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Abstract

We evaluate five highly-publicized polar 'geoengineering' proposals and point to significant issues and risks relating to technological availability, logistical feasibility, cost, predictable adverse consequences, environmental damage, scalability (in time and space), governance, and ethics. According to our assessment, no current geoengineering idea passes an objective and comprehensive test regarding its use in the coming decades. Rather, many of the proposed ideas are environmentally dangerous. Given their feasibility challenges and risks of negative consequences, these ideas should not distract from the priority to reduce greenhouse gas emissions.
Safeguarding the polar regions from dangerous
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geoengineering
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Non peer-reviewed pre-print, submitted to Frontiers in Science, 24 October 2024
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Martin Siegert1*, Heïdi Sevestre2, Michael J. Bentley3, Julie Brigham-Grette4, Henry
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Burgess5, Sammie Buzzard6, Marie Cavitte7, Steven L Chown8, Florence Colleoni9, Robert
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M. DeConto4, Helen Amanda Fricker10, Edward Gasson1, Susie M. Grant11, Adriana Maria
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Gulisano12, Susana Hancock13, Katharine R. Hendry11, Sian F. Henley14, Regine Hock15,16,
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Kevin A. Hughes11, Deneb Karentz17, James D. Kirkham13,11, Bernd Kulessa18, Robert D.
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Larter11, Andrew Mackintosh8, Valérie Masson-Delmotte19, Felicity S. McCormack8, Helen
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Millman20, Ruth Mottram21, Twila A. Moon22, Tim Naish23, Chandrika Nath24, Ben Orlove25,
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Pam Pearson13, Joeri Rogelj26,27, Jane Rumble28, Sarah Seabrook29, Alessandro Silvano30,
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Martin Sommerkorn31, Leigh A. Stearns32, Chris R. Stokes3, Julienne Stroeve33, Martin
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Truffer16
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1 University of Exeter, Penryn Campus, Penryn, United Kingdom
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2 Arctic Monitoring and Assessment Programme, Tromsø, Norway
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3 University of Durham, Durham, United Kingdom
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4 University of Massachusetts-Amherst, Amherst, MA, United States
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5 Natural Environment Research Council (NERC) Arctic Office, Cambridge, United Kingdom
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6 Northumbria University, Newcastle upon Tyne, United Kingdom
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7 Vrije Universiteit Brussel (VUB), Belgium
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8 Securing Antarctica's Environmental Future, Monash University, Victoria, Australia
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9 National Institute of Oceanography and Applied Geophysics, Trieste, Italy
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10 Scripps Institution of Oceanography, University of California, San Diego, CA, United States
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11 British Antarctic Survey, Cambridge, United Kingdom
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12 Instituto Antártico Argentino, Buenos Aires, Argentina
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13 International Cryosphere Climate Initiative, Stockholm, Sweden
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14 School of GeoSciences, University of Edinburgh, Edinburgh, UK
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15 University of Oslo, Oslo, Norway
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16 University of Alaska Fairbanks, Fairbanks, AK, United States
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17 University of San Francisco, San Francisco, CA, United States
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18 Swansea University, Swansea, United Kingdom
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19 LSCE, Institut Pierre Simon Laplace, Université Paris Saclay, Gif-sur-Yvette, France
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20 University of Exeter, Exeter, United Kingdom
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21 Danish Meteorological Institute, Copenhagen, Denmark
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22 University of Colorado Boulder, Boulder, CO, United States
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23 Victoria University of Wellington, Wellington, New Zealand
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24 University of Cambridge, Cambridge, United Kingdom
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25 Columbia University, New York, NY, United States
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26 Imperial College London, United Kingdom
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27 International Institute for Applied Systems Analysis, Laxenburg, Austria
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28 Foreign, Commonwealth and Development Office, London, United Kingdom
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29 National Institute of Water and Atmospheric Research, Wellington, New Zealand
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30 University of Southampton, Southampton, United Kingdom
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31. WWF Global Arctic Programme, Solna, Sweden
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32 University of Pennsylvania, United States
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33 University of Manitoba, Winnipeg, Canada
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* m.siegert@exeter.ac.uk
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Keywords: global warming, sea level rise, decarbonizing, geoengineering, governance,
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Arctic, Antarctic, Polar
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Siegert, M. et al. Safeguarding from dangerous polar geoengineering. Non peer-reviewed submission
to Frontiers in Science, 24 October 2024
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Abstract
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Fossil-fuel burning is heating the planet with catastrophic consequences for its habitability
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and for the natural world on which our existence depends. Halting global warming requires
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rapid and deep decarbonization to net zero carbon dioxide emissions and this needs to be
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achieved by mid-century if warming is to be halted within the limits set out by the 2015 Paris
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Agreement. However, the public debate and investors are increasingly exposed to claims
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from some scientists and engineers who fear this target will not be achieved and who are
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instead focusing on technological geoengineering fixesthat might delay or mask some of
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the projected impacts. In particular, the need to slow warming in polar regions is often cited
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by such groups because these regions are experiencing rates of warming higher than the
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global average, with projected severe and irreversible consequences both locally (e.g., on
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fragile ecosystems) and globally (e.g., on sea level). Several geoengineering ideas have been
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proposed for these regions, but without a full examination by the polar science community or
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the integration of its understanding of polar dynamics and responses. Here, we evaluate five
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highly-publicized polar geoengineering proposals and point to significant issues and risks
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relating to technological availability, logistical feasibility, cost, predictable adverse
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consequences, environmental damage, scalability (in time and space), governance, and ethics.
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According to our assessment, no current geoengineering idea passes an objective and
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comprehensive test regarding its use in the coming decades. Rather, many of the proposed
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ideas are environmentally dangerous. Given their feasibility challenges and risks of negative
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consequences, these ideas should not distract from the priority to reduce greenhouse gas
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emissions.
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Siegert, M. et al. Safeguarding from dangerous polar geoengineering. Non peer-reviewed submission
to Frontiers in Science, 24 October 2024
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Key points
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Several “geoengineering” concepts proposed for the polar regions fail to meet essential
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criteria to be considered responsible approaches towards limiting the escalation of
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climate-related risks, including feasibility and likelihood of success.
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Polar geoengineering would cause severe environmental damage and comes with the
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possibility of grave unforeseen consequences.
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Polar regions have complex environmental protection and governance frameworks,
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which will likely reject polar geoengineering research efforts and large-scale projects.
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Minimizing risk and damage from climate change is best achieved by mitigating the
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cause of climate harm through immediate, rapid and deep decarbonization, rather than
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attempting interventions in fragile polar ecosystems.
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Polar geoengineering would require $100s billions in initial costs, with decades of
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ongoing maintenance; a level that is presently unavailable and highly unlikely to be
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secured over necessarily short timescales to address climate change.
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For those with vested interests in fossil fuel production and maintaining carbon-intensive
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industries and lifestyles, championing geoengineering serves as a strategy to create an
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illusion of a climate solution without committing to decarbonizing; however, this is both
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an irresponsible and unethical approach.
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Siegert, M. et al. Safeguarding from dangerous polar geoengineering. Non peer-reviewed submission
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Introduction
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The burning of fossil fuels and the resulting global warming are unequivocally damaging the
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polar regions. Human-caused global warming reached 1.3°C above the preindustrial level in
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2023 (Betts et al., 2023; Forster et al., 2024). The Arctic is currently warming three times
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faster than the global average (AMAP, 2022; Rantanen et al., 2022), resulting in
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unprecedented loss of sea ice extent and volume (Meier et al., 2023; Notz & Stroeve, 2018),
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changes in snow duration and extent (Mudryk et al., 2020), widespread permafrost thaw
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(Biskaborn et al., 2019), glacier retreat (Hugonnet et al. 2021), accelerating Greenland ice
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loss (Otosaka et al., 2022), increasing wildfires (Descals et al. 2022), changing vegetation
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distributions (Myers-Smith et al. 2020), and other profound ecosystem changes. These
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changes are already impacting the daily lives of indigenous and local communities (AMAP,
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2022) that rely on local-to-regional resources. Across Antarctica, the average warming rate is
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twice the global average (Casado et al., 2023). Over the past two decades, ice shelves along
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the Antarctic periphery have collapsed (Gudmundsson et al., 2019a). The West Antarctic Ice
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Sheet has experienced accelerating mass loss (Otosaka et al., 2022) and record-high
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temperatures have been observed in the Antarctic Peninsula (Gorodetskaya et al., 2023) and
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over the East Antarctic plateau (Wille et al., 2024a; Wille et al., 2024b). Record lows in
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Antarctic sea ice extent have also been observed in recent years (Parkinson, 2019; Gilbert &
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Holmes, 2024). These changes are harming marine and terrestrial species, ecosystems, and
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ecosystem services across the Antarctic and Southern Ocean and these effects are projected to
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increase (Rintoul et al., 2018; Brooks et al. 2022; Chown et al., 2022).
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Polar environments provide substantial and important services and benefits to humanity
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(Stoeckl et al., 2024) and so changes here have far-reaching implications for the entire planet.
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Global sea level rise is accelerated by land ice loss from mountain glaciers and the Greenland
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Siegert, M. et al. Safeguarding from dangerous polar geoengineering. Non peer-reviewed submission
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and Antarctic ice sheets (Otosaka et al., 2022; IPCC, 2023). Additionally, the polar regions
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influence the global climate through extreme weather events, disruptions to the global ocean
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circulation, carbon cycling, ocean acidification, and other feedback mechanisms (Meredith et
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al., 2019). The large, bright surfaces of sea ice and ice sheets reflect a significant portion of
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incoming solar radiation back into space, helping to cool the polar regions and the planet
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overall. The polar regions support a high level of biodiversity, particularly in marine
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environments, making them some of the most important yet fragile ecosystems on Earth (Post
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et al., 2013; Constable et al., 2023). Both the Arctic and Antarctic play crucial roles in carbon
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sequestration, whether in permafrost, tundra, boreal forests (Hugelius et al., 2020; Sabine et
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al., 2004; Williams et al., 2023), or in the Arctic and Southern oceans, which accounts for at
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least half of all carbon dioxide (CO2) uptake by the world’s oceans (e.g., Long et al., 2021).
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This makes them an important carbon sink but exposes their marine environments to greater
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acidification, threatening the viability of shelled organisms at the base of polar marine food
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webs (Dupont and Portner, 2013; AMAP, 2018).
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The polar regions are vital to the overturning circulation of the world’s oceans, driving the
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sinking of cold, dense water, which is essential to global ocean currents (Marshall & Speer,
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2012, Lee et al., 2023). Direct measurements in the deep Southern Ocean suggest that a
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~30% slowdown in the Antarctic overturning has occurred over the last few decades in both
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the Weddell and Ross Seas, linked to both meltwater and wind changes (Gunn et al., 2023,
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Zhou et al. 2023). Model projections suggest this slowdown will continue for at least the next
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few decades and that the southern limb of ocean overturning circulation could collapse this
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century (Li et al., 2023). Associated freshening of the Southern Ocean is affecting ecosystem
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functions and loss.
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Siegert, M. et al. Safeguarding from dangerous polar geoengineering. Non peer-reviewed submission
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Continuing the current trajectory of fossil fuel consumption and associated global heating is
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not viable considering the scale and magnitude of consequences for the polar regions, and
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their severe regional and global implications (Constable et al., 2022); under current policies,
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an intermediate scenario points to an increase from pre-industrial levels of around 3°C by
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2100. Rapid reductions in carbon emissions, with net zero emissions by mid-century, will
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stabilize global temperatures and curb polar changes, protecting the world and future
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generations from the effects of worst-case high emissions (IPCC, 2021; Palazzo-Corner et al.,
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2023).
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As a complement to, or substitute for, such protection, a small number of scientists have
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proposed technological manipulations of the climate, oceans, sea ice, and ice sheets (e.g.,
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Shepherd et al., 2009; MacAyeal et al., 2024). In this article, we assess five prominent
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geoengineering ideas that aim to change the heat uptake or distribution around the planet by
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increasing solar reflectivity within the atmosphere, diverting key ocean circulation patterns
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within the polar regions to reduce ice melting, increasing sea ice albedo or thickness, slowing
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the flow of ice sheets to restrict ice loss to the ocean, or enhancing CO2 uptake by the oceans.
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We show how they: are highly unlikely to work effectively considering the scale and
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immediacy of the climate problem; would have damaging side effects within and far beyond
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polar regions; fail to address key environmental protection concerns; face far more
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governance and financing challenges than already exist in the Paris Agreement context; and
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distract attention from urgent decarbonization, delaying and narrowing remaining and
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feasible carbon reduction pathways.
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Siegert, M. et al. Safeguarding from dangerous polar geoengineering. Non peer-reviewed submission
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Part 1: Polar regions geoengineering assessments
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In this section we evaluate five prominent geoengineering ideas, namely stratospheric aerosol
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injection, sea curtains (or sea walls), sea ice management (modifying albedo and thickening
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sea ice), slowing ice sheet flow, and ocean fertilization. In each case we assess the
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effectiveness, feasibility, negative consequences, cost, and governance of these proposed
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approaches with respect to their deployment at scale in polar regions (Table 1).
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Case study 1: Stratospheric aerosols injection
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Background
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Solar radiation modification (SRM) refers to the intentional modification of the Earth's
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shortwave radiative budget to offset some of the effects of increasing greenhouse gases
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(GHGs)but without reducing the gases themselvesbased on various metrics such as
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surface temperature, precipitation, and regional impacts (IPCC AR6 WGIII; IPCC 2023).
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‘Stratospheric aerosols injection’ (SAI) is one of the proposed methods, which we discuss
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below (Figure 1); others include marine cloud brightening, surface albedo enhancement,
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cirrus cloud thinning and space-based mirrors.
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Budyko (1977) published one of the first studies addressing climate change and the
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possibility of direct climate intervention via aerosols injections. Most of the historical
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research on aerosol injection stems from the study of the climate effects of major explosive
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volcanic eruptions. In 1991, Mount Pinatubo in the Philippines erupted, sending an eruption
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column 40 km into the atmosphere and creating a massive “umbrella cloud” in the middle-to-
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lower stratosphere. This event injected approximately 17 megatons of sulfur dioxide (SO2)
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into the stratosphere. The resulting aerosol cloud quickly spread globally, achieving full
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coverage within a year. It significantly reduced the amount of net radiation reaching the
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Siegert, M. et al. Safeguarding from dangerous polar geoengineering. Non peer-reviewed submission
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Earths surface, causing observable climate effects. Specifically, there was a surface cooling
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of up to 0.50.6°C in the northern hemisphere, equivalent to a reduction in net radiation of 4
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W/m2. Globally, temperatures cooled by about 0.5°C for nearly 2 years (Self et al., 1993).
