Papers on methane emissions

This is a list of papers on methane emissions from a variety of different sources. 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 (December 13, 2016): Yu et al. (2013) added.
UPDATE (August 15, 2013): Nisbet (2002) and Brook et al. (2000) added.
UPDATE (April 1, 2011): Thom et al. (1993) and Eisma et al. (1994) added.
UPDATE (August 7, 2010): Shakhova et al. (2010) added.

Evidence for elevated emissions from high-latitude wetlands contributing to high atmospheric CH₄ concentration in the early Holocene – Yu et al. (2013)
The major increase in atmospheric methane (CH₄) concentration during the last glacial-interglacial transition provides a useful example for understanding the interactions and feedbacks among Earth’s climate, biosphere carbon cycling, and atmospheric chemistry. However, the causes of CH₄ doubling during the last deglaciation are still uncertain and debated. Although the ice-core data consistently suggest a dominant contribution from northern high-latitude wetlands in the early Holocene, identifying the actual sources from the ground-based data has been elusive. Here we present data syntheses and a case study from Alaska to demonstrate the importance of northern wetlands in contributing to high atmospheric CH₄ concentration in the early Holocene. Our data indicate that new peatland formation as well as peat accumulation in northern high-latitude regions increased more than threefold in the early Holocene in response to climate warming and the availability of new habitat as a result of deglaciation. Furthermore, we show that marshes and wet fens that represent early stages of wetland succession were likely more widespread in the early Holocene. These wetlands are associated with high CH₄ emissions due to high primary productivity and the presence of emergent plant species that facilitate CH₄ transport to the atmosphere. We argue that early wetland succession and rapid peat accumulation and expansion (not simply initiation) contributed to high CH₄ emissions from northern regions, potentially contributing to the sharp rise in atmospheric CH₄ at the onset of the Holocene.
[Abstract, FULL TEXT]
Citation: Yu, Z., J. Loisel, M. R. Turetsky, S. Cai, Y. Zhao, S. Frolking, G. M. MacDonald, and J. L. Bubier (2013), Evidence for elevated emissions from high-latitude wetlands contributing to high atmospheric CH4 concentration in the early Holocene, Global Biogeochem. Cycles, 27, 131–140, doi:10.1002/gbc.20025.

Geochemical and geophysical evidence of methane release over the East Siberian Arctic Shelf – Shakhova et al. (2010) “The East Siberian Arctic Shelf (ESAS), which includes the Laptev Sea, the East Siberian Sea, and the Russian part of the Chukchi Sea, has not been considered to be a methane (CH₄) source to hydrosphere or atmosphere because subsea permafrost, which underlies most of the ESAS, was believed, first, not to be conducive to methanogenesis and, second, to act as an impermeable lid, preventing CH₄ escape through the seabed. Here recent observational data obtained during summer (2005–2006) and winter (2007) expeditions indicate the ubiquitous presence of elevated dissolved CH₄ and an elevated atmospheric CH₄ mixing ratio. The CH₄ data were also analyzed together with high resolution seismic (HRS) data obtained by means of a “Sonic M-141” system consisting of a high-resolution profiler and side-scan sonar mounted in a towed fish during the Transdrift-X Expedition (2004) onboard the R/V Yakov Smirnitskiy. Results show anomalously high concentrations of dissolved CH₄ (up to 5 μM) and an episodically (nongradually) increasing atmospheric mixing ratio of CH₄ (up to 8.2 ppm) in some areas of the ESAS. A most likely source is year-round CH₄ release through taliks (columns of thawed sediments within permafrost) from seabed CH₄ reservoirs such as shallow hydrates and geological sources. Such releases occur not only within the areas underlain by fault zones but also outside of them. This points to permafrost’s failure to further preserve CH₄ deposits in the ESAS. The total amount of carbon preserved within the ESAS as organic matter and ready to release CH₄ from seabed deposits is predicted to be ∼1400 Gt. Release of only a small fraction of this reservoir, which was sealed with impermeable permafrost for thousands of years, would significantly alter the annual CH₄ budget and have global implications, because the shallowness of the ESAS allows the majority of CH₄ to pass through the water column and escape to the atmosphere.” N. Shakhova, I. Semiletov, I. Leifer, A. Salyuk, P. Rekant, D. Kosmach, Journal of Geophysical Research: Oceans (1978–2012), Volume 115, Issue C8, August 2010, DOI: 10.1029/2009JC005602.

