The world’s leading climate science authority is facing an unprecedented deadlock over when to publish its next major assessment, raising concerns that governments could enter crucial United Nations climate negotiations in 2028 without an updated scientific assessment of global warming.
The Intergovernmental Panel on Climate Change (IPCC), whose assessments have informed every major UN climate agreement over the past three decades, has been debating its publication schedule for nearly three years. The disagreement reflects deeper divisions between wealthy industrialized nations, major emerging economies and developing countries over climate policy, historical responsibility and the resources needed to produce scientific research.
Representatives from the IPCC’s 195 member states are due to meet in Addis Ababa, Ethiopia, on Monday in what many participants consider their last opportunity to agree on a timeline that would allow the next reports to be published before the UN climate talks in November 2028. Those negotiations will include an assessment of progress toward the goals established under the 2015 Paris Agreement.
The dispute comes as global efforts to reduce greenhouse gas emissions continue to fall short of international targets. Without an updated assessment, countries could face the next phase of climate negotiations with an incomplete picture of the latest scientific findings and their implications for emissions reductions, climate finance and adaptation.
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A Deadline Dispute With Global Consequences
The IPCC plans to publish three major reports covering the causes and extent of climate change, vulnerabilities and adaptation, and options for limiting further warming. The scientists leading the assessments have proposed a schedule under which all three reports would be approved by September 2028.
Robert Vautard, a French co-chair of one of the assessment groups, said the proposed timeline reflected the anticipated scientific workload rather than an attempt to align publication with the 2028 UN summit. He noted that publication schedules are typically agreed upon quickly.
However, several countries want the second and third reports postponed until 2029, arguing that the proposed schedule would leave insufficient time to examine thousands of studies, negotiate the wording of findings and complete expert and government reviews.
The disagreement matters because the 2028 climate negotiations are expected to help guide decisions on national emissions targets and climate financing. Countries advocating an earlier publication date argue that relying on assessments published in 2021 and 2022 would leave negotiators without an authoritative review of important developments in climate science.
The High Ambition Coalition, which includes more than 30 countries spanning Europe, Latin America and small-island states, has expressed concern about the potential delay. In a statement seen by Reuters, the coalition argued that access to current scientific evidence was essential for a fair, equitable and evidence-based response to climate change.
Politics Complicates the Scientific Process
The deadlock has exposed tensions within an institution established to provide governments with a shared scientific foundation for climate negotiations.
The IPCC does not conduct original research. Instead, it reviews existing scientific literature through assessments prepared by hundreds of international experts and approved by its member governments. Its findings have helped shape international climate agreements, informed national policy and been cited in international court rulings.
The organization is now operating in an increasingly contentious political environment. Governments critical of climate policies have argued that emissions restrictions can undermine industrial competitiveness and limit the ability of developing economies to use affordable fossil fuels to meet their development needs. The United States, the IPCC’s largest funder, withdrew from the organization in January.
Some scientists and observers believe the push to delay publication could weaken pressure on governments to accelerate emissions reductions. They note that several major oil-producing countries have advocated a longer preparation period.
Lisa Schipper, an IPCC editor from Sweden, described politics as a central factor in the dispute and warned that some countries could be using the debate to delay action.
Russia’s economy ministry rejected the suggestion that the disagreement should be framed as a confrontation between oil producers and other countries. It argued that synchronizing the IPCC’s assessments with UN negotiations raised questions about the organization’s independence and risked allowing scientific findings to be used to advance predetermined policy objectives.
Thiagarajan Jayaraman, an Indian scientist representing his country at the IPCC, similarly argued that the value of the organization’s work should not be measured solely by whether its reports are available for the 2028 climate talks. Representatives from Saudi Arabia and China have expressed similar views at previous meetings.
The competing positions illustrate the difficulty of separating the scientific process from the political decisions governments must eventually make on climate change.
Developing Countries Demand Greater Representation
A central issue in the dispute is whether developing countries have sufficient opportunities to contribute to the IPCC’s assessments.
Many developing economies argue that their researchers face greater obstacles to producing and publishing peer-reviewed studies. Limited research funding, fewer institutional resources and the difficulty of taking time away from regular employment for unpaid IPCC work can restrict their participation.
India’s Jayaraman has argued that these inequalities affect how questions of fairness and representation are addressed in climate assessments. He has also criticized what he sees as insufficient consideration of the historical contributions of wealthy countries to global warming and the development needs of poorer nations in models used to assess future temperature increases.
These concerns reflect a longstanding disagreement over climate responsibility. India argues that countries whose wealth was built through centuries of fossil fuel consumption should shoulder the largest emissions reductions. Some industrialized countries, meanwhile, maintain that major emerging economies such as India and China must also pursue ambitious cuts because of their substantial current emissions.
The IPCC says it is taking steps to broaden participation. Just over half of the lead authors and editors selected for the next assessment are from developing economies or countries in transition.
IPCC Chair Jim Skea has also said the next reports will include dedicated chapters on climate finance and addressing irreversible harm caused by climate change. Both subjects are particularly important to developing countries seeking greater international support for climate-related losses and adaptation.
However, the representation dispute extends beyond the number of scientists involved. It also concerns which research questions receive attention, how competing evidence is assessed and whether the experiences of vulnerable countries are adequately reflected in global climate scenarios.
Why the Latest Climate Science Matters
The consequences of a delayed assessment extend beyond the scheduling dispute. The next reports are expected to address important scientific questions, including the implications of temporarily exceeding the Paris Agreement’s 1.5-degree Celsius warming threshold and the potential consequences of removing carbon dioxide from the atmosphere.
Global temperatures averaged more than 1.5 degrees Celsius above pre-industrial levels for the first time in 2024, according to the data cited in the original report. Scientists are seeking to improve understanding of what such temperature overshoot means for the climate system and whether, and to what extent, some of its effects could be reversed.
Climate impacts are already placing pressure on governments. The United Nations Environment Programme has repeatedly warned that global efforts to limit warming remain inadequate. Scientists have linked climate change to worsening wildfire conditions in Europe and identified its likely role in intensifying some extreme weather events, including devastating floods and landslides.
Without updated assessments, policymakers could find it more difficult to distinguish established scientific findings from emerging evidence when setting emissions targets, designing adaptation strategies and deciding how climate finance should be allocated.
Jozef Pecho, a climatologist at Slovakia’s GoSpace Labs who uses IPCC reports in his work, warned that the absence of a new assessment could create more opportunities for governments to selectively interpret or distort scientific evidence.
Joeri Rogelj, a Belgian IPCC author, argued that the assessments are most valuable when policymakers can use them in decisions that directly affect climate action.
A Test of Scientific Cooperation and Climate Diplomacy
The IPCC’s impasse highlights a broader challenge facing international climate cooperation: countries must agree not only on how to respond to global warming, but also on the process through which the scientific evidence informing those decisions is assembled and presented.
Publishing the reports before the 2028 negotiations would give governments a more recent common scientific reference point. However, forcing an accelerated schedule without adequately addressing concerns about participation and review time could deepen distrust among countries already divided over climate responsibility.
Delaying publication until 2029, on the other hand, could leave the 2028 negotiations relying on assessments that predate significant scientific and political developments, potentially weakening the shared evidence base for decisions on emissions reductions, adaptation and climate finance.
The upcoming meeting in Addis Ababa will therefore test the IPCC’s ability to balance scientific rigor, inclusive participation and the practical needs of international climate diplomacy.
The outcome will shape more than the publication calendar. It could influence how governments approach the next phase of climate negotiations and whether they can maintain a common scientific foundation while disagreeing over who should bear the costs of addressing global warming.
With information from Reuters.
