as a giant heat dome Hovered over the Pacific Northwest three years ago, Most of North America boils over – And then burnt, Forest fire More than 18.5 million acres of land burned across the continent, with the most land burned in Canada and California.
A new study shows the extent to which human-caused climate change intensified the extraordinary event, with researchers finding the heat dome was 34% larger and lasted nearly 60% longer than in its absence. walked. Global warming, The heat dome was linked to one-third of the area burned in North America that year, according to the study published in Communications Earth & Environment.
“What happens is you get a stable weather pattern — it gets very hot and very dry,” said study author Piyush Jain, a research scientist at Natural Resources Canada. “And it dries out all the vegetation and makes everything on the ground extremely flammable.”
This study adds to the body of literature documenting how fingerprints can be detected in events such as climate change heat wavesDry and forest fire,
Jain was living in Edmonton in late June 2021, when the mercury topped 100 degrees in North America’s northernmost city of one million. “I was shocked,” he said. “Wherever I’ve been, I’ve never experienced temperatures like this.”
Farther south, the town of Lytton, British Columbia, recorded Canada’s hottest temperature, 119 degrees, on June 29 and was largely destroyed by wildfire the next day.
The extreme heat continued for 27 days, from June 18 to July 14, causing hundreds of deaths in the western United States and Canada due to skyrocketing temperatures, resulting in mass extinction of marine life, destroyed crop and timber yields. and infrastructure was damaged. , bending of highways in Washington and melting of train power lines in Portland. Over a five-day period in June, locations in seven U.S. states, including California, surpassed all-time maximum temperature records, according to the National Oceanic and Atmospheric Administration.
The heat wave also increased fire danger, breaking several fire season records across a wide region and helping to fuel wildfires in British Columbia, California, Arizona, Colorado, Utah and Montana. According to the study, more than 7.9 million acres of land burned in North America in July alone – at the time, the largest area in a single month since record keeping began. The smoke spread across the continent, Triggering an air quality alert Throughout much of the East Coast.
Jain had previously worked with other researchers to develop a method To evaluate such extreme weather events by observing anomalies in geopotential heights, which indicate whether there are high or low pressure systems in the upper atmosphere. He said high pressure systems that persist for long periods of time increase the risk of heat waves and fires. And climate change has contributed to rising altitude trends, potentially increasing these events.
In this study, Jain and his colleagues analyzed what the heat dome would have looked like without this trend. They estimated that it would have been 34% smaller, 59% smaller, and 6% less massive.
Researchers also found a strong connection between extreme heat and wildfire activity in 2021. That year, 21% of the land burned in North America was caused by fires started during and within the heat dome, with that figure rising to 34%. The researchers found that fires that started within 10 days took into account.
The size of the heat dome made it particularly troubling because it resulted in what the study authors called widespread simultaneous burning, in which many different areas caught fire at the same time. This poses a challenge for fire agencies as they seek help from other locations if there are not enough resources locally.
“If other regions are facing similar resource stress, you may reach a bottleneck at some point,” Jain said.
When there are not enough resources to control a fire when it first starts, the fire that could have been put out if it was small becomes larger and more difficult to control, resulting in the need for more resources. occurs, said John Abatzoglou, a professor of climate science at UC Merced who also worked on the study. If this type of synchronized activity continues in future years, he said, it could force fire managers to reevaluate the reliability of resource-sharing arrangements.
The study did not specifically look at how the heat that extended to Northern California affected the state’s fire season. That summer, 963,000 acres dixie fireWhich started from 13th July, Became the first to burn from one side of the Sierra Nevada to the otherThis was followed in short order by 221,000 acres caldor fire,
In general, it is difficult to attribute fires solely to any individual factor, because flames are often fueled by a complex interplay of conditions — anything from overstocked forests to wind, Abatzoglu said. Still, in 2021, June to July was the warmest in the observation period in California, and researchers have established a strong link between hot, dry summers and the area burned in the state’s forests, he said.
“It’s obviously difficult to say exactly how responsible the heat dome was for those fires,” Abatzoglu said. “But based on the extremely hot temperatures, significant heat wave events in that month, we can say that those conditions certainly helped to make fuel incredibly available and less resistance to fire after the fires started.” be provided.”
The findings increase understanding of how climate change may affect extreme weather events – and the potential role these events may play in fire activity.
“This is the latest in a growing body of evidence about the causes of wildfire conditions globally, particularly in western North America,” said Stanford University climate scientist Noah Diffenbaugh, who was not involved in the study. “I think this, in particular, is an advancement in linking the weather conditions of a record-breaking fire to specific atmospheric conditions for a specific event.”
Diffenbaugh said it’s important to untangle the impact of climate change on extreme weather events like heat domes, which are increasing in frequency and intensity. A lot of the infrastructure and risk management systems are built based on assumptions about how these events will occur, so if they change, those systems become stressed, he said.
“Through this careful analysis, linking the contribution of climate change to the record-breaking fire weather conditions associated with Heat Dome is really a great example of the kind of research we need to accurately measure the risk of climate change Diffenbaugh said. “Both the climate change we are already living with, and the climate change we can expect to see in the future, even if the world’s ambitious global warming goals are achieved. “
Studies that attempt to measure the role of climate change in individual events can also help calculate the health costs and financial toll of planetary warming from carbon emissions, which is cited in a growing number of lawsuits seeking damages. Has been done by.
Knowing the conditions under which these events occur can also help people understand how a warming climate could lead to more extreme conditions in the future, Jain said.
And all signs suggest that future is fast approaching. Since the study was written, Canada’s 2021 wildfire season was down from 2023, with more than 45 million acres burned. Jain now has a preprint examining how heat waves played a role. While there was no event as severe as the 2021 heat dome, some areas of Canada saw far-above-average heat events, he said.
“So there was no single event dominating 2023, but when you looked at the number of these events overall, it was a very extreme year in terms of heat waves,” he said. “And, of course, 2023 was the hottest year on record globally.”
