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Some Incompatibilities of Global and Regional Climate Models

Paper Reviewed
Evans, J.P. and McCabe, M.F. 2013. Effect of model resolution on a regional climate model simulation over southeast Australia. Climate Research 56: 131-145.

In the words of Evans and McCabe (2013), "climate change impact and adaptation responses are required at regional to local scales to help inform planning and management of infrastructure, urban development, water and energy sectors, agricultural output and a range of other social and economic activities." And, therefore, they indicate that "dynamically downscaling climate projections from global climate models (GCMs) for use in impacts and adaptation research has become a common practice in recent years."

As an example of problems that can occur during this process, Evans and McCabe relate their findings when the CSIRO Mk3.5 GCM was downscaled - using the Weather Research and Forecasting (WRF) regional climate model (RCM) - to medium (50 km) and high (10 km) resolution over southeast Australia. In so doing the two researchers report that (1) "the GCM erroneously transported too much tropical moisture into the domain through the northeast quadrant of the boundary," that (2) "the RCMs were unable to correct for errors in the large scale forcing from the GCM," that (3) "at higher resolutions and with better resolved topography, this extra moisture manifests as too much precipitation compared to the observations," that (4) "resolution modifications ... can be large enough to change the sign of the climate change projected by the GCM," and that (5) "the GCM has a tendency to project increases in extremes even when the mean is projected to decrease."

It would thus appear that regional- to local-scale predictions of GCMs can often be misleading; and corrections imposed by RCM downscaling can also be misleading.

Posted 14 October 2014