Thousands of Nova Scotians fleeing north of Halifax, communities evacuated or on edge across sa国际传媒 and Alberta — the 2023 wildfire season has come harder and earlier than many Canadians are used to.
On Monday, Emergency Preparedness Minister Bill Blair described the situation as "the most severe we have ever witnessed in sa国际传媒."
A day later, wildfires had burned more than 3.7 million hectares, so much of the country that it was on track to surpass an all-time record weeks before the hottest and driest conditions usually appear.
“This is unfortunately what we had envisioned was coming in 30 to 50 years, but we're experiencing it now,” said Lori Daniels, a researcher in the University of British Columbia's Department of Forests and Conservation Science.
But why now?
And what can Canadians expect in the coming decades as a heating planet drives fire weather never faced by modern humans?
The global intensification of fire weather
sa国际传媒 is warming two to three times faster than the global average. That's partly because of its northerly position on the Earth's surface. At the same time, it's almost entirely due to humans' continued practice of burning fossil fuels.
The greenhouse gases produced by those emissions have increasingly locked heat into the planet's oceans and atmosphere. As the planet has warmed, scientists collaborating under the direction of the United Nations warned last year of a "" set off by increasingly hot and dry conditions in some parts of the planet.
By 2090, wildfires are expected to increase in intensity by up to 57 per cent because of human-caused planetary warming, the UN report warned.
That's largely due to fire weather — the conditions that set the stage for forest infernos. Its presence heralds the fire season, when wildfires are most likely to start, spread and cause damage. Early research by Canadian scientists suggests that season has already become longer in parts of the country.
A 2021 from scientists at Natural Resources sa国际传媒 examining global extreme fire weather between 1979 and 2020 found decreasing relative humidity drove up the fire weather index by 14 per cent and a measure of initial spread by 12 per cent.
Rising temperatures, meanwhile, drove 40 per cent of the "significant increases" they saw.
"These trends are likely to continue, as climate change projections suggest global decreases in relative humidity and temperature increases that may increase future fire risk where fuels remain abundant," concluded the researchers.
Across the country, fire weather is expected to become more common, leading to a longer fire season in almost all areas of sa国际传媒 over the coming decades.
Recent research out of the U.S., meanwhile, has drawn a link between the world's heaviest emitters and the burned lands of western North America.
The study, published in the journal Environmental Research Letters in May 2023, found almost 40 per cent of the area burned by wildfires in Western sa国际传媒 and the United States over the last four decades was linked to emissions from .
The culprit: increased temperatures are drying out the atmosphere, raising the risk of fire weather.
sa国际传媒 to see extended fire seasons
The start of the fire season in sa国际传媒 often occurs with the disappearance of snow. Snowy regions — places that get more than 10 centimetres of snow cover for at least three-quarters of January and February — mark the start of their fire season three days after that cover has disappeared and temperatures at noon have climbed to 12 degrees Celsius.
In places without a significant snow cover, the fire season starts when mean daily temperatures hit 6 C for three days straight — the lower temperature limit plants need to grow.
Most of the extended fire season expected over the coming decades in sa国际传媒 results from an earlier start. By 2100, some regions in central and eastern Quebec and northern sa国际传媒 could see fire seasons starting a month earlier.
"Even areas that showed a recent shortening of the fire season length, such as southern coastal British Columbia, are projected to have a longer fire season," according to a Natural Resources sa国际传媒 summary of its preliminary research.
Under a scenario where humanity fails to cut its emissions, the could last between 50 and 100 days longer in large swaths of British Columbia, Alberta and Quebec, according to current estimates.
With that fire will come smoke, something many communities across sa国际传媒 are all too familiar with.
Between 2013 and 2018, the 10 census divisions in the country with the greatest exposure to fine particulate matter (PM2.5) were all in sa国际传媒's Interior, according to a 2021 Health sa国际传媒 analysis of the impacts of air pollution on human health.
Of those, half the census divisions were among the top 10 slices of the country with the highest per capita rates of premature death. That includes the town of Nelson, sa国际传媒, where persistent summer smoke led at least one doctor to clinically in 2021 — likely a global first.
Like in most places in sa国际传媒, the fire season does not end until the onset of winter, seven days after the snow cover has returned and when noon-time temperatures drop below 5 C for a week.
The end of the fire season
In other parts of North America, the idea of a fire season has already disappeared.
"In some parts of the U.S., like New Mexico, they no longer talk about the fire season because the fire season is 12 months of the year," said John Innes, professor at the University of British Columbia's Faculty of Forestry.
If the world doesn't handle its carbon pollution, sa国际传媒 could face a similar situation 50 to 100 years from now, he said.
Long before then, Innes expects prime burning conditions will drive wildfires to encroach onto urban areas more often and with greater ferocity.
"People do like to have trees around their houses, and that basically is a recipe for disaster in the future," he said. "So I think what we will see is more and more fires causing structural damage."
Guides produced by FireSmart are a good place to start. But Innes says homeowners soon need to consider the placement of trees and what species can stay to provide a buffer to extreme heat while also proving relatively fire resistant.
"I live in North West Vancouver, and we have a lot of conifers here. I'm just looking out my window, there's conifers all around me. I'd be a lot more comfortable if there were broad-leaf trees," he said.
"That, I think, is the key."
