Lüthi, D. et al. High-resolution carbon dioxide concentration record 650,000–800,000 years before present. Nature 453, 379–382 (2008).
Bereiter, B. et al. Revision of the EPICA Dome C CO2 record from 800 to 600 kyr before present. Geophys. Res. Lett. 42, 542–549 (2015).
Loulergue, L. et al. Orbital and millennial-scale features of atmospheric CH4 over the past 800,000 years. Nature 453, 383–386 (2008).
Whillans, I. M. & Cassidy, W. A. Catch a falling star: meteorites and old ice. Science 222, 55–57 (1983).
Higgins, J. A. et al. Atmospheric composition 1 million years ago from blue ice in the Allan Hills, Antarctica. Proc. Natl Acad. Sci. USA 112, 6887–6891 (2015).
Yan, Y. et al. Two-million-year-old snapshots of atmospheric gases from Antarctic ice. Nature 574, 663–666 (2019).
Shackleton, S. et al. Miocene and Pliocene ice and air from the Allan Hills blue ice area, East Antarctica. Proc. Natl Acad. Sci. USA 122, e2502681122 (2025).
Clark, P. U., Shakun, J. D., Rosenthal, Y., Köhler, P. & Bartlein, P. J. Global and regional temperature change over the past 4.5 million years. Science 383, 884–890 (2024).
Clark, P. U. et al. Global mean sea level over the past 4.5 million years. Science 390, eadv8389 (2025).
Shackleton, N. J. et al. Oxygen isotope calibration of the onset of ice-rafting and history of glaciation in the North Atlantic region. Nature 307, 620–623 (1984).
Clark, P. U. et al. The middle Pleistocene transition: characteristics, mechanisms, and implications for long-term changes in atmospheric pCO2. Quat. Sci. Rev. 25, 3150–3184 (2006).
DeConto, R. M. et al. Thresholds for Cenozoic bipolar glaciation. Nature 455, 652–656 (2008).
Vizcaíno, M., Rupper, S. & Chiang, J. C. H. Permanent El Niño and the onset of Northern Hemisphere glaciations: mechanism and comparison with other hypotheses. Paleoceanography 25, PA2205 (2010).
Berends, C. J., Köhler, P., Lourens, L. J. & van de Wal, R. S. W. On the cause of the mid-Pleistocene transition. Rev. Geophys. 59, e2020RG000727 (2021).
Ridgwell, A. & Zeebe, R. The role of the global carbonate cycle in the regulation and evolution of the Earth system. Earth Planet. Sci. Lett. 234, 299–315 (2005).
Zeebe, R. E. & Caldeira, K. Close mass balance of long-term carbon fluxes from ice-core CO2 and ocean chemistry records. Nat. Geosci. 1, 312–315 (2008).
Hopcroft, P. O. et al. Polar amplification of Pliocene climate by elevated trace gas radiative forcing. Proc. Natl. Acad. Sci. USA 117, 23401–23407 (2020).
Rae, J. W. B. et al. Atmospheric CO2 over the past 66 million years from marine archives. Annu. Rev. Earth Planet. Sci. 49, 609–641 (2021).
The Cenozoic CO2 Proxy Integration Project (CenCO2PIP) Consortium Toward a Cenozoic history of atmospheric CO2. Science 382, eadi5177 (2023)
Bender, M. L., Barnett, B., Dreyfus, G., Jouzel, J. & Porcelli, D. The contemporary degassing rate of 40Ar from the solid Earth. Proc. Natl Acad. Sci. USA 105, 8232–8237 (2008).
Yan, Y. et al. Enhanced moisture delivery into Victoria Land, East Antarctica, during the early Last Interglacial: implications for West Antarctic Ice Sheet stability. Clim. Past 17, 1841–1855 (2021).
Spaulding, N. E. et al. Climate archives from 90 to 250 ka in horizontal and vertical ice cores from the Allan Hills Blue Ice Area. Antarctica. Quat. Res. 80, 562–574 (2013).
Bereiter, B., Schwander, J., Lüthi, D. & Stocker, T. F. Change in CO2 concentration and O2/N2 ratio in ice cores due to molecular diffusion. Geophys. Res. Lett. 36, L05703 (2009).
Ikeda, T. et al. Extreme fractionation of gases caused by formation of clathrate hydrates in Vostok Antarctic Ice. Geophys. Res. Lett. 26, 91–94 (1999).
Extier, T. et al. On the use of δ18Oatm for ice core dating. Quat. Sci. Rev. 185, 244–257 (2018).
