Comparing emissions scenarios is an essential part of mitigation analysis, as climate targets can be met in various ways with different economic, energy system and co-benefit implications. Typically, a central ‘reference scenario’ acts as a point of comparison, and often this has been a no policy baseline with no explicit mitigative action taken. The use of such baselines is under increasing scrutiny, raising a wider question around the appropriate use of reference scenarios in mitigation analysis. In this Perspective, we assess three critical issues relevant to the use of reference scenarios, demonstrating how different policy contexts merit the use of different scenarios. We provide recommendations to the modelling community on best practice in the creation, use and communication of reference scenarios.
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Adoption of the Paris Agreement FCCC/CP/2015/L.9/Rev.1 (UNFCCC, 2015).
Weyant, J. Some contributions of integrated assessment models of global climate change. Rev. Environ. Econ. Policy 11, 115–137 (2017).
Krey, V. Global energy-climate scenarios and models: a review. Wiley Interdiscip. Rev. Energy Environ. 3, 363–383 (2014).
Pfenninger, S., Hawkes, A. & Keirstead, J. Energy systems modeling for twenty-first century energy challenges. Renew. Sustain. Energy Rev. 33, 74–86 (2014).
IPCC Climate Change 2001: Mitigation (eds Metz, B. et al.) (Cambridge Univ. Press, 2001).
IPCC Climate Change 2007: Impacts, Adaptation and Vulnerability (eds Parry, M. L. et al.) (Cambridge Univ. Press, 2007).
IPCC Climate Change 2014: Mitigation of Climate Change (eds Edenhofer, O. et al.) (Cambridge Univ. Press, 2014).
Rogelj, J. et al. in Special Report on Global Warming of 1.5 °C (eds Masson-Delmotte, V. et al.) Ch. 2 (IPCC, WMO, 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).
van Vuuren, D. P. et al. The shared socio-economic pathways: trajectories for human development and global environmental change. Glob. Environ. Change 42, 148–152 (2017).
O’Neill, B. C. et al. A new scenario framework for climate change research: the concept of shared socioeconomic pathways. Climatic Change 122, 387–400 (2014).
Moss, R. H. et al. The next generation of scenarios for climate change research and assessment. Nature 463, 747–756 (2010).
van Vuuren, D. P. et al. The representative concentration pathways: an overview. Climatic Change 109, 5–31 (2011).
World Energy Outlook 2019 (International Energy Agency, 2019); https://www.iea.org/reports/world-energy-outlook-2019
Annual Energy Outlook 2019 with Projections to 2050 (Energy Information Administration, 2019).
Napp, T. A. et al. The role of advanced demand-sector technologies and energy demand reduction in achieving ambitious carbon budgets. Appl. Energy 238, 351–367 (2019).
Gambhir, A. et al. Assessing the feasibility of global long-term mitigation scenarios. Energies 10, 89 (2017).
Zhang, R., Fujimori, S. & Hanaoka, T. The contribution of transport policies to the mitigation potential and cost of 2 °C and 1.5 °C goals. Environ. Res. Lett. 13, 5 (2018).
Fujimori, S. et al. Will international emissions trading help achieve the objectives of the Paris Agreement? Environ. Res. Lett. 11, 10 (2016).
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).
Luderer, G., Bertram, C., Calvin, K., De Cian, E. & Kriegler, E. Implications of weak near-term climate policies on long-term mitigation pathways. Climatic Change 136, 127–140 (2016).
McPherson, M., Johnson, N. & Strubegger, M. The role of electricity storage and hydrogen technologies in enabling global low-carbon energy transitions. Appl. Energy 216, 649–661 (2018).
Clarke, L. et al. in Climate Change 2014: Mitigation of Climate Change (eds Edenhofer, O. et al.) 413–510 (IPCC, Cambridge Univ. Press, 2014).
Emissions Gap Report 2019 (United Nations Environment Programme, 2019).
