Q.22 Explain green house effect with reference to gases responsible for it and their sources.
Best answer
Answer: Greenhouse effect: the Earth’s surface absorbs incoming short-wave solar radiation and re-emits it as long-wave infrared (heat) radiation. Certain gases in the atmosphere (greenhouse gases) absorb and re-radiate this heat back towards the Earth, so the atmosphere is warmed, like a greenhouse. The natural greenhouse effect keeps the mean temperature of the Earth at about 15 °C; an increase in these gases causes global warming.
| Greenhouse gas | Sources |
|---|---|
| Carbon dioxide (CO2) – about 60% | Burning of fossil fuels (coal, petroleum) in vehicles, industries and power plants; deforestation; burning of wood. |
| Methane (CH4) – about 20% | Paddy fields, marshes, cattle (ruminants), decomposition of organic waste in landfills, biogas leakage. |
| Chlorofluorocarbons (CFCs) – about 14% | Refrigerators, air conditioners, aerosol sprays, foam manufacture. |
| Nitrous oxide (N2O) – about 6% | Nitrogenous fertilizers, burning of fossil fuels and biomass, industries. |
Effects include rise in global temperature, melting of polar ice and glaciers, rise in sea level and changes in climate and rainfall.
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