Sensitivity of projected long-term CO2 emissions across the Shared Socioeconomic Pathways


Scenarios showing future greenhouse gas emissions are needed to estimate climate impacts and the mitigation efforts required for climate stabilization. Recently, the Shared Socioeconomic Pathways (SSPs) have been introduced to describe alternative social, economic and technical narratives, spanning a wide range of plausible futures in terms of challenges to mitigation and adaptation1. Thus far the key drivers of the uncertainty in emissions projections have not been robustly disentangled. Here we assess the sensitivities of future CO2 emissions to key drivers characterizing the SSPs. We use six state-of-the-art integrated assessment models with different structural characteristics, and study the impact of five families of parameters, related to population, income, energy efficiency, fossil fuel availability, and low-carbon energy technology development. A recently developed sensitivity analysis algorithm2 allows us to parsimoniously compute both the direct and interaction effects of each of these drivers on cumulative emissions. The study reveals that the SSP assumptions about energy intensity and economic growth are the most important determinants of future CO2 emissions from energy combustion, both with and without a climate policy. Interaction terms between parameters are shown to be important determinants of the total sensitivities.

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Figure 1: Main CO2 emission drivers for the first three SSP scenarios.
Figure 2: Sensitivities of cumulative CO2 emissions to scenario factors.


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The research leading to these results has received funding from the European Union’s Seventh Framework Programme [FP7/2007-2013] under grant agreement no. 30832 (ADVANCE). V.B. gratefully acknowledges funding from the European Research Council under the European Community’s Programme ‘Ideas’—Call identifier: ERC-2013-StG/ERC grant agreement no 336703—project RISICO ‘RISk and uncertainty in developing and Implementing Climate change pOlicies’. G.M. and M.T. gratefully acknowledge funding from the European Research Council under the European Community’s Programme ‘Ideas’—Call identifier: ERC-2013-StG/ERC—project COBHAM ‘The role of consumer behaviour and heterogeneity in the integrated assessment of energy and climate policies’.

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G.M., M.T., V.B. and E.Ó. designed the experiment. All authors contributed to the final design, implemented the scenarios and provided model output data. G.M. performed the sensitivity computations. G.M. and M.T. wrote the first draft of the paper. All authors contributed to the final writing of the paper.

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Correspondence to G. Marangoni.

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The authors declare no competing financial interests.

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Marangoni, G., Tavoni, M., Bosetti, V. et al. Sensitivity of projected long-term CO2 emissions across the Shared Socioeconomic Pathways. Nature Clim Change 7, 113–117 (2017).

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