After more than two decades of UN negotiations, global greenhouse gas emissions continue to rise, with current projections indicating the planet is on a pathway to a temperature increase of approximately 3.2°C by 2100, well beyond what is considered a safe level. This has spurred scientific and policy interest in the possible role of solar radiation management and carbon dioxide removal geoengineering activities to help avert passing critical climatic thresholds, or to help societies recover if global temperatures overshoot expectations of safe levels. Marine geoengineering proposals show significant diversity in terms of their purpose, scale of application, likely effectiveness, requisite levels of international cooperation and intensity of environmental risks. This diversity of marine geoengineering activities will likely place significant new demands upon the international law system to govern potential risks and opportunities.
International ocean law governance is comprised of a patchwork of global framework agreements, sectoral agreements and customary international law rules that have developed over time in response to disparate issues. These include maritime access, fisheries management, shipping pollution, ocean dumping and marine scientific research. This patchwork of oceans governance contains several bodies of rules that might apply in governing marine geoengineering activities. However, these bodies of rules were negotiated for different purposes, and not specifically for the governance of marine geoengineering. The extent to which this patchwork of rules might contribute to marine geoengineering governance will vary, depending on the purpose of an activity, where it is conducted, which state is responsible for it and the types of impacts it is likely to have. The 2013 amendment to the London Protocol on ocean dumping provides the most developed and specific framework for marine geoengineering governance to date. But the capacity of this amendment to bolster the capacity of international law to govern marine geoengineering activities is limited by some significant shortcomings. Negotiations are under way to establish a new global treaty on conservation of marine biodiversity in areas beyond national jurisdiction, including new rules for area-based management, environmental impact assessments and capacity building/technology transfer. A new agreement has the potential to fill key gaps in the existing patchwork of international law for marine geoengineering activities in high-seas areas. However, it is also important that this new treaty be structured in a way that is not overly restrictive, which might hinder responsible research and development of marine geoengineering in high-seas areas.