By 2100, Humans Might See a Glacier-Free Sierra Nevada for the First Time Ever

A new study suggests some glaciers have existed on the California mountain range for the entirety of known human history in North America

October 6, 2025

Conness Glacier and a blue sky — Conness Glacier. Dcrjsr, CC BY 3.0 via Wikimedia Commons

Some researchers theorize that the glaciers of the Sierra Nevada, a mountain range in eastern California, formed only between 3,000 and 10,000 years ago. Research published last week in the journal Science Advances, however, suggests that some Sierra Nevada glaciers have existed for at least the entire Holocene, the 11,700 years since the end of the last ice age.

That period covers nearly the entirety of human history in North America—and since researchers estimate that the glaciers will be gone by 2100 due to human-caused climate change, it suggests that people alive today might be the first ever to see a glacier-free Sierra Nevada.

Did you know? Many mountains

The Sierra Nevada is part of a larger system called the North American Cordillera, known as the “backbone” of the Western United States.

“Glaciers are touchstones between the past and the present, and it’s just so visceral when you can see how it used to be and how it is today,” Andrew Jones, a geoscientist at the University of Wisconsin-Madison and lead author of the study, tells the Los Angeles Times’ Ian James.

The team studied four of the mountain range’s largest and potentially longest-lived glaciers—Conness, Maclure, Lyell and Palisade—by investigating versions of carbon and beryllium in recently exposed rocks. Jones tells KQED’s Danielle Venton that the rocks are a bit like batteries. When rocks aren’t covered by ice, the sun charges them up, and when the glaciers return, the charge slowly diminishes. Researchers measure the remnants of the charge to estimate glaciers’ age in a process called surface exposure dating.

The team, however, didn’t find any charge at all, according to Jones. Their results suggest that some of the rocks were covered throughout the Holocene, probably by ice. Two of the largest glaciers near Yosemite National Park already existed then, they write. They conclude that the Sierra Nevada hasn’t been glacier-free since before the end of the last ice age.

“Considering that California’s glaciers reached their Last Glacial Maximum positions as early as 30,000 years ago, our reconstructed glacial history indicates that a future glacier-free Sierra Nevada is unprecedented in human history since known peopling of the Americas (about) 20,000 years ago,” the researchers wrote in the study. (Some scientists argue that people reached North America much earlier, as long as 30,000 years ago, which would complicate the “first ever” claims of the new study.)

Either way, though, the study estimates that glaciers thousands of years old will disappear within the next 75 years.

The study dramatically highlights the results of human-caused climate change, Bob Anderson, a geomorphologist at the University of Colorado Boulder who was not involved in the study, tells the San Francisco Chronicle’s Kurtis Alexander. But though humans’ greenhouse gas emissions are driving glacial melting, there’s still time to save some of the world’s glaciers.

“If we can keep warming to a modest level instead of a really high level, you actually preserve a large number of glaciers that would be lost,” Jones tells the Los Angeles Times. “We have to come together, with governmental action, and take steps to reduce man-made greenhouse gas emissions.”

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