scholarly journals An assessment of natural methane fluxes simulated by the CLASS-CTEM model

2018 ◽  
Vol 15 (15) ◽  
pp. 4683-4709 ◽  
Author(s):  
Vivek K. Arora ◽  
Joe R. Melton ◽  
David Plummer
Keyword(s):  
Land Surface ◽  
Methane Concentration ◽  
Middle Atmosphere ◽  
Methane Emissions ◽  
Box Model ◽  
Historical Period ◽  
Atmospheric Methane ◽  
Uncertainty Range ◽  
Natural Emissions ◽  
Methane Sink

Abstract. Natural methane emissions from wetlands and fire, and soil uptake of methane, simulated using the Canadian Land Surface Scheme and Canadian Terrestrial Ecosystem (CLASS-CTEM) modelling framework, over the historical 1850–2008 period, are assessed by using a one-box model of atmospheric methane burden. This one-box model also requires anthropogenic emissions and the methane sink in the atmosphere to simulate the historical evolution of global methane burden. For this purpose, global anthropogenic methane emissions for the period 1850–2008 were reconstructed based on the harmonized representative concentration pathway (RCP) and Emission Database for Global Atmospheric Research (EDGAR) data sets. The methane sink in the atmosphere is represented using bias-corrected methane lifetimes from the Canadian Middle Atmosphere Model (CMAM). The resulting evolution of atmospheric methane concentration over the historical period compares reasonably well with observation-based estimates (correlation  =  0.99, root mean square error  =  35 ppb). The modelled natural emissions are also assessed using an inverse procedure where the methane lifetimes required to reproduce the observed year-to-year increase in atmospheric methane burden are calculated based upon the specified global anthropogenic and modelled natural emissions that we have used here. These calculated methane lifetimes over the historical period fall within the uncertainty range of observation-based estimates. The present-day (2000–2008) values of modelled methane emissions from wetlands (169 Tg CH4 yr−1) and fire (27 Tg CH4 yr−1), methane uptake by soil (29 Tg CH4 yr−1), and the budget terms associated with overall anthropogenic and natural emissions are consistent with estimates reported in a recent global methane budget that is based on top-down approaches constrained by observed atmospheric methane burden. The modelled wetland emissions increase over the historical period in response to both increases in precipitation and in atmospheric CO2 concentration. This increase in wetland emissions over the historical period yields evolution of the atmospheric methane concentration that compares better with observation-based values than the case when wetland emissions are held constant over the historical period.

scholarly journals An assessment of natural methane fluxes simulated by the CLASS-CTEM model

2017 ◽  
Author(s):  
Vivek K. Arora ◽  
Joe R. Melton ◽  
David Plummer
Keyword(s):  
Land Surface ◽  
Methane Concentration ◽  
Middle Atmosphere ◽  
Methane Emissions ◽  
Box Model ◽  
Historical Period ◽  
Atmospheric Methane ◽  
Uncertainty Range ◽  
Natural Emissions ◽  
Methane Sink

Abstract. Natural methane emissions from wetlands and fire, and soil uptake of methane, simulated using the Canadian Land Surface Scheme and Canadian Terrestrial Ecosystem (CLASS-CTEM) modelling framework, over the historical 1850–2008 period, are assessed by using a one box model of atmospheric methane burden. This one box model also requires anthropogenic emissions and the methane sink in the atmosphere to simulate the historical evolution of global methane burden. For this purpose, global anthropogenic methane emissions for the period 1850-2008 were reconstructed based on the harmonized representative concentration pathway (RCP) and Emission Database for Global Atmospheric Research (EDGAR) data sets. The methane sink in the atmosphere is represented using bias-corrected methane lifetimes from the Canadian Middle Atmosphere Model (CMAM). The resulting evolution of atmospheric methane concentration over the historical period compares reasonably well with observation-based estimates. The modelled natural emissions are also assessed using an inverse procedure where the methane lifetimes required to reproduce the observed year-to-year increase in observed atmospheric methane burden are calculated based upon the global anthropogenic and modelled natural emissions that we have used here. These calculated methane lifetimes over the historical period fall within the uncertainty range of observation-based estimates. The present-day (2000–2008) values of modelled methane emissions from wetlands and fire, methane uptake by soil, and the budget terms associated with overall anthropogenic and natural emissions are consistent with estimates reported in a recent global methane budget that is based on top-down approaches constrained by observed atmospheric methane burden. The modelled wetland emissions increase over the historical period in response to both increase in precipitation and increase in atmospheric CO2 concentration. This increase in wetland emissions over the historical period yields evolution of the atmospheric methane concentration that compares better with observation-based values than the case when wetland emissions are held constant over the historical period.

