Landscapes of thermal inequity: disproportionate exposure to urban heat in the three largest US cities

Bruce C Mitchell,Jayajit Chakraborty

doi:10.1088/1748-9326/10/11/115005

Bruce C Mitchell, Jayajit Chakraborty

Open Access

https://doi.org/10.1088/1748-9326/10/11/115005

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Abstract

Heat waves are the most significant cause of mortality in the US compared to other natural hazards. Prior studies have found increased heat exposure for individuals of lower socioeconomic status in several US cities, but few comparative analyses of the social distribution of urban heat have been conducted. To address this gap, our paper examines and compares the environmental justice consequences of urban heat risk in the three largest US cities: New York City, Los Angeles, and Chicago. Risk to urban heat is estimated on the basis of three characteristics of the urban thermal landscape: land surface temperature, vegetation abundance, and structural density of the built urban environment. These variables are combined to develop an urban heat risk index, which is then statistically compared with social vulnerability indicators representing socioeconomic status, age, disability, race/ethnicity, and linguistic isolation. The results indicate a consistent and significant statistical association between lower socioeconomic and minority status and greater urban heat risk, in all three cities. Our findings support a growing body of environmental justice literature that indicates the presence of a landscape of thermal inequity in US cities and underscores the need to conduct comparative analyses of social inequities in exposure to urban heat.

Highlights

In the past two decades, several high mortality heatwave events have been recorded in developed countries
The urban heat island (UHI) effect is the result of several complex factors, including higher structural density and lower amounts of vegetation in urban areas, which create an urban microclimate that is generally hotter than surrounding rural areas (Oke 1992)
Differences in the natural and built landscape of each study area greatly impacted the geographic distribution of urban heat risk index (UHRI) scores, in Los Angeles with its sparsely populated desert areas

Summary

Introduction

In the past two decades, several high mortality heatwave events have been recorded in developed countries. In 2010, a heatwave combined with atmospheric pollution caused by fires in the Moscow region of the Russian Federation caused an excess mortality of over 11 000 (Shaposhnikov et al 2014). While these events were region-wide in scope, the 2003 heatwave affected densely populated urban areas like Paris, France, and its suburbs which suffered the highest rates of mortality (Fouillet et al 2006). Higher rates of heat related mortality have been linked with levels of urbanization and acclimatization, as indicated in an analysis of 50 cities of the US (Medina-Ramón et al 2007)

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