Articles | Volume 23, issue 15
https://doi.org/10.5194/bg-23-5593-2026
© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-23-5593-2026
© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
13 Aug 2026
Research article |
| 13 Aug 2026
| 13 Aug 2026
Uncertainty in Land Carbon Fluxes Simulated by CMIP6 Models from Treatments of Crop Distributions and Photosynthetic Pathways
Joseph Ovwemuvwose
CORRESPONDING AUTHOR
Department of Physics, Imperial College London, London, UK
Ian Colin Prentice
Georgina Mace Centre for the Living Planet, Department of Life Sciences, Imperial College London, London, UK
Department of Earth System Science, Tsinghua University, Beijing, China
Heather Graven
Department of Physics, Imperial College London, London, UK
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Wenyao Gan, Martin Best, Pier Luigi Vidale, I. Colin Prentice, and Sandy P. Harrison
EGUsphere, https://doi.org/10.5194/egusphere-2026-2804, https://doi.org/10.5194/egusphere-2026-2804, 2026
This preprint is open for discussion and under review for Geoscientific Model Development (GMD).
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Plants dynamically adjust their photosynthetic capacity as environmental conditions change, but most land models represent this with fixed parameters set separately for each plant type. We added a simple optimality-based photosynthesis scheme to the Joint UK Land Environment Simulator, allowing photosynthetic capacity to acclimate, and tested it against flux-tower observations together with the standard setups. The new scheme improves simulated carbon uptake without worsening energy fluxes.
Matthew Forrest, Mateus Dantas de Paula, Filipe Gomes de Almeida, Sandy P. Harrison, I. Colin Prentice, and Thomas Hickler
EGUsphere, https://doi.org/10.5194/egusphere-2026-3273, https://doi.org/10.5194/egusphere-2026-3273, 2026
This preprint is open for discussion and under review for Geoscientific Model Development (GMD).
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Global photosynthesis on land is a large flow of carbon in the Earth system which underpins food production and ecosystems. It is particularly important to know how it responds to climate change, but current vegetation models do not agree on this. We implemented a new photosynthesis model based on recent theoretical advances into a vegetation model. We found that it improved the representation of photosynthesis when compared both to global data from satellites and detailed site measurements.
Thomas Laemmel, Dylan Geissbühler, Stephan Henne, Ryo Fujita, Heather Graven, Christophe Espic, Matthias Bantle, Negar Haghipour, Franz Conen, Dominik Brunner, Martin Steinbacher, Giulia Zazzeri, Samuel Hammer, Markus Leuenberger, and Sönke Szidat
EGUsphere, https://doi.org/10.5194/egusphere-2026-265, https://doi.org/10.5194/egusphere-2026-265, 2026
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Carbon dioxide and methane are the two main anthropogenic greenhouse gases responsible for current climate change. Beside the measurement of their atmospheric concentration, the analysis of the abundance of their isotope carbon-14 (14C) gives hints about their origin, either biogenic or fossil. Here we present six years of atmospheric 14CH4 and 14CO2 measurements at a high-elevation alpine site in Switzerland (Jungfraujoch) and discuss the observed trends in both local and global views.
Mengmeng Liu, Iain Colin Prentice, and Sandy P. Harrison
Clim. Past, 22, 205–226, https://doi.org/10.5194/cp-22-205-2026, https://doi.org/10.5194/cp-22-205-2026, 2026
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Dansgaard-Oeschger events were large and rapid climate transitions that occurred multiple times during the last glacial period. We reconstructed the global pattern during these events using fossil pollen records, and found a north-south antiphasing of temperature change, and reduced seasonality in the northern extratropics.
Amin Hassan, Iain Colin Prentice, and Xu Liang
Hydrol. Earth Syst. Sci., 30, 317–341, https://doi.org/10.5194/hess-30-317-2026, https://doi.org/10.5194/hess-30-317-2026, 2026
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Evapotranspiration is evaporation that occurs from plants, soil, and water bodies, but determining these components is difficult. We developed a new method that uses measurements such as streamflow and rainfall to determine the portion of plant evaporation. We found differences among vegetation types and climate conditions, and showed that plant water use peaks in moderately dry regions. The results improve understanding of plant-water interactions and can help improve water and climate models.
Jierong Zhao, Boya Zhou, Sandy P. Harrison, and Colin Prentice
Earth Syst. Dynam., 16, 1655–1669, https://doi.org/10.5194/esd-16-1655-2025, https://doi.org/10.5194/esd-16-1655-2025, 2025
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We used eco-evolutionary optimality modelling to examine how climate and CO2 impacted vegetation at the Last Glacial Maximum (LGM; 21 000 years ago) and the mid-Holocene (MH; 6000 years ago). Low CO2 at the LGM was as important as climate in reducing tree cover and productivity and in increasing C4 plant abundance. Climate had positive effects on MH vegetation, but the low CO2 was a constraint on plant growth. These results show it is important to consider changing CO2 to model ecosystem changes.
