In May 2022, two German judges, a team of lawyers, scientific experts, and a Peruvian farmer named Saúl Luciano Lliuya stood 4,500 metres up in the Andes, gazing out at a vast blue lake glistening in the sunshine.
Above the water, glaciers towered against a clear sky. You could hear them cracking. Every so often, a flurry of ice and snow tumbled down the mountainside. At that altitude every step hurts a little, and the cold wind cut through our clothes. I was there as a researcher and adviser to Lliuya’s legal team.
We had travelled up a perilous dirt road to Lake Palcacocha, which has grown dramatically as warming temperatures accelerate glacial retreat. Scientists have warned it could overflow, sending a devastating flood wave toward the city of Huaraz, where Lliuya owns a house and some 50,000 people live in the danger zone.
RWE, one of Europe’s largest carbon emitters, has no operations in Peru. Yet it was a legal case against it which had carried the company’s lawyers to this lakeshore. The argument was that climate change makes emitters and affected communities neighbours, regardless of the distance between them.
A neighbourly dispute
How did a Peruvian farmer end up in a German courtroom with a major energy company? In 2014, Lliuya met German climate activists searching for legal tools to hold major polluters accountable.
He knew the glaciers above his home were shrinking, and he understood that the cause lay not locally, but in the emissions of wealthy countries and large corporations. Together, they devised a claim built on nuisance law, a legal principle typically applied in disputes between neighbours over interference with property.
The argument was simple. RWE had contributed an estimated 0.47% of global industrial greenhouse gas emissions since the beginning of industrialisation. Those emissions contributed to global warming and the melting of the glaciers above Huaraz. Therefore, they claimed, RWE should pay 0.47% of the cost of protecting Lliuya’s property from flooding: around USD 20,000. The sum was symbolic. The principle was not.
Filed in 2015, the case was initially dismissed by a lower court. But in November 2017, the higher regional court of Hamm found the claim admissible. The presiding judge posed a question that went beyond the legal matter at hand. In the places in the world where money is scarce, can we leave these people on their own even when we are causing the problem over here? Is that just?
A defeat that changed the law
On 28 May 2025, the court handed down its verdict. Lliuya’s claim was dismissed. The judges concluded that the risk of flooding to his property was not high enough to warrant a legal remedy. But the 139-page ruling told a different story.
For the first time anywhere in the world, a court established that major greenhouse gas emitters can in principle be held liable for their contribution to climate harms. The distance between emitter and affected community was no barrier, and regulatory approvals offered no defence.
The court accepted attribution science – an increasingly important discipline which seeks to link human-caused climate change to extreme weather events and phenomena – as evidence. It found that companies like RWE should have known about climate risks since at least the mid-1960s.
Lliuya lost his case, but the legal reasoning was a landmark. Commentators described the outcome as a “success without victory”.
The mountains are still melting
The principles established in the judgement are now available to courts worldwide. Lliuya’s claim fell short because the assessed risk to his particular property was too low. But countless communities face far more immediate and severe climate impacts. They now have a pathway to hold major emitters accountable.
This matters for the clean energy transition. Climate litigation is emerging as a pressure mechanism that complements policy and market forces, raising the legal and financial cost of continued fossil fuel dependence from below: affected communities in the Global South directing claims at major emitters in the Global North.
The case achieved something beyond its legal outcome. A major emitter was forced to confront the consequences of its business model via a melting glacier. A farmer from the Andes got a voice in a system where he would otherwise have had none. And the precedent will far outlast the individual claim.
One lawsuit will not stop climate change. But by asserting that the world’s largest polluters are neighbours to the communities bearing the brunt of their emissions, Lliuya’s case has changed the legal climate.
The mountains above Huaraz are still melting. The question of who should take responsibility is no longer just political. It is legal.
