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Pierre Friedlingstein - One of the best experts on this subject based on the ideXlab platform.
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Interannual variation of terrestrial Carbon Cycle: Issues and perspectives.
Global Change Biology, 2019Co-Authors: Shilong Piao, Pierre Friedlingstein, Philippe Ciais, Xuhui Wang, Kai Wang, Xiangyi Li, Ana Bastos, Josep G. Canadell, Stephen SitchAbstract:With accumulation of Carbon Cycle observations and model developments over the past decades, exploring interannual variation (IAV) of terrestrial Carbon Cycle offers the opportunity to better understand climate-Carbon Cycle relationships. However, despite growing research interest, uncertainties remain on some fundamental issues, such as the contributions of different regions, constituent fluxes and climatic factors to Carbon Cycle IAV. Here we overviewed the literature on Carbon Cycle IAV about current understanding of these issues. Observations and models of the Carbon Cycle unanimously show the dominance of tropical land ecosystems to the signal of global Carbon Cycle IAV, where tropical semiarid ecosystems contribute as much as the combination of all other tropical ecosystems. Vegetation photosynthesis contributes more than ecosystem respiration to IAV of the global net land Carbon flux, but large uncertainties remain on the contribution of fires and other disturbance fluxes. Climatic variations are the major drivers to the IAV of net land Carbon flux. Although debate remains on whether the dominant driver is temperature or moisture variability, their interaction,that is, the dependence of Carbon Cycle sensitivity to temperature on moisture conditions, is emerging as key regulators of the Carbon Cycle IAV. On timescales from the interannual to the centennial, global Carbon Cycle variability will be increasingly contributed by northern land ecosystems and oceans. Therefore, both improving Earth system models (ESMs) with the progressive understanding on the fast processes manifested at interannual timescale and expanding Carbon Cycle observations at broader spatial and longer temporal scales are critical to better prediction on evolution of the Carbon-climate system.
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Climate Change and Carbon Cycle Feedbacks
Oxford Research Encyclopedia of Climate Science, 2016Co-Authors: Pierre FriedlingsteinAbstract:Climate and Carbon Cycle are tightly coupled on many time scales, from the interannual to the multimillennial. Observation always shows a positive feedback between climate and the Carbon Cycle: elevated atmospheric CO2 leads to warming, but warming is expected to further release of Carbon to the atmosphere, enhancing the atmospheric CO2 increase. Earth system models do represent these climate–Carbon Cycle feedbacks, always simulating a positive feedback over the 21st century; that is, climate change will lead to loss of Carbon from the land and ocean reservoirs. These processes partially offset the increases in land and ocean Carbon sinks caused by rising atmospheric CO2. As a result, more of the emitted anthropogenic CO2 will remain in the atmosphere. There is, however, a large uncertainty on the magnitude of this feedback. Recent studies now help to reduce this uncertainty. On short, interannual, time scales, El Niño years record larger-than-average atmospheric CO2 growth rate, with tropical land ecosystems being the main drivers. These climate–Carbon Cycle anomalies can be used as emerging constraint on the tropical land Carbon response to future climate change. On a longer, centennial, time scale, the variability of atmospheric CO2 found in records of the last millennium can be used to constrain the overall global Carbon Cycle response to climate. These independent methods confirm that the climate–Carbon Cycle feedback is positive, but probably more consistent with the lower end of the comprehensive models range, excluding very large climate–Carbon Cycle feedbacks.
