Raphael ThysExtreme Heat Will Change UsHalf the world could soon face dangerous heat. We measured the daily toll it is already taking.
We visited two cities already transformed by climate change — Kuwait City and Basra, Iraq — to document what billions may experience as human emissions warm the planet.
We visited two cities already transformed by climate change — Kuwait City and Basra, Iraq — to document what billions may experience as human emissions warm the planet.
On a treeless street under a blazing sun, Abbas Abdul Karim, a welder with 25 years experience, labors over a metal bench.
Everyone who lives in Basra, Iraq, reckons with intense heat, but for Abbas it is unrelenting. He must do his work during daylight hours to see the iron he deftly bends into swirls for stair railings or welds into door frames.
The heat is so grueling that he never gets used to it. “I feel it burning into my eyes,” he says.
Working outside in southern Iraq’s scalding summer temperatures isn’t just arduous. It can cause long-term damage to the body.
We know the risk for Abbas, because we measured it.
By late morning, the air around Abbas reached a heat index of 125°F Show Celsius, a measure of heat and humidity. That created a high risk for heat stroke — especially with his heavy clothing and the direct sun.
By late morning, the air around Abbas reached a heat index of 125°F Show Celsius, a measure of heat and humidity. That created a high risk for heat stroke — especially with his heavy clothing and the direct sun.
The body’s struggle to sweat and cool itself can cause dehydration and put extra pressure on the kidneys. Over time, this increases the risk of kidney stones and kidney disease.
The body’s struggle to sweat and cool itself can cause dehydration and put extra pressure on the kidneys. Over time, this increases the risk of kidney stones and kidney disease.
The heart works harder, too, laboring to pump more blood to the skin and carry heat out of the body.
The heart works harder, too, laboring to pump more blood to the skin and carry heat out of the body.
As Abbas worked, our monitor found that his pulse rose, indicating to experts that his body temperature had risen by about three degrees, which puts dangerously high stress on the heart.
As Abbas worked, our monitor found that his pulse rose, indicating to experts that his body temperature had risen by about three degrees, which puts dangerously high stress on the heart.
The blood reaching Abbas’s brain was probably reduced for about an hour, as the blood flow was needed elsewhere. He felt unsteady and had to stop. “It feels like the heat is coming out of my head,” he said.
The blood reaching Abbas’s brain was probably reduced for about an hour, as the blood flow was needed elsewhere. He felt unsteady and had to stop. “It feels like the heat is coming out of my head,” he said.
At these extreme temperatures, normal life is impossible. Ordinary activities can turn dangerous. Work slows. Tempers flare. Power grids fail. Hospitals fill up.
Yet what Abbas was experiencing wasn’t a heatwave. It was just an average August day in Basra, a city on the leading edge of climate change — and a glimpse of the future for much of the planet as human carbon emissions warp the climate.
By 2050, nearly half the world may live in areas that have dangerous levels of heat for at least a month, including Miami, Lagos and Shanghai, according to projections by researchers at Harvard University and the University of Washington.
Just how bad it gets will depend on how much humanity curbs climate change. But some of the far-reaching effects of extreme heat are already inevitable, and they will levy a huge tax on entire societies — their economies, health and way of life.
While people in hot climates can build up tolerance to heat as their bodies become more efficient at staying cool, that can protect them only so much.
We measured heat and humidity for the scenes in this story to broadly show heat exposure. We also recorded other factors that determine physical risk, including sun exposure, wind and exertion. See full methodology
As we tracked the daily activities of people in Basra and Kuwait City, we documented their heat exposure and how it had transformed their lives.
What we saw laid bare the tremendous gap between those who have the means to protect themselves and those who do not. We also saw a still more unsettling reality: No one can escape debilitating heat entirely.
Basra, Iraq’s third-largest city, has always been hot. But in the last few decades, Persian Gulf countries have warmed almost twice as fast as the global average, and more than many other parts of the world. The highest heat index recorded last summer was about 5°F higher than the peak value between 1979 and 1998, researchers at Harvard University estimate.
Now, the worst months of the summer are nearly unlivable.
One evening in August, a man rushed into the emergency room of a city hospital carrying his 8-year-old nephew, Mehdi, a diabetic who had collapsed in the street while playing in the heat.
