When Rutam Vora was growing up in Vadodara, a city of about 2 million people near the western coast of India, his parents kept cool each summer by drenching bedsheets in water and hanging them in the windows of their house. When the scorching westerly wind known as the loo swept in and hit the sheets, the evaporating water absorbed the brunt of the heat. White chalk spread on the roof reflected the sun and dropped the temperature further. They were old methods of coping with the heat, like drinking lassis or chaas when “struck by the loo,” and they were effective.

But the weather, already hot, has been getting hotter. In the summer of 2015, it hit 114 degrees Fahrenheit in nearby Ahmedabad, where Vora works as a correspondent for The Hindu. The next summer, it passed 122 degrees, a record. It’s not uncommon for people to wrap their faces in wet cloth when venturing onto the furnace-like streets, and the wind is so hot it feels heavy. “For about a decade, the temperature has been going up,” Vora said. “But now, the last couple summers have been extreme, going beyond normal, bearable conditions.”

Earlier this year, Vora’s mother came down with a bacterial infection, and part of the doctor’s prescription was to stay cool. When the meteorological department warned of yet another punishing summer on the way, Vora decided it was time to buy an air conditioner.

“The last couple summers have been extreme, going beyond normal, bearable conditions.”

Across India, millions of people are making similar calculations. The share of Indians with air conditioning is still small, roughly 5 percent, but it’s growing fast. Rising incomes are making air conditioners more attainable, while rising temperatures are making them a necessity. “There are hundreds of millions of people for whom air conditioning doesn't seem like a luxury good,” said Michael Greenstone, director of the Energy Policy Institute at the University of Chicago. “It can mean the difference between life and death.”

The cooling industry has found a ready market in Ahmedabad, the largest city in the state of Gujarat. The city bakes each summer until the monsoon comes, at which point temperatures drop into the 90s and the humidity rises to stifling levels. Above the city’s winding streets, crowded with fleets of auto rickshaws and mopeds, billboards declare that every home deserves Hitachi cooling. Elsewhere, Panasonic ads extol the speed at which its “life conditioners” can cool a room. Apartment ads list AC first among amenities offered, and restaurants promise relief from the heat. Appliance shops along the roadside display the industry’s major players in big letters on their windows: Hitachi, Mitsubishi, Blue Star, Panasonic, General — the King of Cool, etched in glass with a crown — Daikin, Carrier.

The world is on track to add 700 million new ACs by 2030, and 1.6 billion by 2050, largely in hot, developing countries like India and Indonesia. But the AC boom threatens to worsen the crisis it’s responding to, and widen the divide between those who can afford to stay cool and those left out in the heat.

Air conditioners use refrigerants, and some of the most common types — hydrofluorocarbons, or HFCs — are powerful greenhouse gases, with thousands of times the warming potential of carbon dioxide. If HFC use continues to grow at its current pace, these chemicals could make up as much as 19 percent of emissions by 2050. International initiatives are set to phase down the worst offenders, but air conditioners contribute to climate change in a second way: they consume a tremendous amount of electricity. Handling the growing load will require adding thousands of new power plants to the grid.

The AC boom threatens to worsen the crisis it’s responding to

Air conditioners may be a double-edged tool, but some way of adapting to the rising heat will have to be found. High temperatures are already interfering with people’s ability to work, making people sick, and outright killing thousands. If heating is considered a basic requirement in Western countries, said Satish Kumar, executive chairman of the New Delhi-based Alliance for an Energy Efficient Economy, it’s time to start thinking about cooling the same way. “We are saying that a basic level of thermal comfort in order to be productive, in order to sit comfortably in your home during the night, it should not be a question. Everybody should have access to that level of comfort.”

Vora recalls the first time his family turned on their AC. His father announced that “from now onwards, the summer has gone from our life.” His mother asked the mechanic what temperature to keep it at to minimize electricity bills. “We survived so many decades, my father, and the people of his age, they would have hardly used AC,” Vora said. “But mine, and I imagine the next generation, they can’t live without it.”

