Science assessments indicate that human activities are moving several of Earth's sub-systems outside the range of natural variability typical for the previous 500,000 years (1, 2). Human societies must now change course and steer away from critical tipping points in the Earth system that might lead to rapid and irreversible change (3). This requires fundamental reorientation and restructuring of national and international institutions toward more effective Earth system governance and planetary stewardship.

Although transparency is a key concept of our times, it remains a relatively understudied phenomenon in global environmental politics. The link between transparency and accountable, legitimate and effective governance is assumed, yet the nature and workings of this link require further scrutiny. Transparency via information disclosure is increasingly at the heart of a number of global environmental governance initiatives, termed “governance-by-disclosure” here. The article identifies two assumptions that underpin such governance-by-disclosure initiatives, and calls for comparative analysis of the workings of such assumptions in practice, as a way to illuminate the nature and implications of a transparency turn in global environmental governance and its link to accountable, legitimate and effective governance.

Solar geoengineering is gaining prominence in climate change debates as an issue worth studying; for some it is even a potential future policy option. We argue here against this increasing normalization of solar geoengineering as a speculative part of the climate policy portfolio. We contend, in particular, that solar geoengineering at planetary scale is not governable in a globally inclusive and just manner within the current international political system. We therefore call upon governments and the United Nations to take immediate and effective political control over the development of solar geoengineering technologies. Specifically, we advocate for an International Non‐Use Agreement on Solar Geoengineering and outline the core elements of this proposal. This article is categorized under: Policy and Governance > International Policy Framework