THE CORDILLERA BLANCA, Peru — Once, this was where Saúl Luciano Lliuya came to find peace. The mountain’s pristine beauty ensured his livelihood as a guide; its steady stream of fresh water sustained his family farm. The everlasting ice that gleamed from its rugged crest spoke of a world in balance.

But on this May morning, Luciano Lliuya surveyed Nevado Palcaraju with his eyes narrowed, his forehead creased. The glacier was almost gone, transformed by rising temperatures from solid ice into a large, unstable lagoon. At any moment, an avalanche or rockslide could cause the turquoise meltwater to surge over its banks, hurtle down the mountainside and deluge the city of Huaraz, where he and some 120,000 others lived.

“Muy pensativo,” Luciano Lliuya described his mood in Spanish. Overthinking. Under pressure.

For seven years, Luciano Lliuya has waged a lawsuit against the German energy company RWE — part of a growing cohort of activists who have turned to the courts for climate justice as political solutions remain out of reach.

Citing scientific studies that link pollution from power plants to the retreat of Palcaraju’s glacier, Luciano Lliuya argues that the energy giant should help pay for measures to prevent a catastrophic flood. The company’s lawyers counter that all of its operations were legal, and that the link between greenhouse gas emissions and climate impacts is too complex for any single entity to be held responsible.

Now the court had come to Peru to collect on-the-ground evidence — a global first for any climate case.

In the next few days, a cadre of German judges and technical experts would walk the streets of Huaraz and view the homes that could be inundated. They would ascend the rutted road to Palcaraju, examining the glacier from the very spot where Luciano Lliuya stood.

If the judges saw this place the way he saw it, if they were convinced by Luciano Lliuya’s claims, it would mark a breakthrough in the burgeoning realm of climate litigation. Success in Huaraz would mean that major polluters anywhere may be liable for the increasingly disastrous consequences of greenhouse gas emissions, experts say. It could pave the way for more lawsuits from developing nations that did little to cause climate change, but are bearing the brunt of its impacts. It might force rich countries and giant corporations to reconsider the risks of relying on fossil fuels, and empower those on the front lines of warming to seek restitution for what they have lost.

Luciano Lliuya looked again across the water, where the remains of Palcaraju glacier still clung to the cliffs above the lagoon. So much depended on that precarious balance: His livelihood. His home. Possibly even the planet.

Then there was a low rumble, and a puff of white billowed from the top of the glacier — an avalanche. It was minor, not powerful enough to even ruffle the surface of the lake. But the worry in Luciano Lliuya’s eyes deepened.

“Vámonos,” he said. “Let’s go.”

‘A flood that destroys everything’

In the cooler climate of a bygone era, the Palcaraju glacier resembled a river of ice. It flowed inexorably from the mountain’s crest, gouging a bowl-shaped basin out of the rock and pushing debris into a rubble pile called a moraine.

But as the planet warms, the glacier is retreating. A vast lake, dubbed Palcacocha, has formed in the empty basin. The moraine acts as a dam, stopping the water from spilling into the valley below.

For now.

An avalanche could touch off a disaster, according to a 2016 study that modeled how a glacial lake outburst flood at Laguna Palcacocha might unfold.

Rock and ice would tumble from the deteriorating glacier and weakened mountain slope, falling hundreds of feet before plunging into the deepest part of the lagoon.

The impact would send a massive wave rolling toward the opposite shore. As it reached shallower waters, the wave would grow taller, much the way a tsunami gets bigger as it approaches a beach.

By the time it crossed the lagoon, the wave from a large avalanche would loom 70 feet above the top of the moraine. Nearly 2 million cubic meters of water would go crashing down the mountainside. Soil, boulders and even trees would get mixed up in the flood, adding to its tremendous force. Within an hour, the torrent would arrive at the outskirts of Huaraz.

Some 50,000 people, including Luciano Lliuya, live in the high hazard zone on the banks of the Quilcay River. Here, the inundation would be intense enough to demolish the small brick and adobe homes.

“We are speaking about a flood that destroys everything” said Cesar Portocarrero, 75, a civil engineer from Huaraz who contributed to the 2016 study. “Not only inundates. Not only covers with water. It destroys everything in its path.”

A newly installed early warning system at the lagoon should set off sirens around the city, giving people about 20 minutes to evacuate. Anyone who doesn’t escape before the deluge hits would be unlikely to survive.

