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1
Arora, Vivek K., Joe R. Melton, and David Plummer. "An assessment of natural methane fluxes simulated by the CLASS-CTEM model." Biogeosciences 15, no. 15 (August 1, 2018): 4683–709. http://dx.doi.org/10.5194/bg-15-4683-2018.
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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.
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Jensen, Sigmund, Anders Priemé, and Lars Bakken. "Methanol Improves Methane Uptake in Starved Methanotrophic Microorganisms." Applied and Environmental Microbiology 64, no. 3 (March 1, 1998): 1143–46. http://dx.doi.org/10.1128/aem.64.3.1143-1146.1998.
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ABSTRACT Methanotrophs in enrichment cultures grew and sustained atmospheric methane oxidation when supplied with methanol. If they were not supplied with methanol or formate, their atmospheric methane oxidation came to a halt, but it was restored within hours in response to methanol or formate. Indigenous forest soil methanotrophs were also dependent on a supply of methanol upon reduced methane access but only when exposed to a methane-free atmosphere. Their immediate response to each methanol addition, however, was to shut down the oxidation of atmospheric methane and to reactivate atmospheric methane oxidation as the methanol was depleted.
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Stevens, C. M. "Atmospheric methane." Chemical Geology 71, no. 1-3 (December 1988): 11–21. http://dx.doi.org/10.1016/0009-2541(88)90102-7.
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Gorham, Katrine A., Sam Abernethy, Tyler R. Jones, Peter Hess, Natalie M. Mahowald, Daphne Meidan, Matthew S. Johnson, et al. "Opinion: A research roadmap for exploring atmospheric methane removal via iron salt aerosol." Atmospheric Chemistry and Physics 24, no. 9 (May 15, 2024): 5659–70. http://dx.doi.org/10.5194/acp-24-5659-2024.
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Abstract. The escalating climate crisis requires rapid action to reduce the concentrations of atmospheric greenhouse gases and lower global surface temperatures. Methane will play a critical role in near-term warming due to its high radiative forcing and short atmospheric lifetime. Methane emissions have accelerated in recent years, and there is significant risk and uncertainty associated with the future growth in natural emissions. The largest natural sink of methane occurs through oxidation reactions with atmospheric hydroxyl and chlorine radicals. Enhanced atmospheric oxidation could be a potential approach to remove atmospheric methane. One method proposes the addition of iron salt aerosol (ISA) to the atmosphere, mimicking a natural process proposed to occur when mineral dust mixes with chloride from sea spray to form iron chlorides, which are photolyzed by sunlight to produce chlorine radicals. Under the right conditions, lofting ISA into the atmosphere could potentially reduce atmospheric methane concentrations and lower global surface temperatures. Recognizing that potential atmospheric methane removal must only be considered an additive measure – in addition to, not replacing, crucial anthropogenic greenhouse gas emission reductions and carbon dioxide removal – roadmaps can be a valuable tool to organize and streamline interdisciplinary and multifaceted research to efficiently move towards understanding whether an approach may be viable and socially acceptable or if it is nonviable and further research should be deprioritized. Here we present a 5-year research roadmap to explore whether ISA enhancement of the chlorine radical sink could be a viable and socially acceptable atmospheric methane removal approach.
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Catling, D. C., M. W. Claire, and K. J. Zahnle. "Anaerobic methanotrophy and the rise of atmospheric oxygen." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 365, no. 1856 (May 18, 2007): 1867–88. http://dx.doi.org/10.1098/rsta.2007.2047.
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In modern marine sediments, the anoxic decomposition of organic matter generates a significant flux of methane that is oxidized microbially with sulphate under the seafloor and never reaches the atmosphere. In contrast, prior to ca 2.4 Gyr ago, the ocean had little sulphate to support anaerobic oxidation of methane (AOM) and the ocean should have been an important methane source. As atmospheric O 2 and seawater sulphate levels rose on the early Earth, AOM would have increasingly throttled the release of methane. We use a biogeochemical model to simulate the response of early atmospheric O 2 and CH 4 to changes in marine AOM as sulphate levels increased. Semi-empirical relationships are used to parameterize global AOM rates and the evolution of sulphate levels. Despite broad uncertainties in these relationships, atmospheric O 2 concentrations generally rise more rapidly and to higher levels (of order approx. 10 −3 bar versus approx. 10 −4 bar) as a result of including AOM in the model. Methane levels collapse prior to any significant rise in O 2 , but counter-intuitively, methane re-rises after O 2 rises to higher levels when AOM is included. As O 2 concentrations increase, shielding of the troposphere by stratospheric ozone slows the effective reaction rate between oxygen and methane. This effect dominates over the decrease in the methane source associated with AOM. Thus, even with the inclusion of AOM, the simulated Late Palaeoproterozoic atmosphere has a climatologically significant level of methane of approximately 50 ppmv.
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Buzan, E. M., C. A. Beale, C. D. Boone, and P. F. Bernath. "Global stratospheric measurements of the isotopologues of methane from the Atmospheric Chemistry Experiment Fourier Transform Spectrometer." Atmospheric Measurement Techniques Discussions 8, no. 10 (October 29, 2015): 11171–207. http://dx.doi.org/10.5194/amtd-8-11171-2015.
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Abstract. This paper presents an analysis of observations of methane and its two major isotopologues, CH3D and 13CH4 from the Atmospheric Chemistry Experiment (ACE) satellite between 2004 and 2013. Additionally, atmospheric methane chemistry is modeled using the Whole Atmospheric Community Climate Model (WACCM). ACE retrievals of methane extend from 6 km for all isotopologues to 75 km for 12CH4, 35 km for CH3D, and 50 km for 13CH4. While total methane concentrations retrieved from ACE agree well with the model, values of δD–CH4 and δ13C–CH4 show a bias toward higher δ compared to the model and balloon-based measurements. Calibrating δD and δ13C from ACE using WACCM in the troposphere gives improved agreement in δD in the stratosphere with the balloon measurements, but values of δ13C still disagree. A model analysis of methane's atmospheric sinks is also performed.
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Duda, Adam. "The Impact of Atmospheric Pressure Changes on Methane Emission from Goafs to Coal Mine Workings." Energies 17, no. 1 (December 28, 2023): 173. http://dx.doi.org/10.3390/en17010173.
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Increased effectiveness of methane drainage from sealed post-mining goaves in hard coal mines contributes to reduced methane emission from goaves into the mine ventilation system. This paper focuses on issues concerning the assessment of the additional amount of methane released from the goaf into mine workings during periods of atmospheric pressure drops, which can be captured with a methane drainage system. Thanks to the solutions presented in the paper, it is possible to control the efficiency of the goaf drainage system, which in turn leads to the reduction of methane emission from the mine ventilation air into Earth’s atmosphere. These solutions are of great added value for both the environment and coal mines as they reduce the costs arising from greenhouse gas emissions that are incurred by mining companies, increasing the efficiency of methane capture and its use in gas engines or district heating systems. The paper uses relationships relating to the influence of atmospheric pressure changes on the process of gas release from the goaf according to the hysteresis loop of methane release during atmospheric pressure changes, which was developed based on conducted research. The analysis and conclusions presented in this paper may facilitate the development of strategies aimed at reducing methane emissions from a mine’s ventilated air into Earth’s atmosphere.
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Wang, Jin, and Qinghua Peter He. "Methane Removal from Air: Challenges and Opportunities." Methane 2, no. 4 (November 1, 2023): 404–14. http://dx.doi.org/10.3390/methane2040027.
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Driven by increasing greenhouse gas (GHG) concentrations in the atmosphere, extreme weather events have become more frequent and their impacts on human lives have become more severe. Therefore, the need for short-term GHG mitigations is urgent. Recently, methane has been recognized as an important mitigation target due to its high global warming potential (GWP). However, methane’s low concentration in the atmosphere and stable molecular structure make its removal from the air highly challenging. This review first discusses the fundamental aspects of the challenges in atmospheric methane removal and then briefly reviews the existing research strategies following the mechanisms of natural methane sinks. Although still in its infancy, recent research on methane removal from the air holds great potential for slowing down global warming. At the same time, it is important to carefully examine the energy consumption of these methane removal strategies and whether they will be able to achieve net GHG reduction. In addition, due to the scale of methane removal from the air, any potential solution’s environmental impacts must be carefully evaluated before it can be implemented in practice.
