Global future urban growth and meteorological disaster risks

Abstract: Cities are facing multiple meteorological hazards such as heatwaves, wind chill, floods, water scarcity, and tropical cyclones. Nonetheless, the exposure and adaptation of global urban growth to these hazards under climate change are not well addressed. This study assessed the urban population exposed to the aforementioned hazards globally from 2020 to 2050, and analyzed the impacts of adjusting the spatial patterns of future urban expansion on exposure. In 2020, a total of 2.18 billion (49.85%) urban residents worldwide were exposed to at least one severe hazard. Specifically, the urban population exposed to severe heatwaves, wind chill, tropical cyclones, water scarcity, and floods stood at 1.62 billion, 0.01 billion, 0.09 billion, 0.68 billion, and 0.27 billion, respectively. Additionally, 9.13 million (0.21%) urban residents faced concurrent exposure to more than three severe hazards. By 2050, the global urban population at risk of at least one severe hazard is projected to reach 4.31–4.81 billion (72.71%–75.03%). The projected urban population exposed to the five severe hazards mentioned above will be 3.72–4.25 billion (heatwaves), 0.71–0.71 billion (wind chill), 0.18–0.40 billion (tropical cyclones), 1.30–1.36 billion (water scarcity), and 0.35–0.41 billion (floods), respectively. The number of urban residents facing concurrent exposure to more than three severe hazards is expected to rise to 47.62–72.99 million (0.80%–1.14%). Adjusting the spatial pattern of future urban expansion can effectively reduce the urban population exposed to meteorological hazards. Under the scenario of moderate prevention of all hazards, the urban population exposed to heatwaves, wind chill, tropical cyclones, water scarcity, and floods will decrease by 34.64–35.83 million, 14.19–19.22 million, 41.95–51.57 million, 244.91–275.96 million, and 166.03–205.17 million, respectively. This study provides empirical support for delineating global urban growth boundaries for mitigating meteorological disasters.