But that’s long since changed. According to a study published today in the journal Science Advances, rising temperatures in the Himalayas have melted nearly 30 percent of the region’s total ice mass since 1975. Once nicknamed Earth’s ‘Third Pole’ for its impressive cache of snow and ice, the Himalayas may now have a bleak future ahead. Four decades of satellite data, including recently declassified Cold War-era spy film, suggest these glaciers are currently receding twice as fast as they were at the end of the 20th century.

During the Cold War, there was a heck of a lot more frost—and I’m not just referring to the geopolitical tensions between the United States and the former Soviet Union. Back then, the Himalayas, too, were feeling the chill.

“It’s the climate crisis you haven’t heard of,” Philippus Wester, a researcher at the International Centre for Integrated Mountain Development who was not involved in the study, told Damian Carrington at The Guardian .

The findings underscore the persistent and increasing dangers of global warming in the Himalayas, where disappearing glaciers stand to imperil the water supply of up to a billion people throughout Asia.

The study’s sobering findings come as the result of a massive compilation of data across time and space. While previous studies have documented the trajectories of individual glaciers in the Himalayas, the new findings track 650 glaciers that span a staggering 1,250-mile-wide range across Nepal, Bhutan, India, and China. They also draw on some 40 years of satellite imagery, which the scientists stitched together to reconstruct a digital, three-dimensional portrait of the glacier’s changing surfaces—almost like an ultra-enhanced panorama.

When a team of climatologists analyzed the time series, they found a stark surge in glacier shrinkage. Between 1975 and 2000, an average of about 10 inches of ice were shed from the glaciers each year. Post-Y2K, however, the net loss doubled to around 20 inches per year—a finding in keeping with accelerated rates of warming around the globe.

While previous studies have had difficulty disentangling the relative contributions of rising temperatures, ice-melting pollutants, and reduced rainfall to the boost in glacier melt, the latter two simply aren’t enough to explain the alarming drop in ice mass in recent years, study author Josh Maurer, a researcher at Columbia University’s Lamont-Doherty Earth Observatory, told Eric Niiler at Wired.

“It is really the doubling of the speed of glacier melt that is most concerning,” study Joerg Schaefer told Carrington at The Guardian. “There is no doubt in my mind, not a single grain of doubt, that [the impact of the climate crisis] is what we are seeing.”

A new study leveraged Cold War-era satellite images to construct a series of portraits of the Himalayas over time and space, allowing researchers to track declines in ice mass. Image Credit: gagarych, iStock

As things stand, several billion tons of ice are sloughing off the Himalayas each year without being replaced by snow. That spells serious trouble for the peoples of South Asia, who depend on seasonal Himalayan runoff for agriculture, hydropower, drinking water, and more. Melting glaciers could also prompt destructive floods and threaten local ecosystems, generating a ripple effect that may extend well beyond the boundaries of the mountain’s warming peaks.

This study and others hint that, without serious and drastic interventions, the planet’s forecast looks grim. “We have to prepare the societies living there with realistic predictions of what this landscape will look like in 10 or 20 years,” Schaefer told Niiler.