In 2013, Parties to the UNFCCC were invited to prepare and communicate their Intended Nationally Determined Contributions (INDCs) under a 2015 agreement. Assessment and review of INDCs can help to ensure that these contributions are in line with internationally agreed objectives and principles, help establish and enhance transparency, trust and accountability between Parties, and raise ambition over time.

 This report analyses the existing review processes both under and outside the UNFCCC. It suggests that some form of ex ante assessment and review process of INDCs could help ensure that they are ambitious and fair. Such process can be complemented by assessments by observer organizations and informal discussions among Parties. In addition, a periodic review of collective ambition is desirable from the perspective of environmental effectiveness, and can build on existing review processes.