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Modelling the Indian Ocean Zonal Dipole Mode of Earth's Climate

Paper Reviewed
Liu, L., Xie, S.-P., Zheng, X.-T., Li, T., Du, Y. Huang, G. and Yu, W.-D. 2014. Indian Ocean variability in the CMIP5 multi-model ensemble: the zonal dipole mode. Climate Dynamics 43: 1715-1730.

In introducing their study, Liu et al. (2014) describe how they evaluated the abilities of 21 Coupled Model Intercomparison Project Phase 5 (CMIP5) models to simulate the Indian Ocean Dipole (IOD) mode of Earth's climate, and to thereby determine to what degree this set of models may have improved in this regard compared to the prior set of CMIP3 models. And what did they thereby learn from this exercise?

The seven scientists report that (1) "while observations show a positive feedback among the wind, evaporation and sea surface temperature during the IOD developing phase, about half of the CMIP5 models failed to capture this thermodynamic air-sea feedback," specifically noting that (2) "the CMIP5 ensemble ... produces a worse Bjerknes dynamic feedback than CMIP3," that (3) "the wind response to sea surface temperature forcing ... is underestimated in the newer generation models," that (4) "the thermocline response to surface wind forcing is overestimated," and that (5) "the overall CMIP5 performance in the IOD simulation does not show remarkable improvement compared to the CMIP3 simulations." In some cases, in fact, they indicate that their analysis actually depicts a decrease in model performance from CMIP3 to CMIP5, as is reported in points 2 and 3 above.

All things considered, therefore, and in regard to the specific climatic phenomenon studied by Liu et al. - the Indian Ocean Zonal Dipole - it would appear that essentially no progress has been made in the world of climate modelling between the Fourth and Fifth Assessment Reports of the Intergovernmental Panel on Climate Change.

Posted 6 January 2015