green house effect

The greenhouse effect, first discovered by Joseph Fourier in 1824, and first investigated quantitatively by Svante Arrhenius in 1896, is the process in which the absorption of infrared radiation by an atmosphere warms a planet. Without these greenhouse gases, the Earth's surface would be up to 30 °C cooler. The name comes from an incorrect analogy with the way in which greenhouses are heated by the sun in order to facilitate plant growth. In addition to the Earth, Mars, Venus and other celestial bodies with atmospheres (such as Titan) have greenhouse effects. In common parlance, the term "greenhouse effect" may be used to refer either to the natural greenhouse effect, due to naturally occurring greenhouse gases, or to the enhanced (anthropogenic) greenhouse effect, which results from gases emitted as a result of human activities (see also global warming, scientific opinion on climate change and attribution of recent climate change). The basic mechanism The Earth receives energy from the Sun in the form of radiation. To the extent that the Earth is in a steady state, the energy stored in the atmosphere and ocean does not change in time, so energy equal to the incident solar radiation must be radiated back to space. Radiation leaving the Earth takes two forms: reflected solar radiation and emitted thermal infrared radiation. The Earth reflects about 30% of the incident solar flux; the remaining 70% is absorbed, warms the land, atmosphere and oceans, and powers life on this planet. Eventually this energy is reradiated to space as infrared photons. This thermal, infrared radiation increases with increasing temperature. One can think of the Earth's temperature as being determined by the requirement that it produce the infrared flux needed to balance the absorbed solar flux. Source: http://www.answers.com/greenhouse+effect?initiator=IE7:SearchBox