Regional disparities in the exposure to heat-related mortality risk under 1.5 °c and 2 °c global warming

Abstract

An increase in heat-related mortality risk has emerged to accompany the ravages of climate change, but its unambiguous assessment remains an onerous task, owing to the non-linear associations between the severity of hot temperatures and human body response. The present study assesses the future heat-related mortality risk under different levels of warming (1.5 °C vs. 2 °C) using the multi-models' large ensemble simulations. In order to augment the robustness of the patterns for future changes in heat-related mortality risk, multiple indices representing the excess mortality risk solely attributed to higher temperature are estimated from different meteorological variables (maximum temperature, maximum wet-bulb temperature and mean temperature). The ensemble projections reveal a worldwide surge in heat-related mortality risk, albeit with a regionally diverse pattern. Although comparisons of the different indices show some quantitative differences, they provide remarkably consistent regional hotspots, thus amplifying the possible benefit of a mitigation equivalent to 0.5 °C less warming in the equatorial region. In addition to the severity of hot temperatures, the demographic changes evolving along the different shared socio-economic pathways also determine the exposure to heat-related mortality risk. Based on multiple indices and large ensemble simulations, this study contributes to the identification of regional hotspots in terms of the exposure of (the elderly) population to heat-related mortality risk, underscoring the necessity of regionally-tailored adaptation strategies.