Greenhouse gases are gases that allow sunlight to enter the atmosphere freely but absorb infrared radiation and traps its heat in the atmosphere when sunlight is re-radiated back toward space. This trapping effect of heat is necessary for life on earth but since the industrial revolution , the amount of greenhouse gases has increased, causing a global warming and climate change.

There are 6 main types of greenhouse gases emitted in the U.S.:

• Carbon Dioxide
• Methane
• Nitrous Oxide
• Hydrofluorocarbons (HFCs)
• Perfluorocarbons (PFCs)
• Sulfur hexafluoride

To learn more, go to:
http://tonto.eia.doe.gov/energyexplained/index.cfm?page=environment_about_ghg