Reviewer 2 does geoengineering

Roderick Hyde discusses his recent paper on using high-altitude hoses for solar geoengineering. While most proposals focus on aircraft delivery, Hyde revisits an older but largely dismissed concept. He describes suspending a 20 km hose by balloons to continuously pump sulfur-bearing fluids into the stratosphere, and argues that advances in modern materials and engineering may overcome past barriers.The conversation covers the technical hurdles such as wind dynamics, hose stability, extreme pressures, and material stress, as well as design variations for pumping H₂S as liquid or gas. Hyde explains how streamlining, intermediate pumps, and lightweight aero-shrouds could make the system viable.The discussion also highlights the potential advantages of this approach, including affordability, continuous operation, and scalability. While a single hose could not halt global warming, Hyde suggests that a distributed network of ~20 installations could offset warming from CO₂, offering a near-term, low-cost option to buy time while longer-term climate solutions take effect.Paper: Hyde, R. A. (2025). A Planetary Cooling Hose. arXiv preprint arXiv:2509.07985. https://doi.org/10.48550/arXiv.2509.07985

John Moore joins the podcast to discuss his recent Viewpoint article responding to Siegert et al.'s paper on polar geoengineering. While Siegert and colleagues argue that proposed interventions are infeasible, environmentally dangerous, and a distraction from decarbonization, Moore contrasts the prevailing “consequences-based paradigm” (raising alarms to spur actions) with a new “compassionate harm reduction paradigm” that calls for exploring all potential tools including geoengineering rather than rejecting them outright, so humanity has options to reduce harm if warming overshoots.The conversation covers the risks of melting glaciers and sea-level rise, and specific concepts such as stratospheric aerosol injection. Moore also stresses the importance of Arctic Indigenous leadership, pointing to Saami Council-led review processes as a model for rights-based and knowledge co-produced governance.The discussion also highlights the sharp divides in the climate community over polar geoengineering and raises fundamental questions about the responsibilities of scientists in an era of accelerating climate risk.Papers:Lead Article: Siegert, M., Sevestre, H., Bentley, M. J., Brigham-Grette, J., Burgess, H., Buzzard, S., ... & Truffer, M. (2025). Safeguarding the polar regions from dangerous geoengineering: a critical assessment of proposed concepts and future prospects. Frontiers in Science, 3, 1527393. https://doi.org/10.3389/fsci.2025.1527393Viewpoint: Moore, J. C., Macias-Fauria, M., & Wolovick, M. (2025). A new paradigm from the Arctic. Frontiers in Science, 3, 1657323. https://doi.org/10.3389/fsci.2025.1657323

Jacob Bronsther & Yangyang Xu discuss their recent paper on the socioeconomic costs of Solar Radiation Modification. While SRM's direct technical costs appear modest (~$18B/°C cooling), the authors argue that its broader costs are far greater. They estimate that Stratospheric Aerosol Injection could generate between $0 and $809 billion annually in side-effect harms, with potentially higher figures for Marine Cloud Brightening. The conversation also explores SRM's reliance on unprecedented global cooperation, the political risks of weather accountability, and the dangers of termination, which could impose major financial costs. They contrast these challenges with large-scale Carbon Dioxide Removal, noting that although CDR entails immense technical expenses, it avoids some of SRM's political and termination risks. The discussion highlights the complexity of weighing the full spectrum of costs and benefits when evaluating climate-engineering strategies.Paper: Bronsther, J., & Xu, Y. (2025). The social costs of solar radiation management. npj Climate Action, 4(1), 69. https://doi.org/10.1038/s44168-025-00273-y

Brian Soden discusses his recent study on injecting absorptive aerosols, such as black carbon, into the upper stratosphere to weaken the CO₂ greenhouse effect. The conversation addresses the radiative physics underpinning this concept, its potential cooling efficiency relative to conventional scattering aerosols, and associated environmental risks. While model results indicate the method could theoretically be effective, Soden remains sceptical about its practical viability.Paper: He, H., Soden, B. J., Vecchi, G. A., & Yang, W. (2025). Stratospheric aerosol injection can weaken the carbon dioxide greenhouse effect. Communications earth & environment, 6(1), 485. https://doi.org/10.1038/s43247-025-02466-z

