One evening in November, 2021, a group of men assembled at sundown on the terrace of the Ruckomechi Camp, a safari resort on the Zambezi River. Since arriving by private plane, they had gone out lion-spotting, boated down the river, and landed a giant tiger fish; now they were clinking gin-and-tonics. Hippos wallowed in the water below.

The party was led by Renat Heuberger, a forty-four-year-old Swiss entrepreneur with narrow eyes and a cropped copper beard. Heuberger was the chief executive of South Pole, the world’s largest carbon-offsetting firm, and he had come to Zimbabwe to fight off an urgent threat to his company.

A decade earlier, South Pole had signed a deal to sell carbon offsets from an effort to protect a vast swath of forest on the banks of Lake Kariba, upriver from the camp. The Kariba project, spanning an area ten times the size of New York City, was among the world’s first “avoided deforestation” programs; by deterring local people from chopping down trees, it promised to prevent the release of tens of millions of tons of greenhouse gas. Leading corporations, including Volkswagen, Gucci, Nestlé, Porsche, and Delta Air Lines, paid South Pole nearly a hundred million dollars for Kariba credits, allowing them to market goods or services as “carbon neutral.”

South Pole thus pioneered a model of carbon offsetting that has been counted among our best hopes for staving off climate catastrophe: a mechanism that diverts funds from polluters in wealthy countries to protect crucial ecosystems in the Global South. Heuberger, a kinetic, grandiloquent man, speaks expansively about his mission. “We’re here to save the climate,” he told me.

As a child, Heuberger spent his spare time gluing protest flyers to car windows, and he considered himself an activist. But, as he built his company, he had developed a consumer-friendly brand of climate optimism. “It’s not true that to save the climate we will all need to go into perpetual lockdown or stop having fun,” he said, promoting Porsche’s offsetting program. “In fact, it’s the opposite”—drivers should enjoy their vehicles, knowing that “every ton of CO₂ they compensate for is backed by a verified emission reduction.”

This perspective was enthusiastically received: Heuberger had regular speaking engagements at Davos and a spot in the World Economic Forum’s network of experts. As brands scrambled for inexpensive ways to reduce emissions, the market for offsets surged, quadrupling in 2021 alone. That year, South Pole was approaching a billion-dollar valuation, which would make it the world’s first “carbon unicorn.”

But alarming news had reached the company’s headquarters, in Zurich: it was at risk of losing its most lucrative project. By the terms of the Kariba deal, the company purchased carbon credits from a developer who oversaw the area’s forestland, and sold them for a twenty-five-per-cent commission. Now a competitor had offered the developer a substantial payment to take over the project. To help devise a response, Heuberger turned to an old friend from college, Dirk Muench, who had recently joined South Pole. Muench had left Wall Street to support climate action in the world’s poorest places. He was a self-confessed stickler, and could be too fastidious for Heuberger’s taste—but he was a skilled dealmaker.

When Muench heard the details, he was astonished that South Pole had done so little to secure its most important project. The entire agreement rested on a perfunctory contract that the developer, a white Zimbabwean tycoon named Steve Wentzel, could break anytime. To insure Wentzel’s loyalty, Muench urged Heuberger to buy a stake in his business. They flew to Harare and took a chartered plane to the safari camp to conduct the negotiations in style.

Wentzel, a trim, chiselled man with a buzz cut silvering at the sides, was a former show jumper who had made a fortune in offshore finance and then started investing in gold mines. On safari, he confided that he had no expertise in forest preservation; he had tried out carbon offsetting on a whim, when he was given a parcel of land as payment for a debt. (He told me the same story this July. “I don’t know anything,” he said. “I’m not a tree scientist or anything like that.”)

Muench began to feel perturbed. A core principle of carbon offsetting holds that profits should be shared with local people, and South Pole maintains in its promotional literature that “communities living in the Kariba project area are the owners and main beneficiaries.” But, as Wentzel described his indoor horse-riding range in Harare and his varied business interests, Muench wondered how much of the money that corporations spent on Kariba credits made it to the people on the ground.

As Muench probed Wentzel about the workings of his business, Heuberger was abashed. “If you want to survive as a businessman in Zimbabwe, you have to be a little bit of a special character,” he later said. “We need to treat him with a little bit of respect.” Wentzel told me that the inquiries didn’t bother him: “I was, like, Yeah, whatever. As long as I get my end of the deal.” Still, he had no intention of disclosing his financial practices. “You have your ways and means, and they’re not all traceable, put it that way,” he said. “No one actually has a damn clue about what’s going on. Not even South Pole. I hold the key to Pandora’s box.”

As the men sipped their sundowners, Heuberger made Wentzel a striking offer. South Pole would pay about thirty million dollars for almost eight million credits. It would also open negotiations for a multimillion-dollar equity stake in his company, Carbon Green Investments. Wentzel agreed, and the mood on the terrace turned jubilant. Food and wine were ordered, and the celebrations continued by lantern light.

Muench acknowledged that, commercially speaking, the trip had been a “great success,” but he couldn’t shake a sense of unease about South Pole’s work in Zimbabwe. “I realized, O.K., this is a huge money-making machine,” he told me. Back in Zurich, he kept asking questions. “I said, ‘Do you know what happens with the money?’ And then someone told me, ‘Dirk, you should look at the carbon side of this project—not just at the finances—to understand how bad it is.’ ”

The notion of carbon as a fungible commodity, like coffee or cotton, emerged in the late nineteen-eighties. As humanity reckoned with the harms of fossil fuels, a U.S. power company named Applied Energy Services conceived a novel way to reduce emissions: it could surround its main coal-fired power station with a forest, to absorb the carbon billowing from its chimney.

That plan turned out to be implausible. Scientists calculated that, to absorb the carbon the facility would pump out in its life span, the company needed to plant some fifty-two million trees—an impossibility in densely populated Connecticut. Then an executive named Sheryl Sturges had an inspiration: since the atmosphere was a global commons, why not situate the forest elsewhere? The company eventually paid for forty thousand farmers to plant trees in the mountains of Guatemala. It cost just two million dollars—pennies per ton of carbon.

Sturges’s idea caught the world’s attention. “Antidote for a Smokestack,” a headline in Time magazine announced. A decade later, the concept of carbon offsetting was enshrined in international law, as thirty-seven industrialized nations and the European Union agreed to emissions-reduction targets under the Kyoto Protocol. Through the United Nations’ Clean Development Mechanism, rich countries struggling to meet their goals could compensate by paying for projects in impoverished ones.

Growing up in Zurich, Heuberger had been terrified by the environmental calamities that defined the eighties and nineties: Chernobyl, the ozone hole, acid rain. He was a bright, sensitive boy who spent most of his time alone, biking in the mountains and memorizing train timetables. His anxiety about the threats to the planet became “paralyzing,” he told me. When the Kyoto deal was signed, he had recently returned from a year as an exchange student in Indonesia, where he was “completely overwhelmed” by the experience of poverty. The prospect of a global trade in carbon struck him as a panacea—a way of using capitalist methods for radical aims. “Polluter pays, cleaner earns,” he figured. “You could take the tools of the enemy and make them work for a better world.”

