Bøger af Rathore Aparna

Greenhouse EffectThe Earth's temperature is maintained at a level where it can sustain life by a balancebetween heat from the sun, and cooling from reflecting some of the heat by theEarth's warm surface and atmosphere back to space (Agarwal, 2001). Greenhousegases effectively absorb thermal infrared radiation, emitted by the Earth's surface, bythe atmosphere itself due to the same gases, and by clouds. Atmospheric radiation isemitted to all sides, including downward to the Earth's surface. Thus, greenhousegases trap heat within the surface-troposphere system. This is called the greenhouseeffect. Thermal infrared radiation in the troposphere is strongly coupled to thetemperature of the atmosphere at the altitude at which it is emitted. In thetroposphere, the temperature generally decreases with height. Effectively, infraredradiation emitted to space originates from an altitude with a temperature of, onaverage, -19°C, in balance with the net incoming solar radiation, whereas the Earth'ssurface is kept at a much higher temperature of, on average, +14°C. An increase inthe concentration of greenhouse gases leads to an increased infrared opacity of theatmosphere, and therefore to an effective radiation into space from a higher altitudeat a lower temperature. This causes a radiative forcing that leads to an enhancementof the greenhouse effect, the so-called enhanced greenhouse effect (Solomon et al.,2007).