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In Asia, much effort is put into reducing methane (CH4) emissions due to the region’s contribution to the recent rapid global atmospheric CH4 concentration growth. Accurate quantification of Asia’s CH4 budgets is critical for conducting global stocktake and achieving the long-term temperature goal of the Paris Agreement. In this study, we present top-down estimates of CH4 emissions from 2009 to 2018 deduced from atmospheric observations from surface network and GOSAT satellite with the high-resolution global inverse model NIES-TM-FLEXPART-VAR. The optimized average CH4 budgets are 63.40 ± 10.52 Tg y−1 from East Asia (EA), 45.20 ± 6.22 Tg y−1 from Southeast Asia (SEA), and 64.35 ± 9.28 Tg y−1 from South Asia (SA) within the 10 years. We analyzed two 5 years CH4 emission budgets for three subregions and 13 top-emitting countries with an emission budget larger than 1 Tg y−1, and interannual variabilities for these subregions. Statistically significant increasing trends in emissions are found in EA with a lower emission growth rate during 2014–2018 compared to that during 2009–2013, while trends in SEA are not significant. In contrast to the prior emission, the posterior emission shows a significant decreasing trend in SA. The flux decrease is associated with the transition from strong La Ninña (2010–2011) to strong El Ninño (2015–2016) events, which modulate the surface air temperature and rainfall patterns. The interannual variability in CH4 flux anomalies was larger in SA compared to EA and SEA. The Southern Oscillation Index correlates strongly with interannual CH4 flux anomalies for SA. Our findings suggest that the interannual variability in the total CH4 flux is dominated by climate variability in SA. The contribution of climate variability driving interannual variability in natural and anthropogenic CH4 emissions should be further quantified, especially for tropical countries. Accounting for climate variability may be necessary to improve anthropogenic emission inventories.

Context: East Asia is a crucial region in the global methane (CH4) budget, with significant contributions from the livestock sector. However, the long-term trend and spatial pattern of CH4 emissions from livestock in this region have not been fully assessed. Methods: Here, we estimate CH4 emissions from 10 categories of livestock in East Asia during 1961 – 2019 following the Tier 2 approaches suggested by the 2019 Refinement to the IPCC 2006 Guidelines. Results: livestock-sourced CH4 emission in 2019 was 13.22 [11.42 – 15.01] (mean [minimum%maximum of 95– confidence interval] Tg CH4 yr-1, accounting for an increase of 231% since 1961. The contribution of slaughtered populations to total emissions increased from 3% in 1961 to 24% in 2019. Spatially, the emission hotspots were mostly distributed in eastern China, South Korea, and parts of Japan, but they tend to shift northward after 2000. Conclusion: It is necessary to use dynamic emission factors and include slaughtered populations in the estimation of livestock CH4 emissions. Regions including Northern China, Mongolia, and South Korea deserve more attention in future CH4 mitigation efforts.

Research Highlights: Monitoring of soil CH4 fluxes in African tropical forest conducted run for almost two years, contributing to the scant information on greenhouse gas (GHG) fluxes from forests available from this region. Data showed that the forest soil acted as a net yearly source of CH4. Hotspots of CH4 emissions were measured both in upland and lowland areas of the forest, and on an annual basis they overcame the soil CH4 sink during drier periods or in well-drained areas. Background and Objectives: Atmospheric studies indicate that tropics are a strong CH4 source. Regional budgets attribute the majority of this source to wetland ecosystems and flooded lowland forests, whereas un-flooded forests are considered net CH4 sinks, although few studies in tropical forests, in particular in Africa, are available. The present work aims to contribute to this knowledge gap. Materials and Methods:Monitoring campaigns were conducted along the year in the tropical forest of the Ankasa National Park, Ghana, in two contrasting environments, uphill and downhill, using close static chambers coupled with gas chromatography. Results: The uphill area was a net weak CH4 sink with mean daily fluxes ranging from &minus, 1.29 to 0.44 mg CH4 m&minus, 2 d&minus, 1. The downhill area was a significant CH4 source with mean daily fluxes ranging from &minus, 0.67 to 188.09 mg CH4 m&minus, 1 and with peaks up to 1312 mg CH4 m&minus, 1 in the wet season. Conclusions: The net annual soil CH4 budget for the Ankasa Park, normalizing the proportion of downhill areas over the whole park surface, was a source of about 3.3 kg CH4 ha&minus, 1 yr&minus, 1. Overlooking such areas might lead to underestimates of the total CH4 source strength of forested areas.