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Uncertainties in CMIP5 climate projections due to Carbon Cycle feedbacks
Journal of Climate, 2014Co-Authors: Pierre Friedlingstein, Malte Meinshausen, Vivek K. Arora, Alessandro Anav, Spencer K. Liddicoat, Chris D Jones, Reto KnuttiAbstract:In the context of phase 5 of the Coupled Model Intercomparison Project, most climate simulations use prescribed atmospheric CO2 concentration and therefore do not interactively include the effect of Carbon Cycle feedbacks. However, the representative concentration pathway 8.5 (RCP8.5) scenario has additionally been run by earth system models with prescribed CO2 emissions. This paper analyzes the climate projections of 11 earth system models (ESMs) that performed both emission-driven and concentration-driven RCP8.5 simulations.When forced by RCP8.5 CO2 emissions, models simulate a large spread in atmospheric CO2; the simulated 2100 concentrations range between 795 and 1145 ppm. Seven out of the 11 ESMs simulate a larger CO2 (on average by 44 ppm, 985 6 97ppm by 2100) and hence higher radiative forcing (by 0.25Wm22) when driven by CO2 emissions than for the concentration-driven scenarios (941 ppm). However, most of these models already overestimate the present-day CO2, with the present-day biases reasonably well correlated with future atmospheric concentrations’ departure from the prescribed concentration. The uncertainty in CO2 projections is mainly attributable to uncertainties in the response of the land Carbon Cycle. As a result of simulated higher CO2 concentrations than in the concentration-driven simulations, temperature projections are generally higher when ESMs are driven with CO2 emissions. Global surface temperature change by 2100 (relative to present day) increased by 3.98 6 0.98C for the emission-driven simulations compared to 3.78 6 0.78C in the concentration-driven simulations. Although the lower ends are comparable in both sets of simulations, the highest climate projections are significantly warmer in the emission-driven simulations because of stronger Carbon Cycle feedbacks
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evaluating the land and ocean components of the global Carbon Cycle in the cmip5 earth system models
Journal of Climate, 2013Co-Authors: Alessandro Anav, Laurent Bopp, Pierre Friedlingstein, Chris D Jones, Philippe Ciais, M Kidston, Martin Jung, Ranga B MyneniAbstract:AbstractThe authors assess the ability of 18 Earth system models to simulate the land and ocean Carbon Cycle for the present climate. These models will be used in the next Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report (AR5) for climate projections, and such evaluation allows identification of the strengths and weaknesses of individual coupled Carbon–climate models as well as identification of systematic biases of the models. Results show that models correctly reproduce the main climatic variables controlling the spatial and temporal characteristics of the Carbon Cycle. The seasonal evolution of the variables under examination is well captured. However, weaknesses appear when reproducing specific fields: in particular, considering the land Carbon Cycle, a general overestimation of photosynthesis and leaf area index is found for most of the models, while the ocean evaluation shows that quite a few models underestimate the primary production.The authors also propose climate and car...
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Quantifying Carbon Cycle feedbacks.
Journal of Climate, 2009Co-Authors: Jonathan M. Gregory, P. Cadule, Chris D Jones, Pierre FriedlingsteinAbstract:Abstract Perturbations to the Carbon Cycle could constitute large feedbacks on future changes in atmospheric CO2 concentration and climate. This paper demonstrates how Carbon Cycle feedback can be expressed in formally similar ways to climate feedback, and thus compares their magnitudes. The Carbon Cycle gives rise to two climate feedback terms: the concentration–Carbon feedback, resulting from the uptake of Carbon by land and ocean as a biogeochemical response to the atmospheric CO2 concentration, and the climate–Carbon feedback, resulting from the effect of climate change on Carbon fluxes. In the earth system models of the Coupled Climate–Carbon Cycle Model Intercomparison Project (C4MIP), climate–Carbon feedback on warming is positive and of a similar size to the cloud feedback. The concentration–Carbon feedback is negative; it has generally received less attention in the literature, but in magnitude it is 4 times larger than the climate–Carbon feedback and more uncertain. The concentration–Carbon feed...
Chris D Jones - One of the best experts on this subject based on the ideXlab platform.
