Biogeochemical effects of land cover and land management

2020 ◽  
Author(s):  
Suqi Guo ◽  
Julia Pongratz ◽  
Felix Havermann ◽  
Andrea Alessandri ◽  
Dim Coumou ◽  
...  
Keyword(s):  
Land Cover ◽  
Carbon Cycle ◽  
Land Management ◽  
Temporal Dynamics ◽  
Climate Mitigation ◽  
Earth System ◽  
Model Uncertainties ◽  
System Models ◽  
Wood Harvesting ◽  
Earth System Models

<p>Land cover and land management (LCLM) changes are important sources of anthropogenic CO<sub>2</sub> emissions, constituting about 10% of current annual CO2 emissions, or about one third of cumulative emissions over the industrial era. However, simulations with Earth system models (ESMs) show a large range of CO<sub>2</sub> emissions from LCLM. Several reasons for the divergence in estimates have been identified, in particular differences in simulated biomass and soil carbon stocks, and if and which land management practices are included in models. The divergence of model estimates is particularly worrisome since LCLM practices are discussed as key mitigation tools or “negative emission technologies” to reach the temperature goals of Paris Agreement. In the LAMACLIMA project (land management for climate mitigation and adaptation) we therefore conduct a detailed analysis of several LCLM practices across three ESMs to improve our understanding about model uncertainties. The present study aims to quantify the effects of forest cover changes and wood harvesting on the global carbon cycle, globally important LCLM practices with relevance also for physical climate and economic production.</p> <p>We conduct idealized global experiments of deforestation, afforestation and wood harvesting over a 150-year simulation period under present climate. All forcings (solar, trace gases, aerosols) are held constant at present-day levels to isolate the climatic effects from different LCLM scenarios on the carbon cycle. All experiments are conducted by three different Earth system models (MPI-ESM, EC-EARTH and CESM) to quantify inter-model uncertainty and potentially uncover specific model biases. The analysis focuses on the transient response of carbon fluxes after the LCLM practice is in order to unravel model differences concerning temporal dynamics of LCLM effects and to show how quickly signals emerge that could potentially mitigate climate change.</p> <p>With this research, we will provide a deeper understanding about simulated LCLM effects on the carbon cycle and also report model uncertainties. Together with parallel efforts to quantify biogeophysical effects of LCLM, our study will also lead to assess the overall potential of LCLM as a means for land-based climate mitigation.</p>

scholarly journals Analytically tractable climate–carbon cycle feedbacks under 21st century anthropogenic forcing

2018 ◽  
Vol 9 (2) ◽  
pp. 507-523 ◽  
Author(s):  
Steven J. Lade ◽  
Jonathan F. Donges ◽  
Ingo Fetzer ◽  
John M. Anderies ◽  
Christian Beer ◽  
...  
Keyword(s):  
Carbon Cycle ◽  
Global Climate ◽  
Future Climate Change ◽  
Earth System ◽  
Co2 Solubility ◽  
Carbon Cycle Model ◽  
Ocean Climate ◽  
System Models ◽  
Analytical Expressions ◽  
Earth System Models

Abstract. Changes to climate–carbon cycle feedbacks may significantly affect the Earth system's response to greenhouse gas emissions. These feedbacks are usually analysed from numerical output of complex and arguably opaque Earth system models. Here, we construct a stylised global climate–carbon cycle model, test its output against comprehensive Earth system models, and investigate the strengths of its climate–carbon cycle feedbacks analytically. The analytical expressions we obtain aid understanding of carbon cycle feedbacks and the operation of the carbon cycle. Specific results include that different feedback formalisms measure fundamentally the same climate–carbon cycle processes; temperature dependence of the solubility pump, biological pump, and CO2 solubility all contribute approximately equally to the ocean climate–carbon feedback; and concentration–carbon feedbacks may be more sensitive to future climate change than climate–carbon feedbacks. Simple models such as that developed here also provide workbenches for simple but mechanistically based explorations of Earth system processes, such as interactions and feedbacks between the planetary boundaries, that are currently too uncertain to be included in comprehensive Earth system models.

scholarly journals Plant functional type mapping for earth system models

2011 ◽  
Vol 4 (3) ◽  
pp. 2081-2121 ◽  
Author(s):  
B. Poulter ◽  
P. Ciais ◽  
E. Hodson ◽  
H. Lischke ◽  
F. Maignan ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Land Cover ◽  
Climate Variability ◽  
Forest Cover ◽  
Plant Functional Type ◽  
Earth System ◽  
Functional Type ◽  
System Models ◽  
Satellite Sensors ◽  
Earth System Models

