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greenhouse effect:see global warmingglobal warming,
the gradual increase of the temperature of the earth's lower atmosphere as a result of the increase in greenhouse gases since the Industrial Revolution. Global warming and its effects, such as more intense summer and winter storms, are also referred to as climate
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greenhouse effectA phenomenon in which a rise in temperature is caused because incoming radiation at certain wavelengths can pass through a barrier, be absorbed, and then re-emitted as radiation at longer wavelengths, which is absorbed by the barrier. In a glass greenhouse, solar radiation in the form of visible and (some) ultraviolet radiation is able to pass through the Earth's atmosphere and through the glass of the greenhouse. The radiation is absorbed by any surface it falls on, causing a rise in temperature. As a result these surfaces emit heat radiation (i.e. electromagnetic radiation in the infrared), which is absorbed by the glass, causing an overall increase in temperature inside the greenhouse. The analogous process occurs for a planet with the ‘glass' being the planet's atmosphere. On Earth, for example, the atmosphere allows visible and ultraviolet through, but certain gases in the atmosphere absorb strongly in the infrared. These so-called greenhouse gases include water vapor (the main greenhouse gas), carbon dioxide, and methane. The greenhouse effect is not a bad thing – it is essential for keeping the Earth warm enough to support life. However, in recent times environmentalists have become concerned about the phenomenon of global warming, i.e. an increase of 0.3–0.6°C in the average temperature of air at the Earth's surface since the late 19th century. This could be a part of a natural cycle (essentially the end of the last ‘Little Ice Age’), but there is evidence that this global warming could be the result of the greenhouse effect. The main suspect is carbon dioxide. The concentration of carbon dioxide in the atmosphere has risen by 25–30 % over the last 200 years as a result of human activity – deforestation and the burning of fossil fuels (coal, oil, and natural gas). Levels of methane in the atmosphere have also doubled in the last 100 years. There is a fear that an excess of greenhouse gases in the atmosphere will heat the planet too much and adversely affect weather patterns. A runaway greenhouse effect is responsible for the high surface temperature of Venus, where no water exists and life is impossible. A greenhouse effect also operates in the deep atmospheres of the giant planets and on Saturn's large satellite Titan.
the atmosphere’s property of transmitting solar radiation while holding back terrestrial radiation, thereby contributing to the accumulation of heat by the earth. The atmosphere is comparatively quite transparent to shortwave solar radiation, which is almost entirely absorbed by the earth’s surface, since the albedo of the surface is generally low. The surface of the earth heats up by absorbing solar radiation and becomes a source of terrestrial, chiefly longwave, radiation. The atmosphere does not transmit this radiation very well and, in fact, almost completely absorbs it. Because of the greenhouse effect, when there is a clear sky only about 10–20 percent of the terrestrial radiation is able to pass through the atmosphere into outer space.