the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 13 Mar 2025
Late Pleistocene temperature patterns in the Western Palearctic: insights from rodent associations compared with General Circulation Models
Abstract. Since rodent fossils are preserved in many low and high latitude archaeological and paleontological sites from a wide variety of environments, their associations are a commonly useful proxy for inferring past local climate and environmental conditions. Such a frequent and widespread geographic distribution can help us to better understand past climate evolution by providing access to high spatiotemporal resolution at large geographical scales. The aim of this paper is to develop an approach to generate continental scale temperature maps based on rodent associations and to assess their reliability compared to state-of-the-art General Circulation Models (CGMs). We used the Bioclimatic Model, based on fossil and modern rodent associations, to infer climate zone distribution and local temperatures (Mean Annual Temperature, Mean Temperature of the Warmest month and the Mean Temperature of the Coldest month), at the western Palearctic (Europe, Middle East and North Africa) for six different periods: LGM, Heinrich Stadial, Bølling, Allerød, Younger Dryas and present-day conditions. The Bioclimatic Model is combined with a spatial generalized linear mixed model to interpolate these surface temperatures across the western Palearctic. We show that the spatial patterns in Mean Annual Temperature and Mean Temperature of the Warmest and Coldest months are very similar between our interpolations and GCMs for both present-day and LGM conditions, but the rodent-based approach provides slightly cooler LGM estimations in western Europe and warmer in eastern Europe. Throughout the Late Glacial oscillations, the rodent-based model infers globally small variations in Mean Annual Temperature and Mean Temperature of the Warmest months and slightly larger changes in Mean Temperature of the Coldest months. Nonetheless, some events show weak but significant regional variations depending of the events and the climate variable. For instance, the most important shifts in mean annual temperature between Allerød and Younger Dryas are observed in northwestern regions. Northeastern regions, on the other hand, experienced relatively stable mean annual temperature, although they did experience considerable warming of the warmest month and cooling of the coldest month. Minor discrepancies appear between GCMs and the rodent-based model, the latter showing colder temperature in northwestern Europe, hence a differential west-east gradient in ice-sheet influence. Our results demonstrate that rodent associations are robust proxies for reconstructing and regionalizing past climates at broad scales, offering a readily reproducible approach to be reimplemented in future studies incorporating new rodent data.
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Status: final response (author comments only)
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RC1: 'Comment on egusphere-2025-815', Juan Manuel Lopez, 20 May 2025
Dear authors,
The manuscript is very interesting and with the R script to reproduce de data very useful for the for researchers dedicated to the study of climate and landscape reconstruction in the quaternary small mammals. However, I consider that the manuscript could be published after clarifying some doubts and correcting some minor issues:
Abstract: Abbreviation of General Circulation Model is wrong written is GCMs
Keywords: In my opinion there are two unnecessary ones (paleoclimate and Mammalia) and they are not well ordered: rodent-based reconstructions, temperature patterns, Last Glacial Maximum, Late Glacial, Heinrich Stadial, Bølling-Allerød Interstadial, Younger Dryas.
page 3, line 72: (Rodentia and /or Eulipotyphla)
page 9, line 172-173: write in brackets the scientific name of the species after de common name, Dicrostonyx torquatus and Apodemus agrarius
page 7-lines 141-142. Please better explain the use of the IUCN Red List for species distribution per 50 km, because those maps do not appear to be in the IUCN, 2021.
page 10-line 176: Why you don’t use direct the updated version of OxCal 4.4.4. (Bronk Ramsey, 2021) and the IntCal20 (Reimer et al. 2020). Probably some of the dating that you calibrated are wrong without the updating. Check it.
page 13-238-241. In my opinion, the reason why altitude is omitted in the article needs a better explanation. Although the sites used are few, the altitudinal location is very important. At the same longitude and latitude, at different altitudes, you can have completely different associations of micromammals.
