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As the prospect of average global warming exceeding 1.5°C becomes increasingly likely, interest in supplementing mitigation and adaptation with solar geoengineering (SG) responses will almost certainly rise. For example stratospheric aerosol injection to cool the planet could offset some of the warming for a given accumulation of atmospheric greenhouse gases (1). However, the physical and social science literature on SG remains modest compared with mitigation and adaptation. We outline three research themes for advancing policy-relevant social science related to SG: (i) SG costs, benefits, risks, and uncertainty; (ii) the political economy of SG deployment; and (iii) SG’s role in a climate strategy portfolio. Some concerns have received increased attention in debates over SG and thus illustrate the need for greater social science evidence and understanding. For example, some stakeholders have suggested that undertaking SG research could create a form of moral hazard by deterring emission mitigation efforts, whereas other scholars have challenged this claim. Still other scholars have questioned the ethics of seeking to hide from future generations policy choices that they may wish to consider. And given the evidence of strong free-riding incentives for emission mitigation, it is not clear that there would be much of an additional emission mitigation disincentive from SG. But these questions deserve further study in more realistic models of multiple, heterogeneous actors (1, 2). Further, if a major economy with the technical capacity to implement SG makes a decision about its use, this would have important equity and justice implications, especially for the people living in least developed countries and small island states. These implications take the form of procedural justice—do these peoples have a voice in the decision-making process—as well as the distributive justice of the outcomes associated with a SG intervention decision. Such justice considerations arise regardless of whether the decision is to take or opt against an SG intervention. A critical assessment of the justice implications of SG implementation would enrich the political economy evaluation of government decision-making. SG is one of several emerging climate engineering technologies. For example, carbon dioxide (CO2) removal would reverse the flow of greenhouse gases into the atmosphere through large-scale biological and chemical sequestration and industrial direct air capture technologies. In contrast to CO2 removal, SG faces fewer technological and financial hurdles and would likely influence temperatures more quickly. Indeed, the largest developed and developing nations have the resources and technical means to implement SG interventions in no more than a few years. Despite the potential for SG to reduce climate change risks, the international community has not addressed SG under the UN Framework Convention on Climate Change. This is mirrored by a dearth of national programs and governance. The limited policy landscape provides an opportunity for new social science research to inform the design of institutions, policy, and governance of SG.