| SRM WEEKLY SUMMARY (10 - 16 FEBRUARY 2025) Subscribe to receive the monthly updates:
RESEARCH PAPERSSurprise, K., McLaren, D., Möller, I., Sapinski, J. P., Stabinsky, D., & Stephens, J. C. (2025). Profit-seeking solar geoengineering exemplifies broader risks of market-based climate governance. Earth System Governance, 23, 100242.Abstract: Despite uncertainties about its feasibility and desirability, start-up companies seeking to profit from solar geoengineering have begun to emerge. One company is releasing balloons filled with sulfur dioxide to sell “cooling credits”, claiming that the cooling achieved when 1 g of SO2 is released is equivalent to offsetting one ton of carbon dioxide for one year. Another aspires to deliver returns to investors from the development of a proprietary aerosol for dispersal in the stratosphere. Such for-profit solar geoengineering enterprises should not be understood merely as rogue opportunists. These proposals are not only scientifically questionable, and premature in the absence of effective governance, but they are a predictable consequence of neoliberal, market-driven climate governance. The structures and incentives of market-based climate policy - circumscribed by neoliberalism's emphasis on technological innovation, venture capital, and the marketization of environmental goods - have generated repeated efforts to profit from various forms of geoengineering. With a climate governance regime wherein private, for-profit actors significantly influence and weaken climate policy, de facto governance of solar geoengineering has emerged, dominated by actors linked to Silicon Valley funders and ideologies. Without more explicit efforts to curb the power of private sector actors, including commercial geoengineering bans and non-use provisions, pursuit of techno-market “solutions” could lead to both inadequate mitigation and increasingly risky reliance on geoengineering.
Hernandez Jaramillo, D. C., Harrison, D. P., & Kelaher, B. A review of plume dispersion and measurement techniques applicable to marine cloud brightening. Frontiers in Marine Science, 12, 1450175.Abstract: Rising sea surface temperatures are causing more frequent and intense coral bleaching events, threatening the long-term survival of coral reefs globally. Marine Cloud Brightening (MCB) is a proposed intervention that could be applied globally or regionally to cool sea surface temperatures and reduce the risk and severity of coral bleaching. The effectiveness and logistical feasibility of this technique depends on what fraction of the sea salt aerosols are incorporated into clouds after being emitted from a seawater spraying operation at the ocean surface. Here, we review the literature on the dispersion of MCB sea salt aerosols from a point source within the marine boundary layer. We focus our consideration on the processes, mechanisms, and current ability to predict the horizontal and vertical evolution of the plume from its generation at surface level to its downwind dispersion and mixing to cloud height. Overall, we found that in the more than three decades since the MCB concept was first proposed there have been eight studies investigating this aspect of MCB, which is crucial to informing engineering systems design, marine logistics, and assessing the overall potential effectiveness of MCB. To date, only one study has validated the modelling of the aerosol dispersion using empirical experiments and only a few studies have considered non-passive processes such as the negative buoyancy associated with the evaporative cooling of the water droplets, as well as particle scavenging due to coagulation and deposition. Priority areas for future research are identified as far-field dispersion of the MCB plume and estimations of the portion of MCB aerosol reaching cloud base. Coral reefs, known as biodiversity hotspots, are particularly vulnerable to warming oceans (Bureau of Meteorology & CSIRO, 2020). They provide critical services, such as coastal protection and fisheries, that support livelihoods for millions of people globally (Oxford-Economics, 2009;Rolfe & Valck, 2021;Stoeckl et al., 2011). However, without intervention, the increasing intensity and frequency of marine heatwaves are expected to escalate coral bleaching events, threatening coral reef survival.
