Coming to a City Near You: Horrifying Ramifications of Excessive Heat

On a scorching day in downtown Phoenix, when the temperature soars to 115°F or higher, heat becomes a lethal force. Sunshine assaults you, forcing you to seek cover. The air feels solid, a hazy, ozone-soaked curtain of heat. You feel it radiating up from the parking lot through your shoes. Metal bus stops become convection ovens. Flights may be delayed at Sky Harbor International Airport because the planes can’t get enough lift in the thin, hot air. At City Hall, where the entrance to the building is emblazoned with a giant metallic emblem of the sun, workers eat lunch in the lobby rather than trek through the heat to nearby restaurants. On the outskirts of the city, power lines sag and buzz, overloaded with electrons as the demand for air conditioning soars and the entire grid is pushed to the limit. In an Arizona heat wave, electricity is not a convenience, it is a tool for survival.

Still, the multiplying risks of extreme heat are just beginning to be understood, even in places like Phoenix, one of the hottest big cities in America. To Mikhail Chester, the director of the Metis Center for Infrastructure and Sustainable Engineering at Arizona State University, the risk of a heat-driven catastrophe increases every year. “What will the Hurricane Katrina of extreme heat look like?” he wonders aloud as we sit in a cafe near the ASU campus. Katrina, which hit New Orleans in 2005, resulting in nearly 2,000 deaths and more than $100 billion in economic damage, demonstrated just how unprepared a city can be for extreme climate events.

“Hurricane Katrina caused a cascading failure of urban infrastructure in New Orleans that no one really predicted,” Chester explains. “Levees broke. People were stranded. Rescue operations failed. Extreme heat could lead to a similar cascading failure in Phoenix, exposing vulnerabilities and weaknesses in the region’s infrastructure that are difficult to foresee.”

In Chester’s view, a Phoenix heat catastrophe begins with a blackout. It could be triggered any number of ways. During periods of extreme heat, power demand surges, straining the system. Inevitably, something will fail. A wildfire will knock out a power line. A substation will blow. A hacker might crash the grid. In 2011, a utility worker doing routine maintenance near Yuma knocked out a 500-kilovolt power line that shut off power to millions of people for up to 12 hours, including virtually the entire city of San Diego, causing economic losses of $100 million. A major blackout in Phoenix could easily cost much more, says Chester.

But it’s not just about money. When the city goes dark, the order and convenience of modern life begin to fray. Without air conditioning, temperatures in homes and office buildings soar. (Ironically, new, energy-efficient buildings are tightly sealed, making them dangerous heat traps.) Traffic signals go out. Highways gridlock with people fleeing the city. Without power, gas pumps don’t work, leaving vehicles stranded with empty tanks. Water pipes crack from the heat, and water pumps fail, leaving people scrounging for fresh water. Hospitals overflow with people suffering from heat exhaustion and heatstroke. If there are wildfires, the air will become hazy and difficult to breathe. If a blackout during extreme heat continues for long, rioting, looting, and arson could begin.

And people will start dying. How many? “Katrina-like numbers,” Chester predicts. Which is to say, thousands. Chester describes all this coolly, as if a Phoenix heat apocalypse is a matter of fact, not hypothesis.

“How likely is this to happen?” I ask.

“It’s more a question of when,” Chester says, “not if.”

Extreme heat is the most direct, tangible, and deadly consequence of our hellbent consumption of fossil fuels. Rising carbon-dioxide levels in the atmosphere trap heat, which is fundamentally changing our climate system. “Think of the Earth’s temperature as a bell curve,” says Penn State climate scientist Michael Mann. “Climate change is shifting the bell curve toward the hotter end of the temperature scale, making extreme-heat events more likely.” As the temperature rises, ice sheets are melting, seas are rising, hurricanes are getting more intense, rainfall patterns are changing (witness the recent flooding in the Midwest). Drought and flooding inflict tremendous economic damage and create political chaos, but extreme heat is much more likely to kill you directly. The World Health Organization predicts heat stress linked to the climate crisis will cause 38,000 extra deaths a year worldwide between 2030 and 2050. A recent study published in Nature Climate Change found that by 2100, if emissions continue to grow, 74 percent of the world’s population will be exposed to heat waves hot enough to kill. “The more warming you have, the more heat waves you have,” says Michael Wehner, a scientist at Lawrence Berkeley National Laboratory. “The more heat waves you have, the more people die. It’s a pretty simple equation.”

