Here's how heat discriminates, and what Phoenix is doing to help those at risk
Daniel Runyan's towel draped across the bench seat of his blue 1997 Chevrolet pickup. A change of dress clothes hung behind the seat. Instrumental music played over the radio.
At 6 p.m., the temperature in his truck, parked in the speckled shade of a mesquite and its door wide open, was over 110 degrees. He opened a cooler in the truck bed and grabbed a bottle of water from the melting ice.
Runyan lives in his truck. He’s 67 and has cancer. His doctors told him it's terminal.
As he is most weekdays, Runyan was parked near the Desert West Community Center on June 19, the start of the hottest week of the year.
The center near 67th Avenue and Thomas Road is part of Phoenix's "We're Cool" heat-relief network. Anyone can go in to cool off and hydrate. Cases of bottled water are stacked in the front office.
To escape the heat, Runyan spends days at the center's senior program. For a small yearly membership fee, he can eat lunch there. He makes art, does jigsaw puzzles or watches TV.
"The only bad part of it is, it's not open on the weekends," Runyan said. "Yesterday about killed me."
The center also closes at times for city-related business.
The National Weather Service had forecast record temperatures for the week, and Phoenix was bracing for the heat.
"Temperatures may reach as high as 119 degrees this weekend," Phoenix Mayor Greg Stanton said at a press conference about the We're Cool program. "That is potentially deadly."
By the end of the day, the temperature reached 118 degrees and, on Tuesday, Phoenix recorded its hottest day of the year at 119 degrees.
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Runyan is among the most vulnerable populations during a Phoenix summer: someone who is homeless, older and chronically ill, and who can't easily escape the heat or cope with its physical effects.
As temperatures rise from the forces of climate change and a widening urban heat island, those vulnerable populations will suffer disproportionately, scientists say. Cities and social-service agencies try to help, but some of the measures, like cooling centers, are not open all the time and others, like planting more trees, take time and money.
The disparity is not just anecdotal. Sensors placed in two Phoenix neighborhoods documented a nearly 10-degree difference between a house in south Phoenix, where landscaping is sparse and temperatures hotter, and one in central Phoenix, where trees and grass grow in abundance and keep conditions more temperate.
And scientists expect temperatures to get hotter and deadlier.
The people most at risk
Heat does not affect everyone equally. Scientists measure the vulnerability of those at greatest risk in several ways:
- Exposure to heat: Some neighborhoods are hotter than others.
- Sensitivity to heat: Heat affects the elderly and chronically ill to a higher degree.
- Adaptation to heat: Low-income people may lack resources to protect themselves adequately.
Among the most vulnerable people, according to the U.S. Global Change Research Program's 2016 climate change and health assessment, are those who have pre-existing medical conditions, who are low-income or who speak limited English. They are elderly, pregnant or disabled. They live and work in densely populated cities, in urban heat islands that lack shade.
“When we look at the distribution of temperature throughout metropolitan Phoenix, there’s disproportionate stress on certain social groups,” said Darren Ruddell, a University of Southern California geographer. Low-income, minority and elderly residents are exposed to the greatest amount of heat stress.
Low-income people in Phoenix living where vegetation is scant at the urban core and the elderly on the outskirts of Maricopa County were most prone to heat-related illnesses, Union of Concerned Scientists geographer Juan Declet-Barreto found in his 2013 research.
People who are homeless are also exposed to heat more than most others and often face other risk factors, such as health issues, the U.S. Global Change Research Program's assessment said.
In other words, heat discriminates.
The effects of urban development
Urban development pushes temperatures in the central cities higher than in rural areas, an effect distinct from climate change that is known as the urban heat island.
Luke Howard, a British amateur meteorologist, first observed it in London during the early 1800s.
The same conditions exist in Phoenix today.
"These black surfaces, concrete surfaces, are really good, compared to the surrounding desert, at absorbing heat and then releasing it slowly back in to the environment," said David Hondula, an Arizona State University senior sustainability scientist and professor researching heat and health.
In Phoenix, daytime temperatures have risen about 0.9 degrees every decade due to the urban heat-island effect, according to an assessment of Phoenix’s heat mitigation initiatives co-authored by Ariane Middel, an urban climate researcher and professor at Temple University.
The heat continues to radiate after dark.
"In the summer, it's really not cooling down much at night. So the nighttime is really not that much of a respite,” said Declet-Barreto, the geographer.
Depending on the season, the difference between rural and urban nighttime temperatures has ranged from 11 to 23 degrees, with the difference most pronounced in the spring, Phoenix's heat-mitigation assessment said.
