Hysteresis in Heat-Related Labor Productivity under CO₂ Overshoot Scenarios: Economic and Policy Implications

Labor is a fundamental driver of economic productivity but is increasingly threatened by rising heat exposure under climate change. While mitigation policies are often framed around avoided damages and health co-benefits, the persistence of labor productivity losses under negative CO₂ emission pathways remains poorly understood. Here, we use the Community Earth System Model version 1.2 (CESM1.2) large ensemble simulations to investigate hysteresis in Wet Bulb Globe Temperature (WBGT), labor productivity, and associated economic impacts under a CO₂ overshoot scenario. Our results show that midday heat exposure produces the most severe productivity reductions, with WBGT recovery lagging behind surface temperature due to humidity-driven hysteresis. Even after atmospheric CO₂ return to present climate levels, global labor losses remain above 100 billion hours annually, with South Asia, Central Africa, and the Middle East experiencing the strongest irreversibility. These persistent damages account for more than 60% of total climate-related economic losses. We provide the global assessment of hysteresis in labor productivity under overshoot pathways. The findings demonstrate that mitigation alone cannot fully restore labor capacity and highlight the necessity of complementary adaptation strategies—including heat-resilient infrastructure, work-rest scheduling, and legal protections for outdoor workers. Our study emphasizes the importance of incorporating hysteresis effects into benefit–cost assessments of climate policies to more accurately capture long-term economic and social risks, particularly for vulnerable populations in tropical and low-income regions.