Read here. Scientists examined the climate model output and compared it to the abrupt warming experienced in the Northern Hemisphere post-1980. The researchers determined that the rise in temperatures was associated with both an increase in the Arctic Oscillation and a simultaneous weakening of the Pacific Decadal Oscillation, neither of which were influenced by human CO2.
From the their analysis, they found that the IPCC models were unable to simulate even these major climate patterns successfully.
"The researchers report finding that the emergence of an AO-like pattern in the late 1980s and the concomitant weakening of the previously prevailing PDO-like pattern -- occurring in tandem -- were what led to the "accelerated warming in the Northern Hemisphere." And they say that these results, together with results obtained from current IPCC/CMIP3 models, "do not support the scenario that the emerging influence of the AO-like pattern in the 1980s can be attributed to the anthropogenic greenhouse effect."...state in their concluding paragraph that "this study indicates the importance of the changing behavior of the decadal fluctuations in the recent climate regime shift," and they highlight what they call "the insufficient capability of the present state-of-the-art IPCC/CMIP3 models in simulating this change." [Tzu-Ting Lo, Huang-Hsiung Hsu 2010: Atmospheric Science Letters]
Additional climate-model and peer-reviewed postings.
Update: That's what happens when one's in a hurrry - things get spelled incorrectly. The "Their" in title has been corrected.