The Fort McMurray Disaster: Getting Beyond “Is It Climate Change?”

In just two days, the fire engulfing the Canadian city of Fort McMurray in Alberta has seared itself into the North American consciousness. This appears to be the first time in the continent’s history we have seen a city of more than 60,000 residents (officially an “urban service area” rather than a city), located hundreds of miles from any comparable population center, forced to evacuate a furious wildfire. The fact that a city this large is also so remote owes everything to the presence of vast oil sands, the driver that has increased Fort McMurray’s population more than twentyfold since the 1960s. As of Thursday morning, May 5, more than 1,600 structures had been destroyed and 7,500 hectares (18,500 acres) burned as the fire continued to burn out of control. According to Reuters, a hotel north of the airport's main terminal had caught fire, but as the sun rose on Thursday, there was no obvious damage to the airport. There were no deaths from the blaze, but fatalities were reported in at least one vehicle crash along the evacuation route. Weather conditions in Fort McMurray on Wednesday were hellacious for firefighting--a high of 89°F, humidities as low as 7%, and powerful winds sustained at speeds as high as 34 mph, gusting to 45 mph. Thursday's weather is not going to be as bad, with highs in the upper 60s and west-northwest winds of 10 - 20 mph. There is no rain in the forecast until next Wednesday, and temperatures are predicted to once again rise above 80°F in breezy conditions on Saturday. The average high for this time of year is just 59°F.


Figure 1. Smoke rises at Fort McMurray in Alberta, Canada on May 4, 2016. Pyrocumulus clouds formed by major wildfires can sometimes develop into pyrocumulunimbus clouds intense enough to generate lightning, hail, high winds, and tornadoes. Image credit: @tamarackaspenbirch/Instagram.

A fire wildly out of season
The Fort McMurray fire arrived months ahead of when summer wildfire typically races through the boreal forests of northern Alberta. A low-pressure center arcing far north of a typical early-May track brought hot southwest winds across the Fort McMurray region, which lies within the southern edge of the great boreal forests of northern Canada. Fort McMurray saw record daily highs of 91°F on Tuesday and 89°F on Wednesday. The city gets this warm on only about five days in a typical year, and those days are usually in July or August (even then, the average daily high is between 70°F and 75°F). The hot weather struck at an uncommonly bad time for wildfire risk: after winter snows had disappeared, but before the summer green-up had taken hold. Normally the window between these would be quite narrow, but snowfall was light this winter across the region, and it disappeared quickly during record warmth in April. From December through April, Fort McMurray recorded only 1.69” of precipitation, compared to the 1981-2010 average for that period of 3.22”.


Figure 2. Wildfire danger for Canada on May 5, 2016, from the Canadian Wildland Fire Information System. Record heat, strong winds, and dryness due to below-average winter snows and the lack of spring snow cover have conspired to produce extreme fire danger over much of Alberta and Saskatchewan.

El Niño, climate change, and The Question
It’s not rocket science to connect the dots between the preconditions for the Fort McMurray fire and large-scale, long-term trends. High northern latitudes are among the planet’s most rapidly warming regions, just as predicted by climate models that incorporate human-produced greenhouse gases. The advance of Northern Hemisphere snowfall in autumn and winter has seen little significant change--if anything, there is a bit more autumn snow cover (see Figure 3 below)--but in springtime, the snowpack is vanishing far more quickly than it did in decades past, another outcome well predicted by global climate models. On top of all this, El Niño tends to produce warm Canadian winters, so the strong 2015-16 El Niño event added a hot spike to the long-term drumbeat of winter warming across western Canada. This year’s warmth has extended from the Pacific Northwest (where Portland, OR, and Seattle, WA just completed their warmest April on record) to Alaska (where Anchorage saw below-average temperatures on just 3 of the year’s first 124 days, a truly remarkable stretch).


Figure 3. Trends in Northern Hemisphere snow cover since the late 1960s, shown as departures from the monthly average extent in millions of square kilometers for October and November (top) and April and May (bottom). The snow cover last month was the least extensive for any April in the 50-year record. Image credit: Rutgers Global Snow Lab.

Wildfire: the climate plot thickens
Catastrophic wildfire is more than a temperature or precipitation anomaly. Time and again, an intense spell of record heat after weeks of warm, dry weather sets the stage for devastating wildfire. Along with this, there are other preconditions: Is the landscape packed with tinder-dry trees? Has the area burned in recent years or decades? Are local firefighters well equipped to put out small fires quickly? Are there arsonists and copycats lurking in the wings? All of these cofactors make it more difficult to draw a straight line from climate change to specific wildland fires. It’s much the same with flooding, another natural disaster influenced by how humans shape the landscape. Study after study has established that bursts of intense rainfall are becoming heavier in many parts of the world, as predicted by climate change research. Yet the human factors that feed into flooding (urban pavement, river channeling, and the like) complicate the task of attributing a particular flood to climate change.

None of this absolves human-produced greenhouse gases from loading the dice toward fire- and flood-friendly conditions. Rather, it’s to say that even the most elaborate, carefully conducted attribution studies (research designed to show how and when climate change has made a particular event more likely) may not always give the conclusive results people crave when it comes to specific fires and floods--although such work can say quite a bit about long-term trends. In fact, one of the first major attribution studies was ”Detecting the effect of climate change on Canadian forest fires,” a 2004 paper led by Nathan Gillett, which showed a detectable human influence on the area burned by wildfire in Canada between 1959 and 1999. In its February report ”Attribution of Extreme Weather Events in the Context of Climate Change”, the National Academies notes that fire season has lengthened by an average of 19% globally, with increases noted across more than 25% of Earth’s vegetated land area. “What is less clear,” the report adds, “is how climate warming is driving changes in the atmospheric circulation and its teleconnections, resulting in persistent areas of high pressure that lead to large fire years on regional scales. Similarly, it is unclear how climate warming is regulating the shorter-term weather patterns that control extreme fire periods during which fires expand rapidly.”

What do we do?
We don’t need attribution studies to realize that our struggling firefighting resources must be brought up to speed to match the evolving picture of longer fire seasons and more dangerous fires. A U.S. Forest Service report issued last summer sounded the alarm: “...within a decade, the agency will spend more than two-thirds of its budget to battle ever-increasing fires, while mission-critical programs that can help prevent fires in the first place such as forest restoration and watershed and landscape management will continue to suffer. Meanwhile...these catastrophic blazes are projected to burn twice as many acres by 2050.” It is no small irony that Wednesday, May 4, was International Firefighters Day.

In their deadline coverage of the Fort McMurray event, journalists such as Andrew Freedman (Mashable) have done a laudable job pointing out the complex but real connections between climate change and wildfire. We have much more to learn about exactly why and how the atmosphere is moving in directions that favor devastating fire--but for now, perhaps it’s enough simply to know that the dice are being loaded. Together with the many other threats posed by climate change, this should be more than enough motivation to get serious about emission cuts. The vast and profound effects of human-produced greenhouse gases--from intensified downpours and drought impacts to ocean acidification and sea-level rise--call for a sustained commitment to change that transcends any single disaster, even one as compelling as the nightmare unfolding in Fort McMurray.

Bob Henson and Jeff Masters


Video 1. Dashcam footage taken by Michel Chamberland as he evacuates the hard-hit Beacon Hill neighborhood of Fort McMurray, Alberta, on May 3, 2016, at 2 pm. Huge flames leap out along the roadside, and embers fall over the traffic. Chamberland told CBC he was feeling "pretty empty, saddened, devastated, shocked. Still trying to take in the whole situation and what happened. You just never, never expect this."