Regional Climate Models Differ in Extreme Precipitation Event Forecasts
Schliep, E.M., Cooley, D., Sain, S.R. and Hoeting, J.A. 2010. A comparison study of extreme precipitation from six different regional climate models via spatial hierarchical modeling. Extremes 13: 219-239.
The six RCMs showed similar general spatial patterns of extrema across North America, with the highest extremes in the Southeast and along the West Coast. However, when comparing absolute levels, which are most relevant to risk forecasts, the models exhibited strong disagreement. The lowest-predicting model was low almost everywhere in North America compared to the mean of the six models; and, similarly, the highest-predicting model was above the mean almost everywhere. In fact, the difference between the two models was almost 60mm of daily precipitation (for the 100-year extreme event) over much of the United States.
The other four models showed greatly differing spatial patterns of extremes from each other, which differences were found to be statistically significant by F test. And the authors speculate that when driven by multiple GCMs rather than reanalysis data, the range of extreme outcomes would only increase. Thus, the study of Schliep et al. leads to the conclusion that depending on regional models for making policy about extreme rainfall events would be very uncertain and, therefore, essentially an exercise in futility ... and a dangerous one at that!