Increasing frequency of extreme fire weather in Canada with climate change

Abstract

In Canadian forests, the majority of burned area occurs on a small number of days of extreme fire weather. These days lie within the tail end of the distribution of fire weather, and are often the periods when fire suppression capacity is most challenged. We examined the historic and future frequency of such extreme fire weather events across 16 fire regime zones in the forested regions of Canada from 1970 to the year 2090. Two measurements are used to measure the extreme fire weather events, the 95th percentile of Fire Weather Index (FWI₉₅) and the number of spread days. The annual frequency of fire spread days is modelled to increase 35–400 % by 2050 with the greatest absolute increases occurring in the Boreal Plains of Alberta and Saskatchewan. The largest proportional increase in the number of spread days is modelled to occur in coastal and temperate forests. This large increase in spread days was found despite a modest average increase in FWI₉₅. Our findings suggest that the impact of future climate change in Canadian forests is sufficient to increase the number of days with active fire spread. Fire management agencies in coastal and temperate regions may need to adapt their planning and capacity to deal with proportionally larger changes to their fire weather regime compared to the already high fire management capacity found in drier continental regions.