Those who make their homes near the Cordillera Blanca, the ice-capped “white range” that looms above Huaraz, have always recognized this risk. To dwell in the shadow of Peru’s tallest mountains is to live with the possibility of disaster. The region boasts Earth’s largest concentration of tropical glaciers — high-altitude ice masses that are unpredictable at the best of times, but have become increasingly fragile as the planet warms.

In 1941, a glacial lake outburst flood from Palcacocha killed an estimated 1,800 people — about one third of Huaraz’s residents at the time. Survivors recall seeing trees slam into houses like battering rams, blasting holes in walls of brick and stone. The path of destruction extended all the way to the coast, 100 miles away.

A few years later, a flood above the nearby archaeological site of Chavín de Huántar killed 500 people and demolished millennia-old artifacts. Then another outburst wiped out a newly built hydroelectric station. In 1970, an earthquake destabilized the glacier on Peru’s tallest mountain, unleashing an avalanche that engulfed the entire city of Yungay. Some 20,000 people were buried. Just 400 residents survived.

The crises helped push Peru’s government to establish a federal glaciology unit that would shore up the country’s most dangerous glacial lakes.

“We were the pioneers in the world,” said Portocarrero, a former director of the unit who helped build the security system at Laguna Palcacocha in 1973.

Portocarrero described how workers dug drainage channels to empty some of the water from the lagoon and bolstered the moraine with two 20-foot-high stone-covered dams. By creating about 25 feet of “freeboard” between the water surface and the top of the dam, the measures reduced the chance of an overflow.

As decades passed without another deadly outburst, disasters like the 1941 flood faded into distant memory. In 1996, during a period of “decentralization,” Peru disbanded its federal glaciology unit. Its responsibilities were shifted to the regional governments, though they rarely had the resources or expertise to address dangerous lakes.

At the time, few in Huaraz worried about the change. They believed that Palcacocha was already under control. They thought they were safe.

Loss and damage

In 2009, scientists working on a new underwater map of Laguna Palcacocha made a terrifying discovery: Since the security system was first installed, the lake had swelled to 34 times its former volume. It was now even bigger than it had been before the 1941 disaster.

Although the drainage system prevented the water level from rising too high, the glacier’s retreat allowed the lagoon to become much longer, creating potential runway for a massive wave. If a major avalanche occurred, the dams would not be able to hold back the swollen lake.

Peru’s president declared a state of emergency at the lagoon. The regional government built several large plastic pipes to siphon off extra water, lowering the surface level by less than 15 feet. Official “guardians” were paid to live on the mountain and monitor the lake around the clock, and an early warning system was installed to enable evacuations of the communities below. A new road — rugged but navigable — allowed for more frequent checks on the growing hazard.

Luciano Lliuya was not assuaged.

His neighborhood, Nueva Florida, had been wrecked during the 1941 flood. Afterward, officials wanted to prevent people from rebuilding there, arguing it was unsafe. But they could not stop a surge of impoverished settlers — including Luciano Lliuya’s parents — who came from the countryside in search of the jobs a city could provide. Now there were more people than ever living in harm’s way, many of them in informal houses constructed without regard for building codes.

Living in Huaraz allowed Luciano Lliuya to attend school and enroll in a rigorous training program to become a certified mountain guide. It meant he could earn enough to send his son to college and renovate the house his parents had constructed.

But at any moment, Luciano Lliuya knew, another flood could hit, obliterating the life he’d built.

Luciano Lliuya was just as anxious about the slow-motion disasters of heat and drought, which threatened his guiding business and the small family farm where he still cultivated corn, potatoes and wheat. The shimmering ice that gave the Cordillera Blanca its name grew more unstable with each passing season. The land that had yielded an abundant harvest for his parents was becoming parched and meager.

“I am really worried,” he said. “As a guide, as a farmer and as a citizen.”

Portocarrero shared Luciano Lliuya’s concerns. In 2016 the engineer came out of retirement to help draft a proposal to partially drain the Palcacocha lagoon. For about $4 million, he said, officials could reinforce the dam, lower the lake level by an additional 65 feet and redirect the water into a secure reservoir that would supply the area’s people and farms. Studies showed that the project would curb the risk of an outburst and almost halve the size of the high-hazard zone if a flood did occur.

