The future of Iberian droughts: a deeper analysis based on multi-scenario and a multi-model ensemble approach

Abstract

Abstract As a result of warming and precipitation deficits, the increasing shortage of water resources and droughts have become one of the main drivers of desertification, land degradation and food insecurity with direct impacts on ecosystems and society, especially in fragile communities. Over the Iberian Peninsula, a known climate change hotspot, the occurrence of droughts varies in intensity and severity, being its assessment under present and future conditions an important asset for adaptation measures. Here, for the first time, we present a comprehensive analysis of the different plausible evolutions of droughts throughout the 21st century over Iberia at a monthly basis, featuring three different emission scenarios (RCP2.6, RCP4.5, RCP8.5). A multi-variable, multi-model EURO-CORDEX weighted ensemble is used to assess the future drought conditions using the SPI (Standardized Precipitation Index) and SPEI (Standardized Precipitation Evapotranspiration Index). All indexes were computing by considering the full period, from 1971 to 2000 merged with the 2011–2100 period from each RCP scenario. The results clearly show that Iberian Peninsula is greatly vulnerable to climate change, indicating a significant increase in intensity and severity of drought occurrences, even for the low-end RCP2.6 scenario. For the RCP4.5 and RCP8.5 scenarios, the increases are more pronounced and enhanced throughout the 21st century, from 3 up to 12 more severe droughts for the shorter timescales with increases in mean duration above the 30 months for the longer accumulation periods The use of all the RCPs data pooled together with a weighted ensemble approach allows not only a more accurate projection of future droughts, but also ensures comparability among the projections from the three RCP scenarios. The future drought evolution aspires to assist the new Portuguese national roadmap for adaptation for the 21st century, bridging the water sector challenges from mitigation to adaptation in a dynamic way.