The lifetime of a glacier, an enormous slow-moving river of ice, can span many thousands of years. And while glaciers are dynamic, changes to their length and volume happen at an extremely sluggish pace. However, over the last century a number of glaciers in mountain regions around the world dwindled significantly, diminishing in size.
And a new study found with 99 percent certainty that climate change is driving their retreat, or shrinkage, with the likelihood of any other factor causing such dramatic change estimated at 1 in 100,000, the researchers found. This is the first analysis to connect individual glacier retreat to the effects of recent, global climate change.
The scientists investigated 37 glaciers representing five geographic regions: Europe, Scandinavia, Asia, North America and the Southern Hemisphere. They delved into 130 years of records that documented glacier length and mass; how far the glaciers had advanced, or grew, in the past; and how much they retreated. The researchers also noted patterns in local precipitation and temperature that might have affected a glacier’s size and movements.
"The big thing that we focused on was the natural fluctuations of glaciers that would have happened even without climate change," study co-author Gerard Roe, a professor of Earth and Space Sciences at the University of Washington in Seattle, told Live Science.
Roe and his colleagues applied their data to a statistical ratio known as "signal-to-noise," defining the "signal" as fluctuations driven by climate change, and "noise" as the more abundant weather-sensitive fluctuations that a glacier would normally undergo from year to year. This allowed the researchers to predict if each glacier’s current state of reduced ice would have happened even without climate change.
They found that glaciers lost far more ice than could be explained by normal conditions. In some cases, glaciers retreated 10 to 15 times the distance that they would have, were climate change not a factor.