The remaining carbon budget represents the total amount of CO2 that can still be emitted in the future while limiting global warming to a given temperature target. Remaining carbon budget estimates range widely, however, and this uncertainty can be used to either trivialize the most ambitious mitigation targets by characterizing them as impossible, or to argue that there is ample time to allow for a gradual transition to a low-carbon economy. Neither of these extremes is consistent with our best understanding of the policy implications of remaining carbon budgets. Understanding the scientific and socio-economic uncertainties affecting the size of the remaining carbon budgets, as well as the methodological choices and assumptions that underlie their calculation, is essential before applying them as a policy tool. Here we provide recommendations on how to calculate remaining carbon budgets in a traceable and transparent way, and discuss their uncertainties and implications for both international and national climate policies.
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The MAGICC7 model emulator is available from Z.R.J.N. upon request. Codes for producing the figures are available from H.D.M. or K.B.T. upon request.
Rogelj, J., Forster, P. M., Kriegler, E., Smith, C. J. & Séférian, R. Estimating and tracking the remaining carbon budget for stringent climate targets. Nature 571, 335–342 (2019).
Tokarska, K. B. et al. Recommended temperature metrics for carbon budget estimates, model evaluation and climate policy. Nat. Geosci. 12, 964–971 (2019).
Raupach, M. R. et al. Sharing a quota on cumulative carbon emissions. Nat. Clim. Change 4, 873–879 (2014).
Gignac, R. & Matthews, H. D. Allocating a 2 °C cumulative carbon budget to countries. Environ. Res. Lett. 10, 075004 (2015).
Nauels, A. et al. ZERO IN ON the Remaining Carbon Budget and Decadal Warming Rates. The CONSTRAIN Project Annual Report 2019 (2019); https://doi.org/10.5518/100/20
Matthews, H. D. & Caldeira, K. Stabilizing climate requires near-zero emissions. Geophys. Res. Lett. 35, L04705 (2008).
IPCC in Special Report on Global Warming of 1.5 °C (eds Masson-Delmotte, V. et al.) Ch. 2 (WMO, 2018).
Mengis, N., Partanen, A.-I., Jalbert, J. & Matthews, H. D. 1.5 °C carbon budget dependent on carbon cycle uncertainty and future non-CO2 forcing. Sci. Rep. 8, 5831 (2018).
Tokarska, K. B., Gillett, N. P., Arora, V. K., Lee, W. G. & Zickfeld, K. The influence of non-CO2 forcings on cumulative carbon emissions budgets. Environ. Res. Lett. 13, 034039 (2018).
Matthews, H. D. et al. Estimating carbon budgets for ambitious climate targets. Curr. Clim. Change Rep. 3, 69–77 (2017).
Millar, R. J. & Friedlingstein, P. The utility of the historical record for assessing the transient climate response to cumulative emissions. Philos. Trans. R. Soc. A 376, 20160449 (2018).
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).
Zickfeld, K., Arora, V. K. & Gillett, N. P. Is the climate response to CO2 emissions path dependent? Geophys. Res. Lett. 39, L05703 (2012).
Mengis, N. & Matthews, D. Non-CO2 forcing changes will likely decrease the remaining carbon budget for 1.5°C. NPL. Clim. Atmos. Sci. 3, 19 (2020).
Matthews, H. D. et al. An integrated approach to quantifying uncertainties in the remaining carbon budget. Commun. Earth Environ. (in the press).
Arora, V. K. et al. Carbon–concentration and carbon–climate feedbacks in CMIP6 models and their comparison to CMIP5 models. Biogeosciences 17, 4173–4222 (2020).
Jones, C. D. & Friedlingstein, P. Quantifying process-level uncertainty contributions to TCRE and carbon budgets for meeting Paris Agreement climate targets. Environ. Res. Lett. 15, 074019 (2020).
Tokarska, K. B. et al. Past warming trend constrains future warming in CMIP6 models. Sci. Adv. 6, eaaz9549 (2020).
