Search

Urban overheating is the most documented phenomenon of climate change impacting humans. This article presents the most recent developments on the magnitude and characteristics of urban overheating and the potential synergies with global climatic change. It analyses the latest qualitative and quantitative data on the impact of higher urban temperatures on buildings' energy supply and demand, heat-related mortality, morbidity and wellbeing, human productivity, survivability of low-income populations, and environmental quality of cities. It describes the state of the art on the development of innovative mitigation materials, advanced urban greenery, heat dissipation, and evaporative techniques as the main mitigation and adaptation technologies to offset the impact of urban overheating. It also analyses the current knowledge on the impact of each mitigation technology on energy, health, environmental quality, urban economy, and survivability. Finally, this article presents the main future challenges related to urban overheating and proposes a specific research agenda to alleviate and counterbalance its impact on human life. [ABSTRACT FROM AUTHOR]

Urban overheating, driven by global climate change and urban development, is a major contemporary challenge that substantially impacts urban livability and sustainability. Overheating represents a multifaceted threat to the well‐being, performance, and health of individuals as well as the energy efficiency and economy of cities, and it is influenced by complex interactions between building, city, and global scale climates. In recent decades, extensive discipline‐specific research has characterized urban heat and assessed its implications on human life, including ongoing efforts to bridge neighboring disciplines. The research horizon now encompasses complex problems involving a wide range of disciplines, and therefore comprehensive and integrated assessments are needed that address such interdisciplinarity. Here, our objective is to go beyond a review of existing literature and instead provide a broad overview and integrated assessments of urban overheating, defining holistic pathways for addressing the impacts on human life. We (a) detail the characterization of heat hazards and exposure across different scales and in various disciplines, (b) identify individual sensitivities to urban overheating that increase vulnerability and cause adverse impacts in different populations, (c) elaborate on adaptive capacities that individuals and cities can adopt, (d) document the impacts of urban overheating on health and energy, and (e) discuss frontiers of theoretical and applied urban climatology, built environment design, and governance toward reduction of heat exposure and vulnerability at various scales. The most critical challenges in future research and application are identified, targeting both the gaps and the need for greater integration in overheating assessments. Plain Language Summary: Many major cities are faced with the compounding effects of climate change and rapid urbanization. One of the main challenges that result is urban overheating, which leads to negative impacts on human life (deteriorating health, productivity, and well‐being) and urban energy systems. Heat exposure in cities, however, is only the trigger and there are other factors that influence impacts. Urban heat vulnerability exists when sensitive people and infrastructure are exposed to extreme heat, and negative impacts ensue if there is a lack of capacity to respond and adapt. Accordingly, to combat overheating challenges, it is critical that multidisciplinary solutions are integrated to mitigate exposure, reduce sensitivity, and increase adaptive capacities. This paper provides an integrated assessment of urban overheating literature, defining pathways for addressing the impacts on human life. We review the state‐of‐the‐art methods used to quantify heat hazards and exposure, detail the sensitivity of people and infrastructure to overheating, and elaborate on the adaptive capacities that individuals and cities can undertake in response. We provide recommendations for both researchers and policymakers that will minimize overheating impacts. These recommendations range from modifications to urban and building design to engaging citizens and informing urban overheating governance. Key Points: Urban overheating is the exceedance of locally‐defined thermal thresholds that lead to negative impacts on people and urban systemsExposure to heat hazards compounded with sensitivity and reduced adaptive capacity of people and urban systems lead to increased risk levelsResearch and application should provide integrated solutions to mitigate exposure, reduce sensitivity, and increase adaptive capacities [ABSTRACT FROM AUTHOR]

This paper reports the measured solar spectral properties and the thermal performance of 10 prototype cool colored coatings, developed at the National and Kapodistrian University of Athens, using near-infrared reflective color pigments in comparison to color-matched, conventionally pigmented coatings. These coatings are developed to be used in the urban environment to fight the heat island effect. The spectral reflectance and the infrared emittance were measured and the solar reflectance of the samples was calculated. The surface temperature of the coatings when applied to concrete tiles was monitored, using surface temperature sensors and a data logging system, on 24 h basis from August to December 2005 in an effort to investigate the ability of the cool colored coatings to maintain lower surface temperatures than conventionally pigmented color-matched coatings. The data obtained has been extensively analysed and indicate significant success in the development of these cool colored coatings. It was found that all the coatings containing infrared reflective pigments have solar reflectance values higher than those of standard coatings. Furthermore, it was demonstrated that cool colored coatings maintain lower surface temperatures than color-matched conventionally pigmented coatings. This temperature difference is mainly due to differences in solar reflectance. These cool colored coatings can be used on buildings (roofs and walls) and other surfaces in the urban environment. Thus, at building scale, the use of cool colored coatings with increased solar reflectance can improve building comfort and reduce cooling energy use, and at city city-scale it can contribute to the reduction of the air temperature due to the heat-transfer phenomena and therefore improve outdoor thermal comfort and reduce the heat-island effect. Keywords: Cool colored coatings: Solar spectral reflectance: Infrared emittance; Thermal performance; Passive cooling; Ageing