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Atmospheric methane

About: Atmospheric methane is a research topic. Over the lifetime, 2034 publications have been published within this topic receiving 119616 citations.


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Journal ArticleDOI
TL;DR: It is shown that net-zero cost emission reductions can lead to a declining atmospheric burden, but can take three decades to stabilize.
Abstract: 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.

188 citations

Journal ArticleDOI
14 Dec 2017-Nature
TL;DR: Close agreement is found between the ‘top-down’ and combined ‘bottom-up’ estimates of large CH4 emissions from trees adapted to permanent or seasonal inundation can account for the emission source that is required to close the Amazon CH4 budget.
Abstract: Wetlands are the largest global source of atmospheric methane (CH4), a potent greenhouse gas. However, methane emission inventories from the Amazon floodplain, the largest natural geographic source of CH4 in the tropics, consistently underestimate the atmospheric burden of CH4 determined via remote sensing and inversion modelling, pointing to a major gap in our understanding of the contribution of these ecosystems to CH4 emissions. Here we report CH4 fluxes from the stems of 2,357 individual Amazonian floodplain trees from 13 locations across the central Amazon basin. We find that escape of soil gas through wetland trees is the dominant source of regional CH4 emissions. Methane fluxes from Amazon tree stems were up to 200 times larger than emissions reported for temperate wet forests and tropical peat swamp forests, representing the largest non-ebullitive wetland fluxes observed. Emissions from trees had an average stable carbon isotope value (δ13C) of -66.2 ± 6.4 per mil, consistent with a soil biogenic origin. We estimate that floodplain trees emit 15.1 ± 1.8 to 21.2 ± 2.5 teragrams of CH4 a year, in addition to the 20.5 ± 5.3 teragrams a year emitted regionally from other sources. Furthermore, we provide a 'top-down' regional estimate of CH4 emissions of 42.7 ± 5.6 teragrams of CH4 a year for the Amazon basin, based on regular vertical lower-troposphere CH4 profiles covering the period 2010-2013. We find close agreement between our 'top-down' and combined 'bottom-up' estimates, indicating that large CH4 emissions from trees adapted to permanent or seasonal inundation can account for the emission source that is required to close the Amazon CH4 budget. Our findings demonstrate the importance of tree stem surfaces in mediating approximately half of all wetland CH4 emissions in the Amazon floodplain, a region that represents up to one-third of the global wetland CH4 source when trees are combined with other emission sources.

188 citations

Journal ArticleDOI
TL;DR: In this paper, the authors measured Methane fluxes and vertical profiles of CH4 mixing ratios in different German soils both in situ and in soil cores using a method based on relaxation experiments with argon.
Abstract: Methane fluxes and vertical profiles of CH4 mixing ratios were measured in different German soils both in situ and in soil cores. Atmospheric CH4 was oxidized in the soil by microorganisms resulting in an average CH4 flux of −1.39±1.5 μmol-CH4 m−2 h−1. Methane deposition showed only a weak positive correlation (r2 = 0.38) with soil temperature but a relatively strong negative correlation (r2 = 0.61) with soil moisture indicating limitation of the CH4 flux by gas transport. Diffusion experiments in soil cores showed that gas transport between atmosphere and soil was faster than microbial CH4 oxidation. However, the diffusion from the gas-filled soil pores to the CH4 oxidizing microorganisms may have been limiting. The main CH4− oxidizing activity was located in a few centimeter thick subsurface soil layer at the top of the Ah horizon, whereas no activity was found in the overlying O horizons and in deep soil below about 20-cm depth. In contrast, the highest CO2 production was found in the topmost O horizon. The effective diffusion coefficient of CH4 in soil was determined using a method based on relaxation experiments with argon. The diffusion coefficient was used to model the CH4 oxidation in soil cores from the vertical profiles of CH4 mixing ratios. The thus calculated CH4 oxidation rates and their localization in the soil profile compared fairly well with those determined directly from incubated soil samples. Fluxes were similar within a factor of 2–4 whether derived from the model, calculated from the measured CH4 oxidation rates of soil samples, or measured directly.

187 citations

Journal ArticleDOI
11 Aug 2011-Nature
TL;DR: It is shown that the late-twentieth-century changes in the CH4 growth rates are best explained by reduced microbial sources in the Northern Hemisphere, and observations in the interhemispheric difference of 13C effectively exclude reduced fossil fuel emissions as the primary cause of the slowdown.
Abstract: Atmospheric methane (CH(4)) increased through much of the twentieth century, but this trend gradually weakened until a stable state was temporarily reached around the turn of the millennium, after which levels increased once more. The reasons for the slowdown are incompletely understood, with past work identifying changes in fossil fuel, wetland and agricultural sources and hydroxyl (OH) sinks as important causal factors. Here we show that the late-twentieth-century changes in the CH(4) growth rates are best explained by reduced microbial sources in the Northern Hemisphere. Our results, based on synchronous time series of atmospheric CH(4) mixing and (13)C/(12)C ratios and a two-box atmospheric model, indicate that the evolution of the mixing ratio requires no significant change in Southern Hemisphere sources between 1984 and 2005. Observed changes in the interhemispheric difference of (13)C effectively exclude reduced fossil fuel emissions as the primary cause of the slowdown. The (13)C observations are consistent with long-term reductions in agricultural emissions or another microbial source within the Northern Hemisphere. Approximately half (51 ± 18%) of the decrease in Northern Hemisphere CH(4) emissions can be explained by reduced emissions from rice agriculture in Asia over the past three decades associated with increases in fertilizer application and reductions in water use.

186 citations

Journal ArticleDOI
TL;DR: In this paper, a stepwise regression model was used to investigate the role of soil temperature in methane emissions in Swedish landfills, finding that soil temperature was negatively correlated with biological methane oxidation, which strongly suggests that biological oxidation is an important regulating factor.

186 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202395
2022153
202175
202077
201974
201872