The Inventory of U.S. Greenhouse Gas Emissions and Sinks tracks the national trend in greenhouse gas emissions and removals back to 1990. The key findings of the 1990-2012 U.S. Inventory include: In 2012, U.S. greenhouse gas emissions totaled 6,526 million metric tons CO2 Eq.; U.S. emissions decreased by 3.4 percent from 2011 to 2012. Recent trends can be attributed to multiple factors including reduced emissions from electricity generation, improvements in fuel efficiency in vehicles with reductions in miles traveled, and year-to-year changes in the prevailing weather; and Greenhouse gas emissions in 2012 were 10 percent below 2005 levels.