumed that an ideal air traffic management system w

31 Two main methods, market exchange rates and purchasing power parity are used to convert the GDP of a country in national currency terms to a common currency, usually the U.S. dollar. GDP growth rates can differ depending on the conversion method used.

32 However, the forecast doesn’t acco unt for the possibility that some airlines might adopt low-carbon alternative fuels.

33 The United States is currently working on its future air traffic management system, NextGen, as is Europe through the Single European Sk y Air Traffic Management Research Program (SESAR).

Page 20 GAO-09-554 Aviation and Climate Change• 

### IPCC assumed that airport and runway capacity would be sufficient to accommodate future air traffic levels.

However, if IPCC’s assumptions about im provements in fuel efficiency and air traffic management are not realized, aircraft could produce higher emissions levels than IPCC estimated and IPCC’s estimates would be understated. Conversely, if airports and runways have less capacity than IPCC assumed, then air traffic levels could be lower and, according to IPCC and some experts, IPCC’s forecast could overstate future aviation emissions. Finally, IPCC pointed out that its estimate that aviation will contribute 5 percent of positive radiative forcing in 2050 does not include the potential impact of aviation-induced cirrus clouds, which could be substantial. 34



### Because IPCC’s forecasts are based on assumptions about future conditions and scientific understanding of the radiative forcing effects of certain aviation emissions is limited, IPCC’s forecasts are themselves uncertain. According to FAA officials, given the numerous assumptions and inherent uncertainties involved in forecasting aviation emissions levels out to the year 2050, along with the significant shocks and structural changes the aviation community has experienced over the last few years, IPCC’s projections are highly uncertain, even for the midrange scenario. If emissions from aviation and all other sectors continue to grow at about the same relative rate, aviation’s contribution as a portion of overall emissions will not change significantly. However, if significant reductions are made in overall emissions from other sources and aviation emission levels continue to grow, aviation’s contribution could grow.

34 Other studies have estimated aviation’s share of current climate change emissions and find aviation’s contributions to climate change to be larger when the impact of cirrus clouds is included. For example, one environm ental organization in a 2006 report included the upper range for aviation-induced cirrus clouds’ radiative forcing (from Sausen et al, 2005, which was reported in IPCC) in its aviati on radiative forcing total and calculated that aviation contributed 9 percent of total radiati ve forcing due to human activity worldwide in 2000.

Page 21 GAO-09-554 Aviation and Climate Change

### According to experts we interviewed, a number of different technological and operational improvements related to engines, aircraft design, operations, next-generation air traffi c management, and fuel sources are either available now or are anticipated in the future to help reduce carbon dioxide emissions from aircraft. We interviewed and surveyed 18 experts in the fields of aviation and climate change and asked them to assess a number of improvements to reduce emi ssions using a variety of factors, such as potential costs and benefits, and then used the results to inform the following discussion. (Complete survey results can be found in app. III.) The development and adoption of low-emissions technologies is likely to be dependent upon fuel prices or any government policies that price aircraft emissions. Higher fuel prices or prices on emissions—for example through government policies such as an emissions tax—would make the costs of low-emissions technologies relatively cheaper and are likely to encourage their development. In addition, while fuel efficiency and emissions reductions may be important to airlines, so are a number of other factors, including safety, performance, local air quality, and noise levels, and trade-offs may exist between these factors. 

# Experts Believe Future Technological and Operational Improvements Are Likely to Help Reduce Emissions from Commercial Aircraft, but Likely Not by Enough to Fully Offset Estimated Market Growth

Experts Believe That Although Many Technologies Are Expected to Help Reduce Emissions Growth in the Future, They Involve Trade-offs

Improvements to aircraft engines have played a primary role in increasing fuel efficiency and reducing engine emission rates; experts we interviewed expect them to do so in the future—one study estimates that 57 percent of improvements in aircraft energy intensity between 1959 and 1995 were due to improvements in engine efficiency. 35 

### Such improvements have resulted from increasing engine pressure and temperatures (which increases their efficiency and decreases fuel usage) and improving the “bypass ratio,” a 

## A ircraft Engine Improvements

35 Joosung J. Lee, Stephen P. Lukachko, Ian A. Waitz, and Andreas Schafer, “Historical and Future Trends in Aircraft Performance, Cost, and Emissions,” Annual Reviews on Energy and Environment , vol. 26 (2001).

Page 22 GAO-09-554 Aviation and Climate Change

### measure of airflow through the engine. 36 

### However, according to experts we surveyed, further advances in these technologies may face hi development costs (see table 2), and some may not be available for commercial use any time soon because engineers still face challenges in improving engine technology. gh

**Table 2: Selected Potential Aircraft E ngine Improvements to Reduce Emissions** 

**Improvement Potential**  **reduction in carbon**  **dioxide emissions**  **a Potential**  **research and development**  **costs a**  **Estimated time frame for**  **commercial**

**use b**  **Potential for public**  **acceptance a** 
Geared turbofan engine—more fuel efficient engine Medium Medium Short-medium High

Open rotor engine—engine fan blades not enclosed High High Medium Low-medium

Distributed propulsion systems—many small engines instead of few large ones Medium High Long High

Source: GAO survey of experts. Note: Between 8 and 13 experts responded to each of our questions about technological improvements.

a We did not provide definitions for “low,” “medium,” or “high” in these cases.

b Short timeframe (<5 years); medium timefram e (5-15 years); long timeframe (>15 years).



### Some technologies may be available s ooner than others, but all present a range of challenges and tradeoffs:

• 

### One latest-generation aircraft engine, the geared turbofan engine, is likely to be available for use in certain aircraft in the next few years; promises to reduce emissions according to its manufacturer, Pratt & Whitney; and may

36 The higher the bypass ratio, the more air by passes the engine, providing extra propulsion for the engine fan blades and in creasing the engine’s efficiency.

Page 23 GAO-09-554 Aviation and Climate Change

### face few challenges to widespread adoption. 37 

### According to Pratt & Whitney, this engine design is estimated to reduce fuel burn and emissions by 12 percent, compared with similar engines now widely used, in part due to an increase in the engine’s bypass ratio. The geared turbofan engine is the result of research conducted by NASA and Pratt & Whitney. 38

• 

### Another engine technology, which could be introduced in the next 5 to 15 years, is the “open rotor” engine. It may deliver even greater emissions reductions but may face consumer-related challenges. The open rotor engine holds the engine fan blades on the outside of the engine case, thereby increasing the air flow ar ound the engine, the effective bypass ratio, and the efficiency of the engi ne’s propulsion. However, this engine may be noisy and its large, visible engine blades could raise consumer concerns according to experts we surveyed. Research in the United States is currently a joint effort of NASA and General Electric. Rolls-Royce is also pursuing this technology.

• 

### In the longer term, despite some engineering challenges, distributed propulsion technologies also hold promise for reducing aircraft emissions. Distributed propulsion systems would place many small engines throughout an aircraft instead of using a few large engines, as today’s aircraft do. Experts we interviewed said that engineering challenges must be overcome with distributive propulsion, including determining the best and most efficient way to distribute power and store fuel. NASA is currently involved in distributed propulsion research.

Aircraft improvements also have played a role in reducing emissions rates in the past and experts we interviewed expected them to continue to do so. Through improvements in material s used to build aircraft and other improvements that increase aerodynamics and reduce drag, aircraft have become more fuel efficient over time. In the short term, improvements in aircraft materials, leading to decreased weight, and improvements in aerodynamics will help reduce fuel consumption and, thus, emissions rates. In the longer term, new aircra ft designs, primarily a blended wingbody aircraft, hold potential for greater reductions in emissions rates. However, new aircraft concepts face engineering and consumer 

## A ircraft Improvements

37 In addition, General Electri c is developing a new fuel-efficient engine, the GEnx. According to General Electric, this engine will improve fuel bur n by 15 percent, while also reducing NOx emissions, compared with Genera l Electric’s previous generation of engine technologies.

38 The U.S. Air Force also is conducting research into more fuel efficient engines through its ADVENT program, a joint effort with engine ma nufacturers that Air Force officials told us is expected to have commercial applications.

Page 24 GAO-09-554 Aviation and Climate Change

### acceptance challenges and new technologies are likely to incur high development costs (see table 3).

**Table 3**  **: Selected Aircraft Improvem ents to Reduce Emissions** 

**Improvement Potential**  **reduction in carbon dioxide**  **emissions a**  **Potential research**  **and development**  **costs a**  **Estimated time frame for**  **commercial**

**use b**  **Potential for public**  **acceptance a**  Blended wing-body— Fuselage and wings as part of one airframe High High Long Low-medium

Lightweight composite airframes— Lightweight materials Medium Medium Medium High

Winglets—Wing attachments to reduce drag Low Low Short c High

Source: GAO survey of experts. Note: Between 11 and 14 experts responded to each of our questions about technological improvements.

a We did not provide definitions for “low,” “medium,” or “high” in these cases.

b Short timeframe (<5 years); medium timefram e (5-15 years); long timeframe (>15 years).

c Winglets are already available and used by a number of airlines.



### The following improvements to aircraft should help reduce aircraft fuel consumption and emissions in the long term, despite costs and challenges:

• 

### The use of lightweight composite mate rials in aircraft construction has led to weight and fuel burn reductions in the past and is expected to continue to do so in the future. Over time, aircraft manufacturers have increasingly replaced more traditional materials such as aluminum with lighter-weight composite materials in airframe construction. For example, according to Boeing, 50 percent of the weight of the airframe of the Boeing 787, expected to be released in 2010, will be attributable to composite materials, compared with 12 percent composites in a currently available Boeing 777. According to Airbus, it first began using composite materials in airframe construction in 1985, and about 25 percent of the airframe weight of an A380 manufactured in 2008 was attributable to composites. By reducing the weight of the airframe, the use of composites reduces aircraft weight, fuel burn, and emissions rates.

• 

### Retrofits such as winglets—wing ex tensions that reduce drag—can be made to aircraft to make them mo re aerodynamic but may have limited

Page 25 GAO-09-554 Aviation and Climate Change

### potential for future emissions reductions according to experts we surveyed. By improving airflow around wings, winglets reduce drag and improve fuel efficiency, thus reduc ing emissions by a modest amount. Boeing estimates that the use of wing lets on a 737 reduces fuel burn by 3.5 percent to 4 percent on trips of over 1,000 nautical miles. Many new aircraft can be purchased with winglets, and existing aircraft also can be retrofitted with them. However winglets have already become very common on U.S. commercial airline aircraft and provide limited benefit for short-haul flights. According to experts we surveyed, there is low potential for future fuel consumption and emissions reductions from winglets.

• 

### Redesigned aircraft, such as a blended wing-body aircraft—that is, an aircraft in which the body and wings are part of one airframe—hold greater potential for reducing emissions, according to experts we surveyed, though these face challenges as well. Several public and private organizations, including NASA and Boeing are conducting research on such aircraft. Many experts expect that blended wing-body aircraft will reduce emissions through improved aerodynamics and lighter weight. Estimates for potential emissions reductions include 33 percent compared with currently available aircraft according to NASA. However, these new designs face challenges; notably, according to experts we interviewed, development costs are likely to be substantial, their radically different appearance may pose consumer accept ance issues, and they may require investments in modifying airports. 39



# Experts Also Expect Operational Improvements to Help Reduce Aircraft Emissions in the Future, but Reductions May Be Limited Airlines have already taken a number of steps to improve fuel efficiency over time; however, the potential for future improvements from these measures may be limited. Airlines have increased their load factors (the percentage of seats occupied on flights), increasing the fuel efficiency of aircraft on a per-passenger basis. Load factors were about 80 percent for U.S. carriers in 2008, compared with about 65 percent in 1995. However, some experts we interviewed said the potential for additional future emissions reductions from increasing load factors may be small because they are already so high. Airlines also have removed many unnecessary items from aircraft and minimized supplies of certain necessary items, such as water, carried on board. As a result, according to some experts we interviewed, there may be little additional improvement in reducing emissions by reducing on-board weight. Airlines also have made other

39 However, National Aeronautics and Space Admi nistration staff told us that no such investments will be necessary.

Page 26 GAO-09-554 Aviation and Climate Change

### voluntary operational changes to reduce emissions, such as reducing speeds on certain routes, which reduces fuel use, and washing aircraft engines to make them cleaner and more efficient. Airlines also have retired less-fuel-efficient aircraft and repl aced them with more-fuel-efficient models. For example, in 2008, Amer ican Airlines announced it was replacing more of its fuel-inefficient MD-80 aircraft with more efficient Boeing 737-800 aircraft. In addition, Continental Airlines, in 2008, replaced regional jets with turboprop planes on many routes. Still other improvements also are available for airlines to reduce emissions in the future, but the experts we interviewed ranked the potential for emissions reductions and consumer acceptance of these improvements as low (see table 4).

**Table 4: Selected Operational Im provements to Reduce Emissions** 

**Improvement Potential**  **reduction in carbon**  **dioxide emissions**  **a Potential**  **research and development**  **costs a**  **Estimated time frame for**  **commercial**

**use b**  **Potential for public**  **acceptance a**  Air-to-air refueling— Air tankers fueling aircraft in flight Low High Long Low

Engine washing— To improve engine performance Low Low Short High

Formation flying— Multiple aircraft flying close together to reduce drag Low Medium-high Medium-long Low

Multi-stage long distance flights— Use of fueling stops on long-distance flights Low-medium Low Short Low

Source: GAO survey of experts. Note: Between 9 and 12 survey respondents answ ered each of our questions about operational improvements to reduce emissions.

a We did not provide definitions for “low,” “medium,” or “high” in these cases.

b Short timeframe (<5 years); medium timefram e (5-15 years); long timeframe (>15 years).



### Airlines could make other operational changes to reduce fuel burn and emissions but are unlikely to do so, because the potential for consumer acceptance of such changes is low according to experts we surveyed. For example, aircraft could fly in formation to improve airflow and reduce fuel

Page 27 GAO-09-554 Aviation and Climate Change

### burn. More specifically, rather than flying individually, several aircraft could fly in proximity to one another, reducing drag of aircraft and subsequently fuel use. However, aircraft would fly closer to one another than FAA’s regulations currently allow and additional technological and aerodynamics research needs to be done. Another potential option, currently used for military purposes, is air-to-air refueling. Under this option, aircraft would be fueled in flight by tanker aircraft, reducing the amount and weight of fuel needed for the flight. However, DOT staff told us that air-to-air refueling may pose safety risks similar to those posed byformation flying. Some experts also have suggested that airlines make inroute on-ground fueling stops on long-haul flights, so they could reduce the amount of fuel they carry. However, more fueling stops could have negative effects on air quality at airports used for these stops as well as on air traffic operations.



# Air Traffic Management Improvements through NextGen Will Incorporate Technological and Operational Improvements to Help Reduce Aircraft Emissions According to Experts According to FAA, some of the air traffic management improvements that are part of NextGen—the planned air traffic management system designed to address the impacts of future traffic growth—can help reduce aircraft fuel consumption and emissions in the United States. Besides improving air traffic management, NextGen has environmental goals, which include accelerating the development of technologies that will lower emissions and noise. According to FAA, it is conducting a review to develop a set of NextGen goals, targets and metrics for climate change, as well as for noise and local air quality emissions. NextGen has the potential to reduce aircraft fuel burn by 2025, according to FAA, in part through technologies and procedures that reduce congestion and create more direct routing. Some procedures and technologies of NextGen have already been implemented and have already led to emissions reductions. Similarly, in Europe through the Single European Sky Air Traffic Management Research Program (SESAR), air tr affic management technologies and procedures will be upgraded and indi vidual national airspace systems will be merged into one, helping to redu ce emissions per flight by 10 percent according to EUROCONTROL, the European Organization for the Safety of Air Navigation. However, some experts we met with said that because some of SESAR’s technologies and procedures have already been implemented, future fuel savings might be lower. Table 5 provides information on selected components of NextGen that hold potential for reducing aircraft emissions.