Giulia Zazzeri, Lukas Wacker, Negar Haghipour, Philip Gautschi, Thomas Laemmel, Sönke Szidat, and Heather Graven
Atmos. Meas. Tech., 18, 319–325, https://doi.org/10.5194/amt-18-319-2025, https://doi.org/10.5194/amt-18-319-2025, 2025
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Radiocarbon (14C) is an optimal tracer of methane (CH4) emissions, as 14C measurements enable distinguishing between fossil methane and biogenic methane. However, these measurements are particularly challenging, mainly due to technical difficulties in the sampling procedure. We made the sample extraction much simpler and time efficient, providing a new technology that can be used by any research group, with the goal of expanding 14C measurements for an improved understanding of methane sources.
Alexander S. Brunmayr, Frank Hagedorn, Margaux Moreno Duborgel, Luisa I. Minich, and Heather D. Graven
Geosci. Model Dev., 17, 5961–5985, https://doi.org/10.5194/gmd-17-5961-2024, https://doi.org/10.5194/gmd-17-5961-2024, 2024
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A new generation of soil models promises to more accurately predict the carbon cycle in soils under climate change. However, measurements of 14C (the radioactive carbon isotope) in soils reveal that the new soil models face similar problems to the traditional models: they underestimate the residence time of carbon in soils and may therefore overestimate the net uptake of CO2 by the land ecosystem. Proposed solutions include restructuring the models and calibrating model parameters with 14C data.
David Sandoval, Iain Colin Prentice, and Rodolfo L. B. Nóbrega
Geosci. Model Dev., 17, 4229–4309, https://doi.org/10.5194/gmd-17-4229-2024, https://doi.org/10.5194/gmd-17-4229-2024, 2024
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Numerous estimates of water and energy balances depend on empirical equations requiring site-specific calibration, posing risks of "the right answers for the wrong reasons". We introduce novel first-principles formulations to calculate key quantities without requiring local calibration, matching predictions from complex land surface models.
Katie R. Blackford, Matthew Kasoar, Chantelle Burton, Eleanor Burke, Iain Colin Prentice, and Apostolos Voulgarakis
Geosci. Model Dev., 17, 3063–3079, https://doi.org/10.5194/gmd-17-3063-2024, https://doi.org/10.5194/gmd-17-3063-2024, 2024
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Peatlands are globally important stores of carbon which are being increasingly threatened by wildfires with knock-on effects on the climate system. Here we introduce a novel peat fire parameterization in the northern high latitudes to the INFERNO global fire model. Representing peat fires increases annual burnt area across the high latitudes, alongside improvements in how we capture year-to-year variation in burning and emissions.
Hannah Chawner, Eric Saboya, Karina E. Adcock, Tim Arnold, Yuri Artioli, Caroline Dylag, Grant L. Forster, Anita Ganesan, Heather Graven, Gennadi Lessin, Peter Levy, Ingrid T. Luijkx, Alistair Manning, Penelope A. Pickers, Chris Rennick, Christian Rödenbeck, and Matthew Rigby
Atmos. Chem. Phys., 24, 4231–4252, https://doi.org/10.5194/acp-24-4231-2024, https://doi.org/10.5194/acp-24-4231-2024, 2024
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The quantity of atmospheric potential oxygen (APO), derived from coincident measurements of carbon dioxide (CO2) and oxygen (O2), has been proposed as a tracer for fossil fuel CO2 emissions. In this model sensitivity study, we examine the use of APO for this purpose in the UK and compare our model to observations. We find that our model simulations are most sensitive to uncertainties relating to ocean fluxes and boundary conditions.
Huiying Xu, Han Wang, Iain Colin Prentice, and Sandy P. Harrison
Biogeosciences, 20, 4511–4525, https://doi.org/10.5194/bg-20-4511-2023, https://doi.org/10.5194/bg-20-4511-2023, 2023
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Leaf carbon (C) and nitrogen (N) are crucial elements in leaf construction and physiological processes. This study reconciled the roles of phylogeny, species identity, and climate in stoichiometric traits at individual and community levels. The variations in community-level leaf N and C : N ratio were captured by optimality-based models using climate data. Our results provide an approach to improve the representation of leaf stoichiometry in vegetation models to better couple N with C cycling.
Esmeralda Cruz-Silva, Sandy P. Harrison, I. Colin Prentice, Elena Marinova, Patrick J. Bartlein, Hans Renssen, and Yurui Zhang
Clim. Past, 19, 2093–2108, https://doi.org/10.5194/cp-19-2093-2023, https://doi.org/10.5194/cp-19-2093-2023, 2023
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We examined 71 pollen records (12.3 ka to present) in the eastern Mediterranean, reconstructing climate changes. Over 9000 years, winters gradually warmed due to orbital factors. Summer temperatures peaked at 4.5–5 ka, likely declining because of ice sheets. Moisture increased post-11 kyr, remaining high from 10–6 kyr before a slow decrease. Climate models face challenges in replicating moisture transport.
