Carbon–concentration and carbon–climate feedbacks in CMIP6 models and their comparison to CMIP5 models
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Published:2020-08-18
Issue:16
Volume:17
Page:4173-4222
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ISSN:1726-4189
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Container-title:Biogeosciences
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language:en
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Short-container-title:Biogeosciences
Author:
Arora Vivek K., Katavouta AnnaORCID, Williams Richard G.ORCID, Jones Chris D.ORCID, Brovkin VictorORCID, Friedlingstein PierreORCID, Schwinger JörgORCID, Bopp Laurent, Boucher OlivierORCID, Cadule Patricia, Chamberlain Matthew A., Christian James R., Delire Christine, Fisher Rosie A., Hajima Tomohiro, Ilyina TatianaORCID, Joetzjer Emilie, Kawamiya Michio, Koven Charles D.ORCID, Krasting John P., Law Rachel M.ORCID, Lawrence David M., Lenton Andrew, Lindsay KeithORCID, Pongratz Julia, Raddatz Thomas, Séférian RolandORCID, Tachiiri Kaoru, Tjiputra Jerry F., Wiltshire Andy, Wu TongwenORCID, Ziehn TiloORCID
Abstract
Abstract. Results from the fully and biogeochemically coupled simulations in which
CO2 increases at a rate of 1 % yr−1
(1pctCO2) from its
preindustrial value are analyzed to quantify the magnitude of
carbon–concentration and carbon–climate feedback parameters which measure
the response of ocean and terrestrial carbon pools to changes in atmospheric
CO2 concentration and the resulting change in global climate,
respectively. The results are based on 11 comprehensive Earth system
models from the most recent (sixth) Coupled Model Intercomparison Project
(CMIP6) and compared with eight models from the fifth CMIP (CMIP5). The
strength of the carbon–concentration feedback is of comparable magnitudes
over land (mean ± standard deviation = 0.97 ± 0.40 PgC ppm−1) and ocean (0.79 ± 0.07 PgC ppm−1), while the
carbon–climate feedback over land (−45.1 ± 50.6 PgC ∘C−1) is about 3 times larger than over ocean (−17.2 ± 5.0 PgC ∘C−1). The strength of both feedbacks is an order of
magnitude more uncertain over land than over ocean as has been seen in
existing studies. These values and their spread from 11 CMIP6 models
have not changed significantly compared to CMIP5 models. The absolute values
of feedback parameters are lower for land with models that include a
representation of nitrogen cycle. The transient climate response to
cumulative emissions (TCRE) from the 11 CMIP6 models considered here is
1.77 ± 0.37 ∘C EgC−1 and is similar to that found in
CMIP5 models (1.63 ± 0.48 ∘C EgC−1) but with somewhat
reduced model spread. The expressions for feedback parameters based on the
fully and biogeochemically coupled configurations of the 1pctCO2 simulation
are simplified when the small temperature change in the
biogeochemically coupled simulation is ignored. Decomposition of the terms
of these simplified expressions for the feedback parameters is used to gain
insight into the reasons for differing responses among ocean and land carbon
cycle models.
Publisher
Copernicus GmbH
Subject
Earth-Surface Processes,Ecology, Evolution, Behavior and Systematics
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