Review of "Field-warmed soil carbon changes imply high 21st century modeled uncertainty"

2018 ◽  
Author(s):  
Anonymous
Keyword(s):  
Soil Carbon ◽  
21St Century

ARGUMENTS AND FACTS AGAINST THE INITIATIVE «SOIL CARBON 4 PER MILLE»

2020 ◽  
Author(s):  
Boris Kogut ◽  
Keyword(s):  
Carbon Sequestration ◽  
Soil Carbon ◽  
21St Century ◽  
Critical Analysis ◽  
Soil Layer

A critical analysis of the 4‰-initiative ideas is given. Data on the actual sizes of carbon sequestration in the upper soil layer are presented. The “Soil carbon 4 per mille” initiative is too politicized and commercialized. It does not withstand any scientific criticism and cannot be implemented in the 21st century.

scholarly journals Field-warmed soil carbon changes imply high 21st century modeled uncertainty

2018 ◽  
Author(s):  
Katherine Todd-Brown ◽  
Bin Zheng ◽  
Thomas Crowther
Keyword(s):  
Organic Carbon ◽  
Soil Carbon ◽  
21St Century ◽  
Temperature Sensitivity ◽  
Carbon Stock ◽  
Earth System Model ◽  
System Model ◽  
Earth System ◽  
Soil Carbon Stock ◽  
Q10 Values

Abstract. The feedback between planetary warming and soil carbon loss has been the focus of considerable scientific attention in recent decades, due to its potential to accelerate anthropogenic climate change. The soil carbon temperature sensitivity is traditionally estimated from short-term respiration measurements – either from laboratory incubations that are artificially manipulated, or field measurements that cannot distinguish between plant and microbial respiration. To address these limitations of previous approaches, we developed a new method to estimate temperature sensitivity (Q10) of soil carbon directly from warming-induced changes in soil carbon stocks measured in 36 field experiments across the world. Variations in warming magnitude and control organic carbon percentage explained much of field-warmed organic carbon percentage (R2 = 0.96), revealing Q10 across sites of 2.2, [1.6, 2.7] 95 % Confidence Interval (CI). When these field-derived Q10 values were extrapolated over the 21st century using a post-hoc correction of 20 CMIP5 Earth system model outputs, the multi-model mean soil carbon stock changes shifted from the previous value of 83 ± 156 Pg-carbon (weighted mean ± 1 SD), to 16 ± 156 Pg-carbon with a Q10 driven 95 % CI of 245 ± 194 to −99 ± 208 Pg-carbon. On average, incorporating the field-derived Q10 values into Earth system model simulations led to reductions in the projected amount of carbon sequestered in the soil over the 21st century. However, the considerable parameter uncertainty led to extremely high variability in soil carbon stock projections within each model; intra-model uncertainty driven by the measured Q10 was as great as that between model variation. This study demonstrates that data integration may not improve model certainty, but instead should strive to capture the variation of the system as well as mean trends.

scholarly journals Field-warmed soil carbon changes imply high 21st-century modeling uncertainty

2018 ◽  
Vol 15 (12) ◽  
pp. 3659-3671 ◽  
Author(s):  
Katherine Todd-Brown ◽  
Bin Zheng ◽  
Thomas W. Crowther
Keyword(s):  
Organic Carbon ◽  
Soil Carbon ◽  
21St Century ◽  
Temperature Sensitivity ◽  
Carbon Stock ◽  
Earth System Model ◽  
System Model ◽  
Earth System ◽  
Soil Carbon Stock ◽  
Q10 Values

Abstract. The feedback between planetary warming and soil carbon loss has been the focus of considerable scientific attention in recent decades, due to its potential to accelerate anthropogenic climate change. The soil carbon temperature sensitivity is traditionally estimated from short-term respiration measurements – either from laboratory incubations that are artificially manipulated or from field measurements that cannot distinguish between plant and microbial respiration. To address these limitations of previous approaches, we developed a new method to estimate soil temperature sensitivity (Q10) of soil carbon directly from warming-induced changes in soil carbon stocks measured in 36 field experiments across the world. Variations in warming magnitude and control organic carbon percentage explained much of field-warmed organic carbon percentage (R2 = 0.96), revealing Q10 across sites of 2.2 [1.6, 2.7] 95 % confidence interval (CI). When these field-derived Q10 values were extrapolated over the 21st century using a post hoc correction of 20 Coupled Model Intercomparison Project Phase 5 (CMIP5) Earth system model outputs, the multi-model mean soil carbon stock changes shifted from the previous value of 88 ± 153 Pg carbon (weighted mean ± 1 SD) to 19 ± 155 Pg carbon with a Q10-driven 95 % CI of 248 ± 191 to −95 ± 209 Pg carbon. On average, incorporating the field-derived Q10 values into Earth system model simulations led to reductions in the projected amount of carbon sequestered in the soil over the 21st century. However, the considerable parameter uncertainty led to extremely high variability in soil carbon stock projections within each model; intra-model uncertainty driven by the field-derived Q10 was as great as that between model variation. This study demonstrates that data integration should capture the variation of the system, as well as mean trends.

