The Energy Information Administration report indicates that discharges of the warming gas from their principal sources within the U.S. is also 12 percent less than it was during 2007, when they reached a high point.
In 2007, total U.S. CO2 emissions were 6,023 million metric tons, while in 2012 they were 5,290 million metric tons. The trend line since 2007 has been generally downward, though emissions bumped up in 2010 following the recession of 2008-2009.
The data for 2009 showed the biggest decline in carbon dioxide emissions in any year since 1990, most likely because of the economic downturn.
The annualized rate of decline for 2012 was 3.8 percent.
Major drivers of the decline were improved fuel efficiency in motor vehicles, reduced use of coal as a source of electricity, and a winter that was less severe than usual, which resulted in less energy consumption for heating of homes and businesses.
The trend may not be permanent, though.
EIA also concluded that GHG emissions are on the rise again. So far in 2013, they are up by more than 2 percent over 2012. During future years, GHG emissions might keep going up because market forces could be encouraging a return to coal burning for electric power.
In addition, more reliance on shale gas could drive carbon dioxide pollution higher. A September report from the Stanford Energy Modeling Forum predicted that emissions would increase under any expected natural gas use scenario.
The trend could prevent the Obama administration from achieving its goal of a 17 percent reduction in GHG emissions by 2020. To meet that objective it will probably be necessary for EPA to finalize and implement regulations aimed at reducing the discharge of warming gases to the atmosphere.
