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Science
| 05/11/16

Fort McMurray will need climate-aware reconstruction

TCE

Scientists say the risks posed by climate change must be planned for in the rebuilding of Fort McMurray—and by other settlements surrounded by forests—in the face of the national and global trend toward longer, hotter and drier fire seasons.

A political firestorm erupted this week over whether global warming caused the massive wildfire that forced the evacuation of 80,000 residents from Fort Mac last Tuesday. Prime Minister Justin Trudeau warned against linking the fire to climate change saying it was “not helpful”, while the BC and Ontario premiers did exactly that, and an employee of an Albertan municipality has even been suspended for tweeting comments along these lines.

What do scientists say about the matter? It is true that until recently, researchers have been very reluctant to attribute a specific natural disaster to human-caused global warming, even though it is widely accepted that a rise in average global temperatures will increase the frequency and intensity of extreme weather events.

However, what researchers can say is that the wildfire season in Canada is starting earlier and lasting longer than it has historically. In 2004, Canadian scientists published a paper in the journal Geophysical Research Letters that described how the area burnt by forest fires in Canada has steadily increased over the previous forty years in concert with increasing summer temperatures. They used computer models to conclude that climate change had a “detectable influence” on this phenomenon.

Mike Flannigan, a University of Alberta professor and one of the authors of the 2004 paper, this week put some hard percentages on those increases, stating that the area burnt in Canada has doubled since the 1970’s. Factors behind the trend include modern land use patterns and firefighting techniques that leave more fuel, such as undergrowth, to burn. But he told CBC News the stand-out factor was rising temperatures.

Last week, temperatures were unusually warm in Alberta for May, pushing beyond the mid 30s Celsius. Performing the heavy lifting here was the strongest El Niño event since 1997-98 being in effect during 2015 and early 2016. In the prairies, this resulted in a warmer, drier winter and spring, and precipitation over the winter was unusually low for the area.

The most recent UN climate report, published in 2014, said that North America would experience increasing wildfires due to a drying trend and warmer temperatures.

Meanwhile, satellite data put out by the Rutgers Global Snow Lab showed that last month experienced the lowest snow cover extent in the northern hemisphere of any April in five decades. The crucial effect being that an earlier melt means an earlier drying out of soil and organic fuel (plant material) in forests and grasslands.

“It will be important pretty quickly to talk about the risks that the reconstructed city will be exposed to.”

Francis Zwiers, another of the authors of the 2004 paper and the director of PICS sister organisation, the Pacific Climate Impacts Consortium, is sympathetic to the idea that we can wait to make attribution assessments. “But it will be important pretty quickly to talk about the role of climate change and the risks that the reconstructed city will be exposed to.”

He says that Fort McMurray, and other locations, need to analyze the varying past, present and future risk of extreme events, rather than assume, as is current engineering norms, that the risk is the same at all times.

 

Journal links:

Gillett, N. P., 2004: Detecting the effect of climate change on Canadian forest fires. Geophys. Res. Lett. Geophysical Research Letters, 31, doi:10.1029/2004gl020876.

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