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Emissions of Greenhouse Gases Report
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Overview
  Total Emissions | Greenhouse Gas Intensity | Greenhouse Gas Emissions in the U.S. Economy |
  U.S. Emissions in a Global Perspective | Recent U.S. and International Developments in Global Climate Change |
  Units for Measuring Greenhouse Gases

For the most recent Energy-Related CO2 Estimates (2007)
Report Chapters

Overview
Carbon Dioxide Emissions
Methane Emissions
Nitrous Oxide Emissions
High GWP Cases
Land-Use Emissions
New in This Report   

Latest Documentation
Total Emissions    
Total U.S. greenhouse gas emissions in 2006 were 1.5 percent below the 2005 total—the first annual drop since 2001 and only the third since 1990.
The total emissions reduction, from 7,181.4 million metric tons carbon dioxide equivalent (MMTCO2e) in 2005 to 7,075.6 MMTCO2e in 2006, was largely a result of reductions in carbon dioxide (CO2) emissions. There were smaller reductions in emissions of methane (CH4) and man-made gases with high global warming potentials (high-GWP gases) (Table 1 below).
U.S. carbon dioxide emissions in 2006 were 110.6 million metric tons (MMT) below their 2005 level of 6,045.0 MMT, due to favorable weather conditions; higher energy prices; a decline in the carbon intensity of electric power generation that resulted from increased use of natural gas, the least carbon-intensive fossil fuel; and greater reliance on non-fossil energy sources.
Methane emissions totaled 605.1 MMTCO2e in 2006 (Figure 1 on right), down by 2.3 MMTCO2e from 2005, with decreases in emissions from energy sources, agriculture, and industrial processes.
U.S. emissions of high-GWP gases, which totaled 157.6 MMTCO2e in 2006, were 3.6 MMTCO2e below the 2005 total, as the result of a drop in hydrofluorocarbon (HFC) emissions.
Emissions of nitrous oxide (N2O), unlike the other greenhouse gases, increased by 10.6 MMTCO2e from 2005 to a 2006 total of 378.6 MMTCO2e. The increase is attributed primarily to an increase of 9.9 MMTCO2e in emissions from agricultural sources.
In 2005, the latest year for which data are available, U.S. land use, land-use change, and forestry activities resulted in total carbon sequestration of 828.5 MMTCO2e, equal to 11.5 percent of U.S. greenhouse gas emissions in 2005.

Table 1. U.S. Emissions of Greenhouse Gases, Based on Global Warming Potential, 1990, 1995, and 1999-2006 (million metric tons carbon diioxide equivalent). Need help, contact the National Energy Information Center at 202-586-8800.


  
Figure 1. U.S. Greenhouse Gas Emissions by Gas, 2006. Need help, contact the National Energy Information Center at 202-586-8800.

U.S. Anthropogenic Greenhouse Gase Emissions, 1990, 2005, and 2006 Table. Need help, contact the National Energy Information Center at 202-586-8800.
Greenhouse Gas Intensity    
Total U.S. greenhouse gas emissions in 2006 were 1.5 percent below the 2005 total—the first annual dropsince 2001 and only the third since 1990.
From 2005 to 2006, the greenhouse gas intensity of the U.S. economy—measured as metric tons carbon dioxide equivalent (MTCO2e) emitted per million dollars of gross domestic product (GDP)—fell by 4.2 percent, the largest annual decrease since the 1990 base year.
Relatively robust economic growth in 2006, at 2.9 percent, coupled with a 1.5-percent drop in total greenhouse gas emissions, led to the decrease in greenhouse gas intensity (Table 2 below).
Some of the factors that led to the decrease (such as weather) are variable; others (such as increased use of renewable energy for electricity generation) may indicate trends that are likely to continue.
Since 2002, the base year for the Bush Administration’s emissions intensity reduction goal of 18 percent in a decade, U.S. greenhouse gas intensity has fallen by an average of 2.5 percent per year, resulting in a total reduction of almost 10 percent from 2002 to 2006.
The steady decrease in carbon intensity (carbon/GDP) has resulted mainly from reductions in energy use per unit of GDP (energy/GDP) rather than increased use of low-carbon fuels, as indicated by the carbon/energy ratio shown in Figure 2 at right.