But officials in the Ancash regional government said they didn’t have the funds for such an ambitious project. Melvin Grimaldo Rodriguez Minchola, its director of natural resources and environmental management, detailed the area’s many other problems: A struggling economy, deteriorating roads, poor and ailing citizens. Not to mention the climate-induced crises of drought, forest loss and at least 50 other potentially dangerous glacial lakes in the Cordillera Blanca.

“We have just a few resources to deal with all these challenges,” Rodriguez Minchola said in a recent interview at his office in Huaraz. “We are handling [the flood risk] as best we can.”

Portocarrero questioned that claim. Ancash’s gold, copper and zinc mines make it one of Peru’s wealthiest regions. The government could invest in the project if it wanted, he said — but corruption, dysfunction and decentralization have gotten in the way.

Yet he and Rodriguez Minchola agreed on one thing: It seemed fundamentally unfair that those least responsible for the climate crisis were forced to cope with its worst impacts on their own.

Peru contributed less than 0.4 percent of the world’s greenhouse gas emissions in 2019, yet it consistently ranks among the nations at high risk from climate damages. The country’s glaciers have lost about half of their surface area in the last half century. Tens of thousands of people have been displaced by extreme rainfall amplified by warming. Rising temperatures have brought agricultural pests to ever higher elevations, imperiling crops that rural communities need to survive.

And because countries like Peru didn’t become rich from burning fossil fuels over the last 150 years, they have few resources to cope with the dangers they now face. They struggle to implement measures, such as the Palcacocha drainage project, that could save lives and livelihoods. If tragedy does occur — a drought destroys an entire year’s harvest, a flood devastates a city — they are less able to recover.

At international climate talks, low-income countries have sought help for adaptation and “loss and damage” — the unavoidable, irreversible harms caused by climate change — even as they push major emitters to curb their pollution.

It’s been an uphill battle on all fronts. Money available through U.N.-administered funds, which depend on donations, is dwarfed by the scale of developing nations’ need. Wealthy countries including the United States have resisted any kind of financial commitment to assist with loss and damage, worried that it would imply legal liability for climate change’s escalating toll.

Meanwhile, global emissions keep rising, and the impacts only grow worse.

Luciano Lliuya often wondered if those responsible for warming the planet would ever be held accountable for the consequences. The big emitters had all the wealth and power, while the people suffering the most from climate disasters possessed only the moral high ground.

“Imagine the Peruvian government making demands of Germany,” he said. “That would be so crazy.”

And a single Peruvian trying to demand change? That would be even more crazy, he said. Practically impossible.

‘Justice heard the mountains crying’

A group of German strangers sat in Luciano Lliuya’s kitchen, eating a meal of home-cooked guinea pig and homegrown potatoes, asking him to contemplate the impossible.

It was December 2014. In the wake of a lackluster U.N. climate summit in Lima, activists from the environmental nonprofit Germanwatch had traveled to the Cordillera Blanca in hopes of witnessing the effects of global warming firsthand.

A colleague introduced them to Luciano Lliuya, and it quickly became clear he was the kind of man they were looking for.

For several years, Germanwatch policy director Christoph Bals had been contemplating filing a nuisance claim on behalf of a climate change victim — the same kind of lawsuit a homeowner might file if his neighbor’s tree fell on his house. The tactic had been tried before, without much success. But an emerging field of research known as “attribution science” was helping pinpoint exactly how human greenhouse gas emissions contributed to specific climate disasters, providing a whole new kind of evidence. With the right plaintiff, Bals thought, perhaps their case could set a precedent for using attribution studies to hold polluters accountable.

Bals was deeply impressed by Luciano Lliuya — his humility and moral clarity, his commitment to protecting his home. And the attribution research linking the threat from Palcacocha to planet-warming pollution was strong.

Luciano Lliuya wasn’t so certain. A lawsuit would require years of effort and long stretches of time away from his family. It would invite the scrutiny of politicians, journalists and lawyers. Was he ready for all that travel and attention? And even if he was, would a German court care about the concerns of a man from half a world away?

But then Luciano Lliuya thought about the mountains he loved. If those peaks were people, he reflected, surely they would want to defend themselves. If they could speak, they would ask the world act.

This was an opportunity to tell the mountains’ story, he told himself. “To do nothing would be irresponsible.”

Finally, Luciano Lliuya spoke. “Claro,” he said. “Sure.”

Bals was thrilled. “We’re going to court!”

