Define greenhouse effect and greenhouse gases.

The earth's atmosphere traps the heat energy that comes from the sun and prevents the earth from becoming too cold at night. This is known as the greenhouse effect. There are gases which absorb the heat energy and maintain a liveable temperature on the earth. Theses gases are called the greenhouse gases. Some of them are carbon dioxide (CO₂), nitrous oxide (N₂O), chlorofluorocarbons (CFCs), methane (CH₄) and water vapour.