New Evidence: Volcanic Eruption in 1345 May Have Helped Trigger the Black Death

Volcanic Cooling, Famine and a Pandemic: How a 1345 Eruption May Have Set Off the Black Death

New tree‑ring research suggests that one or more previously unrecognised volcanic eruptions in 1345 reduced incoming sunlight across southern Europe, producing unusually cold, wet summers from 1345 to 1347. That abrupt climate shock damaged harvests, contributed to famine, and helped create conditions that allowed the plague to reach and spread through medieval Europe.

Tree Rings and Written Records

Researchers analysed tree rings from the Pyrenees to reconstruct summer temperatures and moisture for the mid‑14th century. When those climate reconstructions were compared with contemporary written accounts, the authors found consistent evidence for reduced sunlight and cooler, wetter summers beginning in 1345—patterns commonly associated with volcanic aerosol emissions in the atmosphere.

Trade, Grain Shipments and Unintended Consequences

Italian maritime powers such as Venice, Genoa and Pisa responded to crop failures by importing grain along long‑distance trade routes across the Mediterranean and Black Sea. According to historians quoted in the study, grain shipments from regions controlled by the Golden Horde in Central Asia likely carried rats whose fleas were infected with Yersinia pestis. These stowaways are widely considered a plausible vector for introducing bubonic plague to port cities and then inland.

"Powerful Italian city‑states had established long‑distance trade routes across the Mediterranean and the Black Sea, allowing them to activate a highly efficient system to prevent starvation," said Martin Bauch of the Leibniz Institute for the History and Culture of Eastern Europe. "But ultimately, these would inadvertently lead to a far bigger catastrophe."

Impact and Caution

The pandemic that followed—the Black Death—is estimated to have killed between 25 and 50 million people across Europe and neighbouring regions, with local mortality in some areas reaching as high as 60 percent. The new study does not claim a single cause; rather, it argues that an uncommon coincidence of environmental, economic and social factors may have aligned to facilitate the pandemic’s arrival and rapid spread.

Contemporary Relevance

Study co‑author Ulf Buentgen of Cambridge University warned that climate‑driven disruptions could increase the risk that zoonotic diseases emerge and spread in an interconnected world. He noted the parallels with recent global experience of pandemics such as Covid‑19 and urged careful monitoring of how climate variability and human mobility interact to shape disease risk.

Publication: The research was published in Communications Earth & Environment.