scholarly journals Bipolar carbon and hydrogen isotope constraints of the Holocene methane budget

2018 ◽  
Author(s):  
Jonas Beck ◽  
Michael Bock ◽  
Jochen Schmitt ◽  
Barbara Seth ◽  
Thomas Blunier ◽  
...  
Keyword(s):  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Methane Concentration ◽  
Methane Emissions ◽  
Anthropogenic Influence ◽  
Atmospheric Methane ◽  
The Holocene ◽  
Ch4 Emissions ◽  
Methane Budget ◽  
Natural Emissions

Abstract. Atmospheric methane concentration shows a well-known decrease over the first half of the Holocene following the northern hemisphere summer insolation before it started to increase again to preindustrial values. There is a debate about what caused this change in the methane concentration trend, in particular, whether an early anthropogenic influence or natural emissions led to the reversal of the atmospheric CH4 concentration. Here, we present new methane concentration and stable hydrogen and carbon isotope data measured on ice core samples from both Greenland and Antarctica over the Holocene. With the help of a two-box model and the full suite of CH4 parameters, the new data allow us to quantify the total methane emissions in the northern and southern hemispheres separately as well as their isotopic signatures, while interpretation of isotopic records of only one hemisphere may lead to erroneous conclusions. For the first half of the Holocene our results indicate a decrease in northern and southern hemisphere CH4 emissions by more than 30 Tg CH4/yr in total accompanied by a drop in the northern carbon isotopic source signature of about −3 ‰. This cannot be explained by a change in the source mix alone, but requires shifts in the isotopic signature of the sources themselves caused by changes in the precursor material for the methane production. In the second half of the Holocene global CH4 emissions increased by about 30 Tg CH4/yr, while preindustrial isotopic emission signatures remained more a less constant. However, our results show that the increase of methane emissions starting in the mid-Holocene took place in the southern hemisphere, while northern hemisphere emissions started to increase only about 2000 years ago. Accordingly, natural emissions in the southern tropics appear to be the main cause of the CH4 increase starting 5000 years ago in contradiction to an early anthropogenic influence on the global methane budget by East Asian land use changes.

scholarly journals Seasonal and interannual variability in wetland methane emissions simulated by CLM4Me' and CAM-chem and comparisons to observations of concentrations

2015 ◽  
Vol 12 (13) ◽  
pp. 4029-4049 ◽  
Author(s):  
L. Meng ◽  
R. Paudel ◽  
P. G. M. Hess ◽  
N. M. Mahowald
Keyword(s):  
Interannual Variability ◽  
Spatial Patterns ◽  
Methane Emission ◽  
Methane Concentration ◽  
Methane Emissions ◽  
Data Availability ◽  
Latitudinal Gradients ◽  
Atmospheric Methane ◽  
Seasonal And Interannual Variability ◽  
Methane Concentrations

