Longwave radiation

Outgoing Longwave Radiation (OLR) is the energy leaving the earth as infrared radiation at low energy. Earth's radiation balance is very closely achieved since the OLR very nearly equals the Shortwave Absorbed Radiation received at high energy from the sun. Thus, the First Law of Thermodynamics (energy conservation) is satisfied and the earth's average temperature is very nearly stable. The OLR is affected by clouds and dust in the atmosphere, which tend to reduce it below clear sky values.  Greenhouse gases, such as Methane (CH4), Nitrous Oxide (N2O), water vapor (H2O) and carbon dioxide (CO2), increase reflection of the OLR back to the Earth's surface, thereby increasing the average temperature of the earth and contributing to global warming.
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The radiation emitted in the spectral wavelength greater than 4 micrometers corresponding to the radiation emitted from the Earth and atmosphere. It is sometimes referred to as terrestrial radiation or infrared radiation, although somewhat imprecisely. See infrared radiation.