Climate change threatens existence, top court rules

In a historic, long-awaited judgement, the world’s top court has ruled that climate change is an existential threat and that aggrieved countries can sue each other over emissions of planet-warming gases.

But Judge Yuji Iwasawa, president of the International Court of Justice (ICJ) in The Hague, Netherlands, on Wednesday, while issuing the court’s highly-anticipated advisory opinion, said untangling who caused which part of climate change could be difficult.

The groundbreaking ruling says States must act urgently to address the “existential threat” of climate change by cooperating to cut emissions, following through on global climate agreements, and protecting vulnerable populations and ecosystems from harm.

Judge Iwasawa said greenhouse gas emissions are “unequivocally” caused by human activities and have cross-border effects.

“Failure of a State to take appropriate action to protect the climate system … may constitute an internationally wrongful act,” Iwasawa said. He called the climate crisis “an existential problem of planetary proportions that imperils all forms of life and the very health of our planet”.

Although the ruling is non-binding, it could have wide-ranging consequences, as the ICJ is considered the world’s highest court with global jurisdiction.

Judges waded through tens of thousands of pages of written submissions and heard two weeks of oral arguments during the ICJ’s biggest-ever case, as they sought to pull together different strands of environmental law into a definitive international standard.

Unanimous decision

A “clean, healthy and sustainable environment” is a human right, said the judges at the top court of the United Nations, who pondered two fundamental questions:

What are states’ obligations under international law to address climate change for present and future generations? And, what are the legal consequences under these obligations for states failing to do so?

Judge Iwasawa said the questions “represent more than a legal problem: they concern an existential problem of planetary proportions that imperils all forms of life and the very health of our planet.”

The landmark opinion of the 15 judges, who all voted unanimously in favour of the opinion, will carry legal and political weight and is likely to determine the course of future climate action across the world, including whether polluters should be made to pay for their actions.

Lawyers told international media that the opinion could be used as early as next week, including in national courts outside of the ICJ. The court’s decision is expected to be used in future litigation and to support political negotiations by vulnerable states.

It is not clear how much an individual country could have to pay in damages if any claim was successful. An analysis published in Nature, estimated that between 2000 and 2019 there were US$2.8 trillion losses from climate change – about US$16 million per hour. During the evidence sessions in December, the Marshall Islands highlighted that the costs for their island to adapt to climate change are US$9 billion.

“That is US$9 billion the Marshall Islands does not have. Climate change is a problem they have not caused, but they are forced to consider relocating their capital,” said barrister Stephanie Robinson.

Campaigners and climate lawyers hope the landmark decision will now pave the way for compensation from countries that have historically burned the most fossil fuels and are therefore the most responsible for global warming.

Many poorer countries had backed the case out of frustration, claiming that developed nations are failing to keep existing promises to tackle the growing problem. It will be seen as a victory for countries that are more vulnerable to climate change, who came to court after feeling frustrated about lack of global progress in tackling the problem.

But developed countries, including the UK, argued that existing climate agreements, including the landmark UN Paris Agreement of 2015, are sufficient and no further legal obligations should be imposed. On Wednesday, the court rejected that argument.

In the Paris Agreement, all governments signed up to limiting global temperature rise to “well below 2 degrees Celsius above pre-industrial levels” and to pursuing efforts to limit the temperature increase to 1.5°C above pre-industrial levels, recognising that this would significantly reduce the risks and impacts of climate change.

Judge Iwasawa also said if countries do not develop the most ambitious possible plans to tackle climate change this would constitute a breach of their promises in the Paris Agreement. He added that broader international law applies, which means that countries which are not signed up to the Paris Agreement – or want to leave, like the US – are still required to protect the environment, including the climate system.

Legal floodgates

The non-binding opinion runs to more than 500 pages and is seen as a potential turning point in international climate law. Enshrining a sustainable environment as a human right paves the way for other legal actions, including States returning to the ICJ to hold each other to account, as well as domestic lawsuits.

“The consequences of climate change are severe and far-reaching: they affect both natural ecosystems and human populations. These consequences underscore the urgent and existential threat posed by climate change,” said Judge Iwasawa.

The ICJ was instructed to produce this document by the UN in 2023, after years of campaigning by a group of Pacific island law students and diplomacy led by the Pacific island nation of Vanuatu. One of those students, Siosiua Veikune from Tonga, was in The Hague to hear the decision.

“I’m lost for words. This is so exciting. There’s a tonne of emotions rushing through us. This is a win we take proudly back home to our communities,” he told BBC News.

In December, representatives of vulnerable States told judges that a handful of countries should be held legally responsible for the continuing impacts of climate change. But the world’s top greenhouse gas emitters denied any legal responsibility.

The ICJ is the third of four top courts to publish an advisory opinion on climate change. Earlier this month, the Inter-American Court of Human Rights (IACHR) concluded that there is a human right to a healthy climate. And both the IACHR and the International Tribunal for the Law of the Sea said States have a legal responsibility to control greenhouse gases.

The African Court on Human and People’s Rights has only just begun the process. Of all these, the ICJ is the court with the widest jurisdiction and it has the role of harmonising and integrating international law.

Advisory opinions are technically non-binding but are considered authoritative because they summarise existing law rather than create law. Jotham Napat, the prime minister of Vanuatu, said this was a “turning point” in the fight for climate justice.

“This process has elevated the voices of climate-vulnerable nations, driven global awareness, and set the stage for stronger climate action,” said Napat. “This ruling will give us a foundation to build upon, and this moment will inspire continued efforts for stronger action and accountability, inspiring bold efforts to protect our planet.”

The International Union for Conservation of Nature (IUCN) Director General Dr Grethel Aguilar said the advisory opinion was particularly encouraging for its recognition of nature and the need for a human rights-based approach to limiting climate change.

“By undermining ecosystems, climate change weakens the life-support systems upon which people’s rights to life, health, food, water, and culture depend. States must strengthen their commitments — recognising that protecting nature is not just part of the solution, it is essential to delivering climate justice and safeguarding our collective future”.

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