U.S. Greenhouse Gas Emissions by Gas

In 2012, the United States emitted 6.5 billion metric tons of greenhouse gases (CO2e). Carbon dioxide accounted for the largest percentage of greenhouse gases (82%), followed by methane (9%), nitrous oxide (6%), and other greenhouse gases (3%). Total U.S. emissions for 2012 totaled 6,525 million metric tons of CO2e and net emissions, taking sinks into account, totaled 5,522 tons CO2e.

Source: Inventory of U.S. Greenhouse Gas Emissions and Sinks 1990-2012 (EPA 2014)