The Intergovernmental Panel on Climate Change’s (IPCC) latest assessment cycle has been beset by disagreements between nations over the timeline for publishing its next landmark report.

During the UN climate science body’s last five “sessions” – biannual meetings where governments discuss matters related to the IPCC’s work – governments have been unable to sign off on the delivery date of the “working group” reports.

The deadlock over the delivery plan for the seventh assessment cycle (AR7) has been described as “unprecedented”.

Some countries have pushed for reports to be approved in 2028, in time to inform the “second global stocktake”, which is due to conclude at COP33 that year and is designed to inform the next round of national climate goals under the Paris Agreement.

Other nations have argued that developing countries need more time to review and approve the reports – meaning that one, or more, would not be published until after the stocktake.

The next IPCC meeting – due to take place in Addis Ababa in October – is likely the last moment where a timeline could be agreed that would see the reports synchronised with the stocktake.

One expert tells Carbon Brief that the failure to align the IPCC’s reports with the stocktake would be a “major historical break [that] would be used to weaken the international climate process and Paris Agreement”.

In this Q&A, Carbon Brief explores the ongoing disagreements over the AR7 timeline.

• How does the IPCC assessment report cycle work?
• How have timeline negotiations been different for AR7?
• Why have negotiations over the timeline of AR7 faltered?
• Why are some countries calling for a slower timeline for AR7 reports?
• How is the IPCC managing the impasse?
• Is delivering the reports in time for the global stocktake still possible?
• What could be the implications of an extended timeline for AR7?

How does the IPCC assessment report cycle work?

For almost 40 years, the IPCC has been one of the most visible examples of a “science-policy interface” – an institution that helps science to inform policy.

The UN General Assembly resolution that established the IPCC in December 1988 states that the panel will “provide internationally coordinated scientific assessments of the magnitude, timing and potential environmental and socioeconomic impact of climate change and realistic response strategies”.

Four years later, the UN Framework Convention on Climate Change (UNFCCC) was created, with an objective of “stabilising greenhouse gas concentrations at a level that would prevent dangerous anthropogenic [human-caused] interference with the climate system”.

The IPCC’s official rulebook, last updated in 2013, highlights the IPCC’s role in producing comprehensive assessments of the state of human-caused climate change. It stipulates that its assessments must provide “relevant” information – and that reports should be “neutral with respect to policy”.

The IPCC’s work has long helped inform the work of the UNFCCC, which meets annually for its “conference of the parties” (COP).

For example, the reports of the fifth assessment cycle (AR5), published over 2013-14, have been credited for informing the Paris Agreement’s headline goal to hold global temperature rise at “well below 2C” and “pursue efforts” to limit increases to 1.5C.

During each assessment cycle, the IPCC produces three “working group” (WG) reports on physical science (WG1), impacts and adaptation (WG2) and mitigation (WG3). These are summarised in a “synthesis” report (SYR). It also produces special reports and methodology reports.

There are a number of stages to the creation of an IPCC working group report, as shown in the graphic below.

How have timeline negotiations been different for AR7?

The current assessment cycle – AR7 – formally began in July 2023, at the IPCC’s 59th session (IPCC-59) in Nairobi.

In January 2024, governments agreed to publish the AR7 synthesis report in 2029.

However, governments are yet to ratify a timeline for publication of the working group reports that will precede it, after negotiations on the issue ended in deadlock in Istanbul, Sofia, Hangzhou, Lima and Bangkok.

This puts AR7 at odds with the previous assessment cycles, where timelines were agreed more quickly. This is shown in the table below.

Assessment cycle	Start date	Report timeline agreed*	Time until decision	WG1	WG2	WG3	SYR
First	IPCC-1, Nov 1988	IPCC-2, Jun 1989	7 months	Aug 1990	Jun 1990	Jun 1990	Aug 1990
Second	IPCC-7, Feb 1992	IPCC-9, Jun 1993	1 year, 4 months	Dec 1995	Oct 1995	Oct 1995	Dec 1995
Third	IPCC-13, Sep 1997	IPCC-14, Oct 1998	1 year, 1 months	Jan 2001	Feb 2001	Mar 2001	Sep 2001
Fourth	IPCC-19, Apr 2002	IPCC-21, Nov 2003	1 year, 8 months	Feb 2007	Apr 2007	May 2007	Nov 2007
Fifth	IPCC-28, Apr 2008	IPCC-31, Oct 2009	1 year, 5 months	Sep 2013	Mar 2014	Apr 2014	Nov 2014
Sixth	IPCC-42, Oct 2015	IPCC-46, Sep 2017	1 year, 11 months	Aug 2021	Feb 2022	Apr 2022	Mar 2023
Seventh	IPCC-59, Jul 2023	–	2 years, 9 months and counting	–	–	–	2029

“Report timeline agreed” refers to when delivery timeline of working group reports was agreed. WG = working group and SYR = synthesis report. Analysis by Carbon Brief.