Jiménez-de-la-Cuesta, D. & Mauritsen, T. Emergent constraints on Earth’s transient and equilibrium response to doubled CO2 from post-1970s global warming. Nat. Geosci. 12, 902–905 (2019).
Leduc, M., Matthews, H. D. & de Elía, R. Quantifying the limits of a linear temperature response to cumulative CO2 emissions. J. Clim. 28, 9955–9968 (2015).
Tokarska, K. B., Gillett, N. P., Weaver, A. J., Arora, V. K. & Eby, M. The climate response to five trillion tonnes of carbon. Nat. Clim. Change 6, 851–855 (2016).
Leduc, M., Matthews, H. D. & de Elía, R. Regional estimates of the transient climate response to cumulative CO2 emissions. Nat. Clim. Change 6, 474–478 (2016).
Herrington, T. & Zickfeld, K. Path independence of climate and carbon cycle response over a broad range of cumulative carbon emissions. Earth Syst. Dynam. 5, 409–422 (2014).
Winton, M., Takahashi, K. & Held, I. M. Importance of ocean heat uptake efficacy to transient climate change. J. Clim. 23, 2333–2344 (2010).
Armour, K. C., Bitz, C. M. & Roe, G. H. Time-varying climate sensitivity from regional feedbacks. J. Clim. 26, 4518–4534 (2013).
Andrews, T. et al. Accounting for changing temperature patterns increases historical estimates of climate sensitivity. Geophys. Res. Lett. 45, 8490–8499 (2018).
Gasser, T. et al. Path-dependent reductions in CO2 emission budgets caused by permafrost carbon release. Nat. Geosci. 11, 830–835 (2018).
Comyn-Platt, E. et al. Carbon budgets for 1.5 and 2 °C targets lowered by natural wetland and permafrost feedbacks. Nat. Geosci. 11, 568–573 (2018).
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).
IPCC in Climate Change 2013: The Physical Science Basis (eds Stocker, T. F. et al.) 1029–1136 (Cambridge Univ. Press, 2013).
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).
Tokarska, K. B., Zickfeld, K. & Rogelj, J. Path independence of carbon budgets when meeting a stringent global mean temperature target after an overshoot. Earth’s Future 7, 1283–1295 (2019).
MacDougall, A. H. et al. Is there warming in the pipeline? A multi-model analysis of the Zero Emissions Commitment from CO2. Biogeosciences 17, 2987–3016 (2020).
Hienola, A. et al. The impact of aerosol emissions on the 1.5 °C pathways. Environ. Res. Lett. 13, 044011 (2018).
Lelieveld, J. et al. Effects of fossil fuel and total anthropogenic emission removal on public health and climate. Proc. Natl Acad. Sci. USA 116, 7192–7197 (2019).
Rogelj, J. et al. Air-pollution emission ranges consistent with the representative concentration pathways. Nat. Clim. Change 4, 446–450 (2014).
Rogelj, J. et al. Mitigation choices impact carbon budget size compatible with low temperature goals. Environ. Res. Lett. 10, 075003 (2015).
Rogelj, J. et al. Differences between carbon budget estimates unravelled. Nat. Clim. Change 6, 245–252 (2016).
Haustein, K. et al. A real-time global warming index. Sci. Rep. 7, 15417 (2017).
Rogelj, J., Schleussner, C.-F. & Hare, W. Getting it right matters: temperature goal interpretations in geoscience research. Geophys. Res. Lett. 44, 10662–10665 (2017).
United Nations Framework Convention on Climate Change (United Nations, 1992); https://unfccc.int/resource/docs/convkp/conveng.pdf
Schleussner, C.-F. et al. Science and policy characteristics of the Paris Agreement temperature goal. Nat. Clim. Change 6, 827–835 (2016).
Tokarska, K. B. et al. Uncertainty in carbon budget estimates due to internal climate variability. Environ. Res. Lett. 15, 104064 (2020).
Adoption of the Paris Agreement FCCC/CP/2015/L.9/Rev.1 (UNFCCC, 2015).
