04-02-12 Little Ice Age began with a bang

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 in Geophysical Research Letters.We have been able to identify the beginning of the Little Ice Age,something thats been very difficult to do in the past,says Gifford Miller,a paleoclimatologist and geologist at the University of Colorado Boulder.This cooling wasnt gradual;it was an abrupt shift.Its 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 Londons frozen River Thames became popular.To pin down when this climate change began,Millers 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 Baffins 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.