Urban Heat Island Mitigation Strategies
According to the Intergovernmental Panel on Climate Change (IPCC), eleven of the hottest twelve years ever observed were recorded since 1995 and are attributable to rising levels of greenhouse gases in the atmosphere. North American cities “that currently experience heat waves are expected to be further challenged by an increased number, intensity and duration of heat waves”.
In Québec, the hottest ten years of the century have been recorded since the 1980s (Natural Resources Canada, 2004). Forecasts indicate that average temperatures will continue to rise in the coming decades.
This observed and forecast constant increase in temperature will accentuate a problem with which we are already familiar: the urban heat island effect. This phenomenon is characterized by higher summer temperatures in urban environments than in surrounding rural areas. According to observations, this temperature difference, which is primarily attributable to the urban built environment, ranges from 2°C to 12°C and may pose particular risks to the urban population. Certain cities such as Paris and Chicago learned this first hand following heat waves that proved to be very deadly.
Many cities have adopted strategies to mitigate urban heat islands. Québec cities must also react to these changing climatic realities, in particular by implementing urban heat island mitigation measures and creating urban cool zones. These types of initiatives protect the population by increasing their ability to adapt to these phenomena.
This literature review was carried out primarily for the benefit of the staff of non-profit organizations and municipalities working in this field and supports the focus of the projects submitted under the Québec Action Plan on Climate Change – Health Component. The objective of this review is to identify and publicize the main urban heat island mitigation strategies and the many successful initiatives in this field, both in Québec and internationally. This document does not claim to replace the recommendations of experts in the fields concerned by urban heat island mitigation strategies, including architecture, urban planning, transportation and engineering.
Section 2 of this literature review discusses the causes and impacts of urban heat islands, while section 3 describes the areas in Québec vulnerable to urban heat islands. Section 4 examines the various urban heat island mitigation strategies adapted to Québec cities, while section 5 provides examples of applications of these measures and strategies in various cities in Québec and around the world. Finally, section 6 provides a summary and comparison of urban heat island mitigation strategies as well as suggestions for their application in Québec, followed by recommendations.