A wave of volcanic cold, a hungry Mediterranean, and a desperate scramble for grain may explain why the Black Death hit Europe, according to a new study in Communications Earth & Environment.
The authors argue that climate‑driven shifts in grain trade helped bring the plague bacterium into Italian ports in 1347 and turned a regional disease into a continent‑wide catastrophe.
The Black Death killed a large share of Europe’s population between 1347 and 1353, but historians and scientists still debate why it erupted so suddenly and spread so fast. This new research links that crisis to an earlier one: a powerful volcanic eruption, or cluster of eruptions, in the mid‑1340s.
“This is something I’ve wanted to understand for a long time,” said study co-author Ulf Büntgen from Cambridge’s Department of Geography. “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.”
According to the study, ice cores from Greenland and Antarctica show a large burst of sulphur into the stratosphere around 1345, on a scale comparable to some of the biggest eruptions of the past 2,000 years. Tree‑ring records from eight regions across Europe then reveal a string of unusually cold summers from 1345 to 1347, the coldest such run in the Northern Hemisphere since the famous Samalas eruption in 1257. Written sources from Europe and the Middle East describe dimmed skies, “foggy” conditions, harsh winters, floods, droughts, and locust swarms in roughly the same window.
The researchers argue that, taken together, these records point to a sharp climate downturn just before the plague arrived. For farmers from Spain to the Levant, that meant repeated harvest failures and mounting hunger.
And as all those European farmers grew less grain, prices began to rise.
Grain prices from Catalonia, several Italian cities, Cairo, and Mecca all show a major spike in 1347, the highest level in at least eight decades in these records. Detailed historical records show that city governments responded with emergency measures such as forced loans, strict regulations on grain sales, and new bans on exports.
Late medieval Italy, with its dense network of city‑states, was especially vulnerable. Urban populations had long outgrown their local fields, and cities relied on complex import systems to keep granaries stocked. Since the 13th century, Venice, Genoa, and Pisa had built far‑flung grain links across the Mediterranean into Apulia, Sicily, Sardinia, North Africa, and the Aegean.
“For more than a century, these 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,” explained Dr Martin Bauch, a historian of medieval climate and epidemiology, in a press release. “But ultimately, these would inadvertently lead to a far bigger catastrophe.”
When nearby regions also suffered bad harvests in the mid‑1340s, those normal suppliers could no longer meet demand. So, they decided to turn to old enemies and initiated trade talks. Commerce and money can thaw the frostiest of relationships.
Documents from Venetian and Tuscan archives show the crisis escalated quickly, so Venice resumed trade with the Mamluk sultanate in Egypt with papal approval and ordered a giant grain ship to be built. As shortages worsened, authorities requisitioned private vessels and poured public money into grain purchases. In April 1347, Venice agreed to a “ceasefire” and lifted a trade embargo on the Mongol Golden Horde, opening the way to new sources of grain around the northern Black Sea and the Sea of Azov.
A few months later, Venetian ships were sailing to Tana, near the mouth of the Don River, and to Asia Minor to secure grain. In later testimony, officials said bluntly that grain from the Black Sea had saved the city from starvation in 1347.
“Upon return in the second half of 1347 CE, the Italian trade fleets, however, not only brought grain back to the Mediterranean harbours, but also carried the plague bacterium Yersinia pestis most likely via fleas that were feeding on grain dust during their long journey,” the study authors write. “The first human plague cases in Venice were reported less than two months after the arrival of the last grain ships.”
Contemporary chronologies place early outbreaks in Messina, Genoa, and Marseille in the autumn and winter of 1347, followed by Palma de Mallorca and Venice around the turn of the year. Inland cities such as Florence, Siena, and Padua report their first cases through 1348, often after new grain shipments arrived from afflicted hubs.
The study argues that this is not a coincidence. Yersinia pestis is now known to have spread from wildlife reservoirs in Central Asia along trade routes to the northern Black Sea region in the early 1340s. Fleas that carry the bacterium can survive for long periods without feeding on warm‑blooded hosts, especially if they can draw some sustenance from grain dust and other material in cargo holds.
The authors suggest that emergency grain imports from the Golden Horde in 1347, organized specifically to cope with the famine, created a direct, high‑volume link between plague‑endemic regions and Italian ports. Once the disease landed in places like Venice and Genoa, their own grain redistribution systems, designed to shore up food security in smaller cities, helped drive the infection inland. Padua’s outbreak, for example, follows closely after Venice authorizes grain exports there in early 1348, and Trento’s epidemic arrives after further Venetian shipments up into the Alps.
Meanwhile, the pattern of cities that appear to have escaped the first wave is telling.
“And yet, we could also demonstrate that many Italian cities, even large ones like Milan and Rome, were most probably not affected by the Black Death, apparently because they did not need to import grain after 1345,” explained Bauch. “The climate-famine-grain connection has potential for explaining other plague waves.”
Since Milan, Rome, and several grain‑producing centres in the Po Valley and along the Adriatic coast did not import Black Sea grain in 1347 and 1348, they saw little or no plague in that initial phase.
On the surface, this all makes sense, but the study authors admit there are a few holes that need to be plugged. Most importantly, the volcano itself remains unidentified. Ice cores clearly show a large sulphur injection around 1345, and written accounts of darkened skies support the idea of a major eruption, but there is no agreement yet on which volcano was responsible.
Moreover, medieval observation and centuries-old archival records are limited and patchy at best. It is unclear if proper records were kept, and written accounts have gone missing over the years. The apparent absence of Black Sea grain imports or early plague in some towns may reflect missing documents rather than be evidence for Asian grain shipments and killer bacteria making the rounds.
The authors are cautious on these points, stressing that they are reconstructing the “most likely” pathway rather than claiming a single proven cause. Still, as with any investigation, the collection of climate data, food prices, political decisions and the geography of early outbreaks all point in the same direction. It’s not a smoking gun, but it is a tightly argued scenario of how climate, trade and disease intertwined to produce one of the greatest crises in medieval Europe.
MJ Banias covers space, security, and technology with The Debrief. You can email him at mj@thedebrief.org or follow him on Twitter @mjbanias.