Earth Radiation Components
CERES Instrument Team, NASA Langley Research Center,
The only way the Earth receives the energy that keeps the surface warm is through sunlight. Some of the incoming sunlight is reflected back up into space by the Earth's surface, atmosphere, and clouds; some of it is absorbed and stored as heat. When the surface and atmosphere warm, they emit heat, or thermal energy, to space. The "radiation budget" is an accounting of these energy flows. If the radiation budget is in balance, then, the surface of the Earth should be neither warming nor cooling, on average.