Arguments
What is methane's contribution to global warming?
What the science says...
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Basic
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Intermediate
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Methane plays a minor role in global warming but could get much worse if permafrost starts to melt. |
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Climate Myth...
It's methane
"A United Nations report has identified the world's rapidly growing herds of cattle as the greatest threat to the climate, forests and wildlife. ...
...Livestock are responsible for 18 per cent of the greenhouse gases that cause global warming, more than cars, planes and all other forms of transport put together.
Burning fuel to produce fertiliser to grow feed, to produce meat and to transport it - and clearing vegetation for grazing - produces 9 per cent of all emissions of carbon dioxide, the most common greenhouse gas. And their wind and manure emit more than one third of emissions of another, methane, which warms the world 20 times faster than carbon dioxide." (Geoffrey Lean)
At a glance
Just like CO2, methane is a colourless, odourless gas. But the similarity ends there. Methane is highly reactive, to the extent that it can form a highly explosive mixture with oxygen. Methane explosions are a leading cause of mining disasters. For domestic use, the gas has an odour-producer added to it, so you can 'smell gas', in the event of a leak.
That reactivity is a good thing, since methane is a potent greenhouse gas, many times more effective at trapping heat in the atmosphere than CO2. It has caused almost a third of recent global warming. But methane oxidises quickly. The atmospheric lifetime of a molecule of methane is typically no more than 12 years. This is much shorter than the long atmospheric lifetime of CO2.
Due to that reactivity, the concentration of methane in the atmosphere is much smaller than that of CO2. For that reason, it is expressed in parts per billion (ppb). A thousand parts per billion is one part per million (ppm). Currently, the average methane concentration is 1894 ppb or 1.894 ppm. That is about 2.5 times pre-industrial levels.
Current sources of methane are a mixture of natural and manmade processes, according to the International Energy Agency. Man-made sources make up more than two thirds of the total. The key natural source is wetlands. However, there is also the poorly-understood potential for releases from methane hydrate deposits.
Methane hydrate, or methane clathrate as it's sometimes called, is a white, snow-like solid. Although it looks like snow, the resemblance ends there, because you can set fire to it. Methane hydrate occurs in marine sediments, where it forms during the bacterial decomposition of organic matter. Vast stores of the substance can build up in the sediment, over time.
Importantly though, methane hydrate is only stable at very high pressures and low temperatures. Such environments are typically found within the slopes that lead down from the continental shelves into the oceanic depths. Here, the water is deep and cold enough and there is still plenty of organic matter too. For methane hydrate, the conditions are perfect. Destabilisation of this buried 'flammable snow' could lead to methane release on a substantial scale. But it's important to bear in mind that this remains an incompletely-understood area - despite occasional scary headlines in the media. Vast-scale methane-release is regarded as very unlikely to occur under any plausible near-term emissions pathway.
Methane outgassing from melted permafrost is much better understood. You may have seen videos of methane ignition at lakes in permafrost-country. But currently, compared to man-made sources, this is still insignificant in the great scheme of things.
The leading source of man-made methane emissions is agriculture but the energy sector comes a close second. Waste treatment, in particular landfill, is also significant. Improvements are possible in all such sectors and are in some cases being implemented. Meanwhile, emitting CO2 at the rate of over 40 billion tons per annum, as we are now doing, still remains a seriously bad Idea. Methane should not distract us from that.
Please use this form to provide feedback about this new "At a glance" section. Read a more technical version below or dig deeper via the tabs above!
Further details
While methane is a more potent greenhouse gas than CO2, there is over 220 times more CO2 than methane in the atmosphere - as of 2022, 417 ppm as opposed to 1.894 ppm. The amount of warming attributed to methane is calculated to be around 30% of the warming CO2 contributes. And the atmospheric concentration of both continues to rise (fig. 1).
Fig. 1: The continued rise in CO2 and methane. Global column-averaged CO2 and CH4 concentrations as measured by satellites, denoted XCH4, for 2003–2022 Monthly averages (red) and 12-months average (black). Redrawn from an original illustration at Copernicus, the European climate change agency.
