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Pollution likely caused historic glacial retreat

An Environment Canada report to the United Nations indicates British Columbia is currently meeting its legislated targets to cut greenhouse gas pollution. Peter Holy/NASA

TORONTO – In the early 14th century right through to the mid-19th century, glaciers around the world expanded and annual temperatures in the Northern Hemisphere dropped by about 0.6 C.

This period, known as the Little Ice Age wrecked havoc across central Europe, particularly England.

However, between 1860 and 1930, records showed that glaciers in the Alps retreated by almost a kilometre, something not witnessed in the previous few hundred years. More interesting was the fact the temperatures didn’t warm, but rather continued to cool.

Over the years, glaciologists and climatologists have been struggling to determine why the retreat took place, despite the conflict between climate and glacial records.

“Something was missing from the equation,” said Thomas Painter, a snow and ice scientist at NASA’s Jet Propulsion Laboratory in Pasadena, Calif., who led the study.

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“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. This result suggests that human influence on glaciers extends back to well before the industrial temperature increases.”

A NASA-led team of scientists are now suggesting that soot from the use of coal – which increased during the 1860s – is the answer.

The researchers claim that black carbon – which is the strongest sunlight-observing particle – settled on the glaciers and sped up the melting process, exposing the underlying glacier ice to sunlight and warmer temperatures earlier in the year. As the snow melted, the glaciers melted faster and faster.

“We must now look more closely at other regions on Earth, such as the Himalaya [mountains], to study the present-day impacts of black carbon on glaciers in these regions,” said Georg Kaser, a study co-author from the University of Innsbruck, Austria, and lead author of the Working Group I Cryosphere chapter of the Intergovernmental Panel on Climate Change’s upcoming Fifth Assessment Report.

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

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