Foster, R., Shumway, N., Harrison, D., & Fidelman, P. (2025). Governing marine cloud brightening for ecosystem conservation under a warming climate. Earth System Governance, 23, 100240.Abstract: Marine Cloud Brightening (MCB) is an emerging technology designed to mitigate the impacts of climate change by increasing the reflectivity of low-lying marine clouds. As research into this technology advances, the question of how to govern its trials and deployment becomes increasingly important. This paper identifies 12 challenges and 13 recommendations for governance of MCB, based on a systematic review of 27 publications. These findings are explored in relation to the design of effective MCB governance, with a particular focus on potential small-scale applications for ecosystem conservation purposes, like coral bleaching mitigation. The paper underscores the existing knowledge gaps and potential avenues for future MCB governance research, contributing to the burgeoning literature on the governance of innovative technologies aimed at addressing global environmental challenges. To manage potential risks and maximise potential benefits, it is crucial to understand the governance challenges MCB presents and explore options to address these challenges.
Du, H., Tan, M. L., Xia, L., Tew, Y. L., & Yaseen, Z. M. (2025). Tropical hydro-climatic responses to global warming and solar radiation modification in the Kelantan River Basin, Malaysia. Journal of Water and Climate Change, jwc2025587.Abstract: Solar radiation modification (SRM) has been discussed as a potential strategy to rapidly mitigate global warming by reflecting more sunlight into space. However, its impact on tropical hydrological cycles remains underexplored. This study investigates the potential impacts of SRM on streamflow of the Kelantan River Basin (KRB) by incorporating climate projections from the Geoengineering Model Intercomparison Project Phase 6 (GeoMIP6) into the Soil and Water Assessment Tool plus (SWAT+) model. The findings reveal that UKESM1-0-LL and MPI-ESM1-2-LR exhibit greater uncertainty in representing the climate of the KRB compared to CNRM-ESM2-1 and IPSL-CM6A-LR. Maximum and minimum temperatures under SSP5-8.5 are projected to increase by up to 3.52 °C by the end of the 21st century, while these increases could be limited to between 1.72 and 2.33 °C under SRM scenarios, corresponding to 1.96 to 2.22 °C under SSP2-4.5. The multi-model ensemble mean projected an inverse V-shaped trend in annual precipitation, with a peak in the mid-21st century before declining, except for G6sulfur, which exhibits a steady decrease. Increases in monthly precipitation during the 2045–2064 period may intensify flooding in the KRB. Meanwhile, decreases in streamflow during dry months are projected for the periods 2045–2064 and 2065–2085 under G6sulfur, particularly in the middle and upper basins.
Guo, X., Liu, Y., Xie, T., Li, Y., Liu, H., & Wang, Q. (2025). Impact of Ecological Restoration on Carbon Sink Function in Coastal Wetlands: A Review. Water, 17(4), 488.Abstract: Over the past two decades, anthropogenic emission reductions and global warming have impacted marine low clouds through aerosol-cloud interactions (ACI) and cloud feedback, yet their quantitative contributions remain unclear. This study employs a deep learning model (CNNMet−Nd) and Community Earth System Model version 2 (CESM2) to disentangle these effects. CNNMet−Nd reveals that aerosol-driven changes in cloud droplet number concentration dominate near-global marine low cloud shortwave radiative effect changes (ΔCRE), contributing 0.42 ± 0.08 Wm⁻² per 20 years, compared to 0.05 ± 0.37 Wm⁻² from cloud feedback. CESM2 effectively reproduces the predominant influence of aerosol reductions on ΔCRE by CNNMet−Nd, lending us confidence for a stronger estimate of global effective radiative forcing due to ACI (ERFaci) of -1.29 Wm⁻² since the preindustrial era. These findings highlight the critical role of ACI in shaping marine low cloud trends and its broader climate implications, especially under ongoing emission reduction efforts.
