| Effects of air pollution |
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Sun’s energy, which is transmitted in short wavelengths (visible light, ultraviolet, etc.) penetrates our atmosphere and strikes the Earth's surface. The atmospheric gases like water vapour, carbon dioxide and other select gases (called greenhouse gases) absorb the energy, which is transmitted in long wavelengths (such as infrared, thermal radiation or heat). Various objects on the earth’s surface absorb short wavelength visible light from the sun. The warmed objects then emit infrared energy. Much of this infrared energy is absorbed and re-emitted back to the ground by the greenhouse gases. Thus these infrared radiations build up and keep Earth warm. This phenomenon, known as the greenhouse effect, enables life to flourish on Earth.
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The greenhouse effect in the Earth’s atmosphere. Solar radiation is absorbed by Earth and the objects on it. Earth then emits infrared radiation. Carbon dioxide, water vapor, and other greenhouse gases in the atmosphere absorb and re-emit heat that would otherwise be radiated from the Earth into space. |
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Without this natural greenhouse effect, the temperature of the Earth would be about 00 F (-180C) instead of its present 570F (140C). Greenhouse warming also occurs on Venus but to a far greater extent. The atmosphere surrounding Venus is much thicker than the Earth’s atmosphere, and its composition is 95 percent carbon dioxide, which brings surface temperatures to a scorching 4500C. There is also the "man-made" greenhouse effect, which is the enhancement of Earth's natural greenhouse effect by the addition of greenhouse gases from the burning of fossil fuels (mainly petroleum, coal, and natural gas) and deforestation. About 80-90% of the Earth's natural greenhouse effect is due to water vapor, a strong greenhouse gas. The remainder is due to carbon dioxide, methane, and a few other minor gases. It is the carbon dioxide concentration that is increasing, due to the burning of fossil fuels, deforestation, which destroys a net absorber of carbon dioxide during photosynthesis and increased population who are responsible for activities that result in the output of carbon dioxide. |
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