More intense and equal compound heatwaves driven by urbanization

Urban populations are increasingly exposed to severe and disproportionate heatwaves. While existing studies address urban heatwaves and intra-urban disparities, there remain gaps in understanding of the impact of urbanization on heatwaves and the associated inequalities. In this study, we analyzed urban compound heatwave (UCHW) and associated inequality across 936 global cities. Our findings reveal a sustained increase in UCHW under global urbanization, accompanied by a general decline in associated inequalities from 2003 to 2019. This trend is particularly pronounced in the Global South, where the intensification of UCHWs has outpaced that in the Global North, accompanied by a more significant reduction in related inequalities. Urbanization intensifies UCHWs by increasing impervious surfaces and reducing urban greenery, while concurrently decreasing their spatial heterogeneity and thus lowering UCHW inequality. Our study highlights the impact of the urbanization on UCHWs and associated inequalities, which is crucial for sustainability of cities.