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This highlighted that the release of 1520 megatons of SO2 into the stratosphere could
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generate enough aerosols to counteract some global warming. More recent studies show that
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SAI would require lofting hundreds of thousands to millions of tons of material each year to
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altitudes up to 20 km to counter a substantial fraction of warming caused by GHG loading
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(Smith and Wagner, 2018; IPCC, 2018; IPCC 2023).
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Current research focuses primarily on the following types of aerosols: (i) SO2, which is
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converted to sulfuric acid aerosols in the stratosphere; (ii) Sulfate aerosols similar to those
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produced by volcanic eruptions. These effectively reflect sunlight and thus could reduce
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global temperatures but also pose risks, such as potential damage to the ozone layer and the
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creation of acid rain (Huynh and McNeill 2024; Malinina et al., 2021); (iii) Titanium dioxide
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(TiO2), which is potentially less chemically reactive than SO2, and thus may be less
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damaging to the ozone layer, but is still in the experimental stage (Huynh and McNeill 2024);
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and (iv) Calcium carbonate (CaCO3), which might neutralize some of the acidifying effects
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of other aerosols and reduce ozone depletion risks, but is also investigational (Huynh and
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McNeill 2024; Malinina et al., 2021).
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Effectiveness and feasibility
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In the absence of any field assessments and pilot studies, and based on a variety of modelling
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investigations, the Intergovernmental Panel on Climate Change (IPCC, 2023) has noted large
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uncertainties in the effectiveness of deployment of solar geoengineering (De Coninck et al.,
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2018), substantial knowledge gaps regarding its cost-effectiveness, and a range of risks
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around deployment.
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Siegert, M. et al. Safeguarding from dangerous polar geoengineering. Non peer-reviewed submission
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It has been suggested that aerosols could be injected into the stratosphere using balloons,
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airships, and/or artillery. However, the most efficient method is likely to involve a fleet of
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custom-built and/or specially modified aircraft (Moriyama et al., 2017). Smith and Wagner
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(2018) estimate that 60,000 flights annually0.15% of all current flights globally (OAG
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2024)could be required for a lasting effect. Smith et al. (2024) recently highlighted the
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Boeing 777F as a potential candidate, albeit requiring substantial modifications, with a fleet
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of 90 planes focusing on deployment in the polar regions. Deployment strategies include
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aerosol injection: (i) in the tropics or subtropics (at or equatorward of 30°), (ii) uniformly
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across all latitudes, and (iii) in the sub-polar or polar regions (at or poleward of 60°).
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Typically, the tropopause is lowest in altitude in the polar regions, facilitating larger payloads
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and requiring fewer planes to achieve a given injection mass (Lee et al., 2021; Moriyama et
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al., 2017; Smith, 2020).
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SAIs would need a highly specific deployment to have significant impact in polar regions
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(Goddard et al., 2023; Lee et al., 2023). The radiative forcing from stratospheric aerosols
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depends on local incoming solar radiation and top-of-atmosphere albedo. Polar regions are
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less responsive to aerosol injection during sunlit periods because of their lower insolation and
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higher albedo produced by ice and snow (Govindasamy & Caldeira, 2000; Tilmes et al.,
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2018). Furthermore, injections are totally ineffective during the winter months in the polar
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regions. The Brewer-Dobson circulation, characterized by rising air in the tropics and
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descending air in the mid and high latitudes, affects the distribution and lifetime of
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stratospheric aerosols. Aerosols injected at high latitudes therefore have a shorter lifetime and
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more localized cooling effects owing to their rapid removal by the poleward movement and
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descent of air (Robock et al., 2008; Kravitz et al., 2017) questioning the effectiveness of SAI
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in the Arctic.
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If deployed at the necessary scale, SAI would only have discernible effects (within climate
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variability) over 20 years (Duffey et al., 2023)the same time horizon over which the effects
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of sharp mitigation by reduced GHG emissions would be seen (Tilmes et al., 2020).
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Termination shock is the rapid and severe warming that could occur by the unmasking of
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ongoing GHG emissions if any future large-scale deployment of solar geoengineering were
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halted (Parker and Irvine, 2018). The sudden cessation would remove the reflective aerosols
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from the stratosphere, causing the Earth’s climate to adjust abruptly to the conditions dictated
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by GHG concentrations and bringing a swift, significant rise in global temperatures. Climate
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models suggest that following SAI termination, surface temperatures would increase within a
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decade or two to values consistent with GHG forcing. Major water cycle changes would
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occur, including a rapid increase in global mean precipitation (Douville et al., 2021). Parker
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and Irvine (2018) claim that timely policies could avert termination shock. However, relying
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on SAI without GHG removal would likely require prolonged (even permanent) injection at
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continued financial, ecological and human costs.
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The readiness of SAI for implementation varies greatly between polar-specific and global
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deployments (Diamond et al., 2023). If a launch decision were made by 2030, polar SAI
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could theoretically be operational by 2040. On a global scale, if a decision to proceed were
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made by 2050, it could take until 2060 for SAI to be fully operational (Smith et al., 2024).
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However, many obstacles stand in the way of what is theoretically possible, including
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finance, governance, and the determination of and responsibility for negative
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consequences. Importantly, there is no international governance framework to oversee such
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work. Overcoming this and other issues will take far longer than the implementation of
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available actions to strengthen greenhouse gas emission reductions and engage
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transformative adaptation.
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Negative consequences
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In the polar regions, atmospheric injections would be ineffective in winter owing to the lack
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of sunlight, and instead could lead to residual warming in winter (due to the blanketing effect
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of cloud cover), potentially altering the high-latitude seasonal cycle (Jiang et al., 2019;
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Banerjee et al., 2021), with potential consequences for the water cycle through atmospheric
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drying. It could also cause stratospheric heating, which may alter atmospheric circulation
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patterns, leading to wintertime warming over northern Eurasia and potentially other
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unintended consequences (Banerjee et al., 2021; Jones et al., 2021).
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SAIs would not address non-temperature related effects of GHG emissions, such as ocean
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acidification. Rather they could exacerbate acidification, especially if sulfates (the original
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“acid rain” emissions source from coal-fired power) were used, with consequent negative
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impacts on ecosystems and economies. Both the Arctic and Southern Oceans already show
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seasonally corrosive conditions for shelled life due to today’s atmospheric CO2 levels, and
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shell damage from increasing acidification was observed from samples taken as early as the
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2000s (Bednarsek et al, 2020). Year-round corrosive conditions are projected to spread
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throughout much of the polar marine ecosystem with even moderate emissions pathways, at
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CO2 levels above 450 ppm (IPCC, 2019). Ocean acidification is also a very long-term
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problem, with a return to today’s pH levels taking 30,00050,000 years (Honisch et al, 2012).
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Indeed, acidification rates are higher today than at any point in the last 300 million years
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(Pelejero et al, 2010). This raises the specter of extinctions for many polar marine shelled
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animals and the economically important species that depend on them, such as krill and cod
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(AMAP, 2018; Green et al, 2021).
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Injections using sulfate aerosols can also lead to chemical reactions in the stratosphere that
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deplete ozone (Tilmes et al., 2008). Ozone depletion increases the amount of ultraviolet
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radiation reaching the Earth’s surface, causing harmful effects on human health (see below),
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ecosystems, and biodiversity as a whole (Moch et al., 2023; Zarnetske et al., 2021).
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Using SAI to differentially cool one polar region alone could disrupt global climate patterns.
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An imbalance in cooling between the hemispheres could shift the Intertropical Convergence
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Zone, potentially interfering with seasons (Haywood et al., 2013; Kravitz et al., 2017;
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Määttänen et al., 2024) and reducing rainfall in some regions thereby affecting water
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availability and agriculture (Tilmes et al., 2022).
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The reduction in sunlight reaching the Earth’s surface could reduce photosynthesis and
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agricultural productivity, as occurred in 1815 when the eruption of Indonesia’s Mount
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Tambora eruption released sulfate aerosols into the atmosphere (Oppenheimer, 2003).
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Reduced sunlight could negatively affect crop yields, threatening food security and
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potentially leading to higher food prices. This would disproportionately affect poorer regions
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that rely heavily on agriculture (Wang et al., 2023). Uneven effects of SAI might potentially
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harm those already most vulnerable to disturbances in food production, and with less means
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to protect themselves if benefits to more powerful populations are optimized (Honegger et al.,
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2021). The effects of SAI on ocean circulation are also uncertain. Crucially, some models
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suggest the Atlantic Meridional Overturning Circulation (AMOC) could be weakened, with
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implications for regional climates and weather patterns (Tilmes et al., 2020).
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Concerns also exist regarding the effect of aerosol inhalation on human health (Carslon et al.,
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2022). Sulfuric acid aerosols can irritate the respiratory system, causing coughing, airway
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irritation and inflammation and, in severe cases, respiratory distress. Chronic exposure has
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been associated with an increased risk of laryngeal cancer owing to long-term irritation and
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inflammation. This could lead to increased healthcare costs and add a burden on medical
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infrastructure, with particular risks for vulnerable populations (Effiong and Neitzel, 2016a,b).
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Cost
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SAI is frequently portrayed as a relatively inexpensive method of climate intervention.
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However, Smith et al. (2024) estimate the direct costs at approximately $13.5 billion for
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acquiring 90 Boeing 777 aircraft, US$3.2 billion for necessary infrastructure, and around $1
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billion annually for operations. If these expenses were distributed among 30 countries, each
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would contribute roughly $590 million/year. However, these calculations assume the
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interventions work as planned, only consider direct costs, and exclude indirect expenses such
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as monitoring and measuring possible impacts, and the loss and damage relating to adverse
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impacts. Previous studies, such as Reynolds et al. (2016), indicate that the perception of SAI
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as a low-cost solution is a misleading oversimplification of the financial realities.
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Furthermore, such estimates do not include potential unforeseen negative impacts on: (1)
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weather systems, ecosystems, human health, and agriculture; (2) the effectiveness of
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renewable energy technologies and the requirements of multi-century commitments (Baur et
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al., 2023, 2024a,b); (3) associated and immense potential costs of a termination shock (see
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below); (4) the mistrust and rivalry concerning geopolitical and economic interests among
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key states (Corry et al. 2024); and (5) the legal challenges in determining and assigning
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attribution and liability for such impacts, and the absence of insurance and/or whether
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insurance is even possible.
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Governance
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The lack of governance on SAI and the absence of deliberation spaces (Fritz et al., 2024) are
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major challenges (NAS, 2021), with some arguing that deployment may be largely
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ungovernable (e.g. Lockley et al., 2023; Biermann et al., 2022). For the Polar regions it could
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even be used as a disruptive tool in a wider geopolitical context (Corry et al., 2024). The
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unilateral deployment of SAI by one country or a group of countries, but opposed by others,
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could make international cooperation on addressing climate change harder to achieve and
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lead to increased general geopolitical tensions (Sovacool et al., 2023). Though political
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disputes around geoengineering have already been shown to include much deeper issues
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(McLaren and Corry, 2020), these tensions are most commonly ascribed to the fact that SAI
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has global effects that could vary between countries. While some regions might experience
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cooling and reduced climate risks, others might face adverse effects such as changes in
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precipitation patterns and agricultural productivity. This could exacerbate existing
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inequalities between developed and developing countries, and no current international
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agreements explicitly prevent countries from using geoengineering strategies that could
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negatively impact other countries (Brent and McGee, 2012). In the current geopolitical
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environment characterized by increasing tension and rivalry, SAI might also prove politically
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infeasible owing to countries mistrusting the intentions of states advocating for research or
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deployment and may contribute to international tension if subject to disinformation
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campaigns (Corry et al., 2024).
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So far, no framework exists for international cooperation on SAI, despite some calls for an
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ethical framework (NAS, 2021; AGU, 2022), which are seen by most governments as a step
347
towards deployment, which they oppose. For example, efforts to introduce the topic at
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successive UN Environment Assemblies have failed due to widespread opposition among
349
governments. In 2021, the Swedish Space Agency rejected serving as host for the Harvard-
350
based Stratospheric Controlled Perturbation Experiment (SCoPEx) due to opposition from
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the Saami Council, civil society and several Swedish universities; the same project was
352
originally slated to take place over Navajo lands in the U.S. (Saami Council 2021). In
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January 2022, 400 scientists proposed a non-use agreement on solar geoengineering with five
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core principles: no public funding, no outdoor experiments, no patents, no deployment, and
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no support in international institutions; for which the African Union and European Parliament
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have called for support (Solar Geoengineering Non Use Agreement:
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https://www.solargeoeng.org/). In January 2023, Mexico announced it would ban solar
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geoengineering experiments following unauthorized tests conducted by the US-based startup
359
Make Sunsets (https://www.gob.mx/semarnat/prensa/la-experimentacion-con-geoingenieria-
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solar-no-sera-permitida-en-mexico), which released weather balloons containing SO2 into the
361
atmosphere without governmental authorization. The EU has stated that it “…does not
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consider SRM as a solution, as it does not address the root cause of the problem, which is the
363
increase in greenhouse gases in the atmosphere” (https://research-and-
364
innovation.ec.europa.eu/system/files/2023-08/Scoping_paper_SRM.pdf). In its report in
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response to a Congressional mandate asking the Biden Administration to examine SRM, the
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White House stressed that the U.S. “remains focused on reducing emissions” and had “no
367
plans” to establish any new research programs into SAI
368
https://www.whitehouse.gov/ostp/news-updates/2023/06/30/congressionally-mandated-
369
report-on-solar-radiation-modification/). Understanding the power relations and risks
370
inherent in non-state funding of solar geoengineering is a further related challenge (Surprise
371
and Sapinski, 2023).
372
Another significant concern is that the implementation of SAI would inevitably increase the
373
pressure to maintain business as usual, potentially distracting and detracting from
374
necessary efforts to reduce GHGs (McLaren, 2016).
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The potential social disruptions of this technique cannot be understated. There could be
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significant public resistance due to concerns about potential side effects and ethical
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considerations of deliberately altering the climate. Public protests and legal challenges might
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arise, complicating the implementation of such programs (Tracy et al., 2022).
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Case study 2: Sea curtains/sea walls
380
Background
381
Wolovick and Moore (2018) and Moore et al. (2018) proposed installing artificial structures
382
to prevent warm water masses reaching the buttressing ice shelves and grounding zones of
383
the Antarctic and Greenland ice sheets to reduce ocean warmth-induced ice-sheet melting and
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mass loss. The initial idea to build artificial sills up to 100 m high, or artificial pinning points
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300 m high, on which an ice shelf could ground, have now been discarded. Now favored are
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flexible seabed curtains” (Wolovick et al., 2023; Keefer et al., 2023) comprising flexible
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buoyant structures anchored to the seabed at depths between 700 and 1000 m (Wolovick et
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al., 2023), with 150500 m high curtains (depending on location) extending upwards as a
389
series of thin, flexible overlapping panels (Figure 2).
