We have seen that the vast majority of energy in the climate system comes from the sun in the form of electromagnetic radiation, and most of that visible light. From the discussion of blackbody radiation, we saw that the emission temperature of Earth was much colder than the actually global mean temperature. It is the presence of the atmosphere -- because of its ability to absorb the emitted infrared radiation -- that the surface temperature is a much more comfortable temperature. This process is called the greenhouse effect (sometimes modified as the "natural greenhouse effect"). What is it that allows the atmosphere to absorb infrared radiation, and for that matter, why is it so transparent to visible radiation?
To answer these questions completely requires a full treatment of radiative transfer and atmospheric chemistry, which are beyond the scope of this Wikibook. However, we can begin to understand these processes with basic physical principles.
Some topics to addEdit
- albedo - surface, cloud, ice, and snow
- infrared absorption - water vapor, carbon dioxide, other greenhouse gases
- feedbacks - positive/negative, albedo, cloud, water vapor, vegetative, snow/ice