Climate change poses an immediate and catastrophic threat to human health worldwide, the World Health Organization (WHO) chief warned the UN’s highest court on Friday as it considers a landmark case that could establish fresh legal obligations for nations to cut emissions and pay for climate damages.
WHO director-general Dr Tedros Adhanom Ghebreyesus testified to the International Court of Justice (ICJ) that climate change is “fundamentally a health crisis” that is already “wreaking havoc” on human health, societies, economies, and overwhelming healthcare systems worldwide.
The case, brought by the Pacific island nation of Vanuatu, represents the largest in ICJ history, with nearly 100 countries and organizations participating. While the court’s advisory opinion, expected next year, will not be binding, legal experts say the ruling could strengthen climate litigation worldwide. For small island nations, the stakes are existential – climate models predict many will disappear beneath Pacific waters without dramatic cuts to global emissions.
“The climate crisis is among the most significant health challenges facing humanity today,” Tedros told the court. “It is not a hypothetical crisis in the future. It is here and now. Without immediate action, climate-related increases in disease prevalence, destruction of health infrastructure, and growing societal burdens could overwhelm already over-burdened health systems around the world.”
The UN health chief highlighted how climate change is already altering disease transmission patterns for infections like malaria, dengue and cholera, while extreme weather events are destroying health infrastructure and claiming thousands of lives. Tedros also emphasized that non-communicable diseases, including cancers and cardiovascular conditions, are linked to climate change and air pollution.
An estimated 920 million children currently face water scarcity, a situation he warned would worsen as climate change intensifies droughts and contaminates water supplies. Rising temperatures are also increasing heat-related deaths and illnesses. Tedros further articulated fears of massive population displacement and projected that over 130 million people could be pushed into extreme poverty by 2030, with devastating impacts on health.
“Millions are expected to be pushed into poverty. This will dramatically increase health burdens and disparities,” he said. “Not enough is being done…to avoid the most catastrophic impacts related to climate change.”
‘Health at the centre’
The WHO chief criticised “massive fossil fuel subsidies,” citing International Monetary Fund projections that appropriate fossil fuel pricing that includes health and environmental costs could prevent 1.2 million air pollution deaths annually. The UN health agency estimated last month ahead of COP29 in Baku meeting climate targets could save two million lives a year.
“The value of health improvements from mitigation significantly outweighs the costs,” Tedros said. “The failure to respond to climate change is undoubtedly the most costly approach.”
WHO’s chief legal counsel Derek Walton urged the court to place health considerations at the center of its advisory opinion, emphasizing that “science and technical evidence should be at the heart of the court’s consideration.”
“WHO respectfully requests the court to place health at the center of its advisory opinion, and in this regard, to give full effect to the fundamental right of every human being to the highest attainable standard of health,” Walton said.
Walton further cited precedents in ICJ rulings that consider health as a human right, pointing to the court’s 1996 ruling on nuclear weapons.
“As the court stated nearly three decades ago in its advisory opinion on nuclear weapons, the environment is not an abstraction, but represents the living space, the quality of life and the very health of Human beings, including generations unborn,” Walton said. “We respectfully ask you to allow the science and the technical evidence to guide your analysis.”
Out of the COPs and to the courts
The proceedings come just weeks after December’s UN climate summit in Baku ended without meaningful commitments on emissions cuts or climate finance, even as global carbon dioxide emissions hit record highs and 2024 is confirmed as the hottest year on record.
Throughout the two-week proceedings in the Hague, which concluded on Friday, major emitters pushed back against the ICJ’s jurisdiction in the case. China urged the court to defer to existing UN climate mechanisms as “the primary channel for global climate governance,” while Saudi Arabia insisted national climate pledges represent only “an obligation of best efforts, not of results.” The United States and several EU members similarly argued existing treaties should be sufficient.
Low-lying islands, several of which called the outcome at COP29 a death sentence, argued the failure of current UN climate instruments is precisely why this case is before the court.
“We’ve heard much about the Paris Agreement as being the solution, but the reason why the climate-vulnerable states have come before the court is that the Paris Agreement has failed,” said Payam Akhavan, counsel for small island states, pointing to projections of 3.1C warming by century’s end.
Small islands represent just 1% of the global population, economy and emissions, but face existential threats from rising seas. In his remarks, Tedros recounted meeting a boy, Falou, on the island of Tuvalu five years ago who shared discussions with friends about what they would do if their island disappeared.
“They worry about the survival of their island homes due to the emissions produced by distant nations,” he said. “This reality weighs heavily on their young shoulders.”
Falou’s island home is projected to be the first nation to disappear beneath the waves. “Tuvalu will not go quietly into the rising sea,” its representative Philippa Webb told the court on Friday.
The court’s opinion, which small island states and developing countries hope to leverage in climate lawsuits worldwide, is expected in 2025. Though not legally binding, the ruling will carry significant moral and legal weight, legal experts say.
“States’ long-standing duties to prevent transboundary environmental harm and human rights violations, including from climate change, did not begin with the UNFCCC or the Paris Agreement, and they do not end with any COP deal,” said Nikki Reisch, director of the Climate and Energy Program at the Center for International Environmental Law (CIEL).
“The ICJ can and must make clear that when States breach their climate obligations, and harm ensues — as it so evidently has — they must right the wrongs,” Reisch said.