Escape of methane gas from the seabed along the West Spitsbergen continental margin – Westbrook et al. (2009) “More than 250 plumes of gas bubbles have been discovered emanating from the seabed of the West Spitsbergen continental margin, in a depth range of 150–400 m, at and above the present upper limit of the gas hydrate stability zone (GHSZ). Some of the plumes extend upward to within 50 m of the sea surface. The gas is predominantly methane. Warming of the northward-flowing West Spitsbergen current by 1°C over the last thirty years is likely to have increased the release of methane from the seabed by reducing the extent of the GHSZ, causing the liberation of methane from decomposing hydrate. If this process becomes widespread along Arctic continental margins, tens of Teragrams of methane per year could be released into the ocean.” [Full text]

Tropical methane emissions: A revised view from SCIAMACHY onboard ENVISAT – Frankenberg et al. (2008) “Methane retrievals from near-infrared spectra recorded by the SCIAMACHY instrument onboard ENVISAT hitherto suggested unexpectedly large tropical emissions. Even though recent studies confirm substantial tropical emissions, there were indications for an unresolved error in the satellite retrievals. 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. The new retrievals are applied in a four-dimensional variational (4D-VAR) data assimilation system to derive a first estimate of the impact on tropical CH₄ sources. Compared to inversions based on previous SCIAMACHY retrievals, annual tropical emission estimates are reduced from 260 to about 201 Tg CH₄ but still remain higher than previously anticipated.” [Full text]

Anomalies of methane in the atmosphere over the East Siberian shelf: Is there any sign of methane leakage from shallow shelf hydrates? – Shakhova et al. (2008) “Extremely high concentrations of methane (up to 8 ppm) in the atmospheric layer above the sea surface along with anomalously high concentrations of dissolved methane in the water column (up to 560 nM, or 12000% of super saturation), registered during a summertime cruise over the ESS in September 2005, were analyzed together with available data obtained during previous and subsequent expeditions to distinguish between possible methane sources of different origin, potential, and mobility. Using indirect evidence it was shown that one such source may be highly potential and extremely mobile shallow methane hydrates, whose stability zone is seabed permafrost-related and could be disturbed upon permafrost development, degradation, and thawing. … …we consider release of up to 50 Gt of predicted amount of hydrate storage as highly possible for abrupt release at any time. That may cause ~12-times increase of modern atmospheric methane burden with consequent catastrophic greenhouse warming.”

Early anthropogenic CH₄ emissions and the variation of CH₄ and ¹³CH₄ over the last millennium – Houweling et al. (2008) “The main idea is that emissions of isotopically depleted CH₄, from, for example, rice cultivation, domestic ruminants, and waste treatment started increasing earlier than the isotopically enriched emissions from fossil fuel, which started with the start of industrialization. However, because the observed increase of atmospheric methane only started around 1750 A.D., these preindustrial anthropogenic emissions must have been accompanied by a net reduction of natural CH₄ sources during the Little Ice Age (LIA) compensating for the increase of anthropogenic emissions during that period. Results of transient box model simulations for the last millennium show that under the new hypothesis a close agreement can be obtained between model and measurements.” [Full text]

Methane hydrate stability and anthropogenic climate change – Archer (2007) “The hydrate reservoir is so large that if 10% of the methane were released to the atmosphere within a few years, it would have an impact on the Earth’s radiation budget equivalent to a factor of 10 increase in atmospheric CO₂. … Hydrates are releasing methane to the atmosphere today in response to anthropogenic warming, for example along the Arctic coastline of Siberia. However most of the hydrates are located at depths in soils and ocean sediments where anthropogenic warming and any possible methane release will take place over time scales of millennia. Individual catastrophic releases like landslides and pockmark explosions are too small to reach a sizable fraction of the hydrates. The carbon isotopic excursion at the end of the Paleocene has been interpreted as the release of thousands of Gton C, possibly from hydrates, but the time scale of the release appears to have been thousands of years, chronic rather than catastrophic.” [Full text]

