Q&A: What Trump’s US exit from UNFCCC and IPCC could mean for climate action

The Trump administration in the US has announced its intention to withdraw from the UN’s landmark climate treaty, alongside 65 other international bodies that “no longer serve American interests”.

Every nation in the world has committed to tackling “dangerous anthropogenic interference with the climate system” under the 1992 UN Framework Convention on Climate Change (UNFCCC).

During Donald Trump’s second presidency, the US has already failed to meet a number of its UN climate treaty obligations, including reporting its emissions and funding the UNFCCC – and it has not attended recent climate summits.

However, pulling out of the UNFCCC would be an unprecedented step and would mark the latest move by the US to disavow global cooperation and climate action.

Among the other organisations the US plans to leave is the Intergovernmental Panel on Climate Change (IPCC), the UN body seen as the global authority on climate science.

In this article, Carbon Brief considers the implications of the US leaving these bodies, as well as the potential for it rejoining the UNFCCC in the future.

Carbon Brief has also spoken to experts about the contested legality of leaving the UNFCCC and what practical changes – if any – will result from the US departure.

• What is the process for pulling out of the UNFCCC?
• Is it legal for Trump to take the US out of the UNFCCC unilaterally?
• How could the US rejoin the UNFCCC and Paris Agreement?
• What changes when the US withdraws from the UNFCCC?
• What about the US withdrawal from the IPCC?
• What other organisations are affected?

What is the process for pulling out of the UNFCCC?

The Trump administration set out its intention to withdraw from the UNFCCC and the IPCC in a White House presidential memorandum issued on 7 January 2026.

It claims authority “vested in me as president by the constitution and laws of the US” to withdraw the country from the treaty, along with 65 other international and UN bodies.

However, the memo includes a caveat around its instructions, stating:

“For UN entities, withdrawal means ceasing participation in or funding to those entities to the extent permitted by law.”

(In an 8 January interview with the New York Times, Trump said he did not “need international law” and that his powers were constrained only by his “own morality”.)

The US is the first and only country in the world to announce it wants to withdraw from the UNFCCC.

The convention was adopted at the UN headquarters in New York in May 1992 and opened for signatures at the Rio Earth summit the following month. The US became the first industrialised nation to ratify the treaty that same year.

It was ultimately signed by every nation on Earth – making it one of the most ratified global treaties in history.

Article 25 of the treaty states that any party may withdraw by giving written notification to the “depositary”, which is elsewhere defined as being the UN secretary general – currently, António Guterres.

The article, shown below, adds that the withdrawal will come into force a year after a written notification is supplied.

The treaty adds that any party that withdraws from the convention shall be considered as also having left any related protocol. 

The UNFCCC has two main protocols: the Kyoto Protocol of 1997 and the Paris Agreement of 2015.

Although former US president Bill Clinton signed the Kyoto Protocol in 1998, its formal ratification faced opposition from the Senate and the treaty was ultimately rejected by his successor, president George W Bush, in 2001.

Domestic opposition to the protocol centred around the exclusion of major developing countries, such as China and India, from emissions reduction measures.

The US did ratify the Paris Agreement, but Trump signed an executive order to take the nation out of the pact for a second time on his first resumed day in office in January 2025.

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Is it legal for Trump to take the US out of the UNFCCC unilaterally?

Whether Trump can legally pull the US out of the UNFCCC without the consent of the Senate remains unclear. 

The US previously left the Paris Agreement during Trump’s first term. 

Both the UNFCCC and the Paris Agreement allow any party to withdraw with a year’s written notice. However, both treaties state that parties cannot withdraw within the first three years of ratification. 

As such, the first Trump administration filed notice to exit the Paris Agreement in November 2019 and became the first nation in the world to formally leave a year later – the day after Democrat Joe Biden won the 2020 presidential election. 

On his first day in office in 2021, Biden rejoined the Paris Agreement. This took 30 days from notifying the UNFCCC to come into force.

The legalities of leaving the UNFCCC are murkier, due to how it was adopted. 

As Michael B Gerrard, director of the Sabin Center for Climate Change Law at Columbia Law School, explains to Carbon Brief, the Paris Agreement was ratified without Senate approval.

Article 2 of the US Constitution says presidents have the power to make or join treaties subject to the “advice and consent” of the Senate – including a two-thirds majority vote (see below).

However, Barack Obama took the position that, as the Paris Agreement “did not impose binding legal obligations on the US, it was not a treaty that required Senate ratification”, Gerrard tells Carbon Brief. 

