Twomey effect

The Twomey effect describes how cloud condensation nuclei (CCN), possibly from anthropogenic pollution, may increase the amount of solar radiation reflected by clouds. This is an indirect effect.

Aerosol particles can act as CCN's creating more droplets which have a smaller size distribution. This increases the cloud albedo as clouds appear whiter and larger, leading to a cooling of between -0.3 and -1.8 Wm⁻². For example, we observe trails of white clouds from ships crossing the oceans due to this effect.