Quantifying the impacts of urban adaptation measures to reduce heat stress in Belgium

Climate change is driving higher global temperatures and more frequent heatwaves. Urban populations are exposed to high temperatures and heat stress because of the urban heat island. For effective adaptation planning, quantifying the additional heat burden for urban populations during heat waves and finding possible heat mitigation strategies is key. Our study focusses on Brussels during the record-breaking heat wave of 2019 in Belgium, where temperatures approached 40°C.  We use high-resolution models to characterise spatial variations in heat exposure across the city, and quantify how certain adaptation strategies like urban greening can reduce heat exposure and related health impacts.

To quantify the influence of the urban presence as well as detect spatial differences in heat exposure, we compare urban and non-urban scenarios using three urban climate models: UrbClim at 100m, WRF with BEP/BEM at 1km and COSMO-CLM with TERRA_URB at 2.8km. Additionally, we link the temperature output from the simulations to mortality data for Brussels using existing temperature-health relationships to quantify the mortality attributable to the heatwave. For each of the models in the urban mini-ensemble, the same adaptation strategy is implemented at hotspot locations. Three different scenarios are tested: increasing the permeable surface, implementing cool roofs and a combination of both. The mini-ensemble allows for a better understanding of the uncertainties related to implementing such strategies, particularly the effects of different model parameterizations. These results help us understand the potential of mitigation measures to reduce impacts from heat stress, and thereby serve as an important basis for urban adaptation and planning policy.