Abstract. The sensitivity of global carbon and water cycling to climate variability is coupled directly to land cover and the distribution of vegetation. To investigate biogeochemistry-climate interactions, earth system models require a representation of vegetation distributions that are either prescribed from remote sensing data or simulated via biogeography models. However, the abstraction of earth system state variables in models means that data products derived from remote sensing need to be post-processed for model-data assimilation. Dynamic global vegetation models (DGVM) rely on the concept of plant functional types (PFT) to group shared traits of thousands of plant species into just several classes. Available databases of observed PFT distributions must be relevant to existing satellite sensors and their derived products, and to the present day distribution of managed lands. Here, we develop four PFT datasets based on land-cover information from three satellite sensors (EOS-MODIS 1 km and 0.5 km, SPOT4-VEGETATION 1 km, and ENVISAT-MERIS 0.3 km spatial resolution) that are merged with spatially-consistent Köppen-Geiger climate zones. Using a beta (β) diversity metric to assess reclassification similarity, we find that the greatest uncertainty in PFT classifications occur most frequently between cropland and grassland categories, and in dryland systems between shrubland, grassland and forest categories because of differences in the minimum threshold required for forest cover. The biogeography-biogeochemistry DGVM, LPJmL, is used in diagnostic mode with the four PFT datasets prescribed to quantify the effect of land-cover uncertainty on climatic sensitivity of gross primary productivity (GPP) and transpiration fluxes. Our results show that land-cover uncertainty has large effects in arid regions, contributing up to 30 % (20 %) uncertainty in the sensitivity of GPP (transpiration) to precipitation. The availability of plant functional type datasets that are consistent with current satellite products and adapted for earth system models is an important component for reducing the uncertainty of terrestrial biogeochemistry to climate variability.

The Transient Response of the Carbon-Cycle-Climate Continuum to CO2 Emissions is Pathway Dependent 

2021 ◽  
Author(s):  
Alexander J. Winkler ◽  
Ranga B. Myneni ◽  
Markus Reichstein ◽  
Victor Brovkin
Keyword(s):  
Carbon Cycle ◽  
Emission Rate ◽  
Transient Temperature ◽  
Emission Rates ◽  
Earth System ◽  
Max Planck ◽  
System Models ◽  
The Impact ◽  
Fully Coupled ◽  
Earth System Models

<div> <div> <div> <p>The prevailing understanding of the carbon-cycle response to anthropogenic CO<sub>2 </sub>emissions suggests that it depends only on the magnitude of this forcing, not on its timing. However, a recent study (Winkler <em>et al</em>., <em>Earth System Dynamics</em>, 2019) demonstrated that the same magnitude of CO<sub>2 </sub>forcing causes considerably different responses in various Earth system models when realized following different temporal trajectories. Because the modeling community focuses on concentration-driven runs that do not represent a fully-coupled carbon-cycle-climate continuum, and the experimental setups are mainly limited to exponential forcing timelines, the effect of different temporal trajectories of CO<sub>2 </sub>emissions in the system is under-explored. Together, this could lead to an incomplete notion of the carbon-cycle response to anthropogenic CO<sub>2 </sub>emissions.</p> <p>We use the latest CMIP6 version of the Max-Planck-Institute Earth System Model (MPI-ESM1.2) with a fully-coupled carbon cycle to investigate the effect of emission timing in form of four drastically different pathways. All pathways emit an identical total of 1200 Pg C over 200 years, which is about the IPCC estimate to stay below 2 °K of warming, and the approximate amount needed to double the atmospheric CO<sub>2 </sub>concentration. The four pathways differ only in their CO<sub>2 </sub>emission rates, which include a constant, a negative parabolic (ramp-up/ramp-down), a linearly decreasing, and an exponentially increasing emission trajectory. These experiments are idealized, but designed not to exceed the observed maximum emission rates, and thus can be placed in the context of the observed system.</p> <p>We find that the resulting atmospheric CO<sub>2 </sub>concentration, after all the carbon has been emitted, can vary as much as 100 ppm between the different pathways. The simulations show that for pathways, where the system is exposed to higher rates of CO<sub>2 </sub>emissions early in the forcing timeline, there is considerably less excess CO<sub>2 </sub>in the atmosphere at the end. These pathways also show an airborne fraction approaching zero in the final decades of the simulation. At this point, the carbon sinks have reached a strength that removes more carbon from the atmosphere than is emitted. In contrast, the exponentially increasing pathway with high CO<sub>2 </sub>emission rates in the last decades of the simulation, the pathway usually studied, shows a fairly stable airborne fraction. We propose a new general framework to estimate the atmospheric growth rate of CO<sub>2 </sub>not only as a function of the emission rate, but also include the aspect of time the system has been exposed to excess CO<sub>2 </sub>in the atmosphere. As a result, the transient temperature response is a function not only of the cumulative CO<sub>2 </sub>emissions, but also of the time the system was exposed to the excess CO<sub>2</sub>. We also apply this framework to other Earth system models and observational records of CO<sub>2 </sub>concentration and emissions.</p> </div> </div> </div><div> <div> <div> <p>The Earth system is currently in a phase of increasing, nearly exponential CO<sub>2 </sub>forcing. The impact of excess CO<sub>2 </sub>exposure time could become apparent as we approach the point of maximum CO<sub>2 </sub>emission rate, affecting the achievability of the climate targets.</p> </div> </div> </div>

scholarly journals Use of various remote sensing land cover products for PFT mapping over Siberia