Heat waves are driven not just by rising temperatures but by a change in the dynamics of the Earth’s climate system. As the atmosphere warms, the temperature difference between the poles and the subtropics is shrinking, which is changing the path of the jet stream, the big river of wind 35,000 feet up in the sky that drives our weather system. The jet stream’s path is shaped by atmospheric waves called Rossby waves, which are created naturally as the Earth spins. Mann explains that as the Earth’s temperature gradient flattens, the Rossby waves tend to bend, resulting in a curvy jet stream that is more likely to get “stuck,” trapping weather systems in place and creating what Mann calls “huge heat domes.”

Extreme heat is already transforming our world in subtle and not-so-subtle ways. Disney executives recently voiced concern that rising temperatures will significantly reduce the number of visits to their parks. In Germany, officials were forced to put a speed limit on the autobahn because of fears the road would buckle from heat. The U.S. military has already incurred as much as $1 billion in costs during the past decade — from lost work, retraining, and medical care — due to the health impacts of heat. The warming of the planet “will affect the Department of Defense’s ability to defend the nation and poses immediate risks to U.S. national security,” a recent DOD report said. Forests and soils are drying out, contributing to explosive and unprecedented wildfires. Habitation zones for plants and animals are changing, forcing them to adapt to a warmer world or die. A U.N. report found that 1 million species are at risk of extinction in the coming decades. Another study by researchers at MIT suggests that rising temperatures and humidity may make much of South Asia, including parts of India and Pakistan, too hot for human existence by the end of the century. As scientist Peter Gleick, co-founder of the Pacific Institute in California, told me, “There is a shocking, unreported, fundamental change coming to the habitability of many parts of the planet, including the USA.”

Since the Industrial Revolution, the Earth’s temperature has risen by 1.8°F (1°C). As we burn more fossil fuels, the warming is accelerating. The planet’s average surface temperature in 2018 was the fourth-highest since 1880, when record-keeping began. Gavin Schmidt, a climate scientist at NASA, said there’s a “90 percent chance” that 2019 will turn out to be even hotter. Nine of the 10 warmest years in recorded history have occurred since 2005. This past June was the hottest June ever recorded. Astonishingly, July was the hottest month in human history.

But warming is not happening at the same rate everywhere. The Arctic, for example, is warming twice as fast as the rest of the world. Why? It’s a classic climate feedback loop: Ice and snow are highly reflective, bouncing sunlight back into space. But as the region warms, sea and land ice declines, exposing more open land and ocean, which are darker and absorb more heat. As temperatures rise, the permafrost melts, which releases methane, a potent greenhouse gas, which further accelerates the melting. Greenland is in the midst of one of the biggest melt seasons ever recorded, with temperatures as much as 40°F above normal. And as the Arctic heats up and dries out, it burns. There have been unprecedented wildfires this year, with more than 100 massive fires raging across the region since June. The burning peat has already emitted more than 100 million tons of greenhouse gases (nearly the annual carbon emissions of Belgium), further accelerating the climate feedback cycle that’s cooking the planet.

But the greatest risk to human health may be in areas that are already hot, where temperature increases will strain habitability. In the U.S., the fastest-warming cities are in the Southwest. Las Vegas, El Paso, Tucson, and Phoenix have warmed the most, each by at least 4.3°F since 1970. Globally, many of the hottest cities are in India. In May, a deadly heat wave sent temperatures above 120°F in the north. The desert city of Churu recorded a high of 123°F, nearly breaking India’s record of 123.8°F, set in 2016. There were warnings not to go outside after 11 a.m. Authorities poured water on roads to keep them from melting. A 33-year-old man was reportedly beaten to death in a fight over water. The preliminary death toll in India for this summer’s heat wave is already more than 200, and that number is likely to grow.

