octobre 2025
A sweeping review by researchers from the University of Pennsylvania, Berkeley, and Oxford exposes the uncomfortable truth behind the booming carbon offset industry:
Most carbon credits don’t actually offset anything.
Across compliance and voluntary markets, offsets have overstated their climate benefits five- to tenfold, making them one of the most unreliable pillars of “net zero” strategies. With COP29 setting the stage for a global carbon credit market under the Paris Agreement, the authors warn: Without radical reform, we risk repeating decades of greenwashing.
From Kyoto to COP29 — How we got here
Since the early 2000s, mechanisms like the Clean Development Mechanism (CDM) and Joint Implementation (JI) were designed to help rich countries fund emissions reductions in poorer ones. In theory: 1 carbon credit = 1 ton of CO₂ reduced. In reality: most credits represent phantom reductions.
- CDM: 85% of projects had “low environmental integrity.”
- JI: 75% of projects were nonadditional — meaning they would have happened anyway.
- Voluntary Carbon Market (VCM): grew to $2B in 2021, then collapsed amid scandals over false claims.
Even the most sophisticated systems, like California’s compliance program or Australia’s carbon market, suffer from systemic overcrediting.
Why the system keeps failing
Despite 20+ years of reform attempts, the same flaws persist:
- Overcrediting Many credits represent imaginary emissions reductions. Studies show a 1:13 ratio of real to fake credits in REDD+ forest projects. Cookstove and forest management offsets routinely exaggerate impacts by 5–9×.
- Additionality & Gaming Projects often claim credit for activities that would have happened anyway — for instance, renewable energy plants that were already economically viable.
- Leakage Preventing deforestation in one area often just shifts logging elsewhere, with leakage rates up to 100%.
- Permanence Nature-based projects promise “100-year storage,” but forests can burn or die within decades. Experts now argue that true neutrality requires geological storage lasting 1,000+ years.
- Low-Quality Demand Corporations prefer cheap, low-quality offsets because they can still market themselves as “carbon neutral”. As one researcher notes: “Bad credits are driving out good credits.”
Paris Agreement complications
The Paris carbon market (Article 6) is supposed to prevent double counting — where both the seller and buyer claim the same reduction. Yet confusion persists between “authorized offsets” (with corresponding adjustments) and “contribution claims”(voluntary funding not tied to ownership of emissions cuts). This complexity risks making the Paris market both expensive and opaque, while voluntary markets could undercut it entirely.
The equity and justice dimension
Offsets often promise social and environmental “co-benefits” — jobs, biodiversity, development. But in practice, many projects:
- Expropriate land from Indigenous communities,
- Restrict local resource access, and
- Worsen inequality through corruption and elite capture.
Some researchers go as far as calling these mechanisms “neocolonial carbon appropriation.” Even when benefits exist, monitoring and accountability remain weak.
As a striking testimonial, last week, a group of Maasai representatives were in Brussels to shed light on the underreported human rights dimension of carbon market projects.
By sharing their own experiences and insights, the Maasai representatives illustrated some of the biggest challenges facing carbon market projects. These included safeguarding the free, prior and informed consent of local communities and indigenous peoples, sharing benefits fairly with them and putting in place effective and robust grievance mechanisms, not to mention ensuring that richer countries don’t shift the burden of climate action to those least responsible for it.
The market fallout
After years of explosive growth, the voluntary market contracted sharply after 2023 following media exposés and academic criticism. Attempts to introduce “core carbon principles” and independent ratings (e.g., ICVCM, Carbon Credit Quality Initiative) are under way — but trust is hard to rebuild.
Where do we go from here?
The authors are blunt:
“Most popular offset project types feature intractable quality problems.”
They propose:
- Shifting focus to high-integrity carbon removal with multi-century storage.
- Ending claims of carbon neutrality based on avoided or temporary reductions.
- Redirecting finance from offsets to direct decarbonization and durable CDR (e.g., mineralization, geologic storage).
- Recognizing contribution claims for conservation and development projects — without counting them as “offsets.”
The takeaway
“Offsets don’t offset — at least, not yet. Until they do, the safest ton of carbon is the one that never enters the atmosphere.”