Abstract. Understanding the temporal and spatial variation of wetland methane emissions is essential to the estimation of the global methane budget. Our goal for this study is three-fold: (i) to evaluate the wetland methane fluxes simulated in two versions of the Community Land Model, the Carbon-Nitrogen (CN; i.e., CLM4.0) and the Biogeochemistry (BGC; i.e., CLM4.5) versions using the methane emission model CLM4Me' so as to determine the sensitivity of the emissions to the underlying carbon model; (ii) to compare the simulated atmospheric methane concentrations to observations, including latitudinal gradients and interannual variability so as to determine the extent to which the atmospheric observations constrain the emissions; (iii) to understand the drivers of seasonal and interannual variability in atmospheric methane concentrations. Simulations of the transport and removal of methane use the Community Atmosphere Model with chemistry (CAM-chem) model in conjunction with CLM4Me' methane emissions from both CN and BGC simulations and other methane emission sources from literature. In each case we compare model-simulated atmospheric methane concentration with observations. In addition, we simulate the atmospheric concentrations based on the TransCom wetland and rice paddy emissions derived from a different terrestrial ecosystem model, Vegetation Integrative Simulator for Trace gases (VISIT). Our analysis indicates CN wetland methane emissions are higher in the tropics and lower at high latitudes than emissions from BGC. In CN, methane emissions decrease from 1993 to 2004 while this trend does not appear in the BGC version. In the CN version, methane emission variations follow satellite-derived inundation wetlands closely. However, they are dissimilar in BGC due to its different carbon cycle. CAM-chem simulations with CLM4Me' methane emissions suggest that both prescribed anthropogenic and predicted wetlands methane emissions contribute substantially to seasonal and interannual variability in atmospheric methane concentration. Simulated atmospheric CH4 concentrations in CAM-chem are highly correlated with observations at most of the 14 measurement stations evaluated with an average correlation between 0.71 and 0.80 depending on the simulation (for the period of 1993–2004 for most stations based on data availability). Our results suggest that different spatial patterns of wetland emissions can have significant impacts on Northern and Southern hemisphere (N–S) atmospheric CH4 concentration gradients and growth rates. This study suggests that both anthropogenic and wetland emissions have significant contributions to seasonal and interannual variations in atmospheric CH4 concentrations. However, our analysis also indicates the existence of large uncertainties in terms of spatial patterns and magnitude of global wetland methane budgets, and that substantial uncertainty comes from the carbon model underlying the methane flux modules.

scholarly journals Country-Scale Analysis of Methane Emissions with a High-Resolution Inverse Model Using GOSAT and Surface Observations

2020 ◽  
Vol 12 (3) ◽  
pp. 375 ◽  
Author(s):  
Rajesh Janardanan ◽  
Shamil Maksyutov ◽  
Aki Tsuruta ◽  
Fenjuan Wang ◽  
Yogesh K. Tiwari ◽  
...  
Keyword(s):  
United States ◽  
High Resolution ◽  
The United States ◽  
Methane Emissions ◽  
Inverse Model ◽  
Anthropogenic Emissions ◽  
Observation Data ◽  
Scale Analysis ◽  
Uncertainty Range ◽  
Natural Emissions

We employed a global high-resolution inverse model to optimize the CH4 emission using Greenhouse gas Observing Satellite (GOSAT) and surface observation data for a period from 2011–2017 for the two main source categories of anthropogenic and natural emissions. We used the Emission Database for Global Atmospheric Research (EDGAR v4.3.2) for anthropogenic methane emission and scaled them by country to match the national inventories reported to the United Nations Framework Convention on Climate Change (UNFCCC). Wetland and soil sink prior fluxes were simulated using the Vegetation Integrative Simulator of Trace gases (VISIT) model. Biomass burning prior fluxes were provided by the Global Fire Assimilation System (GFAS). We estimated a global total anthropogenic and natural methane emissions of 340.9 Tg CH4 yr−1 and 232.5 Tg CH4 yr−1, respectively. Country-scale analysis of the estimated anthropogenic emissions showed that all the top-emitting countries showed differences with their respective inventories to be within the uncertainty range of the inventories, confirming that the posterior anthropogenic emissions did not deviate from nationally reported values. Large countries, such as China, Russia, and the United States, had the mean estimated emission of 45.7 ± 8.6, 31.9 ± 7.8, and 29.8 ± 7.8 Tg CH4 yr−1, respectively. For natural wetland emissions, we estimated large emissions for Brazil (39.8 ± 12.4 Tg CH4 yr−1), the United States (25.9 ± 8.3 Tg CH4 yr−1), Russia (13.2 ± 9.3 Tg CH4 yr−1), India (12.3 ± 6.4 Tg CH4 yr−1), and Canada (12.2 ± 5.1 Tg CH4 yr−1). In both emission categories, the major emitting countries all had the model corrections to emissions within the uncertainty range of inventories. The advantages of the approach used in this study were: (1) use of high-resolution transport, useful for simulations near emission hotspots, (2) prior anthropogenic emissions adjusted to the UNFCCC reports, (3) combining surface and satellite observations, which improves the estimation of both natural and anthropogenic methane emissions over spatial scale of countries.