How hot will it get? That depends largely on how far and how fast carbon-dioxide levels rise, which depends on how much fossil fuel the world continues to burn. The Paris Climate Agreement (which President Trump pulled the U.S. out of) aims to limit the warming to 3.6°F (2°C). Given the current trajectory of carbon pollution, hitting that target is all but impossible. Unless nations of the world take dramatic action soon, we are headed for a warming of at least 5.4°F (3°C) by the end of the century, making the Earth roughly as warm as it was 3 million years ago during the Pliocene era, long before Homo sapiens came along. “Human beings have literally never lived on a planet as hot as it is today,” says Wehner. A 5.4°F-warmer world would be radically different from the one we know now, with cities swamped by rising seas and epic droughts turning rainforests into deserts. The increased heat alone would kill significant numbers of people. A recent report from the University of Bristol estimated that with 5.4°F of warming, about 5,800 people could die each year in New York due to the heat, 2,500 could die in Los Angeles, and 2,300 in Miami. “The relationship between heat and mortality is clear,” Eunice Lo, a climate scientist at the University of Bristol and the lead author of the report, tells me. “The warmer the world becomes, the more people die.”

The properties of heat confused scientists and philosophers for centuries. In Greek mythology, heat was controlled by Ankhiale, the goddess of warmth. Eighteenth-century chemist Antoine Lavoisier believed heat was an invisible fluid, known as the caloric, that flowed from hotter bodies to colder bodies. It wasn’t until the mid-19th century that scientists understood that when you feel heat, what you’re really feeling is energy released by the vibration of molecules. The faster something vibrates, the higher its temperature, and the more energy it releases. The sun is a big ball of hydrogen that burns at about 10,000°F and releases vast amounts of energy into space, which travels in the form of waves until colliding with something, such as a rock or a building or a human being. That, in turn, speeds up the vibrations within that object. These accelerating vibrations are what we humans sense as “getting hotter.”

Not surprisingly, heat regulation is one of the body’s most important functions. One way to think about the human body is as a giant multicellular heat engine that strives to maintain a constant internal state of 98.6°F. The very process of living — of eating, breathing, moving, thinking, having sex — generates heat. The outside air is usually lower than 98.6°F, so our bodies release heat, mostly by circulating blood to capillaries close to the surface of our skin, where the heat can be dissipated (that’s why your body is warm to the touch). Without a cooling mechanism, just our basic metabolism would result in about a 2°F hourly rise in body temperature. We wouldn’t even make it through the day.

If the equilibrium between body temperature and the outside world gets too far out of whack, the body quickly deploys its only emergency heat-release system: It sweats. For sweating to be effective, however, the water has to evaporate. High humidity is uncomfortable (and potentially deadly) because the air, already filled with water, has little capacity to add more, so the sweat simply sits on the surface.

The loss of water through sweat is itself a health hazard. The average person contains roughly 40 liters of fluid. On a hot day, when the body is struggling to keep from overheating, a person can easily lose a liter of sweat per hour. When the body is down one liter, basic functions are impaired. When it’s down five, fatigue and dizziness set in. Ten liters disturbs hearing and vision and you will likely collapse — a condition known as heat stress.

But if it’s hot and humid enough, even drinking plenty of water won’t help. As the body’s temperature rises, it tries to cool itself by pumping more and more blood to capillaries under the skin. The heart pumps faster, the chest pounds, the pulse races. As the body loses water, our blood becomes thicker and harder to propel. When the body temperature hits 103°F or so, the metabolism will be running flat out in an emergency effort to dump heat. Eventually, the most vital organs can’t keep up, and the body’s neurological system begins to collapse. At 105°F, the body is in serious trouble. The brain swells, often causing hallucinations and convulsions. Pupils become dilated and fixed. Sweating stops, and the skin feels hot and dry to the touch. At that point, if the body temperature isn’t lowered immediately by emergency cooling measures such as being packed in ice or a plunge into cold water, the person could die of heatstroke.

The psychological impacts of extreme heat are obvious to anyone who’s ever felt cranky on a hot day. But the impacts go beyond crankiness. When temperatures rise, suicide rates can go up at a pace similar to the impact of economic recessions. Some aspects of higher cognition are impaired. School test scores decline, with one study showing decreases across five measures of cognitive function, including reaction times and working memory.

