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White roofs and shade trees: How cities try to soften heat
Five cities including Dallas and Boston are signing up for a nonprofit's program that guides them to reducing summer heat.
CLIMATEWIRE | Five U.S. cities including Dallas and Boston are launching efforts to reduce their summer temperatures and flash flooding by repainting roof surfaces to reflect solar rays and installing massive new tree canopies.
The effort marks a new strategy to address urban climate impacts that involves selecting an array of heat- and flood-mitigation measures tailored to each city instead of undertaking one effort such as painting outdoor parking lots white.
Dallas; Boston; Atlanta; New Orleans; and Columbia, S.C., are the first group of U.S. cities to collectively sign up for a program run by the Smart Surfaces Coalition, a nonprofit that promotes new urban surfaces that reflect heat and absorb rainfall.
The Washington-based coalition helps cities select physical improvements that can reduce summer heat by up to 5 degrees Fahrenheit and minimize flooding that occurs when rainfall overflows sewer systems. The improvements include reflective rooftops and pavement, tree canopies, roads that are more porous, and rain gardens.
“With more shade, less radiant heat and better air quality, the cities can feel 10 to 15 degrees cooler,” coalition founder and CEO Greg Kats said. “In the summer, that’s the difference between being outside versus being stuck inside an air-conditioned box.”
If cities find the right blend of policies, Kats said, the initial investment for new pavement, rooftops and rain gardens will save lives and lead to a tenfold return over the next 20 years. Kats’ coalition of more than 40 U.S. and international groups provides free consulting to cities.
Heat waves are the deadliest climate anomalies, said Katherine Catalano, a deputy director of the Center for Climate, Health and Equity at the American Public Health Association, a coalition member. Excessive heat increases the risk of heatstroke and hinders clear thinking and anger control, Catalano said.
“Protecting yourself by staying indoors isn't the best solution,” Catalano said. “If we go the entire months of the summer telling people in cities to avoid walking and exercising outdoors, that'll have longer-term health impacts.”
Typical city roofs and pavement absorb almost all sunlight and prevent rainfall from permeating underground, which exacerbates heat waves and urban flooding, Kats said.
Darkly painted roofs, for example, retain 95 percent of the energy from sunlight, heating up homes and cities, according to a recent report from Smart Surfaces Coalition. Roofs painted in lighter colors absorb less than 20 percent of solar heat, reducing air conditioning use, power demand and carbon emissions, Kats said.
The coalition will support the five cities in applying for $1 billion available from the Inflation Reduction Act for city projects to enlarge their tree canopies, said Peyton Siler Jones, a sustainability program director at the National League of Cities, a coalition member.
Cities also might be able to fund heat- or flood-reduction efforts through $2.8 billion in EPA environmental justice grants included in the massive spending law that target disadvantaged communities.
In the Baltimore area, higher-income suburbs are on average 14 degrees cooler than inner-city neighborhoods during heat waves, according to the coalition report.
The report projects that in Baltimore city, which in 2021 became the first city to sign up for coalition help, the downtown will be 4.3 degrees cooler on summer days after all mitigation measures are completed.
The interest in coalition help with grant applications and policy analysis shows a shift in how local governments think about climate adaptation, Jones said.
“There's a recognition that everyone who works in a city really is a climate employee,” Jones said. “Climate change touches parks and recreation planning, public works, finance, and everything.
“You might not think of city procurement and public works as an environmental policy, but when it comes to resilient infrastructure, it really is,” Jones said.
