A combination of climate change and extraordinary bad luck contributed to the deadly heat wave in the Pacific Northwest in 2021, according to a UCLA study published Wednesday.
The extreme heat wave in the Pacific Northwest was described as a once in a 10,000 years event, linked to climate change and natural variability, but is not necessarily a sign that extreme heat waves are happening more than predicted.
The Pacific Northwest heat wave in 2021 brought 121 degree temperatures, buckled roads, melted power lines, killed hundreds of people and caused a destructive wildfire.
“It was outrageous how extreme and severe that heat wave was,” said climate scientist and statistician Karen McKinnon, an assistant professor of atmospheric and oceanic sciences, who is also part of the UCLA Institute of the Environment and Sustainability. “Climate models struggle to capture events this extreme, and most early research puts the chances of it occurring at zero.”
The UCLA study is in the Sept. 28 issue of the journal Geophysical Research Letters. Researchers analyzed trends in weather stations in Washington, Oregon and British Columbia and received climate model simulations for the study. In their research, it was determined climate models could simulate heat waves comparable to the one in 2021 with a probability of them occurring roughly once every 10,000 years. In cities that experienced the most extreme temperatures during the heat wave, the probability was once every 100,000 years.
Researchers also concluded climate change is increasing the frequency of heat waves and average summer temperatures at the same pace.
“We don’t see historical evidence of hot temperatures increasing faster than average temperatures during the early summertime when the heat wave occurred,” McKinnon said. “The 2021 Pacific Northwest heat wave appears to be the result of climate change and extraordinarily bad luck with natural variability.”
The study does not provide evidence that extreme heat waves should start happening regularly. However, the summer of 2022 saw record-breaking heat waves in the United Kingdom, China and California.
“We need to continue evaluating whether these very extreme events are telling us something new about how the climate is changing, and whether they confirm or refute our latest findings,” McKinnon said.
The research was supported by the National Science Foundation and the Packard Foundation.