One of the dangerous things about heat is the way it can sneak up on you. We deal with hot days all the time, and generally, they’re uncomfortable at worst. We wear light clothes, stand in the shade, fan ourselves, and commiserate. Our bodies work to stay at around 98.6 degrees: blood vessels dilate to move heat to the skin where it can be radiated into the air. If that’s not enough, we produce sweat, and heat gets absorbed turning it to vapor. But the effects of heat are nonlinear, and the line between discomfort and danger can be hard to detect. When the air becomes hotter than the body, skin stops radiating heat and starts to absorb it. If humidity is high, sweat can’t evaporate into the already saturated air. If you exert yourself, your core temperature will start to climb, and your body will struggle to bring it down.

Discomfort turns into fatigue, nausea, disorientation — symptoms of a fever, which is what it is. Skin turns bright red and sweat pours out as the body’s cooling systems go into overdrive. The heart starts to pound as it struggles to pump thickening blood, muscles spasm, sweat runs dry. At that point, the body is uncontrollably overheating. If its temperature isn’t brought down by ice baths and intravenous fluids, the cells’ mitochondria start to break down, organs fail, and death follows.

Seemingly small increases in global average temperatures hide a crucial shift in the extremes. What were uncomfortably hot days are becoming dangerously hot, dangerously hot days are becoming deadly ones. This shift is already perceptible in India: the mean summer temperature has risen less than a degree since 1960, but heat waves that kill more than a hundred people have become more than twice as likely.

“Our choices now are between bad and terrible.”

By the end of the century, almost half the people on Earth will face deadly heat and humidity for more than 20 days a year, according to a study by Camilo Mora, a researcher at the University of Hawaii. And that’s the best-case scenario, with drastic reductions in carbon emissions. If emissions continue on their current trajectory, three-quarters of humanity will face deadly heat. Regions in the Persian Gulf, Bangladesh, and northeast India may become so hot and humid that, in the words of another recent study, they pass the “upper limit on human survivability,” deadly to anyone who ventures outside for more than a few hours. “Our choices now are between bad and terrible,” Mora said.

For the past century, the best technology we’ve had for coping with heat has been the air conditioner. Air conditioners run refrigerant through coils in a loop. The refrigerant absorbs heat from inside a room as it turns from liquid to gas, then deposits heat outside as it’s condensed into liquid again. Because cooler air holds less moisture, water vapor condenses on the conditioner’s coils, lowering the humidity. (That condensate is the liquid that drops on city-dwellers’ heads in the summer.)

Though primarily thought of as a comfort appliance, ACs also save lives. As air conditioning spread through movie theaters, offices, and homes in the 20th century United States, heat-related deaths plummeted. (Without AC, heat and humidity in places like Florida can quickly become deadly, as became clear when several residents died at a nursing home after Hurricane Irma.) Air conditioning enabled the growth of hot cities like Phoenix and Houston, but it eventually became standard even in temperate regions, finding its way into 87 percent of US homes.

“AC has become a necessity, like a fan.”

Now air conditioning is spreading in India. Indians bought about 5 million room ACs last year, according to Frost and Sullivan, and the market is growing at 10 to 12 percent annually, with some of the more aggressive companies expanding far faster. International vendors are vying for a share of the market. General, a joint venture between Japan’s Fujitsu and the Emirati company ETA, is selling a “hyper tropical” line meant for temperatures up to 125 degrees, which it unveiled with a Bollywood performance. The Japanese company Daikin opened a factory in Rajasthan that’s pumping out half a million units a year and plans to double production. The industry is well aware that rising temperatures are juicing demand. (The tagline for this year’s air-conditioning exhibition in New Delhi was “witness global cooling.”) “Beyond a status symbol, AC has become a necessity, like a fan,” said Gaurav Mehtani, divisional manager at Daikin’s New Delhi office.

