The newly appointed chief heat officers in Miami-Dade County and Phoenix are using innovative materials and data to address urban heat challenges.
Around the world, rising temperatures and heat waves have become more frequent and more extreme, and the growing hazard of urban heat is prompting cities to appoint chief heat officers.
Miami-Dade County and the city of Phoenix have created offices dedicated to heat mitigation. In September, Phoenix, already one of the fastest warming cities in the country, announced that Arizona State University Environmental Sciences Professor David Hondula would lead the city’s newly created Office of Heat Response & Mitigation. The news came on the back of Miami-Dade County announcing Jane Gilbert as the first CHO in the country.
Though the climates differ in type of heat -- wet vs. dry -- both have focused their efforts on reducing the effect of “regional urban heat islands,” areas with dense concentrations of asphalt, pavement and other building materials that absorb and retain heat. Data from the Environmental Protection Agency has shown that nighttime temperatures in heat islands can be as much as 22 degrees warmer than other regions.
In Phoenix, one of the biggest challenges has been finding and applying materials to use in the built environment that do not contribute to urban heat island effect or create particularly hot microclimates, Hondula said in an email to GCN.
The city's Cool Pavement Pilot Program, though, has seen success. The initiative out of the Street Transportation Department and Office of Sustainability applies a water-based asphalt sealant that “reflects a higher portion of the sunlight that hits it, hence absorbing less heat,” the city website said. Temperature sensors embedded in the pavement and thermal images taken by helicopter flyovers have shown that pavement with the asphalt treatment is 10.5 to 12 degrees Fahrenheit lower than traditional asphalt at noon and during the afternoon hours.
In Miami, Gilbert took on the CHO role after a few years as Miami’s chief resilience officer. She said heat response has typically been addressed in departmental silos.
“Emergency management has their own heat risk procedures. And then our Department of Public Works and Transportation, they may or may not … consider heat as they are designing streets and open spaces,” she said. “So there’s been no one looking at this across all sectors.”
Gilbert has made it a priority to look toward data driven approaches to counteract the urban heat challenges.
“One of the things I’m first doing is getting the data that I need to really understand the excess disease burden that happens at higher heat times, over years,” she said. “The goal is to create a heat vulnerability index by using census data.”
With help from the National Weather Service, the local health departments and university partners, Gilbert plans to launch a robust “heat season” awareness campaign starting in May. The elevated risk of a widespread power outage [and loss of air conditioning] requires disadvantaged populations know what to expect in a heat emergency, she said. Additionally, different communities like young, single mothers or outdoor workers will need different kinds of messaging.
Besides the need for more local pilot programs, Gilbert said she plans to work with the National Weather Service to develop a common understanding of when agencies send heat alerts. Currently, official heat advisories are only sent after the Miami heat index -- which factors in temperature, humidity and topology -- hits 108.
“We know that most hospitalizations and deaths occur at lower levels,” she said. “That may be the right threshold for emergency responders to take action, but there also may be different messaging we need to release earlier. And we need to help the public understand that.”
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