U.S. EPA submits 2003 greenhouse gas inventory to U.N.

May 1, 2005

The US Environmental Protection Agency (EPA) has released an official annual report to the United Nations (UN) on greenhouse gas emissions in the United States. The report is drafted, held for 30 days of public comment, then released to the Secretariat of the UN Framework Convention on Climate Change (UNFCCC) each year in April.

This year's report is the ninth since the EPA began producing the emissions inventory in 1997, after the US signed and ratified the UNFCCC in 1992. The UNFCCC, a legally non-binding treaty created to address global warming, is not as well known as the Kyoto Protocol, which is a more recently updated protocol based on that treaty. The United States did not ratify the Kyoto Protocol; however, it was ratified by 127 other nations and went into effect for them on February 16, 2005.

Major findings
The EPA report covers the period 1990-2003, with particular emphasis on the 2003 period (there is a one-year delay in preparation). Major findings include:
 * Between 1990 and 2003, US emissions increased overall by 13 percent, during which time the US economy has grown at a comparatively higher rate of 46 percent; one can conclude from these figures that the economy is becoming more efficient at making monetary profits (economic output) relative to its greenhouse gas emissions. This relative growth is illustrated in the first graph above (click the graph to enlarge for readability).  The graph shows that emissions per person (or "per capita") is holding steady, but emissions per unit of economic output is decreasing as economic output (or Real Gross Domestic Product, called Real GDP) rises strongly and steadily.
 * From 2002 to 2003, US emissions increased overall by 0.6 percent. A year-to-year comparison and overall growth of US emissions is shown in the graph below (click the graph to enlarge).  In two different years, 1991 and 2001, the greenhouse gas emissions actually decreased; however, the general overall trend continues to be toward increasing emissions.  You may recall that 2001 was a year of economic setbacks for the US, with a stock market crisis and the destruction of the World Trade Center on 9/11, which no doubt contributed to the temporary reduction of emissions.

The period beginning in 1990 is of interest, since that is the period addressed by the Kyoto Protocol, which attempts to reduce the average greenhouse gas emissions for each country to 5.2 percent below 1990 levels.



Gases covered
Gases covered in the report included six major greenhouse gases. The first three gases are produced both naturally and by human activity, but the last three gases are mainly produced by human activity:
 * Carbon dioxide (chemical formula CO 2 ); in 2003, 95 percent of carbon dioxide emissions in the United States were produced by the combustion of fuel.
 * Methane (chemical formula CH 4 ), mainly from natural and agricultural sources. This gas has 20 times the potential effect on global warming as carbon dioxide; however, methane levels in the United States have been declining steadily since 1990.
 * Nitrous oxide (chemical formula N 2 O), commonly known as "laughing gas" for its effect when inhaled. This gas has 200 times the potential effect on global warming as carbon dioxide, if you consider equal amounts of each gas; however, the total amount of nitrous oxide currently in the atmosphere is much less.
 * Hydrochlorofluorocarbon (HCFCs) and chlorofluorocarbons (CFCs)
 * Perfluorocarbons (PFCs)
 * Sulfur hexafluoride

About 80% of the total emissions came from the burning of fossil fuels. Other major natural greenhouse gases are water vapor (H 2 O), which actually traps more heat in the atmosphere than all the listed gases combined; and ozone (O 3 ), a gas well-known for a "hole" in the ozone layer being discovered over the earth's polar regions in recent decades.

Background Reading

 * global warming - introductory NPOV article on global warming, including an extensive list of references to external sources, classified by their likely biases