Ancient trees show how hot summers have gotten

The cross section of a tree trunk shows a pattern of light and dark rings of wood.
The annual rings on the trunk of a conifer tree. | Photo: Getty Images

A summer marked by deadly heatwaves across Asia, Europe, and North America last year turns out to have been the hottest in the Northern Hemisphere in at least 2,000 years, according to a new study published in the journal Nature.

Officially, 2023 went down in history books as the hottest on record for the planet — but those records only started in 1850. To see how drastically the climate has changed over millennia, the authors of the new paper studied ancient tree rings to gauge fluctuations in temperatures over the years.

The results show us how extreme the weather is becoming. And while temperatures have reached unprecedented peaks, they’re also a warning of what’s to come unless policymakers do more to turn down the heat.

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