Dimensions of Thermal Inequity: Neighborhood Social Demographics and Urban Heat in the Southwestern US

Exposure to heat is a growing public health concern as climate change accelerates worldwide. Different socioeconomic and racial groups often face unequal exposure to heat as well as increased heat-related sickness, mortality, and energy costs. We provide new insight into thermal inequities by analyzing 20 Southwestern U.S. metropolitan regions at the census block group scale for three temperature scenarios (average summer heat, extreme summer heat, and average summer nighttime heat). We first compared average temperatures for top and bottom decile block groups according to demographic variables. Then we used spatial regression models to investigate the extent to which exposure to heat (measured by land surface temperature) varies according to income and race. Large thermal inequities exist within all the regions studied. On average, the poorest 10% of neighborhoods in an urban region were 2.2 degrees C (4 degrees F) hotter than the wealthiest 10% on both extreme heat days and average summer days. The difference was as high as 3.3-3.7 degrees C (6-7 degrees F) in California metro areas such as Palm Springs and the Inland Empire. A similar pattern held for Latinx neighborhoods. Temperature disparities at night were much smaller (usually similar to 1 degrees F). Disparities for Black neighborhoods were also lower, perhaps because Black populations are small in most of these cities. California urban regions show stronger thermal disparities than those in other Southwestern states, perhaps because inexpensive water has led to more extensive vegetation in affluent neighborhoods. Our findings provide new details about urban thermal inequities and reinforce the need for programs to reduce the disproportionate heat experienced by disadvantaged communities.

Automated summary

Exposure to heat is increasingly becoming a global public health issue due to climate change, with different socioeconomic and racial groups facing unequal exposure leading to adverse health effects and increased energy costs. Research shows significant thermal inequities in Southwestern U.S. metropolitan regions, with the poorest neighborhoods being hotter than the wealthiest neighborhoods by 2.2 degrees Celsius on average, and even larger differences in California urban areas. This highlights the need for programs to address and reduce the disproportionate heat experienced by disadvantaged communities.