To understand how global warming can be kept well below 2 degrees Celsius and even 1.5 degrees Celsius, climate policy uses scenarios that describe how society could reduce its greenhouse gas emissions. However, current scenarios have a key weakness: they typically focus on reaching specific climate goals in 2100. This choice may encourage risky pathways that delay action, reach higher-than-acceptable mid-century warming, and rely on net removal of carbon dioxide thereafter to undo their initial shortfall in reductions of emissions. Here we draw on insights from physical science to propose a scenario framework that focuses on capping global warming at a specific maximum level with either temperature stabilization or reversal thereafter. The ambition of climate action until carbon neutrality determines peak warming, and can be followed by a variety of long-term states with different sustainability implications. The approach proposed here closely mirrors the intentions of the United Nations Paris Agreement, and makes questions of intergenerational equity into explicit design choices.
Subscribe to Journal
Get full journal access for 1 year
only $3.90 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Rent or Buy article
Get time limited or full article access on ReadCube.
All prices are NET prices.
The MESSAGEix modelling framework61, including its macroeconomic module MACRO, is available under an APACHE 2.0 open-source license at http://github.com/iiasa/message_ix. Data can be analysed online via a dedicated scenario explorer instance at https://data.ene.iiasa.ac.at/paris-lttg-explorer; further analytical codes for producing figures are not available.
United Nations Framework Convention on Climate Change 1–25 (United Nations, Rio de Janeiro, 1992).
Randalls, S. History of the 2 °C climate target. Wiley Interdiscip. Rev. Clim. Chang. 1, 598–605 (2010).
Knutti, R., Rogelj, J., Sedlacek, J. & Fischer, E. M. A scientific critique of the two-degree climate change target. Nat. Geosci. 9, 13–18 (2016).
O’Neill, B. C. et al. IPCC reasons for concern regarding climate change risks. Nat. Clim. Chang. 7, 28–37 (2017).
Seneviratne, S. I., Donat, M. G., Pitman, A. J., Knutti, R. & Wilby, R. L. Allowable CO2 emissions based on regional and impact-related climate targets. Nature 529, 477–483 (2016).
UNFCCC Paris Agreement 1–25 (UNFCCC, Paris, 2015).
Schleussner, C.-F. et al. Science and policy characteristics of the Paris Agreement temperature goal. Nat. Clim. Chang. 6, 827–835 (2016).
Clarke, L. et al. in Climate Change 2014: Mitigation of Climate Change. Contribution of Working Group III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (eds O. Edenhofer et al.) Ch. 6, 413–510 (Cambridge Univ. Press, 2014).
Fisher, B. et al. in Climate Change 2007: Mitigation. Contribution of Working Group III to the Fourth Assessment Report of the Inter-governmental Panel on Climate Change (eds B. Metz et al.) Ch. 3, 169–250 (Cambridge Univ. Press, 2007).
Clarke, L. et al. International climate policy architectures: overview of the EMF 22 International Scenarios. Energy Econ. 31, S64–S81 (2009).
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. Clim. Change 123, 353–367 (2014).
IEA. World Energy Outlook 2015 (International Energy Agency, 2015).
van Vuuren, D. P. et al. A new scenario framework for climate change research: scenario matrix architecture. Clim. Change 122, 373–386 (2014).
Meinshausen, M. et al. Greenhouse-gas emission targets for limiting global warming to 2 °C. Nature 458, 1158–1162 (2009).
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).
Fuss, S. et al. Betting on negative emissions. Nat. Clim. Chang. 4, 850–853 (2014).
Shue, H. Climate dreaming: negative emissions, risk transfer, and irreversibility. J. Hum. Rights Environ. 8, 203–216 (2017).
Williamson, P. Emissions reduction: scrutinize CO2 removal methods. Nature 530, 153–155 (2016).
Azar, C., Johansson, D. J. A. & Mattsson, N. Meeting global temperature targets—the role of bioenergy with carbon capture and storage. Environ. Res. Lett. 8, 034004 (2013).
Minx, J. C., Lamb, W. F., Callaghan, M. W., Bornmann, L. & Fuss, S. Fast growing research on negative emissions. Environ. Res. Lett. 12, 035007 (2017).
Smith, P. et al. Biophysical and economic limits to negative CO2 emissions. Nat. Clim. Chang. 6, 42–50 (2016).
Popp, A. et al. Land-use futures in the shared socio-economic pathways. Glob. Environ. Change 42, 331–345 (2017).
