Robust assessment of Solar Radiation Modification risks and uncertainties must include shocks and societal feedbacks

Abstract.

Conventional climate scenarios omit fast-timescale human-system dynamics like policy rollback or economic shocks. The climate system's slow response to GHG emissions allows these `fast' terms to be averaged out, a simplification that obscures event-driven risks. Solar Radiation Modification (SRM) invalidates this assumption: rapid, sub-decadal climate responses couple directly to fast political and societal dynamics. This creates an analytical problem: acknowledged primary risks of SRM (termination shock, geopolitical conflict, moral hazard) cannot be resolved in smooth pathways but require an event-based perspective. To address this, we propose the Solar Radiation Modification Pathway (SRMP) framework, introducing five typologies that define governing logic for human-physical system interactions across timescales. We illustrate how SRM-driven shocks could fundamentally divert trajectories from static SSP narratives, revealing limitations in frameworks that assume fixed socio-political contexts. The SRMP framework serves as a diagnostic tool identifying what must be represented for adequate SRM risk assessment. By naming dynamics that current architectures cannot capture, it establishes minimum conditions for assessment that represents the fundamental risks of real-world SRM deployment. If SRM is evaluated primarily through idealised "best-case'' scenarios, the research community risks providing a systematically distorted evidence base for decisions that could prove irreversible.