A team of scientists has used an advanced computer modeling technique to measure the extent to which non-white and lower-income residents of US cities are exposed to higher summertime temperatures and greater heat stress. The research provides a more direct measurement of heat exposure than earlier findings that relied on satellite measurements and can help with efforts to better protect vulnerable populations from increasingly severe heat waves.
The study, led by scientists at the Pacific Northwest National Laboratory with a co-author at the National Center for Atmospheric Research (NCAR), shows that residents who live in predominantly black neighborhoods are exposed to air that is 0.28°C (0.5°F) warmer than the city average. In contrast, white urban residents are likely to live where air temperature is cooler than the city average by 0.22°C (0.4°F).
Lower-income residents in general face higher temperatures, but the relationship between heat stress and race-based residential segregation is more pronounced.
Although the difference of a few-tenths of a degree may not sound significant, the authors note that the impacts can be quite adverse, especially since poorer populations frequently lack resources such as household air conditioning to help cope during extreme heat.
The research team found that the overwhelming majority of US urban residents —94%, or 228 million – live in cities where the poor are disproportionately burdened by peak heat stress in the summer. But they also found that inequities in heat stress exposure, although stark, are actually somewhat less than previous estimates based on satellite measurements.
Whereas satellites measure temperature at the ground, the research team relied on an NCAR-based database that draws on advanced computer models to estimate the temperature and humidity of ambient air in the urban environment, which is more closely related to heat stress and associated health impacts.
This new database captures heat stress in US cities since 1981 at a resolution of 1km (0.6 miles), showing variations in heat and humidity in different neighborhoods. This resolution, along with information on humidity, gives researchers an important new tool as they work to learn more about urban heat and human health.