The next hot thing: Belgian heatwaves in a warming world

Recent decades have seen an increase in the frequency and intensity of extreme heat events. Such events have a profound impact on society, as they increase human exposure to heat stress and can negatively affect energy consumption and agriculture. These effects are further amplified in urban environments due to climate change. Belgium, among the most urbanised countries worldwide, has experienced an increasing number of heatwaves in recent years, with several years recording multiple events. However, the future extent and characteristics of heatwaves remain unclear, making it difficult to assess whether current suggested adaptation strategies and heat action plans for today's climate will remain effective under future warming. With this research, we aim to develop a storyline-based selection method to quantify single future heat waves based on the characteristics of past events and thereby enable the identification of relevant case studies for assessing future risks.

With the new Belgian climate projections from the CORDEX.be II project, different global warming levels are being explored (1.5°C, 2°C, 3°C and 4°C), to gain insights into different future extreme events. In this study, we analyse high-resolution data from the regional climate model COSMO-CLM, in which urban areas are explicitly modelled, forced by the global climate model EC-Earth3-Veg (SSP5-8.5), at two horizontal resolutions: 12.5 km (all warming levels) and 2.8 km (2°C and 3°C). By identifying historical extreme events and mapping events with similar characteristics in higher warming levels using different heat metrics, we quantify changes in event duration, temperature characteristics, and intensity relative to the recent past to obtain interesting future cases.