Understanding the atmospheric phenomenon known as the greenhouse effect is critical to understanding global climate change. The Earth's atmosphere includes various gases--water vapor, carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O)--that collectively act as a greenhouse by preventing too much heat from escaping from the Earth's atmosphere and are therefore classified as greenhouse gases (GHGs). Other powerful GHGs that result from industrial processes and are not naturally occurring include hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF6). GHGs are essential for regulating our climate because they absorb and hold heat from the sun in the atmosphere around the Earth. The climate control process begins with a wave of solar radiation passing through the atmosphere. Most of this radiation is absorbed by the Earth's surface, but some of the energy is reflected off the Earth's surface back into space as infrared radiation, which has a longer wavelength than solar radiation. Infrared waves can be trapped by GHGs, helping to keep the planet at a temperature suitable for life.