Methane emissions from terrestrial plants under aerobic conditions – Keppler et al. (2006) “Here we demonstrate using stable carbon isotopes that methane is readily formed in situ in terrestrial plants under oxic conditions by a hitherto unrecognized process. Significant methane emissions from both intact plants and detached leaves were observed during incubation experiments in the laboratory and in the field. If our measurements are typical for short-lived biomass and scaled on a global basis, we estimate a methane source strength of 62–236 Tg yr^-1 for living plants and 1–7 Tg yr^-1 for plant litter (1 Tg = 10¹² g).” [Full text]

Late Quaternary Atmospheric CH₄ Isotope Record Suggests Marine Clathrates Are Stable – Sowers (2006) “One explanation for the abrupt increases in atmospheric CH₄, that occurred repeatedly during the last glacial cycle involves clathrate destabalization events. Because marine clathrates have a distinct deuterium/hydrogen (D/H) isotope ratio, any such destabilization event should cause the D/H ratio of atmospheric CH₄ (δD_CH4) to increase. Analyses of air trapped in the ice from the second Greenland ice sheet project show stable and/or decreasing δD_CH4 values during the end of the Younger and Older Dryas periods and one stadial period, suggesting that marine clathrates were stable during these abrupt warming episodes. Elevated glacial δD_CH4 values may be the result of a lower ratio of net to gross wetland CH₄ emissions and an increase in petroleum-based emissions.”

Methane bubbling from Siberian thaw lakes as a positive feedback to climate warming – Walter et al. (2006) “Thaw lakes in North Siberia are known to emit methane, but the magnitude of these emissions remains uncertain because most methane is released through ebullition (bubbling), which is spatially and temporally variable. Here we report a new method of measuring ebullition and use it to quantify methane emissions from two thaw lakes in North Siberia. … We find that thawing permafrost along lake margins accounts for most of the methane released from the lakes, and estimate that an expansion of thaw lakes between 1974 and 2000, which was concurrent with regional warming, increased methane emissions in our study region by 58 per cent. Furthermore, the Pleistocene age (35,260–42,900 years) of methane emitted from hotspots along thawing lake margins indicates that this positive feedback to climate warming has led to the release of old carbon stocks previously stored in permafrost.” [Full text]

Assessing Methane Emissions from Global Space-Borne Observations – Frankenberg et al. (2005) “In the past two centuries, atmospheric methane has more than doubled and now constitutes 20% of the anthropogenic climate forcing by greenhouse gases. Yet its sources are not well quantified, introducing uncertainties in its global budget. We retrieved the global methane distribution by using spaceborne near-infrared absorption spectroscopy. In addition to the expected latitudinal gradient, we detected large-scale patterns of anthropogenic and natural methane emissions. Furthermore, we observed unexpectedly high methane concentrations over tropical rainforests, revealing that emission inventories considerably underestimated methane sources in these regions during the time period of investigation (August through November 2003).” [Full text]

The distribution of methane on the Siberian Arctic shelves: Implications for the marine methane cycle – Shakhova et al. (2005) “We present two years of data obtained during the late summer period (September 2003 and September 2004) for both the ESS and LS shelves. According to our data, the surface layer of shelf water was supersaturated up to 2500% relative to the present average atmospheric methane content of 1.85 ppm. Anomalously high concentrations (up to 154 nM or 4400% supersaturation) of dissolved methane in the bottom layer of shelf water suggest that the bottom layer is somehow affected by near-bottom sources. Considering the possible formation mechanisms of such plumes, we favor thermo-abrasion and the effects of shallow gas or gas hydrates release.” [Full text]

Global inventory of methane clathrate: sensitivity to changes in the deep ocean – Buffett & Archer (2004) “We present a mechanistic model for the distribution of methane clathrate in marine sediments, and use it to predict the sensitivity of the steady-state methane inventory to changes in the deep ocean. … Preferred values for these parameters are taken from previous studies of both passive and active margins, yielding a global estimate of 3×10¹⁸ g of carbon (3000 Gton C) in clathrate and 2×10¹⁸ g (2000 Gton C) in methane bubbles. The predicted methane inventory decreases by 85% in response to 3 °C of warming.” [Full text]

