When we talk about summer heat, we usually refer to the temperature of the air, but another important indicator is the temperature of roads, sidewalks, buildings, parking lots, and other outdoor surfaces. Hot surfaces make the places where people live and work unsafe and increase the risk of burns on contact.
Consider this recent satellite image showing surface temperatures across Phoenix.
Source: USGS Landsat (via Google Earth Engine), U.S. Census.
Note: Satellite image taken at 12:03 pm local time. Pixels with high uncertainty have been removed.
Around noon on July 10, much of the nation’s fastest-growing metropolis was 120 degrees Fahrenheit, or hotter. If you were unlucky or unwise enough to actually come into contact with bare skin, you could have been injured within minutes.
In the desert on the edge of the city, in areas governed by Native American tribes, temperatures were even hotter, exceeding 150 degrees Fahrenheit.
The Arizona Burn Center, which serves Phoenix and the entire Southwest, has admitted 65 people with severe heatstroke so far this summer, said Dr. Kevin Foster, the center’s director. Six of those people have died from their injuries. Last summer, the center recorded 14 such deaths.
But even that figure is still small compared to the 645 heatstroke deaths confirmed in Maricopa County, which includes Phoenix, last year, the most on record for the county. (The county has reported 23 heatstroke deaths so far this year, with another 322 deaths under investigation.)
Ladd Keith, an associate professor in the University of Arizona’s School of Landscape Architecture and Planning, said surface temperature is just one of many factors cities consider when trying to protect residents from extreme heat.
Dr Keith said in complex environments like cities, where heat can harm people, pets and wildlife in a variety of situations and circumstances, it can be difficult for officials to determine which combination of policies and actions will be most beneficial to public health.
Phoenix, for example, is trying to plant more trees to provide more shade; its “Cool Pavement” program has treated 120 miles of asphalt to reflect more sunlight and stay cooler. But from a cost-effectiveness perspective, wouldn’t it make more sense to use those resources to build more heat-resistant housing or solve homelessness? “It’s really hard to know what that combination is,” Dr. Keith said.
What’s clear, he says, is the urgent need for a solution. “Heat deaths are rising faster than our investments in preventing them,” he says. And human-caused global warming continues to increase the frequency and intensity of dangerous heat waves. “We’re chasing a moving target very slowly,” he says.
Source: USGS Landsat (via Google Earth Engine), U.S. Census.
Note: Satellite image taken at 11:45 AM local time. Pixels with high uncertainty have been removed.
Sacramento is proudly known as the “City of Trees,” but its tree cover is not evenly distributed, nor is it subject to scorching heat. Low-income residents north and south of California’s capital have long struggled with a lack of shade and green space on sweltering days like last week’s.
Victoria Vásquez, manager of grants and public policy for California Relief, a coalition of nonprofits that protect and grow the state’s urban forests, says the effort is always underfunded. Even as the West experiences record heat, little has changed. “I wish it could happen,” she says.
Still, she sees signs of movement in the right direction: Sacramento is considering a plan to increase citywide tree cover from 19 percent to 35 percent by 2045, and under the Inflation Control Act, the U.S. Forest Service has received $1.5 billion to support urban forestry programs.
Once neighborhood associations see how quickly they can reap the benefits of planting and maintaining trees, “it’s a contagious, positive change,” Vásquez says.
Source: USGS Landsat (via Google Earth Engine), U.S. Census.
Note: Satellite image taken at 11:55 AM local time. Pixels with high uncertainty have been removed.
In Portland, Oregon, tree-covered areas like Forest Park on the city’s west side offered a cool oasis last week. But Vivek Shandas, a professor of urban planning at Portland State University, and his colleagues recently found that the city’s overall tree cover has declined somewhat between 2014 and 2020. One possible reason is that trees are often cut down as homes are sold and neighborhoods are redeveloped.
The Multnomah County coroner’s office, which includes Portland, said last week it was investigating five deaths related to the recent heatwaves.
Dr. Shandas said Portland has in many ways become much more responsive to heat threats since heat waves killed hundreds in Oregon and Washington state in the summer of 2021. The city has been more proactive in communicating the risks and has provided portable cooling units to low-income residents. Dr. Shandas said changes to building codes and construction practices that would truly prepare Portland for hotter periods in the coming years and decades are still missing.
“I think the low-hanging fruit at this point has been largely completed,” he said. “What about the long-term, sustained, major upgrades that the city needs to prepare for more intense and more frequent heat waves in the future? I haven’t seen any of that yet.”