To represent Luciano Lliuya, Germanwatch tapped Roda Verheyen, a prominent environmental lawyer. Then the group had to choose a target for the lawsuit — an entity that had benefited from burning fossil fuels, but was not paying for the consequences.

It consulted an analysis tracing the majority of greenhouse gases in the atmosphere back to 90 fossil fuel, energy and cement producers, dubbed “the carbon majors.” RWE was among the top investor-owned companies on the list, its mines and power stations responsible for 0.47 percent of all emissions produced by people in the industrial era.

Suing RWE also meant the case would unfold in German courts. While almost all legal systems allow a homeowner to sue his neighbors if their behavior harms his property, German judges have interpreted this rule especially broadly, defining a “neighborhood” to extend as far as potential harm can reach.

In the context of greenhouse gas pollution, Verheyen planned to argue, RWE’s “neighborhood” encompassed the whole world.

In November 2015, Luciano Lliuya filed his claim with the district court of Essen, home to RWE headquarters. The demand was modest: The lawsuit asked the firm to pay roughly $20,000, about 0.47 percent of the cost of the Palcacocha drainage project — commensurate with the company’s contribution to global emissions.

But its true ambitions were much more sweeping, Verheyen explained. If major emitters begin to fear that they will be held liable for climate damages anywhere in the world, she said, they may adopt more sustainable practices rather than face an onslaught of lawsuits. Similarly, wealthy countries may be more willing to pay for adaptation and loss and damage if the alternative meant fighting in court.

“When you must actually take responsibility for your [past] actions,” she said, “you will also change what you do right now.”

The stakes for RWE and other “carbon majors” were made clear when a judge suggested that the company might settle the case out of court. The company’s lawyers rejected the proposal, saying it was a matter of precedent.

Instead, RWE has sought to have Luciano Lliuya’s claim dismissed.

“It is still our position individual emitters cannot be held liable for universally rooted and globally effective processes like climate change,” RWE media relations manager Regina Wolter said in a statement. She pointed out that RWE has already committed to become carbon neutral by 2040 and has invested billions in renewable energy development.

Citing a report from the U.N. Intergovernmental Panel on Climate Change, a 2016 filing from the company also alleges that “climate change is not caused by humans alone.”

In fact, the IPCC report stated that “human influence on the climate system is clear” and greenhouse gas emissions are “extremely likely to have been the dominant cause of the observed warming since the mid-20th century.” In a more recent report, the panel stated “unequivocally” that humans are fueling climate change.

The district court in Essen at first sided with RWE, ruling that Luciano Lliuya’s claim was invalid because he couldn’t prove that the company’s emissions had directly contributed to the threat from Laguna Palcacocha. Luciano Lliuya’s team appealed, and the case came before a three-judge panel in the upper state court of Hamm.

Verheyen recalled sitting in the courtroom in November 2017, heart racing as she awaited the judges’ ruling.

The case would move forward into the evidence-collecting phase, the panel decided. The next step was to determine whether Luciano Lliuya’s property was truly in danger, whether that threat could be traced to greenhouse gas emissions and what fraction of planet-warming pollution RWE was responsible for.

Verheyen looked over at Luciano Lliuya, who listened uncomprehending to the slew of German words. “Todo va bien, todo va bien,” she reassured him in Spanish. “It’s all going well.”

Only after they left the courtroom could Verheyen fully explain the significance of what had happened: In accepting Luciano Lliuya’s case, the court had embraced the argument that major greenhouse gas emitters can be held liable for the consequences of global warming. Even if the evidentiary phase didn’t go as hoped, a new precedent had been set, one that could lead to other lawsuits from climate change victims across the globe.

Luciano Lliuya smiled.

“The lakes are the tears of the mountains,” he said. “Today, justice heard the mountains crying.”

A new precedent

The shores of Laguna Palcacocha were swarming with people — judges, lawyers, scientists, politicians — the sounds of the wind and water drowned out by the babble of multiple languages and the buzz of a drone.

Luciano Lliuya never imagined the case would come this far. First his legal team and RWE’s couldn’t agree on experts to assess the evidence, so the court had to appoint its own. Then the coronavirus pandemic prevented anyone from traveling to Peru.

Now the court was finally here, and Luciano Lliuya was exhausted. Every day he bounced between hearings and interviews. The near-constant conversation left his mind weary and his throat parched. Camera crews trailed him around Huaraz while children shouted at journalists from their windows, “Periodista, periodista, interview me!”

