Untangling aerosol effects on clouds and precipitation in a buffered system


It is thought that changes in the concentration of cloud-active aerosol can alter the precipitation efficiency of clouds, thereby changing cloud amount and, hence, the radiative forcing of the climate system. Despite decades of research, it has proved frustratingly difficult to establish climatically meaningful relationships among the aerosol, clouds and precipitation. As a result, the climatic effect of the aerosol remains controversial. We propose that the difficulty in untangling relationships among the aerosol, clouds and precipitation reflects the inadequacy of existing tools and methodologies and a failure to account for processes that buffer cloud and precipitation responses to aerosol perturbations.

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Figure 1: The lifetime (and albedo) effect as originally proposed.
Figure 2: Satellite image of the northeast Pacific Ocean showing ship tracks, both in thin closed-cellular stratocumulus regions and in open-cellular regions.
Figure 3: Aerosol–cloud interactions in the context of the atmospheric component of the Earth system.
Figure 4: The deepening effect.


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We thank M. O. Andreae, T. Garrett, J. Marotzke, L. Nuijens, R. Pincus, I. Sandu, A. Seifert and R. Wood for comments on an earlier draft of this manuscript. We also wish to acknowledge contributions to this document arising through the course of many discussions with members of the Aerosol, Clouds, Precipitation and Climate Initiative planning team.

Author Contributions The ideas presented here were developed jointly by B.S. and G.F., and both authors participated actively in the writing of the manuscript and the drafting of the figures.

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Correspondence to Bjorn Stevens.

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Stevens, B., Feingold, G. Untangling aerosol effects on clouds and precipitation in a buffered system. Nature 461, 607–613 (2009). https://doi.org/10.1038/nature08281

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