Field, C. B. & Mach, K. J. Rightsizing carbon dioxide removal. Science 356, 706–707 (2017).
Boysen, L. R. et al. The limits to global-warming mitigation by terrestrial carbon removal. Earths Futur. 5, 463–474 (2017).
Morrow, D. R. & Svoboda, T. Geoengineering and Non-Ideal Theory. Public Aff. Q. 30, 85–104 (2016).
Obersteiner, M. et al. How to spend a dwindling greenhouse gas budget. Nat. Clim. Chang. 8, 7–10 (2018).
Anderson, K. & Peters, G. The trouble with negative emissions. Science 354, 182–183 (2016).
Huppmann, D., Rogelj, J., Kriegler, E., Krey, V. & Riahi, K. A new scenario resource for integrated 1.5 °C research. Nat. Clim. Chang. 8, 1027–1030 (2018).
Rogelj, J. et al. in Global Warming of 1.5 °C: An IPCC Special Report on the Impacts of Global Warming of 1.5 °C Above Pre-industrial Levels and Related Global Greenhouse Gas Emission Pathways, in the Context of Strengthening the Global Response to the Threat of Climate Change, Sustainable Development, and Efforts to Eradicate Poverty (eds Flato, G., Fuglestvedt, J., Mrabet, R. & Schaeffer, R.) Ch. 2, 93–174 (IPCC/WMO, 2018).
Wigley, T. M. L., Richels, R. & Edmonds, J. A. Economic and environmental choices in the stabilization of atmospheric CO2 concentrations. Nature 379, 240–243 (1996).
Rogelj, J., Schleussner, C.-F. & Hare, W. Getting it right matters: temperature goal interpretations in geoscience research. Geophys. Res. Lett. 44, 10662–10665 (2017).
O’Neill, B. C. et al. A new scenario framework for climate change research: the concept of shared socioeconomic pathways. Clim. Change 122, 387–400 (2014).
Fuglestvedt, J. et al. Implications of possible interpretations of ‘greenhouse gas balance’ in the Paris Agreement. Philos. Trans. R. Soc. A https://doi.org/10.1098/rsta.2016.0445 (2018).
Collins, M. 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.) Ch. 12, 1029–1136 (Cambridge Univ. Press, 2013).
Knutti, R. & Rogelj, J. The legacy of our CO2 emissions: a clash of scientific facts, politics and ethics. Clim. Change 133, 361–373 (2015).
Matthews, H. D., Solomon, S. & Pierrehumbert, R. Cumulative carbon as a policy framework for achieving climate stabilization. Philos. Trans. R. Soc. Lond. A 370, 4365–4379 (2012).
Matthews, H. D. & Solomon, S. Atmosphere. Irreversible does not mean unavoidable. Science 340, 438–439 (2013).
Matthews, H. D. & Caldeira, K. Stabilizing climate requires near-zero emissions. Geophys. Res. Lett. 35, (2008).
Haites, E., Yamin, F. & Höhne, N. Possible elements of a 2015 legal agreement on climate change. IDDRI SciencesPo Working Paper 1–24 (2013).
Rogelj, J. et al. Zero emission targets as long-term global goals for climate protection. Environ. Res. Lett. 10, 105007 (2015).
Geden, O. An actionable climate target. Nat. Geosci. 9, 340 (2016).
Weyant, J. P., de la Chesnaye, F. C. & Blanford, G. J. Overview of EMF-21: multigas mitigation and climate policy. Energy J. 27, 1–32 (2006).
Shindell, D. et al. Simultaneously mitigating near-term climate change and improving human health and food security. Science 335, 183–189 (2012).
Höglund-Isaksson, L. et al. Cost estimates of the Kigali Amendment to phase-down hydrofluorocarbons. Environ. Sci. Policy 75, 138–147 (2017).
Tokarska, K. B. & Zickfeld, K. The effectiveness of net negative carbon dioxide emissions in reversing anthropogenic climate change. Environ. Res. Lett. 10, 094013 (2015).
Creutzig, F. et al. Bioenergy and climate change mitigation: an assessment. Glob. Change Biol. Bioenergy 7, 916–944 (2015).
de Coninck, H. et al. in Global Warming of 1.5 °C: An IPCC Special Report on the Impacts of Global Warming of 1.5 °C Above Pre-industrial Levels and Related Global Greenhouse Gas Emission Pathways, in the Context of Strengthening the Global Response to the Threat of Climate Change, Sustainable Development, and Efforts to Eradicate Poverty (eds Abdulla, A., Boer, R., Howden, M. & Ürge-Vorsatz, D.) Ch. 4 (World Meteorological Organisation, 2018).
