Legitimacy and procedural justice: how might stratospheric aerosol injection function in the public interest?

The paper examines how stratospheric aerosol injection (SAI)—a high-leverage, rapidly deployable form of solar geoengineering—might be developed and operated in the public interest by embedding legitimacy and procedural justice. Treating SAI as an institution that spans research, development, experimentation, and gradual deployment, the article argues that given accelerating climate risks and inadequate decarbonization trajectories, SAI could gain urgency. However, its many uncertainties, potential for elite capture, and governance challenges necessitate a prior normative framework. The author defines public interest as actions that benefit society as a whole by protecting and promoting social well-being through minimization of climate-related harm. The research question is how to secure long-term legitimacy (external relations with stakeholders) and procedural justice (internal decision-making qualities) so SAI remains open, inclusive, and independent, thereby capable of serving the public interest.

The article surveys normative and governance-oriented scholarship on solar geoengineering and SAI. Prior work has evaluated effectiveness, efficiency, distributive justice, and political feasibility, and discussed legitimacy in various forms. Some authors caution against creating new governance systems, suggesting existing legal and UN-based structures suffice; others recommend sub-state, international, polycentric, or global deliberative systems to lend legitimacy. Studies also highlight risks of elite capture, moral hazard, governance difficulties, and even ungovernability. The paper positions itself against descriptive (acceptance-based) legitimacy approaches prevalent in parts of the literature, advancing instead a normative output-legitimacy framework focused on serving the public interest. It further notes limited treatment of procedural justice in existing work and addresses this gap by specifying criteria and actionable standards tailored to SAI.

Conceptual normative analysis. The author: (1) conceptualizes SAI as an institution and delineates external (legitimacy) and internal (procedural justice) domains; (2) adopts a normative output-legitimacy framework (after Scharpf/Steffek), oriented to serving the public interest; (3) specifies criteria for legitimacy—avoidance of serious injustice and provision of reliable information; (4) specifies criteria for procedural justice—impartiality (parity of participation) and equality of opportunity (equal ability to understand issues); (5) derives epistemically accessible standards as proxies for these criteria: priority (to the more vulnerable) and transparency (for legitimacy); involvement and knowledge (for procedural justice); (6) proposes morally sound governance options to operationalize these standards (e.g., social-vulnerability–informed prioritization, transparent information systems, an independent consultative forum, and an involvement/knowledge platform); (7) recommends continuous checking, calibration, and context-sensitive operationalization via iterative social learning and an independent, inclusive forum. No empirical data are collected; examples from existing institutions illustrate feasibility.

• Two legitimacy criteria suitable for SAI: • Avoidance of serious injustice: SAI must prioritize the needs of more vulnerable populations to prevent disproportionate burdens; benefits from SAI’s climate effects should accrue progressively in line with social vulnerability. • Provision of reliable information: SAI must maintain long-term public trust by producing and sharing accurate, accessible, and actionable information to manage disagreement and uncertainty, enabling accountability.
• Two procedural justice criteria suitable for SAI: • Impartiality: Agents directly involved in SAI should have parity of participation under consistent, non-arbitrary rules; decisions should be modifiable and reversible; diversity should be maximized. • Equality of opportunity: All involved agents must have equal opportunities to understand SAI, supported by access to accurate, validated knowledge enabling evidence-based participation.
• Corresponding standards (criteria-to-standard mapping): • Legitimacy → Priority (to the more vulnerable) and Transparency. • Procedural justice → Involvement and Knowledge.
• Governance options to implement standards: • Priority: Employ a social vulnerability index across climate subregions to allocate benefits and design operations so more vulnerable populations receive proportionally greater benefits (consistent with progressivity principles). • Transparency: Regularly provide accurate, usable information on goals, procedures, and performance; enable criticism and proposals for change; establish an independent consultative forum to monitor public-interest alignment and accountability (analogy: Frontex Consultative Forum). • Involvement: Create a platform (including virtual) enabling involved agents to audit consistency of decisions, request revisions, and ensure compatibility with moral and cultural values (analogous procedural mechanisms in the Council of Europe). • Knowledge: Through the same platform, generate, integrate, and disseminate robust, fit-for-purpose knowledge to reduce complexity and support adaptive reframing as evidence and values evolve.
• Two cross-cutting recommendations: • Continuous check and calibration: Iterative learning to reassess and update criteria/standards as contexts change; leverage transparency and knowledge standards for critical review. • Continuous operationalization: Use an independent, inclusive consultative forum (external to SAI initiatives; composed of experts, practitioners, and civil society, with attention to global South/North balance and vulnerable groups) to tailor and revise standards to specific SAI enterprises over time.

By articulating specific criteria and actionable standards for legitimacy and procedural justice, the paper addresses the core challenge of ensuring SAI works in the public interest rather than serving vested interests. Prioritizing the vulnerable mitigates risks of serious injustice from uneven or uncertain impacts. Transparency and reliable information combat opaqueness and enable accountability, reducing opportunities for elite capture. Internally, impartial involvement and equal opportunities for understanding align decision-making with fairness and competence, supporting durable acceptance. The proposed independent consultative forum and involvement/knowledge platform operationalize openness, inclusiveness, and independence, while continuous checking and adaptive calibration maintain alignment as scientific, political, and social conditions evolve. Together, these measures enhance the prospects that, if pursued, SAI can be legitimately governed and procedurally just, thereby meriting public-interest support.

The article offers a normative framework to embed long-term legitimacy and procedural justice in SAI so it can operate in the public interest. It defines tailored criteria (avoidance of serious injustice; provision of reliable information; impartiality; equality of opportunity) and translates them into accessible standards (priority, transparency, involvement, knowledge) with concrete governance options (social-vulnerability prioritization, transparency mechanisms, independent consultative forum, and an involvement/knowledge platform). It further recommends continuous checking, calibration, and context-specific operationalization via an independent, inclusive forum. In a fragmented, polycentric climate governance landscape, these measures can build converging support across diverse actors and reduce the risk of elite capture, enhancing SAI’s capacity to protect social well-being by minimizing climate-related harm. Future research can refine operational tools, test governance designs in simulations or analog domains, and develop metrics for evaluating adherence to the proposed standards over time.

• Conceptual, normative analysis without empirical testing; effectiveness of proposed standards and mechanisms is unverified.
• Standards are general and must be continually contextualized; their effectiveness may vary across SAI enterprises and over time.
• SAI is currently hypothetical/inexistent operationally; unknowns and uncertainties limit prescriptive specificity.
• The paper does not resolve debates over creating new external governance systems versus using existing ones, focusing instead on endogenizing legitimacy/justice within SAI.
• Practical inclusion of lay publics is constrained by complexity; reliance on expert/practitioner fora may introduce representation challenges despite efforts for inclusivity.