Projecting Livability from Heat Stress with Climate Change

Anthropogenic climate change is causing extreme heat events to become more frequent, intense, and longer in duration, raising questions about humans’ ability to live and work in a rapidly warming climate. New physiology-based modeling methods introduced in Vanos et al. (2023) as the Python Human Heat Balance model (PyHHB) allow assessment of livability. Livability is expressed as the range of human activity levels that are safely sustainable under different temperature and humidity conditions, quantified as a maximum metabolic rate. By applying PyHHB to state-of-the-art climate model projections, this project describes nuanced projections of livability under future heat stress. We apply PyHHB to historical, near-present, and end-of-century time frames for a range of climate models. Separate projections are created for a range of CMIP6 Shared Socioeconomic Pathways as well as key warming levels. End-of-century livability projections consider the impact of age-related sweat deficiencies by accounting for world population demographic projections from the United Nations Department of Economic and Social Affairs. The project results display how future livability is thus constrained by climate model variability, warming scenario, demographic projections, and human physiology. Livability projections inform what areas of the world may most benefit from climate adaptation efforts and provide implications for the feasibility of tasks requiring heavy manual labor.