For the salesmen and mechanics on the frontlines of the boom, summer can be a grueling time. Sundresh Nambiar has worked in the business for eight years, though he bought his first AC just this summer. (Like Vora, it was out of concern for his parents’ health.) His shop, and the two that sit next to his beneath a pizza place by the side of a busy road, is typical of many in Ahmedabad: a narrow room, fluorescent lit, its walls entirely covered with AC units.

As the temperature climbs, Nambiar’s days grow longer, starting at 7:30AM and stretching past midnight. Customers get irate if their ACs can’t be installed immediately, and sometimes they try to bribe their way to the front of the line. Nambiar proudly said it’s first come, first served, except in cases of medical emergencies. The heat that’s driving sales is brutal to work in: Nambiar’s mechanics drench their clothes in water and spray down their tools to avoid searing their hands. It’s happened to Nambiar before.

Mechanics spray down their tools to avoid searing their hands

Temperatures in Ahmedabad sometimes get so high that older ACs stop functioning, and repairmen like Dinesh Sata have found a lucrative business in keeping them running. “Because of climate change, machines break with overheating,” he said. Five years ago, it was just him and a couple employees. Now he has a staff of 14 and runs them like a fire department, dispatching teams of two as calls come in. In the summer, they work from 7:30 in the morning to 3AM, each duo taking as many as 20 calls a day. They move through the city on mopeds, so as to better weave through Ahmedabad’s snarled traffic. The repairmen, Sata said, “don’t even have time for food — just small snacks.”

Access to cooling falls along class lines, and Sata can read the affluence of a neighborhood by its air conditioners: older, probably secondhand units on one end, brands like Samsung and LG in the middle, and Mitsubishi and General at the top.

The houses of the very wealthiest are lavishly cooled. “I installed one in a kitchen,” Sata said, incredulously. “And in the toilet.” The house, an old mansion owned by diamond dealers, had 29 ACs in total. Most people, of course, have none at all. “The poorer people,” he said, “they are suffering the most.”

Sata himself has no AC, but by choice. His work entails spending long hours in scorching heat, and he’s seen how dependent people become on ACs once they’re exposed to them. “If I get used to AC, I won’t be able to work.”

Sata can read the affluence of a neighborhood by its air conditioners

All the new ACs set to be installed from India to Brazil have added urgency to the race to make them less damaging to the climate. Last year in Kigali, Rwanda, negotiators from 197 countries amended the Montreal Protocol to phase down use of the most potent greenhouse gas refrigerants, a measure that’s projected to avoid almost a degree of warming by 2100. India has until 2028 to start its reductions, but several companies active there have already begun switching to less-damaging chemicals.

Meanwhile, India has begun programs meant to reduce the tremendous energy demand the AC boom will bring. It has a five-star rating system meant to encourage people to purchase more efficient ACs, and the shops in Ahmedabad display the stars with large stickers on each device. Several companies have released lines of 5.8-star ACs. Godrej, a New Delhi-based company, uses climate-friendly, though flammable, propane as a refrigerant; it boasts it’s broken the scale with a six-star AC. In order to drive down the price for consumers, earlier this summer, the Indian government arranged the bulk purchase of 100,000 superefficient ACs from Panasonic and Godrej, and is planning to order half a million more.

Even with increasing efficiency and better refrigerants, however, the energy demand will still be immense. The ACs India alone is expected to install by 2030 will be the equivalent of adding several new midsize countries to the global grid. With air conditioners already accounting for up to 60 percent of the summertime electricity use in cities like New Delhi, simply meeting the demand — and meeting it without burning huge amounts of fossil fuels — will be a challenge. “This AC load should be kind of taken with the same level of seriousness as renewable energy policies are taken,” said Nikit Abhyankar, a researcher at Lawrence Berkeley National Laboratory, pointing out that even incremental improvements in efficiency will greatly reduce energy use.

In Ahmedabad, health officials worry that all the new ACs are pumping heat out into the streets, raising the temperature for anyone who can’t afford an AC of their own. If air conditioners become the only way of dealing with rising temperatures, the same dynamic risks playing out on a global scale.

