Papers on carbon cycle feedback

This is a list of papers on carbon cycle feedback. Note that the list is not only observational papers, there are modelling papers also. The list is not complete, and will most likely be updated in the future in order to make it more thorough and more representative.

Quantifying Carbon Cycle Feedbacks – Gregory et al. (2009) “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.”

A revised estimate of the processes contributing to global warming due to climate-carbon feedback – Cadule et al. (2009) “We show here that, because of the specific spatial and temporal distribution of the radiative forcing exerted by those external perturbations, the temperature gains are all different. Based on our revised method, we found that, for the SRES A2 scenario, the projected global warming in 2100, due to increases in atmospheric CO₂, non-CO₂ GHGs and anthropogenic sulphate aerosols, is 2.3–5.6°C. This is accidentally nearly equal to the original one of Meehl et al. (2007) (2.4–5.6°C).”

What determines the magnitude of carbon cycle-climate feedbacks? – Matthews et al. (2007) “In this study, we use a coupled climate-carbon model to investigate how the response of vegetation photosynthesis to climate change contributes to the overall strength of carbon cycle-climate feedbacks. We find that the feedback strength is particularly sensitive to the model representation of the photosynthesis-temperature response, with lesser sensitivity to the parameterization of soil moisture and nitrogen availability. In all simulations, large feedbacks are associated with a climatic suppression of terrestrial primary productivity and consequent reduction of terrestrial carbon uptake.” [Link to PDF]

Terrestrial Carbon–Cycle Feedback to Climate Warming – Luo (2007) A review article. “Nonetheless, experimental results are so variable that we have not generated the necessary insights on ecosystem responses to effectively improve global models. To constrain model projections of carbon-climate feedbacks, we need more empirical data from whole-ecosystem warming experiments across a wide range of biomes, particularly in tropic regions, and closer interactions between models and experiments.” [Link to PDF]

Climate–Carbon Cycle Feedback Analysis: Results from the C⁴MIP Model Intercomparison – Friedlingstein et al. (2006) “Eleven coupled climate–carbon cycle models used a common protocol to study the coupling between climate change and the carbon cycle. … 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.” [Link to PDF]

Positive feedback between global warming and atmospheric CO₂ concentration inferred from past climate change – Scheffer et al. (2006) “Here we present an alternative way of estimating the magnitude of the feedback effect based on reconstructed past changes. Linking this information with the mid-range Intergovernmental Panel on Climate Change estimation of the greenhouse gas effect on temperature we suggest that the feedback of global temperature on atmospheric CO₂ will promote warming by an extra 15–78% on a century-scale.” [Link to PDF]

Primary productivity control of simulated carbon cycle–climate feedbacks – Matthews et al. (2005) “In this study, we demonstrate that the response of vegetation primary productivity to climate changes is a critical controlling factor in determining the strength of simulated carbon cycle-climate feedbacks. This conclusion sheds new light on coupled climate-carbon cycle model results, and highlights the need for improved model representation of photosynthesis processes so as to better constrain future projections of climate change.”

How strong is carbon cycle-climate feedback under global warming? – Zeng et al. (2004) Thesis paper on modelling carbon cycle feedback. “The behavior of the coupled carbon cycle and physical climate system in a global warming scenario is studied using an Earth system model including the atmosphere, land, ocean, and the carbon cycle embedded in these components. … Results indicate a positive feedback to global warming from the interactive carbon cycle, with an additional increase of 90 ppmv in the atmospheric CO₂, and 0.6 degree additional warming, thus confirming recent results from the Hadley Centre and IPSL.” [Link to PDF]

Quantifying the effects of CO₂-fertilized vegetation on future global climate and carbon dynamics – Thompson et al. (2004) “In particular, the response of the land biosphere to the ongoing increase in atmospheric CO₂ is not well understood. To evaluate the approximate upper and lower limits of land carbon uptake, we perform simulations using a comprehensive climate-carbon model. … In a second case, CO₂ fertilization saturates in year 2000; here the land becomes an additional source of CO₂ by 2050. The predicted atmospheric CO₂ concentration at year 2100 differs by 40% between the two cases. We show that current uncertainties preclude determination of whether the land biosphere will amplify or damp atmospheric CO₂ increases by the end of the century.” [Link to PDF]

How positive is the feedback between climate change and the carbon cycle? – Friedlingstein et al. (2003) “Here we perform a detailed feedback analysis to show that such differences are due to two key processes that are still poorly constrained in these coupled models: first Southern Ocean circulation, which primarily controls the geochemical uptake of CO₂, and second vegetation and soil carbon response to global warming. Our analytical analysis reproduces remarkably the results obtained by the fully coupled models. Also it allows us to identify that, amongst the two processes mentioned above, the latter (the land response to global warming) is the one that essentially explains the differences between the IPSL and the Hadley results.” [Link to PDF]

Strong carbon cycle feedbacks in a climate model with interactive CO₂ and sulphate aerosols – Jones et al. (2003) “A climate change experiment is presented which uses a General Circulation Model (GCM) in which both interactive carbon and sulphur cycles have been included for the first time, along with the natural climate forcings due to solar changes and volcanic aerosol. … The additional forcings act to delay by more than a decade the conversion of the land carbon sink to a source, but ultimately result in a more abrupt rate of CO₂ increase with the land carbon source (which reaches 7 GtC yr^-1 by 2100) exceeding the ocean carbon sink (which saturates at 5 GtC yr^-1 by 2100) beyond about 2080.”

On the magnitude of positive feedback between future climate change and the carbon cycle – Dufresne et al. (2002) “We use an ocean-atmosphere general circulation model coupled to land and ocean carbon models to simulate the evolution of climate and atmospheric CO₂ from 1860 to 2100. … By 2100, we estimate that atmospheric CO₂ will be 18% higher due to the climate change impact on the carbon cycle. Such a positive feedback has also been found by Cox et al. [2000] . However, the amplitude of our feedback is three times smaller than the one they simulated. We show that the partitioning between carbon stored in the living biomass or in the soil, and their respective sensitivity to increased CO₂ and climate change largely explain this discrepancy.” [Link to PDF]

Positive feedback between future climate change and the carbon cycle – Friedlingstein et al. (2001) “Here, using climate and carbon three‐dimensional models forced by a 1% per year increase in atmospheric CO₂, we show that there is a positive feedback between the climate system and the carbon cycle. Climate change reduces land and ocean uptake of CO₂, respectively by 54% and 35% at 4 × CO₂. This negative impact implies that for prescribed anthropogenic CO₂ emissions, the atmospheric CO₂ would be higher than the level reached if climate change does not affect the carbon cycle. We estimate the gain of this climate‐carbon cycle feedback to be 10% at 2 × CO₂ and 20% at 4 × CO₂. This translates into a 15% higher mean temperature increase.”

Acceleration of global warming due to carbon-cycle feedbacks in a coupled climate model – Cox et al. (2000) “Here we present results from a fully coupled, three-dimensional carbon–climate model, indicating that carbon-cycle feedbacks could significantly accelerate climate change over the twenty-first century. We find that under a ‘business as usual’ scenario, the terrestrial biosphere acts as an overall carbon sink until about 2050, but turns into a source thereafter. By 2100, the ocean uptake rate of 5 Gt C yr^-1 is balanced by the terrestrial carbon source, and atmospheric CO₂ concentrations are 250 p.p.m.v. higher in our fully coupled simulation than in uncoupled carbon models, resulting in a global-mean warming of 5.5 K, as compared to 4 K without the carbon-cycle feedback.” [Link to PDF]

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