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Differences between carbon budget estimates unravelled

Nature Climate Change volume 6, pages 245–252 (2016)Cite this article

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Abstract

Several methods exist to estimate the cumulative carbon emissions that would keep global warming to below a given temperature limit. Here we review estimates reported by the IPCC and the recent literature, and discuss the reasons underlying their differences. The most scientifically robust number — the carbon budget for CO2-induced warming only — is also the least relevant for real-world policy. Including all greenhouse gases and using methods based on scenarios that avoid instead of exceed a given temperature limit results in lower carbon budgets. For a >66% chance of limiting warming below the internationally agreed temperature limit of 2 °C relative to pre-industrial levels, the most appropriate carbon budget estimate is 590–1,240 GtCO2 from 2015 onwards. Variations within this range depend on the probability of staying below 2 °C and on end-of-century non-CO2 warming. Current CO2 emissions are about 40 GtCO2 yr−1, and global CO2 emissions thus have to be reduced urgently to keep within a 2 °C-compatible budget.

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Figure 1: Proportionality of global-mean temperature increase to cumulative emissions of CO2.
Figure 2: An illustration of the methods for computing TEBs versus TABs.
Figure 3: Non-CO2 forcing and cumulative CO2 emissions.

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References

  1. United Nations Framework Convention on Climate Change (UN, 1992).

  2. Adoption of the Paris Agreement FCC/CP/2015/L.9/Rev.1 (UNFCCC, 2015).

  3. Andrew, H. M., Kirsten, Z., Reto, K. & Matthews, H. D. Sensitivity of carbon budgets to permafrost carbon feedbacks and non-CO2 forcings. Environ. Res. Lett. 10, 125003 (2015).

    Article  Google Scholar 

  4. Matthews, H. D. & Caldeira, K. Stabilizing climate requires near-zero emissions. Geophys. Res. Lett. 35, L04705 (2008).

    Article  Google Scholar 

  5. 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).

    Article  CAS  Google Scholar 

  6. 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).

    Article  CAS  Google Scholar 

  7. Meinshausen, M. et al. Greenhouse-gas emission targets for limiting global warming to 2 °C. Nature 458, 1158–1162 (2009).

    Article  CAS  Google Scholar 

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

    Article  CAS  Google Scholar 

  9. Gillett, N. P., Arora, V. K., Zickfeld, K., Marshall, S. J. & Merryfield, W. J. Ongoing climate change following a complete cessation of carbon dioxide emissions. Nature Geosci. 4, 83–87 (2011).

    Article  CAS  Google Scholar 

  10. Gillett, N. P., Arora, V. K., Matthews, D. & Allen, M. R. Constraining the ratio of global warming to cumulative CO2 emissions using CMIP5 simulations. J. Clim. 26, 6844–6858 (2013).

    Article  Google Scholar 

  11. Knutti, R. & Rogelj, J. The legacy of our CO2 emissions: a clash of scientific facts, politics and ethics. Climatic Change 133, 361–373 (2015).

    Article  CAS  Google Scholar 

  12. Smith, S. M. et al. Equivalence of greenhouse-gas emissions for peak temperature limits. Nature Clim. Change 2, 535–538 (2012).

    Article  CAS  Google Scholar 

  13. Bowerman, N. H. A. et al. The role of short-lived climate pollutants in meeting temperature goals. Nature Clim. Change 3, 1021–1024 (2013).

    Article  CAS  Google Scholar 

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

    Article  CAS  Google Scholar 

  15. Collins, M. R. et al. in Climate Change 2013: The Physical Science Basis (eds Stocker, T. F. et al.) 1029–1136 (IPCC, Cambridge Univ. Press, 2013).

    Google Scholar 

  16. Frolicher, T. L., Winton, M. & Sarmiento, J. L. Continued global warming after CO2 emissions stoppage. Nature Clim. Change 4, 40–44 (2014).

    Article  CAS  Google Scholar 

  17. Mastrandrea, M. D. et al. Guidance Notes for Lead Authors of the IPCC Fifth Assessment Report on Consistent Treatment of Uncertainties 5 (IPCC, 2010).

    Google Scholar 

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

    Google Scholar 

  19. Van Vuuren, D. P. et al. Temperature increase of 21st century mitigation scenarios. Proc. Natl Acad. Sci. USA 105, 15258–15262 (2008).

    Article  CAS  Google Scholar 

  20. Obersteiner, M. et al. Managing climate risk. Science 294, 786–787 (2001).

    Article  CAS  Google Scholar 

  21. Azar, C. et al. The feasibility of low CO2 concentration targets and the role of bio-energy with carbon capture and storage (BECCS). Climatic Change 100, 195–202 (2010).

