By Dr. Tim Sandle
SCIENCE EDITOR
December 13, 2025
People watch lava at a volcanic eruption at Litli Hrutur near Reykjavik, Iceland
- Copyright AFP Kristinn Magnusson
The Black Death, also known as the Bubonic Plague, was a devastating pandemic that occurred in Europe from 1346 to 1353, resulting in the deaths of millions, possibly 50% of Europe’s population at the time. Since then there have been repeated outbreaks, such as the plague pandemic that swept through India towards the end of the nineteenth century.
The plague and its disease-causing bacterium (Yersinia pestis) are with us today. Currently, Peru, the Democratic Republic of the Congo and Madagascar are the so-called ‘plague hotspots’ in the world today. Such is the continual concern, I wrote an academic paper a few years ago titled “Could the ‘Black Death’ Become a Re-Emerging Infectious Disease?”
What triggered the Black Death is a subject that fascinates historians. Could a climate disaster have been the cause?
A newly analysed set of climate data points to a major volcanic eruption that may have played a key role in the Black Death’s arrival. Cooling and crop failures across Europe pushed Italian states to bring in grain from the Black Sea. Those shipments may have carried plague-infected fleas. The study ties together tree rings, ice cores, and historical writings to reframe how the pandemic began.
This new theory comes from the academics Martin Bauch (Leibniz Institute for the History and Culture of Eastern Europe) and Ulf Büntgen (Department of Geography, University of Cambridge), who have evaluated research on tree ring growth from eight regions in Europe, measurements of volcanic sulphur preserved in Antarctic and Greenland ice cores, and written reports from the fourteenth century.
The Black Death, also known as the Bubonic Plague, was a devastating pandemic that occurred in Europe from 1346 to 1353, resulting in the deaths of millions, possibly 50% of Europe’s population at the time. Since then there have been repeated outbreaks, such as the plague pandemic that swept through India towards the end of the nineteenth century.
The plague and its disease-causing bacterium (Yersinia pestis) are with us today. Currently, Peru, the Democratic Republic of the Congo and Madagascar are the so-called ‘plague hotspots’ in the world today. Such is the continual concern, I wrote an academic paper a few years ago titled “Could the ‘Black Death’ Become a Re-Emerging Infectious Disease?”
What triggered the Black Death is a subject that fascinates historians. Could a climate disaster have been the cause?
A newly analysed set of climate data points to a major volcanic eruption that may have played a key role in the Black Death’s arrival. Cooling and crop failures across Europe pushed Italian states to bring in grain from the Black Sea. Those shipments may have carried plague-infected fleas. The study ties together tree rings, ice cores, and historical writings to reframe how the pandemic began.
This new theory comes from the academics Martin Bauch (Leibniz Institute for the History and Culture of Eastern Europe) and Ulf Büntgen (Department of Geography, University of Cambridge), who have evaluated research on tree ring growth from eight regions in Europe, measurements of volcanic sulphur preserved in Antarctic and Greenland ice cores, and written reports from the fourteenth century.
Italy in medieval times. Image by Tim Sandle
Together, these records point to a significant volcanic eruption somewhere in the tropics around 1345 CE (ice cores from Greenland and Antarctica show a large burst of sulphur into the stratosphere around 1345). The eruption appears to have increased atmospheric sulphur and ash, which contributed to colder and wetter conditions across southern Europe and the Mediterranean.
“This is something I’ve wanted to understand for a long time,” says Büntgen. “What were the drivers of the onset and transmission of the Black Death, and how unusual were they? Why did it happen at this exact time and place in European history? It’s such an interesting question, but it’s one no one can answer alone.”
Historical accounts describe widespread crop failures and famine during this period in Spain, southern France, northern and central Italy, Egypt, and the Levant. The post-volcanic climate downturn and trans-Mediterranean famine prompted Italian maritime powers — such as Venice, Genoa and Pisa — to negotiate a ceasefire in a conflict with the Mongols of the Golden Horde (around the Sea of Azov, also referred to as the Kipchak Khanate) so they could secure grain shipments from the Black Sea region around 1347 CE.
A few months later, Venetian ships were sailing to Tana, near the mouth of the Don River, and to Asia Minor to secure grain. Also supporting this premise is the fact that Milan, Rome, and several grain‑producing centres in the Po Valley and along the Adriatic coast did not import Black Sea grain during 1347 and 1348. Consequently, these regions saw little or no plague during this initial phase.
The researchers point out that Venetian sources suggest that these imports helped prevent mass starvation. However, the timing of arriving grain ships and the first plague outbreaks in cities that received them raises another possibility.
Fleas carrying Y. pestis may have travelled with the grain. As the shipments were moved to additional cities, including Padua, these fleas could have helped accelerate the spread of the Black Death throughout Europe.
What is known is that the first human plague cases in Venice were reported less than two months after the arrival of the last grain ships.
The authors conclude, in their research paper, that this combination of climatic disruption, famine, and grain transport offers a plausible explanation for how the Black Death began and spread across Europe.
The findings appear in the journal Communications Earth, with the research titled “Climate-driven changes in Mediterranean grain trade mitigated famine but introduced the Black Death to medieval Europe.”
Together, these records point to a significant volcanic eruption somewhere in the tropics around 1345 CE (ice cores from Greenland and Antarctica show a large burst of sulphur into the stratosphere around 1345). The eruption appears to have increased atmospheric sulphur and ash, which contributed to colder and wetter conditions across southern Europe and the Mediterranean.
“This is something I’ve wanted to understand for a long time,” says Büntgen. “What were the drivers of the onset and transmission of the Black Death, and how unusual were they? Why did it happen at this exact time and place in European history? It’s such an interesting question, but it’s one no one can answer alone.”
Historical accounts describe widespread crop failures and famine during this period in Spain, southern France, northern and central Italy, Egypt, and the Levant. The post-volcanic climate downturn and trans-Mediterranean famine prompted Italian maritime powers — such as Venice, Genoa and Pisa — to negotiate a ceasefire in a conflict with the Mongols of the Golden Horde (around the Sea of Azov, also referred to as the Kipchak Khanate) so they could secure grain shipments from the Black Sea region around 1347 CE.
A few months later, Venetian ships were sailing to Tana, near the mouth of the Don River, and to Asia Minor to secure grain. Also supporting this premise is the fact that Milan, Rome, and several grain‑producing centres in the Po Valley and along the Adriatic coast did not import Black Sea grain during 1347 and 1348. Consequently, these regions saw little or no plague during this initial phase.
The researchers point out that Venetian sources suggest that these imports helped prevent mass starvation. However, the timing of arriving grain ships and the first plague outbreaks in cities that received them raises another possibility.
Fleas carrying Y. pestis may have travelled with the grain. As the shipments were moved to additional cities, including Padua, these fleas could have helped accelerate the spread of the Black Death throughout Europe.
What is known is that the first human plague cases in Venice were reported less than two months after the arrival of the last grain ships.
The authors conclude, in their research paper, that this combination of climatic disruption, famine, and grain transport offers a plausible explanation for how the Black Death began and spread across Europe.
The findings appear in the journal Communications Earth, with the research titled “Climate-driven changes in Mediterranean grain trade mitigated famine but introduced the Black Death to medieval Europe.”
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