This discussion brief builds upon the workshop DzReviewing )implementation and Compliance under the Paris Agreement, held at Arizona State University, 7-8 April 2016. Authors have contributed to this brief in their personal capacities; views expressed here do not necessarily reflect those of the institutions with which the authors are affiliated. The authors would like to thank Christina Voigt and Jake Werksman for comments on an earlier draft.
To succeed, the hybrid model of international climate policy embodied in the Paris Agreement requires countries to deliver their nationally determined contributions (NDCs) and to progressively increase collective and individual efforts over time. The effectiveness of this type of regime will require international review processes that provide robust information about countries’ efforts and trajectories and give substantial opportunities for state and non-state actor engagement with this information. The Paris Agreement creates three different review processes, but leaves critical details regarding each to future decisions:
 It provides for a review of implementation of individual NDCs under an enhanced transparency framework , comprising a technical expert review and multilateral consideration Article .
 It puts in place a global stocktake every five years to assess the collective progress towards achieving the purpose and long-term goals of the Agreement (Article 14), preceded by a mitigation-focused facilitative dialogue in 2018.
 It establishes a mechanism to facilitate implementation and promote compliance through a committee that is expert-based, non- adversarial and non-punitive. (Article 15).
It is essential for Parties to develop effective modalities, procedures and guidelines, as mandated by Decision 1/CP.21, for each of these processes. To this end, this discussion brief highlights essential considerations and potential options for each process.

Effective review in a hybrid regime
The Paris Agreement shifts the United Nations climate regime away from a top-down system of negotiated, legally-binding emissions targets enshrined in global protocols. The new hybrid system is a mix of bottom-up and top-down elements in which Parties are required to submit a non-legally binding NDC every five years, which is then subject to a number of mandatory review processes. National contributions, in aggregate, might (and currently do) fall short of overall goals. Under the previous regime, these problems were front-loaded into the negotiation process. The Paris Agreement instead back-loads questions of effectiveness and equity into the review and stock-taking phases.
At present, nearly every country in the world has submitted a national contribution. Parties’ contributions range from economy-wide emissions targets, to mitigation policies and measures, with some also including adaptation components and some made partly conditional on the support provided by other Parties. The heterogeneous contents of Parties’ contributions will shape the review system that emerges over time.
In this hybrid system, the importance of effective review cannot be understated. Because the targets set out in the NDCs are not made legally binding by the Paris Agreement, the review systems are the chief tools to make the agreement effective by generating information and providing an opportunity for political pressure to be applied to help ensure that countries are meeting their political commitments, including those contained in their NDCs. As the review processes do not start until the Paris Agreement comes into force (with the exception of the 2018 facilitative dialogue on collective progress toward the Paris Agreement’s mitigation goals , there is now a window of time to develop a reliable review system that supports a progressive dynamic of increased contributions over time.
The review processes, which are detailed below, are three separate but functionally linked systems. While each was preliminarily designed to fulfil specific, potentially discrete functions, when looked at collectively, they highlight some important functions and potential benefits as a whole. First, as mentioned above, effective review is essential for tracking how NDCs align collectively with internationally agreed objectives and principles, such as staying well below 2 °C and pursuing 1.5 °C, and equity considerations. Second, the process can and is expected to enhance transparency, trust and accountability between Parties by creating a shared understanding of Parties’ contributions and implementation efforts, as well as the underlying information, data and assumptions. Third, it can identify obstacles to implementation of NDCs, and help channel resources to countries to overcome such barriers. Finally, and maybe most importantly, review can help to increase ambition by providing an opportunity for feedback and exchange of ideas and approaches, and by encouraging additional reciprocal actions from other Parties. In essence, the review process is key for the success of the Paris Agreement on multiple dimensions of effectiveness.

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