    Article  CAS  Google Scholar 

  22. Tavoni, M. & Socolow, R. Modeling meets science and technology: an introduction to a special issue on negative emissions. Climatic Change 118, 1–14 (2013).

    Article  Google Scholar 

  23. Meinshausen, M., Raper, S. C. B. & Wigley, T. M. L. Emulating coupled atmosphere–ocean and carbon cycle models with a simpler model, MAGICC6 – Part 1: Model description and calibration. Atmos. Chem. Phys. 11, 1417–1456 (2011).

    Article  CAS  Google Scholar 

  24. Rogelj, J., Meinshausen, M. & Knutti, R. Global warming under old and new scenarios using IPCC climate sensitivity range estimates. Nature Clim. Change 2, 248–253 (2012).

    Article  Google Scholar 

  25. Matthews, H. D., Solomon, S. & Pierrehumbert, R. Cumulative carbon as a policy framework for achieving climate stabilization. Phil. Trans. R. Soc. A 370, 4365–4379 (2012).

    Article  Google Scholar 

  26. IPCC Summary for Policymakers in Climate Change 2013: The Physical Science Basis (eds Stocker, T. F. et al.) 1–29 (Cambridge Univ. Press, 2013).

  27. Clarke, L. et al. International climate policy architectures: overview of the EMF 22 International Scenarios. Energy Econ. 31, S64–S81 (2009).

    Article  Google Scholar 

  28. Riahi, K. et al. in Global Energy Assessment—Toward a Sustainable Future (eds Johansson, T. B., Patwardhan, A., Nakicenovic, N. & Gomez-Echeverri, L.) 1203–1306 (Cambridge Univ. Press and IIASA, 2012).

    Google Scholar 

  29. Kriegler, E. et al. The role of technology for achieving climate policy objectives: overview of the EMF 27 study on global technology and climate policy strategies. Climatic Change 123, 353–367 (2014).

    Article  Google Scholar 

  30. Moss, R. H. et al. The next generation of scenarios for climate change research and assessment. Nature 463, 747–756 (2010).

    Article  CAS  Google Scholar 

  31. Van Vuuren, D. P. et al. The representative concentration pathways: an overview. Climatic Change 109, 5–31 (2011).

    Article  Google Scholar 

  32. Taylor, K. E., Stouffer, R. J. & Meehl, G. A. An Overview of CMIP5 and the Experiment Design. Bull. Am. Meteorol. Soc. 93, 485–498 (2011).

    Article  Google Scholar 

  33. IPCC Summary for Policymakers in Climate Change 2014: Synthesis Report (eds Pachauri, R. K. et al.) 1–33 (Cambridge Univ. Press, 2014).

  34. IPCC Summary for Policymakers in Climate Change 2014: Mitigation of Climate Change (eds Edenhofer, O. et al.) 1–33 (Cambridge Univ. Press, 2014).

  35. Clarke, L. et al. in Climate Change 2014: Mitigation of Climate Change (eds Edenhofer, O. et al.) 413–450 (Cambridge Univ. Press, 2014).

    Google Scholar 

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

    Article  CAS  Google Scholar 

  37. Schaeffer, M. et al. Mid- and long-term climate projections for fragmented and delayed-action scenarios. Technol. Forecast. Soc. Change 90, 257–268 (2015).

    Article  Google Scholar 

  38. Rogelj, J. et al. Energy system transformations for limiting end-of-century warming to below 1.5°C. Nature Clim. Change 5, 519–527 (2015).

    Article  Google Scholar 

  39. Riahi, K. et al. RCP 8.5 — A scenario of comparatively high greenhouse gas emissions. Climatic Change 109, 33–57 (2011).

    Article  CAS  Google Scholar 

  40. 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).

    Article  Google Scholar 

  41. Zickfeld, K. et al. Long-term climate change commitment and reversibility: an EMIC intercomparison. J. Clim. 26, 5782–5809 (2013).

    Article  Google Scholar 

  42. Stocker, T. F. et al. in Climate Change 2013: The Physical Science Basis (eds Stocker, T. F. et al.) 33–115 (Cambridge Univ. Press, 2013).

    Google Scholar 

  43. Meinshausen, M., Wigley, T. M. L. & Raper, S. C. B. Emulating atmosphere–ocean and carbon cycle models with a simpler model, MAGICC6 – Part 2: Applications. Atmos. Chem. Phys. 11, 1457–1471 (2011).

    Article  CAS  Google Scholar 

  44. Rogelj, J., Meinshausen, M., Sedláček, J. & Knutti, R. Implications of potentially lower climate sensitivity on climate projections and policy. Environ. Res. Lett. 9, 031003 (2014).

    Article  Google Scholar 

  45. Smith, L. A. & Stern, N. Uncertainty in science and its role in climate policy. Phil. Trans. R. Soc. A 369, 4818–4841 (2011).

