An Assessment of the Primary Sources of Spread of Global Warming Estimates from Coupled Atmosphere–Ocean Models

Climate feedback analysis constitutes a useful framework for comparing the global mean surface temperature responses to an external forcing predicted by general circulation models (GCMs). Nevertheless, the contributions of the different radiative feedbacks to global warming (in equilibrium or transi...

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Bibliographic Details
Published in:	Journal of climate 2008-10, Vol.21 (19), p.5135-5144
Main Authors:	Dufresne, Jean-Louis, Bony, Sandrine
Format:	Article
Language:	eng
Subjects:	Atmosphere Atmospheric models Climate change Climate feedback Climate models Climatic analysis Climatology. Bioclimatology. Climate change Clouds Combined water Data analysis Decomposition Earth, ocean, space Equilibrium Exact sciences and technology External geophysics Feedback General circulation models Geophysics. Techniques, methods, instrumentation and models Global warming Greenhouse effect Heat Intercomparison Intergovernmental Panel on Climate Change Marine Meteorology NOTES AND CORRESPONDENCE Ocean models Ocean, Atmosphere Oceans Parametric models Primary literature Radiative forcing Research methodology Sciences of the Universe Surface temperature Uptake Water vapor Water vapour
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Summary:	Climate feedback analysis constitutes a useful framework for comparing the global mean surface temperature responses to an external forcing predicted by general circulation models (GCMs). Nevertheless, the contributions of the different radiative feedbacks to global warming (in equilibrium or transient conditions) and their comparison with the6 contribution of other processes (e.g., the ocean heat uptake) have not been quantified explicitly. Here these contributions from the classical feedback analysis framework are defined and quantified for an ensemble of 12 third phase of the Coupled Model Intercomparison Project (CMIP3)/Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4) coupled atmosphere–ocean GCMs. In transient simulations, the multimodel mean contributions to global warming associated with the combined water vapor–lapse-rate feedback, cloud feedback, and ocean heat uptake are comparable. However, intermodel differences in cloud feedbacks constitute by far the most primary source of spread of both equilibrium and transient climate responses simulated by GCMs. The spread associated with intermodel differences in cloud feedbacks appears to be roughly 3 times larger than that associated either with the combined water vapor–lapse-rate feedback, the ocean heat uptake, or the radiative forcing.
ISSN:	0894-8755 1520-0442