Sanchez, D. L. & Kammen, D. M. A commercialization strategy for carbon-negative energy. Nat. Energy 1, 15002 (2016).
Reiner, D. M. Learning through a portfolio of carbon capture and storage demonstration projects. Nat. Energy 1, 15011 (2016).
Krey, V., Luderer, G., Clarke, L. & Kriegler, E. Getting from here to there – energy technology transformation pathways in the EMF27 scenarios. Clim. Change 123, 369–382 (2014).
Luderer, G. et al. Residual fossil CO2 emissions in 1.5–2 °C pathways. Nat. Clim. Chang. 8, 626–633 (2018).
Geden, O., Peters, G. P. & Scott, V. Targeting carbon dioxide removal in the European Union. Clim. Policy 19, 487–494 (2019).
Davis, S. J. et al. Net-zero emissions energy systems. Science 360, eaas9793 (2018).
Riahi, K. et al. The Shared Socioeconomic Pathways and their energy, land use, and greenhouse gas emissions implications: an overview. Glob. Environ. Change 42, 153–168 (2017).
Rogelj, J., McCollum, D. L., Reisinger, A., Meinshausen, M. & Riahi, K. Probabilistic cost estimates for climate change mitigation. Nature 493, 79–83 (2013).
Maier, H. R. et al. An uncertain future, deep uncertainty, scenarios, robustness and adaptation: how do they fit together? Environ. Model. Softw. 81, 154–164 (2016).
Ricke, K. L. & Caldeira, K. Maximum warming occurs about one decade after a carbon dioxide emission. Environ. Res. Lett. 9, 124002 (2014).
UNFCCC. FCCC/CP/2010/7/Add.1 Decision 1/CP.16—The Cancun Agreements: Outcome of the work of the Ad Hoc Working Group on Long-term Cooperative Action under the Convention (UNFCCC, 2010).
UNEP. The Emissions Gap Report 2013 p. 64 (UNEP, Nairobi, 2013).
UNFCCC. FCCC/CP/2015/7: Synthesis Report on the Aggregate Effect of the Intended Nationally Determined Contributions p. 66 (UNFCCC, Bonn, 2015).
Huppmann, D. et al. The MESSAGEix Integrated Assessment Model and the ix modeling platform (ixmp): an open framework for integrated and cross-cutting analysis of energy, climate, the environment, and sustainable development. Environ. Model. Softw. 112, 143–156 (2019).
Fricko, O. et al. The marker quantification of the Shared Socioeconomic Pathway 2: a middle-of-the-road scenario for the 21st century. Glob. Environ. Change 42, 251–267 (2017).
Krey, V. et al. MESSAGE-GLOBIOM 1.0 Documentation (International Institute for Applied Systems Analysis (IIASA), Laxenburg, 2016).
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).
Schneider von Deimling, T. et al. Estimating the near-surface permafrost-carbon feedback on global warming. Biogeosciences 9, 649–665 (2012).
Etminan, M., Myhre, G., Highwood, E. J. & Shine, K. P. Radiative forcing of carbon dioxide, methane, and nitrous oxide: a significant revision of the methane radiative forcing. Geophysic. Res. Lett. 43, 12614–12623 (2016).
Schädel, C. et al. Circumpolar assessment of permafrost C quality and its vulnerability over time using long-term incubation data. Glob. Change Biol. 20, 641–652 (2014).
Burke, E. J. et al. Quantifying uncertainties of permafrost carbon–climate feedbacks. Biogeosciences 14, 3051–3066 (2017).
Rogelj, J. et al. Disentangling the effects of CO2 and short-lived climate forcer mitigation. Proc. Natl Acad. Sci. USA 111, 16325–16330 (2014).
Bond, T. C. et al. Bounding the role of black carbon in the climate system: a scientific assessment. J. Geophys. Res. D Atmospheres 118, 5380–5552 (2013).
Rogelj, J. et al. Air-pollution emission ranges consistent with the representative concentration pathways. Nat. Clim. Chang. 4, 446–450 (2014).
Rao, S. et al. Future air pollution in the shared socio-economic pathways. Glob. Environ. Change 42, 346–358 (2017).
