The Methane Gun

Julian Cribb | October 29, 2019 | Leave a Comment Download as PDF

Thousands of methane filled bubbles are waiting to explode in Siberia | 

In all the sound and fury over climate change, too little public and media attention has been devoted to the ‘methane gun’ (1) – and yet this terrifying phenomenon could usher humans unceremoniously off Earth’s stage for good. 

Like CO2, methane (CH4) is a greenhouse gas that helps trap the sun’s heat within the Earth’s atmosphere. The big difference is that it is 25-84 times more potent at doing so. 

The planet has massive stores of methane, locked as frozen ice in the seabed (the world’s largest natural gas reserve), in the frozen soils of the Canadian, US and Russian Arctic, and buried in the sediments of tropical swamps and peatlands. Like the bubbles in a stagnant pond, the gas is mostly the work of bacteria digesting organic matter over millions of years.

How large these reserves of methane are is still a matter for scientific debate – but estimates fall between 1.5 and 5 trillion tonnes. Very, very large indeed. If released suddenly, these are thought more than capable of driving the Earth’s temperature up by another 7-10 degrees, on top of the 2-5 degrees likely to result from human emissions from burning fossil fuels and clearing land (currently rising at record rates (2)).  

The worst-case scenario – a large-scale, rapid release of trapped gas known as the ‘methane gun’ – could potentially render the Earth uninhabitable by humans and other large animals. This is why we need to pay attention. Now.

What has some scientists concerned – and others frightened – is that atmospheric levels of methane which have doubled since the Industrial Revolution and have been rising for steadily for the past 30 years, began to rise more steeply in the past five years, as the following graph shows:

Atmospheric methane concentrations up to October 2019: Mauna Loa Observatory, USA.
Atmospheric methane concentrations up to October 2019: Mauna Loa Observatory, USA.


The source of the new methane is debated. Is it mainly caused by the mining of natural gas, petroleum and coal – as several lines of evidence suggest? Is it released by expanding world cattle and rice production, the draining of tropical swamps and burning of tropical forests? Is it the frozen gas seeping out of the oceans and tundra as the planet warms and its ice vanishes? Or is it all of the above? The evidence is starting to favour the latter view (3)  – but the scientific jury remains undecided.

We know that a mass-release of methane can be catastrophic for life on Earth, because that’s exactly what took place 55 million years ago in an event known as PETM – the Palaeocene-Eocene Thermal Maximum – when global temperatures shot up by 5-10 degrees, wiping out a number of species (4). There were no humans round then to release carbon, so it was probably due to one or more of the natural sources rapidly giving up its gas. Recently opinion has narrowed in favour of tropical swamps and peatlands drying out and catching fire during a warming cycle, as the main source. The frozen methane, apparently, remained largely undisturbed in the ocean and tundra.

But that is not the case today. Not only are tropical forests burning and swamps being drained, but scientists have observed major escapes of methane from the Arctic tundra in the form of exploding pingos – mounts of frozen methane, mud and water – and the eruption of melted methane ice from the seabed. In October 2019 veteran Russian researcher Igor Semiletor, from Tomsk Polytechnic University, reported “the most powerful seep I have ever been able to observe” venting in a potent eruption of gas bubbles in the East Siberian Sea (5).

Two years earlier, in June 2017, Russian reindeer herders reported a violent explosion that left a 50- metre deep crater in the tundra of the Yamal Peninsula, Siberia, which scientists attributed to a methane blast. In recent years researchers have reported numerous craters left by explosions across Siberia, the Canadian and Alaskan tundra – and even craters in the seabed. Many are recent – but some are up to 12,000 years old, and still leaking gas. Therein lies the uncertainty: are the methane explosions observed today part of a process that occurs more or less constantly through Earth history – or do they represent the start of a sudden release, ramping up to runaway global warming? The scientific jury is at odds. 

