The greenhouse effect refers to the change in the steady state temperature of a planet or moon by the presence of an atmosphere containing gas that absorbs and emits infrared radiation. Greenhouse gases, which include water vapor, carbon dioxide and methane, warm the atmosphere by efficiently absorbing thermal infrared radiation emitted by the Earth’s surface, by the atmosphere itself, and by clouds. As a result of its warmth, the atmosphere also radiates thermal infrared in all directions, including downward to the Earth’s surface. Thus, greenhouse gases trap heat within the surface-troposphere system. This mechanism is fundamentally different from the mechanism of an actual greenhouse, which instead isolates air inside the structure so that the heat is not lost by convection and conduction, as discussed below. The greenhouse effect was discovered by Joseph Fourier in 1824, first reliably experimented on byJohn Tyndall in the year 1858 and first reported quantitatively by Svante Arrhenius in his 1896 paper.
In the absence of the greenhouse effect and an atmosphere, the Earth's average surface temperature of 14 °C (57 °F) could be as low as −18 °C (−0.4 °F), the black body temperature of the Earth.
Anthropogenic global warming (AGW), a recent warming of the Earth's lower atmosphere as evidenced by the global mean temperature anomaly trend, is believed to be the result of an "enhanced greenhouse effect" mainly due to human-produced increased concentrations ofgreenhouse gases in the atmosphere and changes in the use of land.
The greenhouse effect is one of several factors that affect the temperature of the Earth. Other positive and negative feedbacks dampen or amplify the greenhouse effect.
In our solar system, Mars, Venus, and the moon Titan also exhibit greenhouse effects according to their respective environments. In addition, Titan has an anti-greenhouse effect and Plutoexhibits behavior similar to the anti-greenhouse effect.
(wikipedia.org)
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