The list of sites with the different chronological periods presented is impressive and very complete. I only missed one site, published a couple of years ago, which has two levels from the end of the Late Ice Age. Here's the reference, perhaps it could be included:
Arjanto, D.Q., Fernández-García, M., López-García, J.M., Vergès, J.M., 2023. The end of Late Glacial in north-eastern Iberia: the small mammal assemblage from Cudó Cave (Mont-Ral, Tarragona). Earth and Environmental Science Transactions of the Royal Society of Edinburgh 114 (1–2), 21–33.
Yours Sincerely
Dr. Juan Manuel López-García
Citation: https://doi.org/10.5194/egusphere-2025-815-RC1 - AC1: 'Reply on RC1', Aurélien Royer, 15 Jul 2025
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RC2: 'Comment on egusphere-2025-815', Anonymous Referee #2, 09 Jun 2025
Overall, this is a strong, nice paper that infers temperature for Eurasia based on modern and fossil rodent assemblages, then compares the estimates to different model-based temperature estimates. It contributes a good perspective of faunal estimates, in contrast to the GCM and pollen-based estimates that are more common. The method that the authors use has been well-validated, and here they extend it to more sites and taxa, and do the detailed benchmarking necessary to establish rodent assemblages as a valid proxy.
My overall impression is that rodent assemblages are good proxies for MAT, less good but still strong for MTWA, but perhaps not super robust approximations of MTCO. I don’t have as clear of a “takeway” for other aspects of the paper - there were interesting differences in the spatial patterns between rodents and the other estimates of paleoclimate that could indicate that the rodents do a better job than models in some places, or a worse job than models in other places. I think the lack of clear takeaways is partly because the data themselves are muddled, but it may also partly be due to the length of the discussion of anomalies and gradients, which overwhelmed the author’s messages at times. I wonder if additional subheadings that state the main submessages would help with paper structure, and help draw out the main takeaways for the paper?
Line-by-line comments:
Line 49-50, “Our results demonstrate that rodent associations are robust proxies for reconstructing and regionalizing past climates at broad scales…”. Since the authors tackle temperature only, I would narrow this to “reconstructing and regionalizing past temperature at broad scales”.
Line 169, “obtained through adequate sample sizes”. Is there a specific threshold, or taxon-specific value? Or a citation for this?
Lines 175-176, “we selected mainly stratigraphic units associated with radiocarbon dates restricted to a single time interval”. This is a good step. Is there an estimate of overall uncertainty associated with site chronologies? I assume that most of the radiocarbon dates are indirect, i.e. representing one or a few dates on a few specimens, but not all species in a unit are dated. How certain are the authors that the assemblages as a whole can be assigned to the climatic period they are associated with?
Table 1. I’m sure this would be worked out in production, but the lines and Zonobiome descriptions for Zones VII and VIII are confusing. Which zone does “Boreal coniferous forest” and (taiga) and “coniferous” belong to?
Line 226. I understand why the authors chose to focus only on temperature values – this is a big undertaking. But for future work, seeing how measures of precipitation perform would be valuable, since many small mammals are very sensitive to precipitation (likely through its effects on vegetation).
Section 2.3, and especially lines 215 – 229. There are two places where the bioclimatic model estimates values for extinct communities – it estimates the bioclimatic zone using linear discriminant functions, and it estimates different climate variables using transfer functions. For this second part, the authors write “The second part of the Bioclimatic Model is built from transfer functions by means of multiple linear regression analyses of climatic parameters and modern bioclimatic spectra. These models are ultimately used to infer climatic variables for additional observations (i.e., extinct communities).” The focus in these sentences is on inferring climate for past communities. But for the modern communities, how does model validation work? Is the model validated by leaving out sets of modern communities? Or have the transfer functions already been validated and even though there is new CRI data for some species, the authors rely on those same transfer functions? I understand the authors are building on other work here (e.g., Hernández Fernández & Peláez-Campomanes, 2005; Royer et al., 2020), but a few additional details would be helpful.