Nachmany, M., Fankhauser, S., Setzer, J. & Averchenkova, A. Global Trends in Climate Change Legislation and Litigation: 2017 Update (Grantham Research Institute on Climate Change and the Environment, 2017); http://www.lse.ac.uk/GranthamInstitute/publication/global-trends-in-climate-change-legislation-and-litigation-2017-update/.
Mager, B., Grimes, J. & Becker, M. Business as unusual. Nat. Energy 8, 17150 (2017).
Winning, M. et al. Nationally determined contributions under the Paris Agreement and the costs of delayed action. Clim. Policy 19, 947–958 (2019).
Hausfather, Z. & Peters, G. P. Emissions – the ‘business as usual’ story is misleading. Nature 577, 2020–2022 (2020).
Metayer, M., Breyer, C. & Fell, H.-J. The projections for the future and quality in the past of the World Energy Outlook for solar PV and other renewable energy technologies. In 31st Eur. PV Solar Energy Conf. Exhib. (EU PVSEC, 2015); http://doi.org/cbwn.
Vartiainen, E., Breyer, C., Moser, D. & Medina, E. R. Impact of weighted average cost of capital, capital expenditure, and other parameters on future utility-scale PV levelised cost of electricity. Prog. Photovolt. Res. Appl. 28, 439–453 (2019).
Hausfather, Z. Explainer: the high-emissions ‘RCP8.5′ global warming scenario. Carbon Brief https://www.carbonbrief.org/explainer-the-high-emissions-rcp8-5-global-warming-scenario (2019).
Lawrence, J., Haasnoot, M. & Lempert, R. Climate change: making decisions in the face of deep uncertainty. Nature 580, 456–456 (2020).
Hsiang, S. et al. Estimating economic damage from climate change in the United States. Science 356, 1362–1369 (2017).
Burke, M., Davis, W. M. & Diffenbaugh, N. S. Large potential reduction in economic damages under UN mitigation targets. Nature 557, 549–553 (2018).
Kriegler, E. et al. Fossil-fueled development (SSP5): an energy and resource intensive scenario for the 21st century. Glob. Environ. Change 42, 297–315 (2017).
Lomborg, B. U. N. Ignores economics of climate. Wall Street Journal https://www.wsj.com/articles/u-n-ignores-economics-of-climate-1539125496 (2018).
Stern, N. Stern Review: The Economics of Climate Change (HM Treasury, 2006).
Glanemann, N., Willner, S. N. & Levermann, A. Paris Climate Agreement passes the cost-benefit test. Nat. Commun. 11, 110 (2020).
Hof, A. F. et al. Global and regional abatement costs of nationally determined contributions (NDCs) and of enhanced action to levels well below 2 °C and 1.5 °C. Environ. Sci. Policy 71, 30–40 (2017).
Mace, M. J. Mitigation commitments under the Paris Agreement and the way forward. Climate Law 6, 21–39 (2016).
Kriegler, E. et al. Making or breaking climate targets — the AMPERE study on staged accession scenarios for climate policy. Technol. Forecast. Soc. Change 99, 273–276 (2015).
McCollum, D. L. et al. Energy investment needs for fulfilling the Paris Agreement and achieving the Sustainable Development Goals. Nat. Energy 3, 589–599 (2018).
Fawcett, A. A. et al. Can Paris pledges avert severe climate change? Science 350, 1168–1169 (2015).
van Soest, H. L. et al. Early action on Paris Agreement allows for more time to change energy systems. Clim. Change 144, 165–179 (2017).
Clarke, L., Weyant, J. & Birky, A. On the sources of technological change: assessing the evidence. Energy Econ. 28, 579–595 (2006).
Grubb, M., Köhler, J. & Anderson, D. Induced technical change in energy and environmental modeling: analytic approaches and policy implications. Annu. Rev. Environ. Resour. 27, 271–308 (2002).
Yu, C. F., Van Sark, W. G. J. H. M. & Alsema, E. A. Unraveling the photovoltaic technology learning curve by incorporation of input price changes and scale effects. Renew. Sustain. Energy Rev. 15, 324–337 (2011).