Daniel Bodansky discusses his recent article on the drawbacks of a global moratorium on solar radiation management deployment.The conversation critiques whether a moratorium is feasible or effective, arguing it could hinder critical research, be difficult to enforce, and unintentionally become a proxy for a permanent ban. Instead, the discussion highlights the need for more research and stronger governance frameworks to better understand and responsibly manage geoengineering.Article: Biniaz, S., & Bodansky, D. (2025, May 13). Why a global “moratorium” on solar radiation management deployment should get a chilly reception. Just Security. https://www.justsecurity.org/113295/moratorium-srm-deployment-chilly-reception/

Diego Villanueva discusses his paper on mixed-phase regime cloud thinning (MCT). This geoengineering approach involves using ice-nucleating particles to reduce the heat-trapping effects of polar clouds.Using climate and cloud-resolving models, the study finds MCT could offset up to 25% of polar ocean warming from CO₂ doubling and increase sea ice by 8% in the Arctic and 14% in Antarctica. In the podcast, we discuss the science behind this method, its potential benefits, limitations, and broader implications. Paper: Villanueva, D., Possner, A., Neubauer, D., Gasparini, B., Lohmann, U., & Tesche, M. (2022). Mixed-phase regime cloud thinning could help restore sea ice. Environmental Research Letters, 17(11), 114057. https://doi.org/10.1088/1748-9326/aca16d

@geoengineering1 interviews Fabien Bardinet, co-founder of CIRCEO [linkedin.com/company/circeocc], a new company focused on marine-based carbon capture. CIRCEO is developing semi-autonomous sailing drones that generate electricity from wind to power onboard electrochemical systems that remove carbon from seawater. The company is currently hiring a CDR Electrochemist Co-founder: linkedin.com/jobs/view/4205443622.

Tyler Felgenhauer and @geoengineering1 discuss risk-risk trade-offs. Paper: Tyler Felgenhauer, Govindasamy Bala, Mark E Borsuk, Inés Camilloni, Jonathan B Wiener, Jianhua Xu, Practical paths to risk-risk analysis of solar radiation modification, Oxford Open Climate Change, Volume 5, Issue 1, 2025, kgaf012, https://doi.org/10.1093/oxfclm/kgaf012 Guest info: Tyler Felgenhauer, PhD; Senior Research Scientist; Research Director; The Duke Center on Risk; Duke University link for the RFF workshop. https://www.rff.org/events/conferences/2025-rff-and-harvard-srm-social-science-research-workshop-governance-in-a-fractured-world/

Jeffrey Nielsen and @geoengineering1 discuss how the strategic relationship between the US and China will interact with SRM. Paper: Jeffrey Nielsen, The big green button: stratospheric aerosol injection as a geopolitical dilemma during strategic competition between the United States and China, and implications for expanding aerosol injection near-term research, Oxford Open Climate Change, Volume 5, Issue 1, 2025, kgaf009, https://doi.org/10.1093/oxfclm/kgaf009

Enrico Prats Salvado discusses the benefits and challenges of using the sun's heat for DAC desorb. Paper Prats-Salvado, E., Monnerie, N. & Sattler, C. Powering Direct Air Capture: Overview of Existing Concepts and the Overlooked Role of Concentrated Solar Thermal Technologies. Curr Sustainable Renewable Energy Rep 12, 8 (2025). https://doi.org/10.1007/s40518-025-00255-y

Claire Nelson, founder of Cella mineral storage, explains how underground injections of water alternating with CO2 might aid mineralsation. Paper: Water-alternating-gas injections for optimized mineral carbon storage in basalt https://www.sciencedirect.com/science/article/abs/pii/S1750583624002263 Poppin' Fresh, more widely known as the Pillsbury Doughboy, is also, rather randomly, discussed https://en.wikipedia.org/wiki/Pillsbury_Doughboy