Within an hour of getting fluids and insulin, Mehdi was half-conscious and appeared stable. But for diabetics, even one severe episode like this can increase the probability of long-term cognitive deficits.
Within an hour of getting fluids and insulin, Mehdi was half-conscious and appeared stable. But for diabetics, even one severe episode like this can increase the probability of long-term cognitive deficits.
Other families crowded into the waiting area with loved ones suffering from heat-related ailments.
Some had painful bites and stings from snakes and scorpions that had crawled into their houses — or even their shoes — to escape the heat.
Others, like this woman, arrived writhing from kidney stones. Chronic dehydration allows the stones to form more easily, a problem made worse by the high levels of salt in Basra’s drinking water.
With the heat disorienting laborers, work accidents were also common, including broken bones, cuts and burns sustained when workers fell from scaffolding or mishandled their tools.
As the crowd grew, relatives of the sick and injured shouted, threatened, pushed and begged the policeman at the door to let them see a doctor.
By the time the doctor in charge went home at 2 a.m., the emergency ward had treated about 200 patients just on his shift, nearly all of them affected by the heat.
Not long after the emergency room doctor finished his shift, the heat roused Kadhim Fadhil Enad from sleep. His family’s air-conditioner had stopped, and he found himself sweating in the dark.
High temperatures would govern the rest of his day. For him and many others in his city, the growing heat has turned workdays and sleep schedules upside down.
When Kadhim, 25, and his brother, Rahda, left for work just after 4 a.m., the air outside was a steam bath, so hot and humid that it felt like 114 degrees.
Kadhim and Radha work in construction as day laborers. In the sweltering summers of southern Iraq, that means racing to finish as much as possible before the sun comes up and ushers in the harshest heat of the day.
Across Basra and the wider Gulf region, people’s lives have been reshaped by the extreme heat.
Even if they can adapt their schedule, as Kadhim has, and start their job in the middle of the night, it is still so hot that exhaustion truncates the workday, reducing productivity and chipping away at earnings.
At a society-wide level, it means every project takes longer to get done.
And it makes doing anything else — from working a second job to going to school — doubly difficult.
Sports and social life start late and end later, meaning that many whose workday begins before dawn struggle with constant sleep deprivation.
The heat also wears on infrastructure, leading to power outages and contaminated water. People get sick. Emergency rooms fill up.
It is not just countries in the Gulf. Extreme heat is altering life across the globe, including in Pakistan, India, Tunisia, Mexico, central China and elsewhere. And the more temperatures rise, the greater the number of workers who will be affected.
Already, the effects of extreme heat add up to hundreds of billions of dollars in lost work each year worldwide.
To survive the heat, Basra residents try to adapt.
The day before, these garbage collectors said, three of their coworkers fainted, and one went to the hospital. All were dehydrated.
One told us he had a headache. Another was dizzy. All three moved as if in slow-motion.
Kadhim returned home around 9 a.m. exhausted and eager to rest in his family’s air-conditioned living room. But as he cooled down, the women in his family began the hottest part of their day.
In the kitchen, his mother, Zainab, cooked a giant pot of chicken and rice for a religious holiday. The room had neither air-conditioning nor a fan, but she and her daughters-in-law still wore traditional long black dresses that kept the heat in.
But Zainab felt obliged to keep cooking for the festival.
“I told my family I did not want to do the cooking this year,” she said. “But they insisted.”
It was 5:30 a.m. in Kuwait City when Abdullah Husain, 36, left his apartment to walk his dogs. The sun had barely risen, but the day was already so sweltering and the air so laden with vapor that it coated his body in a hot film, sticking his clothes to his skin.
In the summer, he said, he has to get the dogs out early, before the asphalt gets so hot that it will burn their paws.
“Everything after sunrise is hell,” he said.
Abdullah, an assistant professor of environmental sciences at Kuwait University, lives a very different life from Kadhim in Basra. But both men’s days are shaped by inexorable heat.
Basra and Kuwait City lie only 80 miles apart and usually have the same weather, with summertime temperatures climbing into the triple digits for weeks on end.
But in other ways, they are worlds apart.
Both places produce oil, but in Kuwait it has produced great wealth and provided citizens with a high standard of living.