    Article  Google Scholar 

  46. Ricke, K. L. & Caldeira, K. Maximum warming occurs about one decade after a carbon dioxide emission. Environ. Res. Lett. 9, 124002 (2014).

    Article  Google Scholar 

  47. Zickfeld, K. & Herrington, T. The time lag between a carbon dioxide emission and maximum warming increases with the size of the emission. Environ. Res. Lett. 10, 031001 (2015).

    Article  Google Scholar 

  48. Rogelj, J. et al. Air-pollution emission ranges consistent with the representative concentration pathways. Nature Clim. Change 4, 446–450 (2014).

    Article  CAS  Google Scholar 

  49. Gernaat, D. E. H. J. et al. Understanding the contribution of non-carbon dioxide gases in deep mitigation scenarios. Glob. Environ. Change 33, 142–153 (2015).

    Article  Google Scholar 

  50. Rogelj, J. et al. Mitigation choices impact carbon budget size compatible with low temperature goals. Environ. Res. Lett. 10, 075003 (2015).

    Article  Google Scholar 

  51. Rogelj, J., Meinshausen, M., Schaeffer, M., Knutti, R. & Riahi, K. Impact of short-lived non-CO2 mitigation on carbon budgets for stabilizing global warming. Environ. Res. Lett. 10, 075001 (2015).

    Article  Google Scholar 

  52. Le Quéré, C. et al. Global carbon budget 2014. Earth Syst. Sci. Data Discuss 7, 521–610 (2014).

    Article  Google Scholar 

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

    Google Scholar 

  54. Boucher, O. & Reddy, M. S. Climate trade-off between black carbon and carbon dioxide emissions. Energy Policy 36, 193–200 (2008).

    Article  Google Scholar 

  55. Brohan, P., Kennedy, J. J., Harris, I., Tett, S. F. B. & Jones, P. D. Uncertainty estimates in regional and global observed temperature changes: a new data set from 1850. J. Geophys. Res.-Atmos. 111, D12106 (2006).

    Article  Google Scholar 

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Acknowledgements

We acknowledge the work by IAM modellers that contributed to the IPCC AR5 Scenario Database and the climate modelling teams contributing to CMIP5. We thank IIASA for hosting the IPCC AR5 Scenario Database, and M. Meinshausen for detailed comments and feedback on the manuscript.

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Authors and Affiliations

  1. ENE Program, International Institute for Applied Systems Analysis (IIASA), Schlossplatz 1, Laxenburg, A-2361, Austria

    Joeri Rogelj & Keywan Riahi

  2. Institute for Atmospheric and Climate Science, ETH Zurich, Universitätstrasse 16, Zürich, CH-8092, Switzerland

    Joeri Rogelj & Reto Knutti

  3. Climate Analytics, Karl-Liebknechtstrasse 5, Berlin, 10178, Germany

    Michiel Schaeffer

  4. Environmental Systems Analysis Group, Wageningen University and Research Centre, PO Box 47, Wageningen, 6700 AA, the Netherlands

    Michiel Schaeffer

  5. College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter, EX4 4QF, UK

    Pierre Friedlingstein

  6. Canadian Centre for Climate Modelling and Analysis, Environment Canada, University of Victoria, PO Box 1700, STN CSC, Victoria, V8W 2Y2, British Columbia, Canada

    Nathan P. Gillett

  7. PBL Netherlands Environmental Assessment Agency, PO Box 303, Bilthoven, 3720 AH, the Netherlands

    Detlef P. van Vuuren

  8. Copernicus Institute of Sustainable Development, Faculty of Geosciences, Utrecht University, Budapestlaan 4, Utrecht, 3584 CD, the Netherlands

    Detlef P. van Vuuren

  9. Graz University of Technology, Inffeldgasse, Graz, A-8010, Austria

    Keywan Riahi

  10. ECI, School of Geography and the Environment, University of Oxford, Oxford, OX1 3QY, UK

    Myles Allen

  11. Department of Physics, University of Oxford, Parks Road, Oxford, OX1 3PU, UK

    Myles Allen

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Contributions

All authors contributed to parts of the underlying research during the writing process of the IPCC AR5. J.R. coordinated the conception and the writing of the paper. J.R. carried out the research with significant contributions from M.S., and developed the TEB and TAB conceptual framework. J.R. produced the figures and wrote the first draft of the manuscript. All authors contributed to interpreting and discussing the results, and writing the paper.

Corresponding author

Correspondence to Joeri Rogelj.

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The authors declare no competing financial interests.

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Rogelj, J., Schaeffer, M., Friedlingstein, P. et al. Differences between carbon budget estimates unravelled. Nature Clim Change 6, 245–252 (2016). https://doi.org/10.1038/nclimate2868

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