Heuberger enrolled to study environmental science at the Swiss Federal Institute of Technology, where he found like-minded peers: young environmentalists who gathered to dream up gambits, from supplying the campus with organic coffee to publishing a magazine about sustainability. Among them was Muench, who was studying industrial engineering. “Renat was a little bit socially awkward, but also genuinely impressive,” he told me. “He was like one of those activist environmentalists, whereas I was a typical business guy.”

In 2002, as they neared the end of their studies, Heuberger, Muench, and a classmate named Patrick Bürgi were invited to a sustainability conference in Costa Rica. Preparing a presentation on carbon trading, Heuberger and Bürgi decided to make the concept more tangible by asking attendees to pay to offset the emissions from their flights. They got hold of a credit-card imprinter and ambushed delegates after each session: “Do you know that you emitted two tons of CO₂ by coming to this conference?” They raised more than ten thousand dollars. “It was quite easy to convince them,” Bürgi said. “And then we started to get nervous—‘What are we going to do with the money?’ ”

In the end, they donated the funds to the university hosting the event, to install solar heaters in place of a diesel boiler that supplied gym showers—an intervention that, by their reckoning, saved around seventy tons of carbon a year. “It was all kind of handmade and improvised,” Bürgi said. “But it was so successful.” Back home, he and Heuberger, along with a few friends, registered a nonprofit named MyClimate to continue offering offsets. (Muench, less confident in the project, left to pursue a career in investment banking.) They set up shop in the office of a supportive professor, launching a rudimentary Web site that allowed people to calculate their emissions and pay the appropriate penance. Carbon “tickets” were printed out and mailed to customers—until the venture became so successful that the professor complained they were using up all his toner.

By the time the Kyoto Protocol was ratified, in 2005, MyClimate was financing significant climate-action projects, including an initiative to supply clean electricity to a hundred Indian villages; it soon won a contract to compensate for emissions from the fifa World Cup in Germany. The founders were still operating on a tiny budget, yet, as the U.N.’s carbon-trading system got under way, they saw new possibilities. In a multibillion-dollar market, perhaps the profit motive would be the most effective way to spur action. “Capitalism works very efficiently,” Heuberger said. “The idea that you could actually make money is a massive driver.” The following year, he and Bürgi left their student venture behind and registered a company with three other friends, with a maxim of “profit for purpose.”

The new business would focus on cultivating projects to sell credits through the U.N. system. The name, South Pole, referred both to Antarctica’s melting ice caps and to the Global South, where most of its projects would be based. Heuberger borrowed twenty thousand francs from his parents for his stake in the business, and the entrepreneurs secured a workspace: a disused university chemistry lab, with long banks of sinks and cannisters of nitrogen that clients sometimes mistook for sequestered carbon. In the summer, they took breaks to swim in the Limmat, and in the winter they skied together.

Their first breakthrough came easily. China had just announced a five-year plan for renewable energy, and developers of wind, solar, and hydropower plants were gathering for the country’s first Carbon Expo. Heuberger called a backpacking buddy who spoke Chinese and asked him to meet in Beijing. They printed business cards with a penguin logo, and scheduled meetings with developers in the lobbies of five-star hotels, though they were sleeping in a youth hostel.

South Pole’s pitch was simple: it would help developers sell credits based on the carbon that would have been emitted if the power they produced had instead come from fossil fuels. The income would be small compared with what they made selling electricity, but it would come at no cost; South Pole would take care of all the complex carbon accounting, in exchange for a commission.

Heuberger’s meetings at the conference led to several large projects, including a sprawling network of hydropower plants in the mountains of southwest China. After that, the company expanded rapidly. The founders scattered across Asia, Africa, and Latin America, signing up hundreds more projects. Soon, South Pole had opened branches in Thailand, Mexico, Indonesia, and India. Staffers, who came to be known as “penguins,” greeted new employees with cries of “Welcome to the iceberg!”

In the years after the Kyoto targets came into effect, thousands of projects were registered under the U.N.’s Clean Development Mechanism, and hundreds of millions of credits were issued, each worth one metric ton of carbon. Yet, as the market grew, so did questions about its integrity. Scholars worried that developers would inflate their projects’ climate impact. Many environmentalists dismissed offsetting as a system of empty indulgences. One online spoof invited unfaithful spouses to pay someone else to remain faithful: “By paying Cheat Neutral, you’re funding monogamy-boosting offset projects.”

At parties in Zurich, South Pole’s founders were grilled about the ethics of the carbon trade. “We were constantly challenged by friends,” Bürgi told me. But Heuberger brushed aside such concerns. If humanity was to have any chance of saving itself, he was convinced, “there must be a positive narrative to climate action.” When skeptics disagreed, he told me, his reaction was “Shut up. Keep it to yourself. Because we are on a mission here.”

In 2009, South Pole attracted its first major investment, from BP. An executive in the oil company’s alternative-energy division, Justin Adams, took a seat on South Pole’s board, and made a close study of Heuberger. “Renat’s a complex character, who I think is extremely strategic and thoughtful about how you can give people some hope in a time of fear,” he told me. “But I suspect, like so many of us, there are deeper shadows in our own psyches. He had all the makings of a little emperor, and he’s incredibly tough.”

The association with a major oil company didn’t trouble Heuberger. “We can talk to the biggest boys in the world,” he said. With the market flourishing, he became increasingly focussed on maximizing revenue. “I want to spin a big wheel,” he told me. “With more money we can have more impact. We can do better, bigger things.”

One day in 2010, an e-mail from Steve Wentzel, the Zimbabwean tycoon, arrived in the in-box of one of South Pole’s founders—a tall, bluff German man named Christian Dannecker. It invited the company to enter new territory.

Wentzel ran a business in Guernsey that promised to “provide financial liberty through modern off shore financial services,” as well as a money-lending enterprise based in Mauritius. He had recently acquired a parcel of woodland from a debtor who had failed to repay a large loan. The surrounding area was thronged with endangered wildlife, but the plot had been devastated by trophy hunting—“If you see a rabbit, it’s a tourist,” Wentzel said. At first, he thought that the land had little use. Then he heard about carbon credits and thought, “Let’s see whether we can recoup our money that way.” He found South Pole through Google.

Dannecker was thrilled. He had a passion for trees, and had often urged Heuberger to consider forest-carbon projects. “It’s bloody tricky, but it needs to work, because otherwise climate finance will not reach those remote corners of the world,” he said.