Climate change would raise urban heat island temperatures even more, according to research by the Environmental Protection Agency. The agency's recommended cooling strategies include increasing shade and vegetation, while reducing greenhouse gas emissions.
In line with one recommendation, the city of Phoenix coated its buildings' roofs with a reflective paint.
It has a minimal impact on the temperature, Middel said, but it could reduce the city's energy consumption.
The city also adopted a tree and shade master plan in 2010 to mitigate the urban heat-island effect, in part, by increasing the tree canopy to 25 percent by 2030.
Trees lower temperatures with shade and by absorbing moisture.
How trees can cool an area
A tree canopy shelters the city from solar radiation that urban sprawl would otherwise absorb and store, said Richard Adkins, the city’s forestry supervisor.
"It also provides evapotranspiration, so you have a cooling effect underneath the canopy of the tree," he said.
High-income neighborhoods generally have more tree cover than low-income neighborhoodsin an array of large cities across the country, researchers from multiple universities found in a 2015 study. Fewer trees can also expose residents to more heat.
Runyan began living near the Desert Park West area because of the trees and the shade they provide. He has watched some of the trees die and said others look like they may not survive much longer.
Every year, Phoenix loses about 1,000 trees to various causes, according to a city manager's budget document.
In May, the Phoenix City Council approved more funding to maintain and replace trees.
If the city reaches its goal, a tree canopy of 25 percent would cool a typical neighborhood by 4.3 degrees. If the neighborhood is completely bare at the start, the 25 percent goal could cool it by 7.9 degrees, the assessment said.
That would be a lot of trees for the city, Middel said. But the city will only reach its goal if the public participates by planting and maintaining trees on private land.
The city is striving to exemplify good tree management so others will follow, Adkins said. “There’s no way we can do it by just the city. We have to partner with everybody.”
One tree at a time, the city of Phoenix is trying to increase its shade canopy to 25 percent by the year 2030. David Wallace/azcentral.com
Low-income areas stay hotter
Middel worries the city's tree canopy goal could leave behind low-income neighborhoods with fewer resources.
In Phoenix, for every $10,000 increase in a neighborhood’s median income, vegetation also typically increased and the temperature dropped one-half degree, University of California, Riverside, ecologist Darrel Jenerette and his colleagues found in a 2007 study.
“There are many hot spots in the city that we are concerned about,” Hondula said. “We might think of it as a constellation of islands or a series of islands, rather than one particular hot spot in the city.”
Low-income neighborhoods are typically hotter, and residents are often vulnerable to the heat for multiple reasons, Declet-Barreto said.
"The vulnerable population already lives in areas that are hotter than the average neighborhood in Phoenix, but then they won't be able to afford those measures of planting trees to provide shade to cool down the neighborhoods," Middel said. "So they are basically punished twice, in a sense."
Planting trees in low-income neighborhoods without tree cover is a priority, especially on walking routes to public transportation, said Mark Hartman, the city of Phoenix’s chief sustainability officer.
Adkins, the city forester, stresses the importance of selecting appropriate species.
The right tree doesn’t need much water, he said. And rainwater harvesting could make use of rain that would otherwise wash away.
“I see water harvesting, especially off our streets, as a very important component of us reaching this goal,” Adkins said. “I see water harvesting as part of our future, absolutely.”
In 2015, an EPA environmental justice grant jump-started the non-profit Sonora Environmental Research Institute's program to mitigate the urban heat islands in low-income Tucson neighborhoods with rainwater-harvesting systems that water shade trees.
Assisted by Tucson Water, the organization covers the up-front installation costs with a no-interest loan. An additional grant of up to $400 is available for families, depending on their income. Tucson Water gives families a rainwater-harvesting rebate of up to $2,000.
The project seeks to improve water management for a hotter and drier future as global climate change and the urban heat island effect advance.
Limits to tree planting
At a neighborhood association meeting in a south Phoenix church, the association's president, Emma Cordova, addressed the tree cover.
"We lost a lot of trees this summer," she said. The park in that neighborhood doesn't have enough shade, she and other residents told Jose Antonio Habre, a representative of the Phoenix parks department.
Industrial warehouses and plots of wholesale building materials border their south Phoenix neighborhood to the north. Interstate 17 borders it to the west.
The park, Sherman Parkway, extends into the neighborhood from a freeway frontage road. It’s three blocks long and less than 100 feet wide. Electrical transmission towers carry power lines above it.
Park resources, like manpower, are tight, Habre said. Residents need to outline specific requests to get what they want.
