It is unlawful for governments to return people to countries where their lives might be threatened by the climate crisis, a landmark ruling by the United Nations human rights committee has found.

The judgment – which is the first of its kind – represents a legal “tipping point” and a moment that “opens the doorway” to future protection claims for people whose lives and wellbeing have been threatened due to global heating, experts say.

Tens of millions of people are expected to be displaced by global heating in the next decade.

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The judgment relates to the case of Ioane Teitiota, a man from the Pacific nation of Kiribati, which is considered one of the countries most threatened by rising sea levels. He applied for protection in New Zealand in 2013, claiming his and his family’s lives were at risk.

The committee heard evidence of overcrowding on the island of South Tarawa, where Teitiota lived, saying that the population there had increased from 1,641 in 1947 to 50,000 in 2010 due to sea level rising leading to other islands becoming uninhabitable, which had led to violence and social tensions.

He also spoke of the lack of fresh water and difficulty growing crops due to salinity of the water table causing serious health issues for his family. He said that as Kiribati was predicted to be uninhabitable in 10 to 15 years, his life was endangered by remaining there.

The New Zealand courts rejected Teitiota’s claim for protection. The UN human rights committee upheld New Zealand’s decision on the grounds that while “sea level rise is likely to render the republic of Kiribati uninhabitable … the timeframe of 10 to 15 years, as suggested by [Teitiota], could allow for intervening acts by the republic of Kiribati, with the assistance of the international community, to take affirmative measures to protect and, where necessary, relocate its population”.

However experts say the committee’s ruling opens the way for other claims based on the threat to life posed by the climate crisis. The committee ruled that “the effects of climate change in receiving states may expose individuals to a violation of their rights … thereby triggering the non-refoulement obligations of sending states”.

“On a personal level for Ioane and his family it is bad news, because obviously it’s decided that his claim that his right to life was threatened in Kiribati wasn’t strong enough,” said Kate Schuetze, Pacific researcher for Amnesty International. “But they said it wasn’t strong enough based on his personal circumstances and the evidence they put before the court and then they made some very strong statements clarifying the roles and responsibilities of states to say … there would be a trigger of international responsibility for other governments not to return people to places where their life is at risk because of climate-induced changes.”

While the judgment is not formally binding on countries, it points to legal obligations that countries have under international law.

“What’s really important here, and why it’s quite a landmark case, is that the committee recognised that without robust action on climate at some point in the future it could well be that governments will, under international human rights law, be prohibited from sending people to places where their life is at risk or where they would face inhuman or degrading treatment,” said Prof Jane McAdam, director of the Kaldor centre for international refugee law at the University of New South Wales.

“Even though in this particular case there was no violation found, it effectively put governments on notice.

“There have been cases brought in Australia and New Zealand since the mid-1990s about environmental harm and climate change and to date they’ve all been unsuccessful ... But now we’ve got a very clear, legal authoritative statement now that it’s almost like: watch this space.”

Schuetze said there were roughly a dozen cases in the New Zealand court system similar to Teitiota’s, with people, mostly from Tuvalu and Kiribati, claiming the impacts of the climate crisis affected their right to life.

“The Pacific Islands will be the canary in the coalmines for climate-induced migrants,” said Schuetze.

“The message in this case is clear: Pacific Island states don’t need to be underwater before triggering those human rights obligations … I think we will see those cases start to emerge.”

Two of the 18 members of the committee issued dissenting opinions on the case, saying they did not agree with the conclusion that New Zealand was justified in removing Teitiota to Kiribati, with one writing that just because “deaths are not occurring with regularity on account of the conditions … it should not mean that the threshold had been reached”.

“The fact that this [difficulty growing crops and accessing safe drinking water] is a reality for many others in the country, does not make it any more dignified for the persons living in such conditions. New Zealand’s action is more like forcing a drowning person back into a sinking vessel, with the ‘justification’ that after all there are other voyagers on board.”