Exposure and Vulnerability as Modifiers of Heatwave Impacts

This chapter considers how exposure and vulnerability work to shape the impacts of heatwaves across various scales. It begins by defining exposure as the extent to which an entity encounters heat, emphasizing the critical dimensions of frequency, duration, and intensity. To lend a geographical perspective to heat exposure the concept of heatwave climates is introduced, identifying regions where significant heatwave-related human mortality has been recorded, using the Köppen-Geiger climate classification as a framework. The chapter then explores vulnerability, defined as the propensity to be adversely affected, and outlines factors that determine vulnerability for human populations, including demographic, health, physical, socioeconomic, behavioural, and institutional factors. How socioeconomic factors, such as poverty and social isolation, may exacerbate heatwave related vulnerability is emphasised. Because smoothly functioning infrastructure is critical to society and economy and heatwaves can compromise the integrity of transportation, energy, and water systems, heatwave related vulnerability of infrastructure is also outlined with the issue of how failures in one system can cascade into others, exacerbating the overall impact of heatwaves highlighted. In addition to human populations, the chapter examines the vulnerability of natural systems. It discusses some of the factors that determine exposure and make terrestrial, marine, and aquatic ecosystems heatwave vulnerable, noting that the health status of these systems significantly affects their ability to withstand heat stress. The chapter concludes by emphasizing the need for further research on the determinants of heatwave exposure and vulnerability especially in the case of natural systems and infrastructure.