Total U.S. human-caused greenhouse gas emissions in 2009 were 5.8 percent below 2008 levels. The decline in total emissions—from 6,983 million metric tons carbon dioxide equivalent (MMTCO2e) in 2008 to 6,576 MMTCO₂e in 2009—was the largest since 1990 when emissions were first tracked , according to a new report from the Energy Information Administration.

EIA said the drop was largely the result of a 419 MMTCO2e drop in carbon dioxide (CO₂) emissions (7.1 percent). It reported an increase of 7 MMTCO2e (0.9 percent) in methane (CH₄) emissions and an increase of 8 MMTCO₂e (4.9 percent) based on partial data in emissions of man-made gases with high global warming potentials.

Emissions of nitrous oxide (N₂O) fell by 4 MMTCO₂e (1.7 percent).

The decrease in U.S. CO₂ emissions in 2009 resulted primarily from three factors: an economy in recession, a particularly hard-hit energy-intensive industries sector and a large drop in the price of natural gas that caused fuel switching away from coal to natural gas in the electric power sector.

Methane emissions totaled 731 MMTCO₂e in 2009, up by 7 MMTCO₂e (0.9 percent) from 2008. Increases in energy-related methane emissions (largely from underground coal mining) were offset by decreases in emissions from agricultural sources. Methane emissions from waste management systems rose by 7 MMTCO₂e, while industrial emissions declined by 0.4 MMTCO₂e.

Emissions of nitrous oxide dropped by 4 MMTCO₂e (1.7 percent) to 220 MMTCO₂e. The decrease came mainly from a reduction in energy-related emissions, as well as declines in industrial-related and agricultural nitrous oxide emissions.

Based on a partial estimate, U.S. emissions of high global warming potential gases totaled 178 MMTCO₂e in 2009. That was 8 MMTCO₂e (4.9 percent) above the 2008 level. Emissions of hydrofluorocarbons (HFCs) rose by 7 MMTCO₂e (5.4 percent) from 2008 to 2009.

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