= Planetary effective radiating temperature
{title2=$T_{\rm eff}=({\rm OLR}/\sigma)^{1/4}$}
Define a planet's effective radiating temperature by its actual outgoing longwave flux, regardless of the surface temperature. In radiative equilibrium with solar irradiance $S_0$ and <Bond albedo> A, $\sigma T_{\rm eff}^4=(1-A)S_0/4$. A <greenhouse effect> changes the surface temperature needed to emit that flux. An effective emissivity relating OLR to surface temperature is a diagnostic of the atmosphere–surface system, not necessarily a material emissivity. Away from equilibrium, the outgoing-flux definition and the temperature inferred from absorbed sunlight need not agree.
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