Vanuatu has opened proceedings in a landmark climate case brought before the UN's top court, arguing international law and the warming of the atmosphere demands broader action.
The Pacific state is leading two weeks of hearings at the International Court of Justice, beginning Monday, seeking an formal advisory opinion on whether high-emitting countries should do more to stave off climate catastrophe.
Vanuatu's climate envoy Ralph Regenvanu, who has led the Melanesian country's advocacy, said the stakes could not be higher.
"I choose my words carefully when I say that this may well be the most consequential case in the history of humanity," he told the court.
"We find ourselves on the front lines of a crisis we did not create, a crisis that threatens our very existence."
Vanuatu - as well as other Pacific nations and developing states - are arguing there is a legal responsibility beyond the internationally-negotiated UN frameworks like the Paris Agreement.
Mr Regenvanu told AAP prior to his statement that their central contention was that "all the conventions we've been signing - customary international law - all create obligations for states to act on climate change to prevent harm to future generations into the environment".
"The opposing argument, put by high-emitting states, will be basically that only the UNFCCC and the Paris Agreement is the only legal agreement that matters."
The Paris Agreement is the key inter-governmental agreement to limit human-induced climate change.
The world has warmed 1.3 degrees since pre-industrial times, and there are doubts as to whether the biggest nations will meet their Paris Agreement commitments.
It is not clear how Australia will argue when it makes its submissions about 2am on Tuesday (AEDT).
Vanuatu's day in court comes after years of diplomatic effort to win over fellow nations for the right to bring this case.
Australia was one of more than 100 countries to join with Vanuatu last year to petition for the ICJ to issue an advisory opinion, but Mr Regenvanu said those signatures of support for a hearing should not be confused with support for their position.
"I wouldn't say they're behind us," he said.
"There'll be countries for and against ... states will be arguing for less responsibility, less obligations, less consequences, and there will be states pushing the other angle."
A record number of countries and organisations will submit before the ICJ.
The dynamic is similar to annual COP climate talks - such as last month's meeting in Azerbaijan - which feature negotiations on how to progress climate policy.
However, a key difference at the ICJ hearing is that unlike the backroom negotiations at COP talks, in The Hague, arguments will be made in public, with judges ruling on the way forward.
"That's a key difference," Mr Regenvanu says, "and of course we, Vanuatu, have equal standing before the court."
"Regardless of our actual diplomatic power, which manifests at places like COP, when you appear before the court, you are all equal in the eyes of the court
"That gives us greater possibility to some real change that we want to see."
In The Hague, Mr Regenvanu was blunt.
"Let us not allow future generations to look back and wonder why the cause of their doom was condoned," he said.
Hearings are scheduled to last a fortnight, featuring dozens of countries from across the globe.
Given the magnitude of the possible ramifications, climate activists from across the globe have gathered in The Hague for the landmark case.
Many advocates, disappointed by the outcome of the Azerbaijan-hosted COP last month, have turned to these hearings in the hope of pushing action forward.
"For our generation and for the Pacific Islands, the climate crisis is an existential threat," Vishal Prasad, of Pacific Islands Students Fighting Climate Change, said.
"It is a matter of survival, and the world's biggest economies are not taking this crisis seriously. We need the ICJ to protect the rights of people at the front lines."
The ICJ isn't expected to make a finding until mid-2025.
