[A-CG34] Projection and detection of global environmental change

[ACG34-P07] Consistency of global carbon budget between concentration- and emission-driven historical experiments simulated by CMIP6 Earth system models

*Tomohiro Hajima¹, Michio Kawamiya¹, Akihiko Ito², Kaoru Tachiiri¹, Chris D Jones³, Vivek Arora⁴, Victor Brovkin⁵, Roland Séférian⁶, Spencer Liddicoat³, Pierre Friedlingstein⁷, Elena Shevliakova⁸ (1.Japan Agency for Marine-Earth Science and Technology, 2.The University of Tokyo, 3.Met Office Hadley Centre, 4.Canadian Centre for Climate Modelling and Analysis, University of Victoria, 5.Max-Planck-Institute for Meteorology, 6.Centre National de Recherches Météorologiques, 7.University of Exeter, 8.NOAA/Geophysical Fluid Dynamics Laboratory)

Keywords:Carbon cycle, Earth system model, CO2

Anthropogenically emitted CO2 from fossil fuel use and land use change is partly absorbed by terrestrial ecosystems and the ocean, while the remainder retained in the atmosphere adds to the ongoing increase in atmospheric CO2 concentration. Earth system models (ESMs) can simulate such dynamics of the global carbon cycle and consider its interaction with the physical climate system. This study investigated the cause of CO2 concentration biases in ESMs and identified how they might be reduced. For this purpose, we first compared simulated historical carbon budgets in two types of experiments: one with prescribed CO2 emissions (the emission-driven experiment, “E-HIST”) and the other with prescribed CO2 concentration (the concentration-driven experiment, “C-HIST”). It was confirmed that the multi-model means of the carbon budgets simulated by one type of experiment generally showed good agreement with those simulated by the other. Next, we investigated the potential linkages of two types of carbon cycle indices: simulated CO2 concentration in E-HIST and compatible fossil fuel emission in C-HIST. It was confirmed quantitatively that the two indices are reasonable indicators of overall model performance in the context of carbon cycle feedbacks. Other suggestions were also obtained from this study, and one of them is that accurate reproduction of land use change emission is critical for better reproduction of the global carbon budget and CO2 concentration.