Talk:Atmospheric methane/Archive 1

Archive 1

Concerning section on 'Sudden release from methane clathrates'

The statements seem perfectly reasonable with the exception of the word 'sudden'. How quickly must the methane clathrates be release to qualify as sudden? Days, months, years, decades? In the context of the Paleocene–Eocene Thermal Maximum of 55 million years ago, would one thousand years be sudden? I'm going to edit out sudden and remove the tag "This section needs additional citations for verification. Please help improve this article by adding reliable references. Unsourced material may be challenged and removed. (July 2008)". Please let me know your views on this matter.

--Id447 (talk) 20:02, 20 June 2010 (UTC)

File:MethaneSourcePieChart.jpg Nominated for speedy Deletion

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File:MethaneSourcePieChart.jpg Nominated for speedy Deletion

An image used in this article, File:MethaneSourcePieChart.jpg, has been nominated for speedy deletion at Wikimedia Commons for the following reason: Copyright violations What should I do?

Speedy deletions at commons tend to take longer than they do on Wikipedia, so there is no rush to respond. If you feel the deletion can be contested then please do so (commons:COM:SPEEDY has further information). Otherwise consider finding a replacement image before deletion occurs. A further notification will be placed when/if the image is deleted. This notification is provided by a Bot, currently under trial --CommonsNotification (talk) 10:43, 6 May 2011 (UTC)

obsolete

See section above #Updated Graphs. (this section a template placeholder). Green Cardamom (talk) 04:39, 14 December 2011 (UTC)

Yes, someone should do something about that William M. Connolley (talk) 18:56, 19 December 2011 (UTC)

Al Rodger has given permission for https://sites.google.com/site/marclimategraphs/_/rsrc/1321521600926/collection/G04.jpg to be used and I have inserted it. crandles (talk) 23:11, 20 December 2011 (UTC)

The old one has the rate of change on, too, which would be nice to have William M. Connolley (talk) 23:37, 20 December 2011 (UTC)

Water Vapor

Methane plus oxygen plus ultraviolet light yields water vapor and carbon monoxide and infrared radiation. Carbon monoxide plus ultraviolet light plus oxygen yields carbon dioxide and infrared radiation. Water vapor is far more efficient as an absorbent of infrared than is carbon dioxide. Additionally, all of the biogenic producers of methane also produce carbon dioxide and water vapor as well as infrared radiation which are all released into the atmosphere. My point? Methane is far more important as a greenhouse gas than carbon dioxide is because it leads to such a large increase in atmospheric water vapor. -- Brothernight (talk) 13:04, 17 December 2011 (UTC)

As with so many other "I figured something out that scientists haven't", there is a flaw in your argumentation. The flaw is that you assume that the total amount of water vapor in the atmosphere increases... it doesn't. The residence time for water vapor is short. See Water vapor#Water vapor in Earth's atmosphere... in very simplistic terms (and thus a Lie to children), the total amount of water vapor in the atmosphere only changes if the temperature or pressure changes. --Kim D. Petersen (talk) 13:51, 17 December 2011 (UTC)

Largely true, but with one wrinkle, which is that (assuming I remember right) above the tropopause methane is a fair source of WV, since little WV makes it through the tropopause. But I think the absolute amounts would still be low William M. Connolley (talk) 23:39, 20 December 2011 (UTC)

Added impacts section with Ramanathan quote to back up your memory crandles (talk) 23:29, 23 December 2011 (UTC)

Could do with some more on impacts section like effects on ozone ..... crandles (talk) 23:48, 23 December 2011 (UTC)

Global Methane Cycle

Item C. in the list is "Forest fire – Mass burning of organic matter releases huge amounts of methane into the atmosphere." Methane released during forest fires would also burn in the fire (just like in Natural Gas). The Article should be edited to remove the above item C.Ugaap (talk) 02:32, 30 December 2012 (UTC)

Contribution of landfills

The section on landfills states:

Due to the large collections of organic matter and availability of anaerobic conditions, landfills serve to be the largest source of atmospheric methane in the United States.

A footnote gives the website uspowerpartners.org as a reference for this statement. The web page linked from the reference does not offer any further information about how they have derived this purported fact, and it is at odds with official government statistics compiled by the EPA, see [1]. According to figures given by the EPA for 2009, landfills in the US emitted 117.5 TgCO2-equiv, which puts them in a distant third place behind “natural gas systems” (221.2 TgCO2-equiv) and “enteric fermentation” (139.8 TgCO2-equiv).

It is possible that someone at Power Partners misinterpreted a sentence in the EPA report which begins: “In the United States, the largest methane emissions come from the decomposition of wastes in landfills ...” but in its entirety reads: “In the United States, the largest methane emissions come from the decomposition of wastes in landfills, ruminant digestion and manure management associated with domestic livestock, natural gas and oil systems, and coal mining.” For some odd reason, EPA has chosen to list contributing factors in more or less reverse order of their significance, with fossil fuel extraction and distribution at the end of the list.

Subject to objections, suggestions, and further discussion of same, I will soon correct the sentence in question to read:

Due to the large collections of organic matter and availability of anaerobic conditions, landfills are the third largest source of atmospheric methane in the United States.

Piperh (talk) 00:09, 8 January 2013 (UTC)

Graph shows "current period" at left but is only 280ppm CO2, That's not "current."

Methane concentrations (green curve) in 420,000 years of ice core data from Vostok, Antarctica research station. Current period is at the left.

Graph shows "current period" at left but is only 280ppm CO2, That's not "current" so what year is actually "at the left"? Raquel Baranow (talk) 06:15, 6 March 2015 (UTC)

Year zero is preindustrial. Source I'll add that to the caption.