As noted in a post by Jake Schmidt, a senior strategic director at the environmental NGO Natural Resources Defense Council (NRDC), the US has other mechanisms for entering international agreements. It says the US has joined more than 90% of the international agreements it is party to through different mechanisms.

In contrast, George H Bush did submit the UNFCCC to the Senate in 1992, where it was unanimously ratified by a 92-0 vote, ahead of his signing it into law. 

Reversing this is uncertain legal territory. Gerrard tells Carbon Brief: 

“There is an open legal question whether a president can unilaterally withdraw the US from a Senate-ratified treaty. A case raising that question reached the US Supreme Court in 1979 (Goldwater vs Carter), but the Supreme Court ruled this was a political question not suitable for the courts.”

Unlike ratifying a treaty, the US Constitution does not explicitly specify whether the consent of the Senate is required to leave one. 

This has created legal uncertainty around the process. 

Given the lack of clarity on the legal precedent, some have suggested that, in practice, Trump can pull the US out of treaties unilaterally.

Sue Biniaz, former US principal deputy special envoy for climate and a key legal architect of the Paris Agreement, tells Carbon Brief: 

“In terms of domestic law, while the Supreme Court has not spoken to this issue (it treated the issue as non-justifiable in the Goldwater v Carter case), it has been US practice, and the mainstream legal view, that the president may constitutionally withdraw unilaterally from a treaty, ie without going back to the Senate.”

Additionally, the potential for Congress to block the withdrawal from the UNFCCC and other treaties is unclear. When asked by Carbon Brief if it could play a role, Biniaz says: 

“Theoretically, but politically unlikely, Congress could pass a law prohibiting the president from unilaterally withdrawing from the UNFCCC. (The 2024 NDAA contains such a provision with respect to NATO.) In such case, its constitutionality would likely be the subject of debate.”

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How could the US rejoin the UNFCCC and Paris Agreement?

The US would be able to rejoin the UNFCCC in future, but experts disagree on how straightforward the process would be and whether it would require a political vote. 

In addition to it being unclear whether a two-thirds “supermajority” vote in the Senate is required to leave a treaty, it is unclear whether rejoining would require a similar vote again – or if the original 1992 Senate consent would still hold. 

Citing arguments set out by Prof Jean Galbraith of the University of Pennsylvania law school, Schmidt’s NRDC post says that a future president could rejoin the convention within 90 days of a formal decision, under the merit of the previous Senate approval.

Biniaz tells Carbon Brief that there are “multiple future pathways to rejoining”, adding: 

“For example, Prof Jean Galbraith has persuasively laid out the view that the original Senate resolution of advice and consent with respect to the UNFCCC continues in effect and provides the legal authority for a future president to rejoin. Of course, the Senate could also give its advice and consent again. In any case, per Article 23 of the UNFCCC, it would enter into force for the US 90 days after the deposit of its instrument.”

Prof Oona Hathaway, an international law professor at Yale Law School, believes there is a “very strong case that a future president could rejoin the treaty without another Senate vote”. 

She tells Carbon Brief that there is precedent for this based on US leaders quitting and rejoining global organisations in the past, explaining:

“The US joined the International Labour Organization in 1934. In 1975, the Ford administration unilaterally withdrew, and in 1980, the Carter administration rejoined without seeking congressional approval. 

“Similarly, the US became a member of the United Nations Educational, Scientific and Cultural Organization (UNESCO) in 1946. In the 1980s, the Reagan administration unilaterally withdrew the US. The Bush administration rejoined UNESCO in 2002, but in 2019 the Trump administration once again withdrew. The Biden administration rejoined in 2023, and the Trump Administration announced its withdrawal again in 2025.” 

But this “legal theory” of a future US president specifically re-entering the UNFCCC “based on the prior Senate ratification” has “never been tested in court”, Prof Gerrard from Columbia Law School tells Carbon Brief.

Dr Joanna Depledge, an expert on global climate negotiations and research fellow at the University of Cambridge, tells Carbon Brief:

“Due to the need for Senate ratification of the UNFCCC (in my interpretation), there is no way back now for the US into the climate treaties. But there is nothing to stop a future US president applying [the treaty] rules or – what is more important – adopting aggressive climate policy independently of them.”

If it were required, achieving Senate approval to rejoin the UNFCCC would take a “significant shift in US domestic politics”, public policy professor Thomas Hale from the University of Oxford notes on Bluesky.

