How hot will our summer become?

Valley’s slate of 100-degree days keeps growing

Arizona’s infamous summer heat is a worsening menace.

Global warming and Phoenix’s sun-soaked urban core make blistering heat waves like last week’s increasingly dangerous, especially to the poor and elderly.

Last year, 130 people died of heat-related causes in Maricopa County, the most yet in a decade of tracking, and the risk has grown with the exposure to heat: The hot season has lengthened by a month in the past century.

Imagine a Phoenix that tops out at 125 degrees, 130 degrees or worse. Climate scien-

tists say the city is on track for that in the second half of this century, even without accounting for the degree of temperature that concrete and asphalt loads on every decade or so.

And as temperature records — like Monday’s 118 degrees, Tuesday’s 119 degrees and Wednesday’s 117 degrees — keep falling, some officials are advocating steps like planting more trees and incorporating cool-roof technology to reverse or stall the urban-heating trend.

“The downtown area’s gotten hotter and hotter all the time,” said Terry Reck, a former trucker who is now homeless. He spends nights at a McDowell Road car wash and days with a Chihuahua and a cocker spaniel under a tree outside central Phoenix’s Burton Barr Library.

“The more buildings you put in,” he said, “the hotter she’s gonna get.”

Hotter, longer summers

Phoenix’s past 20 summers have averaged 38 more 100-degree days than the first 20 of the last century did. The city now endures 110 days over 100 degrees per year, on average.

But while summer heat is as natural as the sunrise, climate experts say it doesn’t have to be this hot. Help could be as near as a few trees — if only they grew where they were needed.

“Access to shade is huge,” Arizona State University urban climate researcher David Sailor said.

The vegetation that provides it is most lacking in the neighborhoods where residents are least able to afford to own or operate an air-conditioner.

They’re missing the upwind shade that can slash degrees from a home as its interior constantly exchanges air with its surroundings.

Adding shade and otherwise engineering cooler city neighborhoods has the potential to shave more off air temperatures than the roughly 6 degrees Fahrenheit that Phoenix already has warmed on average in the past century, state climatologist Nancy Selover said.

That figure includes the effects of urban heat retention.

Selover compared recent Phoenix Sky Harbor International Airport readings to early 20th-century readings from downtown Phoenix to calculate the extra 38 days that the city tops 100. Those days are spread throughout a hot season that now starts 21 days earlier, on average, and ends 10 days later in the fall.

Last year’s last 100-degree day was the latest on record: Oct. 27.

Hot nights add to the misery

Corking some of the world’s carbon emissions could lop another several degrees — or even double digits — from the worst future scenarios. Phoenix has its sights on a carbon-neutral future by 2050 and got voter approval for a massive public-transit upgrade, but the city ultimately is at the mercy of global polluters.

“This high-heat season is going to be longer and hotter,” University of Arizona climatologist Gregg Garfin said.

Even without an urban-heat-island effect, he said, central Arizona’s climate has warmed by more than 3 degrees since 1900. Nighttime lows will likely be 5 degrees higher after midcentury.

Thursday morning’s low of 91 degrees beat the last record for the same date by a degree.

“If we can’t cool down, that puts a lot more strain on air-conditioners and on the most vulnerable people — the indigent, homeless, people who don’t have air-conditioning,” Garfin said. “That really amps up the public-health risk.”

Finding the human cost

The risk was readily apparent during the midweek heat spike.

A homeless couple hunkered under the scant shade of a short palm tree Tuesday as the airport-bound light-rail train whisked past on East Washington Street. They awaited the return of a preacher who might give them bus tickets out of the desert.

A woman living on disability in south Phoenix’s Matthew Henson Apartments avoided stepping out for the mail or cigarettes for days and kept her thermostat as high as she could bear to save on her power bill.

A Gilbert woman whose bills kept her from fixing her broken central air-conditioner slept at her son’s house. She toughed out early June by hanging a wet sheet in front of an industrial fan, but gave in and left after continually waking and retching from the heat.

Sharon Harlan, a professor of health sciences and sociology at Northeastern University in Boston, has studied heat and income inequality for 15 years. She and other researchers found that while it is not only warmer in low-income neighborhoods, residents also faced health risks associated with that heat.

“People in poorer, lower-income neighborhoods in the metro area actually have higher rates of death and hospitalization and emergency-room visits caused by heat exposure,” she said.

It’s not just the late-June extremes that vex Arizonans. Spring and fall dangers are trending up.

A 2014 National Climate Assessment, whose Southwest chapter Garfin co-authored, projected about a month more of 100-degree days after midcentury. That’s on top of the month-plus of “summer” that Phoenix already has gained.

The deadly side of summer

It doesn’t take that much to kill. When the Valley sweltered at a record 96 degrees during spring training on March 19, a 75-year-old Sun City woman who declined to attend a ballgame for fear of the heat nonetheless fell and died in her yard.

Carlene Ledyard spent her life serving others. She worked as a registered nurse until she was 55, when she and her husband, Philip, retired and spent nearly two decades volunteering across the continent. They traversed coast to coast, from Mexico to Canada, in an RV, doing everything from helping the homeless to working in gardens to giving away quilts she sewed for the needy. In 2010, the Michigan couple bought a house in Sun City to enjoy their retirement.

