Snow guns blasted human-made snow during the winter of 2021–2022 at Diavolezza—a 3,000-meter-high ridge in Switzerland’s Upper Engadine Mountains with nine ski slopes, a cable car and views of some of the Alps’ highest peaks. But the gun operators weren’t just trying to enhance ski conditions. They were testing a new way to make snow, with a goal of helping to save the disappearing Morteratsch Glacier, just to the west.

This pilot study was urgent. Morteratsch, a readily accessible 16-square-kilometer glacier complex, has long been a magnet for tourists, hikers and scientists. But since 1860 it has lost three kilometers, about a third of its total length (the distance from the glacier’s downslope terminus to its uppermost point.) Around the world, many mountain glaciers are melting fast. New research has found that even keeping global temperature rise to 1.5 degrees Celsius from preindustrial levels by 2100—generally regarded as the best-case, if increasingly unlikely, scenario—would result in half of the world’s mountain glaciers disappearing. The consequences have already been disastrous, from catastrophic floods when glaciers melt quickly to water shortages if they dry up to rock falls and even rising seas.

Some regions are especially vulnerable, including the Alps, where temperatures are rising more than twice as quickly as the Northern Hemisphere average. Swiss glaciers already have lost 60 percent of their volume since 1850. Just last year Switzerland’s glaciers lost 6 percent, the worst loss on record. “People were shocked, including glaciologists,” says University of Zurich glaciologist Christian Huggel. “Retreat is going faster than thought.”

Climate experts say the only lasting fix is reducing greenhouse gas emissions. In the meantime, people who love mountain glaciers—which, in Europe, are often home to ski resorts—have tried to devise local solutions. In Switzerland, one professor floated the idea of erecting giant shields to protect the ice from katabatic winds (dense, high-elevation airflows that can scrub away snow and ice). In the Andes, researchers have proposed whitewashing rocks to reflect warming sunlight.

Dramatic-sounding ideas to protect other ice and snow formations have gotten more traction. As early as 1947, residents around Switzerland’s Aletsch glacier were spreading sawdust across the roof of an ice cave created for tourists to shield it from the sun’s radiation. And since the 1990s some ski resorts on glaciers have spread giant white “blankets” across key slopes. These coverings are usually made of layers of plastics and fleecelike material that insulate against solar radiation yet allow water to permeate. Today nine sites in Switzerland use blankets that cover 10,000 to 50,000 square meters; the largest could shroud seven professional soccer pitches. Such “geotextile” coverings can reduce ice melt “by about 50 to 60, 70 percent,” says glaciologist Matthias Huss of the University of Fribourg in Switzerland, head of the glacier monitoring network Glamos and lead author of a recent study on geotextile use. Huss estimates that using geotextiles for seven years at the Rhône Glacier in southern Switzerland preserved around 35 meters in ice thickness.

Shading key portions of a lucrative ski area might be worth the cost, but Huss says using “blankets” to cover the world’s glaciers—or even one entire glacier—seems impractical, if not impossible. His calculations suggest that if geotextiles were used on Switzerland’s largest 1,000 glaciers, they could prevent two thirds of average annual volume loss, but they would cost around $1.52 billion per year. Geotextiles, Huss says, were “never intended as a way to save the glaciers.”

Huggel agrees. “It’s not feasible at a larger scale of a whole glacier,” he says. “That would be absurd.”

Snow Saves Ice

Another potential glacier-preserving approach is the snowmaking technology that was tested at Diavolezza by the University of Lucerne in Switzerland and GlaciersAlive, a nonprofit organization that focuses on water conservation.

Whether natural or human-made, snow’s especially high albedo (reflectivity) can bounce a lot of the sun’s radiation skyward, staving off melting. But traditional snowmaking methods are water-intensive and often involve a small amount of chemical additives. A 2011 study estimated that making just three cubic meters of snow requires as much energy as a Swiss household consumes in an entire day.

The snow-making industry, trying to cut its carbon footprint, has crafted a new system powered by elevation rather than electricity, including the one used at Diavolezza. For it to work, water from rain, snow, ice melt or other sources enters the system 200 meters or more above where snow is needed. The water provides the liquid for the artificial snow itself, and the gravitational energy provides enough water pressure—20 bars, or about 290 psi—to operate the guns, which look like showerheads that spray snow. For the pilot project at Diavolezza, towers 15 meters tall were strung with suspension cables punctuated by downward-pointing guns.

The Diavolezza pilot was a way for GlaciersAlive co-founder Johannes Oerlemans and glaciologist Felix Keller of the Swiss Federal Institute of Technology in Zurich to test whether this kind of system could work on the nearby Morteratsch and recycle the glacier’s own meltwater into snow. Oerlemans says the trial showed that it “is technically possible,” calling it “a big step.” The team is looking for a smaller glacier for its next test—and is seeking investment. Oerlemans says the pilot cost about $2.15 million and was funded by Innosuisse, a Swiss government agency that promotes innovation.

Models run by Oerlemans’s team have found that if the system was rolled out on Morteratsch, it could not only slow the glacier’s retreat—but reverse that trend. Covering almost a square kilometer of the glacier with snow consistently, year after year, for 30 years (which Oerlemans admits “is quite a lot”) could increase Morteratsch’s length by around half a kilometer by 2100, according to a 2017 feasibility study by Oerlemans, Keller and co-author Martin Haag. Without snow, the researchers estimated, the glacier would lose roughly half a kilometer.

These projections are far too rosy, says Huss, who recently completed an independent study of the proposed project. One issue is the emissions scenario the GlaciersAlive team used. Huss says the team based its estimate of the glacier’s growth on countries meeting the Paris climate agreement’s goal of global net-zero emissions by 2050—which most experts agree is a longshot. He also claims that the project underestimates how much ice Morteratsch would lose before an extensive system could be implemented, noting that the glacier lost more than 10 percent of its volume in 2022 alone.

Huss says that snowmaking “always slows down the losses. And the process that is suggested absolutely works.” Still, he adds, under the Paris climate scenario, by 2060 the glacier will lose 35 percent of its volume even with the proposed snowmaking. It could lose 56 to 71 percent without this effort.

The project could also cause environmental disruption. According to a 2021 planning study, capturing meltwater for snowmaking would entail blocking off a natural depression in the glacier to act as a reservoir with a concrete wall 31 meters high and 650 meters long. A 900-meter tunnel would be dug from the reservoir to the snow system below. The snowmaking itself would require eight different cables, from 850 to 1,200 meters long, strung across the landscape. “It’s a huge construction site,” Huss says, one that threatens the pristine environment “to try and save one element.”

Future scalability is an open question. The Morteratsch application would cost around $163 million. Investing that much money in innovative new technologies to reduce CO2 emissions, Huss says, could help “the whole of humanity, not just ... a few tourists going up to Saint Moritz, [Switzerland].”

Oerlemans is accustomed to such critiques. He agrees that glaciers can’t really be “saved” without cutting emissions. Still, he says, the pilot showed the potential of the gravity system for ski resorts in particular and could lead to investment for glacier protection as an alternative to more conventional, power-hungry snowmaking. That may be the ultimate benefit of the various glacier-saving ideas: on a hyperlocal scale, they may help stave off some melting—at least for a while.