U.S. Greenhouse Gas Emissions by Gas

In 2010, the United States emitted over 6.8 billion metric tons of greenhouse gases (CO2e). Carbon dioxide accounted for the largest percentage of greenhouse gases (84%), followed by methane (10%), nitrous oxide (4%), and other greenhouse gases (2%). Total U.S. emissions for 2010 totaled 6,821 million metric tons of CO2e and net emissions, taking sinks into account, totaled 5,747 tons CO2e.

Source: Inventory of U.S. Greenhouse Gas Emissions and Sinks 1990-2010 (EPA 2012)