Emission budgets are defined as the cumulative amount of anthropogenic CO2 emission compatible with a global temperature-change target. The simplicity of the concept has made it attractive to policy-makers, yet it relies on a linear approximation of the global carbon–climate system’s response to anthropogenic CO2 emissions. Here we investigate how emission budgets are impacted by the inclusion of CO2 and CH4 emissions caused by permafrost thaw, a non-linear and tipping process of the Earth system. We use the compact Earth system model OSCAR v2.2.1, in which parameterizations of permafrost thaw, soil organic matter decomposition and CO2 and CH4 emission were introduced based on four complex land surface models that specifically represent high-latitude processes. We found that permafrost carbon release makes emission budgets path dependent (that is, budgets also depend on the pathway followed to reach the target). The median remaining budget for the 2 °C target reduces by 8% (1–25%) if the target is avoided and net negative emissions prove feasible, by 13% (2–34%) if they do not prove feasible, by 16% (3–44%) if the target is overshot by 0.5 °C and by 25% (5–63%) if it is overshot by 1 °C. (Uncertainties are the minimum-to-maximum range across the permafrost models and scenarios.) For the 1.5 °C target, reductions in the median remaining budget range from ~10% to more than 100%. We conclude that the world is closer to exceeding the budget for the long-term target of the Paris Climate Agreement than previously thought.

Access optionsAccess options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Data availability

RCP scenarios are available at http://www.pik-potsdam.de/~mmalte/rcps/. The data that support the findings of this study are available from the corresponding author upon request.

Additional information

Publisher’s note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Change history

  • 21 November 2018

    In the version of this Article originally published, data given for total exceedance budgets of CO2 for 1.5 °C and 2 °C targets were incorrect in the main text, although the correct values were given in Supplementary Table 1. These errors also resulted in an incorrect estimation of the percentage difference between the authors’ results and estimates by the IPCC. These errors have now been corrected in the online versions.


  1. 1.

    Matthews, H. D., Gillett, N. P., Stott, P. A. & Zickfeld, K. The proportionality of global warming to cumulative carbon emissions. Nature 459, 829–832 (2009).

  2. 2.

    Zickfeld, K., Eby, M., Matthews, H. D. & Weaver, A. J. Setting cumulative emissions targets to reduce the risk of dangerous climate change. Proc. Natl Acad. Sci. USA 106, 16129–16134 (2009).

  3. 3.

    Steinacher, M., Joos, F. & Stocker, T. F. Allowable carbon emissions lowered by multiple climate targets. Nature 499, 197–201 (2013).

  4. 4.

    Allen, M. R. & Stocker, T. F. Impact of delay in reducing carbon dioxide emissions. Nat. Clim. Change 4, 23–26 (2014).

  5. 5.

    Friedlingstein, P. et al. Persistent growth of CO2 emissions and implications for reaching climate targets. Nat. Geosci. 7, 709–715 (2014).

  6. 6.

    IPCC Climate Change 2014: Synthesis Report (eds Core Writing Team, Pachauri, R. K. & Meyer L. A.) (IPCC, 2015).

  7. 7.

    Millar, R. J. et al. Emission budgets and pathways consistent with limiting warming to 1.5 °C. Nat. Geosci. 10, 741–747 (2017).

  8. 8.

    Schurer, A. P. et al. Interpretations of the Paris climate target. Nat. Geosci. 11, 220–221 (2018).

  9. 9.

    Tokarska, K. B. & Gillett, N. P. Cumulative carbon emissions budgets consistent with 1.5 °C global warming. Nat. Clim. Change 8, 296–299 (2018).

  10. 10.

    Goodwin, P. et al. Pathways to 1.5 °C and 2 °C warming based on observational and geological constraints. Nat. Geosci. 11, 102–107 (2018).

  11. 11.

    Schaefer, K., Zhang, T., Bruhwiler, L. & Barrett, A. P. Amount and timing of permafrost carbon release in response to climate warming. Tellus B 63, 165–180 (2011).

  12. 12.

    MacDougall, A. H., Zickfeld, K., Knutti, R. & Matthews, H. D. Sensitivity of carbon budgets to permafrost carbon feedbacks and non-CO2 forcings. Environ. Res. Lett. 10, 125003 (2015).

  13. 13.

    Schaefer, K., Lantuit, H., Romanovsky, V. E., Schuur, E. A. G. & Witt, R. The impact of the permafrost carbon feedback on global climate. Environ. Res. Lett. 9, 085003 (2014).

