There is a complex interplay of environmental and societal factors that contributed to the onset of the Black Death in the mid-14th century. It is a pandemic that caused one of the greatest mortality crises in human history. Earlier research has focused on the late antique period, specifically volcanic eruptions and climatic downturn preceding the Justinianic plague; less attention has been given to the major but previously undetected volcanic event around 1345 CE and its possible role in creating the conditions that allowed the second plague pandemic to occur. Understanding how climate disturbances, famine, and socio-economic systems interacted during the 1340s is important to explaining why the Black Death erupted when and where it did and why it proved so devastating for Europe, the Middle East, and the Mediterranean.
The aim of this study was to determine whether a combination of volcanic-induced climate anomalies and subsequent socio-economic responses contributed to the emergence and rapid spread of plague in 1347 CE. The researchers sought to evaluate how climate cooling, agricultural failure, famine, and long-distance maritime grain trade created conditions that enabled Yersinia pestis, most likely carried by fleas in grain cargo, to spread.
Researchers used an interdisciplinary method that combines paleoclimatology, dendrochronology, and historical documentary analysis. Climate conditions were reconstructed using maximum latewood density (MXD) measurements from tree rings collected in 8 European regions. It was standardized as z-scores relative to 1300 to 1346 CE. These data were compared with ice core-derived estimates of volcanic sulphur injection to detect main eruptions and their temporal correlations with climate anomalies. Historical sources like chronicles, administrative records, poetry, grain price data, trade documents, and climate-sensitive grape harvest records were analyzed to reconstruct weather conditions, famine severity, grain supply methods, and economic stresses between 1345 and 1349 CE. This integration of natural and documentary evidence allowed for a detailed assessment of climate impact on agriculture and the reconstruction of grain trade patterns immediately preceding the first plague outbreaks in the Mediterranean ports.
The result shows that around 1345 CE, a major volcanic eruption or series of eruptions released around 14 Tg of sulphur into the stratosphere, causing substantial atmospheric disturbances and cooling in Eurasia from 1345 to 1347 CE. Tree ring evidence, like the rare occurrence of consecutive “Blue Rings” in the Pyrenees, indicates a severe decrease in summer temperature. MXD-based reconstructions reveal that 1345 to 1347 CE was the coldest period in the Northern Hemisphere extra-tropics since the major Samalas eruption of 1257 CE.
Historical accounts indicate extreme weather events such as cold, wet summers in Italy and France, drought and locust infestation in Lebanon, and heavy precipitation and flooding in central and northern Italy. These climatic anomalies led to widespread agricultural failure across large parts of Europe and the Mediterranean, which produced a transregional famine from 1346 to 1347 CE. As local harvests collapsed, grain production elsewhere rose to its highest levels in decades, and Italian city-states, already highly urbanized and reliant on imported grain, activated emergency supply networks to prevent starvation. Venice, Genoa, and Pisa increasingly sourced grain from the Black Sea region controlled by the Golden Horde.
The study suggests that grain ships returning to Venice in 1347 CE carried plague-infected fleas that survived the voyage by feeding on grain dust, coinciding with the first recorded plague cases two months later. Cities that did not rely on Black Sea grain imports, like Milan, Rome, Verona, Ferrara, and Bari, escaped the earliest plague wave, while ports deeply integrated into this trade network, like Marseille, Mallorca, Tunis, and numerous Italian coastal cities, experienced some of the first outbreaks. This pattern aligns with documented grain shipment routes and supports the hypothesis that emergency grain trade served as a primary transmission pathway for Yersinia pestis.
As per this study, the Black Death resulted from a rare combination of volcanic climatic abnormality, severe starvation, and long-distance grain import networks. All this accidentally brought the disease of Mediterranean ports. The grain systems that had previously ensured Italian food security surprisingly increased disease spread under climate duress. These findings illustrate how climate changes can interact with socioeconomic systems to create major crises, providing insights into climate-disease dynamics relevant to today’s globalized and warming world.
Reference: Bauch M, BĂĽntgen U. Climate-driven changes in Mediterranean grain trade mitigated famine but introduced the Black Death to medieval Europe. Commun Earth Environ. 2025;6:986. doi:10.1038/s43247-025-02964-0
