Climate Change Impacted Western Heat Wave, Analysis Findings


An international team of climate researchers said Wednesday that the extraordinary heatwave that scorched the Pacific Northwest last week would certainly not have happened without global warming.

The temperatures were so extreme—including readings of 116 degrees Fahrenheit in Portland, Ore., and a Canadian record of 121 degrees in British Columbia—that researchers had a hard time saying how rare it was. heat wave was. But they estimated such a probability to be only 0.1 percent in any given year. intense heat wave is occurring.

“Although it is a rare event, it would have been almost impossible without climate change,” said Geert Jan van Oldenborgh of the Royal Netherlands Meteorological Institute.

Similar events wouldn’t be so rare if the world warmed another 1.5 degrees Fahrenheit, which could happen this century without serious cuts in greenhouse gas emissions, the researchers said. The probability of such a severe heatwave occurring anywhere in the world would increase by up to 20 percent in a given year.

“For heatwaves, climate change is an absolute game changer,” said Friederike Otto of the University of Oxford in England, one of the researchers.

Alexander Gershunov, a research meteorologist at the Scripps Institution of Oceanography in San Diego, said the findings are in line with what is known about the effects of global warming on heat waves.

Not included in the study, Dr. “Extreme weather conditions are the most impacted by climate change,” Gershunov said. As for the Pacific Northwest thing, he said, “climate change has clearly only made it stronger.”

Temperature records for cities and towns in the region have been broken, by a much larger margin than researchers have ever seen in a heatwave. With that in mind, they also raised the possibility of witnessing a shift in how the world’s warming climate behaves. Perhaps the climate has crossed a threshold where a relatively small increase in global temperatures could greatly increase the likelihood of a large jump in extreme heat, they said.

Dr. “We are worried,” van Oldenborgh said. “We are much less sure about how heatwaves behave than we were two weeks ago.”

He stressed that this idea is just a hypothesis. He said a lot of research is needed to try to determine whether and how this change might occur, which this rapid study hasn’t addressed.

The heatwave in the Pacific Northwest occurred at the end of June, when a large swath of high-pressure air called a heat dome hovered over the region. Temperatures soared for four days, as did heat-related deaths, where acclimatization wasn’t as common as in some other parts of North America.

Several hundred people were estimated to have died, and this number is expected to increase substantially in the coming months as death certificates and death data are analyzed. The heat contributed crop errors and helped start the bushfires that destroyed the town of Lytton in British Columbia, where Canada’s heat record was broken the day before.

The study is the latest in a growing body of research called “quick association” analysis, which aims to determine whether there is a link between climate change and certain extreme events such as heat waves, heavy rainstorms and flooding. The goal is to quickly publicize any climate link, in part to discourage climate deniers who might argue that global warming has no effect on a particular event.

The study, which took just over a week, has yet to be published in a peer-reviewed or scientific journal. However, it uses techniques that were peer-reviewed more than a decade ago when such studies were conducted. World Weather Attribution has completed about 30 of them since 2015.

Essentially, the research uses a total of 21 computer simulations for this analysis to compare what’s going on in the current world, which has warmed about 2 degrees Fahrenheit since the rise of the industry and the accompanying emissions, to a hypothetical world where humans never pumped. any greenhouse gases into the atmosphere.

Climate scientists are confident that global warming is making heat waves worse. base temperatures where they start is higher than they were decades ago. Rapid association analysis attempts to answer two questions about a particular heat event: how much worse and how more likely has climate change made it?

For the Pacific Northwest heatwave, the analysis showed that while rare, it was much more likely in the current warming world than in a world without warming. And if the heat wave had occurred in such a hypothetical world, it wouldn’t have been this hot with maximum temperatures about 3.5 degrees lower.

But the extreme nature of this heat wave has given scientists pause. Maximum temperatures in many places are 7 to 9 degrees higher than previous records, roughly twice the increase seen in other heatwaves.

Dr. “It was by far the biggest leap on record,” Otto said. “We’ve seen pretty big increases, but never that big.”

Dr. van Oldenborgh said there are two possible explanations for this. The first is that the Pacific Northwest has been hit by an extremely rare combination of factors – the impact of climate change on the heatwave is perhaps exacerbated by the recent severe drought or changes in the jet stream penetrating the West. or both.

“People there were extremely unlucky and caught these extreme heat,” he said in that statement.

Dr. Van Oldenborgh said it was urgent to determine whether the other explanation that some kind of climate threshold had been crossed was justified, and whether there would be similarly extreme heat waves in the future.

“This is something that no one has seen coming,” he said. “Could it be elsewhere? We just don’t know right now.”


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