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(Photo: IPCC)
Last week’s Intergovernmental Panel on Climate Change (IPCC) meeting in Hangzhou, China, marked the third time that governments have failed to agree on a timeline for the organisation’s seventh assessment cycle (AR7).
A large group of countries pushed for the reports to be published by the end of 2028, to allow them to feed into the UN’s second global stocktake – a mechanism that will gauge progress towards the Paris Agreement goals.
However, others – including the Chinese hosts – pushed for a longer deadline, warning of “compression in the timeline” that could affect participation, particularly from developing countries.
The meeting ran over by more than 30 hours, meaning that many small delegations – especially small-island developing states and least-developed countries – were unable to stay to the end.
As a result, the final decisions were made without their participation.
According to the Earth Negotiations Bulletin (ENB), reporting from inside the meeting, timeline discussions will be taken up again in the next IPCC meeting in late 2025, “with hope that the panel can finally break its deadlock”.
“The absence of a timeline puts potential contributing scientists in a difficult position,” one IPCC scientist tells Carbon Brief.
He notes that the “call for authors” will open soon, but warns how challenging it will be to accept a nomination “if there is no clarity on when a massive time commitment for the IPCC is expected”.
The meeting also saw outlines agreed for AR7’s three main reports – despite the “entrenched positions” of some delegations “complicating efforts to find consensus”, the ENB reports.
Speaking to Carbon Brief, IPCC chair Prof Jim Skea says the process was “probably the most difficult session I can recall”.
In a further complication, reports emerged ahead of the meeting that US officials had been denied permission to attend and a contract for the technical support unit of one of the working groups had been terminated.
It was the first US absence in IPCC history.
Skea says that the IPCC will “have to start thinking more seriously” about how to manage a potential US withdrawal, but the priority last week had been to “get through” the meeting and its lengthy agenda.
He adds that the IPCC has still “had no formal communication from the US at all”.
Below, Carbon Brief unpacks the deliberations at the meeting and the decisions that were made.
Splits in Sofia
IPCC “sessions” are meetings that bring together officials and experts from member countries and observer organisations.
Collectively, they decide on the work of the IPCC, including the scope, outline and timeline for reports – all overseen by the IPCC’s “bureau” of elected scientists.
With its sixth assessment report (AR6) completed in 2023, the focus of the IPCC has turned to the seventh assessment (AR7) and the reports it will deliver over the next five years.
At its meetings in Istanbul and Sofia in 2024, the IPCC agreed that AR7 should include – among other outputs – the traditional set of three “working group” reports, one “special” report on cities and two “methodology” reports on “short-lived climate forcers” and “carbon dioxide removal technologies, carbon capture utilisation and storage”.
The three working group reports – each typically running to thousands of pages – focus on climate science (WG1), impacts and adaptation (WG2) and mitigation (WG3).
However, the timeline for these reports was not agreed at either meeting. Countries were split on whether the working group reports should be published in time to inform the UN’s second global stocktake, which will be completed in 2028. The stocktake will gauge international progress towards the Paris Agreement goals. (See: AR7 schedule)
The final decision on the AR7 timeline was, thus, postponed to 2025. As a result, the Hangzhou meeting would need to revisit the timeline – as well as approve the scope and outline of the working group reports themselves.
The Hangzhou meeting, originally slated for five days over 24-28 February, brought together almost 450 participants from governments, international organisations and civil society – including 300 delegates from 124 member countries and 48 observer organisations.
IPCC chair Prof Jim Skea tells Carbon Brief that the agenda contained “six days’ worth [of items] rather than five” and they “started with three sessions a day right from the beginning to try and get ahead”.
US no-show
Just a few days before the meeting opened, Axios reported that government officials from the US had been “denied” permission to attend. Furthermore, it said, the contract for the technical support unit for WG3 had been “terminated” by its provider NASA, meaning its staff “will also not be traveling to China or supporting the IPCC process moving forward”.
(Each working group has a technical support unit, or TSU, which provides scientific and operational support for report authors and the group’s leadership.)
In further reporting, Nature quoted a NASA spokesperson, who said that the move was prompted by guidance “to eliminate non-essential consulting contracts”. The Washington Post reported that the group of 10 TSU staff “still have their jobs…but have been blocked from doing any IPCC-related work since 14 February”. Bloomberg added that WG3 co-chair and NASA chief scientist Dr Kate Cavlin would also not attend the meeting.
Axios speculated that the move “could be the beginning of a bigger withdrawal from US involvement in international climate science work”.
Carbon Brief analysis suggests that the US has provided around 30% of the voluntary contributions to IPCC budgets since it was established in 1988. Totalling more than 53m Swiss francs (£46m), this is more than four times that of the next-largest direct contributor, the European Union.
The first Trump administration cut its contributions to the IPCC in 2017, with other countries stepping up their funding in response. The US subsequently resumed its contributions.
Chart showing the 10 largest direct contributors to the IPCC since its inception in 1988, with the US (red bars), European Union (dark blue) and UNFCCC (mid blue) highlighted. Grey bars show all other contributors combined. Source: IPCC (2025) and (2010). Contributions have been adjusted, as per IPCC footnotes, so they appear in the year they are received, rather than pledged.
peaking to Carbon Brief, Skea says the absence of the US at the meeting itself “didn’t disturb the basic way that the meeting operated”. He adds:
“Every meeting we have 60 countries that don’t turn up out of our membership – the US was now one of that group. I mean, frankly, nobody within the meeting mentioned the US absence. We just got on and did it.”
