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The Volcano Gambit

Anyone reading pundits and politicians pontificating profusely about climate or environmental science will, at some point, have come across the “volcano gambit”. During the discussion they will make a claim that volcanoes (or even a single volcano) produce many times more pollutant emissions than human activities. Often the factor is extremely precise to help give an illusion of science-iness and, remarkably, almost any pollutant can be referenced. This “volcano gambit” is an infallible sign that indicates the author is clueless about climate science, but few are aware of its long and interesting history…

From Augustine to Mt. St. Helens

The ur-usage was a legitimate paper in Science in July 1980 by seismologist David Johnston writing about chlorine emissions in eruptions:

Earlier estimates of the chlorine emission from volcanoes, based upon evaluations of the pre-eruption magmatic chlorine content, are too low for some explosive volcanoes by a factor of 20 to 40 or more. Degassing of ash erupted during 1976 by Augustine Volcano in Alaska released 525 x 106 kg of chlorine (±40%), of which 82 x 106 to 175 x 106 kg may have been ejected into the stratosphere as hydrogen chloride [HCl]. This stratospheric contribution is equivalent to 17 to 36% of the 1975 world industrial production of chlorine in fluorocarbons.

In the main text, there was also this quote:

[The] eruption of the Bishop Tuff from Long Valley Caldera, California, 700,000 years ago generated 100 km3 of air-fall ash(19). If the magma degassed 0.25% chlorine (equivalent to Augustine Volcano), this eruption may have injected 289 x 109 kg of HCl into the stratosphere, equivalent to about 570 times the 1975 world industrial production of chlorine in fluorocarbons.

For context, a big issue at the time was to characterise the budget for chlorine in the stratosphere, given it’s importance in ozone depletion. While there is quite a lot of HCl emitted by volcanoes, that form of chlorine is soluble, and is swiftly rained out, unlike the much less reactive human-made chlorofluorocarbons (CFCs) which can stay in the atmosphere from many decades. Multiple studies subsequent to the Johnston paper confirmed that the volcanic contribution to stratospheric chlorine is actually very small, but this paper was a genuine attempt to constrain this term. To summarise, there are two cases mentioned, Augustine (in Alaska, 1976) and the Long Valley Caldera (California, 700,000 yrs ago), with estimated multiples of 0.17-0.36 and 570 of HCl injection into the stratosphere compared to the annual industrial source of Cl in CFCs. [Note – if anyone has an earlier usage, please let me know].

An important volcanic event in 1980 was of course the huge eruption of Mount St Helens in May of that year. Tragically, the author of the Science paper, David Johnston, an up-and-coming USGS volcanologist, was himself killed in the blast a couple of months before his paper appeared.

Later that year, in October, Ronald Reagan commented on the eruption, suggesting that “one little mountain out there [Mt. St. Helens], in these last several months, has probably released more sulfur dioxide into the atmosphere than has been released in the last ten years of automobile driving or things of that kind.” However, while the volcano emitted roughly 2×106 metric tons SO2, annual emissions from cars were 30 x 106 tons (out of a total human emission of ~131×106 tons). Reagan was out by a factor of 150. This was just the beginning of the mangling.

More relevant for the growth of the volcano gambit, these results got more and more warped in subsequent retellings. For instance, in 1990, Dixy Lee Ray, the ex-marine biologist and former (Democratic) governor of Washington, wrote in her book: “The eruption of Mt. St. Augustine in 1976 injected 289 billion kilograms of hydrochloric acid directly into the stratosphere. That amount is 570 times the total world production of chlorine and fluorocarbon compounds in the year 1975…. So much is known.” She mixed up the huge eruption 700,000 years ago, with a much smaller one in 1976, but it would get worse.

The Johnston paper also became a staple of the folks engaged in rearguard defenses against the 1989 Montreal Protocol, in particular, the Maduro and Schauerhammer book “Holes in the Ozone Scare” quotes the paper accurately, but ignores subsequent work ruling out the HCl source for stratospheric chlorine. This was well discussed by Sherwood Rowland in a 1993 Science commentary which aptly enough was focused on the need for better scientific communication with the public.

