A past, present and future perspective on the European summer vapour pressure deficit

Abstract. The response of evapotranspiration to anthropogenic warming is of critical importance to the water and carbon cycle. Con-flicting observations about changes of evapotranspiration stem mostly from the brevity of observations in time and space as well as a high degree of internal variability. Here we present the first gridded reconstruction of the European summer vapour pressure deficit (VPD) for the past four centuries. The gridded reconstruction is based on 26 European tree-ring oxygen iso-tope records and is performed using a Random Forest approach. Based on our reconstruction, we show that from the mid-1700s a trend towards higher VPD occurred in Central Europe and the Mediterranean region which is based on the simulta-neous increase in temperature and decrease in precipitation. This increasing VPD trend continues throughout the observation-al period and recent times. Climate model projections show this increase in VPD for the Mediterranean region continuing until the end of the 21^st century, whereby the extent depends on the amount of greenhouse gas emissions. In contrast, pro-jected VPD in North and Central Europe shows a tendency towards higher VPD only in the highest emission scenario (the produced data is available here: https://doi.org/10.5281/zenodo.5958837 (Balting, D. F. et al., 2022).