Assessing variability in urban heat stress and associated human health risks using mPET (modified Physiologically Equivalent Temperature): Implications for enhancing resilience in a changing climate

Urban heat stress exposure varies significantly within cities. This variability and its profound implications for public health are assessed in the present work, focusing on the Athen’s complex urban basin, Greece. Employing the modified Physiologically Equivalent Temperature (mPET), strong intra-urban differences are revealed. West and Central Athens experience the most frequent and prolonged strong heat stress (SHS) exposure, leading to elevated relative risk (RR) of mortality, predominantly due to hot and dry conditions associated with compact overbuilding and scarcity of green areas. In contrast, the combination of higher elevation, increased greenery, and the cooling influence of Etesians (large-scale northerly winds during the summer) reduces SHS exposure in North Athens, thereby lowering the associated mortality RR. Coastal areas (South Athens and Piraeus) benefit from sea breeze currents, which help lower SHS exposure and related mortality RR. However, increased atmospheric moisture induced by these local-scale circulations can also exacerbate heat stress and elevate the associated mortality risks. These findings, along with insights on population-wide variability in heat stress and RR, contribute to strengthening resilience against the urban heat impact on human health. They, specifically, played a key role in shaping an advanced Heat-Health Warning System, which was operationally deployed and tested during the 2024 warm period. Furthermore, they lay the groundwork for advancing future climate heat-health impact assessments in urban agglomerations, supporting the development of adaptation and mitigation strategies tailored to evolving bioclimatic conditions. Building on this foundation, the current work also introduces a pioneering concept for exploring future human thermal bIoclimate pathways and their associated health responses in three major urban hubs in Europe. Using mPET, the concept emphasizes the incorporation of human thermoregulation principles into heat-health risk modelling, considering plausible thermo-physiological and behavioral adaptive responses to the anticipated warmer future climate.

 

Christos Giannaros acknowledges the support provided by the CLIMPACT ("Support for Enhancing the Operation of the National Network for Climate Change") project (National Development Program, General Secretariat of Research and Innovation; 2023ΝA11900001—Ν. 5201588)