| 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. |
greenhouse effect  (click for larger image in new window) n.
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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.