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Meteorologist Cliff Mass faces ire of climate establishment by rejecting heatwave climate connection

Seattle meteorologist Cliff Mass sparks controversy by diving into heat wave climate science

By Hal Bernton
Seattle Times staff reporter

On Thursday, June 24, as the Northwest’s record-shattering heat wave approached, Cliff Mass posted a forecast he found hard to believe. By Monday, temperatures near the western Cascades foothills would exceed 108 degrees and they would reach 104 degrees and higher around Puget Sound.

“The event being predicted is so extreme and so beyond expectations that my natural inclination is to dismiss it,” Mass wrote. “But I can’t.”

His blog succinctly captured the historic event about to unfold in the kind of post that has helped make Mass, a professor at the University of Washington’s Department of Atmospheric Sciences, one of the region’s most influential meteorologists.

After the heat wave, he quickly assumed a far more controversial role as an outspoken critic of scientists who say climate change plays a big role in extreme weather events.

In a July 6 post, Mass declared that without global warming, we “still would have experienced the most severe heat wave of the past century.” In a follow-up post on July 13, he blasted as “profoundly flawed” a World Weather Attribution report by a team of 27 international scientists that concluded the heat wave would have been virtually impossible without human-caused climate change.

His blog posts serve as an online megaphone for Mass, who says it garners some 20,000 views on a typical day, and has received more than a half million views during some weather events.

His recent posts came at a time when Puget Sound governments and others in our region are scrambling to better prepare for such events. The heat wave contributed to the deaths of at least 125 people, according to preliminary state Department of Health data. And Mass has gotten strong pushback from scientists involved in the report as well as some other climatologists who say his ridicule increasingly makes him an outlier among scientists assessing the impacts of global warming.

The World Weather Attribution researchers, using statistical analysis, estimated the odds of this summer’s heat wave were one in 1,000 in today’s world but would have been at least 150 times more unlikely in preindustrial times. As early as the 2040s, their report said such events could occur, somewhere in the world, every five to 10 years.

In their models, the overall global impact of climate change resembles a kind of loading of the dice that can increase intensity of extreme-temperature events like the Northwest heat wave. In this case, they found climate change intensified the heat by about 4 degrees in the Seattle area to reach 108 degrees, significantly increasing the chances of death, according to a rebuttal document six of the researchers prepared in response to Mass.

Mass’s perspective differs.

He concluded climate change didn’t play a central role in an event largely caused by the natural variability of our regional weather. He notes the temperature soared by more than 40 degrees above the normal high, and climate change added only a few degrees, thus “a record-breaking unique heat wave” would have occurred even without global warming. In his blog, he lays out a golden rule that — based on this analysis — the bigger the temperature surge in an extreme event, the smaller the role of climate change, and accuses the World Weather Attribution report of “misinforming millions.”

Mass says his criticism is grounded in a deep knowledge of the intricate mix of ocean, mountains and atmospheric flows that help to produce Northwest weather, as well as climate models he runs.

A controversial figure

Mass says he does think climate change — caused by greenhouse gases from burning fossil fuel and other humans sources — is a problem. He is convinced this will result in more frequent heat waves and extremes later this century, and says “mankind should work to reduce emissions.” But he says his research leads him to conclude that in western Washington — due to a weakening of east winds that bring interior heat — these will be less intense than others forecast. And he doubts there will be a repeat of temperatures experienced in this summer’s heat wave in the next few decades.

“I don’t believe we are facing any kind of existential threat,” Mass said. “But it is not a good idea to muck around with the climate of the planet.”

Mass has sometimes gotten into very public disputes with other scientists, such as questioning the findings of a study about mountain snowpack decline in the West. He also has frequently derided the news media — including The Seattle Times — for headlines and reporting he believes overstate the threat of climate change.