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Biogeosciences An interactive open-access journal of the European Geosciences Union
doi:10.5194/bg-2016-544
© Author(s) 2017. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
05 Jan 2017
Review status
A revision of this discussion paper is under review for the journal Biogeosciences (BG).
Quantifying uncertainties of permafrost carbon-climate feedbacks
Eleanor J. Burke1, Altug Ekici2,3, Ye Huang4, Sarah E. Chadburn2,5, Chris Huntingford6, Philippe Ciais4, Pierre Friedlingstein2, Shushi Peng4,7, and Gerhard Krinner8 1Met Office Hadley Centre, FitzRoy Road, Exeter, EX1 3PB, UK
2University of Exeter, College of Engineering, Mathematics and Physical Sciences, Exeter, EX4 4QF, UK
3Uni Research Climate and Bjerknes Centre for Climate Research, Bergen, Norway
4Laboratoire des Sciences du Climat et de l'Environnement, UMR 1572 CEA-CNRS-UVSQ, Gif sur Yvette 91191, France
5University of Leeds, School of Earth and Environment, Leeds, LS2 9JT, UK
6Centre for Ecology and Hydrology, Wallingford, Oxfordshire, OX10 8BB, UK
7Sino-French Institute for Earth System Science, College of Urban and Environmental Sciences, Peking University, Beijing 100871, China
8Laboratoire de Glaciologie et Géophysique de l'Environnement, 54 rue Molière, F-38402, Saint Martin d'Hères, France
Abstract. The land surface models JULES (two versions) and ORCHIDEE-MICT, each with a revised representation of permafrost carbon, were coupled to the IMOGEN intermediate complexity climate and ocean carbon uptake model. IMOGEN calculates atmospheric carbon dioxide (CO2) and local monthly surface climate for a given emission scenario with the land-atmosphere CO2 flux exchange from either JULES or ORCHIDEE-MICT. These simulations include feedbacks associated with permafrost carbon changes in a warming world. Both IMOGEN-JULES and IMOGEN-ORCHIDEE-MICT were forced by historical and three alternative future CO2 emission scenarios. Simulations were performed for different climate sensitivities and regional climate change patterns based on 22 different Earth System Models (ESM) used for CMIP3 (phase 3 of the Coupled Model Intercomparison Project), allowing us to explore climate uncertainties in the context of permafrost carbon – climate feedbacks. Three future emission scenarios consistent with three representative concentration pathways: RCP2.6; RCP4.5 and RCP8.5 were used. Paired simulations with and without frozen carbon processes were required to quantify the impact of the permafrost carbon feedback on climate change. The additional warming from the permafrost carbon feedback is between 0.2 and 12 % of the change in the global mean temperature (ΔT) by year 2100 and 0.5 and 17 % of ΔT by 2300, this range reflecting differences in land surface models, climate models and emissions pathway. As a percentage of ΔT, the permafrost carbon feedback has a greater impact on the low emission scenario (RCP2.6) than on the higher emissions scenarios suggesting that permafrost carbon should be taken into account when evaluating heavy mitigation and stabilizations scenarios. Structural differences between the land surface models are found to be a larger source of uncertainties than differences between climate models, in particular due to different representations of soil carbon decomposition. Inertia in the permafrost carbon system means that the permafrost carbon response is dependent on the temporal trajectory of warming as well as the absolute amount of warming. We propose a new policy relevant metric – the Frozen Carbon Vulnerability timescale (FCVt) in years – that can be derived from the more complex land surface models and used to quantify the permafrost carbon response given any pathway of global temperature change.

Citation: Burke, E. J., Ekici, A., Huang, Y., Chadburn, S. E., Huntingford, C., Ciais, P., Friedlingstein, P., Peng, S., and Krinner, G.: Quantifying uncertainties of permafrost carbon-climate feedbacks, Biogeosciences Discuss., doi:10.5194/bg-2016-544, in review, 2017.
Eleanor J. Burke et al.
Eleanor J. Burke et al.
Eleanor J. Burke et al.

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Short summary
There are large reserves of carbon within the permafrost which might be released to the atmosphere under global warming. Our models suggest this release may cause an additional global temperature increase of 0.005 to 0.2 °C by the year 2100 and 0.01 to 0.34 °C by the year 2300. Under climate mitigation scenarios this is between 1.5 and 9 % (by 2100) and 6 and 16 % (by 2300) of the global mean temperature change. There is a large uncertainty associated with these results.
There are large reserves of carbon within the permafrost which might be released to the...
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