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Climate: Heat-trapping greenhouse gases the biggest driver of global glacier meltdown

‘In our data we find unambiguous evidence of anthropogenic contribution to glacier mass loss’

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Shrinking glaciers on the Dachstein Mountains in Austria will affect water supplies far downstream in local areas and in distant rivers. bberwyn photo.

Staff Report

FRISCO — Some of the world’s glaciers were shrinking before the onset of unchecked heat-trapping pollution, but the human factor in the glacial equation has grown exponentially in the past few decades.

A new modeling study led by scientists at the University of Innsbruck (Austria) shows that only about 25 percent of the global glacier mass loss during the period of 1851 to 2010 is attributable to anthropogenic causes. However, between 1991 and 2010 the fraction increased to about two-thirds.

“In the 19th and first half of 20th century we observed that glacier mass loss attributable to human activity is hardly noticeable but since then has steadily increased,” said researcher Ben Marzeion, explaining that scaled-down regional models can detect an anthropogenic influence in America and the Alps, where glacier changes are particularly well documented.

The ongoing global glacier retreat is raising sea level, changing seasonal water availability and increasing geo-hazards. But pinpointing the effects of greenhouse gases isn’t easy.

“Typically, it takes glaciers decades or centuries to adjust to climate changes,” said Marzeion, with the Institute of Meteorology and Geophysics of the University of Innsbruck.

The global retreat of glaciers observed today started around the middle of the 19th century at the end of the Little Ice Age,” he explained Glaciers respond both to naturally caused climate change of past centuries, for example solar variability, and to anthropogenic changes. The real extent of human contribution to glacier mass loss has been unclear until now.

Marzeion’s team of researchers simulated glacier changes during the period of 1851 and 2010 in a model of glacier evolution.

“The results of our models are consistent with observed glacier mass balances,” says Marzeion. All glaciers in the world outside Antarctica were included in the study. The recently established Randolph Glacier Inventory, a complete inventory of all glaciers worldwide, enabled the scientists to run their model. “The RGI provides data of nearly all glaciers on the Earth in machine-readable format,” said Graham Cogley from Trent University in Canada, one of the coordinators of the RGI and co-author of the current study/

Since the climate researchers are able to include different factors contributing to climate change in their model, they can differentiate between natural and anthropogenic influences on glacier mass loss.

“While we keep factors such as solar variability and volcanic eruptions unchanged, we are able to modify land use changes and greenhouse gas emissions in our models,” said Marzeion. “In our data we find unambiguous evidence of anthropogenic contribution to glacier mass loss.”

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