Glacial cooling and climate sensitivity revisited
Open accessAbstract
The Last Glacial Maximum (LGM), one of the best-studied paleoclimatic intervals, offers a prime opportunity to investigate how the climate system responds to changes in greenhouse gases (GHGs) and the cryosphere. Previous work has sought to constrain the magnitude and pattern of glacial cooling from paleothermometers, but the uneven distribution of the proxies, as well as their uncertainties, has challenged the construction of a full-field view of the LGM climate state. Here, we combine a large collection of geochemical proxies for sea-surface temperature with an isotope-enabled climate model ensemble to produce a field reconstruction of LGM temperatures using data assimilation. The reconstruction is validated with withheld proxies as well as independent ice core and speleothem d18O measurements. Our assimilated product provides a precise constraint on global mean LGM cooling of -5.9˚C (-6.3 – -5.6˚C, 95% CI). Given assumptions concerning the radiative forcing of GHGs, ice sheets, and aerosols, this cooling translates to an equilibrium climate sensitivity (ECS) of 3.2˚C (2.2 – 4.3˚C, 95% CI), a value that is higher than previous estimates and but consistent with the traditional consensus range of 2 – 4.5˚C.
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Over the last ∼50 million years, global average surface temperatures steadily decreased from nearly 30°C during the early Eocene to less than 10°C during the most recent Pleistocene glacial epoch.
“For example, over the last ∼50 million years, global average surface temperatures have steadily decreased from nearly 30°C during the early Eocene (Burke et al. 2018, Hansen et al. 2013) to less than 10°C during the most recent Pleistocene glacial epoch (e.g., Tierney et al. 2020).”
From The History of Ocean Oxygenation (2022) · cites this paper as Tierney et al. 2020
The paper’s LGM temperature-results section reports that global mean surface temperature was 5.9°C lower than in the Late Holocene. It reports a temperature change, not an absolute LGM temperature, so it does not establish the cited claim of less than 10°C. The early-Eocene figure is attributed to other citations in the sentence. (LLM, conf=0.82)
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Cites
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Cited by
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An Assessment of Earth's Climate Sensitivity Using Multiple Lines of Evidence
Sherwood, S. C., Webb, M. J., Annan, J. D., Armour, K. C., Forster, P. M., Hargreaves, J. C., Hegerl, G., Klein, S. A., Marvel, K. D., Rohling, E. J., et al. (2020) · Reviews of Geophysics · doi:10.1029/2019rg000678 · Cited by 1,254 · see citing works
Globally resolved surface temperatures since the Last Glacial Maximum
Osman, M. B., Tierney, J. E., Zhu, J., Tardif, R., Hakim, G. J., King, J., & Poulsen, C. J. (2021) · Nature · doi:10.1038/s41586-021-03984-4 · Cited by 574 · see citing works
Self-citationWidespread six degrees Celsius cooling on land during the Last Glacial Maximum
Seltzer, A. M., Ng, J., Aeschbach, W., Kipfer, R., Kulongoski, J. T., Severinghaus, J. P., & Stute, M. (2021) · Nature · doi:10.1038/s41586-021-03467-6 · Cited by 133 · see citing works
The History of Ocean Oxygenation
Reinhard, C. T., & Planavsky, N. J. (2022) · Annual Review of Marine Science · doi:10.1146/annurev-marine-031721-104005 · Cited by 91 · see citing works
- Authors
- Tierney, J. E., Zhu, J., King, J., Malevich, S. B., Hakim, G. J., & Poulsen, C. J.
- Affiliations
- University of Arizona (US)
- NSF National Center for Atmospheric Research (US)
- University of Washington (US)
- University of Michigan (US)
- Corresponding author
- Tierney, Jessica E.
- ORCID
- Venue
- Nature
- Published
- 2020-08-26
- Volume
- 584
- Issue
- 7822
- Pages
- 569-573
- ISSN
- 0028-0836 (ISSN-L)
- 1476-4687
- OpenAlex
- W2996825230
- Cited by
- 573
- References
- 1
- Citations by year
- 2026: 60 · 2025: 92 · 2024: 85 · 2023: 128 · 2022: 108 · 2021: 90 · 2020: 10
- FWCI
- 26.74
- Type
- journal article
- Language
- en
- Open access
- green
- doi.org
- Locations
- Nature (publishedVersion)
- PubMed (publishedVersion)
- EarthArXiv (California Digital Library) (submittedVersion, cc-by)
- RePEc: Research Papers in Economics (submittedVersion)
- EarthArXiv (OSF Preprints) (submittedVersion)
- EarthArXiv (OSF Preprints) (submittedVersion, cc-by)
- Funders
- National Science Foundation (1602301, 1602223)
- Topics
- Physical Sciences › Earth and Planetary Sciences › Atmospheric Science › Geology and Paleoclimatology Research
- Physical Sciences › Environmental Science › Global and Planetary Change › Climate variability and models
- Physical Sciences › Earth and Planetary Sciences › Atmospheric Science › Cryospheric studies and observations
- Keywords
- Last Glacial Maximum, glacial cooling, equilibrium climate sensitivity, sea surface temperature reconstruction, geochemical proxies, data assimilation, isotope-enabled climate model, speleothem δ18O, greenhouse gas forcing, ice sheets, mineral dust aerosols
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