Papers on atmospheric methane concentration
Posted by Ari Jokimäki on April 8, 2010
This is a list of papers on atmospheric methane concentration measurements. The list is not complete, and will most likely be updated in the future in order to make it more thorough and more representative.
UPDATE (September 4, 2013): Dlugokencky et al. (2009), Frankenberg et al. (2011), and Rigby et al. (2008) moved to a separate list on recent renewed growth of atmospheric methane.
UPDATE (February 18, 2011): Dlugokencky et al. (2009) and Frankenberg et al. (2011) added.
UPDATE (April 27, 2010): Couple of methane related papers moved here from the general GHG measurement list. Sasakawa et al. (2010) added.
Modern methane concentration
There’s a separate list for papers on recent renewed growth of atmospheric methane.
Continuous measurements of methane from a tower network over Siberia – Sasakawa et al. (2010) “We have been conducting continuous measurements of CH4 concentration from an expanding network of towers (JR-STATION: Japan–Russia Siberian Tall Tower Inland Observation Network) located in taiga, steppe, and wetland biomes of Siberia since 2004. High daytime means (>2000 ppb) observed simultaneously at several towers during winter, together with in-situ weather data and NCEP/NCAR reanalysis data, indicate that high pressure systems caused CH4 accumulation at sub-continental scale due to the widespread formation of an inversion layer. Daytime means sometimes exceeded 2000 ppb, particularly in the summer of 2007 when temperature and precipitation rates were anomalously high over West Siberia, which implies that CH4 emission from wetlands were exceptionally high in 2007. Many hot spots detected by MODIS in the summer of 2007 illustrate that the contribution of biomass burning also cannot be neglected. Daytime mean CH4 concentrations from the Siberian tower sites were generally higher than CH4 values reported at NOAA coastal sites in the same latitudinal zone, and the difference in concentrations between two sets of sites was reproduced with a coupled Eulerian–Lagrangian transport model. Simulations of emissions from different CH4 sources suggested that the major contributor to variation switched from wetlands during summer to fossil fuel during winter.”
A new insight on tropospheric methane in the Tropics – first year from IASI hyperspectral infrared observations – Crevoisier et al. (2009) Seasonal cycle and spatial distribution of methane measured. “Simultaneous observations from the Infrared Atmospheric Sounding Interferometer (IASI) and from the Advanced Microwave Sounding Unit (AMSU), launched together onboard the European MetOp platform in October 2006, are used to retrieve a mid-to-upper tropospheric content of methane (CH4) in clear-sky conditions, in the Tropics, over sea, for the first 16 months of operation of MetOp (July 2007–October 2008).” [Full text]
Tropical methane emissions: A revised view from SCIAMACHY onboard ENVISAT – Frankenberg et al. (2008) “Here we identify a retrieval error related to inaccuracies in water vapor spectroscopic parameters, causing a substantial overestimation of methane correlated with high water vapor abundances. We report on the overall implications of an update in water spectroscopy on methane retrievals with special focus on the tropics where the impact is largest.” [Full text]
Seasonal cycles of mixing ratio and 13C in atmospheric methane at Suva, Fiji – Lowe et al. (2004) “A series of clean air samples has been collected at a coastal site near Suva, Fiji (18°08′S, 178°26′E) by researchers at the University of the South Pacific. These samples, covering the period 1994 to mid-2002, have been analyzed for methane mixing ratio and δ13C and provide the first ever time series of these species reported for this part of the tropical South Pacific. The data show large variability when compared to similar time series of the same species measured farther south in the extratropical Pacific. In particular, summer variability at the Fiji site is high, especially through La Niña conditions.”
