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Whenever there is an instance of severe weather, or a natural disaster heavily-influenced by the weather, such as the wildfires currently burning in northern Alberta, a question that often arises is "was this caused by climate change?"
OUT OF THIS WORLD | Earth, Space And The Stuff In Between - a daily journey through weather, space and science with meteorologist/science writer Scott Sutherland

Wildfires to grow worse in Canada as the world warms

Scott Sutherland
Meteorologist/Science Writer

Wednesday, May 18, 2016, 9:23 AM - Whenever there is an instance of severe weather, or a natural disaster heavily-influenced by the weather, such as the wildfires currently burning in northern Alberta, a question that often arises is "was this caused by climate change?"

There is some evidence that the wildfire that caused the evacuation of Fort McMurray had a human cause. Mike Flannigan, Professor of Wildland Fire at the University of Alberta, told the Canadian Press just days after the fires started that there was no indication of lightning strikes in the area when the fire first started. Along with the proximity to the community, that likely points to a human cause to the fire.

Did climate change have anything to do with it, though? 

We've seen the average area burned by wildfires roughly double over the past 3 or 4 decades, and looking at the weather conditions in western Canada over the past few years, they have certainly been a little unusual.

In 2014 -- a year when conditions were not considered particularly favourable for wildfires -- the Northwest Territories still suffered one of the worst fire seasons on record. A total area of 4.6 million hectares of forest was consumed that year, triple the 20 year average for the region. In 2015, after an unusually warm, dry winter due to "The Blob" over the northeastern Pacific, B.C., Alberta and Saskatchewan experienced extreme wildfire seasons. For 2016, an unusually warm El Niño had resulted in even more warm, dry conditions over the past winter, as it typically does for western Canada, which has set up the current situation of moderate to severe drought in northern and southeastern Alberta. These factors have made the region even more vulnerable to wildfires this year, and certainly more susceptible to large, severe wildfires.

Is there a connection to climate change? Last year, oceanographer Richard Dewey told Maclean’s Magazine that nothing as extraordinary as The Blob had been seen before, and that it could be a precursor to what climate change will bring.

According to Simon Donner, an Associate Professor of Climatology at the University of British Columbia, there has been an overall increase in El Niño temperatures seen in the records, which has definite ties to climate change. 
Neither of these facts can be used to point to a cause for the fires, however.

"Fires have happened in the past and fires would happen in the future, even if there wasn't a human impact on the climate, and how a fire starts may have nothing to do with climate change," Donner told The Weather Network. "The issue is how much these fires can spread, and how quickly they can spread. That is what climate change is doing."

Thus, while the conditions in western Canada over the past two years have been set up, first by the Blob and then El Niño, to make the region more vulnerable to the spread of wildfires, there's really no way to point to a specific wildfire and say it was "caused" by climate change.

As Weather Network chief meteorologist Chris Scott said in the video above, "We can't say that climate change has made individual fires like this happen."

"What climate change does is essentially load the dice. It changes the odds of getting certain types of events," he explained. "Did climate change cause this fire? Absolutely not. Does it make fires like this more likely in the future? Yes, it does."

Wildfires in a warming world

Even as wildfires continue to burn out of control near Fort McMurray and other parts of northern Alberta and northern British Columbia, Canada is being set up for even worse fires and fire seasons in the future, due to climate change.

Wildfires are a natural and expected part of life in Canada's boreal forests. As long as there is available fuel, something to ignite it and weather to drive the flames, they will continue to be a part of the ecosystem. Some are spread by the wind, such as those seen in the Slave Lake area in 2011. Others are driven by convection as they consume abundant fuel sources and even generate their own fire weather. Fort McMurray is an example of this, and the fire even generated its own pyrocumulus clouds, resulting in lightning strikes that sparked off even more fires.

While destructive to the forest in the short-term, they act as part of the natural renewal cycle of the ecosystem, removing dead or diseased trees, ridding the forest of pests, and clearing the way for new trees to populate the area.

From all indications, though, human-caused climate change is setting up conditions - most notably higher temperatures - that are expected to make wildfires more common, as well as larger and more severe, which is good for neither us, nor the forest.

According to Flannigan, the reason why rising temperatures are so important for the future of wildfires is three-fold:

1) The fire season is getting longer. Alberta officially started their fire season on March 1 this year, a full month earlier than usual. Normally, a cold, snowy winter provides enough moisture to the forest for fire conditions to "reset" at their lowest level by the start of spring. The warm, dry winter seen across Western Canada prevented this reset, leaving the province with conditions more likely to be seen at the beginning of summer, thus prompting the earlier start.

