This past week, I attended the Intergovernmental Panel on Climate Change (IPCC) meeting in Hangzhou, China. Delegates from nearly 190 nations came together to discuss—and, in theory, make decisions about—next steps for the 7th assessment cycle. In previous posts, I’ve explained what the IPCC is, why this assessment cycle is crucial, and highlighted its role in climate action.
As climate change advances, the IPCC’s goal—to provide policy-relevant science—becomes increasingly urgent. And yet, as I walked away last week, it was clear that urgency is not universally shared: we saw the weakening of scientific language, delayed deadlines, and a failure to reach consensus on some of the most fundamental and pressing areas of research.
The Goals of the Hangzhou Plenary
The agenda for this Plenary was packed with essential tasks shaping the next IPCC reports in this cycle. The main objectives included:
- Approving and adopting outlines for the three major working group reports and an additional methodology report on carbon dioxide removal (CDR).
- Approving report timelines to clearly state when working group reports will be completed.
- Approving expert meetings and passing the budget.
While the IPCC reports are a synthesis of scientific literatures written by scientists, it’s important to remember these Plenary meetings are not a scientific gathering. Rather, they’re negotiations where member countries review plans and make decisions about the structure and process of IPCC reports.
Key Discussions and Outcomes
As is often the case with IPCC Plenary meetings, discussions can feel slow. Many debates repeated points from earlier sessions, as delegations revisited unresolved issues. By the end of the session, some key decisions were made, although it took longer than anticipated—nearly every day of the week long meeting ran late and delegates worked more than 38 hours straight on the final day.
1. Working Group Report Outlines Approved
After much debate, outlines for each of the three work group reports were approved. Since these outlines were already drafted by experts nominated by the panel, agreeing to these outlines was the bare minimum. Each IPCC Working Group (WG) plays a distinct yet interconnected role in the 7th Assessment Report (AR7):
- Working Group 1: Physical Science Basis – Examines the fundamental climate science, including observed and projected changes in temperature, precipitation, extreme events, and Earth system processes.
- Working Group 2: Impacts, Adaptation, and Vulnerability – Assesses the risks climate change poses to human and natural systems, the effectiveness of adaptation strategies, and emerging challenges such as climate-related displacement and health risks.
- Working Group 3: Mitigation of Climate Change – Evaluates pathways for reducing greenhouse gas emissions, sustainable development strategies, and the role of finance, technology, and policy in achieving net-zero emissions.
During the Hangzhou plenary, governments had the opportunity to review and adjust the draft outlines developed at earlier expert meetings. These outlines serve as a roadmap for the scientists who will write the reports, shaping the scope of each assessment. Although they are indicative rather than prescriptive, delegates debated word choices—sometimes late into the night—before finally approving the chapter structures for all three Working Groups.
2. The CDR Methodology Report Failed to Achieve Consensus
One of the most contentious discussions revolved around the outline for the proposed IPCC methodology report on carbon dioxide removal (CDR). The report, initially scoped in 2024 and planned for completion by 2027, aims to provide technical guidance on measuring, reporting, and verifying emissions removals from CDR technologies. However, disagreements over the inclusion of marine CDR prevented consensus, meaning the outline will be revisited at the next plenary.
This debate is not just technical—it is deeply tied to ethics, governance, and the role of the IPCC in assessing emerging technologies.
Delegates questioned when (or if) the IPCC should develop methodologies for technologies with unclear risks. The IPCC’s core mandate is to assess existing science and provide neutral guidance, but defining methods for speculative technologies raises important ethical questions. Marine CDR lacks long-term observational data and has potential ecological risks. Some countries argued that including methods for ocean alkalinity enhancement and direct ocean carbon capture, two experimental marine CDR technologies, could prematurely legitimize these technologies before their environmental impacts are fully understood.
3. Working Group Report Timelines Decision Delayed, Again.
Although the outlines were approved, the timeline for producing each report was pushed back, again. Ultimately, delegates decided to postpone setting any hard deadlines. The key question remains whether timing will allow these reports to inform the next UNFCCC Global Stocktake (GST), expected to take place in 2028. The GST is a cornerstone of the Paris Agreement, designed to periodically gauge collective progress and identify gaps in ambition. Delays in the IPCC’s work could mean that policymakers won’t have the most up-to-date science in time for the stocktake discussions.
