Major questions about differentiation in the international climate negotiations include what the global burden is; which country characteristics should be used to differentiate obligations; and what kinds of country categories should be designed.

Although the 2015 agreement accords considerable importance to differentiation, there are several limitations, given the scope of transformation required for global mitigation and action on climate-impacts.

Challenges of differentiation, as it is currently framed, include its zero-sum, burden-sharing approach, and the continued ambiguity about such key concepts as capabilities and national circumstance.

In order to support broad and deep collective action post-Paris, differentiation will need to address climate impacts better, and work towards including the possibility of benefits from climate action within differentiation discussions.

In addition, post-2015 discussions about equity should be expanded beyond differentiation amongst countries at the aggregate level per se, examining how UNFCCC mechanisms could be designed to ensure that they shift opportunity structures in ways that will reduce inequality during transformational changes.