SAI can weaken CO2 greenhouse effect - Soden

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