Bouchet, M. et al. The Antarctic Ice Core Chronology 2023 (AICC2023) chronological framework and associated timescale for the European Project for Ice Coring in Antarctica (EPICA) Dome C ice core. Clim. Past 19, 2257–2286 (2023).
Landais, A. et al. What drives the millennial and orbital variations of δ18Oatm? Quat. Sci. Rev. 29, 235–246 (2010).
Berner, W., Stauffer, B. & Oeschger, H. Past atmospheric composition and climate, gas parameters measured on ice cores. Nature 276, 53–55 (1978).
Neftel, A., Oeschger, H., Schwander, J. & Stauffer, B. Carbon dioxide concentration in bubbles of natural cold ice. J. Phys. Chem. 87, 4116–4120 (1983).
Anklin, M., Barnola, J.-M., Schwander, J., Stauffer, B. & Raynaud, D. Processes affecting the CO2 concentrations measured in Greenland ice. Tellus B 47, 461–470 (1995).
Souchez, R., Janssens, L., Lemmens, M. & Stauffer, B. Very low oxygen concentration in basal ice from Summit, central Greenland. Geophys. Res. Lett. 22, 2001–2004 (1995).
Smith, H. J., Wahlen, M., Mastroianni, D., Taylor, K. & Mayewski, P. The CO2 concentration of air trapped in Greenland Ice Sheet Project 2 ice formed during periods of rapid climate change. J. Geophys. Res. Oceans 102, 26577–26582 (1997).
Eggleston, S., Schmitt, J., Bereiter, B., Schneider, R. & Fischer, H. Evolution of the stable carbon isotope composition of atmospheric CO2 over the last glacial cycle. Paleoceanography 31, 434–452 (2016).
Bauska, T. K., Marcott, S. A. & Brook, E. J. Abrupt changes in the global carbon cycle during the last glacial period. Nat. Geosci. 14, 91–96 (2021).
Chalk, T. B. et al. Causes of ice age intensification across the Mid-Pleistocene Transition. Proc. Natl Acad. Sci. USA 114, 13114–13119 (2017).
Hönisch, B., Hemming, N. G., Archer, D., Siddall, M. & McManus, J. F. Atmospheric carbon dioxide concentration across the mid-Pleistocene transition. Science 324, 1551–1554 (2009).
Shackleton, S. et al. Global ocean heat content over the past 3 million years. Nature https://doi.org/10.1038/s41586-026-10116-3 (2026).
Snyder, C. W. Evolution of global temperature over the past two million years. Nature 538, 226–228 (2016).
Brierley, C. M. & Fedorov, A. V. Relative importance of meridional and zonal sea surface temperature gradients for the onset of the ice ages and Pliocene-Pleistocene climate evolution. Paleoceanography 25, PA2214 (2010).
Martínez-Garcia, A., Rosell-Melé, A., McClymont, E. L., Gersonde, R. & Haug, G. H. Subpolar link to the emergence of the modern Equatorial Pacific Cold Tongue. Science 328, 1550–1553 (2010).
Howell, F. W., Haywood, A. M., Dowsett, H. J. & Pickering, S. J. Sensitivity of Pliocene Arctic climate to orbital forcing, atmospheric CO2 and sea ice albedo parameterisation. Earth Planet. Sci. Lett. 441, 133–142 (2016).
Feng, R. et al. Amplified Late Pliocene terrestrial warmth in northern high latitudes from greater radiative forcing and closed Arctic Ocean gateways. Earth Planet. Sci. Lett. 466, 129–138 (2017).
Burton, L. E. et al. On the climatic influence of CO2 forcing in the Pliocene. Clim. Past 19, 747–764 (2023).
Siever, R. Sedimentological consequences of a steady-state ocean-atmosphere. Sedimentology 11, 5–29 (1968).
Walker, J. C. G. Carbon dioxide on the early earth. Origins Life Evol. Biosphere 16, 117–127 (1985).
Coogan, L. A. & Dosso, S. E. Controls on the evolution of Cenozoic seawater chemistry. Geochim. Cosmochim. Acta 329, 22–37 (2022).
Isson, T. T. et al. Evolution of the global carbon cycle and climate regulation on Earth. Global Biogeochem. Cycles 34, e2018GB006061 (2020).
Takahashi, T., Olafsson, J., Goddard, J. G., Chipman, D. W. & Sutherland, S. C. Seasonal variation of CO2 and nutrients in the high-latitude surface oceans: a comparative study. Global Biogeochem. Cycles 7, 843–878 (1993).
