The radiative character of energy radiated from the warmer earth to cooler space, often derived from window channel measurements from satellites in polar orbit.

Outgoing Longwave Radiation (OLR) is the energy leaving the earth as infrared radiation at low exergy. Earth's radiation balance is very closely achieved since the OLR very nearly equals the Shortwave Absorbed Radiation received at high exergy from the sun. Thus, the First Law of Thermodynamics (energy conservation) is satisfied and the earth's average temperature is very nearly stable.