Dannecker flew to Zimbabwe with a team of experts to assess the possibilities. Wentzel’s land was in the Binga district, south of Lake Kariba, an area threatened by economic turbulence. Zimbabwe was beset by hyperinflation—the South Pole team brought home a trillion-dollar bill as a souvenir—and by mass unemployment. Subsistence farmers were clearing patches of forest to plant crops, graze animals, and gather firewood. Dannecker and Wentzel figured that they could change those habits, largely by providing training in sustainable agriculture, and then sell credits based on the trees that they protected. “It’s the bloody poorest area in the world that I have ever been in,” Dannecker said. “This is where the money should go.”

To secure coöperation in the area, flyers were distributed with cartoons of trees growing in the shape of dollar signs. Wentzel persuaded local chiefs to allow him to expand the project across four large districts, spanning two million acres of forest. In exchange, he promised that seventy per cent of his revenues from the sale of carbon credits would be invested in Kariba and shared with the populace. “They all jumped on the bandwagon,” Wentzel told me.

To Wentzel’s mind, the people living in the forest would be getting money for nothing. “Don’t cut the trees down, that’s about the sum total of what they have to do,” he said. “We don’t ask them to get up in the morning, we don’t ask them to do press-ups, we don’t ask the birds to fly backwards. It is just a net positive for them.”

He set up a company, Carbon Green Investments, to receive the sales proceeds from South Pole, and opened its accounts in the tax haven of Guernsey. “You have to use certain conduits,” he told me. “Ultimately, my goal is to make sure that the project succeeds, and everyone gets the benefit. How it gets there? I’d rather you didn’t ask those questions.”

There is no hope of curbing the worst effects of climate change without saving our remaining forests. Earth’s three trillion trees absorb nearly a third of humanity’s carbon output, yet they continue to be destroyed at an alarming rate, releasing those stores back into the atmosphere. Forest-based offsetting rests on a simple premise: if this carbon payload can be sold, it becomes more lucrative to leave trees standing than to cut them down.

Yet it is extraordinarily difficult to quantify how much carbon these schemes really save. To do so, you must demonstrate that the forest would have been razed without protection—a counterfactual that is nearly impossible to prove. There are also issues of “leakage”: even if the agents of deforestation are driven out of one area, they may cut down trees someplace else. Then there is the question of permanence. Greenhouse gases can linger in the atmosphere for thousands of years—but forests are vulnerable to wildfires and other calamities, and most protection schemes last no more than a few decades. Twenty years after Applied Energy Services funded the Guatemalan tree-planting project, researchers found that it had largely failed. (A.E.S. disputes this.) The enormous amount of land and labor devoted to forestry had led to food shortages, and arguments had broken out; some farmers had simply refused to plant the trees. In the end, the researchers calculated, the program had offset only about ten per cent of the emissions from the coal plant in Connecticut.

The U.N.’s carbon system allowed offsets in a variety of categories, but it excluded forest-carbon projects, because of the particular challenges of verifying their benefits. U.N. officials had deliberated over an assessment framework called redd—“reducing emissions from deforestation and forest degradation in developing countries”—to distinguish the worthwhile forest-carbon projects from the boondoggles. But, from the beginning, there was controversy over the science, and concern over the human cost of a forest-carbon boom. White developers had begun buying up forestland in the Global South, and reports emerged of “carbon cowboys” using violence and trickery to drive Indigenous people from their territories.

Though the U.N. carbon-trading system never implemented the redd framework, it was taken up by a rival source of accreditation: a nonprofit in Washington, D.C., launched by carbon-industry players. The agency, which became known as Verra, had adopted the U.N.’s accounting methodologies, promising to apply them with a lighter touch.

Verra allowed developers to choose among several different ways to calculate the credits that their projects would generate. That alarmed critics, who warned that developers would simply select whatever model yielded the most credits. The agency’s longtime chief executive, an environmental entrepreneur named David Antonioli, acknowledged the problem but told me, “If you require perfection, you’ll have a hundred million dollars’ worth of climate action. If you’re more pragmatic about it, you might have two billion or five billion.”

To register the Kariba project with Verra, South Pole had to predict how much of the forest would be lost without any intervention, and thus determine how much carbon the scheme would conserve over a thirty-year life span. Credits would be issued every year against that total, and the prediction would be checked once a decade, by comparing Kariba with an unguarded reference area nearby. South Pole’s data analysts initially estimated that the program could save around fifty-two million tons of carbon. But Verra required them to rerun these calculations using one of its approved methodologies. The scientists used one named VM9, which generated a startlingly different projection: if the Kariba site was left undefended, deforestation would explode, resulting in the eventual loss of ninety-six per cent of the forest. On that basis, the project would be eligible for almost two hundred million credits—four times the initial estimate.

Wentzel was delighted. At the time, the price of a single credit was about ten euros, suggesting that his cut might amount to hundreds of millions. The project began operating in 2011, opening a patchwork of community gardens and beehives across the site. “This is me on the way to getting this money back,” he said. Then, with shocking abruptness, the carbon market collapsed.

“Iremember watching the price curve in disbelief,” Heuberger told me. “You’d check at 9 a.m., you’d check at 10 a.m., you’d check at 11 a.m., and every time it has fallen another five cents.” By the end of 2012, the price of a single credit, which had peaked at twenty-five euros, had tumbled to thirty-nine cents.

Since the Kyoto Protocol had come into force, the market had been driven by government regulations, which obliged polluters that couldn’t reduce their emissions to buy credits instead. When the financial crisis caused a slump in industrial activity, demand plunged.

Investors’ confidence was further eroded by a series of scandals. Boiler-room scams selling fake offsets had sprung up across Europe, and hackers had penetrated the carbon registries of national governments to siphon off credits. One sprawling fraud, described by French police as “the heist of the century,” had cost tax authorities five billion euros. After it was exposed, the Danish government admitted that eighty per cent of the country’s carbon-trading firms were fronts for the racket.

Even the legitimate programs inspired little confidence. The U.N.’s Clean Development Mechanism had issued more than a billion carbon credits—three-quarters of which researchers later found to be environmentally dubious. Many of the projects were in China, including the sorts of renewable-energy schemes that South Pole was marketing. These plants, critics said, were too profitable to need carbon finance, and the credits they sold gave buyers license to go on polluting. Still more problematic were coolant factories that deliberately increased production of greenhouse gases, then profited by capturing and destroying them.

The greatest blow to the market was the failure of international climate agreements. The U.N.’s Copenhagen summit, in 2009, was supposed to produce new binding emissions limits, but the negotiations collapsed. Three years later, the Kyoto Protocol’s first commitment period skittered to a chaotic end, with almost half the participants having missed their targets and major players refusing to accept new ones. (The U.S. never ratified the agreement.)

“After ten years of believing that governments are lifting up the better world, the plug was out,” Heuberger said. He resolved that the market must be rebuilt, but this time the private sector would have to take the lead. “The U.N. was gone, the governments were gone. We and Verra were still around, so we did it ourselves,” he said. “Of course, it was not perfect. But it was the only show in town.”

