The decades-long dwindling of glaciers is “categorical evidence of climate change,” a new study affirms.
The link between global warming and glacial retreat had previously garnered only a “likely,” or at least 66 percent probability, rating from the Intergovernmental Panel on Climate Change. Comparing the long-term decline of 37 glaciers, researchers estimate that all but one are “very likely” – or with at least 90 percent probability – the result of climate change.
Natural variability and complex dynamics make sussing out climate change’s role in glacial retreat difficult. Earth system scientist Gerard Roe of the University of Washington in Seattle and colleagues calculated the natural ups and downs of well-documented glaciers from around the world. The researchers then noted how far the glaciers have drifted from that natural variability and compared that trend with changes in the nearby climate.
For 21 out of the 37 glaciers, the researchers say it is “virtually certain” that climate change caused the glaciers’ retreat, the researchers report December 12 in Nature Geoscience. Glaciers hold about 75 percent of Earth’s freshwater and their decline serves as a canary in the coal mine for climate change.