PNNL

Abstract

Artificially increasing the albedo of marine boundary layer clouds by the mechanical emission of sea spray aerosol has been proposed as a geoengineering technique to slow the warming caused by anthropogenic greenhouse gases. A previous global model study (Korhonen et al., 2010) found that only modest increases (250–300 nm, the background aerosol loading is large (=150 cm-3) and the in-cloud updraught velocity is low (50% cloud cover, irrespective of the amount of aerosol injected. But at stronger updraft speeds (0.2 ms-1), higher values of CDN are achievable due to the elevated in-cloud supersaturations. Achieving a value of 375 cm-3 in regions dominated by stratocumulus clouds with relatively weak updrafts cannot be attained regardless of the number of injected particles, thereby limiting the efficacy of sea spray geoengineering.