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.2025.1527393

Viewpoint: 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