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Bussmann, Ingeborg, Eric P. Achterberg, Holger Brix, Nicolas Brüggemann, Götz Flöser, Claudia Schütze, and Philipp Fischer. "Influence of wind strength and direction on diffusive methane fluxes and atmospheric methane concentrations above the North Sea." Biogeosciences 21, no. 16 (August 29, 2024): 3819–38. http://dx.doi.org/10.5194/bg-21-3819-2024.
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Abstract. Quantification of the diffusive methane fluxes between the coastal ocean and atmosphere is important to constrain the atmospheric methane budget. The determination of the fluxes in coastal waters is characterized by a high level of uncertainty. To improve the accuracy of the estimation of coastal methane fluxes, high temporal and spatial sampling frequencies of dissolved methane in seawater are required, as well as the quantification of atmospheric methane concentrations, wind speed and wind direction above the ocean. In most cases, these atmospheric data are obtained from land-based atmospheric and meteorological monitoring stations in the vicinity of the coastal ocean methane observations. In this study, we measured wind speed, wind direction and atmospheric methane directly on board three research vessels in the southern North Sea and compared the local and remote atmospheric and meteorological measurements on the quality of the flux data. In addition, we assessed the source of the atmospheric methane measured in the study area in the German Bight using air mass back-trajectory assessments. The choice of the wind speed data source had a strong impact on the flux calculations. Fluxes based on wind data from nearby weather stations amounted to only 58 ± 34 % of values based on in situ data. Using in situ data, we calculated an average diffusive methane sea-to-air flux of 221 ± 351 µmol m−2 d−1 (n = 941) and 159 ± 444 µmol m−2 d−1 (n = 3028) for our study area in September 2019 and 2020, respectively. The area-weighted diffusive flux for the entire area of Helgoland Bay (3.78 × 109 m2) was 836 ± 97 and 600 ± 111 kmol d−1 for September 2019 and 2020, respectively. Using the median value of the diffusive fluxes for these extrapolations resulted in much lower values compared to area-weighted extrapolations or mean-based extrapolations. In general, at high wind speeds, the surface water turbulence is enhanced, and the diffusive flux increases. However, this enhanced methane input is quickly diluted within the air mass. Hence, a significant correlation between the methane flux and the atmospheric concentration was observed only at wind speeds < 5 m s−1. The atmospheric methane concentration was mainly influenced by the wind direction, i.e., the origin of the transported air mass. Air masses coming from industrial regions resulted in elevated atmospheric methane concentrations, while air masses coming from the North Sea transported reduced methane levels. With our detailed study on the spatial distribution of methane fluxes we were able to provide a detailed and more realistic estimation of coastal methane fluxes.
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Meng, L., R. Paudel, P. G. M. Hess, and N. M. Mahowald. "Seasonal and interannual variability in wetland methane emissions simulated by CLM4Me' and CAM-chem and comparisons to observations of concentrations." Biogeosciences 12, no. 13 (July 3, 2015): 4029–49. http://dx.doi.org/10.5194/bg-12-4029-2015.
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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.
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Berchet, Antoine, Philippe Bousquet, Isabelle Pison, Robin Locatelli, Frédéric Chevallier, Jean-Daniel Paris, Ed J. Dlugokencky, et al. "Atmospheric constraints on the methane emissions from the East Siberian Shelf." Atmospheric Chemistry and Physics 16, no. 6 (March 30, 2016): 4147–57. http://dx.doi.org/10.5194/acp-16-4147-2016.
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Abstract. Subsea permafrost and hydrates in the East Siberian Arctic Shelf (ESAS) constitute a substantial carbon pool, and a potentially large source of methane to the atmosphere. Previous studies based on interpolated oceanographic campaigns estimated atmospheric emissions from this area at 8–17 TgCH4 yr−1. Here, we propose insights based on atmospheric observations to evaluate these estimates. The comparison of high-resolution simulations of atmospheric methane mole fractions to continuous methane observations during the whole year 2012 confirms the high variability and heterogeneity of the methane releases from ESAS. A reference scenario with ESAS emissions of 8 TgCH4 yr−1, in the lower part of previously estimated emissions, is found to largely overestimate atmospheric observations in winter, likely related to overestimated methane leakage through sea ice. In contrast, in summer, simulations are more consistent with observations. Based on a comprehensive statistical analysis of the observations and of the simulations, annual methane emissions from ESAS are estimated to range from 0.0 to 4.5 TgCH4 yr−1. Isotopic observations suggest a biogenic origin (either terrestrial or marine) of the methane in air masses originating from ESAS during late summer 2008 and 2009.
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Keppler, Frank, Mihály Boros, Christian Frankenberg, Jos Lelieveld, Andrew McLeod, Anna Maria Pirttilä, Thomas Röckmann, and Jörg-Peter Schnitzler. "Methane formation in aerobic environments." Environmental Chemistry 6, no. 6 (2009): 459. http://dx.doi.org/10.1071/en09137.
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Environmental context. Methane is an important greenhouse gas and its atmospheric concentration has drastically increased since pre-industrial times. Until recently biological methane formation has been associated exclusively with anoxic environments and microbial activity. In this article we discuss several alternative formation pathways of methane in aerobic environments and suggest that non-microbial methane formation may be ubiquitous in terrestrial and marine ecosystems. Abstract. Methane (CH4), the second principal anthropogenic greenhouse gas after CO2, is the most abundant reduced organic compound in the atmosphere and plays a central role in atmospheric chemistry. Therefore a comprehensive understanding of its sources and sinks and the parameters that control emissions is prerequisite to simulate past, present and future atmospheric conditions. Until recently biological CH4 formation has been associated exclusively with anoxic environments and methanogenic activity. However, there is growing and convincing evidence of alternative pathways in the aerobic biosphere including terrestrial plants, soils, marine algae and animals. Identifying and describing these sources is essential to complete our understanding of the biogeochemical cycles that control CH4 in the atmospheric environment and its influence as a greenhouse gas.
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Meng, L., R. Paudel, P. G. M. Hess, and N. M. Mahowald. "Seasonal and inter-annual variability in wetland methane emissions simulated by CLM4Me' and CAM-chem and comparisons to observations of concentrations." Biogeosciences Discussions 12, no. 3 (February 2, 2015): 2161–212. http://dx.doi.org/10.5194/bgd-12-2161-2015.
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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.
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Allen, Robert J., Xueying Zhao, Cynthia A. Randles, Ryan J. Kramer, Bjørn H. Samset, and Christopher J. Smith. "Present-day methane shortwave absorption mutes surface warming relative to preindustrial conditions." Atmospheric Chemistry and Physics 24, no. 19 (October 9, 2024): 11207–26. http://dx.doi.org/10.5194/acp-24-11207-2024.
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Abstract. Recent analyses show the importance of methane shortwave absorption, which many climate models lack. In particular, Allen et al. (2023) used idealized climate model simulations to show that methane shortwave absorption mutes up to 30 % of the surface warming and 60 % of the precipitation increase associated with its longwave radiative effects. Here, we explicitly quantify the radiative and climate impacts due to shortwave absorption of the present-day methane perturbation. Our results corroborate the hypothesis that present-day methane shortwave absorption mutes the warming effects of longwave absorption. For example, the global mean cooling in response to the present-day methane shortwave absorption is -0.10±0.07 K, which offsets 28 % (7 %–55 %) of the surface warming associated with present-day methane longwave radiative effects. The precipitation increase associated with the longwave radiative effects of the present-day methane perturbation (0.012±0.006 mm d−1) is also muted by shortwave absorption but not significantly so (-0.008±0.009 mm d−1). The unique responses to methane shortwave absorption are related to its negative top-of-the-atmosphere effective radiative forcing but positive atmospheric heating and in part to methane's distinctive vertical atmospheric solar heating profile. We also find that the present-day methane shortwave radiative effects, relative to its longwave radiative effects, are about 5 times larger than those under idealized carbon dioxide perturbations. Additional analyses show consistent but non-significant differences between the longwave versus shortwave radiative effects for both methane and carbon dioxide, including a stronger (negative) climate feedback when shortwave radiative effects are included (particularly for methane). We conclude by reiterating that methane remains a potent greenhouse gas.
