The gradual continuous increase in average temperature of surface of the Earth...
The gradual continuous increase in average temperature of surface of the Earth as a result of increase in concentration of greenhouse gases is termed as global warming.
Increase in the level of greenhouse gases (C02, CFCs, etc.) in the atmosphere. These gases allow the heat waves to reach earth but prevent their escape and thus the earth becomes warm.
The temperature of the earth has increased by 0.60C in last three decades, which will lead to changes in precipitation patterns.
Rise in temperature leads to deleterious changes in environment resulting in odd climatic changes called El Nino effect.
The rise in temperature will lead to the increased melting of polar ice caps which will cause the rise in sea level and many coastal areas will be submerged.
Increased temperature will lead to increased weed growth, eruption of diseases and pests. Thus, crop productivity will decrease.
Control of global warming
Global warming can be controlled by:
Planting trees (afforestation)
Slowing down the growth of human population
Reduction of emission of greenhouse gases into the atmosphere
Cutting down use of fossil fuels
Improving efficiency of energy usage.
Decrease in the thickness or concentration of ozone layer.
Cause of ozone depletion
Ozone degradation has increased due to chlorofluorocarbons (CFCs).
CFCs are refrigerants which react with UV in stratosphere to release chloride atoms.
Chloride atoms act as catalyst to degrade ozone and release molecular oxygen.
CFCs have permanent and continued effect as chloride atoms are not consumed.
Over the Antarctic region, there has been thinning of large area of ozone layer that has resulted in formation of ozone hole.
UV-B damages DNA and proteins of living organisms causing mutation.
It causes skin aging, skin cell damage and skin cancers.
UV-B is absorbed by human eye and in high dose, it causes inflammation of cornea. This is called snow-blindness cataract.
Control of ozone depletion
An international treaty, Montreal Protocol, was signed at Montreal, Canada, in 1987 to curb the emission of ozone depleting substances.
More protocols have been laid down in controlling emission of CFCs.