Climate change impacts on human health in Portugal based on downscaled CMIP6 future climate scenarios: an analysis using thermal comfort indices

Abstract This study assesses the projected impacts of climate change on human thermal comfort in mainland Portugal using high-resolution downscaling of a CMIP6 GCM (MPI-ESM-1.2-HR) with the Weather Research and Forecasting model for three CMIP6 future climate scenarios Shared Socioeconomic Pathway (SSP2-4.5, SSP3-7.0, and SSP5-8.5). Two bioclimatic indices—the Thom discomfort index (TDI) and the universal thermal climate index (UTCI)—were analyzed to evaluate changes in population exposure to heat and cold stress. Results indicate a consistent increase in heat-related discomfort across all scenarios and time periods, accompanied by a reduction in cold-related stress. By mid-century (2041–2070), both TDI and UTCI show widespread warming, particularly in spring and summer, with the strongest increases occurring in southern and interior regions. Toward the end of the century (2071–2100), the frequency and duration of high and extreme heat stress days rise substantially, especially under SSP5-8.5, while cold stress days become increasingly rare. These findings highlight a clear shift toward hotter and more uncomfortable climatic conditions throughout Portugal, posing significant health challenges for vulnerable populations. The results underscore the importance of integrating thermal comfort metrics such as TDI and UTCI into climate adaptation and public health planning strategies.