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Uncertainties in CMIP5 climate projections due to Carbon Cycle feedbacks
Journal of Climate, 2014Co-Authors: Pierre Friedlingstein, Malte Meinshausen, Vivek K. Arora, Alessandro Anav, Spencer K. Liddicoat, Chris D Jones, Reto KnuttiAbstract:In the context of phase 5 of the Coupled Model Intercomparison Project, most climate simulations use prescribed atmospheric CO2 concentration and therefore do not interactively include the effect of Carbon Cycle feedbacks. However, the representative concentration pathway 8.5 (RCP8.5) scenario has additionally been run by earth system models with prescribed CO2 emissions. This paper analyzes the climate projections of 11 earth system models (ESMs) that performed both emission-driven and concentration-driven RCP8.5 simulations.When forced by RCP8.5 CO2 emissions, models simulate a large spread in atmospheric CO2; the simulated 2100 concentrations range between 795 and 1145 ppm. Seven out of the 11 ESMs simulate a larger CO2 (on average by 44 ppm, 985 6 97ppm by 2100) and hence higher radiative forcing (by 0.25Wm22) when driven by CO2 emissions than for the concentration-driven scenarios (941 ppm). However, most of these models already overestimate the present-day CO2, with the present-day biases reasonably well correlated with future atmospheric concentrations’ departure from the prescribed concentration. The uncertainty in CO2 projections is mainly attributable to uncertainties in the response of the land Carbon Cycle. As a result of simulated higher CO2 concentrations than in the concentration-driven simulations, temperature projections are generally higher when ESMs are driven with CO2 emissions. Global surface temperature change by 2100 (relative to present day) increased by 3.98 6 0.98C for the emission-driven simulations compared to 3.78 6 0.78C in the concentration-driven simulations. Although the lower ends are comparable in both sets of simulations, the highest climate projections are significantly warmer in the emission-driven simulations because of stronger Carbon Cycle feedbacks
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evaluating the land and ocean components of the global Carbon Cycle in the cmip5 earth system models
Journal of Climate, 2013Co-Authors: Alessandro Anav, Laurent Bopp, Pierre Friedlingstein, Chris D Jones, Philippe Ciais, M Kidston, Martin Jung, Ranga B MyneniAbstract:AbstractThe authors assess the ability of 18 Earth system models to simulate the land and ocean Carbon Cycle for the present climate. These models will be used in the next Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report (AR5) for climate projections, and such evaluation allows identification of the strengths and weaknesses of individual coupled Carbon–climate models as well as identification of systematic biases of the models. Results show that models correctly reproduce the main climatic variables controlling the spatial and temporal characteristics of the Carbon Cycle. The seasonal evolution of the variables under examination is well captured. However, weaknesses appear when reproducing specific fields: in particular, considering the land Carbon Cycle, a general overestimation of photosynthesis and leaf area index is found for most of the models, while the ocean evaluation shows that quite a few models underestimate the primary production.The authors also propose climate and car...
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high sensitivity of future global warming to land Carbon Cycle processes
Environmental Research Letters, 2012Co-Authors: Ben B B Booth, Chris D Jones, Stephen Sitch, Mat Collins, I Totterdell, Chris Huntingford, Richard Betts, Glen R Harris, Jon LloydAbstract:Unknowns in future global warming are usually assumed to arise from uncertainties either in the amount of anthropogenic greenhouse gas emissions or in the sensitivity of the climate to changes in greenhouse gas concentrations. Characterizing the additional uncertainty in relating CO2 emissions to atmospheric concentrations has relied on either a small number of complex models with diversity in process representations, or simple models. To date, these models indicate that the relevant Carbon Cycle uncertainties are smaller than the uncertainties in physical climate feedbacks and emissions. Here, for a single emissions scenario, we use a full coupled climate–Carbon Cycle model and a systematic method to explore uncertainties in the land Carbon Cycle feedback. We find a plausible range of climate–Carbon Cycle feedbacks significantly larger than previously estimated. Indeed the range of CO2 concentrations arising from our single emissions scenario is greater than that previously estimated across the full range of IPCC SRES emissions scenarios with Carbon Cycle uncertainties ignored. The sensitivity of photosynthetic metabolism to temperature emerges as the most important uncertainty. This highlights an aspect of current land Carbon modelling where there are open questions about the potential role of plant acclimation to increasing temperatures. There is an urgent need for better understanding of plant photosynthetic responses to high temperature, as these responses are shown here to be key contributors to the magnitude of future change.
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Quantifying Carbon Cycle feedbacks.