"The more political they are the more attention they get," he said. "You gotta be flexing."
But more than city politics limits the park's tree canopy.
Adkins can’t plant many trees there because of the APS power lines.
“I have very few tree species that can be planted there,” Adkins said. “They’re not going to be your big shade tree species, because that’s just not something that’s allowed by APS.”
In addition to scant shade, a few years back the city covered the park's grass with gravel across the street from Cordova's house. It has since felt hotter, she said.
While having a park is better than more asphalt or concrete, Ruddell said, Cordova's observation has a physical explanation.
"When we have rock ... that absorbs incoming solar radiation to a much greater extent than grass does," he said.
"Not only does it absorb solar radiation," he said, "but it retains that heat much longer."
Measuring the heat
To test the differences between neighborhoods, The Arizona Republic placed outdoor temperature sensors at two locations.
One of the sensors was left in a front yard belonging to G.G. George, the president of the Encanto Citizens Association. The yard was near North 11th Avenue and West Palm Lane in the older central Phoenix neighborhood.
The second sensor was placed in Cordova's front yard near 23rd Avenue and West Sherman Street, just east of Interstate 17 in south Phoenix.
Over a four-day period from Sept. 28 to Oct. 2, Cordova's front yard was almost 4 degrees hotter than George's, according to the sensors, borrowed from ASU's School of Geographical Sciences and Urban Planning.
At night, temperatures in George's yard dropped quicker and lower than Cordova's. The largest gap between the two yards came on Oct. 1, at 11 p.m., when Cordova's yard was 9 degrees warmer than George's.
The two neighborhoods are separated by more than location.
More than 47 percent of the households in Cordova's block group live below the poverty line, compared with 7 percent in George's, according to the U.S. Census Bureau's 2011-2015 American Community Survey data.
George's neighborhood, Encanto, has more grass, trees and shade. And it borders a lush city golf course and park.
Fewer resources to cope
Not only are low-income neighborhoods typically hotter, residents also have fewer resources to cope with heat, said Declet-Barreto, the geographer.
“In lower-income neighborhoods, we think that some of the behaviors that people might use to adapt or cope with heat are more limited than neighborhoods where people have higher incomes,” Hondula said.
Air-conditioning is a good example, he said. While most homes have air-conditioning in Phoenix, electricity is expensive, and residents’ ability to run, repair and maintain their air-conditioning is highly variable.
In south Phoenix, Cordova's neighbor, Eleanor Hernandez, kept the air-conditioning running this summer, but her electricity bill reached $600 a month. To pay it meant choosing not to pay other bills, and she fell behind on water and car insurance at different times.
About 95 percent of households in Maricopa County have central air-conditioning, while the remaining five percent mostly rely on evaporative coolers, Hondula and his colleagues found in a 2016 study.
"What we are starting to see is that, even if they have an air-conditioning, their indoor experiences can be drastically different from home to home," said Mary Wright, a Ph.D. student at ASU's School of Geographical Sciences and Urban Planning.
Wright and her colleagues put sensors in 46 homes during the summer of 2016. Lower-income families generally experienced "huge swings in temperature," she said. Temperatures in higher-income homes were consistent, according to their preliminary findings.
Cordova and another neighbor, Art Murillo, both have evaporative coolers.
“I would like to have air-conditioning, but my structure is not built for it,” Murillo said.
Within a five-day period in July, Cordova's evaporative cooler generally kept her house cooler than a house in Tempe with the air-conditioning off, according to indoor temperature sensors placed and monitored by The Republic.
Several times in the afternoons, however, her house was as warm or warmer than the house with the A/C turned off.
Meanwhile, at 9 a.m. on July 15, when the Desert West Community Center's senior program was closed, the temperature in Runyan's truck was 10 degrees higher than Cordova's house, although the temperature in his truck generally dipped lower at night, according to the sensors.
Runyan's truck has air-conditioning, but he seldom turns it on, he said. Gas is too expensive.
Hondula cautioned that not all residents in low-income, hot neighborhoods are "heat vulnerable." Researchers are still learning about coping strategies, such as checking in on family or neighbors, that are less costly than air-conditioning and protect residents from high-risk scenarios for heat-related illness or death, he said.
Runyan's coping strategy isn't complicated. He drinks water and stays in the shade. He likes to fish Desert West Lake or color adult coloring books in his truck.
"I'm out here in 112, 114 degrees. I have a little fan that blows air, and I'm fine," he said. "I mean, I don't like it, but I'm used to it."
Cordova once wrapped her grandchildren in cool, damp towels to help them sleep when a monsoon storm knocked her power out for three days.
