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... New analyses of tree ring data, ice cores and historical accounts suggest that a powerful volcanic eruption somewhere in the tropics around 1345 sent clouds of ash around the world, darkening the skies over Europe, researchers report December 4 in Communications Earth & Environment.

The ash lingered through several growing seasons, turning Europe's climate colder and wetter -- and that, in turn, caused widespread crop failure across southern Europe and the Mediterranean region. Grain became scarce and prices skyrocketed. Famine gripped the region. ...

To ease the burden of starvation, in 1347 many of Italy's city-states, including Venice and Genoa, decided to import grain from the Mongol-controlled lands around the Black Sea and the Sea of Azov.

That lifesaving grain wasn't the only cargo the Italian trade ships brought back. A strain of the bacterium Yersinia pestis, which had originated in the steppes of central Asia around 1338, was by 1347 spreading through the wild rodent populations around the Black Sea.

And, the researchers note, the routes of the trade ships delivering grain from port to port around the Italian peninsula closely tracks to the region's first plague outbreaks in 1347. ...

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