Exacerbated heat stress induced by urban browning in the Global South

Abstract

Cities in the Global South face dual pressures from intensifying heat stress and widespread urban browning. However, the specific trends in urban heat stress across these cities, alongside those induced by urban browning, remain inadequately quantified, hampering effective urban planning and intervention strategies. Here we present a data-driven methodology to generate high-resolution (1 km) summertime Heat Index (HI) maps for over 2,300 Global South cities (2003–2020). This dataset recalibrates HI-based warming rates, revealing a mean trend (KHI) of 0.41 ± 0.01 °C per decade (mean ± standard error) across these cities. Urban browning exacerbates heat stress significantly, with KHI increases surpassing 0.05 °C per decade in cities such as those in Nigeria, contrasting starkly with greening-induced cooling observed in many Global North cities. Our analysis pinpoints cities in dire need of intervention, such as those in Botswana and Côte d’Ivoire facing browning-driven HI increases without commensurate economic growth. Contrastingly, Chinese and Indian cities exhibit a paradoxical cooling trend, potentially linked to greening initiatives amid economic development. Our findings highlight key action imperatives for South–South knowledge exchange to develop targeted governance strategies for achieving urban sustainability. This study measured urban moist heating rates in more than 2,300 cities in the Global South between 2003 and 2020 with a new dataset. It found an increase in urban moist heat of 0.41 ± 0.01 °C per decade, exacerbated by urban browning by 0.05 °C per decade in cities such as those in Nigeria.