… to Mt. Pinatubo

In June 1991, Mt. Pinatubo in the Philippines erupted, and unsurprisingly became the volcano of choice for the contrarians.

Rush Limbaugh discussed this at various points in 1992 and in his 1993 book. On Nightline he stated: “it is man-made products which are causing the ozone depletion, yet Mount Pinatubo has put 570 times the amount of chlorine into the atmosphere in one eruption than all of man-made chlorofluorocarbons in one year”. (Note the further confusion attributing the eruption 700,000 yrs to the one that just happened). In his book “The Way Things Ought To Be” (1993) Limbaugh stretched the facts still further: “Mount Pinatubo in the Philippines spewed forth more than a thousand times the amount of ozone-depleting chemical in one eruption than all the fluorocarbons manufactured by wicked, diabolical, and insensitive corporations in history.” He claims he got this information from Dixy Lee Ray’s book, “the most footnoted, documented book I have ever read.” Which, as noted above was already garbled. (More discussion on Limbaugh’s errors here and here).

From Chlorine to Greenhouse Gases

The Dixy Lee Ray book turns out to be a major source for disinformation, though with little evidence anyone read it carefully or looked up the references. In 2004, the conservative commentator, Jude Wannski mis-remembered Dixy Lee Ray: “[the] book she wrote, Trashing the Planet … debunked a number of myths about the environment. In it she had the following line: “The eruption of Mt. St. Helens in 1980 dumped more greenhouse gases into the atmosphere than all that has been released since the industrial revolution. Volcanoes have been erupting for millions of years with the same result. If this really affected climate, don’t you think it would have happened by now?””. This swaps HCl for greenhouse gases, conflates Mt St. Helens with St Augustine in her text (which in any case should have been the Long Valley Caldera)…

As environmental concern moved to the impact of global warming on ice sheets, so disinformers moved the volcanoes accordingly. In 2006, Christopher Monckton (“the Potty Peer”) said “In a good year for eruptions, Erebus can put out as much CFCs as Man used to.”

A year later (2007), Martin Durkin in his execrable documentary claimed that “One volcanic eruption for example, puts more pollution into the atmosphere than ten years worth of human activity.” This, despite being totally unspecific (which pollutant does he think he is referring to?), is of course wrong in any case. Perhaps he was channeling Reagan?

As in 1992, a new eruption gave rise to a new eruption of the gambit. In 2009, the “Stop Global Cooling” crowd stated: “Sure, volcanoes like the one spouting off in Alaska right now spew much more CO2 than humans could ever think of”. Similarly, Congressman Dana Rohrabacher in March of that year added: “Can one huge volcano spew more CO2 into the atmosphere than all the people? Yes”. Ummm… no.

And yet it goes on. Ian Plimer in another contrarian tome included some even more made up facts: “massive volcanic eruptions (e.g. Pinatubo) emit the equivalent of a years’ human CO2 emissions in a few days” (p472) and “Volcanoes produce more CO2 then the world’s cars and industries combined” (p413). On p217 he claims that while “Mt. Pinatubo . . . released 20 millions tonnes of sulphur dioxide” it also released “very large quantities of chlorofluorocarbons”, citing Brasseur and Granier (1992) who don’t say there were any CFCs in the eruption, and even on chlorine, actually say the opposite: “after the eruption of Mount Pinatubo, the input of chlorine to the stratosphere was probably small”.

From Pinatubo to Eyjafjallajökull

In 2013, it was the turn of Eyjafjallajökull in Iceland to steal the limelight. Ex-Gov. Mike Huckabee said: “The volcano that erupted over in Northern Europe actually poured more CO2 into the air in that single act of nature than all of humans have in something like the past 100 years.“. Senator Lisa Murkowski in 2014 similarly mentioned a volcano she “had heard about” in Iceland. “The emissions that are being put in the air by that volcano are a thousand years’ worth of emissions that would come from all of the vehicles, all of the manufacturing in Europe,” she said. Huckabee was using the same point as recently as July 2015: “a volcano, in one blast, will contribute more [CO2] than 100 years of human activity“. A century or a millennium – who’s counting?