  14. 14.

    Schuur, E. A. G. et al. Climate change and the permafrost carbon feedback. Nature 520, 171–179 (2015).

  15. 15.

    Lenton, T. M. et al. Tipping elements in the Earth’s climate system. Proc. Natl Acad. Sci. USA 105, 1786–1793 (2008).

  16. 16.

    Allen, M. R. et al. Warming caused by cumulative carbon emissions towards the trillionth tonne. Nature 458, 1163–1166 (2009).

  17. 17.

    Zickfeld, K., Arora, V. K. & Gillet, N. P. Is the climate response to CO2 emissions path dependent?. Geophys. Res. Lett. 39, L05703 (2012).

  18. 18.

    Gasser, T. et al. The compact Earth system model OSCARv2.2: description and first results. Geosci. Model Dev. 10, 271–319 (2017).

  19. 19.

    Guimberteau, M. et al. ORCHIDEE-MICT (v8.4.1), a land surface model for the high latitudes: model description and validation. Geosci. Model Dev. 11, 121–163 (2018).

  20. 20.

    Burke, E. J., Chadburn, S. E., & Ekici, A. A vertical representation of soil carbon in the JULES land surface scheme (vn4.3_permafrost) with a focus on permafrost regions. Geosci. Model Dev. 10, 959–975 (2017).

  21. 21.

    Burke, E. J. et al. Quantifying uncertainties of permafrost carbon–climate feedbacks. Biogeosciences 14, 3051–3066 (2017).

  22. 22.

    Rogelj, J. et al. Differences between carbon budget estimates unravelled. Nat. Clim. Change 6, 245–252 (2016).

  23. 23.

    Meinshausen, M. et al. The RCP greenhouse gas concentrations and their extensions from 1765 to 2300. Clim. Change 109, 213–241 (2011).

  24. 24.

    Cramer, W. et al. Global response of terrestrial ecosystem structure and function to CO2 and climate change: results from six dynamic global vegetation models. Global Change Biol. 7, 357–373 (2001).

  25. 25.

    Huntingford, C. et al. Simulated resilience of tropical rainforests to CO2-induced climate change. Nat. Geosci. 6, 268–273 (2013).

  26. 26.

    MacDougall, A. H., & Knutti, R. Projecting the release of carbon from permafrost soils using a perturbed parameter ensemble modelling approach. Biogeosciences 13, 2123–2136 (2016).

  27. 27.

    Burke, E. J., Chadburn, S. E., Huntingford, C. & Jones, C. D. CO2 loss by permafrost thawing implies additional emissions reductions to limit warming to 1.5 or 2 °C. Environ. Res. Lett. 13, 024024 (2018).

  28. 28.

    Gasser, T., Guivarch, C., Tachiiri, K., Jones, C. D. & Ciais, P. Negative emissions physically needed to keep global warming below 2 °C. Nat. Commun. 6, 7958 (2015).

  29. 29.

    Zickfeld, K., MacDougall, A. H. & Matthews, H. D. On the proportionality between global temperature change and cumulative CO2 emissions during periods of net negative CO2 emissions. Environ. Res. Lett. 11, 055006 (2016).

  30. 30.

    Koven, C. D. et al. A simplified, data-constrained approach to estimate the permafrost carbon–climate feedback. Phil. Trans. R. Soc. A 373, 20140423 (2015).

  31. 31.

    Voigt, C. et al. Increased nitrous oxide emissions from Arctic peatlands after permafrost thaw. Proc. Natl Acad. Sci. USA 114, 6238–6243 (2017).

  32. 32.

    Mack, M. C., Schuur, E. A. G., Bret-Harte, M. S., Shaver, G. R. & Chapin, F. S. Ecosystem carbon storage in arctic tundra reduced by long-term nutrient fertilization. Nature 431, 440–443 (2004).

  33. 33.

    Schuur, E. A. G. et al. Expert assessment of vulnerability of permafrost carbon to climate change. Clim. Change 119, 359–374 (2013).

  34. 34.

    Schädel, C. et al. Potential carbon emissions dominated by carbon dioxide from thawed permafrost soils. Nat. Clim. Change 6, 950–953 (2016).

  35. 35.

    Nzotungicimpaye, C.-M. & Zickfeld, K. The contribution from methane to the permafrost carbon feedback. Curr. Clim. Change Rep. 3, 58–68 (2017).