2013 ◽  
Vol 6 (1) ◽  
pp. 255-296
Author(s):  
C. Ottlé ◽  
J. Lescure ◽  
F. Maignan ◽  
B. Poulter ◽  
T. Wang ◽  
...  
Keyword(s):  
High Resolution ◽  
Land Cover ◽  
Land Surface ◽  
Land Cover Classification ◽  
Classification Systems ◽  
Tree Cover ◽  
Surface Model ◽  
Earth System ◽  
System Models ◽  
Earth System Models

Abstract. High-latitude ecosystems play an important role in the global carbon cycle and in regulating the climate system and are presently undergoing rapid environmental change. Accurate land cover datasets are required to both document these changes as well as to provide land-surface information for benchmarking and initializing earth system models. Earth system models also require specific land cover classification systems based on plant functional types, rather than species or ecosystems, and so post-processing of existing land cover data is often required. This study compares over Siberia, multiple land cover datasets against one another and with auxiliary data to identify key uncertainties that contribute to variability in Plant Functional Type (PFT) classifications that would introduce errors in earth system modeling. Land cover classification systems from GLC 2000, GlobCover 2005 and 2009, and MODIS collections 5 and 5.1 are first aggregated to a common legend, and then compared to high-resolution land cover classification systems, continuous vegetation fields (MODIS-VCF) and satellite-derived tree heights (to discriminate against sparse, shrub, and forest vegetation). The GlobCover dataset, with a lower threshold for tree cover and taller tree heights and a better spatial resolution, tends to have better distributions of tree cover compared to high-resolution data. It has therefore been chosen to build new PFTs maps for the ORCHIDEE land surface model at 1 km scale. Compared to the original PFT dataset, the new PFT maps based on GlobCover 2005 and an updated cross-walking approach mainly differ in the characterization of forests and degree of tree cover. The partition of grasslands and bare soils now appears more realistic compared with ground-truth data. This new vegetation map provides a framework for further development of new PFTs in the ORCHIDEE model like shrubs, lichens and mosses, to better represent the water and carbon cycles in northern latitudes. Updated land cover datasets are critical for improving and maintaining the relevance of earth system models for assessing climate and human impacts on biogeochemistry and biophysics. The new PFT map at 5 km scale is available for download from the PANGAEA website, at: doi:10.1594/PANGAEA.810709.

Compatible Fossil Fuel CO2 emissions in the CMIP6 Earth System Models’ Historical and Shared Socioeconomic Pathway experiments of the 21st Century

2020 ◽  
pp. 1-72
Author(s):  
Spencer K. Liddicoat ◽  
Andy J. Wiltshire ◽  
Chris D. Jones ◽  
Vivek K. Arora ◽  
Victor Brovkin ◽  
...  
Keyword(s):  
Carbon Cycle ◽  
Fossil Fuel ◽  
Coupled Model ◽  
Historical Record ◽  
Emission Rates ◽  
Earth System ◽  
Uncertainty Range ◽  
System Models ◽  
Earth System Models ◽  
Fossil Fuel Emissions

AbstractWe present the compatible CO2 emissions from fossil fuel burning and industry, calculated from the historical and Shared Socioeconomic Pathway (SSP) experiments of nine Earth System Models (ESMs) participating in the sixth phase of the Coupled Model Intercomparison Project (CMIP6). The multi-model mean FF emissions match the historical record well and are close to the data-based estimate of cumulative emissions (392±63 GtC vs 400±20 GtC respectively). Only two models fall inside the observed uncertainty range; while two exceed the upper bound, five fall slightly below the lower bound, due primarily to the plateau in CO2 concentration in the 1940s. The ESMs’ diagnosed FF emission rates are consistent with those generated by the Integrated Assessment Models (IAMs) from which the SSPs’ CO2 concentration pathways were constructed; the simpler IAMs’ emissions lie within the ESMs’ spread for seven of the eight SSP experiments, the other being only marginally lower, providing confidence in the relationship between the IAMs’ FF emission rates and concentration pathways. The ESMs require fossil fuel emissions to reduce to zero and subsequently become negative in SSP1-1.9, SSP1-2.6, SSP4-3.4 and SSP5-3.4over. We also present the ocean and land carbon cycle responses of the ESMs in the historical and SSP scenarios. The models’ ocean carbon cycle responses are in close agreement, but there is considerable spread in their land carbon cycle responses. Land use and land cover change emissions have a strong influence over the magnitude of diagnosed fossil fuel emissions, with the suggestion of an inverse relationship between the two.