Again this is all patent nonsense – the amount of CO2 emitted by Eyjafjallajökull was in fact more than 20 times smaller than just European aviation emissions per day – and the claim was rightly debunked by, Slate, and HuffPo at the time.


So let’s recap with a simple graphic charting the use and abuse of these claims, colour-coded by the degree of wrongness:

To summarise, a speculative paper (that was later contradicted) about HCl emitted in a volcano 700,000 years ago is the progenitor of statements related to SO2, CO2, greenhouse gases or just “pollutants” in general, and has been associated with Mt. Augustine, Mt. St. Helens, Mt. Pinatubo, Erebus and Eyjafjallajökull, with comparisons to all industrial emissions in a year, 100 years, or since the industrial revolution, all cars in a decade, or indeed a thousand years.

The volcano gambit is the universal comparison, untethered to any actual facts, and look for it to resurface again the next time a big volcano hits the news.


  1. D.A. JOHNSTON, "Volcanic Contribution of Chlorine to the Stratosphere: More Significant to Ozone Than Previously Estimated?", Science, vol. 209, pp. 491-493, 1980.
  2. F.S. Rowland, "President's Lecture: The Need for Scientific Communication with the Public", Science, vol. 260, pp. 1571-1576, 1993.
  3. G. Brasseur, and C. Granier, "Mount Pinatubo Aerosols, Chlorofluorocarbons, and Ozone Depletion", Science, vol. 257, pp. 1239-1242, 1992.

122 Responses to “The Volcano Gambit”

  1. 1
    Mitch says:

    The flip side of this is the claim that all that excess CO2 is being injected by undersea volcanoes along the mid-ocean ridges. Never mind that this would be easily traceable by ocean carbon chemistry, with low pH water plumes streaming from the ridge crests.

    The best solution is to keep current estimates of volcanism up to date, e.g., the Gerlach 2011 paper in EOS (

  2. 2

    Thank you for some great science reporting.

    I was one of many Seattle TV news photographers covering the Mt St Helen’s eruption (a cold and rainy day – we wondered “is that snow or is that ash falling through the heavy cloud cover?”) Over the subsequent decades, May 18th days in this region have been very warm.

    But I must apologize for the news industry – it panders excitement and fluff and anything to attract or distract. It is very important that to know that corporate-owned, mass-media news is advertiser supported. Such news is designed and edited to bring in more viewers and push them closer to advertisements. Careful precision in mass media news is a stated goal, but it is not the top objective. Intended but not really possible – so news reports become self-shallowing, pop-idiomatic expressions.

    Thank you for setting the record straight. And news consumers and scientists should know it is most important to keep open lines of communication to news organizations. This RC page will serve as a simple link to share in letters to editors, story authors or to leave in comments. Thanks so much for this.

  3. 3
    Richard Caldwell says:


    Remember back to science class in K-12? You know, like everybody else? When the teacher was talking, you’d get flashes of predictions as to which side or the other was going to be the direction for the conclusion. “And it goes Left.” How many times was the real answer “Right”?

    Such lessons often started with opposing forces of unknown magnitudes. Will A dominate or B?

    Humans evolved to make quick guesses, to be able to use sparse data to accurately react to novel but recognizable situations. And by react, I don’t mean all the stuff you do, but whether what you do do is based on A or B.

    We also like to be right, so modern humans tend to alight on whatever factoid fits snugly into the conclusion they carry around and then, job done, do a little decorating.

    My favorite is the oft-stated claim that we can’t have speed limiters because serious acceleration can be needed to avoid an accident. (That’s true, but resorting to that technique drastically increases the cost of failure) Well, a five-second grace period with the car deciding whether to extend that based on what’s happening would be easy to program.

  4. 4
    Bill Azevedo says:

    Thanks. Excellent graphic. Useful post.

  5. 5
    ES says:

    I would like to nominate this graphic for Graph of the Year.

    Also: thank you for this comprehensive pocket takedown.

