April 05, 2013
The assessment concludes that some 5.3 billion metric tons of CO2 were emitted from coal, natural gas, and oil consumption during the year, a 3.7 percent decline relative to 2011 and 12.1 percent below the peak of 6 billion tons hit in 2007. The EIA cited increased use of natural gas and falling consumption of coal as the primary reason for the drop in emissions of the greenhouse gas.
"The largest drop in emissions in 2012 came from coal, which is used almost exclusively for electricity generation," said the agency in a post on its web site. "During 2012, particularly in the spring and early summer, low natural gas prices led to competition between natural gas- and coal-fired electric power generators. Lower natural gas prices resulted in reduced levels of coal generation, and increased natural gas generation—a less carbon-intensive fuel for power generation, which shifted power generation from the most carbon-intensive fossil fuel (coal) to the least carbon-intensive fossil fuel (natural gas)."
Coal emissions fell 11.3 percent during 2012, while natural gas emissions rose 4.4 percent. Coal emissions are down nearly a quarter since their 2005 high.
The EIA also noted other factors behind the decline in emissions. Warmer winter temperatures — 2012 was the warmest year on record in the U.S. — and reduced demand for transport fuels also helped cut CO2 levels.
The U.S. is the world's second highest CO2 emitter after China, whose 2011 emissions were estimated at 8.6 billion tons.
CO2 emissions from human activity are primarily a product of fossil fuels use. Conversion of carbon dense landscapes like forests and peatlands is the second largest source of greenhouse gas emissions, accounting for 10-15 percent of total emissions annually.
According to scientists, carbon dioxide emissions are a key driver of the increase in temperatures observed globally over the past century.
Comparison of carbon emissions from six leading countries. Click image to enlarge.
Largest increase in carbon emissions. Click image to enlarge.
Largest percentage increase in carbon emissions. Click image to enlarge.
Largest decrease in carbon emissions. Click image to enlarge.
Largest percentage decrease in carbon emissions. Click image to enlarge.
Per capita carbon emissions. Click image to enlarge.
More information at Charts: comparing the largest carbon emitters.