  36. 36.

    Myhre, G. et al. in Climate Change 2013: The Physical Science Basis (eds Stocker, T. F. et al.) Ch. 8, 659–740 (IPCC, Cambridge Univ. Press, Cambridge, 2013).

  37. 37.

    Pierrehumbert, R. T. Short-lived climate pollution. Annu. Rev. Earth. Planet. Sci. 42, 341–379 (2014).

  38. 38.

    Shine, K. P., Allan, R. P., Collins, W. J., & Fuglestvedt, J. S. Metrics for linking emissions of gases and aerosols to global precipitation changes. Earth Syst. Dynam 6, 525–540 (2015).

  39. 39.

    Gasser, T. et al. Accounting for the climate–carbon feedback in emission metrics. Earth Syst. Dynam 8, 235–253 (2017).

  40. 40.

    Allen, M. R. et al. New use of global warming potentials to compare cumulative and short-lived climate pollutants. Nat. Clim. Change 6, 773–776 (2016).

  41. 41.

    Kunreuther, H. et al. Risk management and climate change. Nat. Clim. Change 3, 447–450 (2013).

  42. 42.

    Hall, J. W. et al. Robust climate policies under uncertainty: a comparison of robust decision making and info-gap methods. Risk Anal. 32, 1657–1672 (2012).

  43. 43.

    Hallegatte, S. Strategies to adapt to an uncertain climate change. Global Environ. Change 19, 240–247 (2009).

  44. 44.

    Le Quéré, C. et al. Global carbon budget 2017. Earth Syst. Sci. Data 10, 405–448 (2018).

  45. 45.

    Quilcaille, Y. et al. Uncertainty in projected climate change arising from uncertain fossil-fuel emission factors. Environ. Res. Lett. 13, 044017 (2018).

  46. 46.

    Rogelj, J. et al. Disentangling the effects of CO2 and short-lived climate forcer mitigation. Proc. Natl Acad. Sci. USA 111, 16325–16330 (2014).

  47. 47.

    Shindell, D. et al. Simultaneously mitigating near-term climate change and improving human health and food security. Science 335, 183–189 (2012).

  48. 48.

    Schneider von Deimling, T. et al. Estimating the near-surface permafrost-carbon feedback on global warming. Biogeosciences 9, 649–665 (2012).

  49. 49.

    Schneider von Deimling, T. et al. Observation-based modelling of permafrost carbon fluxes with accounting for deep carbon deposits and thermokarst activity. Biogeosciences 12, 3469–3488 (2015).

  50. 50.

    Sitch, S. et al. Recent trends and drivers of regional sources and sinks of carbon dioxide. Biogeosciences 12, 653–679 (2015).

  51. 51.

    Arora, V. K. et al. Carbon-concentration and carbon-climate feedbacks in CMIP5 earth system models. J. Clim. 26, 5289–5314 (2013).

  52. 52.

    Joos, F. et al. An efficient and accurate representation of complex oceanic and biospheric models of anthropogenic carbon uptake. Tellus B 48, 394–417 (1996).

  53. 53.

    Geoffroy, O. et al. Transient climate response in a two-layer energy-balance model. Part I: analytical solution and parameter calibration using CMIP5 AOGCM experiments. J. Clim. 26, 1841–1857 (2013).

  54. 54.

    Holmes, C. D., Prather, M. J., Søvde, O. A., & Myhre, G. Future methane, hydroxyl, and their uncertainties: key climate and emission parameters for future predictions. Atmos. Chem. Phys 13, 285–302 (2013).

  55. 55.

    Jones, C. et al. Twenty-first-century compatible CO2 emissions and airborne fraction simulated by CMIP5 earth system models under four representative concentration pathways. J. Clim. 26, 4398–4413 (2013).

  56. 56.

    Hurtt, G. C. et al. Harmonization of land-use scenarios for the period 1500–2100: 600 years of global gridded annual land-use transitions, wood harvest, and resulting secondary lands. Clim. Change 109, 117 (2011).

  57. 57.

    Giorgetta, M. A. et al. Climate and carbon cycle changes from 1850 to 2100 in MPI-ESM simulations for the Coupled Model Intercomparison Project phase 5. J. Adv. Model. Earth Syst. 5, 572–597 (2013).

  58. 58.