  6. 6
    John Wise says:

    Excellent summary. Thank you for bringing together all this nonsense in one entertaining an informative article.

  7. 7

    Annual average tonnes of CO2 emitted by every volcano in the world, per US Geological Survey: 200 million.

    CO2 emitted by human technology last year, per US Dept. of Commerce Energy Information Agency: 35 billion.

    Divide A by B. Discuss.

  8. 8
    Edward Greisch says:

    This article is a classic, like the global cooling mole, that we will need a copy of, from time to time. It needs to be a downloadable pdf with the URL in the article.

  9. 9
    Russell says:

    America used to have higher standards of malapropism.

    In the wake of the 1938 hurricane , a New England governor went on the radio to warn citizens of” flood waters rising in a terrible conflagration.”

    I like Gavin’s Rise of the Volcano Gambit graph, as it recalls another depicting hype running contrary to the sense of the science — from 1983 until Thompson & Schneider published ‘Nuclear Winter Reappraised , op-ed casualty estimates soared even as the modeling numbers declined.

  10. 10
    L Hamilton says:

    On a series of general-public surveys in 2012-2013, we asked a question inspired by the volcano gambit:

    Which of the following three statements do you think is more accurate? Over the past few decades,
    1. Human activities have released much more CO2 than volcanoes (40%)
    2. Humans and volcanoes have released about the same amounts of CO2 (16%)
    3. Volcanoes have released much more CO2 than humans (12%)
    4. don’t know/no answer (32%)
    (Weighted percentages based on 2,039 interviews; confidence intervals are narrower than +/-2.5 points.)

    Many people honestly said they don’t know, and certainly there is no reason they should. More interestingly, two-thirds of the sample did choose an answer, and many of those were wrong. Their wrongness was not random, however, as it might be if people were just guessing. Although higher education raises the odds of an accurate answer, political identity turns out to be a stronger predictor by far. Odds of responding “volcanoes more” instead of “humans more” are almost 8 times higher among Tea Party supporters than among Democrats of similar age, education and gender. Self-identified Independents and non-Tea Party Republicans fall between these extremes. This pattern must partly reflect dissemination paths (and biased assimilation) of the volcano gambit that Gavin describes.

    “Did the Arctic ice recover? Demographics of true and false climate facts” (2012) in the AMS journal Weather, Climate, and Society introduced these surveys, including a preliminary analysis of the volcanoes question.

    More recent work along these lines, though without volcanoes, appeared last year as “Polar facts in the age of polarization” (2015), Polar Geography.

  11. 11
    Les Porter says:

    Gavin, et al.,

    I’m trying to relate a point.

    Concerning anti-science

    I am not surprised that Jude Wannski would preferentially “mis-remember” Dixie Lee Ray’s book [or claim to when confronted with printed evidence] about what was actually presented. On the witness stand or under congressional examination even Alberto Gonzalez [One of W’s Attorney Generals, you might recall] did warrior’s duty damaging DOJ’s attorneys -and not recalling or of memory fuzzy episodes concerning that which might be criminal activities. Climate contrarian’s seldom get to get examined by Congressional Committees — though a number of them have offered contrary to science testimony.

    While at USGS, I’d heard of David Johnston, never met him, and was moving into a rural double-wide rental when Mt. St. Helen’s detonated. I was doing USGS field work on the Idaho-Montana Border area. I could see the cloud headed our way where we were near Superior, Montana. It was possibly 5 pm MDT when the ash began falling on us that far away. That was a Sunday. Local authorities and TV news reports relayed local scientists and med professionals concerns about potential sulfur and don’t inhale it. [it was best to stay indoors if there was no “dust”. Outside, you could not escape it and we looked like bandits; and vehicles stirred the dust for more than two weeks. A couple of snow storms helped as did later rain. The sulfur component was quickly of no concern. But later silicosis might be.

    Of course Johnston’s work [though Reagan would mangle it] showed truthful characterizations of volcanic gas releases than any proper contrarian would espouse.

    But you have to look at what Reagan had shackled USGS’s overlord {Department of Interior} with.