4. Expert Meetings and Budget
The IPCC will move forward with expert workshops on engaging diverse knowledge, which will include work on both Indigenous knowledge and using AI systems, and methods of assessment. The Plenary deferred decision on the proposal for an expert meeting on high-impact events and earth systems tipping points. The budget was also ultimately approved, however, much is up in the air since the overall timeline for the reports remains unknown.
Backsliding on Science, Stonewalling on Deadlines
While the approval of the AR7 Working Group outlines represents a significant step forward, several concerning trends emerged during the Plenary discussions—raising questions about whether the IPCC process and the heavy-handed role of the country delegations could end up limiting the scope and clarity of scientific assessments.
Scientific Language and the Removal of Key Concepts
Throughout the plenary, some delegations pushed for edits that weakened or removed previously accepted scientific language. While Working Group I (Physical Science Basis) largely retained its core concepts, Working Groups II (Impacts, Adaptation, and Vulnerability) and III (Mitigation) saw key terms and phrases—many central to prior IPCC reports—either watered down, or removed entirely.
Some of the most notable omissions from the approved outlines include:
- Lock-in and maladaptation, both fundamental concepts for adaptation and resilience planning, were removed from the outline.
- Fossil fuels, which are central to mitigation discussions but were largely avoided, reflecting ongoing political tensions.
- Cost of inaction, subsidies, and trade, all key factors shaping climate policy decisions, were watered down or removed.
- Policy evaluation, including ex-post assessments of mitigation and adaptation strategies, raising concerns about the ability to reflect on past successes and failures.
- Removal of all legal references, including climate litigation and deletion of explicit language on corporate accountability and attribution in WG-II.
The scientists writing AR7 still have the flexibility to incorporate these topics based on available research, but the removal of these terms from the official outlines signals a worrying trend—one that could make it harder to communicate critical findings in a clear and policy-relevant way.
The Push Against Plain-Language Summaries to Promote Accessibility
A proposal from Working Group I experts to include plain-language summaries in each chapter—aimed at making climate science more accessible—was rejected. While many delegates strongly advocated for clear, direct language, others expressed concerns that these summaries might be perceived as too policy prescriptive, ultimately preventing their inclusion.
This decision underscores a broader challenge: as the climate crisis worsens, clear and effective communication of scientific findings is more critical than ever. The rejection of plain-language summaries risks making IPCC reports less accessible to decision-makers, journalists, and the public—undermining their impact at a time when clarity is essential.
The Problem of Extended Negotiations and Equity in Decision-Making
Another major issue is the repeated extension of negotiations, which once again ran late into the night and well past the scheduled close of the plenary. This disproportionately disadvantaged smaller delegations—many from climate-vulnerable nations—who often lack the financial resources to extend their stay and had to leave before the final decisions were made.
This recurring problem within the IPCC raises concerns about whose voices are heard at the most critical moments. While the Plenary operates by consensus, the reality is that practical constraints, including funding and logistical challenges, mean some nations are effectively excluded from last-minute negotiations. This is particularly troubling given that these same nations are often the most affected by climate change and have the most at stake.
What’s Next for the IPCC?
Despite slow progress and ongoing challenges, the IPCC continues to move forward. With outlines now finalized for all three Working Groups, the next critical step is the call for authors—a process where countries and observer organizations, including UCS, can nominate experts to contribute to AR7.
Experts selected as Coordinating Lead Authors, Lead Authors, and Review Editors will be responsible for assessing the latest science, drafting report chapters, and responding to expert and government reviews. Given the scale and importance of this assessment, it is essential that scientists from diverse backgrounds and disciplines stay engaged in the process. The absence of the US from this Plenary raises concerns about official US government engagement in AR7. However, US-based scientists can still participate if nominated through other channels, such as observer organization like the Union of Concerned Scientists.
The IPCC remains a cornerstone of global climate science, shaping the foundation for climate policy and action worldwide. With AR7 now in motion, the real work begins. Scientists must remain engaged, ensuring the reports reflect the best available evidence, not just what is politically convenient. Despite the debate that dragged on in the Plenary, the strength of the IPCC lies in its scientific rigor, collective expertise, and global collaboration. .