1. U.S. Emissions of Greenhouse Gases: Background and Context

About This Report

The Energy Policy Act of 1992 requires the Energy Information Administration (EIA) to prepare an inventory of aggregate U.S. national emissions of greenhouse gases for the period 1987-1990, with annual updates thereafter. This report contains data from the thirteenth annual inventory update, covering national emissions over the period 1990-2004, with preliminary estimates of emissions for 2005.

EIA continually reviews its methods for estimating emissions of greenhouse gases. As better methods and information become available, EIA revises both current and historical emissions estimates (see “What’s New”).

This introductory chapter provides background information on U.S. greenhouse gases in a global context, the greenhouse effect and global climate change, and recent domestic and international developments to address climate change. Chapters 2 through 4 cover emissions of carbon dioxide, methane, and nitrous oxide, respectively. Chapter 5 focuses on emissions of gases with high global warming potentials (GWPs), including hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride. Chapter 6 describes potential sequestration and emissions of greenhouse gases as a result of land-use changes.

What’s New

Carbon Dioxide

In preparing for this year’s report, it was determined that EIA had been miscounting an adjustment to ethanol consumption. The corrected value for ethanol consumption increases the value for carbon dioxide emissions resulting from the consumption of motor gasoline; however, the trend remains the same.

Methane

In calculating methane emissions from landfills, EIA uses estimates of municipal solid waste (MSW) generated and MSW landfilled, published by Biocycle magazine. In its April 2006 issue, Biocycle reported estimates of MSW generated in 2002 and 2004 that were more than 20 percent below its previously published estimates. The reason for the revisions is that Biocycle now excludes certain non-MSW materials (such as construction and demolition debris and industrial waste) from its MSW generation estimates.

To ensure that EIA’s estimates of methane emissions from landfills are consistent over the entire 1990-2005 time frame, waste generation estimates for the years 1989 through 2004 have been adjusted downward, based on the implied downward revision of the Biocycle data most recently reported for 2002 and 2004. EIA assumed a constant ratio of actual MSW generation to reported MSW generation for the period 1989 through 2004 and adjusted the estimates of waste generation—and methane emissions from landfills—for those years downward, to ensure that all the earlier estimates (1990-2004) are consistent with Biocycle’s new method.

Other Gases: Hydrofluorocarbons, Perfluorocarbons, and Sulfur Hexafluoride

Difluoromethane (HFC-32). In this annual edition of EIA’s greenhouse gas emissions inventory, data on hydrofluorocarbon (HFC) emissions for the first time include emissions of HFC-32, which increasingly is being used to replace HCFC-22 in refrigerant blends. Its inclusion in the inventory, based on data from the U.S. Environmental Protection Agency (EPA), adds 0.4 million metric tons carbon dioxide equivalent (MMTCO₂e) to EIA’s estimate of total greenhouse gas emissions in 2005.

Electricity Transmission and Distribution. Changes in the calculations of emissions from electricity transmission and distribution resulted in an average annual increase in estimated SF₆ emissions from electric power systems of 0.1 to 0.6 million metric tons carbon dioxide equivalent (MMTCO₂e) for the 1990-2003 period.¹

Magnesium Production and Processing. Emissions estimates from the EPA have been revised to reflect more accurate data on emission factors for sand casting activities and updated historical secondary production data from the U.S. Geological Survey (USGS). The changes resulted in a decrease in estimated SF₆ emissions from magnesium production and processing of 0.1 MMTCO₂e (5 percent) for 2002.²

Substitution of Ozone-Depleting Substances. The EPA has updated assumptions for its Vintaging Model pertaining to trends in chemical substitutions, market size and growth rates, and amounts used. The changes resulted in an average annual net decrease in estimated HFC and PFC emissions of 2.0 MMTCO₂e (3 percent) for the 1990-2003 period.³

Aluminum Production. The EPA has revised smelter-specific emissions factors and aluminum production levels to reflect recently reported data on smelter operating parameters. The changes resulted in an average annual increase of less than 0.5 MMTCO₂e (0.4 percent) for the 1990-2003 period.⁴

Land-Use Issues

This year’s report includes separate estimates for carbon stocks in three new land-use categories: land converted to cropland, grassland remaining grassland, and land converted to grassland. In last year’s report, carbon stocks in these categories were not reported separately but were included in the category of cropland remaining cropland.

