Retreat of individual glaciers provides categorical evidence for climate change

Retreating glaciers clearly document regional climate change over decade-long periods of time, reports a paper published online in Nature Geoscience this week. The study suggests that today’s shrinking glaciers thus serve as conclusive evidence of twentieth and early-twenty-first century climate change in many regions around the world.

Shrinking glaciers have been documented in many regions of the world, and have been used to illustrate the effects of global warming. However, the latest report from the Intergovernmental Panel on Climate Change concluded that it was only ‘likely’ (probability of at least 66%) that a substantial part of glacier retreat is due to human-induced climate change, which is a relatively weak attribution compared to other metrics of climate change.

Here, Gerard Roe and colleagues assessed individual glacier change by combining glacier observations with the better-resolved local meteorological measurements, which allows them to make stronger conclusions about glacial change. They then analysed glacier observations along with local meteorological measurements from 37 glaciers that are widely dispersed globally and found that for 36 of these glaciers, retreat is very likely (probability of at least 90%) caused by climate change. The team note that the cause of this climate change cannot be determined purely from observations, but, given that the observed glacier retreat is globally distributed and present on a centennial timescale, it is unlikely to be natural decadal variability and most likely to be human-induced warming.