Uncertainty in land carbon budget simulated by terrestrial biosphere models: the role of atmospheric forcing

Lucas Hardouin; Christine Delire; Bertrand Decharme; David M. Lawrence; Julia E.M.S. Nabel; Victor Brovkin; Nathan Collier; Rosie Fisher; Forrest M. Hoffman; Charles D. Koven; Roland Séférian; Tobias Stacke

doi:10.1088/1748-9326/ac888d

Uncertainty in land carbon budget simulated by terrestrial biosphere models: the role of atmospheric forcing

Lucas Hardouin, Christine Delire, Bertrand Decharme, David M. Lawrence, Julia E.M.S. Nabel, Victor Brovkin, Nathan Collier, Rosie Fisher, Forrest M. Hoffman, Charles D. Koven, Roland Séférian, Tobias Stacke

Computational Earth Sciences Group

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6 Scopus citations

Abstract

Global estimates of the land carbon sink are often based on simulations by terrestrial biosphere models (TBMs). The use of a large number of models that differ in their underlying hypotheses, structure and parameters is one way to assess the uncertainty in the historical land carbon sink. Here we show that the atmospheric forcing datasets used to drive these TBMs represent a significant source of uncertainty that is currently not systematically accounted for in land carbon cycle evaluations. We present results from three TBMs each forced with three different historical atmospheric forcing reconstructions over the period 1850-2015. We perform an analysis of variance to quantify the relative uncertainty in carbon fluxes arising from the models themselves, atmospheric forcing, and model-forcing interactions. We find that atmospheric forcing in this set of simulations plays a dominant role on uncertainties in global gross primary productivity (GPP) (75% of variability) and autotrophic respiration (90%), and a significant but reduced role on net primary productivity and heterotrophic respiration (30%). Atmospheric forcing is the dominant driver (52%) of variability for the net ecosystem exchange flux, defined as the difference between GPP and respiration (both autotrophic and heterotrophic respiration). In contrast, for wildfire-driven carbon emissions model uncertainties dominate and, as a result, model uncertainties dominate for net ecosystem productivity. At regional scales, the contribution of atmospheric forcing to uncertainty shows a very heterogeneous pattern and is smaller on average than at the global scale. We find that this difference in the relative importance of forcing uncertainty between global and regional scales is related to large differences in regional model flux estimates, which partially offset each other when integrated globally, while the flux differences driven by forcing are mainly consistent across the world and therefore add up to a larger fractional contribution to global uncertainty.

Original language	English
Article number	094033
Journal	Environmental Research Letters
Volume	17
Issue number	9
DOIs	https://doi.org/10.1088/1748-9326/ac888d
State	Published - Sep 1 2022

Funding

L H, C D, B D, R S, T S and R F acknowledge funding by the European Union’s Horizon 2020 (H2020) research and innovation program under Grant Agreement No. 641816 (CRESCENDO) for L H, B D, C D and T S, No. 101003536 (ESM2025 – Earth System Models for the Future) for R S and No. 821003 (4C) for R F. C D and B D are supported by the ‘Centre National de Recherches Météorologiques’ (CNRM) of Météo-France and the ‘Centre National de la Recherche Scientifique’ (CNRS) of the French research ministry. D M L is supported by the National Center for Atmospheric Research, which is a major facility sponsored by the NSF under Cooperative Agreement 1852977 and by the U.S. Department of Energy, Office of Biological and Environmental Research Grant DE-FC03-97ER62402/A0101. J E M S N and T S would like to thank Veronika Gayler for conducting many of the CMIP6 MPI-ESM1.2-LR simulations. T S work was funded by the EU CRESCENDO Project. C D K acknowledges support by the Director, Office of Science, Office of Biological and Environmental Research of the U.S. Department of Energy under Contract DE-AC02-05CH11231 through the Early Career Research Program and the Regional and Global Model Analysis Program (RUBISCO SFA).

Funders	Funder number
C D and T S	ESM2025, 821003, 101003536
Centre national de recherches météorologiques
National Science Foundation	1852977
U.S. Department of Energy
National Center for Atmospheric Research
Office of Science	DE-AC02-05CH11231
Biological and Environmental Research	DE-FC03-97ER62402/A0101
Horizon 2020 Framework Programme	641816
Center for Neuroscience and Regenerative Medicine
European Commission
Centre National de la Recherche Scientifique

Keywords

atmospheric forcing dataset
land carbon sink
terrestrial biosphere model
uncertainty

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10.1088/1748-9326/ac888d

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Hardouin, L., Delire, C., Decharme, B., Lawrence, D. M., Nabel, J. E. M. S., Brovkin, V., Collier, N., Fisher, R., Hoffman, F. M., Koven, C. D., Séférian, R., & Stacke, T. (2022). Uncertainty in land carbon budget simulated by terrestrial biosphere models: the role of atmospheric forcing. Environmental Research Letters, 17(9), Article 094033. https://doi.org/10.1088/1748-9326/ac888d

