The Unbearable Summer
After this summer’s first searing heat wave baked the Pacific Northwest, the environmental scientist Robert Rohde posted an unusual observation on Twitter.
Looking through a report that analyzed temperature patterns for the region over the past 70 years, he noted, “the heatwave was statistically ‘impossible.’” Obviously, the heat wave wasn’t literally impossible, given that, after all, it happened. But the broiling temperature that the Northwest reached—108 degrees Fahrenheit at one point in Seattle, 121 degrees in British Columbia—was so far beyond the observed experience, he explained, that it exceeded even statistical models’ outmost potential extremes for the area.
A few weeks later, I caught up with Rohde, the lead scientist for Berkeley Earth, a nonprofit research group that analyzes current and historical climate data, via Zoom from Zurich, where he’s now living. He reiterated that the Northwest temperatures reached this summer were outside the boundaries “of what we thought was possible.”
Rohde allowed that such seemingly impossible events do in fact “sometimes” occur. But, he told me, it’s much more common for extreme events to match a rare high point with at least some historic precedent—hence the idea, say, of the 1,000-year flood. Truly unprecedented events that shatter any previous experience, he said, have been much rarer. “It is not that common,” he said drily, “to find results that look impossible.”
Rohde offered two explanations for such a unique event. The heat wave, he suggested, might have represented a meteorological black swan: “a rare dynamical interaction that has always been possible, but so rare that in 70 years of data we never observed a weather pattern that was qualitatively similar.” But there was also, he said, a second, “scarier” explanation for the surge, which led to hundreds of excess deaths across Washington and Oregon, as well as mass die-offs for shellfish that were literally baked in their shells: The climate is changing in ways we don’t entirely understand. “Once in a while, Mother Nature can throw surprises at us, and what we have experienced in the past is not always a good predictor of the future,” he told me. “And climate models are telling us that some things that are coming are not necessarily what we are familiar with.”
Across the western United States, 2021 is the year when the unimaginable became the unavoidable. The severity of the threat has been matched only by its breadth. Record heat this summer has battered not just the Northwest, but also the Southwest (where California’s Death Valley reached 130 degrees Fahrenheit, or 54.4 Celsius, ). Drought conditions have been reached this year in virtually every western state, including Montana, Idaho, Washington, Oregon, California, Nevada, Arizona, New Mexico, Colorado, and Utah, an expanse of at least 1.1 million square miles. The heat and drought alone, which puts the state clearly on track, with months left in the fire season, .)
