Study: Northwest heat wave impossible without climate change

The deadly heat wave roasting the Pacific Northwest and western Canada would have been nearly impossible without human-caused climate change, which added a few extra degrees to record-breaking temperatures, a new accelerated scientific analysis found.

An international team of 27 scientists calculated that climate change has increased the chances of extreme heat at least 150 times, but the chances are much higher.

The study, not yet peer-reviewed, said that before the industrial era, the region’s late-June triple-digit heat was the type that would not have occurred in human civilization. And even in today’s warming world, it said, summer was a millennial phenomenon.

Wednesday’s study by World Weather Attribution said the world once again warmed by 1.4 degrees (0.8 degrees Celsius) would occur once every five to 10 years. One study author said that if carbon pollution continues at its current pace, such extreme heat could be 40 or 50 years away.

Study co-author Gabriel Vecchi, a climate scientist at Princeton University, said this type of extreme heat “will go from essentially nearly impossible to relatively normal.” “It’s a huge change.”

“This study is telling us that climate change is killing people,” said Abby, who endured the scorching heat in Seattle. She said the death toll from June’s summer eruption could be calculated, but it was likely to be in the hundreds or thousands. “Heat is Americans’ No. 1 meteorological killer.”

In Oregon alone, the state medical examiner reported 116 heat wave-related deaths on Wednesday.

According to the National Academy of Sciences, the team of scientists used a well-established and reliable method to discover the role of climate change in extreme weather. He observed what happened and fed them into 21 computer models and ran several simulations. He then simulated a world without greenhouse gases by the burning of coal, oil and natural gas. The difference between the two scenarios is part of climate change.

“This event would not have happened without climate change,” said senior author Frederick Otto, a climate scientist at the University of Oxford.

What made the Northwest heat wave so remarkable was how hot it was compared to the old record and what climate models had predicted. Scientists say it hints that some sort of major climate change may be at play – and in places they didn’t expect.

Study co-author Geert Jan van Oldenborg, a Dutch climate scientist, said: “Everyone is really concerned about the effects of this event. It’s something no one saw coming, no one thought possible. And we think we don’t understand. Heat waves go as well as we thought we did. The big question for many people is: Can it happen in multiple places?

The World Weather Attribution team performs these quick analyses, which are then published in peer-reviewed journals. In the past, they have found similar large climate change effects in many heat waves, including in Europe and Siberia. But sometimes the team finds that climate change was not a factor, as they did in a Brazilian drought and a heat wave in India.

Six outside scientists said the accelerated study understated and probably underestimated the extent of climate change’s role in the heat wave.

That’s because climate models used in simulations typically underestimate how climate change alters the jet stream that parks “heat domes” in areas and causes some heat waves, according to Pennsylvania State University’s researchers. Climate scientist Michael Mann said.

Daniel Swain, a climate scientist at UCLA and the Nature Conservancy, said the models also underestimate how dry soils dissipate heat because there is less water to evaporate, which feeds the vicious cycle of drought.

The study hit home for Andrew Weaver, a climate scientist at the University of Victoria, who was not part of the research team.

“Victoria, known for its mild climate, felt like Death Valley last week,” Weaver said. “I’ve been in a lot of hot places in the world, and it was the worst I’ve ever had.

“But you haven’t seen anything yet,” he said. “It’s going to be very bad.”

———— . Read more stories on climate issues by The Associated Press at


Follow Seth Borenstein on Twitter at @borenbears.


The Associated Press Department of Health and Science receives support from the Howard Hughes Medical Institute’s Department of Science Education. AP is solely responsible for all content.


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