No kidding reference problem

The atmospheric half life of Methane of 7 years references the page at Phys.org. But the Phys.org page, references wikipedia. We have a reference looping problem -- self reference. Blue Tie (talk) 03:53, 22 March 2015 (UTC)

Updated Graphs

Here are the updated NOAA Graphs: 2008 Methane Graph (with Slope/Growth Rate). ftp://ftp.cmdl.noaa.gov/ccg/figures/ch4_tr_global.png

2011 Methane Graph (only Mauna Loa) http://www.esrl.noaa.gov/gmd/webdata/ccgg/iadv/graph/mlo/mlo_ch4_ts_obs_03437.png

They don't seem to be providing an updated version of the "Growth Rate" graph. However, both of these graphs clearly show Methane Growth beyond 2005. I'm having troubles updating the image page to reflect new figures without starting a whole new page.Keelec (talk) 12:05, 2 February 2011 (UTC)

Here is a global graph http://www.esrl.noaa.gov/gmd/aggi/aggi_2010.fig2.png but it includes graphs for other gasses. Is it acceptable to create a new png from a quarter of that giving credit to ESRL / NOAA or are there copyright issues? NOAA = US Government therefore can be used freely? crandles (talk) 11:56, 4 March 2011 (UTC)

I added an {update} template to the graph because there has been a significant change in methane emissions since 2005, when the current graph ends. The NOAA data is in the public domain. Green Cardamom (talk) 04:26, 14 December 2011 (UTC)

Could someone please provide with latest concentration graphs and IPCC projections, as they might be of interest? Thanks! --84.250.122.35 (talk) 17:51, 4 May 2015 (UTC)

Methane atmospheric forcing stated in 100 years GWP

It's odd to me that the forcing of methane would be listed in 100 year GWP terms given that for 93 of those years more than half of the methane will not be present. Contrary to assertions some people make, 100 year has no basis in science as a gold standard for GWP. It's nearly be chosen as a reference point to discuss GHGs with very warming different potentials and life-spans in the atmosphere relative to an anthropic scale. It would make a lot more sense to use the ten year or twenty year Global Warming Potential of methane when introducing the gas.

Given the IPCC has chosen 20yr and 100yr as reference scales to use with regularity, 20 year lifespan and associated GWP is the logical choice. Using 100 GWP greatly reduces the apparent impact in the next twenty years during which time many climatic tipping points may have been crossed that are, effectively for mankind at this time, irreversible. Please change methane's GWP to 86x CO2-e in the 20 year timescale in the introduction. Or at least state that first and then the 100yr GWP. WideEyedPupil (talk) 04:50, 18 February 2016 (UTC)

Methane from plants

The article gives some prominence to the idea that plants are (or may be) an important source of atmospheric methane. Citation of the IPCC (AR4 Climate Change 2007 "Ch.2 Changes in Atmospheric Constituents and in Radiative Forcing") for this appears spurious. A computer search for the word "plant" in that chapter indicates no basis for this citation. The same source is also cited later for a claim, although that source explicitly supports only part of the claim. The paper by Keppler et al. (2006) is cited, which suggested that plants are an important source of atmospheric methane. The article then states: "These findings have been called into question in a 2007 paper...", which might imply to a reader that only the latter paper (Dueck et al. 2007, called "Duek" in the Wikipedia citation) has disagreed with the findings and/or the magnitudes suggested. However, there have been several others, e.g. the paper of Nisbet et al. [2009. Proc. Roy. Soc. Lond. B: Biol. Sci. 276(1660): 1347-1354] which indicates that plants possess no known biochemical pathway which would produce methane, and that the appearance of methane production by plants can simply be due to transpiration of methane absorbed in water from soil. Such methane translocation by transpiration had been reported by Sebacher et al. (1985. J. Env. Qual. 14: 40-46), whose paper was not among literature cited by Nisbet et al. There have been several other papers on the subject of methane from plants, some indicating some methane emission (but several of those do not appear to have excluded the transpirational mechanism), and some suggesting abiological reactions that might produce some methane in plants. Several of the papers on this subject were briefly reviewed in the USEPA's "Methane and Nitrous Oxide Emissions From Natural Sources" (EPA 430-R-10-001). It might be appropriate to rewrite the subsection on plants, giving more weight to review sources and verified information. Schafhirt (talk) 22:51, 19 February 2016 (UTC)

Ecological conversion: nitrogen effects

With no reference citation, the article states: "Conversion of forests and natural environments into agricultural plots increases the amount of nitrogen in the soil, which inhibits methane oxidation, weakening the ability of the methanotrophic bacteria in the soil to act as sinks." Although this effect of nitrogen has occurred in some cases, the claim gives an extremely limited, and therefore misleading, view of how an increase in soil nitrogen can affect methane. In addition to cases in which nitrogen addition in agricultural soils has reduced methane oxidation, there are cases where it has increased methane oxidation, as noted by Bodelier and Laanbroek (2004. FEMS Microbiology Ecology 47: 265-277). Among other matters, these authors comment on different kinds of methanotrophs that tend to occur under different soil conditions. The net effect of nitrogen addition on methane production and methane degradation is sometimes a substantial reduction of methane emissions. An example is the study of Cai et al. (1997. Plant and soil 196: 7-14), which measured reduction of methane emissions by 7 percent to 60 percent on rice fields where nitrogen fertilizer was applied, depending on the form and amount of nitrogen fertilizer used. Denitrification can interfere with methanogenesis (Akunna et al. 1998. Environ. Technol. 19: 1249-1254); this has been attributed to inhibition by denitrification intermediates (Roy and Conrad. 1999. FEMS Microbiology Ecology 28: 49-61) Also, denitrification can contribute to methane oxidation under anoxic conditions, as shown in numerous studies, e.g. Islas-Lima et al. (2004. Water Research, 38: 13-16) and Raghoebarsing et al. [2006. Nature, 440(7086): 918-921]. Thus denitrification of nitrate (which might be added as fertilizer or produced by nitrification of ammonium from other nitrogenous fertilizer) may be implicated in some of the cases where nitrogen fertilizer reduces methane emissions. Recent reviews, such as that of Banger et al. (2012. Global Change Biology, 18: 3259-3267), which examined 33 papers, offer useful summaries of research findings regarding nitrogen effects on methanogenesis and methane oxidation. Article revision to reflect the scope of such findings could correct the impression given that the effect of soil N on methane is necessarily and exclusively inhibition of oxidation. Schafhirt (talk) 22:55, 19 February 2016 (UTC)

