Gases that trap the heat of the sun in the Earth's atmosphere, producing the greenhouse effect. The two major greenhouse gases are water vapor and carbon dioxide. Other greenhouse gases include methane, ozone, chlorofluorocarbons, and nitrous oxide?.

Total U.S. greenhouse gas emissions were 7,053 million metric tons carbon dioxide equivalent MMTCO2e in 2008¹, a decrease of 2.2% from the 2007 level, according to a report released in December 2009 by the U.S. Energy Information Administration.

Since 1990, U.S. GHG emissions have grown at an average annual rate of 0.7%. Total estimated U.S. GHG emissions in 2008 consisted of:
* 5,839.3 million metric tons of carbon dioxide or 82.8% of total emissions
* 737.4 MMTCO2e of methane or 10.5% of total emissions
* 300.3 MMTCO2e of nitrous oxide? or 4.3% of total emissions
* 175.6 MMTCO2e of hydrofluorocarbons? also known as HFCs?, perfluorocarbons? PFCs?, and sulfur hexafluoride? SF6? which together were 2.5% of total emissions

Emissions of energy-related carbon dioxide decreased by 2.9% in 2008, having risen at an average annual rate of 1.0% per year from 1990 to 2007. Factors that influenced the emissions decrease included record-high oil prices and a decline in economic activity in three out of four quarters of the year.

Oil-related emissions declined by 5.9% in 2008, accounting for the bulk of overall reduction in energy-related carbon dioxide emissions. The 2.9% decline in 2008 energy-related carbon dioxide emissions reflects the combined effects of a 0.4-percent increase in Gross Domestic Product GDP?, a 2.5% decrease in energy use per dollar of GDP, and a 0.8% decrease in carbon dioxide emissions per unit of energy.

Methane emissions increased by 2.0%, while nitrous oxide emissions rose by 0.1% in 2008. Based on partial data constituting about 85% of the category, combined emissions of HFCs, PFCs and SF6 increased by 3.1%.

References and external links:

¹ Emissions of Greenhouse Gases in the United States - a report by the EIA