As California wakes up to a heightened risk of extreme weather events, researchers shed new light on last year’s abnormal and extreme Pacific Northwest heat wave. A study published this week said such heat waves could become 20 times more likely to occur if current carbon emissions continue unabated. Another said they could also be nearly 10 degrees warmer.
The nine-day event in late June and early July 2021 scorched parts of northern California, Oregon, Washington and British Columbia, where Canada experienced its highest temperature on record, 121 .3 degrees. The heat wave has claimed hundreds of lives, sparked several devastating wildfires and killed an estimated 1 billion sea creatures.
Such an event would have been “virtually impossible” in the 1950s, but atmospheric warming has already increased its probability to about a 0.5% chance per year, according to a Columbia University study, published Thursday in the journal Nature. Climate Change. If warming were to exceed 2 degrees Celsius – the upper limit set by the Intergovernmental Panel on Climate Change – this probability could reach a 10% chance per year as early as 2050.
“The biggest control on the severity of heat waves – beyond their current severity – is the amount of CO2 we release into the atmosphere,” said Samuel Bartusek, Ph.D. student at Columbia’s Lamont-Doherty Earth Observatory and lead author of the study. “There’s really only one solution to the problem of putting more carbon dioxide into the atmosphere, and that’s to stop doing it.”
Bartusek said the extraordinary heat wave was “shocking” both for people who experienced it and for the scientific community, which is why researchers hope to better understand its physical mechanisms and its relationship to climate change. .
“It was an extremely strange event,” said Michael Wehner, a climatologist at Lawrence Berkeley National Laboratory, co-author of another paper on the heat wave published last week in the journal Geophysical Research Letters. “It was also tragic, of course, because of the resulting mortality.”
Among other findings, this paper found that the heat wave was so unprecedented that it essentially broke most standard tools used to measure human influence on heat waves.
“At the end of the day, we calculated that not only was the event impossible without climate change, but it was impossible with climate change. And of course it happened, so that means the model is wrong” , Wehner said.
Wehner said such statistical outliers make it difficult to predict with certainty the future frequency of such events. However, his paper includes findings on temperature, noting that global warming caused a 1.8 degree rise in maximum temperatures during the heat wave.
Future warming could cause heat wave temperatures to increase by about 9 degrees by the end of the 21st century, the paper said.
“The bottom line is that how much climate change we get is really determined by us and who we elect to mitigate or not to mitigate emissions of carbon dioxide and other greenhouse gases,” he said. -he declares. “And the less we do, the worse things get.”
The Columbia researchers also found that several factors converged to help create the blistering heat dome, including abnormally dry soils and jet stream disturbances.
In California and other parts of the western United States, increased heat, drought and aridification are contributing to long-term drying of soils, which means there are has less water to evaporate into the air, Bartusek explained.
“And if there’s less evaporative capacity to come out of the ground, there’s a greater heating effect – where the air just above the surface will be heated more efficiently,” a- he declared. He added that in some areas it’s likely there was “this feedback process going on where the land surface helped amplify some of the higher temperatures.”
According to the study, the jet stream – the fast-flowing air currents in the upper level of the atmosphere that guide weather systems from west to east – also played a role in the heat wave. Before and during the event, the jet stream “formed” into waves and slowed down, essentially shutting down the weather system in place and allowing the heat dome to build up over the region.
The researchers noted that the effect of climate change on the jet stream is still the subject of debate, although some scientists believe these wave patterns are becoming more frequent and extreme due to human activity. Wehner said the question is “one of the most interesting problems in climate science right now.”
“There definitely remains a possibility that we will see more of these unusual types of flows with global warming,” he said.
Kai Kornhuber, deputy associate researcher at the Lamont-Doherty Earth Observatory and another of the Columbia study authors, said the results highlight how discrepancies between soil moisture levels, the current -jet and other factors can cause temperatures even beyond their usual magnitudes.
“Sometimes those factors line up and you get those conditions that cause a perfect storm,” he said. “What is important to mention here, however, is that each of these factors exhibit increasing trends associated with climate change…These types of coincidences could occur with higher probability in the future, simply because these common factors are all related to climate trends.
As for the likelihood of such heat waves reaching that 10% annual probability by 2050, much depends on the emissions path society eventually takes. But “given the accelerating trends in extreme weather events around the world, there’s reason to believe that these estimates might even be a little conservative,” Kornhuber said.
He and the other researchers noted that while some numbers and predictions from the studies may differ, their key messages are very similar – that the extreme heat wave was essentially impossible at pre-industrial emission levels.
“What’s important about this aspect is that these methods all agree that climate change plays a major role in every heat wave we observe these days,” Kornhuber said.
Although the results are dire, the researchers said they could help inform future modeling of such events and help people better prepare. Many parts of the Pacific Northwest were unequipped for such extreme heat, including homes without air conditioning and infrastructure systems unable to handle such strain. Wehner said improving adaptation efforts and contingency plans will help, but ultimately such events “are going to get worse because there’s a lot of climate change that’s built into the system.” .
“The more we can reduce our emissions – eventually reducing them to zero, to zero – and the sooner we can do it, the better to avoid even worse tragedies,” he said.
California Daily Newspapers