Off the charts: What the era of ‘statistically impossible’ heatwaves means for the world

In the summer of 2021, Canada’s all-time temperature record was smashed by almost five degrees Celsius. Its new record of 49.6 degrees Celsius is hotter than anything ever recorded in Spain, Turkey or indeed anywhere in Europe.

The record was set in Lytton, a small village a few hours’ drive from Vancouver, in a part of the world that doesn’t really look like it should experience such temperatures.

Lytton was the peak of a heatwave that hit the Pacific Northwest of the US and Canada that summer and left many scientists shocked. From a purely statistical point of view, it should have been impossible.

I am part of a team of climate scientists who wanted to find out if the Pacific Northwest heatwave was unique, or whether any other regions had experienced such statistically implausible events. And we wanted to assess which regions were most at risk in future. Our results are now published in the journal Nature Communications.

Tracking these outlier heatwaves is important not just because the heatwaves themselves are dangerous, but because countries tend to prepare to around the level of the most extreme event within collective memory. An unprecedented heatwave can therefore provoke policy responses to reduce the impact of future heat.

For instance, a...

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