Brief communication: Contrasting Estimates of Global Glacier Mass Balance in 2025

Abstract. Global glaciers were recently reported to have lost 408 ± 132 Gt in 2025, ranking it as the sixth-most negative year since 1975. Here, we provide an independent assessment using observations from NASA’s Ice, Cloud, and land Elevation Satellite-2 (ICESat-2) and ESA’s Cryosphere Satellite-2 (CryoSat-2) radar altimeter. The two altimeters indicate global losses of 260 ± 56 Gt and 235 ± 121 Gt, respectively, substantially smaller than the reported value and below the respective mean rates of the past two decades. The reduced global loss estimate is primarily due to low mass losses or net mass gains in several regions that normally dominate global variability, particularly Alaska, Subantarctic & Antarctic Islands, and Arctic Canada, while High Mountain Asia experiences greater mass loss than its historical average. These results do not indicate that 2025 was a near-record year for global glacier mass loss. The contrast among recent estimates highlights the added value of combining in situ, altimetric, and gravimetric observations in annual global assessments as well as the large inter-annual variability in global glacier mass balance measurements.