Global and regional changes in working-age population exposure to heat extremes under climate change

Despite recent progress in assessing future population exposure, few studies have focused on the exposure of certain vulnerable groups, such as working people. Working in hot environments can increase the heat-related risk to human health and reduce worker productivity, resulting in broad social and economic implications. Based on the daily climatic simulations from the Coupled Model Intercomparison Project phase 6 (CMIP6) and the age group-specific population projections, we investigate future changes in working-age population exposure to heat extremes under multiple scenarios at global and continental scales. Projections show little variability in exposure across scenarios by mid-century (2031-2060), whereas significantly greater increases occur under SSP3-7.0 for the late century (2071-2100) compared to lower-end emission scenarios. Global exposure is expected to increase approximately 2-fold, 6-fold and 16-fold relative to the historical time (1981-2010) under SSP1-2.6, SSP2-4.5 and SSP3-7.0, respectively. Asia will have the largest absolute exposure increase, while in relative terms, the most affected region is Africa. At the global level, future exposure increases are primarily caused by climate change and the combined effect of climate and working-age population changes. Climate change is the dominant driver in enhancing future continental exposure except in Africa, where the main contributor is the combined effect.