Yale University, USA
Over the next decades, climate change is projected to increase the intensity and frequency of extreme heat events. The severity and periodicity of these extreme heat events are likely to be further compounded by the urban heat island (UHI), thereby increasing the risk to urban populations and places. However, there is little known about how climate change-induced changes in extreme heat will interact with UHI, and what this will mean for the exposure of urban populations to heat extremes. This work aims to fill this knowledge gap by using climate data from 2000 to 2015 to generate spatially explicit forecasts of compound urban temperature extremes through 2050. The respective contributions from climate change, UHI and their interaction vary across different types of cities. In most of the cases, the interaction is as important as climate change and UHI acting separately in aggravating heat extremes. The interaction is a stronger contributor in cities with lower vegetation cover, bigger population, larger built-up area and higher density. The resulting compound heat extremes will be more intense and frequent in emerging Asian and African megacities located in tropical/subtropical climates, due to their unprecedented sizes and the significantly reduced evaporation. Previous studies neglecting this interaction have underestimated exposure to heat extremes in urban areas, and this factor needs to be considered in urban climate adaptation.
Keywords: Urban heat island, Climate change, Urban climate adaptation