Have sudden large releases of methane from geological reservoirs occurred since the Last Glacial Maximum, and could such releases occur again? – Nisbet (2002) “Methane emissions from geological reservoirs may have played a major role in the sudden events terminating glaciation, both at the start of the Bølling/Allerød and also at the end of the Younger Dryas. These reservoirs include Arctic methane hydrates and also methane hydrate stored in offshore marine sediments in tropical and temperate latitudes. Emissions from hydrate stores may have resonated with tropical wetland emissions, each reinforcing the other. Because methane is such a powerful greenhouse gas, much smaller emissions of methane, compared with carbon dioxide, are required in order to have the same short–term impact by climate forcing. The methane–linked hypothesis has much geological support from sea–floor evidence of emission. However, Greenland ice–core records have been interpreted as showing methane as a consequential factor, rather than the leader, of change. This interpretation can be challenged on the grounds that temperature gradients in Greenland ice record local changes and local timing of a step–like shift in weather fronts, while methane concentrations record changes on a hemispheric and global scale. There are large remaining hydrate reservoirs in the Arctic and in shelf sediments globally, and there is substantial risk of further emissions.” Euan G. Nisbet, Phil. Trans. R. Soc. Lond. A 15 April 2002 vol. 360 no. 1793 581-607, doi: 10.1098/rsta.2001.0958.

Measurements of an anomalous global methane increase during 1998 – Dlugokencky et al. (2001) “The increased growth rate during 1998 corresponds to an increase in the imbalance between CH₄ sources and sinks equal to ∼24 Tg CH₄, the largest perturbation observed in 16 years of measurements. We suggest that wetland and boreal biomass burning sources may have contributed to the anomaly.”

On the origin and timing of rapid changes in atmospheric methane during the Last Glacial Period – Brook et al. (2000) “We present high resolution records of atmospheric methane from the GISP2 (Greenland Ice Sheet Project 2) ice core for four rapid climate transitions that occurred during the past 50 ka: the end of the Younger Dryas at 11.8 ka, the beginning of the Bølling-Allerød period at 14.8 ka, the beginning of interstadial 8 at 38.2 ka, and the beginning of interstadial 12 at 45.5 ka. During these events, atmospheric methane concentrations increased by 200–300 ppb over time periods of 100–300 years, significantly more slowly than associated temperature and snow accumulation changes recorded in the ice core record. We suggest that the slower rise in methane concentration may reflect the timescale of terrestrial ecosystem response to rapid climate change. We find no evidence for rapid, massive methane emissions that might be associated with large-scale decomposition of methane hydrates in sediments. With additional results from the Taylor Dome Ice Core (Antarctica) we also reconstruct changes in the interpolar methane gradient (an indicator of the geographical distribution of methane sources) associated with some of the rapid changes in atmospheric methane. The results indicate that the rise in methane at the beginning of the Bølling-Allerød period and the later rise at the end of the Younger Dryas were driven by increases in both tropical and boreal methane sources. During the Younger Dryas (a 1.3 ka cold period during the last deglaciation) the relative contribution from boreal sources was reduced relative to the early and middle Holocene periods.” Edward J. Brook, Susan Harder, Jeff Severinghaus, Eric J. Steig, Cara M. Sucher, Global Biogeochemical Cycles, Volume 14, Issue 2, pages 559–572, June 2000, DOI: 10.1029/1999GB001182. [Full text]

Continuing decline in the growth rate of the atmospheric methane burden – Dlugokencky et al. (1998) “Measurements have revealed that although the global atmospheric methane burden continues to increase with significant interannual variability, the overall rate of increase has slowed. 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.”

Changing concentration, lifetime and climate forcing of atmospheric methane – Lelieveld et al. (1998) “Here, we review sources and sink estimates and we present global 3D model calculations, showing that the main features of the global CH₄ distribution are well represented. The model has been used to derive the total CH₄ emission source, being about 600 Tg yr^-1. Based on published results of isotope measurements the total contribution of fossil fuel related CH₄ emissions has been estimated to be about 110 Tg yr^-1.”

