Total emissions of the six main greenhouse gases in 2007 were equivalent to 7,150 million metric tons of carbon dioxide. These gases include carbon dioxide, methane, nitrous oxide, hydrofluorocarbons, perfluorocarbons and sulfur hexafluoride. The report indicates that overall emissions have grown by 17.2 percent from 1990 to 2007. The increase in emissions in 2007 was due primarily to an increase in carbon dioxide emissions associated with fuel and electricity consumption.
The following factors were primary contributors to this increase:
(1) increased demand for heating fuels and electricity due to cooler winter and warmer summer conditions in 2007 than in 2006;
(2) increased consumption of fossil fuels to generate electricity; and
(3) a significant decrease (14.2 percent) in hydropower generation used to meet this demand.
EPA prepares the annual report in collaboration with experts from multiple federal agencies and after gathering comments from a broad range of stakeholders across the country. The inventory tracks annual greenhouse gas emissions at the national level and presents historical emissions from 1990 to 2007. The inventory also calculates carbon dioxide emissions that are removed from the atmosphere by “sinks,” e.g., through the uptake of carbon by forests, vegetation and soils. Information on the greenhouse gas inventory report