Soot billowing across Western Europe during the Industrial Revolution may have caused the abrupt and unexpected retreat of European glaciers during a climatically cool period in the 19th century, new research suggests. Mountain glaciers in the European Alps retreated by an average of nearly 0.6 miles (1 kilometer) between 1860 and 1930. This period falls at the end of Europe's so-called Little Ice Age, when temperatures dipped below average by about 1.8 degrees Fahrenheit (1 degree Celsius) across much of the continent. Now, researchers based at NASA's Jet Propulsion Laboratory in Pasadena, Calif., have honed in on the potential anthropogenic — or human-induced — causes of the retreat. This causes the surface to absorb significantly more heat than it otherwise would, which eventually thins the snow down to the glacial ice that sits below the surface layer, causing further retreat. To examine whether this effect would have been strong enough to induce the abrupt glacial retreat in the European Alps, the team analyzed ice cores collected from several European mountain glaciers and measured the levels of soot in various ice layers. 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. 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.
– This much isn't in dispute: The glaciers of the European Alps retreated by an average of 0.6 miles between 1860 and 1930. But why, especially when the temperature of the continent itself actually cooled in the same period? Now a team of scientists thinks it has the answer, reports LiveScience: Soot from the Industrial Revolution. All those coal-burning factories and homes blanketed the mountains with thick black "particulate carbon," say researchers at NASA's Jet Propulsion Lab in Pasadena. They concluded as much after drilling ice cores from the Alpine glaciers and measuring remnants of the black stuff, reports Discovery, which explains the melting process thusly: "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." That exposed the glacier's underlying ice, which melted, too. If not for the soot, the glaciers would have kept expanding until about 1910, say the scientists, according to the LA Times.