International court rules GHGs are marine pollution

Credit: Flavio Coelho via Getty Images

May 23, 2024

Matthew Ward Agius
Matthew Agius is a science writer for Cosmos Magazine.


Small island nations have hailed a ruling by the International Tribunal for the Law of the Sea that greenhouse gases are a form of marine pollution.

The International Tribunal for the Law of the Sea (ITLOS) is an independent judicial body that adjudicates maritime disputes that come under the 1982 UN Convention on the Law of the Sea.

On Tuesday, ITLOS ruled on a 2022 request from 9 small Pacific and Caribbean island nations to consider greenhouse gas emissions as a form of pollution, which is regulated by the Convention.

Greenhouse gases are molecules like carbon dioxide and methane that cause global temperatures to rise due to their heat-trapping effect on the atmosphere and the oceans.

This causes ocean warming, acidification, ice sheet melt and disruption to other marine systems. Ocean warming and its knock-on effects are forecast to cause sea level rise that will inundate many small island nations.

In a unanimous opinion, the ITLOS found “anthropogenic [created by human activity] greenhouse gas emissions into the atmosphere constitute pollution of the marine environment”.

It means 168 nations that are parties to the Convention, which includes Australia, have “the specific obligations to take all necessary measures to prevent, reduce and control marine pollution from anthropogenic greenhouse gas emissions and to endeavour to harmonise their policies in this connection.”

There’s also a significant scientific component in the ruling, which says these necessary measures “should be determined objectively, taking into account… the best available science and relevant international rules and standards contained in climate change treaties such as the UNFCCC [Climate Change Convention] and the Paris Agreement”.

The ruling is an advisory opinion and is not legally binding. However it is seen by experts on the law of the sea as offering a potential precedent for courts – including within nations themselves – on states’ obligations under the Convention.

Constantinos Yiallourides, deputy director of the Centre of Environmental Law at Macquarie University, says the ruling would have “authoritative value” in how states engage with the Convention.

“It would reinforce the global environment and climate change regime, and it is likely that other international and national courts would consider the ITLOS Advisory Opinion when making assessments on climate-related cases, including challenging the legality of high-emitting activities due to their potential carbon footprint on the oceans,” Yiallourides says.

It’s a view echoed by Melbourne University’s Margaret Young, an international law specialist with expertise in the law of the sea.

Young says the need for state parties to consider scientific evidence in their actions is noteworthy.

That includes a requirement in the ruling for state parties to uphold a stringent standard of due diligence in controlling greenhouse gas emissions.

“There’s a real emphasis of ‘best available science’ in this judgement,” Young says.

“What the court is really cleverly doing is saying states have to act with due diligence to prevent marine pollution from greenhouse gas emissions. ‘Due diligence’ is increasingly being discussed by these international courts because it does require states to act to a particular standard.

“The court is not about to say specifically what each country has to do, but it is able to give a sense of the seriousness with which it treats this issue, especially where pollution crosses state boundaries: ‘stringent’ is a really important word that’s been used here.”