Journal of Climate, 2009Co-Authors: Jonathan M. Gregory, P. Cadule, Chris D Jones, Pierre FriedlingsteinAbstract:Abstract Perturbations to the Carbon Cycle could constitute large feedbacks on future changes in atmospheric CO2 concentration and climate. This paper demonstrates how Carbon Cycle feedback can be expressed in formally similar ways to climate feedback, and thus compares their magnitudes. The Carbon Cycle gives rise to two climate feedback terms: the concentration–Carbon feedback, resulting from the uptake of Carbon by land and ocean as a biogeochemical response to the atmospheric CO2 concentration, and the climate–Carbon feedback, resulting from the effect of climate change on Carbon fluxes. In the earth system models of the Coupled Climate–Carbon Cycle Model Intercomparison Project (C4MIP), climate–Carbon feedback on warming is positive and of a similar size to the cloud feedback. The concentration–Carbon feedback is negative; it has generally received less attention in the literature, but in magnitude it is 4 times larger than the climate–Carbon feedback and more uncertain. The concentration–Carbon feed...
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amazonian forest dieback under climate Carbon Cycle projections for the 21st century
Theoretical and Applied Climatology, 2004Co-Authors: Richard Betts, Chris Huntingford, Matthew D. Collins, Phil P Harris, Chris D JonesAbstract:The first GCM climate change projections to include dynamic vegetation and an interactive Carbon Cycle produced a very significant amplification of global warming over the 21st century. Under the IS92a “business as usual” emissions scenario CO2 concentrations reached about 980 ppmv by 2100, which is about 280 ppmv higher than when these feedbacks were ignored. The major contribution to the increased CO2 arose from reductions in soil Carbon because global warming is assumed to accelerate respiration. However, there was also a lesser contribution from an alarming loss of the Amazonian rainforest. This paper describes the phenomenon of Amazonian forest dieback under elevated CO2 in the Hadley Centre climate-Carbon Cycle model.
I. Fung - One of the best experts on this subject based on the ideXlab platform.
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climate Carbon Cycle feedback analysis results from the c4mip model intercomparison
Journal of Climate, 2006Co-Authors: Pierre Friedlingstein, S Doney, W. Von Bloh, Peter M. Cox, P. Cadule, Michael Eby, Laurent Bopp, Victor Brovkin, Richard Betts, I. FungAbstract:Eleven coupled climate–Carbon Cycle models used a common protocol to study the coupling between climate change and the Carbon Cycle. The models were forced by historical emissions and the Intergovernmental Panel on Climate Change (IPCC) Special Report on Emissions Scenarios (SRES) A2 anthropogenic emissions of CO2 for the 1850–2100 time period. For each model, two simulations were performed in order to isolate the impact of climate change on the land and ocean Carbon Cycle, and therefore the climate feedback on the atmospheric CO2 concentration growth rate. There was unanimous agreement among the models that future climate change will reduce the efficiency of the earth system to absorb the anthropogenic Carbon perturbation. A larger fraction of anthropogenic CO2 will stay airborne if climate change is accounted for. By the end of the twenty-first century, this additional CO2 varied between 20 and 200 ppm for the two extreme models, the majority of the models lying between 50 and 100 ppm. The higher CO2 levels led to an additional climate warming ranging between 0.1° and 1.5°C. All models simulated a negative sensitivity for both the land and the ocean Carbon Cycle to future climate. However, there was still a large uncertainty on the magnitude of these sensitivities. Eight models attributed most of the changes to the land, while three attributed it to the ocean. Also, a majority of the models located the reduction of land Carbon uptake in the Tropics. However, the attribution of the land sensitivity to changes in net primary productivity versus changes in respiration is still subject to debate; no consensus emerged among the models.