Dhandapani, C., Kaul, C. M., Pressel, K. G., Blossey, P. N., Wood, R., & Kulkarni, G. (2025). Sensitivities of large eddy simulations of aerosol plume transport and cloud response. Journal of Advances in Modeling Earth Systems, 17(2), e2024MS004546.Abstract: Cloud responses to surface-based sources of aerosol perturbation partially depend on how turbulent transport of the aerosol to cloud base affects the spatial and temporal distribution of aerosol. Here, scenarios of plume injection below a marine stratocumulus cloud are modeled using large eddy simulations coupled to a prognostic bulk aerosol and cloud microphysics scheme. Both passive plumes, consisting of an inert tracer, and active plumes are investigated, where the latter are representative of saltwater droplet plumes such as have been proposed for marine cloud brightening. Passive plume scenarios show higher in-plume cloud brightness (relative to out-of-plume) due to the predominant transport of the passive plume tracer from the near-surface to the cloud layer within updrafts. These updrafts rise into brighter areas within the cloud deck, even in the absence of an aerosol perturbation associated with an active plume. Comparing albedo at in-plume to out-of-plume locations associates the inert plume with the brightest cloud locations, without any causal effect of the plume on the cloud. Numerical sensitivities are first assessed to establish a suitable model configuration. Then sensitivity to particle injection rate is investigated. Trade-offs are identified between the number of injected particles and the suppressive effect of droplet evaporation on plume loft and spread. Furthermore, as the near-field in-plume brightening effect does not depend significantly on injection rate given a suitable definition of perturbed versus unperturbed regions of the flow, plume area is a key controlling factor on the overall cloud brightening effect of an aerosol perturbation.
Clark, B., Robock, A., Xia, L., Rabin, S. S., Guarin, J. R., Hoogenboom, G., & Jägermeyr, J. (2025). Maize yield changes under sulfate aerosol climate intervention using three global gridded crop models. Earth's Future, 13(2), e2024EF005269.Abstract: As the severity of climate change and its associated impacts continue to worsen, schemes for artificially cooling surface temperatures via planetary albedo modification are being studied. The method with the most attention in the literature is stratospheric sulfate aerosol intervention (SAI). Placing reflective aerosols in the stratosphere would have profound impacts on the entire Earth system, with potentially far-reaching societal impacts. How global crop productivity would be affected by such an intervention strategy is still uncertain, and existing evidence is based on theoretical experiments or isolated modeling studies that use crop models missing key processes associated with SAI that affect plant growth, development, and ultimately yield. Here, we utilize three global gridded process-based crop models to better understand the potential impacts of one SAI scenario on global maize productivity. Two of the crop models that simulate diffuse radiation fertilization show similar, yet small increases in global maize productivity from increased diffuse radiation. Three crop models show diverse responses to the same climate perturbation from SAI relative to the reference future climate change scenario. We find that future SAI implementation relative to a climate change scenario benefits global maize productivity ranging between 0% and 11% depending on the crop model. These production increases are attributed to reduced surface temperatures and higher fractions of diffuse radiation. The range across model outcomes highlights the need for more systematic multi-model ensemble assessments using multiple climate model forcings under different SAI scenarios.
Pantling, J., Worster, M. G., & Fitzgerald, S. D. (2025). Modelling the response of an ice disc to radial water flow in the context of sea ice thickening. Experiments in Fluids, 66(2), 1-15.Abstract: Arctic sea ice is melting rapidly, and the Arctic is likely to experience its first ice-free summer in the next few decades unless action is taken locally. One proposed method of reducing or perhaps reversing the melting of Arctic sea ice is pumping seawater onto the surface of the sea ice where it should freeze faster and thicken the ice. This may in turn enable it to last longer or even survive the summer melting period, reflecting more sunlight and becoming stronger multi-year ice with increased resistance to future melting. Despite appearing to be a relatively simple physical problem, the technique has not been researched in depth. Here, the response of ice to water being pumped over its surface is investigated theoretically and experimentally for radial axisymmetric water flow. The dominant heat transfer mechanisms during the period shortly after placement of water onto ice are conduction through the ice away from the water–ice interface and heat transfer from the water to the interface. During this initial period of evolution, advection and radiation to the atmosphere are much smaller in magnitude and hence not included. The heat transfer from the water flow to the interface is modelled for three flows: a well-mixed uniform film flow; a uniform flow with a developing thermal boundary layer; and a laminar, viscous flow with a developing thermal boundary layer. Predictions from these models are compared with data from laboratory experiments using various initial water temperatures. The predictions of the model with a fully developed, laminar viscous flow and a developing thermal boundary layer for the evolution of the ice profile were found to be closest to the data obtained from laboratory experiments with water supplied at 0.5, 1.0 and 1.5∘C.
