Solar-cycle response in global climate models assessed by IPCC AR4

Do IPCC models underestimate the earth's climate response to solar variation? The adequacy of the IPCC models in this regard can be checked by examining their response to the 11-year solar cycle, whose forcing has been measured accurately by satellites since 1978. In response to this cyclic forcing previous generation of GCMs produced a very weak warming signal at the Earth's surface, of the order of 0.06 C from solar min to solar max, leading to cautionary comments even in AR4 that current models may underestimate solar response, in both long-term and 11-year variations. Haig [1996] pointed out that the previous attempts at GCM simulation of the 11-year solar cycle used fixed sea-surface temperature, which may have inhibited the various climate feedback processes. The GCMs assessed by IPCC AR4 incorporates coupled ocean and atmosphere dynamics, but due to a lack of study at this point it is not clear if the solar cycle response is correctly reproduced in these models. Using multi-model archived outputs in the repository, we compare model temperature responses in models with and without solar cycle forcing. These are additionally compared with the recent observational result of Camp and Tung [2007], who found a globally averaged warming of almost 0.2 C from solar min to solar max.