The link between heat and violence is particularly intriguing. “There is growing evidence of a psychological mechanism that is impacted by heat, although we can’t yet say exactly what that is,” says Solomon Hsiang, a professor of public policy at Berkeley. Some scientists speculate that higher temperatures impact neurotransmitters in the brain, resulting in lower levels of serotonin, which has been shown to lead to aggressive behavior. So rising heat may literally alter the chemistry in our brains. One study showed that police officers were more likely to fire on intruders during training exercises when it was hot. Andrew Shaver, a professor of political science at the University of California, Merced, analyzed data about conflicts in Afghanistan and Iraq and found that attacks by insurgents involving RPGs and assault rifles increased with higher temperatures, while planned attacks did not. “During conflicts, higher temperatures seem to provoke more impulsive aggression,” Shaver says. One speculative paper projects that by 2099, due to rising heat, the U.S. could see an additional 22,000 murders, 180,000 rapes, 3.5 million assaults, and 3.76 million robberies, burglaries, and acts of larceny.

The city of Phoenix has no master plan to deal with heat, no radical remaking of the building codes or zoning laws in place, and no heat czar who is in charge of reimagining the city for the 21st century. Re-engineering a city like Phoenix for extreme heat is a long-term project that has only just begun, says David Hondula, a senior sustainability scientist at Arizona State University. “Think about places like Minnesota, and what they have done to engineer for cold winters,” Hondula says. “They have tunnels you walk through in the winter, the heating systems are optimized, you drive cars with snow tires and all-wheel drive. We have done nothing like that in Phoenix, or in any city, really, when it comes to thinking about heat. The whole idea of engineering for extreme heat is still in its infancy.”

Retrofitting Phoenix — including reining in suburban sprawl, revising building codes to improve energy efficiency and ventilation, and creating greener urban spaces — is certainly imaginable, but “if we are going to be serious about this, a big investment is required,” Hondula says. “We need billions of dollars.”

It will also require leadership from city and state officials. A recent poll found that two-thirds of Arizonans accept that climate change is happening, but most elected officials in the state, including Republican Gov. Doug Ducey, are hardly climate activists. Arizona is one of the sunniest states in the nation, and yet only 6.5 percent of the state’s electricity comes from solar power. A statewide ballot initiative in 2018 to require 50 percent renewable power by 2030 was soundly defeated, in part because the parent company of Arizona Public Service, the big public utility in the state, spent more than $37 million on false and misleading arguments about how transitioning to renewable power would raise power bills and destroy the Arizona economy.

“We have a large number of elected officials who don’t believe in climate change, period,” says Stacey Champion, a longtime Phoenix energy and climate activist. “How do you get effective, data-driven policy if you have people pushing hard against it because they are batshit crazy, or they are afraid it will spook companies like Nike who want to come here?”

But as the world heats up, cities will get the worst of it. They are built of concrete and asphalt and steel, materials that absorb and amplify heat during the day, then radiate it out at night. Air conditioners blow out hot air, exacerbating the problem of urban heat buildup. Downtown Phoenix, for example, can be as much as 21°F hotter than the surrounding area. This phenomenon, which is called Urban Heat Island Effect, impacts most cities in the world. On average, cities are 2 to 5°F warmer than their leafy suburbs during the day — and as much as 22°F warmer during some evenings. The effect is so pervasive that some climate skeptics have seriously claimed that global warming is merely an illusion created by thousands of once-rural meteorological stations becoming surrounded by urban development.

Counterintuitively, the biggest health effects of rising heat often occur at night, when vulnerable people such as the elderly badly need the chance to cool down. Without that chance, they can succumb to heatstroke, dehydration, and heart attacks. This appears to be what happened during the heat wave that hit Europe in 2003, killing 70,000 people, mostly in buildings without air conditioning. Research has shown that the cause of many deaths was not so much the 104°F daytime temperatures, but the fact that nights stayed in the seventies or higher.

To reduce the heat-absorbing impacts of urban areas, some cities are experimenting with white roofs. The idea is to change the reflectivity of the rooftop to bounce more light off so that the building absorbs less heat. New York, for instance, introduced rules on white roofs into its building codes as long ago as 2012. Volunteers and workers have taken white paint to 10 million square feet of roofs in the city, though that is still less than one percent of New York’s total roof area.

