Participation, ambition and compliance: can the Paris Agreement solve the effectiveness trilemma?

An effective climate agreement should simultaneously foster broad participation, high ambition, and sufficient compliance: this is the ‘effectiveness trilemma’. While the Paris Agreement has been acclaimed for spurring universal participation, its mitigation mechanism – an unenforced bottom-up framework of voluntary pledges – has been criticized for lacking ambition and incentivizing free riding. Does the Paris Agreement come with effectiveness trade-offs? How ambitious is the Agreement, and how likely is it that countries will comply with it? Using an effectiveness formula to assess ambition, I find that the Paris Agreement constitutes an important improvement compared to business-as-usual. Further, based on evidence from interviews with 21 climate negotiators and observers, the compliance prospects of the Agreement are evaluated as moderately positive. I conclude that the Agreement has the potential to overcome the effectiveness trilemma, and outline policy measures for achieving that objective.