Soot from the mid-1800s may be to blame for the retreat of mountain glaciers in the European Alps.

According to a new study published in the Journal Proceedings of the National Academy of Sciences, soot, or black carbon, produced during the period of rapid industrialization caused the abrupt retreat of mountain glaciers after the long cold spell known as the Little Ice Age.

"Before now, most scientists have believed the end of the Little Ice Age in the 1800s was due to a natural climatic shift, distinct and well before emissions of carbon dioxide reached levels that could start to influence climate and glaciers in the 20th century,” lead author Thomas Painter, a snow and ice scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif., said in a statement.

Between 1860 and 1930, large valley glaciers in the Alps abruptly retreated at an average rate of nearly 0.6 miles, even though temperatures actually dropped by 1.8 degrees Fahrenheit. During that time, mass industrialization from the coal, steel and rail industries in Western Europe spewed large amounts of coal in the atmosphere.

Black carbon, the strongest absorber of sunlight, settles on the lower parts of the mountain glaciers where temperatures are higher, causing them to melt. Scientists had previously thought there wasn’t enough soot that reached high enough to affect glacier melting, Nature.com reports.

“This study offers a very elegant and plausible explanation for the glacier conundrum. It appears that in central Europe soot prematurely stopped the Little Ice Age,” Andreas Vieli, a glaciologist at the University of Zurich in Switzerland who was not involved in the study, told Nature.com.

While the study sheds light on a period more than 100 years ago, the phenomenon continues to exist today, scientists say.

“It’s an ongoing concern — for the melting of the glaciers in the Himalayas, for reduced duration of the snowpack in the Sierra Nevada and Rocky Mountains and the impact that has on water supplies, as well as the more rapid melting of ice in the Arctic and in Greenland,” Richard A. VanCuren, an air particles expert with the UC Davis Air Quality Research Center, said.

Researchers came to the conclusion after studying data from ice cores drilled from 4,000 or so large and small Alpine glaciers to find out how much soot was in the atmosphere and snow when the Alps began to retreat.

“This study uncovers likely human fingerprints on our changing environment,” study coauthor Waleed Abdalati, director of the Cooperative Institute for Research and Environmental Sciences at the University of Colorado Boulder, said. “It’s a reminder that the actions we take have far-reaching impacts on the environment in which we live.”

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