Page 28 GAO-09-554 Aviation and Climate Change**Table 5: Selected Air Traffic Manageme nt Improvements to Reduce Emissions** 

**Improvement Potential**  **reduction in carbon**  **dioxide emissions**  **a Potential**  **research and development**  **costs a**  **Estimated time frame for**  **commercial**

**use b**  **Potential for public**  **acceptance a**  Required navigation performance—More precise routes Medium Medium Medium High

Automatic DependentSurveillanceBroadcast— Satellite navigation system Medium Medium Short High

Continuous Descent Arrival— More fuel efficient landings Low-Medium Medium Short High

NextGen NetworkEnabled Weather— Advanced real-time weather data Medium Medium Medium High

Source: GAO survey of experts, Note: 7 to 13 experts answered each of our survey questions about NextGen improvements

a We did not provide definitions for “low,” “medium,” or “high” in these cases.

b Short timeframe (<5 years); medium timefram e (5-15 years); long timeframe (>15 years)



### NextGen has the potential to reduce fuel consumption and emissions through technologies and operational procedures:

• 

### NextGen makes use of air traffic technologies to reduce emissions. For example, the Automatic Dependent Surveillance-Broadcast (ADS-B) satellite navigation system is designed to enable more precise control of aircraft during flight, approach, and descent, allowing for more direct routing and thus reducing fuel co nsumption and emissions. Also, Area Navigation (RNAV) will compute an aircraft’s position and ground speed and provide meaningful information on the flight route to pilots, enabling them to save fuel through impro ved navigational capability. NextGen Network-Enabled Weather will provide real-time weather data across the national airspace system, helping reduce weather-related delays and allowing aircraft to best use weather conditions to improve efficiency.

• 

### NextGen also relies on operational changes that have demonstrated the potential to reduce fuel consumption and emissions rates. Continuous Descent Arrivals (CDA) allow aircraft to remain at cruise altitudes longer

Page 29 GAO-09-554 Aviation and Climate Change

### as they approach destination airports, use lower power levels, and therefore produce lower emissions duri ng landings. CDAs are already in place in a number of U.S. airports and according to FAA, the use of CDAs at Atlanta Hartsfield International Airport reduces carbon dioxide emissions by an average of about 1,300 pounds per flight. Required Navigation Performance (RNP) also permits an aircraft to descend on a more precise route, reducing its consumption of fuel and lowering its carbon dioxide emissions. According to FAA, over 500 RNAV and RNP procedures and routes have been implemented. Funding and other challenges, however, affect FAA’s implementation of these various NextGen procedures and technologies. 40



# Alternative Fuel Sources Have Potential for Reducing Aircraft Greenhouse Gas Emissions, but Challenges Exist The use of alternative fuels, including those derived from biological sources (biofuels), has the potential to reduce greenhouse gas emissions from aircraft in the future; however, these fuels also present a number of challenges and environmental concer ns. While the production and use of biofuels result in greenhouse gas emissions, the extent to which they provide a reduction in greenhouse gas emissions depends on whether their emissions on an energy-content basis are less than those resulting from the production and use of fossil fuels. 41 

### To date, some assessments of biofuels have shown a potential reduction in greenhouse gas emissions when compared with fossil fuels, such as jet fuel. However, researchers have not agreed on the best approach for determining the greenhouse gas effects of biofuels and the magnitude of any greenhouse gas reductions attributable to their production and use. 42 

### FAA, EPA, and U.S. Air Force officials we met with said that quantifying the life-cycle emission of

40 For more information on challenges in NextGen implementation see GAO, Next Generation Air Transportation System: Issues Associated with Midterm Implementation of Capabilities and Full System Transformation
, GAO-09-481T (Washington, D.C.: Mar. 25, 2009).

41 Although plants converted into biofuels remove carbon dioxide from the air during growth, the biofuel production process is not emissions-free. For instance, nitrous oxide— a powerful greenhouse gas—may be emitted when nitrogen-based fertilizers are applied to soils to increase yields of important biofuel feedstocks such as co rn. In addition, fossil fuels are burned during the harvesting, tran sporting and refining of biofuel feedstock plants. Finally, researchers ha ve raised concerns that increased biofuel production could result in additional greenhouse gas impacts due to the conversion of lands not previously used for biofuel crop production.

42 On May 26, 2009, EPA issued a Notice of Pr oposed Rulemaking regarding the renewable fuel standard, as required by the Energy Independence and Security Act of 2007 (EISA). When finalized, the proposed rule would impl ement EISA’s changes to the renewable fuel standard. 74 Fed. Reg. 24904 (May 26, 2009).

Page 30 GAO-09-554 Aviation and Climate Change

### biofuels is difficult, but work in this area is currently under way. 43 

### For example, according to EPA, the agency has developed a comprehensive methodology to determine the life-cycl e emissions, including both direct and indirect emissions, of a range of biofuels. This methodology, which involved extensive coordination with experts outside of and across the federal government, was included in the recent notice of proposed rulemaking on the renewable fuel standard. Non-oil-energy sources, such as hydrogen, have potential for providing energy for ground transport, but many experts we met with said that such sources are unlikely to have use for commercial aircraft given technological, cost, and potential safety issues. 44



### According to experts we interviewed, a variety of sources could be used to produce biofuels for aircraft, including biomasses such as switchgrass and forest and municipal waste; and oils from jatropha (a drought-resistant plant that can grow in marginal soil), algae, camelina (a member of the mustard family that can grow in semiarid regions), palm, and soy. However, many experts claim that some of these crops are unsuitable for use as biofuels because they may have negative environmental and economic consequences, such as potentially reducing the supply and quality of water, reducing air quality and biodiversity, and limiting global food supplies. For example, cultivating palm for biofuel production might lead to deforestation, thereby increasing both greenhouse gas emissions and habitat loss. In addition, jatropha has been identified as an invasive species in some regions and, becaus e of its aggressive growth, may have the potential to reduce available habitat for native species. According to experts we met with, algae, on the other hand, are seen as a potentially viable source: they can be grown using saltwater and in a variety of other environments. In addition, according to DOT, camelina appears to be a potential biofuel source in the short te rm as it is not currently used for food and uses limited water for development.

43 In addition, FAA and the U.S. Air Force, through the Partnership for AiR Transportation Noise and Emissions Reducti on (PARTNER) program—an FAA-NASA-Transport Canadasponsored Center of Excellence, is sponsoring a project that aims to develop a tool that can estimate the life-cycle environmental impact from alternative jet fuels. The U.S. Air Force is leading an interagen cy working group including EP A, FAA, the Department of Energy and researchers to develop a documen t of life-cycle analys is best practices.

44 While in 2008 Boeing conducted a test flight of a small aircraft powered by hydrogen fuel cells, the manufacturer indicated it does not e xpect that large aircraft will be able to derive their primary energy from such sources.

Page 31 GAO-09-554 Aviation and Climate Change

### However, many experts we interviewed raised questions about the availability of future supplies of biofuels. According to the experts, large investments in fuel production facilities will likely be needed because little industrial capacity and compatible infr astructure currently exist to create biofuels. 45 

### The cost of current algae conversion technology has, for example raised obstacles to the commercial-scale production needed to obtain significant supplies in the future. Given that future alternative fuels will have many uses, airlines will co mpete with other sources, including road transportation, for those limited supplies. Compared with the market for ground transport, the market for fuels for commercial aviation is small, leading some experts to believe that fuel companies are more likely to focus their biofuel efforts on the ground transport market than on the commercial aviation market. Some experts we met with said that given the relatively small size of the market, limited biofuel supplies should be devoted to road transportation since road transportation is the largest contributor of emissions from the transportation sector. 46



### A large number of industry and government participants, including airlines, fuel producers, and manufacturers, are currently conducting research and development on alternative fuels for aircraft. One effort is the Commercial Aviation Alternative Fuels Initiative, whose members include FAA, airlines, airports, a nd manufacturers. The goal of this initiative is to “promote the development of alternative fuels that offer equivalent levels of safety and compare favorably with petroleum-based jet fuel on cost and environmental bases, with the specific goal of enhancing security of energy supply.” Any developed biofuel will be subject to the same certification as petroleum-based jet fuel to help ensure its safety. In addition, other government efforts are under way, most notably the Biomass Research and Development Initiative. This initiative is a multiagency effort to coordinate and accelerate all federal biobased products and bioenergy research an d development. The Department of Transportation is one of the initiative’s participants.

45 For a discussion of biofuel production see GAO, Biofuels: DOE Lacks a Strategic Approach to Coordinate Increasing Produc tion with Infrastruc ture Development and Vehicle Needs GAO-07-713 (Washington, D.C. : June 8, 2007).

46 However, according to DOT, it could also be ar gued that because aircraft do not face the potential for non-liquid fuel sources of energy—for exam ple, electricity—and because there is a proportionally higher premium for refining jet fuel, aviation may be a more certain consumer of biofuel supplies.

Page 32 GAO-09-554 Aviation and Climate Change

### Finally, the aviation industry has conducted a number of test flights using a mixture of biofuels and jet fuel. These test flights have demonstrated that fuel blends containing biofuels have potential for use in commercial aircraft. In February 2008, Virg in Atlantic Airlines conducted a demonstration flight of a Boeing 747 fueled by a blend of jet fuel (80 percent) and coconut- and babassu-oil-based fuels (20 percent). In December 2008, Air New Zealand conducte d a test flight of a Boeing 747 fueled by a blend consisting of an equa l mixture of jet fuel and jatropha oil. In January 2009, Continental Airlines conducted a test flight using a fuel blend of 50 percent jet fuel, and a jatropha and algae biofuel blend on a Boeing 737. 47 

### In January 2009, Japan Airlines conducted a test flight of a Boeing 747 fueled by a blend including camelina oil. According to the airlines, the results of all these tests indicate that there was no change in performance when engines were fueled using the biofuel blends. Forexample, the pilot of the Air New Zealand test flight noted that both onground and in-flight tests indicated that the aircraft engines performed well while using the biofuel.



# Improvements to Reduce Emissions from Aircraft Face Challenges and According to Experts Adopting Them May Not Be Enough to Offset Future Market and Emissions Growth Future fuel prices are likely to be a major factor in influencing the development of low-emissions technologies for commercial aviation. According to the airline industry, fuel costs provide an incentive for airlines to reduce fuel consumption and emissions. However, according to some experts we interviewed, short-term increases in fuel prices may notprovide enough of an incentive for the industry to adopt certain lowemission improvements. For example, the commercial airlines would have greater incentive to adopt fuel saving technologies if the projected fuel savings are greater than the improvement’s additional life-cycle cost. The higher existing and projected fuel pr ices are, the more likely airlines would undertake such improvements, all else the same. One expert said that if fuel costs were expected to consistently exceed $140 per barrel in the future, much more effort would be made to develop a finished open rotor engine quickly. The price of fuel as a factor in providing an incentive for the development and adoption of low-emission technologies is seen in some historical examples in NASA research. While winglets were first developed through a NASA research program in the 1970s, they were not used commercially until a few years ago when higher fuel prices justified their price. Additionally, although NASA currently is sponsoring research into open rotor engines, the agency also did so in the 1980s in response to

47

Algae-based biofuel composed only 2. 5 percent of the fuel blend.

Page 33 GAO-09-554 Aviation and Climate Change

### high fuel prices. That research was discontinued before the technology could be matured, however, when fuel prices dropped dramatically in the late 1980s.

In addition, the current economic recession has impacted commercial airlines and may cause some airlines to cut back on purchases of newer and more fuel-efficient aircraft. For example, the U.S. airline industry lost about $3.7 billion in 2008, and while analysts are uncertain about its profitability 2009, some analysts pr edict industry profits of around $4 billion to $10 billion. In addition, Boeing has reported a number of recent cancellations of orders for the fuel-efficient 787 Dreamliner. According to one expert we met with, when airlines are low on cash, they are unlikely to undertake improvements that will reduce their fuel consumption and emissions, even if the savings from fuel reductions will ultimately be greater than the cost of the improvement because they have so little cash. This expert said, for example, that although it may make financial sense for airlines to engage in additional nonsafety-related engine maintenance to reduce fuel burn and emissions, they may not do so because they lack sufficient cash.

Although some airlines may adopt technologies to reduce their future emissions, these efforts may not be enough to mitigate the expected growth in air traffic and related increase in overall emissions through 2050. Although IPCC’s forecast, as mentioned earlier, assumes future technological improvements leading to annual improvements in fuel efficiency, it excludes or doesn’t account for the possibility that some airlines might adopt biofuels or other potential breakthrough technologies. Nonetheless, even if airlines adopt such technologies, some experts believe that emissions will still be hi gher in 2050 under certain conditions than they were in 2000. One expert we met with did a rough estimate of future emissions from aircraft assu ming the adoption of many low-carbon technologies such as blended wing-body, operational improvements, and biofuels. He used IPCC’s midrange forecast of emissions to 2050 as a baseline for future traffic and found that even assuming the introduction of these technologies, global emissions in 2050 would continue to exceed

Page 34 GAO-09-554 Aviation and Climate Change

### 2000 emissions levels. 48 

### Had a lower baseline of emissions been used, forecasted emissions may have been lower. He acknowledged that more work needs to be done in this area. Another study by a German research organization modeled future emissions assuming the adoption of technological improvements, as well as biofuels, to reduce emissions. This study assumed future traffic growth averaging 4.8 percent between 2006 and 2026 and 2.6 percent between 2027 and 2050. 49 

### While this study forecasted improvements in emissions relative to expected market growth, it estimated that by 2050 total emissions would still remain greater than 2000 emissions levels.

Governments have a number of policy options—including policies that set a price on emissions, market-based measures like a cap-and-trade program or a tax, regulatory standards, and funding for research and development—they could use to help reduce greenhouse gas emissions from commercial aviation and other sectors of the economy. The social benefits (for example, resulting from emissions reductions) and costs associated with each option vary, and the policies may affect industries and consumers differently. However, economic research indicates that market-based policies are more likely to better balance the benefits and costs of achieving reductions in gr eenhouse gases and other emissions (or, in other words, to be more economically efficient). In addition, research and development spending could complement market-based measures orstandards to help facilitate the development and deployment of lowemissions technologies. However, given the relatively small current and forecasted percentage of global emissions generated by the aviation sector, actions taken to reduce aviation emissions alone, and not 

# Governments Can Use a Variety of Policy Options to Help Reduce Commercial Aircraft Emissions, but the Costs and Benefits of Each Vary

48 This analysis assumed that biofuels are firs t available in 2015 and their usage increases at a rate of 2 percent per year, and through life-cycle carbon emissions , biofuels emit 20 percent the carbon dioxide as jet fuel. For blended-wing body aircraft, the analysis assumed an 18 percent fuel burn reduction and introduction of the aircraft into global fleets in 2025 with a 30-year time frame to ac hieve a penetration of 33 percent of global aircraft fleets. The analysis also assumed th e adoption of other improvements, including the use of lightweight materials, open rotor en gines, formation flying , and multistage longdistance travel. We did not review the reliability of this analysis.

49 A lower assumed traffic growth rate would have reduced the study’s forecast of emissions. With respect to biofuels, this st udy assumed that biofuels would be used between 2010 and 2050 (at which time they woul d represent 25 percent of aviation fuels) and would produce 10 percent of the carbon dioxide emissions of fossil fuels. We did not review the reliability of this analysis.

Page 35 GAO-09-554 Aviation and Climate Change

### emissions from other sectors, could be costly and have little potential impact on reducing global greenhouse gas emissions. 50



# Market-Based Policies Could Be Used to Provide Airlines and Other Sources with an Economic Incentive to Reduce Greenhouse Gas Emissions Economists and other experts we interv iewed stated that establishing a price on greenhouse gas emissions throug h market-based policies, such as a cap-and-trade program or a tax on emissions from commercial aircraft and other sources, would provide these sources with an economic incentive to reduce their emissions. Ge nerally, a cap-and-trade program or an emissions tax (for example, on carbon dioxide) can achieve emissions reductions at less cost than other policies because they would give firms and consumers the flexibility to decide when and how to reduce their emissions. Many experts we surveyed said that establishing a price on emissions through a cap-and-trade pr ogram or a tax would help promote the development and adoption of a number of low-emissions technologies for airlines, including open rotor engines and blended wing-body aircraft. Another market-based policy, subsid y programs, such as a payment per unit of emissions reduction, can in principle provide incentives for firms and consumers to reduce their gr eenhouse gas emissions. However, subsidy programs need to be financed—for example through existing taxes or by raising taxes—and can create perverse incentives resulting in higher emissions.