Farm animals subsection

Under "Farm animals", in the first paragraph, the first sentence refers to GHG emissions that included nitrous oxide and carbon dioxide, not just methane. Not only has that FAO estimate been superseded, but the comparison with transportation emissions was problematic, as noted by Mitloehner and acknowledged by one of the FAO report's co-authors. The paragraph's only content specific to atmospheric methane is an FAO estimate that livestock account for 37 percent of anthropogenic methane. The remaining paragraph content could be eliminated, to be replaced by other estimates from other sources, e.g. that of the Intergovernmental Panel on Climate Change AR5 (27 percent attributed to ruminants) and the USEPA (2012. EPA 430-R-12-006) global figures for 2005 (28 percent attributable to enteric fermentation, 3 percent attributable to manure management).

In the second paragraph, the first sentence says nothing about methane in relation to eructation, and the remainder of the paragraph says nothing about farm animals. Containing nothing relevant to the subsection topic, the whole paragraph should be deleted. The third paragraph's claim by Cicerone that methane is the second most important greenhouse gas in the atmosphere is incorrect. Both water vapor and carbon dioxide are more important than methane. Although Cicerone presumably intended to refer to anthropogenic greenhouse gas, he did not say that. The claim should be deleted. (As such a claim is not specific to farm animals, it does not really belong in this subsection, anyway.) The third paragraph also mentions Cicerone's claim that methane from cows is now "big" and is not a trivial issue. All the bits attributed to Cicerone are from a newspaper article, and we are not told about the context in which he stated them. Wikipedia readers would be better served with more substance. Although methane from cows (and from other cattle) is indeed not trivial, it may be unnecessary to distract the reader from the larger issue of methane from all classes of livestock. Over the period 1980 to 2012, global methane emissions from cattle increased by 13 percent while those from all livestock increased by 19 percent (FAOSTAT figures for enteric fermentation).

It might be of interest to comment on regional changes in methane emissions from livestock. FAOSTAT estimates (based on Tier 1 calculations by recent IPCC methods) indicate that, from 1980 to 2012, methane emissions from enteric fermentation in livestock decreased by 12 percent for Australia and New Zealand combined, 15 percent for the US and Canada combined, and 51 percent for Europe, but increased by 40 percent in South America, 65 percent in Asia, 83 percent in Africa, and 19 percent globally. Such data illustrate that increases in atmospheric methane from livestock sources over the past 30+ years are primarily a reflection of increased methane emissions from livestock in the developing world, which are not wholly offset by the decreases in methane emission from livestock that have been occurring in the developed world.

In the subsection's final paragraph, which lacks a supporting citation, it is claimed that "Approximately 5% of the methane is released via the flatus, whereas the other 95% is released via eructation." There is no identification of the kind[s] of animals to which the claim pertains. (In those animals producing methane wholly by hindgut fermentation, one would expect little or no methane to be released by eructation.) Also, the above claim ignores exhalation of methane from the lungs. It would be appropriate to have a claim on these matters supported by one or more credible literature citations. For example, the study of Murray et al. (1976. Br. J. Nutr. 39: 337-345) found that for sheep, about 83 percent of the methane produced is emitted by eructation, about 16 percent from the lungs, and about 1 percent from the anus. In that study, most (about 89 percent) of hindgut methane was absorbed across the intestinal wall, entered the bloodstream, and was exhaled from the lungs. Also, some methane from the rumen (roughly 5 percent) was emitted by exhalation from the lungs, rather than by eructation. Using intracecal infusions of tritiated methane and radiocarbon methane, Murray et al. found no evidence of methane transfer from the hindgut to the rumen, which indicates that no significant release of hindgut methane would occur by eructation. Schafhirt (talk) 22:58, 19 February 2016 (UTC)

Methane management techniques

The article claims "For example, in order to counteract the immense amount of methane that ruminants give off, a type of drug called monensin (marketed as rumensin™) has been developed." However, monensin was not developed to counteract methane emission from ruminants. It was introduced in the US in 1971 as a coccidiostat, to combat coccidiosis in poultry (Chapman et al. 2010. Poultry Sci. 89: 1788-1801). [See also: Russell and Houlihan. 2003. FEMS Microbiology Reviews, 27: 65-74.] Richardson et al. and Dinius et al. subsequently published papers showing that it could be used to increase feed conversion efficiency in cattle. The application for a monensin patent "for improving ruminant feed efficiency" assigned to Eli Lilly Co. (filed Jan. 15, 1973) mentioned the effect on methane production associated with acetate derived from pyruvate degradation in the rumen, but this was subsequent to monensin development. The article makes no mention of other ionophores which reduce methane emission from ruminants, described in several papers and reviews.

In addition to use of certain ionophores (which divert hydrogen ions from rumen methanogens, limiting reduction of carbon dioxide to methane), techniques for reducing methane emission from ruminants include reducing ruminal protozoan populations within which methanogen populations tend to be concentrated, and using various feeds of higher quality, e.g. increasing the proportion of grain in the feed (Boadi et al. 2004. Can. J. Anim. Sci. 84: 319-335). In essence, any dietary change that tends to increase the fraction of propionate produced among ruminal volatile fatty acid anions is likely to reduce methane emission from ruminants. [See, for example, the discussion of ruminant methane production by Van Soest (1994. Nutritional ecology of the ruminant. Cornell University Press.] Some mention of these other methods for reducing rumen methane production would seem appropriate in this section of the article. Schafhirt (talk) 23:04, 19 February 2016 (UTC)

Methane in soil and water

The "Wetlands" subsection states: "When the water table is higher, then the methane produced in the soil can more easily diffuse through the water and escape into the atmosphere. " The sentence has a Citation needed tag, but it needs some correction, not just citation. It is true that higher water tables are conducive to more methane emission into the atmosphere. This is partly because a higher water table tends to increase the anoxic fraction of the biologically active soil zone, enabling more methanogenesis. It is also partly because, by decreasing the aerated diffusion path length to the atmosphere, it decreases the probability that a methane molecule diffusing toward the overlying atmosphere will encounter and be metabolized by a methanotroph. However, a higher water table has no effect on ease of methane diffusion through water.

