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Observed Trends and Model Forecasts of North American Storminess
Reference
Hayden, B.P.  1999.  Climate change and extratropical storminess in the United States: An assessment.  Journal of the American Water Resources Association 35: 1387-1397.

What was done
The author examined observed trends in the frequency of North American storms at a grid-box resolution of 2.5° latitude by 5° longitude between 25°N and 55°N latitude and 60°W and 125°W longitude over the period 1885-1996.  The observed findings were then used as a basis for evaluating model output of future storminess based on GCM projections of a CO2-induced climate change using the Hadley Center General Circulation Model HADCM2.

What was learned
Very large regional changes in storminess were noted over the 112-year period, but when integrated over the entire geographic area studied, "no net climate change in storminess [was] found."  With respect to the HADCM2 model projections of future storminess in this region, the author noted that "the model with its current spatial resolution and physics is unable to resolve storms to a degree adequate for regional studies of storminess or changes in storm frequency and magnitude in a carbon dioxide enriched world."

What it means
In the words of the author, "the lack of detectable sensitivity on the part of the model is disturbing.  If the models cannot make adequate projections about these fundamental synoptic features of the general circulation of the atmosphere, how then are parameterized output variables of the model, like precipitation and related hydrological processes, to be estimated with confidence?"  We couldn't have asked a better question.  Again, quoting the author, "it should also be clear that little can or should be said about change in variability of storminess in future, carbon dioxide enriched years."  We agree wholeheartedly.


Reviewed 15 March 2000