scholarly journals Bipolar carbon and hydrogen isotope constraints on the Holocene methane budget

2018 ◽  
Vol 15 (23) ◽  
pp. 7155-7175 ◽  
Author(s):  
Jonas Beck ◽  
Michael Bock ◽  
Jochen Schmitt ◽  
Barbara Seth ◽  
Thomas Blunier ◽  
...  
Keyword(s):  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Methane Concentration ◽  
Methane Emissions ◽  
Anthropogenic Influence ◽  
The Holocene ◽  
Ch4 Emissions ◽  
Methane Budget ◽  
Natural Emissions ◽  
Concentration Evolution

Abstract. Atmospheric methane concentration shows a well-known decrease over the first half of the Holocene following the Northern Hemisphere summer insolation before it started to increase again to preindustrial values. There is a debate about what caused this change in the methane concentration evolution, in particular, whether an early anthropogenic influence or natural emissions led to the reversal of the atmospheric CH4 concentration evolution. Here, we present new methane concentration and stable hydrogen and carbon isotope data measured on ice core samples from both Greenland and Antarctica over the Holocene. With the help of a two-box model and the full suite of CH4 parameters, the new data allow us to quantify the total methane emissions in the Northern Hemisphere and Southern Hemisphere separately as well as their stable isotopic signatures, while interpretation of isotopic records of only one hemisphere may lead to erroneous conclusions. For the first half of the Holocene our results indicate an asynchronous decrease in Northern Hemisphere and Southern Hemisphere CH4 emissions by more than 30 Tg CH4 yr−1 in total, accompanied by a drop in the northern carbon isotopic source signature of about −3 ‰. This cannot be explained by a change in the source mix alone but requires shifts in the isotopic signature of the sources themselves caused by changes in the precursor material for the methane production. In the second half of the Holocene, global CH4 emissions increased by about 30 Tg CH4 yr−1, while preindustrial isotopic emission signatures remained more or less constant. However, our results show that this early increase in methane emissions took place in the Southern Hemisphere, while Northern Hemisphere emissions started to increase only about 2000 years ago. Accordingly, natural emissions in the southern tropics appear to be the main cause of the CH4 increase starting 5000 years before present, not supporting an early anthropogenic influence on the global methane budget by East Asian land use changes.

scholarly journals Seasonal and inter-annual variability in wetland methane emissions simulated by CLM4Me' and CAM-chem and comparisons to observations of concentrations

2015 ◽  
Vol 12 (3) ◽  
pp. 2161-2212 ◽  
Author(s):  
L. Meng ◽  
R. Paudel ◽  
P. G. M. Hess ◽  
N. M. Mahowald
Keyword(s):  
Spatial Patterns ◽  
Methane Concentration ◽  
Terrestrial Ecosystem ◽  
Methane Flux ◽  
Rice Paddy ◽  
Methane Emissions ◽  
Atmospheric Methane ◽  
Community Land Model ◽  
Terrestrial Ecosystem Model ◽  
Annual Variability

