Global Projections of Human-Perceived Heat Stress in Cities Under Climate Change

Abstract:

Climate change is projected to contribute to increased severity, frequency, and duration of heat waves. Ongoing massive and rapid urbanization increases the number of people who are exposed and vulnerable to heat stress. Heat stress can cause a host of health-related issues, and disproportionately affects economically, physically, and socially disadvantaged groups. This paper seeks to elucidate the interactions of background climate change, heat waves and urban heat island in cities in order to develop a more nuanced understanding of global spatiotemporal patterns of human-perceived heat stress in cities. This paper compares projected wet-bulb temperature to 2-m height air temperature and suggests that the common use of 2-m height air temperature may overestimate the urban heat island effect as it pertains to human-perceived heat. Our results indicate a strong spatial heterogeneity in wet-bulb temperature and suggest that 2-m air temperature hotspots often do not correlate in location or intensity with wet bulb temperature hotspots. This study also takes advantage of the improved urban representation in the CESM2 (Community Earth Systems Model) to conduct a global comparison of human-perceived heat stress in cities. Additionally, this study explores the geospatial nature of green infrastructure cooling potential, projected temperatures above a human adaptability threshold, and varying urban densities. By further elucidating the interactions between drivers of heat stress, this study presents a more nuanced understanding of the spatial dimension and intensity of future heat stress and guide mitigation and adaptation efforts.