Publicly-funded SAI research is increasing rapidly
GEOENGINEERING MONITOR
The UK’s Advanced Research and Innovation Agency (ARIA) has awarded funding to five SAI (Stratospheric Aerosol Injection) projects
ARIA is a UK government research funding agency. Its £57 million “Climate Cooling” research programme is funding research into a number of geoengineering technologies which have been covered in other articles in this series, including space-based schemes, solar geoengineering in the lower atmosphere such as MCB, and SAI. Five of the 22 research teams are investigating SAI-related issues:
- The PULSE project (Public Understanding, Leadership, and Social Ethics in the Governance of Earth Cooling Technologies in Communities Impacted by Volcanic Activity in the Philippine Context), is based at the University of the Philippines, Los Baños, has received £0.15 million and runs from 2025 to 2027. It aims to explore public opinion and ethical considerations relating to SAI and SRM, and to recommend governance structures for decision-making processes.
- The TRUSS project (Toward Robust and Unbiased validation of SAI Simulations), is based at the Institut Teknologi Sepuluh Nopember in Indonesia and has received £0.35 million. It runs from 2025 to 2028 and seeks to refine climate intervention models to enhance the reliability of SAI modelling outputs and impact assessments. Its aim is to quantify and reduce uncertainties in SAI simulations.
- Defining the minimum scale of an SAI test: a fundamental first step towards an outdoor large scale experiment, is a project based at Cornell University in the US which runs from July 2025 to July 2027, and has received £0.5 million. It aims to determine the scope of a field experiment that would be necessary to meaningfully limit uncertainties when deploying SO₂ from an aircraft, such as the movement of air plumes. To this end, a hypothetical experiment will be conducted that is as realistic as possible, enabling the conclusions to be applied to real-life scenarios.
- The StratoGuard project (Global Monitoring of Geoengineering using Micro High-Altitude Balloons), is being conducted by Voltitude Limited, in Farnborough, UK. It runs from 2025 to 2028 and has received £0.6 million. It aims to develop core technologies for a global sensor system for solar-powered micro-altitude balloons (mHABs), which will be deployed primarily in the stratosphere and is intended to serve as a basic monitoring tool for SRM. The project will demonstrate an optimised mHAB, incorporating technical developments such as the integration and demonstration of a particle counter probe.
- The Novel Materials for Stratospheric Aerosol Injection project is based at Cambridge University in the UK. It runs from June 2025 to June 2028 and has received £5.5 million. It aims to expand knowledge of various Alternative SAI Materials (ASAIMs) by combining field experiments, laboratory work and modelling. The chemical and optical properties of the particles will be investigated using stratospheric balloon and aeroplane flights, but no substances will be released into the stratosphere during these flights. The dispersion and dispersal of the aerosols will be measured in laboratory tests and the climate impact of the ASAIMs will be modelled.
In addition to these five SAI-focused projects, The Degrees Initiative has received £2 million in funding from ARIA for its GRID-CC (Global to Regional Impacts Downscaling for Climate Cooling) project. The project plans to create a freely accessible repository of detailed climate data for the Global South, which will be hosted at the University of Cape Town in South Africa. This data is intended to enable high-resolution climate projections to facilitate global and regional modelling. The impacts of SRM will be compared with those of climate change, with a focus on preventing tipping points. This kind of problematic risk-risk framing is discussed in other sections of this article.
The UK’s Natural Environment Research Council (NERC) is funding a five-year study into the climate impacts of SAI and MCB
NERC’s Marine CLOUD Brightening (MACLOUD) and Evaluation of Climate Intervention through novel Potential Strategies (ECLIPSE) research programmes aim to model the potential impacts of implementing SRM techniques on a large scale. The five-year programme runs from 2025 to 2030 and has a budget of £10.5 million and will not include field experiments. It will examine the climate impacts of SAI and MCB using natural analogues, such as volcanic eruptions and changes in shipping emissions, as well as reviewing existing data. It will also examine lesser-studied SRM techniques, including the use of cellulose nanocrystals for SAI. Project partners include the British universities of Birmingham, Cambridge, Edinburgh, Exeter, Leeds, Manchester, Oxford, Reading, andImperial College London, and the Center for International Climate and Environmental Research in Norway. The studies form part of NERC’s Modelling environmental responses to SRM programme.
Research projects funded by the European Space Agency seek to minimise uncertainties in climate models
The Aerosol Cloud Interactions for Cooling (ACtIon4Cooling) project, funded by the European Space Agency (ESA), aims to assess the feasibility and risks of SRM, as well as providing input for governance, research and a potential deployment framework. To this end, the project seeks to improve the understanding of aerosol-cloud interactions (ACIs), thereby reducing uncertainties in climate models and enabling more accurate evaluation of SRM approaches, including SAI, Marine Cloud Brightening (MCB) and Cirrus Cloud Thinning (CCT). ACI investigations include satellite and ground-based observations and data acquisition, as well as the evaluation of measurements of volcanic aerosols, marine clouds affected by ship-track emissions and aviation-relevant cirrus clouds. This data will be processed to inform global and regional climate simulations. The results will also be used to facilitate “the development of monitoring and attribution requirements for a dedicated SRM satellite mission”. The project is led by the German Aerospace Center, in collaboration with the National Observatory of Athens in Greece and the University of Leipzig in Germany.
