Sierra Nevada Glaciers Vanishing, May Be Unprecedented in Human History

The Los Angeles Times reported on October 1, 2025, that as California's Sierra Nevada glaciers disappear due to rising temperatures, new research indicates they have likely existed continuously since the last Ice Age. A study in the journal Science Advances suggests the current melting is unprecedented in human history and projects the glaciers will vanish entirely this century. Scientists from the National Park Service and several universities analyzed rock samples collected between 2018 and 2023, determining the ground beneath has been covered by ice for thousands of years, which counters previous estimates that the glaciers were much younger.

sfchronicle.com reported, The melting is linked to a 3.6-degree Fahrenheit increase in regional summer temperatures over the past century. These glaciers are important for alpine hydrology, releasing critical meltwater into streams during dry late-summer months when winter snowpack is gone. Data shows some of the largest glaciers in the range, including the Lyell and Palisade glaciers, have already lost an average of 75% of their surface area compared to the early 1900s. Researchers state that a future with ice-free peaks in the Sierra Nevada is now expected.