Overview
- Tree‑ring records across Europe and sulfur spikes in Greenland and Antarctic ice cores point to a major tropical eruption around 1345 that cooled the Mediterranean.
- Archival sources describe 1345–47 harvest failures and soaring grain prices from Spain to the Levant, prompting Venice and Genoa to secure emergency shipments from the Black Sea in 1347.
- The authors propose fleas surviving on grain dust ferried Yersinia pestis into ports, with early outbreaks in Messina, Genoa, Marseille and Venice aligning with the arrival and redistribution of shipments.
- Several large cities that did not rely on imports, including Rome and Milan, show little evidence of early outbreaks, supporting an import‑linked transmission route.
- The scenario is presented as plausible rather than proven, the responsible volcano remains unidentified, and external experts say the work clarifies how climate shocks interacting with trade can elevate pandemic risk.