Olivia Haas, Iain Colin Prentice, and Sandy P. Harrison
Biogeosciences, 20, 3981–3995, https://doi.org/10.5194/bg-20-3981-2023, https://doi.org/10.5194/bg-20-3981-2023, 2023
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We quantify the impact of CO2 and climate on global patterns of burnt area, fire size, and intensity under Last Glacial Maximum (LGM) conditions using three climate scenarios. Climate change alone did not produce the observed LGM reduction in burnt area, but low CO2 did through reducing vegetation productivity. Fire intensity was sensitive to CO2 but strongly affected by changes in atmospheric dryness. Low CO2 caused smaller fires; climate had the opposite effect except in the driest scenario.
Giulia Mengoli, Sandy P. Harrison, and I. Colin Prentice
EGUsphere, https://doi.org/10.5194/egusphere-2023-1261, https://doi.org/10.5194/egusphere-2023-1261, 2023
Preprint archived
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Soil water availability affects plant carbon uptake by reducing leaf area and/or by closing stomata, which reduces its efficiency. We present a new formulation of how climatic dryness reduces both maximum carbon uptake and the soil-moisture threshold below which it declines further. This formulation illustrates how plants adapt their water conservation strategy to thrive in dry climates, and is step towards a better representation of soil-moisture effects in climate models.
Mengmeng Liu, Yicheng Shen, Penelope González-Sampériz, Graciela Gil-Romera, Cajo J. F. ter Braak, Iain Colin Prentice, and Sandy P. Harrison
Clim. Past, 19, 803–834, https://doi.org/10.5194/cp-19-803-2023, https://doi.org/10.5194/cp-19-803-2023, 2023
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We reconstructed the Holocene climates in the Iberian Peninsula using a large pollen data set and found that the west–east moisture gradient was much flatter than today. We also found that the winter was much colder, which can be expected from the low winter insolation during the Holocene. However, summer temperature did not follow the trend of summer insolation, instead, it was strongly correlated with moisture.
Jing M. Chen, Rong Wang, Yihong Liu, Liming He, Holly Croft, Xiangzhong Luo, Han Wang, Nicholas G. Smith, Trevor F. Keenan, I. Colin Prentice, Yongguang Zhang, Weimin Ju, and Ning Dong
Earth Syst. Sci. Data, 14, 4077–4093, https://doi.org/10.5194/essd-14-4077-2022, https://doi.org/10.5194/essd-14-4077-2022, 2022
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Green leaves contain chlorophyll pigments that harvest light for photosynthesis and also emit chlorophyll fluorescence as a byproduct. Both chlorophyll pigments and fluorescence can be measured by Earth-orbiting satellite sensors. Here we demonstrate that leaf photosynthetic capacity can be reliably derived globally using these measurements. This new satellite-based information overcomes a bottleneck in global ecological research where such spatially explicit information is currently lacking.
Yicheng Shen, Luke Sweeney, Mengmeng Liu, Jose Antonio Lopez Saez, Sebastián Pérez-Díaz, Reyes Luelmo-Lautenschlaeger, Graciela Gil-Romera, Dana Hoefer, Gonzalo Jiménez-Moreno, Heike Schneider, I. Colin Prentice, and Sandy P. Harrison
Clim. Past, 18, 1189–1201, https://doi.org/10.5194/cp-18-1189-2022, https://doi.org/10.5194/cp-18-1189-2022, 2022
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We present a method to reconstruct burnt area using a relationship between pollen and charcoal abundances and the calibration of charcoal abundance using modern observations of burnt area. We use this method to reconstruct changes in burnt area over the past 12 000 years from sites in Iberia. We show that regional changes in burnt area reflect known changes in climate, with a high burnt area during warming intervals and low burnt area when the climate was cooler and/or wetter than today.
Eric Saboya, Giulia Zazzeri, Heather Graven, Alistair J. Manning, and Sylvia Englund Michel
Atmos. Chem. Phys., 22, 3595–3613, https://doi.org/10.5194/acp-22-3595-2022, https://doi.org/10.5194/acp-22-3595-2022, 2022
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Continuous measurements of atmospheric methane concentrations and its carbon-13 isotope have been made in central London since early 2018. These measurements were used to evaluate methane emissions reported in global and UK-specific emission inventories for the London area. Compared to atmospheric methane measurements from March 2018 to October 2020, both inventories are under-reporting natural gas leakage for the London area.
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Short summary
This work examines the roles of cropland representation and the treatment of photosynthetic pathways in the uncertainties of carbon flux simulations in Earth System Models (ESMs). Our results show that reducing these uncertainties will require improvements in the representation of C3 and C4 crops and natural vegetation area coverage, as well as the theories underpinning the simulation of their carbon uptake processes, specifically the implementation of photosynthetic pathways.
This work examines the roles of cropland representation and the treatment of photosynthetic...
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