Gases

Certain gases in the atmosphere, mainly carbon dioxide, methane and CFCs, act like the glass in a greenhouse, allowing sunlight through to heat the Earth's surface but trapping some of the heat as it radiates back into space. Without this the Earth would be frozen and lifeless. However, owing to Man's activities,'greenhouse gases' are building up in the atmosphere, causing a greater amount of heat to be reflected back to Earth. The result is an increase in average world temperatures and in the future this could lead to the flooding of cities world wide and more hurricanes etc.