Zheng, C. & Kammen, D. M. An innovation-focused roadmap for a sustainable global photovoltaic industry. Energ. Policy 67, 159–169 (2014).
Nemet, G. F. Beyond the learning curve: factors influencing cost reductions in photovoltaics. Energ. Policy 34, 3218–3232 (2006).
Gallagher, K. S., Grübler, A., Kuhl, L., Nemet, G. & Wilson, C. The energy technology innovation system. Annu. Rev. Environ. Resour. 37, 137–162 (2012).
Jamasb, T. Technical change theory and learning curves: patterns of progress in energy technologies. Energ. J. 28, 51–71 (2006).
Nagy, B., Farmer, J. D., Bui, Q. M. & Trancik, J. E. Statistical basis for predicting technological progress. PLoS ONE 8, e52669 (2013).
Moore, G. E. Cramming more components onto integrated circuits. Electronics 38, 114 (1965).
Wright, T. P. Factors affecting the cost of airplanes. J. Aeronaut. Sci. 3, 122–128 (1936).
Clarke, L., Weyant, J. & Edmonds, J. On the sources of technological change: what do the models assume? Energy Econ. 30, 409–424 (2008).
Azar, C. & Dowlatabadi, H. Review of technical change in assessment of climate policy. Annu. Rev. Energy Environ. 24, 513–544 (1999).
Gambhir, A., Sandwell, P. & Nelson, J. The future costs of OPV – a bottom-up model of material and manufacturing costs with uncertainty analysis. Sol. Energy Mater. Sol. Cells 156, 49–58 (2016).
Creutzig, F. et al. The underestimated potential of solar energy to mitigate climate change. Nat. Energy 2, 17140 (2017).
Sussams, L. & Leaton, J. Expect the Unexpected: The Disruptive Power of Low-carbon Technology (Carbon Tracker Initiative, Imperial College London, 2017); https://www.imperial.ac.uk/media/imperial-college/grantham-institute/public/publications/collaborative-publications/Expect-the-Unexpected_CTI_Imperial.pdf
Nykvist, B. & Nilsson, M. Rapidly falling costs of battery packs for electric vehicles. Nat. Clim. Change 5, 100–103 (2015).
Kavlak, G., McNerney, J. & Trancik, J. E. Evaluating the causes of cost reduction in photovoltaic modules. Energ. Policy 123, 700–710 (2018).
Krey, V. et al. Looking under the hood: a comparison of techno-economic assumptions across national and global integrated assessment models. Energy 172, 1254–1267 (2018).
Current and Future Cost of Photovoltaics: Long-term Scenarios for Market Development, System Prices and LCOE of Utility-Scale PV Systems (Fraunhofer ISE, 2015).
The Power to Change: Solar and Wind Cost Reduction Potential to 2025 (International Renewable Energy Agency, 2016).
Schröder, A. et al. Current and Prospective Costs of Electricity Generation until 2050 (DIW Berlin, German Institute for Economic Research, 2013).
2019 ATB. U.S. Department of Energy https://atb.nrel.gov/electricity/2019/ (2019).
Vaidyula, M. & Hood, C. Accounting for Baseline Targets in NDCs: Issues and Options for Guidance (OECD/IEA, 2018).
UK Department for Business Energy and Industrial Strategy (BEIS). UK becomes first major economy to pass net zero emissions law. Gov.uk https://www.gov.uk/government/news/uk-becomes-first-major-economy-to-pass-net-zero-emissions-law (2019).
Riahi, K. et al. Locked into Copenhagen pledges — implications of short-term emission targets for the cost and feasibility of long-term climate goals. Technol. Forecast. Soc. Change 90, 8–23 (2015).
Krey, V., Luderer, G., Clarke, L. & Kriegler, E. Getting from here to there — energy technology transformation pathways in the EMF27 scenarios. Climatic Change 123, 369–382 (2014).
