Chalmers Climate Dynamics Group

The expansion of urban built–up areas and loss of urban greenspace alter the surface energy balance, exacerbating heat stress. While the greenspace loss reduces biophysical cooling, urbanization can indirectly promote vegetation growth, partially offsetting this effect. Here, using 1 km resolution air temperature data, satellite observations, and city–based random forest model, we quantified the cooling potential of indirect growth effects (IGEs) on compound heatwaves across 499 cities globally. On average, IGEs reduced cumulative heat by 0.35°C, offsetting 4.6% of urbanization-amplified compound heatwaves. Cooling effects were stronger in Global North cities (-0.48 °C) than in Global South cities (-0.25 °C). Scenario simulation show that a sustained increase in IGEs could double the cooling potential: if all cities attained the 90^th percentile value, IGEs could mitigate up to 1.16°C, offsetting 18.3% of urbanization–amplified compound heatwaves. These findings highlight the significant potential for advancing heat risk management and promoting sustainable cities through Nature-based Solutions.