In 2009, the United States emitted over 6.5 billion metric tons of greenhouse gases (CO2E). Carbon dioxide accounted for the largest percentage of greenhouse gases (83%), followed by methane (10%), nitrous oxide (5%), and other greenhouse gases (2%). Total U.S. emissions for 2009 totaled 6,633 tons of CO2E and net emissions, taking sinks into account, totaled 5,618 tons CO2E.
[1]
Source: Inventory of U.S. Greenhouse Gas Emissions and Sinks 1990-2009 (EPA 2011)
Links:
[1] http://www.pewclimate.org/docUploads/facts-figure1-us-emissions.jpg