The research, which involved a
The Little Ice Age was a relatively recent few-hundred-year period of long, severe winters across much of the planet. Glaciers encroached on mountain villages and rivers and harbors froze over.
Between 1860 and 1930, large glaciers in the Alps retreated an average of nearly 1 kilometer while temperatures in that region actually dropped nearly 1.8 ° Fahrenheit (1 degree Celsius), according to
"Something was missing from the equation," said
The researchers looked to history for answers.
To figure out how much black carbon was in the air and the snow when the Alpine ice began to dissipate, the researchers examined records from ice cores drilled from several European mountain glaciers. They used the amount of carbon particles in the ice core layers to estimate how much black carbon landed on the lower parts of the glaciers where melting occurred.
Then the team ran computer models of glacier behavior, starting with recorded weather conditions and adding the new black carbon data.
"Our model treats the sunlight photons like pinballs bouncing through the ice crystals that make up the snow," Flanner said. "Every once in a while, one of the photons encounters a dark soot particle, which absorbs it and heats up."
Once they knew the increase in glacier heating, they were able to simulate glacier mass loss and timing in a way that mirrored historic glacier records-despite the cooling that occurred during that period. The results provide strong evidence that the Little Ice Age, as defined by glacier length, ended in
"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," Painter said. "This result suggests that human influence on glaciers extends back to well before the industrial temperature increases."
"It's interesting that soot had a larger effect in19th century
While the study was focused on explaining the past, the findings could be relevant now in places like
"The retreat of glaciers in the Alps has long been a focal point of exploration of changes in the Earth system," said
"We must now look closer at other regions on Earth, such as the present-day impacts of black carbon on glaciers in the Himalaya."
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