Mitigating urban heat stress through green infrastructure: A climate service approach

As the global urban population grows, city dwellers are increasingly exposed to outdoor thermal conditions that threaten their well-being in a warming climate. In this study, we characterized the heat stress and addressed its mitigation from a climate service perspective using a mid-sized city as case study. We simulated mean radiant temperature to assess the Universal Thermal Climate Index (UTCI) at fine spatial (2 m) and temporal (1 hr) resolutions for winter and summer. Thermal conditions were evaluated for different age groups across key Local Climate Zones, and the benefits of increased green infrastructure were examined across four scenarios. To achieve this, we proposed a comprehensive framework that incorporates an algorithm to enhance tree cover. This algorithm optimizes urban spaces by replacing smaller trees with larger specimens, coupled with planting new, larger trees. Together, these components form a customized tool that climate service users can leverage. The city center, home to the largest elderly population, featured highest heat exposure, with the greatest number of hours under strong and very strong heat stress. Increasing tree canopy cover by more than two-fold reduced the UTCI by up to 2.1 °C on average, and as much as 3.1 °C during the hottest hours of the day. These findings showed that the proposed framework is well-suited for climate-sensitive applications and offers a user-friendly, cost-effective tool for cities to assess and design strategies to mitigate heat stress by increasing tree coverage.