This summer’s heat won’t affect everyone equally – UNC researchers map heat stress disparities in Durham 

August 2, 2024

North Carolina has experienced record heat this summer, the Triangle is no exception. Extreme heat can be taxing on the mind and body, but its effects won’t be felt equally.  

The Data-Driven EnviroLab (DDL) at UNC’s Institute for the Environment is actively evaluating disparities in heat stress in Durham through lenses of environmental and climate injustice.  

Led by Angel Hsu, director of the DDL and assistant professor of public policy, they will utilize direct air temperature measurements, machine learning and microclimate modeling to generate data that reflects real heat disparities felt by pedestrians.  

“For policymakers and planners to design appropriate heat mitigation and adaptation responses, they need to know who are the most vulnerable,” explains Hsu.  

Wicked Urban Heat 

In the United States, people of color and low-income individuals are disproportionately at risk for heat exposure, according to research by DDL. This is partially due to the Urban Heat Island Effect (UHI), a phenomenon which describes that urbanized areas experience overall higher temperatures than rural ones. In urban areas, densely developed asphalt roads and buildings absorb energy from the sun during the day and re-release it as heat, making the city warmer overall.  

“Our prior research has found that across nearly all major U.S. cities, people of color and those living below poverty are exposed to higher temperatures, largely due to the lack of tree cover, green space access and greater proximity to highways or greater density of impervious surface,” explains Hsu.  

When investigating disparities in heat stress, researchers traditionally compare satellite land surface data. This data describes ground temperature or temperatures on the roofs of buildings; however, this data gives an incomplete picture of what it feels like to be a pedestrian in a particular environment. Commonly used satellite data doesn’t include air temperature or radiant temperature–the heat you feel from the sun warming up your skin. These two factors impact an individual’s heat stress, thus their human health.  

A Comprehensive Heat Study of Durham 

To understand disparities in heat exposure, the DDL is collecting air temperature and relative humidity data across Durham.  

To develop a comprehensive data set, they’ve broken the city into ten heat deciles based on satellite-derived land surface temperature. Within each decile, they installed four sensors with locations selected for variation in shading conditions and land-cover type–vegetated or impervious. By placing sensors in diverse locations, the researchers will have an inclusive data set outlining what it feels like to be a pedestrian in each part of the city. Their sensors will be installed through September, collecting critical data in the hottest summer months.  

 

 

In addition to establishing a sensor network, the DDL team has assembled a community stakeholder advisory board with representatives from historically marginalized communities in Durham. Members on the board have a wide range of expertise from language to citizenship, community engagement, data availability and more.  

The board is working together to design research questions, discuss solutions, and ensure what is learned from this study is accessible to all members of the community. Additionally, members can confirm the tangibility of climate inequalities felt in their communities and advocate their needs for research to provide evidence of these disparities.   

“In order for them to get their neighborhoods to change and for heat mitigation efforts to be put in, they need the evidence,” explains Sarah Berk, a postdoctoral research associate in the DDL.  

Durham heat deciles and sensor locations map. From the DDL’s website. 

Next Steps 

Upon the completion of data collection, the team will use a microclimate model to assess how cities can reduce their disparities in heat stress and reduce heat exposure at large through heat mitigation strategies. For example, in an identified hot spot, the team can implement mitigation strategies like tree planting or albedo (light reflection) management. Community stakeholders can then use those outcomes as leveraging points to their local governments to argue the need for increased mitigation strategies.  

Once the methodology and microclimate model have been developed for Durham, N.C., the research team will make it broadly applicable to North American cities. They will then work with partners in Phoenix, Ariz., Philadelphia, Pa., and Chicago, Ill., to analyze the policy relevance of their maps.   

When completed, the team plans to make their research and data publicly available on their website. This project is funded by a $1.5 million grant from NASA. 

Learn more about this project on the Data-Driven EnviroLab website.  

Story and photography by Sarah Dean
Sarah Dean is a rising senior at UNC-Chapel Hill who is studying environmental studies and studio art. She is currently working as a communications intern with the Institute for the Environment. Additionally, she is the service coordinator for Alpha Phi Omega, UNC’s gender-inclusive community service fraternity. She hopes to pursue a career at the intersection of sustainability and design.