New research published in Communications Earth & Environment suggests that a major volcanic eruption or series of eruptions in the mid-14th century played a significant role in triggering the spread of the Black Death pandemic across Europe. The study combines paleoclimatic data and historical records to trace how climate events led to food shortages and, indirectly, to one of history’s deadliest outbreaks.
The researchers found evidence from ice core analyses that around 1345 CE, an unidentified tropical volcanic eruption injected about 14 teragrams of sulfur into the stratosphere—more than double the amount released by the 1991 Mount Pinatubo eruption. This event is believed to have caused a sharp cooling period in the Northern Hemisphere, with particularly severe impacts in southern Europe.
Tree-ring data from regions including the Alps and Pyrenees confirmed that 1345–1347 were among the coldest consecutive summers since 1257. In some areas, such as the Pyrenees, these cold conditions produced rare wood features known as "Blue Rings," indicating extreme freezing during growing seasons.
These environmental shocks resulted in widespread harvest failures and record-high wheat prices by 1347. In response to food shortages, Italian maritime republics like Venice and Genoa imported grain from Black Sea territories controlled by the Golden Horde. According to historical sources, these trade routes may have inadvertently transported plague-infected fleas into Mediterranean ports.
Venetian ships returning from the Black Sea reportedly brought grain—and possibly infected fleas—back to Italy in late 1347. Plague cases appeared in Venice within two months of these shipments. By contrast, cities such as Milan and Rome, which did not rely on Black Sea grain imports at that time, avoided the initial wave of infections.
The study highlights: "The sophisticated conventional Italian food security system, designed to provide resilience against dearth, paradoxically served as the gateway for the pandemic." The authors also caution that other transmission pathways or multiple introductions could have contributed and require further investigation.
The research concludes that environmental changes combined with globalized trade networks created conditions ripe for rapid disease spread. The authors state: "In an increasingly interconnected and warming world, climate shocks interacting with globalized trade networks are likely to raise the probability that zoonotic pathogens cross ecological and geographic boundaries," drawing parallels with recent pandemics.
This interdisciplinary approach aims to clarify longstanding debates about how climate variability may have influenced both timing and severity of historic pandemics such as the Black Death.