Heuberger summoned his team to a seaside resort in Krabi, on the coast of Thailand—a province of white-sand beaches, mangrove forests, and jungle islands. There, he outlined a plan to reposition South Pole. Rather than cater to clients struggling to meet government emissions caps, it would serve the so-called voluntary market—companies who chose to diminish their climate impact, for reasons of ethics or public relations.

Even with the market in retreat, South Pole planned to continue signing up new projects and stockpiling credits. Heuberger was convinced that the demand would soon rebound, and that his company would occupy a position of unchallenged dominance. “Everyone else is dead,” he said. “We are going to come out big here.” As it happened, it would take years for the market to recover, but Heuberger was right that the absence of competition would provide an advantage. South Pole could “very easily contract with project developers, because there were no other buyers,” Hannes Zimmermann, a former corporate-investment director at the company, told me.

As South Pole grew more dominant, some employees felt that it was straying from its purpose. Among the dozens of current and former staffers I spoke to, one quit after being asked to work with a chemical company whose carbon-offsetting proposals seemed to have no climate value. A second resigned after becoming concerned that South Pole was making exaggerated claims about its projects’ benefits for local communities. Others objected to deals with commercial timber companies, which could earn credits by leaving tree plantations standing for a short time before cutting them down. One such scheme, which South Pole told clients would transform “degraded land in rural Mexico by sustainably growing teak trees,” was run by a company that derives more than ninety-seven per cent of its revenues from logging.

Christoph Sutter, who served as the company’s founding C.E.O. before agreeing to share the role with Heuberger, had written a doctoral thesis on assessing the impact of offsetting projects. But, in six years leading South Pole, he had come to doubt the value of the carbon trade, particularly the sort of large renewable-energy projects South Pole was promoting. “I was building up this worry,” he said. “It’s just paper credits.” He told me that he remained friends with Heuberger, but did not share his encompassing faith in offsetting. “The big majority of what you see in the market, in my view, boils down to a lot of greenwashing, a lot of marketing, a lot of money-making,” he said. Heuberger had little patience for that sort of negativity. “Investors can smell it if the mood is not good,” he said. Sutter quietly resigned in 2012.

In the depths of the crash, Wentzel became increasingly disillusioned. His income from credit sales had collapsed, and yet, by his estimate, it cost about sixty thousand dollars a month to pay for his project’s staff and initiatives—community gardens, beehives, wells, fire protection. “I got myself into quite a big hole,” he told me.

Local people were hardly lining up to thank him. In 2014, a community leader named Elmon Mudenda travelled to a Transparency International workshop in Harare and suggested that the Kariba project was a scam. “We have not seen anything really tangible,” he said, according to the Zimbabwe Herald.

The following year, two Zimbabwean researchers travelled to the site to interview residents and published a damning study, “Struggles Over Carbon in the Zambezi Valley.” They reported that the project’s developers believed that “communal resources, including forests and wildlife, are there for the taking.” The district councils, the study found, were “like a sleeping partner, with very little knowledge of what the project is all about and with no voice in its direction.”

As pressure from the community mounted, Wentzel lost patience. One Saturday, he called South Pole and threatened to scrap the whole enterprise. “Carbon is nonsense,” Dannecker recalled him saying. Wentzel demanded a million dollars by Monday to keep the project alive. Heuberger was at a friend’s wedding in Italy when he heard the news. “We made a snap decision to ship the money,” he told me. “Of course, we wanted something against that money. So we just took a few credits.”

In fact, South Pole bought three million credits, at a low price of fifty cents apiece; it bought about the same number the following year. Ordinarily, the company made money by acting as an intermediary, selling credits on behalf of developers and charging a commission. Now it bought the credits directly, meaning that it would keep all the profits when they were sold. Wentzel told me that, after receiving the funds, he drove through the Kariba site, settling his obligations with bundles of cash. “A hundred thousand dollars is only as big as a brick,” he said. “It’s not difficult to carry it around.”

The intervention revived the project. Mudenda, the community leader who had previously criticized Kariba, now praised its beekeeping efforts to a local newspaper; villagers were making four hundred dollars for harvests of organic honey. In 2016, Dannecker flew to Zimbabwe, and blogged about his visit under the heading “Why I Get Out of Bed Every Morning.” The area had undergone a drought, but the project’s wells had provided water, and its farming efforts had yielded food. “Sometimes, the business feels like what it is—a business,” he wrote. “But it’s actually much more: our business has a purpose.”

Yet the company’s business in Zimbabwe rested on a shaky foundation. Project monitors had surveyed the site and found fewer trees than South Pole planned to claim credit for. Then Dannecker learned something even more alarming: the rate of forest loss in the project’s reference region—the benchmark against which its success would be measured—was starkly lower than projected. The wave of deforestation that South Pole’s efforts were supposed to prevent was looking more like a trickle, which could significantly diminish the value of the project.

Dannecker decided not to do anything rash. “There was no urgency, for two reasons,” he told me. First, there were still years to go before South Pole was due to check its model against reality. Second, amid the market slump, “there was no bloody demand” for the Kariba credits anyway. But that was about to change.

One Friday in August, 2018, a small figure in a yellow raincoat shuffled up to the Swedish Parliament in Stockholm and sat down at the foot of the building. Beside her was a sign painted with block letters: “skolstrejk för klimatet.”

Greta Thunberg’s “school strike” represented something rare in an age of futility: an individual act that reverberated around the world. The movement that she inspired, in which millions of children skipped class to demand climate action, gave rise to the biggest environmental protests in history. To Heuberger, himself a former child activist, the fifteen-year-old Swede seemed like a kindred spirit. “Greta Thunberg and the climate strike were of outstanding importance,” he said at the time. “Today, no listed company can afford to be on the sidelines when it comes to climate protection.”

The strike, playing out amid wildfires and increasingly apocalyptic weather, put renewed pressure on the world’s largest companies. South Pole’s business soared. “Going carbon neutral is the latest luxury trend,” the company proclaimed, after Gucci announced that it would use South Pole credits to cancel out the emissions of its supply chain. Nestlé soon declared that Kit Kats and Nespresso pods would become carbon neutral. Porsche assured customers that the emissions from ten thousand miles in a Cayenne could be scrubbed for as little as sixty-seven dollars. “Climate action has to move away from this idea that only completely green people are part of it, the kind of people wearing hemp shirts and walking everywhere,” Heuberger said, in an interview promoting the scheme.

Even after Thunberg denounced offsetting as “a dangerous climate lie,” her movement fuelled the market. JetBlue announced that it would use South Pole credits to help offset the emissions from its U.S. flights. Delta followed with a billion-dollar pledge. Scores of other companies used South Pole offsets toward their net-neutrality claims.

Though South Pole has a portfolio of more than a thousand projects, its partnership with Wentzel proved singularly lucrative—not least because of the credits it had bought directly during the slump, for fifty cents apiece. The sale of these credits provided no additional funding to the project, but the margins for South Pole were huge. Kariba credits would ultimately be worth more than fifteen dollars.

