What factors affect the earth’s radiation balance?
While all the energy that enters the earth’s system comes from the sun, about 30 percent of the solar radiation that reaches the earth’s atmosphere is reflected back to space by light-colored features, including clouds, dust, deserts and ice. The ratio between solar radiation reflected back to space and incoming solar radiation is called albedo. The energy that remains in the system is absorbed by the earth. To balance this, the planet radiates heat that is, on average, equal to the radiation it absorbs. Unlike solar radiation, which is primarily in the form of shortwave visible light, the longwave heat energy is trapped by greenhouse gases that occur naturally in the atmosphere. There are three fundamental ways to change the radiation balance of the planet: • Changing the incoming solar radiation, by changes in the earth’s orbit or by changes in the sun itself. • Changing the fraction of solar radiation that is reflected back to space (albedo). • Changing the concentration of greenhou
