As climate change fuels more days of extreme heat every year, American cities are becoming increasingly familiar with the urban heat island effect. Heat islands are areas that experience increased air temperatures in urban zones due to reduced shade and a lack of heat-reflective surfaces. High concentrations of buildings, pavement and other infrastructure made of heat-absorbent material like asphalt, brick and steel can make urban spaces up to 20 degrees Fahrenheit warmer than greener spaces and suburbs.

Now, a team of researchers from the University of Delaware’s Gerard J. Mangone Climate Change Science and Policy Hub, UD’s Center for Environmental Monitoring and Analysis (CEMA) and Delaware’s Department of Natural Resources and Environmental Control (DNREC) is mapping heat in Wilmington, Delaware.

Extreme heat is the number one cause of weather-related death in the United States, making urban heat islands a significant public health concern. This threat is especially salient for individuals most prone to heat-related illnesses, such as young children, the elderly and those with chronic health conditions. Heat islands also have a cumulative effect on workers with outdoor-based jobs and residents without easy access to air conditioning or cooling.

Areas with high heat-absorbance such as urban environments consume more energy, thereby creating more emissions. Enhanced daytime heat and reduced nightly cooldowns mean greater electricity dependency for air-conditioning, and peak demands put a heavy strain on energy systems that can lead to mitigation efforts such as controlled blackouts, or even result in citywide power outages.

The exacerbation of urban heat island impacts due to climate change has prompted a wave of urban sustainability planning and cooling strategies.

A drive for data

In 2017, the National Oceanic and Atmospheric Administration (NOAA) began funding CAPA Strategies’ Heat Watch campaign and has since led more than 60 cities in mapping summertime urban heat islands. CAPA’s data collection works as a volunteer-driven field campaign. Citizens of funded cities learn the impacts of uneven heat distribution while gathering near-surface air temperature data.

“Climate change is often seen as this scary, abstract topic,” said Richard Johnson from The Nature Conservancy in Pennsylvania. “But these heat mapping campaigns connect it to people’s lives and give them an opportunity to be part of the solution.” Johnson was a contributor to the 2022 Philly Heat Watch and offered guidance to organizers in Wilmington.

The 2023 WiST (Wilmington and Surrounding Townships) Heat Watch has been in the works since late 2021. The initial proposals were developed by CEMA and DNREC. UD’s Climate Hub became the coordinating entity soon after.

“This was our first externally funded project that allowed the Hub to serve the role we envisioned for it, as a central point of contact and communication, a facilitator networking amongst many partners across different sectors,” said Dana Veron, professor and co-director of the Climate Hub. Veron and fellow co-director A.R. Siders began meeting with CEMA and DNREC early in 2022 to lay out a plan of action and communicate with potential state and regional partners.

A crucial partner for the WiST Heat Watch was the Delaware Resilience Hub, a disaster relief initiative founded by Wilmington’s own Stacey Henry. Designed for residents facing emergencies often intensified by climate change, the Resilience Hub is intended to serve as an emergency cooling center, offering refuge for vulnerable residents during dangerously hot days.

As CEMA identified ideal mapping days in partnership with the National Weather Service and the Climate Hub organized virtual town halls for volunteers, the Resilience Hub established their Wilmington facility which was used as the WiST Heat Watch home base.

The WiST Heat Watch’s mapping took place in July 2023 with doctoral candidate Keihan Hassanzadehkermanshahi leading project coordination efforts. City volunteers, partners and UD students were organized into driver-navigator pairs, each receiving a vehicle-mounted thermometric sensor designed to record air temperature and humidity data tied to GPS coordinates.

Pairs were instructed to drive six routes spanning Wilmington and the greater region. These routes were pre-planned by campaign coordinators, incorporating different types of land usage to ensure the data offered a full spectrum of heat levels across the region. The routes also incorporated locations identified by the campaign partners as important to the community. Each route was driven three times to observe the daily heat cycle.

Next steps

Every Heat Watch mapping campaign develops a report detailing heat distribution across the target city. Digital maps that display predictive heat-index models mindful of land coverage and topography are also publicly released.

“This is the beginning of the work,” said Veron. “All the partners are anxious to get the map because what’s really exciting is what happens next.”

Dozens of other Heat Watch campaign teams have incorporated their findings into climate and heat mitigation strategies. In Virginia, Richmond officials have made heat vulnerability and urban heat islands a determining factor in their upcoming city and sustainability planning endeavors. In New Jersey, the city of Newark introduced several proposals offering equitable solutions to heat emergencies, including increased funding for cooling centers and urban green spaces.

“The Nature Conservancy substituted campaign measurements for Land Surface Temperatures in the Philly Tree Plan, the city’s plan to equitably grow and protect its urban forest,” Johnson said. “[The Nature Conservancy] and local partners also released a story map entitled Citywide Heat Ride to show how investments in Philadelphia’s urban forest and the Philly Tree Plan would equitably address extreme heat, and highlight ways residents can get involved to help strengthen their own community’s climate resiliency."

“We’re very lucky that we’re following a heat mapping campaign last year in Philadelphia and one from a couple of years ago in Baltimore,” Veron said. “UD’s Climate Hub is starting to think about this from a regional standpoint as well. How can we connect with other groups that are really trying to think about ways to mitigate extreme heat, and protect and serve the populations that live in this region? Heat doesn’t know city, county or state borders.”

Veron hopes that a larger heat network will be born from the campaign, allowing people and groups with similar intentions for the region to connect and support one another. In the meantime, ideas have started flowing.

Emily Rodden from Delaware Sea Grant sees the geographic data as “a resource to put more green infrastructure, bioretention areas, rain gardens, and urban street trees in and around the city of Wilmington, which will work to reduce urban heat island effects but also improve air quality, water quality, and provide nicer greenspaces to recreate and relax in.”

The Climate Hub team will present the WiST Heat Watch preliminary results in a virtual town hall meeting on Thursday, Feb. 8. This will be the start of a conversation about what it could mean for University and statewide climate research and adaptation, but having the results on the table already spells success.

“This is a great demonstration of how UD’s Climate Hub can leverage the expertise and resources at the University and work with external partners to bring something to fruition that is really needed in the community,” Veron said. “We were able to lead and provide support in a way that was hard for our external partners to do on their own. We will continue to look for opportunities to do that.”

This heat network also presents new opportunities for the Climate Hub’s undergraduate Climate Scholars. Veron sees a future with the partners fostered over the campaign, one in which students may engage in research that brings climate initiatives to life and assist in educational and community outreach as new emergency cooling centers are established across the state.

To attend the virtual town hall to learn more about the WiST Heat Watch results, please register online.