scholarly journals Models meet data: Challenges and opportunities in implementing land management in Earth system models

2017 ◽  
Vol 24 (4) ◽  
pp. 1470-1487 ◽  
Author(s):  
Julia Pongratz ◽  
Han Dolman ◽  
Axel Don ◽  
Karl-Heinz Erb ◽  
Richard Fuchs ◽  
...  
Keyword(s):  
Land Management ◽  
Earth System ◽  
System Models ◽  
Challenges And Opportunities ◽  
Meet Data ◽  
Earth System Models

scholarly journals Evaluation of biospheric components in Earth system models using modern and palaeo observations: the state-of-the-art

2013 ◽  
Vol 10 (7) ◽  
pp. 10937-10995 ◽  
Author(s):  
A. M. Foley ◽  
D. Dalmonech ◽  
A. D. Friend ◽  
F. Aires ◽  
A. Archibald ◽  
...  
Keyword(s):  
Carbon Cycle ◽  
Model Evaluation ◽  
State Of The Art ◽  
The State ◽  
System Level ◽  
Earth System ◽  
Evaluation Methodologies ◽  
System Models ◽  
Wide Range ◽  
Earth System Models

Abstract. Earth system models are increasing in complexity and incorporating more processes than their predecessors, making them important tools for studying the global carbon cycle. However, their coupled behaviour has only recently been examined in any detail, and has yielded a very wide range of outcomes, with coupled climate-carbon cycle models that represent land-use change simulating total land carbon stores by 2100 that vary by as much as 600 Pg C given the same emissions scenario. This large uncertainty is associated with differences in how key processes are simulated in different models, and illustrates the necessity of determining which models are most realistic using rigorous model evaluation methodologies. Here we assess the state-of-the-art with respect to evaluation of Earth system models, with a particular emphasis on the simulation of the carbon cycle and associated biospheric processes. We examine some of the new advances and remaining uncertainties relating to (i) modern and palaeo data and (ii) metrics for evaluation, and discuss a range of strategies, such as the inclusion of pre-calibration, combined process- and system-level evaluation, and the use of emergent constraints, that can contribute towards the development of more robust evaluation schemes. An increasingly data-rich environment offers more opportunities for model evaluation, but it is also a challenge, as more knowledge about data uncertainties is required in order to determine robust evaluation methodologies that move the field of ESM evaluation from "beauty contest" toward the development of useful constraints on model behaviour.

scholarly journals Terrestrial Carbon Cycle: Climate Relations in Eight CMIP5 Earth System Models

2013 ◽  
Vol 26 (22) ◽  
pp. 8744-8764 ◽  
Author(s):  
Pu Shao ◽  
Xubin Zeng ◽  
Koichi Sakaguchi ◽  
Russell K. Monson ◽  
Xiaodong Zeng
Keyword(s):  
Soil Moisture ◽  
Carbon Cycle ◽  
Carbon Fluxes ◽  
Net Ecosystem Production ◽  
First Century ◽  
Earth System ◽  
System Models ◽  
Ecosystem Production ◽  
Twenty First Century ◽  
Earth System Models

Abstract Eight Earth System Models from phase 5 of the Coupled Model Intercomparison Project (CMIP5) are evaluated, focusing on both the net carbon dioxide flux and its components and their relation with climatic variables (temperature, precipitation, and soil moisture) in the historical (1850–2005) and representative concentration pathway 4.5 (RCP4.5; 2006–2100) simulations. While model results differ, their median globally averaged production and respiration terms from 1976 to 2005 agree reasonably with available observation-based products. Disturbances such as land use change are roughly represented but crucial in determining whether the land is a carbon source or sink over many regions in both simulations. While carbon fluxes vary with latitude and between the two simulations, the ratio of net to gross primary production, representing the ecosystem carbon use efficiency, is less dependent on latitude and does not differ significantly in the historical and RCP4.5 simulations. The linear trend of increased land carbon fluxes (except net ecosystem production) is accelerated in the twenty-first century. The cumulative net ecosystem production by 2100 is positive (i.e., carbon sink) in all models and the tropical and boreal latitudes become major carbon sinks in most models. The temporal correlations between annual-mean carbon cycle and climate variables vary substantially (including the change of sign) among the eight models in both the historical and twenty-first-century simulations. The ranges of correlations of carbon cycle variables with precipitation and soil moisture are also quite different, reflecting the important impact of the model treatment of the hydrological cycle on the carbon cycle.

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