Keith Oleson of the National Center for Atmospheric Research in Boulder, Colorado, looked at what might happen if every roof in large cities around the world were painted white. He found it could decrease the Urban Heat Island Effect by a third — enough to reduce the maximum daytime temperatures by about 1°F, and even more in hot, sunny regions such as the Arabian Peninsula and Brazil.

In Los Angeles, city officials are experimenting with asphalt sealants that give roads a light-reflective surface. Manufacturers claim they can reduce the surface temperature by up to 30°F. Greg Spotts, chief sustainability officer in the Los Angeles Bureau of Street Services, says the sealants have worked well so far, but cost (it’s roughly three times more expensive than conventional sealant) and questions about durability have limited their use. Spotts estimates that of the 23,000 miles of streets in L.A., less than 10 miles have been covered with reflective coating. “But we know it works, because dogs always move over to walk on the white streets when they can,” says Spotts.

Other places, such as Stuttgart, Germany, are trying to re-engineer the airflow of the whole city. Stuttgart is an industrial town surrounded by steep hills at the bottom of a river valley, where heat and polluted air linger. To help cool things off, city planners have built a number of wide, tree-flanked arterial roads that work as ventilation corridors and help clean, cool air flow down from the hills. Officials have also restricted new buildings from going up on certain hillsides in order to keep the air moving.

Many urban centers are trying to combat heat the old-fashioned way: by planting shade trees. Since 2011, Louisville, Kentucky, has planted about 100,000 trees. Paris Mayor Anne Hidalgo has plans to create “urban forests” in the center of the city. In May, I visited Singapore, a tropical city that is far more densely developed than Phoenix. It’s hard to find a single inch of Singapore that is in any way “natural,” but since the 1960s, there has been a deliberate government-led effort to green the city. The highways are canopied with lush trees, urban parks have been expanded, and thousands of sidewalk trees have been planted. Wandering downtown, I felt like I was in a jungle, there were so many vines and plants hanging from windows.

“There used to be a lot of nice big shade trees in Phoenix, but they cut them all down in the 1960s because they were worried about how much water they used,” Mark Hartman, Phoenix’s chief sustainability officer, says with a bit of an eye roll. (In fact, climate-appropriate trees like mesquite or ash only require extra water for the first year or two after they’re planted — when they get bigger, the increased shade often increases soil moisture by reducing evaporation.) In 2010, as the problems of extreme heat became more obvious, Phoenix officials set a goal of doubling the percentage of the city covered with tree canopy from 12 to 25 percent. Then came the inevitable budget cuts and layoffs after the recession. According to Hartman, “Tree planting was cut back to stay only slightly ahead of those lost to storms and drought.” Today, the tree-canopy cover in Phoenix remains virtually unchanged from what it was a decade ago.

But if you look closely, you can find signs that a few people in Phoenix are starting to think differently about life in a rapidly warming world. You will hear about plans for “walkable shade corridors.” Most commercial buildings are now constructed with white roofs. At one light-rail stop, you can push a button and get sprayed with a cool mist of water while you wait for the train. One Phoenix city official has been known to walk around downtown passing out umbrellas on hot days. And the city launched an aggressive social media campaign to alert people to the risks of extreme heat.

But mostly what you see in Phoenix is asphalt and concrete, cars and malls, and big, crowded highways. In this sense, it is like virtually every other city in America, except with a few more palm trees (which are purely decorative — they provide zero shade) and a heavy dependence on air conditioning. As Hondula says one afternoon as we drive through Encanto Village, a historic middle-class neighborhood in Phoenix, “The number-one heat adaptation here is forking over money for the electric bill.”

In research labs around the country, you can find experiments with walls engineered to suck heat out of buildings, and wood that’s altered to be stronger, cooler, and better for insulation. But right now, the only technology deployed at scale against extreme heat is air conditioning. Nearly 90 percent of the homes in America have it — it’s as necessary as running water and a toilet.

