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Fall of Roman Empire linked to wild shifts in climate
19:00 13 January 2011 by Michael Marshall

Centuries of unpredictable climate may have been partly to blame for the fall of the western Roman Empire. A detailed record of 2500 years of European climate has uncovered several links between changing climate and the rise and fall of civilisations.

Climate fluctuation was a contributing factor alongside political failures and barbarian invasions, says Ulf Büntgen of the Swiss Federal Institute for Forest, Snow and Landscape Research in Birmensdorf, Switzerland, who led the project.

Büntgen used tree rings to build up a history of European climate. Using nearly 9000 samples from oak, pine and larch, Büntgen and colleagues were able to reconstruct how temperatures and rainfall in western Europe changed over the last 2500 years.

Climate flips and Black Death

From AD 250 to 550, the climate flipped, from one decade to the next, between dry and cool, and warm and wet. "Such decadal changes seem to have the most impact" on civilisations, Büntgen says, because they harm agriculture but are not prolonged enough for people to adapt their behaviour.

The climatic turmoil coincided with political upheaval and waves of human migrations. By AD 500, the western Roman Empire had fallen.

In other notable periods, the relatively stable medieval society was characterised by more constant climatic conditions. But the Black Death coincided with a wet spell and the disease spreads faster in humid conditions.