Increasing urban albedo to reduce heat-related mortality in Toronto and Montreal, Canada

Abstract

Heat-related mortality (HRM) is increasing because of the climate change and urbanization leading to extreme heat events. This paper summarizes the results of the excess mortality attributed to excessive heat events in two largest cities in Canada, Toronto and Montreal, during three heat wave periods. We present an application of a fine-resolution, urban-mesoscale model to assess the impacts of heat and heat mitigation strategy on heat death. The Weather Research and Forecasting model (WRF) is coupled with a multi-layer of the Urban Canopy Model (ML-UCM) to assess the impacts of heat and heat mitigation strategy on heat -related death. The background albedo of 0.2 for urban surfaces are respectively increased to 0.65, 0.60, and 0.45 for roofs, walls, and grounds. The changes of the air mass category, ambient and apparent temperatures interpret the impacts of extreme heat and the potential of increasing surface albedo (ISA) on HRM. Here, the calculations and estimations of HRM is based on the data obtained from Canadian Environmental Health Atlas (CEHA) indicating an average of 120 heat-induced deaths in Toronto and Montreal. ISA affords a reduction in air temperature (1–2 °C), a decrease in dew point temperature (0.2–0.5 °C), and a slight increase in near-surface wind speed (−0.01 to −0.4 m/s). Increase in albedo shifts days into more benign conditions by nearly 60%. The HRM will lessen by 3–7%, pointing that seven to eighteen lives could be saved. Cooling the urban climate will improve discomfort index, lessen the impacts of elevated temperature, enhance human thermal comfort, and decrease HRM to some significant extent.