Ease of diffusion, i.e. diffusivity, of methane in water is essentially a function of water temperature. (Ease of diffusion, i.e. the diffusion coefficient, of methane in water-saturated soil is further influenced by the soil volume fraction occupied by water and by the tortuosity of the available diffusion path.) The sentence could be fixed by simply deleting the phrase "diffuse through the water". Schafhirt (talk) 23:06, 19 February 2016 (UTC)

Methane from animals

The "Animals" subsection has only one citation, pertaining to termites. The subsection begins: "Ruminant animals, particularly cows and sheep, contain bacteria in their gastrointestinal systems that help to break down plant material." There is no apparent rationale for use of "particularly"; the claim applies generally to domestic and wild ruminants (in addition to several other taxa). It would be appropriate to substitute "such as" for "particularly".

The subsection continues: "Some of these microorganisms use the acetate from the plant material to produce methane..." This is egregiously misleading, not only because there is no acknowledgment that such organisms and their use of acetate are, at most, extremely minor sources of methane in animals, but also because there is no mention at all of the methanogens and methanogenesis which are important in animals. The methanogenesis of concern in animals is that which reduces carbon dioxide to methane, not that which uses acetate. A quote from Peter Van Soest's "Nutritional Ecology of the Ruminant" sums up the matter: "If acetate were converted to methane in the rumen, this would represent a serious energy loss for the animal. Fortunately for the host, acetate-fermenting methanogens have a generation time of about 4 days, but rumen turnover time for the slowest fractions (fiber) does not ordinarily exceed 2 days, so these methanogens cannot survive."

The subsection claims that "The amount of methane emitted by one cow is equivalent to the amount of methane that 2.5 acres of methanotrophic bacteria can consume." We are not told what is meant by an acre of methanotrophic bacteria. The equivalence given suggests that it is not a typical real-world acre of land containing such bacteria. Is the intended meaning the equivalent of a continuous layer of such bacteria, covering an acre of land? If so, how thick is the layer? We have no way to determine what the claim means, short of finding references on our own and doing calculations for ourselves. Methane degradation in soil per acre of land varies greatly, and the reader is given no information to relate the comparison to the range of such real-world figures. Moreover, even if we knew the microbial biomass involved in the claim, we have no way of determining what conditions of soil pH, water regime, temperature, etc. are assumed in the claimed equivalence. Without more information, the claim's meaning is wholly uncertain and an attempted interpretion by a reader could be seriously in error. The claim should be deleted. Schafhirt (talk) 23:09, 19 February 2016 (UTC)

Article references to GWP

The article claims that the 100-year global warming potential (GWP) of methane is 29, citing IPCC AR5 WG1 (2013). "Climate Change 2013: The Physical Science Basis - Anthropogenic and Natural Radiative Forcing Supplementary Material". Perhaps that figure is a result of a Wikipedia editor having rounded up that reference's figure of 28.5, found in Table 8.SM.17, on p. 8SM-39. However, as the latter figure may itself have been rounded up, a more verifiable claim expressed to just 2 significant figures may be 28, as specified by IPCC AR5 WG1 (2013). "Climate Change 2013: The Physical Science Basis", p. 714. The figure of 28 is for methane without climate-carbon feedbacks; the same source indicates 34, with climate-carbon feedbacks. (The latter figure from the IPCC is not mentioned in the Wikipedia article.)

The article states: "Methane in the Earth's atmosphere is a strong greenhouse gas with a global warming potential of 29 over a 100-year period. This means that a methane emission will have 29 times the impact on temperature of a carbon dioxide emission of the same mass over the following 100 years." This problematic explanation needs some improvement. The references to "methane emission" and "carbon dioxide emission" are incorrect. Instead the explanation could refer to an "atmospheric methane content increase" and an "atmospheric carbon dioxide content increase". (For example, in some years between 1999 and 2007, although there was considerable methane emission, there was no consequent significant effect on warming, because methane degradation was sufficient to result in no significant change in atmospheric methane content.) Also, the effect is calculated for the heat balance, not for temperature change. Schafhirt (talk) 23:12, 19 February 2016 (UTC)

Emissions accounting of methane: misidentified source and muddled figures

The text of this section claims that the data of the section's table are from Houweling et al. (1999). However, the figures in the table are obviously from the IPCC AR3's The Scientific Basis, p. 250, where they are attributed to Lelieveld et al. (1998) for 1992. The estimates of Houweling et al. (1999) are quite different. Moreover, the data presented are muddled, due to some IPCC authors' errors in attempting to summarize the figures of Lelieveld et al. The IPCC authors added figures for domestic ruminants (80 Tg), wild ruminants (5 Tg) and animal wastes (30 Tg), ascribing the sum (115 Tg) to "Ruminants" under the heading "Anthropogenic sources". However, the 5 Tg for wild ruminants obviously belongs under the heading "Natural sources". Moreover, the methane from animal wastes represents monogastric animal waste sources (e.g. swine manure slurry) in addition to ruminant waste sources. (In this connection, see data sources used by Lelieveld et al.) Thus, identifying the sum as pertaining only to ruminants was erroneous. The Wikipedia article not only misidentifies the original source of the figures, but also repeats the IPCC errors in presenting them.

