A Gathering Storm: How Marine Geoengineering Threatens All Ocean Basins

A report by the Center for International Environmental Law (CIEL) and Friends of the Earth US analyzing the risks and geographic scope of marine geoengineering technologies, arguing that these speculative interventions threaten all ocean basins and distract from fossil fuel phaseout.

• Marine geoengineering is divided into two primary categories: marine carbon dioxide removal (mCDR), which aims to store CO2 in the ocean, and marine solar radiation modification (SRM), which seeks to reflect sunlight to lower temperatures without reducing atmospheric CO2.
• Proposed deployment zones for marine geoengineering span every ocean basin, meaning no country is exempt from potential physical, ecological, or social consequences, as impacts would extend across borders and regions.
• The report argues that marine geoengineering is a 'dangerous distraction' that diverts resources and political will away from proven climate solutions, specifically the fast, fair, and fully funded phaseout of fossil fuels.
• Ocean Alkalinity Enhancement (OAE) faces significant logistical and environmental hurdles; achieving a climatically relevant scale of one gigaton of CO2 would require mining operations comparable to the current global iron ore industry.
• Ocean Fertilization (OF) is criticized as environmentally dangerous and infeasible, with evidence suggesting it could rob nutrients from downstream regions and cause a 5% decline in the biomass of fish and marine species.
• Biomass sinking, including the use of crop residues or seaweed, risks smothering seafloor life and causing chemical changes such as reductions in oxygen and increases in methane and nitrous oxide.
• Marine Cloud Brightening (MCB) and Artificial Upwelling (AU) both carry the risk of 'termination shock,' where a sudden cessation of the technology leads to an abrupt and rapid rise in temperatures.
• The report highlights a lack of robust monitoring, reporting, and verification (MRV) for mCDR, asserting that without accurate accounting of CO2 uptake, the premise of these technologies is fundamentally undermined.
• Current global governance, including the Convention on Biological Diversity (CBD) and the London Convention/London Protocol (LC/LP), generally prohibits or restricts marine geoengineering to small-scale scientific research.
• The Arctic Ice Project ceased operations in January 2025 after ecotoxicological tests indicated that its proposed hollow glass microspheres posed a risk to the Arctic food chain.

APA

Carlson, A. M., Church, M., & Day, B. (2025). A Gathering Storm: How Marine Geoengineering Threatens All Ocean Basins. Center for International Environmental Law. https://www.ciel.org/wp-content/uploads/2025/10/A_Gathering_Storm-_How_Marine_Geoengineering_Threatens_All_Ocean_Basins_report.pdf

Chicago

Carlson, Alana M., Mary Church, and Benjamin Day. A Gathering Storm: How Marine Geoengineering Threatens All Ocean Basins. Center for International Environmental Law, 2025. https://www.ciel.org/wp-content/uploads/2025/10/A_Gathering_Storm-_How_Marine_Geoengineering_Threatens_All_Ocean_Basins_report.pdf.

Wikipedia

{{cite report |last1=Carlson |first1=Alana M. |last2=Church |first2=Mary |last3=Day |first3=Benjamin |title=A Gathering Storm: How Marine Geoengineering Threatens All Ocean Basins |publisher=Center for International Environmental Law |date=2025 |url=https://www.ciel.org/wp-content/uploads/2025/10/A_Gathering_Storm-_How_Marine_Geoengineering_Threatens_All_Ocean_Basins_report.pdf |access-date=17 August 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{carlson2025gathering, author = {Carlson, Alana M. and Church, Mary and Day, Benjamin}, title = {{A Gathering Storm: How Marine Geoengineering Threatens All Ocean Basins}}, institution = {Center for International Environmental Law}, year = {2025}, url = {https://www.ciel.org/wp-content/uploads/2025/10/A_Gathering_Storm-_How_Marine_Geoengineering_Threatens_All_Ocean_Basins_report.pdf}, urldate = {2026-08-17}, note = {Indexed by Climate Insights Directory} }