Discuss the causes of global warming. What measures need to be taken to control global warming?

Explanation

Global Warming. It is the rise in the mean temperature of the lower atmosphere and surface of the earth.
Causes. The cause of global warming is the increase in the quantity of radiatively active green house gases (GHGs) viz. `CO_2, CH_4,NO_2O`, CFCs. These gases allow the heat waves to reach earth but prevent their escape. Warming effect can be observed in a glass house and closed car due to glass panes.
1. Carbon Dioxide (`CO_2`). It contributes to 60% of total global warming. Concentration of `CO_2` was 280 ppm in 1750s, 368 ppm in 2000. It is due to excessive combustion of fossil fuels, biomass burning and deforestation.
2. Methane (`CH_4`). Its atmospheric concentration has doubled from 700 ppb in 1750s to 1450 ppb in 2000. The gas contributes 20% to global warming. The major sources are paddy field enteric fermentation is cattle and wetlands.
3. Chlorofluorocarbons (CFCs). They are synthetic compounds of carbon and halogens used in aerosols, refrigeration, foaming, cleaning and drying. Though their manufacture is now dwindling, the ones already in the atmosphere contribute 14% to global warming.
4. Nitrous Oxide `(N_2O)`. It comes from burning of nitrogen rich fuel. Contribution to global warming is 6%.
Measures to control Global Warming.
Global wanning can be reduced by

(i) Reduction in fossil fuel usage.
(ii) Energy should be effciently used.
(iii) Deforestation should be reduced.