Abstract. Understanding the temporal and spatial variation of wetland methane emissions is essential to the estimation of the global methane budget. We examine the seasonal and inter-annual variability in wetland methane emissions simulated in the Community Land Model (CLM4Me'). Methane emissions from both the Carbon-Nitrogen (CN, i.e. CLM4.0) and the Biogeochemistry (BGC, i.e. CLM4.5) versions of the CLM are evaluated. We further conduct simulations of the transport and removal of methane using the Community Atmosphere Model (CAM-chem) model using CLM4Me' methane emissions from both CN and BGC along with other methane sources and compare model simulated atmospheric methane concentration with observations. In addition, we simulate the atmospheric concentrations based on the TransCom wetland and rice paddy emissions from a different terrestrial ecosystem model VISIT. Our analysis suggests CN wetland methane emissions are higher in tropics and lower in high latitudes than BGC. In CN, methane emissions decrease from 1993 to 2004 while this trend does not appear in the BGC version. In the CN versions, methane emission variations follow satellite-derived inundation wetlands closely. However, they are dissimilar in BGC due to its different carbon cycle. CAM-chem model simulations with CLM4Me' methane emissions suggest that both prescribed anthropogenic and predicted wetlands methane emissions contribute substantially to seasonal and inter-annual variability in atmospheric methane concentration. It also suggests that different spatial patterns of wetland emissions can have significant impacts on N–S atmospheric CH4 concentration gradients and growth rates. This study suggests that large uncertainties still exist in terms of spatial patterns and magnitude of global wetland methane budgets, and that substantial uncertainty comes from the carbon model underlying the methane flux modules.

Sources of atmospheric methane in Arctic: observations and model simulation

2021 ◽  
Author(s):  
Yury Shtabkin ◽  
Konstantin Moiseenko ◽  
Andrey Skorokhod
Keyword(s):  
Methane Concentration ◽  
Transport Model ◽  
Model Simulation ◽  
Methane Emissions ◽  
Atmospheric Methane ◽  
Chemical Transport Model ◽  
Noticeable Increase ◽  
Regional Sources ◽  
The Impact

<p>The second most important greenhouse gas in atmosphere after carbon dioxide (CO<sub>2</sub>) is methane, CH<sub>4</sub>. The limited data of surface methane observations in Arctic makes it difficult to quantify the impact of methane emissions from major regional anthropogenic and biogenic sources on this region. This gap is partially filled by long-term observations at arctic and subarctic stations. According to these observations, since 2005, there has been a noticeable increase in the surface methane concentration. The reasons of this increase are still not fully understood. This work provides quantitative estimates of possible contribution into surface CH<sub>4</sub> observed long-term variability from the most important regional sources of methane emissions.</p><p>To analyze variations in surface methane concentration was used the data from observations at background monitoring stations, as well as numerical calculations performed by GEOS-Chem chemical-transport model, which is widely used in international community for calculating the fields of chemically active and greenhouse gases.</p>

Country scale analysis of natural and anthropogenic methane emissions with a high-resolution inverse model using GOSAT and ground-based observations

2020 ◽  
Author(s):  
Rajesh Janardanan ◽  
Shamil Maksyutov ◽  
Aki Tsuruta ◽  
Fenjuan Wang ◽  
Yogesh Tiwari ◽  
...  
Keyword(s):  
United States ◽  
High Resolution ◽  
The United States ◽  
Methane Emissions ◽  
Inverse Model ◽  
Anthropogenic Emissions ◽  
Observation Data ◽  
Scale Analysis ◽  
Uncertainty Range ◽  
Natural Emissions