In late July, on the leafy campus of Ahmedabad’s CEPT University, Professor Rajan Rawal stood outside his lab, drinking chai with his students, sheltering from a monsoon rain that was flooding the city. Tall, with short gray hair and dark mustache, he speaks with patrician weariness about the folly of the world of cooling.

Refrigerated cooling first caught on as a way to preserve food, then to control humidity in factories. Finally it was used to cool people, but, Rawal said, it’s a blunt instrument, and shouldn’t be the only one. “You can’t simply take one pill and cure everything, or just take a fighter jet and win a war. You need various kinds of weapons and various medicines, in same way you need various strategies for buildings.”

Some examples lay strewn about his lab: a segment of brick wall on a wheeled rack, meant to study heat absorption; a model building surrounded by lights on arcing tracks, meant to observe shade as the sun’s position changes; in the basement, a climate-controlled chamber where students sometimes sit to test the effectiveness of various cooling technologies.

Air conditioning is “the modern building’s iron lung”

The proliferation of air conditioning enabled building designs that were wholly dependent on air conditioning. Age-old cooling tricks like courtyards, crossbreeze-promoting corners, eaves, porches, and other architectural features were dispensed with. Developers, eager to capitalize on cheap designs and interior floor space that would’ve been stiflingly hot previously, turned to solid office blocks, glass towers, and boxy, mass-produced tract homes, relying on air conditioning to make them habitable. Air conditioning, writes Gail Cooper in Air-Conditioning America, “was the modern building’s iron lung.”

As India urbanizes, the CEPT team sees an opportunity to take a different path when it comes to cooling, one with a smaller role for the air conditioner. “Do we go the route of the US and Western countries, not worry about efficiency, just whatever provides the cooling?” Yash Shukla, another researcher in Rawal’s program, asked me. “The climate impact of that is significant. If we can find a better approach to have the same level of comfort, why not do it the better way?”

Their research took them somewhere esoteric: thermal comfort standards. When figuring out what sort of HVAC equipment to put in a building, engineers use models that attempt to predict what temperature and humidity levels occupants will be happy with. It’s a necessarily difficult attempt to quantify something subjective. One of the widest-used thermal comfort standards, the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Standard 55, acknowledges thermal comfort is “a condition of mind” before setting out on a valiant effort to model everything from the metabolic rate of someone typing to the insulation factor of calf-length socks.

ASHRAE dictates a comfortable temperature in the range of 67 to 82 degrees, depending on the season and other variables, yet it’s become a widely acknowledged problem that air-conditioned buildings are too cold. Figuring out exactly why — whether the standard is resulting in overpowered AC systems, building managers are overcooling so men can wear suits in summer, or some other reason — is “the holy grail,” in the words of one researcher, and the subject of ongoing research.

There are big gains to be had in raising building temperatures. In 2005, Japan launched an energy-saving initiative called Cool Biz, setting office thermostats at 82 and encouraging workers to forgo ties and heavy business suits. After the 2011 nuclear meltdown, the program became Super Cool Biz: jackets came off, and polos, even aloha shirts were encouraged. If you needed sartorial guidance, Uniqlo published recommendations, and the Environment Ministry sponsored a fashion show where men demonstrated how to pull off a blazer with shorts. By 2010, the latest year for which data is available, Japan estimated that the program cut as much CO2 as almost 4 million households would emit in a month.

The CEPT researchers felt India’s standards needed revising, too. Most of the international comfort standards were developed by institutions in the global north, based largely on surveys of people unaccustomed to India’s heat. “The premise was that occupants in buildings in India are very different from occupants in Europe or the US, which is where the international standards come from,” said Sanyogita Manu, who led the study. “We didn’t have a thermal comfort model of our own.”

“We didn’t have a thermal comfort model of our own.”

Manu traveled to office buildings from humid Chennai in southern India to mountainous Shimla in the Himalayan foothills, wielding monitors to test the temperature, humidity, and airspeed, and asking workers whether they were comfortable.

