Exploring the probability of occurrence of the present-climate deadliest heatwaves in Spain in the mid- and end-century

Spain is a country located in Southwestern Europe highly vulnerable to different extreme weather-related events such as heatwaves, droughts, and wildfires, causing detrimental effects on the environment, economy, and society. Under projected scenarios, the assessment of the exposure and vulnerability to these phenomena, and particularly to the most impactful events, is a priority to improve management and adaptation measures. Following the framework of the European project titled “Extreme meteorological and hydrological risk in Spain: impact assessment, future scenarios and tools to improve resilience and adaptation to climate change (EXMERISK)”, we aimed to conduct a high-resolution analysis identifying specific types of heatwaves linked to a higher number of deaths in Spain and estimating their probability of occurrence in future periods simulated under the SSP585 scenario (2036-2065, mid-century, and 2071-2100, end-century). Daily non-external, circulatory, and respiratory mortality for all population in Spain and separated by sex groups were provided by the Spanish National Institute, between 1985 to 2014. We used Weather Research and Forecasting (WRF) forced with ERA5 reanalysis and the outputs of the Community Earth System Model V2 (CESM2) to obtain dynamic simulations of climatic variables. Heatwaves were defined following the Spanish Meteorological Agency criteria (AEMET), in which for at least three consecutive days daily maximum temperature exceeded the 95^th percentile between July-August and affecting at least 10% of the area under study. We determined specific characteristics of heatwaves linked to a higher number of deaths in Spain and estimated the probability of occurrence of future heatwaves of durations and magnitudes equal or higher than those associated with them. This study has relevant implications in the public health field, to better understand the expected occurrence of heatwaves which may be more impactful in terms of death and develop further measures to reduce the health burden and vulnerability associated with climate change.