Monday, 10 February 2003: 1:30 PM
Factors affecting climate sensitivity in global coupled climate models
Four global coupled climate models are analyzed to test the hypothesis that the relevant global-scale feedbacks involved with coupled climate model sensitivity are "managed" mostly by the atmospheric model component, with ocean, sea ice and land secondary to first order. Thus models with similar atmospheric model components should show similar global-scale response in spite of different ocean, sea ice, and land formulations, and models with different atmospheric components should be most different in terms of response. Here we compare two models with identical atmospheres and different ocean and sea ice (PCM and PCTM). These are compared to a third model with a similar atmosphere and different ocean and sea ice components (CSM). Finally, a fourth model (CCSM) with a different atmosphere but similar ocean and sea ice is compared to the PCTM. Relevant feedbacks examined are ice/albedo, water vapor and cloud. Comparison among the four models supports the hypothesis in that the two models with identical atmospheres but different ocean and sea ice components (PCM and PCTM) have the most similar global-scale response to increasing CO2, followed closely by CSM with comparable atmosphere and different ocean and sea ice from either PCM or PCTM. The CCSM has a different global response from either of the other three and, in particular, is different from PCTM in spite of very similar ocean and sea ice but a different atmospheric model component.