Vishwamitra Futures
Issue #016
Solar geoengineering remains scientifically plausible but politically contested. Research, detection, carbon removal costs and fragmented governance will shape the choices ahead.
Geoengineering is a problem of competing constraints. The science remains uncertain, carbon removal is expensive, and international governance is fragmented. The central question is not simply whether climate intervention is technically possible, but whether institutions can assess its risks, establish rules and prevent unilateral action from outrunning public accountability.
By Santhosh Vishwamitra
Large-scale climate intervention encompasses two distinct approaches. Solar Radiation Modification (SRM), including stratospheric aerosol injection (SAI), aims to cool the planet by reflecting more sunlight. Carbon Dioxide Removal (CDR), including Direct Air Capture with Carbon Storage (DACCS) and Bioenergy with Carbon Capture and Storage (BECCS), seeks to remove carbon dioxide from the atmosphere.
These approaches solve different problems. SRM could reduce some warming effects without removing atmospheric CO₂. CDR addresses atmospheric carbon directly, but its potential depends on cost, energy, storage permanence and the ability to scale. Neither should be treated as a substitute for reducing greenhouse gas emissions.
Large-scale SRM deployment has not been demonstrated in real-world climate conditions. Research and modelling can inform decisions, but they cannot establish every consequence of a sustained intervention. Meanwhile, carbon removal projects remain far below the scale discussed in many climate pathways.
The future therefore depends on more than laboratory feasibility. Research governance, detection, liability, international cooperation and the economics of carbon removal will influence whether geoengineering remains a limited research field, becomes a source of strategic competition, or faces stronger non-use restrictions.
Confirmed Baseline: Risks, Costs and the Absence of Deployment at Scale
The United Nations Secretary-General's Scientific Advisory Board published a brief on SRM in May 2025. It described the potential for temporary cooling alongside substantial environmental, geopolitical and ethical risks. These include uneven regional effects, changes in weather patterns, possible ozone impacts and the risk that expectations of future cooling could weaken incentives to cut emissions.
One concern is termination shock. If sustained SRM deployment were abruptly stopped, the masking effect of reduced incoming sunlight could disappear while greenhouse gas concentrations remained elevated. The resulting rapid warming could place additional stress on ecosystems and societies. The magnitude of the consequences would depend on the deployment scenario and the climate conditions at the time.
Germany's Federal Environment Agency has also taken a strongly precautionary position. Its research and policy publications discuss the potentially serious ecological and geopolitical risks of SRM, the limits of current knowledge and the difficulties of governing an intervention that could affect regions differently.
The IPCC's Sixth Assessment Report treats CDR as an important component of pathways that limit warming. The required quantity varies by pathway and method. Some scenarios rely heavily on land-based biological removal and BECCS, while others include DACCS. There is no single universal annual CDR requirement that applies to every 2050 pathway.
A 2025 study in Scientific Reports examined practical constraints on SAI strategies, including aerosol properties, injection logistics, supply chains and the relationship between deployment choices and environmental risks. Its findings reinforce an important distinction: idealised modelling assumptions do not automatically translate into a workable real-world intervention.
The evidence supports neither a simple emergency-brake narrative nor the assumption that every proposed intervention is inherently identical in its risks. Each approach requires scrutiny of its physical effects, technical limits, environmental consequences and governance requirements.
Carbon Removal: The Cost and Scale Problem
A 2025 European Parliament study on Direct Air Capture examined the costs and investment requirements associated with scaling DACCS in the European Union. Its estimates illustrate how strongly total expenditure depends on the assumed cost per tonne and the quantity removed.
At an illustrative cost of €200 to €900 per tonne of CO₂, removing 1 gigatonne annually would imply €200 billion to €900 billion per year. This is a simple multiplication of the stated unit-cost range, not a prediction of the actual cost of a future global removal system.
The distinction matters. First-plant costs, future cost projections and the costs of operating an integrated removal system at scale are not interchangeable. Actual results will depend on energy supply, infrastructure, construction, financing, transport, storage and technological performance.
Even if costs decline, removing several gigatonnes annually would require extensive infrastructure and durable storage. The economic challenge is therefore not merely to demonstrate that carbon can be captured. It is to deliver reliable net removal at scale while maintaining credible lifecycle accounting.
Research Is Advancing, but Research Is Not Deployment
SRM research continues to develop through modelling, observation, analysis of historical climate events and proposals for carefully controlled experiments. These activities can reduce uncertainty, but they do not establish that large-scale deployment would be safe, effective or politically legitimate.