Table 2. U.S. Greenhouse Gas Intensity and Related Factors, 1990, 1995, and 1999-2006. Need help, contact the National Energy Information Center at 202-586-8800.
Data for all years 1990-2006


 
Figure 2. Intensity Ratios: Carbon/Energy, Energy/GDP, and Carbon/GDP, 1980-2006. Need help, contact the Naational Energy Information Center at 202-586-8800.

U.S. Greenhouse Gas Intensity, 1990, 2005, and 2006 Table. Need help, contact the National Energy Information Center at 202-586-8800.
Greenhouse Gas Emissions in the U.S. Economy    

The diagram on right illustrates the flow of U.S. greenhouse gas emissions in 2006, from their sources to their distribution across the U.S. end-use sectors. The left side shows CO2 by fuel sources and quantities and other gases by quantities; the right side shows their distribution by sector. The center of the diagram indicates the split between CO2 emissions from direct fuel combustion and electricity conversion. Adjustments indicated at the top of the diagram for U.S. territories and international bunker fuels correspond to greenhouse gas reporting requirements developed by the United Nations Framework Convention on Climate Change (UNFCCC).

CO2. CO2 emission sources include energy-related emissions (primarily from fossil fuel combustion) and emissions from industrial processes. The energy subtotal (5,890 MMTCO2e) includes petroleum, coal, and natural gas consumption and smaller amounts from renewable sources, including municipal solid waste and geothermal power generation. The energy subtotal also includes emissions from nonfuel uses of fossil fuels, mainly as inputs to other products. Industrial process emissions (109 MMTCO2e) include cement manufacture, limestone and dolomite calcination, soda ash manufacture and consumption, carbon dioxide manufacture, and aluminum production. The sum of the energy subtotal and industrial processes equals unadjusted CO2 emissions (5,999 MMTCO2e). The energy component of unadjusted emissions can be divided into direct fuel use (3,546 MMTCO2e) and fuel converted to electricity (2,344 MMTCO2e).

Non-CO2 Gases. Methane (605 MMTCO2e) and nitrous oxide (379 MMTCO2e) sources include emissions related to energy, agriculture, waste management, and industrial processes. Other, high-GWP gases (158 MMTCO2e) include hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF6). These gases have a variety of uses in the U.S. economy, including refrigerants, insulators, solvents, and aerosols; as etching, cleaning, and firefighting agents; and as cover gases in various manufacturing processes.

Adjustments. In keeping with the UNFCCC, CO2 emissions from U.S. Territories (61 MMTCO2e) are added to the U.S. total, and CO2 emissions from fuels used for international transport (both oceangoing vessels and airplanes) (126 MMTCO2e) are subtracted to derive total U.S. greenhouse gas emissions (7,076 MMTCO2e).

Emissions by End-Use Sector. CO2 emissions by end-use sectors are based on EIA’s estimates of energy consumption (direct fuel use and purchased electricity) by sector and on the attribution of industrial process emissions by sector. CO2 emissions from purchased electricity are allocated to the end-use sectors based on their shares of total electricity sales. Non-CO2 gases are allocated by direct emissions in those sectors plus emissions in the electric power sector that can be attributed to the end-use sectors based on electricity sales.

Residential emissions (1,234 MMTCO2e) include energy-related CO2 emissions (1,217 MMTCO2e); and non-CO2 emissions (17 MMTCO2e). The non-CO2 sources include direct methane and nitrous oxide emissions from direct fuel use. Non-CO2 indirect emissions attributable to purchased electricity, including methane and nitrous oxide emissions from electric power generation and SF6 emissions related to electricity transmission and distribution, are also included.

