Greenhouse effect

The greenhouse effect, first discovered by Joseph Fourier in 1824, is the process by which an atmosphere warms a planet.

Real greenhouses

The term 'greenhouse effect' originally came from the greenhouses used for gardening, but it is a misnomer since greenhouses operate differently http://www.ems.psu.edu/~fraser/Bad/BadGreenhouse.html http://www.wmconnolley.org.uk/sci/wood_rw.1909.html. A greenhouse is built of glass; it heats up primarily because the Sun warms the ground inside it, which warms the air near the ground, and this air is prevented from rising and flowing away. The warming inside a greenhouse thus occurs by suppressing convection and turbulent mixing. This can be demonstrated by opening a small window near the roof of a greenhouse: the temperature will drop considerably. It has also been demonstrated experimentally (Wood, 1909): a "greenhouse" built of rock salt (which is transparent to IR) heats up just as one built of glass does. Greenhouses thus work primarily by preventing convection; the greenhouse effect however reduces radiation loss, not convection. It is quite common, however, to find sources (e.g.

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http://pangea.stanford.edu/courses/gp025/webbook/07_clement.html http://www.numberwatch.co.uk/greenhouse_effect.htm http://www.ngdc.noaa.gov/paleo/globalwarming/greeneffect.html) that make the "greenhouse" analogy. Although the primary mechanism for warming greenhouses is the prevention of mixing with the free atmosphere, the radiative properties of the glazing can still be important to commercial growers. With the modern development of new plastic surfaces and glazings for greenhouses, this has permitted construction of greenhouses which selectively control radiation transmittance in order to better control the growing environment.http://ag.arizona.edu/ceac/research/archive/HortGlazing.pdf.

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