Community estimate of global glacier mass changes from 2000 to 2023

Abstract

Glaciers are indicators of ongoing anthropogenic climate change. Their melting leads to increased local geohazards, and impacts marine and terrestrial ecosystems, regional freshwater resources, and both global water and energy cycles. Together with the Greenland and Antarctic ice sheets, glaciers are essential drivers of present and future sea-level rise. Previous assessments of global glacier mass changes have been hampered by spatial and temporal limitations and the heterogeneity of existing data series. Here we show in an intercomparison exercise that glaciers worldwide lost 273 +- 16 gigatonnes in mass annually from 2000 to 2023, with an increase of 36 +- 10% from the first (2000-2011) to the second (2012-2023) half of the period. Since 2000, glaciers have lost between 2% and 39% of their ice regionally and about 5% globally. Glacier mass loss is about 18% larger than the loss from the Greenland Ice Sheet and more than twice that from the Antarctic Ice Sheet. Our results arise from a scientific community effort to collect, homogenize, combine and analyse glacier mass changes from in situ and remote-sensing observations. Although our estimates are in agreement with findings from previous assessments at a global scale, we found some large regional deviations owing to systematic differences among observation methods. Our results provide a refined baseline for better understanding observational differences and for calibrating model ensembles, which will help to narrow projection uncertainty for the twenty-first century.