the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 23 Jun 2026
Robust attribution of global industrial-era glacier mass loss to anthropogenic climate change
Abstract. We apply formal climate-attribution methods to industrial-era glacier mass loss at both regional and individual glacier scales. Using a combination of observed temperatures and climate-model simulations, we show that warming across all glacierized regions of the globe is attributable to anthropogenic climate change. Our central estimates are that the magnitude of the anthropogenic warming over the industrial era ranges from from 91–98 % of the observed, depending on region. These temperature changes equate to regional equilibrium-line-altitude (ELA) rises of 107–340 m, all of which are at least extremely likely anthropogenic in origin.
We examine 75 individual glaciers around the world, using realistic geometries and mass-balance profiles to reconstruct approximate preindustrial glacier geometries. Using these preindustrial geometries as reference surfaces, we analyze mass balance on these surfaces and show that anthropogenic ELA rise has produced sweeping changes in ablation and accumulation across all sampled glaciers. We find that a glacier's sensitivity to ELA rise is governed more strongly by local catchment geometry than by climatic setting. Since these industrial-era mass-balance changes are driven by the anthropogenic warming, our central estimates of the anthropogenic contribution are the same as for temperature.
Finally, we compare these anthropogenically driven changes against the distribution of natural mass-balance variability drawn from both climate-model counterfactual simulations and last-millennium reconstructions at each of our 75 glaciers. Across all glacierized regions, it is virtually certain the anthropogenic mass-balance signal is outside the envelope of natural variability, as characterized by both preindustrial climate reconstructions and the CMIP counterfactual ensemble. Within our analysis framework, we conclude it is very likely that anthropogenic warming is the primary driver of industrial-era mass loss.
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Status: final response (author comments only)
- RC1: 'Comment on egusphere-2026-3164', Anonymous Referee #1, 02 Aug 2026
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RC2: 'Comment on egusphere-2026-3164', Anonymous Referee #2, 27 Sep 2026
This paper attempts to make an attribution of glacier mass loss during the industrial era to anthropogenic climate change. The authors apply methods of various complexity to determine how much of the observed glacier mass loss is related to human greenhouse gas emissions and how much is natural.
While the main research questions and results are highly relevant, I struggled with the paper’s structure and the applied methodologies. On the one hand this is due to specific approaches and assumptions that I found questionable. On the other hand, I failed to follow the basic concept of the paper following up on the gaps identified in the introduction. For these reasons, I partly lost track of the arguments, especially towards the end. Major work is required to restructure the paper and better explain and/or revise the approaches if the paper should become publishable. Furthermore, more effort should be invested to make the attribution relevant in a temporal sense, and not just over the entire industrial era.
Substantive comments:
- The structure of the paper is convoluted. The same study sites and data are introduced several times throughout the manuscript in the context of different experiments. The methods of those experiments are described in the many individual sections. This makes it difficult to keep track of applied approaches that are often on a pretty different level (e.g. detailed modelling using OGGM in comparison to very simple mass balance gradient assumptions).
- The main problem with the paper is, in my opinion, the failure to answer the relevant questions: The outcome of the paper is that over the whole industrial era (i.e. since about 1880), the anthropogenic contribution to glacier retreat is 100%. Is that surprising? If the climate models indicate zero warming without anthropogenic influence of this time period, could the result be any different over the entire time frame? The open question – as also very nicely put up in the introduction when referring to a poorly backed-up statement in IPCC – is from WHEN onwards the anthropogenic contribution started to be significant. I cannot see that this point is answered here, nor can be answered with the approaches applied. So, the paper starts with an excellent motivation about explaining when anthropogenic warming matters but then compresses all interpretation into the industrial era as a whole. The temporal dimension is key in my view as during the industrial era there were clearly climatic variations as well (on top of the anthropogenic trend) that were most likely natural. In order to be credible, we need an explanation for these periods too and cannot broadly state that 100% (all the time) is human-induced. This is a basic concept of the study that would need a major re-definition of the approaches used. But it is crucial for the useability of the study.
- Regarding individual approaches, I most struggled with (1) the assumption that precipitation does not matter, and (2) the flowline model applied (see below). These are rather detailed methodological concepts that could probably be addressed in a revision by adapting the corresponding methodology. However, the reformulation of the approaches would still need major efforts and might also lead to different conclusions.
Detailed comment
- line 52: I was surprised to see that precipitation does not seem to be a factor.
- line 55: Isn't this a contradiction? Above it was argued that glacier retreat may have been a lagged response to the LIA climate. So, this can only be a dynamic effect and disregarding dynamics with using reference mass balances thus seems surprising.
- Line 57: I found this paragraph strange: The final results are stated in the introduction (without context). The introduction should indicate the context and goal of the study but not present the findings.
- Line 86: Right, there are no long-term trends. But there’s a large year-to-year and also decadal variability. Intermediate advance periods can partly attributed to this.
- Line 95: I’m getting lost with the structure… What is the method for mass balance modelling? First, all data / study sites should be described, followed by the Methods. It would make sense to adhere to that basic structure for a TC paper.
- Line 100: This statement and the references come as a surprise. What do these studies say? I would have expected more background than just IPCC report in the introduction. It implies that this was an understudied topic so far, but obviously it is not.