Meanwhile, his neighbors resented the attention he’d brought to Nueva Florida. Who was he, they asked, to call their homes unsafe?

Luciano Lliuya craved the soothing silence of having this mountaintop all to himself.

And he worried about what was to come. “How will the company react if we win?” he asked. “It’s a huge company. … I think they may not be happy.”

RWE could still appeal a decision in Luciano Lliuya’s favor. That would mean more travel, more courtrooms, more interviews. Even if the company was forced to pay, there was no guarantee that the enhanced security system at Palcacocha would ever get built.

But as he watched the crowd survey the landscape he knew so well, another emotion bloomed in Luciano Lliuya’s chest: Pride.

“I brought all those people from abroad to show them what’s really happening here — the risk and the glacier retreat,” he said. “They have the information and the evidence to understand the problem. And maybe they will change their minds.”

It would be many months before the court-appointed experts completed their assessment of the threat to Huaraz. The judges in Hamm aren’t expected to make a ruling until at least 2023.

Yet, Luciano Lliuya felt his case was strong and continues to get stronger. An attribution study published in the journal Nature Geoscience in 2021 found that the Palcaraju glacier’s retreat and Laguna Palcacocha’s resulting expansion would be virtually impossible in a world without climate change. The imminent threat to Huaraz is a “direct consequence” of human-caused warming, the authors wrote.

The outlook for climate litigation was also shifting. Since Luciano Lliuya first filed his claim, more than 2,000 other climate lawsuits have been launched against companies and governments around the world, according to an analysis by the Grantham Institute for Climate Change and the Environment at Imperial College London. Of the cases that have been decided, more than half led to positive outcomes for climate. Last year alone, a Dutch court ruled that the oil giant Shell had to dramatically boost its climate commitments, the French state was convicted of failing to curb greenhouse gases and the German Supreme Court decided that the country was constitutionally obligated to “do its part” to avoid catastrophic warming.

“These precedents build on one another,” said Carol Muffett, president of the Washington-based Center for International Environmental Law. “Each progressive decision brings us one step closer to accountability.”

If other climate change victims draw on this precedent to file their own lawsuits, “that’s when Saúl Luciano Lliuya’s story becomes truly important,” Muffett continued. “He is one man from one community in a remote part of Peru. But his story is like a billion other stories on this planet.”

Even in Huaraz, it seemed that change was underway. That spring, the Ancash Regional Government issued a statement in support of Luciano Lliuya’s lawsuit. His picture was splashed across the front page of the local newspaper.

Luciana Olaza La Rosa, a nature-loving 16-year-old who had once taken an English class with Luciano Lliuya, was astonished to see someone she knew at the center of a globally important case.

“I didn’t know people like him could do these kinds of judgments,” she said. “I only thought, like, big companies can fight with other companies about these issues.”

If her soft-spoken former classmate could take a major corporation to court, the teenager thought, what could she do? Could she convince her school to reduce its emissions? Could she combat trash on the mountain biking paths where she rode every weekend? Could she make a difference in Huaraz, in Peru, in the world?

“It gives me, I think, power, or something like that,” Olaza La Rosa said. “It gives me the power of saying, ‘You too, having only 16 years, you can do big things if you want.’ ”

Witness

Luciano Lliuya stood at his farm amid the mountains, pulling up the stalks of dried-out corn. Occasionally, he lifted a stalk to his mouth, peeled it with his teeth and sucked the sweet, rich juice from its marrow.

The air was thick with the scents of grass and mint and manure. A creek burbled, insects sang.

Then Luciano Lliuya’s phone buzzed, reminding him that a camera crew was on its way.

He had come to terms with his loss of tranquility. “I believe I am like a witness,” he said. “Because I see the mountains and what’s happening to them. And I share what is going on.”

What other choice was there? If the world remains on its current warming track, the glaciers of the Cordillera Blanca will disappear by the end of the century. The people of Peru may face conditions so hot and humid that parts of the country become uninhabitable. Poor communities around the globe will be devastated by hunger, disaster and disease.

Luciano Lliuya trudged back to his house, poured a cup of coffee, and readied himself for the next interview. He would keep telling his story as long as someone would listen. He would keep fighting for the glacier as long as it still clung to the cliffs of Palcaraju — threatening disaster, asking to be saved.