    You can’t let these people continually get approved; If you have to make them something make them ambassadors to the gradually disappearing island nations.

    NOT Secretary of INTERIOR … to wit

    If you scan down this article from USGS’s oral histories and open file reports you can see why even in the federal science performance there are ‘political’impediments that go beyond Coal Oil and Fossil fuel inerests.

    Robert Wallace recounts this jewel . . .

    — One story will illustrate the type of difficulty Dallas had with James Watt, the Reagan administration’s first Secretary of Interior. At a meeting with Secretary Watt, Dallas was enthusiastically reporting about how USGS water scientists had used new microwave imaging techniques to map previously unknown underground water channels in rocks a million or more years old. Secretary Watt shook his head and retorted, “That can’t be so, Dr. Peck, the world is only 6,000 years old!” When I asked Dallas about the story, he said it was absolutely true, and added, “What could I say or do, other than just stop right there?” —

    I knew about this, alright, and I retired from USGS, one month before 911, but eventually longtime family friend Sen. Ken Salazar became Secretary of Interior. When Marcia Mcnutt was nominated for Director USGS, I hurried a note of congratulations to her [with the above open file anecdote, my friendship with her new boss and hope for her to be able to help Secretary Salazar with his science knowledge as opposed to a 6000 year old Earth.] at her Monterrey Bay Aquarium Research Institute email and was promptly emailed a thank you

    Next thing I heard was that Marcia Mcnutt was officially designated Science Adviser to the Secretary.

    Whether my note to her and mention of Ken as a friend helped, I do not know, but it could not have hurt.

    “Science is not a body of facts. Science is a method for deciding whether what we choose to believe has a basis in the laws of nature or not.” —Marcia Mcnutt

  12. 12
    Russ Doty says:

    In addition to volcanos, the CEO of a Montana rural electric cooperative recently claimed to me that forest fires put more CO2 into our air than coal-fire electric generation. He read it somewhere. Any rebuttal?

  13. 13
    CM says:

    Thanks for this entertaining, informative and (sadly) useful debunking. For the actual facts about volcanoes and CO2, I usually refer people to Gerlach (2011), “Volcanic Versus Anthropogenic Carbon Dioxide,” doi:10.1029/2011EO240001, which is short, clear and not paywalled. Are there similarly accessible, authoritative resources that should be listed?

  14. 14
    Hank Roberts says:

    I see great potential for furthering confusion but it might help to mention sulfates (whether volcanic or geoengineering) (also in Unforced V’s):

    “… While [ozone depleting substance] ODS levels remain high, a large stratospheric sulfuric aerosol enhancement due to a major volcanic eruption or geoengineering activities would result in a substantial chemical depletion of ozone over much of the globe.”

    Brasseur and Branier anticipated:

    potential effects on the Earth’s climate. Changes in the solar and infrared radiation budget caused by the eruption should produce …

    Can we say it’s probable that the following year’s observation of increased ozone loss confirmed that, or is there enough signal to say?

  15. 15
    WT says:

    It’s a good article. Although with the picture in the background of the graph, it looks like it could have been drawn by Willis Eschenbach.

  16. 16

    #12–Sure, here’s a rebuttal:

    The amount of CO2 emitted from fires in the US is equivalent to 4–6% of anthropogenic emissions at the continental scale and, at the state-level, fire emissions of CO2 can, in some cases, exceed annual emissions of CO2 from fossil fuel usage…

    The CO2 released from fires, overall, is a small fraction of the estimated average annual Net Primary Productivity and, unlike fossil fuel CO2 emissions, the pulsed emissions of CO2 during fires are partially counterbalanced by uptake of CO2 by regrowing vegetation in the decades following fire.

  17. 17
    Daniel Schiffer says:

    Let us not forget that all natural pollution activity goes on and we can do absolutely nothing about it.
    All man made pollution just goes on top of any natural one.
    What frightens me is the thought that maybe all we can do (or are willing to do) to reduce pollution will not be sufficient.
    Should not the World bodies prepare for such a contingency?
    Does the scientific community try to estimate the probability of this occurring in foreseeable future?
    Can you put my mind at ease and say the the probability of Global Warming becoming critical even if we do our best is negligable.