390
Effectiveness and feasibility
391
The installation of such structures at depth and on various substrates is extremely
392
challenging, compounded further by the harsh environment and the remoteness of the
393
envisaged target areas, especially in the Amundsen Sea region of West Antarctica. The
394
prefabricated foundations will have to be substantial to counteract the buoyancy forces of the
395
curtain, and their necessary size may even exceed the capacity of ships to transport them
396
(Keefer et al., 2023). The proposed “outer” curtain route in the Amundsen Sea is on soft sea-
397
floor sediment. The potential for instability and mass movement due to “loading” on the
398
seabed would need to be carefully assessed. In contrast, the “inner” curtain routes would
399
require foundations built at least partly on rough bedrock channels, with steep slopes and
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potential for strong currents scouring the topography (Kirkham et al., 2019; Hogan et al.,
401
2020; Hogan et al; 2022). Shaping a prefabricated foundation structure to such a rough
402
surface would be challenging even on land, let alone at depths of several hundred meters in
403
Antarctic waters with icebergs and sea ice present, and especially with the need for precise
404
installation of anchors in both hard and soft surfaces (Keefer et al., 2023). The rough surface
405
would also introduce substantial challenges to curtain design where adjacent elements would
406
be at different orientations.
407
According to numerical modelling, such structures might successfully divert warm water
408
from one ice shelf system, but their net efficacy may be compromised by unintended
409
rerouting of this water to other systems (Gürses et al., 2019). Another modelling study
410
concluded that reducing grounding line melt rates by up to 5 m y1 below present levels could
411
promote re-advance of some ice streams (even after extensive prior retreat), but reversing
412
Antarctica’s contribution to sea level rise also requires a substantially increased ice-surface
413
accumulation (Alevropoulos-Borrill et al., 2024). Feldmann et al. (2019) estimate that at least
414
7 Gt of artificial snow would be required to balance the ice sheet around the Amundsen Sea,
415
but this vast amount of ice (2 mm of sea level equivalent) would need to be applied over 10
416
years to be effective and, presumably, sustained at a high level thereafter. These studies call
417
into question the usefulness and practicality of the approach.
418
Another challenge is that the deployment site is in one of the harshest and most remote
419
environments on Earth, with a transit time of over 1 week from the nearest port and access
420
likely to be possible only for a few months each year owing to polar darkness and extreme ice
421
and climate conditions. Even today, the handful of research ships that try to undertake short
422
cruises in this area are hampered by such conditions, often have to change work locations,
423
and frequently fail to get to the region entirely due to impenetrable sea ice. Hostile sea ice
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and iceberg collision risk have frequently thwarted attempts to reach the installation sites
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proposed by Keefer et al. (2023) over the 40-year period in which this region has been
426
targeted by ice-breaking vessels for academic research. A literature survey of cruise reports
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and interviews with principal investigators of research expeditions undertaken in the region
428
reveals that 56% of cruises experienced at least partial disruption due to sea ice, or had
429
significant difficulties entering or exiting the area; 22% were unable to access the region
430
altogether (Larter et al., 2014, Dorschel et al., 2022). For example, the Inner Bay curtain site
431
proposed for offshore Thwaites Glacier (Keefer et al., 2023) has only been accessed once in
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the last 40 years despite frequent expeditions targeting the glacier front (Hogan et al., 2020),
433
whilst several oceanographic moorings remain unrecovered in other parts of the Amundsen
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Sea continental shelf region despite multiple attempts to retrieve them over different years.
435
Furthermore, even in years when sea ice conditions have been favorable, the risk of iceberg
436
collisions has forced the abandonment of activities. This includes several locations where
437
ships necessarily remain stationary for relatively short periods of time, such as for sediment
438
drilling (e.g., Gohl et al., 2017), let alone the far greater task of installing complex
439
foundations across rugged topography.
440
Keefer et al. (2023) argue that all installing vessels would need to be ice-class strengthened to
441
Lloyds A1 classification and able to hold position. Currently, very few ships have such
442
capability and most are committed to northern hemisphere operations; new ones would cost
443
several US$100 million each. These cost estimates are only based on sea curtains in the
444
Amundsen Sea area but there are other parts of the ice sheet margin that are potentially
445
vulnerable and even more remote from logistic hubs, such as the Cook Ice Shelf, Mertz, and
446
Ninnis Glaciers in East Antarctica (Stokes et al., 2022). Any installation elsewhere in
447
Antarctica would scale in cost accordingly. Similar ideas have been proposed for Greenland,
448
where artificial barriers could be built in glacial fjords to prevent warm deep waters reaching
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Siegert, M. et al. Safeguarding from dangerous polar geoengineering. Non peer-reviewed submission
to Frontiers in Science, 24 October 2024
19
marine-terminating glaciers (Moore et al. 2018). While building a berm in Greenland fjords
450
would be logistically less challenging than in Antarctica, the effectiveness of such
451
interventions might be limited since the Greenland Ice Sheet is highly susceptible to
452
atmospheric-driven melting (Hanna et al., 2024).
453
Negative consequences
454
The installation of sea curtain structures is likely to have far-reaching detrimental
455
consequences. These include potential effects on oceanic circulation, sea ice and marine
456
ecosystems from interception of circulating water masses, deflection of water masses
457
elsewhere, and impacts of any water masses that leak through barriers or “overtop their
458
uppermost elements (Keefer et al., 2023).
459
The presence of barriers to water masses will also act as a barrier to marine life, for example,
460
to demersal fish, mobile benthic invertebrates, and the seabirds and marine mammals that
461
feed at depth in these regions (e.g. Zheng et al., 2021). Interception of inflowing water
462
masses and the consequent changes to circulation and sea ice will affect the delivery of
463
nutrients most notably iron (Dinniman et al., 2020) from upwelling and from ice melt in
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the region, with consequent impacts on primary productivity and carbon sequestration.
465
Installation of towed floating structures, as suggested by Keefer et al. (2023), may also
466
introduce non-native species to the seabed and water column around Antarctica with
467
unknown consequences for marine ecosystems (McCarthy et al., 2019; Cape et al., 2019).
468
Other potential consequences include pollution from installation and damage to curtains,
469
additional emissions associated with transportation and installation, and the need for ongoing
470
maintenance over decadal timescales (the planned lifetime of the curtains being 25 years).
471
The material to be used for the curtains is not yet clear. There is the possibility that elements
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of the curtains, hundreds of meters long, could degrade over time and/or become dislodged
473
posing a severe hazard to marine life and shipping.
474
Installing such a structure would entail considerable emissions. Transiting an icebreaker over
475
2500 km from the nearest major port while towing large floating structures through rough
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seas would be operationally risky and carbon intensive. For example, the German research
477
vessel Polarstern consumes approximately 900 tonnes of fuel/month (equivalent to 2800
478
tonnes of CO2) with a far higher consumption when breaking through sea ice. Towing large
479
structures through sea-ice is extremely difficult and so the working season would likely be <3
480
months/year. Each transit for a single curtain section would likely take well over a month
481
with a likely maximum of four to five round trips per year being possible, each ship emitting
482
10,00015,000 tonnes of CO2.
483
Cost
484
The costs of installing sea curtains are likely to far exceed the maximum of US$80 billion for
485
an 80 km structure, spread over a decade, estimated by Keefer et al. (2023). Their cost
486
estimate of $1 billion/km can be compared with the real-world cost of the Thames Barrier, a
487
500 m long structure across the River Thames in London, United Kingdom. This was built at
488
the surface in water <10 m deep immediately adjacent to an enormous logistic hub (i.e., with
489
no shipping required). Nevertheless, it took 8 years to build and cost £535 million in 1982
490
(https://www.gov.uk/government/news/the-thames-barrier-protecting-london-and-the-
491
thames-estuary-for-40-years ), equivalent to £2.4 billion ($3.1 billion or $6.2 billion/km) at
492
2024 prices. The Three Gorges Dam in China, which is approximately 2 km wide and 180 m
493
high, cost ~US$37 billion in 2008 (https://www.reuters.com/article/economy/china-says-
494
three-gorges-dam-cost-37-billion-
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idUSPEK84588/#:~:text=BEIJING%2C%20Sept%2014%20(Reuters),several%20times%20a
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21
n%20original%20estimate), equivalent to US$54 billion in 2024; about 25 times more per km
497
than presently reported for the Amundsen Sea curtain.
498
Governance
499
The governance of sea curtains in Antarctica would fall under the Antarctic Treaty System.
500
Article 8 of the Protocol on Environmental Protection requires a Comprehensive
501
Environmental Evaluation for any activity with more than a minor or transitory impact.
502
The Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR)
503
may also have concerns regarding the potential consequences to the marine ecosystem. Sea
504
curtain installation would be orders of magnitude larger than any construction activity seen
505
previously in Antarctica and would require not only estimation of all likely impacts, but a
506
rigorous associated program of impact monitoring and mitigation. Obtaining international
507
consensus to intervene in Antarctic processes at such a huge scale has never been attempted
508
before, and those advocating sea curtains have given this necessary item scant consideration
509
thus far. Flamm and Shibata (in press, 2025) point to significant potential problems for such
510
an idea within the Antarctic Treaty System (see Part 3), suggesting even if sea curtains
511
could work without negative impacts it may precipitate political fragmentation and make
512
the Antarctic a “scene of international discord” through concerns over authority,
513
sovereignty, and security”.
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Siegert, M. et al. Safeguarding from dangerous polar geoengineering. Non peer-reviewed submission
to Frontiers in Science, 24 October 2024
22
Case study 3: Sea ice managementmodifying albedo and
515
thickening sea ice
516
Sea ice albedo
517
Background
518
Sea ice cools the Earth by reflecting solar energy. Sea ice loss over recent years has left the
519
Earth’s surface less reflective: according to a recent global study, sea ice has lost 1315% of
520
its radiative cooling effect since the 1980s, leading to enhanced solar heating (Duspayev et
521
al., 2024). Scattering hollow glass beads on first-year Arctic sea ice could increase its albedo,
522
promoting its survival into a second winter and beyond to re-establish multi-year ice (Field et
523
al., 2018).
524
Negative consequences and feasibility
525
The use of glass beads raises significant concerns that must urgently be addressed (Figure 3).
526
Firstly, there are risks of ecotoxicity. Ecotoxicology tests are underway in vertebrates (Field
527
et al., 2018) but the impact on invertebrates appears unknown. The potential effects on
528
zooplankton feeding behavior are of particular concern, given the size and nature of the
529
beads. Secondly, the glass beads are metastable and will dissolve readily in the
530
undersaturated seawater [e.g., (Rickert et al., 2002)], potentially reducing their efficacy. Any
531
means used to decrease the solubility of the beads will enhance ecotoxicological concerns.
532
The biogeochemical impact of bead dissolution in the low-silicon waters of the Arctic surface
533
ocean, where diatom growth is seasonally silicon-limited (Krause et al., 2018, 2019;
534
Giesbrecht et al., 2021), is unknown. Finally, Webster and Warren (2022) show that massive
535
quantities of glass beads would be requiredabout 360 megatons annually, an amount
536
equivalent to the annual global production of plasticposing significant logistical challenges
537
and substantial emissions during production. They also found that microspheres have a net
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warming effect on Arctic sea ice. They can absorb a significant portion of solar radiation,
539
darkening surfaces with high albedo and accelerating sea ice loss rather than preserving it.
540
Governance
541
Glass beads also present important governance challenges. Ocean currents and surface winds
542
carry sea ice across Arctic Ocean sovereignty boundaries. The international legality of a
543
single nation introducing an environmental disturbance onto another would be a serious issue
544
requiring resolution before any deployment. No such agreements exist at present, effectively
545
blocking the roll-out of this technology. Another essential governance factor concerns
546
Indigenous Arctic communities, and their preparedness for and support of such interventions
547
on the natural systems they depend on for food and culture (Chuffart et al., 2023).
548
Arctic sea ice freezing
549
Background
550
There has been much debate on whether Arctic sea ice can be artificially thickened to
551
counter sea ice loss (Figure 4). Desch et al. (2017) claim that “where appropriate devices are
552
employed”, winter sea ice could be thickened by ~1 m and that deployment across 10% of the
553
Arctic Ocean (especially where sea ice loss is critical) could “more than reverse current
554
trends of ice loss in the Arctic, using existing industrial capacity”. Since 2017 experiments
555
have shown how sea ice can be thickened by pumping sea water either onto the ice surface
556
and then directly refreezing, or into the air, where it will freeze and fall as snow. Using
557
modelling, Zampieri and Goessling (2019) estimated that this could be accomplished by “a
558
large number” of wind turbines that pump seawater onto the ice. They claim, “it is possible to
559
keep the late-summer sea ice cover at the current extent for the next 60 years”.
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Effectiveness and feasibility
561
The main issue for this idea is not whether the technique itself can work (although there are
562
many reasons to be skeptical about this) but whether it is feasible for use at the scale
563
necessary and in the time available. Long-term average Arctic sea ice extent varies between
564
summer and winter from 516 million km2. If we assume a single device could cover 1 km2
565
(that would be an enormous, arguably implausible, machine) >10 million devices would be
566
needed to cover today’s winter sea ice. If we accept Desch et al.’s claim that only 10% cover
567
is needed, this would necessitate 1 million devices. If we then assume 1,000 devices could be
568
deployed every year (another colossal undertaking) it would still take 1000 years to cover
569
10% of the present Arctic sea ice cover. In other words, sea ice thickening is simply not
570
feasible for use at a scale and rate that would be meaningful for sea-ice protection.
571
Notwithstanding this critical failure, the scale of implementing the method would require an
572
unprecedented level of human presence in the High Arctic for construction in the first
573
instance and for maintenance thereafter. Other inherent challenges may render the idea
574
infeasible even at a local scale, such as the difficulty in keeping the pumps in place
575
(considering the strong sea ice drift), the need for year-round maintenance over such a wide
576
area, the sinking of pumps if sea ice melts or breaks up, and governance issuesespecially
577
considering the Arctic Ocean is becoming an increasingly congested space.
578
Governance
579
Any large-scale intervention affecting natural systems in the Arctic must be undertaken with
580
an appreciation of the applicable sovereign and international governance structures (see Part
581
3). As with the glass beads” idea, the flow of sea ice across sovereign boundaries means that
582
issues may well arise between nations that agree to the installation of ice-thickening
583
machinery and those that do not, especially for maintenance and removal purposes.
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Siegert, M. et al. Safeguarding from dangerous polar geoengineering. Non peer-reviewed submission
to Frontiers in Science, 24 October 2024
25
Case study 4: Slowing ice sheet flow through basal water removal
585
Background
586
The rate at which ice is discharged from ice sheets to the ocean is determined by the flow of
587
outlet glaciers and ice streams towards their margins. Increases in flow rates, where they are
588
not balanced by increased accumulation, contribute to global mean sea-level rise. While
589
mountain glaciers dominated the cryosphere contribution to sea level rise over most of the
590
20th century, ice sheet contributions have risen rapidly since the 1990s, and the combined
591
contribution from both Greenland and Antarctica now exceeds that of mountain glaciers,
592
adding 11.9 mm to global mean sea level between 2006 and 2018 (Fox-Kemper et al., 2021).
