Glaciers, defined as perennial masses of ice on land excluding the massive ice sheets of Antarctica and Greenland, play a critical role in Earth's climate system, freshwater supply, and sea level regulation.
As of 2025, these glaciers—numbering around 220,000 worldwide—cover approximately 700,000 square kilometers. However, they are rapidly diminishing due to climate change, with significant implications for global water resources and rising oceans.
Estimated Total Remaining Glacier Ice Volume
The most recent baseline estimate for the total volume of glacier ice (excluding ice sheets) is approximately 158,000 cubic kilometers (km³), equivalent to about 145,000 gigatonnes (Gt) of ice mass or 0.32 meters of potential sea level rise if fully melted (after accounting for ice below current sea level).
This figure originates from comprehensive modeling and satellite data up to 2019, but ongoing mass losses have reduced it further.
Adjusting for recent losses, from 2000 to 2023, glaciers have shed a total of 6,542 ± 387 Gt of mass (in water equivalent), representing about 5% of their volume in 2000.
This equates to an approximate remaining ice volume of around 150,000 km³ as of the end of 2023, based on conversions using ice density (0.917 g/cm³).
For 2024, an additional loss of roughly 434 Gt (equivalent to 1.2 mm of sea level rise) further depletes this, bringing the estimated remaining volume to about 149,000 km³ by early 2025.
Regionally, smaller glacier systems (areas ≤15,000 km²) have lost 20-39% of their ice since 2000, while larger ones have lost 2-12%.
Trends in Glacier Mass Loss
Glacier mass balance—the difference between accumulation (from snowfall) and ablation (from melting and sublimation)—has been overwhelmingly negative in recent decades.
The average annual mass loss from 2000 to 2023 was 273 ± 16 Gt per year, contributing 0.75 ± 0.04 mm annually to global sea level rise.
This rate accelerated by 36 ± 10% from the first half of the period (2000-2011: 231 ± 23 Gt/yr) to the second (2012-2023: 314 ± 23 Gt/yr).
Recent years have seen record-breaking declines:
- In 2023, glaciers lost a staggering 548 ± 120 Gt, equivalent to 1.51 ± 0.33 mm of sea level rise—the highest on record.
- For 2024, preliminary data indicates a loss of about 434 Gt (1.2 mm sea level rise), comparable to four times the ice volume of all European Alps glaciers.
Longer-term data from reference glaciers (with over 30 years of observations) shows cumulative losses exceeding 30 meters water equivalent (m w.e.) since 1950, with eight of the ten most negative years occurring since 2010.
The last three years (2021-2024) averaged over 1 m w.e. loss annually, translating to about 1.1 meters of ice thickness reduction per year.
Implications and Future Outlook
This ongoing thaw affects billions reliant on glacial meltwater for drinking, agriculture, and hydropower, particularly in regions like the Himalayas and Andes.
It also exacerbates sea level rise, with glaciers contributing over 25 mm since 1976—41% of that in the last decade alone.
If trends continue, projections suggest further acceleration, potentially leading to the near-total disappearance of glaciers in some regions by 2100.
Monitoring efforts by organizations like the World Glacier Monitoring Service (WGMS) and satellite missions (e.g., GRACE-FO) provide these insights, emphasizing the urgency of mitigating climate change.
Sources
The GlaMBIE Consortium (2025), Community estimate of global glacier mass changes from 2000 to 2023
Copernicus Climate Change Service (2025), Glaciers
Farinotti et al. (2019), A consensus estimate for the ice thickness distribution of all glaciers on Earth
World Glacier Monitoring Service (2025), Global Glacier State