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Buzan, Eric M., Chris A. Beale, Chris D. Boone, and Peter F. Bernath. "Global stratospheric measurements of the isotopologues of methane from the Atmospheric Chemistry Experiment Fourier transform spectrometer." Atmospheric Measurement Techniques 9, no. 3 (March 18, 2016): 1095–111. http://dx.doi.org/10.5194/amt-9-1095-2016.
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Abstract. This paper presents an analysis of observations of methane and its two major isotopologues, CH3D and 13CH4, from the Atmospheric Chemistry Experiment (ACE) satellite between 2004 and 2013. Additionally, atmospheric methane chemistry is modeled using the Whole Atmospheric Community Climate Model (WACCM). ACE retrievals of methane extend from 6 km for all isotopologues to 75 km for 12CH4, 35 km for CH3D, and 50 km for 13CH4. While total methane concentrations retrieved from ACE agree well with the model, values of δD–CH4 and δ13C–CH4 show a bias toward higher δ compared to the model and balloon-based measurements. Errors in spectroscopic constants used during the retrieval process are the primary source of this disagreement. Calibrating δD and δ13C from ACE using WACCM in the troposphere gives improved agreement in δD in the stratosphere with the balloon measurements, but values of δ13C still disagree. A model analysis of methane's atmospheric sinks is also performed.
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Pekarnikova, M. Е., and K. B. Valiullina. "Legal Regulation of Methane Emissions and Its Role in Supporting the Goal of the Paris Agreement: General Issues." Uchenye Zapiski Kazanskogo Universiteta Seriya Gumanitarnye Nauki 166, no. 6 (January 19, 2025): 145–59. https://doi.org/10.26907/2541-7738.2024.6.145-159.
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This article explores the current legal and regulatory practices on lowering atmospheric methane, the main short-lived gaseous pollutant, adopted by the world’s largest methane emitters. In 2021, many countries joined the Global Methane Pledge (GMP), a joint international initiative, which has since been the guiding framework for estimating and reducing global methane levels. The GMP’s primary task is to support the goal of the Paris Agreement on climate change. Due to methane’s short life and the phenomenon referred to as the methane paradox, it has become clear that abandoning hydrocarbons completely would not guarantee a swift decrease in the radiative forcing of the lower troposphere. Reduction of aerosol emissions will lead to more intense warming during the first ten years, as aerosols are rapidly removed from the atmosphere. The only way to mitigate this effect is to curb short-lived methane emissions. Our findings reinforce previous conclusions and stress the critical need for developing legally binding regulations, both national and international, on greenhouse gas emissions.
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Mazánková, V., L. Töröková, D. Trunec, F. Krčma, S. Matejčík, and N. J. Mason. "Diagnostics of Nitrogen-methane Atmospheric Glow Discharge Used for a Mimic of Prebiotic Atmosphere." PLASMA PHYSICS AND TECHNOLOGY 4, no. 1 (2017): 83–86. http://dx.doi.org/10.14311/ppt.2017.1.83.
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The exploration of planetary atmosphere is being advanced by the exciting results of the Cassin-Huygens mission to Titan. The complex chemistry revealed in such atmospheres leading to the synthesis of bigger molecules is providing new insights into our understanding of how life on Earth developed. This work extends our previous investigation of nitrogen-methane (N<sub>2</sub>-CH<sub>4</sub>) atmospheric glow discharge for simulation chemical processes in prebiotic atmospheres. In presented experiments 2 % of water vapor were addet to nitrogen-methane gas mixture. Exhaust products of discharge in this gas mixture were in-situ analysed by Fourier Transform Infra Red spectroscopy (FTIR). The major products identified in spectra were: hydrogen cyanide, acetylene and acetonitrile.
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Stevenson, David S., Richard G. Derwent, Oliver Wild, and William J. Collins. "COVID-19 lockdown emission reductions have the potential to explain over half of the coincident increase in global atmospheric methane." Atmospheric Chemistry and Physics 22, no. 21 (November 8, 2022): 14243–52. http://dx.doi.org/10.5194/acp-22-14243-2022.
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Abstract. Compared with 2019, measurements of the global growth rate of background (marine air) atmospheric methane rose by 5.3 ppb yr−1 in 2020, reaching 15.0 ppb yr−1. Global atmospheric chemistry models have previously shown that reductions in nitrogen oxide (NOx) emissions reduce levels of the hydroxyl radical (OH) and lengthen the methane lifetime. Acting in the opposite sense, reductions in carbon monoxide (CO) and non-methane volatile organic compound (NMVOC) emissions increase OH and shorten methane's lifetime. Using estimates of NOx, CO, and NMVOC emission reductions associated with COVID-19 lockdowns around the world in 2020 as well as model-derived regional and aviation sensitivities of methane to these emissions, we find that NOx emission reductions led to a 4.8 (3.8 to 5.8) ppb yr−1 increase in the global methane growth rate. Reductions in CO and NMVOC emissions partly counteracted this, changing (reducing) the methane growth rate by −1.4 (−1.1 to −1.7) ppb yr−1 (CO) and −0.5 (−0.1 to −0.9) ppb yr−1 (NMVOC), yielding a net increase of 2.9 (1.7 to 4.0) ppb yr−1. Uncertainties refer to ±1 standard deviation model ranges in sensitivities. Whilst changes in anthropogenic emissions related to COVID-19 lockdowns are probably not the only important factor that influenced methane during 2020, these results indicate that they have had a large impact and that the net effect of NOx, CO, and NMVOC emission changes can explain over half of the observed 2020 methane changes. Large uncertainties remain in both emission changes during the lockdowns and methane's response to them; nevertheless, this analysis suggests that further research into how the atmospheric composition changed over the lockdown periods will help us to interpret past methane changes and to constrain future methane projections.
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Berchet, A., P. Bousquet, I. Pison, R. Locatelli, F. Chevallier, J. D. Paris, E. J. Dlugokencky, et al. "Atmospheric constraints on the methane emissions from the East Siberian Shelf." Atmospheric Chemistry and Physics Discussions 15, no. 18 (September 17, 2015): 25477–501. http://dx.doi.org/10.5194/acpd-15-25477-2015.
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Abstract. Sub-sea permafrost and hydrates in the East Siberian Arctic Ocean Continental Shelf (ESAS) constitute a substantial carbon pool, and a potentially large source of methane to the atmosphere. Previous studies based on interpolated oceanographic campaigns estimated atmospheric emissions from this area at 8–17 Tg CH4 y−1. Here, we propose insights based on atmospheric observations to evaluate these estimates. Isotopic observations suggest a biogenic origin (either terrestrial or marine) of the methane in air masses originating from ESAS during summer 2010. The comparison of high-resolution simulations of atmospheric methane mole fractions to continuous methane observations during the entire year 2012 confirms the high variability and heterogeneity of the methane releases from ESAS. Simulated mole fractions including a 8 Tg CH4 y−1 source from ESAS are found largely overestimated compared to the observations in winter, whereas summer signals are more consistent with each other. Based on a comprehensive statistical analysis of the observations and of the simulations, annual methane emissions from ESAS are estimated in a range of 0.5–4.3 Tg CH4 y−1.
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Jackson, Robert B., Sam Abernethy, Josep G. Canadell, Matteo Cargnello, Steven J. Davis, Sarah Féron, Sabine Fuss, et al. "Atmospheric methane removal: a research agenda." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 379, no. 2210 (September 27, 2021): 20200454. http://dx.doi.org/10.1098/rsta.2020.0454.
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Atmospheric methane removal (e.g. in situ methane oxidation to carbon dioxide) may be needed to offset continued methane release and limit the global warming contribution of this potent greenhouse gas. Because mitigating most anthropogenic emissions of methane is uncertain this century, and sudden methane releases from the Arctic or elsewhere cannot be excluded, technologies for methane removal or oxidation may be required. Carbon dioxide removal has an increasingly well-established research agenda and technological foundation. No similar framework exists for methane removal. We believe that a research agenda for negative methane emissions—‘removal' or atmospheric methane oxidation—is needed. We outline some considerations for such an agenda here, including a proposed Methane Removal Model Intercomparison Project (MR-MIP). This article is part of a discussion meeting issue 'Rising methane: is warming feeding warming? (part 1)'.
