Greenhouse effect keeps the climate of earth warm by receiving energy of sun in the form of visible light. Earth absorbs visible light from the sun and then re-radiates it as thermal radiation. Sun emits light both of shorter and longer wavelengths. Short wavelength of visible light emitted from the sun is absorbed whereas longer wavelength of infrared radiations is trapped and unable to pass. These trapped infrared radiations that escaped from the earth makes the earth surface warmer. It has been analyzed by the researchers that about 50% of sun energy is absorbed at earth surface while the remaining is reflected and absorbed by the atmosphere. The infrared radiations emitted from the sun are trapped by gases known collectively as Greenhouse Gases. Joseph Fourier discovered the Greenhouse effect in 1824. But it was first experiment by John Tyndall in 1858. Now the question arises that which gases contribute to the composition of greenhouse gases?
Greenhouses gases involves all the triatomic gases of earth's atmosphere. Gases with three or more atoms are only able to interact with infrared radiations. It is known that diatomic gases like oxygen and nitrogen together forms about 99% of earth atmosphere. Only 1% earth atmosphere constitutes the greenhouse gases. Major Greenhouse gases include:
1) Water Vapor: constitute 36% to 70% of greenhouse gases
2) Carbon dioxide: constitute 9% to 26% of greenhouse gases
3) Methane: 4 % to 9 %
4) Ozone: constitute 3% to 7%
5) Clouds also absorb and emit infrared radiations.
Importance of Greenhouse effect:
Greenhouse effect is very important for all living beings. It's only the greenhouse effect which has maintained the temperature of earth. Scientist's estimates that without the greenhouse effect the temperature of earth would not be warm enough to sustain our ecosystem. Temperature without it is estimated to be about 54 degrees Fahrenheit. On the other hand a little extra warming is also harmful for our ecosystem. In warmer conditions vector borne disease like malaria and dengue become widespread. The range of these insects and mosquitoes expand in warmer climate. Apart from that poor people who depend on the land and weather for living will be affected to a greater extent. They will not be able to survive in such harsh climatic conditions.
Greenhouses are generally of two types:
1) Natural greenhouse
2) Artificial or Man-made greenhouse.
Artificial greenhouses looks like a simple glass house. The glasses of these houses trap in light but keep heat from escaping. This heat up the greenhouse just exactly like the closed car parked in sunlight. This heat of greenhouses helps in growing plants in winters. Human activities are creating larger amount of greenhouse gases than what is naturally required to warm the environment. Some of the human activities that are distorting this natural process include:
1) Burning of natural gas, coal and gasoline from automobiles: these are raising the level carbon dioxide in the atmosphere to a greater extent. It has been estimated by scientists that carbon dioxide level is increasing 10% in every 20 years.
2) Deforestation: Today people are destroying forests for building houses and roads. Decrease in trees lead to lesser consumption of carbon dioxide and lesser production of oxygen. Both of which are necessary for maintain the temperature of earth. The result of this deforestation is global warming. Steps should be taken to avoid to cutting of trees.
Increase in greenhouse gases means trapping of more infrared radiations. This results in more warming of our earth's atmosphere.
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