2) A warmer atmosphere means more lightning. Basically, as more heat is added to the atmosphere, and thus more energy, storm convection will increase, and more storm convection produces more lightning. Studies have shown that lightning strikes are expected to happen roughly 12 per cent more for every degree Celsius rise in temperature. Lightning strikes are only responsible for roughly 35 per cent of wildfires in Canada, according to Flannigan, however those wildfires started by lightning are responsible for around 85 per cent of the roughly 2 million hectares of forest area that are currently consumed by wildfires, on average, each year.

3) A warmer atmosphere holds more moisture. As the temperature rises, the air is capable of holding more water vapour, and it will fill this extra capacity from any available source. In Canada's boreal forests, this means the trees, plants, debris and soil, as well as any wetlands in the environment, will have water drawn out of them by evaporation. This dries out the fuel source for the wildfires, making it easier for them to ignite and easier for them to spread.

Increases in wildfire activity for 2030 and 2090, from Canadian
Climate Centre general circulation model (GCM).
"Implications of changing climate for global wildland fire"
Flannigan et al. 2009.

The influence of this last factor, the amount of moisture that is evaporated from the potential fuel source, can be reduced if there is a corresponding increase in precipitation to go along with the temperature rise. While precipitation amounts are expected to increase as moisture content in the air rises, it does not appear that it will be enough. Flannigan, along with colleagues from the University of Alberta, Natural Resources Canada and the University of Toronto, ran climate model simulations to test for this, and reported their findings in a study published earlier this year.

"Almost never, in the future, will the precipitation compensate for the increased warming," Flannigan told The Weather Network. "For most parts of Canada, it appears that with warming, we will see drier fuels, and with drier fuels that means it's easier for wildfires to start and spread."

According to Flannigan, since the early 1970s, the average area burned by wildfires each year has increased from around 1 million hectares to the current average of roughly 2 million hectares. The total area burned goes up and down, year to year, as specific weather patterns can produce a "good" or "bad" fire season each year, however a doubling of the average burn area over a 30-40 year time scale is certainly a noticeable impact of human-caused climate change.

As temperatures continue to climb, this will only get worse in the future, resulting in more frequent "bad" fire seasons.

Increased threat to communities and the forest

It's easy to see why larger, more frequent and increasingly severe wildfires are not good news for communities in Canada's boreal forests. We only need to look to at what has happened in Fort McMurray since the beginning of May, and the latest evacuations in northwestern Alberta, for examples of what we may be seeing more often in the future.

Since wildfires are a natural part of the ecosystem, though, why would having more fires, or even larger ones, be bad for the forest? It really comes down to the timing and severity.

If a wildfire sweeps through a particular area of the forest, it burns down old growth and dried out debris on the forest floor, eliminating any pests or diseases present in that area along the way. Eventually, that area will recover, as new, healthy trees grow up in the aftermath. These new, green growths are typically protected from wildfires for roughly 15 to 20 years, according to Flannigan, simply due to the difficulty in burning young growth and the lack of fuel on the forest floor.

When a region of the forest is hit twice on a short time-scale, however, it may not recover.

"I call it a double whammy," Flannigan said. "If you have a harvesting (trees are cut down for delivery to a mill) and then a severe fire, it takes a long time to recover and it may not recover the way it normally does."

"If the fire is so severe that it burns a young forest," he explained, "as we saw in the Northwest Territories in 2014, when a wildfire re-burned a 2004 burn, it's basically like a desert there, since the fire consumed everything."

A site near Sandy River, NWT suffered a severe wildfire in 2014, only 10 years after a previous burn. With all the new growth consumed, the area is now like a desert. Photo Credit: Dennis Quintilio

What can we do?

As for the links to climate change, the best way to deal with that problem is for the world to switch from fossil fuels to renewable energy sources like hydroelectric, solar, wind, tidal and geothermal. This cuts the source of human-caused climate change off at its source. While we'll still be dealing with at least some climate change from the greenhouse gas emissions already released into the atmosphere, we may be able to at least stabilize the situation. Given time, the ecosystem will either adapt or it may return to something more "normal" than we're seeing now.

With the likely human cause for the Fort McMurray wildfire, and with climate change raising the risk of wildfires in Canada's boreal forests, there is an even stronger case for us to take care when dealing with fire, and being even more vigilant when it comes to potential sources of fire.

Primarily, this means showing a greater respect for fire and its capabilities. A wildfire can start from a campfire that gets out of control or is not properly extinguished, a discarded cigarette butt, a poorly maintained lawn mower or other piece of outdoor equipment, or even something like a chain being dragged behind a vehicle.

The old adage "it only takes a spark" has even greater meaning when the area that you are living in or visiting is suffering through a drought.

Somewhere around 65 per cent of all wildfires are human-caused, based on the statistics. Although these tend to be smaller and more easily-contained fires, thus only accounting for about 15 per cent of the total area burned, in a world more susceptible to the spread of fires, that 65 per cent can begin to take a larger overall toll.

Source: CBC

Watch below: Fort McMurray Sky Turns Orange as Fire Forces Oil Workers to Evacuate Again

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