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Murphy, Matthew M., Thomas G. Beatty, Luis Welbanks, and Guangwei Fu. "HST Transmission Spectra of the Hot Neptune HD 219666 b: Detection of Water and the Challenge of Constraining Both Water and Methane." Astronomical Journal 169, no. 6 (May 2, 2025): 286. https://doi.org/10.3847/1538-3881/adc684.
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Abstract Although Neptunian-sized (2–5 R ⊕) planets appear to be extremely common in the Galaxy, many mysteries remain about their overall nature. To date, only 11 Neptunian-sized planets have had their atmospheres spectroscopically characterized, and these observations hint at interesting diversity within this class of planets. Much of our understanding of these worlds and others derive from transmission spectroscopy with the Hubble Space Telescope’s Wide Field Camera 3 (HST/WFC3). One key outcome of HST/WFC3 observations has been the consistent detection of water but no methane in Neptunian atmospheres, though recent James Webb Space Telescope (JWST) observations are potentially starting to overturn this “missing methane” paradigm. In this work, we present the transmission spectrum of the hot Neptune HD 219666 b from 1.1 to 1.6 μm from two transit observations using HST/WFC3 G141. Our fiducial atmospheric retrieval detects water at ∼3σ in HD 219666 b’s atmosphere and prefers no contribution from methane, similar to these previous observations of other planets. Motivated by recent detections of methane in Neptunian atmospheres by JWST, we explore additional models and find that a methane-only scenario could adequately fit the data, though it is not preferred and likely unphysical. We discuss the impact of this methane detection challenge on our understanding of planetary atmospheres based on HST/WFC3 observations alone, and where JWST observations offer a solution.
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SHUKLA, J. B., SHYAM SUNDAR, ASHISH KUMAR MISHRA, and RAM NARESH. "NUMERICAL MODEL ON METHANE EMISSIONS FROM AGRICULTURE SECTOR." International Journal of Big Data Mining for Global Warming 02, no. 01 (June 2020): 2050003. http://dx.doi.org/10.1142/s2630534820500035.
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Atmospheric methane, emitted from agriculture sector such as production of rice paddies and farming of livestock populations, is one of the important factors responsible for increasing the average atmospheric temperature leading to global warming. It is, therefore, crucial to comprehend the dynamics of methane emission and its effect on global warming. In this paper, a nonlinear mathematical model is proposed and analyzed to study the increase of average atmospheric temperature (or average global warming temperature) caused by emission of methane due to various processes involved in the production of rice paddies and farming of livestock populations simultaneously. In the modeling process, six variables are considered, namely, the cumulative biomass density of rice paddies, the cumulative density of livestock populations, the cumulative density of methane formed by various processes involved in the production of rice paddies, the cumulative density of methane formed by various processes involved in the farming of livestock populations, the atmospheric concentration of methane and the average atmospheric temperature. It is assumed that both the cumulative biomass densities of rice paddies and livestock populations follow logistic models with their respective growth rates and carrying capacities. The growth rate of concentration of methane in the atmosphere is assumed to be directly proportional to the cumulative densities of various processes involved in the production of rice paddies as well as in the farming of livestock populations. This growth rate also increases with a constant rate from various natural sources such as wetlands, etc. The growth rate of average global warming temperature is assumed to be proportional to the increased level of methane concentration in the atmosphere from its equilibrium value. It is also assumed that this temperature decreases with a rate proportional to its enhanced level from its equilibrium level caused by various natural factors such as rain fall, snowfall, etc. The proposed model is analyzed using the stability theory of differential equations and numerical simulation. The analysis shows that as the emission of methane from various processes involved in the production of rice paddies and farming of livestock populations increase, the average global warming temperature increases considerably from its equilibrium level. The numerical simulation of the model confirms the analytical results.
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Foschi, Martino, Joseph A. Cartwright, Christopher W. MacMinn, and Giuseppe Etiope. "Evidence for massive emission of methane from a deep‐water gas field during the Pliocene." Proceedings of the National Academy of Sciences 117, no. 45 (October 26, 2020): 27869–76. http://dx.doi.org/10.1073/pnas.2001904117.
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Geologic hydrocarbon seepage is considered to be the dominant natural source of atmospheric methane in terrestrial and shallow‐water areas; in deep‐water areas, in contrast, hydrocarbon seepage is expected to have no atmospheric impact because the gas is typically consumed throughout the water column. Here, we present evidence for a sudden expulsion of a reservoir‐size quantity of methane from a deep‐water seep during the Pliocene, resulting from natural reservoir overpressure. Combining three-dimensional seismic data, borehole data and fluid‐flow modeling, we estimate that 18–27 of the 23–31 Tg of methane released at the seafloor could have reached the atmosphere over 39–241 days. This emission is ∼10% and ∼28% of present‐day, annual natural and petroleum‐industry methane emissions, respectively. While no such ultraseepage events have been documented in modern times and their frequency is unknown, seismic data suggest they were not rare in the past and may potentially occur at present in critically pressurized reservoirs. This neglected phenomenon can influence decadal changes in atmospheric methane.
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Zazzeri, Giulia, Dave Lowry, Rebecca E. Fisher, James L. France, Mathias Lanoisellé, Bryce F. J. Kelly, Jaroslaw M. Necki, et al. "Carbon isotopic signature of coal-derived methane emissions to the atmosphere: from coalification to alteration." Atmospheric Chemistry and Physics 16, no. 21 (November 3, 2016): 13669–80. http://dx.doi.org/10.5194/acp-16-13669-2016.
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Abstract. Currently, the atmospheric methane burden is rising rapidly, but the extent to which shifts in coal production contribute to this rise is not known. Coalbed methane emissions into the atmosphere are poorly characterised, and this study provides representative δ13CCH4 signatures of methane emissions from specific coalfields. Integrated methane emissions from both underground and opencast coal mines in the UK, Australia and Poland were sampled and isotopically characterised. Progression in coal rank and secondary biogenic production of methane due to incursion of water are suggested as the processes affecting the isotopic composition of coal-derived methane. An averaged value of −65 ‰ has been assigned to bituminous coal exploited in open cast mines and of −55 ‰ in deep mines, whereas values of −40 and −30 ‰ can be allocated to anthracite opencast and deep mines respectively. However, the isotopic signatures that are included in global atmospheric modelling of coal emissions should be region- or nation-specific, as greater detail is needed, given the wide global variation in coal type.
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Turner, Alexander J., Christian Frankenberg, and Eric A. Kort. "Interpreting contemporary trends in atmospheric methane." Proceedings of the National Academy of Sciences 116, no. 8 (February 7, 2019): 2805–13. http://dx.doi.org/10.1073/pnas.1814297116.
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Atmospheric methane plays a major role in controlling climate, yet contemporary methane trends (1982–2017) have defied explanation with numerous, often conflicting, hypotheses proposed in the literature. Specifically, atmospheric observations of methane from 1982 to 2017 have exhibited periods of both increasing concentrations (from 1982 to 2000 and from 2007 to 2017) and stabilization (from 2000 to 2007). Explanations for the increases and stabilization have invoked changes in tropical wetlands, livestock, fossil fuels, biomass burning, and the methane sink. Contradictions in these hypotheses arise because our current observational network cannot unambiguously link recent methane variations to specific sources. This raises some fundamental questions: (i) What do we know about sources, sinks, and underlying processes driving observed trends in atmospheric methane? (ii) How will global methane respond to changes in anthropogenic emissions? And (iii), What future observations could help resolve changes in the methane budget? To address these questions, we discuss potential drivers of atmospheric methane abundances over the last four decades in light of various observational constraints as well as process-based knowledge. While uncertainties in the methane budget exist, they should not detract from the potential of methane emissions mitigation strategies. We show that net-zero cost emission reductions can lead to a declining atmospheric burden, but can take three decades to stabilize. Moving forward, we make recommendations for observations to better constrain contemporary trends in atmospheric methane and to provide mitigation support.