Methane levels have increased more quickly than CO2 from the pre-industrial baseline concentration of some 700 ppb. That represents a 2.7 times increase, whereas CO2 has 'only' gone up by 50%. Man-made methane sources outnumber natural ones by about two thirds of the total. If we look at a breakdown of these, the key one is agriculture - in particular ruminant farming and rice-paddies. Although the exact figures vary according to the source of the information, a good ballpark figure is that 36% of anthropogenic methane emissions are due to livestock farming and rice cultivation alone. Coming close behind is the energy sector with 33% of emissions. Landfills and other waste treatment processes come third (fig. 2).
Progress is being made - in some sectors and in some countries - to reduce such emissions, but there is still a long way to go. As indeed pointed out by the myth-provider at the top of this page, some countries have better agricultural standards than others - and most of us understand that replacing rain-forests with cattle-ranches is about as insane as it gets. We should simply know better.
Fig. 2: Natural and anthropogenic sources of methane, in millions of tonnes. Figure redrawn from an original at the International Energy Agency website.
What about other methane sources that have featured in the news at times?
When permafrost thaws out, natural processes that were paused when it froze up are restarted, releasing both methane and CO2. As things stand, more work is required to quantify such methane sources, although their effects are well known and have been discussed many times here at Skeptical Science - just try entering 'permafrost' in the top left search bar to see!
There is also methane hydrate, or clathrate, to consider. Methane hydrate is a white, snow-like solid, composed of methane molecules trapped in cage-like structures formed from water molecules. The methane is generated by bacterial decomposition of organic matter such as the remains of plankton. Vast stores of the substance can build up in deeply buried marine sediments over time.
Methane hydrate is only stable at high pressures of 35 bars or more and at low temperatures, both confined to the world's deeper marine basins. What can destabilise methane hydrate deposits? Two things stand out: falls in overhead pressure and/or increases in local temperature. Pressure-falls can be brought about by a fall in sea level or by tectonic uplift of the sea-bed, both making the overhead water-column shallower. Temperature-increases can occur either through direct warming or changes in ocean circulation, or both. Any such change of circumstances that brings a methane hydrate deposit out of its stability zone could trigger its destabilisation, leading to significant outgassing of the methane.
These hazards remain to be fully understood but a lot of effort is going into investigating methane hydrate deposits and their potential role in sudden global warming, both in the past and potentially in future.
Methane should not be underestimated. Once in the atmosphere it has various effects and associated feedbacks that contribute indirectly to warming. Realclimate has an authoritative post detailing some of those, here.
In AR6, the changes in radiative forcing due to methane and other greenhouse gases are presented (fig. 3). The figure shows that while CO2 is the biggest of our problems, methane is still significant and efforts to reduce its emissions should nevertheless continue to be implemented. But never at the same time let it distract from CO2. It's not a case of one or the other. They are both big problems requiring different solutions.
Fig. 3: Radiative forcing changes due to various agents, from 1750-2019. Graphic 7_6 from IPCC AR6 WGI Chapter 7
Last updated on 17 December 2023 by John Mason. View Archives
Tom Curtis @25,
That CH4 forcing cannot be right.
Rather than test my own arthmetical skills, there is a year-by-year table 1979-to-date for the various GHG forcings is given by ESRL on that very page you link to. For 2015, CO2=1.939 Wm^-2 & CH4=0.504 Wm^-2.
Mind, the global temperature increase since pre-industrial times (I assume this is Dipper's "excess heating we experience this year") results from the whole bucket of GHGs. If the analysis includes them all, CO2 & CH4 are only 82%. And if we are to consider that forcings of past emissions continue to operate, different GHGs have quite different concentrations histories.
So, Dipper @23.
How sophisticated do you want to get?
Sincere thanks to HK, Tom Curtis and MA Rodger for responding so quickly and thoroughly. Lots of stuff for me to go and read up on. My simple calculations clearly not what is needed. Much appreciated!
MA Rodger @26, thankyou for the correction.
