Question

CO2 passes short wave length light (visible) but blocks long wave length radiation (IR). Explain how adding CO2 to an atmosphere increases the surface temperature of a planet. Consider the temperature of the sources of radiation in and out.

Answer 1

Our Earths is continiously heated by the Sun, but Earth does not retain any amount of heath of that as it reflect back the same, this is evident as the temperature at night falls, and the average tempearature of any plcae in a year remain same.  Earth gets heat as energetic “visible” light emitted by the hot sun. Earth, being much cooler, re-emits this heat as less energetic “infrared” light.

Our atmosphere provides a passage for the sunlight to reach the surface of the earth. Sunlight consist of UV, IR and other types of radiation i.e. it consist of short wave and long wave. When the Earth reflect the less energetic Infrared light it is absorbed by water , CO2 and some other gases in the air.

The atmosphere re-emits this heat. Some of the re-emitted heat goes out to space, but some goes back down to the Earth’s surface, providing an additional warming.

Some of the re-emitted heat goes out to space, but some goes back down to the Earth’s surface, providing an additional warming. This extra warming associated with re-emission of outgoing Earth heat or light is called the “greenhouse effect”. The greenhouse effect traps some Earth heat on the planet, making it warmer than it would be if there were no water or CO2 in the atmosphere.