A new study has identified "hotspots" where temperatures are spiking far beyond what is expected as the planet warms, with some of the most striking examples occurring in the Pacific Northwest and southwestern Canada.
In June 2021, an unprecedented nine-day heat wave struck the Pacific Northwest, as daily temperatures broke records by as much as 54 degrees Fahrenheit in some areas.
Lytton, British Columbia, reached 121.3 degrees Fahrenheit—the highest temperature ever recorded in Canada—and the town was destroyed the next day in a wildfire fueled by the dried-out vegetation.
Hundreds of people in Oregon, Washington and British Columbia succumbed to heat-related illnesses during this period, with the region ill-equipped to handle such extreme conditions because of limited access to air conditioning.
"This is about extreme trends that are the outcome of physical interactions we might not completely understand," lead author Kai Kornhuber, an adjunct scientist at the Columbia Climate School's Lamont-Doherty Earth Observatory, said in a statement.
"These regions become temporary hothouses," he added.
The study highlights that these extraordinary heat waves have disproportionately struck in the past five years, though sporadic events have occurred earlier.
In Canada, the Northwest Territories and High Arctic islands are seeing alarming temperature accelerations. The findings also extend to parts of Texas and New Mexico in the U.S., though these areas are not experiencing the most extreme margins.
The study identified "tail-widening" trends—statistical anomalies where maximum temperatures exceeded projections by enormous margins.
While the Arctic's rapid warming destabilizes the jet stream, leading to weather phenomena such as Rossby waves that trap heat in specific regions. The researchers cautioned that no single factor fully explained these extreme outbreaks.
For instance, the Pacific Northwest's deadly 2021 heat wave involved a confluence of factors, including rising background temperatures, drying vegetation and atmospheric waves funneling heat from the Pacific Ocean inland.
The heat wave "was so extreme, it's tempting to apply the label of a 'black swan' event, one that can't be predicted," co-author Samuel Bartusek said in the statement.
"But there's a boundary between the totally unpredictable, the plausible and the totally expected that's hard to categorize," he added. "I would call this more of a gray swan."
In the United States, heat waves kill more people annually than hurricanes, tornadoes and floods combined, with 2,325 deaths recorded in 2023—a figure that has doubled since 1999, research showed.
Experts are now urging governments to name heat waves, similar to hurricanes, to heighten public awareness and improve preparedness.
With temperatures 2.12 degrees Fahrenheit above the 20th-century average, 2023 was the hottest year on record. This year is expected to be another record breaker for heat across the globe.
The extreme heat waves extend far beyond North America. Other hard-hit regions include China, Japan, Korea, the Arabian Peninsula, eastern Australia and parts of Africa.
Northwestern Europe is experiencing the most intense and significant heat waves, according to the study. In recent years, countries such as Germany, France, the United Kingdom and the Netherlands have been experiencing hot days that are warming twice as fast as mean temperatures.
Unlike many places in the U.S., these places are poorly equipped to deal with such heat, with the populations lacking necessities such as air conditioning.
"Due to their unprecedented nature, these heat waves are usually linked to very severe health impacts and can be disastrous for agriculture, vegetation and infrastructure," Kornhuber said. "We're not built for them, and we might not be able to adapt fast enough."
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References
Kornhuber, K., Bartusek, S., Seager, R., Schellnhuber, H. J., & Ting, M. (2024). Global emergence of regional heatwave hotspots outpaces climate model simulations. Proceedings of the National Academy of Sciences, 121(49), e2411258121. https://doi.org/10.1073/pnas.2411258121
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