U.S. Emissions in a Global Perspective

This report estimates that U.S. energy-related carbon dioxide emissions in 2003 (including nonfuel uses of fossil fuels) totaled 5,800 million metric tons (MMTCO₂). To put U.S. emissions in a global perspective, total energy-related carbon dioxide emissions for the world in 2003 are estimated at 25,033 MMTCO₂, making U.S. emissions about 23 percent of the world total (Table 1).⁵ Emissions for the mature economies of countries that are members of the Organization for Economic Cooperation

and Development (OECD)—including OECD North America, OECD Europe, Japan, and Australia/New Zealand—in 2003 are estimated at 13,155 MMTCO₂, or about 53 percent of the world total. The remaining 47 percent of worldwide energy-related carbon dioxide emissions in 2003 (11,878 MMTCO₂) is attributed to the transitional and developing economies of countries that are not OECD members. Emissions for the transitional economies of non-OECD Europe and Eurasia (including Russia and the other countries of the former Soviet Union) are estimated at 2,725 MMTCO₂.

U.S. energy-related carbon dioxide emissions are projected to increase at an average annual rate of 1.3 percent from 2003 to 2030, while emissions from the non-OECD economies are projected to grow by 3.0 percent per year.⁶ As a result, the U.S. share of world carbon dioxide emissions is projected to fall to 19 percent in 2030 (8,115 MMTCO₂ out of a global total of 43,676 MMTCO₂).

The Greenhouse Effect and Global Climate Change

The Earth is warmed by radiant energy from the Sun. Over time, the amount of energy transmitted to the Earth’s surface is equal to the amount of energy re-radiated back into space in the form of infrared radiation, and the temperature of the Earth’s surface stays roughly constant; however, the temperature of the Earth is strongly influenced by the existence, density, and composition of its atmosphere. Many gases in the Earth’s atmosphere absorb infrared radiation re-radiated from the surface, trapping heat in the lower atmosphere. Without the natural greenhouse effect, it is likely that the average temperature of the Earth’s surface would be on the order of -19^o Celsius, rather than the +14^o Celsius actually observed.⁷ The gases that help trap the Sun’s heat close to the Earth’s surface are referred to as “greenhouse gases.” All greenhouse gases absorb infrared radiation (heat) at particular wavelengths.

The most important greenhouse gases are water vapor (H₂O), carbon dioxide (CO₂), methane (CH₄), nitrous oxide (N₂O), and several high-GWP gases, such as HFCs, perfluorocarbons (PFCs), and sulfur hexafluoride (SF₆). Water vapor is by far the most common, with an atmospheric concentration of nearly 1 percent, compared with less than 0.04 percent for carbon dioxide. The effect of human activity on global water vapor concentrations is considered negligible, however, and anthropogenic (human-made) emissions of water vapor are not factored into national greenhouse gas emission inventories for the purposes of meeting the requirements of the United Nations Framework Convention on Climate Change (UNFCCC) or the Kyoto Protocol.⁸ Concentrations of other greenhouse gases, such as methane and nitrous oxide, are a fraction of that for carbon dioxide (Table 2).

Scientists recognized in the early 1960s that concentrations of carbon dioxide in the Earth’s atmosphere were increasing every year. Subsequently, they discovered that atmospheric concentrations of methane, nitrous oxide, and many high-GWP greenhouse gas chemicals also were rising. Because current concentrations of greenhouse gases keep the Earth at its present temperature, scientists began to postulate that increasing concentrations of greenhouse gases would make the Earth warmer.

