Lagged glacier response to past climate forcing and its role in recent volume loss

Glaciers are currently losing mass at unprecedented rates. These losses are often attributed to past climate forcing. However, a substantial share of glacier volume loss reflects the delayed adjustment of glacier geometry to past climate conditions. This lag arises because glacier geometry can evolve only as fast as ice can flow and surface mass balance can add or remove ice, making glacier change a continual race to adapt to changing climatic conditions.

In this study, we globally quantify the fraction of glacier volume loss that is committed to past climate forcing, relative to losses driven by concurrent climate conditions. Using the Open Global Glacier Model (OGGM), we decompose volume loss over the preceding decade for reference years. Each period is simulated twice: once forced by the climate of the reference period and once with the climate from a preceding period. This allows us to isolate the fraction of volume loss attributable to committed adjustment. Preliminary results indicate that of the 4.5% global glacier volume loss between 2000 and 2019, approximately 90% would also have occurred under the climate conditions of 2000–2010 alone, and nearly half can be attributed to climate conditions from 1990–2000.

Our results provide a new perspective on the evolving balance between glacier geometry and climate forcing, enabling a clearer interpretation of recent glacier change and its underlying drivers.