Almost 40% of world’s glaciers already doomed due to climate crisis – study

By Siyu Li

Research Article: https://www.science.org/doi/10.1126/science.adu4675

News Article: https://www.theguardian.com/environment/2025/may/29/almost-40-of-worlds-glaciers-already-doomed-due-to-climate-crisis-study

Background

   Glaciers are among the most critical natural resources and serve as indicators of ongoing anthropogenic climate change¹. They act as major freshwater reservoirs, influencing the water resources of millions of people downstream², and their melt is a major driver of global sea level rise³. Glacier loss also reshapes ecosystems⁴ and alters the surface energy balance⁵. Unlike short-lived weather events, glacier responses to climate change play out over decades to thousands of years due to their immense mass and the slow dynamics of ice flow⁶. Even if global temperature stopped rising today, most glaciers would continue to lose mass for a long time while they equilibrate to the warmer climate. The committed mass loss from past and current warming makes near-term limits on temperature especially important.

News Article

    The Guardian article, "Almost 40% of world's glaciers already doomed due to climate crisis – study," by Damian Carrington, reports on the new glacier study with a straightforward title. It also opens directly with the most stark conclusion: approximately 40% of the world's glaciers are already committed to melting due to past and present warming. The article notes that a current policy–based path leading to +2.7°C of warming over preindustrial could result in a long-term loss of about 75% of glaciers compared to the 2020 level. In contrast, it highlights that limiting warming to the +1.5°C Paris Agreement goal would preserve nearly twice as much glacier ice as the 2.7 °C scenario. The article notes that these findings are based on simulations over thousands of years using eight different glacier models; despite acknowledged uncertainties, the overall conclusion of substantial ice loss is certain.

    The article also effectively communicates other key findings. It emphasizes the significant regional differences in glacier vulnerability, noting the severe losses expected in the western U.S. and Canada, while also acknowledging the greater resilience of glaciers in parts of the Hindu Kush–Karakoram region. However, they will still retreat significantly as global temperatures rise. Furthermore, the report details the direct impact on sea-level rise, projecting a contribution of approximately 23 cm at +2.7°C, which is reduced to 14 cm if warming is limited to +1.5°C. 

    Carrington connects these scientific findings to their direct societal consequences, from risks to coastal populations to threats to water and food security. He also uses quotes from the study's co-leads, Dr. Harry Zekollari and Dr. Lilian Schuster, to emphasize the importance of immediate emission cuts and to highlight that current actions will determine the long-term outcomes for centuries. 

    Finally, the article includes an external perspective from Prof. Andrew Shepherd of Northumbria University, who describes the assessment as "sobering" and confirms that glacier change will continue for generations. The article concludes by linking the fate of distant ice to everyday fossil-fuel consumption, as a powerful call for the audience to recognize their role and take immediate action.

Research Article

    The peer-reviewed article published in Science," Glacier preservation doubled by limiting warming to 1.5°C versus 2.7°C," by Zekollari et al., aims to quantify the long-term, committed mass loss of the world's glaciers under various stabilized warming scenarios, thereby highlighting the profound differences in outcomes between stringent climate policy and the current trajectory. The paper moves beyond typical 21st-century projections to model how glaciers will eventually reach a new, smaller equilibrium with a warmer climate, revealing that a substantial amount of ice loss is already unavoidable due to past and present emissions.

    To accomplish this, the researchers utilized an ensemble of eight glacier evolution models, running them for a 2000-year simulation across 80 constant-climate scenarios, allowing ~200,000 glaciers to fully stabilize. This long-term approach reveals the full extent of committed mass loss. The most striking finding is that even if global temperatures stabilize at their present-day level (ΔT = +1.2 °C above preindustrial), the world's glaciers are already committed to losing 39% (range, 15-55%) of their mass relative to 2020 (Fig. 1A), which corresponds to an 113 mm (range, 43-204 mm) of sea-level rise.

    The study then illustrates how policy choices directly determine the future of glaciers (Fig. 1A).

•  Limiting warming to the Paris Agreement goal of +1.5°C would still result in a 47% loss of glacier mass (range: 20-64%) and a sea level rise of 138 mm (range: 59-237 mm)
• Under current policy commitments, warming is projected to reach +2.7°C by 2100, with a 76% loss of glacier mass (range: 54-82%), leaving only about 24%, and a sea level rise of 230 mm (range: 159-302 mm).
• These results demonstrate that the +1.5°C target would preserve more than twice as much glacier ice as the +2.7°C path in the long term.

    The study also examines the sensitivity of glacial mass loss to changes in temperature. Every extra 0.1 °C of warming between 1.5 °C and 3 °C costs about 2% of global glacier mass and adds 6.5 mm to sea level (Fig. 1B).