Paul Reginato explains how biotech can be applied to CDR. Paper: Biotechnology in direct air capture, enhanced weathering, and methane removal: emerging opportunities and gaps. https://doi.org/10.3389/fclim.2024.1440833

Can we just throw carbon in the sea - like a mobile phone with incriminating evidence on? Brenna Boehman and Erica Dorr from Sinkco and Riverse come on to discuss their Marine Carbon Burial Methodology with @geoengineering1

Martin Freimüller introduces Octavia Carbon, explaining how they're making DAC work in Kenya's Great Rift Valley. Hosted by @geoengineering1

Smoggies Humbul (Suleman), Omar, and Faizan discuss their research detailed in this press release https://www.tees.ac.uk/sections/news/pressreleases_story.cfm?story_id=8651 It's a fancy form of hydrochar, pimped by chemical manipulation.

Can COVID policy be compared to geoengineering policy? Hosea Olayiwola Patrick discusses "Reflections on COVID-19 Adaptive Responses as a Template for Climate Intervention-Geoengineering Engagement" with @geoengineering1 https://www.preprints.org/manuscript/202501.1715/v1

Would a whiter sky be noticeable, under SAI geoengineering? Ansar Lemon discusses what humans and animals could see. Paper: Under a not so white sky: visual impacts of stratospheric aerosol injection - Ansar Lemon et al 2025 Environ. Res. Lett. 20 024060 DOI 10.1088/1748-9326/ada2ae A link to his music is here https://youtu.be/EpQ7rnQTDDU?si=ubVwa7p45uZ9mw_q

Are you allowed to throw alkaline minerals into the sea? Ashwin Murthy explains how to do Ocean Alkalinity Enhancement, without ending up in jail. Ashwin Murthy, Korey Silverman-Roati & Romany M. Webb, State Authority to Regulate Ocean Alkalinity Enhancement, Sabin Center for Climate Change Law, Columbia Law School, December 2024 (2024). Available at: https://scholarship.law.columbia.edu/sabin_climate_change/237

David McEvoy discusses expert opinions on SRM. What do they think, and how do we know? The strategic and governance implications of solar radiation modification: perspectives from delegates of international climate negotiations Todd L Cherry et al 2025 Environ. Res. Lett. 20 014053 DOI 10.1088/1748-9326/ad9d62

Thomas Hahn discusses his paper on historical emissions and responsibility for them. Hahn, T., Morfeldt, J., Höglund, R. et al. Estimating countries' additional carbon accountability for closing the mitigation gap based on past and future emissions. Nat Commun 15, 9707 (2024). https://doi.org/10.1038/s41467-024-54039-x

Is it too late for SRM to save South American glaciers? Alfonso Fernandez discusses his paper on the impact of SRM on the glaciers of the Andes. Fernández, A., Manquehual-Cheuque, F. & Somos-Valenzuela, M. Impact of Solar Radiation Management on Andean glacier-wide surface mass balance. npj Clim Atmos Sci 7, 257 (2024). https://doi.org/10.1038/s41612-024-00807-x

AGU Ethical Framework Principles for SRM research Tyler Felgenhauer, Duke University https://news.agu.org/press-release/ethical-framework-climate-intervention-research/

Juliet Kirby explains how gentoo.earth uses AI to match carbon removal buyers and sellers. Despite @geoengineering1 trying his best to wind her up for lulz, she doesn't break character. NB this isn't paid promotion; gentoo hasn't sponsored this episode. No penguins (gentoo or otherwise) were harmed in the making of this episode.