Understanding and quantifying the global methane (CH4) budgetis important for assessing realistic pathways to mitigate climate change.Atmospheric emissions and concentrations of CH4 continue to increase,making CH4 the second most important human-influenced greenhouse gas interms of climate forcing, after carbon dioxide (CO2). The relativeimportance of CH4 compared to CO2 depends on its shorteratmospheric lifetime, stronger warming potential, and variations inatmospheric growth rate over the past decade, the causes of which are stilldebated. Two major challenges in reducing uncertainties in the atmosphericgrowth rate arise from the variety of geographically overlapping CH4sources and from the destruction of CH4 by short-lived hydroxylradicals (OH). To address these challenges, we have established aconsortium of multidisciplinary scientists under the umbrella of the GlobalCarbon Project to synthesize and stimulate new research aimed at improvingand regularly updating the global methane budget. Following Saunois et al. (2016), we present here the second version of the living review paperdedicated to the decadal methane budget, integrating results of top-downstudies (atmospheric observations within an atmospheric inverse-modellingframework) and bottom-up estimates (including process-based models forestimating land surface emissions and atmospheric chemistry, inventories ofanthropogenic emissions, and data-driven extrapolations). For the 2008–2017 decade, global methane emissions are estimated byatmospheric inversions (a top-down approach) to be 576 Tg CH4 yr−1 (range 550–594, corresponding to the minimum and maximumestimates of the model ensemble). Of this total, 359 Tg CH4 yr−1 or∼ 60 % is attributed to anthropogenic sources, that isemissions caused by direct human activity (i.e. anthropogenic emissions; range 336–376 Tg CH4 yr−1 or 50 %–65 %). The mean annual total emission for the new decade (2008–2017) is29 Tg CH4 yr−1 larger than our estimate for the previous decade (2000–2009),and 24 Tg CH4 yr−1 larger than the one reported in the previousbudget for 2003–2012 (Saunois et al. 2016). Since 2012, global CH4emissions have been tracking the warmest scenarios assessed by theIntergovernmental Panel on Climate Change. Bottom-up methods suggest almost30 % larger global emissions (737 Tg CH4 yr−1, range 594–881)than top-down inversion methods. Indeed, bottom-up estimates for naturalsources such as natural wetlands, other inland water systems, and geologicalsources are higher than top-down estimates. The atmospheric constraints onthe top-down budget suggest that at least some of these bottom-up emissionsare overestimated. The latitudinal distribution of atmosphericobservation-based emissions indicates a predominance of tropical emissions(∼ 65 % of the global budget, info:eu-repo/semantics/published

Many inland waters exhibit complete or partial desiccation, or have vanished due to global change, exposing sediments to the atmosphere. Yet, data on carbon dioxide (CO2) emissions from these sediments are too scarce to upscale emissions for global estimates or to understand their fundamental drivers. Here, we present the results of a global survey covering 196 dry inland waters across diverse ecosystem types and climate zones. We show that their CO2 emissions share fundamental drivers and constitute a substantial fraction of the carbon cycled by inland waters. CO2 emissions were consistent across ecosystem types and climate zones, with local characteristics explaining much of the variability. Accounting for such emissions increases global estimates of carbon emissions from inland waters by 6% (~0.12 Pg C y−1). Our results indicate that emissions from dry inland waters represent a significant and likely increasing component of the inland waters carbon cycle., Many inland waters seasonally or permanently dry up, thus exposing sediments to the atmosphere. Here the authors show that a substantial amount of CO2 is emitted from these dry sediments, increasing current inland water carbon flux estimates by 6%.

