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A Host of Problems Associated with CMIP3 and 5 Climate Models

Paper Reviewed
Mayer, M., Fasullo, J.T., Trenberth, K.E. and Haimberger, L. 2016. ENSO-driven energy budget perturbations in observations and CMIP models. Climate Dynamics 47: 4009-4029.

Writing as background for their work, Mayer et al. (2016) state that "various observation-based datasets are employed to robustly quantify changes in ocean heat content (OHC), anomalous ocean–atmosphere energy exchanges and atmospheric energy transports during El Niño-Southern Oscillation (ENSO)," adding that "these results are used as a benchmark to evaluate the energy pathways during ENSO as simulated by coupled climate model runs from the CMIP3 and CMIP5 archives." So how well do climate models perform in such simulations?

Apparently, not very good, according to the four researchers, "the models are able to qualitatively reproduce the observed patterns of ENSO-related energy budget variability to some degree." However, they also found that (1) "key aspects are seriously biased," that (2) "area-averaged tropical Pacific OHC variability associated with ENSO is greatly underestimated by all models," as a result of (3) "strongly biased responses of net radiation at [the] top-of-the-atmosphere to ENSO," which (4) "are related to biases of mean convective activity in the models" that (5) "project on surface energy fluxes in the eastern Pacific Intertropical Convergence Zone region."

In addition, Mayer et al. state that the models (6,7) "underestimate horizontal and vertical OHC redistribution in association with [8] the generally too weak Bjerknes feedback," leading to (9) "a modeled ENSO affecting a too shallow layer of the Pacific." In fact, they say that "vertical links between sea surface temperature and OHC redistribution in association with the generally too weak Berknes feedback, leading to [10] a modeled ENSO affecting a too shallow layer of the Pacific." In fact, they find that (11) "vertical links between SST and OHC variability are too weak even in models driven with observed winds, indicating [12] shortcomings of the ocean models."

Furthermore, as the four researchers report, (13) "modeled teleconnections as measured by tropical Atlantic OHC variability are too weak and [14] the tropical zonal mean ENSO signal is strongly underestimated or even completely missing in most of the considered models." And in light of these facts, Mayer et al. are forced to conclude that (15) "attempts to infer insight about climate sensitivity from ENSO-related variability are likely to be hampered by biases in ENSO in CMIP simulations that do not bear a clear link to future changes."

Posted 8 February 2017