Most of those who walk the John Muir trail along the Tuolumne River and then take the Lyell Fork route to the peak of Mount Lyell are unaware of the drama being played out before their eyes. The glacier on the way to Yosemite National Park’s highest summit is quickly fading away, right before the eyes of a select few who have known the glacier and studied it over the years. The Mount Lyell Glacier used to be a sweeping expanse of ice covered in deep snow, but now much of the snow is gone, exposing a greatly reduced glacier with rocks and boulders rising to its surface with increased water flow evident even in winter.
The changes in Yosemite are now dramatic enough that even those who have come here for decades merely for recreation can observe the drama unfolding. But what may not be apparent to the casual observer is the wide-reaching impact of what they see before them. While the melting glaciers almost irrefutably indicate global warming, the changes will have an impact locally. Sixty-five percent of California’s water comes from the Sierra Mountain’s snowpack and as that dwindles so does the state’s water supply. Rather than snow fall, the Sierra Nevada Mountain range is experiencing more rain which seeps into the land rather than the snowmelt which would run into the rivers. The snow that does fall is arriving later, and melting off earlier. All of these events are dramatically reducing the amount of water available around the State of California.
Yosemite National Park has already lost some glaciers such as the first one discovered at Yosemite in 1871 by John Muir. There are roughly one hundred glaciers remaining in Yosemite but all of those are shrinking, and dramatically so in the case of the Mount Lyell Glacier – currently the second largest in the park. The glaciers are losing their snow cover, which exposes the ice to direct sunlight and speeds the melting process. The water runoff from the ice melting contributes to more melting and the exposed rocks and ground lend to the surrounding warmth, creating a self-perpetuating warming trend, resulting in what is now obvious not just to the scientists studying the effects of global warming, but possibly more ominously, even to the tourists and casual observers who have wandered away from the tourist Mecca of Yosemite Valley into the more remote regions of Yosemite National Park where the glaciers can be found. The melting can be experienced by even those visiting the glaciers for the first time. All one has to do is pull out a U.S. Geological Survey map and compare. You can find Yosemite’s glaciers listed there, but what you’ll observe in reality, are shapes and sizes of those glaciers that barely resemble their former glory. In an instant you can see for yourself that Yosemite National Park, the Sierra Nevada Mountain Range, and the State of California, are all seeing their greatest natural resource, evaporate.
