PCMDI > WCRP CMIP3 Model Output > Diagnostic Subprojects

PI:	Myles Allenmyles.allen@physics.ox.ac.uk
Institution:	University of Oxford
Abstract:
Almost all simple and intermediate-complexity climate models either use or imply a single, constant value of the atmospheric feedback parameter, lambda, which determines the climate sensitivity. All studies that attempt to estimate sensitivity from observations assume lambda has a constant value. The long-term behavior of the CMIP-3 ensemble, supporting past research by, e.g. Senior and Mitchell (2000), suggests that feedbacks tend to weaken (increasing effective sensitivity), as models come into equilibrium. We are interested in attempting to parameterize this behavior in a very simple energy balance model in order to explore its implications for constraining climate sensitivity with observations, following Andronova and Schlesinger (2001), Forest et al (2002), Frame et al (2005), Hegerl et al (2006) et seq et seq et seq. To do this, we need to compute effective sensitivity as a function of global mean temperature for the 2xCO2 and 4xCO2 simulations, requiring global mean temperature and net TOA flux data.
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