Collective Obligation in the Paris Agreement

Abstract

The 2015 Paris Agreement’s defining obligation for states is a “collective” one. The treaty aims at a specific quantifiable and measurable outcome, namely the containment of global average warming below a 2°C ceiling. Achievement of this outcome is the key collective obligation of parties to the Paris Agreement. A notion of collective obligation exists in international law, however the obligation created by the Paris Agreement is a collective one in a new sense. States are legally obliged as a collective to achieve the containment outcome, and if they fail to do so they are legally liable, again as a collective. In the collective logic of the Paris Agreement, a state must set its mitigation ambition so that it is a fair contribution compared with the effort of other states and leads to mitigation that, in combination with that of other states, ensures that global average warming does not exceed 2°C. Alas, in setting their mitigation ambition, states have been perpetuating a practice dating to the beginning of the Kyoto Protocol whereby each state declares a mitigation target and proceeds to measure its progress against it without consideration of comparative effort or aggregate result. The Paris Agreement contains no clear process to end this isolationist and decidedly bottom-up practice. There is thus a discontinuity in the treaty between global aim and state action, aggravating the risk that the Agreement’s collective obligation on the 2°C ceiling will be breached. The Agreement’s Global Stocktake process is the only element of the new regime which might conceivably be used to oversee the 2°C collective obligation.