One market-based option for contro lling emissions is a cap-and-trade program. Also known as an emissions trading program, a cap-and-trade program would limit the total amount of emissions from regulated sources. These sources w ould receive, from the government, allowances to emit up to a specific limit—the “cap.” The government could sell the allowances through an auction or provide them free of charge (or some combination of the two). In addition, the government would establish a market under which the regulated sources could buy and sell allowances with one another. Sources that can reduce emissions at the lowest cost could sell their allowances to other sources with higher emissions reduction costs. In this way, the market would establish an allowance price, which would represent the price of carbon dioxide (or other greenhouse gas) emissions. Generally, according to economists, by 

## Cap-and-Trade Program

50 For a comprehensive discussion of the economi cs of policy options to address climate change as well as discussion of a comb ination of such options, see GAO, Climate Change: Expert Opinion on the Economics of Policy Options to Address Climate Change
, GAO-08-605 (Washington, D. C.: May 9, 2008).

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### allowing sources to trade allowances, policy makers can achieve emissions reductions at the lowest cost.

A cap-and-trade program can be designed to cap emissions at different points in the economy. For example, a cap-and-trade program could be designed to cap “upstream” sources li ke fuel processors, extractors, and importers. Under this approach, a cap would be set on the emissions potential that is inherent in the fossil fuel. The upstream cap would restrain the supply and increase the pri ces of fossil fuels and thus the price of jet fuel relative to less carbon-intensive alternatives. Alternatively, under a “downstream” program, direct emitters, such as commercial airlines, would be required to hold allowances equal to their total carbon emissions each year. (See fig. 9.) However, economic research indicates that both types of programs would provide commercial airlines with an incentive to reduce their fuel consumption in the most cost-effective way for each airline, such as by reducing weight, consolidating flights, or using more fuel-efficient aircraft, if they were included in such a program. To the extent that airlines would pass along any program costs to customers through higher passenger fares and sh ipping rates, travelers and shippers could respond in various ways, including by traveling less frequently or using a different, cheape r transportation mode. 51

51 However, to the extent that a cap-and-trad e program regulates other transportation sectors as well, costs of using alternative tran sportation modes are likely to be higher as well.

Page 37 GAO-09-554 Aviation and Climate Change**Figure 9: A Potential Cap-and- Trade Program Regulating Airlin**  **es and Other Emissions Sources**

Free a llow a nce s

A u ctioned a llow a nce s Free a llow a nce s **Government**

S o u rce: GAO. A u ctioned a llow a nce s 

## $$ $ Free
a llow a nce s Free
a llow a nce s A u ctioned
a llow a nce s

A u ctioned
a llow a nce s Allow a nce s 

## $

**Airline A Airline B**  **Factory** Allow a nce s 

## $

Airline A exceed s their emi ss ion s
a llow a nce s a nd p u rch as e s
a llow a nce s from other

a irline s a nd ind us trie s Airline B

m a ke s low-co s t emi ss ion s red u ction s a nd s ell s it s
exce ss a llow a nce s to
a irline A Thi s f a ctory

m a ke s low-co s t emi ss ion s red u ction s
a nd s ell s it s exce ss
a llow a nce s to a irline A



### The effectiveness of a cap-and-trade program in balancing the benefits and costs of the emission reductions could depend on factors included in its design. Generally, by establishing an upper limit on total emissions from regulated sources, a cap-and-trade program can provide greater certainty than other policies (for example, an emissions tax) that emissions will be reduced to the desired level. Regulated sources would be required to hold allowances equal to their total emissions, regardless of the cost. However, allowance prices could be volatile, depending on factors such as changes

Page 38 GAO-09-554 Aviation and Climate Change

### in energy prices, available technologies, and weather, 52 

### making it more expensive for sources to meet the cap. To limit price volatility, a costcontainment mechanism called a “safety valve” could be incorporated into the cap-and-trade program to establish a ceiling on the price of allowances. For example, if allowance prices rose to the safety-valve price, the government could sell regulated sources as many allowances as they would like to buy at the safety-valve price. 53 

### Although the safety valve could limit price spikes, the emissions cap would be exceeded if the safety valve were triggered.

In addition, the baseline that is used to project future emissions and set the emissions cap can affect the extent to which a cap-and-trade program will contain or reduce emissions. 54 

### The point in time on which a baseline is set also can influence the environmental benefits of a cap-and-trade program. For example, some environmental interest groups in Europe have claimed that the environmental benefits of including aviation in the EU ETS will be minimal, since the emissions cap will be based on the mean average of aviation emissions from 2004 through 2006, leading to minimal future emissions reductions. 55



### In addition, industry groups and other experts have raised concerns that a cap-and-trade program could be administratively burdensome to the government, which would need to determine how to allocate the allowances to sources, oversee allowance trading, and monitor and enforce compliance with the program. Generally speaking, an upstream

52 For example, the demand for energy may in crease during unexpectedly hot or cold periods, leading to price spikes and making it more expensive for sour ces to meet the cap.

53 The safety valve would help prevent the price of allowances from exceeding the expected benefits of the emissions reductions. Unde r a cap-and-trade program, the emissions cap could be set at a level that balances the expe cted marginal cost of meeting the cap with an estimate of the marginal benefits. The safe ty valve price could be set just above the expected marginal costs to avoid the possi bility that the cap is overly stringent.

54 We have reported on the importance of se tting an emissions baseline. For example, setting a baseline with poor historical data coul d lead to the creation of a baseline that is above actual emissions, leading to no emission reductions. See GAO, Climate Change Science: High Quality Greenhouse Gas Emissions Data Are a Cornerstone of Programs to Address Climate Change
, GAO-09-423T (Washington, D.C.: Feb. 24, 2009).

55 However, some interest groups have expressed concern that an emissions cap does not take into account emissions reductions that airlines have achieved in recent years and claim that it unfairly penalizes those airlines that have reduced emissions.

Page 39 GAO-09-554 Aviation and Climate Change

### program may have lower administrati ve costs than a downstream program because it would likely involve fewer emissions sources.

Some members of the aviation indus try have said they view open and global cap-and-trade programs positivel y, although they report that not all types of cap-and-trade programs will work for them. For instance, ICAO and other industry organizations have said they would prefer an open capand-trade program (in which airlines are allowed to trade allowances with other sectors and sources) to a closed one (in which airlines are allowed to trade emissions allowances only with one another) because an open program would give airlines more fl exibility in meeting their emissions cap. Staff we met with at the Association of European Airlines expressed willingness for aviation to participate in a cap-and-trade program as long as it is global in scope, is an open system, is not in addition to similar taxes, and does not double-count emissions. 56 

### In addition, some industry groups and government agencies we met with said that a global program would best ensure that all airlines would take part in reducing emissions.

Cap-and-Trade Plans and Legislation

Some countries are planning to addr ess aviation emissions through capand-trade programs. The European Union originally implemented the EU ETS in 2005, covering industries representing about 50 percent of its carbon dioxide emissions. 57 

### The EU is planning on including all covered flights by aircraft operators flying into or out of EU airports, starting in 2012. 58 

### Please see appendix I for more details on the EU ETS, including a comprehensive discussion of the potential legal implications and

56 For example, Association of European Airlin es expressed a concern that because some countries in Europe have taxes on aircraft carbon dioxide emissions, airlines may be subject to those taxes as well as the ETS, me aning that their emissions would be counted twice by two different regulations.

57 We have reported on lessons learned from the EU ETS. See GAO, International Climate Change Programs: Lessons Learned from the European Union’s Emissions Trading Scheme and the Kyoto Protocol’s Clean Development Mechanism
, GAO-09-151 (Washington, D.C.: Nov. 18, 2008).

58 With respect to aircraft, the ETS currentl y regulates only carbon dioxide emissions. However, according to the European Commission, it has agreed to ad dress nitrogen oxide emissions from aircraft through a separate le gislative measure. As of May 2009, no EU legislative proposal has specifically addresse d nitrogen oxide emissions from aircraft.

Page 40 GAO-09-554 Aviation and Climate Change

### stakeholders’ positions on this ne w framework. Other countries are considering cap-and-trade programs that would affect the aviation sector. 59



### In addition, the United States is currently considering and has previously considered cap-and-trade programs:

• 

### H.R. 2454, the American Clean Energy and Security Act of 2009, 111th Cong. (2009), would create a cap- and-trade program for greenhouse gas emissions for entities responsible for 85 percent of emissions in the United States. The current language propos es to regulate producers and importers of any petroleum-based liquid fuel, including aircraft fuel, as well as other entities, and calls for an emissions cap in 2050 that would be 83 percent lower than 2005 emissions. The bill also calls for the emissions cap in 2012 to be 3 percent below 2005 levels, and in 2020 to be 20 percent below 2005 levels. In addition, the Obama Administration’s fiscal year 2010 budget calls for the implementation of a cap-and-trade program to regulate emissions in the United States. The budget calls for emissions reductions so that emissions in 2020 are 14 percent below 2005 levels and emissions in 2050 are 83 percent below 2005 levels.

• 

### Additionally in this Congress, the Cap and Dividend Act, 60 

### also proposes a cap-and-trade program for carbon dioxide emissions beginning in 2012, which would include jet fuel emissions. This program’s covered entities would include entities that would make the first sale in U.S. markets of oil or a derivative product used as a combustible fuel, including jet fuel. The bill would require the Secretary of th e Treasury, in consultation with the EPA Administrator, to establis h the program’s emission caps in accordance with the following targets: the 2012 cap would equal 2005 emissions; the 2020 cap would equal 75 percent of 2005 emissions; the 2030 cap would equal 55 percent of 2005 emissions; the 2040 cap would equal 35 percent of 2005 emissions; and the 2050 cap would equal 15 percent of 2005 emissions.

• 

### A number of bills creating a cap-and-trade program also were introduced in the 110th Congress but did not pass. For example, a bill sponsored bySenators Boxer, Warner, and Lieberman would have established a cap-andtrade program that covered petrol eum refiners and importers, among other entities. 61 

### The costs of the regulation would have been borne by

59 For example, Japan is considering creating a voluntary cap-and-trade program and Japan Airlines already has indicated that it will part icipate in the scheme, but only based on its domestic flights.

60 H.R. 1862, 111th Cong. (2009).

61 S. 3036, 110th Cong. (2008).

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### these refiners and importers who would likely have passed on those costs to airlines through increases in the price of jet fuel.

An emissions tax is another market-based policy that could be used to reduce emissions from commercial avi ation and other emissions sources. Under a tax on carbon dioxide (or other greenhouse gas), the governmentwould levy a fee for every ton of carbon dioxide emitted. Similar to a capand-trade program, a tax would provide a price signal to commercial airlines and other emission sources, creating an economic incentive for them to reduce their emissions. A carbon tax could be applied to “upstream” sources such as fuel prod ucers, which may in turn pass along the tax in the form of higher prices to fuel purchasers, including commercial airlines. Similar to a cap- and-trade program, emissions taxes would provide regulated sources including commercial airlines with an incentive to reduce emissions in the most cost-effective way, which might include reducing weight, consolidating flights, or using more fuel-efficient aircraft. 

## Emissions Taxes

According to economic theory, an emissions tax should be set at a level that represents the social cost of the emissions. 62 

### Nonetheless, estimates of the social costs associated with greenhouse gas emissions vary. Fo example, IPCC reported that the social costs of damages associated with greenhouse gas emissions average about $12 per metric ton r

63 

### of carbon dioxide (in 2005 dollars) with a range of $3 to $95 per ton (in 2005 dollars).

Economic research indicates that an emissions tax is generally a more economically efficient policy tool to address greenhouse gas emissions than other policies, including a cap-and-trade program, because it would better balance the social benefits and costs associated with the emissions reductions. In addition, compared to a cap-and-trade program, an emissions tax would provide greater certa inty as to the price of emissions. However, it would in concept provide less certainty about emissions

62 For example, the social cost of carbon refl ects the present value of economic damages caused by an additional quantity of emissions . Under an economically optimal policy, the price would be set at a point where the marg inal damages from global warming equal the marginal cost of controlling emissions.

63 A metric ton equals 2,205 pounds.

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### reductions because the reductions would depend on the level of the tax and how firms and consumers respond to the tax. 64



### Subsidies are another market-based instrument that could, in principle, provide incentives for sources to reduce their emissions. For example, experts we met with said that the government could use subsidies to encourage industry and others to adopt existing low-emissions technologies and improvements, such as winglets. In addition, some experts told us that NextGen-related technologies are candidates for subsidies because of the high costs of the technologies and the benefits that they will provide to the national airspace system. According to IPCC, subsidies can encourage the diffusion of new low-emissions technologiesand can effectively reduce emissions. For example, as newer, more fuelefficient engines are developed and become commercially available, subsidies or tax credits could lower their relative costs and encourage airlines to purchase them. 

## Subsidies

Although subsidies are similar to taxe s, economic research indicates that some subsidy programs can be economically inefficient, and need to be financed (for example, using current tax revenue or by raising taxes). For example, although some subsidy pr ograms could lead to emissions reductions from individual sources, th ey may also result in an overall increase by encouraging some firms to remain in business longer than they would have under other policies such as an emissions tax.

Both a cap-and-trade program and an emissions tax would impose costs on the aviation sector and other users of carbon-based fuels. The extent to which the costs associated with an emissions control program are incurred by commercial airlines and passed on will depend on a number of economic factors, such as the level of market competition and the responsiveness of passengers to changes in price. Officials of some industry organizations we met with sa id that because airlines are in a competitive industry with a high elasticity of demand, 65 

### they are constrained in passing on their costs, and the costs to industry likely will 

## Distribution of Costs under Market-based Measures

64 The extent to which a cap-and-trade prog ram would provide greater certainty about emissions reductions depends on the design of the particular program. For example, some programs may include cost containment measur es that allow total emissions to exceed the cap under certain conditions.

65 Price elasticity of demand is a measure of the responsiveness in quantity demanded as a result of a change in price. Goods and serv ices with a high elasticity of demand will see larger changes in the quantity de manded than the change in price.

Page 43 GAO-09-554 Aviation and Climate Change

### be large. The Association of European Airlines reported that airlines will have very limited ability to pass on the costs of the EU ETS. Furthermore, the International Air Transport Association has estimated that the costs to the industry of complying with the EU ETS will be € 3.5 billion in 2012, 66 

### with annual costs subsequently increasing. 67 

### Others we interviewed, however, stated that airlines will be able to pass on costs, and the increases in ticket prices will not be large. For example, the EU estimates that airlines will be able to pass on most of the costs of their compliance with the EU ETS, which will result in an average ticket price increase of € 9 on a medium-haul flight. 68 

### However, the revenue generated by the tax or by auctioning allowances could be used to lessen the overall impact on the economy, or the impact on certain gr oups (for example, low income) or sectors of the economy by, for example, reducing other taxes. 69



### Finally, according to some airline industry representatives, a program to control greenhouse gas emissions woul d add to the financial burden the aviation industry and its consumers already face with respect to other taxes and fees. For example, passenger tickets in the United States are subject to a federal passenger ticket tax of 7.5 percent, a segment charge of $3.40 per flight segment, and fees for security and airport facilities (up to $4.50 per airport). In addition, international flights are subject to departure taxes and customs-related fees. However, none of these taxes and fees attempt to account for the cost of greenhouse gas emissions, as a tax or cap-and-trade program would do. In addition, the revenue generated from an emissions tax or by aucti oning allowances under a cap-and-trade program, could be used to offset other taxes, thereby lessening the economic impact of the program.

66 Equivalent to about $4.5 billion based on exchange rates on Apr. 20, 2009.

67

According to industry interests groups we met with, to the ex tent that airlines incur the costs of a tax or for cap-and-trade allowances , their resources for upgrading their fleets with more fuel-efficient aircraft and for impl ementing other emissions-reduction measures will be more limited.

