Why the timing of climate assessments matters

As we approach the United Nations COP meeting in Baku in November, a clash is evident in the climate community. Scientific and policy workflows are moving at different paces, even as both aim to ratchet up global efforts to limit average warming to well below 2 °C — the goal of the 2015 Paris climate agreement.
As a climate scientist and a scientific adviser to the Chilean focal point of the Intergovernmental Panel on Climate Change (IPCC), I think that the production of the next set of scientific reports around climate change should align with the review schedules of the Paris agreement, rather than being separate.
This is a crucial moment. Last year, the IPCC began work on its seventh assessment report (AR7). Published since 1990 every six or seven years, these massive compilations of scientific evidence on global warming have swayed governmental actions on climate change the world over.
But the policy landscape has changed since the Paris climate agreement was signed off. The global climate-policy community now paces itself around its five-year cycles. Nations will update their emissions-reduction plans in 2025 and 2030, and review progress midway in 2028 and 2033. November COP meetings are the world’s crucible for such international discussions.
No timeline has been set for the release of AR7, although a likely window is between early 2028 and early 2029. In my view, the IPCC should ensure that the earlier deadline is met. The availability of these reports will be essential for the global stocktake of climate actions in November 2028.
The IPCC straddles science and policy communities. Scientists assess the literature and write the reports, making sure they are scientifically accurate. A panel of governmental delegates from 195 member countries ensures that the IPCC reports are relevant to policy. This panel also decides on the structure, products and timeline of each IPCC cycle.
Until now, the duration of IPCC cycles has been largely a scientific issue, its rhythm modulated by the generation of new climate models and experiments developed by the Climate Model Intercomparison Project. But the Paris timeline poses a conundrum for the IPCC. Should it stay synchronous with the slower, model-driven process and prioritize a more-complete scientific output, or should it align its schedule with the Paris agreement cycles and prioritize policy relevance?
On the one hand, the IPCC should provide governments with the best available science and therefore not rush its assessments before many quality papers have been published. On the other hand, the IPCC was set up to provide policy-relevant information, not periodical long reports.
The Paris global emissions stocktakes are a prominent and an integral part of international efforts to tackle climate change. If the IPCC does not provide punctual, policy-relevant information for stocktakes when it can, why does it exist at all? Indeed, the decision text for the first stocktake explicitly invited the IPCC to work together and provide relevant and timely information.
There are two perspectives among the nations represented in the IPCC. Most emphasize the policy relevance of the IPCC and would prefer to publish all three reports in 2028, in time to inform the global stocktake. But some advocate thoroughness. They argue that the proposed timeline is too constrained for an in-depth literature assessment and comprehensive government review, especially for low- or middle-income countries (LMICs), so a 2028 deadline would make the process less inclusive.
These are valid points. High-income countries (HICs) have teams of government officials and scientists working in established networks. These connections are under-developed in LMICs, so they might have to burden a single person with all the governmental review work.
Publication of local studies relevant for the IPCC also takes longer in LMICs, and these papers are sometimes not published in English. Indeed, AR6 highlighted glaring differences between HICs and LMICs in the availability of, agreement with and confidence in scientific evidence — issues that must be addressed in AR7.
However, as has been well argued by colleagues in LMICs, delaying the publication of AR7 — for as little as six or nine months at most — would not address these structural problems. Indeed, excluding any of the AR7 reports from the global stocktake in 2028 would weaken climate action. That would have a bigger negative impact on global inclusivity and equality, because LMICs are more vulnerable to the effects of climate change.
In my view, it is unnecessary to trade policy relevance for inclusivity. In terms of the science, it is possible to publish all three AR7 reports by mid-2028. There will be enough new literature to assess by then. The IPCC is also taking steps to improve inclusivity in AR7, for example by aiming to include more non-English publications and ‘grey’ non-peer-reviewed literature, and supporting the creation of climate networks in LMICs.
I urge climate scientists in all countries to join or establish national climate networks. Reach out to your IPCC focal point and inform it, as well as your government, of your willingness to participate. Make the case that publishing all three AR7 reports before the 2028 global stocktake will benefit your country, and the world, in the long term.