For the second time since the Paris Agreement on climate change was adopted, the US this week formally withdrew from the global pact following a 12-month mandatory period since President Donald Trump announced he would pull his country out on his first day in office in January 2025.

Since then, the US has axed most of its international climate funding and this month said it would exit the UN climate convention (UNFCCC) – which underpins the UN climate process and the Paris Agreement – the Intergovernmental Panel on Climate Change (IPCC), which is the world’s most authoritative climate science body, and the Green Climate Fund (GCF), the world’s biggest multilateral climate fund.

Trump to pull US out of UN climate convention and climate science body

As the Trump administration turns its back on the UN climate regime, UN climate chief Simon Stiell described the move as a “colossal own goal”, while the GCF – to which the US has failed to deliver billions of dollars in promised support – said the country would lose its board seat but operations would continue.

Climate diplomacy experts say some of the changes announced by the US president could remain symbolic or be reversed in the future, while warning that the reputation of the world’s second-biggest emitting country could suffer a big hit in the long term.

Other countries may follow US Paris exit

Marta Schaaf, Amnesty International’s climate programme director, said the US’s second exit from the Paris Agreement on January 27 (the first was during Trump’s first term) “sets a disturbing precedent” that could instigate a “race to the bottom”, encouraging other countries to leave.

“The US is one of several powerful anti-climate actors but as an influential superpower, this decision, along with acts of coercion and bullying of other countries and powerful actors to double down on fossil fuels, causes particular harm and threatens to reverse more than a decade of global climate progress under the agreement,” she said in a statement.

So far no other signatories have publicly announced they will quit the 2015 climate agreement, but Israeli media recently reported that the country is discussing a withdrawal under pressure from the US. Last year, Argentina also hinted at a possible exit but did not follow through.

COP30 chief calls for two-tier climate system to speed up action beyond consensus

COP30 President André Aranha Corrêa do Lago said himself that in the months leading up to last year’s UN climate conference in Brazil, there was “a lot of noise about possible additional exits”, after the world’s largest economy said it would withdraw.

The Trump administration has been called out in other UN processes, after being accused of employing “bullying” tactics at the International Maritime Organization (IMO) to persuade smaller countries to vote against the entry into force of a green shipping deal. This pressure resulted in a delayed decision.

Allie Rosenbluth, Oil Change International’s US campaign manager, said the US withdrawal from the Paris Agreement “is a betrayal of the communities at risk from climate disaster, especially those on the frontlines of the crisis in the Global South”.

Legal uncertainties around UNFCCC withdrawal

This January, in an unprecedented move, the White House also announced the US would leave the broader UN Framework Convention on Climate Change (UNFCCC). This would take effect one year after formally notifying the UN, which it had yet to do as of the time of publication.

The UNFCCC could be harder to rejoin than the Paris Agreement – which was last done through an executive order issued by former President Joe Biden – because the US Senate first gave unamimous “advice and consent” for ratification of the UNFCCC in 1992, making the legal situation more complex.

Some experts believe the US would need Senate authorisation to formally withdraw from the UNFCCC, and there are questions around whether the move would be legal at all.

Trump’s presidential memorandum says that “for United Nations entities, withdrawal means ceasing participation in or funding to those entities to the extent permitted by law”. To all intents and purposes, the US had already disengaged from the UN climate process during Trump’s first year in office, cutting funding for the UN’s climate body and not sending a delegation to COP30.

However, if the US does not formally notify the UN of its withdrawal from the UNFCCC, that could potentially ease legal concerns for the Trump administration, according to Michael Gerrard, climate change law professor at Columbia Law School.

Could the US rejoin the UNFCCC?

Gerrard told Climate Home News that if the Trump administration does not officially withdraw from the UNFCCC, “then I don’t see a legal obstacle to a subsequent administration resuming funding and participation”. “Even if the US does formally withdraw now, a new president might well be able to rely on the prior consent in rejoining; that issue has never been decided by the Supreme Court,” he added.

Sue Biniaz, the US State Department’s Principal Deputy Special Envoy for Climate until January 2025, and Jean Galbraith, professor at the University of Pennsylvania Carey Law School, wrote on the Just Security blog that the mainstream legal view is that the president may constitutionally withdraw the US from a Senate-approved treaty where – as here – the withdrawal is lawful under international law and neither the Senate’s resolution of “advice and consent” nor a congressional law has put limits on withdrawal.

Under international law, they added, rejoining is straightforward. For the UNFCCC, a state can become a party 90 days after depositing its instrument of ratification or accession, and following that, the US could rejoin the Paris Agreement, which would take 30 days after the deposit of its instrument.

From the perspective of domestic law, the two climate law experts argued that the original Senate resolution remains in effect (unless repealed by the Senate) and provides the legal authority needed for a future president to rejoin the UNFCCC. He or she could also seek a second round of “advice and consent”, ask Congress to approve rejoining, or potentially join the UNFCCC under the president’s independent constitutional powers, they added.

Loss of US leadership and credibility

Irrespective of whether the White House does move to rejoin the UN climate regime at any point, analysts said the Trump administration’s hostile attitude and disengagement has damaged the standing of the US when it comes to global climate action and the energy transition.

Biniaz and Galbraith wrote that the world is used to the US “flip-flopping on climate”, because it refused to ratify the Kyoto Protocol and quit the Paris Agreement once before, but “withdrawal from the entire regime takes US abdication of climate leadership to a new level”.

Though many countries may be relieved that the Trump administration is not participating given its current policies, they said: “in the longer term, US absence could have a negative impact on the effectiveness of the regime and the willingness of other countries to take ambitious action.”

Nikki Reisch, climate and energy director at the Center for International Environmental Law, warned that “it will not be easy for the US to regain credibility or leadership on climate.”

While an “informal withdrawal” from the UNFCCC may “avoid some paperwork” and avoid potential lawsuits, she said it would not “insulate this administration from scrutiny and legal challenge on other grounds, particularly as it continues to unwind climate progress, dismantle environmental protections, and expand production of the fossil fuels”.

Reisch noted that US states and local governments have been making efforts to “fill the void where the federal government has abdicated its duties”. “Other countries, too, should see the Trump administration’s retreat as an invitation to step up, stand together and move forward,” she added.

The post Explainer: Out of Paris, but will the US formally quit the UN climate regime? appeared first on Climate Home News.

Explainer: Out of Paris, but will the US formally quit the UN climate regime?