Analysis of the IPCC AR5 transformation pathways with a new compact Earth system model
Résumé
The climate impacts of all transformation pathways from IPCC AR5WG3 (AR5 WG3 Ch.6) were estimated with a single model named MAGICC. It was shown to produce consistent climate projections when concentration-driven (AR5 WG1 Ch. 12). However, its carbon-cycle - and therefore its ability to be emission-driven - was shown to be slightly biased (AR5 WG1 Ch. 6). A large fraction of non-CO2 forcings - as expected in low-carbon scenarios- also makes its projections span a narrower range than that of complex models (AR5 WG1 Ch. 12).
Here, we use OSCAR 2.2, a new reduced-form Earth system model to analyze the AR5 WG3 transformation pathways. Our analysis aims at detecting and understanding the cause of any systematic bias induced by using only one reduced-form model. Ultimately, the use of two compact Earth system models, instead of a single one, will help the analysis of socio-economic scenarios to gain in reliability, and will therefore improve the next IPCC special report on the 1.5C target.
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