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a theorized change in the earth's climate caused by accumulation of solar heat in the earth's surface and atmosphere. Human activity contributes increasing amounts of the so-called greenhouse gases, such as carbon dioxide, methane, and chlorofluorocarbon, to the atmosphere. Some of the particles and gases in the atmosphere also allow more sunlight to filter through to the earth's surface but reflect much of the radiant infrared energy that otherwise would escape through the atmosphere back into space. See also global warming.
Planetary warming as a result of the trapping of solar energy beneath atmospheric gases. The composition and concentration of the gases in the atmosphere influence the earth's surface temperature because some gases more effectively retain heat than others. Fossil fuel combustion, which has increased at a rapid rate since the 1950s, has deposited increasing amounts of carbon dioxide in the upper atmosphere. This is thought to be a contributory factor in global warming, a phenomenon suspected of having widespread effects on all ecosystems. See: global warming; ozone
greenhouse effectThe progressive earth-heating effect resulting from the transparency of the atmosphere to sun (solar) radiation at high frequencies and its relative opacity to energy re-radiated by the earth at a lower, less penetrative, frequency. Water vapour and carbon dioxide are the main elements concerned, and any increase in these, mainly from the burning of fossil fuels, enhances the heating effect. A rise in surface temperature could melt polar ice and cause widespread flooding.
- an effect occurring in greenhouses in which the glass transmits short wavelengths but absorbs and re-radiates longer wavelengths, thus heating the interior.
- the application of this effect to the earth's atmosphere. Infrared radiation tends to be trapped by carbon dioxide and water vapour in the earth's atmosphere and some of it is re-radiated back to the earth's surface.