The U.S. Environmental Protection Agency (EPA) released its 20th Inventory of U.S. Greenhouse Gas Emissions and Sinks, showing a 2% increase in greenhouse gas emissions in 2013 from 2012 levels, but a 9% drop in emissions since 2005.

Total U.S. greenhouse emissions were 6,673 million metric tons of carbon dioxide equivalent in 2013. By sector, power plants were the largest source of emissions, accounting for 31% of total U.S. greenhouse gas pollution. The transportation sector was the second largest source, at 27%. Industry and manufacturing were the third largest source, at 21%. The increase in total national greenhouse gas emissions between 2012 and 2013 was due to increased energy consumption across all sectors in the U.S. economy and greater use of coal for electricity generation.

This year, EPA says it is publishing key data in an online Greenhouse Gas Inventory Data Explorer tool, which allows users to view, graph and download data by sector, year and greenhouse gas.

The agency prepares the inventory annually in collaboration with other federal agencies, and submits the report to the Secretariat of the United National Framework Convention on Climate Change every year on April 15. The Inventory presents historical emissions since 1990 and covers seven key greenhouse gases: carbon dioxide, methane, nitrous oxide, hydrofluorocarbons, perfluorocarbons, sulfur hexafluoride, and nitrogen trifluoride. In addition to tracking U.S. greenhouse gas emissions, the inventory also calculates carbon dioxide that is removed from the atmosphere through the uptake of carbon in forests and other vegetation. EPA has been publishing the inventory since 1994, but tracks back to 1990.

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