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. (Read more discoveries stories.)