Tropospheric methane retrieved from ground-based near-IR solar absorption spectra – Washenfelder et al. (2003) “High-resolution near-infrared solar absorption spectra recorded between 1977 and 1995 at the Kitt Peak National Solar Observatory are analyzed to retrieve column abundances of methane (CH4), hydrogen fluoride (HF), and oxygen (O2). Employing a stratospheric “slope equilibrium” relationship between CH4 and HF, the varying contribution of stratospheric CH4 to the total column is inferred. Variations in the CH4 column due to changes in surface pressure are determined from the O2 column abundances. By this technique, CH4 tropospheric volume mixing ratios are determined with a precision of ~0.5%. These display behavior similar to Mauna Loa in situ surface measurements, with a seasonal peak-to-peak amplitude of approximately 30 ppbv and a nearly linear increase between 1977 and 1983 of 18.0 ± 0.8 ppbv yr−1, slowing significantly after 1990.” [Full text]
Atmospheric methane levels off: Temporary pause or a new steady-state? – Dlugokencky et al. (2003) “The globally-averaged atmospheric methane abundance determined from an extensive network of surface air sampling sites was constant at ~1751 ppb from 1999 through 2002. Assuming that the methane lifetime has been constant, this implies that during this 4-year period the global methane budget has been at steady state. We also observed a significant decrease in the difference between northern and southern polar zonal annual averages of CH4 from 1991 to 1992. … Based on current knowledge of the global methane budget and how it has changed with time, it is not possible to tell if the atmospheric methane burden has peaked, or if we are only observing a persistent, but temporary pause in its increase.” [Full text]
In situ measurements of atmospheric methane at GAGE/AGAGE sites during 1985–2000 and resulting source inferences – Cunnold et al. (2002) “Continuous measurements of methane since 1986 at the Global Atmospherics Gases Experiment/Advanced Global Atmospherics Gases Experiment (GAGE/AGAGE) surface sites are described. … The measurements exhibit good agreement with coincident measurements of air samples from the same locations analyzed by Climate Monitoring and Diagnostics Laboratory (CMDL) except for differences of approximately 5 ppb before 1989 (GAGE lower) and about 4 ppb from 1991 to 1995 (GAGE higher). … The measurements combined with a 12-box atmospheric model and an assumed atmospheric lifetime of 9.1 years indicates net annual emissions (emissions minus soil sinks) of 545 Tg CH4 with a variability of only ±20 Tg from 1985 to 1997 but an increase in the emissions in 1998 of 37 ± 10 Tg.”
Methane concentration and isotopic composition measurements with a mid-infrared quantum-cascade laser – Kosterev et al. (1999) “A quantum-cascade laser operating at a wavelength of 8.1μm was used for high-sensitivity absorption spectroscopy of methane (CH4). … A CH4 concentration of 15.6 parts in 106(ppm) in 50 Torr of air was measured in a 43-cm path length with ±0.5-ppm accuracy when the signal was averaged over 400 scans.” [Full text]
Continuing decline in the growth rate of the atmospheric methane burden – Dlugokencky et al. (1998) “Here we present an analysis of methane measurements from a global air sampling network that suggests that, assuming constant OH concentration, global annual methane emissions have remained nearly constant during the period 1984–96, and that the decreasing growth rate in atmospheric methane reflects the approach to a steady state on a timescale comparable to methane’s atmospheric lifetime.”
The growth rate and distribution of atmospheric methane – Dlugokencky et al. (1994) “Methane was measured in air samples collected approximately weekly from a globally distributed network of sites from 1983 to 1992. Sites range in latitude from 90°S to 82°N. … The data reveal a strong north‐south gradient in methane with an annual mean difference of about 140 ppb between the northernmost and southernmost sampling sites. … Seasonal cycle amplitudes in the high north are about twice those observed in the high southern hemisphere. … The average increase in the globally averaged methane mixing ratio over the period of these measurements is (11.1 ± 0.2) ppb yr−1. Globally, the growth rate for methane decreased from approximately 13.5 ppb yr−1 in 1983 to about 9.3 ppb yr−1 in 1991. The growth rate of methane in the northern hemisphere during 1992 was near zero. Various possibilities for the long‐term, slow decrease in the methane growth rate over the last decade and the rapid change in growth rate in the northern hemisphere in 1992 are given. The most likely explanation is a change in a methane source influenced directly by human activities, such as fossil fuel production.”