Among alternatives might be presentation of the top-down and bottom-up estimates for 2000-2009 from Table 6.8, p. 507 of the IPCC's 5AR "Climate Change 2013 – The Physical Science Basis". Not only do those estimates pertain to a more recent period, but bracketed figures are included to indicate the range of estimates found in the sources used for the compilation. 23:14, 19 February 2016 (UTC) — Preceding unsigned comment added by Schafhirt (talk • contribs)

Methane from human body

There is no mention in this article about the amount of methane produced during the human digestion cycle. I know that it may be minimal on an individual level, and may not be produced by everyone, but it is perhaps the most direct anthropogenic source and I'm shocked it's not included.Nemoscis (talk) 14:32, 4 October 2016 (UTC)

Rice Agriculture Is Not a Natural Source of Methane

Anthropogenic percentage goes from 55% from the table up to 71% from the pie chart. This is a major discrepancy and error that has existed since this atmospheric methane article was originally split off the methane article in 2009.

The numbers in that table seem to be original research and mistakenly attribute rice agriculture as a natural source of methane. NO source is given for that table (that I can see) and it does not match the data in the references included for the graphic either.

The statement that "Slightly over half of the total emission is due to human activity." may come from an authoritative source, but that statement merely serves to reinforce the accounting error in the article and seems like an error in the cited source, unless 71% equates to 'slightly over half'.

I am not a climate scientist and not the person to correct this accounting. I am not even sure how to document the problem in this talk page properly, but someone has to do it.

Until it is fixed, I am flagging the article as contradictory, and the table as unsourced original research. Note, I have not done any substantial editing before and am unfamiliar with the mechanics. If I flag it incorrectly, please feel free to flag it correctly, or better yet, fix it.CherylJosie (talk) 19:30, 17 May 2016 (UTC)

see http://www.ipcc-nggip.iges.or.jp/public/gl/guidelin/ch4ref5.pdf and sources therein. Plantsurfer 20:01, 17 May 2016 (UTC)

To clarify from the source above: The parameters that affect methane emissions vary widely both spatially and temporally. Multiple year data sets near the same location and under similar conditions can lead to substantial differences in seasonal methane emission levels, making it difficult to establish a single number as the methane emission level from a field,let alone at a regional or country level.

The stated range is 5-20% of anthropogenic methane comes from cultivated rice fields. So although it should not be considered "natural", it also doesn't contribute significantly at 5%, but does so at 20%. This should be reflected in the graphs and description. Wolfbeast (talk) 11:52, 3 June 2016 (UTC)

The rice agriculture is not a 100% man made situation. Most areas where rice is grown always were wetlands, man planted rice in them and did not significantly change the methane generation. And man has increased wetlands to grow rice which does generate more methane. I doubt we could even estimate the two different situations. Dougmcdonell (talk) 16:57, 17 June 2016 (UTC)

It's not inconsistent per se to provide different data from two different sources, as long as the sources are identified. That's just science in action. I've updated the chart to show more of the original data and modified the caption to list the source. Praemonitus (talk) 15:50, 20 December 2016 (UTC)

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Methane as a greenhouse gas section: It doesn't add up

Methane as a greenhouse gas section: If methane has a half-life of 7 years and it's 20-year greenhouse warming potential is 86, it's "at a given time"-potential can't be anywhere close to 100. It must be about 300 or so. Plus, I would very much like to see a source for the amount of "large effect" on a truly brief period, if the reader like me is interested in a period << 20 years. Thank you very much --2A02:8070:23C1:8D00:1C02:5487:6795:6520 (talk) 15:29, 20 July 2014 (UTC) There is a NASA paper that put it at 104x forcing of CO2(-e) in the atmosphere not considering any timeframe as I understand it. will look for link. I'm not sure the shape of the depletion curve but you would think it would be something like a decay curve. the products of (oxidation for want of a better word) also have a GHG effect. WideEyedPupil (talk) 04:50, 18 February 2016 (UTC)

Thank you very much, that link would be appreciated! I calculated with 1:1 CO2 as decay product and an exponential decay curve. --129.13.156.13 (talk) 13:27, 22 February 2016 (UTC)

I wasn't able to find that paper, and I didn't solve my issue with the greenhouse impact of methane. Maybe stratospheric water does count as a major factor into the long-term effect? If yes, then I could understand why my rough calculations might have been erroneous. --129.13.156.135 (talk) 15:29, 10 April 2017 (UTC)

I cannot make sense of the numbers here. Firstly, I don't understand what 'lifetime' means in connection with atmospheric methane: is this referring to a half life? If so, that needs to be clear. As commented above, the 20 and 100 year impacts appear far too high based on the [half] life and the impact per mole. — Preceding unsigned comment added by 82.22.18.74 (talk) 08:32, 8 July 2017 (UTC)

To answer your question about lifetime and half-life: Lifetime is usually defined as the time until 1/e (=36.8%, i.e. less then half) of the substance remains.

Just to attract more experts here: This question still remains unsolved --129.13.156.135 (talk) 11:48, 24 October 2017 (UTC)

I understand the concept of half-life very well. But I had never heard "lifetime" defined as when 1/e of the substance remains. If the article is going to continue to speak of methane's "lifetime," it should explicitly state this definition of lifetime. Otherwise, the article mistakenly gives the impression that methane released into the atmosphere will suddenly disappear altogether 8.4 years later.

This could all be avoided if the article spoke in terms of half-life, not lifetime. Here is a source that says its atmospheric half-life is 7 years. 75.163.207.72 (talk) 21:31, 23 June 2018 (UTC)I agree and note that the article on exponential decay referenced below comments that half life is a more intuitive concept.

