Science reports:

In June 2021, a jet stream charged with heat and chaotic energy from a nearby cyclone stalled over the Pacific Northwest. The mass of trapped air baked the already hot landscape below to a record 49.6°C. More than 1000 people died from heat exposure.

Scientists quickly began working to figure out how much of the blame for the heat wave could be laid to global warming. But the heat was so unusual, the weather so weird, that it broke their methods. “It challenged our techniques, our climate models, and our statistical analysis methods,” says Michael Wehner, a climate scientist at Lawrence Berkeley National Laboratory who participates in the World Weather Attribution (WWA) initiative. WWA ultimately issued a statement, finding the heat wave was “virtually impossible” without global warming. But, Wehner admits, that statement masked plenty of doubts. “We sort of kludged it.”

Next time, he and fellow modelers expect to do better.

Critics complain that extreme event attribution, as the effort is known, overemphasizes public communications and underestimates uncertainty. But new approaches promise to increase the field’s rigor and more precisely capture the relationship between climate change and extreme weather—even for events so extreme that there is no historical record for comparison. [Continue reading…]