The US withdraws from the UNFCCC and the IPCC

On January 7th, President Trump issued a Presidential Memorandum indicating that the US will be withdrawing from the UNFCCC and the IPCC, as well as over 60 other international organizations and agreements. 

The move sparked a global dialogue on whether a US president can unilaterally exit these agreements and how the decision will impact climate science and other international organizations to which the US is still a party. 

Legal limbo: Authority to exit the UNFCCC remains unclear

The legal grounds for President Trump’s authority to unilaterally exit the UNFCCC remain dubious. When President George H.W. Bush entered the convention in 1992, the administration sought the advice and consent of the Senate, consistent with the Constitution's requirements for a president to enter international treaties. It remains unclear whether a president has the authority to independently withdraw from international agreements without the Senate’s approval. 

The constitutional ambiguity may elicit legal challenges. But regardless of how courts rule, the decision will make it more difficult for future presidents to rejoin the UNFCCC or Paris Agreement. Article 20 of the Paris Agreement makes clear that the Agreement is subject to ratification only by Parties to the UNFCCC. 

By exiting the UNFCCC, the Trump Administration has added an additional layer of bureaucratic process that future administrations will likely need to navigate to rejoin the Paris Agreement, which would again require Senate approval. 

Ripple effects for global climate cooperation and funding  

Regardless of legality, the US withdrawal from the UNFCCC and the IPCC will reduce the financial resources, expertise, and data available to the international climate science and policy community. The IPCC records show that, although at lower volumes than under the Obama and Biden administrations, the US still provided around $1.9 million in funding for the organization during the first Trump administration. 

However, beyond the near-term financial and brain drain implications, the move to exit these international bodies may yield additional tensions within other international bodies of which the US is still a member. 

CORSIA and carbon credit market implications

The Presidential Memorandum did not signal an intent to withdraw from the International Civil Aviation Organization (ICAO), which administers CORSIA. Participating member states are required to establish national frameworks to ensure that their registered airlines comply with CORSIA requirements. 

Yet while there has been no explicit change to US participation, it appears increasingly unlikely that the federal government will introduce or actively enforce CORSIA-related obligations. Three US airlines (United, Delta, American) rank among the global top 10 for CORSIA-eligible emissions in 2024. US non-participation could depress demand for carbon credits within the scheme.

Still, uncertainty about US involvement in ICAO is not new. In September 2025, US Secretary of Transportation Sean Duffy delivered a speech accusing ICAO of “wasting critical resources on social programs or climate financing initiatives work.” The message was clear: align with US administration priorities or lose US funding.   

IMO climate policy and US negotiation tactics

The Presidential Memorandum did not indicate an intent to withdraw from the International Maritime Organization (IMO). In 2025, the administration successfully delayed a decision on the proposed Net-Zero Framework - which would have introduced a carbon levy on international shipping - until 2026. There has been no indication of a change in the US position since that time. 

The heavy-handed tactics employed by the US tell the story: visa restrictions, additional port fees, and evaluation of sanctions for countries that support the framework. The US may be willing to leverage policy measures outside of formal negotiations to achieve desired outcomes in global policy.

Article 6 carbon market to continue without US participation

Other international frameworks and cooperative mechanisms will likely remain relatively unchanged. The Trump administration already signaled its intention to withdraw from the Paris Agreement in January 2025, effective January 27, 2026. 

Even under the Biden administration, the US Nationally Determined Contribution (NDC) did not demonstrate a clear intent to engage with Article 6 mechanisms by issuing or procuring Internationally Transferred Mitigation Outcomes (ITMOs). Nor had the US entered into any such agreements. As a result, the decision is not expected to have a direct impact on Article 6 transactions. 

Several other major economies, such as Japan, the European Union, and South Korea, have communicated strong plans to use ITMOs to achieve their NDCs, signaling that the Article 6 carbon market will continue to develop with or without US participation.

What comes next for global climate policy

The US departure from the UNFCCC and the IPCC will have clear and harmful impacts on the capacity and efficacy of global coordination on climate science and political cooperation. While the UNFCCC has indicated the US will be welcome to rejoin in the future, the body’s leadership has also indicated the decision will undercut US competitiveness. 

Beyond the UNFCCC and the IPCC, the US’s ongoing participation in ICAO and IMO demonstrates a commitment to hinder global climate policy through less conventional tactics outside of formal negotiations. Even as a non-party to the UNFCCC and the IPCC, the US influence over member nations may impair their capacity to effectively participate in these bodies.   

The implications are clear. Global climate policy is entering uncharted territory, and the rules of engagement are being rewritten in real time.