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Question

Write a short note on global warming:
Name two important sources of these pollutants.

Solution
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The greenhouse effect received its name because the earth's atmosphere acts much like the glass or plastic roof and walls of a greenhouse. Sunlight enters a greenhouse through the transparent roof and heat the plants but the heat emitted by the plants in the form of infrared radiation cannot pass through the roof and walls. As a result, the temperature inside the house increases. An effect similar to greenhouse is responsible for keeping the earth's surface warmer. The atmosphere around the earth acts like a glass of the greenhouse chamber. This is known as $$Greenhouse$$ $$effect$$.

About half of the solar energy that enters the atmosphere is either reflected or absorbed by the molecules of the air. UV radiations of shorter wavelengths are prevented from entering the troposphere by the presence of oxygen and the ozone layer in the stratosphere. The rays that do reach the surface of the earth are largely in the visible and infrared (heat) regions. These radiations are absorbed by the earth.
Most of the radiation emitted by the earth lies in the infrared region.
Almost 84% of the heat radiated by the earth is absorbed by gases in the atmosphere and re-radiated back to the earth's surface.
Increase in the global temperature. This is known as $$Global$$ $$warming$$.

The gases present in the atmosphere which is responsible for global warming are Carbon dioxide, water vapour, oxides of nitrogen, methane, ozone, chlorofluorocarbons, etc

Two important sources of pollutants are as follows:
i) The common sources of CFCs are refrigerants, but fire suppression systems for aircraft and aerosols also emit CFCs into the atmosphere.

ii) The common sources of $$CO_2$$ are burning of fossil fuels like coal, oil and natural gas in industries, power plants.
Deforestation has caused an increase in the level of carbon dioxide.

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