Projections of Human Exposure to Dangerous Heat in African Cities Under Multiple Socioeconomic and Climate Scenarios

Abstract

Human exposure to dangerous heat, driven by climatic and demographic changes, is increasing worldwide. Being located in hot regions and showing high rates of urban population growth, African cities appear particularly likely to face significantly increased exposure to dangerous heat in the coming decades. We combined projections of urban population under five socioeconomic scenarios—shared socioeconomic pathways—with projections of apparent temperature under three representative concentration pathways in order to explore future exposure to dangerous heat across 173 large African cities. Employing multiple shared socioeconomic pathway and representative concentration pathway combinations, we demonstrated that the aggregate exposure in African cities will increase by a multiple of 20–52, reaching 86–217 billion person‐days per year by the 2090s, depending on the scenario. The most exposed cities are located in Western and Central Africa, although several Eastern African cities showed an increase of more than 2,000 times the current level by the 2090s, due to the emergence of dangerous heat conditions combined with steady urban population growth. In most cases, we found future exposure to be predominantly driven by changes in population alone or by concurrent changes in climate and population, with the influence of changes in climate alone being minimal. We also demonstrated that shifting from a high to a low urban population growth pathway leads to a slightly greater reduction in aggregate exposure than shifting from a high to a low emissions pathway (51% vs. 48%). This emphasizes the critical role that socioeconomic development plays in shaping heat‐related health challenges in African cities.

Increased population exposure to precipitation extremes under future warmer climates

“…Understanding the impacts of changes in climate extremes to humans is critical to shaping disaster risk and for further effective adaptation. Existing studies have documented that population exposure to dangerous heat temperatures is projected to significantly increase around the world, especially over Africa, South Asia, East Asia, and North America, under the future warming scenarios (Jones et al 2015, Liu et al 2017, Coffel et al 2018, Rohat et al 2019, Zhan et al 2018. Additionally, with the increase of drought occurrence over China, the corresponding exposure presents a remarkable increase in the future even though the population is projected to sharply decrease .…”

Urban Areas and Urban–Rural Contrasts under Climate Change: What Does the EURO-CORDEX Ensemble Tell Us?—Investigating near Surface Humidity in Berlin and Its Surroundings

“…Changes in moisture in urban areas under climate change could impact city sectors such as building structure, health, and biodiversity, resulting in a profound effect on the livability of cities. For instance, relative humidity is of direct importance to human heat stress and health [33][34][35]. Additionally, moisture levels can influence the sustainability of buildings by, for instance, altering the moist risks or endurance of building material [36,37].…”

Intersecting vulnerabilities: Climatic and demographic contributions to future population exposure to Aedes-borne viruses in the United States

“…Population exposure is therefore expressed in terms of person-months of exposure per year, in line with metrics used in other climate impact studies, e.g. (Jones et al, 2015, Rohat et al, 2019. The main advantage of this exposure metric lies in that it accounts for the duration (in months) of the exposure event.…”

“…We also computed the interaction effect between the two, that is, the difference between the total projected change in exposure and the sum of the climate and population effects. The interaction effect is interesting in that it represents the process by which concurrent changes in population and climatic conditions affect the population exposure (Rohat et al, 2019). We explored the population, climate, and interaction effects at the county scale for the four SSP*RCP combinations separately for both increased and decreased exposure.…”

“…This scenario framework is made up of climate scenarios -Representative Concentration Pathways, RCPs (van Vuuren et al, 2011) -and socioeconomic scenarios -Shared Socioeconomic Pathways, SSPs -combined together into a scenario matrix . This framework (hereafter referred as SSP*RCP framework) is being increasingly used in IAV studies to explore future population exposure -under socioeconomic and climatic uncertainty -to a wide range of climate-related risks such as extreme heat (e.g., Jones et al, 2018, Rohat et al, 2019, inland and coastal flooding (e.g., Alfieri et al, 2015, Brown et al, 2018, fire risk (Knorr et al, 2016), air pollution (Chowdhury et al, 2018), and food security (e.g., Hasegawa et al, 2014). The SSP*RCP framework has been applied to some VBD-related studies (e.g., Monaghan et al 2016.…”