On 2 March 2026, the Environmental Defense Fund announced the first nine projects in its SRM research programme. The projects use data from past events, including volcanic eruptions and wildfires, to investigate potential effects on ecosystems, agriculture and water availability. The programme focuses on improving the evidence base, particularly for regional impacts.
China's research posture has also attracted attention. An American Council for Capital Formation report published on 15 September 2026 argued that China had increased dedicated SRM research funding and was seeking a greater role in international research coordination and governance discussions.
The ACCF report cites RMB 40 million for two SRM-specific projects in a 2024 Earth System and Global Change programme, compared with approximately RMB 14.5 million for an earlier, broader geoengineering programme. These are figures reported by ACCF and should be understood in that context. They do not, by themselves, establish the scale of China's overall research effort or demonstrate an operational international alliance.
The same report describes an initiative to establish an International Alliance for Solar Radiation Modification. Its operational status, membership and concrete programme of work require independent confirmation before the initiative can be treated as an established institution.
The United Kingdom's position illustrates another distinction between research and deployment. In a policy statement published on 29 September 2026, the government said it does not support SRM deployment and does not plan to deploy it. The statement also supports responsible research that complies with domestic and international regulations.
The UK policy document identifies £56.8 million in public spending for the Advanced Research and Invention Agency's Exploring Climate Cooling programme, ongoing since 2024. It describes foundational research, monitoring, modelling and carefully controlled small-scale outdoor experiments, subject to legal and environmental assessment. These research activities should not be conflated with a decision to deploy SRM.
Reflective's SAI Research Roadmap, launched in September 2026, offers another example. It maps research activities and decision gates intended to improve understanding of SAI. The organisation estimates that an informed decision about whether to begin monitored cooling could be reached in approximately 10 to 22 years, at an estimated cost of US$370 million to US$1.36 billion.
Those figures describe a proposed research pathway, not a deployment budget or a guarantee that deployment would be justified at the end. Reflective also states that its roadmap does not advocate deployment or recommend diverting attention from decarbonisation.
Small private releases and research proposals raise separate questions about oversight, transparency and accountability. Their existence does not establish that large-scale SRM is technically mature, safe or internationally accepted. Specific claims about release quantities, funding and regulatory responses should be supported by traceable records rather than extrapolated from announcements.
Governance: Rules, Liability and Unequal Exposure
SRM presents a difficult governance problem because its effects could cross borders even when a decision to intervene is made by one state or a small coalition. Changes in regional precipitation, atmospheric circulation or other climate patterns could distribute benefits and harms unevenly.
Existing international agreements address particular activities and legal concerns, but they do not provide a single comprehensive framework covering every SRM technique, research activity and deployment scenario. The legal position must therefore be assessed instrument by instrument rather than described as either complete regulation or a total absence of law.
Liability is another unresolved issue. A workable system would need to consider causation, attribution, standards of proof, responsibility, compensation and the treatment of uncertain climate impacts. Establishing that an intervention occurred would not automatically establish that it caused a specific drought or precipitation shift.
Opposition to SRM also arises from more than one concern. Critics point to physical risks, the possibility of delaying emissions reductions, unequal decision-making power, international-law questions, the difficulty of obtaining consent and the ethical implications of deliberately altering the climate system.
These objections are not interchangeable. Some concern scientific uncertainty, others institutional legitimacy, and others the distribution of risk and power. A credible governance debate needs to address each on its own terms.
SRM also does not directly remove atmospheric CO₂ or stop ocean acidification. Cooling the planet would not eliminate the chemical consequences of elevated atmospheric carbon dioxide. Treating SRM as a comprehensive climate solution would therefore obscure a fundamental limitation.
Three Plausible Pathways
Three broad institutional pathways help organise the choices ahead. They are conditional scenarios, not probability-ranked forecasts. Their relevance depends on decisions, evidence and events that remain uncertain.
Coordinated Research and Detection Capacity
In this pathway, research funders and governments prioritise transparent scientific work, monitoring and the ability to identify and attribute outdoor activities. Research remains distinct from deployment, and legal and liability questions are addressed alongside scientific work.
The UK policy position, EDF's natural-analogue research and Reflective's staged roadmap illustrate different ways to investigate uncertainty without treating deployment as a foregone conclusion. Their existence does not establish that a common international research framework has emerged.
This pathway would become more credible if major research programmes adopted shared disclosure standards, independent review, accessible data and explicit limits on the activities they support. It would be weakened by opaque experiments, unilateral releases or an inability to agree on basic reporting and oversight.
Formal Non-Use or Moratorium Regimes
In this pathway, governments and international institutions conclude that deployment risks, unequal exposure and governance difficulties justify stronger restrictions. Such measures could take different forms, from national prohibitions and funding limits to an international non-use agreement.
