what is green house affect?

Greenhouse effect may be defined as the process of  steady increase in the temperature of the earth's atmosphere due to the presence of green house gases such as carbon dioxide, methane, chloroflorocarbons etc. These green house gases forms a blanket around the earth which allow the sun rays (short wave radiation) to pass through it but restricts the passage of reflected heat rays (long wave radiation) from going out of the atmosphere. This results in trapping the heat in the atmosphere leading to increase in temperature.