Carbon dioxide and water vapour absorb infrared radiation coming to the earth and partly reflect it back to the earthâ€™s surface, as shown in figure. Due to this, the surface of the earth gets heated up. This phenomenon of heating up of the surface of the earth is called green house effect. Due to deforestation, the quantity of carbon dioxide in the atmosphere is increasing. Normally, carbon dioxide gets absorbed by plants present in (during photosynthesis) sea water and biomass presentation in the sea. When fossil fuels are burnt oxygen levels do not change much, but carbon dioxide levels are very much affected. Because of this, global climate is affected. A 50% increase in carbon dioxide level increases the surface temperature of the earth by 30C. If there is a 10 C increase in the temperature, the following bad effects are predicted:
1. The ice caps of the polar region melt thereby increasing the level of the sea water by 90 cm. due to which many countries like The Netherlands, Bangladesh, Maldives etc. will get submerged. Other places like England, Miami in U.S., Shanghai in China, Chennai, Goa in India will also get affected very badly.
2. Due to global warming, the rate of evaporation of water from the seas, rivers, ponds will increase. This leads to untimely rains, cyclones and hurricanes.
3. Agricultural sector will be badly affected due to fast evaporation of surface water. There will be a shortage in the supply of water for agricultural purposes.
Other greenhouse gases: Gases apart from carbon dioxide which can cause green house effect are.
CFC 17%; *O3 18%; NO 4%; Water vapour 2%
[Ozone in the stratosphere acts as a protective layer, but harmful if it is present in the troposphere]