NPR: Michael Mann comments on "Could climate change have led to The Fall Of Rome?"

Could Climate Change Have Led To The Fall Of Rome?

by NPR STAFF, January 22, 2011

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EnlargeGregorio Borgia/AP

Ruins of the Villa of the Quintilii on the outskirts of Rome.

Rome may have more than a thousand years ago, but much of the civilization the Romans built still dots the landscape today. One team of scientists recently unearthed a different kind of Roman artifact that may hold a strange clue to the empire's downfall.

A study of tree rings recently published in the journal Science provides evidence of climate shifts that, perhaps not coincidentally, occurred from A.D. 250 to 550, a period better known as the fall of the Roman Empire.

Ulf Buentgen and his team of researchers at the Swiss Federal Institute for Forest, Snow and Landscape Research collected tree-ring data from ancient wood found in medieval castles and Roman ruins. They created a detailed history of climate change over the past 2,500 years and found the data point at the end of the Roman Empire as a period of exceptional climate change.

Michael Mann, professor of meteorology at Penn State, was not a member of the research team, but explains how the information found in tree rings changes what we know of the last centuries of Roman imperialism.

"They were able to tease out two pieces of information from these trees," Mann explains. "They can get some idea of how warm the summers were, and how wet the sort of late-spring/early summer was."

That's because trees create a new ring each year. A big ring occurs in times of good climate, and a small ring occurs in years of drought or extreme temperatures. Wood samples from this time period show a climate flip-flopping unpredictably, which would have been bad for the Roman Empire.

"Like any large civilization — including the civilization we have today — it was highly dependent on predictability of natural resources," Mann says. "It was very heavily adapted to the climate conditions that had persisted for centuries."

But while the tree rings show variability, there is no data for why these climate changes occurred. Global warming contributes to modern climate change, but Rome fell from power long before industrialization.

"Presumably it was some combination of these external natural factors like solar variability and volcanic eruptions, and just the pure sort of chaotic variability of the climate system," Mann speculates.

This new research may not establish cause-and-effect, but it does contribute another factor to explain Rome's fall. It also creates another clue for scientists sleuthing their way into an uncertain climate future.

Link:  http://www.npr.org/2011/01/22/133143758/could-climate-change-have-led-to-the-fall-of-rome