593
These trends are expected to continue, with the IPCC Sixth Assessment Report being unable
594
to rule out low confidence projections that exceed 15 m sea level rise by 2300 under a high-
595
emissions scenario (Fox-Kemper et al., 2021). It follows, therefore, that reducing the rapid
596
flow of outlet glaciers and ice streams in Greenland and Antarctica could, in principle,
597
mitigate future sea level rise, especially mass losses from Antarctica, which experiences
598
much less surface melting than Greenland. Building on this logic, some researchers (e.g.,
599
Moore et al., 2018; Lockley et al., 2020) have proposed geoengineering strategies aimed at
600
increasing basal friction to ultimately slow down glacier flow, with a particular focus on
601
removing the lubrication provided by the pressurized subglacial drainage system (Moore et
602
al., 2018). We present here our logic for why we believe that these intervention strategies are
603
scientifically flawed and likely to be logistically impossible.
604
Ice streams and outlet glaciers lie on a spectrum from those that flow through deep troughs to
605
those that flow over relatively flat beds (Truffer and Echelmeyer, 2003; Stokes, 2018). The
606
former (topographic ice streams) are common in both Greenland and Antarctica, but the
607
latter (“pure ice streams”) are exemplified by those that drain the Siple Coast of West
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to Frontiers in Science, 24 October 2024
26
Antarctica, but do not exist in Greenland. Interestingly, the Siple Coast ice streams
609
dominated much of the earlier literature on ice stream flow mechanisms (Stokes, 2018) and
610
are often cited as case studies in the limited geoengineering literature, but they are not a
611
major contributor to recent sea level rise from Antarctica. Worryingly, the glacier
612
experiencing the most ice loss, Thwaites Glacier, appears unconstrained by basal topography,
613
and its deglaciation would likely impact the whole West Antarctic Ice Sheet (Holt et al.,
614
2006; Reese et al., 2023). Irrespective of their topographic setting, the rapid movement of ice
615
streams and outlet glaciers is predominantly driven by basal slidingice slipping along the
616
beda phenomenon resulting from a combination of sliding at the ice-bed interface, and
617
deformation of the bed itself (Cuffey and Paterson, 2010; Stokes, 2018). The fastest-flowing
618
ice streams are generally found in regions where water is routed down topographic troughs or
619
accumulates at the base, acting as a lubricant and reducing the effective pressure of the
620
overlying ice. Higher water pressures in these areas are directly linked to increased glacier
621
velocity, resulting in accelerated ice movement (Schoof, 2010).
622
In Antarctica, subglacial water is generated at the bed primarily by the melting of basal ice
623
due to a combination of frictional heating, geothermal heating, and pressure melting (Dow et
624
al., 2022). Unlike in Greenland, supraglacial meltwater does not reach the bed in appreciable
625
quantities. It may also be sourced from Antarctic groundwater, a relatively new area of
626
investigation that could account for around half of the water found in ice stream beds
627
(Christoffersen et al., 2014; Siegert et al., 2018). While groundwater has been identified at
628
the margin of the ice sheets (Mikucki et al., 2015), at present there is only limited evidence of
629
groundwater systems in Antarctica (e.g., Gustafson et al., 2022). However, as there are huge
630
sedimentary basins present beneath the ice (Aitken et al., 2023) it is highly likely water from
631
these basins play a major role in modulating ice flow (Aitken et al., 2022) especially on
632
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to Frontiers in Science, 24 October 2024
27
decadal timescales (Robel et al., 2023). Hence, any study looking to extract basal water to
633
reduce water pressure must account for the presently unknown role of groundwater.
634
The rates of basal meltwater production are generally low (mm/year) but over large areas of
635
the ice sheet bed, this leads to large volumes of subglacial water. Moreover, the subglacial
636
water system is interconnected and continuously replenishing, comprising a network of
637
subglacial streams and lakes (Fricker et al., 2007; Livingstone et al., 2022). In contrast,
638
Greenland’s subglacial water is mostly generated at the surface and is then delivered to the
639
bed via moulins, providing a direct link between subglacial water and climate change.
640
Tulaczyk et al. (2000) proposed a thermodynamic feedback mechanism linking glacier flow
641
to meltwater production, highlighting the significant influence of subglacial hydrology on
642
water pressure and flow dynamics. Importantly, in Antarctica there is no widespread link
643
between basal melting and the atmosphere.
644
Geoengineering strategies to reduce ice stream and glacier sliding fall into three categories
645
(Lockley et al., 2020):
646
(i) Drilling/drying: this involves drilling to the subglacial bed and reducing water pressure
647
there by pumping subglacial water to the ice surface. The objective is to increase basal drag
648
by reducing water pressure, thereby slowing glacier flow
649
(ii) Cooling: these approaches aim to reduce glacier flow rates by promoting heat flow from
650
the bed to the surface or by introducing coolants into the bed
651
(iii) Obstructing: this involves constructing obstacles (such as artificial rock outcrops) at the
652
bed to increase basal friction and reduce the dependency of friction on water pressure,
653
thereby impeding glacier flow (Schoof, 2005).
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to Frontiers in Science, 24 October 2024
28
Effectiveness and feasibility
655
We focus here on the scientific and logistical challenges of drilling/drying, but many of these
656
apply equally to cooling and obstructing (Figure 5). We anticipate limited effectiveness of
657
drilling/drying owing to the highly dynamic spatial and temporal nature of subglacial
658
drainage. The location, timing, and sphere of influence of each drill hole would be critical.
659
In Antarctica Subglacial water production is spatially extensive, but most basal water flows
660
in discrete channels (Dow et al., 2023) that form intricately branched subglacial hydrologic
661
systems. Therefore, multiple drill holes would be required, each syphoning a different
662
branchassuming these could be accurately located from surface geophysical survey. This
663
also assumes that the subglacial drainage system is stable, yet a wealth of evidence shows it
664
to be highly variable, both spatially and temporally (Bell, 2008; Bartholomew et al., 2012;
665
Siegfried and Fricker, 2021). Furthermore, once the ice stream bed is accessed by a drill,
666
basal sliding will quickly move the drill base downstream. So, even if a channel or subglacial
667
lake is connected to the surface by the drill hole, ice flow above would act to break the
668
connection within days to weeks. Regarding groundwater, we presently have no means to
669
consider its extraction.
670
In Greenland, surface water could be removed to prevent it from reaching the bed, but the
671
transient nature of the supraglacial system (Das et al., 2008; Bartholomew et al., 2012) would
672
necessitate adaptable camps, machinery and logistics. Maintaining infrastructure on a melting
673
ice surface is a significant challenge requiring almost constant maintenance. Water would
674
have to be removed from the ice sheet and routed elsewhere without it reaching the bed via
675
downstream moulins or crevasses. Additionally, this would have no impact on meltwater
676
generated by frictional heating at the bed of large topographic ice streams (Echelmeyer and
677
Harrison, 1989). Furthermore, channeling large quantities of supraglacial water to the bed
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to Frontiers in Science, 24 October 2024
29
leads to low-pressure channelized drainage systems that act to reduce annual ice flow
679
velocities, rather than increase them (Davidson et al., 2019). Greenland subglacial hydrology
680
evolves seasonally; towards the end of the melt season, high subglacial water volumes evolve
681
into efficient channelized drainage systems that lubricate less of the basal area, decelerating
682
the ice flow (Sundal et al., 2011). Therefore it seems highly unlikely that basal water
683
extraction in Greenland, either directly or from supraglacial diversion, is a feasible means to
684
decelerate ice flow and it could even have the reverse effect.
685
Turning back to the Antarctic, targeting the ice stream trunk for water removal is unlikely to
686
work as the cumulative velocity of the entire ice stream needs to be reduced. Removing water
687
from upstream and/or in the onset zone of ice streams would be the most effective way to
688
reduce the overall water supply. However, the inland plateau is the hardest place to access
689
and has the thickest ice, making drilling even more challenging. Moreover, boreholes would
690
have to be kept constantly open because subglacial water production is continuous.
691
Draining the bed in the onset zone or upstream portion of an ice stream would theoretically
692
steepen the ice surface slope and thereby increase driving stresses and pressure melting at the
693
bed, much in the same way that glacier surging is triggered. Indeed, even if drainage slowed
694
ice flow in a particular area, the ice sheet/stream would thicken upstream and the resulting
695
changes in the ice surface slope would displace basal water to neighboring regions,
696
potentially accelerating flow elsewhere (Wright et al., 2008). This water piracy mechanism
697
has been blamed for the shutdown of the Kamb Ice Stream (formerly Ice Stream C)
698
(Anandakrishnan and Alley, 1997), which is likely to oscillate between periods of fast and
699
slow flow and which might reactivate this century (van der Wel et al., 2013). Thus, both
700
observations and modelling show that the Siple Coast ice streams exhibit significant short-
701
term variability owing to the complex interplay between adjacent ice streams (Catania et al.,
702
Siegert, M. et al. Safeguarding from dangerous polar geoengineering. Non peer-reviewed submission
to Frontiers in Science, 24 October 2024
30
2012). Hence, even if it were theoretically possible to slow a portion of an ice stream, likely
703
the resultant thickening would reactivate the ice stream or neighboring ice streams would
704
capture ice or meltwater (Conway et al., 2002). Such flow-switching is preserved in the
705
geological record of palaeo-ice stream activity (Dowdeswell et al., 2006; Ó Cofaigh et al.,
706
2010; Stokes et al., 2009; Winsborrow et al., 2012; Stokes et al., 2016). This self-organized”
707
behavior is replicated in numerical ice sheet models (Payne et al., 1997; Robel et al., 2013;
708
Kyrke-Smith et al., 2015) and during deglaciation of palaeo-ice sheets (Stokes et al., 2016). It
709
implies that, even if it were possible to slow the flow of one ice stream, this is very likely to
710
have knock-on effects elsewhere, with other ice streams increasing in flow or reactivating to
711
remove the excess mass.
712
The rapid flow of major outlet glaciers and ice streams can also be triggered by conditions at
713
the terminus (e.g., major calving events, ice shelf thinning, or grounding line retreat along
714
retrograde bed-slopes), which then propagate inland through increased flow velocity and
715
dynamic thinning (Pfeffer, 2007; Nick et al., 2009; Gudmundsson et al., 2019b). Hence, even
716
if upstream adjustments to water pressure and flow were successful, continued ice loss at the
717
terminus may lead to modifications to glaciological change at the sites of boreholes,
718
rendering the sites sub-optimal.
719
720
A reduced flux of ice into the grounding zone could actually lead to rapid glacier retreat if
721
mass losses at the front (by iceberg calving and submarine melt) do not change. A system
722
already close to instability could be pushed over the edge if the ice supply were insufficient
723
to keep the grounding zone stable. For example, the grounding zone of the Institute Ice
724
Siegert, M. et al. Safeguarding from dangerous polar geoengineering. Non peer-reviewed submission
to Frontiers in Science, 24 October 2024
31
Stream in West Antarctica sits atop a major reverse bed slope, kept stable by a balance
725
between basal melt rates and ice flow (Ross et al., 2012).
726
Logistically, drilling subglacial water presents significant challenges and potential
727
consequences. Firstly, drilling to the base of an ice sheet is a monumental undertaking,
728
necessitating advanced equipment and expertise (Siegert et al., 2014). To be most effective,
729
this technique would require numerous drill holes scattered across the ice sheet, a logistical
730
feat unprecedented in polar fieldwork. The sheer size of an ice sheet means that the endeavor
731
is virtually impossible to execute.
732
Water at pressure deep beneath the ice surface will not naturally escape in significant
733
volume: the puncture of Lake Vostok in 2012 created a colossal hydrological shock that bent
734
the drill head and caused massive hydro-fractures in the ice base (Siegert, 2018). Only 5 m3
735
of drilling fluid escaped the surface, however, because the water froze in the borehole.
736
Experience at Lake Ellsworth in 2012 also points to major challenges in drilling deep holes
737
with water once, let alone repeatedly, and even if successful they will freeze after 24 hours
738
unless frequently reamedrequiring more hot surface water (Siegert et al., 2014). Borehole
739
pumping would have to be maintained over long timescales, as the continuously produced
740
basal water would need to be extracted throughout the year, including in winter. Again,
741
because the ice in the Antarctic interior is extremely cold, the boreholes would freeze rapidly
742
(within hours) without continuous heating. Above the water level, the borehole would close
743
under overburden pressure and require regular reopening or casing. This issue becomes non-
744
linearly more difficult as the water level drops.
745
Pumping water out from the subglacial system would be a significant task requiring
746
considerable energy resources. Existing hot water drills use pumps that recover water from
747
Siegert, M. et al. Safeguarding from dangerous polar geoengineering. Non peer-reviewed submission
to Frontiers in Science, 24 October 2024
32
depths of about 100 m. This corresponds to the water level at overburden pressure in a 1000
748
m deep borehole. If lowering water pressure was successful, then the water would have to be
749
pumped against an ever-increasing hydraulic head. Depending on how much water level
750
lowering is needed (currently this is completely unknown), this dramatically increases power
751
requirements and might even exceed the capacity of existing down-hole pump technology.
752
Entirely new approaches, such those as used in oil extraction, might be needed. Those
753
approaches would require casing of the holes yet, in active areas of the ice, significant
754
borehole deformation would make casings vulnerable. Furthermore, successful drying would
755
cause higher basal stresses, which would increase shearing and affect borehole operations.
756
A cursory power calculation estimates power requirements in the multiple MW range (as
757
exemplified by various deep-drilling projects in Antarctica, e.g., ANDRILL, SWAIS 2C,
758
Subglacial Lake Ellsworth, and IceCube). This is a colossal level of power to accomplish in a
759
remote location and operating year-round in extreme cold and windy conditions is far beyond
760
the capabilities of existing technologies. Moreover, providing such power requirements using
761
fossil fuels would defeat the entire purpose, while nuclear power would be highly
762
controversial in the context of the Antarctic Treaty. Solar farms at that scale are not realistic
763
given the long polar winter and the formidable challenge of wind drifts. Wind turbines could
764
theoretically work, but existing structures on moving ice are several orders of magnitude
765
smaller than would be necessary.
766
At present, kerosene is commonly used for power in remote field locations, which poses
767
another environmental risk: the deposition of black carbon on the ice surface. At the scale
768
required for widespread intervention, such deposition would likely be counterproductive,
769
exacerbating rather than mitigating the challenges posed by rapid glacier flow. Plus, for every
770
1 barrel of kerosene made available in central Antarctica, around 12 are needed to get it there.
