The Greenhouse Effect
Most of the sun's energy that reaches the earth is absorbed by the oceans and land masses and radiated back into the atmosphere in the form of heat or infrared radiation. Most of this infrared energy is absorbed and reradiated by atmospheric gases such as water vapor and carbon dioxide. This phenomenon, referred to as the greenhouse effect (below), serves to keep the earth some 33°C (60°F) warmer than it would otherwise be. As concentrations of gases that absorb and reradiate infrared energy (i.e., greenhouse gases GHGs) increase, the warming effect increases.
Note: Greenhouse gases are shown as a layer to simplify the drawing. In reality, they are dispersed throughout the atmosphere. Although the atmosphere consists largely of oxygen and nitrogen, neither absorbs infrared energy; thus, they do not play a role in warming the earth and are not greenhouse gases.
Source: Rekacewicz, 2000.