Redoing the calculation using CH4 concentrations expressed in part per billion (ppb) rather than ppm, ie, the typical unit used to express CH4 concentrations, I obtain a forcing of 0.576 W/m^2, with the remainder of the difference being due to my leaving of the NO2 correction. Clearly the units used is critical in this equation.
When I consider the spirit that John Cook started this page; it seems you halted on animal prodcution (both your pages which touch on animal agriculture is a bit hindsighted, and it seems strange to have them seperated instead of just having one article on animal agriculture). This is indeed a climate science page, but you fail to take into account the potential CO2 mitigation by converting animal agricultural land to e.g., forests, or other crops that bind carbon to the soil. You also don't take into account future projections of climate impact from this sector. Which is the real suprise to me.
The projection in increased CH4 due to animal prodcution shows a great increase (1).
From (1) "We suggest that, by 2050, the livestock sector alone may either occupy the majority of, or significantly overshoot, recently published estimates of humanity’s “safe operating space” in each of these domains."
By 2050 we will also expand our agricultural land by more then 1 billion hektars (2). The situation is dire, and you guys, for once, don't promote looking a head in time. I'm baffled, maybe even shocked. This 1 billion hectar isn't going to come from deserts. Its going to be carbon binding areas.
If china picks up a american diet they alone increase the production of animal products by 30 % (3).
All in all, the projections of climate impact from the agricultural sector is increasing not decreasing or stabalizing. One of the major contributers is CH4. To me, your articles on animal agriculture are close to red herring with a touch of a nirvana fallacy. Red herring because you only evaluate the past, and don't look ahead. Nirvana fallacy because it is not a silver bullet, and that you don't take into account the relative change of emissions.
Correct me if I'm wrong but, it is still true that animal agriculture has bigger emissions than all of transport combined---so why is it in your myth section?
(1) http://www.pnas.org/content/107/43/18371.full
(2) http://science.sciencemag.org/content/292/5515/281.full
(3) http://www.pnas.org/content/110/51/20617?ijkey=2df9956a32971f1382740597a2ba246ddc06173d&keytype2=tf_ipsecsha
[DB] Your claims are best addressed on this thread. Please read that thread and the comments in their entirety. If you still have questions, place them there. Thanks!.
To add to my previews comment, I wonder if you have had a look at recent research by Susan Solomon involving methan (1)?
It seems that we have underestimated the effects of short-lived GHG's.
(1) https://www.theatlantic.com/science/archive/2017/01/short-lived-methane-sea-levels-for-800-years-solomon/512588/
When will you update this nonsense that CH4 is not increasing anymore?
As it definetly is:
https://www.esrl.noaa.gov/gmd/ccgg/trends_ch4/
Let's look at atmospheric methane levels, shall we?
First, we see that overall levels of atmospheric methane are indeed rising:
We can also look at the global methane budget:
We can even look at atmospheric levels of methane by latitude band:
From the available evidence, we see that the primary sources of the recent rise are from the tropics and mid-latitudes of the Northern Hemisphere, with some further contributions from animal agriculture and fugitive emissions from industry.
Doubtless further research will elucidate better quantifications.
Your contributions from Zickfeld et al (not Solomon) are noted. But the sheer size of the bolus emissions from CO2 have multi-millennial consequences, too:
Per Zhang and Caldeira 2015, when you burn a lump of coal or some gas, the greenhouse effect from the resulting CO2 will over time warm the Earth 100,000 times more than the heat released upon combustion.
(1 min video on their new study comparing CO2 and direct thermal warming from fossil fuels)
At the end of The Long Thaw, David Archer calculates that the amount of energy that is trapped by the CO2 produced by burning gasoline today is, over its atmospheric lifetime, 40 million times the amount of fuel energy released today.
The 'Solomon' paper you obliquely reference is found here:
http://www.pnas.org/content/114/4/657
The sources that explain the rise of methane in the atmosphere, its dangers, why graphs need to updated to explain escaping methane from fracking pipes:
Www.thinkprogress.org/methane-leaks-erase-climate-benefit
I would like to see this updated with more data on arctic methane releases, including the Siberian methane explosions, as well as the methan hydrate outgassing from the ocean floor. I want to know how soon we might reach the point where the amount of methane already released would cause enough warming to ensure the release of all the frozen sources.
