Drought events are increasingly impacting Europe. The study of past droughts helps disentangle the different factors that trigger hydrological drought, helping to forecast future drought severity. Here we identify the historical drought events of the twentieth and twenty-first centuries in geochemical records of a stalagmite from Caumont cave in Northern France and develop a mechanistic understanding of their root causes. Subannually-resolved stable carbon isotope (δ 13 C) and trace element data are directly compared with historical climatic records. δ 13 C, Mg, and Sr peaks align well with most of the historical drought events of the twentieth and twenty-first centuries. The comparison reveals a good correspondence between summer effective rainfall and δ 13 C, Mg, and Sr concentrations. Further comparison of geochemical records with the precipitation-evapotranspiration index (SPEI) reveals a change in the drought forcings for the past two decades. During most of the twentieth century, droughts appear driven by a pluvial regime, whereas since the late 1990s, drought was driven by higher evapotranspiration due to increased temperature.

Historical records highlight the extended dry phases in north-western France during twentieth century. These dry episodes affected not only Normandy (northern France), but large parts of Western and Central Europe 1,2 . Droughts events are amongst the natural hazards responsible for the most significant economic losses 3 , affecting ecosystems 4 , agriculture, water and energy supply 5 . Droughts are mainly driven by regional precipitation deficits and/or increased temperature 6,7 . A precipitation deficit is classified as lower than normal conditions in the hydrological system in combination with high (potential) evapotranspiration 5 . Droughts can be classified into four categories, depending on the type of impact: i) meteorological (precipitation deficit over a specific period), ii) agricultural (as a consequence of meteorological conditions that affect crops), iii) hydrological (manifested as reduced river runoff and lake levels after meteorological and agricultural droughts), and iv) socio-economic (negative economic impacts on population) 8 .

Given the increasing impact of recent droughts in Europe, resources are being directed towards the reconstruction of past droughts using palaeoclimate archives 9,10 . Tree ring records from the Tatra region, northwestern Carpathian mountains, show that during the last millennia, lower temperature align with pandemic episodes across Europe 11 . Additionally, tree rings based reconstructions from the eastern part of Europe indicate that the recent drought events are unmatched over the last 700 years 12 .

With global warming as a backdrop, droughts are becoming an increasing concern for modern societies. The recent report from the Group of Intergovernmental Experts about climate evolution 13 , confirms a clear trend of increasing European drought, affecting water resources, aquifer recharge, and soil. The droughts of the recent years in France have left many towns with water shortages during the summer 14 and caused the shutdown of nuclear reactors along the Franco-Belgian border 15 .

Droughts are well documented in European historical data 16,17 , but speleothem records can extend records back further in time, and provide insight where historical records are lacking.