Energy-related carbon dioxide emissions declined in 2012

"Energy-related carbon dioxide (CO₂) emissions in 2012 were the lowest in the United States since 1994, at 5.3 billion metric tons of CO₂ .
 With the exception of 2010, emissions have declined every year since 2007.
The largest drop in emissions in 2012 came from coal, which is used almost exclusively for electricity generation (see figure below). 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..."
Carbon Dioxide Emissions: 2012