Pennsylvania State climate scientist Prof Michael Mann, for instance, characterises the methane bomb idea as “catastrophism” and claims it is being exploited by the climate denial lobby to discredit climate theory generally. He says the amount of methane released will be “small compared to human emissions” of carbon (6). Other scientists, like Gavin Schmidt of the NASA Goddard Institute, argue that it is highly unlikely that a large volume of seabed methane would be released suddenly, i.e. over a period less than thousands of years, because it did not do so in past warming events. Instead it will continue to trickle out.

Oceanography and ice expert Prof Peter Wadhams disagrees. He says loss of Arctic sea ice from the shallow continental margins could trigger such a release which “could happen very suddenly and … is the greatest single threat that we face”. He says that mainstream science, represented by the Intergovernmental Panel on Climate Change (IPCC), does not generally recognise the threat (7).

Australian National University earth scientist Prof. Andrew Glikson cites the Global Carbon project finding that there are 1.4 trillion tonnes of accumulated methane stored on land and 16 trillion tonnes in the ocean, available for release if the planet grew warm enough, and this ‘could have catastrophic effects on the biosphere’.  He points out there is already clear evidence for the explosive release of methane, on land and at sea. With Arctic temperatures already 3-8 degrees warmer due to global warming, the risks of a sudden methane release “have not yet been fully accounted for in climate projections” (8).  

At temperatures above +4 degrees, many scientists now consider the risk is increasing of the planet becoming partly or wholly uninhabitable to humans and large animals. Certainly, such heat and climate instability would destroy most of our current food production systems, spilling billions of climate refugees across the planet and causing wars to break out between and within nation states (9). 

How many would die in such an event is not knowable, because we cannot predict how humans will respond, how many wars we will start, or how many nukes we will unleash in the ensuing chaos. Potsdam Institute climatologist John Schellnhuber has said: “At 4 C Earth’s… carrying capacity estimates are below 1 billion people.” Prof Kevin Anderson of the U.K.’s Tyndall Centre for Climate Change concurs: “Only about 10 per cent of the planet’s population would survive at 4 C.” Several scientists have voiced the view that the human population will be reduced from 9-10 billion to around 1-3 billion in the long run (10).

We already know that our physical survival is in jeopardy in extended periods above 35 degrees Celsius – that is, where daytime temperatures constantly reach 40-50 degrees C or more. Such temperatures will occur frequently with +7 degrees of global warming and will render large parts of the earth uninhabitable – including the most heavily populated. Above +12 degrees of global warming, human survival becomes physically impossible (11). However long before our heat tolerance limits are reached, local and global food and water supplies will collapse, prompting mass migration and war. Without urgent worldwide action, the global economy – and with it civilized society – are predicted to go down as we approach +4 degrees. Such warnings come, not from ‘radical greens’, but from authorities no less conservative than Bank of England governor Marc Carney (12), who states that the global financial system is currently investing in catastrophe by backing new fossil fuel projects (13).

These numbers represent the current most-informed estimates of the impact of the unfolding climate crisis, should world efforts to halt it fail  and should the climate deniers triumph. 

The risk for humanity posed by the ‘methane gun’ is that rapid global mass-release may be ‘locked and loaded’ and firing before we have sufficient scientific data to confirm it. It is, as they say, an event of low probability – but very high impact. Is it a risk that a rational person would take?

Once the gun has begun to fire, there is practically nothing humans can do to stop it. It will unleash other dangerous feedbacks, potentially leading to runaway warming. It will shift the planet from its present warming state to a ‘hothouse Earth’ state (14) where human survival comes into question.

The only viable strategy – possibly – is preventative: to move civilization far faster towards total elimination of all fossil fuels and land clearing worldwide – and plant billions of trees as quickly as possible, to slow the global warming trend before it triggers the methane gun. 

This means that countries like America, Australia, Brazil and Russia must cease their dangerous do-nothing policies, and stop mining coal, oil and gas, and clearing land. Countries like India and China need to cease building coal-fired power stations immediately. And every country needs to scale back carbon emissions on an accelerated time-scale from transport, agriculture, concrete and industry.

