scholarly journals Recent pause in the growth rate of atmospheric CO2 due to enhanced terrestrial carbon uptake

2016 ◽  
Vol 7 (1) ◽  
Author(s):  
Trevor F Keenan ◽  
I. Colin Prentice ◽  
Josep G Canadell ◽  
Christopher A Williams ◽  
Han Wang ◽  
...  
Keyword(s):  
Growth Rate ◽  
Carbon Sink ◽  
Large Fraction ◽  
Terrestrial Ecosystems ◽  
Anthropogenic Emissions ◽  
Terrestrial Carbon ◽  
Vegetation Models ◽  
Terrestrial Carbon Sink ◽  
Global Vegetation ◽  
Global Carbon

Abstract Terrestrial ecosystems play a significant role in the global carbon cycle and offset a large fraction of anthropogenic CO2 emissions. The terrestrial carbon sink is increasing, yet the mechanisms responsible for its enhancement, and implications for the growth rate of atmospheric CO2, remain unclear. Here using global carbon budget estimates, ground, atmospheric and satellite observations, and multiple global vegetation models, we report a recent pause in the growth rate of atmospheric CO2, and a decline in the fraction of anthropogenic emissions that remain in the atmosphere, despite increasing anthropogenic emissions. We attribute the observed decline to increases in the terrestrial sink during the past decade, associated with the effects of rising atmospheric CO2 on vegetation and the slowdown in the rate of warming on global respiration. The pause in the atmospheric CO2 growth rate provides further evidence of the roles of CO2 fertilization and warming-induced respiration, and highlights the need to protect both existing carbon stocks and regions, where the sink is growing rapidly.

scholarly journals Vegetation distribution and terrestrial carbon cycle in a carbon-cycle configuration of JULES4.6 with new plant functional types

2018 ◽  
Author(s):  
Anna B. Harper ◽  
Andrew J. Wiltshire ◽  
Peter M. Cox ◽  
Pierre Friedlingstein ◽  
Chris D. Jones ◽  
...  
Keyword(s):  
Carbon Cycle ◽  
Soil Carbon ◽  
Boreal Forests ◽  
Carbon Sink ◽  
Vegetation Distribution ◽  
Terrestrial Carbon ◽  
Terrestrial Carbon Cycle ◽  
Vegetation Carbon ◽  
Global Vegetation ◽  
Global Carbon

Abstract. Dynamic global vegetation models (DGVMs) are used for studying historical and future changes to vegetation and the terrestrial carbon cycle. JULES (the Joint UK Land Environment Simulator) represents the land surface in the Hadley Centre climate models and in the UK Earth System Model. Recently the number of plant functional types (PFTs) in JULES were expanded from 5 to 9 to better represent functional diversity in global ecosystems. Here we introduce a more mechanistic representation of vegetation dynamics in TRIFFID, the dynamic vegetation component of JULES, that allows for any number of PFTs to compete based solely on their height, removing the previous hardwired dominance hierarchy where dominant types are assumed to outcompete subdominant types. With the new set of 9 PFTs, JULES is able to more accurately reproduce global vegetation distribution compared to the former 5 PFT version. Improvements include the coverage of trees within tropical and boreal forests, and a reduction in shrubs, which dominated at high latitudes. We show that JULES is able to realistically represent several aspects of the global carbon cycle. The simulated gross primary productivity (GPP) is within the range of observations, but simulated net primary productivity (NPP) is slightly too high. GPP in JULES from 1982–2011 was 133 PgC yr−1, compared to observation-based estimates between 123±8 (over the same time period) and 150–175 PgC yr−1. NPP from 2000–2013 was 72 PgC yr−1, compared to satellite-derived NPP of 55 PgC yr−1 over the same period and independent estimates of 56.2±14.3 PgC yr−1. The simulated carbon stored in vegetation is 542 PgC, compared to an observation-based range of 400–600 PgC. Soil carbon is much lower (1422 PgC) than estimates from measurements (>2400 PgC), with large underestimations of soil carbon in the tropical and boreal forests. We also examined some aspects of the historical terrestrial carbon sink as simulated by JULES. Between the 1900s and 2000s, increased atmospheric carbon dioxide levels enhanced vegetation productivity and litter inputs into the soils, while land-use change removed vegetation and reduced soil carbon. The result was a simulated increase in soil carbon of 57 PgC but a decrease in vegetation carbon by of PgC. JULES simulated a loss of soil and vegetation carbon of 14 and 124 PgC, respectively, due to land-use change from 1900–2009. The simulated land carbon sink was 2.0±1.0 PgC yr−1 from 2000–2009, in close agreement to estimates from the IPCC and Global Carbon Project.

