Warming of the Earth's surface and lower atmosphere that tends to intensify with an increase in atmospheric carbon dioxide and certain other gases.
Visible light from the Sun heats the Earth's surface. Part of this energy is reradiated in the form of long-wave infrared radiation , much of which is absorbed by molecules of carbon dioxide and water vapour in the atmosphere and reradiated back toward the surface as more heat. This process is analogous to the glass panes of a greenhouse that transmit sunlight but hold in heat. The trapping of infrared radiation causes the Earth's surface and lower atmosphere to warm more than they otherwise would, making the surface habitable. The increase in atmospheric carbon dioxide caused by widespread combustion of fossil fuel s may intensify the greenhouse effect and cause long-term climatic changes. An increase in atmospheric concentrations of other trace gases such as chlorofluorocarbon s, nitrous oxide , and methane may also aggravate greenhouse conditions. It is estimated that since the beginning of the Industrial Revolution the amount of atmospheric carbon dioxide has increased 30%, while the amount of methane has doubled. Today the U.S. is responsible for about one-fifth of all human-produced greenhouse-gas emissions. See also global warming .