Define reference scenario(s)

Without a credible, transparent, end-to-end reference scenario (or small set of scenarios), grounded in engineering realities, policymakers cannot realistically assess SAI's feasibility, costs, and consequences, nor understand governance and monitoring requirements. SAI studies often rely on idealized and potentially technically infeasible scenarios, leading to significant challenges for informed decision-making. In the absence of a thoroughly detailed, technically feasible, public-facing scenario, the only detailed deployment plans available to decision makers may be driven primarily by financial interests rather than scientific rigor.

While a handful of studies (e.g., Wheeler et al., 2025) have started to integrate climate science with engineering and logistical analysis to produce this type of scenario, no comprehensive reference scenario has been developed. A comprehensive reference scenario is a prerequisite for moving SAI discussions from abstract debate to concrete evaluation.

This activity involves developing a comprehensive, internally consistent reference scenario for early-stage SAI deployment. The scenario encompasses four integrated components: 

1. Scenario definition — specifying a plausible deployment ramp (or ramps), sulfur precursor selection and quantities, injection altitudes, and supply chain logistics.
2. Delivery and dispersal engineering — including aeronautical trade studies for aircraft platform selection, injection system design, and plume evolution analysis.
3. Observing system design — defining the monitoring architecture needed to track actual deployment outcomes.
4. Data assimilation and feedback control prototyping — developing a working system to estimate actual intervention effects in real time and adjust deployment strategy accordingly.

The output will be packaged as a timestamped, publicly available release, including an executive summary accessible to non-technical audiences, a comprehensive main report documenting assumptions and derivations, detailed technical appendices, and open-source code and data wherever possible. Critically, the scenario will explicitly identify uncertainties and variants — showing how different plausible choices (e.g., different injection locations or altitudes) would affect feasibility, costs, and controllability. The reference scenario will undergo rigorous independent technical review by experts across the relevant fields before public release, and researchers will message-test the communication framing to ensure the scenario is understood as an illustrative engineering study rather than advocacy for or against deployment.