Scientific uncertainty alone would not automatically produce a moratorium. The political outcome would depend on how states assess the risks of intervention against the risks of continued warming, and whether they believe a restriction could be implemented and monitored effectively.
Support for non-use measures could strengthen after a controversial experiment, a serious governance failure or evidence that regional effects cannot be managed to an acceptable standard. It could weaken if governments conclude that research restrictions would leave them unable to evaluate or respond to unilateral activity.
Unilateral Acceleration Under Strategic Competition
In this pathway, research and deployment capability become entangled with national security, strategic competition and claims of sovereign decision-making. Governments or private actors could proceed without broad international agreement, particularly if they believe that rivals are advancing faster.
China's reported funding shift and the alliance initiative described by ACCF are relevant to this discussion, but they do not prove that a competitive deployment race is already under way. The scenario remains conditional on future policy decisions, institutional arrangements and evidence of actual activity.
Unilateral acceleration would become more plausible if major states prioritised national capability over shared governance, disclosure remained limited, and no credible mechanism emerged to address cross-border harm. Even then, research expansion alone would not establish that a state had decided to deploy SRM.
Residual Uncertainties
Several questions remain central to any assessment of geoengineering's future.
- Regional climate response: How would sustained SAI affect monsoons, precipitation and other regional climate patterns? Model results and regional impacts need careful evaluation.
- Carbon removal costs: How far can DACCS costs fall, and under what energy, infrastructure and storage conditions? Projections are not substitutes for performance data at scale.
- Liability and attribution: How would international institutions establish responsibility and compensation for alleged transboundary harm?
- Private and state activity: What outdoor releases have occurred, at what scale, and what regulatory responses followed? Public claims require verifiable records.
- Chinese alliance initiative: What are its actual membership, operational status, funding and work programme?
- Research versus deployment: What criteria would allow policymakers and the public to distinguish legitimate uncertainty-reduction research from activities that materially advance deployment?
These uncertainties do not make analysis pointless. They define what responsible analysis must acknowledge. Any forecast should identify its assumptions and distinguish evidence of current activity from expectations about future decisions.
What the Current Evidence Reveals
The evidence points to an uneven picture. International institutions have identified substantial SRM risks. Researchers are investigating regional impacts and technical uncertainties. The UK has explicitly separated its opposition to deployment from its support for responsible research. Reflective has published a staged research roadmap, while ACCF has reported a shift in China's dedicated SRM research funding and international ambitions.
These developments do not establish a single global direction. They show that research, political legitimacy and deployment decisions remain distinct issues, even as they influence one another.
Carbon removal faces a different constraint: the gap between projected climate needs and the cost and infrastructure required to remove carbon at scale. SRM raises a different set of questions about regional climate effects, continuity, accountability and who has the authority to intervene.
The decisive issue is therefore not whether a technique can be described in a laboratory or a model. It is whether the evidence, economics, institutions and political safeguards are adequate for the decisions being considered. Research may narrow uncertainty. It cannot, by itself, settle questions of legitimacy or consent.
Santhosh Vishwamitra
Vishwamitra Chronicles
Sources
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United Nations Secretary-General's Scientific Advisory Board,
Solar Radiation Modification, May 2025.
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German Federal Environment Agency,
Solar Radiation Modification: Intractable Governance and Uncertain Science, April 2024.
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European Parliament, Policy Department for Transformation, Innovation and Health,
The Role of Direct Air Capture Technologies in the EU's Decarbonisation Effort, 2025.
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IPCC, Sixth Assessment Report, Working Group III,
Technical Summary: Carbon Dioxide Removal, 2022.
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Hack, M. et al.,
Engineering and Logistical Concerns Add Practical Limitations to Stratospheric Aerosol Injection Strategies, Scientific Reports, 21 October 2025.
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Environmental Defense Fund,
Environmental Defense Fund Announces First Grantees in SRM Research Program, 2 March 2026.
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American Council for Capital Formation,
New Report: China Sharply Expands Investment and Global Ambitions in Solar Radiation Modification, 15 September 2026.
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UK Government,
Solar Radiation Modification Approaches: The Government's View, 29 September 2026.
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Reflective,
SAI Research Roadmap, launched 10 September 2026.
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United Nations Environment Programme,
Solar Radiation Modification: Scientific Evidence Does Not Support SRM as a Viable Climate Solution, May 2026.
Research cut-off: 9 October 2026. Cost estimates, projections and reported developments should be interpreted according to their source, date, methodology and status. The ACCF funding figures and Chinese alliance initiative remain attributed claims rather than independently established measures of operational capability. No numerical probability is assigned to the three pathways.
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