Atmospheric methane data for the period 1986-1988 from the NOAA /CMDL global cooperative flask sampling network – Lang et al. (1990) “The memorandum builds on previous work (Lang et al., 1987) to extend by three years the record of atmospheric methane measurements made through the NOAA/CMDL cooperative flask sampling network. The format of the data presentations given here follows very closely that used by Lang et al., (1990). Details of the flask sampling methods and the analytical and calibrational procedures are given. Results from individual flask samples are both tabulated and plotted. Monthly average methane concentrations at each site are also tabulated.”
Atmospheric methane data for the period 1983-1985 from the NOAA /GMCC global cooperative flask sampling network – Lang et al. (1990) “Details of relevant aspects of the NOAA Global Monitoring for Climate Change (GMCC) program to measure atmospheric methane concentrations through its global, cooperative, flask sampling network are discussed. These aspects include the history of the development of the program; details of the sampling network; the flasks and the flask sampling methods; the analytical instrumentation and methods; and the calibration gases and methods. The data from individual flask samples are tabulated, as are the monthly average methane concentrations. Through adequate documentation it is more likely that the full value of these methane measurements will be realized in long-term studies of the greenhouse effect and climate change.”
World-wide increase in tropospheric methane, 1978–1983 – Blake & Rowland (1986) “Tropospheric concentrations of methane in remote locations have averaged a yearly world-wide increase of 0.018±0.002 parts per million by volume (ppmv) during the period from January 1978 to December 1983. The concentrations in the north temperate zone are always greater than those in the south temperate zone by 7±1% because the major methane sources are all predominantly located in the northern hemisphere. The average world-wide tropospheric concentration of methane in dry air was 1.625 ppmv at the end of 1983, measured against an NBS standard certified as 0.97 ppmv (but with an accuracy of only ±1%).”
Sources, Sinks, and Seasonal Cycles of Atmospheric Methane – Khalil & Rasmussen (1983) “The extensive set of self consistent measurements of methane are reported and analyzed showing that methane has increased during the last 3–4 years at rates of 1–1.9% per year all over the world at sites ranging from inside the arctic circle to the south pole. Observational results are used to estimate the sources, sinks, seasonal cycles of CH4, and the effects of human activities on its atmospheric abundance.”
Atmospheric Methane (CH4): Trends and Seasonal Cycles – Rasmussen & Khalil (1981) “On the basis of 22 months of almost continuous, automated, GC/FID measurements of atmospheric CH4 at Cape Meares (45°N), we show that the concentration of CH4 is increasing at about 2% per yr (±0.5% yr−1). The data also revealed stable seasonal cycles with peak concentrations in October and minimum concentrations in July. The magnitude of the seasonal variations during these months is about ±20 ppbv from the average (∼±1.2%).”
Methane concentration in the past
Orbital and millennial-scale features of atmospheric CH4 over the past 800,000 years – Loulergue et al. (2008) “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.” [Full text]
Atmospheric Methane and Nitrous Oxide of the Late Pleistocene from Antarctic Ice Cores – Spahni et al. (2005) “The European Project for Ice Coring in Antarctica Dome C ice core enables us to extend existing records of atmospheric methane (CH4) and nitrous oxide (N2O) back to 650,000 years before the present. A combined record of CH4 measured along the Dome C and the Vostok ice cores demonstrates, within the resolution of our measurements, that preindustrial concentrations over Antarctica have not exceeded 773 ± 15 ppbv (parts per billion by volume) during the past 650,000 years. Before 420,000 years ago, when interglacials were cooler, maximum CH4 concentrations were only about 600 ppbv, similar to lower Holocene values.” [supplementary information]
Variations in atmospheric methane concentration during the Holocene epoch – Blunier et al. (2002) “Here we present a continuous, high-resolution record of atmospheric methane from 8,000 to 1,000 yr BP, from the GRIP ice core in central Greenland. Unlike most other climate proxies from ice cores (such as oxygen isotope composition and electrical conductivity), methane concentrations show significant variations—up to 15%—during the Holocene. We have proposed1 that variations in the hydrological cycle at low latitudes are the dominant control on past levels of atmospheric methane. This is now supported by the observation that the lowest methane concentrations in our new record occur in the mid-Holocene, when many tropical lakes dried up. The concentration increases during the Late Holocene, probably owing to an increasing contribution from northern wetlands.”
