Computing comfort days under sun–shade adaptive and static outdoor exposure

Climate-driven changes in outdoor thermal comfort critically influence daytime human activity and well-being. Most previous studies have estimated outdoor thermal comfort under fully static exposure assumptions, considering individuals to remain either continuously shaded or continuously sun-exposed throughout the daytime. These assumptions are appropriate for some occupational settings, such as construction and agricultural work under direct sunlight or industrial and service work in predominantly shaded or indoor environments. However, they may be less applicable to non-occupational outdoor activities where individuals have some flexibility to modify their sun–shade exposure (e.g., walking, commuting, recreation, and tourism).Here, we introduce a sun–shade adaptive exposure framework as an alternative behavioral assumption for representing non-occupational outdoor activities where discretionary sun–shade adjustment is possible. Using the Universal Thermal Climate Index (UTCI) derived from hourly ERA5 reanalysis data, we develop Python scripts to quantify the global annual frequency and long-term trends of comfort days, as well as population exposure, under this adaptive framework. These results are compared with estimates obtained under traditional static (shaded and unshaded) exposure assumptions.By comparing these alternative exposure assumptions, this work quantifies how estimates of global daytime thermal comfort and population exposure differ depending on the assumed patterns of sun–shade exposure, thereby providing a broader perspective on outdoor thermal comfort under a changing climate.CitationTo use or adapt these Python scripts, please cite the associated publication as follows:Yan, Y., Yue, S., Wang, T., Liu, Y., & Zhang, M. (2026). Human Sun–Shade Adaptation Reshapes Global Outdoor Thermal Comfort Assessments. Earth’s Future, 14(9), e2026EF008556. https://doi.org/10.1029/2026EF008556