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Smith, H. J. "ATMOSPHERIC SCIENCE: Sourcing Methane." Science 316, no. 5826 (May 11, 2007): 799b. http://dx.doi.org/10.1126/science.316.5826.799b.
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Wilson, Jason. "Natural atmospheric methane contributions." Marine Pollution Bulletin 28, no. 4 (April 1994): 194–95. http://dx.doi.org/10.1016/0025-326x(94)90085-x.
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Badr, O., S. D. Probert, and P. W. O'Callaghan. "Origins of atmospheric methane." Applied Energy 40, no. 3 (January 1991): 189–231. http://dx.doi.org/10.1016/0306-2619(91)90057-5.
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Badr, O., S. D. Probert, and P. W. O'Callaghan. "Sinks for atmospheric methane." Applied Energy 41, no. 2 (January 1992): 137–47. http://dx.doi.org/10.1016/0306-2619(92)90041-9.
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Kleinen, Thomas, Sergey Gromov, Benedikt Steil, and Victor Brovkin. "Atmospheric methane since the last glacial maximum was driven by wetland sources." Climate of the Past 19, no. 5 (June 1, 2023): 1081–99. http://dx.doi.org/10.5194/cp-19-1081-2023.
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Abstract. Atmospheric methane (CH4) has changed considerably in the time between the last glacial maximum (LGM) and the preindustrial (PI) periods. We investigate these changes in transient experiments with an Earth system model capable of simulating the global methane cycle interactively, focusing on the rapid changes during the deglaciation, especially pronounced in the Bølling–Allerød (BA) and Younger Dryas (YD) periods. We consider all relevant natural sources and sinks of methane and examine the drivers of changes in methane emissions as well as in the atmospheric lifetime of methane. We find that the evolution of atmospheric methane is largely driven by emissions from tropical wetlands, while variations in the methane atmospheric lifetime are small but not negligible. Our model reproduces most changes in atmospheric methane very well, with the exception of the mid-Holocene decrease in methane, although the timing of ice-sheet meltwater fluxes needs to be adjusted slightly in order to exactly reproduce the variations in the BA and YD.
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Bange, Hermann W., Tom G. Bell, Marcela Cornejo, Alina Freing, Günther Uher, Rob C. Upstill-Goddard, and Guiling Zhang. "MEMENTO: a proposal to develop a database of marine nitrous oxide and methane measurements." Environmental Chemistry 6, no. 3 (2009): 195. http://dx.doi.org/10.1071/en09033.
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Environmental context. Nitrous oxide and methane are atmospheric trace gases and, because they are strong greenhouse gases, they contribute significantly to the ongoing global warming of the Earth’s atmosphere. Despite the well established fact that the world’s oceans release nitrous oxide and methane to the atmosphere, the oceanic emission estimates of both gases are only poorly quantified. The MEMENTO (MarinE MethanE and NiTrous Oxide) database initiative is proposed as an effective way by which existing nitrous oxide and methane measurements can be used to reduce the uncertainty of the oceanic emissions estimates by establishing a global database.
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Holmes, Andrew J., Peter Roslev, Ian R. McDonald, Niels Iversen, Kaj Henriksen, and J. Colin Murrell. "Characterization of Methanotrophic Bacterial Populations in Soils Showing Atmospheric Methane Uptake." Applied and Environmental Microbiology 65, no. 8 (August 1, 1999): 3312–18. http://dx.doi.org/10.1128/aem.65.8.3312-3318.1999.
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ABSTRACT The global methane cycle includes both terrestrial and atmospheric processes and may contribute to feedback regulation of the climate. Most oxic soils are a net sink for methane, and these soils consume approximately 20 to 60 Tg of methane per year. The soil sink for atmospheric methane is microbially mediated and sensitive to disturbance. A decrease in the capacity of this sink may have contributed to the ∼1% · year−1 increase in the atmospheric methane level in this century. The organisms responsible for methane uptake by soils (the atmospheric methane sink) are not known, and factors that influence the activity of these organisms are poorly understood. In this study the soil methane-oxidizing population was characterized by both labelling soil microbiota with14CH4 and analyzing a total soil monooxygenase gene library. Comparative analyses of [14C]phospholipid ester-linked fatty acid profiles performed with representative methane-oxidizing bacteria revealed that the soil sink for atmospheric methane consists of an unknown group of methanotrophic bacteria that exhibit some similarity to type II methanotrophs. An analysis of monooxygenase gene libraries from the same soil samples indicated that an unknown group of bacteria belonging to the α subclass of the class Proteobacteria was present; these organisms were only distantly related to extant methane-oxidizing strains. Studies on factors that affect the activity, population dynamics, and contribution to global methane flux of “atmospheric methane oxidizers” should be greatly facilitated by use of biomarkers identified in this study.
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Topp, Edward, and Elizabeth Pattey. "Soils as sources and sinks for atmospheric methane." Canadian Journal of Soil Science 77, no. 2 (May 1, 1997): 167–77. http://dx.doi.org/10.4141/s96-107.
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Methane is considered to be a significant greenhouse gas. Methane is produced in soils as the end product of the anaerobic decomposition of organic matter. In the absence of oxygen, methane is very stable, but under aerobic conditions it is mineralized to carbon dioxide by methanotrophic bacteria. Soil methane emissions, primarily from natural wetlands, landfills and rice paddies, are estimated to represent about half of the annual global methane production. Oxidation of atmospheric methane by well-drained soils accounts for about 10% of the global methane sink. Whether a soil is a net source or sink for methane depends on the relative rates of methanogenic and methanotrophic activity. A number of factors including pH, Eh, temperature and moisture content influence methane transforming bacterial populations and soil fluxes. Several techniques are available for measuring methane fluxes. Flux estimation is complicated by spatial and temporal variability. Soil management can impact methane transformations. For example, landfilling of organic matter can result in significant methane emissions, whereas some cultural practices such as nitrogen fertilization inhibit methane oxidation by agricultural soils. Key words: Methane, methanogenesis, methane oxidation, soil, flux measurement
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Madhusudhan, Nikku, Subhajit Sarkar, Savvas Constantinou, Måns Holmberg, Anjali A. A. Piette, and Julianne I. Moses. "Carbon-bearing Molecules in a Possible Hycean Atmosphere." Astrophysical Journal Letters 956, no. 1 (October 1, 2023): L13. http://dx.doi.org/10.3847/2041-8213/acf577.
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Abstract The search for habitable environments and biomarkers in exoplanetary atmospheres is the holy grail of exoplanet science. The detection of atmospheric signatures of habitable Earth-like exoplanets is challenging owing to their small planet–star size contrast and thin atmospheres with high mean molecular weight. Recently, a new class of habitable exoplanets, called Hycean worlds, has been proposed, defined as temperate ocean-covered worlds with H2-rich atmospheres. Their large sizes and extended atmospheres, compared to rocky planets of the same mass, make Hycean worlds significantly more accessible to atmospheric spectroscopy with JWST. Here we report a transmission spectrum of the candidate Hycean world K2-18 b, observed with the JWST NIRISS and NIRSpec instruments in the 0.9–5.2 μm range. The spectrum reveals strong detections of methane (CH4) and carbon dioxide (CO2) at 5σ and 3σ confidence, respectively, with high volume mixing ratios of ∼1% each in a H2-rich atmosphere. The abundant CH4 and CO2, along with the nondetection of ammonia (NH3), are consistent with chemical predictions for an ocean under a temperate H2-rich atmosphere on K2-18 b. The spectrum also suggests potential signs of dimethyl sulfide (DMS), which has been predicted to be an observable biomarker in Hycean worlds, motivating considerations of possible biological activity on the planet. The detection of CH4 resolves the long-standing missing methane problem for temperate exoplanets and the degeneracy in the atmospheric composition of K2-18 b from previous observations. We discuss possible implications of the findings, open questions, and future observations to explore this new regime in the search for life elsewhere.
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Joelsson, L. M. T., J. A. Schmidt, E. J. K. Nilsson, T. Blunier, D. W. T. Griffith, S. Ono, and M. S. Johnson. "Development of a new methane tracer: kinetic isotope effect of <sup>13</sup>CH<sub>3</sub>D + OH from 278 to 313 K." Atmospheric Chemistry and Physics Discussions 15, no. 19 (October 15, 2015): 27853–75. http://dx.doi.org/10.5194/acpd-15-27853-2015.