Wetlands are one of the most significant natural sources of methane (CH4) to the atmosphere. They emit CH4 because decomposition of soil organic matter in waterlogged anoxic conditions produces CH4, in addition to carbon dioxide (CO2). Production of CH4 and how much of it escapes to the atmosphere depend on a multitude of environmental drivers. Models simulating the processes leading to CH4 emissions are thus needed for upscaling observations to estimate present CH4 emissions and for producing scenarios of future atmospheric CH4 concentrations. Aiming at a CH4 model that can be added to models describing peatland carbon cycling, we composed a model called HIMMELI that describes CH4 build-up in and emissions from peatland soils. It is not a full peatland carbon cycle model but it requires the rate of anoxic soil respiration as input. Driven by soil temperature, leaf area index (LAI) of aerenchymatous peatland vegetation, and water table depth (WTD), it simulates the concentrations and transport of CH4, CO2, and oxygen (O2) in a layered one-dimensional peat column. Here, we present the HIMMELI model structure and results of tests on the model sensitivity to the input data and to the description of the peat column (peat depth and layer thickness), and demonstrate that HIMMELI outputs realistic fluxes by comparing modeled and measured fluxes at two peatland sites. As HIMMELI describes only the CH4-related processes, not the full carbon cycle, our analysis revealed mechanisms and dependencies that may remain hidden when testing CH4 models connected to complete peatland carbon models, which is usually the case. Our results indicated that (1) the model is flexible and robust and thus suitable for different environments; (2) the simulated CH4 emissions largely depend on the prescribed rate of anoxic respiration; (3) the sensitivity of the total CH4 emission to other input variables is mainly mediated via the concentrations of dissolved gases, in particular, the O2 concentrations that affect the CH4 production and oxidation rates; (4) with given input respiration, the peat column description does not significantly affect the simulated CH4 emissions in this model version., published version, peerReviewed

We measured methane (CH4) exchange rates with automatic chambers at the forest floor of a nutrient-rich drained peatland in 2011–2013. The fen, located in southern Finland, was drained for forestry in 1969 and the tree stand is now a mixture of Scots pine, Norway spruce, and pubescent birch. Our measurement system consisted of six transparent chambers and stainless steel frames, positioned on a number of different field and moss layer compositions. Gas concentrations were measured with an online cavity ring-down spectroscopy gas analyzer. Fluxes were calculated with both linear and exponential regression. The use of linear regression resulted in systematically smaller CH4 fluxes by 10–45 % as compared to exponential regression. However, the use of exponential regression with small fluxes ( 4 m−2 h−1) typically resulted in anomalously large absolute fluxes and high hour-to-hour deviations. Therefore, we recommend that fluxes are initially calculated with linear regression to determine the threshold for low fluxes and that higher fluxes are then recalculated using exponential regression. The exponential flux was clearly affected by the length of the fitting period when this period was 4 flux: the forest floor acted as a CH4 sink particularly from early summer until the end of the year, while in late winter the flux was very small and fluctuated around zero. However, the magnitude of fluxes was relatively small throughout the year, ranging mainly from −130 to +100 µg CH4 m−2 h−1. CH4 emission peaks were observed occasionally, mostly in summer during heavy rainfall events. Diurnal variation, showing a lower CH4 uptake rate during the daytime, was observed in all of the chambers, mainly in the summer and late spring, particularly in dry conditions. It was attributed more to changes in wind speed than air or soil temperature, which suggest that physical rather than biological phenomena are responsible for the observed variation. The annual net CH4 exchange varied from −104 ± 30 to −505 ± 39 mg CH4 m−2 yr−1 among the six chambers, with an average of −219 mg CH4 m−2 yr−1 over the 2-year measurement period.

Sparse data coverage in the Arctic hampers our understanding of its carbon cycle dynamics and our predictions of the fate of its vast carbon reservoirs in a changing climate. In this paper, we present accurate measurements of atmospheric carbon dioxide (CO2) and methane (CH4) dry air mole fractions at the new atmospheric carbon observation station Ambarchik, which closes a large gap in the atmospheric trace gas monitoring network in northeastern Siberia. The site, which has been operational since August 2014, is located near the delta of the Kolyma River at the coast of the Arctic Ocean. Data quality control of CO2 and CH4 measurements includes frequent calibrations traced to World Meteorological Organization (WMO) scales, employment of a novel water vapor correction, an algorithm to detect the influence of local polluters, and meteorological measurements that enable data selection. The available CO2 and CH4 record was characterized in comparison with in situ data from Barrow, Alaska. A footprint analysis reveals that the station is sensitive to signals from the East Siberian Sea, as well as the northeast Siberian tundra and taiga regions. This makes data from Ambarchik highly valuable for inverse modeling studies aimed at constraining carbon budgets within the pan-Arctic domain, as well as for regional studies focusing on Siberia and the adjacent shelf areas of the Arctic Ocean. Sparse data coverage in the Arctic hampers our understanding of its carbon cycle dynamics and our predictions of the fate of its vast carbon reservoirs in a changing climate. In this paper, we present accurate measurements of atmospheric carbon dioxide (CO2) and methane (CH4) dry air mole fractions at the new atmospheric carbon observation station Ambarchik, which closes a large gap in the atmospheric trace gas monitoring network in northeastern Siberia. The site, which has been operational since August 2014, is located near the delta of the Kolyma River at the coast of the Arctic Ocean. Data quality control of CO2 and CH4 measurements includes frequent calibrations traced to World Meteorological Organization (WMO) scales, employment of a novel water vapor correction, an algorithm to detect the influence of local polluters, and meteorological measurements that enable data selection. The available CO2 and CH4 record was characterized in comparison with in situ data from Barrow, Alaska. A footprint analysis reveals that the station is sensitive to signals from the East Siberian Sea, as well as the northeast Siberian tundra and taiga regions. This makes data from Ambarchik highly valuable for inverse modeling studies aimed at constraining carbon budgets within the pan-Arctic domain, as well as for regional studies focusing on Siberia and the adjacent shelf areas of the Arctic Ocean.