scholarly journals Historical CO<sub>2</sub> emissions from land-use and land-cover change and their uncertainty

2020 ◽  
Author(s):  
Thomas Gasser ◽  
Léa Crepin ◽  
Yann Quilcaille ◽  
Richard A. Houghton ◽  
Philippe Ciais ◽  
...  
Keyword(s):  
Land Use ◽  
Land Cover ◽  
Land Cover Change ◽  
Carbon Sink ◽  
Data Sets ◽  
Tropical Regions ◽  
Dynamic Global Vegetation Models ◽  
Vegetation Models ◽  
Global Vegetation ◽  
Global Carbon

Abstract. Emissions from land-use and land-cover change are a key component of the global carbon cycle. Models are required to disentangle these emissions and the land carbon sink, however, because only the sum of both can be physically observed. Their assessment within the yearly community-wide effort known as the Global Carbon Budget remains a major difficulty, because it combines two lines of evidence that are inherently inconsistent: bookkeeping models and dynamic global vegetation models. Here, we propose a unifying approach relying on a bookkeeping model that embeds processes and parameters calibrated on dynamic global vegetation models, and the use of an empirical constraint. We estimate global CO2 emissions from land-use and land-cover change were 1.36 ± 0.42 Pg C yr−1 (1-σ range) on average over 2009–2018, and 206 ± 57 Pg C cumulated over 1750–2018. We also estimate that land-cover change induced a global loss of additional sink capacity – that is, a foregone carbon removal, not part of the emissions – of 0.68 ± 0.57 Pg C yr−1 and 32 ± 23 Pg C over the same periods, respectively. Additionally, we provide a breakdown of our results' uncertainty following aspects that include the land-use and land-cover change data sets used as input, and the model's biogeochemical parameters. We find the biogeochemical uncertainty dominates our global and regional estimates, with the exception of tropical regions in which the input data dominates. Our analysis further identifies key sources of uncertainty, and suggests ways to strengthen the robustness of future Global Carbon Budgets.

scholarly journals Changes in global terrestrial live biomass over the 21st century

2021 ◽  
Vol 7 (27) ◽  
pp. eabe9829
Author(s):  
Liang Xu ◽  
Sassan S. Saatchi ◽  
Yan Yang ◽  
Yifan Yu ◽  
Julia Pongratz ◽  
...  
Keyword(s):  
Carbon Sink ◽  
Spatially Explicit ◽  
Terrestrial Carbon ◽  
Lateral Transport ◽  
Boreal Ecosystems ◽  
Live Biomass ◽  
Terrestrial Carbon Sink ◽  
The Tropics ◽  
Natural Climate ◽  
Global Carbon

Live woody vegetation is the largest reservoir of biomass carbon, with its restoration considered one of the most effective natural climate solutions. However, terrestrial carbon fluxes remain the largest uncertainty in the global carbon cycle. Here, we develop spatially explicit estimates of carbon stock changes of live woody biomass from 2000 to 2019 using measurements from ground, air, and space. We show that live biomass has removed 4.9 to 5.5 PgC year−1 from the atmosphere, offsetting 4.6 ± 0.1 PgC year−1 of gross emissions from disturbances and adding substantially (0.23 to 0.88 PgC year−1) to the global carbon stocks. Gross emissions and removals in the tropics were four times larger than temperate and boreal ecosystems combined. Although live biomass is responsible for more than 80% of gross terrestrial fluxes, soil, dead organic matter, and lateral transport may play important roles in terrestrial carbon sink.

