Facing the urban overheating: Recent developments. Mitigation potential and sensitivity of the main technologies

Urban overheating represents an internationally acknowledged anthropogenic phenomenon related to climate change and to the massive shift of population worldwide toward urban areas, which are increasingly enlarging their size and density. The consequences of this urban warming (i.e., urban heat island) may compromise citizens' quality of life in urban areas, indoor and outdoor comfort perception, and building energy performance in summer conditions. In this panorama, this review presents recent contributions demonstrating the effectiveness and urgent need of existing mitigation strategies. The same strategies are also comparatively assessed by means of a sensitivity analysis demonstrating their effect with varying climate conditions and urban context. Results of existing studies, validated by the present assessment, aimed at quantitatively investigating the effect of mitigation strategies for reducing building cooling needs and enhancing urban well-being, thanks to international scientific effort carried out in the last decades. To this aim, the logical flow of the review deals with the main technologies for urban warming mitigation are described, together with the main findings of numerical and experimental research initiatives, demonstrating the field effect of improving pedestrians comfort and urban well-being all around the world. Then, the mitigation potential of key green, water and cool strategies is critically reviewed, and further scientific and implementation needs are discussed. All the reviewed contributions demonstrate an undeniable technology readiness level for their practical implementation and highlight the true necessity of a shared and synergistic policy effort worldwide.