Implementation of marine CO2 removal for climate mitigation: The challenges of additionality, predictability, and governability

Bach, Lennart T., Vaughan, Naomi E. ORCID:, Law, Cliff S. and Williamson, Phillip ORCID: (2024) Implementation of marine CO2 removal for climate mitigation: The challenges of additionality, predictability, and governability. Elementa, 12 (1). ISSN 2325-1026

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Achieving net zero CO2 emissions requires gigatonne-scale atmospheric CO2 removal (CDR) to balance residual emissions that are extremely difficult to eliminate. Marine CDR (mCDR) methods are seen increasingly as potentially important additions to a global portfolio of climate policy actions. The most widely considered mCDR methods are coastal blue carbon and seaweed farming that primarily depend on biological manipulations; ocean iron fertilisation, ocean alkalinity enhancement, and direct ocean capture that depend on chemical manipulations; and artificial upwelling that depends on physical manipulation of the ocean system. It is currently highly uncertain which, if any, of these approaches might be implemented at sufficient scale to make a meaningful contribution to net zero. Here, we derive a framework based on additionality, predictability, and governability to assess implementation challenges for these mCDR methods. We argue that additionality, the net increase of CO2 sequestration due to mCDR relative to the baseline state, will be harder to determine for those mCDR methods with relatively large inherent complexity, and therefore higher potential for unpredictable impacts, both climatic and non-climatic. Predictability is inherently lower for mCDR methods that depend on biology than for methods relying on chemical or physical manipulations. Furthermore, predictability is lower for methods that require manipulation of multiple components of the ocean system. The predictability of an mCDR method also affects its governability, as highly complex mCDR methods with uncertain outcomes and greater likelihood of unintended consequences will require more monitoring and regulation, both for risk management and verified carbon accounting. We argue that systematic assessment of additionality, predictability, and governability of mCDR approaches increases their chances of leading to a net climatic benefit and informs political decision-making around their potential implementation.

Item Type: Article
Additional Information: Funding Information: LTB acknowledges funding from the Australian Research Council by Future Fellowship (FT200100846) and the Carbon to Sea Initiative. CSL was supported by New Zealand SSIF via the NIWA Oceans Centre. This publication resulted in part from support from the U.S. National Science Foundation (Grant OCE-1840868) to the Scientific Committee on Oceanic Research (SCOR). Data accessibility statement: There were no datasets generated in the preparation of this paper.
Uncontrolled Keywords: climate engineering,geoengineering,marine biogeochemistry,net zero,ocean ecosystems,ocean solutions,oceanography,environmental engineering,ecology,geotechnical engineering and engineering geology,geology,atmospheric science,sdg 13 - climate action,sdg 14 - life below water ,/dk/atira/pure/subjectarea/asjc/1900/1910
Faculty \ School: Faculty of Science > School of Environmental Sciences
UEA Research Groups: University of East Anglia Schools > Faculty of Science > Tyndall Centre for Climate Change Research
Faculty of Science > Research Centres > Tyndall Centre for Climate Change Research
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Depositing User: LivePure Connector
Date Deposited: 07 May 2024 10:32
Last Modified: 13 May 2024 00:11
DOI: 10.1525/elementa.2023.00034


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