Here you go:
The remainder can be split into 2 buckets: Terrestrial (land-based) carbon sources and Marine (maritime-based) carbon sources.
Land-based permafrost is indeed melting, reducing in both area and volume. However, the vast majority of carbon emissions from those land-based melting permafrost areas are in the form of carbon dioxide, not methane.
There is an extensive amount of published research on the subject of GHG emissions from warming land-based permafrost and the possible releases from seabed methane clathrates in the Arctic. Let's look at land-based warming permafrost GHG emissions first...
Per Gao et al 2013 - Permafrost degradation and methane: low risk of biogeochemical climate-warming feedback
And, as the Gao et al paper I linked to notes, CH4 from permafrost will drive an expected temperature increase by 2100 of about 0.1 C. Schaefer et al 2014 now calculates a total temperature rise contribution from ALL permafrost carbon stocks (CO2 AND CH4) by 2100 of about 0.29 ± 0.21 (0.08-0.5 C).
Schaefer et al 2014 - The impact of the permafrost carbon feedback on global climate
Per Schuur et al 2015, an abrupt permafrost climate feedback is unlikely, according to the experts, but the bad news is that the already difficult task of keeping warming under 2°C becomes much harder once we face up to the consequences of Arctic permafrost feedbacks.
Per Sweeney et al 2016 - No significant increase in long-term CH4 emissions on North Slope of Alaska despite significant increase in air temperature
And
Now let's examine the literature on Arctic seabed clathrate/methane emissions:
Dmitrenko et al 2011 - Recent changes in shelf hydrography in the Siberian Arctic: Potential for subsea permafrost instability
And
Berndt et al 2014 - Temporal Constraints on Hydrate-Controlled Methane Seepage off Svalbard
James et al 2016 - Effects of climate change on methane emissions from seafloor sediments in the Arctic Ocean_A review
And
And
Per Myhre et al 2016 - Extensive release of methane from Arctic seabed west of Svalbard during summer 2014 does not influence the atmosphere
Ruppel and Kessler 2017 - The interaction of climate change and methane hydrates
And
To sum, the vast majority of warming land-based permafrost GHG emissions are in the form of carbon dioxide, due to natural factors that help break down any methane releases into various components plus carbon dioxide (methane is much less stable than carbon dioxide).
Similarly, the vast majority of gases expelled from degrading seabed methane clathrates are oxidized in the water column and do not reach the surface. Further, much of what we do measure in the form of existing releases are traced to the much longer warming present earlier in the Holocene. And that these same clathrates survived earlier interglacials, wherein global temperatures exceeded those of today...for millennia. So they are actually pretty stable.
Baraliuh @29-31, has there been any resolution to your questions on Animal Agriculture?
Baraliuh @29-31, here's a recent Nature article showing the enormous carbon sequestration potential of grasslands returning to native forests: https://www.nature.com/articles/nature25138.epdf
In recent years, atmospheric methane concentration has increased again. It has been reported that "if you leak more than 2 or 3 percent [of methane] it’s worse for climate change than coal", so I checked Google Scholar to find out whether U.S. fracking might be why methane increased. In short, the answer is no. Nisbet et al. (2016) says
But people should realise that CO2 builds up in the atmosphere, so natural gas still causes global warming even though it emits less CO2 than coal.
Perhaps someone here can help me to clear up some confusion about methane and the Arctic. No one seems to be asking the question I have.
OK, I got the memo: I'm supposed to be freaked out because arctic thawing is going to release methane from the clathrates on the continental shelf. A little red meat for you: Shahkova, Wadhams, Beckwith, others. They're the ones that seem to be screaming the loudest about this.
Let's not get into the deep clathrates, or the land permafrost, as those releases are going to be pretty slow anyway. I'll stick to the clathrates on the Arctic Ocean continental shelf, which are shallow enough to be released quickly. Supposedly.
