Last year around this time, the Alpine glaciers were excellently protected under an exceptional snow cover. After that, the summer melt unexpectedly accelerated, and the past winter brought little snow. From this week until around October, more ice will melt than the snowfall from last winter. This early start to the decrease in glacier ice volume may result in significant ice loss for 2025.

Warm August 2024 erases exceptionally good starting situation 

Every year at the end of September, the mass balance of the Alpine glaciers is calculated. In the summer months, the glaciers melt and evaporate when they are exposed after the “fresh” winter snow has melted away. With fixed reference points in the snow layers, it is assessed how much a glacier has net grown or shrunk, expressed in meters or weight of water. Figure 1 shows that the Swiss glaciers had an above-average high mass until August 2024. This was due to heavy snowfall. August 2024 was exceptionally warm in the high mountains with 3.8 °C above average (1991-2020) and resulted in a melting record for August (aided by little cloud cover and accumulated Saharan sand that reflects less sunlight).