Pollution and smoke aerosols can increase or decrease the cloud cover. This duality in the aerosol effects forms one of the largest uncertainties in climate research. Using solar measurements from AERONET sites around the globe, we show an increase in the cloud cover with an increase in the aerosol column concentration and an inverse dependence on the aerosol absorption of sunlight. The emerging rule appears to be independent of the geographical location or aerosol type, thus increasing our confidence in the understanding of these aerosol effects on the clouds and climate. Preliminary estimates suggest an increase of 5% in cloud cover.

Yoram J. Kaufman
NASA/Goddard Space Flight Center, 613.2, Greenbelt MD 20771 USA.

Ilan Koren
Department of Environmental Sciences and Energy Research, Weizmann Institute, Rehovot 76100, Israel.
E-mail: ilan.koren@weizmann.ac.il

Source: http://www.sciencemag.org/cgi/content/abstract/1126232v1