Why have negotiations over the timeline of AR7 faltered?

Part of the disagreement over the AR7 timeline centres on the question of whether the IPCC’s seventh assessment cycle should align with the second global stocktake, a process that is due to culminate in the autumn of 2028 at COP33.

While a number of different timelines have been proposed, there are, broadly speaking, two camps in the AR7 timeline debate.

The first group has argued that all three working group reports should be published in 2028, so that they can inform the second global stocktake.

The other faction has advocated for a longer timeline, which would mean WG2 and WG3 would be finished after the stocktake is completed.

Established in 2015 under the Paris Agreement, the global stocktake is a five-yearly assessment of the world’s collective progress on tackling climate change. Under the terms of the treaty, countries pledged to consider the “best available science” during the process.

The first global stocktake concluded at COP29 in Dubai in 2023. Its outcomes informed national 2035 climate goals, which were due to the UN in 2025.

In the outcome decision of the first global stocktake, the UNFCCC officially invited the IPCC to consider how to “best align” with the “second and subsequent global stocktakes”.

The document also invited the IPCC to “provide relevant and timely information for the next global stocktake”.

Dr Bill Hare, CEO and senior scientist of Climate Analytics, tells Carbon Brief the stocktake is “at the guts, or heart, or the Paris Agreement’s ambition mechanism”.

He explains that the IPCC’s sixth assessment reports (AR6) – published over 2021-23 – were a “critical element” in the first global stocktake process:

“You had the IPCC reports there. You’ve had the IPCC co-chairs, or authors, in the discussions [and] workshops, pushing back on arguments from [countries]…They were able to anchor the fact that the world hasn’t done enough, that the NDCs [“nationally determined contributions”, or climate pledges] haven’t met the 1.5C goal by a wide margin – and that the cost of doing stuff is relatively cheap, which was a critical output of the WG3 report last time.”

Dozens of counties have advocated for a global stocktake-aligned timeline for AR7 reports, arguing that it is critical that findings from all working groups inform the exercise.

For example, the small-island state of Vanuatu said at IPCC-63 in Lima that delaying the reports would deprive countries of important scientific information ahead of key international meetings, according to the Earth Negotiations Bulletin (ENB), reporting from inside the meeting.

Meanwhile, the Netherlands said at IPCC-64 in Bangkok that the delivery of reports after the stocktake would “significantly lower the policy relevance of AR7”, according to ENB.

A timeline where the reports are published ahead of the stocktake has been backed by co-chairs of IPCC reports. (See: How is the IPCC managing the impasse?)

Hare says that, in his analysis, a timeline where the AR7 reports align with the stocktake is supported by the “majority of countries, across geographies and levels of development, including least developed countries and small-island developing states”.

However, a number of emerging-economy nations have argued that a timeline where all reports are delivered by 2028 is too tight.

Why are some countries calling for a slower timeline for AR7 reports?

Among the most vocal proponents for the WG2 and WG3 reports being delivered after the stocktake, according to the ENB’s write-ups of negotiations in Bangkok and Lima, are India, Kenya, Russia and Saudi Arabia.

These countries have argued that authors, experts and governments from developing nations with fewer resources need more time to prepare, review and approve working group reports.

Some of the arguments in favour for a slower timeline are captured below in an excerpt from the ENB’s write-up of last October’s IPCC-63 in Lima.

An article published in 2025 in Africa Climate Insights summarised some of the arguments in favour of a slower timeline. It says a stocktake-aligned timeline would have overlapping review periods for different working group reports that would place more pressure on governments and experts.

It also notes that researchers from the global south – who face greater institutional barriers to publishing research in academic journals – would benefit from a later cut-off date for scientific literature for the AR7 reports. It quotes Dr Patricia Nying’uro – Kenya’s IPCC “focal point” – saying:

“The current timeline does not provide adequate time for developing countries to conduct research, publish their findings and have meaningful input.”

On top of citing inclusivity concerns, countries have also argued that aligning reports with the global stocktake is not an IPCC priority.