Ron Baiman discusses his expansive paper summarising all known SRM and other direct climate cooling techniques https://academic.oup.com/oocc/article/4/1/kgae014/7731760 Plus his letter to the International Maritime Organization https://academic.oup.com/oocc/article/4/1/kgae008/7706251

Benjamin Hofbauer discusses 3 papers from his PhD, on the ethics of Solar geoengineering. Hofbauer, B. (2023). Systemic risks and solar climate engineering research. Integrating technology ethics into the governance of systemic risks. Journal of Risk Research, 26(12), 1383–1395. https://doi.org/10.1080/13669877.2023.2288010 Hofbauer, B. (2023). Normative Uncertainty in Solar Climate Engineering Research Governance. Ethics, Policy & Environment, 1–20. https://doi.org/10.1080/21550085.2023.2216148 Benjamin Hofbauer. Techno-moral change through solar geoengineering: How geoengineering challenges sustainability. Prometheus. 2022. Vol. 38(1). DOI: 10.13169/prometheus.38.1.0082

Charly Moras explains how grain size affects reaction kinetics in ocean alkalinity enhancement. Paper:- Effects of grain size and seawater salinity on magnesium hydroxide dissolution and secondary calcium carbonate precipitation kinetics: implications for ocean alkalinity enhancement https://egusphere.copernicus.org/preprints/2024/egusphere-2024-645/

In this spooky Halloween episode, @geoengineering1 and Ken Buesseler investigate alleged sightings of Ocean Iron Fertilisation - which is rumoured to have risen from its unquiet grave. Paper: Next steps for assessing ocean iron fertilization for marine carbon dioxide removal. https://www.frontiersin.org/journals/climate/articles/10.3389/fclim.2024.1430957

Kai Jeggle explains to @geoengineering1 how off-target effects of cirrus cloud thinning mean that it can never be used effectively. Paper; Jeggle, K., Neubauer, D., Binder, H., and Lohmann, U.: Cirrus formation regimes – Data driven identification and quantification of mineral dust effect, EGUsphere [preprint], https://doi.org/10.5194/egusphere-2024-2559, 2024.

Got wood? Looking for somewhere to stick it? Ning Zeng can solve your problem! @geoengineering1 learns all about how to do it properly. Zeng, N., Hausmann, H. Wood Vault: remove atmospheric CO2 with trees, store wood for carbon sequestration for now and as biomass, bioenergy and carbon reserve for the future. Carbon Balance Manage 17, 2 (2022). https://doi.org/10.1186/s13021-022-00202-0

Do not adjust your set; the fidelity of this recording is particularly poor. Luna Geerts and @geoengineering1 discuss coastal enhanced weathering of olivine. The paper is/was open to review, here. https://egusphere.copernicus.org/preprints/2024/egusphere-2024-1824/

What would a mid-century polar geoengineering program look like? What airports and aircraft would be needed - and at what cost? Wake Smith answers all these questions.

How does SAI affect extra-tropical cyclones? Michelle Simões Reboita explains during a tight interview slot, but @geoengineering1 fails to understand (it takes him at least an hour to understand ANYTHING). With fluency approaching that of the Trump Biden debate, he stumbles through the episode, only occasionally realising where he is and what he's doing. Can anyone do a better job? Please tweet us, if you can... Please? Paper: Response of the Southern Hemisphere extratropical cyclone climatology to climate intervention with stratospheric aerosol injection. https://iopscience.iop.org/article/10.1088/2752-5295/ad519e/meta

What control can we exercise over MCB? Should it be confined to small, climatically sensitive areas - or expanded at great cost, to minimise inter-regional disparities? Walker Lee discusses the issue in depth. (See PT 2 for a discussion on disability and diversity). Jack's first paper: https://doi.org/10.22541/essoar.171322700.02512514/v1 Jack's second paper: https://doi.org/10.22541/essoar.171201044.45268441/v1

We've extracted this very interesting discussion from Walker Lee's new episode, because a) it's a standalone section and b) the main episode was already quite long. Here, Walker Lee describes in vibrant and very personal terms his own academic journey, touching on important issues of ideological diversity and disability discrimination. It's not trad R2, but we liked it. Enjoy!

