1. In radiation, the net flux of radiation into or out of a system. As a consequence of radiative forcing there must be some change to the nonradiative energy states of the system (e.g., its temperature may change). 2. In climatology, a systematic perturbation to the climatological value of the net radiant flux density at some point in the earth's climate system. For example, this perturbation may be due to a change in concentration of the radiatively active gases, a change in solar radiation reaching the earth, or changes in surface albedo.