Climate change exacerbates the compounding of heat stress and flooding in the mid-latitudes

Heat stress and flood impacts have been extensively studied separately because of their significant societal and economic impacts, albeit apart from each other. Here we show that heat stress can trigger floods across large areas of North and South America, southern Africa, Asia and eastern Australia. We also show that the compounding of heat stress and floods is projected to worsen under climate change. This effect is magnified as we move from the Shared Socioeconomic Pathways (SSPs) 1-2.6 to 5-8.5. Moreover, in the future, the compounding between heat stress and floods is projected to extend to Europe and Russia, two areas where it has not been identified as relevant in the past. Moreover, by intersecting our results with future projections of the population of urban agglomerations, we find that heat stress/flood compound can pose a serious risk to a large portion of the world population. These results highlight the need towards improved preparation and mitigation measures that account for the compound nature of heat stress and flooding, and how the compounding is expected to be exacerbated because of climate change. Heat stress tends to precede many summer floods in the mid-latitudes, representing a weather precursor for these events. The shared socioeconomic pathway projections show an increase in the compounding percentage across the different subzones we considered, and close to 100% in large areas of the globe. This is particularly evident for increasing greenhouse gas emissions. The potential societal impacts of this compound hazard are projected to impact a large segment of the population living in urban areas. image