Lines 306-307. This sentence needs editing for clarity. I am not sure exactly what the authors are trying to say with the second part (“and the benefit of using the Bioclimatic Model to partially overcome these limitations”). I think they maybe mean “and using the Bioclimatic Model helps to partially overcome these limitations”.
Figure 2, and other places throughout the paper. The labels on Figure 2 indicate the “Biozone”. But the term “biozone” only really is used in the figures. In other places (ie, the caption to figure 2, “3.2.1 Climate zone classification”, many other places in the main text), the zones are called “climate zones”. This led to confusion for me initially - I thought these were two separate things. I would try to use the same terminology throughout.
Figure 3, Fig 6, Fig 9, Fig 10, Fig 11, Fig 12, Fig 13. The site icons (triangles, squares, circles, etc) are very small, and difficult to see clearly without zooming in quite far. And the colors of the labels vs background makes it extra difficult for some figures. Thus, the authors should consider increasing the size of the site icons (such as in Figure 2) or perhaps outlining the icons in black – while the spatial location may appear less precise, at the scale of the study that level of precision is not necessary.
Figure 6 vs Figures 9b and Fig 12. In some cases, the legend in the box to the left of the maps on these figures does not reflect the map values. e.g., Fig 6 top row, it says “delta rodents – ERA5”. I think this is accurate - the authors are mapping the difference (delta) between rodents and ERA5 [i.e., delta (rodents – ERA5)]. But in other cases (e.g., Fig 9b), the authors use the exact same notation (“delta rodents – Beyer2020” and “delta rodents – GCMs”), but in this case the caption indicates that what is mapped is “delta rodents - delta Beyer2020” and “delta rodents - delta GCMs”. And same for Figure 12 - I think the label should be “delta rodents - delta Beyer2020”. But perhaps I have gotten my interpretations wrong here. Regardless, I encourage the authors to critically examine the figure labels to ensure they all accurately reflect what is being mapped.
Line 529, “This environment is far to be restricted to a tundra”. This word choice is a bit unclear, so I’m not quite sure what the authors mean.
Line 547: “based on faunal species”. Do you mean based on OTHER faunal species? Or perhaps “colder than OTHER estimations based on faunal species”, if the Puzachenko and Markova estimates are from rodents as well.
Figure 10 - some of the panels are offset from one another along the x axis. Are all panels spanning to 60°E longitude or do some of the panels/models end before then? If they are all the same, please re-size panels accordingly.
Line 580, “showing much LGM temperatures that are much colder”. The first “much” can be deleted, I think.
Line 580, “zonal gradient’. I think this means “longitudinal”, but it’s not clear if it’s supposed to mean that or the biozones/climate zones.
Line 668: “closed to” or “close to”? I think it’s supposed to be the latter.
Figure 13 - because the site labels are so small, it’s difficult to tell apart circles from triangles. And when I zoom in, resolution issues also mean I can’t easily differentiate.
Lines 693-694. What about the sea level rise? I think you should add “and the sea level rise [progressively eliminating some areas]”.
Line 707, “spatial pattern [different?] from Beyer2020”.
Lines 718-720 if the rodent associations “generate colder temperature values in the western part of Europe and warmer in Eastern Europe” compared to GCMs, wouldn’t there be a “[stronger] west-east temperature gradient”? I am unsure about the authors use of the word “weaker” in the original text.
Lines 721-722. What do you mean by “The physical interpretation …. is questionable”? Here, are you effectively saying it’s not clear which scenario (rodents, GCMs) reflects real-world conditions during the LGM?
Update: ah, I see. Yes, I think this is what you are saying, based on what is in the next paragraph. I think this would be more clear if you moved the sentence starting with “The physical interpretation” to be the start of the new paragraph, merged with lines 723 - 743.
Line 751, “given niche species”. Needs rewording. I think the authors mean the following: “underestimating the plasticity and adaptation of species niches with new abiotic and biotic constraints.”
Citation: https://doi.org/10.5194/egusphere-2025-815-RC2
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