Heat and diseases
The mosquitoes were terrible during those three days without power, Cordova said. She would take her grandchildren outside because they couldn’t stand the heat indoors.
Temperatures reached above 110 degrees, she said.
The urban heat island effect creates a better environment at night for mosquitoes carrying vector-borne diseases, such as West Nile virus, said Abba Gumel, an ASU mathematics professor researching the effects of climate change on vector-borne diseases. “They thrive mostly at night. They bite during the late evening time.”
Vector-borne diseases are infections transmitted by mosquitoes, ticks, fleas and similar insects.
As temperatures warm, mosquitoes tend to develop more quickly, said Heidi Brown, a public-health professor at the University of Arizona. They can lay eggs more quickly, leading to population growth.
Heat and vector-borne diseases are separately more hazardous in certain areas of a city, she said. Sometimes they overlap, and sometimes they don’t.
Air-conditioning in a well-sealed house, for example, limits exposure to mosquitoes as it does to heat, she said. Green spaces, on the other hand, can sometimes benefit mosquitoes, but reduce the urban heat-island effect.
A lack of data makes it difficult to say if a warming climate creates an overall greater risk for vector-borne diseases in Arizona, she said. Changes in precipitation and human behavior due to climate change also make it hard to draw conclusions.
Brown is currently researching how well water drains from neighborhoods and if poor infrastructure creates more habitats for mosquitoes carrying diseases.
In September, Cordova pointed to a puddle in the street in front of her house. Greenish water ran down her block. It’s a pipe leak, she said. The puddle hadn’t gone away for some time. “If this were a nicer neighborhood, they would have fixed that.”
After more than two months of calling the city, workers fixed the leak in October, she said.
Mosquitoes need only a small amount of water to lay eggs, according to the U.S. Centers for Disease Control and Prevention.
Luckily the mosquitoes haven’t been bad this year, unlike with the past two, Cordova said.
When heat grows extreme
In 2014, the city had about a 10 percent tree canopy, according to the 2014 assessment of the city's heat-mitigation strategies. If Phoenix reaches 25 percent citywide, it would not offset a maximum 6-degree increase projected under a high greenhouse gas emission scenario from 2041 to 2070. That scenario is one of the least-optimistic.
A 6-degree increase in average temperature might not seem like much, but a changing climate also brings extreme events, such as heat waves, that could be critical, Middel said.
While Arizona doesn’t have hurricanes like Harvey or Irma, she said, it has the heat.
"The average might not be the temperature that's really critical," Middel said. "It might be those spikes that we see more and more that are really critical."
Hartman, the city sustainability officer, has thought of scenarios in which temperatures are so hot that people would need to evacuate their homes.
“If there was a power outage, what would we do?" he said. "Where are there cooling centers? Where could people go?”
He has thought about what would happen, for example, if the city hit 122 or even 130 degrees and the airport shut down, preventing outside emergency help.
The city is working to make sure power and water would be kept on at core shelters capable of holding lots of people, Hartman said.
Some people might drive to Flagstaff and stay in a hotel, he said. If they have to sit in traffic on the way there, that wouldn’t be a problem because they would have air-conditioning.
But other more vulnerable populations like the poor, elderly or disabled might not have that option, he said. That’s who Hartman is most worried about.
“This is a top priority for the city,” he said.
Even if temperatures hit 130 degrees, Cordova is more likely to seek out family than go to a cooling center, she said.
Vulnerable populations might have adequate resources, like an evaporative cooler, for current temperatures, Hartman said, but not for extreme temperatures.
Emergency managers have learned a lot from events like Hurricanes Katrina, Harvey and Irma, Hartman said.
The city would send people out to direct residents to a cooling center, but they wouldn’t have the resources to provide transportation for everyone, Hartman said.
Only 2 percent of households, however, can access a cooling center in Maricopa County by foot, according to a 2016 study. But 39 percent are in walking distance of a cool public space such as a library or store.
Everyone would need to help. Hartman hopes the community would come together, as with Hurricane Harvey.
Runyan remembers a time in Phoenix when the heat island wasn't as intense. He lived by an alfalfa field years back. When the wind blew, it felt like an evaporative cooler, he said. The city became steadily hotter as it expanded, he said.
"You'd have to be pretty stupid not to realize it," Runyan said. "It's like putting a rock on a fire."
Environmental coverage on azcentral.com and in The Arizona Republic is supported by a grant from the Nina Mason Pulliam Charitable Trust. Follow The Republic environmental reporting team at OurGrandAZ on Facebook, Twitter and Instagram.