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Climate–Carbon Cycle Feedback Analysis: Results from the C 4 MIP Model Intercomparison
Journal of Climate, 2006Co-Authors: Pierre Friedlingstein, S Doney, P. Cox, W. Von Bloh, P. Cadule, Michael Eby, Laurent Bopp, R. Betts, Victor Brovkin, I. FungAbstract:Abstract Eleven coupled climate–Carbon Cycle models used a common protocol to study the coupling between climate change and the Carbon Cycle. The models were forced by historical emissions and the Intergovernmental Panel on Climate Change (IPCC) Special Report on Emissions Scenarios (SRES) A2 anthropogenic emissions of CO2 for the 1850–2100 time period. For each model, two simulations were performed in order to isolate the impact of climate change on the land and ocean Carbon Cycle, and therefore the climate feedback on the atmospheric CO2 concentration growth rate. There was unanimous agreement among the models that future climate change will reduce the efficiency of the earth system to absorb the anthropogenic Carbon perturbation. A larger fraction of anthropogenic CO2 will stay airborne if climate change is accounted for. By the end of the twenty-first century, this additional CO2 varied between 20 and 200 ppm for the two extreme models, the majority of the models lying between 50 and 100 ppm. The high...
Victor Brovkin - One of the best experts on this subject based on the ideXlab platform.
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climate and Carbon Cycle variability over the last millennium
Climate of The Past, 2010Co-Authors: Johann H Jungclaus, Victor Brovkin, Stephan J Lorenz, Claudia Timmreck, Christian H Reick, Joachim Segschneider, Marco A Giorgetta, Thomas J Crowley, Julia Pongratz, N A KrivovaAbstract:Abstract. A long-standing task in climate research has been to distinguish between anthropogenic climate change and natural climate variability. A prerequisite for fulfilling this task is the understanding of the relative roles of external drivers and internal variability of climate and the Carbon Cycle. Here, we present the first ensemble simulations over the last 1200 years with a comprehensive Earth system model including a fully interactive Carbon Cycle. Applying up-to-date reconstructions of external forcing including the recent low-amplitude estimates of solar variations, the ensemble simulations reproduce temperature evolutions consistent with the range of reconstructions. The 20th-century warming trend stands out against all pre-industrial trends within the ensemble. Volcanic eruptions are necessary to explain variations in pre-industrial climate such as the Little Ice Age; yet only the strongest, repeated eruptions lead to cooling trends that differ significantly from the internal variability across all ensemble members. The simulated atmospheric CO2 concentrations exhibit a stable Carbon Cycle over the pre-industrial era with multi-centennial variations somewhat smaller than in the observational records. Early land-cover changes have modulated atmospheric CO2 concentrations only slightly. We provide a model-based quantification of the sensitivity (termed γ) of the global Carbon Cycle to temperature for a variety of climate and forcing conditions. We diagnose a distinct dependence of γ on the forcing strength and time-scales involved, thus providing a possible explanation for the systematic difference in the observational estimates for different segments of the last millennium.
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long term climate commitments projected with climate Carbon Cycle models
Journal of Climate, 2008Co-Authors: Giankasper Plattner, Victor Brovkin, Reto Knutti, Thomas F Stocker, Fortunat Joos, W Von Bloh, D R Cameron, E Driesschaert, Stephanie Dutkiewicz, N R EdwardsAbstract:Eight earth system models of intermediate complexity (EMICs) are used to project climate change commitments for the recent Intergovernmental Panel on Climate Change’s (IPCC’s) Fourth Assessment Report (AR4). Simulations are run until the year 3000 A.D. and extend substantially farther into the future than conceptually similar simulations with atmosphere–ocean general circulation models (AOGCMs) coupled to Carbon Cycle models. In this paper the following are investigated: 1) the climate change commitment in response to stabilized greenhouse gases and stabilized total radiative forcing, 2) the climate change commitment in response to earlier CO2 emissions, and 3) emission trajectories for profiles leading to the stabilization of atmospheric CO2 and their uncertainties due to Carbon Cycle processes. Results over the twenty-first century compare reasonably well with results from AOGCMs, and the suite of EMICs proves well suited to complement more complex models. Substantial climate change commitments for sea level rise and global mean surface temperature increase after a stabilization of atmospheric greenhouse gases and radiative forcing in the year 2100 are identified. The additional warming