scholarly journals Microbial decomposition processes and vulnerable arctic soil organic carbon in the 21st century

2018 ◽  
Vol 15 (18) ◽  
pp. 5621-5634 ◽  
Author(s):  
Junrong Zha ◽  
Qianlai Zhuang
Keyword(s):  
Soil Carbon ◽  
20Th Century ◽  
21St Century ◽  
Carbon Budget ◽  
Carbon Sink ◽  
The Arctic ◽  
Microbial Decomposition ◽  
New Model ◽  
Terrestrial Ecosystem Model ◽  
Rcp 8.5

Abstract. Various levels of representations of biogeochemical processes in current biogeochemistry models contribute to a large uncertainty in carbon budget quantification. Here, we present an uncertainty analysis with a process-based biogeochemistry model, the Terrestrial Ecosystem Model (TEM), into which detailed microbial mechanisms were incorporated. Ensemble regional simulations with the new model (MIC-TEM) estimated that the carbon budget of the arctic ecosystems is 76.0±114.8 Pg C during the 20th century, i.e., -3.1±61.7 Pg C under the RCP 2.6 scenario and 94.7±46 Pg C under the RCP 8.5 scenario during the 21st century. Positive values indicate the regional carbon sink while negative values are a source to the atmosphere. Compared to the estimates using a simpler soil decomposition algorithm in TEM, the new model estimated that the arctic terrestrial ecosystems stored 12 Pg less carbon over the 20th century, i.e., 19 and 30 Pg C less under the RCP 8.5 and RCP 2.6 scenarios, respectively, during the 21st century. When soil carbon within depths of 30, 100, and 300 cm was considered as initial carbon in the 21st century simulations, the region was estimated to accumulate 65.4, 88.6, and 109.8 Pg C, respectively, under the RCP 8.5 scenario. In contrast, under the RCP 2.6 scenario, the region lost 0.7, 2.2, and 3 Pg C, respectively, to the atmosphere. We conclude that the future regional carbon budget evaluation largely depends on whether or not adequate microbial activities are represented in earth system models and on the sizes of soil carbon considered in model simulations.

scholarly journals Microbial decomposition processes and vulnerable Arctic soil organic carbon in the 21st century

2018 ◽  
Author(s):  
Junrong Zha ◽  
Qianlai Zhuang
Keyword(s):  
Soil Carbon ◽  
20Th Century ◽  
21St Century ◽  
Carbon Budget ◽  
Terrestrial Ecosystem ◽  
Terrestrial Ecosystems ◽  
The Arctic ◽  
Microbial Decomposition ◽  
Terrestrial Ecosystem Model ◽  
Rcp 8.5

Abstract. Inadequate representation of biogeochemical processes in current biogeochemistry models results in a large uncertainty in carbon budget quantification. Here, detailed microbial mechanisms were incorporated into a process-based biogeochemistry model, the Terrestrial Ecosystem Model (TEM). Ensemble regional simulations with the model estimated the Arctic ecosystem carbon budget is 76.0 ± 114.8 Pg C during the 20th century, −3.1 ± 61.7 Pg C under the RCP 2.6 scenario and a sink of 94.7 ± 46 Pg C under the RCP 8.5 scenario during the 21st century. Compared to the estimates using a simpler soil decomposition algorithm in TEM, the new model estimated that the Arctic terrestrial ecosystems stored 12 Pg less carbon over the 20th century, 19 Pg C and 30 Pg C less under the RCP 8.5 and RCP 2.6 scenarios, respectively, during the 21st century. When soil carbon within depths 30 cm, 100 cm and 300 cm was considered as initial carbon in the 21st century simulations, the region was estimated to accumulate 65.4, 88.6, and 109.8 Pg C, respectively, under the RCP 8.5 scenario. In contrast, under the RCP 2.6 scenario, the region lost 0.7, 2.2, and 3 Pg C, respectively, to the atmosphere. We conclude that the future regional carbon budget evaluation largely depends on whether or not the adequate microbial activities are represented in earth system models and the sizes of soil carbon considered in model simulations.

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