She found that Indians are indeed comfortable at slightly higher temperatures than existing models would predict, particularly when in buildings that aren’t sealed up and air conditioned. Previous research has shown that in buildings without AC, people are comfortable at higher indoor temperatures the hotter it is outside; they don’t expect refrigerated coolness, they wear lighter clothes, they open windows, they use fans, and their bodies adjust to the heat. The mere feeling of control over things like windows and fans also makes people feel more comfortable, even if the temperature remains the same. The models that reflect this are called “adaptive,” but they’re typically only used for buildings that aren’t air conditioned at all. The CEPT team found that the same phenomenon also applied to mixed-mode buildings — buildings that switch on the AC when it gets hot — and that people were comfortable in environments up to almost 88 degrees. Last year, the Indian government adopted their model in the national building code. It’s expected to reduce energy spent to cool a building by a third.

The expanded threshold opens up new options for cooling. As we walked through the CEPT lab, Rawal pointed out the ceiling tiles: pipes of cold water run through them, emanating cool air downward on the researchers below. Ceiling fans stirred the air, and tower fans were scattered about, available for anyone dissatisfied with the office climate. Clamped to each researcher’s desk was a monitor, testing the temperature, humidity, and airspeed. Nestled in the trees of the campus, positioned to minimize direct sun exposure, and equipped with a suite of various cooling technologies, the building is able to coast without air conditioning until the heat gets extreme. With solar panels on the roof, the building produces more energy than it uses over the course of the year. The air inside felt slightly damp, but cool.

Rawal and his team say buildings like this are the way forward for India, but they’re well aware of the challenges to widespread adoption. Buildings like CEPT’s require bespoke design, whereas air-conditioned buildings can be mass-produced and are cheap to make, if not to keep cool. “You get a bad building, you still buy it because a split AC can make it habitable,” Rawal said. “Hence people are making it because they know you’ll find a way to make it habitable.”

Rawal is particularly intrigued by one technology in particular: the evaporative cooler. It uses far less electricity than an air conditioner, and doesn’t use refrigerants. Instead, a fan blows on a wetted pad, cooling hot air through evaporation. Also known as an air cooler or swamp cooler, it’s an electric version of the drenched sheets Vora’s parents used. One such machine sits in the lab’s thermal comfort chamber, amid fans and thermometers and a sensor-filled manikin dressed in a beige kurti, sitting at a desk.

The world’s largest cooler manufacturer, Symphony, is based in Ahmedabad, in a conspicuously modern concrete building sitting amid trees and empty lots off the highway. Founded in 1988, the company is now worth over a billion dollars and has made its founder and chairman, Achal Bakeri, one of the country’s richest people.

Bakeri, the scion of a prominent real estate family, offers a classic startup origin story for the company’s founding. Home after completing an MBA at the University of Southern California, he was sitting in his parents’ living room when he was struck by the ugliness of their air cooler. “It worked really well, but the product was aesthetically very bad and made a lot of noise,” he said. He took it apart and started learning how it worked. Seeing an opportunity, he put a small team together to design a better version. They set up shop in the parking garage of one of his family’s construction sites and built the first Symphony air cooler. Their first run sold out within a week.

Today, the company is focused on air coolers and air coolers only, and it’s expanding into markets abroad — markets that climate change is helping open. In 2010, Russia was hit by an unprecedented and deadly heat wave, with temperatures in Moscow passing 100 degrees. Soon after, Symphony began getting inquiries from dealers in Russia interested in carrying their products.

“Not even in our wildest of dreams did we consider that a market.”

“Not even in our wildest of dreams did we consider that a market,” said Rajesh Mishra, vice president of sales. “But we realized that heat is relative. In Russia, the moment it touches 35 [95 Fahrenheit] people just go crazy. Four or five years back, temperatures in the UK touched about 27 [80.6 Fahrenheit] and everybody jumped into the lake,” he said, laughing. (He sets his AC to 80 Fahrenheit.) “There were photographs of people stripping off their shirts, jumping in fountains.” Now the UK is buying Symphony coolers, too.

