Climate Justice: Assessing the spatial distribution of urban heat island impacts on populations living in the United States

The Intergovernmental Panel on Climate Change (IPCC) reports that heat waves have been increasing toward the end of the 20th century and are projected to continue to increase in frequency, intensity and duration. Due largely to changes in global climate patterns, these heat waves can overwhelm a person's ability to thermoregulate, resulting in physiological heat stress which can lead to death. Urban populations are particularly vulnerable, due to the densities of heat trapping materials, such as roads, rooftops, and other asphalt surfaces. Recent developments in remote sensing and geographic information systems allow for a characterization and identification of areas within cities where urban heat can increase the likelihood of heat related illnesses. Using empirical assessment of urban heat in the Portland (OR) metropolitan region, we develop a spatially-explicit statistical model for assessing the distribution of heat in 13 cities across the United States (US). Using demographic data from the US Census we further describe the locations of populations most at risk from future heat waves. Our findings suggest a consistent pattern of populations impacted by future heat waves, including lower-income, older and minority communities, although their spatial distribution varies across the urban regions of the country. Our results help to frame a pro-active approach to engaging community groups in adaptation efforts, some of which are being developed in the Portland region. We conclude by offering recommendations for improving conditions for specific urban populations during extreme heat events, and describe a framework for engaging the public in developing adaptation strategies.