High level review of a wide range of proposed marine geoengineering techniques.

Abstract

This is the first dedicated assessment of the wide range of proposed marine geoengineering approaches. It catalogues 27 approaches (including variations of approaches) and details 8 illustrative examples from the categories spanning Carbon Dioxide Removal (CDR), Albedo Modification (AM), and hybrid (i.e., for purposes extending beyond CDR or AM) technologies. • The information available on proposed marine geoengineering techniques varies widely, ranging from the promotion of initial concepts on web sites to theoretical examinations of potential efficacy and risks in the peer-reviewed literature, supported by some basic descriptions of matching technology. Techniques have been proposed by scientists and by the private sector. • Descriptions are provided for >20 techniques and are structured to include: approach/rationale; underlying principle(s); extent of knowledge; evidence of concept; proposed deployment zone(s); potential scale of use; duration of deployment; evidence of feasibility; and appraisal of potential impacts. • Detailed information and evidence are essential to assess the efficacy and the potential long-term benefits and risks of a marine geoengineering approach. It was agreed that if there is no substantive science behind a proposal, it is not possible to provide a scientific review of it nor to provide solid policy recommendations beyond providing guidelines as to how to proceed. For each and every technique, information on marine geoengineering approaches available in the permanent public record, and/or as peer-reviewed documents, is inadequate to permit a robust scientific assessment, much less one that can be readily intercompared with other approaches to climate intervention. • Although decisions on policy formulation or governance often have to be based on incomplete information, for many of the marine geoengineering approaches examined the knowledge available was viewed to be insufficient for evidence-based decision-making. These major gaps also raise issues regarding the ability to effectively communicate the many aspects of geoengineering to the general public. In the report we have attempted to provide guidelines for proponents on the series of steps needed to support an evidence-based assessment. • Despite the widespread knowledge gaps, it was possible to provide an evaluation of eight illustrative marine geoengineering approaches using the most applicable and pertinent criteria from prior reports (NAS, CBD) bolstered with additional essential criteria (Summary Table). The most important of these criteria is the availability of information on the performance and impacts of these approaches as attained by scientific testing and experimentation.