The trajectory of global climate governance leading into and out of the landmark 2015 Paris Agreement reveals substantial change in the kinds of mechanisms in play. In their Introduction to this collection, Bäckstrand, Kuyper, Linnér, and Lövbrand (2017) capture these developments under the rubric of ‘hybrid multilateralism’, defined by emerging linkage between the established multilateral negotiations and the plethora of self-organizing governance initiatives involving varieties of non-state actors cooperating with one another (and sometimes with states). These two governance options were long seen as, if not exactly mutually exclusive, at least as involving very different and rival agendas. Proponents of decentralization took as their starting point the failure of multilateralism. This recognition of failure led Matthew Hoffmann (2011) to celebrate the multiplicity of what he called (somewhat inaccurately, as Abbott (2017) points out) experimental governance as an alternative to ‘mega-multilateralism.’ Experimental governance, for Hoffman, involves numerous cooperative, market-oriented voluntary initiatives (which he neglects to demonstrate will collectively do enough good). Buoyed by her Nobel Prize, Elinor Ostrom (2009) advocated a polycentric approach involving numerous overlapping programs at multiple levels of government, though again she was short on evidence of effectiveness from climate governance itself. David Victor (2011) for his part stressed the formation of clubs of relatively high ambition countries to enable movement beyond impasse in multilateral negotiations. Frank Biermann (2014), in contrast, believes that the solution to any failure of multilateralism is to try much harder, to move toward stronger and reinvigorated multilateralism. He laments at the same time fragmentation in global governance, which Hoffman and Ostrom would surely applaud. Now it seems that the world has moved on. The 2015 Paris Conference of the Parties to the United Nations Framework Convention on Climate Change did produce a multilateral agreement. But all the critics of multilateralism and advocates of decentralization could at least console themselves that the multilateral process now embraced multiple transnational governance initiatives.