This conclusion synthesises the book’s findings on ocean acidification (OA) governance. The study demonstrates that OA is a complex problem spanning ocean, atmosphere, and land systems with varying temporal and spatial dimensions. The current governance landscape constitutes a regime complex involving multiple institutions across different issue areas. Global experimentalist governance emerges as the most suitable approach because it can accommodate OA’s complexity and build upon existing fragmented governance structures. Two case studies – the Ocean Acidification Alliance and International Maritime Organization – reveal partial implementation of experimentalist governance features but significant limitations. Both institutions struggle with setting specific metrics, systematic reporting, peer review, and feedback mechanisms essential for recursive learning. Key obstacles include scientific uncertainty making concrete targets difficult, institutional reluctance towards delegation and provisionality, and weak communication across governance levels. Despite incomplete realisation, experimentalist governance remains promising for OA because it provides necessary flexibility and adaptability. The book concludes that while current institutions show experimentalist features, full implementation requires addressing institutional apprehensions and developing stronger communicative infrastructures for effective multilevel coordination in tackling this emerging environmental challenge.