While some scientists urge geoengineering solutions, such as the artificial release of sulphate aerosol particles to erect a giant sunshade over the Earth, this represents a counsel of despair. It means allowing the atmosphere to attain virtual temperatures that would cook humans, then trying to chill them down with a planet-sized ‘air-conditioner’. The consequences, should our air conditioner fail, would be terminal. That really only leaves us with the option of trying to contain global warming by eliminating human carbon emissions – before the methane gun fires.

In the end, the worst that can happen by banning fossil fuels and regreening the planet is that we get a new clean energy system, cheaper energy, renewed economic growth and a more sustainable Earth.

If the climate deniers – fifty huge energy corporates and their political and media cheer squad – get their way, the worst that can happen is human extinction.

Which risk do you prefer?


  1. Originally dubbed the ‘clathrate gun’, the theory describes the abrupt release of oceanic methane as a potential driver of major climate changes of the past, from a cool planet state to a hot one. See Kennett JP et al, Methane Hydrates in Quaternary Climate Change: The Clathrate Gun Hypothesis, Volume 54, American Geophysical Union, 2003.
  2. Cooper R, Global carbon emissions increased at a record rate in 2018. Climate Action. Mar 17, 2019.
  3. NASA.  What is Behind Rising Levels of Methane in the Atmosphere?
  4. Jardine P, The Paleocene–Eocene Thermal Maximum, Palaeontology Online 1.5.
  6. Mann M, see:
  7. Wadhams P, see:
  8. Glikson A, The Methane Time Bomb. International Carbon Conference 2018.
  9. Cribb JHJ, Food or War, Cambridge University Press 2019,
  10. Rees WE, Yes, the Climate Crisis May Wipe out Six Billion People, The Tyee, Sep 18, 2019.
  11. Sherwood SC and Huber M, An adaptability limit to climate change due to heat stress, PNAS, May 25, 2010.
  12. Carrington D, Firms ignoring climate crisis will go bankrupt, says Mark Carney, The Guardian, Oct 13, 2019.
  13.  Carney, M.  Bank of England boss says global finance is funding 4C temperature rise. The Guardian, Oct 16, 2019.
  14. Steffen W et al., Trajectories of the Earth System in the Anthropocene, PNAS, August 2018.

Julian Cribb FRSA FTSE is an Australian author and science communicator. A former newspaper editor, his published work includes over 9000 articles, 3000 science media releases and eleven books, the latest four on the existential emergency facing humanity and potential solutions to it. He has received over 30 awards for journalism. Julian Cribb’s latest book, Food or War,  ties the existential threats faced by humanity to the food choices each of us makes every day. It will be released this summer by Cambridge University Press. 

The MAHB Blog is a venture of the Millennium Alliance for Humanity and the Biosphere. Questions should be directed to

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  • PattiMichelle Sheaffer

    See my model results on the methane gun from the AGU Chapman Conference (2019) using the GISS ModelE AOGCM. It parallels Prof. Wadhams’ models.

  • Andrew Gaines

    Julian is right that advocating slowing the economy would produce a severe backlash. Hence the need for citizen education to prepare the ground. Ordinary people need to get that growth is destroying us. To the extent that this is accepted, the backlash will be less. I am encouraged by the fact that there are cultural creatives who are not invested in growth.

    I received a passionate email. My response is relevant to this thread.

    Hi Esther,
    You are a clear and passionate, and it is terrible the way we blindly over-breed and destroy other species. I carry my own awareness is this like a hairshirt. Life is to be enjoyed – yes – and these things are happening on our watch.

    What to do?
    I think we need to inspire mainstream commitment to doing everything required to turn things around. Perhaps this is impossible. No matter. It is what is needed, and people are waking up. So let’s go for it!

    I have set up the Great Transition Initiative is a platform for citizen educators. I would be pleased if you would read Catalysing mass commitment to transformational change, and lend your intelligence and passion to it (
    I’m happy to talk.


    Andrew Gaines
    Great Transition Initiative
    Accelerating the transition to a life-affirming culture

  • Bellmeio

    I find the prospect of a runaway greenhouse loop fed by methane to be terrifying. There is no excuse for ignorance or inaction.

