How America’s hottest city will survive climate change
By Sarah Kaplan for The Washington Post.
High noon in America’s hottest city. The sun blazed in a cloudless sky, making the air shimmer above the softening asphalt. A thermometer registered more than 100 degrees in the shade. Not that there’s much shade to speak of in the central Phoenix neighborhood of Edison-Eastlake, hemmed in by highways and covered in scorching concrete.
Martha Ortiz knew it was not safe to be out on this recent afternoon, but the 55-year-old had an urgent errand. Though she carried a parasol and a water bottle, her legs grew weak as she made the 10-minute journey. By the time she climbed the 14 steps back to her apartment, her vision was blurry and her head spun.
Welcome to summer in Phoenix, where a cocktail of climate change and rapid development has pushed temperatures into the danger zone. The threats are greatest in black, Latino and low-income communities, which are significantly hotter than wealthier, leafier parts of the city.
This month, Phoenix is a hotspot in every sense of the word. The coronavirus is raging out of control. Protesters have flooded the streets after police officers fatally shot a man in a parked car on July 4. It’s been more than a month since the daily maximum temperature dropped below 100 degrees.
Yet the city is working to fight the literal heat. The goal is for Phoenix to become the country’s first heat-ready city — equipped to survive a rapidly warming world.
Each year, more Americans die from extreme heat than are killed by storms, floods and wildfires combined. In few places is the problem more pronounced than in Maricopa County, home to Phoenix and its suburbs. In 2019, the region saw 103 days of triple-digit temperaturesand 197 fatalities from heat-related causes. It was the highest number of heat-associated deaths on record for the county, and the fourth year in a row of record-setting heat deaths there. Those numbers are only expected to increase as the climate changes.
But Phoenix may also serve as a role model for cities seeking ways to cool down. Ortiz and other community activists are helping residents develop heat action plans and fight for shade structures in their neighborhoods. Local scientists are working with the city’s sustainability office to establish a framework for “heat ready” certification, which would evaluate a community’s preparedness for extreme temperatures in the way the National Weather Service’s “storm ready” program sets the standard for responding to bad weather. Mayor Kate Gallego (D), who holds an environmental science degree, wants Phoenix to be a model for the nation.
Heat is inevitable in the desert, Gallego said. But dangerous heat — “that’s not something we have to accept passively.”
“We understand that necessity breeds invention,” said Gallego, who was elected in 2018. “And we hope … that we will produce the innovations that make it possible for people to adapt.”
Islands of heat
Phoenix’s fight against heat is a war with many fronts, said David Hondula, a sustainability scientist at Arizona State University and a leading researcher studying the intersection of heat and health.
One is high up in the atmosphere, where accumulating greenhouse gases from human activities are causing global average temperatures to steadily rise. The average annual temperature in Maricopa County is 3.4 degrees higher than it was in 1895, according to a Washington Post analysis of records going back more than 100 years. That translates into summers that are hotter, longer and drier.
Drastically reducing heat-trapping emissions on a planet-wide scale is essential to averting catastrophic heat waves and other dangers from global warming, scientists say.
But there are also changes that can be made much closer to home, Hondula said. Phoenix’s rapid development in recent decades has made it a victim of what researchers call the “heat island effect.” All the trademarks of the urban environment — towering glass buildings, bustling industry, vast expanses of concrete and asphalt — absorb and amplify the heat of the sun.
“We talk about climate … as something mysterious and ambiguous that comes from the sky. But it is also something we are driving with the way we are paving our streets,” Hondula said. “Urbanization is a critical part of the story.”
Natural environments, he explained, are incredibly effective at getting rid of heat. That’s because of the way trees and other vegetation release water into the surrounding air, a process called evapotranspiration. Turning water from a liquid to a gas uses heat energy, and it can result in air temperatures in a healthy tree grove being 10 degrees lower than in open terrain. Even scrubby desert plants are capable of cooling their environments, especially at night.
In paving over the desert, Phoenix’s developers not only lost this cooling capacity but they made the problem worse. Tall buildings create canyons in which heat gets trapped close to the ground. Hard surfaces like pavement absorb and hold on to heat even after the sun goes down, causing daytime high temperatures to linger into the night. Human activities, like driving cars or running factories, also produce “waste heat” that compounds the problem.
In Edison-Eastlake, where Ortiz lives, the summertime average temperature is 105 degrees. Most residents are people of color, a legacy of discriminatory housing practices known as redlining. And the majority of people live in public housing built more than 50 years ago — concrete structures that trap heat, which can overwhelm aging air-conditioning systems.
At night, it’s as much as 10 degrees hotter in Edison-Eastlake than in wealthier communities. Just over 5 percent of the neighborhood has trees, making it one of the most barren and sunbaked communities in Maricopa County.
