The 1820s Marks a Shift to Hotter-Drier Summers in Western Europe Since 1360

Recent soil moisture (SM) reconstructions revealed plunging trends and enhanced SM-temperature couplings over the last two decades in dry regions. However, how SM changed and whether the land-atmosphere interaction was intensified over time in humid regions remained unknown. Here we reported the first six-century-long regional summer SM reconstruction (1360–2000 CE) in western Europe (WE) using three individual tree-ring δ¹⁸O chronologies in England and France. A sharp wet-to-dry change occurred around 1820, earlier than 1850–1900 CE, the commonly used historical baseline of anthropogenic climate changes. Enhanced coupling of SM-temperature followed, with stronger summer sea level pressure anomalies in dry years after the 1820s. Our results reveal that the hotter-drier regime has also become more frequent in humid WE under global warming.