U.S. Greenhouse Gas Emissions Rose by 1.4 Percent in 2007

The figures are contained in an annual report titled, "Emissions of Greenhouse Gases in the United States 2007," released today by the Energy Information Administration, the independent statistical and analytical agency within the U.S. Department of Energy.

Since 1990, U.S. greenhouse gas emissions have grown at an average annual rate of 0.9 percent.

U.S. greenhouse gas emissions per unit of gross domestic product, known as greenhouse gas intensity, fell from 636 metric tons per million 2000 constant dollars of Gross Domestic Product in 2006 to 632 million metric tons carbon dioxide equivalent per million dollars of GDP in 2007 - a decline of 0.6 percent from the 2006 level.

Reliant Energy's coal-fired Pleasants power plant in West Virginia (Photo by Stefan Schlöhmer)

Since 1990, the annual average decline in greenhouse gas intensity has been 1.9 percent.

The United States keeps track of six greenhouse gases - the same six gases governed by the Kyoto Protocol, an international treaty limiting greenhouse gas emissions which the U.S. government signed but never ratified.

The six gases are carbon dioxide, methane, nitrous oxide, hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride.

Total estimated U.S. greenhouse gas emissions in 2007 consisted of 6,022 million metric tons of carbon dioxide, which represents 82.6 percent of the total greenhouse gases emitted from U.S. sources.

In 2007, the U.S. emitted 700 million metric tons carbon dioxide equivalent of methane (9.6 percent of total emissions); 384 million metric tons carbon dioxide equivalent of nitrous oxide (5.3 percent of total emissions); and 177 million metric tons carbon dioxide equivalent of hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride (2.4 percent of total emissions).

Burning of the fossil fuels coal, oil and gas as well as deforestation leads to higher carbon dioxide concentrations in the atmosphere.

Emissions of carbon dioxide from energy consumption and industrial processes, which had risen at an average annual rate of 1.1 percent per year from 1990 to 2006, increased by 1.3 percent in 2007.

Unfavorable weather patterns, where both heating and cooling degree-days were higher in 2007 than 2006, and an increase in the carbon intensity of electricity generation, driven by decreased availability of hydropower, both contributed to higher energy-related carbon dioxide emissions in 2007, explains the Energy Information Administration report.

Methane emissions increased by 1.9 percent, while nitrous oxide emissions rose by 2.2 percent.

Methane is emitted by livestock enteric fermentation and manure management, paddy rice farming, land use and wetland changes, pipeline losses, and covered vented landfill emissions, leading to higher methane atmospheric concentrations.

Agricultural activities, including the use of fertilizers, lead to higher nitrous oxide concentrations in the atmosphere.

Emissions of HFCs, PFCs, and SF6, a group labeled collectively as "high-GWP gases" because of their high heat-trapping capabilities, increased by 3.3 percent. These last three are human-made gases, sometimes called potent industrial greenhouse gases or fluorinated greenhouse gases.

HFCs, PFCs and SF6 have extremely high global warming potentials and are being emitted at a rapidly increasing rate - predictions indicate worldwide emissions could rise 150 percent between 1995 and 2010.

U.S. energy-related carbon dioxide emissions are projected to increase at an average annual rate of 0.5 percent from 2005 to 2030, while emissions from the developing economies are projected to grow by 2.5 percent per year.

As a result, the U.S. share of world carbon dioxide emissions is projected to fall to 16 percent in 2030, down from about 21 percent of the world total in 2005.

According to a preliminary estimate by the Netherlands Environmental Assessment Agency, the largest national producer of carbon dioxide emissions since 2006 has been China with an estimated annual production of about 6200 megatonnes.

China is followed by the United States with about 5,800 megatonnes. Yet the per capita emission figures of China are still about one quarter of those of the U.S. population.

To read the full U.S. Energy Information Administration report click here.

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