A Peruvian farmer’s home is in “concrete danger” from climate change, a court has heard, in the resumption of a decade-long legal battle to get German coal giant RWE to contribute to flood defences in the Andes.

Lawyers for Saúl Luciano Lliuya, who say his home is threatened by rapidly melting glaciers, told the upper regional court in Hamm on Wednesday that the risk of extreme flooding represented a breach of civil law.

Lliuya filed a case in 2015 against RWE, one of the world’s biggest greenhouse gas polluters but which has never operated in Peru.

The case was thrown out by a lower court in Essen but, on appeal in 2017, a court in Hamm found the case to be “admissible”, potentially opening the door for fossil fuel companies to be held liable in civil courts for global harms.

“This case is just the beginning,” said Roda Verheyen, Lliuya’s lawyer. “It’s a trampoline for similar cases.”

The case against RWE, which has dragged out over several years because of bureaucracy and the coronavirus pandemic, highlights a key difficulty in legal efforts to attribute personal harm to carbon pollution.

The judges heard differing evaluations of the chance of climate-fuelled floods hitting Lliuya’s home in the Andean town of Huaraz, large parts of which were wiped out in 1941 when Lake Palcacocha overflowed and triggered floods that killed thousands.

Scientists have established that the pollution from burning fossil fuels has heated the planet and melted glaciers, which are projected to lose one quarter of their global mass by 2100 even in a best-case scenario for cutting emissions.

But the chance of the Palcacocha flooding Lliuya’s home – as well as the fraction of that they can attribute to climate change – is harder to quantify.

Rolf Katzenbach, a court-appointed expert, estimated the risk of a glacier lake outburst flood in Lake Palcacocha in the next 30 years at about 1%.

He criticised the methodologies of some scientific papers cited by the plaintiff and dismissed research that relied on results from better-studied Alpine regions, for which scientists have more data, because of differences in local geology.

Verheyen countered that Katzenbach’s assessment had relied on a limited sample of historical events and failed to properly factor in the effects of climate change, such as melting permafrost.

A verdict is expected on 14 April. The judges, who spent several hours questioning Katzenbach on Monday and Wednesday, at one stage expressed scepticism at the plaintiff’s claim that there was a direct and serious risk to the house.

“You have to convince us that in the next 30 years there is a concrete threat to your client’s property,” lead judge Rolf Meyer told the plaintiff’s lawyers. “Personally, I don’t yet see it.”

Lliuya, the farmer and mountain guide at the centre of the case, took RWE to court to try to make the company contribute to local flood defences in line with its share of planet-heating pollution. The proportion was calculated by a report from Carbon Majors at 0.47% of global emissions when the case began, and has since shrunk to 0.38%.

Speaking to the Guardian after the hearing, Lliuya, who is supported by nonprofit Germanwatch, said the danger of a flood caused by an avalanche was real.

“Living with this risk makes you scared,” he said. “It’s not just the physical danger, it’s also the psychological effects.”

The case could open the door for claimants across the world hit by carbon-aggravated weather extremes. Similar cases have been filed in Belgium, where a cattle farmer is targeting French oil giant Total, and in Switzerland, where four Indonesians from the island of Pari are targeting cement maker Holcim.

Moritz Becker, the Freshfields lawyer representing RWE, said in closing remarks that the company was not disputing climate change or RWE’s responsibility for climate action, but argued that going through civil courts would either lead to individual cases of symbolism or a dog-eat-dog world of lawsuits. “In neither case does this help combat the climate crisis.”

Judge Meyer had rejected the argument in opening remarks on Monday, referring to statements made to the media by RWE that the case would leave every motorist liable for their emissions.

“We are talking about huge amounts of CO₂,” he said. “Not about individuals driving cars.”