Q.What is green house effect? Name the gases that cause green house effect.

The greenhouse effect is the trapping of outgoing heat radiation by certain atmospheric gases, warming the earth; the main such gases are CO2, methane, water vapour, nitrous oxide, ozone, and CFCs.

Sunlight (mostly visible and some UV radiation) passes through the earth's atmosphere and warms the earth's surface. The warmed surface then re-radiates this absorbed energy back outwards, but as longer-wavelength infrared (heat) radiation. Certain gases present in the atmosphere — called greenhouse gases — are able to absorb this outgoing infrared radiation and re-emit part of it back towards the earth's surface, rather than letting it all escape into space. This trapping of heat within the atmosphere, which keeps the earth substantially warmer than it would otherwise be, is called the greenhouse effect, by analogy with how the glass of a greenhouse traps heat inside it.

The greenhouse effect is a natural and essential phenomenon that keeps the earth's average temperature suitable for life; the problem of 'global warming' arises when human activity increases the concentration of these gases beyond natural levels, intensifying the effect.

Major greenhouse gases include:

• Carbon dioxide (CO2) — from combustion of fossil fuels, deforestation …