    Tuomi, M., Vanhala, P., Karhu, K., Fritze, H. & Liski, J. Heterotrophic soil respiration—comparison of different models describing its temperature dependence. Ecol. Model. 211, 182–190 (2008).

  59. 59.

    Raupach, M. R. et al. The relationship between peak warming and cumulative CO2 emissions, and its use to quantify vulnerabilities in the carbon–climate–human system. Tellus B 63, 145–164 (2011).

  60. 60.

    Brovkin, V. et al. Evaluation of vegetation cover and land-surface albedo in MPI-ESM CMIP5 simulations. J. Adv. Model. Earth Syst. 5, 48–57 (2013).

  61. 61.

    Schneck, R., Reick, C. H. & Raddatz, T. Land contribution to natural CO2 variability on time scales of centuries. J. Adv. Model. Earth Syst, 5, 354–365 (2013).

  62. 62.

    Hagemann, S. & Stacke, T. Impact of the soil hydrology scheme on simulated soil moisture memory. Clim. Dynam. 44, 1731–1750 (2015).

  63. 63.

    Ekici, A. et al. Simulating high-latitude permafrost regions by the JSBACH terrestrial ecosystem model. Geosci. Model Dev 7, 631–647 (2014).

  64. 64.

    Goll, D. S. et al. Strong dependence of CO2 emissions from anthropogenic land cover change on initial land cover and soil carbon parametrization. Global. Biogeochem. Cycles 29, 1511–1523 (2015).

  65. 65.

    Hugelius, G. et al. A new data set for estimating organic carbon storage to 3 m depth in soils of the northern circumpolar permafrost region. Earth Syst. Sci. Data 5, 393–402 (2013).

Download references


We thank A. H. MacDougall for sharing data and O. Boucher for data used in Supplementary Fig. 6. This work is part of the European Research Council Synergy project ‘Imbalance-P’ (grant no. ERC-2013-SyG-610028). Simulations with OSCAR were carried out on the IPSL Prodiguer-Ciclad facility, which is supported by CNRS, UPMC and Labex L-IPSL, and funded by the ANR (grant no. ANR-10-LABX-0018) and the European FP7 IS-ENES2 project (grant no. 312979). E.J.B. was supported by PAGE21 (EU project no. GA282700), CRESCENDO (EU project no. 641816) and the Joint UK DECC/Defra Met Office Hadley Centre Climate Programme (GA01101). A.E. was also supported by PAGE21.

Author information


  1. International Institute for Applied Systems Analysis (IIASA), Laxenburg, Austria

    • T. Gasser
    • , M. Kechiar
    •  & M. Obersteiner
  2. École Polytechnique, Palaiseau, France

    • M. Kechiar
  3. Laboratoire des Sciences du Climat et de l’Environnement, LSCE/IPSL, Université Paris-Saclay, CEA – CNRS – UVSQ, Gif-sur-Yvette, France

    • P. Ciais
    • , D. Zhu
    •  & Y. Huang
  4. Met Office Hadley Centre, Exeter, UK

    • E. J. Burke
  5. Max Planck Institut für Meteorologie, Hamburg, Germany

    • T. Kleinen
  6. Climate and Environmental Physics, Physics Institute, University of Bern, Bern, Switzerland

    • A. Ekici
  7. Oeschger Centre for Climate Change Research, University of Bern, Bern, Switzerland

    • A. Ekici


  1. Search for T. Gasser in:

  2. Search for M. Kechiar in:

  3. Search for P. Ciais in:

  4. Search for E. J. Burke in:

  5. Search for T. Kleinen in:

  6. Search for D. Zhu in:

  7. Search for Y. Huang in:

  8. Search for A. Ekici in:

  9. Search for M. Obersteiner in:


T.G. designed the study. T.G. developed the permafrost emulator with inputs from P.C. and M.K. T.K. provided JSBACH data. Y.H., D.Z. and P.C. provided ORCHIDEE data. E.J.B. and A.E. provided JULES data. T.G. and M.K. set up the simulations with OSCAR, processed the outputs and created the figures. T.G., M.K., P.C. and M.O. discussed the preliminary results. T.G. wrote the manuscript with contributions from all the authors.

Competing interests

The authors declare no competing interests.

Corresponding author

Correspondence to T. Gasser.

Supplementary information

  1. Supplementary Information

    Supplementary Figures 1–10 and Supplementary Tables 1–5

About this article

Publication history