The consequences for residents can be dire. The heat mortality rate in Edison-Eastlake is 20 times the county average.
And the threats aren’t just physical. Research shows that extreme heat can create stress and exacerbate mental illness. One California study found that for every 10 degree Fahrenheit increase in mean temperature, residents’ risk of being admitted to the emergency room for self harm or suicide increased nearly 6 percent.
When Diana Bermudez moved to Phoenix in 2017 to become the director of special projects for the Nature Conservancy’s Arizona office, heat was already a priority. Urban conservation program manager Maggie Messerschmidt had envisioned a project called “Nature’s Cooling Systems,” which would harness the power of natural processes like evapotranspiration to cool the neighborhoods most in need.
For the project to work, Bermudez and Messerschmidt knew they needed the input of the people who understood heat best: those who live with it.
Working with the grass-roots nonprofit Phoenix Revitalization Corporation, the Nature Conservancy identified three of the hottest neighborhoods in the county: Lindo Park-Roesley Park, Mesa Care and Edison-Eastlake. They held workshops in each community, inviting ASU scientists such as Hondula to teach residents the science behind urban heat islands and ways to counter their effects.
Hondula was struck by the “sense of fatalism” around heat at the early meetings. Many Edison-Eastlake residents said they remembered when summers weren’t quite so scorching, but they didn’t think it was something they could change. One man told him, “You know it’s hot. You know people are going to die. And you hope it’s not you.”
But it didn’t take long for that mentality to shift. Bermudez recalled how excited residents were to learn about the “cooling solutions” and how quickly they identified the spots where interventions would be most effective. Often residents pointed out issues that organizers had initially overlooked — the need for shade at the school bus stop, the shortage of water fountains in the neighborhood. “That kind of knowledge was really something we couldn’t have come up with ourselves,” Bermudez said.
In 2019, residents of each neighborhood developed a 20-page “heat action plan” for their community. Edison-Eastlake’s plan calls for repaving the sidewalks with materials that stay cool by reflecting the sun, installing shade structures at bus stops and creating tree-covered “talking spaces” in a planned park.
According to Hondula, these interventions could in some spots lead to a 40-degree decrease in the mean radiant temperature — a measure of heat that takes into account the effects of sunlight and radiation from nearby surfaces. It is the difference between the baking sensation of standing in direct sunlight and the relief of moving into the shade of a tall oak.
Phoenix’s housing department, which in 2018 was awarded a $30 million federal grant to redevelop Edison-Eastlake’s aging public housing, has said the project will incorporate heat recommendations from residents.
But the action plan was just the beginning. After learning how pavement exacerbates heat, Ortiz spoke at a housing department meeting to oppose plans for a parking lot where a demolished building had once been. The spot will instead feature mixed-income housing with a shaded seating area and a path to a community garden, the city said.
“It’s perfect,” Ortiz said.
A relentlessly positive mother of seven, Ortiz also serves as the unofficial heat guru for her apartment complex. On scorching days, she reminds friends to wear a hat and carry water. She checks in with elderly neighbors and keeps an eye on the kids playing in the courtyard.
This kind of solution is just as important as the technical ones, Hondula said. Research shows that social isolation is a strong risk factor for heat illness. During a 2003 heat wave in France that killed 15,000 people, those who had no social activities — choir practice with church groups, lunch with friends — were six times as likely to die.
That value of community is enshrined in the neighborhood’s heat action plan, which recommends that the city develop a first-aid program that would certify residents as “qualified heat responders" so they can help their neighbors in need.
The plan also includes an ode to the community penned by Ortiz.
“Uniting our voices in one vision,” it reads.
“Projecting our vision towards the future …
We are an example for the generations that follow
What we see now, tomorrow will be different.”
‘Systems that are safe to fail’
If Phoenix’s present is already scorching, just imagine what the future will bring.
By 2050, climate change will make the city’s summers look more like those in Baghdad, according to a study published last year in the journal PLOS One. The city is projected to experience more than two dozen additional “dangerous” days when the heat index is above 105 degrees (these conditions are already felt for about four months of the year). Heat waves will lengthen, and summertime droughts will become far more severe.
“Heat is something you can’t escape or relieve if you don’t have the critical services" — such as air conditioning and water — “that we take for granted,” said Susan Clark, the director of the Sustainable Urban Environments Initiative at the University at Buffalo. “And at some point we’re going to reach thresholds that our physical systems, our infrastructure — they’re just too stressed.”
In a 2018 study in the journal Sustainable and Resilient Infrastructure, Clark probed what might happen if Phoenix reached such a threshold.
Many of the city’s essential systems share vulnerabilities, she said. Power plants depend on water for their cooling towers; during heat waves, the water can get too hot, disrupting power generation. Severe droughts make the city susceptible to wildfires, which might ignite power lines and cut off electricity. Power outages will shut off gas pumps and make streetlights go dark — a major problem for a car-centric city.