  • anotherneighborhoodactivist

    “the worst that can happen by banning fossil fuels and regreening the planet is that we get a new clean energy system, cheaper energy, renewed economic growth and a more sustainable Earth.”

    Are you serious? This sentence undermines the entire piece with its (barely) unstated assumption that we can continue “economic growth” and that a transition to a post fossil fuel economy doesn’t require a significant reduction in humans’ collective metabolism. This is a patently ridiculous assumption, contrary to the second law of thermodynamics. There are dozens of papers on systems ecology that analyze this fact. Frankly, I’m rather surprised to see such a statement at MAHB. Very disappointing.

    • Julian Cribb

      I think you underestimate the potential for a circular, ‘ideas’ economy. First of all a circular economy no longer requires new (finite) resources, as it re-uses everything. It becomes feasible as soon as women reverse population growth, which is due to happen in the 2060s. Secondly an ‘ideas’ economy can still achieve ‘growth’, because it is based upon an infinite resource, the human imagination, not on finite material goods. Thirdly, we need an Earth Standard Currency to avoid an infinite money supply ruining a finite Planet (see my article on MAHB ). I also deal with all these issues in ‘Surviving the 21st Century’.
      Politically, I fear that any attempt to terminate the ‘growth economy’ concept would meet with such a public backlash as to make climate denial seem tame by comparison, since almost every profession depends on it. It is all very well discussed in academic circles over a glass of port, but will it fly politically? If you believe that it will, then please stand as a political candidate on this platform at the next convenient election and prove it. I would be happy to vote for you.

      • anotherneighborhoodactivist

        Discussions over a glass of port are irrelevant. The second law doesn’t give a whit about political feasibility. It is time to challenge the embedded assumption that we can continue to “grow the economy.” Here’s a piece on the question by one of the best energy analysts:

        Whether or not someone can get elected on a platform that challenges growth is also irrelevant. The downscaling of human metabolism is going to happen one way (with preparation) or another (horribly). Probably some of both, depending on location. Sooner better than later, as the content of your article clearly implies.

        If you want my reading list on the subject (sustainability), please email me: louploup at louploup dot net

        Here’s one item from the list, concerning the metabolism of economic structures:

        • Julian Cribb

          I’m not arguing about the idea. I’m questioning whether you can persuade every human on Earth to abandon ‘growth’ in time. And if not, ought we to seek a more practical solution?

          • anotherneighborhoodactivist

            We’ve gone into the fish trap of fossil fuel driven overshoot. Call it Western modernism, progress, global capitalism, whatever labels you want, but there are no “solutions” that can put us back into the Holocene.

            In any case, the reason I posted an intemperate reaction to your penultimate sentence is that acceptance of the myth of continued economic growth is most definitely the opposite of a “practical solution.” It is a recipe to move us off the cliff as fast as possible. Maybe the rest of the biosphere would appreciate if if we did commit species suicide, but the shred of optimism I do have is that some of us appear to be capable of understanding that there are limits. I was upset to see a blatant disregard of that truth on “a platform to help global civil society address the interconnections among the greatest threats to human well-being…”

            By the look of your tiny photo, we’re a similar age. We may or may not live to see the big unraveling in earnest. Those who are young now probably will. Tipping points can move things along quite rapidly.

            IMO, the most “practical solution” us educated elders can do is to keep teaching that more growth is a dead end. BAU is suicide.

          • anotherneighborhoodactivist

            No, you cannot. Seeking a “practical solution” is an absurd framing.

      • anotherneighborhoodactivist

        I’ve now watched
        and thought about our exchange more. I think you overestimate the potential for a circular, recycling economy. The changes we need to make involve a heck of a lot less “stuff” and a lot less moving around. They both take large amounts of resources. It seems to me that there is an irreducible minimum flux of energy and material needed for people to have a basic comfortable life. Clearly it is a lot less than the quantity we are using now. OTOH, it is pretty clear to me that there is not enough energy and material on Earth to provide a basic minimum for 7 or 10 billion people on a long term (“sustainable”). Thus I greatly appreciate your point that we need to put women in charge. But I still disagree with putting “renewed economic growth” anywhere in the conversation as a positive meme.

