For the 'greenhouse effect' consider statements I to III.

(I) Sunlight is received by Earth. Some incoming radiations are reflected back into space by the atmosphere and some is absorbed such as certain UV light by stratosphere ozone.

(II) Earth's surface emits IR radiations.
(III) Emitted IR radiations are less intense than that emitted by Earth's surface. CO₂ along with IR radiations warm the atmosphere.

Select the correct statements.

CO₂(g) is not assumed to be an air pollutant because it is non-toxic. However, a build up of CO₂(g) in the atmosphere may disturb energy balance on earth. Its atmosphere is transparent to visible and UV radiation form the Sun. Infrared radiation is absorbed at earth's surface and warms it. But some of this absorbed energy is reradiated as IR radiation. Certain atmospheric gases as CO₂ and water vapour absorb these IR radiations. Energy retained in the atmosphere produces a warming effect. Thus, thermal energy is retained in a greenhouse-greenhouse effect.