The problem I have with all this talk is simple. The claim is that the global warming we're going to have (depending on whom you ask, either by 2100, or sooner, or even already) is going to cause a catastrophic release of methane from clathrates at shallow depths, where it can warm more quickly because it's really cold at those high latitudes. And we're told that this amounts to hundreds of billions of tonnes of carbon.
Well, it's also well known that the Earth's gas, oil, and coal was laid down over the last 500 million years or so; more at some intervals than others, but overall, over hundreds of millions of years. Now, during the last 400 to 500 million years, the Earth has often been warmer than now, by several degrees C. In fact, the Earth has been in this "hothouse" condition for most of that time.
Then, if it's true that a warming of a couple of degrees C, or even say 6 degrees, is enough to release a big part of this stored gas catsatrophically, within a few decades (some, apparently, think within a matter of years), then how is it that there is even any methane left at all? It should have all been released long ago. In particular, that especially nasty time, about 250 million years ago, when all that H2S came out of the stinking ocean, should have eliminated all of the clathrates at that time.
Sure, some clathrates could have formed later, but if so, how could those amount to more than all the coal and oil, as some are saying?
For me, this doesn't add up at all.
[DB] You seem to be exposed to misinformation. Please read this post on methane clathrates and put any relevant comments on the subject there, not here.
Claims made in the media are basically irrelevant. Science is not an agenda to be prosecuted in the media.
Lastly, this is an evidence- and science-based venue. The burden is on the user (you) to support contentions and claims with citations to credible sources. Preferably when you make them or, at the bare minimum, when asked. Please read the Comments Policy and ensure that all comments comply with it. Thanks!
mondosinistro - I have further responded on the topic indicated by the moderator.
I found this page because I was looking for an authoritative answer to the question "Is methane a more effective driver of climate change than CO2 (as I have believed since 1980), and if so by how much?". I don't feel any wiser. It seems clear that the answer is "yes" but the "how much" lacks agreement. What's the latest best guess, or range of such?
I want this because the municipal authority where I live plans to withdraw facilities for composting garden waste and replace them with kerbside collections which go to landfill. On the logic that organic waste in landfill generates methane, this plan seems insane and I want a reliable datum to say just how insane.
Richard Bramhall @44,
The magic term you seek is "Global Warming Potential" (GWP) which is a measure of the resulting AGW caused by emissions of a gas by-weight relative to the warming caused by the same weight of CO2=1. As methane is less long-lived in the atmosphere, the GWP of methane depends on the length of your assessment period, the two period-lengths usually used being 20 years & 100 years. The EPA are presumably authorative enough for you and they are using the values from the IPCC AR5. These are GWP(100 yr) = 28 to36 and GWP(20 yr) = 84 to 87.
I would add that while landfill does produce methane (being anaerobic) and garden composting CO2 (being aerobic), in my neck of the woods (UK) methane from landfill is being put to good use generating electricity although it can also be carted away and pre-processed before landfilling, (plans for such pre-processing being in hand for the tip over the hill from me). Thus collection of garden waste for landfill can be improving on the emissions from garden composting that waste as the renewable energy produced reduces the generation and thus emissions from fossil-fuelled power-stations.
MA Roger @45 Thank you. That's exactly what I wanted. I am in UK too and I did wonder about the methane harvesting possibility but my neck of the woods is Powys in Wales which has a pathetic county council and I doubted that their heads are in the right century. I could be maligning them. I'll check and get back to you.
Just read the USA today opinion article entitled, "Let them eat steak: Hold the shame, red meat is not bad for you or climate change."
https://www.yahoo.com/news/let-them-eat-steak-hold-090012002.html
My concern was not over whether eating meat was unhealthy or not. It was the claim that it didn't effect AGW because livestock only account for a 2,6% increase in CHG's. I checked a 2017 study in PNAS which verified the 2.6% reduction in greenhouse gases due to other factors ivolved in increasing the amount of plant production.
https://www.pnas.org/content/114/48/E10301
The thing for me is; are we bound to keep producing plant based food under the methods were producing it today? Do we have to keep producing plant based food with the same CHG intensity that were presently producing it at? My family grows 16 acres of organically grown vegetables in field and high tunnels but I'm skeptical that it can be the solution for feeding the world at this point in time.