771
Siegert, M. et al. Safeguarding from dangerous polar geoengineering. Non peer-reviewed submission
to Frontiers in Science, 24 October 2024
33
The management of pumped-out water on the surface is another significant challenge. A
772
proposed solution is to turn this into snow, using snow-making equipment commonly used in
773
ski areas. This is doable in principle but would produce a large amount of snow and entails
774
additional energy requirements. The necessary management of this snow would require
775
automated procedures to move it away from the snow cannons. The maintenance of surface
776
infrastructure through extreme cold and wind, drifting snow, and riming (freezing water on
777
solar-heated surfaces) is also a serious impediment. For example, equipment commonly gets
778
drifted in in the Thwaites area, where there is relatively high snow accumulation and wind
779
drift (Johnson et al., 2018). Both the pumping infrastructure and snow-making equipment
780
would require protection somehow from snow drifting.
781
Many of these challenges require entirely new engineering approaches that will take many
782
years or even decades to develop, even with unlimited resources, and yet we have no idea
783
whether this approach would even work.
784
Negative consequences
785
Notwithstanding the scientific flaws of attempting to slow an ice stream, drilling activities
786
could introduce contaminants into pristine subglacial environments, damaging delicate,
787
biodiverse ecosystems that have likely evolved over many millennia. Such consequences
788
underscore the importance of thorough risk assessment considering all environmental
789
impacts. The Scientific Committee on Antarctic Research has agreed a code of conduct for
790
Antarctic subglacial access (Siegert and Kennicutt, 2018), endorsed by the Antarctic Treaty
791
Consultative Meeting (ATCM) through Resolution 2 (2017). The ATCM’s Committee for
792
Environmental Protection (CEP) has assessed deep-drill access to the ice-sheet bed, and in
793
accordance with its advice, authorization is only likely to be granted if procedures with
794
proven effectiveness are used to sterilize drill water (Siegert et al., 2012). Hot-water drilling
795
Siegert, M. et al. Safeguarding from dangerous polar geoengineering. Non peer-reviewed submission
to Frontiers in Science, 24 October 2024
34
with pasteurized water could be possible, but such work is technically challenging (Siegert et
796
al., 2014) and increases energy consumption. Use of ice cores, which use an antifreeze
797
drilling fluid, would likely be incompatible with environmental protection. Drilling may also
798
lead to unintended altering of the ice structure and crevasse formation (Scott et al., 2010).
799
Cost
800
The Subglacial Lake Ellsworth program, which in 2012 unsuccessfully aimed to create a 3
801
km borehole for just 24 hours, cost approximately US$13 million (equivalent to US$18
802
million in 2024) (Siegert et al., 2012). The proposed method of water removal would require
803
multiple holes (10s-100s), and continuous connection to the bed (i.e., 365 days/year for years
804
to come), adding at least three orders of magnitude to the Lake Ellsworth figure plus
805
maintenance and monitoring. It is difficult to imagine such a large undertaking being possible
806
without the establishment of a new coastal station in the vicinity to which materials could be
807
delivered by sea and which would serve as a year-round base for operations. The construction
808
of IceCube would not have been possible without the existence of McMurdo, Antarctica’s
809
largest base, and Amundsen-Scott station at South Pole. Planning, approval, and construction
810
of such bases is a decades-long undertaking.
811
Governance
812
In common with sea curtains (Case study 2), the implementation of this activity in Antarctica
813
would fall under the Antarctic Treaty system. Article 8 of the Protocol on Environmental
814
Protection requires a Comprehensive Environmental Evaluation for any activity with more
815
than a minor or transitory impact. This activity would require not only estimation of all
816
likely impacts but a rigorous associated program of monitoring and mitigation of impacts.
817
Siegert, M. et al. Safeguarding from dangerous polar geoengineering. Non peer-reviewed submission
to Frontiers in Science, 24 October 2024
35
Case study 5: Ocean fertilization
818
Background
819
Ocean fertilization is a form of geoengineering wherein nutrients whose availability limit
820
phytoplankton growth (e.g., iron) are added to ocean surface water to promote photosynthesis
821
and stimulate blooms, thereby increasing the biological drawdown of CO2 from the
822
atmosphere (Arrigo and Tagliabue, 2005) (Figure 6). This enhanced fixation of carbon in
823
surface waters is then expected to sink as particulate organic carbon (POC) to the deep ocean
824
for long-term sequestration. This vertical advection is known as the “biological carbon
825
pump” (BCP), where a suite of biota from bacteria to zooplankton and fish control the
826
magnitude and efficiency of carbon export to the deep ocean (Jiang et al., 2024).
827
Prime ocean areas for ocean fertilization are regions of high nutrient and low chlorophyll
828
(HNLC) concentrations, specifically where macronutrients (e.g., nitrogen, phosphorus,
829
dissolved silicon) are abundant, but phytoplankton growth is restricted by other factors, such
830
as a lack of micronutrients (e.g., iron). The Southern Ocean, an HNLC environment where
831
productivity is limited by low iron availability, is considered an ideal location for ocean iron
832
fertilization (OIF) (Martin et al., 1990; Oschlies et al. 2010; Jiang et al., 2024).
833
Effectiveness and feasibility
834
From 1993 to 2011, 19 in situ OIF experiments tested the “iron hypothesis”: 12 in the
835
Southern Ocean, three in the Equatorial Pacific Ocean, one in the tropical Atlantic Ocean,
836
and three in the Subarctic (North Pacific Ocean) (Yoon et al., 2018). These gave uncertain
837
results regarding the ability of OIF to increase the vertical export of POC to the deep ocean
838
(de Baar et al., 2005; Aumont & Bopp, 2006; Queguiner, 2013). In the Southern Ocean, OIF
839
enhanced photosynthesis, but increased carbon export to depth was only documented in one
840
Siegert, M. et al. Safeguarding from dangerous polar geoengineering. Non peer-reviewed submission
to Frontiers in Science, 24 October 2024
36
experiment (Yoon et al., 2018). Notably, export was only monitored for 26 weeks following
841
iron addition, so it is not known if longer term observations might yield more positive results
842
(Boyd & Law, 2001; Buesseler & Boyd, 2004; Yoon et al., 2018).
843
In terms of feasibility, full-scale deployment would require considerable effort and resources
844
(see later)involving an armada of ships designed to transfer and deposit iron at
845
considerable ocean-wide scale. Means for the creation and supply of suitable material, and
846
docks to support its loading, would also need to be established. None of this is available at
847
present, making its feasibility questionable.
848
Negative consequences
849
Scientists have expressed various concerns about the impacts of OIF on marine communities
850
and ecosystems. While the addition of a limiting nutrient such as iron could enhance
851
phytoplankton growth, there is no control over which species or groups of phytoplankton will
852
be stimulated (Queguiner, 2013). Phytoplankton communities are typically a diverse mix of
853
taxa. In the Southern Ocean, hundreds of species continually shift in terms of their standing
854
stock and relative abundance. Diatoms, dinoflagellates, chrysophytes, and other groups can
855
all be present at once with great spatial and temporal variation in which groups and species
856
dominate. Natural changes in light, temperature, macro- and micronutrients, and grazing
857
pressure act synergistically to control species succession patterns. The species-specific
858
impact of OIF within this mix of physical and biological controls is unknown and indeed
859
unpredictable. Since phytoplankton cells and colonies range in size from a few microns to
860
millimeters, changes in species composition due to competition and grazing could potentially
861
restructure the size distribution within communities, affecting grazing efficiency among
862
zooplankton and the nutritional value of the phytoplankton. Associated feedback effects on
863
microbial communities in regions of OIF have often been observed (West et al., 2008). Such
864
Siegert, M. et al. Safeguarding from dangerous polar geoengineering. Non peer-reviewed submission
to Frontiers in Science, 24 October 2024
37
changes at the base of a food web and in the microbial loop would affect energy transfer,
865
trophic dynamics, and biogeochemical cycling throughout the Antarctic marine ecosystem.
866
Increased carbon export to depth is an intended consequence of OIF. Other (unintended)
867
consequences could result from the trapping of nutrients below fertilized regions, alongside
868
feedback effects, including deoxygenation and the production of other GHGs (e.g., methane
869
and nitrous oxide; N2O). The nutrient robbing impact of OIF has garnered a lot of attention
870
because of the potential broad impacts on net productivity elsewhere in the world. The
871
Southern Ocean has a major role in the transport of nutrients to lower latitudes (Sarmiento et
872
al., 2004), effectively regulating rates of global primary productivity, the efficacy of the BCP,
873
and the transfer of energy to higher trophic levels (including fisheries). As OIF stimulates
874
productivity, it simultaneously depletes stocks of major nutrients, limiting the amount of
875
nutrients transported and consequently decreasing net primary production in regions outside
876
of the fertilization area. In the Southern Ocean, the signal of this nutrient robbing is
877
exported to lower latitudes by the Subpolar Mode Waters and the Antarctic Intermediate
878
Water, leading to nutrient-depleted surface waters in the tropics (Oschlies et al., 2010).
879
Reductions in biological production and organic matter export have been well documented in
880
waters outside fertilization areas (Sarmiento & Orr, 1991, Oschlies et al., 2010). Indeed,
881
recent modelling work has highlighted that when OIF is undertaken in the Southern Ocean,
882
the greater nutrient consumption, coupled with ongoing climate stressors (e.g. increased
883
stratification), leads to a reduction in higher trophic-level organisms in the tropics (Tagliabue
884
et al., 2023). This cascading effect damages important fisheries in the tropical Pacific that are
885
critical to coastal and island communities and for commercial exports a major social equity
886
concern. These consequences of nutrient robbing” could be slightly mitigated if OIF were
887
limited to only higher latitude zones of the Southern Ocean, further from where the
888
intermediate and mode waters originate. However, this would provide a far smaller
889
Siegert, M. et al. Safeguarding from dangerous polar geoengineering. Non peer-reviewed submission
to Frontiers in Science, 24 October 2024
38
contribution to atmospheric CO2 removal, while still having negative consequences (e.g.
890
Oschlies et al., 2010, Tagliabue et al., 2023).
891
Biogeochemical effects of OIF include deoxygenation and the production of N2O and
892
methane (Oschlies et al. 2010). OIF increases oxygen consumption via the remineralization
893
of the organic matter it produces. This compounds the deoxygenation that global climate
894
change is already causing through warmer waters and increased stratification. N2O and
895
methane are produced during the remineralization of organic matter produced by OIF, and
896
both have a global warming potential greater than that of CO2 on a 100-year timescale (300-
897
fold and 20-fold, respectively). While the production of methane is a minor concern, since its
898
highest production only occurs in anoxic waters, N2O generation following OIF ranged from
899
512% of equivalent CO2 captured during a given OIF event [e.g. (Oschlies et al., 2010)].
900
Cost
901
The practicality of OIF to mitigate anthropogenic carbon addition to the atmosphere has been
902
questioned based on the difficulty of scaling it up to the magnitude that would be required for
903
commercial application (Rohr, 2019). Buesseler and Boyd (2003) estimated that the effort
904
needed (relative to the amount of iron used for fertilization) would be six orders of magnitude
905
higher than any single experiment conducted in the Southern Ocean, and the area treated
906
would need to be 10-fold larger than the Southern Ocean (which they defined as the area
907
south of 50° latitude, equivalent to the area of Asia). The estimated price of OIF per tonne of
908
CO2 removed from the atmosphere varies by location from <US$100/tonne on the shelf to
909
>>US$1,000/tonne in offshore areas (Bach et al., 2023). For reference, world CO2 emissions
910
in 2022 were 37.15 billion tonnes (Richie & Roser, 2020).
911
Siegert, M. et al. Safeguarding from dangerous polar geoengineering. Non peer-reviewed submission
to Frontiers in Science, 24 October 2024
39
Governance
912
A primary challenge to early OIF experiments lay in determining the legality of adding iron
913
(a pollutant) to the ocean (Freestone & Rayfuse, 2008; Eick, 2013). The UN took up this
914
issue in 1999 and OIF is now regulated by the London Protocol to the Convention on the
915
Prevention of Marine Pollution by Dumping of Wastes and Other Matter 1972 (or the
916
London Convention) (IMO). A 2013 amendment to the London Convention states that,
917
“An ocean fertilization activity may only be considered for a permit if it is assessed as
918
constituting legitimate scientific research taking into account any specific placement
919
assessment framework (IMO). So, no large-scale mitigation OIF projects can be
920
implemented. National authorities are responsible for permitting OIF experiments, but
921
several other international agreements address OIF (Keating-Bitonti, 2022). The UN
922
Convention on Biological Diversity (CBD) does not currently support OIF and the Kyoto
923
Protocol of the UN Framework Convention on Climate Change (UNFCCC) does not allow
924
OIF to be used for carbon credits. OIF is not addressed by the UN Convention on the Law of
925
the Sea (UNCLOS), though it might fall under the UNCLOS definition of marine pollution.
926
The Antarctic Treaty System has not specifically considered OIF; it does have an annex to its
927
Protocol on Environmental Protection on the prevention of marine pollution, but this pertains
928
to waste from ship operations (e.g., food, trash, oil). Potential impacts of OIF on Southern
929
Ocean ecosystems, food webs and fisheries would also be of concern to CCAMLR.
930
Notably, OIF is the only geoengineering scheme tested in situ in the Southern Ocean, the last
931
experiment being in 2011 (Bowie et al., 2015). While there has been a long hiatus in OIF
932
experimentation worldwide, there is a resurgence of interest in researching geoengineering
933
methods for marine CO2 removal (mCDR) to alleviate both carbon accumulation in the
934
atmosphere and ocean acidification resulting from diffusion of CO2 into the ocean. For
935
Siegert, M. et al. Safeguarding from dangerous polar geoengineering. Non peer-reviewed submission
to Frontiers in Science, 24 October 2024
40
example, in 2023 the US National Oceanic and Atmospheric Administration announced the
936
availability of US$24.3 million for such research endeavors (NOAA 2023) and the US
937
Department of Energy (Dept of Energy 2023) has allocated US$36 million for this joint
938
program. Moreover, new computer technologies (e.g., digital twins) are being used in marine
939
conservation management, including the planning of OIF strategies (Tzachor et al. 2023).
940
Part 2: Debunking geoengineering arguments
941
In this section we briefly address four arguments commonly used by geoengineering
942
proponents.
943
Argument 1: Mitigation is not happening fast enough
944
It is clear that current policies are insufficient to meet the decade-long emissions reductions
945
required to meet the climate goals set out in the Paris Agreement. Best estimate projections
946
for global warming by the end of the century under existing policies that are being
947
implemented by countries are about 3°C (Rogelj et al., 2023a). When countries fully
948
implement the emission reduction pledges they submitted to the Paris Agreement, the central
949
warming estimate for 2100 lands at 2.5°C. The latter cases mostly focus on pledges to be
950
implemented by 2030. However, countries have also communicated longer-term targets,
951
which often aim to achieve net-zero CO2 or total GHG emissions (Höhne et al, 2021; Rogelj
952
et al, 2021). Taking into account these longer-term targets reduces the central warming
953
estimate to 2.0°C (Rogelj et al., 2023b).
