Critical insolation–CO2 relation for diagnosing past and future glacial inception

Journal name:
Nature
Volume:
529,
Pages:
200–203
Date published:
DOI:
doi:10.1038/nature16494
Received
Accepted
Published online

The past rapid growth of Northern Hemisphere continental ice sheets, which terminated warm and stable climate periods, is generally attributed to reduced summer insolation in boreal latitudes1, 2, 3. Yet such summer insolation is near to its minimum at present4, and there are no signs of a new ice age5. This challenges our understanding of the mechanisms driving glacial cycles and our ability to predict the next glacial inception6. Here we propose a critical functional relationship between boreal summer insolation and global carbon dioxide (CO2) concentration, which explains the beginning of the past eight glacial cycles and might anticipate future periods of glacial inception. Using an ensemble of simulations generated by an Earth system model of intermediate complexity constrained by palaeoclimatic data, we suggest that glacial inception was narrowly missed before the beginning of the Industrial Revolution. The missed inception can be accounted for by the combined effect of relatively high late-Holocene CO2 concentrations and the low orbital eccentricity of the Earth7. Additionally, our analysis suggests that even in the absence of human perturbations no substantial build-up of ice sheets would occur within the next several thousand years and that the current interglacial would probably last for another 50,000 years. However, moderate anthropogenic cumulative CO2 emissions of 1,000 to 1,500 gigatonnes of carbon will postpone the next glacial inception by at least 100,000 years8, 9. Our simulations demonstrate that under natural conditions alone the Earth system would be expected to remain in the present delicately balanced interglacial climate state, steering clear of both large-scale glaciation of the Northern Hemisphere and its complete deglaciation, for an unusually long time.

At a glance

Figures

  1. Orbital parameters.
    Figure 1: Orbital parameters.

    Comparison of Earth’s orbital parameters and CO2 concentrations for MIS1 (green), MIS11 (blue) and MIS19 (black). The vertical dashed line corresponds to the present day for MIS1 and the minima of the precessional component of insolation for MIS11 and MIS19.

  2. Evolution of the Northern Hemisphere ice volume.
    Figure 2: Evolution of the Northern Hemisphere ice volume.

    Ice volume (excluding the Greenland Ice Sheet) is given in metres of sea-level equivalent for the Holocene and near future with a CO2 concentration of 280 p.p.m. (a), the Holocene and near future with a CO2 concentration of 240 p.p.m. (b), MIS11 with a CO2 concentration of 280 p.p.m. (c), and MIS19 with a CO2 concentration of 240 p.p.m. (d). Individual model simulations from the subset of model versions compatible with the empirical constraints are shown; the shading illustrates the entire range. For MIS1 (the Holocene), with a CO2 concentration of 280 p.p.m. (a), the model realizations that are not compatible with the observational constraints are shown as grey lines. The vertical dashed lines correspond to the minima of the precessional component of insolation.

  3. Critical insolation–CO2 relation.
    Figure 3: Critical insolation–CO2 relation.

    a, Best-fit logarithmic relation (black line) between the maximum summer insolation at 65° N and the CO2 threshold for glacial inception; grey shaded area indicates ±1 s.d. Blue dots correspond to the coldest model version and red dots to the warmest. b, The locations of previous glacial inceptions in insolation–CO2 phase space relative to the best-fit logarithmic curve from a. Glacial inception is only possible when the point is located below the insolation–CO2 curve. c, The timing of past and future glacial inceptions can be explained by the CO2 concentration and the insolation–CO2 relation. The thin grey line depicts the CO2 threshold value for glacial inception, derived as a function of the maximum summer insolation at 65° N. The CO2 concentration from ice core data10, 11 for the past 800,000 years is shown (blue line), along with the CO2 scenarios of 0 Gt C cumulative anthropogenic emissions (blue line), 500 Gt C (orange line), 1,000 Gt C (red line) and 1,500 Gt C (dark red line). Pale blue vertical bars indicate the time periods when the reconstructed value is below the critical CO2 concentration, and the light blue bar shows the timing of a possible next glacial inception. The horizontal dotted line indicates the present-day CO2 level. The lower curve depicts a proxy for the global ice volume25 (thick grey line).

