Heatwave Responses: Mitigation

This chapter begins by making a case for a distinction between mitigation (modifying the physical hazard) and adaptation (behaviour change) in relation to heatwave risk reduction in urban environments. Specifically, it asserts that modifying the physical nature of heat, as the fundamental property of heatwaves, via urban surface radiative and energy balance management, sets mitigation apart from adaptation. After briefly exploring the historical context of urban heat mitigation the Chapter moves on to consider modern strategies, categorizing urban heat mitigation into three broad approaches: modifications to urban surfaces, nature-based solutions (NBS), and changes to urban morphology and built form. Cool pavements and cool roofs are discussed in the context of the modification of urban surfaces. Various types of cool pavements are identified. Cool roofs and their impacts on the reduction of heat transfer into buildings and lowering indoor temperatures and energy consumption as well as their efficacy for curtailing air temperature extremes are also examined. The characteristics of a range of NBS such as green roofs, vertical greenery systems, and urban greenspaces and blue spaces, are described with their potential to mitigate urban heat through shading, evapotranspiration and evaporation considered. Their effectiveness in different urban settings and climates is reviewed. The chapter also discusses how alterations to urban morphology and built form might achieve heatwave mitigation. Although the importance of integrating multiple mitigation options to achieve heatwave mitigation, such as combining cool roofs with increased vegetation, is emphasised, the prospect that the level of heatwave mitigation required to achieve meaningful reductions in temperature extremes during heatwaves may not be obtained, even with widespread application of the most effective mitigation options, is raised. The chapter concludes by stressing the need for interdisciplinary research to understand the long-term impacts and scalability of the mitigation strategies discussed. It highlights the potential societal resistance and financial challenges associated with large-scale implementation and calls for collaboration among stakeholders to optimize co-benefits such as improved air quality and energy efficiency. The chapter underscores that while urban heat mitigation is crucial, it must be complemented by global efforts to reduce greenhouse gas emissions to effectively manage global heat in the face of climate change.