Environmental integrity of international carbon market mechanisms under the Paris Agreement

The Paris Agreement establishes provisions for using international carbon market mechanisms to achieve climate mitigation contributions. Environmental integrity is a key principle for using such mechanisms under the Agreement. This paper systematically identifies and categorizes issues and options to achieve environmental integrity, including how it could be defined, what influences it, and what approaches could mitigate environmental integrity risks. Here, environmental integrity is assumed to be ensured if the engagement in international transfers of carbon market units leads to the same or lower aggregated global emissions. Four factors are identified that influence environmental integrity: the accounting for international transfers; the quality of units generated, i.e. whether the mechanism ensures that the issuance or transfer of units leads to emission reductions in the transferring country; the ambition and scope of the mitigation target of the transferring country; and incentives or disincentives for future mitigation action, such as possible disincentives for transferring countries to define future mitigation targets less ambitiously or more narrowly in order to sell more units. It is recommended that policy-makers combine several approaches to address the significant risks to environmental integrity.Key policy insights Robust accounting is a key prerequisite for ensuring environmental integrity. The diversity of nationally determined contributions is an important challenge, in particular for avoiding double counting and for ensuring that the accounting for international transfers is representative for the mitigation efforts by Parties over time.Unit quality can, in theory, be ensured through appropriate design of carbon market mechanisms; in practice, existing mechanisms face considerable challenges in ensuring unit quality. Unit quality could be promoted through guidance under Paris Agreement Article 6, and reporting and review under Article 13.The ambition and scope of mitigation targets is key for the incentive for transferring countries to ensure unit quality because countries with ambitious and economy-wide targets would have to compensate for any transfer of units that lack quality. Encouraging countries to adopt ambitious and economy-wide NDC targets would therefore facilitate achieving environmental integrity.Restricting transfers in instances of high environmental integrity risk – through eligibility criteria or limits – could complement these approaches.