Components of past cold mega-droughts and modern warm dry events in central Europe could interfere constructively in the future

Mega-droughts are notable manifestations of the American Southwest, but not so much of the European climate. By using long-term hydrological and meteorological observations, as well as paleoclimate reconstructions, we show that central Europe has experienced much longer and severe droughts during the Spörer Minimum (~AD 1400 – 1500) and Dalton Minimum (~AD 1770 – 1850), than the ones observed during the 21^st century. These two mega-droughts appear to be linked with a weak state of the Atlantic Meridional Overturning Circulation (AMOC) and enhanced winter atmospheric blocking activity over the British islands and western part of Europe, associated with reduced solar forcing and explosive volcanism. In contrast with these mega-droughts, present-day extreme dry events in Europe are mainly related to high temperature levels. Since numerical simulations indicate a future slowdown of AMOC in a globally warming world, we argue that these two forcing factors for droughts, weakening ocean circulation and temperature increase, could interfere constructively in the future. Consequently, this will potentially lead to an increase in the frequency of hot and dry summers, especially over the central part of Europe, posing enormous challenges to governments and society.