The study also concludes, "the removal of animals resulted in diets that are nonviable in the long or short term to support the nutritional needs of the US population without nutrient supplementation." My wife and son eat absolutley no meat and I'm what I like to term a "social caravore." If your serving meat I'll partake but that's the extent of my fleash eating activity. I'm 72 and my wife is 69 and my son is 38. Last year when I told my doctor that unlike my friends and I've never had a stress test or an EKG. She ordered up an EKG. The tech came in and did the test. About 15 minutes he popped her head in the door and said, "Your an athlete, arn't you?" to which I replied, I'm a farmer. I'm not sure why our diets would need suplamention. I'm concerned about what I'm reading.
Estoma@47,
As a pursuer of improved awareness and understanding, and the application of that constant learning to help develop lasting improvements for all of humanity far far into the future (this planet should be habitable for about 1 billion years), my understanding is that what matters regarding food is:
The Sustainable Development Goals provide a robustly developed comprehensive basis for evaluating the acceptability of: what has developed, the required types of new developments, and corrections that are required.
And pursuing improved awareness and understanding makes it clear that competition for impressions of superiority measured by popularity and profit have driven the development, and resistance to correction of, the following harmful unsustainable food production and consumption results:
A major driver of harmful unsustainable developments is successful disinformation and misinformation marketing (Misleading storytelling). That success is due to people developing an 'interest in trying to Win in harmful ultimately unsustainable ways', combined with developing an easily impressed population that resists improving understanding when that awareness and understanding would require changing developed popular and profitable activity and related perceptions of prosperity or opportunity for personal benefit.
The supposedly more advanced nations have not succeeded at developing populations that pursue improved awareness and understanding. What they have developed is populations easily tempted to be passionately triggered by misleading marketing developed and delivered by pursuers of harmful and unsustainable popularity or profit.
And Social Media and News Media pursuing popularity and profit can be seen to be publishing a lot of misleading stories that do not help improve the awareness and understanding of what is really going on regarding food.
The need to correct many things regarding food production and consumption does not mean 'eliminating those things'. However, the fossil fuel burning related to food does indeed need to be ended, not just be reduced.
With that understanding in mind your concerns are warranted. Reread the article. It will likely become obvious how much of it is sensationalist extremist correction resistant storytelling trying to defend the 'harmful unsustainable creations developed by competition for impressions of superiority measured by popularity and profit' rather than 'helpfulness to developing a sustainable improving future for all of humanity'.
Many popular and profitable developments of competition for status do indeed need to be corrected to develop a sustainable improving future for all of humanity. Reducing climate change impacts is a major, but not exclusive, part of the required corrections. Human activities that create accumulating negative impacts, like the use of fossil fuels need to be ended. Other changes of human activity that would reduce GHG levels in the atmosphere are also helpful, but do not need to be taken to the extreme correction (the elimination of them) that is required regarding fossil fuel use.
One Planet Only Forever, thank you for your interesting reply. There hasn't ever been a time when humans haven't advertised to the detrament of society. I fear that by the time we come to the realization that it might be to little to late.
Estoma,
I hope that the development of the Sustainable Development Goals improve awareness and understanding of how fatally flawed the developed ways of living are, including but not limited to the problem of methane resulting from human activities.
There are many examples of undeniably 'unsustainable and harmful developments'. And in each major case there is evidence of damaging resistance to correction.
The most glaring example of harmful developments and resistance to correction is fossil fuel use. Climate science has unwittingly produced the powerful proof of how fatally flawed the developed socioeconomic-political systems are.
Hopefully the Climate Science case will be a Tipping-point regarding the awareness and understanding of the need for Governing/Limiting what is allowed to happen to ensure that the results will be sustainable improvements for humanity. Ethical governing/limiting to achieve and improve the Sustainable Development Goals, including limits on merthane production, is undeniably required when people pursue Personal Benefit or Status relative to Others, especially in Competitions for Popularity and Profit.