The marker quantification of the Shared Socioeconomic Pathway 2: A middle-of-the-road scenario for the 21st century
Open accessAbstract
Studies of global environmental change make extensive use of scenarios to explore how the future can evolve under a consistent set of assumptions. The recently developed Shared Socioeconomic Pathways (SSPs) create a framework for the study of climate-related scenario outcomes. Their five narratives span a wide range of worlds that vary in their challenges for climate change mitigation and adaptation. Here we provide background on the quantification that has been selected to serve as the reference, or ‘marker’, implementation for SSP2. The SSP2 narrative describes a middle-of-the-road development in the mitigation and adaptation challenges space. We explain how the narrative has been translated into quantitative assumptions in the IIASA Integrated Assessment Modelling Framework . We show that our SSP2 marker implementation occupies a central position for key metrics along the mitigation and adaptation challenge dimensions. For many dimensions the SSP2 marker implementation also reflects an extension of the historical experience, particularly in terms of carbon and energy intensity improvements in its baseline. This leads to a steady emissions increase over the 21st century, with projected end-of-century warming nearing 4 °C relative to preindustrial levels. On the other hand, SSP2 also shows that global-mean temperature increase can be limited to below 2 °C, pending stringent climate policies throughout the world. The added value of the SSP2 marker implementation for the wider scientific community is that it can serve as a starting point to further explore integrated solutions for achieving multiple societal objectives in light of the climate adaptation and mitigation challenges that society could face over the 21st century.
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A reduction in surface pollutants is generally expected in future scenarios independently of SAI implementation.
“we generally expect a reduction in surface pollutants in future scenarios independently of SAI implementation (Fricko et al., 2017; Hussain, 2025; Nazarenko et al., 2022)”
From Air quality impacts of stratospheric aerosol injections are likely small and mainly driven by changes in climate, not aerosol settling (2026) · cites this paper as Fricko et al., 2017
Section 4.3.1 (page unavailable) discusses future baseline trajectories of air-pollutant emissions and says they differ across SSP scenarios. Our copy does not establish a general reduction in surface pollutant concentrations or assess whether such a reduction is independent of SAI (searched for pollutant declines, surface concentrations, and stratospheric aerosol injection). (LLM, conf=0.72)
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“This scenario is based on the assumption of the SSP1 narrative (Fricko et al., 2017), and also considers more sustainable consumption patterns with lower domestic waste.”
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- Authors
- Fricko, O., Havlik, P., Rogelj, J., Klimont, Z., Gusti, M., Johnson, N., Kolp, P., Strubegger, M., Valin, H., Amann, M., Ermolieva, T., Forsell, N., Herrero, M., Heyes, C., Kindermann, G., Krey, V., McCollum, D. L., Obersteiner, M., Pachauri, S., Rao, S., Schmid, E., Schoepp, W., & Riahi, K.
- Affiliations
- International Institute for Applied Systems Analysis (AT)
- Commonwealth Scientific and Industrial Research Organisation (AU)
- BOKU University (AT)
- Corresponding author
- Fricko, Oliver
- ORCID
- Venue
- Global Environmental Change
- Publisher
- Elsevier BV
- Published
- 2017-01
- Volume
- 42
- Pages
- 251-267
- ISSN
- 0959-3780 (ISSN-L)
- OpenAlex
- W2473101521
- Cited by
- 1,075
- References
- 4
- Citations by year
- 2026: 101 · 2025: 141 · 2024: 165 · 2023: 146 · 2022: 127 · 2021: 148 · 2020: 93 · 2019: 66 · 2018: 52 · 2017: 27 · 2016: 8 · 2014: 1
- FWCI
- 99.25
- Type
- journal article
- Language
- en
- Open access
- hybrid
- doi.org
- Licence
- Locations
- Global Environmental Change (publishedVersion, cc-by-nc-nd)
- IIASA PURE (International Institute of Applied Systems Analysis) (acceptedVersion)
- CGSPace A Repository of Agricultural Research Outputs (Consultative Group for International Agricultural Research) (submittedVersion, other-oa)
- Spiral (Imperial College London) (submittedVersion, cc-by-nc-nd)
- Funders
- European Union-funded project ‘An integration of mitigation and adaptation options for sustainable livestock production under climate change’ (266018)
- Topics
- Social Sciences › Economics, Econometrics and Finance › Economics and Econometrics › Climate Change Policy and Economics
- Physical Sciences › Environmental Science › Global and Planetary Change › Sustainability and Climate Change Governance
- Physical Sciences › Environmental Science › Global and Planetary Change › Climate variability and models
- Keywords
- Shared Socioeconomic Pathways, SSP2, climate change scenarios, climate change mitigation, climate change adaptation, carbon intensity, energy intensity, greenhouse gas emissions projections, global mean temperature increase, climate policy
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