As the Industrial Revolution began to pick up steam in Europe, the glaciers of the Alps retreated. However, the average temperature of the continent cooled at that time, which created a glacial melting mystery for scientists.
"Something was missing from the equation," Thomas Painter, of NASA's Jet Propulsion Laboratory said in a press release. Painter led a team of scientists that recently found a clue identifying the Alpine glacier's attacker.
Soot in the smoke billowing from coal-burning factories, steam engines and other sources seems to have sullied the white glaciers, causing them to melt, according to Painter's study published in the Proceedings of the National Academy of Sciences.
America's Top 10 Climate Change Polluters
Painter's team discovered the filthy fingerprint of Industrial Age soot in ice cores drilled from Alpine glaciers. The soot probably settled on the snow overlaying the glaciers and caused the insulating blanket of snow to heat up like a black car in the sun. After the snow melted, the underlying ice of the glacier was left open to the sunlight and melted as well.
The glaciers melted an average one kilometer (0.6 miles) between 1860 and 1930. However, Europe's average temperature dropped by nearly one degree Celsius (1.8 degrees F) during that same time.
"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, from the University of Innsbruck and co-author of the study.
IMAGE: Glacier Blanc in the Alps (Tom Corser, Wikimedia Commons)