Characterizing greenhouse gas (GHG) emissions and global warming potential (GWP) has become a key step in the estimation of atmospheric GHG concentrations and their potential mitigation by cropland management. However, the impacts of organic amendments on GHG, GWP, and yield-scaled GWP on cropland have not been well documented. Here, we investigate four amendment treatments (no amendment, mineral fertilizers, and pig slurry or crop residue combined with mineral fertilizers) during a two-year field experiment in rain-fed wheat-maize cropping systems. The results show that the average annual cumulative methane (CH4) flux ranged from &minus, 2.60 to &minus, 2.97 kg&middot, C&middot, ha&minus, 1 while nitrous oxide (N2O) flux ranged from 0.44 to 4.58 kg&middot, N&middot, 1 across all four treatments. N2O emissions were significantly correlated with soil inorganic nitrogen (i.e., NH4+-N and NO3&minus, N), and soil dissolved organic carbon (DOC) during both the winter wheat and summer maize seasons. On average, organic amendments combined with mineral fertilizers increased the annual GWP by 26&ndash, 74% and yield-scaled GWP by 19&ndash, 71% compared to those under only mineral fertilizers application. This study indicates that the fertilization strategy for Eutric Regosols can shift from only mineral fertilizers to organic amendments combined with mineral fertilizers, which can help mitigate GHG emissions and GWP while maintaining crop yields.

Forests cover around 30% of the global land area and forest ecosystems can store over 70% of total soil organic carbon (SOC) of all terrestrial ecosystems, but SOC stocks and greenhouse gas (GHG) emissions may be affected by both natural and anthropogenic disturbances. Even though the changes in forest soil C pool can have a significant effect on climate change, there are some contradictory results regarding the role of forest disturbance on SOC sequestration, GHG emissions, and the mitigation of global changes. Therefore, there is a need to better understand the impact of different disturbance regimes on forest soil C storage and GHG emissions. A Special Issue was therefore organized for discussing the responses of soil C storage and GHG emissions to various types of disturbances in forest ecosystems and a total of 15 studies were accepted for this special issue to assess these responses. This Special Issue includes the effects of storms and beetle outbreaks, Karstification, rock desertification, warming, nitrogen addition, land-use change, field tillage, and biochar application on soil C dynamics and/or GHG emissions.

