Mountain glaciers in US national parks, particularly in California's Sierra Nevada, are rapidly melting due to climate change. A study highlights the unprecedented nature of this melt, with glaciers like Conness, Maclure, Lyell, and Palisade showing significant historical resilience. The disappearance of these glaciers by 2100 CE marks a significant change in the region's glacial history. Globally, glaciers are melting at alarming rates, with Europe experiencing severe losses. While there is potential for recovery if global warming is reversed, it would take centuries or longer.