Emergent constraints on global carbon-climate feedbacks from regional atmospheric aridity

2020 ◽  
Author(s):  
Armineh Barkhordarian ◽  
Kevin W. Bowman ◽  
Noel Cressie ◽  
Jeffrey Jewell ◽  
Johanna Baehr
Keyword(s):  
Carbon Sink ◽  
Earth System ◽  
Climate Feedbacks ◽  
Terrestrial Carbon ◽  
Terrestrial Carbon Sequestration ◽  
Interannual Fluctuations ◽  
Terrestrial Carbon Sink ◽  
Emergent Constraint ◽  
Global Carbon

&lt;p&gt;The vulnerability of terrestrial carbon sequestration to increases in fossil fuel emissions is one of the most important feedbacks in the Earth System.&amp;#160; However, the relative importance of temperature and moisture controls on regional terrestrial CO2 fluxes varies substantially and yet critical to unraveling their roles in carbon-climate feedbacks. Here, we employ the Hierarchical Emergent Constraint (HEC) to quantify an emergent relationship between spatially- explicit sensitivities of carbon fluxes to atmospheric aridity across an ensemble of Earth System Models (ESMs) and the long-term sensitivity of tropical land-carbon storage to atmospheric aridity.&amp;#160; Our results show that interannual fluctuations in atmospheric aridity, as an important driver of atmospheric water demand for plants, substantially impact the terrestrial carbon sink. However, this analysis, which is conditioned on observations, leads to a substantially lower feedback than predicted by ESMs alone. Furthermore, we show that a relatively small number of regions have an out-sized impact on global carbon climate-feedbacks.&amp;#160; These findings underscore the role of both water and temperature on carbon-climate feedbacks while the regional attribution provided by HEC points to areas for further process-based research.&lt;/p&gt;

scholarly journals Historical CO<sub>2</sub> emissions from land use and land cover change and their uncertainty

2020 ◽  
Vol 17 (15) ◽  
pp. 4075-4101 ◽  
Author(s):  
Thomas Gasser ◽  
Léa Crepin ◽  
Yann Quilcaille ◽  
Richard A. Houghton ◽  
Philippe Ciais ◽  
...  
Keyword(s):  
Land Use ◽  
Land Cover ◽  
Land Cover Change ◽  
Carbon Budget ◽  
Carbon Sink ◽  
Global Carbon Budget ◽  
Dynamic Global Vegetation Models ◽  
Vegetation Models ◽  
Global Vegetation ◽  
Global Carbon

Abstract. Emissions from land use and land cover change are a key component of the global carbon cycle. However, models are required to disentangle these emissions from the land carbon sink, as only the sum of both can be physically observed. Their assessment within the yearly community-wide effort known as the “Global Carbon Budget” remains a major difficulty, because it combines two lines of evidence that are inherently inconsistent: bookkeeping models and dynamic global vegetation models. Here, we propose a unifying approach that relies on a bookkeeping model, which embeds processes and parameters calibrated on dynamic global vegetation models, and the use of an empirical constraint. We estimate that the global CO2 emissions from land use and land cover change were 1.36±0.42 PgC yr−1 (1σ range) on average over the 2009–2018 period and reached a cumulative total of 206±57 PgC over the 1750–2018 period. We also estimate that land cover change induced a global loss of additional sink capacity – that is, a foregone carbon removal, not part of the emissions – of 0.68±0.57 PgC yr−1 and 32±23 PgC over the same periods, respectively. Additionally, we provide a breakdown of our results' uncertainty, including aspects such as the land use and land cover change data sets used as input and the model's biogeochemical parameters. We find that the biogeochemical uncertainty dominates our global and regional estimates with the exception of tropical regions in which the input data dominates. Our analysis further identifies key sources of uncertainty and suggests ways to strengthen the robustness of future Global Carbon Budget estimates.

scholarly journals Vegetation distribution and terrestrial carbon cycle in a carbon cycle configuration of JULES4.6 with new plant functional types