by the year 3000 is 0.6–1.6 K for the low-CO2 IPCC Special Report on Emissions Scenarios (SRES) B1 scenario and 1.3–2.2 K for the high-CO2 SRES A2 scenario. Correspondingly, the post-2100 thermal expansion commitment is 0.3–1.1 m for SRES B1 and 0.5–2.2 m for SRES A2. Sea level continues to rise due to thermal expansion for several centuries after CO2 stabilization. In contrast, surface temperature changes slow down after a century. The meridional overturning circulation is weakened in all EMICs, but recovers to nearly initial values in all but one of the models after centuries for the scenarios considered. Emissions during the twenty-first century continue to impact atmospheric CO2 and climate even at year 3000. All models find that most of the anthropogenic Carbon emissions are eventually taken up by the ocean (49%–62%) in year 3000, and that a substantial fraction (15%–28%) is still airborne even 900 yr after Carbon emissions have ceased. Future stabilization of atmospheric CO2 and climate change requires a substantial reduction of CO2 emissions below present levels in all EMICs. This reduction needs to be substantially larger if Carbon Cycle–climate feedbacks are accounted for or if terrestrial CO2 fertilization is not operating. Large differences among EMICs are identified in both the response to increasing atmospheric CO2 and the response to climate change. This highlights the need for improved representations of Carbon Cycle processes in these models apart from the sensitivity to climate change. Sensitivity simulations with one single EMIC indicate that both Carbon Cycle and climate sensitivity related uncertainties on projected allowable emissions are substantial.
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climate Carbon Cycle feedback analysis results from the c4mip model intercomparison
Journal of Climate, 2006Co-Authors: Pierre Friedlingstein, S Doney, W. Von Bloh, Peter M. Cox, P. Cadule, Michael Eby, Laurent Bopp, Victor Brovkin, Richard Betts, I. FungAbstract:Eleven coupled climate–Carbon Cycle models used a common protocol to study the coupling between climate change and the Carbon Cycle. The models were forced by historical emissions and the Intergovernmental Panel on Climate Change (IPCC) Special Report on Emissions Scenarios (SRES) A2 anthropogenic emissions of CO2 for the 1850–2100 time period. For each model, two simulations were performed in order to isolate the impact of climate change on the land and ocean Carbon Cycle, and therefore the climate feedback on the atmospheric CO2 concentration growth rate. There was unanimous agreement among the models that future climate change will reduce the efficiency of the earth system to absorb the anthropogenic Carbon perturbation. A larger fraction of anthropogenic CO2 will stay airborne if climate change is accounted for. By the end of the twenty-first century, this additional CO2 varied between 20 and 200 ppm for the two extreme models, the majority of the models lying between 50 and 100 ppm. The higher CO2 levels led to an additional climate warming ranging between 0.1° and 1.5°C. All models simulated a negative sensitivity for both the land and the ocean Carbon Cycle to future climate. However, there was still a large uncertainty on the magnitude of these sensitivities. Eight models attributed most of the changes to the land, while three attributed it to the ocean. Also, a majority of the models located the reduction of land Carbon uptake in the Tropics. However, the attribution of the land sensitivity to changes in net primary productivity versus changes in respiration is still subject to debate; no consensus emerged among the models.
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Climate–Carbon Cycle Feedback Analysis: Results from the C 4 MIP Model Intercomparison
Journal of Climate, 2006Co-Authors: Pierre Friedlingstein, S Doney, P. Cox, W. Von Bloh, P. Cadule, Michael Eby, Laurent Bopp, R. Betts, Victor Brovkin, I. FungAbstract:Abstract Eleven coupled climate–Carbon Cycle models used a common protocol to study the coupling between climate change and the Carbon Cycle. The models were forced by historical emissions and the Intergovernmental Panel on Climate Change (IPCC) Special Report on Emissions Scenarios (SRES) A2 anthropogenic emissions of CO2 for the 1850–2100 time period. For each model, two simulations were performed in order to isolate the impact of climate change on the land and ocean Carbon Cycle, and therefore the climate feedback on the atmospheric CO2 concentration growth rate. There was unanimous agreement among the models that future climate change will reduce the efficiency of the earth system to absorb the anthropogenic Carbon perturbation. A larger fraction of anthropogenic CO2 will stay airborne if climate change is accounted for. By the end of the twenty-first century, this additional CO2 varied between 20 and 200 ppm for the two extreme models, the majority of the models lying between 50 and 100 ppm. The high...
