The United States is set to quit the world’s landmark climate convention next February, after the Trump administration formally notified the UN of its previously announced decision to withdraw.

UN Secretary-General António Guterres communicated last Friday that the UN treaty depository had received Washington’s formal notice to leave the UN Framework Convention on Climate Change (UNFCCC).

Adopted in 1992 at the Rio Earth Summit, the climate treaty is the cornerstone of global efforts to curb climate change and tackle its impacts.

The US withdrawal will take effect on 27 February 2027 – one year after the formal notification – as required by the terms of the convention.

The US, the world’s second-largest emitter, will be the first nation to formally exit the treaty and the only one recognised by the UN outside of it.

‘Colossal own goal’

In January, President Donald Trump, who has called climate change a “con job”, announced his administration’s intention to quit the UNFCCC and 65 other international organisations and instruments, including the Intergovernmental Panel on Climate Change (IPCC), the most authoritative global voice on climate science, and the Green Climate Fund (GCF), the world’s largest multilateral climate fund.

A White House factsheet said President Trump was ending US participation in international organisations that “undermine America’s independence and waste taxpayer dollars on ineffective or hostile agendas”.

“Many of these bodies promote radical climate policies, global governance, and ideological programmes that conflict with US sovereignty and economic strength,” it added.

At the time, the UNFCCC chief Simon Stiell called the US decision to leave the convention “a colossal own goal which will leave the US less secure and less prosperous”.

“While all other nations are stepping forward together, this latest step back from global leadership, climate cooperation and science can only harm the US economy, jobs and living standards, as wildfires, floods, mega-storms and droughts get rapidly worse,” he added.

Relinquishing obligations

At the end of January 2026, the US already formally left the Paris Agreement, under which countries agreed in 2015 to try to limit global warming to “well below” 2 degrees Celsius above pre-industrial levels and to issue regular emissions-reduction plans. Trump pulled the US out of the accord in 2020 before President Biden re-joined it in 2021.

While the Trump administration had effectively already disengaged from global climate action immediately after its inauguration, its formal departure from the UNFCCC will free it from formal obligations, including reporting detailed greenhouse gas emissions inventories and providing funding for the convention.

The US already stopped funding the UNFCCC and failed to submit its emissions data last year. The federal administration also sent no delegates to the COP30 summit in Brazil last November.

Washington remains involved in other international negotiations with climate implications – including talks on a UN treaty to curb plastics pollution and efforts to price emissions in the shipping sector – where it has sought to slow progress and block binding global measures.

A route back in?

The US could potentially rejoin the UNFCCC in future, likely under a different administration, but there are different views on how complicated that process would be.

The US Senate ratified the UN climate convention – with no opposition – in 1992 and some experts believe a future president could rejoin the UNFCCC within 90 days of a formal decision based on the original “advice and consent” of the Senate.

But other legal experts told Carbon Brief that theory has never been tested in court and a new two-third majority vote in the Senate might be required, which would be challenging with the vast majority of Republican Senators currently opposed to membership.

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US set to exit UN climate convention in February 2027