      • Arnold Byron

        I totally reject your comment: — “as soon as women reverse population growth, which is due to happen in the 2060s.” Is it a male thing that makes you want to lay all of the responsibility for saving humanity into the hands of mothers, sisters and female friends? Do men have no responsibility in helping to reverse population growth?

        I am a 78 year old Caucasian male, United States born and bred. What makes sense to me is that in order to reduce the population and to be fair about it is to use contraception devices in a fair and orderly manner. [1] If the objective is to reduce the population then birth control is used until a woman has her first child. Then the woman is fitted with an IUD and the father of the child undergoes a vasectomy. [2] If the objective is to maintain the population then the female is provided the contraceptive device after her second child and the male, having been the father of two children would have his vasectomy at that time. The point is that it is past time that the males (and that includes all of the male writers to this blog) step up and be the men that they are. Tell your women folk not to worry; that you will take care of them; that you will not be afraid to have a vasectomy.

        This means that we all have to push the nations to organize a global office so that there will be thousands of local offices [a] staffed by medical people to deal with the population rules; [b] engineers to build and run mini refineries that will change carbonaceous materials into petroleum products and remove carbon dioxide; [c] agronomists to work with local people to do regenerative agriculture to reverse desertification and remove carbon dioxide [d] and to build some of the new geoengineering concepts that are designed to remove carbon dioxide.

        Guess what! If we remove the excess carbon dioxide the methane threat goes away. But the very first step is for the homo sapien male to realize that we have reached the ceiling of overshoot and we have no other choice than to limit ourselves to only two children, forever, until the sun goes nova. If the men step up we won’t have to wait until the 2060’s. We can start reducing the population and saving humanity tomorrow.

        Regulating the number of children will not be easy, but it will be easier for the men to have a vasectomy and then go on with their lives than it will be for the women to deal with an IUD until they are past menopause. By the way; I think that after one generation everyone will be okay with contraception. The male has a vasectomy when the female has a healthy child.

  • This article is welcome, even if the news is not. It is time to call out Michael Mann about the ‘catastroiphism’ smear. He was conspicuous in the BBC’s ‘Climate Facts’ movies as saying “its all happening much faster than many of us thought possible”.

    No wonder he says that, all significant feedback effects were omitted from the models used in the preparation of IPCC AR5

    even though this denided at the time

  • Andrew Gaines

    The only solution for dealing with children’s fears about climate change is for adults to change the systems that make climate change worse.

    This article, like so many brilliant MAHB articles, only analyses the problem. Since the people on MAHB by and large already know a lot about the problem, we are preaching to the converted.

    I occasionally pop up on MAHB and say hey – we should be catalysing an educational movement to inspire mainstream commitment to turning things around. But frankly, I don’t get much response from MAHB. Why aren’t we having a conversation about shifting consciousness instead of talking to ourselves?

    Anyway, GREATTRANSITION.NET has communication tools and a strategy for engaging mainstream people – people who are not in our thought bubble. And yes, there are colleagues working on this.

    Andrew Gaines
    Great Transition Initiative
    +612 8005-8382
    Accelerating the transition to a life-affirming culture

    • Second that – It should help to address ‘children’s fears’ the way Greta Thunberg did; point to the evidence she quote in IPCC SR 1.5and ask people to make their comments in the light of that.

    • César Valdivieso

      Thank you very much for the information regarding the Great Transition Initiative.

    • Julian Cribb

      Andrew is right. We need to be working on the solutions, including educating citizens worldwide about them. My piece, which was commissioned by MAHB, is intended purely to inform people about the scale and nature of the problem and the character of the scientific discussion around it, as the first step towards devising solutions.

    • Bellmeio

      I encourage you to read Julian Cribb’s excellent new book, FOOD OR WAR.