It's an apocalyptic scene in the far North: Tens of thousands fleeing an onrushing wildfire, struggling to find gasoline in the heart of Canada's oil patch.
But the disaster unfolding in Alberta isn't just a "one-off," as one scientist puts it. Canada has seen its annual fire season get longer and bigger for the past several decades as its climate warms, raising the odds of a massive blaze like the one now tearing through Fort McMurray.
The city, located more than 400 km (250 miles) north of the provincial capital Edmonton, is home to more than 80,000 people. It's the hub of the tar sand country, where oil companies extract a thick, sludgy crude known as bitumen — one of the most carbon-intensive forms of petroleum — from the ground, yet the evacuation was hampered by shortages of fuel.
Drivers were stranded on roadsides outside the city, and authorities rushed tank trucks into the area to get them out. Once the evacuation orders were issued, it was "chaos," with kilometer-long gas lines and people walking with jerry cans in search of fuel, said Justin Ossachuk, a water and sewer superintendent.
"People were driving on the sidewalks, on the grass," he said. "There were accidents everywhere — not much moving. The traffic was real slow."
The rapidly spreading fire was whipped up further by unseasonably warm temperatures and winds of nearly 40 kph (25 mph). Tuesday's high of 32 degrees Celsius (90 Fahrenheit) is far warmer than the area's normal high of 16 C (60 F), Canada's weather service reported.
That's an unusual spike —but overall, the number of hot days in Alberta has gone up sharply since 1950, according to provincial government statistics. And as a result, the blazes in the boreal forests of Canada's northwest are getting worse, said Mike Flannigan, a wildfire researcher at the University of Alberta.
"There's a lot of year-to-year variability in area burned, but we have doubled since the 1970s," Flannigan said. "And the last three years have been very active fire years. We typically burn more than 2 million hectares (7,700 square miles) a year now, which is half the size of our province of Nova Scotia."
Northwestern Canada has warmed more than the country as a whole. That's meant the plants and fallen limbs that lie on the forest floors are drier. The wetlands around them are drying up as well, turning from a potential firebreak to a new source of fuel. And warmer weather means more lightning, which can touch off a blaze: Recent studies indicate a 1-degree increase in temperature can lead to 12 percent more lighting, Flannigan said.
That combination is leading to more extreme fires like the one ravaging Fort McMurray now, he said. Only about 3 percent of fires involve more than 200 hectares (500 acres) — but those are responsible for 97 percent of the area destroyed.
"Right now, we have two or three bad fire years in a decade," Flannigan said. "By mid-century, I expect four or five bad years in a decade."
The Fort McMurray fire had destroyed 1,600 buildings by Thursday morning, Alberta's provincial Premier Rachel Notley told reporters. The local government reported 70 percent of the homes were destroyed in one Fort McMurray neighborhood, home to more than 2,200 people, and a thick, choking haze hung over the area.
"This is the single biggest evacuation that we've seen from a fire and biggest overall impact on a community in the history of province," Notley said.
But amid the carnage, 88,000 people had been evacuated without injury, the Regional Municipality of Wood Buffalo, which includes Fort McMurray, reported.
Canada's military is contributing helicopters for search-and-rescue work and cargo planes to help with evacuations and bring in fresh supplies and firefighters, Notley said. And many of the oil companies that work in the tar sands had opened up their camps to evacuees.
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