Mishra sees a unique opportunity for Symphony in the extreme and unpredictable heat waves brought on by climate change. Coolers are cheap and use little power, making them affordable to many for whom ACs are out of reach. They’re also relatively easy to set up — you just need to fill them with water and plug them in. In a generally temperate place like Germany, it wouldn't be worth the hassle and expense of installing an AC, Mishra said, but a cooler would be easy to roll out of the closet in the event of a freak heat wave.

The major drawback of coolers is that they don’t work when it’s humid, for the same reason sweating loses its effectiveness. If the air is nearly saturated with moisture already, water won’t evaporate off the pad, the air won’t cool, and the device will function more like fan that makes the room even muggier. But in hot and dry regions, they work very well. In addition to India, Symphony’s core markets are arid countries in the Middle East and Africa. In 2009, they scooped up IMPCO, a Phoenix-based company that has been producing coolers since the 1930s. Its manufacturing facilities in Mexico have opened up new markets in Latin America, and eventually perhaps the American Southwest.

Symphony’s biggest project so far — the biggest air cooler project anywhere so far — is Mecca

Coolers can also do something air conditioners can’t: because they lower the temperature of the air that passes through them, rather than removing heat from a sealed room, they can cool people in huge open spaces and even outdoors. Symphony’s biggest project so far — the biggest air cooler project anywhere so far — is Mecca. In 2006, Symphony installed 200 giant coolers on the Jamarat Bridge, which millions of pilgrims cross each year, and 50,000 units in the residential section, where cooler intakes jut up from each tent like chimneys.

Cavernous factories, warehouses, outdoor restaurants, and amusement parks will be growing markets for coolers, Mishra said, especially as temperatures rise. In 2015, Symphony bought the Chinese cooler company Keruilai, and is now cooling automobile factories and train maintenance yards there. “As the temperature goes up, working conditions will become harsher in factories,” Mishra said. “The demand for air coolers will be enormous.”

Mishra recognizes climate change as a threat, and a business opportunity. “It looks bright!” he said, laughing, when I asked him about the future of the cooling industry. “Because of the changing climate, unfortunately. This is an irreversible process, and now with the great Mr. Donald Trump pulling out of the treaty, things will become even worse,” he said, smiling grimly.

During the summer of 2010, Tejas Shah, a deputy health officer with the Ahmedabad Municipal Corporation, noticed a strange increase in deaths. “Between the 19th of May and 23rd, the number of deaths each day were somewhere around 300, which is three times the normal,” Shah said, sitting at a desk strewn with folders and maps of his jurisdiction. The city first suspected there was an unknown epidemic, but found no outbreaks. Then they checked the temperature. “In these four or five days, the temperature was beyond 45 [113 Fahrenheit]. There was no other obvious reason.”

Despite being among the deadliest natural disasters, heat waves often escape notice. They’re largely invisible when they happen, and leave no wrecked buildings behind. They frequently kill indirectly, by fatally stressing existing health conditions, so their full toll is only evident much later, statistically. And they kill the most vulnerable and overlooked: the elderly or already sick; the socially isolated, who have no one to check in on them; and the working poor, who have to risk laboring in the heat or go without food.

After the 2010 heat wave became apparent, Ahmedabad began formulating a plan for coping with extreme temperatures. Working with the Natural Resource Defense Council, Georgia Tech, and other institutions, Ahmedabad developed an early-warning system and a strategy for mobilizing the city in advance of impending heat waves. Shah is now the coordinating heat officer for the city of five and a half million, in addition to other emergency management duties that result in an unending barrage of calls, texts, and knocks at the door, which he greets with wry forbearance.

When extreme heat is forecast, Shah sends out WhatsApp alerts to health officers, hospital liaisons, the fire department, the police, the parks department, and other officials. Color-coded heat warnings are announced in newspapers, on television, and through social media. Phone companies send out SMS warnings. Social workers go into slums, where these warnings might not reach, and hand out rehydration packets and pamphlets on heat safety. Hospitals prepare ice packs and heat wards, water stations are set up on street corners, and temples, mosques, and malls double as cooling centers. It’s proven effective: in 2015, when heat waves killed over 2,500 people across India, Ahmedabad reported fewer than 20 heat-related deaths. The model is now being copied by Nagpur, Gondia, and 15 other Indian cities.

