A dramatic climate shift may have pushed medieval Europe into turmoil. A volcanic eruption around the tropics likely caused cooler summers, damaging harvests and changing trade routes.
This shift may have helped the plague reach Mediterranean ports in 1347. A recent study connects these climate changes to Italy’s grain shortages and a pandemic that wiped out up to 60% of the population in some areas.
Climate Shock Disrupted Europe
In the mid-1340s, heavy clouds darkened the Mediterranean skies. Farmers suffered first as crops failed. Cities like Venice and Genoa quickly adapted, sourcing grain from the Black Sea to avoid famine.
Martin Bauch, a historian at the Leibniz Institute, studies these environmental crises. He highlights how the colder summers and increased rain flooded fields and damaged crops. As city-states grew larger and hungrier, a few harsh years tightened food supplies, leading officials to negotiate new trading routes.
Cloud patterns hinted at significant climate change, as dark skies hinted at aerosols reflecting sunlight. This made summers cooler and affected harvests across Italy.
Grain Ships and Disease Spread
As grain began to move, the risk of disease increased. Fleas thrive in packed environments, easily moving from grain ships to rodents and then to people. Research shows that fleas can live off wheat flour, making them resilient during long journeys.
By 1347, ships returning to Venice and Genoa brought not just grain but also news of plague outbreaks in port cities. Bauch notes that these shifts in trade saved many from starvation but also spread the plague rapidly through Europe.
Evidence of Climate Change
Ice core samples from around 1345 show a significant volcanic eruption. Estimates indicate that around 14 teragrams of sulfur were injected into the stratosphere, indicating a serious climate disturbance.
Tree rings depict some of the coldest summers in Europe during those years. Market records show rising grain prices and tight controls as city leaders scrambled to maintain order amid food shortages.
Aftermath of the Climate Shock
This combination of factors—climate change, famine, and trade—created a vulnerable situation for Europe. In crises, city leaders often act faster and take risks they wouldn’t normally consider. Merchants seized the moment to advocate for new trading routes, pushing through stalled agreements.
Ongoing Risks and Lessons
Plague remains a zoonotic disease, existing in wildlife reservoirs. It can reappear under favorable environmental conditions. A comprehensive review highlights how these reservoirs sustain the pathogen between human outbreaks.
Recent findings trace the plague’s ancestor to cemeteries near Lake Issyk-Kul in Kyrgyzstan around 1338, aligning with trade links from that region later on.
Bauch emphasizes that while we can’t pinpoint the exact volcanic eruption, its effects remind us of a critical lesson for today. Climate extremes and shifts in trade could still redirect diseases in our interconnected world, making effective risk management essential.
This study is available in the journal Communications Earth & Environment.
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