The major contributors to the decrease in emissions from 2011-2012 were said to be the decrease in energy consumption across all sectors in the US economy, and the decrease in carbon intensity for electricity generation due to fuel switching from coal to natural gas. Other factors included a decrease in transportation sector emissions attributed to an increase in fuel efficiency across different transportation modes and limited new demand for passenger transportation.
According to the report, GHG emissions in 2012 showed a 10% drop below 2005 levels. Total emissions of the six main greenhouse gases in 2012 were equivalent to 6,526 million tonnes of carbon dioxide. These gases include carbon dioxide, methane, nitrous oxide, hydrofluorocarbons, perfluorocarbons and sulphur hexafluoride.
Emissions of HFC23 during the production of HCFC22 was said to be a primary contributor to aggregate HFC emissions which increased by 114.3 Tg CO2e, or 309.6%, between 1990 and 2012.