Heuberger liked to say that business was like surfing: you waited for the wave to come, and then you rode it all the way. South Pole launched a major expansion, growing to twelve hundred employees and twenty-nine international offices. To celebrate the opening of its New York branch, it announced that it had made the entire city carbon neutral for one hour. It repeated the trick during the city’s 2019 Climate Week—but this time it claimed that, for the span of one second, it had neutralized the emissions of the entire world.

The carbon market grew sevenfold after the school strike, to two billion dollars a year—but that was still smaller than global sales of nail clippers, or fireworks, or pepper. In September, 2020, a new initiative emerged that promised to radically expand the trade.

The Taskforce on Scaling Voluntary Carbon Markets was a corporate powerhouse, led by Mark Carney, the former head of the Bank of England. It had some four hundred members, including many of the world’s largest suppliers of fossil fuels. Oil companies presented particularly voracious demand; their net-zero pledges required cancelling out several billion tons of carbon a year—far more than the world’s supply of offsets. Carbon credits had typically been sold from a single developer to a single buyer, often with the aid of an intermediary like South Pole. Carney’s vision was to effectively create a stock market for offsets, so that they could be traded with the same speed and ease as any other financial instrument.

By the logic of the markets, such trading would help facilitate funding to environmental projects. In practice, it often diverted funds to speculators. BP and Shell had opened carbon-trading desks, and the Saudi government did, too. Gilles Dufrasne, of the nonprofit Carbon Market Watch, observed that credits could be traded over and over before being used to offset emissions: “When you buy a carbon credit, what is the chance that somewhere in the value chain it was once owned by Shell, and that some of what you pay represents the cut they took?”

When the task force held a promotional event at a U.N. climate summit in Glasgow, Thunberg and other protesters were filmed outside, singing, “You can shove your climate crisis up your arse.” Later, she tweeted an addendum: “I’ve decided to go net-zero on swear words and bad language. In the event that I should say something inappropriate I pledge to compensate that by saying something nice.”

Despite the controversy, South Pole was quick to capitalize on the demand. It made deals with Gazprom and Chevron. TotalEnergies announced that it had delivered its first shipment of “carbon neutral liquefied natural gas” using Kariba credits, and the Dutch provider Greenchoice bought millions more to market its gas as “sustainable.” South Pole’s willingness to do business with energy giants rankled its workforce. The staffers were largely young and idealistic, and many felt that the company was helping the world’s worst polluters repair their image. Heuberger defended the choice: “Why wouldn’t those guys who make gazillions of dollars of profits put a portion of that money into funding climate action?”

The head of South Pole’s sustainable-finance consultancy division, Rebecca Self, was concerned that the company was awarding “Climate Neutral” badges to clients who seemed to be making little meaningful effort to cut their emissions. But, she told me, when she raised these objections, Heuberger accused her of “sounding like an N.G.O.” and “trying to kill the projects.” (Heuberger maintains that he does not recall saying this, but in our conversations he repeatedly condemned environmental nonprofits, complaining about their “destructive all-out bashing” of the carbon market and even suggesting that such organizations are secretly chaos agents funded by the oil industry.) Not long afterward, Self learned that South Pole had helped the Qatar World Cup substantiate a carbon-neutrality claim that excluded most of the emissions from the construction of seven air-conditioned stadiums. She put her concerns in writing and resigned.

South Pole’s growth continued unimpeded, and it acquired five smaller rivals. The founders began selling their own shares to wealthy investors, including the government of Singapore, the Liechtenstein royal family, and Salesforce. A deal with Swisscom secured South Pole’s billion-dollar valuation, though Heuberger told me that he came to regret the status it conferred. “As long as we were a startup, we were everybody’s darling,” he said. “People think if you’re a unicorn you must have made a shitload of money and completely ripped everybody off.” Still, he remained afraid of being outpaced by some fast-growing competitor. “We have to defend our market share,” he reasoned. “Doubling is for losers, because everybody else is tripling.”

When Dirk Muench went to work at South Pole, in May, 2021, it felt like a homecoming. In his early days on Wall Street, he had been enthralled by the “prestige and grandeur,” he told me, but he had come to see all that as “smoke and mirrors.” He had left JPMorgan, studied climate science at Columbia, and eventually reached out to his old roommate Patrick Bürgi. “What I really want to do is try to direct large amounts of capital towards climate projects,” Muench said.

Hired as the head of corporate investments, he rejoined his college friends at the Technopark, a hulking research complex in Zurich that had housed South Pole’s first office. The company now occupied a much grander space there, but the founders still swam together in the river. “Everything felt really good,” Muench told me.

Gradually, though, he realized that South Pole was far less deeply involved than he had believed in the projects it presented as its own. “They have created this image of being a project developer that protects the climate,” he said. “They are nothing of that sort. They are a broker.” Heuberger was hard to recognize as the radical environmentalist he had admired in college. “I started to see that he’s lost,” Muench told me. “If you’re in a business that’s so lucrative, so good, and you’ve gained your power, your status, and your money from that, you do all you can to protect it.”

When Muench went to Zimbabwe to salvage the Kariba project, he returned even more troubled. Asked to perform due diligence on the investment South Pole planned to make in Wentzel’s company, he pulled the records of payments to Kariba and saw that all the money—some forty million dollars—had been wired to a single account in Guernsey. He told Wentzel that he needed evidence of where the funds from that account had gone. But, after six months of e-mails and phone calls and another meeting in Zimbabwe, Wentzel remained evasive. South Pole had hardly any idea what had happened to tens of millions of dollars its clients had spent supposedly offsetting their carbon emissions.

The published project literature outlined what should have happened to that money: Wentzel’s company was to keep thirty per cent, and the rest was to be used to pay district councils, fund project activities, and top up a rainy-day fund. Some of it had clearly been spent on the Kariba site. Along with the farming activities, there were new school huts and clinics, anti-poaching patrols, and fire-suppression measures. But, Muench said, when Wentzel finally sent a spreadsheet of his spending, in the summer of 2022, it accounted for only around six million euros. Even that, he told me, had “no backing, nothing behind it.”

On July 9th, Muench sent an e-mail to Heuberger and other executives, with the subject line “Red Flag.” He reported that, after a long investigation, he could only conclude that most of the funds for the Kariba project had gone astray. In private, he says, he urged Heuberger to admit the problems: “We need to come public before it is in the press.” Heuberger was disinclined to listen to Muench. “He’s very driven—the mind-set is totally on impact,” Heuberger told me. “For him, there’s only good and bad.” South Pole removed Muench from the inquiry into Wentzel’s finances, after which “the relationship and flow of information proved to be more productive again,” the company said. To Heuberger’s mind, the Kariba project was as good as it needed to be: “Is it perfect? Is the guy a hundred per cent? Every dollar always a hundred per cent?” He shrugged. “You have to navigate your way around.”