William Morrissey explains how SAI could lead to conflict and counter-geoengineering. @geoengineering1 isn't convinced it will all end so badly. Avoiding atmospheric anarchy: Geoengineering as a source of interstate tension William Morrissey https://doi.org/10.1177/27538796231221597

Roll up! Roll up! Grab your buckets, and get ready to do a science! Bach is back (again) to discuss institutional collaboration and citizen science in OAE. Bach, L. T., Ferderer, A. J., LaRoche, J., and Schulz, K. G.: Technical note: Ocean Alkalinity Enhancement Pelagic Impact Intercomparison Project (OAEPIIP), EGUsphere [preprint], https://doi.org/10.5194/egusphere-2024-692, 2024 Identifying the Most (Cost-)Efficient Regions for CO2 Removal With Iron Fertilization in the Southern Ocean Lennart T. Bach, Veronica Tamsitt, Kimberlee Baldry, Jeffrey McGee, Emmanuel C. Laurenceau-Cornec, Robert F. Strzepek, Yinghuan Xie, Philip W. Boyd First published: 16 November 2023 https://doi.org/10.1029/2023GB007754

How do you establish and grow a DAC company? Anca Timofte has utilised a career leg-up from Climeworks to start her own DAC outfit, with some pretty fancy chemistry. @geoengineering1 gets the lowdown on how she did it - and what the future challenges are https://theholocene.co/

Is the supply of carbon removal fundamentally limited, and how should it be allocated? Comrade Allanah Paul from Bellona sends @geoengineering1 to the reeducation camps in an attempt to expunge his bourgeois thinking. report: https://www.negemproject.eu/wp-content/uploads/2023/11/D6.5_Who-should-use-NETPS.pdf

Gunter Flipkens explains why everyone is worried about heavy metals leaching from olivine coastal weathering experiments. Then he explains how he tests the exact toxicity to animals, plus how to reduce it. Thesis link https://www.researchgate.net/publication/379406915_Coastal_enhanced_olivine_weathering_for_climate_change_mitigation_investigating_the_CO2_sequestration_potential_and_ecotoxicological_risks

Moritz Günther tries valiantly to get @geoengineering1 to understand the atmospheric dynamics of SAI's impacts on the warm pool, but it's rather like watching him trying to train a baboon to use Photoshop - there's some engagement, and the occasional flash of comprehension before it all gets too much for him. Günther, M., Schmidt, H., Timmreck, C., and Toohey, M.: Why does stratospheric aerosol forcing strongly cool the warm pool?, EGUsphere [preprint], https://doi.org/10.5194/egusphere-2024-429, 2024.

Christian Claudel comes on to explore the issues around using drones to distribute MCB particles. These are made by anti-solvent precipitation (much like diluting Ricard spirit). Despite @geoengineering1 being AN ACTUAL AUTHOR on the paper he still finds plenty of opportunities for nitpicking. Paper: Marine-cloud brightening: an airborne concept Christian Claudel, Andrew John Lockley, Fabian Hoffmann and Younan Xia DOI 10.1088/2515-7620/ad2f71

Michael Fuhr gives @geoengineering1 news on what happens when you throw rocks in the sea (yawn). Then they go on a massive rant about how Gen Z academics don't know how to party anymore (yey!). But which one of them ended a conference locked in a laundry cage being rolled through a hotel foyer? Find out, inside. Paper https://doi.org/10.3389/fclim.2024.1338556 This article is part of the Research Topic Quantifying Carbon Removal by Negative Emissions Technologies Alkaline mineral addition to anoxic to hypoxic Baltic Sea sediments as a potentially efficient CO2-removal technique

What could be the eventual scale of the CDR market? What technologies will it use? And how do choices made today affect where it ends up? Robert Hoglund discusses with @geoengineering1 Some works discussed CDR.fyi annual report https://www.cdr.fyi/blog/2023-year-in-review Carbon removal is not a finite resource https://marginalcarbon.substack.com/p/carbon-removal-is-not-a-finite-resource Emergent methane mitigation and removal approaches: A review Ishita Mundra, Andrew Lockley https://doi.org/10.1016/j.aeaoa.2023.100223

