The effects of greenhouse gas emissions have become a more popular topic in the U.S. as environmental issues have been spotlighted.

Following are some facts and statistics about greenhouse gas emissions from the Energy Information Administration:

• In 2008, total U.S. greenhouse gas emissions decreased 2.2 percent compared with 2007, dropping from 7,209.8 million metric tons carbon dioxide equivalent to 7,052.6 million metric tons carbon dioxide equivalent.
• Petroleum is the largest fossil fuel source for energy-related carbon dioxide emissions, contributing 41.9 percent of the total. It is followed by coal, which contributes 36.5 percent of the total, and natural gas, which contributes 21.4 percent of the total.
• The greenhouse gas intensity of the U.S. economy—measured as metric tons carbon dioxide equivalent per million dollars of real gross domestic product—fell by 2.6 percent from 2007 to 2008. This improvement resulted from the decrease in total greenhouse gas emissions and economic growth of 0.4 percent.
• Total U.S. energy-related carbon dioxide emissions in 2006 were about 20 percent of the 2006 world total for energy-related carbon dioxide emissions.

High Country News offers some other facts about greenhouse gas emissions:

• Each mile of commercial air travel produces a little more than half a pound of carbon dioxide per person. Each passenger on a one-way flight from Denver to San Francisco is responsible for about 608 pounds of carbon dioxide emissions.
• Almost 20 pounds of carbon dioxide are emitted when burning a gallon of gasoline. A typical late-model, mid-sized sedan produces about 9,500 pounds of carbon dioxide each year; a hybrid car produces about 4,300 pounds.
• Preserving an average acre of forest in the U.S. keeps more than 260,000 pounds of carbon dioxide out of the atmosphere.
• Every ton of waste that is recycled instead of sent to a landfill keeps the equivalent of more than 6,500 pounds of carbon dioxide out of the atmosphere.
• In 2001, Portland, Ore., replaced about 13,300 incandescent traffic lights with LED lamps. The LED bulbs keep almost 5 million pounds of carbon dioxide out of the atmosphere each year. The cost of purchasing and installing the bulbs was recouped in less than three years, and the bulbs reportedly save about $400,000 in energy and maintenance costs each year.
• The average U.S. household puts about 35,000 pounds of carbon dioxide and other greenhouse gases into the atmosphere each year.

This Web exclusive information is a supplement to Capitol Hill.