Future regional intensity-duration-frequency curves of Edmonton due to potential impact of global warming

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In recent decades, hydrologic extremes have been occurring more frequently and in greater severity worldwide, which many scientists attribute to the effect of global warming. In the 4th Assessment of the Intergovernmental Panel of Climate Change report (2007) which won the Nobel Peace Prize of 2007, simulations of global climate models unanimously demonstrated that anthropogenic forcing of increased greenhouse gases have caused unprecedented, observed temperature rise at global scale in recent decades. As the Earth warms, higher temperatures will lead to higher rates of evaporation and precipitation, and more precipitation will likely fall over shorter time intervals, thus increasing the frequency and severity of extreme storm events. In other words, global warming could modify future Intensity-Duration-Frequency (IDF) curves of various Canadian cities, including that of Edmonton. In this study, we will derive possible future IDF curves of central Alberta based on extreme rainfall simulated by the mesoscale atmospheric model, MM5, using a multi-site, regional frequency analysis of the General Extreme Value (GEV) probability distribution and the probability weighted moment (PWM) method. These new IDF curves will reflect possible impact of global warming based on various SRES (Special Report on Emission Scenarios) climate scenarios projected by selected GCMs of the IPCC (2007), for three 30-year periods (2010-2039, 2040-2069, 2070-2099). Besides the CGCM2 of Canada considered in Phase I, to consider uncertainties of climate projections, in this Phase II, major GCMs such as CCSRNIES (Japan), ECHAM4 (Germany), HadCM3 (UK), CSIRO (Australia), GFDLR (USA), and NCAR-PCM (USA) for four SRES climate scenarios (A1FI, A1, B1, and B2) will also be applied to MM5 running at stand-alone mode to simulate the possible future changes to the extreme rainfall of Edmonton, Alberta. A total of 54 GCM simulations will be conducted. The new IDF curves that reflect the possible impact of climate change will help the City to avoid possible pitfalls of under-design problems in the development of its future infrastructure and drainage services.