  4. The next glacial inception.
    Figure 4: The next glacial inception.

    The top panel shows the temporal evolution of the maximum summer insolation at 65° N. The middle panel shows the simulated CO2 concentration during the next 100,000 years for different cumulative CO2 emission scenarios: 0 Gt C anthropogenic emissions (blue), 500 Gt C (orange), 1,000 Gt C (red) and 1,500 Gt C (dark red line). The bottom panel shows simulated ice volume corresponding to the different CO2 emission scenarios. Individual simulations are shown for the 1,500 Gt C scenario; for the other scenarios, the range is given as shading.

  5. Ice sheet at 0 kyr bp.
    Extended Data Fig. 1: Ice sheet at 0 kyr bp.

    The extension and elevation of simulated Northern Hemisphere ice sheets at the time corresponding to present-day (0 kyr bp, ‘OK’) insolation are shown for constant CO2 concentrations of 280 p.p.m. (a) and 240 p.p.m. (b). Experiments were performed with the coldest of the accepted model versions.

  6. Detection of the critical CO2 value.
    Extended Data Fig. 2: Detection of the critical CO2 value.

    For the orbital configuration corresponding to 777 kyr bp we show the prescribed CO2 concentration (a), the simulated Northern Hemisphere (NH) ice volume in metres of sea-level equivalent (msl; b), and the simulated global mean surface air temperature (SAT) (c). Blue lines correspond to the coldest of accepted model versions and red lines to the warmest. The figure shows only the part of 200,000-year-long simulations for which glacial inceptions are simulated by both model versions. We note that the simulation time is ten times larger for the ice-sheet component than for the climate component (see bottom axis).

  7. Past glacial inceptions.
    Extended Data Fig. 3: Past glacial inceptions.

    Past glacial inceptions, detected using the critical insolation–CO2 relation, are shown in comparison to three different reconstructions of ice-volume variations over the past 800 kyr (refs 25, 29 and 30) and results of model simulations16.

References

  1. Milanković, M. M. Canon of Insolation and the Ice-Age Problem (Koniglich Serbische Academie, 1941)
  2. Hays, J. D., Imbrie, J. & Shackleton, N. J. Variations in the Earth’s orbit: pacemaker of the Ice Ages. Science 194, 11211132 (1976)
  3. Paillard, D. The timing of Pleistocene glaciations from a simple multiple-state climate model. Nature 391, 378381 (1998)
  4. Berger, A. & Loutre, M. F. An exceptionally long interglacial ahead? Science 297, 12871288 (2002)
  5. Kemp, A. C. et al. Climate related sea-level variations over the past two millennia. Proc. Natl Acad. Sci. USA 108, 1101711022 (2011)
  6. Masson-Delmotte, V. et al. in Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (eds Stocker, T. F. et al.) 383464 (Cambridge Univ. Press, 2013)
  7. Loutre, M. F. & Berger, A. Marine Isotope Stage 11 as an analogue for the present interglacial. Global Planet. Change 36, 209217 (2003)
  8. Archer, D. & Ganopolski, A. A movable trigger: fossil fuel CO2 and the onset of the next glaciation. Geochem. Geophys. Geosyst. 6, Q05003 (2005)
  9. Paillard, D. What drives the Ice Age cycle? Science 313, 455456 (2006)
  10. Petit, J. R. et al. Climate and atmospheric history of the past 420,000 years from the Vostok ice core, Antarctica. Nature 399, 429436 (1999)
  11. Augustin, L. et al. Eight glacial cycles from an Antarctic ice core. Nature 429, 623628 (2004)
  12. Lambeck, K. et al. in Understanding Sea-Level Rise and Variability (eds Church, J. A., Woodworth, P. L., Aarup, T. & Wilson, W. S. ) 61121 (Wiley-Blackwell, 2010)
  13. Tzedakis, P. C., Channell, J. E. T., Hodell, D. A., Skinner, L. C. & Kleiven, H. F. Determining the natural length of the current interglacial. Nature Geosci. 5, 138141 (2012)
  14. Petoukhov, V. et al. CLIMBER-2: a climate system model of intermediate complexity. Part I: model description and performance for present climate. Clim. Dyn. 16, 117 (2000)
  15. Greve, R. A continuum-mechanical formulation for shallow polythermal ice sheets. Phil. Trans. R. Soc. A 355, 921974 (1997)
  16. Ganopolski, A. & Calov, R. The role of orbital forcing, carbon dioxide and regolith in 100 kyr cycles. Clim. Past 7, 14151425 (2011)
  17. Weertman, J. Milankovitch solar radiation variations and ice age ice sheet sizes. Nature 261, 1720 (1976)
  18. Cochelin, A.-S., Mysak, L. A. & Wang, Z. Simulation of long-term future climate changes with the green McGill paleoclimate model: the next glacial inception. Clim. Change 79, 381401 (2006)
  19. Calov, R. & Ganopolski, A. Multistability and hysteresis in the climate-cryosphere system under orbital forcing. Geophys. Res. Lett. 32, L21717 (2005)
  20. Abe-Ouchi, A. et al. Insolation-driven 100,000-year glacial cycles and hysteresis of ice-sheet volume. Nature 500, 190193 (2013)
  21. Ruddiman, W. F. The anthropogenic greenhouse era began thousands of years ago. Clim. Change 61, 261293 (2003)
  22. Stocker, B. D., Strassmann, K. & Joos, F. Sensitivity of Holocene atmospheric CO2 and the modern carbon budget to early human land use: analyses with a process-based model. Biogeosciences 8, 6988 (2011)
  23. Ciais, P. et al. in Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (eds Stocker, T. F. et al.) 465570 (Cambridge Univ. Press, 2013)
  24. Brovkin, V., Ganopolski, A., Archer, D. & Munhoven, G. Glacial CO2 cycle as a succession of key physical and biogeochemical processes. Clim. Past 8, 251264 (2012)
  25. Lisiecki, L. E. & Raymo, M. E. A. Pliocene-Pleistocene stack of 57 globally distributed benthic δ18O records. Paleoceanography 20, PA1003 (2005)
  26. Mauritsen, T. et al. Tuning the climate of a global model. J. Adv. Model. Earth Syst. 4, M00A01 (2012)
  27. Laskar, J. et al. A long-term numerical solution for the insolation quantities of the Earth. Astron. Astrophys. 428, 261285 (2004)
  28. Yin, Q. & Berger, A. Individual contribution of insolation and CO2 to the interglacial climates of the past 800,000 years. Clim. Dyn. 38, 709724 (2012)
  29. Elderfield, H. et al. Evolution of ocean temperature and ice volume through the mid-Pleistocene climate transition. Science 337, 704709 (2012)
  30. Grant, K. M. et al. Sea-level variability over five glacial cycles. Nature Commun. 5, 5076 (2014)