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Abstract. Methane is the second most important long lived greenhouse gas and impacts the oxidative capacity of the Earth's atmosphere. Nontheless there are significant uncertainties in its source budget. Analysis of the isotopic composition of atmospheric methane, including doubly substituted species (e.g. 13CH3D), offers new constraints on the methane source budget as the sources and sinks have distinct isotopic signatures. The most important sink of atmospheric methane is oxidation by OH which accounts for around 90 % of methane removal in the troposphere. Here we present experimentally derived methane + OH kinetic isotope effects and their temperature dependence over the range of 278 to 313 K for CH3D and 13CH3D; the latter is reported here for the first time. We find kCH4/kCH3D=1.31 ± 0.01 and kCH4/k13CH3D = 1.34 ± 0.03 at room temperature, implying that the methane + OH kinetic isotope effect is multiplicative such that (kCH4/k13CH4)(kCH4/kCH3D) = kCH4/k13CH3D to within the experimental uncertainty. In addition the kinetic isotope effect were characterized using transition state theory with tunneling correction. Good agreement between the experimental, quantum chemical and available literature values was obtained. The theoretical calculations show that 13CH3D isotope effects is the product of D- and 13C-isotope effect. Based on the results we conclude that the OH reaction at steady-state can produce an atmospheric clumped isotope signal (Δ(13CH3D) = ln([CH4][13CH3D]/[13CH4][CH3D])) of 0.02 ± 0.02.
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Ferretti, D. F., J. B. Miller, J. W. C. White, K. R. Lassey, D. C. Lowe, and D. M. Etheridge. "Stable isotopes provide revised global limits of aerobic methane emissions from plants." Atmospheric Chemistry and Physics 7, no. 1 (January 17, 2007): 237–41. http://dx.doi.org/10.5194/acp-7-237-2007.
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Abstract. Recently Keppler et al. (2006) discovered a surprising new source of methane – terrestrial plants under aerobic conditions, with an estimated global production of 62–236 Tg yr−1 by an unknown mechanism. This is ~10–40% of the annual total of methane entering the modern atmosphere and ~30–100% of annual methane entering the pre-industrial (0 to 1700 AD) atmosphere. Here we test this reported global production of methane from plants against ice core records of atmospheric methane concentration (CH4) and stable carbon isotope ratios (δ13CH4) over the last 2000 years. Our top-down approach determines that global plant emissions must be much lower than proposed by Keppler et al. (2006) during the last 2000 years and are likely to lie in the range 0–46 Tg yr−1 and 0–176 Tg yr−1 during the pre-industrial and modern eras, respectively.
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Tveit, Alexander T., Anne Grethe Hestnes, Serina L. Robinson, Arno Schintlmeister, Svetlana N. Dedysh, Nico Jehmlich, Martin von Bergen, et al. "Widespread soil bacterium that oxidizes atmospheric methane." Proceedings of the National Academy of Sciences 116, no. 17 (April 8, 2019): 8515–24. http://dx.doi.org/10.1073/pnas.1817812116.
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The global atmospheric level of methane (CH4), the second most important greenhouse gas, is currently increasing by ∼10 million tons per year. Microbial oxidation in unsaturated soils is the only known biological process that removes CH4from the atmosphere, but so far, bacteria that can grow on atmospheric CH4have eluded all cultivation efforts. In this study, we have isolated a pure culture of a bacterium, strain MG08 that grows on air at atmospheric concentrations of CH4[1.86 parts per million volume (p.p.m.v.)]. This organism, namedMethylocapsa gorgona, is globally distributed in soils and closely related to uncultured members of the upland soil cluster α. CH4oxidation experiments and13C-single cell isotope analyses demonstrated that it oxidizes atmospheric CH4aerobically and assimilates carbon from both CH4and CO2. Its estimated specific affinity for CH4(a0s) is the highest for any cultivated methanotroph. However, growth on ambient air was also confirmed forMethylocapsa acidiphilaandMethylocapsa aurea, close relatives with a lower specific affinity for CH4, suggesting that the ability to utilize atmospheric CH4for growth is more widespread than previously believed. The closed genome ofM. gorgonaMG08 encodes a single particulate methane monooxygenase, the serine cycle for assimilation of carbon from CH4and CO2, and CO2fixation via the recently postulated reductive glycine pathway. It also fixes dinitrogen and expresses the genes for a high-affinity hydrogenase and carbon monoxide dehydrogenase, suggesting that atmospheric CH4oxidizers harvest additional energy from oxidation of the atmospheric trace gases carbon monoxide (0.2 p.p.m.v.) and hydrogen (0.5 p.p.m.v.).
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Zhou, Wencai, Xueying Qiu, Yuheng Jiang, Yingying Fan, Shilei Wei, Dongxue Han, Li Niu, and Zhiyong Tang. "Highly selective aerobic oxidation of methane to methanol over gold decorated zinc oxide via photocatalysis." Journal of Materials Chemistry A 8, no. 26 (2020): 13277–84. http://dx.doi.org/10.1039/d0ta02793f.
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Benstead, J., G. M. King, and H. G. Williams. "Methanol Promotes Atmospheric Methane Oxidation by Methanotrophic Cultures and Soils." Applied and Environmental Microbiology 64, no. 3 (March 1, 1998): 1091–98. http://dx.doi.org/10.1128/aem.64.3.1091-1098.1998.
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ABSTRACT Two methanotrophic bacteria, Methylobacter albus BG8 and Methylosinus trichosporium OB3b, oxidized atmospheric methane during batch growth on methanol. Methane consumption was rapidly and substantially diminished (95% over 9 days) when washed cell suspensions were incubated without methanol in the presence of atmospheric methane (1.7 ppm). Methanotrophic activity was stimulated after methanol (10 mM) but not methane (1,000 ppm) addition. M. albus BG8 grown in continuous culture for 80 days with methanol retained the ability to oxidize atmospheric methane and oxidized methane in a chemostat air supply. Methane oxidation during growth on methanol was not affected by methane deprivation. Differences in the kinetics of methane uptake (apparent Km andV max) were observed between batch- and chemostat-grown cultures. The V max and apparent Km values (means ± standard errors) for methanol-limited chemostat cultures were 133 ± 46 nmol of methane 108 cells−1 h−1and 916 ± 235 ppm of methane (1.2 μM), respectively. These values were significantly lower than those determined with batch-grown cultures (V max of 648 ± 195 nmol of methane 108 cells−1 h−1 and apparent Km of 5,025 ± 1,234 ppm of methane [6.3 μM]). Methane consumption by soils was stimulated by the addition of methanol. These results suggest that methanol or other nonmethane substrates may promote atmospheric methane oxidation in situ.
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Joelsson, L. M. T., J. A. Schmidt, E. J. K. Nilsson, T. Blunier, D. W. T. Griffith, S. Ono, and M. S. Johnson. "Kinetic isotope effects of <sup>12</sup>CH<sub>3</sub>D + OH and <sup>13</sup>CH<sub>3</sub>D + OH from 278 to 313 K." Atmospheric Chemistry and Physics 16, no. 7 (April 11, 2016): 4439–49. http://dx.doi.org/10.5194/acp-16-4439-2016.
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Abstract. Methane is the second most important long-lived greenhouse gas and plays a central role in the chemistry of the Earth's atmosphere. Nonetheless there are significant uncertainties in its source budget. Analysis of the isotopic composition of atmospheric methane, including the doubly substituted species 13CH3D, offers new insight into the methane budget as the sources and sinks have distinct isotopic signatures. The most important sink of atmospheric methane is oxidation by OH in the troposphere, which accounts for around 84 % of all methane removal. Here we present experimentally derived methane + OH kinetic isotope effects and their temperature dependence over the range of 278 to 313 K for CH3D and 13CH3D; the latter is reported here for the first time. We find kCH4/kCH3D = 1.31 ± 0.01 and kCH4/k13CH3D = 1.34 ± 0.03 at room temperature, implying that the methane + OH kinetic isotope effect is multiplicative such that (kCH4/k13CH4)(kCH4/kCH3D) = kCH4/k13CH3D, within the experimental uncertainty, given the literature value of kCH4/k13CH4 = 1.0039 ± 0.0002. In addition, the kinetic isotope effects were characterized using transition state theory with tunneling corrections. Good agreement between the experimental, quantum chemical, and available literature values was obtained. Based on the results we conclude that the OH reaction (the main sink of methane) at steady state can produce an atmospheric clumped isotope signal (Δ(13CH3D) = ln([CH4][13CH3D]/[13CH4][CH3D])) of 0.02 ± 0.02. This implies that the bulk tropospheric Δ(13CH3D) reflects the source signal with relatively small adjustment due to the sink signal (i.e., mainly OH oxidation).