68 Equivalent to about $11.60 based on exchange rates on April 20, 2009.

69 Some organizations we met believe that revenues collected through the auctions of allowances should be used for climate change mitigation and adaptation as well as to help fund low-emissions technologies.

Page 44 GAO-09-554 Aviation and Climate Change

### Mandating the use of certain technologies or placing emissions limits on aircraft and aircraft engines are also potential options for governments to address aircraft emissions. Standards include both technology standards,which mandate a specific control technology such as a particular fuelefficient engine, and performance standards, which may require polluters to meet an emissions standard using any available method. The flexibility in the performance standards reduces the cost of compliance compared with technology-based standards and, according to DOT, avoids potential aviation safety implications that may occur from forcing a specific technology across a wide range of operations and conditions. 

# Emissions Standards Could Limit Emissions from Specific Technologies, but Are Generally Not an Economically Efficient Approach for Reducing Greenhouse Gas Emissions

For example, by placing a strict limit on aircraft emissions, a standard would limit the emissions levels from an engine or aircraft. Regulations on specific emissions have been used to achieve specific environmental goals. ICAO’s nitrogen oxide standards place limits on nitrogen oxide emissions from newly certified aircraft engines. These standards were first adopted in 1981 and became effective in 1986. Although no government has yet promulgated standards on aircraft carbon dioxide emissions or fuel economy, emissions standards are being discussed within ICAO’s Committee on Aviation Environmental Protection and, in December 2007, a number of environmental interest groups filed petitions with EPA asking the agency to promulgate regulations for greenhouse gas emissions from aircraft and aircraft engines. In addition, the American Clean Energy and Security Act of 2009 would require EPA to issue standards for greenhouse gas emissions from new aircraft and new engines used in aircraft by December 31, 2012. 70



### Although standards can be used to limit greenhouse gas emissions levels from aircraft, economic research indi cates that they generally are not as economically efficient as market-based instruments because they do not effectively balance the benefits and costs associated with the emissions reductions. 71 

### For example, unlike market-based instruments, technology standards would give engine manufacturers little choice about how to reduce emissions and may not encourage them to find cost effective ways

70 H.R. 2454, § 221(b), 111 th Cong. (2009).

71 Emissions standards typically do not equaliz e marginal costs across sources, a basic condition for efficiency. In the case of gree nhouse gas emissions, emissions are uniformly mixed and abatement costs vary widely across sources. These characteristics favor marketbased instruments, which can achieve signifi cant cost savings by encouraging low-cost sources to make the bulk of the emissions reductions.

Page 45 GAO-09-554 Aviation and Climate Change

### of controlling emissions. 72 

### In addition, according to IPCC, because technology standards may require emissions to be reduced in specified ways, they may not provide the flexibilit y to encourage industry to search for other options for reducing emissions. However, according to EPA, performance standards to address certain emissions from airlines, such as those adopted by ICAO and EPA, gave manufacturers flexibility in deciding which technologies to use to reduce emissions. 73 

### Nonetheless, although performance standards can provide greater flexibility and therefore be more cost-effective th an technology standards, economic research indicates that standards generally provide sources with fewer incentives to reduce emissions beyond what is required for compliance, compared to market-based approaches. Moreover, standards typically apply to new, rather than existing, engines or aircraft, making new engines or aircraft more expensive, and as a result, the higher costs may delay purchases of more fuel-efficient aircraft and engines.

Current international aviation standards also may require international cooperation. Because ICAO sets stan dards for all international aviation issues, it may be difficult for the U.S. government, or any national government, to set a standard that is not adopted by ICAO, although member states are allowed to do so. Industry groups we met with said that any standards should be set through ICAO and then adopted by the United States and other nations and, as me ntioned earlier, some environmental groups have petitioned EPA to set such standards.

72 According to FAA and EPA, existing aircra ft engine standards do not mandate specific technologies and are developed on the ba sis of technological practicability.

73 According to EPA, well designed standards could give aircraft engine manufacturers the flexibility to make cost-effective reductions. In addition, accordi ng to an official in EPA’s Office of Air and Radiation, with the projected increase in jet fuel consumption and related emissions, addressing greenhouse gas emissions will require consideration of technology measures and market-based measures. However , under a market-based program such as cap-and-trade, emissions caps set the total em issions level and sour ces would need to determine how to accommodate business growth while complying with the cap. Such an approach gives sources an in centive to innovate and search for low-cost ways to reduce emissions.

Page 46 GAO-09-554 Aviation and Climate Change

### Government-sponsored research into low-fuel consumption and lowemissions technologies can help foster the development of such technologies, particularly in combination with a tax or a cap-and-trade program. Experts we surveyed said that increased government research and development could be used to encourage a number of low-emissions technologies, including open rotor engines and blended wing-body aircraft. According to the Final Report of the Commission on the Future of the United States Aerospace Industry , issued in 2002, the lack of longterm investments in aeros pace research is inhibiting innovation in the industry and economic growth. This st udy also asserted that national research and development on aircraft emissions is small when compared with the magnitude of the problem and the potential payoffs that research drives. Experts we met with said that government sponsorship is crucial, especially for long-term fundamental research, because private companies may not have a sufficiently long-term perspective to engage in research that will result in products for multiple decades into the future. According to one expert we interviewed, the return on investment is too far off into the future to make it worthwhile for private companies. NASA officials said that private industry generally focuses only on what NASA deems the “next generation conventional tube and wing technologies,” which are usually projected no more than 20 years into the future. Furthermore, raising fuel prices or placing a pr ice on emissions through a tax or capand-trade program is likely to encourage greater research by both the public and private sectors into low-emissions technologies because it increases the pay off associated with developing such technologies. 

# Government-Sponsored Research and Development Can Help Encourage the Development andAdoption of LowEmissions Technologies, but May Be Costly to Governments

Various U.S. federal agencies, including NASA and FAA, have long been involved in research involving low-emissions technologies. 74 

### For example, NASA’s subsonic fixed-wing research program is devoted to the development of technologies that increase aircraft performance, as well as reduce both noise levels and fuel burn. Through this program, NASA is researching a number of different technologies to achieve those goals, including propulsion, lightweight materials, and drag reduction. The subsonic fixed-wing program is looking to develop three generations of aircraft with increasing degrees in technology development and fuel burn improvements—the next-generation con ventional tube and wing aircraft, the unconventional hybrid wing-body aircraft, and advanced aircraft

74 In addition, the U.S. Air For ce conducts research that has potential for applicability for commercial aviation. For exam ple, through the ADVENT program, the Air Force is researching fuel-efficient engine technologies.

Page 47 GAO-09-554 Aviation and Climate Change

### concepts. 75 

### NASA follows goals set by the National Plan for Aeronautics Research and Development and Related Infrastructure for fuel efficiency improvements 76 

### for each of these generations (see table 6). 77

**Table 6: NASA’s Subsonic Fixed-Win g Research Fuel-Reduction Goals** 

**Research generation Next generation**  **tube and wing Unconventional**  **hybrid wing-body Advanced aircraft**  **concepts**
Aircraft fuel burn reduction goal 33 percent fuel reduction (relative to Boeing 737) 40 percent fuel reduction (relative to Boeing 777) Better than 70 percent fuel reduction
Time frame 2015 2020 2030-2035

Source: NASA.



### However, budget issues may affect NASA ’s research schedule. As we have reported, NASA’s budget for aeronautics research was cut by about half in the decade leading up to fiscal year 2007, when the budget was $717 million. 78 

### Furthermore, NASA’s proposed fi scal year 2010 budget calls for significant cuts in aeronautics research, with a budget of $569 million. As NASA’s aeronautics budget has declined, it has focused more on fundamental research and less on demonstration work. However, as we have reported, NASA and other officials and experts agree that federal research and development efforts are an effective means of achieving emissions reductions in the longer term. 79 

### According to NASA officials, the research budget for its subsonic fixed-wing research program, much of which is devoted to technologies to reduce emissions and improve fuel efficiency, will be about $69 million in 2009.

75 NASA refers to the three generations of technologies as N+1, N+2, and N+3.

76 The plan also sets goals for future noi se levels and nitrogen oxide emissions.

77 National Science and Technology Council, National Plan for Aeronautics Research and Development and Related Infrastructure (Washington, D.C., Jan. 18, 2008).

78 GAO, Aviation and the Environment: FAA’s and NASA’s Research and Development Plans for Noise Reduction Are Aligned, but the Prospects of Achieving Noise Reduction Goals Are Uncertain
, GAO-08-384 (Washington, D.C., Feb. 15, 2008).

79 GAO, Aviation and the Environment: NextGen and Research and Development Are Keys to Reducing Emissions and Thei r Impact on Health and Climate
, GAO-08-706T (Washington, D.C., May 6, 2008).

Page 48 GAO-09-554 Aviation and Climate Change

### FAA has proposed creating a new research consortium to focus on emissions and other issues. Specifically, FAA has proposed the Consortium for Lower Energy, Emi ssions, and Noise, which would fund, on a 50-50 cost share basis with private partners, research and advanced development into low-emissions and low-noise technologies, including alternative fuels, over 5 years. FAA plans that the consortium will mature technologies to levels that facilitate uptake by the aviation industry. The consortium contributes to the goal set by the National Plan for Aeronautics, Research and Development and Related Infrastructure to reduce fuel burn by 33 percent compared with current technologies. The House FAA Reauthorization Bill (H .R. 915, 111th Cong. (2009)) would provide up to $108 million in funding for the consortium for fiscal years 2010 through 2012.

Lastly, the EU has two major efforts dedicated to reducing aviation emissions. The Advisory Council for Aeronautics Research in Europe (ACARE) is a collaborative group of governments and manufacturers committed to conducting strategic aeronautics research in Europe. According to officials with the European Commission Directorate General of Research, about € 150 million to € 200 million per year 80 

### is devoted to basic research through ACARE. Another research effort in Europe is the Clean Sky Joint Technology Initiative, which will provide € 1.6 billion 81 

### over 7 years to fund various demonstration technologies.

We provided a draft copy of this report to the Department of Defense, the Department of State, the Department of Transportation, the National Aeronautics and Space Administration, and the Environmental Protection Agency for their review. 

# Agency Comments and Our Evaluation

The Department of Defense had no comments. The Department of State provided comments via email. These comments were technical in nature and we incorporated them as appropriate.

The Department of Transportation provided comments via email. Most of these comments were technical in nature and we incorporated them as appropriate. In addition, DOT stated that our statements indicating that the use of future technological and operational improvem ents may not be

80 About $200 million to $267 million per year based on exchange rates on Apr. 29, 2009.

81 Equivalent to approximately $2.1 billion based on exchange rates on Mar. 31, 2009.

Page 49 GAO-09-554 Aviation and Climate Change

### enough to offset expected emissions growth is not accurate given the potential adoption of alternative fuels. We agree that alternative fuels do have potential to reduce aircraft emissions in the future; to the extent that a low-emission (on a life-cycle basis) alternative fuel is available in substantial quantities for the aviation industry, emissions from the aviation industry are likely to be less than th ey otherwise would be. However, we maintain that given concerns over the potential environmental impacts of alternative fuels, including their life-cycle emissions, as well as the extent to which such fuels are available in adequate supplies at a competitive price, there may be a somewhat limited potential for alternative fuel use to reduce emissions from commercial airc raft in the future, especially the short term. DOT also suggested that we clarify the sources for our discussion about policy options that can be used to address aviation emissions. As much of that discussi on is based on economic research and experience with market-based instrume nts and other policies, we clarified our sources where appropriate.

NASA provided a written response (see app. V) in which they stated that our draft provided an accurate and balanced view of issues relating to aviation and climate change. NASA also provided technical comments that were incorporated as appropriate. EPA provided technical comments via email that were incorporated as appropriate and also provided a written response. (see app. VI).

EPA was concerned that characterizin g aircraft emissions standards as being economically inefficient especially compared to market-based measures, might lead readers to be lieve that emissions standards cannot be designed in a manner that fosters technological innovations and economic efficiency. EPA officials explained that, based on their experience, standards can be designed to optimize technical responses, provide regulated entities with flexibility for compliance and that studies show that EPA regulations have generated benefits in excess of costs. We agree that allowing regulated sources more flexibility in how they meet emissions standards can reduce the costs associated with achieving the emissions reductions. However, economic research indicates that for addressing greenhouse gas emissions, market-based measures such as emissions taxes or cap-and-trade programs would be economically efficient (that is, would maximize net benefits) compared to other approaches, in part because market-based measures can give firms and consumers more flexibility to decide when and how to reduce their emissions. Emissions standards, for example, generally give regulated sources fewer incentives to reduce emissions beyond what is required for compliance. The ultimate choice of what specific policy option or

Page 50 GAO-09-554 Aviation and Climate Change

### combination of options governments might use and how it should be designed is a complex decision and beyond the scope of our discussion.

Finally, EPA was concerned that our draft report did not adequately discuss the increases in fuel consumption and emissions that have resulted from high rates of market growth and expected continued growth. We believe that our report adequately discusses fuel efficiency as well as fuel consumption and emissions output. In addition, our report discusses that aviation emissions are expected to gr ow in the long term, despite the potential availability of a number of technological and operational options that can help increase fuel efficiency. In response to this comment, we added additional information on forecasted fuel use by U.S.-based commercial airlines.

We are sending copies of this report to the Secretaries of Defense, State, and Transportation and the Administrators of the Environmental Protection Agency and the Na tional Aeronautics and Space Administration. This report is also available at no charge on the GAO Web site at http://www.gao.gov

.
If you or your staffs have any questi ons concerning this report, please contact me at (202) 512-2834 or flemings@gao.gov . Contact points for our Offices of Congressional Relations and Public Affairs may be found on the last page of this report. Staff members making key contributions to this

Susan Fleming report are listed in appendix VII.

irector, Physical Infrastructure Issues D

Page 51 GAO-09-554 Aviation and Climate Change

### List of Congressional Requesters

The Honorable Bart Gordon Chairman The Honorable Ralph Hall Ranking Member Committee on Science and Technology House of Representatives

The Honorable James L. Oberstar Chairman The Honorable John L. Mica Ranking Member Committee on Transportation and Infrastructure House of Representatives

The Honorable Jerry F. Costello Chairman The Honorable Thomas E. Petri Ranking Member Subcommittee on Aviation Committee on Transportation and Infrastructure House of Representatives

Page 52 GAO-09-554 Aviation and Climate ChangeA Unio

ppendix I: Legal Impl ications of European n Emissions Trading Scheme

Page 53 GAO-09-554 

# Appendix I: Legal Implications of European Union Emissions Trading Scheme

The European Union’s recent decision to include aviation in the European Union’s Emissions Trading Scheme (EU ETS), which includes U.S. carriers flying in and out of Europe, is a complex and controversial matter. Preparations by U.S. carriers are al ready underway for 2012, the first year aircraft operators will be included in the ETS. The inclusion of aviation in the current EU ETS implicates a number of international treaties and agreements and has raised concerns among stakeholders both within and outside the United States. Many stakeholders within the United States have posed that the inclusion of aviati on in the ETS violates provisions of these international agreements and is contrary to international resolutions. Others, primarily in Europe, disagree and find aviation’s inclusion in the current ETS to be well within the authority set forth in these agreements. In light of these disagreements, the EU may confront a number of hurdles in attempting to include U.S. carriers in the current EU ETS framework.



# EU ETS Law In 2005, the EU implemented its ETS, a cap-and-trade program to control carbon dioxide emissions from various energy and industrial sectors. On December 20, 2006, the European Commission set forth a legislative proposal to amend the law, or directive, which established the ETS so as to include aviation in the ETS. 1 

### On July 8, 2008, the European Parliament adopted the legislative resolution of the European Council and on October, 24, 2008, the Council adopted the directive, signaling its final approval. 2 

### The directive was published in the Official Journal on January 13, 2009, and became effective on February 2, 2009. 3



### Under the amended ETS Directive, begi nning on January 1, 2012, a cap will be placed on total carbon dioxide emissions from all covered flights by

1 The European Commission initiates the legislat ive process by drafting specific pieces of legislation and proposing them to the C ouncil of the European Union and European Parliament, who together serve as the EU’s legislative branch.

