Study shows pollution melted glaciers even as temperatures cooled
By Summit Voice
FRISCO — Matching climate records with ice core samples, scientists say the rapid retreat of Alpine Glaciers in Europe at the end of the Little Ice Age was probably linked with the sudden accumulation of soot particles associated with the beginning of the industrial Age.
Soot from industrial sources and even from wildfires has recently been implicated in the darkening of the Greenland ice sheet, leading to increased surface melt.
The new study helps resolve what had been a puzzle, as the sudden glacier decline coincided with a period of cooling regional temperatures. Between 1860 and 1930, temperatures in Europe cooled by nearly two degrees, yet at the same time, any large valley glaciers retreated by an average of about 0.6 miles (1kilometer).
“Something was missing from the equation,” said lead author Tom Painter, a snow and ice scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California. The study was published Sept. 2 in the Proceedings of the National Academy of Sciences.
The scientists already knew that Europe experienced profound economic and social changes during that era, burning coal in earnest and spewing huge quantities of black carbon and other dark particles into the atmosphere.
When black carbon particles settle on snow, they darken the surface. This melts the snow and exposes the underlying glacier ice to sunlight and relatively warm air earlier in the year, allowing more and faster melt.
“This study uncovers some likely human fingerprints on our changing environment,” said Waleed Abdalati, director of the Cooperative Institute for Research in Environmental Sciences at the University of Colorado Boulder.. “It’s a reminder that the actions we take have far-reaching impacts on the environment in which we live,” Abdalati said.
“We must now look closer at other regions on Earth, such as the Himalaya, to study the present-day impacts of black carbon on glaciers,” said Georg Kaser, a study co-author from the University of Innsbruck and lead author of the Working Group I Cryosphere chapter of the Intergovernmental Panel on Climate Change’s upcoming Fifth Assessment Report.
The researchers measured levels of carbon in ice cores drilled high in the Alps, extrapolating the data to estimate how much black carbon was deposited on glacial surfaces at lower elevations, where levels of black carbon tend to be highest.
Based on the data, the team developed computer models of glacier behavior, starting with recorded weather conditions and adding the impact of lower-elevation black carbon. By including this impact, the simulated glacier mass loss and timing finally were consistent with the historic record of glacial retreat, despite the cool temperatures of the time.