Sunday, May 13, 2012

Was Little Ice Age Caused By Increased Volcanism In The Middle Ages?

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Was Little Ice Age Caused By Increased Volcanism In The Middle Ages? - Red Orbit

 A large part of the Northern Hemisphere was in the midst of an unusual cold snap for nearly 500 years, from the Middle Ages through the early 19th century, in what scientists now call the “Little Ice Age.”

A new study, published in the journal Geophysical Research Letters, has probed the longstanding mystery of when this event actually began, what caused it and how it was sustained for such a long period.

Gifford Miller, a climatologist at the University of Colorado at Boulder and lead author of the study, said there has been a vague consensus by experts on when this period of cooling actually began, with estimates ranging from the 13th century to the 16th century.

EARTH Magazine reports that, to narrow the date of onset, Miller and colleagues used radiocarbon dating on dead vegetation emerging from the ice caps on Baffin Island in the Canadian Arctic to get a clearer understanding on when the cooling may have begun. Their dating methods revealed a number of dates that clustered around two distinct periods of time: 1275 and 1450.

“Everybody tends to think of this as a gradual cooling, so we were quite surprised when we got the dates back,” said Miller, adding that during both cooling events, plants at lower elevations froze at nearly the same time as those at higher elevations, indicating a fairly rapid onset.

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