“I think the lesson from this is that persistent [climate] perturbation of a few decades had a consequence that lasted centuries. That’s the way the climate system works, with thresholds and feedbacks. Unless we understand them well, we should be careful what we do.”
Volcanic eruptions kick-started the Little Ice Age, and resulting changes in Arctic sea ice helped prolong the extended cooling, according to a new study.
The research, which draws on samples of ancient plants, ice cores, sediment cores and computer modeling, offers an answer to a long-standing climate puzzle.
Scientists agree that the Little Ice Age ended in the mid-19th century but have struggled to reach consensus on when and why the period of widespread cooling, centered in northern Europe, commenced. Prior studies place the beginning of the Little Ice Age anywhere from the 13th to the 16th century.
“The original concept of the Little Ice Age comes out of the Swiss Alps and Norway, where glaciers advanced and overrode villages” in the 1500s, said lead author Gifford Miller, a geologist at the University of Colorado’s Institute of Arctic and Alpine Research. “The dilemma there is that those events must occur well after the cold time begins, because the glacier has to accumulate mass and start to flow. It’s extremely difficult to date the onset of the cold.”
But that’s exactly what Miller and his colleagues in Iceland, Scotland and the United States believe they’ve done.
Their analysis, published this week in the journal Geophysical Research Letters, suggests that the Little Ice Age began relatively abruptly, with a series of four huge volcanic eruptions in the tropics between A.D. 1275 and 1300.
Each eruption sent a massive cloud of sulfur particles high into the atmosphere, where they cooled the planet by deflecting sunlight away from the Earth.
One such eruption can cool the atmosphere for up to three years, Miller said, but its cooling influence on the ocean can linger for decades…