Emissions in the commercial sector (1,287 MMTCO2e) include both energy-related CO2 emissions (1,056 MMTCO2e) and non-CO2 emissions (231 MMTCO2e). The non-CO2 emissions include direct emissions from landfills, wastewater treatment plants, commercial refrigerants, and stationary combustion emissions of methane and nitrous oxide. Non-CO2 indirect emissions attributable to purchased electricity, including methane and nitrous oxide emissions from electric power generation and SF6 emissions related to electricity transmission and distribution, are also included.

Industrial emissions (2,544 MMTCO2e) include CO2 emissions (1,777 MMTCO2e)—which can be broken down between combustion (1,668 MMTCO2e) and process emissions (109 MMTCO2e)—and non-CO2 emissions (767 MMTCO2e). The non-CO2 direct emissions include emissions from agriculture (methane and nitrous oxide), coal mines (methane), petroleum and natural gas pipelines (methane), industrial process emissions (methane, nitrous oxide, HFCs, PFCs and SF6), and direct stationary combustion emissions of methane and nitrous oxide. Non-CO2 indirect emissions attributable to purchased electricity, including methane and nitrous oxide emissions from electric power generation and SF6 emissions related to electricity transmission and distribution, are also included.

Transportation emissions (2,010 MMTCO2e) include energy-related CO2 emissions from mobile source combustion (1,885 MMTCO2e); and non-CO2 emissions (126 MMTCO2e). The non-CO2 emissions include methane and nitrous oxide emissions from mobile source combustion and HFC emissions from the use of refrigerants for mobile source air-conditioning units.

Distribution of Total U.S. Greenhouse Gas Emissions by End-Use Sector, 2006 Table. Need help, contact the National Energy Information Center at 202-586-8800.



 
Diagram illustrating the flow of U.s. greenhouse gas emissions in 2006, from their sources to their distribution across the U.S. end-use sectors. Need help, contact the National Energy Information Center at 202-586-8800.
Click Chart to Enlarge
U.S. Emissions in a Global Perspective    

In EIA’s 2005 emissions inventory report, total U.S. energy-related carbon dioxide emissions in 2004 (including nonfuel uses of fossil fuels) were estimated at 5,923.2 MMT. With the 2004 world total for energy-related carbon dioxide emissions estimated at 26,922 MMT, U.S. emissions were about 22 percent of the world total (see Table 3 below).

Carbon dioxide emissions related to energy use in 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—are estimated at 13,457 MMT, or about one-half of the world total. With the remaining 50 percent of worldwide energy-related carbon dioxide emissions (13,465 MMT) coming from non-OECD countries, 2004 marked the first year in which global emissions were split evenly between the OECD and non-OECD economies (Figure 3 at right).
In EIA’s International Energy Outlook 2007 (IEO2007) reference case, projections of energy use and emissions are sensitive to economic growth rates and energy prices. Projections for a range of alternative growth and price scenarios are presented in IEO2007.
U.S. energy-related carbon dioxide emissions are projected to increase at an average annual rate of 1.1 percent from 2004 to 2030, while emissions from the non-OECD economies are projected to grow by 2.6 percent per year. As a result, the U.S. share of world carbon dioxide emissions is projected to fall to 19 percent in 2030 (7,950 MMT out of a global total of 42,880 MMT) (Figure 4 at right).
Table 3. World Energy-Related Carbon Dioxide Emissions by Region, 1990-2030 (million metric tons carbon dioxide). Need help, contact the National Energy Information Center at 202-586-8800.

No data for all years
 
World Energy-Related Carbon Dioxide Emissions, 1990, 2004, and 2030 Table. Need help, contact the National Energy Information Center at 202-586-8800.

Figure 3. World Carbon Dioxide Emissions by Regio, 1990, 2004, 2020, and 2030 (Million metric tons carbon dioxide). Need help, contact the National Energy Information Center at 202-586-8800.