Laurent Bopp - One of the best experts on this subject based on the ideXlab platform.
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Including an ocean Carbon Cycle model into iLOVECLIM (v1.0)
Geoscientific Model Development, 2015Co-Authors: N. Bouttes, Didier M. Roche, V. Mariotti, Laurent BoppAbstract:Abstract. The atmospheric Carbon dioxide concentration plays a crucial role in the radiative balance and as such has a strong influence on the evolution of climate. Because of the numerous interactions between climate and the Carbon Cycle, it is necessary to include a model of the Carbon Cycle within a climate model to understand and simulate past and future changes of the Carbon Cycle. In particular, natural variations of atmospheric CO2 have happened in the past, while anthropogenic Carbon emissions are likely to continue in the future. To study changes of the Carbon Cycle and climate on timescales of a few hundred to a few thousand years, we have included a simple Carbon Cycle model into the iLOVECLIM Earth System Model. In this study, we describe the ocean and terrestrial biosphere Carbon Cycle models and their performance relative to observational data. We focus on the main Carbon Cycle variables including the Carbon isotope ratios δ13C and the Δ14C. We show that the model results are in good agreement with modern observations both at the surface and in the deep ocean for the main variables, in particular phosphates, dissolved inorganic Carbon and the Carbon isotopes.
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evaluating the land and ocean components of the global Carbon Cycle in the cmip5 earth system models
Journal of Climate, 2013Co-Authors: Alessandro Anav, Laurent Bopp, Pierre Friedlingstein, Chris D Jones, Philippe Ciais, M Kidston, Martin Jung, Ranga B MyneniAbstract:AbstractThe authors assess the ability of 18 Earth system models to simulate the land and ocean Carbon Cycle for the present climate. These models will be used in the next Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report (AR5) for climate projections, and such evaluation allows identification of the strengths and weaknesses of individual coupled Carbon–climate models as well as identification of systematic biases of the models. Results show that models correctly reproduce the main climatic variables controlling the spatial and temporal characteristics of the Carbon Cycle. The seasonal evolution of the variables under examination is well captured. However, weaknesses appear when reproducing specific fields: in particular, considering the land Carbon Cycle, a general overestimation of photosynthesis and leaf area index is found for most of the models, while the ocean evaluation shows that quite a few models underestimate the primary production.The authors also propose climate and car...
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variability of the ocean Carbon Cycle in response to the north atlantic oscillation
Tellus B, 2012Co-Authors: Kathrin M Keller, Laurent Bopp, Fortunat Joos, Christoph C Raible, Valentina Cocco, Thomas L Frolicher, John P Dunne, Marion Gehlen, Jerry Tjiputra, Christoph HeinzeAbstract:Climate modes such as the North Atlantic Oscillation (NAO), representing internal variability of the climate system, influence the ocean Carbon Cycle and may mask trends in the sink of anthropogenic Carbon. Here, utilising control runs of six fully coupled Earth System Models, the response of the ocean Carbon Cycle to the NAO is quantified. The dominating response, a seesaw pattern between the subtropical gyre and the subpolar Northern Atlantic, is instantaneous (<3 months) and dynamically consistent over all models and with observations for a range of physical and biogeochemical variables. All models show asymmetric responses to NAO + and NAO − forcing, implying non-linearity in the connection between NAO and the ocean Carbon Cycle. However, model differences in regional expression and magnitude and conflicting results with regard to air–sea flux and CO 2 partial pressure remain. Typical NAO-driven variations are ±10 mmol/m 3 in the surface concentration of dissolved inorganic Carbon and alkalinity and ±8 ppm in the air–sea partial pressure difference. The effect on the basin-wide air–sea CO 2 flux is small due to compensating fluxes on