In computer-based simulation models, rising concentrations of greenhouse gases nearly always produce an increase in the average temperature of the Earth. Rising temperatures may, in turn, produce changes in weather and in the level of the oceans that might prove disruptive to current patterns of land use and human settlement, as well as to existing ecosystems. To date, however, it has proven difficult to disentangle the human impact on climate from normal temporal and spatial variations in temperature on both a global scale and geologic timeframe. The most recent report of the Intergovernmental Panel on Climate Change (IPCC), an international assemblage of scientists commissioned by the United Nations to assess the scientific, technical, and socioeconomic information relevant for the understanding of the risk of human-induced climate change, estimates that the global average surface temperature has increased by 0.6 ± 0.2^o Celsius since the late 19th century.⁹ The IPCC goes on to conclude that: “There is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities.”¹⁰

Greenhouse Gas Sources and Sinks

Most greenhouse gases have both natural and human-made emission sources, and there are significant natural mechanisms (land-based or ocean-based “sinks”) for removing them from the atmosphere; however, increased levels of anthropogenic emissions have pushed the total level of greenhouse gas emissions (both natural and anthropogenic) above their natural absorption rates. The positive imbalance between emissions and absorption has resulted in the continuing growth in atmospheric concentrations of these gases. Table 3 illustrates the relationship between anthropogenic and natural emissions and absorption of the principal greenhouse gases on an annual average basis during the 1990s.

Relative Forcing Effects of Various Gases

The ability of a greenhouse gas to affect global temperatures depends not only on its radiative or heat-trapping properties but also on its lifetime or stability in the atmosphere. Because the radiative properties and lifetimes of greenhouse gases vary greatly, comparable increases in the concentrations of different greenhouse gases can have vastly different heat-trapping effects. The cumulative effect (radiative forcing—measured in watts per square meter) can vary substantially from the marginal impact of a gas. For example, among the “Kyoto gases,” carbon dioxide is the most prominent in terms of emissions, atmospheric concentration, and radiative forcing (1.46 watts per square meter), but it is among the least effective as a greenhouse gas in terms of the marginal impact of each additional gram of gas added to the atmosphere. Other compounds, on a gram-per-gram basis, appear to have much greater marginal effects.

There has been extensive study of the relative effectiveness of various greenhouse gases in trapping the Earth’s heat. Such research has led to the development of the concept of a “global warming potential,” or GWP. The GWP is intended to illustrate the relative impacts on global warming of an additional unit of a given gas relative to carbon dioxide over a specific time horizon. The IPCC has conducted an extensive research program aimed at summarizing the effects of various greenhouse gases through a set of GWPs. The results of that work were originally released in 1995 in an IPCC report, Climate Change 1994,¹¹ and subsequently updated in Climate Change 1995¹² and Climate Change 2001.¹³

The calculation of a GWP is based on the radiative efficiency (heat-absorbing ability) of the gas relative to the radiative efficiency of the reference gas (carbon dioxide), as well as the removal process (or decay rate) for the gas relative to the reference gas over a specified time horizon. Table 4 summarizes the consensus results of the most recent studies by scientists working on behalf of the IPCC, showing estimates of atmospheric lifetimes and global warming potentials across various time scales. For the purposes of calculating “CO₂ equivalent” units for this report, 100-year GWPs are used.

Current U.S. Climate Change Initiatives

Federal Initiatives

The Bush Administration is pursuing a broad range of strategies to address the issues of global climate change through the implementation of multiple new initiatives. Details of these initiatives were initially provided on February 14, 2002, when the President announced the Global Climate Change Initiative. This initiative sets a national goal for the United States to reduce its greenhouse gas intensity (total greenhouse gas emissions per unit of gross domestic product [GDP]) by 18 percent between 2002 and 2012 through voluntary measures.

To meet this goal and encourage the development of strategies and technologies that can be used to limit greenhouse gas emissions both at home and abroad, the Administration has implemented a number of related initiatives, including the following:¹⁴

• Climate Change Technology Program (CCTP): The CCTP is a multi-agency program to accelerate the development and deployment of key technologies that can achieve substantial reductions in greenhouse gas emissions. The program’s most recent Strategic Plan was released in September 2006.¹⁵ The CCTP coordinates and prioritizes the Federal Government’s portfolio of investments in climate-related technology research, development, demonstration, and deployment (RDD&D), which totals about $3 billion for 2006. It also takes a century-long look at the nature of the climate change challenge and the potential for technological solutions across a range of uncertainties. The technologies outlined in the 2006 Strategic Plan include hydrogen, biorefining, clean coal, carbon sequestration, and nuclear fission and fusion, among others.

