Question

What are green house gases ? How are they responsible for global warming ?

Answer 1

Gases which contribute for the green house effect are called as green house gases. Green houses gases are carbon dioxide, water vapour, oxides of Nitrogen, methane, chloro fluoro carbons etc.

Mechanism:

Sunlight reaching Earth consists of three types of radiation-UV radiation, visible radiation and IR radiation. As sunlight passes through the atmosphere, most UV radiation is absorbed by ozone; $30$ % of IR radiation reaches the Earth’s surface, heating it up. As the Earth’s surface becomes hot, it starts emitting radiation with less energy than the incoming radiation and thus with longer wavelength. Some emitted IR radiation escapes from the Earth’s surface and some are absorbed by $C{O}_2$, thus remaining on the Earth. Trapped radiation warms the Earth’s surface and lower layers of the atmosphere.