A recent study published in Science used glacier models to better understand the effect that each degree of global warming will have on worldwide glacier melt. The impacts of the warming the Earth has already experienced are yet to be fully realized, because glaciers have not reached equilibrium with the changing climate. The models provide insight into how much ice the world is already set to lose, and how much more can be saved by limiting our emissions and warming.

“Eight different glacier evolution models were used to simulate the evolution of glaciers under a total of 80 warming scenarios,” Harry Zekollari told GlacierHub in an interview. Zekollari is the lead author for the study and an associate professor for glaciology at the Vrije Universiteit Brussel in Belgium. “This was a community effort realized within the framework of the Glacier Model Intercomparison Project (GlacierMIP3). There was a protocol to follow for anyone who wanted to join and conduct the experiments, and it was open to all. We could use the information from all the models to make global estimates,” he said.

The warming scenarios rested on the assumption that the temperature would hit a peak level and then stop warming. Should temperatures hit that peak today, glaciers will continue to melt in the coming years, regardless. This is because it takes some time for glaciers to respond to changing climatic conditions.

“Glaciers are so out of balance with present warming, in general, it takes them some time to ‘catch up’ and reach a new equilibrium or steady state,” said Mike Kaplan, a geologist at the Lamont-Doherty Earth Observatory, which is part of the Columbia Climate School. He studies how glaciers, climates and landscapes have changed in the past. “Even if we stopped human impacts on climate this very minute, we must consider that things do not just adjust immediately.”

“See it a bit like an ice cube that you take out of a freezer,” explained Zekollari. “It will not immediately melt, but will take quite some time. The same applies for glaciers, but on a larger spatial and longer temporal scale.”

The planet has already reached 1.2 degrees Celsius of warming above pre-industrial levels. According to the study, at this temperature, we are locked in to losing 40 percent of glacial ice on Earth. No matter the mitigation efforts made, this ice is as good as gone. But the remaining ice still holds potential to be saved. Reaching a peak temperature sooner, at a lower temperature, rather than later at a higher one, could preserve a significant amount of glacial ice. 

“In the long term, for every tenth of a degree less global warming that can be limited between 3.0 degrees Celsius and 1.5 degrees Celsius, 2 percent additional glacier mass can be preserved,” said Lilian Schuster, who worked on the study as part of her dissertation research at the department of atmospheric and cryospheric sciences at the University of Innsbruck in Austria, and then became a postdoctoral research fellow there. For this ice to be saved, humans will need to drastically shift from the current trajectory.

“With current policies, we are heading to a warming of about 2.7 degrees Celsius above pre-industrial levels, which would, in the long-term, result in a loss of three quarters of the global glacier mass,” said Zekollari. “If we are able to limit warming to 1.5 degrees Celsius, in line with the Paris Agreement, then only about half of that glacier mass would be lost.”

Glaciers are very sensitive to each small change in temperature. Kaplan described them as, “the proverbial canary in the coal mine. They are a direct physical manifestation of atmospheric conditions and will always be very sensitive to warming.”

These findings indicate that there are several different levels of glacier loss that the Earth may experience, depending on how much warming can be limited. Though these differences are significant, in all scenarios human populations will be feeling the impacts of a world with melting ice.

“The vast majority of the lost ice will eventually reach the oceans, thereby contributing to sea level rise. Sea-levels are currently rising by about 4 mm/year, of which about 1 mm/year comes from melting glaciers,” said Zekollari. The remaining sea-level rise comes from ice sheet melt (2 mm/year) and thermal expansion (1 mm/year).

“There are many more reasons to care about glacier loss: changes in water supply affect ecosystems and they are important for mountain communities as they have spiritual and touristic value,” Zekollari continued. Mountain communities are also dependent on streams fed by glacier melt for irrigation and domestic supplies. Though a warming climate that melts glaciers may provide more water in the short term, in the long term, these communities will face the risk of greater water scarcity. Through modeling glaciers in studies like this one, the global world can be more prepared for the lasting repercussions of climate change.

“The situation is grim, but there is still hope, and we can save a substantial part of our glaciers if we’re able to limit warming,” said Zekollari.