Lifetime is usually defined as I presented here (see also https://en.wikipedia.org/wiki/Exponential_decay), since many processes in nature are exponential or approximately exponential. And a half-life of 7 years and a lifetime of ~10 years may fit (the IPCC reports state 10 years for its lifetime). Either way, this side-topic doesn't answer my question about the immediate impact of methane, comparing immediate with long-time impact. Either way, exponential decay doesn't seem to answer this correctly (a straight-forward calculation leads to a ridiculously high impact of current methane levels compared to CO2, not fitting to the IPCC report estimate of 1.82 W/m² for current CO2 and (only) 0.48 W/m² for current CH4), and I'm calling for every help available in calculating the short-time methane impact the right way. --129.13.156.135 (talk) 14:35, 29 August 2018 (UTC)

I've done some digging and calculating, and I've come up with a yet unconfirmed solution: It's about the decay curve of CO2, which goes into the calculations. Reason: The factors of methane emission impact are normalized to CO2 emission impact, hence CO2's decay curve has to be taken into account - I was aware of this from the start. But: The current IPCC report doesn't seem to state a lifetime of 120 years for CO2 any more, it states that the CO2 decay [decay as a math term meaning removal from the atmosphere] is not a straight-forward exponential and just more complicated. However, the "more complicated" CO2 decay equation appears to not have been explicitly given within the IPCC report, possibly because there wasn't an agreement reached on the best mathematical representation. If I take this info and assume a CO2 "exponential fit" lifetime of 33 years on the 100 year timescale, but of only 15 years on the 20 year timescale, my numbers fit to the radiative forcing numbers of the climate community. A presumed solution working for me. However I'd really like to back up my thinking by an expert. --129.13.156.135 (talk) 10:52, 4 September 2018 (UTC)

Okay I've finally understood an aspect with expert help. Methane doesn't decay exponentially, so definitions for exponential decay of both half-life and lifetime do not apply. The IPCC uses a definition of lifetime of "Total concentration in the atmosphere / Current rate of removal". That definition is entirely different to the established definition used in exponential decay, but apparently for a good reason (i.e., neither CO2's nor methane's atmospheric removal is one simple exponential). Since the rate of removal depends on various factors including the gas concentration at a timestep, this definition doesn't really tell how long methane will survive. It just gives a hint on how the removal function would start, if emissions were zero. However, understanding this still doesn't help me in explicitly getting the discussed numbers ;(. --129.13.156.135 (talk) 10:42, 8 March 2019 (UTC)

paragraph about sequestration

I just removed the following from the article

One of the most significant consequences of using a GWP 100 year time horizon for all GHGs regardless of their lifetime and warming potential is in sequestration. Here it leads to a serious underestimation, by a factor of approximately 3, for the volumes of CO₂ sequestration which would be required to counter the warming effects of a given volume of methane. On the other hand, the benefits of rapid direct reductions of methane are also thought to be substantially obscured by this choice of warming time horizon for methane.

because after reviewing the WP:PRIMARY source I have concerns this might be WP:Original research.

Something that might be useful for our climate reporting is this source says most mitigation policy is "CO2-centric" and encourages focus on other GHGs like methane saying it would take a big bite out of short term GW.NewsAndEventsGuy (talk) 11:36, 4 September 2018 (UTC)

References

Yes, that particular claim does not seem to be present in that particular source. In any case it is accurate that 100 year models assume no change in carbon sequestration which is a very tenuous assumption. Alec Gargett (talk) 01:22, 20 November 2019 (UTC)

Preindustrial CH4 indicates greater anthropogenic fossil CH4 emissions

A study by Benjamin Hmiel et al., published today in the journal Nature,[2] shows that the natural emission of CH4 had been overestimated by about a factor of 10, and anthropogenic emissions are 25-40% higher than recent estimates. This affects the accuracy of much of the information presented in the article. Renerpho (talk) 23:41, 20 February 2020 (UTC)

From methane article

In February 2020, it was reported methane emissions from the fossil fuel industry may have been significantly underestimated.

Many other RSs also. X1\ (talk) 23:29, 24 February 2020 (UTC)

References

Is anyone else getting "access denied" for this source?

Is anyone else getting "Access denied" for this source? https://icp.giss.nasa.gov/education/methane/intro/cycle.html Alec Gargett (talk) 01:23, 20 November 2019 (UTC)

Yes, but a snapshot is available at https://web.archive.org/web/20191002060712/https://icp.giss.nasa.gov/education/methane/intro/cycle.html Jzandin (talk) 07:24, 15 June 2020 (UTC)

Please update section "Emissions accounting of methane" with "The Global Methane Budget 2000–2017" and "Increasing anthropogenic methane emissions arise equally from agricultural and fossil fuel sources"

Please update section "Emissions accounting of methane" with "The Global Methane Budget 2000–2017" and "Increasing anthropogenic methane emissions arise equally from agricultural and fossil fuel sources". There should be two new columns in the section's table – search the studies for "Tg" to find their results.

Info on these 2 studies is included in 2020 in science.

Thank you.

--Prototyperspective (talk) 14:25, 14 September 2020 (UTC)

If you are able, you can update the information. If you can't, I will do it but will you provide me with specific locations for the information? It would be very helpful. Also, is the diagram by the Global Carbon Project incorrect or outdated? Andrew Z. Colvin • Talk 10:39, 4 July 2021 (UTC)

Please do update it. Maybe I could check if there's something to improve upon in your edit but probably won't. Info from the former study was already added here so there may not be much or even anything to add now. The latter study is also co-authored by Saunois. In it it e.g. says Average estimated global methane emissions for 2017 were 596 Tg CH4 yr−1 so I'm not sure if there's something missing in the article because I couldn't find that number there. On that website just search (ctrl+f) for "Tg" to see that data (other conclusions and data may also be relevant to this article though). I don't know if that diagram is incorrect or outdated but don't think anything indicates that it is (looks like 2017 is the latest comprehensive data and I don't think there's a newer diagram or a diagram claimed to be more correct). --Prototyperspective (talk) 17:16, 4 July 2021 (UTC)

Wiki Education Foundation-supported course assignment

This article is or was the subject of a Wiki Education Foundation-supported course assignment. Further details are available on the course page. Student editor(s): Marcbremenkamp, Jangho.lee.92.