Joshua Schwarz explains how dispersing ice nucleating particles in one tiny region of the tropical tropopause layer off Northern Australia can address around 1pc of global warming. He also discusses his involvement in the SABRE stratospheric flights. Paper: Considering intentional stratospheric dehydration for climate benefits DOI: 10.1126/sciadv.adk0593 Other papers discussed Pyrocumulonimbus affect average stratospheric aerosol composition J. M. KATICH DOI: 10.1126/science.add3101 Marine-cloud brightening: an airborne concept Christian Claudel, Andrew John Lockley, Fabian Hoffmann and Younan Xia DOI 10.1088/2515-7620/ad2f71

What is nature? Does it matter beyond its direct usefulness? Do animals only have rights if they're conscious? When did man become morally responsible for environmental degradation? When can and should we fiddle with the natural world? Elliott Woodhouse explains the differing views to @geoengineering1. A blog post is available, summarising his PhD https://www.sheffield.ac.uk/lc3m/blogs/phd-spotlight-elliott-woodhouses-ethics-climate-engineering

NPC vs IAM. Oliver Perkins explains why simple agent-based models (non playable characters, if you like) might outperform the integrated assessment models that have led to such outlandish predictions for CDR. Paper: Toward quantification of the feasible potential of land-based carbon dioxide removal https://doi.org/10.1016/j.oneear.2023.11.011

The highly prolific Chris Jones thoroughly intimidates the normally boisterous @geoengineering1, while discussing sorbents that can tolerate a wide range of climate conditions. Paper Sub-Ambient Temperature Direct Air Capture of CO2 using Amine-Impregnated MIL-101(Cr) Enables Ambient Temperature CO2 Recovery https://doi.org/10.1021/jacsau.1c00414 Here's some more links about Chris and the subjects discussed in this episode. DAC bibliometric analysis https://www.sciencedirect.com/science/article/pii/S2772826922000086 https://www.sciencedirect.com/science/article/pii/S277282692300010X DirACC Publication list (GT DAC Center) https://sites.gatech.edu/dac-center/publications/ Jones web page: https://jones.chbe.gatech.edu/dr-jones/ Jones Google Scholar page: https://scholar.google.com/citations?user=ltWKpYgAAAAJ&hl=en Jones Wikipedia page: https://en.wikipedia.org/wiki/Christopher_W._Jones

Gloria Reithmaier talks to @geoengineering1 about coastal blue carbon, work/life balance, and being a mum in academia. Paper: Reithmaier, G.M.S., Cabral, A., Akhand, A. et al. Carbonate chemistry and carbon sequestration driven by inorganic carbon outwelling from mangroves and saltmarshes. Nat Commun 14, 8196 (2023). https://doi.org/10.1038/s41467-023-44037-w

Celebrate Xmas day with Holly, discussing Solar geoengineering research in the global public interest: A proposal for how to do it https://www.sciencedirect.com/science/article/pii/S2590332223005481

How can you make a sunshade stay in place? How can you make it beam down solar power to Earth? @geoengineering1 finds out from Tharshan Maheswaran. Paper - International planetary sunshade concept with a function-integrated and scalable support structure based on coreless filament winding DOI 10.1088/1742-6596/2526/1/012113

Should the army be allowed to blow people up with a volcano? If your geothermal power plant triggers an eruption, is that just a risk of doing business? Should we fiddle with volcanoes to make them safer? Is even researching this opening a can of worms? Gideon Futurman interviews Michael Cassidy (giving @geoengineering1 a month long editing nightmare, but with results we hope you'll like). Paper: The Ethics of Volcano Geoengineering Michael Cassidy, Anders Sandberg, Lara Mani https://doi.org/10.1029/2023EF003714