This vast economic gap is never clearer than when it comes to how well people can protect themselves from the heat, a divide between rich and poor that is increasingly playing out across the globe.
Abdullah drives to work on broad highways in an air-conditioned car. Kadhim walks to work on streets lined with swiftly rotting garbage.
Abdullah teaches at a heavily air-conditioned university. Even working at night, Kadhim cannot escape his heating world.
Kuwait’s tremendous oil wealth allows it to protect people from the heat — but those protections carry their own cost, crimping culture and lifestyle alike.
People don’t just shop at malls, they walk around them to exercise. Zoo animals live in air-conditioned cages. Children play indoors, rarely touching trees, grass or dirt.
Many Kuwaitis never step outside for longer than it takes to walk to their cars. The rest of life is air-conditioned: where they sleep, exercise, work and socialize.
That affects their health. Despite the abundance of sun, many Kuwaitis suffer from deficiencies of vitamin D, which the body uses sunlight to produce. Many are also overweight.
By the end of the century, Basra, Kuwait City and many other cities will most likely have many more dangerously hot days per year. Just how many depends on what humans do in the meantime.
According to forecasts by researchers at Harvard University, even if humans significantly reduce carbon emissions, by the year 2100, Kuwait City and Basra will experience months of heat and humidity that feel hotter than 103 degrees, far more than they have had in the last decade.
Estimates long into the future are inexact, but scientists agree that the situation will worsen — and could be catastrophic if emissions aren’t reined in. In that scenario, Miami, for instance, could experience dangerous heat for nearly half the year.
Abdullah, the professor, said most Kuwaitis don’t think about the relationship between burning fossil fuels and the heat.
“People complain about it, but it is not something that registers action or a change of behavior,” he said. “They use it to tan or go to the beach, but if it is too hot, they stay home in the air-conditioning.”
And since atmospheric emissions don’t respect borders, Kuwait City and Basra will continue to get hotter regardless of what they do, unless major emitters like the United States and China change course.
For now, Abdullah, like many Kuwaitis, spends his day moving between air-conditioned pockets.
The apartment he shares with two dogs and two cats is filled with plants that would quickly wither outside.
He works out in a sleek gym with exposed piping, a juice bar and glass walls that show the desolation outside. In one direction, a lap pool with no one in it because it is too hot. In another, a grassy golf course, also empty. In yet another, an empty tennis court, baking in the sun.
Abdullah spent 13 years as a student in Oregon, and thinks back on all the people spending time outside walking, fishing and enjoying nature. Kuwait, he said, is a place that is much more resistant to environmentalists. He worries that in insulating themselves from the heat, Kuwaitis have lost touch with the natural world.
“No one really cares about what is outside their door,” he said. “And when it doesn't factor into their thought process, it doesn’t even matter. They don't see it.”
While Kuwaitis with the means can insulate themselves from the heat, their lifestyle depends on a caste system of sorts.
The bulk of the work needed to keep society running is done by low-paid foreign laborers from India, Bangladesh, Egypt and elsewhere. These include gardeners, herders, plumbers, construction workers, airport baggage handlers, air-conditioner repairmen, paramedics, ice cream vendors and trash collectors.
He brings a piece of cardboard to sit on and three frozen water bottles that he holds next to his body to try to keep cool. It doesn’t really work.
“I go home completely finished off,” he said.
Before Abbas, the welder, was born in 1983, Basra was a greener, cooler city.
Expansive groves of date palms softened the temperature, and canals that irrigated Basra’s gardens earned it the nickname "the Venice of the East."
Many of those stately palm groves were being cut down when Abbas was a child, so many fewer remained when Kadhim, the construction worker, was growing up in the early 2000s. But even then, the city was still dotted with tamarisks, hearty shrubs that erupted yearly with pink and white flowers.
“It was a joy to see the street full of tamarisk trees and flowers,” Kadhim said. “Whenever you see green, you feel at peace.”
Now, most of those are gone too.
Without them, Basra has become a drab city of concrete and asphalt, which soaks up the sun and radiates heat long after sundown. Sewage and trash clog Basra’s canals, which now do little to moderate the scorching temperatures.
In the future, many people around the world will migrate to escape the heat. But there will most likely be many others who, like Abbas and Kadhim, lack the resources to make it to a greener country. And richer countries that have already tightened their borders will probably make immigration even more difficult as climate pressures increase.