Figure 4. Regional Shares of World Carbon Dioxide Emissions, 1990, 2004, 2020, and 2030 (Percent of world total). Need help, contact the National Energy Information Center at 202-586-8800.
Recent U.S. and International Developments in Global Climate Change    
United States
In December 2005, seven Northeastern and Mid- Atlantic States issued a Memorandum of Understanding to implement the Regional Greenhouse Gas Initiative (RGGI), a multi-State agreement that establishes a cap-and-trade system for carbon dioxide emissions from electric power plants.1 RGGI aims to stabilize utilities’ CO2 emissions at current levels through 2015 and then reduce them by 10 percent by 2020. The first compliance period under RGGI begins January 1, 2009.2 In 2007, three additional States joined RGGI: Massachusetts and Rhode Island in January and Maryland in April.
On February 26, 2007, the Governors of Arizona, California, New Mexico, Oregon, and Washington signed an agreement establishing the Western Climate Initiative,3 a joint effort to reduce greenhouse gas emissions and address climate change. Since then, Utah and the Canadian Provinces of Manitoba and British Columbia have joined the initiative as full partners. Five U.S. States, three Canadian Provinces, and one Mexican State are observers.4 In August 2007, the partners released their regional greenhouse gas emissions reduction goal of 15 percent below 2005 levels by 2020.
On April 2, 2007, the U.S. Supreme Court, in Massachusetts v. the Environmental Protection Agency, ruled that section 202(a)(1) of the Clean Air Act gives the U.S. Environmental Protection Agency authority to regulate tailpipe emissions of greenhouse gases.5
On May 8, 2007, 31 U.S. States and one Tribal Nation signed on as charter members in the development of The Climate Registry (TCR), a voluntary, common system for entities to report greenhouse gas emissions.6 Founding members also include those States, Provinces, and Nations that joined TCR before the May 25, 2007, press release announcing the program.7 TCR will incorporate the California Climate Action Registry (CCAR), the Eastern Climate Registry, the Western Regional Air Partnership, and the Lake Michigan Air Directors Consortium (LADCO), making it the largest State- and Province-based effort to date to track greenhouse gas emissions.8 States that previously had passed reporting and registry legislation plan to roll their programs into TCR. As of October 2007, 9 additional U.S. States and the District of Columbia, 1 Mexican State, and 2 additional Tribal Nations had joined the effort.9
On May 14, 2007, President Bush issued a “Twenty in Ten” Executive Order, directing Federal agencies to write rules for expanding the alternative fuel mandate and boosting vehicle fuel efficiency standards. The rules are to be completed by December 2008.
Also in May 2007, the Chicago Climate Exchange (CCX) announced the formation of a California Climate Exchange to develop and trade financial products with the aim of helping the State meet its mandatory emissions reductions goals.10 In August 2007, Germany’s foreign minister met with California Governor Arnold Schwarzenegger to promote integra-tion of the European carbon market with the emissions trading scheme emerging in the western United States.11
Washington State Governor Christine Gregoire signed Substitute Senate Bill 6001 (SSB 6001) in May 2007, baseload electricity generation (similar to SB 1368 in California).12 Oregon is considering adopting a similar emissions performance standard for long-term power purchase agreements. Also in May 2007, Montana adopted a carbon dioxide emissions performance standard for electric generating units in the State.13 The State Public Utility Commission cannot approve generating units constructed after January 1, 2007, that are fueled primarily by coal unless a minimum of 50 percent of the carbon dioxide produced by the facilities is captured and sequestered.
At the local level, as of September 2007, 681 mayors from the 50 States, the District of Columbia, and Puerto Rico had signed on to the Climate Protection Agreement. Originally adopted in June 2005,14 the Agreement follows the Kyoto Protocol in setting a goal of reducing greenhouse gas emissions to 7 percent below 1990 levels by 2012.
As of October 2007, 210 U.S. cities had joined more than 800 local governments across the world in the Cities for Climate Protection (CCP) initiative run by the International Council for Local Environmental Initiatives (ICLEI).15 CCP assists cities in adopting policies and implementing quantifiable measures to reduce local greenhouse gas emissions, improve air quality, and enhance urban livability and sustainability.