• Climate Change Science Program (CCSP): The CCSP was launched in February 2002 as a collaborative interagency program under a new cabinet-level organization designed to improve the government-wide management of climate science and climate-related technology development. The core mission of the CCSP is to apply the best possible scientific knowledge to help manage climate variability and global climate change. The CCSP incorporates and integrates the U.S. Global Change Research Program (USGCRP) with the Administration’s U.S. Climate Change Research Initiative (CCRI).

The USGCRP was established by the Global Change Research Act of 1990 to enhance understanding of natural and human-induced changes in the Earth’s global environmental system; to monitor, understand, and predict global change; and to provide a sound scientific basis for national and international decisionmaking. The CCRI builds on the USGCRP, with a focus on accelerating progress over a 5-year period on the most important issues and uncertainties in climate science, enhancing climate observation systems, and improving the integration of scientific knowledge into policy and management decisions and evaluation of management strategies and choices. The CCSP Strategic Plan calls for a series of more than 20 synthesis and assessment reports. The most recent, Synthesis Product 2.2, was released on September 19, 2006, for public review and comment and is scheduled for completion in the first quarter of 2007.¹⁶

• International Cooperation: The United States is engaged in international efforts on climate change, both through multilateral and bilateral activities. Multilaterally, the United States is the largest donor to activities under the UNFCCC and the IPCC. Since 2001, the United States has launched bilateral partnerships with numerous countries on issues ranging from climate change science, to energy and sequestration technologies, to policy approaches.

• Asia-Pacific Partnership on Clean Development and Climate: In June 2005, the United States launched a new international effort, the Asia-Pacific Partnership on Clean Development and Climate, which involves the United States, Australia, China, India, Japan, and South Korea. The partnership will collaborate to promote the development, diffusion, deployment, and transfer of existing and emerging cost-effective, cleaner technologies and practices. Areas for collaboration may include energy efficiency, clean coal, integrated gasification combined cycle, liquefied natural gas, carbon capture and storage, combined heat and power, methane capture and use, civilian nuclear power, geothermal power, rural/village energy systems, advanced transportation, building and home construction and operation, bioenergy, agriculture and forestry, hydropower, wind power, solar power, and other renewables.¹⁷

• Methane to Markets Partnership: In July 2004, the United States announced the Methane to Markets Partnership. The partnership is an international initiative that advances cost-effective, near-term methane recovery and use as a clean energy source. Its goal is to reduce global methane emissions in order to enhance economic growth, strengthen energy security, improve air quality, improve industrial safety, and reduce emissions of greenhouse gases. Participating countries include Argentina, Australia, Brazil, Canada, China, Colombia, Ecuador, Germany, India, Italy, Japan, Mexico, Nigeria, Republic of Korea, Russia, Ukraine, United Kingdom, and the United States. The United States will commit up to $53 million to the partnership through 2009 for work with the private sector on sharing and expanding the use of profitable technologies to capture methane emissions that are now wasted in the course of industrial processes and use them as a new energy source.¹⁸

• Near-Term Greenhouse Gas Reduction Initiatives: The Federal Government administers a wide array of voluntary, regulatory, and incentive-based programs on energy efficiency, agricultural practices, and greenhouse gas reductions. Major initiatives announced by the Bush Administration include:

• Climate VISION Partnership: In February 2003, President Bush announced that 12 major industrial sectors and the membership of the Business Roundtable had committed to work with the EPA and three Federal departments (Energy, Transportation, and Agriculture) to reduce greenhouse gas emissions in the next decade. Participating industries include electric utilities; petroleum refiners and natural gas producers; automobile, iron and steel, chemical, and magnesium manufacturers; forest and paper producers; railroads; and the cement, mining, aluminum, lime, and semiconductor industries. In May 2005, the Industrial Minerals Association–North America joined the list of participating industries.

