I have alway had this nagging suspicion that when sun spots are lowest the volcanic activity is higher, but have not found the data to confirm my suspicions.This paper reported on in Science News may prompt me to redouble my effort.
Frozen moss suggests climate cooling kicked off fast, possibly with help from volcanoes
The Little Ice Age, a centuries-long spell of cold summers in Europe and elsewhere, began suddenly late in the 13th century, a new study finds. A string of volcanic explosions may have set off this change in climate by belching particles that reflected sunlight and allowed Arctic sea ice to reach epic proportions, researchers report online January 31 inGeophysical Research Letters.
“We’ve been able to identify the beginning of the Little Ice Age, something that’s been very difficult to do in the past,” says Gifford Miller, a paleoclimatologist and geologist at the University of Colorado Boulder. “This cooling wasn’t gradual; it was an abrupt shift.”
It’s long been known that much of the globe became chillier during the Renaissance. By the 17th century, temperatures in the Northern Hemisphere had fallen by half a degree Celsius compared with medieval times. Ice skating on London’s frozen River Thames became popular.
To pin down when this climate change began, Miller’s team traveled to Baffin Island on the northern fringes of Canada. Small glaciers in this region tend to respond quickly to temperature changes. Carbon dating of moss entombed in Baffin’s ice revealed two sudden advances of the snow line that killed off the vegetation: a sudden cold spell between 1275 to 1300, followed by intensifying cold between 1430 and 1455.
Testing whether this chill extended beyond Canada took the researchers to the Langjökull glacier, the second largest ice cap in Iceland. Layered sediments from a nearby lake appeared progressively thicker in the 14th century — exactly what would be expected if the glacier expanded and ground away the landscape.
These chillier conditions began during an especially active time for volcanoes. “The second half of the 13th century had the most volcanism of any period of the past 1,500 years,” says Alan Robock, an atmospheric scientist at Rutgers University in New Brunswick, N.J.
Miller and his colleagues may not have noticed, is that both cooling periods occurred in sync with low sunspot activity. Those two periods of low sunspot activity are known respectively as the Wolf Minimum and the Sporer Minimum.