954
While this current shortfall in climate action is acknowledged by all, arguments that suggest
955
that this supports geoengineering as an important alternative or solution ignore at least two
956
critical aspects. First, even if current climate pledges and policies are insufficient to limit
957
Siegert, M. et al. Safeguarding from dangerous polar geoengineering. Non peer-reviewed submission
to Frontiers in Science, 24 October 2024
41
warming to 1.5°C, they at present already give a 1-in-7 chance that warming is kept to 1.5°C
958
if all countries live up to their pledges (Rogelj et al., 2023a; Rogelj et al., 2023b). Having a 6-
959
in-7 chance that warming exceeds 1.5°C is concerning but does not mean that 1.5°C is
960
exceeded by a large amount. The same case that gives a 1-in-7 chance that warming is kept to
961
1.5°C will hold warming below 2°C with a 2-in-3 chance, with a best estimate of 1.8°C.
962
Second, many mitigation actions are underway, some at increasing rates and geographic
963
scales. Focusing on boosting the uptake of effective mitigation strategies has the potential to
964
create more rapid emissions reductions, especially when using existing technologies.
965
This is particularly true in the context of a Paris Agreement architecture that pursues the
966
ratcheting up of climate action interspersed with 5-yearly stocktaking cycles. The first Global
967
Stocktake has just concluded and countries are currently tasked to put forward new, updated,
968
and strengthened near-term pledges. This legally binding process is anticipated to further
969
increase the likelihood of warming being kept as closely to 1.5°C as possible.
970
Geoengineering proponents not only ignore, but also act to decrease, the probability of
971
mitigation actions that are economically and technically feasible, but which still lack political
972
will at present (IPCC, 2022; Lenton et al, 2023).
973
Argument 2: It is our moral duty to look at all the options
974
Though there is an intuitive appeal to the notion that all options” should be considered in the
975
search for approaches to address anthropogenic warming and its consequences, it is also
976
important to recognize certain options can carry a significant negative effect, termed here
977
“moral hazard”. Moral hazards are understood as actions or steps that lead an individual,
978
organization or society to increase their exposure to risk because they believe that they do not
979
bear the full risk (Rowell & Connelly, 2012). We suggest that geoengineering can constitute
980
Siegert, M. et al. Safeguarding from dangerous polar geoengineering. Non peer-reviewed submission
to Frontiers in Science, 24 October 2024
42
a moral hazard or more widely constitute mitigation deterrence”. We highlight here two
981
moral hazards associated with geoengineering: complacency and predatory delay.
982
Discussions of geoengineering can lull actors, whether individual or collective, into
983
complacency. Rather than continuing to explore a wide range of options, they may decide
984
that geoengineering can offer sufficient protection against climate risks. They fall victim to
985
what is termed the “single action bias”— the closing off of searches for alternate solutions,
986
once one step has been taken (Weber, 2017). Empirical studies have demonstrated this bias in
987
a variety of settings, whether homeowners in flood-prone areas who are less likely to
988
purchase insurance or elevate their homes if they have simply stocked up on water,
989
flashlights, and batteries (Buchanan et al., 2019), or consumers in a cafeteria who undertake
990
fewer behaviors to reduce food waste (e.g., ordering less food) if they are told that uneaten
991
food will be composted (Qi & Rose, 2017). Similarly, there is the risk that attention to
992
geoengineering might reduce engagement with decarbonization, a costly and difficult
993
process. Termed “mitigation deterrence” (McLaren, 2016), this effect has been discussed by
994
others (Mahajan et al., 2019; Stephens et al., 2023).
995
Predatory delay differs from the form of delay discussed above, which is a largely unintended
996
consequence of the complacency generated by a particular action. First introduced by Steffen
997
(2016), the term predatory delay refers to deliberate efforts by powerful institutions, such as
998
fossil fuel firms and petrostates, to slow the implementation of actions that address root
999
causes of problems in order to preserve their own financial and political power. Though some
1000
individuals within the institutions may have genuine motivations to seek alternative actions,
1001
the overall goal of the institution is to postpone actions that would be costly to them, even if
1002
the actions would bring wide benefits to society and the environment. Kramer (2020) details
1003
the interactions of large firms and lobbyists to influence policymakers and regulatory
1004
Siegert, M. et al. Safeguarding from dangerous polar geoengineering. Non peer-reviewed submission
to Frontiers in Science, 24 October 2024
43
agencies to create such delays. Muffett and Feit (2019) detail the funding of geoengineering
1005
research by fossil fuel firms, showing how this research is used to support the ongoing
1006
production and utilization of oil, gas, and coal for the next several decades. In this way,
1007
geoengineering could be compared to the efforts of tobacco companies to propose filter
1008
cigarettes as a way to reduce the risk of cancer without reducing the consumption of tobacco
1009
(Harris, 2011).
1010
There is also a growing literature on how geoengineering funding (including from super-rich
1011
individuals and foundations), while being based on a perception of moral duty”, may lead to
1012
the installation of undemocratic values and power relations (Surprise & Sapinksi, 2022),
1013
increased unilateralism (Stephens et al., 2022), misconstrued morals and public acceptance
1014
(Cherry et al., 2022; Fritz et al. 2024), and lack of awareness of international conflict versus
1015
cooperation (Buck et al., 2022).
1016
Argument 3: Geoengineering will buy us time to adapt and find
1017
other solutions
1018
Overwhelmingly, geoengineering concepts and methods are in the early-to-middle stages of
1019
research and design. Irrespective of their effectiveness, which we dispute, they face vexing
1020
issues regarding policy, deliberation and decision-making processes, power relations, global
1021
governance, ethics, materials, and funding. Progress on all of these fronts requires many
1022
different types of resources, all of which are limited. Even with very large resources, the
1023
challenges put these “solutions” decades into the future. In contrast, many mitigation
1024
technologies already exist and are ready to scale locally and globally. It therefore makes more
1025
sense to invest limited resources in improving and scaling existing technologies that reduce
1026
emissions, rather than working on speculative technologies that do not address emissions.
1027
With an increased focus on implementation of existing technologies, we can make substantial
1028
Siegert, M. et al. Safeguarding from dangerous polar geoengineering. Non peer-reviewed submission
to Frontiers in Science, 24 October 2024
44
global progress on emissions reduction with limited need for additional new technology
1029
solutions.
1030
Argument 4: Geoengineering will prevent tipping points being
1031
crossed
1032
The polar regions are home to, or have a direct influence on, four of the five most vulnerable
1033
climate tipping points: Greenland Ice Sheet collapse, West Antarctic Ice Sheet collapse,
1034
abrupt permafrost thaw, and the collapse of the Labrador-Irminger Subpolar Gyre
1035
(Armstrong McKay, 2022; IPCC AR6 WGI). These Earth system components are at risk of
1036
crossing their tipping points at ~1.5°C of warming, with risks growing as temperatures rise.
1037
Some could have already crossed such thresholds (Rosier et al., 2021; Lenton et al., 2023;
1038
Hill et al., 2023; Reese et al., 2023; Klose et al., 2024).
1039
While several studies frame SRM as a means to delay the crossing of potential tipping points
1040
(Xie et al., 2022; Moore et al., 2019; Sutter et al., 2023; Chen et al., 2023), they indicate that
1041
it is less effective than GHG mitigation strategies. Moreover, they rely on simplified
1042
scenarios that neglect sociopolitical factors that may cause harms, or raise ethical dilemmas,
1043
that further restrict the potential of geoengineering as an emergency solution (Sillmann et al.,
1044
2015; Corry, 2017; McLaren, 2018; Lenton et al. 2023).
1045
The development of CO2 removal (CDR) technologies, such as direct air carbon capture, and
1046
their potential impact on climate tipping points is still in its early stages. However, several
1047
challenges hinder its implementation, including significant scaling difficulties, slower
1048
operation than other mitigation strategies, and substantial financial burdens associated with
1049
its development and deployment. These factors restrict its potential, as compared with GHG
1050
emission reduction efforts. Furthermore, it is crucial to ensure that CDR technologies
1051
Siegert, M. et al. Safeguarding from dangerous polar geoengineering. Non peer-reviewed submission
to Frontiers in Science, 24 October 2024
45
complement GHG emission reduction strategies to bring CO2 concentrations and
1052
temperatures down once carbon neutrality is reached. Failure to do so could result in
1053
mitigation deterrence, potentially leading to additional warming of up to 1.4°C above the
1054
1.5°C target (McLaren, 2020).
1055
Geoengineering interventions face significant challenges due to the limited timeframe for
1056
their deployment. The urgent need for immediate action to prevent the crossing of tipping
1057
points necessitates rapid implementation of strategies. However, the development and
1058
application of geoengineering methods would require extensive research, planning, and
1059
international cooperation, making it impossible to meet the narrow window available.
1060
Given the substantial uncertainties and challenges associated with geoengineering, it should
1061
not be relied upon as a dependable solution to prevent Earth system tipping points being
1062
passed. The focus, therefore, should remain on aggressive emission reduction strategies,
1063
robust adaptation measures, and developing a deeper understanding of Earth system tipping
1064
points to minimize associated risks.
1065
Part 3: International governance and decision-making
1066
In Part 1 we touch on “governance” matters that would need to be overcome before the
1067
deployment of any geoengineering intervention. In this section we discuss more broadly the
1068
governance arrangements that exist internationally within the polar regions and whether/how
1069
they are set up to perform an essential role in preventing, or setting strict terms for, such
1070
interventions. Notably, geoengineering presents particular obstacles to effective governance
1071
not found in other arenas of international environmental collaboration (e.g., in transnational
1072
river basin management or stratospheric ozone management). Firstly, the typologies of
1073
approaches differ greatly between the technology centered geoengineering advocates and the
1074
Siegert, M. et al. Safeguarding from dangerous polar geoengineering. Non peer-reviewed submission
to Frontiers in Science, 24 October 2024
46
institutional and legal frameworks of international regulatory agencies, so they lack common
1075
sets of reference on which to base planning. Secondly, the stakeholders who seek approval
1076
from governance authorities operate on short-term timeframes, while researchers and
1077
government regulators adopt medium- and long-term timeframes to address the numerous
1078
uncertainties in this area. Finally, geoengineering promoters emphasize trade-offs between
1079
risks, which conflict with the precautionary priorities of environmental governance. Together,
1080
these barriers severely impede the discussions that are a necessary precursor of effective
1081
governance (Möller 2020).
1082
Antarctica and the Southern Ocean
1083
Antarctic governance is through the Antarctic Treaty system, using a consensus-based model
1084
for decision-making (Triggs, 2011; Hughes et al., 2023). The Antarctic Treaty, which entered
1085
into force in 1961 and currently has 57 signatory states, sets Antarctica aside as a continent
1086
for peace and science. The Protocol on Environmental Protection to the Antarctic Treaty
1087
(hereafter ‘the Protocol’), which entered into force in 1998, states that activities in the
1088
Antarctic Treaty area (the areas south of latitude 60S) shall be planned and conducted so as
1089
to limit adverse impacts on the Antarctic environment and dependent and associated
1090
ecosystems and to avoid, amongst other things, (i) adverse effects on climate or weather
1091
patterns; (ii) significant adverse effects on air or water quality; (iii) significant changes in the
1092
atmospheric, terrestrial (including aquatic), glacial or marine environments; and (iv)
1093
detrimental changes in the distribution, abundance or productivity of species or populations
1094
of species of fauna and flora [Article 3(2a and b)]. The Protocol also states that activities in
1095
the Antarctic Treaty area shall be planned and conducted on the basis of information
1096
sufficient to allow prior assessments of, and informed judgments about, their possible
1097
impacts on the Antarctic environment [Article 3(2c)]. Where there is insufficient information
1098
Siegert, M. et al. Safeguarding from dangerous polar geoengineering. Non peer-reviewed submission
to Frontiers in Science, 24 October 2024
47
on the likely impacts, the use of geoengineering technologies would be contrary to the
1099
Protocol and consequently unlikely to receive authorization to proceed.
1100
All activities undertaken within the Antarctic Treaty area must be subject to an
1101
Environmental Impact Assessment (EIA), as stipulated in Annex I to the Protocol (Bastmeijer
1102
and Roura, 2007). The level of EIA prepared by the Party undertaking the activity will
1103
depend upon whether the anticipated activity is likely to have an impact that is less than,
1104
equal to, or greater than minor or transitory”. The Protocol does not define these terms, but
1105
any geoengineering activities would almost certainly trigger the highest level of EIA, known
1106
as a Comprehensive Environmental Evaluation (CEE). Until now, CEEs have been
1107
undertaken for activities such as station construction, and some proposed geoengineering
1108
projects are of a scale several orders of magnitude greater. The CEP advises the ATCM on
1109
the implementation of the Protocol. The draft CEE for the proposed activity must be
1110
presented to the CEP 120 days prior to the ATCM meeting at which it is to be considered.
1111
The 29 Antarctic Treaty Consultative Parties (ATCPs, i.e., those Parties entitled to participate
1112
in ATCM decision-making) are then given the opportunity to consider the CEE, on the advice
1113
of the CEP. The final CEE must address the comments provided by Parties and must be made
1114
publicly available 60 days prior to the commencement of the activity. However, the ATCM
1115
does not have the authority to prevent an activity going ahead; rather, the proposing Party
1116
must decide whether or not to approve activities undertaken by those under its jurisdiction.
1117
The Protocol also sets out monitoring requirements to ensure the impacts of the activity are
1118
consistent with the Protocol and to provide information useful for minimizing or mitigating
1119
impacts, and, where appropriate, information on the need for suspension, cancellation, or
1120
modification of the activity (Annex I, Article 5).
1121
Siegert, M. et al. Safeguarding from dangerous polar geoengineering. Non peer-reviewed submission
to Frontiers in Science, 24 October 2024
48
International consultation is key to Antarctic governance and, in a system driven by
1122
consensus-based decision-making, controversial or unproven geoengineering activities have a
1123
very low likelihood of approval. Promoters of geoengineering from the ~139 countries that
1124
have not acceded to the Antarctic Treaty (representing ~35% of the global population) are not
1125
obliged to comply with any of these requirements. However, non-Treaty parties are unlikely
1126
to be able to support independent expeditions to the continent, and the use of large-scale
1127
geoengineering methods without sufficient consultation with the ATCM would likely result
1128
in an international outcry (Honegger et al., 2021), as ATCM Parties closely guard the status
1129
of the Treaty and rights as Parties.