Knutti, R. & Rogelj, J. The legacy of our CO2 emissions: a clash of scientific facts, politics and ethics. Clim. Change 133, 361–373 (2015).
IPCC in Global Warming of 1.5 °C (eds Masson-Delmotte, V. et al.) Ch. 1 (WMO, 2018).
Hawkins, E. et al. Estimating changes in global temperature since the preindustrial period. Bull. Am. Meteorol. Soc. 98, 1841–1856 (2017).
Schurer, A. P., Mann, M. E., Hawkins, E., Tett, S. F. B. & Hegerl, G. C. Importance of the pre-industrial baseline for likelihood of exceeding Paris goals. Nat. Clim. Change 7, 563–568 (2017).
Richardson, M., Cowtan, K., Hawkins, E. & Stolpe, M. B. Reconciled climate response estimates from climate models and the energy budget of Earth. Nat. Clim. Change 6, 931–935 (2016).
The Emissions Gap Report 2019 (United Nations Environment Programme, 2019); https://go.nature.com/3erYx1u
Rogelj, J. et al. Understanding the origin of Paris Agreement emission uncertainties. Nat. Commun. 8, 15748 (2017).
den Elzen, M., Janssen, M., Rotmans, J., Swart, R. & Vries, B. Allocating constrained global carbon budgets: inter-regional and inter-generational equity for a sustainable world. Int. J. Glob. Energy Issues 4, 287–301 (1992).
Robiou du Pont, Y., Jeffery, M. L., Gütschow, J., Christoff, P. & Meinshausen, M. National contributions for decarbonizing the world economy in line with the G7 agreement. Environ. Res. Lett. 11, 054005 (2016).
Höhne, N., den Elzen, M. & Escalante, D. Regional GHG reduction targets based on effort sharing: a comparison of studies. Clim. Policy 14, 122–147 (2014).
Gibson, R. B. et al. From Paris to Projects: Clarifying the Implications of Canada’s Climate Change Mitigation Commitments for the Planning and Assessment of Projects and Strategic Undertakings (University of Waterloo, 2019).
Crownshaw, T. et al. Over the horizon: exploring the conditions of a post-growth world. Anthr. Rev. 6, 117–141 (2019).
Smith, C. J. et al. Current fossil fuel infrastructure does not yet commit us to 1.5 °C warming. Nat. Commun. 10, 101 (2019).
Tong, D. et al. Committed emissions from existing energy infrastructure jeopardize 1.5 °C climate target. Nature 572, 373–377 (2019).
Matthews, H. D. Quantifying historical carbon and climate debts among nations. Nat. Clim. Change 6, 60–64 (2016).
Rogelj, J. et al. A new scenario logic for the Paris Agreement long-term temperature goal. Nature 573, 357–363 (2019).
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).
Smith, P. et al. Biophysical and economic limits to negative CO2 emissions. Nat. Clim. Change 6, 42–50 (2016).
Fuss, S. et al. Negative emissions—part 2: costs, potentials and side effects. Environ. Res. Lett. 13, 063002 (2018).
Cao, L. & Caldeira, K. Atmospheric carbon dioxide removal: long-term consequences and commitment. Environ. Res. Lett. 5, 024011 (2010).
Jones, C. D. et al. Simulating the Earth system response to negative emissions. Environ. Res. Lett. 11, 095012 (2016).
Tokarska, K. B. & Zickfeld, K. The effectiveness of net negative carbon dioxide emissions in reversing anthropogenic climate change. Environ. Res. Lett. 10, 094013 (2015).
Nemet, G. F. et al. Negative emissions—part 3: Innovation and upscaling. Environ. Res. Lett. 13, 063003 (2018).
Frölicher, T. L. & Joos, F. Reversible and irreversible impacts of greenhouse gas emissions in multi-century projections with the NCAR global coupled carbon cycle-climate model. Clim. Dyn. 35, 1439–1459 (2010).
