This paper concludes the collection on an extended scenario exercise that examined governance challenges and potential responses for solar geoengineering. It synthesizes the experiences of eight participant groups who worked with four scenarios of unauthorized use of solar geoengineering. It draws both substantive insights about solar geoengineering risks and governance and methodological insights for the use of scenario exercises to explore this issue, as well as identifying major uncertainties and questions raised by the exercise. Prominent themes include the need for strategic sequencing of actions by those initiating and responding to solar geoengineering challenges; the nature and foundations of potential opposition; the widespread interest in normalizing or domesticating a disruptive intervention after the fact; the importance of embedding solar geoengineering actions in the broader context of climate policy and the difficulty of doing so given their disruptive character; and the importance and likely structure of negotiations to move from initial disruptive action, whatever its initiators and form, to broaden participation and embed solar geoengineering decisions in a broadly legitimate multilateral governance structure. In the closing section, we propose directions for further scenario-based explorations of solar geoengineering and its governance challenges.