The summer of 1540 was burning hot in the vine-covered hills of Burgundy, France—so hot as to be “almost unbearable,” according to one written account from the time.
In fact, it was hot all across Europe that year. In the Alps, glaciers melted, their snouts retreating up steep-sided valleys. Fires burned from France to Poland. And in the wine country of central France, the grapes withered to raisins on the vine, so sugary the wine made from them was syrupy and extra-alcoholic.
Normally, winemakers harvested grapes at the very end of September or early October. But that year, they had to scurry to get overripe grapes off the vine weeks earlier than usual.
Now, a nearly 700-year-long record of harvest dates from the town of Beaune, in Burgundy, shows that early harvest dates like the one from 1540 are now par for the course, thanks to climate change. Scientists and historians stitched together a record of grape harvest dates going back to 1354. They found that air temperatures have warmed so much—and especially in the last 30 years—that grapes are...