Methodology
What we measured for this article
To understand the risks of extreme heat to the people in this story:
— We used temperature and humidity monitors to measure the heat index, which captures how hot it feels to the human body.
— We used a thermal camera and an infrared thermometer to capture surface temperatures.
— We asked some of the people we interviewed to wear heart rate monitors as they worked, so we could estimate the changes to their body temperature.
Researchers who study heat stress helped us understand the risks to each person’s health given these measurements and other factors, including sun exposure, wind, clothing and exertion. Climate researchers modeled the number of high heat index days around the world expected in the coming decades.
How we measured heat index
There are a few ways to measure what heat feels like to the human body. We measured the heat index, commonly known as the “feels-like” temperature, which is based on temperature and relative humidity.
While heat index is a commonly used measure of evaluating the risk to humans in certain conditions, other measures can offer more precision. Wet-bulb temperature, which is regularly used in heat-stress studies, takes into account wind speed, cloud cover and sun angle. Some recent research indicates that wet-bulb temperature is a more precise gauge of physiological stress caused by working in the heat than heat index alone.
While it was not practical to record every factor for every location in the story, we did record additional factors for primary subjects working in the heat, including sun exposure, clothing and exertion level. Heat stress researchers reviewed these observations, along with videos of the subjects, to help give us a deeper understanding of the risks they were facing.
To determine the heat index of locations described in this article, we placed a temperature and humidity monitor nearby. The device, a Lascar EL-USB-2-LCD, logged the temperature and relative humidity of the environment every 15 seconds.
The device’s temperature readings have been found to be accurate within ±1°F, and its humidity readings within ±2.25%. The heat index was calculated from those measurements using an equation that has an error margin of ±1.3°F.
We placed the measurement device near each subject in the shade, to avoid artificially high readings from direct sunlight. This may understate the actual risk. The National Weather Service estimates that in direct sunlight, heat index values can be as much as 15 degrees higher.
To account for fluctuations in local humidity, we used a five-minute rolling average of humidity for each heat index value. And because temperature loggers need time to acclimatize when switched between indoor and outdoor areas, we used multiple monitors and kept them dedicated to separate tasks.
In a few instances, we needed to substitute a later heat index measurement from the same location. All of the measurements are within 15 minutes of the time each video was shot.
Heat indexes above 103°F (39°C) are classified as dangerous by the U.S. National Oceanic and Atmospheric Administration, and mean that heat exhaustion is likely and heat stroke is possible with extended exposure. Heat indexes above 125°F (53°C) are categorized as extremely dangerous, meaning that heat stroke is highly likely.
How we measured spot temperatures
To capture thermal video for some of the hottest places in this story, we used a radiometric sensor, a FLIR Lepton 3.5. Instead of capturing visible light, the uncooled sensor calculated surface temperatures by measuring the intensity of longwave infrared signals between 8 µm and 14 µm with a thermal sensitivity less than 50mK.
We soldered a modified USB cable to a PureThermal Mini Pro JST-SR development board, containing the FLIR sensor and an STM32F412 ARM microprocessor, so we could capture thermal video on a Linux laptop. The microprocessor analyzed the incoming images and recorded video using open source firmware and software from GroupGets. The sensor’s frame rate was capped at 8.7 Hz in order to comply with federal regulations.
We measured surface temperatures using a Bosch Infrared Thermometer that had an accuracy of ±1.8°F (1.0°C). We adjusted the thermometer to account for the emissivity of the materials we measured. Environmental factors such as dust or steam, along with the reflectivity of the material being measured, could affect the accuracy of the temperature readings.
How we estimated Abbas’s rise in body temperature
We relied on several methods to estimate that the welder’s body temperature rose by about three degrees as he worked. While the figure is an estimate, several heat stress researchers said the estimate was consistent with data we collected about the welder and his surroundings.
Abbas wore a monitor that measured his heart rate. We monitored the heat, humidity and sunlight exposure in his workspace, as well as the heat given off by his tools. We also observed his heavy clothing, protective equipment, water intake and rest times. And we noted when he said he felt unsteady and needed to take a break.
As he worked, Abbas’s heart rate rose by about 45 beats per minute. Research on heart rate under heat stress suggests such an increase corresponds to a roughly 3 degree rise in core body temperature.
