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Historical Diurnal Temperature Range Trends in CMIP5 Models

Paper Reviewed
Lewis, S.C. and Karoly, D.J. 2013. Evaluation of historical diurnal temperature range trends in CMIP5 models. Journal of Climate 26: 9077-9089.

In prefacing their work Lewis and Karoly (2013) write that "changes in diurnal temperature range (DTR) are an identifiable characteristic of recent climatic change and also provide a useful diagnostic index for evaluating global climate models (GCMs)," citing Braganza et al. (2004); but they note that "the precise causes of DTR changes and their spatial and seasonal characteristics remain poorly understood," citing Stone and Weaver (2003). In a review of recent progress on this topic of study, Lewis and Karoly set out to examine DTR trends using "the latest generation of global climate models participating in phase 5 of the Coupled Model Intercomparison Project (CMIP5)." And what did that examination reveal?

The two Australian researchers report that "the observed global decrease in diurnal temperature range over the period of 1951-2005 resulting from the relatively larger increase in minimum temperatures than maximum temperatures is not captured in historical experiments of CMIP5 participating models." In light of this finding, Lewis and Karoly conclude that "ubiquitous model deficiencies in cloud cover and land surface processes that impact the accurate simulation of regional minimum or maximum temperature changes" are likely responsible for the models' inability to simulate the real-world DTR observations.

References
Braganza, K., Karoly, D.J. and Arblaster, J.M. 2004. Diurnal temperature range as an index of global climate change during the twentieth century. Geophysical Research Letters 31: 10.1029/2004GL019998.

Stone, D. and Weaver, A. 2003. Factors contributing to diurnal temperature range trends in twentieth and twenty-first century simulations of the CCCma coupled model. Climate Dynamics 20: 435-445.

Posted 20 October 2014