Global warming- The rise in the mean temperature of the earth is called global warming.
Causes of global warming- Global warming is mainly caused due to the increased amounts of greenhouse gases in the atmosphere. These gases allow long wave radiations to enter into the atmosphere but do not let them leave, so these radiations remain trapped in the atmosphere and cause the mean temperature to rise. This is similar to the effect of glass walls in a greenhouse on the plants. The main greenhouse gases are:
1. Carbon dioxide- 60% of global warming is caused by carbon dioxide. The atmospheric concentration of carbon dioxide has risen to 280 ppm in 1750 to 380 ppm in 2007 and until 2019 it has risen to above 400. The main reason for the increase in the combustion of fossil fuels and deforestation.
2. Methane- It contributes to 20 % of global warming. The main reason for increase includes incomplete combustions, anaerobic decomposition, chimneys, paddy fields etc.
3. Chlorofluorocarbons- These are compounds of carbon and halogens used as propellants in aerosols, refrigerants, fire extinguishers, plastic foams, jet fuels etc.
4. Nitrous oxide- they are responsible for causing 6 % of global warming. It is formed during the combustion of nitrogen-rich fuels.
Effects of global warming
1. Melting of snow- Due to the increase in global temperature, the polar ice caps and snow mountains will start melting.
2. Sea level- Due to the melting of snow, the sea level will rise leading to submerging of coastal areas.
3. Odd climatic changes- Global warming will lead to odd climatic changes such as a reduction in precipitation, rise in El Nino effect, more floods and droughts, change in the global air current etc.
4. Vegetation- Forest will be turned into scrub vegetation, tropic will have more desserts.
5. Food production- Global warming may lead to a reduction in food production.