Mathesius, S., Hofmann, M., Caldeira, K. & Schellnhuber, H. J. Long-term response of oceans to CO2 removal from the atmosphere. Nat. Clim. Change 5, 1107–1113 (2015).
Li, X., Zickfeld, K., Mathesius, S., Kohfeld, K. & Matthews, J. B. R. Irreversibility of marine climate change impacts under carbon dioxide removal. Geophys. Res. Lett. 47, e2020GL088507 (2020).
Meinshausen, M. et al. National post-2020 greenhouse gas targets and diversity-aware leadership. Nat. Clim. Change 5, 1098–1106 (2015).
Morice, C. P., Kennedy, J. J., Rayner, N. A. & Jones, P. D. Quantifying uncertainties in global and regional temperature change using an ensemble of observational estimates: the HadCRUT4 data set. J. Geophys. Res. Atmospheres 117, D08101 (2012).
Cowtan, K. Coverage Bias in the HadCRUT4 Temperature Series and its Impact on Recent Temperature Trends. UPDATE: COBE-SST2 Based Land-Ocean Dataset (2017); https://www-users.york.ac.uk/~kdc3/papers/coverage2013/update.171107.pdf
Cowtan, K. et al. Robust comparison of climate models with observations using blended land air and ocean sea surface temperatures. Geophys. Res. Lett. 42, 6526–6534 (2015).
Pfleiderer, P., Schleussner, C.-F., Mengel, M. & Rogelj, J. Global mean temperature indicators linked to warming levels avoiding climate risks. Environ. Res. Lett. 13, 064015 (2018).
Schurer, A. et al. Estimating the Transient Climate Response from Observed Warming. J. Clim. 31, 8645–8663 (2018).
Meinshausen, M. et al. Greenhouse-gas emission targets for limiting global warming to 2 °C. Nature 458, 1158–1162 (2009).
Kumar, S. et al. Land use/cover change impacts in CMIP5 climate simulations: a new methodology and 21st century challenges. J. Geophys. Res. Atmospheres 118, 6337–6353 (2013).
Simmons, C. T. & Matthews, H. D. Assessing the implications of human land-use change for the transient climate response to cumulative carbon emissions. Environ. Res. Lett. 11, 035001 (2016).
Lawrence, D. M. et al. The Land Use Model Intercomparison Project (LUMIP) contribution to CMIP6: rationale and experimental design. Geosci. Model Dev. 9, 2973–2998 (2016).
IPCC in Climate Change 2013: The Physical Science Basis (eds T. F. Stocker et al.) 33–115 (Cambridge Univ. Press, 2013).
Millar, R. J. et al. Emission budgets and pathways consistent with limiting warming to 1.5 °C. Nat. Geosci. 10, 741–747 (2017).
Tokarska, K. B. & Gillett, N. P. Cumulative carbon emissions budgets consistent with 1.5 °C global warming. Nat. Clim. Change 8, 296–299 (2018).
Frölicher, T. L. & Paynter, D. J. Extending the relationship between global warming and cumulative carbon emissions to multi-millennial timescales. Environ. Res. Lett. 10, 075002 (2015).
Koven, C. D., Lawrence, D. M. & Riley, W. J. Permafrost carbon–climate feedback is sensitive to deep soil carbon decomposability but not deep soil nitrogen dynamics. Proc. Natl Acad. Sci. USA 112, 3752–3757 (2015).
McGuire, A. D. et al. Dependence of the evolution of carbon dynamics in the northern permafrost region on the trajectory of climate change. Proc. Natl Acad. Sci. USA 115, 3882–3887 (2018).
Huppmann, D., Rogelj, J., Kriegler, E., Krey, V. & Riahi, K. A new scenario resource for integrated 1.5 °C research. Nat. Clim. Change 8, 1027–1030 (2018).
Huppmann, D. et al. IAMC 1.5°C Scenario Explorer and Data hosted by IIASA (IIASA, 2018); https://doi.org/10.22022/SR15/08-2018.15429
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).
