The Shared Socioeconomic Pathways and their energy, land use, and greenhouse gas emissions implications: An overview

Abstract

This study presents the overview of the Shared Socioeconomic Pathways (SSPs) and their energy, land use, and emissions implications. The SSPs are part of a new scenario framework, established by the climate change research community in order to facilitate the integrated analysis of future climate impacts, vulnerabilities, adaptation, and mitigation. The pathways were developed over the last years as a joint community effort and describe plausible major global developments that together would lead in the future to different challenges for mitigation and adaptation to climate change. The SSPs are based on five narratives describing alternative socio-economic developments, including sustainable development, regional rivalry, inequality, fossil-fueled development, and middle-of-the-road development. The long-term demographic and economic projections of the SSPs depict a wide uncertainty range consistent with the scenario literature. A multi-model approach was used for the elaboration of the energy, land-use and the emissions trajectories of SSP-based scenarios. The baseline scenarios lead to global energy consumption of 400–1200 EJ in 2100, and feature vastly different land-use dynamics, ranging from a possible reduction in cropland area up to a massive expansion by more than 700 million hectares by 2100. The associated annual CO<sub>2</sub> emissions of the baseline scenarios range from about 25 GtCO<sub>2</sub> to more than 120 GtCO<sub>2</sub> per year by 2100. With respect to mitigation, we find that associated costs strongly depend on three factors: (1) the policy assumptions, (2) the socio-economic narrative, and (3) the stringency of the target. The carbon price for reaching the target of 2.6 W/m<sup>2</sup> that is consistent with a temperature change limit of 2 °C, differs in our analysis thus by about a factor of three across the SSP marker scenarios. Moreover, many models could not reach this target from the SSPs with high mitigation challenges. While the SSPs were designed to represent different mitigation and adaptation challenges, the resulting narratives and quantifications span a wide range of different futures broadly representative of the current literature. This allows their subsequent use and development in new assessments and research projects. Critical next steps for the community scenario process will, among others, involve regional and sectoral extensions, further elaboration of the adaptation and impacts dimension, as well as employing the SSP scenarios with the new generation of earth system models as part of the 6th climate model intercomparison project (CMIP6).

Keywords

Affiliated Institutions

• University of Maryland, College Park US
• Organisation de Coopération et de Développement Economiques FR
• National Institute for Environmental Studies JP
• Fondazione Eni Enrico Mattei IT
• Bocconi University IT
• NSF National Center for Atmospheric Research US
• Wageningen University & Research NL
• Potsdam Institute for Climate Impact Research DE
• Shanghai University CN
• University of Washington US
• Netherlands Environmental Assessment Agency NL
• Politecnico di Milano IT
• CMCC Foundation - Euro-Mediterranean Center on Climate Change IT
• Korea Advanced Institute of Science and Technology KR
• Pacific Northwest National Laboratory US
• Seattle University US
• International Institute for Applied Systems Analysis AT
• Joint Global Change Research Institute US

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