She was the third person to die from heat this year in Maricopa County. She was unconscious and badly sunburned on the sidewalk beside her house when her husband and daughter returned from the game and found her.

She lived for two more weeks in intensive care, but her organs had failed after she laid in the sun for hours.

Her family believes she walked a mile to the store to get fresh fruit and fell just short of home on her return trip. They held a memorial in Arizona and one back in Michigan.

“Everybody said she was a very loving and giving person,” Philip said.

‘That’s a lot of trees’

Every inch of the city’s urban infrastructure contributes to local climate change.

“The materials that we use to construct the city and the geometry of the city, compared to the natural landscape, caused heat to be absorbed and retained in the places where people live,” said David Hondula, an ASU senior sustainability scientist.

Hondula and other researchers are examining the different factors that contribute to heat in certain neighborhoods. They are also looking at ways to mitigate the effects of uncomfortable temperatures in everyday life, like improving someone’s walk to the bus stop by adding trees to the route.

Phoenix has an ambitious plan to vastly increase tree cover. Its urban forestry goal is a canopy shading 25 percent of the city’s surface by 2030. That’s more than a doubling of the current urban forest.

“That’s a lot of trees,” ASU urban landscape researcher Ariane Middel said. It’s thousands upon thousands of trees, and most of them are envisioned for private lands. A tree census three years ago placed the publicly owned forest at around 93,000 trees, but those government-maintained lands covered less than 1 percent of the city.

The city and its residents already struggle to replace 1,000 or so trees that gusty storms topple every year.

If Phoenix could achieve 25 percent coverage, though, Middel’s research suggests a major boost in comfort for residents.

She and colleagues in 2014 modeled the difference in temperatures between greener neighborhoods like Encanto or Arcadia and browner expanses in south Phoenix. They modeled micro-climates for a late-June day in a theoretical neighborhood with no trees or grass, in one with 10 percent tree cover and in one with 25 percent canopy coverage.

The neighborhood with 10 percent tree coverage averaged 3.6 degrees cooler than the bare neighborhood. The shadiest neighborhood dropped another 4.3 degrees. It was just a computer model, Middel cautioned, but she expects actual differences probably routinely exceed 5 degrees. “If you go to those old neighborhoods that are flood-irrigated and have those tall trees,” she said, “those are usually cooler.”

The immediate needs

The Intergovernmental Panel on Climate Change models suggest a dramatic worsening of the problem, especially in scenarios where atmospheric accumulation of greenhouse gases continues to accelerate.

In such a case — essentially the status quo in energy use — Phoenix could expect its average summer highs to increase at least 5 degrees after 2050, Garfin said. That’s just a daytime average, and it would translate into much higher spikes on the hottest days, obliterating the city’s all-time high of 122.

“One day at a time,” Whitey Hurst said when explaining his survival strategy as the heat soared toward a record 119 degrees on Tuesday. He was bedded down against a chain-link fence with his wife, Star, under a palm tree on East Washington Street. “I hope the good Lord watches over us.”

He pulled up his shirt to help explain how he became homeless. A double hernia produced a navel bulge the size of a racquetball, and it kept the 50-year-old from his former construction work. Arizona’s medical-assistance program won’t pay for surgery unless the condition is life-threatening, he said.

The couple carried belongings in two shopping carts, including a hibachi grill for use whenever odd jobs or panhandling produce enough cash for them to buy a steak. They stay in the midday heat instead of heading to one of dozens of posted cooling stations because they want to protect their belongings.

They gratefully accepted icy bottles of water when a Salvation Army “Survival Squad” drove up and offered them.

“By the grace of God and your organization,” Hurst said, “we stay alive.”

Must be something happening

A heat wave can wear down even those who are accustomed to them and have safe homes.

J. Lily Keohane spent most of her childhood in the desert with no air-conditioning. But when her unit broke at the beginning of this summer, the heat was so unbearable that the 64-year-old sometimes dry-heaved in the mornings. She felt too hot to eat anything.

Keohane lives in a tidy suburban house in Gilbert. She did not feel cool air breeze through her home for nearly two months while she faced expensive repairs, only able to pay in two-week increments coinciding with her paycheck.

In the meantime, her house filled with the loud roar of box fans, several in every room. On particularly hot nights, Keohane and her two dogs slept on the floor in her downstairs living room, a wet sheet hanging in one of the room’s doorways with a fan pointed at it. Still, she felt sick. As temperatures ticked up, she was often lethargic and depressed, even occasionally confused.

“It’s about survival,” she said. “What can you do to make it cooler?”

When meteorologists predicted record heat for last week, she decamped to her son’s house. The unit was finally repaired on Wednesday.

Scientists can’t pin this heat wave on climate change, though they know that Arizona’s escalating temperatures make events like it ever more likely.

“It’s kind of like if you go to Vegas and you roll a whole series of snake eyes,” ASU climatologist Randy Cerveny said, suggesting loaded dice. “That tells you there must be something weird happening. If you have (new) record highs for years, with not so many record lows, that tells you something is going on with our climate.”

Environmental coverage on azcentral.com and in The Republic is supported by a grant from the Nina Mason Pulliam Charitable Trust.