Fig. 1. Projected global glacier mass under constant- climate scenarios. (A) Evolution of global glacier mass relative to present day (year 2020; 3- year running mean).  Solid lines show the results for all 80 constant- climate scenarios derived from the sum of the regional medians of the glacier model ensemble. Colors indicate corresponding global mean warming levels above preindustrial (ΔT, range from –0.1° to 6.9°C). Dashed lines refer to the mean of the solid lines for select warming levels. Shading marks the multimodel ensemble likely range (shown for ΔT = 0.0 ± 0.2°C and ΔT = 4.0 ± 0.2°C). (B) Steady- state glacier mass as a function of warming level. Colored dots refer to results for the globally applied glacier models (color coding per glacier model is in Fig. 2). Black dots are obtained by globally summing regional multimodel medians through which a LOWESS fit is added

    

    In addition to the global average, the study uncovers significant regional differences in glacier responses (Fig. 3), which help explain why some glaciers are more vulnerable than others. For instance, the analysis shows that regions where glaciers span a wide elevation range, such as in South Asia West, are more likely to adapt to climate change by retreating to higher, colder elevations. In contrast, regions with a smaller elevation range, such as Arctic Canada South, are projected to lose most of their ice under the current condition of ΔT = +1.2 °C (Fig.3). However, even those more resilient regions still shrink under additional warming because glaciers take longer to respond, and their energy balance continues to shift. The study also found that the timescale of this response is highly related to the geometry of the glacier. Steep, fast-flowing glaciers at Low Latitudes can retreat by 80% in just a few decades. In contrast, the vast, gently sloping glaciers in the Subantarctic and Russian Arctic require many centuries to fully respond to climate change.

Fig. 3. Committed glacier mass loss at different global warming levels above preindustrial (ΔT). In every circle, the colored lines indicate the LOWESS fitted ensemble median estimates of committed mass loss at steady state at different warming levels in the range ΔT = +1.2°C to +5.0°C (increasing in clockwise directions in 0.1°C steps beyond 1.2°C; full circle correspond to 100% committed mass loss). The present- day committed mass loss at steady state (ΔT = +1.2°C) is in light blue, with the loss after 100 simulation years (fig. S6) shown as the dotted line. Numbers in the circle centers are the ΔT at which 50% of the present (year 2020) regional glacier mass is lost.

    

    The authors conclude that focusing solely on outcomes through 2100 significantly underestimates the long-term consequences. Because glaciers adjust over decades to thousands of years, today's policy decisions determine very different futures. Limiting warming to 1.5 °C could preserve more than twice as much glacier ice as a 2.7 °C world and slow sea-level rise. Overall, the work provides a quantitative and policy-relevant message: even a 0.1 °C difference matters, and immediate, stringent mitigation policies are needed to preserve Earth's glaciers.

Analysis/Review

    I would give this news article 8.5/10. The title, "Almost 40% of world's glaciers already doomed due to climate crisis, study," is direct and effectively captures attention, and the article content does an excellent job summarizing the study's core findings, such as the significant difference in long-term ice preservation between a +1.5°C and a +2.7°C warming scenario. I really liked that the author used quotations directly from two co-leaders of this study, which adds credibility and answers potential questions, such as why 2020 was used as a baseline, thereby supplementing details not included in the original paper. The article also makes the data more accessible to the public; for example, it converts sea-level rise from millimeters (mm) to the more commonly understood centimeters (cm), and it also simplifies Figure 1A to display the results more directly. Finally, the article ends with a strong call to action by clearly connecting the fate of distant glaciers to everyday fossil fuel consumption.

News Figure

    

    However, points were deducted for several reasons. First, the word "doomed" in the title, while impactful, could be considered slightly misleading and create a sense of hopelessness rather than a call to action. Additionally, the article's structure is somewhat disorganized, and some sections are redundant. More importantly, it fails to emphasize the critical detail that the study is based on a 2000-year simulation to achieve steady states, which is essential for understanding the long-term nature of the committed mass loss. Finally, it glosses over the significant regional differences in glacier response times. Even so, it remains a strong example of science communication for the public.

Citations

1. Bojinski, S. et al. The Concept of Essential Climate Variables in Support of Climate Research, Applications, and Policy. (2014) doi:10.1175/BAMS-D-13-00047.1.

2. Huss, M. & Hock, R. Global-scale hydrological response to future glacier mass loss. Nature Clim Change 8, 135–140 (2018).

3. Slater, T. et al. Review article: Earth’s ice imbalance. The Cryosphere 15, 233–246 (2021).

4. Bosson, J. B. et al. Future emergence of new ecosystems caused by glacial retreat. Nature 620, 562–569 (2023).

5. von Schuckmann, K. et al. Heat stored in the Earth system 1960–2020: where does the energy go? Earth System Science Data 15, 1675–1709 (2023).

6. Bahr, D. B., Pfeffer, W. T., Sassolas, C. & Meier, M. F. Response time of glaciers as a function of size and mass balance: 1. Theory. doi:10.1029/98JB00507.