the sub-basin scale. Two models show a reduced Carbon sink in the north-eastern North Atlantic during negative NAO phases, qualitatively in accordance with the observed decline during a phase of predominantly negative NAO. The results indicate that wind-driven dynamics are the main driver of the response to the NAO, which – via vertical mixing, upwelling and the associated entrainment of dissolved inorganic Carbon and nutrients – leave an imprint on surface pCO 2 and the air–sea CO 2 flux as well as on biological export production, pH and the calcium Carbonate saturation state. The biogeochemical response to the NAO is predominantly governed by vertical exchange between the surface and the thermocline; large-scale horizontal transport mechanisms are of minor importance. Keywords: North Atlantic Oscillation, Carbon Cycle, ocean biogeochemistry, climate modeling, ocean-atmosphere interaction (Published: 11 December 2012) Citation: Tellus B 2012, 64 , 18738, http://dx.doi.org/10.3402/tellusb.v64i0.18738
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climate Carbon Cycle feedback analysis results from the c4mip model intercomparison
Journal of Climate, 2006Co-Authors: Pierre Friedlingstein, S Doney, W. Von Bloh, Peter M. Cox, P. Cadule, Michael Eby, Laurent Bopp, Victor Brovkin, Richard Betts, I. FungAbstract:Eleven coupled climate–Carbon Cycle models used a common protocol to study the coupling between climate change and the Carbon Cycle. The models were forced by historical emissions and the Intergovernmental Panel on Climate Change (IPCC) Special Report on Emissions Scenarios (SRES) A2 anthropogenic emissions of CO2 for the 1850–2100 time period. For each model, two simulations were performed in order to isolate the impact of climate change on the land and ocean Carbon Cycle, and therefore the climate feedback on the atmospheric CO2 concentration growth rate. There was unanimous agreement among the models that future climate change will reduce the efficiency of the earth system to absorb the anthropogenic Carbon perturbation. A larger fraction of anthropogenic CO2 will stay airborne if climate change is accounted for. By the end of the twenty-first century, this additional CO2 varied between 20 and 200 ppm for the two extreme models, the majority of the models lying between 50 and 100 ppm. The higher CO2 levels led to an additional climate warming ranging between 0.1° and 1.5°C. All models simulated a negative sensitivity for both the land and the ocean Carbon Cycle to future climate. However, there was still a large uncertainty on the magnitude of these sensitivities. Eight models attributed most of the changes to the land, while three attributed it to the ocean. Also, a majority of the models located the reduction of land Carbon uptake in the Tropics. However, the attribution of the land sensitivity to changes in net primary productivity versus changes in respiration is still subject to debate; no consensus emerged among the models.
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Climate–Carbon Cycle Feedback Analysis: Results from the C 4 MIP Model Intercomparison
Journal of Climate, 2006Co-Authors: Pierre Friedlingstein, S Doney, P. Cox, W. Von Bloh, P. Cadule, Michael Eby, Laurent Bopp, R. Betts, Victor Brovkin, I. FungAbstract:Abstract Eleven coupled climate–Carbon Cycle models used a common protocol to study the coupling between climate change and the Carbon Cycle. The models were forced by historical emissions and the Intergovernmental Panel on Climate Change (IPCC) Special Report on Emissions Scenarios (SRES) A2 anthropogenic emissions of CO2 for the 1850–2100 time period. For each model, two simulations were performed in order to isolate the impact of climate change on the land and ocean Carbon Cycle, and therefore the climate feedback on the atmospheric CO2 concentration growth rate. There was unanimous agreement among the models that future climate change will reduce the efficiency of the earth system to absorb the anthropogenic Carbon perturbation. A larger fraction of anthropogenic CO2 will stay airborne if climate change is accounted for. By the end of the twenty-first century, this additional CO2 varied between 20 and 200 ppm for the two extreme models, the majority of the models lying between 50 and 100 ppm. The high...