Simulated Changes in the Freezing Rain Climatology of North America under Global Warming Using a Coupled Climate Model

A precipitation typing algorithm was applied to climate model simulations in order to investigate the effect of global warming on the occurrence of freezing rain over North America. The model used in the study was the Canadian Centre for Climate Modelling and Analysis' CGCM3. Two realizations of the present-day (1981-2000) climate and two realizations of a global warming (2081-2100) simulation were run using scenario A2 from the Special Report on Emissions Scenarios (SRES) prepared by the Intergovernmental Panel on Climate Change (IPCC). The algorithm was applied to the four twenty-year periods in order to determine the change in the number and distribution of freezing rain events. The model results indicate that the present-day freezing rain maximum over eastern North America will shift poleward and weaken with the result that freezing rain events will decrease significantly in the eastern United States and the Atlantic Provinces. To the north of the maximum and over central Canada there will be modest increases in freezing rain. When averaged over North America, there will be an overall decrease in freezing rain events with global warming.