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title = "Uncertainty in land carbon budget simulated by terrestrial biosphere models: the role of atmospheric forcing",

abstract = "Global estimates of the land carbon sink are often based on simulations by terrestrial biosphere models (TBMs). The use of a large number of models that differ in their underlying hypotheses, structure and parameters is one way to assess the uncertainty in the historical land carbon sink. Here we show that the atmospheric forcing datasets used to drive these TBMs represent a significant source of uncertainty that is currently not systematically accounted for in land carbon cycle evaluations. We present results from three TBMs each forced with three different historical atmospheric forcing reconstructions over the period 1850-2015. We perform an analysis of variance to quantify the relative uncertainty in carbon fluxes arising from the models themselves, atmospheric forcing, and model-forcing interactions. We find that atmospheric forcing in this set of simulations plays a dominant role on uncertainties in global gross primary productivity (GPP) (75% of variability) and autotrophic respiration (90%), and a significant but reduced role on net primary productivity and heterotrophic respiration (30%). Atmospheric forcing is the dominant driver (52%) of variability for the net ecosystem exchange flux, defined as the difference between GPP and respiration (both autotrophic and heterotrophic respiration). In contrast, for wildfire-driven carbon emissions model uncertainties dominate and, as a result, model uncertainties dominate for net ecosystem productivity. At regional scales, the contribution of atmospheric forcing to uncertainty shows a very heterogeneous pattern and is smaller on average than at the global scale. We find that this difference in the relative importance of forcing uncertainty between global and regional scales is related to large differences in regional model flux estimates, which partially offset each other when integrated globally, while the flux differences driven by forcing are mainly consistent across the world and therefore add up to a larger fractional contribution to global uncertainty.",

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author = "Lucas Hardouin and Christine Delire and Bertrand Decharme and Lawrence, {David M.} and Nabel, {Julia E.M.S.} and Victor Brovkin and Nathan Collier and Rosie Fisher and Hoffman, {Forrest M.} and Koven, {Charles D.} and Roland S{\'e}f{\'e}rian and Tobias Stacke",

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AU - Hardouin, Lucas

AU - Delire, Christine

AU - Decharme, Bertrand

AU - Lawrence, David M.

AU - Nabel, Julia E.M.S.

AU - Brovkin, Victor

AU - Collier, Nathan

AU - Fisher, Rosie

AU - Hoffman, Forrest M.

AU - Koven, Charles D.

AU - Séférian, Roland

AU - Stacke, Tobias

PY - 2022/9/1

Y1 - 2022/9/1

N2 - Global estimates of the land carbon sink are often based on simulations by terrestrial biosphere models (TBMs). The use of a large number of models that differ in their underlying hypotheses, structure and parameters is one way to assess the uncertainty in the historical land carbon sink. Here we show that the atmospheric forcing datasets used to drive these TBMs represent a significant source of uncertainty that is currently not systematically accounted for in land carbon cycle evaluations. We present results from three TBMs each forced with three different historical atmospheric forcing reconstructions over the period 1850-2015. We perform an analysis of variance to quantify the relative uncertainty in carbon fluxes arising from the models themselves, atmospheric forcing, and model-forcing interactions. We find that atmospheric forcing in this set of simulations plays a dominant role on uncertainties in global gross primary productivity (GPP) (75% of variability) and autotrophic respiration (90%), and a significant but reduced role on net primary productivity and heterotrophic respiration (30%). Atmospheric forcing is the dominant driver (52%) of variability for the net ecosystem exchange flux, defined as the difference between GPP and respiration (both autotrophic and heterotrophic respiration). In contrast, for wildfire-driven carbon emissions model uncertainties dominate and, as a result, model uncertainties dominate for net ecosystem productivity. At regional scales, the contribution of atmospheric forcing to uncertainty shows a very heterogeneous pattern and is smaller on average than at the global scale. We find that this difference in the relative importance of forcing uncertainty between global and regional scales is related to large differences in regional model flux estimates, which partially offset each other when integrated globally, while the flux differences driven by forcing are mainly consistent across the world and therefore add up to a larger fractional contribution to global uncertainty.

AB - Global estimates of the land carbon sink are often based on simulations by terrestrial biosphere models (TBMs). The use of a large number of models that differ in their underlying hypotheses, structure and parameters is one way to assess the uncertainty in the historical land carbon sink. Here we show that the atmospheric forcing datasets used to drive these TBMs represent a significant source of uncertainty that is currently not systematically accounted for in land carbon cycle evaluations. We present results from three TBMs each forced with three different historical atmospheric forcing reconstructions over the period 1850-2015. We perform an analysis of variance to quantify the relative uncertainty in carbon fluxes arising from the models themselves, atmospheric forcing, and model-forcing interactions. We find that atmospheric forcing in this set of simulations plays a dominant role on uncertainties in global gross primary productivity (GPP) (75% of variability) and autotrophic respiration (90%), and a significant but reduced role on net primary productivity and heterotrophic respiration (30%). Atmospheric forcing is the dominant driver (52%) of variability for the net ecosystem exchange flux, defined as the difference between GPP and respiration (both autotrophic and heterotrophic respiration). In contrast, for wildfire-driven carbon emissions model uncertainties dominate and, as a result, model uncertainties dominate for net ecosystem productivity. At regional scales, the contribution of atmospheric forcing to uncertainty shows a very heterogeneous pattern and is smaller on average than at the global scale. We find that this difference in the relative importance of forcing uncertainty between global and regional scales is related to large differences in regional model flux estimates, which partially offset each other when integrated globally, while the flux differences driven by forcing are mainly consistent across the world and therefore add up to a larger fractional contribution to global uncertainty.

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KW - terrestrial biosphere model

KW - uncertainty

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SN - 1748-9318

VL - 17

JO - Environmental Research Letters

JF - Environmental Research Letters

IS - 9

M1 - 094033

ER -

Uncertainty in land carbon budget simulated by terrestrial biosphere models: the role of atmospheric forcing

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