In the absolute worst-case scenario — what Clark calls a “Hurricane Katrina”-size heat disaster — a single disruption to one of these systems might trigger a cascade of deadly consequences. Deprived of water and air conditioning, how long could people survive?
Fear of such a confluence of crises has spawned countless headlines wondering whether Phoenix is doomed.
But the problem is hardly unique to Arizona. The same study that predicted that Phoenix in 2050 will feel like Baghdad found that Boston’s climate will come to resemble that of Atlanta’s and Seattle will be like Rome. Cities that have rarely experienced extreme heat will suddenly be slammed. Infrastructure built for cooler times will falter in such searing conditions.
Governments can try to counter rising temperatures by making systems stronger, “but the thresholds will keep being passed,” Clark said. “The more realistic way to think about it is to create systems that are safe to fail.”
This kind of thinking has spurred many of Phoenix’s “heat ready” initiatives in recent years. A growing fraction of the city’s power comes from solar, which does not depend on water in the way that coal-fired or nuclear power plants do. The local electric utilities are looking to install “microgrids” around the city that could supply power to essential services in case of a major outage.
To ward off shortages, the city recycles all wastewater, and developers in Arizona must guarantee a 100-year water supply for any planned community. Phoenix’s emergency-operations plan includes a 13-page supplement dedicated to heat.
The city spends more than $5 million on tree planting and maintenance, and chief sustainability officer Mark Hartman aspires to extend the city’s tree canopy to as much as a quarter of its area — the county average is 8.8 percent. In the meantime, he is working to develop a network of “cool corridors,” so that no resident is more than a five-minute walk from water and shade. And a multimillion-dollar “cool pavement” pilot program will coat some 36 miles of streets with materials that reflect, rather than absorb, heat.
With ASU scientists and the National Weather Service, Hartman is also leading the city’s efforts to develop its “heat ready” guidelines. In 2018, the city was awarded a $100,000 grant from Bloomberg Philanthropies to refine the program, and Hartman had hoped to unveil the final framework this year so other cities could start to implement it.
But the coronavirus pandemic delayed that framework and complicated other efforts. Staff at the Phoenix Revitalization Corporation had to teach residents to use Zoom so they could hold a “heat leadership” program. When most of the city’s network of air-conditioned cooling centers were shuttered to comply with coronavirus social distancing measures, the cavernous Phoenix Convention Center had to be used instead.
“If there’s been one message over this year, it’s that you cannot anticipate everything that will happen and one crisis does not wait for the other one to finish,” said Gallego, the mayor. “We are aware that we need to have a system that provides us with flexibility to deal with escalating crises.”
A native of the Southwest who suffered from asthma as a child, Gallego is familiar with environmental risk. “When you’re wheezing by the track, it gives you some time to reflect on what you can do about it," said Gallego, 38. While working on economic development and renewable-energy projects for a Phoenix electric utility, she settled on what she would do: promote green growth. She ran for city council, then mayor, on an environmental platform.
This January, less than 10 months after she was sworn in, Gallego led Phoenix to join C40, the group of municipalities working to combat climate change.
Her goal, she says, is to make Phoenix “the most sustainable desert city on the planet."
Seeds of change
Even in the midst of the pandemic, change can still happen — a few trees at a time.
On the same sweltering day that exhausted Ortiz, about a dozen men, women and children gathered at the edge of a formerly empty 19-acre lot in Lindo Park-Roesley Park, another Phoenix neighborhood enrolled in the Nature’s Cooling Solutions project. Their mission: to plant a row of 11 mesquite and Palo Verde trees, 86 shrubs and 25 cacti and succulents.
Like Edison-Eastlake, Lindo-Roesley is a Phoenix “hot spot,” home to mostly low-income residents and vast expanses of dusty pavement. But the Spaces of Opportunity cooperative garden is an oasis, one that residents are eager to support. Families lease 5-by-50-foot gardening plots for $5 a month, and every Saturday growers sell their goods at an on-site farmers market. A hand-painted sign on the lot facing Vineyard Road announces, “These are community trees. Please respect them and we will enjoy the fruit together.”
Esther Villa, a native of temperate Guadalajara, Mexico, said the brutal summers are hard for her two daughters, who developed skin issues after moving to Phoenix 17 years ago. Her home’s swamp cooler was insufficient to combat the oppressive heat; sometimes all she could do was put the kids in a bathtub full of cool water.
That’s why she came out for the day’s tree planting. Even with the sun blazing and sweat drenching her clothes, Villa was hopeful that the day’s efforts would make her community safer for children in the years to come.
“Grandioso,” she called the project. And then she got to work.
Sarah Kaplan is a climate and science reporter covering humanity's response to a warming world. She previously reported on Earth science and the universe.