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Cold Tongue and Warm Pool ENSO Events in CMIP5 Models
Taschetto, A.S., Gupta, A.S., Jourdain, N.C. Santoso, A., Ummenhofer, C.C. and England, M.H. 2014. Cold tongue and warm pool ENSO events in CMIP5 mean state and future projections. Journal of Climate 27: 2861-2885.

The authors write that "the environmental and societal impacts of the El Niņo-Southern Oscillation (ENSO) set against a gradual warming of the background climate has prompted concerted efforts to improve our understanding of ENSO behavior."

What was done
In the words of Taschetto et al., they "assessed the fidelity of climate models submitted to CMIP phase 5 (CMIP5) in simulating the inter-annual SST [sea surface temperature] variability in the tropical Pacific that is largely associated with ENSO."

What was learned
In describing the many model shortcomings they discovered, the six scientists report that (1) "there is varying fidelity across the models, that (2) "there exist systematic biases in the westward extent of ENSO-related SST anomalies," which are driven by (3) "unrealistic westward displacement" and (4) "enhancement of the equatorial wind stress in the western Pacific," that (5) "most models fail to reproduce the asymmetry between the two types of La Niņas," with (6) "CT [cold tongue] stronger than WP [Warm Pool] events, which is opposite to observations," that (7) " the seasonal evolution of ENSO has a large range of behavior across the models," that (8) the CMIP5 models "have biases in the evolution of the other types of events," that (9) "the duration of WP El Niņos is overestimated for most of the models," that (10) "simulated CT La Niņas start about two seasons later than observed," that (11) "WP La Niņas end approximately six months earlier than observed," that (12) "the decay of WP El Niņos "occurs through heat content discharge in the models rather than the advection of SST via anomalous zonal currents, as seems to occur in observations," and that (13) in the Niņo-3 region "only about one-third of the models peak in the correct season."

What it means
As if the shortcomings listed above were not enough, Taschetto et al. declare - in grand understatement - that "good skill in simulating other aspects of ENSO seasonality is not guaranteed."

Reviewed 2 July 2014