“If it remains for a month? It would be a natural disaster.”

But rising temperatures will strain the system the city has put in place. While hospitals in Ahmedabad have been building out heat wards, they would run out of space if a heat wave stuck around for long. And while members of the growing air-conditioned class can shelter in cooled offices and homes, the poor must go out to work on construction sites, build roads, and sell wares on baking streets.

“Suppose for a day or two or three the temperature is between 47 and 48 [116–118 Fahrenheit],” said Bhavin Solanki, Ahmedabad’s chief health officer. “We can control the situation. But if it remains for a month?” he said, pausing. “It would be a natural disaster.”

The scale of what cities will need to do to truly adapt to the heat is daunting. Simply waiting for people to get cooling appliances isn’t enough — too many would be left behind. Public health programs like Ahmedabad’s save many lives, but as temperatures rise, more drastic measures will be needed.

The climate researcher Vimal Mishra, who teaches in nearby Gandhinagar, described India’s situation as a race against temperature. He ran through some of the measures needed to beat the heat; as the list grew, it gradually took on the feel of science fiction. People will have to run air conditioners constantly, and new energy sources will have to be built to power them. There will have to be air-conditioned transit because people won’t be able to bike in the sweltering streets. Working hours will have to be shifted to avoid the hottest parts of the day. New buildings will have to be designed that can stay cool with less energy. Maybe, he said, those buildings will have to be prefabricated in cooled warehouses to minimize time spent outdoors. Maybe workers will have to wear personal cooling gear, like the solar-powered cooling hardhats Qatar is experimenting with. Heat kills animals, too, so livestock will have to be brought inside and cooled.

This is the good scenario, one where carbon emissions are curtailed. The other, where temperatures pass the threshold of human survivability, would entail mass migration, or as Jonathan Buzan, a researcher who works with Mishra put it, fantastical infrastructure projects, citing the Isaac Asimov novel The Caves of Steel, where humanity shelters in climate-controlled domes. It’s a tug-of-war, Mishra said, between rising temperatures and our ability to adapt. “Who, will win? Probably, I would go for humans,” he said, optimistic but hedging.

“Who, will win? Probably, I would go for humans.”

Adapting will be expensive. With every degree of warming that gets locked into the climate system, the more it will cost to maintain something resembling normal life, and the more people there will be who are unable to afford it. The particular problem posed by heat isn’t that it’s impossible to adapt to, it’s that it’s difficult to adapt to equitably and in a way that doesn’t make the problem worse. Like mitigating climate change overall, any cooling solution will require collective action, in the form of international agreements like the Kigali Amendment, efficiency regulations, subsidies, technological advances, new building designs, and civic programs.

This year, Ahmedabad added an element to its heat action plan designed not just to cope with extreme heat, but reduce it. A quarter of the city’s population lives in the slums ringing the city, jammed together in small concrete boxes with tin roofs that turn them into solar ovens. The city has begun painting these roofs white, and covering public buildings with reflective white mosaic tiles. It’s a modest adaptation, but it can drop the indoor temperature by several degrees. “The fact is that the gap between the rich people and the poor people is increasing,” Shah said. “It is going to be very difficult. They are going to be more vulnerable, they are going to face more problems.”

Shah has his own list of immediate adaptations the city needs to make. More trees need to be planted, he said, to lower the city’s temperature. There need to be more cooling centers installed, and mass transit should be expanded so all the internal combustion engines stop heating the streets. There will need to be new regulations around working hours for jobs like construction, so laborers don’t die of heatstroke. The city is looking for ways to build awnings that can shade whole intersections, so vendors and traffic police can get shelter from the sun. Piece by mundane piece, through new appliances and public works, the city will have to reconfigure itself to survive in the changing climate.

“It’s going to be hotter,” Shah said. “It’s not getting cooler anymore.”