2 Under the EU’s co-decision procedure, the le gislative procedure for environmental and certain other types of laws, both the Council of the European Union and European Parliament must approve legislation in orde r to enact a law. Once both bodies approve identical texts of the legislation, it must be published in the Official Journal of the European Union. The law goes into force 20 days after p ublication. Thereafter, each member state has 1 year to transpose the directive into national law.

3 Directive 2008/101/EC, 2009 O.J. (L 8) 3. The directive was amended on Mar. 26, 2009.

Aviation and Climate ChangeAppendix I: Legal Impl ications of European Union Emissions Trading Scheme



### aircraft operators flying into or out of an EU airport. 4 

### Emissions will be calculated for the entire flight. 5 

### For 2012, the cap for all carbon dioxide emissions from covered flights will be set at 97 percent of historical aviation emissions. 6 

### For the 2013-2020 trading period and subsequent trading periods, the cap will be set to reflect annual emissions equal to 95 percent of historical aviation emissions. 7



### The cap represents the total quantity of emissions allowances available for distribution to aircraft operators. In 2012 and each subsequent trading period, 15 percent of allowances must be auctioned to aircraft operators; the remaining allowances will be distributed to these aircraft operators for free based on a benchmarking process. 8 

### Individual member states, in accordance with the EU regulation, will conduct the auctions for aircraft operators assigned to that member state. 9 

### The auction of allowances will be open for anyone to participate. The number of allowances each member state has to auction depends on its proportionate share of the

4 Some flights are excluded from th e cap, including military flig hts, flight operations for emergency purposes, such as firefighting, as well as airlin es with very limited operations. See 2008/101/EC, 2009 O.J. (L 8) 3, Annex I.

5 For instance, a flight from Los Angeles to Lo ndon will have to surrender allowances for its travel in U.S. airspace, internati onal airspace, and U.K. airspace.

6 Historical aviation emissions is defined as the mean average of the annual emissions in calendar years 2004, 2005, and 2006. This will be the baseline for emissions reductions. See Directive 2008/101/EC, 2009 O.J. (L8) 3, art. 3c.

7 See Directive 2008/101/EC, art. 3(c) (establishing the cap). The cap for subsequent trading periods can be adjusted by an amendment to the directive. See also Proposal for a Directive COM(2008) 16 (extending the trading periods to 8 years from 5 years). Although both the European Parliament and the European Council have signaled final approval of the proposed directive, final, formal appro val had not occurred as of June 2, 2009.

8 Three percent of the to tal quantity of allowances to be allocated will be set aside in a special reserve for new aircraft operators or aircraft operators with rapid growth. Eligible aircraft operators must apply to their assigned member states to obtain free allowances from the special reserve. Th e European Commission will determ ine how the allowances in the special reserve will be distributed. Any unallocated allowances will be auctioned.

9 Aircraft operators will be assigned to the member stat e that either: (1) i ssued its operating license or (2) has the greatest estimated emissi ons from flights performed by that aircraft operator in 2006 or the operato r’s first year of operation. See Directive 2008/101/EC, 2009 O.J. (L 8) 3, art. 18(a). These assignments were made in February 2009 and most U.S. airlines were assigned to the United Kingdom. According to the Directorate-General of the Environment (DG Environment), the auctions will be open to an yone to participate and the Commission is currently developing the regula tion containing deta iled provisions for member state auctions.

Page 54 GAO-09-554 Aviation and Climate ChangeAppendix I: Legal Impl ications of European Union Emissions Trading Scheme



### total verified aviation emissions for all member states for a certain year. 10 

### The member states will be able to use the revenues raised from auctions in accordance with the amended directive. 11 

### For each trading period, aircraft operators can apply to their assigned member state to receive free allowances. Member states will allocate the free allowances in accordance with a process the European Commission establishes for each trading period.

After the conclusion of each calendar year, aircraft operators must surrender to their assigned member state a number of allowances equal to their total emissions in that year. If an aircraft operator’s emissions exceed the number of free allowances it receives, it will be required to purchase additional allowances at auction or on the trading market for EU ETS allowances. 12 

### In addition, in 2012, aircraft operators will be able to submit certified emissions reductions (CER) and emission reduction units (ERU)—from projects in other countries undertaken pursuant to the Kyoto Protocol’s Clean Development Mechanism and Joint Implementation—to cover up to 15 percent of their emissions in lieu of ETS allowances. For subsequent trading periods, aircraft operators’ use of CERs and ERUs depends in part on whether a new international agreement on climate change is adopted. However, regardless of whether such an agreement is reached, in the 2013 through 2020 trading period,

10 For 2012, each member state’s total allowances will be based on verified 2010 emissions. In subsequent years, the total a llowances will be based on verified emissions from 2 years prior.

11 According to the 2008 directive, it shall be fo r member states to determine the use to be made of revenues generated from the auctioning of allowances. Those revenues should be used to tackle climate change in the EU and third countries, inter alia; to reduce greenhouse gas emissions; to adapt to the imp acts of climate change in the EU and third countries, especially developing countries ; to fund research and development for mitigation and adaptation, including in partic ular in the fields of aeronautics and air transport; to reduce emissions through low-emission transport; and to cover the cost of administering the Community scheme.

12 Alternatively, if an aircraft operator has ex cess emissions allowances, it will be able to sell those excess allowances on the market.

Page 55 GAO-09-554 Aviation and Climate ChangeAppendix I: Legal Impl ications of European Union Emissions Trading Scheme



### each aircraft operator will be allowed to use CERs and ERUs to cover at least 1.5 percent of their emissions. 13



### If a country not participating in the EU ETS adopts measures for reducing the climate change impact of flights to participating countries, then the European Commission, in consultation with that country, will consider options to provide for “optimal inte raction” between the ETS and that country’s regulatory scheme—for ex ample, the Commission may consider excluding from the ETS flights to part icipating EU ETS countries from that country. 14 

### Although 2012 is the first year aircraft operators must comply with the ETS law, preparations in the EU 15 

### and from U.S. carriers 16 

### began soon after the law went into force.



# Legal Implications of the ETS The inclusion of aviation in the newly amended EU ETS implicates a number of international agreements, policy statements, and a bilateral agreement specific to the United States, including the United Nations Framework Convention on Climat e Change (UNFCCC), the Kyoto Protocol to the UNFCCC, the Convention on International Civil Aviation (the ‘Chicago Convention’), Resolutions of the International Civil Aviation Organization, and the U.S.-EU Air Transport Agreement (the ‘U.S.-EU Open Skies Agreement’).

13 The European Commission will determine the exact percentage of CERs and ERUs that aircraft operators can use in the 2013 throug h 2020 trading period. In determining the percentage of CERs and ERUs that each covered sector can use in the 2012 through 2020 trading period, the Commission will ensure that overall CER and ERU usage does not exceed 50 percent of the emissions reducti ons achieved in Phase II (2007 through 2012), measured from a baseline of 2005 emissions levels.

14 According to the DG Environment, draft legi slation and a number of bills proposed in the 110th Congress would have triggered such consideration. See McCain-Lieberman, S. 280, 110th Cong. (2007); Lieberman- Warner, S. 2191, 110th Cong. (2007); Dingell-Boucher, draft bill; and Waxman-Markey, H.R. 1590, 110th Cong. (2007), H.R. 6186, 110th Cong. (2008).

15 On Feb. 11, 2009, the Commission adopted the Preliminary List of Aircraft Operators and their administering Member States, Commission Notice Pursuant to Article 18a(3)(a) of Directive 2003/87/EC , C(2009) 866. Addition al preparations have included holding a number of stakeholder workshops to discuss implementing th is directive and development of guidelines for monitoring, reporting, and verification of emissions, according to the DG Environment.

16 All operators must submit thei r monitoring plan by the end of August 2009, according to the DG Environment.

Page 56 GAO-09-554 Aviation and Climate ChangeAppendix I: Legal Impl ications of European Union Emissions Trading Scheme



### The UNFCCC, a multilateral treaty on global warming that was signed in 1992 and has been ratified by 192 countries, including the United States, seeks to “achieve stabilization of greenhouse gas concentrations in the atmosphere at a level that woul d prevent dangerous anthropogenic interference with the climate system.” 17 

### Although the UNFCCC required signatory states to formulate a na tional response to climate change, 18 

### its mitigation provisions did not requ ire mandatory national emissions targets. 19



### In order to strengthen the commitments articulated in the UNFCCC, the Kyoto Protocol was developed wi thin the UNFCCC’s framework and adopted in 1997. The Protocol ente red into force in February 2005. 20 

### The Kyoto Protocol established binding greenhouse gas emissions targets for a number of industrialized nations 21 

### and the European Economic Community (EEC). 22 

### Notably, the agreement required these industrialized nations and the EEC to pursue “limitations or reduction of emissions of greenhouse gases ... from aviation ... wo rking through the International Civil Aviation Organization.” 23 

### As of January 2009, 183 countries had ratified the Kyoto Protocol, but not the United States.

Further, the Convention on International Civil Aviation, commonly known as the Chicago Convention, signed on December 7, 1944, sets forth rules on airspace, issues of sovereignty, aircraft licensing and registration, and general international standards and procedures, among others. 24 

### Notably,

17 United Nations Framework Convention on C limate Change, 1992, Article 2, GE.05-62220. (E) 200705.

18

Id . at Article 4(1)(b).

19

Id . at Article 4.

20 Kyoto Protocol to the United Nations Fr amework Convention on Climate Change, 1999 [hereinafter Kyoto Protocol].

21 The Kyoto Protocol recognized that industria lized nations are the largest contributors to greenhouse gas emissions and th erefore divided the signatory countries into two groups— Annex I countries that are industrialized nations subject to binding targets, either emission reduction or limitation requir ements, and Non-Annex I countr ies that are not subject to binding targets.

22 Kyoto Protocol, supra note 20, art. 3(1).

23

Id . at art. 2(2).

24 Convention on International Civil Aviation, Dec. 7, 1944, Ninth ed., 2006, 61 Stat. 1180, 15 U.N.T.S. 295 [hereinafte r Chicago Convention].

Page 57 GAO-09-554 Aviation and Climate ChangeAppendix I: Legal Impl ications of European Union Emissions Trading Scheme



### the treaty sets forth sovereignty provis ions, recognizing that a contracting state has exclusive sovereignty over airspace above its own territory. 25 

### Provisions potentially applicable to the recent amendment incorporating aviation into the ETS include Article 11, 26 

### Article 12, 27 

### Article 15, 28 

### and Article 24. 29



### Established by the Chicago Convention in 1944, the International Civil Aviation Organization (ICAO) is an agency of the United Nations and is tasked with fostering the planning and development of international aviation. ICAO has issued a number of Assembly Resolutions, which are statements of policy rather than law, including a nonbinding ICAO Resolution A36-22 relating to environmental protection and aviation emissions. 30 

### This resolution, which supersedes ICAO Resolution A35-5 which had endorsed the further devel opment of an open emissions trading scheme for international aviation, calls for mutual agreement between contracting states before implementation of an emissions trading scheme. 31 

### Additionally, the Resolution formed a new Group on

25

See Id . at art. 1.

26 Article 11 provides that “[S]ubject to the pr ovisions of this Convention, the laws and regulations of a contracting State relating to the admission to or departure from its territory of aircraft engaged in in ternational navigation . . . shall be applied to the aircraft of all contracting States without distinction as to nationality, and shall be complied with by such aircraft upon entering or departing from or while within the territory of that State.”

27

Article 12 states that “[e]ach contracting Stat e undertakes to adopt measures to insure that every aircraft flying over or maneuvering within its territory and that every aircraft carrying its nationality mark, wherever such ai rcraft may be, shall comply with the rules and regulations relating to the flight and maneu ver of aircraft there in force. . . . Over the high seas, the rules in force shall be those established under this Convention, . . .”

28 Article 15 provides in part that “[n]o fees, dues or other charges shall be imposed by any contracting State in respect solely of the right of transit over or entry into or exit from its territory of any aircraft of a contracting Stat e or persons or property thereon.” Moreover, charges that may be imposed must be non-discriminatory.

29 Article 24 covers customs and related duties for aircraft of contracting states and includes the provision that “[f]uel . . . on board an airc raft of a contracting State, on arrival in the territory of another contracting State and retain ed on board on leaving the territory of that State shall be exempt from customs duty, inspect ion fees or similar national or local duties and charges.”

30 Consolidated Statement on Continuing ICAO Policies and Practices Related to Environmental Protection, ICAO Res. A36- 22, 36th Session, Append ix L, 1(b)(1)(2007) [hereinafter ICAO Res. A36-22].

31 Many positions referred to in this article cite to ICAO Re solution A35-5 rather than the A36-22.

Page 58 GAO-09-554 Aviation and Climate ChangeAppendix I: Legal Impl ications of European Union Emissions Trading Scheme



### International Aviation and Climate Change (GIACC) that was tasked with developing and recommending to the ICAO Council a program of action to address international aviation and climate change. 32 

### GIACC is due to report to the Council later this year.

Finally, the U.S.-EU Air Transport Agreement, 33 

### signed on April 25 and 30, 2007, and provisionally applied as of March 30, 2008, provided greater flexibility for flights between the Unit ed States and the EU, authorizing every U.S. and every EU airline to: operate without restriction on the number of flights, aircraft, and routes, set fares according to market demand; and enter into cooperative a rrangements, including codesharing, franchising, and leasing. It includes enhanced opportunities for EU investment in carriers from almost 30 non-EU countries, and enhanced regulatory cooperation in regard to competition law, government subsidies, the environment, cons umer protection, and security. 34 

### Among the provisions potentially applicable to the newly amended EU ETS is Articles 12 relating to charges for use of airports and related facilities and services and Article 3 which prohibits a party from unilaterally limiting service or aircraft type. 35



### Although a number of international agreements, policy statements, and bilateral agreements are in place currently, climate change policies are constantly changing. In December 2009, the Conference of the Parties to the UNFCCC will meet in Copenhagen to discuss and negotiate an “agreed outcome” in order to implement the UNFCCC “up to and beyond 2012.” 36



# Stakeholder Positions on Legal Issues A number of stakeholders have expressed concern as to the legal basis for aviation’s inclusion in the EU ETS. In the United States, within the EU community, and in countries throughout the world, public and private entities, as well as legal scholars, have expressed opinions as to whether the inclusion of aviation into the ETS is in compliance with international law.

32 ICAO Res. A36-22, supra note 30, Appendix K.

33 This also is referred to as th e U.S.-EU Open Skies Agreement.

34

See generally Id.

35

Id . at art. 12, 3.

36 Bali Action Plan, Decision 1/CP .13, 1 (FCCC/CP/2007/6/Add.1).

Page 59 GAO-09-554 Aviation and Climate ChangeAppendix I: Legal Impl ications of European Union Emissions Trading Scheme



### Stakeholders within the United States, such as the executive branch, members of Congress, and the Air Transport Association (ATA), have weighed in on the legality of the newly amended EU ETS which requires compliance by U.S. carriers. 

## Stakeholder Positions within the United States

In 2007 and 2008, the executive branch expressed the view that the imposition of the ETS was inconsistent with international law, specifically, the Chicago Convention and the U.S.-EU Air Transport Agreement. 37 

### Whilethe executive branch has not articulated a position on this issue since mid2008, it has expressed the importance of climate change and developing a solution on a global level. 38



### The Air Transport Association (ATA), a trade association representing principle U.S. airlines, also has concluded that the EU ETS’s inclusion of aviation violates international law, specifically the Chicago Convention. 39 

### ATA argues that imposition of the ET S on U.S.-based carriers is contrary to Articles 1, 12, 11, 40 

### 15 41 

### and potentially, in the alternative, Article 24. 42 

### In summary, ATA argues that the ETS, as amended, violates Article 1 and Article 12 provisions of sovereignty and authority. Article 1, which provides contracting states exclusive sovereignty over their airspace, 43 

### isviolated by the EU’s extraterritorial reach which covers emissions of nonEU airlines in another states’ airspace . Further, Article 12, which requires

37 Letter of U.S. Ambassador Kristen Silverberg to Jos Delbeke, Acting Director General General, Environment Director ate General, Oct. 30, 2008; and letter from the Ambassadors of Australia, Canada, China, Japan, Korea and the United States to Ambassador Peter Witt of Germany, Apr. 6, 2007 [her einafter Ambassador Letter].

