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CO2 forcing induces semi-direct effects with consequences for climate feedback interepations

Andrews, T and Forster, PM (2008) CO2 forcing induces semi-direct effects with consequences for climate feedback interepations. Geophysical Research Letters, 35 (4). ISSN 0094-8276

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Climate forcing and feedbacks are diagnosed from seven slab-ocean GCMs for 2 × CO2 using a regression method. Results are compared to those using conventional methodologies to derive a semi-direct forcing due to tropospheric adjustment, analogous to the semi-direct effect of absorbing aerosols. All models show a cloud semi-direct effect, indicating a rapid cloud response to CO2; cloud typically decreases, enhancing the warming. Similarly there is evidence of semi-direct effects from water-vapour, lapse-rate, ice and snow. Previous estimates of climate feedbacks are unlikely to have taken these semi-direct effects into account and so misinterpret processes as feedbacks that depend only on the forcing, but not the global surface temperature. We show that the actual cloud feedback is smaller than what previous methods suggest and that a significant part of the cloud response and the large spread between previous model estimates of cloud feedback is due to the semi-direct forcing.

Item Type: Article
Copyright, Publisher and Additional Information: © 2008 American Geophysical Union. Reproduced in accordance with the publisher's self-archiving policy.
Keywords: tropospheric adjustment, semi-direct effects, cloud feedbacks.
Institution: The University of Leeds
Academic Units: The University of Leeds > Faculty of Environment (Leeds) > School of Earth and Environment (Leeds)
Depositing User: Symplectic Publications
Date Deposited: 13 Oct 2011 10:59
Last Modified: 09 Jun 2014 16:03
Published Version: http://dx.doi.org/10.1029/2007GL032273
Status: Published
Publisher: American Geophysical Union
Identification Number: 10.1029/2007GL032273.
Related URLs:
URI: http://eprints.whiterose.ac.uk/id/eprint/43313

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