Meinshausen, M. et al. The shared socio-economic pathway (SSP) greenhouse gas concentrations and their extensions to 2500. Geosci. Model Dev. 13, 3571–3605 (2020).
Friedlingstein, P. et al. Global Carbon Budget 2019. Earth Syst. Sci. Data 11, 1783–1838 (2019).
Allen, M. R. et al. Warming caused by cumulative carbon emissions towards the trillionth tonne. Nature 458, 1163–1166 (2009).
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).
Eyring, V. et al. Overview of the Coupled Model Intercomparison Project Phase 6 (CMIP6) experimental design and organization. Geosci. Model Dev. 9, 1937–1958 (2016).
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).
Forster, P. M., Maycock, A. C., McKenna, C. M. & Smith, C. Latest climate models confirm need for urgent mitigation. Nat. Clim. Change 10, 7–10 (2020).
Sutton, R. T. ESD Ideas: a simple proposal to improve the contribution of IPCC WGI to the assessment and communication of climate change risks. Earth Syst. Dynam. 9, 1155–1158 (2018).
IPCC in Climate Change 2013: The Physical Science Basis. Summary for Policymakers (eds Stocker, T. F. et al.) (Cambridge Univ. Press, 2013).
Jones, C. D. et al. The Zero Emissions Commitment Model Intercomparison Project (ZECMIP) contribution to C4MIP: quantifying committed climate changes following zero carbon emissions. Geosci. Model Dev. 12, 4375–4385 (2019).
Forster, P. M. et al. Evaluating adjusted forcing and model spread for historical and future scenarios in the CMIP5 generation of climate models. J. Geophys. Res. Atmospheres 118, 1139–1150 (2013).
Grose, M. R., Gregory, J., Colman, R. & Andrews, T. What climate sensitivity index is most useful for projections? Geophys. Res. Lett. 45, 1559–1566 (2018).
Höhne, N., den Elzen, M. & Escalante, D. Regional GHG reduction targets based on effort sharing: a comparison of studies. Clim. Policy 14, 122–147 (2014).
McKinnon, C. Climate justice in a carbon budget. Clim. Change 133, 375–384 (2015).
Samson, J., Berteaux, D., McGill, B. J. & Humphries, M. M. Geographic disparities and moral hazards in the predicted impacts of climate change on human populations. Glob. Ecol. Biogeogr. 20, 532–544 (2011).
We are grateful for the opportunity to have discussed these and other issues at the International Workshop on the Remaining Carbon Budget, organized with the support of the Global Carbon Project, the CRESCENDO project, Stanford University, the University of Melbourne, and Simon Fraser University. H.D.M. has been supported by funding from the Concordia University Research Chair programme and the Natural Sciences and Engineering Research Council of Canada (NSERC Discovery Grant RGPIN-2017-04159). K.B.T., J.R., P.M.F., R.K. and R.S. were supported by the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 820829 (CONSTRAIN project). J.G.C. was supported by the Australian National Environmental Science Program – Earth Systems and Climate Change Hub. P.F. and T.L.F. were supported by the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 821003 (4C project). T.L.F. was also supported by the Swiss National Science Foundation under grant PP00P2_170687. A.H.M. and K.Z. are supported by the Natural Sciences and Engineering Research Council of Canada Discovery Grant Program. C.D.J. was supported by the Joint UK BEIS/Defra Met Office Hadley Centre Climate Programme (GA01101) and by H2020 EU project CRESCENDO under grant agreement No. 641816. R.B.J. and J.G.C. acknowledge support from the Gordon and Betty Moore Foundation (GBMF5439). C.K. is supported by the US DOE, BER, RGMA program through the ECRP and RUBISCO projects.
The authors declare no competing interests.
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Matthews, H.D., Tokarska, K.B., Nicholls, Z.R.J. et al. Opportunities and challenges in using remaining carbon budgets to guide climate policy. Nat. Geosci. 13, 769–779 (2020). https://doi.org/10.1038/s41561-020-00663-3
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