For instance, ENB reported at IPCC-64 that Saudi Arabia said “compressing” the cycle to meet “external timelines” would be “improper” because the IPCC “serves a broader mandate than just providing inputs to the global stocktake”.

Meanwhile, Russia said inputs to the global stocktake were “not the key to IPCC success”.

These arguments have faced significant pushback.

At IPCC-63 in Lima, IPCC co-chairs pointed out that overlapping reviews of assessment reports were “intentional” and would allow experts to see both drafts at once, according to ENB.

At the meeting, IPCC chair Prof Jim Skea also pointed to the IPCC rulebook, which states that panel and working group sessions should be scheduled to coordinate “to the extent possible, with other related international meetings”.

Some have contested the framing of a stocktake-aligned timeline as “compressed”.

At IPCC-61 in Sofia, the delegation from Saint Kitts and Nevis argued that the proposed schedule for AR7 was “neither compressed nor rushed”, because, while it was shorter than the schedule for AR6, it would contain fewer special reports.

Meanwhile, at IPCC-62 in Hangzhou, representatives from Luxembourg reminded the conference that AR6 was produced under “global pandemic conditions and was, therefore, delayed”, reported ENB. As such, they said the “proper comparison of the timeline would be to AR5, relative to which the proposed timetable was not rushed”.

(AR6’s seven-year run has been attributed in IPCC documents to the Covid-19 pandemic interrupting workflows and an unprecedented number of reports.)

There have been accusations in some quarters that delegations advocating in favour of a slower timeline are deliberately stalling the process.

For example, in a statement released after the meeting, the French government expressed its “deep concern over attempts to arbitrarily slow down and postpone the publication schedule”.

It said that “any delay in taking into account the relevant scientific data to respond to the climate emergency would seriously compromise climate action on a global scale”.

Some observers have argued that dynamics playing out at the IPCC replicate those in UN climate negotiations. Yao Zhe from Greenpeace East Asia tells Carbon Brief:

“The group of countries that opposed the proposed AR7 timelines is similar to the group that tactically slowed down or blocked negotiations regarding mitigation ambition under the UNFCCC. And they are gaining more influence as global climate governance faces a leadership vacuum.”

Dr Kari de Pryck, a lecturer at the Institute for Environmental Sciences at the University of Geneva, tells Carbon Brief that, “clearly, there is obstruction”. She continues:

“It is in the interest of some countries to ensure that the IPCC reports are not published on time. But there are also interesting and legitimate comments on inclusivity and diversity.”

How is the IPCC managing the impasse?

Despite no formal timeline for report delivery being agreed, report production has continued undeterred, IPCC chair Prof Jim Skea tells Carbon Brief.

He says that, so far, the science “has not been held up” by the report timeline issue, with lead author meetings and drafting of the various working group, special and methodological reports underway.

However, he warns that a final decision will need to be made by the end of 2026 on a timeline. He explains:

“There are multiple proposals that have been made [on timelines] and they start to diverge during 2027 due to the scheduling of specific events, like lead author meetings and review periods. Because we need to establish a budget for 2027, we need to make a decision before the end of 2626 to have some certainty about the entire cycle.

“So far, we’ve operated by taking year by year decisions – you just take the decision for the next year and carry on. That’s been okay so far, because there has not been a divergence [between timeline proposals] at the earlier stages of the cycle. But we will see divergences coming up.”

At IPCC-63 last October, WG1 co-chair Dr Robert Vautard noted that reports production was currently aligned with a schedule that had been “considered” in the previous meeting in Hangzhou. He said this timeline would allow final approval sessions for WG1, WG2 and WG3 to take place in May 2028, June 2028 and July 2028, respectively.

After this timeline failed to garner consensus, WG1 co-chair Dr Xiaoye Zhang and WG2 co-chair Dr Bart Van den Hurk then presented a new “compromise” timeline to delegates.

This extended the expert and government review periods for draft reports and pushed final approval sessions for WG2 and WG3 to July 2028 and September 2028. Discussions about this updated timeline ended in deadlock.

At IPCC-64 in Bangkok in March 2026, the timeline for reports was initially not slated for discussion.

However, an item on “progress on AR7 reports” was added to the agenda on the first day of the conference, after some countries said the issue required structured discussion. In the end, no agreement was reached on how resolution could be reached.

Negotiations have been pushed – alongside a number of other unresolved decisions – to IPCC-65, scheduled to take place in Addis Ababa, Ethiopia, in October 2026.

