Significant thermal disparities exist among predominantly white, Black, Hispanic, and Asian communities in America's 200 most populous cities, according to a new research study from Indiana University’s Daniel Johnson.
Johnson, an associate professor of geography at IUPUI, examined surface urban heat islands, areas within a city that experience much warmer temperatures than their surrounding landscapes. The research will expand understanding of the dynamic nature of inequitable urban heat exposure and provide new insight into actions cities can take to improve the lives of residents.
Previous research conducted took a snapshot in time of the disparities that exist between communities of color and predominately white population; however, Johnson wanted to analyze the differences over time. He says the study showed an increase in the geographic disparity of temperature which is likely due to continuing environmental degradation in warmer areas of the city due to poverty and increased temperatures creating a positive feedback loop.
He examined 44,476 predominantly white, Black, Hispanic, and Asian census tracts and surface heat island intensity, a measure of the disparity between temperatures of surface urban heat islands relative to surrounding areas, during the summer months of 2003 to 2018.
The study found it would take until 2363 for predominantly white communities in U.S. cities to reach the same temperature as Black prevalent ones. White communities will reach thermal parity with Asian communities in 2152, and they will never catch up to Hispanic communities since they are warming at the same rate.
Johnson says the results demonstrate the degree of difference in the current temperature regimes for each demographic group. The simple fact that it will take over 300 years for white prevalent urban census tracts to reach thermal parity with Black prevalent urban tracts is an alarming observation, he says, and it should heighten awareness of this issue. Johnson says, policymakers can use such findings to illicit change and work toward creating better environmental conditions for those most affected.
He also ranked the top 25 American cities by the highest levels of surface urban heat island intensity during the 16-year period.
New Orleans, Louisiana, had the highest surface urban heat island intensity for both Black prevalent communities and predominantly white communities. San Jose, California, was the highest for both Hispanic and Asian prevalent communities.
Johnson says one of the major reasons for the disparities experienced in urban temperatures is due to the "redlining" practice that occurred in the 1930s, where government-sponsored organizations outlined predominantly Black neighborhoods in red on maps, signifying them as being "hazardous."
Remnants of this practice are still persisting, but Johnson hopes this research can help lead to more awareness of the issue and ultimately stimulate ways to disrupt or improve the conditions of these highly vulnerable locations.
As global temperatures continue to rise, Johnson says some of the communities he examined may become unlivable in the summer months due to the scorching temperatures and the associated health effects.
He says this is a very complex problem, and there will not be one solution to it. Urban planning can play a big role, but it will take more than that, because the issue cannot be solved overnight. Instead, he says it will take an inter-generational effort to break this disparity down and have the greatest impacts on making these communities safer for their residents.