The team of scientists used a well-established and credible method to search for climate change’s role in extreme weather, according to the National Academy of Sciences. They logged observations of what happened and fed them into 21 computer models and ran numerous simulations. They then simulated a world without greenhouse gases from the burning of coal, oil and natural gas. The difference between the two scenarios is the climate change portion.
“Without climate change this event would not have happened,” said study senior author Friederike Otto, a climate scientist at the University of Oxford.
What made the north-west heat wave so remarkable is how much hotter it was than old records and what climate models had predicted. Scientists say this hints that some kind of larger climate shift could be in play — and in places that they didn’t expect.
“Everybody is really worried about the implications of this event,” said study co-author Geert Jan van Oldenborgh, a Dutch climate scientist. “This is something that nobody saw coming, that nobody thought possible. And we feel that we do not understand heat waves as well as we thought we did. The big question for many people is: Could this also happen in a lot of places?”
The World Weather Attribution team does these quick analyses, which later get published in peer-reviewed journals. In the past, they have found similar large climate change effects in many heat waves, including ones in Europe and Siberia. But sometimes the team finds climate change wasn’t a factor, as they did in a Brazilian drought and a heat wave in India.
Six scientists who weren’t involved in the research said the quick study made sense and probably underestimated the extent of climate change’s role in the heat wave.
That’s because climate models used in the simulations usually underestimate how climate change alters the jet stream that parks “heat domes” over regions and causes some heat waves, said Pennsylvania State University climate scientist Michael Mann.
The models also underestimate how dry soil worsens heat because there is less water to evaporate, which feeds a vicious cycle of drought, said Daniel Swain, a climate scientist at UCLA and the Nature Conservancy.
The study hit home for University of Victoria climate scientist Andrew Weaver, who wasn’t part of the research team.
“Victoria, which is known for its mild climate, felt more like Death Valley last week,” Weaver said. “I’ve been in a lot of hot places in the world, and this was the worst I’ve ever been in.
“But you ain’t seen nothing yet,” he added. “It’s going to get a lot worse.”