Question

Explain how global warming takes place in the presence of green house gases. Give a reason why the surface temperature of earth is maintained in absence of green house gases.

Answer 1

As light from the sun passes through atmosphere of earth most of the U.V. radiations are absorbed by ozone and only 30% of IR radiations reach earth’s surface and heat it.
As the earth becomes hot, it starts emitting radiations which have now less energy and hence longer wavelength. Some part of reflected IR radiations are absorbed by CO, and this remains on earth and warm up the earth’s surface.

In absence of green house gases surface temperature on earth is maintained. Since heat radiations absorbed after passing clear atmosphere reach earth and some heat., radiations are reflected back.