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Archer, D. "A model of the methane cycle, permafrost, and hydrology of the Siberian continental margin." Biogeosciences 12, no. 10 (May 21, 2015): 2953–74. http://dx.doi.org/10.5194/bg-12-2953-2015.
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Abstract. A two-dimensional model of a sediment column, with Darcy fluid flow, biological and thermal methane production, and permafrost and methane hydrate formation, is subjected to glacial–interglacial cycles in sea level, alternately exposing the continental shelf to the cold atmosphere during glacial times and immersing it in the ocean in interglacial times. The glacial cycles are followed by a "long-tail" 100 kyr warming due to fossil fuel combustion. The salinity of the sediment column in the interior of the shelf can be decreased by hydrological forcing to depths well below sea level when the sediment is exposed to the atmosphere. There is no analogous advective seawater-injecting mechanism upon resubmergence, only slower diffusive mechanisms. This hydrological ratchet is consistent with the existence of freshwater beneath the sea floor on continental shelves around the world, left over from the last glacial period. The salt content of the sediment column affects the relative proportions of the solid and fluid H2O-containing phases, but in the permafrost zone the salinity in the pore fluid brine is a function of temperature only, controlled by equilibrium with ice. Ice can tolerate a higher salinity in the pore fluid than methane hydrate can at low pressure and temperature, excluding methane hydrate from thermodynamic stability in the permafrost zone. The implication is that any methane hydrate existing today will be insulated from anthropogenic climate change by hundreds of meters of sediment, resulting in a response time of thousands of years. The strongest impact of the glacial–interglacial cycles on the atmospheric methane flux is due to bubbles dissolving in the ocean when sea level is high. When sea level is low and the sediment surface is exposed to the atmosphere, the atmospheric flux is sensitive to whether permafrost inhibits bubble migration in the model. If it does, the atmospheric flux is highest during the glaciating, sea level regression (soil-freezing) part of the cycle rather than during deglacial transgression (warming and thawing). The atmospheric flux response to a warming climate is small, relative to the rest of the methane sources to the atmosphere in the global budget, because of the ongoing flooding of the continental shelf. The increased methane flux due to ocean warming could be completely counteracted by a sea level rise of tens of meters on millennial timescales due to the loss of ice sheets, decreasing the efficiency of bubble transit through the water column. The model results give no indication of a mechanism by which methane emissions from the Siberian continental shelf could have a significant impact on the near-term evolution of Earth's climate, but on millennial timescales the release of carbon from hydrate and permafrost could contribute significantly to the fossil fuel carbon burden in the atmosphere–ocean–terrestrial carbon cycle.
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MacAyeal, Douglas R., and Dean R. Lindstrom. "Effects of Glaciation on Methane-Hydrate Stability." Annals of Glaciology 14 (1990): 183–85. http://dx.doi.org/10.3189/s0260305500008533.
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Temperature and pressure changes within subglacial sediments caused by déglaciation favor a phase change from methane hydrate to methane gas. If released to the atmosphere, this gas could have contributed significantly to the increased atmospheric methane concentration during interglacial periods. Using a numerical reconstruction of sediment temperatures and ice-sheet loads, the total sediment volume in the Eurasian Arctic that is subject to this phase change is estimated to be 2.8 × 1014 m3.
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MacAyeal, Douglas R., and Dean R. Lindstrom. "Effects of Glaciation on Methane-Hydrate Stability." Annals of Glaciology 14 (1990): 183–85. http://dx.doi.org/10.1017/s0260305500008533.
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Temperature and pressure changes within subglacial sediments caused by déglaciation favor a phase change from methane hydrate to methane gas. If released to the atmosphere, this gas could have contributed significantly to the increased atmospheric methane concentration during interglacial periods. Using a numerical reconstruction of sediment temperatures and ice-sheet loads, the total sediment volume in the Eurasian Arctic that is subject to this phase change is estimated to be 2.8 × 1014 m3.
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Maasakkers, Joannes D., Daniel J. Jacob, Melissa P. Sulprizio, Tia R. Scarpelli, Hannah Nesser, Jian-Xiong Sheng, Yuzhong Zhang, et al. "Global distribution of methane emissions, emission trends, and OH concentrations and trends inferred from an inversion of GOSAT satellite data for 2010–2015." Atmospheric Chemistry and Physics 19, no. 11 (June 12, 2019): 7859–81. http://dx.doi.org/10.5194/acp-19-7859-2019.
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Abstract. We use 2010–2015 observations of atmospheric methane columns from the GOSAT satellite instrument in a global inverse analysis to improve estimates of methane emissions and their trends over the period, as well as the global concentration of tropospheric OH (the hydroxyl radical, methane's main sink) and its trend. Our inversion solves the Bayesian optimization problem analytically including closed-form characterization of errors. This allows us to (1) quantify the information content from the inversion towards optimizing methane emissions and its trends, (2) diagnose error correlations between constraints on emissions and OH concentrations, and (3) generate a large ensemble of solutions testing different assumptions in the inversion. We show how the analytical approach can be used, even when prior error standard deviation distributions are lognormal. Inversion results show large overestimates of Chinese coal emissions and Middle East oil and gas emissions in the EDGAR v4.3.2 inventory but little error in the United States where we use a new gridded version of the EPA national greenhouse gas inventory as prior estimate. Oil and gas emissions in the EDGAR v4.3.2 inventory show large differences with national totals reported to the United Nations Framework Convention on Climate Change (UNFCCC), and our inversion is generally more consistent with the UNFCCC data. The observed 2010–2015 growth in atmospheric methane is attributed mostly to an increase in emissions from India, China, and areas with large tropical wetlands. The contribution from OH trends is small in comparison. We find that the inversion provides strong independent constraints on global methane emissions (546 Tg a−1) and global mean OH concentrations (atmospheric methane lifetime against oxidation by tropospheric OH of 10.8±0.4 years), indicating that satellite observations of atmospheric methane could provide a proxy for OH concentrations in the future.
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Smith, Amy Tetlow. "Environmental factors affecting global atmospheric methane concentrations." Progress in Physical Geography: Earth and Environment 19, no. 3 (September 1995): 322–35. http://dx.doi.org/10.1177/030913339501900302.
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Methane is a greenhouse gas of largely biological origin. Micro-organisms responsible for production of much of the atmospheric methane are directly affected by climate resulting in potential feedbacks between the atmosphere and the biosphere. Our current understanding of the role of methane in the climate system is reviewed in this article, with a brief discussion of biological, chemical, and physical processes responsible for the spatial and temporal distribution of atmos pheric methane. The magnitude of most methane sources is highly speculative, and their distributions are qualitatively understood. Most terrestrial source regions have been surveyed, but few have been studied in much detail. The strength of enteric sources is based on laboratory measurements of emissions from a few animals and estimates of global populations. Accuracy of the resulting flux size and distribution is highly suspect. Data available on either magnitude or distribution of non-biogenic methane sources are scarce. Models of the influence of climate on biological methane sources are primarily regressions dependent on measures of heat and water in the environment. Process-based models derived from biological and physical principles are called for in order to address environmental conditions unlike the present.
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Xu, Zhichao, Wei Shan, Ying Guo, Chengcheng Zhang, and Lisha Qiu. "Swamp Wetlands in Degraded Permafrost Areas Release Large Amounts of Methane and May Promote Wildfires through Friction Electrification." Sustainability 14, no. 15 (July 27, 2022): 9193. http://dx.doi.org/10.3390/su14159193.