  18. 18

    R: it recalls another depicting hype running contrary to the sense of the science — from 1983 until Thompson & Schneider published ‘Nuclear Winter Reappraised , op-ed casualty estimates soared even as the modeling numbers declined.

    BPL: “Debunking” TTAPS seems to be an obsessions with Russell, as he keeps bringing it up every few months. In case anyone doesn’t know, there were other studies after Thompson and Schneider 1984, at least one of which concluded that T&S was FATALLY FLAWED. Their plume heights were too short by a factor of three, which meant fewer sulfates got into the stratosphere, which meant a much smaller nuclear winter effect. See, for example, TTAPS II from 1991.

  19. 19
    Hank Roberts says:

    > Russ Doty … forest fires … coal

    Coal fires burn fossil carbon.
    Forests don’t.

  20. 20
    Magma says:

    A correction: David Johnston was not a glaciologist but a volcanologist with the USGS. The Science paper he authored was published one month after he was killed during the catastrophic eruption of Mount St. Helens. (In a strange twist, 11 years later the junior colleague whose observing shift Johnston had voluntarily taken over was himself killed by a pyroclastic flow at Mount Unzen, Japan.)

    [Response: Yes of course. Not sure how that crept in! Thanks. – gavin]

  21. 21
    Magma says:

    CM @ 13

    While not authoritative, this USGS page on volcanoes and climate change discusses sulfate aerosols and CO2 and also links to the Gerlach EOS paper. It’s a short treatment suitable for a non-technical audience.

  22. 22
    Edward Greisch says:

    13 CM: That gets mostly a blank page. The very short abstract comes up if you wait.

  23. 23
    Russell says:

    Here for BPL’s edification are“> some primary sources on how TTAPS was recieved.

    The mere history of the matter is that those shouting in denial at Thompson & Schneider were mostly the TTAPS authors themselves.

    Model intercomparison numbers speak more loudly than capitalized cliche’s.

  24. 24

    #12, Russ Dorty:

    Along with other responses above, require that he give you an actual citation with actual numbers. Otherwise, point out to him that he is simply repeating an internet meme that is altogether lacking in even the abstract possibility of logic or evidence. If he pins himself down to concrete claims, then those claim can be directly refuted (using, for example, the materials above.) If he does not pin himself down to a concrete claim, then he must be hammered on the FACT that he is treating unfounded rumors and anecdotal accounts as though they had the same standing as established science.

    My $0.05 worth, anyway.

  25. 25
    James McDonald says:

    @12 Russ: the more important issue about forest fires vs. fossil fuel use is that the carbon in trees recently came from the atmosphere, while (by definition) that from fossil fuels did not.
    If you think of the atmosphere and biosphere together as one unit, growing or burning trees has almost zero effect — it just moves the carbon around.
    But burning fossil fuels adds new carbon to that system that will stick around for millennia.
    And it doesn’t work to argue that all the new carbon goes into plant life, because it doesn’t — most goes into the atmosphere and a lot goes into acidifying the oceans.

  26. 26
    Jamie Cate says:

    #22 Edward, #13 CM, I could access the pdf after clicking on the link in #13. The pdf button appears in the upper left.

  27. 27
    David Lewis says:

    The link to the Sherwood Rowland paper cited, i.e. “President’s Lecture: The Need for Scientific Communication with the Public” is paywalled. A copy for anyone to read is available as a pdf here. It contains detailed discussion of how volcanoes contribute to ozone depletion, how many people misunderstood and continue to misunderstand what scientists discovered, and why.

  28. 28
  29. 29
    Hank Roberts says:

    > 13 CM …
    >> EG “mostly a blank …”

    For paywalled science papers generally, go to Google Scholar
    and search for the paper.

