Highest possible ambition as a minimum requirement for historical high emitters under the Paris Agreement

Parties to the Paris Agreement are committed to submit five-yearly climate pledges, known as Nationally Determined Contribution (NDCs), that describe their intended climate change mitigation actions for the next 5 to 10 years. The Paris Agreement mandates that subsequent NDCs represent a progression compared to earlier NDCs, be a country’s highest possible ambition, and reflect a country’s common but differentiated responsibilities and respective capabilities in the light of different national circumstances. While there is a rich literature on interpreting and operationalising equity and fairness in international climate policy, scholarship on interpreting and operationalising the norms of progression and highest possible ambition is largely absent. In addition, recent literature indicates that because of insufficient past action, several countries find themselves in a position where even their deepest possible emissions reductions do not result in equitable contribution when considered in an appropriate historical context. Here, we will present a framework for the operationalisation of highest possible ambition in NDCs. While this framework is applicable to all countries, it is also presented as a way to inform minimum requirements for the level of ambition of climate change mitigation action under the Paris Agreement by historically high emitters.