Without air conditioning, the world as we know it today wouldn’t exist. It’s inconceivable that there would be a city of 4.5 million people living in the middle of the Southwestern desert — much less 20 million people living in Florida — without air conditioning. After World War II, Americans flocked from chilly Northern states to sunny Southern states. It was one of the great demographic shifts of the 20th century, and it precisely mirrored the proliferation of air conditioners. “Air conditioning was essential to the development of the Sun Belt,” historian Gary Mormino has argued. “It was unquestionably the most significant factor.”

Air conditioning is one of those paradoxical modern technologies that creates just as many problems as it solves. For one thing, it requires a lot of energy, most of which comes from fossil fuels. AC and fans already account for 10 percent of the world’s energy consumption. Globally, the number of air-conditioning units is expected to quadruple by 2050. Even accounting for modest growth in renewable power, the carbon emissions from all this new AC would result in a more than 0.9°F increase in global temperature by the year 2100.

Cheap air conditioning is like crack cocaine for modern civilization, keeping us addicted and putting off serious thinking about more creative (and less fossil-fuel-intensive) solutions. Air conditioning also creates a kind of extreme heat apartheid. If you’re rich, you have a big house with enough air conditioning to chill a martini. And if you are poor, like Leonor Juarez, a 46-year-old single mother whom I met on a recent July afternoon when the temperature was hovering around 115°F, you live in South Phoenix, where sidewalks are dirt and trees are few, and you hope you can squeeze enough money out of your paycheck to run the AC for a few hours on hot summer nights.

On hot days, Juarez’s small apartment feels like a cave. She has heavy purple curtains on the windows to block the sun. “I could not live here without air conditioning,” she tells me. Because she has poor credit, she doesn’t qualify for the usual monthly billing from Salt River Project, her utility. Instead, to pay for electricity and keep her AC running, SRP has given her a card reader that plugs into an outlet that she has to feed like a jukebox to keep the power on. Juarez turns on her AC only a few hours a day — still, her electric bill can run $500 a month during the summer, which is more than she pays for rent. To Juarez, who takes a bus five miles to a laundromat in the middle of the night because washing machines are discounted to 50 cents a load after 1 a.m., $500 is a tremendous amount of money.

She shows me the meter on the card reader: She has $49 worth of credit on it, enough for a few more days of power. And when that runs out? “I am in trouble,” she says bluntly. Juarez, who works as an in-home caretaker for the elderly, says she knows of several people who lived alone and died when they failed to pay their electric bills and tried to live without AC.

One such woman was named Stephanie Pullman, a 72-year-old retiree who lived alone on a fixed income of less than $1,000 a month in a small house in Sun City West, a development north of downtown Phoenix. Last summer, she was late to pay her electric bill and owed $176.84. On September 5th, 2018, Pullman paid $125, leaving $51.84 unpaid. Two days later, when the temperature hit 107°F, her electric company, Arizona Public Service, cut off her power. A week later, Pullman’s daughter became worried when she hadn’t heard from her mother, who had a heart condition, so she alerted locals. A Maricopa County Sheriff’s officer entered the house and found Pullman dead in her bed. Cause of death: heat exposure.

In 2018, APS cut off power to customers more than 110,000 times. Of those, more than 39,000 were during the blistering months of May through September.

Pullman’s death sparked wide media coverage and street protests over APS’s disconnect policy, and pushed Arizona regulators to ban power shut-offs on hot summer days. (APS shut-offs have been linked to at least two other heat-related deaths in recent years.) These deaths also raise larger questions about the future of cities like Phoenix. As temperatures soar in the coming years, the real question is not whether superheated cities are sustainable. With enough money and engineering skill, you can sustain life on Mars. The issue is, sustainable for whom?

Heat is not an equal-opportunity killer. If you’re poor, sick, old, or homeless, you’re more likely to die during a heat wave. Recent immigrants, both legal and undocumented, are particularly at risk. A 2017 study published in the American Journal of Public Health found that immigrants are three times more likely than citizens to die from heat-related illnesses. More than 85 percent of non-U.S. citizens who died from heat-related causes were Hispanic. Researchers hypothesized that working outdoors and in agriculture increased vulnerability.

