The objective of this project was to contribute to a greater understanding of future climate extremes affecting the Columbia Basin. Future climate change projections will be used by communities undertaking climate adaptation plans and workshops with the support of the Columbia Basin Trust (CBT).
These projections typically focus on changes in average values for temperature and precipitation over 30-year periods. This provides an overall assessment of the changing climate but does not necessarily assist in local adaptation decision-making, since impacts are often felt most directly through extreme events.
Methods
The assessment of projected changes in extremes was carried out in two ways. First, output from regional climate models was evaluated using a set of standard indices of climate extremes developed by the World Meteorological Organization Expert Team on Climate Change Detection and Indices. Second, a sophisticated statistical method called extreme value analysis (see, for example, von Storch and Zwiers 1999) was used to estimate changes in long-return period extreme events, such as warm temperatures that might be expected to recur only once every 25 years.
To ensure relevance to regional decision-making, PCIC solicited input from several contributors to CBT climate adaptation projects. The feedback was collected through a series of webinars conducted by PCIC.
Results
Figure 1 shows that the extreme warm day events that would be expected to recur about once in 25 years on average historically (based on the 1971-2000 climate) are projected to occur 2.4 to 10 times as often in the future (2050s). In general, we see a pattern of larger increases in extreme temperature for the southeastern portion of the basin.
Figure 1: Maps showing how much more often the baseline 25-year return period warm event is projected to occur in future (as ratio of occurrence in 2050s to 1971-2000) for the Canadian portion of the Columbia Basin. Shown are three of six projections representing (from left to right) low, medium and high estimates, averaged over the basin. CCSM, CGCM3 and HadCM3 are global climate models developed in the US, Canada and UK, respectively. MM5I, CRCM and HRM3 are regional climate models developed in the US, Canada and UK. The global and regional climate model simulations analyzed here used the IPCC SRES A2 emissions scenario. Regional simulations are courtesy of the NARCCAP project.
References
von Storch, H. and F.W. Zwiers, 1999: Statistical Analysis in Climate Research. Cambridge University Press, 484 pp.
Acknowledgements
Columbia Basin Trust: Ingrid Liepa, Kindy Gosal, Michelle Laurie, Cindy Pearce, Greg Utzig, Mel Reasoner, and Meredith Hamstead.
Additional Information
Murdock, T.Q. and A.T. Werner, 2011: Canadian Columbia Basin Climate Trends and Projections -- 2007-2010 Update. Pacific Climate Impacts Consortium, University of Victoria, Victoria, BC, 43pp.
Columbia Basin Trust and the City of Castlegar, 2011: Adapting to Climate Change: Project Summary Report and Action Plan.