U.S. Greenhouse Gas Emissions by Gas

In 2014, the United States emitted 6.9 billion metric tons of greenhouse gases (CO2e). Carbon dioxide accounted for the largest percentage of greenhouse gases (81%), followed by methane (10%), nitrous oxide (6%), and other greenhouse gases (3%). Total U.S. emissions for 2014 totaled 6,873 million metric tons of CO2e and net emissions, taking sinks into account, totaled 6,187 tons CO2e.

Source: Inventory of U.S. Greenhouse Gas Emissions and Sinks 1990-2014 (EPA 2016)