What to know as climate change drives extreme heat

(Reuters, 8 Jul 2021) As heatwaves smash records and claim lives - including in unexpected places like Canada and the U.S. Pacific Northwest - climate scientists explain what's happening and why

An unprecedented heatwave that smashed heat records in the U.S. Pacific Northwest and western Canada in late June has shaken climate scientists, who say they are now unsure where or how often such killer heat might be repeated.

But such an extreme event would be at least 150 times rarer without the influence of climate change, they said in a rapid assessment study released Wednesday, a little over a week after the heatwave, which is thought to have left hundreds dead.

Here's what they say we know - and don't - about worsening extreme heatwaves and how widespread they might become:

Why is the recent "heat dome" event in the U.S. Pacific Northwest and Canada so significant?

The rapid spike in temperatures was well above what scientists thought was possible, even factoring in 1.2 degrees Celsius of global warming since pre-industrial times.

“It was way above the upper bound," of predictions, said Dutch climate scientist Geert Jan van Oldenborgh, a co-author of the study produced by the World Weather Attribution group, which aims to pinpoint the role of climate change in extreme weather. 

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Reuters, 8 Jul 2021: What to know as climate change drives extreme heat