On the longer-term implications, Skea says that “we didn’t spare an awful lot of time for thinking about”. However, the IPCC will “have to start thinking more seriously” once they have more information, he says, noting that “we have had no formal communication from the US at all”.
Regarding the WG3 TSU, there is no “comparable circumstance” in the IPCC’s history, Skea says. Typically, the co-chair from a developed country is “supposed to bring support for a TSU with them”, he says. (Each working group has two co-chairs – one from a developed country and one from a developing country.) However, the WG3 TSU is already partly supported in Malaysia, where co-chair Prof Joy Jacqueline Pereira is based.
(As an IPCC progress report for the Hangzhou meeting points out, the WG3 TSU has already “taken shape”, although it is not yet fully staffed. The “node” in Malaysia was established with the donor support of the US, Norway and New Zealand. There is also a job advert for a “senior science officer” in the WG3 TSU currently on the IPCC’s website.)
Skea suggests that the situation can be resolved with “creative solutions”, adding that the IPCC “can take any decision, regardless of past principles or past decisions. So I think, with ingenuity, there will be ways around it.”
Prof Frank Jotzo, a professor of environmental economics at the Australian National University’s Crawford School of Public Policy and WG3 lead author on AR5 and AR6, describes the situation as “highly unusual”. He tells Carbon Brief:
“I would expect that other developed countries will come to the rescue to fund the WG3 TSU, to rescue the process and to demonstrate that Trump will not upend this multilateral process. Staff positions could then presumably be either in those countries or in Malaysia, home of the other WG3 co-chair.”
On the US involvement in the IPCC more broadly, CNN reported the comments of a “scientist involved in the report”, who said they were “not sure” what the block on US officials will mean for the planned work going forward, or “if US scientists will participate in the writing of the IPCC reports”.
Science reported that, although US contributions to the IPCC are “typically run out of the White House by the Global Change Research Programme, NASA is the lead on managing GCRP’s contracts”. It added that “NASA leadership, not GCRP, decided to end the TSU contract”.
Following the China meeting, member states are set to solicit nominations of scientists to author the working group reports in AR7, Science explained:
“GCRP usually runs the process [for the US], but the administration’s moves have some wondering whether it will proceed as normal. If not, IPCC does allow scientists to self-nominate without their country’s involvement. But US authors might be shut out anyway if travel funding ends.”
For example, the US nominated 250 scientists to be authors on the special report on cities, which will be part of the AR7 cycle. (Authors can also be nominated by other countries, observer organisations and the IPCC bureau.)
Dr Gavin Schmidt, director of the NASA Goddard Institute for Space Studies, posted on social media last week that, “despite some reports, there is no blanket prohibition on US scientists interacting with or serving with the IPCC”.
CDR report
Among the other items on the Hangzhou agenda was the finalisation of the scope and outline of a methodology report on carbon dioxide removal (CDR) and carbon capture, utilisation and storage (CCUS) technologies, slated for publication in 2027.
At a scoping meeting held in Copenhagen in October, the IPCC’s task force on national greenhouse gas inventories – which is coordinating the methodology report – agreed on a title, scope and outline for the forthcoming report.
Delegates in Hangzhou failed to reach agreement on the plan for the report, after disagreements emerged around chapter seven of the proposed outline – which looks at carbon removals from oceans, lakes and rivers.
A number of delegations – including India, France, Belgium, Chile and Turkey – objected to the inclusion of a standalone chapter in the methodology report on carbon removal from waterbodies, the ENB says. The countries argued there is insufficient understanding of the environmental impacts and effectiveness of certain marine CDR technologies, including ocean alkalinity enhancement.
Saudi Arabia was among the countries that argued in favour of a chapter on carbon removal from waterbodies. The Gulf nation said that its removal would set a “worrying precedent” and be a “bad sign” for emerging technologies, according to the ENB.
With no consensus reached, delegates agreed on the title and chapters one to six of the report, but postponed further deliberations on chapter seven until the next plenary meeting.
IPCC chair Skea tells Carbon Brief that delegates “were extremely close to getting agreement” on the report, but had been hampered by a lack of “ingenuity and time”.
He adds that a solution which helped broker agreement on the outline for the special report on short-lived climate forcers at the last IPCC plenary meeting could offer a path forward for the methodology report. (After a debate arose around the inclusion of hydrogen emissions in that report, country delegations compromised on a footnote stating the matter would be addressed in a future cycle.) Skea explains:
“The [IPCC’s] task force on national greenhouse gas inventories always has this issue as to whether there’s enough scientific evidence to justify bringing a technology or a technique in. If there are doubts about the quality of the basic evidence for bringing it in, there are devices for kicking the can down the road just a little bit.”
Some insiders speculated that the standoff over the methodology report in Hangzhou could have consequences for the overall AR7 timeline. They told Carbon Brief the delay to the report’s start could result in shifted review periods and necessitate an extra approval plenary in 2028.
This article was originally published on Carbon Brief under the Creative Commons BY NC ND licence. Read the original article.
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