Rejoining the Paris Agreement, on the other hand, is a simpler process that the US has already undertaken in recent years. (See: Is it legal for Trump to take the US out of the UNFCCC unilaterally?) Biniaz explains:

“In terms of the Paris Agreement, a party to that agreement must also be a party to the UNFCCC (Article 20). Assuming the US had rejoined the UNFCCC, it could rejoin the Paris Agreement as an executive agreement (as it did in early 2021). The agreement would enter into force for the US 30 days after the deposit of its instrument (Article 21).”

The Center for Climate and Energy Solutions, an environmental non-profit, explains that Senate approval was not required for Paris “because it elaborates an existing treaty” – the UNFCCC. 

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What changes when the US withdraws from the UNFCCC?

US withdrawal from the UNFCCC has been described in media coverage as a “massive hit” to global climate efforts that will “significantly limit” the treaty’s influence.

However, experts tell Carbon Brief that, as the Trump administration has already effectively withdrawn from most international climate activities, this latest move will make little difference.

Moreover, Depledge tells Carbon Brief that the international climate regime “will not collapse” as a result of US withdrawal. She says:

“International climate cooperation will not collapse because the UNFCCC has 195 members rather than 196. In a way, the climate treaties have already done their job. The world is already well advanced on the path to a lower-carbon future. Had the US left 10 years ago, it would have been a serious threat, but not today. China and other renewable energy giants will assert even more dominance.”

Depledge adds that while the “path to net-zero will be longer because of the drastic rollback of domestic climate policy in the US”, it “won’t be reversed”.

Technically, US departure from the UNFCCC would formally release it from certain obligations, including the need to report national emissions. 

As the world’s second-largest annual emitter, this is potentially significant.

“The US withdrawal from the UNFCCC undoubtedly impacts on efforts to monitor and report global greenhouse gas emissions,” Dr William Lamb, a senior researcher at the Potsdam Institute for Climate Impact Research (PIK), tells Carbon Brief.

Lamb notes that while scientific bodies, such as the IPCC, often use third-party data, national inventories are still important. The US already failed to report its emissions data last year, in breach of its UNFCCC treaty obligations.

Robbie Andrew, senior researcher at Norwegian climate institute CICERO, says that it will currently be possible for third-party groups to “get pretty close” to the carbon dioxide (CO2) emissions estimates previously published by the US administration. However, he adds:

“The further question, though, is whether the EIA [US Energy Information Administration] will continue reporting all of the energy data they currently do. Will the White House decide that reporting flaring is woke? That even reporting coal consumption is an unnecessary burden on business? I suspect the energy sector would be extremely unhappy with changes to the EIA’s reporting, but there’s nothing at the moment that could guarantee anything at all in that regard.”

Andrew says that estimating CO2 emissions from energy is “relatively straightforward when you have detailed energy data”. In contrast, estimating CO2 emissions from agriculture, land use, land-use change and forestry, as well as other greenhouse gas emissions, is “far more difficult”.

The US Treasury has also announced that the US will withdraw from the UN’s Green Climate Fund (GCF) and give up its seat on the board, “in alignment” with its departure from the UNFCCC. The Trump administration had already cancelled $4bn of pledged funds for the GCF.

Another specific impact of US departure would be on the UNFCCC secretariat budget, which already faces a significant funding gap. US annual contributions typically make up around 22% of the body’s core budget, which comes from member states.

However, as with emissions data and GCF withdrawal, the Trump administration had previously indicated that the US would stop funding the UNFCCC. 

In fact, billionaire and UN special climate envoy Michael Bloomberg has already committed, alongside other philanthropists, to making up the US shortfall.

Veteran French climate negotiator Paul Watkinson tells Carbon Brief:

“In some ways the US has already suspended its participation. It has already stopped paying its budget contributions, it sent no delegation to meetings in 2025. It is not going to do any reporting any longer – although most of that is now under the Paris Agreement. So whether it formally leaves the UNFCCC or not does not change what it is likely to do.”

Dr Joanna Depledge tells Carbon Brief that she agrees:

“This is symbolically and politically huge, but in practice it makes little difference, given that Trump had already announced total disengagement last year.”

The US has a history of either leaving or not joining major environmental treaties and organisations, such as the Paris Agreement and the Kyoto Protocol. (See: What is the process for pulling out of the UNFCCC?)

Dr Jennifer Allan, a global environmental politics researcher at Cardiff University, tells Carbon Brief:

“The US has always been an unreliable partner…Historically speaking, this is kind of more of the same.”

The NRDC’s Jake Schmidt tells Carbon Brief that he doubts US absence will lead to less progress at UN climate negotiations. He adds: 

“[The] Trump team would have only messed things up, so not having them participate will probably actually lead to better outcomes.”

