Radiative forcing — Hyunjoo Park

Radiative forcing is a measure of how much a factor alters the balance of incoming and outgoing energy in the Earth-atmosphere system. $\Phi_{\text{RF, earth over x years}} = \Phi_{\text{incoming earth, ave over x [yr]}} - \Phi_{\text{outgoing, ave over x [yr]}}$

Unit: $\text{W m}^{-2}$

Meaning: if $\Phi_{RF} > 0$ , more energy comes in than goes out. The surplus energy accumulates in the Earth system (atmosphere and oceans) and raises the temperature → see Sensible heat ( $Q = mC_p\Delta T$ ).

Equilibrium: $\Phi_{RF} = 0$ , i.e. IN = OUT. It does not mean the temperature is zero. A warmer Earth emits more infrared radiation, so after a positive forcing the Earth warms up until OUT matches IN again. The new equilibrium is reached at a higher temperature.