The Satellite and Model Data to Inform Solar Radiation Modification Techniques (STATISTICS) project is funded by the ESA and aims to improve the accuracy of climate models by combining climate modelling with satellite-based Earth observation. The project argues that most SRM studies rely on climate modelling and make limited use of real-world observations. STATISTICS deals with SAI, MCB, CCT and Mixed-phase Cloud Thinning. It investigates ACI by examining natural and anthropogenic analogues, such as volcanic eruptions and industrial emissions. The project’s goal is to draw conclusions about the climatic impacts of SRM, such as SAI, by comparing observational studies with climate model results. The thinning of cirrus and mixed-phase clouds will be reassessed by comparing observational studies with climate model results. Furthermore, the verifiability of SRM field experiments and deployment based on natural analogues will be investigated. STATISTICS is led by GRASP SAS (Generalised Retrieval of Aerosol and Surface Properties) in France, in collaboration with the following institutions: CNRS-LOA (Laboratoire d’Optique Atmosphérique) and CNRS-IPSL (Institut Pierre-Simon Laplace) in France; the Max Planck Institute for Meteorology in Germany; the University of Oslo in Norway; the Davos Physical Meteorological Observatory and Perspectives Climate Research in Switzerland.
The STATISTICS project is collaborating with three EU-funded projects: CERTAINTY, CleanCloud and Co-CREATE. CERTAINTY aims to improve our understanding of the interactions between aerosols and clouds, and their impact on the Earth system. To this end, long-term satellite data will be evaluated to enhance forecast models and provide insights into climate mitigation and adaptation. The consortium has, among other things, examined the influence of dust on weather and climate, and modelled sea spray emissions from leads in the Arctic to map their influence on ACIs more accurately. CleanCloud also aims to enhance the understanding of ACIs, thereby improving short- and long-term climate predictions. The Co-CREATE project (Conditions for Responsible Research of SRM – Analysis, Co-Creation, and Ethos) aims to develop guidelines and principles to reduce uncertainties surrounding the conditions and governance arrangements of experimental SRM research. These guidelines and principles are intended to facilitate decision-making for the relevant authorities.
In June 2025, the STATISTICS and the ACtIon4Cooling project, both funded by the European Space Agency (ESA), conducted a workshop on SRM techniques and concluded that “small-scale field experiments may eventually become necessary to resolve key scientific uncertainties that cannot be addressed by model experiments, natural analogues or laboratory studies alone”.
Tipping points as a driver for SRM research and deployment
The IPCC defines a tipping point as a threshold beyond which a system reorganizes itself and does not revert to its original state, even if the initial cause is removed. In the context of the climate system, the term refers to a critical threshold at which the climate changes from one stable state to another, either globally or regionally.
Examples of tipping points include thawing permafrost, which would release huge quantities of methane into the atmosphere, and the Amazon forest dieback, where precipitation levels reduce to the extent that the ecosystem is no longer able to sustain itself. The idea of avoiding tipping points is increasingly being used as an argument for further research into the deployment of SRM:
- The Global Tipping Point Report 2025, for example, recommends a moratorium on SRM deployment and large-scale experiments in order to assess both the risks and potential benefits of it. The report is published by the University of Exeter, whose work on solar geoengineering is supported by ARIA and the Quadrature Climate Foundation, among others.
- Reflective considers SAI to be an effective means of mitigating the impact of climate change and avoiding tipping points.
- Mengying Zhao, et al., researchers at Nanjing University and Zhejiang University in China, and at Cornell University in the US,claim that the SAI strategies they considered would mitigate the risks associated with many tipping elements. Their funders include the Quadrature Climate Foundation and the US National Science Foundation. The latter has supported SRM research, modelling and field trials for more than 15 years, including GLENS,GeoMIP,E-PEACE,VOCALS-REX, and SRM research at Rutgers University and the University of California.
- Mark Symes, one of ARIA’s programme directors, said in an interview with The Guardian in April 2025, that “the looming threat of climate tipping points was a strong reason to research solar geoengineering”.
- Gideon Futerman, et al., researchers from Great Britain, the USA and China, also cite the avoidance of tipping points as a key advantage of SRM and conclude that ”when temperature is a key driver of tipping, well-implemented, homogenous, peak-shaving SRM could be at least partially effective at reducing the risk of hitting most tipping points examined relative to the same emission pathway scenarios without SRM.”
This line of reasoning is a form of “risk-risk” framing that geoengineering proponents seek to introduce into the political discourse surrounding SRM. In an attempt to normalise the discussion around the use of SRM, the risks of its deployment are increasingly being compared to the risks of reaching a tipping point. However, the risks being compared are often deliberately limited to those related to climate change. Deploying SRM would, however, entail a much broader range of environmental, social, economic and geopolitical challenges.
Robert E. Kopp, et al., researchers at the University of Bristol, “critique the ‘tipping point’ framing for oversimplifying the diverse dynamics of complex natural and human systems and for conveying urgency without fostering a meaningful basis for climate action.” They conclude that “the deep uncertainty and perceived abstractness of climate tipping points render them ineffective for triggering action and setting governance goals.”
Duncan P. McLaren published an article in the European Journal of Risk Regulation in which he discusses the risks associated with raising hopes that SRM can avert some of the otherwise unavoidable risks of climate change. He found that:
- “most references to such (risk-risk) analysis appear primarily as rhetorical efforts to argue for continued SRM research”;
- “a detailed review of the leading methodological proposal reveals serious practical and ethical shortcomings arising in both the framing and current methodologies of risk-risk analysis”;
- “the shortcomings mean ethical questions are not resolved, interaction effects between possible responses are downplayed and other potential exceptional responses ignored”;
- He concludes that “rather than identifying possible risk-superior pathways, in this case risk-tradeoff analysis – embedded in a technocratic risk management repertoire – seems likely to encourage excessive reliance on SRM.
Geoengineering Monitor: continue reading
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