However, he acknowledges that “US non-participation over the long-term could be used by climate slow-walking countries as an excuse for inaction”.

Biniaz tells Carbon Brief that the absence of the US is unlikely to unlock reform of the UN climate process – and that it might make negotiations more difficult. She says:

“I don’t see the absence of the US as promoting reform of the COP process. While the US may have had strong views on certain topics, many other parties did as well, and there is unlikely to be agreement among them to move away from the consensus (or near consensus) decision-making process that currently prevails. In fact, the US has historically played quite a significant ‘broker’ role in the negotiations, which might actually make it more difficult for the remaining parties to reach agreement.”

After leaving the UNFCCC, the US would still be able to participate in UN climate talks as an observer, albeit with diminished influence. (It is worth noting that the US did not send a delegation to COP30 last year.)

There is still scope for the US to use its global power and influence to disrupt international climate processes from the outside.

For example, last year, the Trump administration threatened nations and negotiators with tariffs and withdrawn visa rights if they backed an International Maritime Organization (IMO) effort to cut shipping emissions. Ultimately, the measures were delayed due to a lack of consensus.

(Notably, the IMO is among the international bodies that the US has not pledged to leave.)

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What about the US withdrawal from the IPCC?

As a scientific body, rather than a treaty, there is no formal mechanism for “withdrawing” from the IPCC. In its own words, the IPCC is an “organisation of governments that are members of the UN or World Meteorological Organization” (WMO). 

Therefore, just being part of the UN or WMO means a country is eligible to participate in the IPCC. If a country no longer wishes to play a role in the IPCC, it can simply disengage from its activities – for example, by not attending plenary meetings, nominating authors or providing financial support.

This is exactly what the US government has been doing since last year. 

Shortly before the IPCC’s plenary meeting for member governments – known as a “session” – in Hangzhou, China, in March 2025, reports emerged that US officials had been denied permission to attend.

In addition, the contract for the technical support unit for Working Group III (WG3) was terminated by its provider, NASA, which also eliminated the role of chief scientist – the position held by WG3 co-chair Dr Kate Cavlin.

(Each of the IPCC’s three “working groups” has a technical support unit, or TSU, which provides scientific and operational support. These are typically “co-located” between the home countries of a working group’s two co-chairs.)

The Hangzhou session was the first time that the US had missed a plenary since the IPCC was founded in 1988. It then missed another in Lima, Peru, in October 2025.

Although the US government did not nominate any authors for the IPCC’s seventh assessment cycle (AR7), US scientists were still put forward through other channels. Analysis by Carbon Brief shows that, across the three AR7 working group reports, 55 authors are affiliated with US institutions.

However, while IPCC authors are supported by their institutions – they are volunteers and so are not paid by the IPCC – their travel costs for meetings are typically covered by their country’s government. (For scientists from developing countries, there is financial support centrally from the IPCC.) 

Prof Chris Field, co-chair of Working Group II during the IPCC’s fifth assessment (AR5), tells Carbon Brief that a “number of philanthropies have stepped up to facilitate participation by US authors not supported by the US government”.

The US Academic Alliance for the IPCC – a collaboration of US universities and research institutions formed last year to fill the gap left by the government – has been raising funds to support travel.  

In a statement reacting to the US withdrawal, IPCC chair Prof Sir Jim Skea said that the panel’s focus remains on preparing the reports for AR7:

“The panel continues to make decisions by consensus among its member governments at its regular plenary sessions. Our attention remains firmly on the delivery of these reports.”

The various reports will be finalised, reviewed and approved in the coming years – a process that can continue without the US. As it stands, the US government will not have a say on the content and wording of these reports.

Field describes the US withdrawal as a “self-inflicted wound to US prestige and leadership” on climate change. He adds:

“I don’t have a crystal ball, but I hope that the US administration’s animosity toward climate change science will lead other countries to support the IPCC even more strongly. The IPCC is a global treasure.”

The University of Edinburgh’s Prof Gabi Hegerl, who has been involved in multiple IPCC reports, tells Carbon Brief:

“The contribution and influence of US scientists is presently reduced, but there are still a lot of enthusiastic scientists out there that contribute in any way they can even against difficult obstacles.”

