Working Group on Marine Geoengineering

GESAMP agreed to establish Working Group 41 on marine geoengineering under the lead of IMO and supported by IOC of UNESCO and WMO, under the co-chairmanship of Dr. Chris Vivian and Professor Philip Boyd.

The study was needed to:

  1. Better understand the potential environmental (and social/economic) impacts of different marine geoengineering approaches on the marine environment; and
  2. Provide advice to the London Protocol Parties to assist them in identifying those marine geoengineering techniques that it might be sensible to consider for listing in the new Annex 4 of the Protocol.

Terms of Reference

The GESAMP study should provide an overview to GESAMP Agencies and their Member States of a wide range proposed marine geoengineering techniques and their potential implications by:

  1. Providing an initial high level review of a wide range of proposed marine geoengineering techniques, based on published information, addressing:
    • The main rationale, principle and justification of the techniques
    • Their potential scientific practicality and efficacy for climate mitigation purposes
    • The potential impacts of different marine geoengineering approaches on the marine environment and the atmosphere where appropriate
    • Identifying those techniques:
      1. that appear unlikely to have the potential for climate mitigation purposes, and
      2. that appear to be likely to have some potential for climate mitigation purposes and that bear further detailed examination
  2. Providing a detailed focused review of a limited number of proposed marine geoengineering techniques that are likely to have some potential for climate mitigation purposes addressing:
    • The potential environmental and social/economic impacts of those marine geoengineering approaches on the marine environment and the atmosphere where appropriate.
    • An outline of the issues that would need to be addressed in an assessment framework for each of those techniques, using the London Protocol Assessment Framework for Scientific Research Involving Ocean Fertilization as a template.
    • Their potential scientific practicality and efficacy for climate mitigation purposes.
    • An assessment of monitoring and verification issues for each of those marine geoengineering techniques.
    • Identification of significant gaps in knowledge and uncertainties that would require to be addressed to fully assess implications of those techniques for the marine environment and the atmosphere where appropriate.
  3. Produce reports on the above work at appropriate points in the workplan.


  • Marine scientists and engineers with expertise in marine ecology (in particular plankton ecology, macroalgae and benthos), fisheries, marine chemistry/geochemistry/biogeochemistry, physical oceanography (including modelling), atmospheric chemistry and climate science;
  • Scientists and engineers who have studied marine geoengineering techniques and their potential impacts; and
  • Social scientists with expertise including environmental economics.

Recent Activities

First Meeting

Working Group 41 held its first meeting from 23 to 25 May 2016, at the headquarters of IMO in London, United Kingdom. The Working Group discussed how they could best build on prior assessments of geoengineering (such as the 2009 UK Royal Society report and the 2015 US NRC reports). Two key advances were identified by the WG: the development of new metrics (in particular the knowledge available on a specific approach), and secondly the role of modelling to advance the geoengineering debate. In particular the potential of the CRDMiP project (Carbon Dioxide Removal Model Intercomparison Project) as a rigorous tool for an initial quantitative assessment of proposed marine geoengineering methods..

Desirable metrics that were identified included: economics – welfare endpoints; biodiversity – ecological integrity (linked to welfare endpoints via ecosystem services); modelling (to provide Earth system metrics) and knowledge (specifically, the need to provide sufficient information to meet a threshold for inclusion in a scientific assessment). These metrics were then included in a discussion that centred on which metrics to include in the development of a scoring sheet to rank a wide range of marine geoengineering proposals as part of the terms of reference (ToR) for the initial phase of WG41.

The WG recognised that models alone will be insufficient to deliver a more comprehensive assessment. Nonetheless, they have an invaluable role to play in identifying key unknowns that the models are particularly sensitive to. Model simulations could also help to provide a more quantitative comparison between metrics, which was another area the WG identified as problematic in both the development of a scoring sheet, and intercomparisons of the merits of different geoengineering approaches using such a scoring method.

Since the May 2016 inception meeting the WG refined the scoring sheet for assessment criteria and WG members each filled in the scoring sheet with 17 assessment criteria for 29 marine geoengineering approaches. The summarised scores were circulated to the WG members prior to the second meeting.

Second Meeting

The WG’s second meeting was held from 26 to 28 April 2017, at the WMO Headquarters in Geneva, Switzerland.

Guest presentations were given by Janos Pasztor (Carnegie Climate Geoengineering Governance Initiative (C2G2)) on the C2G2 Governance Initiative (26 April), and by Aaron Strong (University of Maine), on Navigating the science-policy boundary in the context of geoengineering.

The co-chairmen reported the results of the scoring exercise. The scoring of each approach in the assessment had been difficult, and in almost all cases was hindered by a lack of information in the permanent record; a major problem in the view of WG 41. However, it was deemed a worthwhile investment and was built upon at the meeting. Debate took place on the rationale for selecting geoengineering approaches to be considered in more detail. Due to the widespread gaps in knowledge about geoengineering approaches, the selection of a subset of approaches to be further scrutinised could not be based on an authoritative view. Thus, the WG decided to select an illustrative approach across each of eight distinct geoengineering categories.

The approaches selected were: ocean iron fertilisation; CO2 storage on the seabed; foams to increase ocean albedo; direct addition of alkaline material; marine cloud brightening; artificial upwelling; macroalgal cultivation; fertilisation for fish stock enhancement.

Due to the paucity of information available on some evaluation criteria, the WG reduced the number of criteria from 15 to 8. This selection of illustrative approaches and evaluation criteria provided an 8 by 8 framework to be further developed by the WG. Critically, the selection of ocean iron fertilisation (for which there is an existing regulatory framework, the London Convention and London Protocol) as part of the detailed assessment enabled other categories of geoengineering approaches to be compared and contrasted with it. Such intercomparisons will help inform the IMO and LP/LC of the diversity of regulations needed to encompass a broader range of geoengineering approaches.

In order to make the WG assessment more relevant for policy-makers, the WG considered that appraisal process must become more multi-faceted and inclusive of other disciplines, particularly the social sciences. As part of this transition, there were several informal presentations by WG members on the role of environmental economics and political science in the WG assessment process. The WG agreed that there was a need to extend the WG for at least a further year to address these issues.

The need to extend the WG was also evident from a discussion around how to obtain sufficient information in the permanent record to produce an authoritative assessment of marine geoengineering approaches. There was agreement on the need to develop a simpler ‘pre-assessment’ knowledge gathering process, that would receive direct scientific feedback as an incentive to obtaining enough information from proponents of geoengineering approaches to produce a robust assessment. The development of such a knowledge platform is essential to both inform other appraisals (based on legal, socio-political, economic and geopolitical characteristics), and to better frame the concurrent development of research governance (i.e. what facets of geoengineering research need to be considered in governance?). This would also form part of any additional work to be done with further funding.

The report

The report of the group was published in March 2018. It provides an initial high-level review of twenty seven proposed marine geoengineering techniques - with its potential subsets - for climate mitigation that focuses on their efficacy, practicality, side-effects, knowledge gaps, verification and potential environmental and socio-economic impacts. The information that underpins each approach varies widely from sufficient to insufficient and suggests that a sequence of developments (from concept development, through to pilot studies, modeling and further studies) will assist in the transition from insufficient to sufficient information in order to permit scientific assessment. The full report can be downloaded here.