In September, Wentzel flew to London on business, and I met him for breakfast at a bistro on Sloane Square. He wore designer chinos, Chelsea boots, and a crisp white shirt, but when he greeted me I noticed that he was missing a front tooth.

I had spent hours in two previous encounters questioning Wentzel over the project’s finances. At first, he had reeled off contradictory figures, getting out a calculator and punching the keys before giving up and pushing it away. In the end, he admitted that his inability to account for the money was no accident. “There’s no paper trail,” he told me.

Years of political and economic instability had made it too precarious to bank in Zimbabwe, he said, and transferring money to a sanctioned state from Guernsey was a bureaucratic headache: “Do you know how much compliance I had to go through to just have one transaction?” So he had devised an untraceable way of moving the funds. “It was illegal,” he acknowledged, “but it got looked over.”

When he needed money for the project, he said, he would transfer it from Guernsey into the account of an acquaintance who wanted electronic funds, in “Mauritius or the Cayman Islands or the Seychelles or Russia or wherever,” and they would arrange for the equivalent in U.S. dollars to be delivered to him in Zimbabwe. Other times, he would pay an invoice for someone else—for a consignment of motorbikes, perhaps—and that person would deliver him the same amount in cash.

“This looks really bad, because you’re just sending money here, there, and everywhere, but, on the receiving side, I can show where we’ve got it,” he told me. “Well, I can show you the bundles of cash on the floor.” When payments arrived, he said, he would “grab the money and run with it,” distributing it among the stakeholders in the project. “For any kind of European or American, that’s not comprehensible,” he said. “How many Western people have carried half a million dollars of cash in their hand?”

Wentzel’s demeanor seemed to lighten as he unburdened himself, and he began to stage a mock interrogation. “Can I see the swift?” he boomed, referring to the code that banks use for international payments. “The money got there swiftly, but I can’t tell you what the swift was.” Suddenly his waggish smile gave way to a frown. “I don’t know what you’re going to report on this, and I hope to God it’s not all of it, because I probably will go to jail,” he said. Then he reassured himself. “I’ll go to jail for the right reasons,” he said. “Savior or villain? I’m right in the damned middle. And I’m happy to be that way.”

The Castello di Modanella is a twelfth-century castle whose battlements rise from the Tuscan hills. It claims to have hosted at least two Popes, and Galileo is said to have been banished to its tower after being convicted of heresy. Its stone chambers are now mainly used for gala dinners and, in recent years, for South Pole’s management retreats.

On a warm night in September, 2022, as staffers partied in the gardens, a circle of weary executives, including Heuberger, Dannecker, and Muench, stood in a courtyard. They were reckoning with bad news.

The previous year had marked a decade since Kariba was launched, which meant that South Pole was required by Verra to check its explosive predictions against reality. After months of reviewing satellite imagery, the company’s data analysts had determined that deforestation in the control zone was dramatically lower than projected. They estimated that only fifteen million of the forty-two million carbon credits generated by the project had actually been backed by avoided emissions. All the rest of those supposedly offset tons of carbon simply weren’t real.

Muench and another executive urged Heuberger to stop selling offsets from the Kariba project immediately. “If it comes out that we’ve knowingly sold credits that weren’t equivalent to a ton of CO₂ emissions avoided, it would do huge damage,” Muench said. Heuberger rejected that idea. The credits had been validated by Verra, he argued: “If you want to scale, you have to rely on certain rules and systems.” (South Pole acknowledges that this conversation occurred but says that it took place after the trip to Tuscany.) Back in Zurich, South Pole continued enthusiastically promoting Kariba. In the months after learning of the miscalculation, it sold more than three million environmentally worthless credits, to Porsche, Nestlé, and Nando’s, along with others including the Cannes Film Festival and a network of Australian zoos.

But scrutiny of the market was increasing. Investigations by the Guardian, Bloomberg, and others had highlighted questionable accounting and community abuses by carbon projects. Greenpeace and other nonprofits had published reports denouncing the trade as a dangerous distraction from genuine efforts to reduce reliance on fossil fuels.

One Friday evening that November, a forest-ecology expert named Elias Ayrey posted a satellite image of the Kariba area online. “I find myself quite upset,” he wrote. “I just reviewed a #carbon project that’s likely receiving more than 30x as many credits as it should.” Ayrey, who works for an independent ratings agency called Renoster, had used nasa satellite imagery to calculate that deforestation in the Kariba reference region was significantly lower than the company had stated. He signed off with a disclaimer: “All opinions are my own. And my own opinion is that everyone involved with this project should be arrested.”

Late that night, Heuberger posted a caustic response: “It looks like you really don’t understand how carbon finance works, and your only goal is to criticize and spread fake news.” His phone soon started buzzing with calls from alarmed clients, and four days later the company finally instructed staff to pause the sale of Kariba credits. By then, South Pole had off-loaded twenty-three million credits from the project—eight million more than it could justify.

The mood around the Technopark was tense. One day that fall, Muench sat down next to Heuberger in the open-plan office and said that he was still worried about Kariba. “You sold credits that weren’t real,” he said. “They didn’t have an impact on the climate that you expected, and, on top, you guys took a lot of money.”

Heuberger was enraged, he told me: “He came and said, ‘Renat, you enriched yourself. I demand that you come out and rectify all those omissions transparently. Talk to your investors and your clients and hand them back their money.’ ”

Muench said that Heuberger screamed at him, “Get out! Get out! You know nothing!” But then he followed his old friend into the street and persuaded him not to leave.

In December, South Pole organized an all-hands meeting to quell the staff’s concerns about Kariba—to “build trust around this truly amazing project,” as one executive said. (A recording of the session was shared with me by Follow the Money, an investigative newsroom in the Netherlands.) Christian Dannecker began his talk with a convoluted disquisition on deforestation curves, counterfactual modelling, and the limitations of nasa satellite data in assessing dryland deforestation. Then he took questions.

“Are the Kariba credits based on reality?” one staffer asked.

“I give the question back: What is reality?” Dannecker snapped.

South Pole’s head of U.S. sales tried again: “We have clients coming to us saying, ‘Hey, the credits that you sold us, that impact that we claimed, did that actually happen? Yes or no?’ ”

A public-affairs executive intervened: “Which is why we’re holding the current verification at the moment—because we want to make sure that that is the case.”

“How much profit has South Pole made by selling Kariba credits?” another staffer asked.

“I didn’t do the numbers, to be honest,” Dannecker replied. “I guess we probably made ten million dollars.” There were audible gasps, before another executive warned, “To be clear, we don’t want to repeat that publicly.”

Muench watched the meeting in disbelief. “It was Machiavellian,” he said. “I think, at the end of the day, they started to lie to themselves.” He left the company three days later, after filing a report through its whistle-blower channel. He received a brief response a few weeks later. “An investigation has been completed and we conclude that South Pole were following the approved Verra methodology,” it read. “We are therefore going to close this case.” That month, Verra certified another seven million credits for the Kariba project.

