greenhouse effect

noun
1.
an atmospheric heating phenomenon, caused by short-wave solar radiation being readily transmitted inward through the earth's atmosphere but longer-wavelength heat radiation less readily transmitted outward, owing to its absorption by atmospheric carbon dioxide, water vapor, methane, and other gases; thus, the rising level of carbon dioxide is viewed with concern.
2.
such a phenomenon on another planet.

Origin:
1935–40

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World English Dictionary
greenhouse effect
 
n
1.  an effect occurring in greenhouses, etc, in which radiant heat from the sun passes through the glass warming the contents, the radiant heat from inside being trapped by the glass
2.  the application of this effect to a planet's atmosphere; carbon dioxide and some other gases in the planet's atmosphere can absorb the infrared radiation emitted by the planet's surface as a result of exposure to solar radiation, thus increasing the mean temperature of the planet

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Science Dictionary
greenhouse effect   (grēn'hous')  Pronunciation Key 


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The retention of part of the Sun's energy in the Earth's atmosphere in the form of heat as a result of the presence of greenhouse gases. solar energy, mostly in the form of short-wavelength visible radiation, penetrates the atmosphere and is absorbed by the Earth's surface. The heated surface then radiates some of that energy into the atmosphere in the form of longer-wavelength infrared radiation. Although some of this radiation escapes into space, much of it is absorbed by greenhouse gases in the lower atmosphere, which in turn re-radiate a portion back to the Earth's surface. The atmosphere thus acts in a manner roughly analagous to the glass in a greenhouse, which allows sunlight to penetrate and warm the plants and soil but which traps most of the resulting heat energy inside. The greenhouse effect is essential to life on Earth; however, the intensification of its effect due to increased levels of greenhouse gases in the atmosphere is considered to be the main contributing factor to global warming.
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American Heritage
Cultural Dictionary

greenhouse effect definition


A term used to describe the heating of the atmosphere owing to the presence of carbon dioxide and other gases. Without the presence of these gases, heat from the sun would return to space in the form of infrared radiation. Carbon dioxide and other gases absorb some of this radiation and prevent its release, thereby warming the Earth. This is an effect analogous to what happens in a greenhouse, where glass traps the infrared radiation and warms the air.

Note: The burning of fossil fuels adds carbon dioxide to the atmosphere, and therefore places the Earth at risk from an increase of this effect.
The American Heritage® New Dictionary of Cultural Literacy, Third Edition
Copyright © 2005 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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Example sentences
The greenhouse effect weakened, the world cooled, and ice spread over the
  oceans from the poles.
Without the natural greenhouse effect, the planet would essentially be frozen.
And by the mid-twentieth century, some of the physical mechanisms behind the
  greenhouse effect had been understood.
Therefore, the total greenhouse effect is not simply the sum of the effect of
  each gas alone.
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