• On February 14, 2006, the Climate VISION partners held a workshop to hear from industry sectors on activities they have undertaken to reduce energy usage and greenhouse gas emissions intensity. The purpose of the workshop was to provide an opportunity for current and prospective industry partners to share experiences and lessons learned through case studies and to explore new opportunities for collaboration.¹⁹

• Climate Leaders: Climate Leaders, established by the EPA in February 2002, is a voluntary partnership that encourages companies to establish and meet clearly defined targets for greenhouse gas emission reductions. Climate Leaders Partners represent a variety of sectors, from heavy manufacturing to banking and retail. As of October 2006, the program had 103 Partners, 59 of which had publicly announced greenhouse gas emission reduction goals. The rest were in the process of completing emissions inventories before setting their reduction goals. (In January 2006, the EPA announced that 5 Partners had achieved their initial reduction goals.) The EPA estimates that emissions reductions by Climate Leaders Partners will prevent emissions equivalent to more than 9 million metric tons of carbon per year—enough to offset annual emissions from more than 6 million cars.²⁰

• Voluntary Reporting of Greenhouse Gases Program: As part of the Climate Change Initiative, announced by President Bush on February 14, 2002, the U.S. Department of Energy (DOE) has developed new reporting guidelines to improve and expand the Voluntary Reporting of Greenhouse Gases Program administered by EIA. The current program has in excess of 200 participating companies, whose emissions represent approximately 13 percent of total U.S. greenhouse gas emissions.²¹ The primary goal of the DOE effort is to create a credible and transparent program for the reporting of real reductions that support the national greenhouse gas intensity goal laid out in the President’s Global Climate Change Initiative.

On April 21, 2006,²² DOE issued final General and Technical Guidelines for the revised Voluntary Reporting of Greenhouse Gases Program, which became effective on June 1, 2006. EIA is currently in the process of developing new reporting forms and instructions, with the goal of finalizing the forms by end of calendar year 2006.²³ New electronic reporting software is also in development, and the new program is intended to be operational in mid-2007.

California State Initiative

California Assembly Bill 32, “California Global Warming Solutions Act of 2006,” which was signed into law by Governor Arnold Schwarzenegger on September 27, 2006,²⁴ calls for a 25-percent reduction in the State’s carbon dioxide emissions by 2020. The first major controls, for the industrial sector, are scheduled to take effect in 2012. The plan grants the California Air Resources Board lead authority for establishing how much industry groups contribute to global warming pollution, assigning emission targets, and setting noncompliance penalties. It sets a 2009 date for establishing how the system will work and then allows 3 years for the State’s industries to prepare for the 2012 startup of mandatory emissions reductions.²⁵

International Developments in Global Climate Change

The primary international agreement addressing climate change is the UNFCCC, which opened for signature at the “Earth Summit” in Rio de Janeiro, Brazil, in June 1992 and entered into force in March 1994.²⁶ The agreement currently has 185 signatories, including the United States. The objective of the Framework Convention is stated as follows:

The ultimate objective of this Convention and any related legal instruments that the Conference of the Parties may adopt is to achieve, in accordance with the relevant provisions of the Convention, stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system.²⁷

The Framework Convention divided its signatories into three groups: the countries listed in Annex I; Annex II, which comprises the Annex I countries minus the countries with economies in transition; and non-Annex I countries, which include countries that ratified or acceded to the UNFCCC but are not included in Annex I. The Annex I countries include the 24 original members of the OECD (including the United States), the European Union, and 14 countries with economies in transition (Russia, Ukraine, and Eastern Europe).²⁸

The Convention requires all parties to undertake “policies and measures” to limit emissions of greenhouse gases, and to provide national inventories of emissions of greenhouse gases (Article 4.1a and b). Annex I parties are further required to take actions “with the aim of returning . . . to their 1990 levels these anthropogenic emissions of carbon dioxide and other greenhouse gases” (Article 4.2a and b). The signatories subsequently agreed that Annex I parties should provide annual inventories of greenhouse gas emissions.