38

See statement of Secretary Clinton: “President Obama and I recognize that the solutions to this crisis are both domes tic and global, that all nations bear responsibility and all nations must work together to find solutions.” See also statement of Special Envoy Stern: “Yet we can only meet the climate challenge with a response that is genuinely global. Eighty percent of greenhouse gas emissions are produced outs ide the United States, and a rapidly growing percentage is produced in emerging market countries.”

39 ATA’s analysis is contained in a non-public Legal Analysis Summary provided to GAO.

40 Chicago Convention, supra note 24, art. 11.

41 Id . at art. 15.

42 Article 24 provides that “fuel...on board an airc raft of a contracting St ate, on arrival in the territory of another... shall be exempt from customs duty, inspection fees or similar national or local duties and charges.”

43 Chicago Convention, supra note 24, art. 1. Article 1 prov ides that every contracting state has “complete and exclusive sovereignty o ver the airspace above its territory.”

Page 60 GAO-09-554 Aviation and Climate ChangeAppendix I: Legal Impl ications of European Union Emissions Trading Scheme



### contracting states to ensure that aircraft under its jurisdiction are in compliance with rules and regulations re lating to the flight and maneuver of aircraft, 44 

### also is violated. ATA argues that Article 12 gives ICAO primary authority, under the Convention, to set rules for the “flight and maneuver of aircraft” over the “high seas,” which precludes the applicatio of rules by one state over the airlines of another state to the extent inconsistent with ICAO rules. Thus, because ICAO has stated that one state can apply emissions trading to the airlines of another state only through mutual consent, ATA contends that the EU’s emissions trading coverage of non-agreeing-EU airlines over the high seas is inconsiste with ICAO’ n

nt s authority.

Additionally, with respect to Article 11, ATA argues that although Article 11 provides authority to states to establish certain rules for admission and departure of aircraft, the authority is limited. States may only establish admission and departure rules consistent with the remainder of the Chicago Convention, which prevents the EU from arguing that Article 11 authorizes EU action. In any event, ATA contends that any rules may only apply “upon entering or departing from or while within the territory of that State,” whereas the European scheme reaches outside European territory. Further, ATA finds that the ETS is contrary to Article 15 45 

### of the Chicago Convention because it imposes a de facto charge for the right to enter or exit an EU member state. In the alternative, ATA argues that there could be a violation of Article 24 of the Convention, which exempts fuel on board an aircraft from duties, fees, and charges. Because the law calculates emissions based on fuel consumption, the purchase of greenhouse gas permits may constitute a “similar ... charge” of fuel on board, according to ATA. Additionally, Article 24 mirrors Article 11 of the U.S.-EU Air Transport Agreement but extends the freedom from taxation/charges on fuel to that purch ased in the EU. Thus, ATA argues, the prohibition against the EU levying a fuel tax applies to fuel already on board as well as fuel purchased in the EU.

ATA has publicly expressed harsh opposition to the ETS’s inclusion of aviation and has stated that there will be a number of legal challenges from around the globe, including from the United States. 46 

### ATA has

44

Id . at art. 12.

45

Id . at art. 15.

46

See Josh Voorhees, Greenwire, EU brings airlines into climate scheme; industry vows court fight (2008), at http://www.eenews.net/ Greenwire/2008/07/08/archive/3.

Page 61 GAO-09-554 Aviation and Climate ChangeAppendix I: Legal Impl ications of European Union Emissions Trading Scheme



### additionally expressed discontent with the newly amended ETS law as a matter of policy, as it siphons money out of aviation which is counterproductive from reinvesting in improving technologies that reduce emissions. 47



### Finally, the Congress is considering the House FAA Reauthorization Bill, H.R. 915, 111th Cong. (2009), which includes an expression of the Sense of the Congress with respect to the newly amended EU ETS. 48 

### The bill states that the EU’s imposition of the ETS, without working through ICAO, is inconsistent with the Chicago Convention, other relevant air service agreements, and “antithetical to building cooperation to address effectively the problem of greenhouse gas emissions by aircraft engaged in international civil aviation.” 49 

### The bill recommends working through ICAO to address these issues. 50



### Stakeholders in the EU community and a not-for-profit business organization have expressed both legal and policy views on the newly amended ETS, as well. An independent contractor for the European Commission’s Directorate-General of the Environment (DG Environment) as well as the International Emissions Trading Association (IETA) have both issued opinions in support of aviation’s inclusion in the ETS. 51 

### IETA supports the inclusion of aviation in the EU ETS from a policy perspective, but has not opined on the legality of its inclusion. 52 

### From a policy standpoint, IETA supports aviation’s inclusion on both EU and non-EU carriers so as to share the burden to combat climate change. 53 

### However, the organization has expressed concerns over a number of issues, some of 

## Stakeholder Positions outside the United States

47 Press Release, Air Transpor t Association Chief Executi ve Says European Aviation Emissions Trading Scheme ‘Contrary to Intern ational Law and Bad Policy’ (Oct. 30, 2008), available at http://www.airlines.org/news/re leases/2008/news_10-30-08.htm.

48 A “Sense of the Congress” is not legally binding if passed.

49 H.R. 915, Sec. 514(1), 111th Cong. (2009).

50

Id . at Sec. 514(2).

51 The legal assessment was conducted by an independent contractor for the DG Environment.

52 IETA, IETA’s position on the Inclusion of Aviation in the EU ETS , available at www.ieta.org/ieta/www/pages/ getfile.php?docID=2413.

53

Id . at 2.

Page 62 GAO-09-554 Aviation and Climate ChangeAppendix I: Legal Impl ications of European Union Emissions Trading Scheme



### which include access to project credits, amount of allowances available for auctioning, and allocation calculation. 54



### From a legal perspective, an independent contractor for the DG Environment 55 

### has issued an opinion supporting aviation’s inclusion in the EU ETS. 56 

### The opinion states that alongside a state’s inherent right to enact legislation and the provisions of the EC Treaty for collective actio by member states, the legal basis for action is contained in the UNFCCC requirement for developed countries to take measures to mitigate climate change, in the Kyoto Protocol which reinforces this position, and under EU law (the EC Treaty), which provides the basis for the EU to act by including aviation in the ETS. n ’s

57 

### Further, the opinion articulates that the ETS does not violate Articles 11, 58 

### 12, 59 

### 15, 60 

### or 24 61 

### of the Chicago Convention. First, Article 11 is consistent with the newly amended ETS law so long as the “laws and regula tions” established do not “discriminate as to nationality of aircraft.” 62 

### Further, Article 12 is inapplicable because emissions trading does not affect the flight or maneuver of aircraft but merely the terms for admission to and departure from EU territory. Additionally, the opinion stated that Article 15 is inapplicable because the coverage of aviation cannot be seen as an “airport charge or similar charge.” Even if payment were to occur under an auction system, the allowances are not designed as compensation for the costs of operation and management of airports and air navigation facilities, and

57

58

60

61

62 54

Id.

55 The legal assessment was conducted by an independent contractor for the DG Environment.

56 Giving Wings to Emissions Trading
, Inclusion of Aviation under the European emissions trading system (ETS): Design and Impacts (The Delft Report), Report to the European Commission, DG Environmen t, No.ENV.C.2./ETU/2004/0074r, July 2005 [hereinafter Delft Report]. This report was pr epared for and endors ed by the European Commission.

Id . at 170-73.

Chicago Convention, supra note 24, art. 11.

59 Article 12 requires contracting states to ensure that aircraft under their jurisdiction are in compliance with rules and regulations relating to the flig ht and maneuver of aircraft.

Chicago Convention, supra note 24, art. 15.

Id . at art. 24.

The Delft Report at 175-77.

Page 63 GAO-09-554 Aviation and Climate ChangeAppendix I: Legal Impl ications of European Union Emissions Trading Scheme



### consequently, Article 15 is inapplicable. 63 

### Finally, Article 24 of the Convention does not apply to the Emissions Trading System because trading allowances are “fundamentally different from customs duties.” 64 

### Additionally, the opinion finds policy support for these legal findin gs in ICAO Resolution A35-5 65 

### and bilateral air transport agreements. 66



### r

n”

n-EU

e

nter to Additionally, countries outside the European Community have joined the United States in an expression of concerns regarding the imposition of the ETS on non-EU carriers. In an April 2007 letter to the German Ambassado to the European Union, the United States, Australia, China, Japan, South Korea, and Canada conveyed a “deep concern and strong dissatisfactio for the then-proposal to include international civil aviation within the scope of the EU ETS. 67 

### The letter asks that the EU ETS not include no aircraft unless done by mutual consent. 68 

### Although supportive of the reduction of greenhouse gas emissions, th e ascribing parties argue that th “unilateral” imposition of the ETS on non-EU carriers would potentially violate the Chicago Convention and bilateral aviation agreements with the parties to the letter. 69 

### Moreover, they write, the proposal runs cou the international consensus that ICAO should handle matters of international aviation, which was articulated with the ICAO Assembly and the ICAO Council in 2004 and 2006, respectively. 70 

### The letter closes with a

7

pendi x 1 (2004) [hereinafter

ns l opportunity to partic ipate in the ETS is already covered under the

e

er to the German Presidency regarding Commission proposal to extend ETS to aviation (Apr. 6, 2007). 63

Id . at 176-7

64

Id . at 177.

65 Consolidated statement of continuing ICAO policies and practices related to environmental protection, ICAO Res. A35-5, 35th Session, Ap ICAO Res. A35-5]. “ICAO endors es an open emission system for international aviation” and requests council focu s on two areas under this framework.

66 The Delft Report further elaborates: “the oper ation of an ETS does not unilaterally limit the volume of traffic ... or aircraft types, as it only provides incentives to reduce emissio over time; fair and equa Chicago Convention’s non-discrimi nation clause and this must be adhered to under th ETS.” See pp. 179-181.

67 Lett

68

Id

.

69

Id

.

70

Id

.

Page 64 GAO-09-554 Aviation and Climate ChangeAppendix I: Legal Impl ications of European Union Emissions Trading Scheme



### reservation of right to take appropriate measures under international law if the ETS is imposed.

sion in s in the legal community, both within the United States and the EU, have provided explanatory articles or position

” 73 

### This

and lly

s

understanding of contentious provisions. 76 

### In conclusion, he proposes that the EU should channel the energy for implementation of the 71



### Given the controversial nature and complexity of aviation’s inclu the EU ETS, a number of scholar

papers on the issue of the consistency of the EU’s plans with its international legal obligations. 72



### One U.S. law review article by Daniel B. Reagan argues that international aviation emission reductions should be pursued through ICAO given the “political, technical, and legal implications raised by the regulation. article sets forth that politically, ICAO is the appropriate body because it can work towards uniformity in a complex regulatory arena, incidentally resulting in increased participation from a variety of stakeholders, reduction of resentment, and a reduced likelihood of non-compliance legal challenges. 74 

### Further, ICAO has the expertise necessary to technica design aviation’s emission reduction regime and is in a position to consider the “economic, political, and technical circumstances of its member states ... .” 75 

### Finally, Reagan argues that pursuing an emission reduction regime through ICAO could avoid likely legal challenges which present themselves under the current ETS, as ICAO could facilitate a

common

current regime into holding ICAO accountable for fulfilling environmental duties. 77

For brevity’s sake, we have not included expl anatory articles because they are repetitive

an, Putting International Aviation Into the European Union Emissions ading Scheme: Can Europe Do It Flying Solo?, 35 B.C. Envtl. Aff. L. Rev. 349 (2008).

74

Id . at 380-81.

75

Id . at 381-82.

76

Id . at 382. 

## Legal Scholar/Researcher Views

71 Id

.

72
of what is contained in this appendix. Here we highlight thos e articles which set forth legal positions on the issue.

73 Daniel B. Reag Tr

77

Id . at 383.

Page 65 GAO-09-554 Aviation and Climate ChangeAppendix I: Legal Impl ications of European Union Emissions Trading Scheme



### In contrast, a law review article published in the European Environmen Law Review in 2007 by Gisbert Schwarze argues that bringing aviation in the EU ETS falls clearly within existing law and is, in fact, mandated. tal
to

policies which include aviation. First, the article sets forth that the

ther

80



### ation on

certain , which covers charges, is similarly inapplicable because emissions allowances on the free market or through

d 78 

### The article presents the case that neither existing traffic rights in member states, bilateral air transport agreements, nor the Chicago Convention pose any legal obstacles. 79 

### He argues, in fact, that the EU has a mandate under the UNFCCC and the Kyoto Protocol to implement climate change

inclusion of aviation does not restrict existing traffic rights or allow or disallow certain aircraft operations in different member states, but ra merely brings the amount of emissions into the decision-making process.

Further, Schwarze explains that imposing the ETS on carriers flying in and out of the EU is well within the Chicago Convention. Article 1 of the Convention provides contracting states exclusive sovereignty over their airspace which provides the EU with the authority to impose obligations relating to arrival and departures, so long as there is no discrimin the basis of nationality, as required by Article 11. 81 

### Additionally, the article sets forth that Article 12, regarding the flight and maneuver of aircraft, is not applicable because, as argued above, the ETS does not regulate aircraft operations. Article 15

the auctioning process do not constitute a charge. 82 

### Finally, Article 24 is inapposite as well because the emissions trading system does not constitute a customs duty. 83



### Additionally, Schwarze argues that th e bilateral air transport agreements with various nations, such as the Open Skies Agreement with the Unite States, do not pose any legal barriers to inclusion of aviation in ETS. 84

78 Gisbert Schwarze, Including Aviation into the Eu ropean Union Emissions Trading ean Environmen tal Law Review (2007).

In the alternative, as argued, even if th is did constitute a charge, Article 15’s only

Gisbert Schwarze, Including Aviation into the Eu ropean Union Emissions Trading 3-14, European Envir onmental Law Review (2007).

t 14. Scheme , Europ

79

Id . at 12-15.

80

Id . at 12-13.

81 Id . at 13-14.

82 applicability is to discrimination as to nationality. Id

.

83 Scheme , p. 1

84

Id . a

Page 66 GAO-09-554 Aviation and Climate ChangeAppendix I: Legal Impl ications of European Union Emissions Trading Scheme



### These agreements contain a prohibition of discrimination similar to Art 11 of the Chicago Convention and a fair competition clause which require fair competition among signatories in international aviation as well as prohibits a party from unilaterally limiting traffic. icle

s

that s the ETS operates without discrimination, it is in conformity with the principle of a sound and economic operation of air services and

g that

reduction of emissions of greenhouse gases ... from aviation ... working through the International Civil Aviation

rganization.” 89 

### And finally, although not legally binding, ICAO Resolution

nges A

re

es 85 

### The article argues so long a

therefore satisfies the fairness clause. 86 

### Finally, since the ETS gives only incentive to reduce emissions, it does not regulate the amount of air traffic. 87



### Finally, Schwarze argues that not only is the inclusion of aviation into the EU ETS legally sound, the UNFCCC and Kyoto Protocol mandate its inclusion. The UNFCCC requires all part ies to the treaty to adopt national policies and take corresponding measures on the mitigation of climate change consistent with the objective of the convention, recognizin this can be done “jointly with other parties.” 88 

### Additionally, the Kyoto Protocol, which sought to strength en UNFCCC, required Annex 1 parties to pursue “limitations or

O A35-5 endorses the development of an open emissions trading system for international aviation. 90



### Implementation of the new ETS directi ve will likely face legal challe before 2012, the first year aircraft operators will be included in the ETS. number of stakeholders, including ATA, have publicly expressed that the will be “government-to-government l egal challenges” and potentially a “multilateral challenge from around the world.” 91 

### Further, countri outside the EU community have joined in support of taking appropriate

limate Change, supra note 17, art. 4(2)(a).