- Line 122: Of course, but what does that tell us about the relevant question? When did man-made climate change start to affect glacier behaviour? if the warming from natural forcing is zero, contribution will always remain on 100%.
- Line 134: Is there a need to speculate here? So, IPCC does not provide any source for the statement "from the 1990s onwards"? i.e. is it impossible to track the provenience of the number? That would be interesting too...
- Caption Fig. 1: This is methods description that is only stated in the figure caption... This needs to be changed. Furthermore, the ELA is not just a function of the temperature lapse rate. It also depends on melt season duration or absolute temperature, radiation totals (N vs S facing slopes), snow distribution patterns / temporal variability. This is a relevant methodological assumption that is far to oversimplified in my opinion. This needs to be improved. I also do not fully understand the concept as obviously the authors use a full mass balance model (OGGM) in their assessment. Why then relying on highly simplified approaches to estimate the ELA. The ELA could directly be taken from the OGGM outputs.
- Line 136: The Abstract said that 75 individual glaciers are investigated. Here there’s suddenly a switch to “all” glaciers.
- Iine 157: It is a major assumption that Delta ELA is just a function of temperature. It needs to be proven that this is the case, including physically-based modelling. The authors could for example check out the classical paper by Ohmura et al. (1992, JoG). ELA is a function of summer temp but with major influences by mean winter precipitation. This is too strongly simplified
- Table 1: I believe this is not relevant. There's no doubt that overall retreat is driven by the warming. But how do glacier dynamics, as evoked in the introduction, play in here?
- Line 182: But in the intro it was argued that retreat may be a dynamic reaction...
- Line 198: What is “each” glacier? Each of the 200’000 globally, or the 70 selected ones? Where is the glacier surface at the LIA maximum taken from? This needs a reference as it is an important data set.
- Line 225: I struggle to get the concept of the study. The authors are using OGGM. Why then is it needed to implement another flowline model? Before it was stated that reference surface mass balance was better suited. What is the purpose of the flowline model then? It may be my failure to understand the basic methodology envisaged by the authors but I think it is crucial to better expose the main concepts of the study, and make them consistent with the motivation and the research question.
- Figure 3a: The dashed line does not show the OGGM profile but the SRTM surface that is evaluated along the OGGM profile
- Figure 3d: There’s an important conceptual problem with the flowline model used here! The width of a glacier can impossibly double in the accumulation area. The geometry of a glacier is constrained by mountain topography there. Glacier advance results in an expansion of the width in the ablation area. This must be an artefact of the model but will have important consequences for the conclusions drawn from it.
- Line 328: I do not understand how this part of the analysis pertains to the research question. This seems to be a side branch that comes on top of the many methodological aspects of the paper.
- Line 386: I do not think this argumentation is right. This would only be relevant as a self-enforcing process if driven by the albedo-difference (snow vs ice). But this is a process that is not in OGGM.
- Line 515: To be honest, I lost track of the arguments in the last part, with new concepts being introduced. It would be much easier to follow the logic of the paper when having one Methods section that clearly exposes the relevant approach applied here. At present there are various approaches introduced at different places in the manuscript. Also, I was surprised to not see any Discussion or Conclusion section. While the discussion is indeed partly already contained in the manuscript (even though not easy to locate), I consider a Conclusion section as absolutely necessary to highlight the main findings.
Citation: https://doi.org/10.5194/egusphere-2026-3164-RC2
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- 1
This paper usefully quantifies, labels, and clearly states the anthropogenic contribution to changes in melt-season air temperatures (as the primary driver of glacier melt and indeed overall mass loss), Equilibrium Line Altitudes (ELAs), and glacier mass balance for two time periods (pre-industrial to modern and last millennium) using a couple of methods, from extracting temperatures from global datasets to flowline modeling with OGGM. It does all of the above first for Argentiere as a case study; the simpler analysis is then done for all glaciers globally, while the flowline modeling is done for a subset of 75 glaciers for which the necessary data are available.
I appreciate this work and find no major flaws in it, insofar as my technical expertise allows. The authors have done a service in using the standardized IPCC language, and in clearly and directly stating their results in these terms. I think many readers, some glaciologists included, will find things are even worse than we thought!
I have only minor comments that are included in the form of an annotated pdf, with the exception that I found the overall structure of the manuscript confusing. Unless this work was first submitted to a short-form journal and only lightly reformatted, I cannot understand the current structure, which progressively reveals methods as the paper goes along. The final section, as an example, is a bit sprawling and includes new results, some discussion, and summary statements. This reader would very much appreciate a more standardized format, though this does not exclude the possibility of interleaving methods and results provided there is a clear outline of what’s to come early on in the paper.
In addition to cleaning up the structure, or the wayfinding at the very least, a more explicit articulation of some of the methods would be appreciated. For example, I don’t think the temperature data are ever downscaled from their native resolution of 1 degree, but I’m not sure. Similarly, I think the method of relating air temperature to ELA is so simple that I did not get it at first; or maybe it’s not simple and I still don’t get it? Please state explicitly what is done or express the calculation unambiguously as an equation. In the spirit of clear communication, many would also appreciate if the standard mass-balance terminology and notation (as enshrined in the Cogley et al. Glossary) were used in such a paper where mass balance is of central importance.
Thanks for an interesting and important analysis! I’m sure I will be using or referring to this paper when it’s published.