Global glacier change observations (1535–2025) and mass loss (1976–2025)

The Fluctuations of Glaciers (FoG) database is the outcome of 130 years of coordinated international glacier monitoring. It is curated by the World Glacier Monitoring Service (WGMS) and regularly updated with observations submitted by a worldwide network of scientific collaborators. Glacier mass, elevation, and length change observations (1535–2025) are complemented by an inventory of glacier-related events (e.g., surges, lake outbursts, and ice avalanches). We will explain the data integration process and evaluate the spatial, temporal, and climatic coverage of the observations.

We will also highlight many enhancements to the database, including structured authorship and bibliographic metadata for each observation, a near-complete full-text archive of all cited literature, glacier names in multiple languages and scripts, the outline used to derive each glacier-wide elevation change, and a representative outline for each in-situ mass change series.

Finally, we will present an annual estimate of global glacier mass loss from 1976 through the 2025 hydrological year. Since 2025, the WGMS combines the latest in-situ mass change observations and remotely-sensed elevation change observations in FoG to calculate a mass-change time series for every glacier on Earth (separate from the Greenland and Antarctic ice sheets) and corresponding regional and global totals.