Recurrence of Drought Events Over Iberia. Part II: Future Changes Using Regional Climate Projections

Abstract

Seasonal droughts are a common feature of the Iberian (Mediterranean) climate. They can have severe impacts on both natural and human life – especially, when recurring in consecutive years. In this study, we investigate the potential impacts of climate change on recurrent drought events in the Iberian Peninsula (IP). With this aim, we use the new set of indices introduced in Moemken and Pinto (2022): the Recurrent Dry Year Index (RDYI) and the Consecutive Drought Year (CDY) Index. These are applied to a large EURO-CORDEX multi-model ensemble consisting of 25 different global-to-regional model (GCM-RCM) chains that follow the RCP8.5 scenario with 12 km horizontal resolution. A drizzle correction and a simple multiplicative approach are used to bias-adjust the daily precipitation sums. Results reveal a general tendency towards more severe drought conditions in IP under different global warming levels (GWLs). Moreover, recurrent drought events are projected to occur more frequent and last longer. While the ensemble mean responses are only moderate for a GWL of +2°C (compared to the pre-industrial average), recurrent drought conditions are strongly enhanced for the +3°C GWL. The magnitude of projected changes shows some sensitivity on the choice of index and model. Typically, changes are more pronounced for indices based on the effective drought index (EDI) and show a larger spread for the individual GCMs than for the various RCMs. Nevertheless, the climate change signals are robust for most of IP and all indices, with a larger model agreement for the +3°C GWL. We conclude that the Iberian Peninsula is confronted with an increased risk of recurrent drought events in future decades. If global warming should exceed the +3°C threshold, the majority of models projects an almost permanent state of drought – which could result in severe implications for the Iberian population and ecosystems.