    That usually will find copies at many sites around the world.
    One of them is likely not paywalled.
    You’ll have to look and find out (or ask a librarian to get a copy)
    assuming you’re not an AGU member so you don’t have online access via AGU to the EOS articles generally.,5

    for that particular paper (Scholar finds 26 copies, as I look at it now),5

  30. 30
    CM says:

    Magma (#21), thanks! That’s a good link (though it wasn’t designed to get around the typically massive confirmation bias of people who resort to the volcano gambit in the first place, and who will probably stop reading at the headline…)

    Edward Greisch (#22), the page seems to have some problems, but it does offer a PDF download. Here’s a direct link

  31. 31
    Vendicar Decarian says:

    You forgot to include Marc Morano and the Idso family, both of which have been in the Ozone Hole and CO2 denialist business for a long, long time.

    Dishonesty is their product.

  32. 32

    There’s a secondary volcanic gambit, too, which is to blame Antarctic ice loss and/or oceanic heating on the sensible heat from submarine vulcanism. Don’t know if there’s a similar ‘legit’ starting point for that nonsense, too.

  33. 33
    Nick O. says:

    #22 and #13 – For the Gerlach article, this was in Eos; the pdf link for the full article is here:

    On a related theme, one concern is that increased melting of ice will lead rapid isostatic rebound and more seismicity, and hence more vulcanicity in some areas.

  34. 34
    Halldór Björnsson says:

    Thanks, this is bizarrely entertaining stuff. Here are some numbers on recent eruptions in Iceland for reference.

    Eyjafjallajökull was a medium size eruption in Iceland, – unusual in duration (39 days, with two explosive phases) and produced about 0.18 km3 (dense rock equivalent) of ejecta [1].
    Next eruption in Iceland was Grimsvötn in the spring of 2011, which produced in a few days (most in ~50 hours) about 0.27 km3 of ejecta (also DRE) [2].

    Both these produced mostly ash, although Eyjafjallajökull had an effusive (lava producing) phase in the latter part of April 2010.

    The most recent eruption in Iceland was the half-a-year Bárðarbunga/Holuhraun effusive eruption that produced about 1.6 km3 (DRE), spread over 85 km2 [3]. For comparison Laki (1783-4) produced about 14km3 during a slightly longer interval.

    Thus, the notoriety of the Eyjafjallajökull eruption has nothing to do with its size, or it’s greenhouse gas emissions.

    Of the three eruptions only the last one was associated with impressive gas emissions. The total SO2 emissions in Bárðarbunga/Holuhraun was about 11 x 10^6 Tonns (for short 11 Mt) and CO2 emissions about 6 Mt [3]. Annual anthropogenic SO2 emissions are about 100 Mt [4].

    So, had Bárðarbunga/Holuhraun continued for a full year at it’s average rate it would have been close to 20 Mt SO2 which is about one fifth of the global anthropogenic emissions. While this is an impressive rate, the emissions were into the lower troposphere and climate effects cannot be compared with similar emissions into the stratosphere. The CO2 emissions are tiny in comparison with global averages which come out at about 36000 Mt CO2 per annum.

    It should be noted that the Bárðarbunga/Holuhraun was a large eruption. Of the three eruptions mentioned here, it is the only one to be significant on a global scale. Effusive eruptions of this intensity and duration do not occur more than once or twice per century. (For perspective, the amount of lava produced would be enough to cover Manhattan with a 25 m thick lava).

    But as a CO2 emission event it was not important.


    and also

    [4] and tables S1 & S2 in

  35. 35

    My old professor would probably ask you to show your work. SO2 emissions from auto exhaust is so low that accurate emission levels are hard to come by. Your figure seems way too high for a single years automobile emissions. The number you quote was all human activities or about 30 million tons. An article quotes an EPA official

    “Jacobson said EPA personnel in Washington, D.C. were attempting to determine how much of that amount was produced by automobiles, but the task was difficult because cars emit little sulfur dioxide.

    ‘Cars principally emit carbon compounds, such as carbon monoxide, and nitrous oxides,’ said Jacobson. ‘Sulfur dioxide is not a problem with auto emissions.'”

    Since any SO2 emitted by cars must be in the fuel and sulfur levels were 150 ppm with newer standards limiting gasoline to 30 ppm there is very little sulphur in gasoline. Now diesel is another story by we were talking about cars.

