For years, the debate over permanence in carbon markets seemed stuck on a single question: is carbon storage permanent, or is it not? That framing never quite matched the science. But there are real signs it is finally loosening, and one of the clearest is unfolding right now in the Article 6.4 process itself.
Among a range of other important topics, the Article 6.4 Methodological Expert Panel (MEP) is examining how the Paris Agreement Crediting Mechanism should treat reversal risk and the robustness of its buffer pool. That the Panel is asking these questions at all, and actively weighing a range of approaches, is itself perhaps a small sign of progress. Yet their framing is still quite negative, and focuses more on risks than opportunities. Now is the time to make a strong case that the evidence has advanced considerably.
This matters well beyond Article 6.4. Decisions taken within the 6.4 process carry the imprimatur of the Paris Agreement, to put it bluntly, and they will likely influence other processes like how the EU approaches the international use of credits for its 2040 target.
The debate has moved – the evidence should move with it.
The permanence conversation advanced visibly at London Climate Action Week, and two new white papers now offer a clear articulation of where the thinking is heading.
The first, from SHIFT-CM (a Yale and TNC collaboration), examines buffer pools and the mechanisms that sit alongside them. The second, from the Beyond Alliance together with RMI and AFF, sets out a framework for contracted durability. Read together, they make a compelling case: framing storage as either permanent or temporary misrepresents the science. Durability is a spectrum, not a binary, and this framing is consistent with how the IPCC itself treats storage over different timeframes.
That distinction is critical. A rigid, permanent-versus-temporary binary does not just misdescribe the world, it narrows the set of credible tools available to carbon markets, and it sidelines nature-based solutions precisely when global funding for nature is most needed.
Reversal risk is manageable, through a portfolio of tools
If durability sits on a spectrum, the question becomes how to manage reversal risk credibly across that spectrum. As the two white papers demonstrate, the evidence base has matured, and the MEP’s own concept note reflects it. The Panel is weighing a range of measures: periodic stress testing of the buffer pool, legal attestations on replenishment obligations, insurance (both for activities and for the buffer pool itself), Party-backed replenishment commitments, and third-party arrangements to cover the post-crediting monitoring period. Emerging vehicles such as carbon trusts, alongside sovereign backstopping, add further options. Yet, the framing of the MEP’s concept note is fairly negative towards these options, judging them to be too nascent and focusing predominantly on risks rather than opportunities. While I am encouraged that they are considering them at all, it is critical that the MEP does not miss the opportunity to constructively think through how these tools can be layered and leveraged to thoroughly remediate risk of reversal to empower the full portfolio of climate solutions we need. Markets mature after standards establish clear rules, responsibilities, eligibility requirements and accountability mechanisms.
The right answer is not a single mechanism. It is a well-designed portfolio, with each tool deployed where it adds the most value. The MEP has raised legitimate questions, including the maturity of insurance markets for long-term comprehensive coverage and the risk of adverse selection between a shared pool and alternative arrangements. These deserve serious answers. But they are best understood as design challenges to be solved, not verdicts that close the door.
One architecture, not competing rulebooks
Underlying all of this is a broader principle that Nature4Climate has consistently advanced: meeting the urgency of climate change requires a portfolio approach that keeps the broadest possible set of credible tools in play. That approach works best when the rules governing those tools converge around shared, high-integrity foundations rather than fragmenting into conflicting or one-off standards.
The carbon market does not need another set of competing definitions. If Article 6.4, the ICVCM Core Carbon Principles, and other frameworks can align around a shared, evidence-based understanding of permanence and reversal risk, the market will become more coherent, more investable, and more credible. Fragmentation does the opposite: it confuses buyers, shrinks the eligible credit pool, and slows the finance that nature urgently needs.
The Article 6.4 consultation is a chance to strengthen that convergence and to keep all effective pathways open, including nature-based solutions.