Cloud Radiative Feedback

Low clouds cool (reflect SW), high clouds warm (trap LW) — net feedback determines sign

40%
25%
Mid
2.0
Strong cooling (−)NeutralStrong warming (+)
Net Cloud Forcing: −0.0 W/m²
Low clouds (stratus, stratocumulus): high optical depth reflects ~30% of incoming solar — strong SW cooling effect. High clouds (cirrus, cumulonimbus anvils): cold cloud tops trap outgoing LW — greenhouse warming effect. The net Cloud Radiative Effect (CRE) = SW_CRE + LW_CRE. Currently Earth's CRE ≈ −20 W/m². How clouds change with warming is the largest uncertainty in climate sensitivity.