Energized electron flows through biological systems sustain nature’s complexity. They drive bacterial, archaeal, and fungal oxidation–reduction processes and enable to introduce CO2 and N2 from the atmospheric pool. Electron flux-based food webs convert soil organic matter (SOM) in virgin forest and permafrost soils, over-fertilized agricultural land, grassland systems, compost/wastewater treatment plants, oceans, rain forests, savannahs, and forests of the temperate climate zones, and have their strategy adapted on the system in which they are active. Thus, the electron driving power is responsible in our industrializing world that carbon and nitrogen returns to the atmosphere presently with an annual N2O-N proportion of 0.5 to 4.2 terragrams (Tg) or an annual atmospheric N2O-N increase of 0.25 %. N2O is a 300-times more potent greenhouse gas than CO2. Nature’s water-soluble soil carbon (CH2O)/NO3 − ratio balancing is seen as a model of how N2O emissions could be kept in a tolerable range. Sub strategies beyond are (a) an annual 400–800 terragrams (Tg) photosynthate-C (90–95 % sugars) release into plant rhizospheres, (b) spot-wise N enriching animal excrement and wide C/N ratio litter fall distributions, (c) viral shunts or life shortcuts to supporting O2 consuming, N supplying, and denitrifying recycler communities, (d) subterranean organic–inorganic soil components mixing and O2 diffusion promoting NO3 − formation, and (e) the release of nitrification inhibiting compounds as neem, karanjin, or specific humic acids which help in controlling nitrate formation and denitrification. Soil microbial transport vehicles are fungal hyphae, plant roots, and subterranean animals. Through their activities, aerobic–anaerobic gradients in the soil crumb mosaics emerge. Plant root intertissue spaces, animal guts, and co-transported soil crumbs where under carbon-dominated CH2O/NO3 − ratios preferred microbes reside are mobile locations in well-aerated soils. In such reduction-equivalent surplus environments, denitrifying communities are forced to use during anaerobic respiration available nitrate-, nitrite ions, NO, and N2O economically. Though at carbon-dominated CH2O/NO3 − ratios more N2O is reduced to N2 than in nitrate surplus environments, a complete prevention of N2O emissions is not a reality and even not desirable from the climate point of view. After describing N2O formation and emissions from a compost pile, a municipal wastewater treatment plant, a constructed wetland, and mineral N-fertilizer, sewage sludge or nitrification inhibitor-stabilized N-fertilizer amended soils with their aerobic-anaerobic mosaics, this review tries to deduce exercisable CN (CH2O/NO3) ratio shaping and N2O emission lowering strategies for ecologists, agriculturists, and waste managers in our industrializing world.

International audience; The MEthane Remote sensing Lidar missioN (MERLIN) aims at demonstrating the spaceborne active measurement of atmospheric methane, a potent greenhouse gas, based on an Integrated Path Differential Absorption (IPDA) nadir-viewing LIght Detecting and Ranging (Lidar) instrument. MERLIN is a joint French and German space mission, with a launch currently scheduled for the timeframe 2021/22. The German Space Agency (DLR) is responsible for the payload, while the platform (MYRIADE Evolutions product line) is developed by the French Space Agency (CNES). The main scientific objective of MERLIN is the delivery of weighted atmospheric columns of methane dry-air mole fractions for all latitudes throughout the year with systematic errors small enough (

The methane (CH4) emissions from municipal solid waste (MSW) landfills in China in 2007 were estimated based on database of the three-dimensional emission factors matrix and point sources, by an IPCC recommended FOD (firstorder decay) model. The location, capacity and age of landfills constitute the three dimensions of the emission factors matrix, which were obtained by laboratory analysis and in situ investigation. Key parameters such as waste composition, degradable organic carbon ratio, CH4 correction factor, oxidation factor and recovery rate, were carefully analyzed in terms of these three dimensions. The point sources database consists of 2,107 MSW landfills in cities and towns of China in 2007. The results show that the CH4 emissions from MSW landfills were 1.186 Mt in 2007. Compared with the CH4 emissions of 2.20 Mt in 2005, the significant discrepancy mainly comes from statistical data of landfills, e.g., number of landfills and amount of waste disposed in landfills. CH4 emissions were lower than 700 t for most of the landfills, whereas there were 279 landfills with emissions larger than 1,000 t, and only 10 landfills with emissions larger than 10,000 t. Jiangsu province ranks the largest emitter with 98,700 t while Tibet is the smallest emitter with 2,100 t. In general, the emissions from eastern provinces, such as Jiangsu, Guangdong and Zhejiang, were larger than those from western provinces, such as Ningxia, Tibet and Qinghai. Citation Cai, B.-F., Liu, J.-G., Gao, Q.-X., et al., 2014. Estimation of methane emissions from municipal solid waste landfills in China based on point emission sources. Adv. Clim. Change Res. 5(2), doi: 10.3724/SP.J.1248.2014.081.

Boreal forests comprise 73% of the world’s coniferous forests. Based on forest floor measurements, they have been considered a significant natural sink of methane (CH4) and a natural source of nitrous oxide (N2O), both of which are important greenhouse gases. However, the role of trees, especially conifers, in ecosystem N2O and CH4 exchange is only poorly understood. We show for the first time that mature Scots pine (Pinus sylvestris L.) trees consistently emit N2O and CH4 from both stems and shoots. The shoot fluxes of N2O and CH4 exceeded the stem flux rates by 16 and 41 times, respectively. Moreover, higher stem N2O and CH4 fluxes were observed from wet than from dry areas of the forest. The N2O release from boreal pine forests may thus be underestimated and the uptake of CH4 may be overestimated when ecosystem flux calculations are based solely on forest floor measurements. The contribution of pine trees to the N2O and CH4 exchange of the boreal pine forest seems to increase considerably under high soil water content, thus highlighting the urgent need to include tree-emissions in greenhouse gas emission inventories.

