Hot Enough For You? Cooling The Worsening Urban Heat Island
This story is part of Degrees Of Change, a series that explores the problem of climate change and how we as a planet are adapting to it. Tell us how you or your community are responding to climate change here.
We’ve known for more than 200 years that cities are hotter than surrounding rural areas. All that concrete and brick soaks up the sun’s rays, then re-emits them as heat long after night has fallen. On top of that, waste heat from the energy we use to power our buildings, vehicle emissions, and even air conditioning units can cause some cities to be as many as 20 degrees Fahrenheit warmer than their rural surroundings—creating “urban heat islands.” Between the toll that heat takes on the body and the concurrent air quality problems that heat exacerbates, heat waves kill more Americans per year than any other weather-related event. And if enough city residents are using air conditioning to beat the heat, power outages from overworked grids can add to the risk of mortality.
As the globe warms, urban heat islands are projected to become more pronounced, with even hotter temperatures and a more stark urban-rural divide. But scientists and engineers have been working on solutions to reflect the sun before it can raise temperatures, such as cooler roofing materials and heat-reflecting pigments, cool pavements, green roofs, and neighborhood green space. Ronnen Levinson of the Lawrence Berkeley National Laboratory joins Ira to describe what we know about cool infrastructure, while Global Cool Cities Alliance executive director Kurt Shickman explains how cities around the world are implementing solutions—and why it may take something as bureaucratic as building codes to see mass adoption of cooling strategies.
The city of Los Angeles passed the first mandate for residential buildings to have high-reflectivity roofs, a step up from the past requirements, which only applied to flat, commercial roofs. Los Angeles is also pouring cool pavements to test their effectiveness in lowering temperatures.
But how do researchers know these interventions are actually working? And how do you pick the right intervention for any given neighborhood in a city with as big and varied a landscape as Los Angeles? USC scientist George Ban-Weiss talks about his work tailoring cool solutions to individual neighborhoods, and the data that’s still missing as communities weigh the costs and benefits of planting trees versus painting pavement or roofs white.
While heat waves are projected to kill thousands of New Yorkers per year by 2080, that pain is not likely to be distributed evenly. Some of New York City’s hottest pockets—near highways and heavy industry, with fewer green spaces—are communities with the most vulnerable populations. And research has found these hotter urban heat islands are home to higher percentages of poor people and people of color. Meanwhile, while New York City alerts residents of heat events and offers cooling shelters for them to go to, the shelters can be difficult for people to access, or even hear about.
But community groups in the Bronx, Harlem, and other parts of the city are working both to cool down their neighborhoods, and connect residents to life-saving cooling. Justine Calma, a reporter for Grist, details the environmental justice problem of the urban heat island, and how New York City is responding.
Phoenix, Arizona, experiences temperatures over 100 degrees in the summer, and researchers are only expecting summers to get hotter and longer. Hot season durations are projected to increase by several weeks on both ends, while the likelihood of temperatures that exceed 115 degrees is only expected to grow. In 2017, an estimated 155 people died of heat-related causes in the Phoenix area.
But the city has been taking the heat seriously. Phoenix has been painting municipal building roofs white since 2006. The city also has ambitious goals to establish shade trees, shelters along public transit routes, and a HeatReady program that would put heat planning on par with disaster preparedness—all with help from scientists like Arizona State University researcher David Hondula. Hondula joins Ira to describe the challenges of getting cities invested in heat preparedness, both short-term and long-term, and what’s next for Phoenix.
How is your county, city, or neighborhood responding to extreme heat? Let us know in the comments below.
Jeremy Hoffman, climate scientist for the Science Museum of Virginia, called in to tell us how his community in Richmond, Virginia developed a method to map urban heat islands. Listen below.
Transcript: In the summer of 2017, the Science Museum of Virginia hosted a citizen science campaign to measure our city’s temperature during a heat wave. We sent teams of volunteer scientists all over the city with thermometers and GPS units to measure temperatures across various land use types in the city’s metro area. We found a 15 degree Fahrenheit difference between the warmest and coolest place in the same city, on the same day, at the same time. Now, we’re working with the city health department to understand thresholds for issuing heat warnings as we identified higher heat-related illness rates in those warmest zip codes.
We’re also coordinating with local non-profits to focus tree plantings and greening projects in the most heat-striken areas, which also tends to be areas of extreme poverty and health inequity. We call a team program we developed with a local education non-profit, “Throwing Shade in RVA,” which advances health and climate equity education for local teens. I have many more stories to tell you about heat enrichment, but we’ve since also recreated the same type of study in Washington, D.C. and Baltimore, Maryland, with this summer campaigns happening all over the country.
Citizen science is the best way for us to empower our communities to understand urban heat and then fight back against it.
Neighbors are using the NextDoor App to post updates on nearby cooling centers.
— Marisela Nuñez (@Marisela_Nunez) June 13, 2019
Kurt Shickman is executive director of the Global Cool Cities Alliance in Washington, D.C.
George Ban-Weiss is a professor of civil and environmental engineering at the University of Southern California, in Los Angeles, California.
Ronnen Levinson is a staff scientist and leader of the Heat Island Group at Lawrence Berkeley National Laboratory in Berkeley, California.
Justine Calma is a staff writer at Grist. She is based in New York, New York.
David Hondula is an assistant professor at the School of Geographical Sciences and Urban Planning and is a senior sustainablity scientist at Julie Ann Wrigley Global Institute of Sustainability at Arizona State University. He is based in Phoenix, Arizona.