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Technical Thematic Report No. 5. - Canadian climate trends, 1950-2007


Canada’s climate has changed considerably since 1950: temperatures have increased over much of the country, and precipitation has also increased, especially over northern Canada. These are driving trends in other climate variables that are of significance to ecosystems, for example a shorter snow cover season, less winter snow accumulation, earlier melt of snow and ice in the spring, an earlier and longer growing season with fewer frost days, and decreasing potential for water availability. These changes are also associated with fundamental shifts in hydrologic regimes such as a decrease in the fraction of precipitation falling as snow over southern Canada, and earlier spring runoff. Studies have suggested that the observed warming trend in Canadian temperature and perhaps the increase in precipitation over northern Canada can be attributed to human emissions of greenhouse gases (Lemke et al., 2007; Min et al., 2008). These trends are also consistent with climate model projections over North America (Meehl et al., 2007) that indicate a warmer and wetter climate for many regions of Canada in the future. The implications of these changes on Canadian ecosystems are discussed in the Technical Ecozone+ Reports.

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