We consulted Andreas D. Flouris, an environmental physiologist at the University of Thessaly in Greece, whose team has performed many field studies into heat stress involving thousands of workers. Dr. Flouris modeled the welder’s core temperature increase using software developed at his laboratory, and he compared our findings with the trends seen in his fieldwork.
Kenzen, the maker of the monitor he wore, also estimated that the welder’s core temperature rose by about 3°F, based on the company’s algorithm, which incorporates weight, fitness levels, environmental temperature, humidity and other factors.
A body temperature rise of roughly 3°F is consistent with all of those methods, Dr. Flouris said.
There are a number of potential sources of error in the estimate, Dr. Flouris and several other researchers said. Unknown medical conditions or variation in sunlight exposure or water intake could throw off the estimates, along with other factors.
Estimating heat in 2050 and 2100
While the future is uncertain, climate scientists widely agree that even in the best-case scenarios — in which humans take dramatic action to lower carbon emissions — days with dangerous levels of heat and humidity are very likely to become more common in much of the world. In many places, they already have.
The forecasts of heat stress shown in this article are by Lucas R. Vargas Zeppetello and Em Murdock at Harvard University and Adrian E. Raftery and David S. Battisti at the University of Washington. The details of this model were described in an article published in Communications Earth & Environment.
Three scenarios are shown, which represent low, median and high estimates of the atmospheric CO2 levels by 2100. These scenarios correspond to increases in the average global temperature of 2.1°C (3.8°F), 3.0°C (5.4°F) and 4.3°C (7.7°F), respectively.
The projections for the number of dangerous days each city will experience in 2050 are based on a global temperature rise of 1.8°C (3.2°F) by 2050. The number of dangerous days is approximate, based on a global dataset with a resolution of approximately 35 square miles. This analysis does not account for local effects, such as cities being hotter than the surrounding rural areas due to human activities.
The 5°F increase in Basra’s highest heat index values is based on ERA5 estimates for 1987 and 2021, and heat index modeling by Lucas Vargas Zeppetello and Em Murdock at Harvard University. Weather station data for Basra between 1979 and 1998 is incomplete, so the ERA5 estimates likely have more uncertainty than other time periods.
Additional sources
— Lucas Vargas Zeppetello, research fellow at Harvard University
— Andreas D. Flouris, an environmental physiologist and associate professor at the University of Thessaly in Greece
— Jason Lee, associate professor at the National University of Singapore, where he is director of the Heat Resilience and Performance Centre
— Dr. Chirag R. Parikh, professor of medicine and director of the nephrology division at Johns Hopkins University School of Medicine
— Matthew J. Levy, associate professor of emergency medicine at the Johns Hopkins School of Medicine, and a former emergency medical technician
— Larry Kenney, professor of physiology and kinesiology at Pennsylvania State University who studies the effects of heat, cold, altitude and dehydration on the human body
— S. Tony Wolf, postdoctoral scholar in kinesiology at Pennsylvania State University
— Lawrence A. Palinkas, professor of social policy and health at the University of Southern California
— Josh Foster, postdoctoral research fellow, Institute for Exercise and Environmental Medicine, University of Texas Southwestern Medical Center
— Daniel R. Brooks, associate professor of epidemiology at Boston University, who studies the effect of heat stress on the development of kidney disease
— Abderrezak Bouchama, chairman of the experimental medicine department at the King Abdullah International Medical Research Center in Riyadh, Saudi Arabia
— Kristie Ebi, professor of environmental, occupational and global health at the University of Washington
— George Havenith, professor of environmental physiology and ergonomics health at Loughborough University, Leicestershire, England
— Barrak Alahmad, research fellow at the Harvard T.H. Chan School of Public Health
— Zeke Hausfather, research scientist at Berkeley Earth
— Jos Lelieveld, director of the Max Planck Institute for Chemistry
— Liz Hanna, Honorary Associate Professor, Fenner School of Environment and Society at the Australian National University
— Zachary J. Schlader, Associate Professor, Department of Kinesiology, School of Public Health, Indiana University
— Stephen Sau-Shing Cheung, professor, kinesiology senior research fellow, Brock University
— Rachel Licker, principal climate scientist, Union of Concerned Scientists