Source attribution: From national emissions to global loss in working hours due to climate-change increased heat

Human-induced climate change has increased heat stress, leading to significant losses in work productivity and subsequent economic repercussions. Not only are the climate change-related losses in work productivity due to heat unequally distributed around the globe, but the contributions of individual nations to these losses through greenhouse gas emissions are also disproportionate. Here, we present a source attribution approach that links historical national emissions to global lost working hours resulting from increased heat exposure.Following the framework of Callahan & Mankin (2022 & 2025), we conduct the source attribution study in three steps: First, we calculate the contribution of past national emissions to the change in global mean surface temperature (GMST) using the reduced-complexity climate model Finite amplitude Impulse Response (FaIR). Second, we apply a pattern scaling technique, trained on outputs from general circulation models, to translate GMST changes into grid-level heat stress metrics, here the wet bulb globe temperature (WBGT). Third, we use the simulated GMST changes due to national emissions, the pattern scaling coefficients, and two literature-based exposure-response functions to estimate the potential loss of working hours attributable to national emissions at grid level. By integrating demographic data on population and employment, we derive estimates of total potential losses in working hours linked to specific nations' emissions. Additionally, we thoroughly assess uncertainties arising from global climate models, the FaIR model, and the exposure-response functions.Our preliminary results highlight the different responsibilities of nations for the costs associated with increased occupational heat stress. The study thereby contributes to the growing body of literature linking individual emitters with experienced harms, providing critical insight into climate liability and national accountability for climate policy. Callahan, C. W., & Mankin, J. S. (2022). National attribution of historical climate damages. Climatic Change, 172(3–4), 1–19. https://doi.org/10.1007/S10584-022-03387-Y/FIGURES/4Callahan, C. W., & Mankin, J. S. (2025). Carbon majors and the scientific case for climate liability. Nature 2025 640:8060, 640(8060), 893–901. https://doi.org/10.1038/s41586-025-08751-3