Using the Clean Development Mechanism for nationally determined contributions and international aviation

The Clean Development Mechanism is the world’s largest greenhouse gas crediting mechanism, issuing 1.8 billion CERs so far. Countries are considering using CERs from emission reductions up to 2020 to achieve post-2020 mitigation targets, under both the Paris Agreement and the Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA).

Using CERs could lower compliance costs, support stranded projects and ensure sufficient supply for CORSIA’s implementation. However, the study finds that purchase programmes or policies that recognize all types of CERs for post-2020 targets are unlikely to trigger significant emission reductions beyond those that would occur in the absence the programme or policy.

Instead, policy-makers could prioritize or limit eligibility to certain CERs for post-2020 targets. This could trigger further emission reductions and ensure economic incentives for project developers and host countries.

The authors recommend that policy-makers limit eligibility to CERs from new projects that are additional, and developed in response to the policy or programme. They also suggest using CERs from already implemented projects that are at risk of discontinuing greenhouse gas abatement.

Robust accounting is also important to avoid double counting, according to the report. The authors also emphasize the importance of appropriately accounting for the vintage of CERs and the time frame of mitigation targets.

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