Above undated message substituted from Template:Dashboard.wikiedu.org assignment by PrimeBOT (talk) 14:56, 16 January 2022 (UTC)

Wiki Education Foundation-supported course assignment

This article was the subject of a Wiki Education Foundation-supported course assignment, between 24 August 2021 and 7 December 2021. Further details are available on the course page. Student editor(s): Adiering3. Peer reviewers: Hydrosasso.

Above undated message substituted from Template:Dashboard.wikiedu.org assignment by PrimeBOT (talk) 17:39, 17 January 2022 (UTC)

New data from WMO

Hi I believe that a new 3-dimensional plot of Copernicus data downloaded from the WMO website shows the unmissable signature of the 'Methane Time bomb. I found the plot by doing a search for methane emissions on their website. The importance of this data cannot be underestimated and shows unequivocally that the biggest source of global methane emissions is coming from above 80 degrees of latitude.

Kevin Maybury 211.26.98.91 (talk) 09:41, 12 November 2022 (UTC)

Should there be a section on concentrations in the geologic past?

I just came to this article for the first time today, after working on carbon dioxide in Earth's atmosphere. It seems like quite a nice article, thank you to previous editors! I've just linked it from climate change now as well. I am just wondering: should it have (at the end) also a section on methane concentrations in the geologic past? Just like the article carbon dioxide in Earth's atmosphere has a section about that at the end. And so does the article ocean acidification. I have no knowledge about methane concentrations in the geologic past, maybe it's not "a thing". EMsmile (talk) 11:59, 9 December 2022 (UTC)

Removed this 2007 content here

"However, most of this reservoir of hydrates appears isolated from changes to the surface climate, so any such release is likely to happen over geological timescales of a millennium or more. cite journal |title=Methane hydrate stability and anthropogenic climate change |last1=Archer |first1=D. |journal=Biogeosciences |volume=4 |issue=4 |pages=521–544 |date=July 2007 |bibcode=2007BGeo....4..521A |doi=10.5194/bg-4-521-2007|doi-access=free"Oceanflynn (talk) 01:01, 16 March 2023 (UTC)

Surprise effect: Methane cools even as it heats

Press release: https://news.ucr.edu/articles/2023/03/27/surprise-effect-methane-cools-even-it-heats

Excerpt: "Most climate models do not yet account for a new UC Riverside discovery: methane traps a great deal of heat in Earth’s atmosphere, but also creates cooling clouds that offset 30% of the heat.

Greenhouse gases like methane create a kind of blanket in the atmosphere, trapping heat from Earth’s surface, called longwave energy, and preventing it from radiating out into space. This makes the planet hotter.

“A blanket doesn’t create heat, unless it’s electric. You feel warm because the blanket inhibits your body’s ability to send its heat into the air. This is the same concept,” explained Robert Allen, UCR assistant professor of Earth sciences.

In addition to absorbing longwave energy, it turns out methane also absorbs incoming energy from the sun, known as shortwave energy. “This should warm the planet,” said Allen, who led the research project. “But counterintuitively, the shortwave absorption encourages changes in clouds that have a slight cooling effect.”

This effect is detailed in the journal Nature Geoscience, alongside a second finding that the research team did not fully expect. Though methane generally increases the amount of precipitation, accounting for the absorption of shortwave energy suppresses that increase by 60%.

Both types of energy — longwave (from Earth) and shortwave (from sun) — escape from the atmosphere more than they are absorbed into it. The atmosphere needs compensation for the escaped energy, which it gets from heat created as water vapor condenses into rain, snow, sleet, or hail.

“Essentially, precipitation acts as a heat source, making sure the atmosphere maintains a balance of energy,” said study co-author Ryan Kramer, a researcher at NASA Goddard Space Flight Center and the University of Maryland, Baltimore County.

Methane changes this equation. By holding on to energy from the sun, methane is introducing heat the atmosphere no longer needs to get from precipitation.

Additionally, methane shortwave absorption decreases the amount of solar radiation reaching Earth’s surface. This in turn reduces the amount of water that evaporates. Generally, precipitation and evaporation are equal, so a decrease in evaporation leads to a decrease in precipitation.

“This has implications for understanding in more detail how methane and perhaps other greenhouses gases can impact the climate system,” Allen said. “Shortwave absorption softens the overall warming and rain-increasing effects but does not eradicate them at all.” Pete Tillman (talk) 02:53, 6 April 2023 (UTC)

So what is your suggestion how this, or a related Wikipedia article, should be modified, User:Tillman? Please also look at greenhouse effect and greenhouse gas. EMsmile (talk) 16:33, 28 July 2023 (UTC)

Removed section with equations

I've removed this section with equations as I think this was far too confusing. Some key equations would be fine but this seems to be a bit of a mess or too detailed:

Mathematical equations:

Reaction with the hydroxyl radical – The major removal mechanism of methane from the atmosphere involves radical chemistry; it reacts with the hydroxyl radical (·OH), initially formed from water vapor broken down by oxygen atoms that come from the cleavage of ozone by ultraviolet radiation. The reaction of methane with hydroxyl in the troposphere or stratosphere creates the methyl radical ·CH₃ and water vapor. In addition to being the largest known sink for atmospheric methane, this reaction is one of the most important sources of water vapor in the upper atmosphere. Following the reaction of methane with the hydroxyl radical, two dominant pathways of methane oxidation exist: [A] which leads to a net production of ozone, and [B] which causes no net ozone change. For methane oxidation to take the pathway that leads to net ozone production, nitric oxide (NO) must be available to react with CH₃O₂·. (Nitric oxide can be formed from nitrogen dioxide by the action of sunlight.) Otherwise, CH₃O₂· reacts with the hydroperoxyl radical (HO₂·), and the oxidation takes the pathway with no net ozone change. Both oxidation pathways lead to a net production of formaldehyde and water vapor.