Skea says the lack of agreement on a way forward in Bangkok leaves the secretariat with the “responsibility to try and figure out the process that will move us in the right direction”. He adds:

“Is there a bridging proposal, some kind of scheme that would help to bring the sides together? That’s what we need to work on over the next few months.”

A key issue the secretariat will need to consider is how to address a “loss of trust between different groups of countries”, as well as the “technicalities of how the timeline is constructed”, he says.

Is delivering the reports in time for the global stocktake still possible?

The IPCC maintains that delivering reports in time for the next global stocktake remains possible, if a decision is made by the end of this year.

Speaking to Carbon Brief, Skea says all timeline options in contention are still feasible “in principle”, if countries show flexibility. He counts four different proposals – two of which would see all reports produced before the stocktake in 2028 and two where WG2 and WG3 would be published in 2029.

He says, though, that he is optimistic a “constructive” result can be delivered in Addis Ababa – but stresses it will only be possible with “a lot of hard work”.

Experts have noted that, even if reports are published in 2028, they will come later in the stocktake process.

Dr Matti Goldberg, director of international climate policy at the Woodwell Climate Research Center and former staffer at the UNFCCC secretariat, explains:

“It is already kind of late. If you want to have a meaningful consideration of the IPCC reports in the global stocktake, they need to be there now or at the beginning of the information collection stage. Otherwise, you’ll have a bunch of parties saying: ‘No, can’t do it. It is too short a timeframe, too big a report.’”

The global stocktake is a process that is split into three phases: an information collection phase to gather inputs; a technical assessment of inputs and other evidence; and a “consideration of outputs” phase where countries decide what to collectively take away from the process.

The information phase of the second global stocktake is due to kick off at COP31 in Antalya, Turkey in November 2026. The technical assessment phase will take place from June 2027 to June 2028, giving way to the final political phase that culminates at COP33 in November 2028.

Under the revised AR7 timeline proposed by IPCC co-chairs in Lima, WG1 would be ready during the technical phase of the second global stocktake and WG2 and WG3 would be able to inform its final, political phase.

Goldberg emphasises that the publication of the reports – and their respective summaries for policymakers – in 2028 would mean countries would face “much higher pressure to deliver stronger messages of ambition” in the second global stocktake.

However, he adds that a faster timeline for the reports will not change the “fundamental calculations of interest” that shape international climate politics:

“There are a series of negotiations: first, over the summary of policymakers and then throughout the whole global stocktake. In the end, that is the process that determines a lot of the result.”

De Pryck from the University of Geneva similarly notes that scientific input is not “the only input” to the stocktake:

“It is a political process. So, at the end of the day, science and expertise is very important – but it’s not going to translate directly into the global stocktake.”

What could be the implications of an extended timeline for AR7?

If AR7 reports are not published until after the global stocktake, governments would likely turn to other sources of science in their submissions, experts tell Carbon Brief.

De Pryck explains that a broad range of science was submitted by governments to the first global stocktake. She says this includes the UN Environment Programme’s annual adaptation and emissions gap reports; updates from the International Energy Agency and climate-finance analysis from Oxfam:

“There are quite a lot of other academic and epistemic reports that could be used by countries in the negotiations that, in a way, could support what the IPCC is doing.”

Greenpeace Asia’s Yao Zhe notes that AR7’s special report on climate change and cities, due to be published in 2027, could play a “good scientific basis” for policy discussions around climate mitigation in the absence of the WG3 report from the stocktake.

Climate Analytics’ Bill Hare warns that a failure to align the the IPCC cycle with the global stocktake could result in less robust science being considered:

“There’s a general consensus that the IPCC is the best available science. It is the formal science, if you like, delivered to the Paris Agreement and climate convention. So, if that doesn’t happen, then it opens the space for other sources of so-called science to come in.”

He adds that any disconnect between the global stocktake cycle and the IPCC assessment cycle would be a “major historical break and one which would be used to weaken the international climate process and Paris Agreement”.

The impacts would also be felt within the climate science community, Hare continues. The IPCC’s role in advising the UNFCCC has long provided a “really strong sense of relevance” to many climate scientists, he says:

“That relevance is a very strong motivator for what [scientists] do. I wonder whether the failure of the IPCC to agree timetable alignment would have a negative impact on that. And that wouldn’t be just for this global stocktake cycle, it would be for subsequent ones.”

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Q&A: Why the standoff between nations over the next IPCC reports matters