In late October, the snow elves—that is to say, employees—of the Zermatt Bergbahnen AG ski area in Switzerland fire up their secret weapon: a 30-ton snow-generating goliath known as Snowmaker. For 20 days straight it runs around the clock, churning out 1,900 tons of snow per day. That snow is then ferried up the mountain on vehicles with caterpillar tracks called “snow cats.”

Wired UK

This story originally appeared on WIRED UK.

But in the recent past, brute technological interventions were far from necessary. “Ten to 20 years ago you could always plan [on] the natural snowfall. In the middle of November, start of December there was a big snowfall every year,” says spokesperson Mathias Imoberdorf. “Now it’s unpredictable.”

The reason is climate change. Skiing was once an activity born of necessity—an efficient means of transport in snowy lands. Today, people ski for sport, fun, and fitness. But the Earth’s atmosphere has changed, turning once snowy slopes into muddy wastelands. As a result of global heating, the Earth no longer produces snow with the same regularity, so ski resorts are being forced to manufacture it instead. At one resort in the Swiss Alps, for example, snow depth during the winter is now roughly 40 percent lower on average than it was in the period from 1909 to 1988.

More than 60 percent of the world’s ski slopes are currently supplemented by snowmaking machines, according to industry analyst Laurent Vanat. “It is a must if you want to keep in business,” he says. But the process isn’t cheap. Market research firm IBISWorld says the US ski industry is now incurring “significant costs” from snowmaking.

Since 2002, Zermatt alone has invested more than £100 million in its snowmaking machines—roughly a quarter of its total expenditure for the period. Snowmaker, installed in 2008, is just the biggest weapon in its arsenal. The resort also has 1,200 snow guns and snow cannons peppered around slopes covering 140 kilometers.

But these smaller devices won’t be able to stand up to climate change forever. They work by spraying microscopic ice balls and water droplets into the cold air, which combine, freeze and then descend as snow—though this “snow” is formed of pellet-like particles, not flakes. Low outdoor temperatures are essential to the process. If it’s not cold enough—ideally around 2.5 degrees Celsius—the machines simply cease to work properly.

In a warming world, Zermatt has invested in Snowmaker because it can function even when it is warm outside. The behemoth creates a vacuum inside its large tank that encourages water to evaporate. With evaporation, energy is expended, which cools the water and helps to form tiny snow crystals. Snow can be taken to the highest, coldest parts of the resort once it is ready.

Still, most snowmakers do rely on cold weather. That’s why some resorts continue to buy more and more of them, so that they can pump out huge volumes of snow, quickly, during the ever-narrowing windows of subzero temperatures.

“It’s been busy,” admits Ian Jarrett, vice president at US-based HKD Snowmakers, which manufactures snowmaking machines. In the northeast US, where HKD is headquartered, skiing is a popular pastime—but one potentially hampered by dwindling snow in the early part of the season. Resorts say they have no choice but to turn to snowmakers because many of their customers choose to visit at traditional times, around Thanksgiving and Christmas.

Automation has also helped to ensure that snow guns only run when it makes sense to do so. “The snow guns on the fully automated side can start and stop, and adjust themselves based on temperature,” explains Jarrett.

But about 900,000 liters of water are still needed to put a foot of snow on one acre of land. Acquiring this resource is another constant headache for resorts. Since the 2018–19 season, for example, Seven Springs ski resort in Pennsylvania has installed 1,500 meters of 50-centimeter diameter piping to bring water from a 681-million-liter uphill lake down to its snow-generating machines.