International: United Nations Framework Convention on Climate Change and the Kyoto Protocol
COP-12 and COP/MOP-2
In November 2006, the Twelfth Conference of the Parties to the United Nation’s Framework Convention on Climate Change (COP-12) and the Second Meeting of the Parties to the Kyoto Protocol (COP/MOP-2) were held in Nairobi, Kenya. Key areas included:
Review of the implementation of the UNFCCC to inform the dialog on long-term mitigation measures (COP-12)
Adverse effects of climate change on developing and least developed countries (COP-12)
Financial mechanisms, national communications, technology transfer, and capacity building (COP-12)
Long-term action on post-2012 targets under the Kyoto Protocol (COP/MOP-2)
Russia’s proposal on voluntary commitments for developing countries (COP/MOP-2)
Review of effectiveness of commitments and implementation (COP/MOP-2)
Increased geographic equity in the use of the Clean Development Mechanism (COP/MOP-2)
First amendment to the Kyoto Protocol to include Belarus and Kazakhstan as Annex B countries with binding targets (COP/MOP-2).

COP-13 and CMP-3
Indonesia will host COP-13 and CMP-3 (shortened from COP/MOP) in Nusa Dua, Bali, December 3-14, 2007.
Among the agenda items to be included:
Implementation of the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (COP-13)
Financial mechanisms of the Convention (COP-13)
National communications (COP-13)
Development and transfer of technologies (COP-13)
Capacity building under the Convention (COP-13)
Implementation of the Buenos Aires program of work on adaption and response measures (COP-13)
Reducing emissions from deforestation in developing countries (COP-13)
Issues relating to the Clean Development Mechanism and Join Implementation (CMP-3)
Report of the Compliance Committee and of the administrator of the Kyoto Protocol International Transaction Log (CMP-3)
Proposal from Belarus to amend Annex B for its inclusion (CMP-3).
 




Units for Measuring Greenhouse Gases    

Emissions data are reported here in metric units, as favored by the international scientific community. Metric tons are relatively intuitive for users of English measurement units, because 1 metric ton is only about 10 percent heavier than 1 English short ton.

Throughout this report, emissions of carbon dioxide and other greenhouse gases are given in carbon dioxide equivalents. In the case of carbon dioxide, emissions denominated in the molecular weight of the gas or in carbon dioxide equivalents are the same. Carbon dioxide equivalent data can be converted to carbon equivalents by multiplying by 12/44.

Emissions of other greenhouse gases (such as methane) can also be measured in carbon dioxide equivalent units by multiplying their emissions (in metric tons) by their global warming potentials (GWPs). Carbon dioxide equivalents are the amount of carbon dioxide by weight emitted into the atmosphere that would produce the same estimated radiative forcing as a given weight of another radiatively active gas.

Carbon dioxide equivalents are computed by multiplying the weight of the gas being measured (for example, methane) by its estimated GWP (which is 23 for methane). In 2001, the Intergovernmental Panel on Climate Change (IPCC) Working Group I released its Third Assessment Report, Climate Change 2001: The Scientific Basis.16 Among other things, the Third Assessment Report updated a number of the GWP estimates that appeared in the IPCC’s Second Assessment Report.17 The GWPs published in the Third Assessment Report were used for the calculation of carbon dioxide equivalent emissions for this report. Generally, the level of total U.S. carbon dioxide equivalent emissions is 0.6 percent higher when the GWPs from the Third Assessment Report are used; however, the trends in growth of greenhouse gas emissions are similar for the two sets of GWP values. GWPs from the Second Assessment Report still are used for comparisons among countries.

    
   
Report Chapters

Overview
Carbon Dioxide Emissions
Methane Emissions
Nitrous Oxide Emissions
High GWP Cases
Land-Use Emissions
New in This Report   

Latest Documentation