[A] Net production of O₃

CH₄ + ·OH → CH₃· + H₂O

CH₃· + O₂ + M → CH₃O₂· + M

CH₃O₂· + NO → NO₂ + CH₃O·

CH₃O· + O₂ → HO₂· + HCHO

HO₂· + NO → NO₂ + ·OH

(2x) NO₂ + hv → O(³P) + NO

(2x) O(³P) + O₂ + M → O₃ + M

[NET: CH₄ + 4O₂ → HCHO + 2O₃ + H₂O]

[B] No net change of O₃

CH₄ + ·OH → CH₃· + H₂O

CH₃· + O₂ + M → CH₃O₂· + M

CH₃O₂· + HO₂· + M → CH₃O₂H + O₂ + M

CH₃O₂H + hv → CH₃O· + ·OH

CH₃O· + O₂ → HO₂· + HCHO

[NET: CH₄ + O₂ → HCHO + H₂O]

M represents a random molecule that facilitates energy transfer during the reaction according to a 2000 publication. Note that for the second reaction, there will be a net loss of radicals in the case where CH₃O₂H is lost to wet deposition before it can undergo photolysis such that: CH₃O₂H + H₂O → wet deposition. This reaction in the troposphere gives a methane mean lifetime of 9.6 years. Two more minor sinks are soil sinks (160-year mean lifetime) and stratospheric loss by reaction with ·OH, ·Cl and ·O¹D in the stratosphere (120-year mean lifetime), giving a net mean lifetime of 8.4 years. Oxidation of methane is the main source of water vapor in the upper stratosphere (beginning at pressure levels around 10 kPa).

The methyl radical formed in the first step can, during normal daytime conditions in the troposphere, react with another hydroxyl radical to form formaldehyde. Though the mechanism is different, the result is the same as in the oxidative pyrolysis which is the first step in the combustion of methane:

CH₄ + O₂ → CH₂O + H₂O

Formaldehyde can react again with a hydroxyl radical to form carbon dioxide and more water vapor. Sidechains in these reactions may interact with nitrogen compounds that will likely produce ozone, thus supplanting radicals required in the initial reaction.

[A] Net production of O₃

CH₄ + ·OH → CH₃· + H₂O

CH₃· + O₂ + M → CH₃O₂· + M

CH₃O₂· + NO → NO₂ + CH₃O·

CH₃O· + O₂ → HO₂· + HCHO

HO₂· + NO → NO₂ + ·OH

(2x) NO₂ + hv → O(³P) + NO

(2x) O(³P) + O₂ + M → O₃ + M

[NET: CH₄ + 4O₂ → HCHO + 2O₃ + H₂O]

[B] No net change of O₃

CH₄ + ·OH → CH₃· + H₂O

CH₃· + O₂ + M → CH₃O₂· + M

CH₃O₂· + HO₂· + M → CH₃O₂H + O₂ + M

CH₃O₂H + hv → CH₃O· + ·OH

CH₃O· + O₂ → HO₂· + HCHO

[NET: CH₄ + O₂ → HCHO + H₂O] EMsmile (talk) 12:49, 18 September 2023 (UTC)

References

EMsmile (talk) 12:49, 18 September 2023 (UTC)

Perhaps some content should be moved to Methane emissions?

Now that @Oceanflynn has improved here it shows up that Methane emissions needs improvement. Perhaps part of that improvement could be moving some content from here to there? Chidgk1 (talk) 09:07, 22 March 2023 (UTC)

I agree @Chidgk1. It would be helpful if there was a form of annotated bibliography or timeline across related articles perhaps in a special page/sandbox? to better understand the way in which RSs are still reliable, how research has evolved, and which statements continue to be accepted science and which are now outdated.Oceanflynn (talk) 16:46, 22 March 2023 (UTC)

Jimmy says AI might help us out eventually

https://www.bbc.co.uk/programmes/w3ct31zw Chidgk1 (talk) 18:38, 23 March 2023 (UTC)

Meanwhile how about we move 3 sections from here:

Human-caused methane emissions

Methane management techniques

Methane emissions monitoring

to Methane emissions and excerpt the lead back here?

Also the "Removal technology" section in that article could be moved here.

Chidgk1 (talk) 18:55, 23 March 2023 (UTC)

Yes! I am glad to see this previous discussion as I was about to suggest the same. I'll go ahead and make those changes now. EMsmile (talk) 11:52, 18 September 2023 (UTC)

I've moved all that content across now. Please check in case I made any mistakes along the way. EMsmile (talk) 14:18, 18 September 2023 (UTC)

typo? source?

I can't find the source for this. "In 2010, methane levels in the Arctic were measured at 1850 nmol/mol..." Also, the 1850 number is identical to the next passage (which I do see in the identified source). Seems like it a) needs a source, b) 1850 probably is a number accidentally copied from the other source. (Not to mention passive voice doesn't belong in an encyclopedia.) 136.36.241.37 (talk) 23:20, 27 July 2023 (UTC)

I agree with you. That whole section needs to be improved. I haven't had time to dig into it properly yet so for now I've just added the "citation needed" tag. EMsmile (talk) 14:22, 18 September 2023 (UTC)

Better graphs?

Hi User:RCraig09 and pinging also User:Uwappa: I did some work on this article and the related methane emissions article. I am just wondering if you have additional/better graphs at your fingertips which we could add to these two articles? There might be more already in Commons, I haven't searched in detail yet; just wanted to check in in case you have something immediately available. Thanks. EMsmile (talk) 09:10, 19 September 2023 (UTC)

No. —RCraig09 (talk) 11:05, 19 September 2023 (UTC)