Lisiecki, L. E. & Raymo, M. E. A Pliocene-Pleistocene stack of 57 globally distributed benthic δ18O records. Paleoceanography 20, PA1003 (2005).
Steig, E. J. et al. Calibrated high-precision 17O-excess measurements using cavity ring-down spectroscopy with laser-current-tuned cavity resonance. Atmos. Meas. Tech. 7, 2421–2435 (2014).
Ahn, J., Brook, E. J. & Howell, K. A high-precision method for measurement of paleoatmospheric CO2 in small polar ice samples. J. Glaciol. 55, 499–506 (2009).
Grachev, A. M., Brook, E. J., Severinghaus, J. P. & Pisias, N. G. Relative timing and variability of atmospheric methane and GISP2 oxygen isotopes between 68 and 86 ka. Glob. Biogeochem. Cycles 23, GB3003 (2009).
Lee, J. E. et al. An 83,000-year-old ice core from Roosevelt Island, Ross Sea, Antarctica. Clim. Past 16, 1691–1713 (2020).
Epifanio, J. A. et al. Millennial and orbital-scale variability in a 54,000-year record of total air content from the South Pole ice core. Cryosphere 17, 4837–4851 (2023).
Bauska, T. K., Brook, E. J., Mix, A. C. & Ross, A. High-precision dual-inlet IRMS measurements of the stable isotopes of CO2 and the N2O/CO2 ratio from polar ice core samples. Atmos. Meas. Tech. 7, 3825–3837 (2014).
Assonov, S. S. & Brenninkmeijer, C. A. M. On the N2O correction used for mass spectrometric analysis of atmospheric CO2. Rapid Commun. Mass Spectrom. 20, 1809–1819 (2006).
Schneider, R., Schmitt, J., Köhler, P., Joos, F. & Fischer, H. A reconstruction of atmospheric carbon dioxide and its stable carbon isotopic composition from the penultimate glacial maximum to the last glacial inception. Clim. Past 9, 2507–2523 (2013).
Bauska, T. K. et al. Carbon isotopes characterize rapid changes in atmospheric carbon dioxide during the last deglaciation. Proc. Natl Acad. Sci. USA 113, 3465–3470 (2016).
Menking, J. A. et al. Multiple carbon cycle mechanisms associated with the glaciation of Marine Isotope Stage 4. Nat. Commun. 13, 5443 (2022).
Tipple, B. J., Meyers, S. R. & Pagani, M. Carbon isotope ratio of Cenozoic CO2: a comparative evaluation of available geochemical proxies. Paleoceanography 25, PA3202 (2010).
Sowers, T., Bender, M. & Raynaud, D. Elemental and isotopic composition of occluded O2 and N2 in polar ice. J. Geophys. Res. Atmos. 94, 5137–5150 (1989).
Baggenstos, D. et al. Atmospheric gas records from Taylor Glacier, Antarctica, reveal ancient ice with ages spanning the entire last glacial cycle. Clim. Past 13, 943–958 (2017).
Stolper, D. A., Bender, M. L., Dreyfus, G. B., Yan, Y. & Higgins, J. A. A Pleistocene ice core record of atmospheric O2 concentrations. Science 353, 1427–1430 (2016).
Yan, Y., Brook, E., Kurbatov, A., Severinghaus, J. & Higgins, J. Ice core evidence for atmospheric oxygen decline since the Mid-Pleistocene transition. Sci. Adv. 7, eabj9341 (2021).
Durand, G. et al. Change in ice rheology during climate variations – implications for ice flow modelling and dating of the EPICA Dome C core. Clim. Past 3, 155–167 (2007).
Krauss, F. Optimisation of a Continuous Sublimation Extraction Technique to Reconstruct Past CO2, CH4, and N2O Concentrations and δ13C-CO2 from Ice Cores. PhD thesis, Univ. Bern (2024).
Zhang, J., Quay, P. D. & Wilbur, D. O. Carbon isotope fractionation during gas-water exchange and dissolution of CO2. Geochim. Cosmochim. Acta 59, 107–114 (1995).
Montross, S. et al. Debris-rich basal ice as a microbial habitat, Taylor Glacier, Antarctica. Geomicrobiol. J. 31, 76–81 (2014).
Orsi, A. J. et al. Differentiating bubble-free layers from melt layers in ice cores using noble gases. J. Glaciol. 61, 585–594 (2015).
Faure, G., Hoefs, J., Jones, L. M., Curtis, J. B. & Pride, D. E. Extreme 18O depletion in calcite and chert clasts from the Elephant Moraine on the East Antarctic ice sheet. Nature 332, 352–354 (1988).
