1. Imbrie, J. et al. On the structure and origin of major glaciation cycles: 2. The 100,000-year cycle. Paleoceanography 8, 699–735 (1993).

2. Lisiecki, L. E. & Raymo, M. E. A Pliocene–Pleistocene stack of 57 globally distributed benthic δ18O records. Paleoceanography 20, PA1003 (2005).

3. Petit, J. R. et al. Climate and atmospheric history of the past 420,000 years from the Vostok ice core, Antarctica. Nature 399, 429–436 (1999).

4. Jouzel, J. et al. Orbital and millennial Antarctic climate variability over the past 800,000 years. Science 317, 793–796 (2007).

5. Siegenthaler, U. et al. Stable carbon cycle-climate relationship during the late Pleistocene. Science 310, 1313–1317 (2005).

6. Lüthi, D. et al. High-resolution carbon dioxide concentration record 650,000–800,000 years before present. Nature 453, 379–382 (2008).

7. Imbrie, J. et al. On the structure and origin of major glaciation cycles: 1. Linear responses to Milankovitch forcing. Paleoceanography 7, 701–738 (1992).

8. Hönisch, B. et al. Atmospheric carbon dioxide concentration across the mid-Pleistocene transition. Science 324, 1551–1554 (2009).

9. Chalk, T. B. et al. Causes of ice age intensification across the mid-Pleistocene transition. Proc. Natl Acad. Sci. USA 114, 13114–13119 (2017).

10. Dyez, K. A. et al. Early Pleistocene obliquity-scale pCO 2 variability at ~1.5 million years ago. Paleoceanography 33, 1270–1291 (2018).

11. Zachos, J. et al. Trends, rhythms, and aberrations in global climate 65 Ma to present. Science 292, 686–693 (2001).

12. Clark, P. U. et al. The middle Pleistocene transition: characteristics. mechanisms, and implications for long-term changes in atmospheric pCO 2 . Quat. Sci. Rev. 25, 3150–3184 (2006).

13. Köhler, P. & Bintanja, R. The carbon cycle during the mid Pleistocene transition: the southern ocean decoupling hypothesis. Clim. Past 4, 311–332 (2008).

14. Lisiecki, L. E. A benthic δ13C-based proxy for atmospheric pCO 2 over the last 1.5 Myr. Geophys. Res. Lett. 37, L21708 (2010).

15. 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).

16. Whillans, I. M. & Cassidy, W. A. Catch a falling star—meteorites and old ice. Science 222, 55–57 (1983).

17. Bender, M. L. et al. The contemporary degassing rate of Ar-40 from the solid Earth. Proc. Natl Acad. Sci. USA 105, 8232–8237 (2008).

18. 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).

19. Bereiter, B. et al. Diffusive equilibration of N 2 , O 2 and CO 2 mixing ratios in a 1.5-million-years-old ice core. Cryosphere 8, 245–256 (2014).

20. Pol, K. et al. New MIS 19 EPICA Dome C high resolution deuterium data: hints for a problematic preservation of climate variability at sub-millennial scale in the ‘oldest ice’. Earth Planet. Sci. Lett. 298, 95–103 (2010).

21. Landais, A. et al. What drives the millennial and orbital variations of δ18O atm ? Quat. Sci. Rev. 29, 235–246 (2010).

22. Raymo, M. E. et al. Influence of late Cenozoic mountain building on ocean geochemical cycles. Geology 16, 649–653 (1988).

23. Berger, A. et al. Modelling northern hemisphere ice volume over the last 3 Ma. Quat. Sci. Rev. 18, 1–11 (1999).

24. Martínez-Garcia, A. et al. Southern ocean dust-climate coupling over the past four million years. Nature 476, 312–315 (2011).

25. Pena, L. D. & Goldstein, S. L. Thermohaline circulation crisis and impacts during the mid-Pleistocene transition. Science 345, 318–322 (2014).

26. Loulergue, L. et al. Orbital and millennial-scale features of atmospheric CH 4 over the past 800,000 years. Nature 453, 383–386 (2008).

27. Fischer, H. et al. Where to find 1.5 million yr old ice for the IPICS ‘oldest-ice’ ice core. Clim. Past 9, 2489–2505 (2013).

28. Bereiter, B. et al. Revision of the EPICA Dome C CO 2 record from 800 to 600 kyr before present. Geophys. Res. Lett. 42, 542–549 (2015).

29. Suwa, M. & Bender, M. L. Chronology of the Vostok ice core constrained by O 2 /N 2 ratios of occluded air, and its implication for the Vostok climate records. Quat. Sci. Rev. 27, 1093–1106 (2008).

30. Dreyfus, G. B. et al. Anomalous flow below 2700 m in the EPICA Dome C ice core detected using δ18O of atmospheric oxygen measurements. Clim. Past 3, 341–353 (2007).

31. Bintanja, R. On the glaciological, meteorological, and climatological significance of Antarctic blue ice areas. Rev. Geophys. 37, 337–359 (1999).

