New Paper “Origin Of The Arctic Warming In Climate Models” By Chung And Räisänen 2011

There is a new paper [h/t to Dallas Staley]

Chung, C. E., and P. Räisänen (2011), Origin of the Arctic warming in climate models, Geophys. Res. Lett., doi:10.1029/2011GL049816, in press

which presents quite a new perspective on the inability of climate models to realistically simulate the real world climate.

The abstract reads [highlight added]

There is a debate on whether the snow/ice change feedback or poleward energy transport from lower latitudes generates the observed Arctic warming amplification. There is another possibility that remotely induced warming in the Arctic can be amplified by snow/ice feedbacks. We demonstrate that this mechanism plays an important role in two independent climate models: CAM3 and ECHAM5. We also show with these two models that the June-August temperature structure in the vertical is a good indicator of how much the climate forcing from lower latitudes contributes to Arctic warming. Compared with the June-August 3D temperature trend in ERA Interim reanalysis, the CMIP3 models simulate warming at higher levels, suggesting that the models over-simulate the role of poleward energy transport in Arctic warming. This finding has implications for climate feedback and aerosol forcing.

They have a section of their paper titled “Implications” which reads

Based on the vertical structure of JJA temperature trends, we have inferred that CMIP3 models overestimate significantly the contribution of poleward energy transport to Arctic warming compared to ERA Interim data. This has important implications for either climate feedbacks or climate forcing. Assuming that the forcing is represented correctly, the implication is that either (1) the model-simulated net feedback is too large (i.e. too positive) at low latitudes (< 60ºN), or (2) the feedback is too small (i.e. too negative) in the Arctic, or both. The first scenario would provide some support to the findings of Lindzen and Choi [2009] who argue that at low latitudes the real feedback is less positive than in climate models (or even negative), with the implication that models overestimate the global climate sensitivity. On the other hand, if the second scenario is correct so that models underestimate the high latitude feedback while representing low-latitude feedbacks more or less correctly, they would tend to underestimate the climate sensitivity. The present analysis does not allow us to distinguish between these two scenarios. Note that the ice feedback in the Arctic warms the lower atmosphere, while the heat transport and general circulation respond mainly to the distribution of the mid-tropospheric temperature [Cai, 2006]. Thus, the ice albedo feedback is largely irrelevant to the strengthening/weakening of poleward energy transport.

If the models simulate climate feedbacks correctly, the indication is that models have significantly incorrect climate forcing. Since GHG forcing is well established, the problem is likely in how the models treat aerosol effects. In this scenario, the real aerosol forcing might be significantly positive in the Arctic and significantly negative outside of the Arctic, while the models miss this feature entirely. Future studies are needed to verify that the models indeed over-simulate the energy transport into the Arctic and to understand why the models do so.

This paper is yet another study that documents shortcomings in the global climate models that are used to make multi-decadal climate predictions.

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