The treatment of domestic and industrial wastewater is one of the major sources of CH4 in the Chinese waste sector. On the basis of statistical data and country-specific emission factors, using IPCC methodology, the characteristics of CH4 emissions from wastewater treatment in China were analyzed. The driving factors of CH4 emissions were studied, and the emission trend and reduction potential were predicted and analyzed according to the current situation. Results show that in 2010, CH4 emissions from the treatment of domestic and industrial wastewater were 0.6110Mt and 1.6237Mt, respectively. Eight major industries account for more than 92% of emissions, and CH4 emissions gradually increased from 2005 to 2010. From the controlling management scenario, we predict that in 2020, CH4 emissions from the treatment of domestic and industrial wastewater will be 1.0136Mt and 2.3393Mt, respectively, and the reduction potential will be 0.0763Mt and 0.2599Mt, respectively. From 2010 to 2020, CH4 emissions from the treatment of domestic and industrial wastewater will increase by 66% and 44%, respectively.

Landfills are a major anthropogenic source of the greenhouse gas methane (CH4). However, much of the CH4 produced during the anaerobic degradation of organic waste is consumed by methanotrophic micro-organisms during passage through the landfill-cover soil. On a section of a closed landfill near Liestal, Switzerland, we performed experiments to compare CH4 fluxes obtained by different methods at or above the cover-soil surface with below-ground fluxes, and to link methanotrophic activity to estimates of CH4 ingress (loading) from the waste body at selected locations. Fluxes of CH4 into or out of the cover soil were quantified by eddy-covariance and static flux-chamber measurements. In addition. CH4 concentrations at the soil surface were monitored using a field-portable FID detector. Near-surface CH4 fluxes and CH4 loading were estimated from soil-gas concentration profiles in conjunction with radon measurements, and gas push-pull tests (GPPTs) were performed to quantify rates of microbial CH4 oxidation. Eddy-covariance measurements yielded by far the largest and probably most representative estimates of overall CH4 emissions from the test section (daily mean up to similar to 91,500 mu mol m(-2) d(-1)), whereas flux-chamber measurements and CH4 concentration profiles indicated that at the majority of locations the cover soil was a net sink for atmospheric CH4 (uptake up to -380 mu mol m(-2) d(-1)) during the experimental period. Methane concentration profiles also indicated strong variability in CH4 loading over short distances in the cover soil, while potential methanotrophic activity derived from GPPTs was high (v(max) similar to 13 mmol L-1(soil air) h(-1)) at a location with substantial CH4 loading. Our results provide a basis to assess spatial and temporal variability of CH4 dynamics in the complex terrain of a landfill-cover soil. (C) 2011 Elsevier Ltd. All rights reserved.

Wetlands are the world's largest natural source of methane, a powerful greenhouse gas. The strong sensitivity of methane emissions to environmental factors such as soil temperature and moisture has led to concerns about potential positive feedbacks to climate change. This risk is particularly relevant at high latitudes, which have experienced pronounced warming and where thawing permafrost could potentially liberate large amounts of labile carbon over the next 100 years. However, global models disagree as to the magnitude and spatial distribution of emissions, due to uncertainties in wetland area and emissions per unit area and a scarcity of in situ observations. Recent intensive field campaigns across the West Siberian Lowland (WSL) make this an ideal region over which to assess the performance of large-scale process-based wetland models in a high-latitude environment. Here we present the results of a follow-up to the Wetland and Wetland CH4 Intercomparison of Models Project (WETCHIMP), focused on the West Siberian Lowland (WETCHIMP-WSL). We assessed 21 models and 5 inversions over this domain in terms of total CH4 emissions, simulated wetland areas, and CH4 fluxes per unit wetland area and compared these results to an intensive in situ CH4 flux data set, several wetland maps, and two satellite surface water products. We found that (a) despite the large scatter of individual estimates, 12-year mean estimates of annual total emissions over the WSL from forward models (5.34 ± 0.54 Tg CH4 yr−1), inversions (6.06 ± 1.22 Tg CH4 yr−1), and in situ observations (3.91 ± 1.29 Tg CH4 yr−1) largely agreed; (b) forward models using surface water products alone to estimate wetland areas suffered from severe biases in CH4 emissions; (c) the interannual time series of models that lacked either soil thermal physics appropriate to the high latitudes or realistic emissions from unsaturated peatlands tended to be dominated by a single environmental driver (inundation or air temperature), unlike those of inversions and more sophisticated forward models; (d) differences in biogeochemical schemes across models had relatively smaller influence over performance; and (e) multiyear or multidecade observational records are crucial for evaluating models' responses to long-term climate change.