Res. A35-5, supra note 66, Appendix I Nr. 2(c)(1). 

# Potential Legal Challenges and Dispute Resolution

85 Id

.

86

Id

.

87

Id

.

88 United Nations Framework Convention on C

89 Kyoto Protocol, supra note 20, art. 2(2).

90 Schwarze at 13. See also ICAO

91 See Voorhees, supra note 46

.

Page 67 GAO-09-554 Aviation and Climate ChangeAppendix I: Legal Impl ications of European Union Emissions Trading Scheme



### actions under international law if the ETS is imposed. 92 

### If challenges are brought forth, they could potentially be brought forth under the Chicag Convention, air service agreements (e.g., U.S.- EU Air Transport Agreement) or potentially in individual member state courts. Each o has its own dispute resolution procedure.

If a challenge is brought forth under the Chicago Convention after fai negotiations, Article 84 of t o

ption

led he Convention (Settlement of Disputes) is invoked. Article 84 provides that if th ere is a disagreement by two or more

t Agreement is no exception. Article 19 of the U.S.-EU Air Transport Agreement provid es that parties to a dispute may

ns

days, efits which

In addition to bringing legal challenges under international treaties, carriers could potentially mount legal challenges in member states’ contracting states which cannot be settled by negotiation, it will be decided upon by the Council. 93 

### A decision by the Council can be appealed to an agreed-upon ad hoc tribunal or to the Permanent Court of International Justice (now the International Court of Justice) whose decision will be binding. 94



### Air service agreements additionally have dispute resolution procedures and the U.S.-EU Air Transpor

submit to binding arbitration through an ad hoc tribunal if negotiatio fail. 95 

### If there is noncompliance with the tribunal’s decision and a subsequent agreement between the parties is not reached within 40 the other party may suspend the application of comparable ben arise under the agreement. 96

ting

penalties are ion. Alternatively, a challenge could potentially be brought against a carrier. If a carrier chooses to move forward and not action could be brought under the Chicago Conven tion Article 87 and he airline to cease operations over any contracting state.

Id . at art. 19(7). 92 See Ambassadors Letter, supra note 37.

93 Chicago Convention, supra note 24, art. 84. The Council is composed of 36 contrac states elected by the Assembly. See Id . at art. 50. When a disagr eement is submitted to the Council, the Council will invoke the Rules of th e Settlement of Differences, established in 1957, which sets forth procedures for disputes.

94

Id . at art. 84. Additional requirements for settlement of disputes and contained in Articles 85, 86, 87 and 88 of the Chicago Convent

comply with the ETS, force t

95

See U.S.-EU Air Transport Agreement, art. 19.

96

See

Page 68 GAO-09-554 Aviation and Climate ChangeAppendix I: Legal Impl ications of Europ Union Emissions Trading Scheme ean

Page 69 GAO-09-554 Aviation and Climate Change 

### national courts, according to some legal scholars. 97 

### Additionally, a

on authority in the state’s European state will potentially be able to take action against a noncompliant carrier under their civil aviati
courts. 98

97

See Aimee Turner, Flight Global, EU warns ICAO it will go it alone if no progress is made with ETS (2007), available at www.flightglobal.com.

98

Id

.Appendix II: List of Experts 

# Appendix II: List of Experts

Gerald Bernstein, Stanford Transportation Group Dennis Bushnell, National Aerona utics and Space Administration Kenneth Button, George Mason Unive rsity

nthony Dean, General Electric

Faber, CE Delft (Netherlands) i, GRA, Incorporated

James Hileman, Massachusetts Institute of Technology

ennifer Holmgren, Universal Oil Products chester Metropolitan University (United Kingdom) Peter Morrell, Cranfield University (United Kingdom) A Robert Deering, American Airlines Christian Dumas, Airbus (France) Jasper Richard Golaszewsk Preston Henne, Gulfstream Aerospace Corporation

J David Lee, Man

Andreas Schafer, University of Cambridge (United Kingdom) Agam Sinha, MITRE Corporation Julian Tishkoff, United States Air Force Ian Waitz, Massachusetts Institute of Technology Donald Wuebbles, University of Illinois

Page 70 GAO-09-554 Aviation and Climate ChangeAppendix III: Detailed Survey Results 

# Appendix III: Detailed Survey Results

The survey tool used to assess options for reducing commercial aircraft emissions is below, complete with detailed results. We do not in clude the responses for open-ended questions.



# Uni Off

Aviatio
Ranking To raft Greenhouse Gas Emissions 

# ted States Government Accountability ice
n and Climate Change
ol for Options to Redu ce Airc



### ntroduction

ation emissions that were identified

rough our interviews with you and other experts, or by GAO. We have pla ptions in three categories—technologies, operations, and alte ert opinion on them. We ask that you rate th viding comments where appropriate.

Instructions for Completing This Tool

ese blanks will expand to fit your answer.

• 

### ease use your mouse to na ougho cum lick g the box you ish to fill in. o not use the “Tab ause doing so ay cause for tting prob ms.
it once; to d select a box, double click on it.

int this tool, complete it by hand, and return it by
ra paper as neces plete the open-ended

e and retur this documen o Matthew by January 9, 2009. Plea save the com leted document to e-mail it as an attachment to I

Th is rating tool follows up on our recent interview with you on commercial aviation and greenhouse gas emissions. The tool contains options for reducing commercial avi th ced the o rnative fuels—and are interested in your exp e options across several factors, pro

Yo u can answer most of the questions by checking boxes or filling in

lanks. A few questions request shor t narrative answers. Please note that b th

Pl vigate thr ut the do ent by c ing

on the field or checkin w D ”

or “Enter” keys, bec m ma le

• 

### T o select a box, click on e

If

you prefer, you may pr fax. Please use ext sary to com
qu estions.

De adline

We ask that you complet n t t Ro senberg your desktop or hard drive and se p

Page 71 GAO-09-554 Aviation and Climate ChangeAppendix III: Detailed Survey Results



### R osenbergMC@gao.gov . If you complete this tool by hand, please fax the completed tool to Matthew Rosenberg at GAO at 312-220-7726.

Contact Inf ormation

ions, please co act Matthew senberg enior 12-220-7645 or RosenbergMC@gao.gov or Cathy Colwell, -220-7655 o v.

help.

our overall knowledge of technological e aircraft carbon dioxide ( O 2 

### ) emissions, such engines and aircraft design technologies, and the those technologies?

0 None Æ SKIP TO QUESTION #9

TO QUESTION #2

2. In your expert opinio e ons for the following options?

**Low potenti**  **Medium potentia**  **High potential**  **Don’t kno**  

### If

you have any quest Analyst, at 3 nt Ro , S

As sistant Director, at 312 r ColwellC@gao.go

Th ank you for your

1. How would you rate y
op tions to reduc as aircraft C

co sts of 

# Part 1: Technology Options

6 Minimal Æ SKIP TO QUESTION #9 4 Basic Æ CONTINUE TO QUESTION #2 1 Proficient Æ CONTINUE TO QUESTION #2 7 Advanced Æ CONTINUE

n, what is the potential for futur fuel

sa vings and CO 2 

### emissions reducti

**al l**  **w**

a. Open roto r engines 0 5 8 1
b. Geared Turbo Fan Engines 2 7 3 2

c. Distributive Propulsi systems on 2 2 5 5

d. Lighter airframes (Compo sites) 2 5 6 1

e. Increased Laminar ntrol Fl ow Co 2 6 3 2

f. Blended wing-body aircraft 0 5 81

g. Winglets 8 3 3 0

h. Riblets 9 1 0 4

Page 72 GAO-09-554 Aviation and Climate ChangeAppendix III: Detailed Survey Results



### 3. In your expert opinion, what would be the potential R&D costs to develop the following options for co mmercial use?

**Lowco edi High c Don’t**  **sts M um**  **cost s**  **osts know** 

a

. Open rotor engines 1 6 6 1
b. Geared Turbo Fan En gines 3 7 3 1

c. Distributiv e Propulsion 0 1 76 sy stems
d. Lighter ai rframes 1 6 61 (C omposites)

e. Increased Lam inar 0 4 73 Fl ow Control

f. Blended wing-body 1 1 1 2 0 ai rcraft

g. Winglets 14 0 0 0

h. Riblets 7 3 0 4



### 4.

co Given your answer to question two, what would be the potential

d

**Medium cost**  **s High costs Don’t know** 

### sts to the air transport industry to procure, operate and maintain the following options to achieve those fuel savings an CO 2 

### emissions reductions?

**Lowcosts**

a. Open rotor engines 2 3 2 7
b. Geared Turbo Fan Engines 2 9 1 2

c. Distributive Propulsion sy stems 0 2 6 6

d. Lighter ai rframes ) 3 6 32 (C omposites

e. Increased Laminar Fl ow Control 1 4 54

f. Blended wing-body ai rcraft 2 3 90

g. Winglets 14 0 0 0

h. Riblets 9 1 0 4

Page 73 GAO-09-554 Aviation and Climate ChangeAppendix III: Detailed Survey Results



### 5. In your expert opinion, what is the level of public acc eptance for the following conceptual options ?

**Medium acceptance**  **High acceptance**  **Don’t know**  **ac Low**  **ceptance**

a. Open rotor engines 6 7 0 1
b. Geared Turbo Fan Engines 0 2 1 1 1

c. Distributive Propulsion sy stems 2 2 46

d. Lighter a irframes (Composites) 0 3 92

e. Increased Laminar Flow 0 4 82 Co ntrol
f. Blended wing-body 4 5 aircraft 2 3

g. Winglets 0 0 13 1

h. Riblets 0 1 9 4



### 6. market conditions, and ab In your expert opinion, given our best knowledge about future s t government intervention, how the private sector to adopt these gies?

**Short timeframe**  **(< 5 years) Medium**  **timeframe (5 - 15**  **years) Long**  **timeframe (> 15**  **years) Never**  **Don’t know**  

### en lo ng would it take for
te chnolo

a. Open rotor engines 1 9 3 0 1
b. Geared Turbo Fan Engines 6 6 00 2

c. Distributive Propulsion systems 0 0 62 6

d. Lighter airframes (Composites) 3 9 10 1

e. Increased Laminar Flow Control 2 4 50 3

f. Blended wing-body aircraft 0 2 1 02 0

g. Winglets 14 0 0 0 0
h. Riblets 5 3 1 0 5a

Page 74 GAO-09-554 Aviation and Climate ChangeAppendix III: Detailed Survey Results

Page 75 GAO-09-554 Aviation and Climate Change 

### 7. What major challenges exist to widespread use of ...

a. Open rotor engines

b. Geared Turbo Fan Engines

c. ve Prop Distributi ulsion systems
d. mes Lighter airfra (Composites)

e. Lamin Increased ar Flow Control

f. bo Blended wing- dy aircraft

g. Winglets

h. R iblets



### 8. W hat actions could the U.S. federal government undertake to promote the development and/or t adop ion of ...

a. Open rotor engines

b. Geared Turbo Fa n Engines

c. Distributive Propulsion systems
d. Lighter airframes (Composites)

e. Increased Laminar Fl ow Control

f. Blended wing-body aircraft

g. Winglets

h. RibletsAppendix III: Detailed Survey Results

Aviation and Climate Change 

### 9. H ow would you rate your overall knowledge of operational options to reduce aircraft fuel usage and CO 2 

### emission

a s, such as

ir traffic management and airline operations?

0 None Æ SKIP TO QUEST 7 QUESTION 7 Æ CONTINUE TO QUE ION #10 TO QUE ION #10 E TO QUE ION #10

hat is the future po ntial fo fuel ductions for the llowing ptions

**Lo potential**  **Mediu potential**  **Hig potential**  **Don’t know**  

### ION #1 5 Minimal Æ SKIP TO #1 7 B asic ST 4 P roficient Æ CONTINUE ST 2 A dvanced Æ CONTINU ST

10

. In your expert opinion, w te r

sa vings and CO 2 

### emissions re fo o ?

**w m**  **h**

a. Reduction of on-board weight 7 4 2 0
b. Engine washing 8 4 0 1

c. Limited use of paint on airf rames 9 3 0 1
d. Increased engine mainten ance 8 3 1 1

e. Single engine taxing 7 6 0 0
f. Use of APU on ground at gate 10 2 0 1

g. Automatic Depen dent Surveillance – B roadcast (ADS-B) 2 6 1 4

h. Required Navigation Performan (RNP) ce 2 4 2 5
i. Continuous Descent Arrivals (CDA) 5 5 2 1 j. NEXTGEN Weather 3 5 1 4

k. Enhanced vision systems 6 3 0 4

l. Synthetic vision systems 6 2 0 5

m. Reduced Vertical Separation 3 8 1 1

n. Flying at slower speeds 5 5 3 0

o. Formation flying 5 2 2 4

p. Air to air refueling 7 1 0 5

q. Reduced flight frequency with larger aircraft 6 3 3 1

r. Multi-stage long distance travel 6 4 1 2 

# Part 2: Operational Options

Page 76 GAO-09-554Appendix III: Detailed Survey Results



### 11. In your expert opinion, what would be the potential R&D costs to develop the following options for commercial use?

**Low Costs**  **Medium Costs**  **High Costs**  **Don’t know** 

a. Reduction of on-board weight 8 4 1 0
b

. Engine washing 11 0 0 2

c. Limited use of paint on airframe s 1 3 0 0 0
d. Increased engine maintenance 1 1 2 0 0

e. Single engine taxing 13 0 0 0
f. Use of APU on ground at gate 1 1 0 0 2

g. Automatic Dependent Surveillance – B roadcast (ADS-B) 1 6 1 5

h. Required Navigation Performance (RNP) 3 4 0 6

i. Continuous Descent Arrivals (CDA) 4 7 0 2 j. NEXTG EN Weather 1 4 3 5

k. Enhanced vision systems 2 5 1 5
l. Synthetic vision syste ms 2 5 1 5

m. Reduced Vertical Separatio n 9 1 1 2

n. Flying at slower speeds 1 3 0 0 0

o. Formation flying 3 3 4 3

p. Air to air refueling 0 3 5 5

q. Reduced flight fre quency with 1 la rger aircraft 2 0 1 0

r. Multi-stage long distance travel 1 1 0 1 1

Page 77 GAO-09-554 Aviation and Climate ChangeAppendix III: Detailed Survey Results



### 12. Given your answer to question ten, what would be the potentia costs to the air transport in

o l dustry to adopt the following ptions to achieve those fuel savings and CO emissions reductions?

