Weak average liquid-cloud-water response to anthropogenic aerosols

Toll, V., Christensen, M., Quaas, J. and Bellouin, N. ORCID: https://orcid.org/0000-0003-2109-9559 (2019) Weak average liquid-cloud-water response to anthropogenic aerosols. Nature, 572 (7767). pp. 51-55. ISSN 0028-0836 doi: 10.1038/s41586-019-1423-9

Abstract/Summary

The cooling of the Earth’s climate through the effects of anthropogenic aerosols on clouds offsets an unknown fraction of greenhouse gas warming. An increase in the amount of water inside liquid-phase clouds induced by aerosols, through the suppression of rain formation, has been postulated to lead to substantial cooling, which would imply that the Earth’s surface temperature is highly sensitive to anthropogenic forcing. Here we provide direct observational evidence that, instead of a strong increase, aerosols cause a relatively weak average decrease in the amount of water in liquid-phase clouds compared with unpolluted clouds. Measurements of polluted clouds downwind of various anthropogenic sources—such as oil refineries, smelters, coal-fired power plants, cities, wildfires and ships—reveal that aerosol-induced cloud-water increases, caused by suppressed rain formation, and decreases, caused by enhanced evaporation of cloud water, partially cancel each other out. We estimate that the observed decrease in cloud water offsets 23% of the global climate-cooling effect caused by aerosol-induced increases in the concentration of cloud droplets. These findings invalidate the hypothesis that increases in cloud water cause a substantial climate cooling effect and translate into reduced uncertainty in projections of future climate.

Item Type	Article
URI	https://reading-clone.eprints-hosting.org/id/eprint/85364
Identification Number/DOI	10.1038/s41586-019-1423-9
Refereed	Yes
Divisions	Science > School of Mathematical, Physical and Computational Sciences > Department of Meteorology
Publisher	Nature Publishing Group
Download/View statistics	View download statistics for this item