Barker, J. D., Grottoli, A. G. & Lyons, W. B. Stable isotope evidence for the biogeochemical transformation of ancient organic matter beneath Suess Glacier, Antarctica. Arctic Antarctic Alpine Res. 50, e1448643 (2018).
Zhang, Y. G. et al. Refining the alkenone-pCO2 method I: lessons from the Quaternary glacial cycles. Geochim. Cosmochim. Acta 260, 177–191 (2019).
Pagani, M., Liu, Z., LaRiviere, J. & Ravelo, A. C. High Earth-system climate sensitivity determined from Pliocene carbon dioxide concentrations. Nat. Geosci. 3, 27–30 (2010).
Stoll, H. M. et al. Upregulation of phytoplankton carbon concentrating mechanisms during low CO2 glacial periods and implications for the phytoplankton pCO2 proxy. Quat. Sci. Rev. 208, 1–20 (2019).
Badger, M. P. S. et al. Insensitivity of alkenone carbon isotopes to atmospheric CO2 at low to moderate CO2 levels. Clim. Past 15, 539–554 (2019).
González-Lanchas, A. et al. Carbon isotopic fractionation of alkenones and gephyrocapsa coccoliths over the Late Quaternary (marine isotope stages 12–9) glacial-interglacial cycles at the Western Tropical Atlantic. Paleoceanogr. Paleoclimatol. 36, e2020PA004175 (2021).
Seki, O. et al. Alkenone and boron-based Pliocene pCO2 records. Earth Planet. Sci. Lett. 292, 201–211 (2010).
Da, J., Zhang, Y. G., Li, G., Meng, X. & Ji, J. Low CO2 levels of the entire Pleistocene epoch. Nat. Commun. 10, 4342 (2019).
Foster, G. L. Seawater pH, pCO2 and [CO2–3] variations in the Caribbean Sea over the last 130 kyr: a boron isotope and B/Ca study of planktic foraminifera. Earth Planet. Sci. Lett. 271, 254–266 (2008).
Martínez-Botí, M. A. et al. Plio-Pleistocene climate sensitivity evaluated using high-resolution CO2 records. Nature 518, 49–54 (2015).
Dyez, K. A., Hönisch, B. & Schmidt, G. A. Early Pleistocene obliquity-scale pCO– variability at ~1.5 million years ago. Paleoceanogr. Paleoclimatol. 33, 1270–1291 (2018).
Sosdian, S. M. et al. Constraining the evolution of Neogene ocean carbonate chemistry using the boron isotope pH proxy. Earth Planet. Sci. Lett. 498, 362–376 (2018).
de la Vega, E., Chalk, T. B., Wilson, P. A., Bysani, R. P. & Foster, G. L. Atmospheric CO2 during the mid-Piacenzian warm period and the M2 glaciation. Sci. Rep. 10, 11002 (2020).
Yamamoto, M. et al. Increased interglacial atmospheric CO2 levels followed the mid-Pleistocene Transition. Nat. Geosci. 15, 307–313 (2022).
van de Wal, R. S. W., de Boer, B., Lourens, L. J., Köhler, P. & Bintanja, R. Reconstruction of a continuous high-resolution CO2 record over the past 20 million years. Clim. Past 7, 1459–1469 (2011).
Stap, L. B. et al. CO2 over the past 5 million years: continuous simulation and new δ11B-based proxy data. Earth Planet. Sci. Lett. 439, 1–10 (2016).
Berends, C. J., de Boer, B., Dolan, A. M., Hill, D. J. & van de Wal, R. S. W. Modelling ice sheet evolution and atmospheric CO2 during the Late Pliocene. Clim. Past 15, 1603–1619 (2019).
Köhler, P. Atmospheric CO2 concentration based on boron isotopes versus simulations of the global carbon cycle during the Plio-Pleistocene. Paleoceanogr. Paleoclimatol. 38, e2022PA004439 (2023).
Willeit, M., Ganopolski, A., Calov, R. & Brovkin, V. Mid-Pleistocene transition in glacial cycles explained by declining CO2 and regolith removal. Sci. Adv. 5, eaav7337 (2019).
Köhler, P. & Munhoven, G. Late Pleistocene carbon cycle revisited by considering solid earth processes. Paleoceanogr. Paleoclimatol. 35, e2020PA004020 (2020).
Jouzel, J. et al. Orbital and millennial Antarctic climate variability over the past 800,000 years. Science 317, 793–796 (2007).

