UW professor, study co-author explains why future heatwaves could kill hundreds

On Friday, KIRO Radio’s Dori Monson expressed his skepticism over a recent study that projected hundreds of heat-related deaths for Seattle in future heatwaves.

In response, University of Washington Global Health Professor Kristie Ebi, who co-authored the study along with 11 environmental experts from Massachusetts and the U.K., told Dori how she and her colleagues arrived at their alarming conclusions.

Lead scientist Y.T. Eunice Lo “looked historically at weather patterns in Seattle and a number of cities around the United States, and estimated how many deaths occurred when there were particular temperatures, specifically at heatwaves that occur about once every 30 years — so a heatwave that would occur two, perhaps three times in a person’s lifetime,” Ebi said. “So these are quite extreme temperatures.”

The scientists set today’s Seattle 100 years into the future, changing only the date and temperatures. All other variables, such as population and age of residents, were held constant. They examined what current global temperature trends could look like in the next century.

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“We looked at what could happen as temperatures rise to 1.5 degrees centigrade above pre-industrial [temperatures] — we’ve already warmed 1 degree, the world has warmed 1 degree — and at 2 degrees and at 3 degrees,” Ebi said.

They then asked the questions, “If those temperatures were imposed on Seattle today for those kinds of extreme heat events, what would the mortality be? What if we held the world constant, we warmed by those different degrees of temperature, what could we see in terms of number of people who could die in heatwaves? ”

The study found that temperatures in Seattle could reach as high as a daily mean of 97 degrees Fahrenheit, with a daytime high of 124 degrees.

It also predicted that 725 Seattle residents could die in each extreme 30-year heat event. While events like these are rare, Ebi said, they are important to study.

“As the climate warms, we’re seeing not just an increase in the average temperatures, but we’re seeing a very large increase in the extremes,” she said. “So there’s a big increase in that tail of the distribution of temperatures, and that’s why we looked at these rare events.”

Ebi pointed out that heatwaves in Europe in the early 2000s caused 70,000 excess deaths.

“Heatwaves kill. Almost no one needs to die in a heatwave … We know that the number  of people who can die in heatwaves is very large, and is largely preventable,” she said.

Dori asked if this could be mitigated in the next century by simple changes, such more people installing air conditioning in their homes. While Ebi acknowledged that the study “did not look at how the population would adapt to higher temperatures,” she noted that likely not everyone who would be at-risk for heat-related health problems would adapt.

“There is solid evidence that the degree of adjustment to higher temperatures is not as fast or as large as it needs to be, and one purpose for our analyses is to point out that there are potential risks,” she said. “And there is a whole range of actions that can be taken to reduce those.”

Listen to the Dori Monson Show weekday afternoons from 12-3 p.m. on KIRO Radio, 97.3 FM. Subscribe to the podcast here.