2018 ◽  
Vol 11 (7) ◽  
pp. 2857-2873 ◽  
Author(s):  
Anna B. Harper ◽  
Andrew J. Wiltshire ◽  
Peter M. Cox ◽  
Pierre Friedlingstein ◽  
Chris D. Jones ◽  
...  
Keyword(s):  
Carbon Cycle ◽  
Soil Carbon ◽  
Boreal Forests ◽  
Carbon Sink ◽  
Vegetation Distribution ◽  
Terrestrial Carbon ◽  
Terrestrial Carbon Cycle ◽  
Vegetation Carbon ◽  
Global Vegetation ◽  
Global Carbon

Abstract. Dynamic global vegetation models (DGVMs) are used for studying historical and future changes to vegetation and the terrestrial carbon cycle. JULES (the Joint UK Land Environment Simulator) represents the land surface in the Hadley Centre climate models and in the UK Earth System Model. Recently the number of plant functional types (PFTs) in JULES was expanded from five to nine to better represent functional diversity in global ecosystems. Here we introduce a more mechanistic representation of vegetation dynamics in TRIFFID, the dynamic vegetation component of JULES, which allows for any number of PFTs to compete based solely on their height; therefore, the previous hardwired dominance hierarchy is removed. With the new set of nine PFTs, JULES is able to more accurately reproduce global vegetation distribution compared to the former five PFT version. Improvements include the coverage of trees within tropical and boreal forests and a reduction in shrubs, the latter of which dominated at high latitudes. We show that JULES is able to realistically represent several aspects of the global carbon (C) cycle. The simulated gross primary productivity (GPP) is within the range of observations, but simulated net primary productivity (NPP) is slightly too high. GPP in JULES from 1982 to 2011 is 133 Pg C yr−1, compared to observation-based estimates (over the same time period) between 123 ± 8 and 150–175 Pg C yr−1. NPP from 2000 to 2013 is 72 Pg C yr−1, compared to satellite-derived NPP of 55 Pg C yr−1 over the same period and independent estimates of 56.2 ± 14.3 Pg C yr−1. The simulated carbon stored in vegetation is 542 Pg C, compared to an observation-based range of 400–600 Pg C. Soil carbon is much lower (1422 Pg C) than estimates from measurements (> 2400 Pg C), with large underestimations of soil carbon in the tropical and boreal forests. We also examined some aspects of the historical terrestrial carbon sink as simulated by JULES. Between the 1900s and 2000s, increased atmospheric carbon dioxide levels enhanced vegetation productivity and litter inputs into the soils, while land use change removed vegetation and reduced soil carbon. The result is a simulated increase in soil carbon of 57 Pg C but a decrease in vegetation carbon of 98 Pg C. The total simulated loss of soil and vegetation carbon due to land use change is 138 Pg C from 1900 to 2009, compared to a recent observationally constrained estimate of 155 ± 50 Pg C from 1901 to 2012. The simulated land carbon sink is 2.0 ± 1.0 Pg C yr−1 from 2000 to 2009, in close agreement with estimates from the IPCC and Global Carbon Project.

Climate forcing of terrestrial carbon sink during the Middle Jurassic greenhouse climate: Chronostratigraphic analysis of the Yan’an Formation, Ordos Basin, North China

2020 ◽  
Author(s):  
Zhihui Zhang ◽  
Tiantian Wang ◽  
Jahandar Ramezani ◽  
Dawei Lv ◽  
Chengshan Wang
Keyword(s):  
Carbon Cycle ◽  
Middle Jurassic ◽  
Carbon Sink ◽  
Ordos Basin ◽  
Global Carbon Cycle ◽  
Central China ◽  
Terrestrial Carbon ◽  
The Ordos Basin ◽  
Terrestrial Carbon Sink ◽  
Global Carbon

