Stratospheric Aerosol Injection

Proposed deliberate climate interventions — principally stratospheric aerosol injection — would modify the atmosphere intentionally, at scale, with substantial but unequally distributed climate effects. The Intervention Leverage Index measures the ratio of cooling benefit per unit of aerosol deployed against the probability of adverse regional precipitation disruption — and reveals why the most effective emergency lever humanity possesses is also the most politically ungovernable.

Surveys the complete absence of international governance for climate geoengineering: no treaty, no authorising institution, no compensation framework — despite the US National Academies recommending a research programme in 2021.

Documents modelling evidence that northern-hemisphere SAI reduces African and Asian monsoon rainfall by 5–10%, affecting the food security of 2.4 billion people in countries that are not among those most likely to initiate deployment.

Examines the SCoPEx cancellation and the Saami Council objection as a case study in the governance vacuum, demonstrating that no existing institution has the authority to authorise, regulate, or compensate for the effects of deliberate climate intervention.

Uses the 1991 Pinatubo eruption as a natural analogue to introduce stratospheric aerosol injection, establishing the Intervention Leverage Index and the asymmetry between its cooling capacity and its governance requirements.