Rogelj, J. et al. Scenarios towards limiting global mean temperature increase below 1.5 °C. Nat. Clim. Chang. 8, 325–332 (2018).
IPCC. Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Intergovernmental Panel on Climate Change Fourth Assessment Report 994 (Cambridge Univ. Press, 2007).
We thank the International Institute for Applied Systems Analysis (IIASA) for hosting and maintaining the IPCC AR5 Scenario Database at https://tntcat.iiasa.ac.at/AR5DB/; O. Fricko for feedback and analysis during the explorative stages of the project; S. Frank and P. Havlík for supplying the MESSAGEix framework with GLOBIOM land-use data; and J. Cook for expert feedback.
The authors declare no competing interests.
Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Peer review information Nature thanks Nathan Gillett and Katharine Mach for their contribution to the peer review of this work.
Extended data figures and tables
a, Emission price trajectories applied to non-CO2 greenhouse gas emissions in the default case and the two sensitivity cases. In line with the scope of emissions covered under the UNFCCC, emissions from aerosol or aerosol precursor species such as black carbon or sulphur dioxide are not explicitly subjected to a carbon price. b–g, Resulting emissions of CO2 and internally consistent evolutions of a selection of non-CO2 emissions. h–j, Effect of non-CO2 sensitivity cases on decadal rate of temperature change in the period 2090–2100. Note that the sensitivity case that assumes zero penalty on non-CO2 emissions is extremely unlikely in light of recent efforts that specifically target reductions in methane and fluorinated gas emissions. Emissions of non-CO2 gases are translated into CO2 equivalence using global warming potentials over a 100-year time horizon as reported in the Fourth Assessment Report of the Intergovernmental Panel on Climate Change74.
Extended Data Fig. 3 Illustration of system configurations and of contributions of CDR technologies to achieve net zero CO2 emissions.
Corresponding system configurations are shown for all cases shown in Fig. 3. The four levels of net negative CO2 emissions to be achieved by the end of the century are for identification purposes only and are not visible on this figure as they will only be achieved after the point of reaching net zero CO2 emissions. In the cases selected here, net zero CO2 emissions are reached in 2050. Five illustrative system variations are shown per level (labelled A–E, defined in Extended Data Tables 3, 4). NA, scenarios did not solve under the imposed CDR and bioenergy constraints (Extended Data Table 4). Fossil fuel and industry CCS contributions (white hatched areas) represent CO2 that is generated but not emitted to the atmosphere. Net negative CO2 emissions are the sum of gross positive CO2 emissions from energy and industrial sources and gross positive land-use CO2 emissions, and are zero by design in this time step. Gross negative CO2 emissions comprise gross negative land-use CO2 emissions and CDR through BECCS. The combined size of all bars per scenario gives an indication of the overall size of the remaining CO2 producing system by the end of the century. Because the timing of CDR upscaling and amount of CDR at the time of reaching global net zero CO2 emissions was not explicitly varied in the set of illustrative scenarios developed for this study, it would be wrong to interpret the narrow degree of variation and general agreement across scenarios as a robust feature. Variations could be explored through additional dedicated studies (Extended Data Table 2).
Extended Data Fig. 4 Illustration of scenario variation and differences between the scenario logic presented in this study and an end-of-century scenario approach.
a, Pink-to-red, scenarios created with the scenario logic presented in this paper; blue dashed, scenarios created with an end-of-century scenario approach (see labelling). b, For a given amount of cumulative CO2 emissions all scenarios result in a similar amount of temperature increase by 2100 (crosses and diamonds), but different levels of maximum (peak) warming (circles and squares). c, Replication of Fig. 3 showing how stable emissions levels in the second half of the century can be achieved by a variety of system configurations with different amounts of CDR. Note that to achieve a scenario that limits global mean temperature rise in 2100 to 1.5 °C, the standard end-of-century scenario approach would suggest net negative CO2 emissions of about 15 Gt CO2 per year in 2100, while the scenario logic presented in this paper allows the construction of scenarios that achieve that temperature in 2100 with zero to about 5 Gt CO2 per year of net negative CO2 emissions, and a variety of gross CDR contributions.
About this article
Cite this article
Rogelj, J., Huppmann, D., Krey, V. et al. A new scenario logic for the Paris Agreement long-term temperature goal. Nature 573, 357–363 (2019) doi:10.1038/s41586-019-1541-4
Nature Climate Change (2019)