Since 1990, U.S. greenhouse gas emissions have grown at an average annual rate of 0.4 percent, said the EIA, the statistical and analytical agency within the U.S. Department of Energy.
But in 2009, total U.S. greenhouse gas emissions were 6,576 million metric tons carbon dioxide equivalent, or MMTCO2e, a drop of 5.8 percent from the 2008 level.
This is the largest percentage decline in total U.S. greenhouse gas emissions since 1990, the starting year for EIA's data on total greenhouse gas emissions.
"The large decline in emissions in 2009 was driven by the economic downturn, combined with an ongoing trend toward a less energy-intensive economy and a decrease in the carbon-intensity of the energy supply," said EIA Administrator Richard Newell.
Emissions of energy-related carbon dioxide decreased by 7.1 percent in 2009, having risen at an average annual rate of 0.8 percent per year from 1990 to 2008.
Gavins Point Dam on the Upper Missouri River (Photo courtesy USACE)
Among the factors that influenced the emissions decrease was a decline in Gross Domestic Product (GDP) of 2.6 percent.
The energy intensity of the U.S. economy, measured as energy consumed per dollar of GDP, fell by 2.2 percent in 2009.
Year-to-year declines in energy intensity are relatively common, said Newell.
There was also a decline in the carbon dioxide intensity (CO2 per unit of energy) of U.S. energy supply in 2009, caused primarily by a drop in the price of natural gas relative to coal that led to more natural gas consumed for the generation of electricity, according to the report.
Also contributing was an increase in renewable energy consumption, led by wind and hydropower.
Methane emissions increased by 0.9 percent, while nitrous oxide emissions fell by 1.7 percent in 2009.
Based on partial data constituting about 77 percent of the category, combined emissions of HFCs, PFCs and SF6 increased by 4.9 percent.
Total estimated U.S. greenhouse gas emissions in 2009 consisted of:
EIA also publishes ongoing monthly estimates of carbon dioxide emissions from the consumption of energy.
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