An increase in the atmospheric concentration of greenhouse gases has resulted in a rise of atmospheric temperature by 0.6oC (global warming) during the 20th century. Confirmation on this is given by the intergovernmental panel on climate change (IPCC) in its reports of 1991 and 1992. In the future, this predictable change affects the climate, sea level, range of species distribution, food production as well as fisheries resources in the oceans.
Causes of global warming:
(i) Rise in the concentration of greenhouse gases.
(ii) Increment in the use of automobiles and fossil fuels.
(iii)Deforestation.
(iv)Emission of CFC and aerosol from refrigerator and airplane.
(v) In the lower atmosphere, there is an increase in particulate matter.
Effects of global warming:
(i) $CO_2$ fertilisation effect.
(ii) The species of plants that are sensitive to temperature will die with a sudden rise in temperature and their place will be taken over by scrub vegetation.
(iii) Loss of biodiversity.
(iv) Rise in sea level.
(v) Possibilities of drought and floods.
(vi) Eruption of plant disease and pests.
(vii) Change in rainfall pattern.
Methods adopted to reduce the atmospheric concentration of greenhouse gases are:
(i) Greenhouse gas emissions can be reduced by limiting the use of fossil fuels, and by developing alternative renewable sources of energy (wind energy, solar energy, etc.)
(ii) For photosynthetic utilization of $CO_2$, the vegetation cover, mainly the forests, can be increased.
(iii)The use of nitrogen fertilizers can be minimized in agriculture for reducing $N_2O$ emissions. (iv)Substitutes can be developed for chlorofluorocarbons.