This post was co-authored by UCS Principal Climate Scientist Kristina Dahl.
Last week, we participated in an IPCC plenary meeting held in Sofia, Bulgaria. Delegates from around the world convened with three main, substantive tasks: approving outlines for a new special report on cities and climate change; approving outlines for a methodology report on short-lived climate pollutants; and agreeing on a timeline for the publishing the three main IPCC working group reports for the organization’s seventh assessment cycle.
As the IPCC has a consensus-based decision-making system, the days involved long, detailed, intense debates. At times, it seemed as though consensus would be impossible to achieve. But as IPCC Chair Jim Skea remarked, the plenary process is about delicate compromise. And in most instances, compromise prevailed. We wished for more ambitious outcomes, but we were heartened to witness the collaborative decisions the IPCC ultimately reached.
So, who is actually making these decisions? What was decided? And, as delegates from UCS, which is an observer organization, what did we observe?
Who is making decisions at IPCC meetings?
The IPCC is a collaborative panel consisting of 195 member governments. Representatives of these member governments convene in Plenary Sessions, like the one we just attended. Each country sends delegations that can include both government officials and scientific experts, collectively forming the Panel. Additionally, roughly 200 observer organizations, such as UCS, can send delegates who watch and weigh in as well.
During these sessions, the Panel makes every decision by consensus. That means that every decision—from the titles and outlines of reports to the budget—must be agreed upon by all delegations. Importantly, though, the Panel is not involved in developing the content of the special reports, methodology reports, and working group reports. That work is left to scientific experts, and governments only review and adopt the reports after the experts have done their work.
What did the IPCC decide at the meeting in Sofia?
At the start of this meeting, the Panel was given draft outlines for two reports that were developed by groups of experts from around the world tasked with identifying the key research needing to be assessed for their respective reports. The Panel was also given a draft schedule for the IPCC’s next working group reports. Starting with these proposals, where did we land?
Outline of a Special Report on Climate Change and Cities
Delegates dissected the proposed outline for the Climate Change and Cities report over several days. Comments from the country delegates and observers led to some helpful improvements, notably:
- A more even balance of how cities can contribute to mitigating climate change and how they can adapt to it;
- Careful language that ensures the report will be relevant to policymakers without prescribing or suggesting specific policies; and
- Increased prominence of losses and damages cities are facing. During late-night sessions, delegates successfully worked to find compromises for how to treat topics such as physical and social tipping points and maladaptation.
In the end, the Panel approved an outline for the report that we think will serve urban decisionmakers well. The report will assess and discuss:
- The wide range of climate risks and vulnerabilities cities face, including losses and damages.
- Historical and current climate trends, urbanization patterns, and the interaction of local and global risks.
- Actions and tools for reducing urban emissions and adapting to climate risks in the context of sustainable urban development.
- Accelerating change through innovative planning, governance, and finance while addressing social equity and justice.
- Solutions—including addressing losses and damages—tailored to different city types, regions, levels of development, and other characteristics.
The call for authors for the Cities report will take place between August 9-September 20 of this year with expected final report review by the Panel in March 2027.
Outline of a Methodology Report on Short-Lived Climate Forcers
Since 2006, the IPCC has provided methodologies that governments around the world use to estimate their greenhouse gas emissions. This methodology report will be the latest in a series of updates to those methodologies and will offer extra guidance on assessing emissions of pollutants, including nitrogen oxides (NOx), carbon monoxide (CO), non-methane volatile organic compounds (NMVOCs), sulfur dioxide (SO2), ammonia (NH3), black carbon (BC), and organic carbon (OC), with BC and OC including emissions of particulate matter. After intense discussions about whether there is sufficient certainty on hydrogen’s effect on the climate, the Panel also decided that there will be an appendix that discusses hydrogen (H2) in this report.
Past methodology reports like this one have commonly included appendices on gases where the science is still evolving, and, when appropriate, subsequent reports have built out fuller methodologies. The Panel also decided that while the science on the health impacts of particulate matter exposure are real and significant, a technical methodology report like this one that focuses simply on estimating greenhouse gas emissions is not the place to elaborate on those health impacts.
The IPCC will issue a call for authors in the upcoming weeks with expected publication of the report in the second half of 2027.
When will the IPCC’s Next Working Group Reports be Published?
Following on the conversations at the IPCC’s last plenary meeting in Istanbul, there continued to be heated and drawn-out debates about the timeline for the schedule for writing and releasing the three IPCC working group reports that make up the core of each assessment cycle. At the core of the debate was whether the IPCC should aim to publish its main reports before the UNFCCC Global Stocktake (GST) in 2028, a key moment in global climate policy. The arguments were divided into two main camps.
One group contended that the proposed timeline was too short, which would compromise the quality of scientific inputs and hinder inclusive participation from experts from developing countries.
The opposing group believed that the proposed planning schedule was consistent with previous cycles and would meet one of the IPCC’s primary charges: to provide timely, policy-relevant assessments of the state of climate science.
The Panel agreed to delay a decision about the report schedule until its next plenary meeting. The hope is that with more information from experts on what these reports will contain, the Panel will FINALLY be able reach consensus around the schedule. We are still assessing whether this will affect the timeline for the publication of the reports, but we will know more later this year when IPCC leaders will once again review a proposed report schedule.
In-the-room observations
Like UCS, the IPCC aims to produce rigorous science that can feed into public policies. As an observer, part of UCS’s role in this space is to encourage the use of the best-available science and to ensure that there is no policymaker interference in the scientific process. To that end, we had a few key observations and contributions:
- The most frightening moment for us was when some countries tried to institute a mid-report review by governments on one report, essentially deciding whether scientists could proceed with their research. As this would constitute policymaker interference in the scientific process, this was incredibly problematic and would have set a terrible precedent. Ultimately, and to our great relief, science prevailed.
- We intervened when the debate veered into specific scientific questions, particularly the question of whether wildfires are being influenced by climate change. UCS clarified that climate change is, indeed, worsening wildfires, so including PM2.5, a short-lived climate forcer generated by wildfires, is important to include in the methodology report under consideration during this meeting. In these moments, the panel should rely on the expertise of specialists.
- We used the meeting as an opportunity to personally encourage the co-chairs of the Task Force on National Greenhouse Gas Inventories to include experts on the social, legal, political, and ecological implications of carbon dioxide removal and carbon capture utilization and storage among those determining the content of a forthcoming report on the topics.
The days were long, and results were mixed, but at the end of the week, key decisions were made to move the IPCC process forward. While we face constant impacts of climate change around the world, it can be painful to sit in these rooms and feel like things are moving incredibly slowly, but we are grateful for the process that brings together people from nearly 200 countries and enables them to talk about and embrace the climate science.