**Low costs**  **Medium costs**  **Hig**

**cos Don’t**  **kno** 2

**h ts**  **w**

a. Reduction of on-board weight 8 5 0 0
b. Engine washing 8 4 0 1

c. Limited use of pa int on airframes 11 2 0 0
d. Increased engine maintena nce 5 6 1 1

e. Single engine taxing 13 0 0 0
f. Use of APU on groun d at gate 10 1 0 2

g. Automatic Dependent Surveillance – B roadcast (ADS-B) 2 4 2 5

h. Required Navigation Performanc e 4 (RNP) 3 0 6

i. Continuous Descent A rrivals (CDA) 8 3 0 1 j. NEXTGEN Weather 2 3 1 6
k. Enhanced vision systems 1 5 2 5
l. Synthetic vision syst ems 1 6 1 5

m. Reduced Ver tical Separation 9 2 0 2

n. Flying at slowe r speeds 11 2 0 0

o. Formation flying 2 4 2 5

p. Air to air refueling 0 4 5 4

q. Reduced flight frequency wi th larger aircraft 9 1 3 0

r. Multi-stage long distance travel 5 4 2 2

Page 78 GAO-09-554 Aviation and Climate ChangeAppendix III: Detailed Survey Results



### 13. In your expert opinion, what is the level of public acceptance for the following options?

**Low acceptance**  **Medium acceptance**  **High acceptance**  **Don’t know**  Reduction of on-board weight 5 8 0 0 Engi ne washing 0 0 11 2

Li mited use of paint on airfra mes 1 2 10 0 Increased engine maintenanc e 0 0 12 1
Si ngle engine taxing 0 2 1 1 0
Us e of APU on ground at gat e 0 2 9 2 Automatic Depend ent Surveillance – 0 0 94 Br oadcast (ADS-B) Required Navigatio n Performance 0 0 85 (R NP)
Co ntinuous Descent Arrivals (CDA) 0 1 1 2 0
NEXTGEN W eather 0 1 8 4

En hanced vision systems 0 1 9 3 Synthetic vision systems 1 1 8 3
Re duced Vertical Separati on 1 6 6 0 Flying at slower speeds 7 5 1 0
Fo rmation flying 8 3 1 1 Air to air refueling 10 1 0 2
Re duced flight frequency w ith larger 7 5 1 ai rcraft 0

Multi-stage lon g distance travel 8 3 0 1

Page 79 GAO-09-554 Aviation and Climate ChangeAppendix III: Detailed Survey Results



### 14. In your expert opinion, given our best knowledge abo ut future market conditions, and absent government intervention, how e priva e sector to adopt these

**hort**

**ame (< 5 years)**  **Medium meframe**  **(5 -15 years) Long**  **timeframe (> 15 years)**  **Never Don’t**  **know** 

### lo ng would it take for th t te chnologies?

**S t**  **imefr ti** 

a. Reduction of on-board

we ight 8 5 00 0

b. Engine washing 11 1 0 0 1

c. Limited use of paint on airframe s 9 4 00 0

d. Increased engine 12

ma intenance 1 0 0 0

e. Single engine taxing 13 0 0 0 0
f. Use of APU on ground at gate 8 3 00 2

g. Automatic Dependent Surveillance – Br oadcast (ADS- B) 3 5 00 5

h. Required Navigatio n 6 1 00 6 Pe rformance (RNP)

i. Continuo us Descent 7 5 00 1 Ar rivals (CDA) j. NEXTGEN Weather 2 5 0 0 6

k. Enhanced vision systems 2 5 10 5

l. Synthetic vision systems 1 4 30 5

m. Reduced Vertical Separation 5 6 10 1

n. Flying at slower speeds 11 0 2 0 0

o. Formation flying 2 4 4 2 1

p. Air to air refueling 0 1 8 1 3

q. Reduced flight frequency with larger aircraft 8 3 11 0

r. Multi-stage long distance travel 6 1 22 2

Page 80 GAO-09-554 Aviation and Climate ChangeAppendix III: Detailed Survey Results



### 15. What major challenges exist to widespread use of ...

a. Reduction of on-board weight
b. Engine washing

c. Limited use of pa int on airframes
d. Increased engine maintenance

e. Single engine taxing

f. Use of APU on groun d at gate

g. Automatic Dependent Surveillan ce – Br oadcast (ADS-B)

h. Required Navigation Performance (R NP)

i. Continuo us Descent Arrivals (CDA) j. NEXTGEN Weather

k. Enhanced vision syst ems
l. Synthetic vision systems

m. Reduced Vertical Separati on

n. Flying at slower speeds

o. Formation flying

p. Air to air refueling

q. Reduced flight freq uency with larger ai rcraft

r. Multi-sta ge long distance travel

Page 81 GAO-09-554 Aviation and Climate ChangeAppendix III: Detailed Survey Results



### 16. What actions could the U.S. federal government undertake to promote the adoption of ...

a. n of onReductio board weight
b. ing Engine wash

c. se of p Limited u aint on airframes
d. in Increased eng e maintenance

e. ta Single engine xing

f. Use of APU on ground at gate

g. A utomatic Dependent Surveillance – Broadcast (ADS-B)

h. Required Navigation Performance (RNP)

i. Continuous Descent Arrivals (CDA ) j. NEXTGEN Weather

k. Enhanced vision systems

l. Synthetic vision systems

m. Reduced Ver tical Separation

n. Flying at slower speeds

o. Formation flyi ng
p. Air to air refueling

q. Reduced flight freque aircraft ncy with larger

r. Multi-stage long distance travel

Page 82 GAO-09-554 Aviation and Climate ChangeAppendix III: Detailed Survey Results

Aviation and Climate Change 

### 17. How would you rate your overall knowledge of alternative fuel options to reduce aircraft CO 2 

### emissions, such as biofu 

# Part 3: Alternative els?

1 None Æ SKIP TO QUESTION #25 7 Minimal Æ SKIP TO QU Æ CONTINUE TO QU TION #1 TINUE TO QU TION #1

ert opinion, compared to jet fuel currently in use, l for future reduction of 2 

### emis ns (on sis) for the following options?

**No potential**  **w potential**  **Medium potential**  **High potential**  **Don’t know**  

# Fuel Options

ESTION #25 2 B asic ES 8 3 P roficient Æ CON 5 Advanced Æ CONTINUE TO QUESTION #18 ES 8

18

. In your exp wh at is the potentia a life-cycle ba CO sio

**Lo**

a. Coal to liquid 7 1 2 0 0
b. Fischer-Tropsch-treate such as d

s 1 3 fe edstocks switchgras 3 3 0

c. Fischer-Tro psch-treated forest waste 1 3 3 3 0

d. Fischer-Tropsch-treated 1 5 1 3 0

mun icipal waste

e. Hydotreated algae 0 3 1 6 0
f. Hydrotreated Palm and Soy Oils 2 3 3 1 1

g

. Hydrotreated camelina 2 3 2 1 2
h. Hydrotreated ja tropha 0 3 3 2 2

i. Fuel cells 6 1 1 0 1 j. Hydrogen 4 2 1 1 1

Page 83 GAO-09-554Appendix III: Detailed Survey Results



### 19. In your expert opinion, what would be the potential R&D costs to develop the following options for commercial use?

**Low costs**  **Medium costs Highcosts**  **Don’t know** 

a. Coal to liquid 3 3 1 3
b. Fischer-Tropsch-treated feedstocks such as switchgrass 1 3 4 2

c. Fischer-Tropsc h-treated 4 fo rest waste 1 3 2

d. Fischer-Tropsch-trea municipal wa ted ste 0 4 42

e. Hydotreated algae 0 4 6 0
f. Hydrotreated Palm and Soy Oils 2 3 3 2

g. Hydrotreated cameli na 2 3 2 3

h. Hydrotreated jatropha 2 3 2 3
i. Fuel cells 0 1 7 2 j. Hydrogen 0 1 8 1



### 20

. In your exp ert opinion, what is the level of p lic accep nce for the following options?

**s Don’t**  **know** 

### ub ta

**Low costs**  **Medium costs**  **High cost** 

a. Coal to liquid 5 3 0 2
b. Fischer-Tropsc fe h-treated 0 3 6 1

edstocks such as switchgrass

c. Fischer-Tropsch-treated fo rest waste 0 4 5 1

d. Fischer -Tropsch-treated 0 3 6 1

mu nicipal waste

e. Hydotreated algae 0 1 7 2
f. Hydrotreated Palm and Soy 5 1 2 2 Oi ls

g. Hydrotreat ed camelina 0 5 2 3

h. Hydrotreat ed jatropha 0 3 4 3

Aviation and Climate Change i. Fuel cells 1 4 3 2 j. Hydrogen 5 2 0 3

Page 84 GAO-09-554Appendix III: Detailed Survey Results



### 21. In your expert opinion, given our best knowledge about fu market conditions, and absent government inter ture vention, how long would it take for the private sector to adopt these s?

**hort mef ame**  **(<10years) Medium**  **timeframe (10-20**  **years) Long**  **timeframe (> 20 years)**  **Don’t know**  

### te chnologie

**N ever**  **S**

**r ti** 

a. Coal to li quid 7 2 0 0 1
b. Fischer-Tropsch-treated fe edstocks such as

sw itchgrass 5 40 01

c. Fischer-Tropsch-treate te d 5 40 01 fo rest was
d. Fischer-Tropsc municipal w h-treated aste 5 40 01

e. Hydotreated algae 3 4 2 0 1
f. Hydrotreated Palm and 5 30 02 Soy Oils

g. Hydrotreated camelina 4 3 0 0 3

h. Hydrotreated jatropha 4 3 0 0 3
i. F uel cells 0 3 6 0 1 j. Hydrogen 1 0 7 1 1



### 22. What major challenges exist to widespread use of ...

a. Coal to liquid

b. Fischer-Tropsch-treated feedstocks such as switchgrass

c. Fischer-Tropsch-treated forest waste
d. Fischer-Tropsch-treated municipal waste

e. Hydotreated algae
f. Hydrotreated Palm and Soy Oils

g. Hydrotreated camelina

h. Hydrotreated jatropha

i. Fuel cells j. Hydrogen

Page 85 GAO-09-554 Aviation and Climate ChangeAppendix III: Detailed Survey Results

Page 86 GAO-09-554 Aviation and Climate Change 

### 23. What actions could the federal government underta promote the development and/or adoption of ...

a. Coal to liquid 

### ke to

b. Fischer-Tropsch-treated feedstocks such as switchgrass

c. Fischer-Tropsch-treated forest waste
d. Fischer-Tropsch-treated municipal waste

e. Hydotreated algae
f. Hydrotreated Palm and Soy Oils

g. Hydrotreated camelina

h. Hydrotreated jatropha

i. Fuel cells j. Hydrogen



### 24. What other government actions, if any, should be undertaken address greenhouse gas emissions from commercial aircraft to ?

is 25. Do you have any other comments about anything covered in th rating tool? If so, please comment here.Appendix IV: Scope and Methodology

Page 87 GAO-09-554 

# Appendix IV: Scope and Methodology

To address our objectives, we interviewed selected officials knowledgeable about the aviation indus try, the industry’s impact on th production of greenhouse gas and other emissions that have an impact on the climate, and options for reducing these emissions. We interviewed federal officials from the Environmental Protection Agency (EPA), FAA, the National Aeronautics and Space Administration (NASA) and the Departments of Defense and State. We also met with representatives of ICAO—a United Nations agency. We interviewed representatives of industry groups, environmental groups, airlines, aircraft manufacturers, aircraft engine manufacturers, alternative fuels manufacturers, economists, and academics. We interviewed officials based in the United States and abroad. We interviewed representatives of the EU and associations about the EU ETS. We completed a literature search reviewed relevant documentation, studi es, and articles related objectives. To specifically address commercial aviation’s contribution to emissions, we asked our interviewees to identify the primary studies that estimate current and future emissions. As a result, we reviewed and summarized the findings of the 1999 International Panel of Climate Change Aviation and the Environment report and its 2007 Fourth Assessment Report , which were most frequently named as the most authoritati sources on global aviation emissions.

To specifically address technological and operational options to reduce commercial aviation’s contribution to greenhouse gases and other emissions that can have an impact on the climate, we contracted with t National Academy of Sciences to identify and recruit experts in aviation and environmental issues. We interviewed 18 experts identified by the Academy, including those with expertise in aeronautics, air traffic management, atmospheric science, chemistry, climate change modeling, e

and
to our

ve

he

economics, environmental scienc e, and transportation policy 1 

### . In conducting these interviews, we used a standardized interview guide to obtain consistent answers from our experts and had the interviews recorded and transcribed. Based on these interviews, we assembled a list

nt tool that instructed the experts to

, of options for reducing aviation emissions, and we asked our experts to assess these options on several dimens ions. We provided each of our experts with a standardized assessme assess the potential of each technological and operational option on the following dimensions: potential fuel savings and emissions reductions potential research and development costs, potential cost to the airline

r a list of the experts we interviewed. 1 See Appendix II fo

Aviation and Climate ChangeAppendix IV: Scope and Methodology



### industry, potential for public acceptance, and time frames for adoption. For each dimension, we asked the experts to asses s each option on a three-point scale. For example, we asked the experts to rate each option

xperts

f ller

s rcraft and ls

ons

e

medium,” and “high” responses. We then determined an overall, or group, answer for each

uestion based on the response the e xperts most commonly selected for each option and dimension. However, if approximately the same number

f experts selected a second response , then we chose both responses as the group answer. For example, rather than reporting that the experts rated a particular option as having “high” potential, we instead reported that they rated it as having “medium-high” potential if approximately the same number of experts selected the “high” response as selected the “medium” response. Finally, if approximately the same number of experts as having “low potential”, “medium potential”, or “high potential” 2 

### for fuel savings and carbon dioxide emissions reductions. 3 

### We directed the e not to answer questions about areas in which they did not have specific knowledge or expertise. As a result, throughout our report, the number o expert responses discussed for each emissions reduction option is sma than 18, the number of experts we interviewed. Besides asking the expert to assess the potential of technological options, such as new ai engine designs, we asked them to assess the potential of alternative fue to reduce carbon dioxide emissions 4 

### . Furthermore, for operational opti we asked the experts to assess included options that the federal government must implement, such as air traffic management improvements, as well as options that the airlines can exercise to reduc fuel burn. We analyzed and summarized the experts’ responses in order to identify those technological and operational options that the experts collectively identified as holding the most promise for reducing emissions. To analyze the results, for each option and dimension, we counted the numbers of experts that selected the “low,” “

q

o

2 We did not provide specific definitions for “low,” “medium,” and “high” and let each respondent determine what it meant to them.

3 See app. III for a copy of the assessment tool that we asked the experts to complete as well as complete results. Additionally, we asked the experts to describe the major challenges to the widespread use of the optio ns and the actions that the U.S. federal government could take to promote the devel opment and/or adoption of any of these options.

4 For alternative fuel options, we used a four-point scale to assess each option’s potential to reduce carbon dioxide emissions (“no potentia l,” “low potential,” “medium potential “or “high potential”).

Page 88 GAO-09-554 Aviation and Climate ChangeAppendix IV: Scope and Methodology

Page 89 GAO-09-554 Aviation and Climate Change 

### selected all responses, then we determined that there was no consensus on that question and reported the result as such 5



### .
In order to determine government opti ons for reducing aviation emissions, we interviewed relevant experts, including those 18 recruited by the National Academy of Sciences, about the potential use and the costs and benefits of these options. We asked our interviewees to provide opinions and information on a variety of go vernmental options, including carbon taxes, cap-and-trade programs, aircraft and engine standards, governmentsponsored research, and governmen tal subsidies. We looked at governmental actions that have been ta ken in the past and at those that have been proposed. We reviewed economic research on the economic impact of policy options for addres sing greenhouse gas emissions. Our review focused on whether policy options could achieve emissions reductions from global sources in an economically efficient manner (for example, maximize net benefits). We in terviewed EU officials to understand how the EU ETS will work and to determine issues related to this scheme, which is slated to include certain flights into and out of EU airports starting in 2012. Additionally, we reviewed and summarized the EU ETS and the legal implications of the scheme (see app. I).

5 We defined “approximately the same number of experts” as being either the exact same number of experts or as one fewer or one more expert.Appendix V: Comments from the National Aeronautics and Space Administration 

# Appendix V: Comments from the N ational Aeronautics and Space Administrat ion

Page 90 GAO-09-554 Aviation and Climate ChangeAppendix VI: Comments from the Environmental Prot ection Agency 

# Appendix VI: Comments from the Environmental Protection Agency

Page 91 GAO-09-554 Aviation and Climate ChangeAppendix VI: Comments from the Environmental Prot ection Agency

Page 92 GAO-09-554 Aviation and Climate ChangeAppendix VI: Comments from the Environmental Prot ection Agency

Page 93 GAO-09-554 Aviation and Climate ChangeAppendix VII: GAO Contact and Staff Acknowledgments

Page 94 GAO-09-554 Aviation and Climate Change 

# Appendix VII: GAO Contact and Staff Acknowledgments

Susan Fleming, (202) 512-4431 or flemings@gao.gov

In addition to the contact above, Cathy Colwell and Faye Morrison (Assistant Directors), Lauren Calhoun, Kate Cardamone, Brad Dubbs, Elizabeth Eisenstadt, Tim Guinane, Michael Hix, Sara Ann Moessbauer, Josh Ormond, Tim Persons (Chief Scientist), Matthew Rosenberg, and Amy Rosewarne made key contributions to this report. 

# GAO Contact

The GAO staff that worked on this report dedicate it to their late colleague, Jacqueline McFarlane, in recognition of the valuable contributions she made 

# Staff Acknowledgements

(541042)

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