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Recent Antarctic Sea Ice Extent in CMIP5 Models
Reference
Turner, J., Bracegirdle, T.J., Phillips, T., Marshall, G.J. and Hosking, J.S. 2013. An initial assessment of Antarctic sea ice extent in the CMIP5 models. Journal of Climate 26: 1473-1484.

Background
The authors write that "Phase 5 of CMIP (CMIP5) will provide the model output that will form the basis of the Fifth Assessment Report (AR5) of the IPCC [Intergovernmental Panel on Climate Change]," and they therefore thought it important to determine how well these models represent reality.

What was done
Turner et al. examined "the annual cycle and trends in Antarctic sea ice extent (SIE) for 18 models used in phase 5 of the Coupled Model Intercomparison Project that were run with historical forcing for the 1850s to 2005."

What was learned
The five researchers report that (1) "the majority of models have too small of an SIE at the minimum in February," that (2) "several of the models have less than two-thirds of the observed SIE at the September maximum," that (3) "in contrast to the satellite data, which exhibit a slight increase in SIE, the mean SIE of the models over 1979-2005 shows a decrease in each month," that (4) "the models have very large differences in SIE over 1860-2005," and that (5) "the negative SIE trends in most of the model runs over 1979-2005 are a continuation of an earlier decline, suggesting that the processes responsible for the observed increase over the last 30 years are not being simulated correctly."

What it means
In the words of Turner et al., "many of the SIE biases in the CMIP3 runs remain in CMIP5." More particularly, for example, they state that "as with CMIP3, the models do not simulate the recent increase in Antarctic SIE observed in the satellite data." And so once again - as in our review of the study of Chang et al. (2013) - we are forced to say: "meet the new models, same as the old models ... and don't get fooled again" ... again!

Reference
Chang, E.K.M., Guo, Y., Xia, X. and Zheng, M. 2013. Storm-track activity in IPCC AR4/CMIP3 model simulations. Journal of Climate 26: 246-260.

Reviewed 19 June 2013