1130
In practice, no Party project for which a CEE has been presented to the ATCPs has been
1131
prevented from going ahead (albeit with delays), including some projects involving what
1132
elsewhere might be considered high-impact activities (Hemmings and Kriwoken, 2010;
1133
Montarroyos et al., 2019; Rothwell, 2021). Given the potential global impact of using large-
1134
scale geoengineering methods in Antarctica and the international effort needed to deliver
1135
them, any concerns might not only be raised in the ATCM system, but face challenges
1136
outside it (e.g., via the UNFCCC, UNEP, or UN General Assembly), which the existing
1137
ATCPs would want to avoid.
1138
In accordance with the Article 7 of Protocol, which prohibits any activity relating to mineral
1139
resources other than scientific research, the ATCM has prevented commercial mineral and
1140
petroleum extraction in Antarctica. Given that the scale of Antarctic geoengineering would
1141
likely be equivalent to that of potential mining and hydrocarbon extraction, the ATCM could
1142
perhaps prevent such work. The ATCM has struggled to differentiate between legitimate
1143
geological research activities and exploratory mineral and hydrocarbon prospecting activities
1144
undertake by some Parties, and raise any associated concerns (Afanasiev and Esau, 2023).
1145
Siegert, M. et al. Safeguarding from dangerous polar geoengineering. Non peer-reviewed submission
to Frontiers in Science, 24 October 2024
49
Some Antarctic Treaty Consultative Parties, in particular China, have worked to preserve the
1146
right to access all areas of Antarctica in order to fulfil their scientific and potential future
1147
economic objectives (Talaly & Zhang, 2022). Almost 20 years after it was agreed, Annex VI
1148
to the Protocol (Liability arising from Environmental Emergencies; 2005) has yet to enter
1149
into force. However, once enacted, it would impose a liability on non-state operators to pay
1150
for response(clean-up) for environmental damage caused.
1151
The largest private organizations operating in Antarctica currently have capacities larger than
1152
those of some national Antarctic programs (NAPs). Owing to investment and increasing
1153
demand for their services among tourists and some scientific researchers, they also appear to
1154
have brighter futures than some NAPs that have faced budget cuts or an inability to deliver
1155
the required capacity (Conroy, 2023; Muntean, 2024). However, a private operator, if it
1156
operates within the jurisdiction of a Treaty Party, will still have to submit to the CEP a CEE
1157
and obtain a permit to proceed from the relevant Party.
1158
Overall, the prospects for addressing proposals for geoengineering activities in the Antarctic
1159
depend on the environmental impact assessments conveyed to the Antarctic Treaty system
1160
and the political will of the members of or parties to the agreements to give effect to the
1161
obligations they have set themselves. In this context, the Scientific Committee on Antarctic
1162
Research (SCAR) has a key role in providing independent and objective evidence to the
1163
Treaty system (Chown et al., 2024).
1164
The Arctic
1165
Unlike the Antarctic, the Arctic region falls predominantly within national jurisdictions
1166
(Figure 7). There are four high seas” areas, as defined by UNCLOS, including the central
1167
Arctic Ocean itself, but this represents a small fraction of the total Arctic Ocean area. While
1168
Siegert, M. et al. Safeguarding from dangerous polar geoengineering. Non peer-reviewed submission
to Frontiers in Science, 24 October 2024
50
the governance of activities and their impacts at the surface and in the water column within
1169
high seas areas resides with a variety of existing international mechanisms, such as the
1170
International Maritime Organization (IMO) and the Convention for the Protection of the
1171
Marine Environment of the North-East Atlantic (OSPAR) and the emerging UN High Seas
1172
Treaty, the governance of activities and their impacts at and below the seafloor may change
1173
in the future. Many coastal Arctic states are conducting long-term research to establish the
1174
northward reach of their continental shelf, thereby seeking to provide evidence to extend their
1175
national seabed boundaries, in many cases out into the central Arctic Ocean. This is all in line
1176
with established UNCLOS requirements and practice. There is no timetable for the resolution
1177
of claims arising from the submission of this evidence.
1178
The IMO, a UN body, has well-defined responsibilities and sets provisions for a range of
1179
issues connected to shipping, including safety, communications, marine biosafety (including
1180
non-native species), security, and environmental protection. In 2017, the International Code
1181
for Ships Operating in Polar Waters (known as the Polar Code) entered into force. The Polar
1182
Code provides for specific regulations for shipping in both polar regions, mainly related to
1183
navigation in ice and ship design.
1184
All land in the Arctic is within nationally regulated and internationally agreed boundaries.
1185
Consequently the dominant legal and regulatory governance mechanisms, including those
1186
that would relate to geoengineering, are overwhelmingly those of the eight Arctic states
1187
themselves: the US, Canada, Kingdom of Denmark (Greenland), Iceland, Norway, Sweden,
1188
Finland, and Russia. The major international organization in the region is the Arctic Council,
1189
created in 1996 to provide a high-level forum promoting cooperation, coordination, and
1190
interaction among the Arctic states and the Permanent Participants (PPs), namely six
1191
representative organizations of Indigenous Peoples. State and non-state Observers also
1192
Siegert, M. et al. Safeguarding from dangerous polar geoengineering. Non peer-reviewed submission
to Frontiers in Science, 24 October 2024
51
participate in discussions at the discretion of Member States and PPs. The Council offers a
1193
discussion space and mechanisms to address issues of common concern, with a special
1194
emphasis on the protection of the Arctic environment and sustainable development.
1195
Established by the Ottawa Declaration, the Council is not a Treaty organization under the
1196
terms of the Vienna Conventionunlike the Antarctic Treaty. There are well-established
1197
procedures for both state and non-state organisations to apply for Observer status to the
1198
Arctic Council, though approval requires consensus by all eight Arctic States. There is no
1199
opportunity for states to unilaterally join the Council, which by definition is limited to states
1200
with territory within the Arctic Circle, unlike Antarctica where no state has legal jurisdiction.
1201
Internationally, the Arctic Council has strongly addressed governance issues across the
1202
Arctic, though rapid climate change and recent geopolitical tensions have placed it under
1203
unprecedented pressure (Smieszek 2019). Nevertheless, history shows that cooperation on
1204
scientific and environmental issues is vulnerable to disruption by overall distrust and
1205
geopolitical dynamics between member states (Kornbech et al., 2024). Following the Russian
1206
full-scale invasion of Ukraine in 2022, the activities of Arctic Council’s six Working Groups
1207
were halted as all member states except Russia announced their non-participation. Under the
1208
current Norwegian Chairship of the Arctic Council (202325) significant working-level
1209
activity has resumed across the Working Groups, but the organization has not yet resumed
1210
the in-person Ministerial and Senior Officials’ meetings with all eight members.
1211
The Arctic Council is not a regulatory or law-making organization, given that States do so
1212
under their respective national jurisdictions. It does not, nor have its States ever intended to
1213
seek, the power to enforce collective decisions. Other organizations, including the North East
1214
Atlantic Fisheries Commission, have the competence to adopt conservation and management
1215
measures across portions of the Arctic Ocean, but only within the scope of agreed national
1216
Siegert, M. et al. Safeguarding from dangerous polar geoengineering. Non peer-reviewed submission
to Frontiers in Science, 24 October 2024
52
jurisdiction. Whilst the Council’s work has covered an extremely wide range of issues
1217
connected to environmental, ecosystem, and human change in the Arcticassessing evidence
1218
and producing guidelines and best practicesit has chosen not to look specifically at
1219
geoengineering.
1220
Under the auspices of the Arctic Council the eight Arctic states have negotiated legally
1221
binding international agreements on: maritime search and rescue; marine oil pollution
1222
prevention and response; and Arctic science cooperation. These are implemented by the
1223
states within their national jurisdictions, not by mechanisms of the Council. Such agreements
1224
may have relevance to proposals for geoengineering activities in the Arctic, including their
1225
banning within the region.
1226
While the Arctic Council might have relatively weak oversight for the international waters
1227
where, for example, any proposed silicate spheres could be located, such efforts almost
1228
certainly would require support activities in national (or asserted national) waters. Objects
1229
that drift from international waters into the territorial waters of a member state (Landriault et
1230
al. 2020) come under that state’s jurisdiction. Any decision for the Arctic Council to address
1231
geoengineering would require both the championing by an incoming Chairship (e.g., the
1232
Kingdom of Denmark in 202527 or Sweden in 202729) and the consensus of all eight
1233
Arctic states during the priority-setting process ahead of each 2-year rotating Chairship.
1234
On more academic fronts, the International Arctic Science Committee (IASC) is leading a
1235
cross-over project that will produce a perspective paper (co-written by Rights Holders and
1236
scientists), following a workshop held in 2024 (https://iasc.info/our-work/working-
1237
groups/cross-cutting-activities/cross-cutting-funded-projects/1129-geoengineering-to-save-the-
1238
arctic-assessing-potential-efficacy-impacts-and-ethical-considerations-across-rightholders-
1239
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to Frontiers in Science, 24 October 2024
53
stakeholders-and-scientific-disciplines), while a small team hosted by the University of the
1240
Arctic another non-state Observers to the Arctic Councilis also assessing the implications
1241
of Arctic geoengineering.
1242
As many parties view the Arctic as an opportunity for economic growth and resource
1243
extraction, and as a zone of geopolitical tension, there is little prospect of long-term
1244
multilateral and low-tension collaboration on geoengineering at present (Kornbech et al.,
1245
2024). While governance responsibility predominantly lies with the individual Arctic
1246
Statesindividually or collectivelythe effects and impacts of geoengineering cannot be
1247
guaranteed to come from or stay within such territorial boundaries.
1248
Finally, it is pertinent to ask: why would a nation such as Greenland embrace a
1249
geoengineering solution to sea level rise, for example? Sea level is not increasing there
1250
rather, the loss of ice sheet mass is causing gravity-induced sea level lowering (Kurtze 2022).
1251
Moreover, the problem of sea level rise elsewhere has not been caused by Greenland and its
1252
local ecosystems would be at risk from geoengineering.
1253
Part 4: Protecting the polar regions without
1254
geoengineering
1255
We offer an alternative approach to protect the polar regions that does not rely on climate
1256
intervention or geoengineering. We do not propose these as isolated solutions or quick-fix
1257
interventions, but rather as components of a transformation of humanity’s relation to our
1258
planet, what has been called climate-resilient development. This transformation comprises
1259
shifts in major systems, such as energy systems, land use systems, food systems, and more,
1260
which can best be addressed jointly (Reckien et al., 2023). We focus on two components
1261
particularly relevant to polar regions.
1262
Siegert, M. et al. Safeguarding from dangerous polar geoengineering. Non peer-reviewed submission
to Frontiers in Science, 24 October 2024
54
Decarbonization
1263
Rapid decarbonization to net zero emissions by mid-century, and into negative emissions”
1264
thereafter will lead to a rapid and permanent climate response (the so-called Zero CO2
1265
Emissions Commitment” or ZEC) (Jones et al., 2019). This decarbonization will require
1266
significant changes in energy, land use, and food systems. The global warming climate
1267
system is likely to stabilize (i.e., global surface temperatures cease increasing) within 20
1268
years of net zero CO2 (Palazzo Corner et al., 2023). Uncertainty involves further warming or
1269
cooling at about 15% of the temperature at net-zero (Dvorak et al., 2022). This assessment
1270
presents good news for the Polar regions across various systems and realms. Not all changes
1271
can be stopped, but their rates of change would be comprehensively reduced if and when net
1272
zero emissions are reached.
1273
Two investigations underline the environmental benefits of net-zero CO2 and climate
1274
stabilization. Rintoul et al. (2018) “hindcast” two scenarios from the perspective of 2070: one
1275
where emissions are unabated and a second where ambitious decarbonization led to net-zero
1276
emissions. In the latter scenario, global temperature was stabilized at 0.9°C above pre-
1277
industrial levels, as opposed to 2.6°C in the former (similarly for Antarctic air temperature).
1278
These scenarios were matched by effective governance of Antarctica and the Southern Ocean
1279
under ambitious decarbonization, as opposed to ineffective policy. The relative benefits of
1280
decarbonization, based on literature and expert opinion, were significant in all cases (Rintoul
1281
et al., 2018). The Antarctic contribution to sea level rise by 2070 was limited to 6 cm, as
1282
opposed to 27 cm under high emissions [see also (Jourdain et al., 2024)]. The rise in Southern
1283
Ocean temperature was limited to 0.7°C as opposed to 1.9°C. Sea ice loss was restricted to
1284
12% of present levels compared with 43%. Ice shelf volume was reduced by only 8%
1285
compared with 23%. In terms of ocean acidification, decarbonization leads to saturation of
1286
Siegert, M. et al. Safeguarding from dangerous polar geoengineering. Non peer-reviewed submission
to Frontiers in Science, 24 October 2024
55
carbon but continued fossil fuel burning and deforestationleading to waters that are
1287
corrosive to aragonite shells of pteropods. Biological invasions were restricted to 2-fold those
1288
of today, versus 10-fold. Ecosystem failure may occur under both scenarios, but under
1289
unabated fossil fuel burning, penguins, krill and salps would all be affected adversely. Under
1290
enhanced policy, far fewer people would be present in the region, with an accompanying
1291
reduction in marine resource extraction. Rintoul et al.’s (2018) simple vision for Antarctica is
1292
appealing, as it explains how every Polar system can be helped by decarbonization, and
1293
certainly to the level where direct intervention (or geoengineering) would be unnecessary.
1294
A similar assessment for the Antarctic Peninsula explained the environmental consequences
1295
of restricting global warming to 1.5°C relative to pre-industrial levels (Siegert et al. 2019).
1296
Such an outcome, under rapid deep decarbonization to net-zero CO2 globally by mid-century,
1297
will benefit all realms of this environment. This study compared the present situation (1.2°C
1298
in 2019) and that at 1.5°C, revealing the magnitude of the best case” changes. For example,
1299
in a 1.5°C scenario the number of days per year on which surface air temperatures exceed
1300
0°C would increase from 2580 to 35130. While the resulting melting may lead to ponding
1301
of water on floating ice shelves, dramatic loss of ice shelves is not expected. Sea ice would be
1302
more limited, but it would remain around the Peninsula, especially in the South. The sea ice
1303
and krill-dependent food web would thus migrate to southwards, leaving the northern
1304
Peninsula with an increase in fur seals, elephant seals, and gentoo penguins.
1305
While such changes are unwelcome, being an indirect but obvious consequence of fossil fuel
1306
burning, they alone would not necessitate an artificial geoengineering intervention at the
1307
scales being proposed, and none of the interventions would address such changes. Further
1308
warming would likely bring an increase in extreme events”, such as atmospheric and marine
1309
heatwaves (Siegert et al., 2023), and continued sharp reductions in sea ice. Yet, while much
1310
Siegert, M. et al. Safeguarding from dangerous polar geoengineering. Non peer-reviewed submission
to Frontiers in Science, 24 October 2024
56
of the natural polar environment would be altered or displaced, it would still be present in a
1311
manner deserving environmental protection (e.g., with respect to its marine biodiversity).
