Assessment of future heat stress in Vietnam using physically based wet-bulb globe temperature and high-resolution downscaled projections

Abstract This study combines high-resolution dynamically downscaled climate projections with a physically based Wet-Bulb Globe Temperature (WBGT) model to assess future heat stress across Vietnam and its seven climatic subregions. Projections are analyzed for the near (2021–2040), mid- (2041–2060), and far future (2081–2100) relative to 1995–2014, under three Shared Socioeconomic Pathways (SSP1-2.6, SSP2-4.5, SSP5-8.5) and four global warming levels (1.5 °C–4 °C above pre-industrial). Heat stress is evaluated using impact-relevant WBGT thresholds linked to human health, labor productivity, and thermal comfort. Results show a clear and consistent intensification of heat stress across Vietnam, with WBGT levels and exceedance frequencies increasing systematically with higher emissions and warming levels. The most pronounced increases occur in low-lying, densely populated, and economically critical subregions, particularly the Red River Delta and the Mekong River Delta, where dangerous heat stress conditions become frequent by the far future. In addition to daytime extremes, nighttime heat stress intensifies markedly, reducing opportunities for thermal recovery and increasing cumulative exposure. Sub-daily analyses indicate that hazardous WBGT conditions increasingly dominate working hours, especially in southern subregions. Even under moderate scenarios and lower warming levels, widespread exceedance of health- and productivity-relevant thresholds is projected by the far future, indicating that heat stress risks will continue to escalate without effective adaptation. Overall, our findings highlight the growing severity and spatial heterogeneity of heat stress across Vietnam and underscore the urgency of targeted mitigation and adaptation strategies to protect vulnerable populations and sustain economic productivity.