On Twitter, Prof Jean-Pascal van Ypersele – IPCC vice-chair during AR5 – wrote that the US withdrawal was “deeply regrettable” and that to claim the IPCC’s work is contrary to US interests is “simply nonsensical”. He continued:

“Let us remember that the creation of the IPCC was facilitated in 1988 by an agreement between Ronald Reagan and Margaret Thatcher, who can hardly be described as ‘woke’. Climate and the environment are not a matter of ideology or political affiliation: they concern everyone.”

Van Ypersele added that while the IPCC will “continue its work in the service of all”, other countries “will have to compensate for the budgetary losses”.

The IPCC’s most recent budget figures show that the US did not make a contribution in 2025.

Carbon Brief analysis shows that the US has provided around 30% of all voluntary contributions in the IPCC’s history. Totalling approximately $67m (£50m), this is more than four times that of the next-largest direct contributor, the EU.

However, this is not the first time that the US has withdrawn funding from the IPCC. During Trump’s first term of office, his administration cut its contributions in 2017, with other countries stepping up their funding in response. The US subsequently resumed its contributions.

At its most recent meeting in Lima, Peru, in October 2025, the IPCC warned of an “accelerating decline” in the level of annual voluntary contributions from countries and other organisations, reported the Earth Negotiations Bulletin. As a result, the IPCC invited member countries to increase their donations “if possible”.

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What other organisations are affected?

In addition to announcing his plan to withdraw the US from the UNFCCC and the IPCC, Trump also called for the nation’s departure from 16 other organisations related to climate change, biodiversity and clean energy.

These include:

• The Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) – the biodiversity equivalent of the IPCC.
• Intergovernmental Forum on Mining, Minerals, Metals and Sustainable Development – a voluntary group of more than 80 countries aiming to make the mining sector more sustainable.
• UN Energy – the principal UN organisation for international collaboration on energy.
• UN Oceans – a UN mechanism responsible for overseeing the International Seabed Authority (ISA) and other UN agencies related to ocean and coastal issues.
• UN Water – the UN agency responsible for water and sanitation.
• UN Collaborative Programme on Reducing Emissions from Deforestation and Forest Degradation in Developing Countries (UN-REDD) – a UN collaborative initiative for creating financial incentives for protecting forests.
• International Renewable Energy Agency – an intergovernmental organisation supporting countries in their transition to renewable energy.
• 24/7 Carbon-Free Energy Compact – a UN initiative launched in 2021 pushing governments, companies and organisations to achieve 100% low-carbon electricity generation.
• Commission for Environmental Cooperation – an organisation aimed at conserving North America’s natural environment.
• Inter-American Institute for Global Change Research – an intergovernmental organisation supported by 19 countries in North and South America for the support of planetary change research.
• International Energy Forum – an intergovernmental platform for dialogue among countries, industry and experts.
• International Solar Alliance – an organisation supporting the development of solar power and the phaseout of fossil fuels.
• International Tropical Timber Organization – an organisation aimed at protecting tropical forest resources.
• International Union for Conservation of Nature – an international nature conservation organisation and authority on the state of biodiversity loss.
• Renewable Energy Policy Network for the 21st Century – a global policy forum for renewable energy leadership.
• Secretariat of the Pacific Regional Environment Programme – a regional organisation aimed at protecting the Pacific’s environment.

As well as participating in the work of these organisations, the US is also a key source of funding for many of them – leaving their futures uncertain.

In a letter to members seen by Carbon Brief, IPBES chair and Kenyan ecologist, Dr David Obura, described Trump’s move as “deeply disappointing”.

He said that IPBES “has not yet received any formal notification” from the US, but “anticipates that the intention expressed to withdraw will mean that the US will soon cease to be a member of IPBES”, adding:

“The US is a founding member of IPBES and scientists, policymakers and stakeholders – including Indigenous peoples and local communities – from the US have been among the most engaged contributors to the work of IPBES since its establishment in 2012, making valuable contributions to objective science-based assessments of the state of the planet, for people and nature.

“The contribution of US experts ranges from leading landmark assessment reports, to presiding over negotiations, serving as authors and reviewers, as well as helping to steer the organisation both scientifically and administratively.” 

Despite being a party to IPBES until now, the US has never been a signatory to the UN Convention on Biological Diversity (CBD), the nature equivalent of the UNFCCC.

It is one of only two nations not to sign the convention, with the other being the Holy See, representing the Vatican City.

The lack of US representation at the CBD has not prevented countries from reaching agreements. In 2022, countries gathered under the CBD adopted the Kunming-Montreal Global Biodiversity Framework, often described as the “Paris Agreement for nature”.

However, some observers have pointed to the lack of US involvement as one of the reasons why biodiversity loss has received less international attention than climate change.

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