32. Delisle, G. & Sievers, J. Sub-ice topography and meteorite finds near the Allan Hills and the near Western Ice Field, Victoria Land, Antarctica. J. Geophys. Res. Planets 96, 15577–15587 (1991).

33. Spaulding, N. E. et al. Ice motion and mass balance at the Allan Hills blue-ice area, Antarctica, with implications for paleoclimate reconstructions. J. Glaciol. 58, 399–406 (2012).

34. Dadic, R. et al. Extreme snow metamorphism in the Allan Hills, Antarctica, as an analogue for glacial conditions with implications for stable isotope composition. J. Glaciol. 61, 1171–1182 (2015).

35. Bender, M. L. Orbital tuning chronology for the Vostok climate record supported by trapped gas composition. Earth Planet. Sci. Lett. 204, 275–289 (2002).

36. Craig, H. et al. Gravitational separation of gases and isotopes in polar ice caps. Science 242, 1675–1678 (1988).

37. Bender, M. L. et al. On the nature of the dirty ice at the bottom of the GISP2 ice core. Earth Planet. Sci. Lett. 299, 466–473 (2010).

38. Kawamura, K. et al. Kinetic fractionation of gases by deep air convection in polar firn. Atmos. Chem. Phys. 13, 11141–11155 (2013).

39. Bereiter, B. et al. Mean global ocean temperatures during the last glacial transition. Nature 553, 39–44 (2018).

40. Severinghaus, J. P. et al. Oxygen-18 of O 2 records the impact of abrupt climate change on the terrestrial biosphere. Science 324, 1431–1434 (2009).

41. Mitchell, L. et al. Constraints on the Late Holocene anthropogenic contribution to the atmospheric methane budget. Science 342, 964–966 (2013).

42. Ahn, J. H. et al. A high-precision method for measurement of paleoatmospheric CO 2 in small polar ice samples. J. Glaciol. 55, 499–506 (2009).

43. Bauska, T. K. et al. High-precision dual-inlet IRMS measurements of the stable isotopes of CO 2 and the N 2 O/CO 2 ratio from polar ice core samples. Atmos. Meas. Tech. 7, 3825–3837 (2014).

44. Elderfield, H. et al. Evolution of ocean temperature and ice volume through the mid-Pleistocene climate transition. Science 337, 704–709 (2012).

45. Rohling, E. J. et al. Sea-level and deep-sea-temperature variability over the past 5.3 million years. Nature 508, 477–482 (2014).

46. Lambert, F. et al. Dust-climate couplings over the past 800,000 years from the EPICA Dome C ice core. Nature 452, 616–619 (2008).

47. Siegert, M. J. Glacial–interglacial variations in central East Antarctic ice accumulation rates. Quat. Sci. Rev. 22, 741–750 (2003).

48. Whillans, I. M. & Grootes, P. M. Isotopic diffusion in cold snow and firn. J. Geophys. Res. Atmos. 90, 3910–3918 (1985).

49. Etheridge, D. M. et al. Natural and anthropogenic changes in atmospheric CO 2 over the last 1000 years from air in Antarctic ice and firn. J. Geophys. Res. Atmos. 101, 4115–4128 (1996).

50. Ikeda-Fukazawa, T. et al. Effects of molecular diffusion on trapped gas composition in polar ice cores. Earth Planet. Sci. Lett. 229, 183–192 (2005).

51. Ikeda-Fukazawa, T. et al. Molecular dynamics studies of molecular diffusion in ice Ih. J. Chem. Phys. 117, 3886–3896 (2002).

52. Salamatin, A. N. et al. Kinetics of air-hydrate nucleation in polar ice sheets. J. Cryst. Growth 223, 285–305 (2001).

53. Ahn, J. et al. CO 2 diffusion in polar ice: observations from naturally formed CO 2 spikes in the Siple Dome (Antarctica) ice core. J. Glaciol. 54, 685–695 (2008).

54. Rempel, A. W. & Wettlaufer, J. S. Isotopic diffusion in polycrystalline ice. J. Glaciol. 49, 397–406 (2003).

55. Vimeux, F. et al. A 420,000 year deuterium excess record from East Antarctica: information on past changes in the origin of precipitation at Vostok. J. Geophys. Res. Atmos. 106, 31863–31873 (2001).

56. Montross, S. et al. Debris-rich basal ice as a microbial habitat, Taylor Glacier, Antarctica. Geomicrobiol. J. 31, 76–81 (2014).

57. Souchez, R. et al. Flow-induced mixing in the GRIP basal ice deduced from the CO 2 and CH 4 records. Geophys. Res. Lett. 22, 41–44 (1995).

58. Sowers, T. et al. Elemental and isotopic composition of occluded O 2 and N 2 in polar ice. J. Geophys. Res. Atmos. 94, 5137–5150 (1989).

59. Eggleston, S. et al. Evolution of the stable carbon isotope composition of atmospheric CO 2 over the last glacial cycle. Paleoceanography 31, 434–452 (2016).

60. Veres, D. et al. The Antarctic ice core chronology (AICC2012): an optimized multi-parameter and multi-site dating approach for the last 120 thousand years. Clim. Past 9, 1733–1748 (2013).