The Black Death may have been triggered by a medieval volcanic eruption

A volcanic eruption in 1345 may have set off a chain reaction that eventually led to the arrival of the Black Death in Europe, according to the latest research. The cooling and rainy years that followed the eruption caused agricultural decline, and together with increased grain imports, the pathogen responsible for the plague also reached the continent.

A new study suggests that a previously unknown volcanic eruption around 1345 triggered the climate changes that ultimately led to the devastating European plague epidemic known as the Black Death, Live Science reports.

Researchers claim that the eruption resulted in a cool and cloudy period in the Mediterranean region, which in turn reduced agricultural output. Due to shortages, Italian merchants began importing grain from the Black Sea region – and with it came the bacterium that causes bubonic plague.

A climatic turning point after 1345

Martin Bauch, a historian at the Leibniz Institute in Leipzig, and Ulf Büntgen of the University of Cambridge mainly sought to answer why the plague reached Europe specifically in 1347, and why it entered via Italy.

Historical sources record reduced sunlight, dense cloud cover and an extraordinary lunar eclipse between 1345 and 1349 in both Asia and Europe.

Palaeoclimatological analyses indicate that sulphur levels in polar ice also increased, pointing to an eruption in the tropics. Although the exact location remains unknown, the impact was enormous – bringing cooling followed by prolonged periods of rain.

Cold summers and poor harvests

European tree-ring studies show that between 1345 and 1347 summers were colder, and autumns far wetter, leading to soil erosion and flooding. Historical accounts clearly indicate that harvests of grapes and grain declined, especially in Italy.