Journal of Geophysical Research: Atmospheres

Cover image for Vol. 121 Issue 21

Impact Factor: 3.318

ISI Journal Citation Reports © Ranking: 2015: 27/184 (Geosciences Multidisciplinary)

Online ISSN: 2169-8996

Associated Title(s): Journal of Geophysical Research

Regional Models Do Not Add Much Value to Climate Change Projections

Global general circulation models are the dominant tool in the effort to forecast the effects of climate change. Given their expansive scope, some simplifications need to be made when representing smaller-scale processes, such as the effects of regional topography. To compensate, regional climate models are sometimes used to add in local influences and, in theory, improve the accuracy of projections of regional climate change. Testing the abilities of a regional model and a global model to represent historically observed climate change for the continental United States, however, Racherla et al. (2012) found that the regional model provided only a small increase in model accuracy and in some cases actually made the forecasts worse. The authors used a regional model to dynamically downscale a global model, creating representations of the continental U.S. climate for two periods, 1967 to 1978 and 1994 to 2005. The authors ran the regional model in two modes: as a stand-alone model and with the calculations being nudged, or constrained, by the global model. They also operated the global model in two modes: at its standard resolution and with the results being interpolated to simulate a higher resolution. They then compared the model results against precipitation and temperature observations. The authors found that when nudged, the regional model outperformed the interpolated global model in representing the climate of the individual decadal periods. The nudged regional model was also more accurate than the global model at representing observed climate changes between the two periods, though the authors suggest neither setup was particularly skilled. When left unnudged, the regional model was less accurate than the interpolated global model on all counts. The authors suggest that future efforts should focus on improving the ability of global models to accurately represent long-term climate changes.

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