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The greenhouse effect is the process by which radiation from a planet's atmosphere warms the planet's surface to a temperature above what it would be in the absence of its atmosphere.〔〔 If a planet's atmosphere contains radiatively active gases (i.e., greenhouse gases) the atmosphere radiates energy in all directions. Part of this radiation is directed towards the surface, warming it. On Earth, solar radiation at the frequencies of visible light largely passes through the atmosphere to warm the planetary surface. The surface itself emits energy at the lower frequencies of infrared thermal radiation. Infrared radiation is absorbed by greenhouse gases in the atmosphere. These gases also radiate energy, some of which is directed to the surface and lower atmosphere. The mechanism is named after the effect of solar radiation passing through glass and warming a greenhouse, but the way it retains heat is fundamentally different as a greenhouse works by reducing airflow, isolating the warm air inside the structure so that heat is not lost by convection.〔〔〔 If an ideal thermally conductive blackbody were the same distance from the Sun as the Earth is, it would have a temperature of about 5.3 °C. However, since the Earth reflects about 30%〔(【引用サイトリンク】title=NASA Earth Fact Sheet )〕〔(【引用サイトリンク】title=Introduction to Atmospheric Chemistry, by Daniel J. Jacob, Princeton University Press, 1999. Chapter 7, "The Greenhouse Effect" )〕 of the incoming sunlight, this idealized planet's effective temperature (the temperature of a blackbody that would emit the same amount of radiation) would be about −18 °C.〔(【引用サイトリンク】title=Solar Radiation and the Earth's Energy Balance )〕〔( Intergovernmental Panel on Climate Change Fourth Assessment Report. Chapter 1: Historical overview of climate change science ) page 97〕 The surface temperature of this hypothetical planet is 33 °C below Earth's actual surface temperature of approximately 14 °C.〔The elusive "absolute surface air temperature," see (GISS discussion )〕 The mechanism that produces this difference between the actual surface temperature and the effective temperature is due to the atmosphere and is known as the greenhouse effect.〔 〕 Earth’s natural greenhouse effect is critical to supporting life. Human activities, primarily the burning of fossil fuels and clearing of forests, have intensified the natural greenhouse effect, causing global warming.〔 (pb: )〕 == History == (詳細はJoseph Fourier in 1824. The argument and the evidence was further strengthened by Claude Pouillet in 1827 and 1838, and reasoned from experimental observations by John Tyndall in 1859.〔John Tyndall, ''(Heat considered as a Mode of Motion )'' (500 pages; year 1863, 1873)〕 The effect was more fully quantified by Svante Arrhenius in 1896.〔 However, the term "greenhouse" wasn't used to describe the effect by any of these scientists; the term was first used in this way by Nils Gustaf Ekholm in 1901. In 1917 Alexander Graham Bell wrote "(unchecked burning of fossil fuels ) would have a sort of greenhouse effect", and "The net result is the greenhouse becomes a sort of hot-house."〔Grosvenor, Edwin S. and Morgan Wesson. ''Alexander Graham Bell: The Life and Times of the Man Who Invented the Telephone''. New York: Harry N. Abrahms, Inc., 1997, p. 274, ISBN 0-8109-4005-1.〕 Bell went on to also advocate the use of alternate energy sources, such as solar energy.〔Grosvenor and Wesson, 1997, p. 269.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Greenhouse effect」の詳細全文を読む スポンサード リンク
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