The objective of this study was to quantify the soil greenhouse gas (GHG) balance after the conversion of native vegetation (NV) to pasture and agricultural land and the conversion of agriculture to crop-pasture rotation (CPR) by evaluating changes in C stocks and N2O and CH4 fluxes. Soil sampling was carried out in March 2007 and April 2009 and GHG fluxes were sampled nine times between April 2007 and March 2009. The conversion of NV to pasture and agriculture decreased soil C stocks, with loss rates ranging from 0.25 to 0.64 Mg C ha(-1) yr(-1), respectively. The implementation of CPR in,agriculture areas increased soil C stocks by 0.60 Mg ha(-1) yr(-1). N2O emissions were higher in CPR and lower in NV. Emission of 1.03 kg CH4-C ha(-1) yr(-1) was observed in pasture, while in other areas consumption of CH4 was observed. The net GHG emission from the soil, including all GHG expressed in C-equivalent, indicated that the conversion of NV to pasture and agricultural land results in emissions of 0.54 and 0.72 Mg C ha(-1) yr(-1), respectively. In contrast, the adoption of CPR in areas under crop succession was a sink of 0.36 Mg ha(-1) yr(-1). Among the evaluated land use changes, only the implementation of CPR proved to be a good strategy to mitigate soil GHG emissions in Brazilian Cerrado.

We used various approaches to establish a comprehensive budget of methane (CH4) emissions from the Seine basin, including direct emissions from livestock and soils as well as emissions from the drainage network. For the direct emissions from livestock, we used official livestock census numbers and emission factors (CH4 emitted by each animal species per head per year) available in the literature. For the emissions from soils, we based our estimates on experimental measurements in closed chambers installed on different agricultural plots, forest, and grasslands in 2008 and 2009. The results were extrapolated to the whole Seine basin, including grassland, cropland, and forest soil distributions in the Seine basin. The CH4 emissions from the Seine drainage network were also based on measurements of sampled waters in various rivers and streams (from headwaters to estuary) during different seasons in 2007, 2008, and 2010. After chemical analysis of CH4 concentrations in the water samples using a gas chromatographic technique and calculation of the CH4 supersaturation by stream order in rivers of the Seine basin (from 1 to 8) and by season we could estimate the CH4 emissions for the whole water surface area of the Seine drainage network. The livestock of the Seine basin produce CH4 emissions amounting to 166 × 106 kg C year−1, among which cattle are responsible for 85 %. The total CH4 emission from the Seine drainage network was estimated at 0.3 × 106 kg C year−1, large rivers being responsible for the largest proportion. Ebullition could account for an additional 0.2 × 106 kg C year−1. Soils of the Seine basin are a net sink for CH4 (9.4 × 106 kg C year−1). The water and soils fluxes are low with regard to emissions by livestock, but domestic waste, through landfills, could contribute an additional 40 × 106 kg C year−1.

The role of trees in the nitrous oxide (N2O) balance of boreal forests has been neglected despite evidence suggesting their substantial contribution. We measured seasonal changes in N2O fluxes from soil and stems of boreal trees in Finland, showing clear seasonality in stem N2O flux following tree physiological activity, particularly processes of CO2 uptake and release. Stem N2O emissions peak during the vegetation season, decrease rapidly in October, and remain low but significant to the annual totals during winter dormancy. Trees growing on dry soils even turn to consumption of N2O from the atmosphere during dormancy, thereby reducing their overall N2O emissions. At an annual scale, pine, spruce and birch are net N2O sources, with spruce being the strongest emitter. Boreal trees thus markedly contribute to the seasonal dynamics of ecosystem N2O exchange, and their species-specific contribution should be included into forest emission inventories. Forest soil is known to be a source of the greenhouse gas N2O, but the impact of what is planted in that soil has long been overlooked. Here Machacova and colleagues quantify seasonal N2O fluxes from common boreal tree species in Finland, finding that all trees are net sources of this gas.