High resolution heat stress over a Sahelian city: Present and future impact assessment and urban green effectiveness

Abstract

Cities in the Sahel are heavily impacted by heat stress. Climate change, growing population rates and urbanization will increase the magnitude and intensity of urban heat stress towards the future. This study provides a comprehensive analysis of the current status of heat stress in Niamey (Niger) and future impacts by combining the results of two models operating at city‐level: UrbClim which simulates (future) climate and GeoDynamiX, providing future city spatial extents combined with the results of a measurement campaign. Additionally, a meter‐scale assessment of heat stress within the city is executed for a selection of city districts. Urban green and trees are effective mitigation tools for heat stress, which is observed in both measurements and model results, being most effective during the hottest hours of the day when they lower heat stress to less health‐impacting levels. Future simulations show a strong increase in the spatial extent and intensity of extreme temperatures within the city. This impacts city dwellers, which will consequently experience much more days with extreme heat stress levels towards the future, doubling or tripling depending on the climate scenario. Socio‐economic impacts for mid‐century are quantified, noting increases in heat‐related mortality of several percentages compared to present‐day values. Additionally, negative economic impacts of several percentages of the Gross Domestic Product are projected as heat stress will prohibit performing moderate or high‐intensity activities during the hottest hours of the day, even in the shade.