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Science 15 August 2008:
Vol. 321. no. 5891, pp. 946 - 949
DOI: 10.1126/science.1159185
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Reports

Smoke Invigoration Versus Inhibition of Clouds over the Amazon

Ilan Koren,1 J. Vanderlei Martins,2,3 Lorraine A. Remer,3 Hila Afargan1

The effect of anthropogenic aerosols on clouds is one of the most important and least understood aspects of human-induced climate change. Small changes in the amount of cloud coverage can produce a climate forcing equivalent in magnitude and opposite in sign to that caused by anthropogenic greenhouse gases, and changes in cloud height can shift the effect of clouds from cooling to warming. Focusing on the Amazon, we show a smooth transition between two opposing effects of aerosols on clouds: the microphysical and the radiative. We show how a feedback between the optical properties of aerosols and the cloud fraction can modify the aerosol forcing, changing the total radiative energy and redistributing it over the atmospheric column.

1 Department of Environmental Sciences, Weizmann Institute, Rehovot 76100, Israel.
2 Department of Physics and Joint Center for Earth Systems Technology, University of Maryland Baltimore County, Baltimore, MD 21250, USA.
3 Laboratory for Atmospheres, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA.

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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Flood or Drought: How Do Aerosols Affect Precipitation?.
D. Rosenfeld, U. Lohmann, G. B. Raga, C. D. O'Dowd, M. Kulmala, S. Fuzzi, A. Reissell, and M. O. Andreae (2008)
Science 321, 1309-1313
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