Observational evidence for a negative shortwave cloud feedback in middle to high latitudes

Ceppi, P., McCoy, D. T. and Hartmann, D. L. (2016) Observational evidence for a negative shortwave cloud feedback in middle to high latitudes. Geophysical Research Letters, 43 (3). pp. 1331-1339. ISSN 0094-8276 doi: 10.1002/2015GL067499

Abstract/Summary

Exploiting the observed robust relationships between temperature and optical depth in extratropical clouds, we calculate the shortwave cloud feedback from historical data, by regressing observed and modeled cloud property histograms onto local temperature in middle to high southern latitudes. In this region, all CMIP5 models and observational data sets predict a negative cloud feedback, mainly driven by optical thickening. Between 45° and 60°S, the mean observed shortwave feedback (−0.91 ± 0.82 W m−2 K−1, relative to local rather than global mean warming) is very close to the multimodel mean feedback in RCP8.5 (−0.98 W m−2 K−1), despite differences in the meridional structure. In models, historical temperature-cloud property relationships reliably predict the forced RCP8.5 response. Because simple theory predicts this optical thickening with warming, and cloud amount changes are relatively small, we conclude that the shortwave cloud feedback is very likely negative in the real world at middle to high latitudes.

Item Type	Article
URI	https://reading-clone.eprints-hosting.org/id/eprint/62400
Identification Number/DOI	10.1002/2015GL067499
Refereed	Yes
Divisions	Science > School of Mathematical, Physical and Computational Sciences > Department of Meteorology
Publisher	American Geophysical Union
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