In the absence of a government regulator, Verra had become the primary standard-setter of the voluntary carbon trade. The agency controlled about two-thirds of the market, and nearly half its projects were forest-carbon schemes like Kariba. As the global trade ignited, the scenes inside its head office had been chaotic. “One day we were just bumbling along, and then the next day it was drinking from a fire hose,” Andrew Beauchamp, who worked at Verra for eight years, told me. The chief executive, David Antonioli, a rangy man with an elastic grin, said that developers applied increasing pressure to wave their applications through. “They got pretty worked up,” he said.

For years, Verra had delegated the oversight of projects to outside environmental auditors. (The Kariba project had been reviewed five times, which Heuberger often cited as evidence of careful supervision.) But the auditors were hired and paid by project developers, potentially creating an incentive to ignore concerns. When Verra staff ran “sniff tests” on some of the auditors’ reports, they found scores of serious errors. “There are a lot of us who believe that this resembles an elaborate fraud,” Danny Cullenward, a climate economist at the University of Pennsylvania, told me. Verra allowed credit sellers to claim that they had undergone a robust certification process, “even though every element of that process, when you dig in, is conducted by financially self-interested parties.”

Many observers felt that Verra had an even greater conflict of its own: it charged a fee to certify each credit. “The more credits they issue, the more money they make,” Niklas Kaskeala, a founder of Compensate, a Finnish nonprofit focussed on carbon-market integrity, told me. “It’s structural corruption.” (Verra recently began overseeing auditors more thoroughly, and is working to revise its procedures around forest carbon—but only after verifying more than a billion credits.)

This January, the Guardian ran a story that alleged, on the basis of three scientific studies, that more than ninety per cent of the forest credits Verra had certified were “worthless.” Though Antonioli resigned soon afterward, Verra disputed the report, arguing that most forests protected through its programs are still standing, despite commercial pressures to cut them down. Several independent agencies and academic studies have since concurred that most forest-carbon projects in existence are selling offsets based on vastly inflated claims. By those reckonings, several hundred million tons of carbon that were supposedly offset will linger in the atmosphere for centuries.

As 2023 began, South Pole was struggling to control the damage to its reputation. It had invited clients to visit the Kariba site, and Dannecker had published a blog post presenting the project as a resounding success. Then, in January, a tape of the staff meeting about the project was leaked to Follow the Money. The resulting story ran under the headline “Showcase project by the world’s biggest carbon trader actually resulted in more carbon emissions.”

South Pole responded with a lengthy rebuttal, complaining of “exaggerated and misleading reporting.” Yet its own statements about its profits were tangled. Dannecker had written in his earlier blog post that the company took a twenty-five-per-cent commission on the Kariba-credit sales and sent the remaining forty million euros to Wentzel, for distribution. Now he acknowledged that the company had made far higher margins on the credits it had bought directly, claiming Wentzel had received fifty-seven million euros, from total revenues of more than a hundred million.

Within South Pole, the handling of the Kariba project inspired dismay, and several staffers resigned. The public, too, was increasingly suspicious of the voluntary market. Consumer groups began suing companies for greenwashing, and the European Parliament proposed banning claims of net neutrality based solely on offsetting, after finding that forty per cent of green marketing in the E.U. was “completely unsubstantiated.” Gucci quietly dropped its carbon-neutral claim. Volkswagen, Barclays, L’Oréal, and McKinsey said that they would stop buying offsets from the Kariba project. As the price of carbon credits tumbled, Heuberger was aghast. “This is now a loose cannon—it’s spinning, spinning, spinning,” he said. “We have to stop the feed.”

A few weeks after the details of the all-hands meeting came out, Muench received an e-mail from South Pole’s lawyers, demanding that he present himself for questioning about the leaked tape. He denied being behind the leak, but the investigation struck him as an opportunity to relay his concerns about Kariba. He agreed to meet the lawyers, and sent them detailed written testimony in advance. The lawyers abruptly cancelled the meeting.

Muench said he heard nothing more about the accusations against him. But, when I met Heuberger this summer, he told me that the Kariba controversy had been concocted by his former friend. “It’s very psychological,” he said. “To his frustration, we were more successful than him. And in his mind there was this story created—like, the only reason South Pole is successful is because it’s a weird company. It’s a little bit fishy. We are cheating.” (I first spoke with Muench after Heuberger mentioned the concerns that he’d raised, but he declined to speak publicly. He eventually agreed to do so only after Heuberger continued criticizing him.)

South Pole insists that all the Kariba credits it sold will ultimately be backed by a real emissions reduction: Verra’s methodology allows it to pay back the over-issuance with offsets generated in the future. But several experts, including sources at Verra, told me that this may be impossible, since the drop in deforestation in the reference region will severely limit the project’s eligibility for new credits.

Justin Adams, the former BP executive who had sat on South Pole’s board, told me after first hearing about the controversy that he believed the company was being unfairly maligned. “Have they got all the calls on Kariba right? No. But have they been a net positive force in a world that’s full of darkness right now? Of course they bloody have,” he said. Yet as he learned more he began to lose sympathy. “As a billion Euro company (a fabled unicorn) SP should have had far greater control and audit mechanisms,” he wrote to me. “Certainly they took a lot of risk early on but the rewards in later years look out of whack. More commensurate with an oil and gas concession than an environmental and community development project.”

People in the area suggest that the project’s impact has been minimal. Iain Foulds, a white Zimbabwean farmer who has become an outspoken critic of Kariba, told me, “It’s nothing to do with the environment or safeguarding our flora and fauna. This was about money. Yes, there’s a bit of petty cash filtering in here and there for their little projects. But the big bucks—where’s all that going?” Nevertheless, community leaders are wary of losing whatever benefit they receive. In June, I spoke with Elmon Mudenda, who joined a video call from a dimly lit room, with cracked plaster and peeling paint. His great fear was that the project would be deserted. “At the end of the day, who suffers is the community. Nobody else,” he told me.

The next month, Follow the Money published another story. Reporters had visited the project site, and disaffected locals had shown them a series of abandoned vegetable gardens. The lead author, Ties Gijzel, told me he and his reporting partners had also heard that Wentzel was involved in trophy hunting.

Big-game hunting is legal in Zimbabwe, but South Pole has portrayed the Kariba project as a haven for wildlife, protecting “numerous endangered species such as the African elephant, the lion, the hippopotamus.” When I questioned Wentzel, he acknowledged that trophy hunting occurs across the project area. He had taken control of the sport himself in one region, granting rights to an operator named Dalton & York, whose Instagram page has dozens of images of hunters displaying dead lions, elephants, and crocodiles. In one, a grinning man holds up the carcass of a leopard as blood drips down his forearms. A video shows hippos being shot through the head as they wallow in the Zambezi.

