During the two-day hearing, the nations – including the Bahamas, Tuvalu, Vanuatu, Antigua and Barbuda among others – will ask the International Tribunal for the Law of the Sea (Itlos) to determine whether greenhouse gas emissions absorbed by the marine environment should be considered pollution.

Most countries have obligations under the legally binding UN convention on the law of the sea to take measures to prevent, reduce and control marine pollution.

If the case, brought by the Commission of Small Island States on Climate Change and International Law (Cosis), is successful, these obligations would include carbon-emission reduction and protection of marine environments already damaged by CO2 pollution.

The states hope it will provide guidance to countries on the emission reductions necessary to meet their commitments under the Paris climate agreement to prevent temperatures rising 1.5C (2.7F) above pre-industrial levels.

“Sea levels are rising rapidly, threatening to sink our lands below the ocean,” Kausea Natano, the prime minister of Tuvalu, said in a statement.

“There are no obligations to keep temperature rise to within 1.5C, beyond which there is a high probability of catastrophic climate change,” said Payam Akhavan, lead counsel and chair of Cosis’s committee of legal experts.

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