Researchers from the University of Innsbruck in Austria and Trent University in Canada have found that 69% of glacier mass loss can be attributed to human activity, according to a paper being published in Science (h/t Andrew Freedman at Mashable), but because glacial melting is a lagging indicator of climate change the real impact that humans are currently having on other systems could be even higher.

Glacier Mass Loss

Human contribution to glacier mass loss much higher than in the past

The paper, written by University of Innsbruck scientists Ben Marzeion, Kristin Richter, and David Parkes and Trent University scientist J. Graham Cogley looked at the rate of glacial melting in two overlapping time periods 1851 – 2010 and 1991 – 2010 to see how much of a role ‘anthropogenic forcing’ played in each. Over the longer time frame the researchers found that people accounted for 25% ± 35% of global glacier mass loss (the negative part of the uncertainty would imply that human behavior had stalled glacier mass loss), while in the more recent time period that jumped to 69% ±24% due to human activity. Those are large error bars to be sure, but the increase is undeniable and the data doesn’t include recent events like the collapsing West Antarctic ice sheets.

Melting glaciers are both symptom and catalyst

Aside from being one of the more striking proofs that the planet is getting warmer, melting glaciers plays a dual role in climate change as both a symptom and a catalyst. As the glaciers melt, they dump more water into the world’s oceans and contribute to sea level rise, with a host of knock on effects (swallowing real estate, damaging farmland in the Nile Delta, and increasing the severity of tsunamis in Bangladesh are a few).

But it also makes climate change itself more severe. Ice reflects most of the sunlight that hits it back into space, only absorbing about 15% of it, while water absorbs more than 90% of it, which translates into faster global warming. Similarly, permafrost is thought to hold a great deal of frozen carbon dioxide and methane (though no one is sure how much), and when it starts to thaw the atmosphere will get a big one-time shot of greenhouse gases. It took human activity to set the ball rolling, but losing the glaciers will only make climate change worse.