May 5, 2022 - Energy & Environment

Last year's Northwest heat wave was one of globe’s worst

Animated illustration of the Earth at the bottom of a thermometer with the ocean liquid rising up and filling the thermometer.

Illustration: Aïda Amer/Axios

The heat wave that enveloped the Pacific Northwest and a swath of western Canada last summer, killing hundreds, was one of the most extreme such events on record for anywhere on Earth, a new study shows.

Driving the news: The study, published Wednesday in the journal Science Advances, ranks the severity of extreme heat events by looking at the difference between the peak air temperatures and that region's typical temperature variability.

  • The team of United Kingdom-based researchers found only five other heat waves around the world since 1960 were more extreme than the Pacific Northwest event of 2021.

Why it matters: The research answers the question of how rare this event was from a global standpoint, and in the process, demonstrates the malicious influence of gradually increasing average temperatures.

  • It shines a light on the boiling a frog in gradually warming water myth (except with climate change, we would be the frog).
  • Previous studies of the Pacific Northwest heat wave have shown that it would have been virtually impossible to occur without human-caused global warming.

What they did: Researchers used two data sets of past global weather conditions as well as simulations of the future climate under varying rates of greenhouse gas emissions to show how heat waves are changing.

  • They calculated 10-year running means for given locations, enabling them to determine how unusual a temperature reading may have been compared to that average (expressed in terms of standard deviations).

What they found: Extreme heat events are becoming more frequent and severe due to the climate change-related increase in average temperatures.

  • Another key conclusion is that regions that have avoided an extreme heat wave in recent decades may not be so lucky as climate change continues, and may see particularly acute impacts since they are not prepared for them.
  • Only five events ranked higher on the study authors' list of severe heat waves, including a 1998 heat wave in Southeast Asia and a 1985 event in southern Brazil.

Yes, but: The study was motivated in part by concerns raised last summer that as global warming continues, extreme temperature events are outracing the average and becoming even more extreme.

  • The findings instead show that heat extremes are increasing in tandem with average temperatures.
  • "The heat extremes will not be more intense, compared to the climatology of that decade — the climatology will get hotter so the extremes will do too," Vikki Thompson, study lead author and a researcher at the University of Bristol, told Axios via email.
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