Extreme droughts in Europe could increase considerably

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The consequences of climate change are now becoming apparent around the globe. Climate projections indicate that extreme weather events will become more frequent and more prolonged for the rest of this century. In the past two decades, episodes of severe drought in Europe – in particular those that occurred in the 2003, 2010 and 2018 – have resulted in significant social, economic and ecological costs. Researchers led by LMU geographer Professor Ralf Ludwig have now simulated future climate trends in Europe, and identified potential hotspots in which the likelihood of summer drought is predicted to increase. Overall, their analyses suggest that Europe can look forward to a future in which periods of severe-to-extreme drought will become more common.

For the purposes of the study, Ludwig and his colleagues divided Europe into eight climatic regions, and used a technique known as ‘ensemble simulations’ to estimate the change in a parameter called 'percent of normal index' (PNI) by the closing decades of this century. In this case, the PNI is defined as the percentage change in monthly rainfall in the future (averaged over the projections for the period 2080 – 2099) relative to the level of precipitation for the same month under pre-industrial concentrations of CO2. The simulations were based on the RCP8.5 climate scenario, which assumes that emissions will continue to rise at the current rate until the end of the century. That model predicts that the average global temperature will rise by approximately 4°C by the turn of the century.

“Our results clearly show a long-term trend towards longer, more frequent and more severe summer droughts towards the end of this century, as defined by the deficit in precipitation relative to pre-industrial values,” says LMU geographer Magdalena Mittermeier, joint first author of the new study together with Andrea Böhnisch. The study pinpoints the Alps, France, the Mediterranean coastal zone and the Iberia as hotspots, in which the frequency of extreme droughts could rise by more than 50%. “That would mean that such drought periods would occur more often than once in every two years,” Ralf Ludwig points out. “Our results show how important it is for Europe to take immediate and effective steps to mitigate the climate crisis.”

Andrea Böhnisch, Magdalena Mittermeier, Martin Leduc, Ralf Ludwig: Hot Spots and Climate Trends of Meteorological Droughts in Europe–Assessing the Percent of Normal Index in a Single-Model Initial-Condition Large Ensemble. Frontiers in Water 2021