Atmospheric methane

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

Termites Facilitate Methane Oxidation and Shape the Methanotrophic Community

Abstract: Termite-derived methane contributes 3 to 4% to the total methane budget globally. Termites are not known to harbor methane-oxidizing microorganisms (methanotrophs). However, a considerable fraction of the methane produced can be consumed by methanotrophs that inhabit the mound material, yet the methanotroph ecology in these environments is virtually unknown. The potential for methane oxidation was determined using slurry incubations under conditions with high (12%) and in situ (∼0.004%) methane concentrations through a vertical profile of a termite (Macrotermes falciger) mound and a reference soil. Interestingly, the mound material showed higher methanotrophic activity. The methanotroph community structure was determined by means of a pmoA-based diagnostic microarray. Although the methanotrophs in the mound were derived from populations in the reference soil, it appears that termite activity selected for a distinct community. Applying an indicator species analysis revealed that putative atmospheric methane oxidizers (high-indicator-value probes specific for the JR3 cluster) were indicative of the active nest area, whereas methanotrophs belonging to both type I and type II were indicative of the reference soil. We conclude that termites modify their environment, resulting in higher methane oxidation and selecting and/or enriching for a distinct methanotroph population.

Simultaneous mass balance inverse modeling of methane and carbon monoxide

Abstract: [1] We perform a simultaneous mass-balance inversion of atmospheric methane (CH4) and carbon monoxide (CO) using measurements from the NOAA/CMDL Cooperative Air Sampling Network and a model of tropospheric transport and background chemistry over the period 1990–2000. Our method has a spatial resolution of a semihemisphere and a temporal resolution of 1 month. The deduced CO sources show relatively low interannual variability except around the major biomass burning event in 1997–1998, when we calculate an anomalous emission between July 1997 and December 1998 of 270 Tg(CO). This is enough to suppress the modeled global air mass weighted hydroxyl radical (OH) concentration during this time by 2.2%, and account for 75% of the observed increase in CH4 mixing ratios during 1998. We compare our implied CH4/CO emissions factors with published biomass burning emissions factors, suggesting that the remainder of the increase in CH4 observed in 1998 is due to anomalously high biomass burning emissions, with CH4 emissions from wetlands showing a small negative anomaly in 1998.

Atmospheric Methane: Trends and Impacts

Abstract: The concentration of methane (CH4), the most abundant organic trace gas in the atmosphere, has increased dramatically over the last few centuries, more than doubling its concentration. Increasing concentrations of methane are of special concern because of their effects on climate and atmospheric chemistry. On a per molecule basis, additional methane is much more effective as a greenhouse gas than additional CO2. Methane is also important to both tropospheric and stratospheric chemistry. Here, we examine past trends in the concentration of methane, the sources and sinks affecting its growth rate, and the factors that could affect its growth rate in the future. This study also examines the current understanding of the effects of methane on atmospheric chemistry and climate.