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Observational evidence for a negative shortwave cloud feedback in middle to high latitudes
Author(s) -
Ceppi Paulo,
McCoy Daniel T.,
Hartmann Dennis L.
Publication year - 2016
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2015gl067499
Subject(s) - shortwave , cloud feedback , latitude , climatology , environmental science , atmospheric sciences , cloud computing , middle latitudes , climate model , extratropical cyclone , climate change , climate sensitivity , geology , physics , computer science , radiative transfer , oceanography , geodesy , quantum mechanics , operating system
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.