Climate science: Disproportionate exposure to heat stress in US cities

Urban heat stress exposure may disproportionally affect people of colour and low-income households in the majority of cities across the United States according to a new study published in Nature Communications this week. Understanding where these disparities in heat exposure exist may inform future efforts to design policy interventions to reduce such inequalities.

The distribution of heat intensity within single cities is uneven due to variations in features such as green space, urban form and city size. This can lead to differences in heat exposure levels to populations living in cities dependent on location.

Angel Hsu, Glenn Sheriff and colleagues combined summer daytime satellite-based temperature data with sociodemographic data from the 2017 US census. They found that the average person of colour lives in a census tract (an administrative area) with higher summer daytime surface urban heat island intensity than non-Hispanic white people in 169 of the largest urbanized areas in the US. In addition, in almost half the urbanized areas, the average person of colour is exposed to a higher summer daytime surface urban heat island intensity than the average person living below poverty, despite on average, only 10 percent of people of colour living below the poverty line in the US. However, households below the poverty line across all racial and ethnic groups face higher heat exposure relative to those at more than two times the poverty line.

The research suggests that there are intra-city differences in heat exposure due to sociodemographic factors, but the inequalities in heat exposure by race and ethnicity may not be well explained by differences in income.