<p>Here, we present the results of a global high-resolution inversion study of methane emissions and their analysis for the large emitting countries. We employ a global high-resolution inverse model to optimize CH<sub>4</sub> emissions using Greenhouse gas Observing Satellite (GOSAT) and surface observation data over the 2011-2017 period for the two main source categories of anthropogenic and natural emissions. As prior emissions, we used the Emission Database for Global Atmospheric Research (EDGAR v4.3.2) for anthropogenic methane emission, scaled by country to match the national emissions reported to the United Nations Framework Convention on Climate Change (UNFCCC). Wetland and soil sink prior fluxes were simulated using Vegetation Integrative Simulator of Trace gases (VISIT) model. Biomass burning prior fluxes were provided by the Global Fire Assimilation System (GFAS). We estimate a global total anthropogenic and natural methane emissions of 340.9 Tg CH<sub>4</sub> yr<sup>-1</sup> and 232.5 Tg CH<sub>4</sub> yr<sup>-1</sup>, respectively. This agrees with recent Global Carbon Project (GCP) estimates of 357 and 215 Tg CH<sub>4</sub> yr<sup>-1</sup>, respectively. Country-scale analysis of the estimated anthropogenic emissions shows that for all the top-emitting countries, differences with their respective nationally reported inventories are within the uncertainty range of the inventories. Large emitting countries such as China, Russia and the United States have mean estimated anthropogenic emission of 45.7±8.6, 31.9±7.8 and 29.8±7.8 Tg CH<sub>4</sub> yr<sup>-1 </sup>respectively. For natural emissions, we estimate large emissions for Brazil (39.8±12.4 Tg CH<sub>4</sub> yr<sup>-1</sup>), the United States (25.9±8.3 Tg CH<sub>4</sub> yr<sup>-1</sup>), Russia (13.2±9.3 Tg CH<sub>4</sub> yr<sup>-1</sup>), India (12.3±6.4 Tg CH<sub>4</sub> yr<sup>-1</sup>), and Canada (12.2±5.1 Tg CH<sub>4</sub> yr<sup>-1</sup>). In both emission categories, natural and anthropogenic, the major emitting countries all had model corrections to their emissions that were within the uncertainty range of the inventories and the inverse model uncertainty. As a special case, we evaluate anthropogenic emissions estimated for India (24.2±5.3 Tg yr<sup>-1</sup>) with aircraft observation data over urban regions over India. On average, the optimized profiles showed a better match with the observations compared to the prior profile confirming improved estimates by the model for India.</p>

Exploring the variation in ecosystem scale methane fluxes and its drivers within a boreal mire complex

2021 ◽  
Author(s):  
Koffi Dodji Noumonvi ◽  
Joshua L. Ratcliffe ◽  
Mats Öquist ◽  
Mats B. Nilsson ◽  
Matthias Peichl
Keyword(s):  
Eddy Covariance ◽  
Land Surface ◽  
Chemical Properties ◽  
Growing Season ◽  
Small Scale ◽  
Atmospheric Methane ◽  
Flux Footprint ◽  
Growing Season Length ◽  
Methane Fluxes ◽  
Northern Peatlands

<p>Northern peatlands cover a small fraction of the earth’s land surface, and yet they are one of the most important natural sources of atmospheric methane. With climate change causing rising temperatures, changes in water balance and increased growing season length, peatland contribution to atmospheric methane concentration is likely to increase, justifying the increased attention given to northern peatland methane dynamics. Northern peatlands often occur as heterogeneous complexes characterized by hydromorphologically distinct features from < 1 m² to tens of km², with differing physical, hydrological and chemical properties. The more commonly understood small-scale variation between hummocks, lawns and hollows has been well explored using chamber measurements. Single tower eddy covariance measurements, with a typical 95% flux footprint of < 0.5 km², have been used to assess the ecosystem scale methane exchange. However, how representative single tower flux measurements are of an entire mire complex is not well understood. To address this knowledge gap, the present study takes advantage of a network of four eddy covariance towers located less than 3 km apart at four mires within a typical boreal mire complex in northern Sweden. The variation of methane fluxes and its drivers between the four sites will be explored at different temporal scales, i.e. half-hourly, daily and at a growing-season scale.</p>

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