Carbon dioxide emissions from all sources in the U.S. peaked in 2007 at 6.02 gigatonnes and "have since fallen by an estimated 13% and in 2012 were likely at their lowest since 1994," according to the findings of a new report by Bloomberg New Energy Finance, the "Sustainable Energy in America 2013 Factbook," available for free download online here. Below is a graph of U.S. carbon dioxide emissions included in the report:
The change came as the U.S. slowly but steadily ratcheted up its dependence on natural gas and renewable energy sources (solar, wind), while decreasing its reliance on other sources of power, namely fossil fuels like coal and oil. Primarily, the U.S. has shifted its power sector "from a coal-heavy fleet to one drawing increasingly on gas," the report notes, and the "decrease in coal-related emissions has more than offset the increase in gas-related emissions." Read the report in full here.
(H/T: Yale e360)
Correction: This post originally stated "other renewable energy sources," implying natural gas was renewable. While biogas, a separate compound, is renewable, natural gas is not. We have since updated the error in copy and regret it.