Feng, E. Y. Assessing Climate Engineering's Impact on Earth System Feedback. Available at SSRN 5132439.Abstract: The uncertainties observed in Earth system modelling simulations for climate engineering (CE), namely solar radiation management (SRM) and carbon dioxide removal (CDR), can be largely attributed to the uncertainties within climate feedback. I use a diagnostic metric with formula similar to CO2-climate sensitivity, to examine how Earth system’s physical feedback and climate-carbon feedback affect the climate mitigation performance of SRM and CDR. This diagnostic metric, when applied to analyse Earth system modelling results of SRM and CDR, can informatively demostrate the climate mitigation contributions of CE’s direct intervention and their perturbations in climate feedback . The analysis confirms climate-carbon feedback can enhance SRM’s global cooling effects, while physical feedback such as air-sea heat exchange can reduce CDR’s climate mitigation effectiveness. This analysis advances the understanding how different types of climate feedback can strengthen or weaken CE’s utility, and it also helps to numerically characterise the fundamental differences between SRM and CDR in respect to their climate intervention nature.
THESISHeenan, N. E. (2025). Producing the Climate: The Political Economy of Climate Engineering in Australia (Doctoral dissertation).Abstract: In response to both the urgency of the climate crisis and the inadequacy of climate action and pledges to date, geoengineering is increasingly being considered alongside mitigation and adaptation as a way of stabilising or ‘repairing’ the climate (McLaren, 2018). This thesis conceptualises geoengineering as part of the production of nature in capitalism, rather than an ‘intervention’ in an external nature (Smith, 1984). Employing this lens and building on existing critical social science on geoengineering (Buck, 2019; Surprise, 2018, Sapinski et al., 2020; McLaren & Corry, 2021), the thesis examines how capitalism adapts to crisis by restructuring the conditions of production to forge new frontiers of accumulation (O’Connor, 1998; Moore, 2015). In response to calls for ‘place-based’ research on geoengineering, and the importance of mapping unevenness and particularity in the geography of capitalism, I analyse two Australian projects aimed at engineering the climate (Buck, 2018; Massey, 1995). Based on semi-structured interviews with teams involved in developing Direct Air Capture (DAC) in New South Wales, and scientists testing Marine Cloud Brightening (MCB) techniques over the Great Barrier Reef in Queensland, the case studies provide a detailed account of the development of small-scale solar radiation modification and carbon removal and storage projects. I critically analyse the potential for these projects to contribute to mitigation deterrence, promises of Australia’s ‘vast’ underground sequestration potential, public and private finance for research and development, a ‘circular economy for carbon’, the political dominance of the fossil fuel industry, and the assurances of ‘co-benefits’ for workers and Indigenous communities. I contend that climate repair may prove to be a strategic battleground in Australian climate politics, opening up possibilities for contesting the capitalist production of nature at multiple sites and scales.
WEB POSTS
JOB OPPORTUNITY"The Blue Cooling Initiative (BCI) is an urgent and critical response to the accelerating climate crisis, spearheaded by a diverse coalition of scientists, opinion leaders, civil servants, and politicians. The Initiative focuses on advancing ocean-based cooling solutions, with a particular emphasis on Marine Cloud Brightening (MCB). By enhancing cloud reflectivity, MCB aims to increase the amount of sunlight reflected back into space, thereby cooling the planet."
UPCOMING EVENTSSolar Geoengineering Events Calendar
YOUTUBE VIDEOSWhat if clouds could be more reflective? Engineering for the Climate | Centre for Climate Repair "In this seminar, we hear from Prof Adam Boies (Stanford) on contrails, plus two Cambridge engineers (Dr Dante McGrath and Orla Hill) researching methods to brighten clouds over the ocean.Engineering has changed the world. But global temperatures are rising due to human action and emissions reduction is not sufficient to protect vulnerable people and places from the worst effects of climate change. What if engineering could help cool the planet?What if we could make more ice? What if clouds could be more reflective? What if GHGs could be captured?"
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