Over the summer, the Zimbabwean government announced plans to centralize control of carbon-trading projects within its borders, and to seize thirty per cent of future profits. Wentzel told me that he didn’t much care what happened to Kariba. “It’s no skin off my nose,” he said. He was already planning a new venture, which he described as “Kariba on steroids.” In his scheme, local women might be employed to stitch car mats for Porsche or to sew beads onto Gucci accessories—though he confessed that neither brand had agreed to the endeavor. He was “struggling to think of something for Nespresso,” he said, but he had been working on a deal to sell driftwood lampshades to an American furniture catalogue. He has already registered the new business in Ireland, under the name Fair Share.

Sylvera, the most prominent of a small group of ratings agencies that are seeking to improve transparency in the carbon market, occupies a plant-filled office in an unassuming building in London. When I visited this June, I was met by the chief executive, Allister Furey, a round-cheeked man in sneakers and a vaguely psychedelic T-shirt.

Furey, a neurobiologist with a Ph.D. in machine learning, worked for a decade in renewable energy before becoming fixated on carbon removal. In order to limit global warming to 1.5 degrees, the U.N. has said, humanity will need to find a way to suck around ten gigatons of carbon a year out of the atmosphere. “The scale of the challenge is so extreme,” Furey told me. “You need to move trillions and trillions of dollars.” Carbon offsetting seemed like a viable source of that kind of funding, so Sylvera was founded in 2020 to stimulate investment by sorting out the good credits from the junk. Since then, using spaceborne radar and satellite imagery, it has estimated that some eighty per cent of the forest-carbon projects it rated were likely over-crediting. “People get paid more for issuing a higher number of credits without going to prison, so there’s a very strong incentive,” Furey said.

Recently, two new initiatives have arisen to encourage higher standards. The Voluntary Carbon Markets Integrity Initiative, launched with backing from the British government, set guidelines to deter corporations from making vacuous claims about the benefits of offsetting. The Integrity Council for the Voluntary Carbon Market, a successor of Mark Carney’s task force, announced a set of “Core Carbon Principles” to assess the quality of existing schemes. “If you build integrity, scale will follow,” Annette Nazareth, the council’s chair, told me. But an analysis by the carbon-data firm Trove Research found that ninety-five per cent of projects on the market would fail to meet these new standards.

Yet offsetting remains central to global plans to reach net zero. The Paris Agreement, signed in 2016, envisaged a new carbon-trading framework—though the details are still being debated seven years later. More than two-thirds of participating countries plan to use offsets to meet their goals, and an alliance of governments and industry figures is lobbying for forest-based projects to be included in the new system.

Experts told me they feared that the same registries they blamed for catastrophic mismanagement of the voluntary market would, by virtue of sheer convenience, end up taking a central role in the U.N. process. Axel Michaelowa, a researcher at the University of Zurich who co-authored several U.N. climate reports, said Verra had been telling officials that, if they used its verification services, “you’ll have a one-stop shop—you don’t have to pay a single cent.” That, he said, “would of course mean that all the shortcomings of these private programs would contaminate the compliance market.”

This November, when world leaders gather in Dubai for the U.N.’s annual climate summit, they will seek agreement on the principles of the new system. To lead the summit, the host country, one of the world’s largest exporters of fossil fuels, has appointed the head of the Abu Dhabi National Oil Company.

One afternoon this July, I met Heuberger at the Technopark. The sky over the city was cobalt blue, and the air felt strikingly clean. We strolled along the Limmat, passing city workers shedding their suits to dive into the water, then turned up a set of dilapidated steps to his house—an unobtrusive cream-colored structure, set into the hillside above the river. When I remarked on its modesty, he nodded. “It was not cheap, but it’s way far away from the villas you can see,” he said, gesturing at the mansions up the hill. Heuberger also has a pied-à-terre near Davos, but he insisted that the allure of business had never really been about money. He saw building his company as a kind of game: “All of us are driven, of course, by winning.”

For the moment, Heuberger was winning his latest fight—what he called the “shitstorm” in the carbon market. He blamed a handful of enemies: Muench, environmental campaigners, oil companies funding secret plots to destroy those seeking to put a price on carbon. As he enumerated these annoyances, he batted his hands in the air, as if swatting gnats. “We are stubborn, whack-a-mole people,” he said. “You can slap us as many times as you want. We always come up.” In recent weeks, Heuberger had been working to “change the narrative.” He had revealed plans to collaborate on carbon-removal projects with Mitsubishi, and had travelled to London for Climate Week, where he joined a panel on preventing misinformation around offsetting. Though his company had spent years awarding its clients badges that proclaimed them “Carbon Neutral,” Heuberger dismissed this designation onstage as “an easy catchphrase.” The times demanded a new approach, he said: “We have to become robust and honest.” To that end, South Pole was launching a new insignia. Its penguin logo would now be encircled with the words “This Company Funds Climate Action.” The announcement was met with cautious applause.

At his house, Heuberger led me through a garden overgrown with lavender and brambles, and into a sparsely furnished living room, where a baby’s play mat was the only splash of color. He has four daughters with his wife, Zani, whom he met in Indonesia while scouting projects for South Pole. Their youngest was born last year. When he talked to his daughters about climate change, he said, he focussed exclusively on messages of empowerment and optimism: “There’s no climate anxiety at all in our house.”

On a deck with sweeping views of the city, Zani was grilling sausages, halloumi, and tempeh kebabs. After dinner, Heuberger sat sipping wine with his feet tucked under him, and grew a little maudlin as he gazed out over the dimming skyline. “We were eating dry bread for many years, happy that we just survived,” he said. “I’m sounding like an old guy now. But I look at those young kids who come with their blockchain-enabled super-transparent solution, and say everything has been shit, what we did. O.K. Calculate Kariba credits. Good luck. It’s not that easy.” In my earlier conversations with Heuberger, he had parried every perceived slight or criticism, but as we kept talking those defenses seemed to slip. He confessed that it had been hard to maintain his positivity. “When you think you have done the right thing, something goes wrong, and somebody says you had bad intentions—that’s the most harmful,” he said. “You have to build a thick wall between you and your true feelings, which are of course depressing.”

He told me he was spending a lot of time cycling these days, on the same battered Titan road bike he had bought with saved-up pocket money as a boy. “I had my beliefs and my convictions and my bicycle,” he recalled fondly. “I was in my own world.” To lift his spirits, he had also taken up the cello again—another childhood pursuit—and started singing lessons. “Except for me, everyone else is a little kid at the class,” he said. In a few weeks, he was due to appear in an amateur opera, a production of “Hansel and Gretel.” Heuberger had been cast as the children’s father—“the bad guy, the weird guy”—who returns triumphantly from a profitable day at the market to find that his children have been abandoned alone in the forest. “He doesn’t really understand,” Heuberger said. “He thinks he’s doing a good thing. But he doesn’t get it at all.”