The Kyoto Protocol

The Kyoto Protocol to the UNFCCC, negotiated in December 1997, is a set of quantified greenhouse gas emissions targets for Annex I countries, which collectively are about 5 percent lower than the 1990 emissions of those countries taken as a group.²⁹ Developing country signatories do not have quantified targets.³⁰ The conditions for ratification of the Kyoto Protocol were met in November 2004, following formal acceptance by the Russian Parliament and President Putin’s signing of the ratifying legislation. Those actions brought the number of ratifying countries to 118, with Annex I countries representing 61.2 percent of total Annex I carbon dioxide emissions in 1990. As of September 28, 2006, 166 states or “regional economic integrating organizations” had ratified the Protocol, which entered into force in February 2005. While the United States is a party to the Framework Convention, it is not a party to the Kyoto Protocol.

Recent and Upcoming Conferences of the Parties and Other International Events

Since the negotiation of the Kyoto Protocol in 1997, much of the work done at periodic (usually annual) meetings of the UNFCCC Conference of the Parties (COP) has been focused on filling in details related to the operation of the UNFCCC, the Protocol, and their respective mechanisms.

COP-11 and MOP-1

Canada hosted the first Meeting of the Parties to the Kyoto Protocol (MOP-1) in conjunction with the eleventh meeting of the Conference of Parties to the Framework Convention (COP-11). The meetings were held in Montreal, Canada, from November 28 to December 9, 2005.³¹ Two key outcomes emerged from the meetings. In MOP-1, the parties finalized the Kyoto Protocol “rulebook,” strengthened the Protocol’s Clean Development Mechanism (CDM), and agreed to begin negotiations on binding requirements for developing countries. In COP-11, agreement was reached on opening a non-binding dialogue on long-term cooperation among the parties to meet the goals of the UNFCCC.³²

COP-12 and MOP-2

Kenya will host the second Meeting of the Parties to the Kyoto Protocol (COP/MOP-2), in conjunction with the twelfth session of the Conference of the Parties to the Climate Change Convention (COP-12) in Nairobi, Kenya, from November 6 to November 17, 2006.

G8 Summit in St. Petersburg, Russia

In a communiqué on global energy security,³³ the leaders of the G8 nations³⁴ meeting in St. Petersburg, Russia, July 16-19, 2006, summarized their position on climate change and sustainable development, including the following:

• “We reaffirm our intention to deliver on commitments made in Gleneagles³⁵ in order to meet our shared and multiple objectives of reducing greenhouse gas emissions . . . .”

• “We also affirm our commitment to the UNFCCC’s ultimate objective of stabilizing greenhouse gas concentrations in the atmosphere at a level that prevents dangerous anthropogenic interference with the climate system.”

• “Those of us committed to making the Kyoto Protocol a success underline the importance we attach to it, view Clean Development Mechanism and the Joint Implementation Mechanism as central elements of this, and look forward to the process to develop it further.”

• “We welcome the progress made at the XI Conference of the Parties to the UNFCCC (Montreal, December 2005) where we committed to engage in a dialogue on long-term cooperative action to address

• climate change by enhancing implementation of the convention . . . .”

• “We reaffirm the importance of the work of the Intergovernmental Panel on Climate Change (IPCC) and look forward to its 2007 report.”

• “We welcome the progress made by the World Bank and the IEA on developing a framework for clean energy and sustainable development and on identifying alternative energy scenarios and strategies to support and implement elements of the Gleneagles Plan of Action.”

• “We welcome the progress made at the first meeting of the Gleneagles Dialogue on Climate Change, Clean Energy and Sustainable Development, held on 1 November last year. We look forward to the next Ministerial meeting in Mexico in October 2006, where we will continue to identify opportunities for greater collaboration to tackle climate change . . . .”

Chapter 1: Notes and Sources

Tables 1-4