2023 set a record but probably won't hold it long

The summer of 2023 was exceptionally hot. Scientists have already established that it was the warmest Northern Hemisphere summer since around 1850, when people started systematically measuring and recording temperatures.

Now, researchers say it was the hottest in 2,000 years, according to a new study published in the journal Nature that compares 2023 with a longer temperature record across most of the Northern Hemisphere. The study goes back before the advent of thermometers and weather stations, to the year A.D. 1, using evidence from tree rings.

“That gives us the full picture of natural climate variability,” said Jan Esper, a climatologist at Johannes Gutenberg University in Mainz, Germany and lead author of the paper.

El Niños and La Niñas notwithstanding, the trend is for more heat.