Increase in the level of green house gases has led to considerable heating effect on Earth, so that there has been constant rise in atmospheric temperature during past 4-5 decades.
During the past antury the temperature of earth has increased by 0.6°C. According to IPPC (inter-government Panel on Climatic Change) average temperature of Earth would rise by 1.4°C to 5.8°C.
According to the forecast of World Climate Programme (WCP) 1988, there will be slight rise in temperature in tropics, moderate in middle latitudes and maximum in Polar Regions.
Effects of Global Warming:
(i) Effect on atmosphere:
Global warming would cause temperature rise in lower layer of atmosphere i.e. upto approximately 8 kms above earth surface. This will lead to cooling in stratosphere and increase in size of ozone holes. Cooling in thermosphere will disrupt radio communications.
(ii) Effect on weather and climate:
The moisture content of air will increase leading to more rain (precipitation) in higher latitudes both in summer and winter but in lower latitudes the winter precipitation will be reduced. Frequency of draught and flood will increase because of uneven distribution of precipitation. Acute water shortage may develop in arid and semiarid zones. There will be release of more energy into atmosphere which would cause very powerful storms. Odd climatic changes like El Nino effect would become common.
(iii) Changes in sea level:
Gradual increase in temperature due to global warming has brought about three major changes, 1. Melting of glaciers, 2. Melting of Greenland ice sheet 3. Thermal expansion of water. It has been observed, Greenland ice has melted between 20 to 100 cm between 1993-1998. During summers, the ice caps and glaciers have shrunk by thousands of square kilometres. Similarly trend has also been observed in glaciers of arctic region, losing about 30% of its volume in less than 2-3 decades.
Sea level has risen by 15 cm during the 20th century. By 2100 year sea level may rise by 88 cm over 1990 level. There is chance of submersion of large costal area. One third of human population lives within 60 km of coast line. The entire Maldives, several other islands, several important cities of the world will be submerged.
(iv) Effects on biosphere:
Response to change in temperature varies from species to species. Species with narrow temperature tolerance will become extinct with rise of temperature. If ocean temperature rises by 1 to 2oC, maximum destruction to coral reef will take place. Besides, mountain ecosystems, coastal wetlands, tundra biome, temperate forests will be highly affected.
Rise of temperature by 2-5°C will push temperate range by 200-500 km pole wards. Many trees will die resulting in conversion of forests into scrub vegetation. On the other hand, many weeds, insects, pests’ disease causing organisms etc. will florish.
(v) Effects on agriculture:
Rise in temperature reduces crop productivity. Exotic and noxious weeds will replace crop plants. Disease causing pathogens and pests would cause further damage to the crops. The crop productivity may increase in temperate region but in tropical and subtropical zone productivity declines due to global warming. Rice yield is likely to decrease by 5% in south-east Asia for every one degree rise in temperature.
Control of Global Warming:
(i) Use of fossil fuel should be replaced by alternate energy resources like solar energy, wind energy, tidal energy or geothermal energy.
(ii) C02 production at source should be controlled.
(iii) Complete replacement of chlorofluorocarbons (CFCs) with other alternative for refrigerators and air conditioners.
(iv) Reduction in use of nitrogen fertilizers to restrict nitrons oxide production.
(v) Increasing green coverage by afforestation, reforestation, social forestry etc.
(vi) Increasing efficiency in energy use.
(vii) Reduction in production of green house gases.
(viii) Control of population explosion.