1312
Indeed, under the ZEC scenario, once net-zero has been achieved negative emissions would
1313
rapidly (within ~20 years) act to cool the planet, potentially reversing changes under 1.5°C
1314
warming. This scenario is already technically, financially, and politically possible (IPCC,
1315
2022; Mann, 2023) and it represents our best means to protect the Antarctic environment,
1316
with major co-benefits for human health and planetary habitability.
1317
The Arctic situation may be profoundly different. Continued global warming will result in
1318
enhanced regional warming here, leading to further sea-ice loss, permafrost thawing, and
1319
ecosystem damage, all of which will adversely affect the livelihoods, cultures and living
1320
environments of Indigenous Peoples. Global climate stabilization offers the best chance to
1321
protect the Arctic, but significant further change may be already unavoidable.
1322
Protected areas across the polar regions
1323
Well-managed protected areas, especially those that are highly protected the equivalent of
1324
International Union for Conservation of Nature (IUCN) Category I or II (Dudley 2008)
1325
significantly benefit biodiversity and ecosystem services. These benefits include higher
1326
species richness, abundance, and functional diversity within protected areas and ecological
1327
spillover benefitting biodiversity outside the protected area. Substantial evidence exists for
1328
these effects on land (Coetzee et al. 2014; Gray et al. 2016; Barnes et al. 2023; Brodie et al.
1329
2023). Marine protected areas have similar benefits: evidence-based syntheses and specific
1330
studies demonstrate higher biomass/abundances and functional diversity of species within
1331
strictly protected areas (compared with outside), along with ecological and fishery spillover
1332
(i.e., outward emigration of individuals that benefits a fishery) (Soykan & Lewison 2015; Gill
1333
et al. 2017; Cheng et al. 2019; Medoff et al. 2022).
1334
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57
Although climate change threatens their efficacy (Bruno et al., 2018; Asamoah et al., 2020),
1335
protected areas provide significant benefits to biodiversity under climate change in both
1336
terrestrial and marine systems (Jacquemont et al., 2022; Xu et al., 2022; Mi et al., 2023).
1337
Moreover, protected areas can mitigate the effects of climate change itself, by ensuring the
1338
maintenance of ecosystem services such as carbon sequestration (Duncanson et al. 2023), and
1339
enhance ecosystem resilience by minimizing other impacts (Constable et al., 2023).
1340
Consequently, protected areas remain a central component of the mitigation response to
1341
climate change impacts on biodiversity. Key priorities include various strategies to grow,
1342
connect, and manage the network of protected areas, and to improve their overall individual
1343
efficacy (Dinerstein et al., 2020; Elsen et al., 2020; Pinsky et al., 2020; Rainus et al., 2023).
1344
The climate change mitigation benefits of protected areas have also been realized for the
1345
Antarctic and Arctic (Hughes et al., 2021; Hindell et al., 2020; Vincent, 2020; Brooks et al.,
1346
2022; James et al., 2024), acknowledging the substantial differences between the two regions
1347
(Wenzel et al., 2016; Chown & Brooks, 2019; Buschman, 2022). Although protected areas
1348
will not entirely mitigate impacts such as ocean acidification (Nissen et al., 2024), they can
1349
play an important role. Moreover, GHG emissions reduction will reduce impacts such as
1350
ocean acidification, whereas geoengineering activities that fail to reduce atmospheric CO2
1351
concentrations will not, leaving biodiversity and ecosystem services exposed to a growing
1352
threat.
1353
To be effective in a climate change impact mitigation framework, polar protected areas will
1354
need broader coverage of biodiversity features and areas, greater connectivity, and more
1355
flexibility in their boundaries in response to changing ecological circumstances. Their
1356
greatest challenge is ultimately political. For example, the ATCPs and the Members of the
1357
Commission on the Conservation of Antarctic Marine Living Resources (CCAMLR) have
1358
Siegert, M. et al. Safeguarding from dangerous polar geoengineering. Non peer-reviewed submission
to Frontiers in Science, 24 October 2024
58
been slow in designating protected areas (Chown et al,. 2017) and there are growing
1359
difficulties in protected area discussions in both of these Antarctic Treaty system bodies
1360
(Brooks et al,. 2016). Yet, previous difficulties in international environmental agreements
1361
have been overcome to great success, such as the 1987 Montreal Protocol to phase out the
1362
production of substances responsible for ozone depletion and agreement under CCAMLR to
1363
designate the Ross Sea region as a Marine Protected Area in 2016.
1364
1365
Siegert, M. et al. Safeguarding from dangerous polar geoengineering. Non peer-reviewed submission
to Frontiers in Science, 24 October 2024
59
Conclusion
1366
Polar geoengineering has gained considerable media and public attention in recent months,
1367
with computer model-driven proposals (and some rudimentary field studies) to increase
1368
Arctic sea ice, enhance atmospheric reflectivity, halt ocean warmth to the grounded ice sheet,
1369
and slow the flow of grounded ice to the ocean. We have delineated many challenges, hurdles
1370
and problems facing five geoengineering approaches, which we can categorize in the
1371
following six ways (Table 1).
1372
First is the scientific robustness of the proposed interventions. All five cases are built on an
1373
idea that natural systems can be forcibly adapted (or even controlled) by intervention.
1374
However, we find significant oversights in the methods being developed that cast doubt on
1375
whether successful implementation would deliver the intended results. An example is the
1376
proposed drilling into ice stream beds to pump out basal water and reduce ice flow speeds. If
1377
water is removed from the beds, water will likely either replace it from other sources (e.g.,
1378
groundwater) or be routed elsewhere, necessitating the continuous drilling of additional
1379
holes. We know remarkably little about the subglacial system in Antarctica and certainly not
1380
enough to effectively plan such work.
1381
The second is the direct environmental damage that these interventions will cause. In many
1382
cases, the geoengineering intervention proposed uses a direct pollutant, such as in the case of
1383
atmospheric aerosol injection with SO2, which would lead to acid rain and increased ocean
1384
acidity, among other negative impacts.
1385
The third is their cost. All of the proposed ideas would require funding at a scale of many
1386
billions of US dollars, presently unavailable by either national or international arrangements.
1387
It is unknown where the funds needed to pursue geoengineering interventions would come
1388
Siegert, M. et al. Safeguarding from dangerous polar geoengineering. Non peer-reviewed submission
to Frontiers in Science, 24 October 2024
60
from, but they would dwarf present scientific budgets. If these billions were made available,
1389
they would be far more effectively spent on efforts to rapidly decarbonize.
1390
The fourth is the governance arrangements to provide legal oversight and environmental
1391
protection for these interventions. None of the geoengineering ideas are supported through
1392
robust governance arrangements. In the case of Antarctica, such arrangements are offered
1393
through the CEP and ATCM, but there has been no engagement with these bodies regarding
1394
geoengineering. Formal comprehensive environmental evaluations, discussed and debated at
1395
the CEP and ATCM, are needed prior to any work commencing. Further, any expansion of
1396
governance arrangements hinges on the consent of most or all affected states. Current
1397
research on the interaction between international politics and geoengineering indicates that
1398
the latter will either prove politically infeasible; it could even contribute to rising geopolitical
1399
tension if deployed unilaterally. Additionally, the international community does seem to be
1400
able to rapidly converge on reducing carbon emissions, which is doable and undisputedly
1401
beneficial. How likely is it then to reach a consensus on potential solutions with far greater
1402
uncertainties and possible counter-productive outcomes?
1403
The fifth is the scale and timing of these interventions. Limiting the escalation of severe
1404
climate-related risks demands we cut demands we cut GHG emissions to net zero by mid-
1405
century. Geoengineering interventions cannot be implemented in such a timeframe, and
1406
hence offer no solution to the climate problem. An example is sea-ice thickening, proposed as
1407
a means to halt Arctic sea ice decline within 60 years. The vast scale of the Arctic (at ~10
1408
million km2) renders this idea impossible.
1409
The sixth relates to vested interests behind these interventions. Geoengineering proposals
1410
give a false hope that the effects of global warming can be avoided by means other than
1411
Siegert, M. et al. Safeguarding from dangerous polar geoengineering. Non peer-reviewed submission
to Frontiers in Science, 24 October 2024
61
rapid, deep cuts to GHG emissions. To some with vested interests in the fossil-fuel economy,
1412
however, such proposals are appealing, as they offer them a way to justify continued
1413
emissions under a pretense of climate action.
1414
The Polar geoengineering interventions discussed here are largely a fantastical science
1415
fiction. They will play no role in mitigating global warming. Decarbonizing to net zero is the
1416
only feasible approach to the problem, and this requires our complete attention without
1417
unnecessary distraction or diversion.
1418
1419
Siegert, M. et al. Safeguarding from dangerous polar geoengineering. Non peer-reviewed submission
to Frontiers in Science, 24 October 2024
62
FIGURES
1420
1421
1422
1423
Figure 1. Stratospheric aerosol injection in polar environments. Stratospheric aerosol
1424
injection in polar regions will not be possible year-round, due to winter darkness, and may
1425
have unwanted and unintended consequences to regional climates, including across territorial
1426
boundaries.
1427
1428
Siegert, M. et al. Safeguarding from dangerous polar geoengineering. Non peer-reviewed submission
to Frontiers in Science, 24 October 2024
63
1429
1430
Figure 2. Sea curtains in front of ice sheet grounding zones. Installing structures many 10s of
1431
km long is a massive technological challenge that will require sustained operations across
1432
some of the roughest seas in the world to ice-covered locations where even modern ice-
1433
strengthened vessels cannot always reach. Such curtains will likely have unwanted
1434
consequences for ocean circulation and ecosystems.
1435
1436
1437
Siegert, M. et al. Safeguarding from dangerous polar geoengineering. Non peer-reviewed submission
to Frontiers in Science, 24 October 2024
64
1438
1439
Figure 3. Glass beads as a means to reflect sunlight off polar surfaces. Changing albedo by
1440
adding particles to the ocean may actually decrease albedo, will require deliberate pollution
1441
of the ecosystems, and is unlikely to be logistically possible to operate at the scale necessary
1442
to make a significant difference.
1443
1444
1445
Siegert, M. et al. Safeguarding from dangerous polar geoengineering. Non peer-reviewed submission
to Frontiers in Science, 24 October 2024
65
1446
1447
Figure 4. Arctic sea ice thickening to counter loss of ice. Techniques to thicken sea ice will
1448
require very large numbers of individual devices to be deployed onto winter sea ice, and is
1449
unlikely to be logistically possible to operate at the scale necessary to make a significant
1450
difference.
1451
1452
1453
Siegert, M. et al. Safeguarding from dangerous polar geoengineering. Non peer-reviewed submission
to Frontiers in Science, 24 October 2024
66
1454
1455
Figure 5. Subglacial water removal in ice sheets to slow ice flow to the ocean. Drilling to the
1456
bed of thick flowing ice is highly challenging technologically and has never been undertaken
1457
for the sustained period required to maintain drainage of subglacial water. Subglacial
1458
drainage networks are currently pristine and not well mapped so introduction of drillholes
1459
into the network will likely be highly challenging to achieve reliably and could cause
1460
contamination both below and above the ice.
1461
1462
1463
Siegert, M. et al. Safeguarding from dangerous polar geoengineering. Non peer-reviewed submission
to Frontiers in Science, 24 October 2024
67
1464
1465
Figure 6. Ocean fertilization to ‘draw down’ atmospheric CO2. Negative impacts will
1466
likely include changes to food chain structure, and that fertilisation may create impacts on
1467
fisheries elsewhere including across territorial boundaries.
1468
1469
1470
1471
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Siegert, M. et al. Safeguarding from dangerous polar geoengineering. Non peer-reviewed submission
to Frontiers in Science, 24 October 2024
68
Figure 7. Arctic governance and maritime jurisdiction (International Boundaries Research
1473
Unit, Durham University, https://www.durham.ac.uk/research/institutes-and-
1474
centres/ibru-borders-research/maps-and-publications/maps/arctic-maps-series/ ).
1475
1476
1477
Siegert, M. et al. Safeguarding from dangerous polar geoengineering. Non peer-reviewed submission
to Frontiers in Science, 24 October 2024
69
Funding
1478
SLC, ANM, and FSM were supported under the Australian Research Council (ARC) Special
1479
Research Initiative (SRI) Securing Antarctica’s Environmental Future (SR200100005). JS
1480
was supported by Canada 150 Research Chairs program, C150 grant number 50296. AMG is
1481
a member of the Carrera del Investigador Cientıfico, CONICET and was partially supported
1482
by the Argentinean grants PICT 2019-02754 (FONCyT-
1483
ANPCyT) and UBACyT-20020190100247BA (UBA). RH received funding from the
1484
Norwegian Research Council Project 324131, ERC-2022-ADG grant no. 01096057
1485
GLACMASS and National Aeronautics & Space Administration (NASA) grant no.
1486
80NSSC20K1296. TRN New Zealand was funded by Antarctic Science Platform Contract ‐
1487
ANTA1801 FSM acknowledges funding from the Australian Research Council (ARC)
1488
Discovery Early Career Research Award (DE210101433) and the ARC Special Research
1489
Initiative (SRI) Securing Antarctica’s Environmental Future (SR200100005). RM was
1490
supported through the Horizon Europe funded OCEAN:ICE project, co-funded by the
1491
European Union programme for research and innovation under Grant Agreement 101060452
1492
and U.K. Research and Innovation (UKRI). VMD received a Synergy Grant from the
1493
European Research Countil (ERC) under the European Union's Horizon 2020 research and
1494
innovation programme (AWACA : Atmospheric WAter Cycle over Antarctica: Past, Present
1495
and Future, grant agreement No 951596).
1496
1497
Conflicts of interest
1498
JRu is employed by the Polar Regions Department of the UK Foreign Commonwealth and
1499
Development Office. The FCDO was not involved in the study design, collection, analysis,
1500
interpretation of data, the writing of this article or the decision to submit it for publication.
1501
SLC declares a perceived conflict of interest as a Past President and current Honorary Life
1502
Member of SCAR. VMD declares a perceived conflict of interest as a member of the French
1503
Climate Change Committee. KRH declares a perceived conflict of interest as Chair of
1504
Antarctic Science Ltd, and Honorary Secretary of the Challenger Society for Marine Science.
1505
HB declares a perceived conflict of interest as President of the International Arctic Science
1506
Committee (2022-26).
1507
1508
The authors declare that the research was conducted in the absence of financial relationships
1509
that could be construed as a potential conflict of interest.
1510
1511
1512
Siegert, M. et al. Safeguarding from dangerous polar geoengineering. Non peer-reviewed submission
to Frontiers in Science, 24 October 2024
70
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