A 1940-2020 spatiotemporal analysis of thermal discomfort days in Southeast Asian countries

Abstract The high temperature and humidity make Southeast Asia (SEA) one of the regions most susceptible to the occurrence of thermal discomfort days (TDDs) in the world. In the context of global warming, SEA’s rapid population growth and urban expansion further exacerbated the region’s exposure to TDD, posing greater risks in public health. However, there exists a significant knowledge gap in the understanding of the long-term spatiotemporal evolution of TDD, as well as its projection in the future. By utilizing the newly released ERA5 datasets of Universal Thermal Climate Index (UTCI) and Mean Radiant Temperature (MRT), this study presented the 81-year analysis of TDDs in SEA countries, spanning from 1940 to 2020, with projections extending to 2100. While the mean increase in UTCI was relatively modest, the corresponding rise in TDD likelihood was disproportionately larger, indicating a heightened risk of exposure. A distinct contrast was observed between continental and maritime regions, with maritime countries showing smaller absolute rises in both indices but larger trends in TDD frequency due to oceanic moderating effects. Seasonal analyses highlighted the dominant influence of the East Asia monsoon over SEA, and spatial analyses revealed a negative correlation between TDD occurrence and elevation, with low-lying areas being hotspots. Projections for 2050 suggest continued warming. These findings underscore the urgency of proactive measures to address climate change impacts, particularly in vulnerable maritime and low-lying areas, providing valuable insights for enhancing climate resilience and adaptation in SEA. Our findings reveal critical insights into the trends and future scenarios of thermal discomfort in the region, underscoring the urgent need for effective climate adaptation strategies.