The Heat Is On: Cities Search For Ways To Cope With Searing Summers
As the globe suffers one of the hottest summers on record, the push to mitigate the impact of heat on U.S. cities has more traction than ever, driven by the desire to protect against the damaging, sometimes deadly effects of scorching temperatures.
Extreme heat exacts a severe toll on communities as residents, particularly those living in underserved areas, go without the resources or systems to keep cool and business costs stack up as municipalities cope with outages and damaged infrastructure.
A built environment of asphalt and concrete, dappled with few green spots — in other words, a typical city — is subject to a phenomenon called the heat island effect, making a blazing summer hotter and more dangerous in urban areas.
A previous scattering of efforts to deal with heat is coalescing and gaining momentum as cities and counties pour resources into the challenge of preparing and protecting people and businesses.
"My job is to be someone who wakes up every morning thinking about extreme heat," said Jane Gilbert, who was appointed the nation's first chief heat officer last year by Miami-Dade County.
Since then, Los Angeles and Phoenix have created such offices, followed by other cities around the world.
"Our focus is how heat impacts the lives and livelihoods of our residents and our visitors and what we have to do to accelerate action to mitigate our urban heat islands and help people adapt to the increasing heat risk," Gilbert said.
Extreme heat has a human cost in death and sickness. It also has a business cost, as it impacts critical infrastructure, Gilbert said, including what is necessary to keep commercial and residential properties functioning smoothly.
Miami-Dade tapped Gilbert, previously the county's chief resiliency officer, for the position at the same time as the municipality established an annual heat season, which starts May 1 and runs through Oct. 31, coinciding with the region's annual hurricane season.
"If we combine all climate-related deaths, heat takes the largest toll,” Miami-Dade Mayor Daniella Levine Cava said when the heat season was rolled out.
Heat mortality is a nationwide concern. More than 11,000 Americans have died from heat-related causes since 1979, according to the Environmental Protection Agency, though that number might be understated. Studies of certain historic heat waves, such as in Chicago in 1995, suggest that there may be many more deaths than were actually reported as heat-related on death certificates.
In 2021, extreme heat was more lethal than any other weather-related disaster, the National Oceanic and Atmospheric Administration reports, edging out floods and tornadoes and killing many more people than hurricanes or winter storms.
Urban heat tends to affect poorer parts of a city the most since they tend to have fewer trees, wider stretches of asphalt and less cooling infrastructure.
Critical infrastructure is at risk as well, including power and transportation, which allow cities and their populations to function economically.
Various organizations have estimated the business cost of extreme heat. Texas loses an average of $30B a year due to heat, according to a report by Adrienne Arsht-Rockefeller Foundation Resilience Center. That toll is forecast to balloon to $110B a year by 2050.
The potential cost is much higher for the state should the Texas power grid fail, as it did in the winter of 2021.
So far, the state has managed to avoid that, though this summer's heat wave inspired the Electric Reliability Council of Texas, the state’s main power grid operator, to ask Texans to cut their use of power during peak daytime heat. Still, the prospect of rolling blackouts hangs over residential and commercial properties.
Communities are ramping up efforts to deal with the heat in two main ways: heat mitigation and heat management, said Buro Happold associate principal Chris Rhie, a specialist in sustainable infrastructure.
"Heat mitigation is about reducing the contributions of the built environment to heat, especially places with a lot of heat-trapping surfaces, such as blacktop and dark roofs and little shade," Rhie said. "Those create a temperature differential between urban and nonurban areas that can be dramatic."
Heat management, on the other hand, is about reducing the impact of extreme heat on people and businesses.
The goal of heat mitigation is more of a long-term infrastructure fix, Rhie said. Less blacktop and lighter roofs, along with more green space, will eventually abate the heat-trapping tendencies of urban areas.
Heat management is about helping people deal with heat in the here and now: more shade, cooling centers and subsidies for electricity to run air conditioning in high-poverty neighborhoods, among other steps.
Miami-Dade's heat strategy includes both mitigation and management. A critical part of mitigation is preventing roofs from becoming heat traps.
"Our building department has proposed an amendment to the Florida Building Code to require cool roofs for all large buildings, including commercial and residential, which would include large rental and condo properties," Gilbert said.
Locally, Miami-Dade has updated its sustainable building ordinance to require cool roofs and higher energy efficiency standards for any building that either the county builds and owns itself, or that it contributes funding to, Gilbert said. That would include most affordable housing projects.
Raising awareness of the problem is also important, Gilbert said, especially in managing the impact of extreme heat. This year, the county rolled out its Heat Vulnerability GIS Story Map, which pinpoints areas that are more vulnerable to heat. The data combines tree canopy, income, heat-related mortality and other factors to offer a picture of places at the highest risk.
The new efforts are building on Miami-Dade's existing heat mitigation initiatives, such as the Million Trees Miami Campaign, the goal of which is to plant 1 million trees to achieve a 30% tree canopy cover for the county.
Other places have rolled out similar initiatives. Chicago has a landscape ordinance that requires planting trees on parkways and landscaping parking lots, loading docks and other vehicular-use areas. The city has also been constructing green roofs on public buildings and providing grants to encourage green roof installations.
New York City has offered property tax abatement incentives for green roofs and modified its building code to require new buildings to have reflective roof areas and existing buildings to add them during renovations.
Los Angeles County has a number of cool roof and tree-planting initiatives, as well as efforts to paint roads lighter colors, and the Los Angeles Department of Water and Power has proposed the Cool LA program, with which customers could purchase reduced-cost cooling systems.
"There's tremendous attention to the planting of trees now in Southern California," Los Angeles Department of Water and Power Commissioner and landscape architect Lia Lehrer said.
"Of course, there is a drought on, so there's also a lot of creativity about how to manage these trees to make sure they do well," Lehrer said. "One way to do that is plant native, resilient trees in the first place."
There is also a major effort to resurface blacktop, she said.
"The department and LA schools have been doing experimental projects to take asphalt out of schools," Lehrer said. "Asphalt was very useful in the 1960s when we needed a lot of schools built quickly, but now it adds to the misery."
Much more needs to be done to reduce blacktop in Southern California, Lehrer said. Private parking lots add to the problem, but little is being done so far.
"We have a lot of asphalt around retail," she said. "And frankly, I don't think we've addressed that at all very well."
Some private property owners are taking on heat mitigation as part of their ESG policies.
Industrial giant Prologis installed white or reflective surfaces on the roofs of its properties nationwide in recent years, using highly reflective paint, tiles, shingles or membrane material. Altogether, the company upped its cool roofs from 6M SF in 2017 to 10M SF in 2021.
New green tech is also focusing on heat mitigation.
Chicago-based architecture firm Jahn designed Europe’s tallest living green wall for the exterior of Eden Tower, a 27-story residential high-rise nearing completion in Frankfurt, Germany.
Containing 186,000 individual plants, the facade uses an array of sensors to control automatic irrigation, fertilization and drainage systems that keep the exterior plant life viable.
“As a system, hanging green walls can be an effective strategy for mitigating the urban heat island effect,” Jahn Managing Director Steven Cook said.