Atmospheric methane between 1000 A.D. and present: Evidence of anthropogenic emissions and climatic variability – Etheridge et al. (1998) “Atmospheric methane mixing ratios from 1000 A.D. to present are measured in three Antarctic ice cores, two Greenland ice cores, the Antarctic firn layer, and archived air from Tasmania, Australia. … From 1000 to 1800 A.D. the global mean methane mixing ratio averaged 695 ppb and varied about 40 ppb, contemporaneous with climatic variations. Interpolar (N-S) differences varied between 24 and 58 ppb. The industrial period is marked by high methane growth rates from 1945 to 1990, peaking at about 17 ppb yr−1 in 1981 and decreasing significantly since.”
Rapid Variations in Atmospheric Methane Concentration During the Past 110,000 Years – Brook et al. (1996) “A methane record from the GISP2 ice core reveals that millennial-scale variations in atmospheric methane concentration characterized much of the past 110,00 years. As previously observed in a shorter record from central Greenland, abrupt concentration shifts of about 50 to 300 parts per billion by volume were coeval with most of the interstadial warming events (better known as Dansgaard-Oeschger events) recorded in the GISP2 ice core throughout the last glacial period. The magnitude of the rapid concentration shifts varied on a longer time scale in a manner consistent with variations in Northern Hemisphere summer insolation, which suggests that insolation may have modulated the effects of interstadial climate change on the terrestrial biosphere.”
Changes in tropospheric methane between 1841 and 1978 from a high accumulation-rate Antarctic ice core – Etheridge et al. (1992) “To determine in detail how the concentration of tropospheric methane has changed from preindustrial until recent times, an ice core with remarkably fine air-age resolution was investigated. The core, called DE08, contains air from as recent as 1978 with an age resolution (80% air-age distribution width) of about 14 years. … Methane concentrations in the DE08 record increased from 823 parts per billion by volume (ppbv, in dry air) in 1841 to 1481 ppbv in 1978. The measurement precision was ± 22 ppbv (1σ). The similarity of the methane records from the DE08 ice core and from Cape Grim, Tasmania implies that there was insignificant modification during the enclosure of air in the ice or during its recovery and analysis. Methane concentrations in the period from 1951 to 1978, which were previously estimated from sporadic and inferred data, are particularly well defined in this core. The DE08 record shows that methane growth rates have generally increased since the onset of the industrial revolution to a level of 14 ppbv year−1 (about 1% per year) by the 1970s. The exception was between about 1920-1945 when the growth rate stabilised at about 5 ppbv year−1.”
Ice-core record of atmospheric methane over the past 160,000 years – Chappellaz et al. (1990) “Methane measurements along the Vostok ice core are reported which reveal strong variations of past CH4 concentrations in the 350-650 ppbv range, well below the present atmospheric conditions. These variations are well-correlated with climate change deduced from the isotopic composition of the Vostok ice core. Spectral analysis of the record indicates periodicities close to those of orbital variations. These CH4 changes are interpreted here as being the result of fluctuations in wetland areas induced by climate changes. It is suggested that the participation of CH4 and associated chemical feedbacks to warming during deglaciations represents about 30 percent of that due to CO2.”
Atmospheric Methane in the Recent and Ancient Atmospheres: Concentrations, Trends, and Interhemispheric Gradient – Rasmussen & Khalil (1984) “Upon analyzing some 80 ice core samples from the polar regions we found that the concentration of methane 250 years ago and earlier was only 700 (±30) ppbv, or about 45% of present levels. A rapid and significant increase of atmospheric methane started about 150 years ago. The rate of increase has escalated since then and is about 1.3%/yr at present. We also found that the concentration of methane in the atmosphere 250 years ago and earlier, when methane was not increasing, was 10% (±4%) higher in the Arctic as compared to the Antarctic. This finding is consistent with the expected ratio of about 1.07–1.11 obtained from a global mass balance model and the primarily land-based natural sources of methane, estimated to be about 280 Tg/yr, which may have been the only sources several hundred years ago, when human activities did not contribute significantly to the global methane cycle.”