A global analysis of satellite data suggests that cloud cover accelerates warming, confirming results from climate models.
As Earth's average temperature rises, clouds will, on the whole, accelerate global warming by trapping more heat. The first planet-wide, observation-based study of the climatic effect of clouds confirms estimates previously produced by models.
Atmospheric scientist Andrew Dessler of Texas A&M University in College Station analysed satellite data gathered between March 2000 and February 2010 to assess short-term variations in the amount of visible and infrared radiation emitted to space1. Subtracting influences such as Earth's surface reflectivity and the heat-trapping effect of atmospheric water vapour, he estimated how clouds affected the planet's radiation balance as a function of temperature over the decade. Dessler's analysis suggests that clouds enhance warming by trapping, on average, an extra 0.54 watts per square metre for every 1-degree-Celsius rise in global average temperature.
But uncertainty in the estimate indicates that clouds could actually exert a small cooling effect as temperature rises, says Dessler. Even so, he notes, that slight negative feedback wouldn't be nearly enough to cancel out larger, well-constrained positive climatic feedbacks, such as that provided by water vapour.
References
Dessler, A. E. A determination of the cloud feedback from climate variations over the past decade. Science 330, 1523–1527 (2010).
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Perkins, S. Clouds' contribution. Nature Clim Change (2010). https://doi.org/10.1038/nclimate1026
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DOI: https://doi.org/10.1038/nclimate1026