Abstract Ice-core, dendrochronological, and climate-model evidence identifies an extraordinarily powerful volcanic eruption around 426 b.c.e. that produced severe multi-year cooling and increased precipitation through strong stratospheric aerosol forcing. Model results indicate sustained cooling and wetter conditions in Babylonia, incompatible with stable date cultivation and likely causing crop failure. Statistical analysis shows a sharp rise in land mortgage contracts in the Murašû Archive from Nippur in the years following the eruption. The pattern is interpreted as a bottom-up economic shock that strained landholders and contributed to wider political instability during the coup against Xerxes II.