Dessens, O., Anandarajah, G. & Gambhir, A. Limiting global warming to 2 °C: what do the latest mitigation studies tell us about costs, technologies and other impacts? Energy Strateg. Rev. 13–14, 67–76 (2016).
van Vliet, J. et al. The impact of technology availability on the timing and costs of emission reductions for achieving long-term climate targets. Climatic Change 123, 559–569 (2014).
Lempert, R. J. & Collins, M. T. Managing the risk of uncertain threshold responses: comparison of robust, optimum, and precautionary approaches. Risk Anal. 27, 1009–1026 (2007).
Lamontagne, J. R. et al. Large ensemble analytic framework for consequence-driven discovery of climate change scenarios. Earth’s Future 6, 488–504 (2018).
Lempert, R. Scenarios that illuminate vulnerabilities and robust responses. Climatic Change 117, 627–646 (2013).
Lempert, R. in Decision Making under Deep Uncertainty: From Theory to Practice (eds Marchau, V. et al.) 23–52 (2019).
McCollum, D. L., Gambhir, A., Rogelj, J. & Wilson, C. Energy modellers should explore extremes more systematically in scenarios. Nat. Energy 5, 104–107 (2020).
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).
Lempert, R., Nakicenovic, N., Sarewitz, D. & Schlesinger, M. Characterizing climate-change uncertainties for decision-makers. An editorial essay. Climatic Change 65, 1–9 (2004).
EU Reference Scenario 2016: Energy, Transport and GHG emissions: Trends to 2050 (European Commission, 2016).
Updated Energy and Emissions Projections 2018 (UK Department for Business Energy and Industrial Strategy, 2019).
Bodansky, D. The Paris climate change agreement: a new hope? Am. J. Int. Law 110, 1–43 (2016).
Vinuales, J. in German Yearbook of International Law (eds von Arnauld, A. & von der Decken, K.) 11–45 (Duncker & Humblot, 2017).
Brunnermeier, S. B. & Cohen, M. A. Determinants of environmental innovation in US manufacturing industries. J. Environ. Econ. Manage. 45, 278–293 (2003).
Taylor, M. R., Rubin, E. S. & Hounshell, D. A. Effect of government actions on technological innovation for SO2 control. Environ. Sci. Technol. 37, 4527–4534 (2003).
Palmer, K. & Jaffe, A. B. Environmental regulation and innovation: a panel data study. Rev. Econ. Stat. 79, 610–619 (1997).
Grubb, M. J., Hope, C. & Fouquet, R. Climatic implications of the Kyoto Protocol: the contribution of international spillover. Climatic Change 54, 11–28 (2002).
Weber, C. et al. Mitigation scenarios must cater to new users. Nat. Clim. Change 8, 845–848 (2018).
DeCarolis, J. et al. Formalizing best practice for energy system optimization modelling. Appl. Energy 194, 184–198 (2017).
Iyer, G. & Edmonds, J. Interpreting energy scenarios. Nat. Energy 3, 357–358 (2018).
Strachan, N., Fais, B. & Daly, H. Reinventing the energy modelling–policy interface. Nat. Energy 1, 16012 (2016).
Peace, J. & Weyant, J. White Paper on Insights not Numbers: the Appropriate use of Economic Models (Pew Center on Global Climate Change, 2008).
N.G. was supported by the Natural Environment Research Council (NERC) (grant no. NE/L002515/1) as well as the Department for Business, Energy and Industrial Strategy (BEIS). A.G. and A.H. acknowledge support from the H2020 European Commission Project PARIS REINFORCE (grant no. 820846). N.G. thanks the Science and Solutions for a Changing Planet Doctoral Training Partnership at the Grantham Institute for support during their PhD studies. We thank J. Rogelj and S. Dietz for insightful comments on an earlier draft. The authors take sole responsibility for the final content of the Perspective.
The authors declare no competing interests.
Peer review information Nature Climate Change thanks Hadi Dowlatabadi, Vanessa Schweizer and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.
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Grant, N., Hawkes, A., Napp, T. et al. The appropriate use of reference scenarios in mitigation analysis. Nat. Clim. Chang. 10, 605–610 (2020). https://doi.org/10.1038/s41558-020-0826-9