Industrially generated soot in the 19th century appears to have sparked the melting of glaciers in the Alps and put a halt to what’s known as the Little Ice Age, a new study has found.
A team of scientists led by NASA published the study in the September 3 issue of the journal Proceedings of the National Academy of Sciences. From 1860 to 1930, large valley glaciers in the Alps drew back suddenly by half a mile, on average, “to lengths not seen in the previous few hundred years,” NASA said in a statement.
"This study uncovers likely human fingerprints on our changing environment," study co-author Waleed Abdalati, director of the Cooperative Institute for Research and Environmental Sciences (CIRES) at the University of Colorado Boulder, said in the statement. "It's a reminder that the actions we take have far-reaching impacts on the environment in which we live."
The decades coincided with the drastic increase in the use of coal for home heating, public transport and manufacturing in Western Europe, NASA said, which spewed sunlight-absorbing black carbon and other dark particles into the atmosphere. This would absorb rather than reflect sunlight, and when the soot drifted down to coat the glaciers, they stopped reflecting heat and light, absorbing it instead—and melting.
The cycle didn’t end there, as the effects compounded, NASA said. Accelerated melting exposed the glacier ice to those elements earlier in the year, which in turn caused faster melt and retreat, the space agency said.
This effectively put a stop to what has been dubbed the Little Ice Age, when mountain glaciers expanded between the 14th and 19th centuries and temperatures in Europe dropped by a good 1.8 degrees Fahrenheit. However, during the decades in question, the temperatures kept dropping even as glaciers retreated. NASA said its study results explain the apparent discrepancy.
"Before now, most glaciologists believed the end of the Little Ice Age came in the mid-1800s when these glaciers retreated, and that the retreat was due to a natural climatic shift, distinct from the carbon dioxide-induced warming that came later in the 20th century,” said study leader Thomas Painter, a snow and ice scientist at NASA's Jet Propulsion Laboratory in Pasadena, in NASA’s statement. “This result suggests that human influence on glaciers extends back to well before the industrial temperature increases."
The study also has implications for current human practices and warming trends.
"We must now look more closely at other regions on Earth, such as the Himalaya, to study the present-day impacts of black carbon on glaciers in these regions," said Georg Kaser, one of the study’s co-authors and a researcher at the University of Innsbruck, Austria. He was also a lead author of the Working Group I Cryosphere chapter of the Intergovernmental Panel on Climate Change's upcoming Fifth Assessment Report.
Previous studies have shown that iconic Mount Everest is melting, along with glaciers in the rest of the Himalayas.
In addition, climatologists worldwide are concerned about the rapidity of the melting ice at both poles.