    Emanuele Lombardi

  36. 36
    Brian Dodge says:

    It’s readily apparent that the most toxic emissions, by a factor of several thousand, are the lies about climate science emanating from the steaming pile of right wingers.

  37. 37
    Russell says:

    35 the sulfur limit in heavy equipment e.g, bulldozer diesel fuel is not 150 ppm- in some states it runs into whole %- tens of thousands of ppm.

  38. 38
    tamino says:

    I covered the Gerlach paper (refuting the volcanic gambit) about 5 years ago:

  39. 39

    R 23: some primary sources on how TTAPS was recieved.

    BPL: I know how it was received. The question is, what’s the state of the issue now? Not 32 years ago, but now?

  40. 40

    This is a math question, I guess. The article said “However, while the volcano emitted roughly 2×106 metric tons SO2, annual emissions from cars were 30 x 106 tons (out of a total human emission of ~131×106 tons). Reagan was out by a factor of 150.”
    This seems to me to be a factor of 15, not 150. Feel free to shoot me a note offline if my math is incorrect.

  41. 41
    Russell says:

    That’s why model intercomparisons are included in the link- rejecting three decades of further studies , the original modelers are still using parameter assumptions from the 1980’s :

    “We do not conduct detailed new studies of the smoke and dust emissions from nuclear attacks here. Rather, we chose emissions based on previous studies so as to make our results comparable to them.” –
    — Toon Robock & Stechnikov JGR July 2007

    and no surprise . are recapitulating 1980’s results

    The intercomparisons speak for themselves- here they are on one page.

  42. 42
    Rick Mendham says:

    Without any doubt what so ever, mankind has polluted the earth. We owe it to our planet to clean it up.
    Regrettably, the notion that we are creating a greenhouse effect, no sorry, we changed to global warming…no sorry we changed that again to climate change (to cover any scare notion) just isnt true…
    The Antartic has experienced its coldest recorded 25 year period. Farmers in Brttany farmed bare chested in the 1300s.
    Its been proven that the living organism…the Great Barrier Reef has self repaired over the last 15 years. Bleaching due to climate chamge is NOT happening. Sea levels predicted to rise by almost wo metres over 40 years ago…rose by just a natural occurance of simple 1.3cms over 40 years.
    Catastrophy, threatened by ill informed scientists and dumb tax seeking politicians are our worst threats. They mill fear to perpetuate their importance and calculating politicians find ways to use the fake notion of climate change to impose taxes.Mankind is not to blame for natures’ natural mankind might wish it could.

  43. 43

    What a great yet simple way to present the ‘volcano gambit’ (one of a number of “zombie myths” we have to endure in the mythosphere). The graphic is particularly powerful in representing the level of wrongheadedness, and calling out those doing it. I wonder if this approach should be applied to other zombie myths, providing similar simple graphics to call out the most egregious examples of those who lazily keep propagating disinformation.

  44. 44


    You’re referring me to a page by Watt’s Up With That? REALLY?

  45. 45
    Aaron Lewis says:

    On the other hand, a good, supervolcano event would take our minds off of AGW.

    And, given the sloth of sources and sinks for atmospheric CO2, we have a chance at spectacular geology before atmospheric CO2 concentrations get back to preindustrial levels. It might even solve some of the problem. : )

  46. 46
    Hank Roberts says:

    > smoke and dust emissions from nuclear attacks

    It’s all fun, games, and modeling — until they do it for real.

    Then we’ll know.

  47. 47
    Ric Merritt says:

    The post is solid, as usual.

    The graph is priceless.

  48. 48

    #40, rogers e george–

    Logic, not math–you forgot to multiply by the ‘ten years’ Reagan claimed.

  49. 49
    Richard Caldwell says:

    rogers e george,
    The Reagan quote was about a decade, while the data showed annual amounts. Therein lies your missing factor of ten.

  50. 50
    john byatt says:

    You will need a new color code for this one “WTF”

    How on earth can anyone believe that meme