The reduction was attributed to a decrease in fuel and electricity consumption across all U.S. economic sectors, and EPA release said Monday.
Total emissions of the six main greenhouse gases in 2009 -- carbon dioxide, methane, nitrous oxide, hydrofluorocarbons, perfluorocarbons and sulfur hexafluoride -- were equivalent to 7,311 million tons of carbon dioxide, the EPA said.
The EPA tracks annual greenhouse gases at the national level and also calculates carbon dioxide emissions that are removed from the atmosphere by carbon "sinks," for example through the uptake of carbon by forests, vegetation and soils.
The report indicates that despite the drop in 2009, overall emissions have grown by more than 7.3 percent from 1990 to 2009.
MAVEN now orbiting Mars