In Arizona, the most visible victims of heat are the homeless. One afternoon, I drive around Glendale, a town just outside Phoenix, with Brian Farretta and Rich Heitz of the Phoenix Rescue Mission, a faith-based group dedicated to getting people off the streets. Recently, the group launched “Code: Red,” an initiative to pass out water and other essentials to people on the street during heat waves. “Our strategy is simple,” Heitz says. “We find people and give them water.”

Heitz, 48, has lived in Arizona most of his adult life. He is a gentle man with a goatee and a Harley-Davidson cap. Before joining the Phoenix Rescue Mission, Heitz spent 10 years on the streets of Phoenix as a heroin addict. “I lost myself in numbness,” he says. He spent a few years in jail for various charges and has now gone clean and is devoting his life to helping others do the same.

We pull into Sands Park, a typical suburban green swath with basketball courts and picnic areas. Heitz and Farretta head to a concrete bathroom, where they find a middle-aged woman sitting in the shade on the floor near the entrance.

She has brown, sunburned skin, long gray hair, and a pleasant smile. She’s dressed in dirty jeans and a T-shirt. Beside her is what looks like a children’s coloring book. On the cover, written in red crayon, are the words “It’s Raining Love.”

“How are you doing, Sherri?” Heitz asks her. “You doing OK in the heat?”

I notice her face is flushed, and there are rings of sweat under her arms.

“Yeah, I’m keeping cool.”

Heitz offers her a couple of bottles of water, which she takes, stockpiling them beside her.

As we walk back to the van, Heitz says this summer will be brutal for her and for all of the homeless in the city. “If you’re smart, you figure out ways to survive, to adapt,” he says. “You find friends with cool houses where you can crash during the day. You learn which churches are open.”

But not everyone is so wise. Heitz tells me about a man he found lying in the heat on the sidewalk. His face was flushed, his eyes were dilated, and he wasn’t moving. “I called 911, and they took him to the hospital,” Heitz says. “The guy was cooking right there on the sidewalk.”

In Phoenix, the brutality of life beyond the halo of air conditioning was evident everywhere I went. A few days after my visit with Heitz, I pull my rental car over to answer some emails near the corner of Indian School Road and Central Avenue. It is a nothing place, just a big intersection where 12 lanes of traffic cross. There are a few palm trees and a concrete sidewalk and some nondescript buildings that look like microprocessors on a giant PC board. I could feel the heat radiating off the asphalt and concrete as if I were standing beside a blast furnace. It was as inhuman and inhospitable a spot on this planet as anywhere I’ve ever been.

It doesn’t have to be that way. You can build a city on a human scale, and in such a way that it does not cook people who can’t afford an iced latte at Starbucks. You can power the world without fossil fuels and stop the buildup of CO2 in the atmosphere. But so far, we haven’t. The sprawl in Phoenix, as in most cities, continues unabated. And until that changes, so too will the heat.

As I fiddle with my phone, I notice a woman pacing the sidewalk ahead of me. She is rail-thin. In her skin, I see years of sun. I assume she is homeless, but maybe not. She approaches the passenger-side window of my car. There is fear in her eyes.

I roll down the window.

“I’m looking for my father,” she says quickly. “Have you seen him?” She describes him and says he is supposed to meet her here every Thursday. She says he is 56 years old and doesn’t have a place to stay and she is worried about him.

I tell her I haven’t seen him, that I was just driving by.

“I want to find him before it gets fucking hot,” she says. “I need to get out of this city. I’m like a bird, you know. I migrate. But I don’t want to leave until I find my father.”

She is jittery. She asks me again if I have seen her father, and I tell her I have not. Then she just turns and continues pacing along the sidewalk.

I thought of her a few days later as the temperature in Phoenix soared past 100°F. The Maricopa County Department of Public Health reported its first heat-related death of 2019: A homeless man had been found dead in a vehicle near downtown. No name or other details were released. I wondered if it might have been that woman’s lost father, but I knew it was unlikely. Still, the worst of the summer heat hadn’t arrived yet, and as the temperatures rise in Phoenix and cities around the world, superheated by the civilized world’s insatiable appetite for fossil fuels, there are so many deaths to come.