Exploring the relationship between coal deposits as an important terrestrial carbon sink and orbital forcing of climate is critical for understanding the global carbon cycle and climate change. The Jurassic greenhouse period, characterized by extensive coal reserves widely distributed in the mid-latitude terrestrial basins, marks a significant coal-forming interval in Earth’s history. However, understanding of the processes that controlled the formation and distribution of coal at this time is inadequate. The Yan’an Formation of the Ordos Basin in north central China is among the largest and most extensively studied Jurassic coal reservoirs of the world. Here we establish a high-resolution age framework for the Yan’an Formation derived from integrated, high-precision U-Pb zircon geochronology using chemical abrasion-isotope dilution-thermal ionization mass spectrometry (CA-ID-TIMS) on interstratified ash beds and cyclostratigraphy based on centimeter-scale magnetic susceptibility. Accordingly, the main coal-forming interval of the Yan’an Formation spanned ca. 174.0 Ma to &lt;171.7 Ma, which coincided with the onset of the Middle Jurassic. The spectral analyses of the Yan’an Formation coal seams demonstrate a strong correlation to minima in the 405 k.y. orbital eccentricity cycles, suggesting a strong climate control on lake level fluctuations and clastic sediment input. Finally, we explore the cyclicity of a large set of published marine carbon isotope data from western Tethys and its phase relationship to cyclic coal deposition in the Ordos Basin. Our resutls underscore the role of terrestrial organic carbon burial in the global carbon cycle during the Middle Jurassic.

scholarly journals Twentieth-Century Droughts and Their Impacts on Terrestrial Carbon Cycling in China

2009 ◽  
Vol 13 (10) ◽  
pp. 1-31 ◽  
Author(s):  
Jingfeng Xiao ◽  
Qianlai Zhuang ◽  
Eryuan Liang ◽  
Xuemei Shao ◽  
A. David McGuire ◽  
...  
Keyword(s):  
Twentieth Century ◽  
Carbon Cycling ◽  
Carbon Balance ◽  
Carbon Sink ◽  
Ring Width ◽  
Terrestrial Ecosystems ◽  
Terrestrial Carbon ◽  
Terrestrial Ecosystem Model ◽  
Terrestrial Carbon Sink ◽  
Drought Effects

Abstract Midlatitude regions experienced frequent droughts during the twentieth century, but their impacts on terrestrial carbon balance are unclear. This paper presents a century-scale study of drought effects on the carbon balance of terrestrial ecosystems in China. The authors first characterized the severe extended droughts over the period 1901–2002 using the Palmer drought severity index and then examined how these droughts affected the terrestrial carbon dynamics using tree-ring width chronologies and a process-based biogeochemistry model, the Terrestrial Ecosystem Model (TEM). It is found that China suffered from a series of severe extended droughts during the twentieth century. The major drought periods included 1920–30, 1939–47, 1956–58, 1960–63, 1965–68, 1978–80, and 1999–2002. Most droughts generally reduced net primary productivity (NPP) and net ecosystem productivity (NEP) in large parts of drought-affected areas. Moreover, some of the droughts substantially reduced the countrywide annual NPP and NEP. Out of the seven droughts, three (1920–30, 1965–68, and 1978–80) caused the countrywide terrestrial ecosystems to switch from a carbon sink to a source, and one (1960–63) substantially reduced the magnitude of the countrywide terrestrial carbon sink. Strong decreases in NPP were mainly responsible for the anomalies in annual NEP during these drought periods. Changes in heterotrophic respiration happened in the same direction, but mostly with smaller magnitude. The results show that severe extended droughts had significant effects on terrestrial carbon cycling in China, although future studies should consider other important processes such as drought-induced mortality and regrowth, land-use change, disturbances (e.g., fire), human management (e.g., fertilization and irrigation), and environmental pollution (e.g., ozone pollution, nitrogen deposition). These drought effects are of particular importance in light of projected widespread summer drying in midlatitude regions during the twenty-first century. Future droughts could lead to a reduced terrestrial carbon sink or even a source and exert a positive feedback to the global climate system.

scholarly journals The Significance of the Erosion-induced Terrestrial Carbon Sink

BioScience ◽  
2007 ◽  
Vol 57 (4) ◽  
pp. 337-346 ◽  
Author(s):  
Asmeret Asefaw Berhe ◽  
John Harte ◽  
Jennifer W. Harden ◽  
Margaret S. Torn
Keyword(s):  
Carbon Sink ◽  
Terrestrial Carbon ◽  
Terrestrial Carbon Sink
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