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Affected by global warming, permafrost degradation releases a large amount of methane gas, and this part of flammable methane may increase the frequency of wildfires. To study the influence mechanism of methane emission on wildfires in degraded permafrost regions, we selected the northwest section of Xiaoxing’an Mountains in China as the study area, and combined with remote sensing data, we conducted long-term monitoring of atmospheric electric field, temperature, methane concentration, and other observation parameters, and further carried out indoor gas–solid friction tests. The study shows that methane gas (the concentration of methane at the centralized leakage point is higher than 10,000 ppm) in the permafrost degradation area will release rapidly in spring, and friction with soil, surface plant residues, and water vapor will accelerate atmospheric convection and generate electrostatic and atmospheric electrodischarge phenomena on the surface. The electrostatic and atmospheric electrodischarge accumulated on the surface will further ignite the combustibles near the surface, such as methane gas and plant residues. Therefore, the gradual release of methane gas into the air promotes the feedback mechanism of lightning–wildfire–vegetation, and increases the risk of wildfire in degraded permafrost areas through frictional electrification (i.e., electrostatic and atmospheric electrodischarge).
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Lassey, K. R., D. C. Lowe, and A. M. Smith. "The atmospheric cycling of radiomethane and the ''fossil fraction'' of the methane source." Atmospheric Chemistry and Physics Discussions 6, no. 3 (June 21, 2006): 5039–56. http://dx.doi.org/10.5194/acpd-6-5039-2006.
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Abstract. The cycling of 14CH4 (''radiomethane'') through the atmosphere has been strongly perturbed in the industrial era by the release of 14C-free methane from geologic reservoirs (''fossil methane'' emissions), and in the nuclear era, especially since ca 1970, by the direct release of nucleogenic radiomethane from nuclear power facilities. Contemporary measurements of atmospheric radiomethane have been used to estimate the proportion of fossil methane in the global methane source (the ''fossil fraction''), but such estimates carry high uncertainty due to the ill-determined nuclear-power source. We exploit an analysis in a companion paper of the global radiomethane budget through the nuclear era, using contemporary measurements of atmospheric radiomethane since 1986 to quantify both the fossil fraction and the strength of the nuclear power source. We deduce that 28.6±1.9% (1 s.d.) of the global methane source has fossil origin, a fraction which may include some 14C-depleted refractory carbon fraction such as in aged peat deposits. The co-estimated strength of the global nuclear-power source of radiomethane is consistent with values inferred independently from local nuclear facilities.
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He, Jian, Vaishali Naik, Larry W. Horowitz, Ed Dlugokencky, and Kirk Thoning. "Investigation of the global methane budget over 1980–2017 using GFDL-AM4.1." Atmospheric Chemistry and Physics 20, no. 2 (January 23, 2020): 805–27. http://dx.doi.org/10.5194/acp-20-805-2020.
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Abstract. Changes in atmospheric methane abundance have implications for both chemistry and climate as methane is both a strong greenhouse gas and an important precursor for tropospheric ozone. A better understanding of the drivers of trends and variability in methane abundance over the recent past is therefore critical for building confidence in projections of future methane levels. In this work, the representation of methane in the atmospheric chemistry model AM4.1 is improved by optimizing total methane emissions (to an annual mean of 580±34 Tg yr−1) to match surface observations over 1980–2017. The simulations with optimized global emissions are in general able to capture the observed trend, variability, seasonal cycle, and latitudinal gradient of methane. Simulations with different emission adjustments suggest that increases in methane emissions (mainly from agriculture, energy, and waste sectors) balanced by increases in methane sinks (mainly due to increases in OH levels) lead to methane stabilization (with an imbalance of 5 Tg yr−1) during 1999–2006 and that increases in methane emissions (mainly from agriculture, energy, and waste sectors) combined with little change in sinks (despite small decreases in OH levels) during 2007–2012 lead to renewed growth in methane (with an imbalance of 14 Tg yr−1 for 2007–2017). Compared to 1999–2006, both methane emissions and sinks are greater (by 31 and 22 Tg yr−1, respectively) during 2007–2017. Our tagged tracer analysis indicates that anthropogenic sources (such as agriculture, energy, and waste sectors) are more likely major contributors to the renewed growth in methane after 2006. A sharp increase in wetland emissions (a likely scenario) with a concomitant sharp decrease in anthropogenic emissions (a less likely scenario), would be required starting in 2006 to drive the methane growth by wetland tracer. Simulations with varying OH levels indicate that a 1 % change in OH levels could lead to an annual mean difference of ∼4 Tg yr−1 in the optimized emissions and a 0.08-year difference in the estimated tropospheric methane lifetime. Continued increases in methane emissions along with decreases in tropospheric OH concentrations during 2008–2015 prolong methane's lifetime and therefore amplify the response of methane concentrations to emission changes. Uncertainties still exist in the partitioning of emissions among individual sources and regions.
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Wang, Jian, Lei Xue, Qianyao Ma, Feng Xu, Gaobin Xu, Shibo Yan, Jiawei Zhang, et al. "The role of oceanic ventilation and terrestrial outflow in atmospheric non-methane hydrocarbons over the Chinese marginal seas." Atmospheric Chemistry and Physics 24, no. 15 (August 8, 2024): 8721–36. http://dx.doi.org/10.5194/acp-24-8721-2024.
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Abstract. Non-methane hydrocarbons (NMHCs) in the marine atmosphere have been studied extensively due to their important roles in regulating atmospheric chemistry and climate. However, very little is known about the distribution and sources of NMHCs in the lower atmosphere over the marginal seas of China. Herein, we characterized the atmospheric NMHCs (C2–C5) in both the coastal cities and the marginal seas of China in the spring of 2021, with a focus on identifying the sources of NMHCs in the coastal atmosphere. The NMHCs in urban atmospheres, especially alkanes, were significantly higher compared to those in the marine atmosphere, suggesting that terrestrial NMHCs may be an important reservoir/source in the marine atmosphere. A significant correlation was observed between the alkane concentrations and the distances from sampling sites to the nearest land or retention of air mass over land, indicating that alkanes in the marine atmosphere are largely influenced by terrestrial inputs through air mass transport. For alkenes, a greater impact from oceanic emissions was determined due to the lower terrestrial concentrations, short atmospheric lifetime, and substantial sea-to-air fluxes of alkenes compared to alkanes (489 ± 454 vs. 129 ± 106 nmol m−2 d−1). As suggested by the positive matrix factorization, terrestrial inputs contributed to 89 % of alkanes and 69.6 % of alkenes in Chinese marginal seas, subsequently contributing to 84 % of the ozone formation potential associated with C2–C5 NMHCs. These findings underscore the significance of terrestrial outflow in controlling the distribution and composition of atmospheric NMHCs in the marginal seas of China.
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Espic, C., M. Liechti, M. Battaglia, D. Paul, T. Röckmann, and S. Szidat. "Compound-Specific Radiocarbon Analysis of Atmospheric Methane: A New Preconcentration and Purification Setup." Radiocarbon 61, no. 5 (July 22, 2019): 1461–76. http://dx.doi.org/10.1017/rdc.2019.76.
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ABSTRACTMethane contributes substantially to global warming as the second most important anthropogenic greenhouse gas. Radiocarbon (14C) measurements of atmospheric methane can be used as a source apportionment tool, as they allow distinction between thermogenic and biogenic methane sources. However, these measurements remain scarce due to labor-intensive methods required. A new setup for the preparation of atmospheric methane samples for radiocarbon analysis is presented. The system combines a methane preconcentration line with a preparative gas chromatography technique to isolate pure methane samples for a compound-specific radiocarbon analysis. In order to minimize sample preparation time, we designed a simplified preconcentration line for the extraction of methane from 50 L atmospheric air, which corresponds to 50 µg C as required for a reliable 14C analysis of methane-derived CO2 gas measurement with accelerator mass spectrometry (AMS). The system guarantees a quantitative extraction of methane from atmospheric air samples for 14C analysis, with a good repeatability and a low processing blank. The setup was originally designed for the measurement of samples with low methane concentrations, but it can also be adapted to apportion sources from environmental compartments with high methane levels such as freshwaters or wetlands.