Methane emissions from cattle – Johnson & Johnson (1995) “Ruminant livestock can produce 250 to 500 L of methane per day. This level of production results in estimates of the contribution by cattle to global warming that may occur in the next 50 to 100 yr to be a little less than 2%.” [Full text]

A dramatic decrease in the growth rate of atmospheric methane in the northern hemisphere during 1992 – Dlugokencky et al. (1994) “Global measurements of atmospheric methane have revealed a sharp decrease in the growth rate in the Northern Hemisphere during 1992. The average trend for the Northern Hemisphere during 1983–1991 was (11.6±0.2) ppbv yr⁻¹, but the increase in 1992 was only (1.8±1.6) ppbv. In the Southern Hemisphere, the average increase (1983–1991) was (11.1±0.2) ppbv yr⁻¹, and the 1992 increase was (7.7±1.0) ppbv. Various possibilities for a change in methane sources or sinks are discussed, but the most likely explanation is a change in an anthropogenic source such as fossil fuel exploitation, which can be rapidly and easily affected by man’s activities.”

Determination of European methane emissions, using concentration and isotope measurements – Eisma et al. (1994) “The determination of methane emissions on a regional scale is needed in order to reduce some of the uncertainties in the global methane budget. Our measurements of the concentration and the Carbon-13 isotope composition (δ¹³C) of atmospheric methane are, combined with trajectories, used to get insight in the type and size of the methane emissions of a large area.” Roos Eisma, Alex T. Vermeulen and W. M. Kieskamp, Environmental Monitoring and Assessment, Volume 31, Numbers 1-2, 197-202, DOI: 10.1007/BF00547197.

The regional budget of atmospheric methane of a highly populated area – Thom et al. (1993) “A regional methane budget for the catchment area of Heidelberg has been established, using quasi-continuous measurements of the atmospheric methane concentration and its stable isotope ratios (¹³C/¹²C, D/H). Methane in Heidelberg shows a mean concentration offset of 155 ppbv relative to background air. This concentration offset is due to a direct influence from – mainly anthropogenic – continental European methane sources. Using parallel atmospheric ²²²Radon observations, and the observed CH₄ concentration offset, we estimated the mean CH₄ flux density within the catchment area to be (12±6) gCH4 m^-2 yr^-1. This is three times the global average for continental surfaces. From the stable isotope observations we derived the isotopic composition of the mean methane source to be δ¹³Csource(PDB) = (−54.3±1.7)‰ and δDsource(SMOW) = (−270±41)‰. In an independent approach we evaluated the distribution of methane sources from source statistics within a catchment area of ca. 500 km radius around Heidelberg. With help of a simple dispersion model we then calculated their contributions to the concentration offset at the sampling site. Using the isotopic composition of the mean source as constraint to adjust the specific emissions of individual sources it turned out that the major contributions to the observed concentration offset in Heidelberg are from cattle (37%), landfills (27%), coal mining (12%), agricultural wastes (11%), burning of fuels (8%), and gas leakages (5%). This source mix is more or less the same as in the whole catchment area (e.g. Central Europe).” Marcus Thom, Rainer Bösinger, Martina Schmidt and Ingeborg Levin, The regional budget of atmospheric methane of a highly populated area, Chemosphere, Volume 26, Issues 1-4, January-February 1993, Pages 143-160, doi:10.1016/0045-6535(93)90418-5.

Role of methane clathrates in past and future climates – MacDonald (1990) “Methane occurrences and the organic carbon content of sediments are the bases used to estimate the amount of carbon currently stored as clathrates. The estimate of about 11,000 Gt of carbon for ocean sediments, and about 400 Gt for sediments under permafrost regions is in rough accord with an independent estimate by Kvenvolden of 10,000 Gt. … The sensitivity of clathrates to surface change, the time scales involved, and the large quantities of carbon stored as clathrate indicate that clathrates may have played a significant role in modifying the composition of the atmosphere during the ice ages. The release of methane and its subsequent oxidation to carbon dioxide may be responsible for the observed swings in atmospheric methane and carbon dioxide concentrations during glacial times.”

Methane Emission From Natural Wetlands: Global Distribution, Area, and Environmental Characteristics of Sources – Matthews & Fung (1987) “A global data base of wetlands at 1º resolution has been developed from the integration of three independent global, digital sources: (1) vegetation, (2) soil properties and (3) fractional inundation in each 1º cell. … The annual methane emission from wetlands is ∽110 Tg, well within the range of previous estimates (11-300 Tg).”