In summer 2021, a stunning heat wave swept western North America, from British Columbia to Washington, Oregon and beyond into other inland areas where the climate is generally mild.
In summer 2021, a stunning heat wave swept western North America, from British Columbia to Washington, Oregon and beyond into other inland areas where the climate is generally mild. Temperature records were set by tens of degrees in many places, wildfires broke out, and at least 1,400 people died. Scientists blamed the event largely on human-driven climate warming, and declared it unprecedented. But without reliable weather data going back more than a century or so, did it really have no precedent?
A new study of tree rings from the region shows that the event was almost certainly the worst in at least the past millennium. The research, published in the journal Climate and Atmospheric Science, established a year-by-year record of summer average temperatures going back to the year 950. Scores of abnormally hot summers showed up, many grouped into multiyear warm periods. But the new study shows that the last 40 years, driven by human-influenced warming, has been the hottest—and that 2021 was the hottest summer in the entire span.
“It’s not that the Pacific Northwest has never before experienced waves of high temperature. But with climate change, their magnitude is much hotter, and they have a much greater impact on the community,” said lead author Karen Heeter, a postdoctoral researcher at Columbia University’s Lamont-Doherty Earth Observatory. “Being able to look at the past and compare that with climate models, and come to similar conclusions, there’s a lot of power in that.”
Read more at Columbia Climate School
Image: Lead author Karen Heeter takes a core sample from an old mountain hemlock near Crater Lake, Oregon, where at least one tree dated to the 1300s. (Credit: Grant Harley/University of Idaho)