In 2009, the United States emitted over 6.5 billion metric tons of greenhouse gases (CO2E). Greenhouse gases are emitted by all sectors of the economy, including electric power (33% of total), transportation (28%), industry (20%), residential/commercial (12%), and agriculture (7%).
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Source: Inventory of U.S. Greenhouse Gas Emissions and Sinks 1990-2009 (EPA 2011)
Links:
[1] http://www.pewclimate.org/docUploads/US-emissions3.jpg