Green House gases are the gases, which absorb and emit the radiation within thermal infrared range. These gases are water vapor, carbon dioxide, nitrogen dioxide and ozone. For an optimum of the earth, there should be the balance of these gases or whatever one sources emit; the same should be absorbed by other sources.
With the industrialization more and more green house gases are emitted by industries and particularly the carbon dioxide. However, the total forest areas and trees, which absorb carbon dioxide are being cut down daily and their number are reducing causing imbalance between the carbon dioxide emission and absorption. This is resulting in the increase in green house gases resulting in the rise in average earth temperature. This green house gas effect is causing global warming.