percent of TgCO2Eq.
Key: GHG = greenhouse gas. TgCO2 Eq. = teragrams of carbon dioxide equivalent. A teragram = 1 million metric tons.
Note: Percents do not add to 100 due to rounding.
Source: U.S. Environmental Protection Agency, Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2011, available at www.epa.gov/climatechange/ghgemissions/usinventoryreport.html as of August 2013.