Topic
Atmospheric methane
About: Atmospheric methane is a research topic. Over the lifetime, 2034 publications have been published within this topic receiving 119616 citations.
Papers published on a yearly basis
Papers
More filters
TL;DR: It is suggested that changes in the strength of tropical methane sources and sinks (wetlands, atmospheric oxidation) controlled the atmospheric methane budget, with an additional source input during major terminations as the retreat of the northern ice sheet allowed higher methane emissions from extending periglacial wetlands.
Abstract: Atmospheric methane is an important greenhouse gas and a sensitive indicator of climate change and millennial-scale temperature variability. Its concentrations over the past 650,000 years have varied between 350 and 800 parts per 109 by volume (p.p.b.v.) during glacial and interglacial periods, respectively. In comparison, present-day methane levels of 1,770 p.p.b.v. have been reported. Insights into the external forcing factors and internal feedbacks controlling atmospheric methane are essential for predicting the methane budget in a warmer world. Here we present a detailed atmospheric methane record from the EPICA Dome C ice core that extends the history of this greenhouse gas to 800,000 yr before present. The average time resolution of the new data is 380 yr and permits the identification of orbital and millennial-scale features. Spectral analyses indicate that the long-term variability in atmospheric methane levels is dominated by 100,000 yr glacial–interglacial cycles up to 400,000 yr ago with an increasing contribution of the precessional component during the four more recent climatic cycles. We suggest that changes in the strength of tropical methane sources and sinks (wetlands, atmospheric oxidation), possibly influenced by changes in monsoon systems and the position of the intertropical convergence zone, controlled the atmospheric methane budget, with an additional source input during major terminations as the retreat of the northern ice sheet allowed higher methane emissions from extending periglacial wetlands. Millennial-scale changes in methane levels identified in our record as being associated with Antarctic isotope maxima events are indicative of ubiquitous millennial-scale temperature variability during the past eight glacial cycles.
839 citations
TL;DR: In this article, the authors examined past trends in the concentration of methane in the atmosphere, the sources and sinks that determine its growth rate, and the factors that will affect its growth rates in the future.
763 citations
TL;DR: A detection of methane in the martian atmosphere by the Planetary Fourier Spectrometer onboard the Mars Express spacecraft is reported, and the global average methane mixing ratio is found to be 10 ± 5 parts per billion by volume.
Abstract: We report a detection of methane in the martian atmosphere by the Planetary Fourier Spectrometer onboard the Mars Express spacecraft. The global average methane mixing ratio is found to be 10 ± 5 parts per billion by volume (ppbv). However, the mixing ratio varies between 0 and 30 ppbv over the planet. The source of methane could be either biogenic or nonbiogenic, including past or present subsurface microorganisms, hydrothermal activity, or cometary impacts.
713 citations
TL;DR: In this paper, the occurrence, production, and origin of natural gas and methane are reviewed, and the physical properties, structure, and chemical reactivity of methane are also reviewed.
Abstract: As the simplest hydride of carbon and the major constituent of natural gas, methane has attracted increased attention in recent years. An important factor has been the recognition of the significance of world natural gas reserves to energy and chemicals production in the 21st century. This expectation is lined to the gradual depletion of oil reserves and to the possible influence of greenhouse global warming effect on energy policy. The combustion of fossil fuel has caused a rise in the CO{sub 2} level in the atmosphere from an estimated preindustrial level of 280 ppm to the current 360 ppm. If current climate models are correct, this may cause a global warming trend in the next few decades. If public resistance to nuclear energy remains strong, natural gas is likely to become a more important energy source. The low C:H ratio of CH{sub 4} means that on combustion it can furnish a much larger amount of energy per CO{sub 2} molecule released than can oil (approximate ratio, CH{sub 2}) or coal (approximate ratio, CH). This article reviews the occurrence, production, and origin of natural gas and methane. The physical properties, structure, and chemical reactivity of methane are also reviewed. 180 refs.
705 citations
TL;DR: In this article, the authors present a 3D model of the global CH 4 distribution, showing that the main features of the CH4 distribution are well represented by the global 3D chemistry-transport and radiative transfer calculations.
Abstract: Previous studies on ice core analyses and recent in situ measurements have shown that CH 4 has increased from about 075–173 μmol/mol during the past 150 years Here, we review sources and sink estimates and we present global 3D model calculations, showing that the main features of the global CH 4 distribution are well represented The model has been used to derive the total CH 4 emission source, being about 600 Tg yr -1 Based on published results of isotope measurements the total contribution of fossil fuel related CH 4 emissions has been estimated to be about 110 Tg yr -1 However, the individual coal, natural gas and oil associated CH 4 emissions can not be accurately quantified In particular natural gas and oil associated emissions remain speculative Since the total anthropogenic CH 4 source is about 410 Tg yr -1 (∼70% of the total source) and the mean recent atmospheric CH 4 increase is ∼20 Tg yr -1 an anthropogenic source reduction of 5% could stabilize the atmospheric CH 4 level We have calculated the indirect chemical effects of increasing CH 4 on climate forcing on the basis of global 3D chemistry-transport and radiative transfer calculations These indicate an enhancement of the direct radiative effect by about 30%, in agreement with previous work The contribution of CH 4 (direct and indirect effects) to climate forcing during the past 150 years is 057W m −2 (direct 044W m −2 , indirect 013 W m −2 ) This is about 35% of the climate forcing by CO 2 (16W m −2 ) and about 22% of the forcing by all long-lived greenhouse gases (26 W m −2 ) Scenario calculations (IPCC-IS92a) indicate that the CH 4 lifetime in the atmosphere increased by about 25–30%during the past 150 years to a current value of 79 years Future lifetime changes are expected to be much smaller, about 6%, mostly due to the expected increase of tropospheric O 3 (→OH) in the tropics The global mean concentration of CH 4 may increase to about 255 μmol/mol, its lifetime is expected to increase to 84 years in the year 2050 Further, we have calculated a CH 4 global warming potential (GWP) of 21 (kgCH 4 /kgCO 2 ) over a time horizon of 100 years, in agreement with IPCC (1996) Scenario calculations indicate that the importance of the climate forcing by CH 4 (including indirect effects) relative to that of CO 2 will decrease in future; currently this is about 35%, while this is expected to decrease to about 15% in the year 2050 DOI: 101034/j1600-08891998t01-1-00002x
704 citations