Data-Driven EnviroLab researchers (left to right) Carlos Carranza, Sarah Berk and Vivien Hines place heat sensors throughout Raleigh to assess the effectiveness of the city’s newly piloted pavement rejuvenation project. (Jeyhoun Allebaugh/UNC-Chapel Hill)
To find relief during hot and humid North Carolina summers, Chapel Hill residents turn to common reprieves: indulging in ice cream at Maple View Farm, taking a dip in Jordan Lake or merely walking down whichever side of Franklin Street is shaded.
How we experience heat, however, varies greatly from one location to the next, even within the same city. Strolling down Franklin Street could be 1 to 7 degrees hotter than sitting on open farmland at Maple View or on Jordan Lake’s shores. Urban areas, with their asphalt roads and concrete buildings, absorb and release heat back into the environment at higher rates than the flora and fauna of natural landscapes.
It’s called the heat island effect. The Data-Driven EnviroLab at UNC-Chapel Hill has long recognized this problem and is studying how to mitigate its effects.
Using data to inform policy
Angel Hsu, director of DDL and a public policy associate professor in the UNC College of Arts and Sciences, has researched environmental issues and how they disproportionately affect communities for over a decade.
Out of college, Hsu worked at a think tank in Washington where she trained companies and governments on how to measure and account for their greenhouse gas emissions. The work took Hsu to places like Mexico, Brazil and China where she worked with businesses and governments to combat environmental challenges.
“Working with communities there, you really understood the value of data, policy and management,” said Hsu. “These were countries that had no international obligation or commitments to reduce their emissions, but they realized it’s an advantage when you have data that allows you to measure the problem and identify hotspots.”
This work led Hsu to pursue a doctorate and eventually create the Urban Environment and Social Inclusion Index, a platform for cities around the world to see how they perform on environmental markers such as air quality, heat and water stress. A grant from the Belonging Forum, formerly known as the Samuel Centre for Social Connectedness, brought the vision to life, but, more importantly, allowed Hsu and DDL to collect preliminary data needed for additional funding.
Exploring disparities and solutions to heat stress
The UESI gave way to DDL’s current project on heat disparities in U.S. cities. Through a $1.5 million NASA grant, the lab launched an extensive heat mapping project to glean urban heat patterns through data collection. The end goal is to develop heat stress models that can be applied to other cities around the country, and eventually, be used to inform policy.
The team uses a combination of direct measurements, machine learning and microclimate modeling to collect data. The team has focused on mapping the Triangle – piloting studies in Chapel Hill, Durham and Raleigh – thus far, with hopes of scaling to other U.S. cities.
To collect data, DDL researchers begin by placing sensors throughout the city they’re mapping.
Sarah Berk, a postdoctoral research associate at DDL, spent the summer placing sensors across Raleigh with the help of two UNC Institute for the Environment interns, Carlos Carranza and Vivien Hines, and graduate student Izzy Bukovnik.
“We place temperature sensors and then use those measurements as data to train machine learning models,” said Berk. "We input information on land cover, like how much tree canopy was in the area, how dense the buildings were and how reflective services in the area are. Then the model predicts air temperature in areas where we don’t have the data.”
While the collected data will inform how best to mitigate heat stress, the team’s methods have already been used to assess existing interventions.
Katherine Burley Farr ’26, a former researcher at DDL, used DDL’s combined data collection method to assess the effectiveness of the City of Raleigh’s ongoing pavement rejuvenation project. By mixing titanium dioxide into their pavement rejuvenator, they hope roads reflect rather than absorb more sunlight.
An interdisciplinary, long-term goal
The heat stress project is just one of several at DDL aiming to initiate change in the climate sector. Hsu has prioritized working alongside faculty, students and community stakeholders from different fields to ensure the climate crisis is understood and solved from all angles.
“If we’re talking about climate and environment, that’s interdisciplinary by nature. Climate is not going to be solved by a single discipline,” said Hsu. The only way to solve the problem, she said, is to combine strong suits across the board.
When she started DDL in 2016, Hsu made the decision to omit her last name from the lab’s title – a common convention researchers follow.
“I wanted this to be a movement. I wanted people who were part of the lab, whether they’re students or collaborators or other faculty, I wanted them to feel like they’re part of the movement,” said Hsu. “We want to use data to drive environmental decision making."
Angel Hsu and the Data-Driven EnviroLab credit much of their success to the ongoing support of the Belonging Forum, formerly known as the Samuel Centre for Social Connectedness. The forum’s continued funding and dedication to DDL’s mission have allowed the lab to launch pilot work crucial to getting projects off the ground and garnering support from federal organizations and grants.