Glacier mass balance intercomparison
The Glacier Mass Balance Intercomparison Exercise (GlaMBIE) is a community-led scientific initiative to analyse global glacier mass changes. This exercise compiled 233 regional estimates from around 450 contributors across 19 predefined regions. The study integrates four key observation methods: in situ glaciological measurements, digital elevation model (DEM) differencing, altimetry, and gravimetry. To ensure consistency, the research team homogenised all datasets for spatial, temporal, and unit characteristics before combining them into a single time series. This approach separates long-term trends from annual variability, providing a robust assessment of mass changes from 2000 to 2023.
Global and regional mass changes
Between 2000 and 2023, the world’s glaciers lost a total of 6,542 gigatonnes (Gt) of ice, which contributed approximately 18 millimetres to global sea-level rise. The average annual loss rate was 273 Gt per year, with a significant acceleration of 36% observed between the first (2000–2011) and second (2012–2023) halves of the period. Regionally, Alaska, the Canadian Arctic, and the periphery of Greenland were the largest contributors, accounting for over half of the total mass loss. Regions with smaller glacier areas saw the greatest relative declines, with Central Europe losing 39% of its ice volume.
Differences among observation methods
The research highlights systematic differences between the various observation techniques used. Altimetry results generally indicated less negative mass changes when compared to DEM differencing. Gravimetry estimates were found to align well with DEM differencing in regions with large glacier areas but were less reliable for smaller regions due to measurement noise. Glaciological observations, based on a limited sample of glaciers, tended to show a more negative trend than the comprehensive regional average. While these discrepancies were often within stated uncertainty margins, they underscore the need for continued methodological refinement.
Comparison with IPCC estimates and outlook
The report’s findings are broadly consistent with recent Intergovernmental Panel on Climate Change (IPCC) assessments, though the GlaMBIE estimates of mass loss are slightly less severe. The analysis shows that global glacier mass loss currently surpasses that of the Greenland Ice Sheet by 18% and is more than double the loss from the Antarctic Ice Sheet. Projections indicate that between 25% and 54% of global glacier mass could be lost by 2100, depending on future emission scenarios. The study concludes by reinforcing the need for urgent action to reduce greenhouse gas emissions and mitigate the impacts of glacier decline.
Online content
Additional resources related to the report are available online. These materials include detailed methodologies, supplementary data and references, reporting summaries, and information regarding author contributions and competing interests. The source data and code used for the analysis are also provided through a digital object identifier for further review.
