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Global warming under old and new scenarios using IPCC climate sensitivity range estimates


Climate projections for the fourth assessment report1 (AR4) of the Intergovernmental Panel on Climate Change (IPCC) were based on scenarios from the Special Report on Emissions Scenarios2 (SRES) and simulations of the third phase of the Coupled Model Intercomparison Project3 (CMIP3). Since then, a new set of four scenarios (the representative concentration pathways or RCPs) was designed4. Climate projections in the IPCC fifth assessment report (AR5) will be based on the fifth phase of the Coupled Model Intercomparison Project5 (CMIP5), which incorporates the latest versions of climate models and focuses on RCPs. This implies that by AR5 both models and scenarios will have changed, making a comparison with earlier literature challenging. To facilitate this comparison, we provide probabilistic climate projections of both SRES scenarios and RCPs in a single consistent framework. These estimates are based on a model set-up that probabilistically takes into account the overall consensus understanding of climate sensitivity uncertainty, synthesizes the understanding of climate system and carbon-cycle behaviour, and is at the same time constrained by the observed historical warming.

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Figure 1: Ensemble of ECS distributions from this study and from the literature.
Figure 2: Probability to stay below specific equilibrium temperature increases relative to pre-industrial as a function of equivalent atmospheric CO2 concentration stabilization levels based on this study’s representative ECS distribution.
Figure 3: Temperature projections for SRES scenarios and RCPs.


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J.R. was supported by the Swiss National Science Foundation (project 200021-135067).

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All authors were involved in designing the research; M.M. developed the set-up of the MAGICC model; J.R. developed the climate sensitivity sampling methodology and carried out the analysis; all authors contributed to writing the paper.

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Correspondence to Joeri Rogelj.

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The authors declare no competing financial interests.

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Rogelj, J., Meinshausen, M. & Knutti, R. Global warming under old and new scenarios using IPCC climate sensitivity range estimates. Nature Clim Change 2, 248–253 (2012).

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