Wednesday, May 4, 2016

Forest Fire in a City: Fort McMurray

We’ve all heard about the dangers of forest fires, but it’s not so common to see a forest fire threaten an entire city. That was the story late yesterday when authorities ordered the evacuation of Fort McMurray. The time lapse video from an office window serves better than a description to convey the magnitude of the event:

About 40,000 people got out of the city yesterday — a substantial accomplishment in itself — and a few more are leaving this morning. An evacuation center in the city had to be evacuated as the fire intensified. With a record-breaking heat wave, there are similar fires burning across northern Alberta and neighboring British Columbia, but most are in sparsely populated areas. The fire that swept across a city is the one that will be remembered. The fire at Fort McMurray is likely to be at its strongest today with hotter weather and wind gusts fanning the flames. The fire chief has said the day’s priority will be to protect the main highway and its river bridge. The one part of the city that appears to be safe from the fire is the airport. An airport runway, by design, cannot be surrounded by trees.

The weather pattern that brought record heat to northwestern Canada is thought to be influenced by the early breakup of ice in the Beaufort Sea, the nearest corner of the Arctic Ocean. The warmer conditions there tend to pull the jet stream in that direction. An unusually warm winter in the Arctic region may also be contributing to the slow movement of the jet stream, allowing dry weather to persist for longer than a week. The latest weather forecast indicates only a slight chance of rain over the next ten days.

Fort McMurray is more isolated than you would imagine for a city its size. There is just one highway to the outside world, and the next city is hours away. The nearest point of comparison in the United States would be Fairbanks, Alaska. The long distances involved in the evacuation present a logistical problem. The entire route was quickly depleted of motor fuel except for what the highway patrol is bringing in for stranded motorists.

The story of the Fort McMurray fire is being closely watched by economists studying climate change because it is expected that similar city fires could become frequent occurrences after about 3 kelvins of global warming, though mainly across tropical and subtropical regions rather than the subpolar location of Fort McMurray. The world just hit 1.5 kelvins of global warming for the first time in February, so the predicted city fires might be about a century away. The story is also being followed closely in Russia, where residents are all too familiar with the threat of summer wildfires.