Following gases are responsible for green house effect. Carbon dioxide CO2 Methane CH4 Water H2O Nitrous oxide NO Ozone O3 Chlorofluorocarbons CFCs They are present near earth's surface. They absorb solar energy radiated back from the earth surface. Due to this, the atmosphere is heated. Thus, these gases are essential for maintaining the temperature of earth for the sustenance of life. In the absence of green house gases, there will be significant decrease in the average temperature of earth. Due to this, life will not be possible on earth.