Searching for Megadroughts in CMIP5 Climate Models
Langford, S., Stevenson, S. and Noone, D. 2014. Analysis of low-frequency precipitation variability in CMIP5 historical simulations for southwestern North America. Journal of Climate 27: 2735-2756.
With respect to problems they identified, the three U.S. researchers report (1) "the CMIP5 models have higher climatological precipitation in southwestern North America than reanalysis products," (2) "shortcomings in summer precipitation in southwestern North America are more severe than for winter precipitation," and (3) "climatological winds along the Gulf of California in July are misrepresented in CMIP5 models." On the other hand, they report "robust coincident anomaly patterns in the tropical and North Pacific Ocean and low-frequency (5 yr) winter California precipitation exist in the CMIP5 historical simulations," but they say these associations are "unable to explain more than 20% of the decadal variability."
In discussing the significance of their findings, Langford et al. conclude "the small fraction of explained variance will limit the predictability of precipitation associated with the decadal variability and persistence offered by the ocean," which means that it's back to the drawing board - or in this case to the super computers - to try yet again to get the models to where they need to be in order to do any real good.
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