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Author information

Affiliations

  1. Potsdam Institute for Climate Impact Research, 14412 Potsdam, Germany

    • A. Ganopolski,
    • R. Winkelmann &
    • H. J. Schellnhuber
  2. Physics Institute, Potsdam University, 14476 Potsdam, Germany

    • R. Winkelmann
  3. Santa Fe Institute, Santa Fe, New Mexico 87501, USA

    • H. J. Schellnhuber

Contributions

A.G. and H.J.S. designed the paper. A.G. developed the methodology and performed the research (with contributions from R.W.). A.G., R.W. and H.J.S. interpreted the results and wrote the paper.

Competing financial interests

The authors declare no competing financial interests.

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Extended data figures and tables

Extended Data Figures

  1. Extended Data Figure 1: Ice sheet at 0 kyr bp. (154 KB)

    The extension and elevation of simulated Northern Hemisphere ice sheets at the time corresponding to present-day (0 kyr bp, ‘OK’) insolation are shown for constant CO2 concentrations of 280 p.p.m. (a) and 240 p.p.m. (b). Experiments were performed with the coldest of the accepted model versions.

  2. Extended Data Figure 2: Detection of the critical CO2 value. (271 KB)

    For the orbital configuration corresponding to 777 kyr bp we show the prescribed CO2 concentration (a), the simulated Northern Hemisphere (NH) ice volume in metres of sea-level equivalent (msl; b), and the simulated global mean surface air temperature (SAT) (c). Blue lines correspond to the coldest of accepted model versions and red lines to the warmest. The figure shows only the part of 200,000-year-long simulations for which glacial inceptions are simulated by both model versions. We note that the simulation time is ten times larger for the ice-sheet component than for the climate component (see bottom axis).

  3. Extended Data Figure 3: Past glacial inceptions. (259 KB)

    Past glacial inceptions, detected using the critical insolation–CO2 relation, are shown in comparison to three different reconstructions of ice-volume variations over the past 800 kyr (refs 25, 29 and 30) and results of model simulations16.

Additional data