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Study: Volcanoes Triggered Little Ice Age

Gifford Miller

Gifford Miller collects dead plant samples from beneath a Baffin Island ice cap. Miller led a new study which indicates the Little Ice Age began roughly A.D. 1275 and was triggered by repeated, explosive volcanism that cooled the atmosphere. (Credit: Gifford Miller, University of Colorado)

Scientists have debated about what caused the Little Ice Age, an unusually cool period that lasted for several centuries and ended in the late 19th century. Some have suggested it was caused by shiny aerosol particles from volcanoes blocking out a portion of sunlight; others have suggested the sun itself was shining less brightly; or, perhaps a bit of both. Until now, the experts couldn’t even agree on when it started. Estimates of onset have ranged from the 13th to the 16th century.

A new study published today in the journal Geophysical Research Letters might settle both questions in one fell swoop. The researchers, led by Gifford Miller, a climate scientist at the University of Colorado, Boulder, say new evidence from northern ice sheets suggests the Little Ice Age was triggered by a series of explosive volcanic eruptions between 1250 and 1300 A.D. The cooling effect from volcanoes is short-lived because aerosols rain out of the atmosphere in just a few years. But, according to Miller and his team, feedbacks with ocean circulation patterns and another set of eruptions 150 years later sustained the cooling.

According to a press release from the American Geophysical Union, which publishes the journal:

During the cool spell, advancing glaciers in mountain valleys in northern Europe destroyed towns. Famous paintings from the period depict people ice-skating on the Thames River in London and canals in the Netherlands, places that were ice-free before and after the Little Ice Age. There is evidence also that the Little Ice Age affected places far from Europe, including South America and China.

To find out how the researchers arrived at their results, read the study, Abrupt onset of the Little Ice Age triggered by volcanism and sustained by sea-ice/ocean feedbacks.

Joanna Foster writes in the New York Times Green blog that there’s a warning here about how quickly and durably global climate can be changed:

Bette Otto-Bliesner, a co-author of the study and a climatologist at the National Center for Atmospheric Research, suggested that the study has important implications for the modern-day climate change discussion.

“I think people might look at the Little Ice Age and think that all we need to save us from rising temperatures are some volcanic eruptions or the geo-engineering equivalent,” she said. “But when you see what happened when global temperatures dropped by just one degree and you look at current predictions of six or seven degree increases for the future, you realize how precarious things are for life as we know it.”

“I don’t see a lot of hope that we can somehow compensate for the climate trajectory we’re on,” she said.

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