An outlook into Iberias population exposure to hot and dry extreme weather events at the end of the century

Climate change is a pressing concern impacting contemporary society, with anticipated global warming trends poised to exacerbate environmental challenges. This study explores the implications for the Iberian Peninsula (IP) at the close of the 21st century, exploring the effects of warming and drying trends on population exposure to hot and dry extreme weather events (HDEs). Despite a potential decline in overall population across the IP, warming and drying trends are expected, as highlighted by various studies. Projections indicate increased temperatures and aridity, and a surge in the frequency and intensity of droughts and heatwaves. For this research, two EURO-CORDEX experiments (13 simulations RCM-GCM (Regional Climate Models Global Climate Models)) were considered, encompassing different time periods, namely the historical period from 1971 to 2000 and the projected end of the century period spanning 2066 to 2095, aligned with two distinct emission scenarios: RCP4.5 and RCP8.5. The Standardized Precipitation-Evapotranspiration Index (SPEI) is used to quantify the duration of droughts, and the number of hot days is used to quantify warm months. Two representative concentration pathways (RCPs), specifically RCP4.5 and RCP8.5, are employed to delineate distinct greenhouse gas emission trajectories. A weighted multi-variable multi-model ensemble was used with the aim of improving climate simulations and providing reliable projections over the IP. The findings of this study reveal a notable projected surge in population exposure to both droughts and warm months throughout the entire IP by the close of the century, with climate change identified as the predominant factor for this escalation. Specific regions may undergo a particularly pronounced increase in drought exposure, while instances of exposure to warm months may surpass the 500% mark. Assessment of exposure to future droughts and warm months indicates that climate change plays a predominant role, accounting for a significant percentage of exposure in both Portugal and Spain. In conclusion, population exposure to droughts and warm months is projected to escalate significantly in the IP by the end of the century, primarily driven by climate change. The study also emphasizes the critical need for mitigation and adaptation strategies to address the potential consequences, particularly in sectors such as water resources, agriculture, human health, and wildfire management. The findings underscore the urgency for regional authorities, policymakers, and society to prioritize adaptation planning and develop a comprehensive understanding of the vulnerabilities and potential strategies to cope with the challenges posed by hot and dry extreme events. This work was funded by the Portuguese Fundao para a Cincia e a Tecnologia (FCT) I.P./MCTES through national funds (PIDDAC) UIDB/50019/2020 (https://doi.org/10.54499/UIDB/50019/2020), UIDP/50019/2020 (https://doi.org/10.54499/UIDP/50019/2020) and LA/P/0068/2020 (https://doi.org/10.54499/LA/P/0068/2020). This work was performed under the scope of project https://doi.org/10.54499/2022.09185.PTDC (DHEFEUS) and supported by national funds through FCT. DL and AR acknowledge FCT I.P./MCTES (Fundao para a Cincia e a Tecnologia) for the FCT https://doi.org/10.54499/2022.03183.CEECIND/CP1715/CT0004 and https://doi.org/10.54499/2022.01167.CEECIND/CP1722/CT0006, respectively.