Clues hidden deep in the trunks of ancient trees have revealed that last summer was the northern hemisphere's hottest in 2,000 years. Last year had already been confirmed as the world's warmest on record by a large margin, at least since 1850, due to climate change.

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 summer of 2023 was the hottest summer in the Northern Hemisphere since the height of the Roman Empire, a new study finds.