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Volcanic vs. Anthropogenic CO2

Filed under: — group @ 4 August 2011

Guest Commentary by Terry Gerlach*

TV screen images of erupting and exploding volcanoes spewing forth emissions are typically spectacular, awesome, and vividly suggestive of huge additions of gas to the atmosphere. By comparison, the smokestack and exhaust pipe venting of anthropogenic emissions is comparatively unexciting, unimpressive, and commonplace. Consequently, it easy to get traction with the general public for claims that volcanic CO2 emissions are far greater than those of human activities, or that the CO2 released in some recent or ongoing eruption exceeds anthropogenic releases in all of human history, or that the threat of a future super-eruption makes concerns about our carbon footprint laughable. The evidence from volcanology, however, does not support these claims.

Volcanic plume ** V Fossil fuel plumes**

My article “Volcanic Versus Anthropogenic Carbon Dioxide” appeared in the June 14 issue of the American Geophysical Union’s publication Eos and addresses the widespread mis-perception in the media, the blogosphere, and much of the climate skeptic literature that volcanic CO2 emissions greatly exceed anthropogenic CO2 emissions. I wrote the article to provide a comprehensive overview of the topic using only published peer-reviewed data with a minimum of technical jargon for a broad spectrum of Earth science researchers and educators, students, policy makers, the media, and the general public. AGU has made the article public; anyone can download a copy. There is also an Eos online supplement, although I have a better formatted pdf version that is available upon request.

The bottom line? Annual anthropogenic CO2 emissions exceed annual volcanic CO2 by two orders of magnitude, and probably exceed the CO2 output of one or more super-eruptions***. Thus there is no scientific basis for using volcanic CO2 emissions as an excuse for failing to manage humanity’s carbon footprint.

*Terry Gerlach is retired from the U.S. Geological Survey where he was a volcanic gas geochemist.The views expressed are his own.
** Yes we are aware that CO2 is colorless and that the plumes in the figures are mostly steam. – Eds.
***Super-eruptions are extremely rare, with recurrence intervals of 100,000–200,000 years; none have occurred historically, the most recent examples being Indonesia’s Toba volcano, which erupted 74,000 years ago, and the United States’ Yellowstone caldera, which erupted 2 million years ago.

115 Responses to “Volcanic vs. Anthropogenic CO2”

  1. 1
    Richard Harvey says:

    Thank you for a useful and much needed explanation about this basic fact of volcanic emissions. Your graph in your EOS article is especially telling.

    [Response: – gavin]

  2. 2
    Slioch says:

    There are authoritative sources of this information already. See for example:

    Volcanic Contributions to the Global Carbon Cycle
    British Geological Survey, 2005.

    This gives similar figures:
    Human caused emissions of CO2 = c. >30 Gigatons/year
    Volcanic (both terrestrial and submarine) = c. 0.3 Gigatons/year

    ie. volcanic emissions of CO2 are about 1% of anthropogenic emissions.

    Someone claiming that volcanic emissions of CO2 exceed human emissions is not a climate sceptic: he/she is either ignorant or is deliberately trying to mislead people.

  3. 3
    Russell says:

    The damage was done by the broadband hyping of supervolcanos on ‘educational’ TV. Half a decade ago I blogged that:

    ‘ the New York Times / Discovery Channel’s “Supervolcano” and PBS’s “Strange Days On Planet Earth”. They round out a quadraphonic post-Tsunami barrage of volcanic doom and gloom on educational and cable TV. It includes every eruption you’ve ever heard of, ranging from Thera to Tambora by way of Pompeii…

    Supervolcano and Strange Days feature a virtual planet from Hell that crackles with the day glow shock fronts only high resolution software can generate. Gone is the good gray PBS screen that used to educate and inform, replaced by a surrealist billboard for images intense enough to brand themselves into the popular imagination — we are being shown the future by design…

    The Earth spewing enough incandescent gore to gag Quentin Tarentino may seem a hard act to follow, but with the explosive growth of computer animation, anything goes. The New York Times’ pop science outlet, the Discovery Channel, has joined with the BBC to bring us high budget hype for high definition TV… The New York Post’s Adam Buckman admits “Discovery has had a reputation for emphasizing science over fiction” which makes “the whole thing seem entirely plausible.”

  4. 4
    Tim Jones says:

    Gavin, your response doesn’t seem to be live.


  5. 5
    Daniel Curewitz says:

    When Eyjafjalajokull was erupting and shut down European/N. Atlantic air traffic for more than a week, folks were trying to estimate the change to carbon emissions… the result I remember was that CO2 emissions into the atmosphere dropping at least 10-fold for that period. Yes, the volcano emitted a lot, but the amount not emitted just from having no European air traffic was much greater.

  6. 6
    wili says:

    The paper gives the figure for 2010 anthropogenic emissions at 35 Gt. I had heard a bit lower than that. Does this include other, non-CO2 GHGs?

    What is the level for total accumulated emissions of CO2. The graph above seems to indicate that it is less than 200 gt, but I had always assumed it was more than that, since we are now emitting more than 30Gt of the stuff per year.

    Thanks for the great paper.

  7. 7

    Thanks for some vivid comparisons to help drive this point home. Unfortunately, in the polarized and politicized context we’re living in, this sort of thing can’t be said often enough.

  8. 8
    Chris Colose says:

    This image should convince anyone. Try to spot the volcanic impact on the CO2….

    Of course, they are important for sustaining the levels of CO2 over geologic time.

  9. 9
    Gordon McGrew says:

    I am not an expert in volcanology, but I am trying to figure out why an eruption would contain significant amounts of CO2, unless the volcano was located over an oil or gas field.

    [Response: Volcanoes are bringing up magma from the crust – which is often subducted ocean sediments (think the ‘ring of fire’ in the Pacific) which are heavy in carbonate rocks. There is probably more to this though… Maybe some passing volcanologist can chime in with a good reference? – gavin]

    [I’m no expert on this either, but I can dust off my undergrad thesis a bit…. You don’t even need the carbonate rocks — that’s just calcium plus dissolved CO2. Plenty of deep ocean water — generally saturated in CO2 — gets subducted along with the sea floor rocks and sediment. You’re both right, of course, that the amount of CO2 in volcanic eruptions varies from place to place of course, depending on what the rock type is, though the idea of a volcano ‘over’ a gas field doesn’t make sense. The roots of a volcano are deep — so if there’s a volcano around, you can be sure there are no oil and gas deposits right underneath it. Interestingly enough there’s a rare type of volcano that actually produces carbonate rock (carbonotite) instead of the normal silicate (basalt, andesite etc.) rock we’re used to thinking of from places like Hawaii or Stromboli. Such a volcano [presumably] emits far more CO2 that others, but there are only a handful of these.–eric]

  10. 10

    #8–Yes, it should. . .

  11. 11
    Gsaun039 says:

    As I recall, Peter Ward makes an argument that most of the mass extinctions on the planet can be tied to changes in the atmospheric concentration of CO2 (which leads to other effects in the Canfield Ocean that has apparently has dominated the oceans through much of the planet’s history).

    These mostly are attributable to certain large scale volcanic events unlike anything seen in recent geologic history. His comparison is to where we are today compared to what the paleotological evidence suggests. His conclusion is that we are poking a tiger with a stick.

  12. 12
    Jaime Frontero says:

    With all due respect, the graph inserted by Gavin as a response/clarification to post #1 does not convey information as it was perhaps intended to: “…with a minimum of technical jargon for a broad spectrum of Earth science researchers and educators, students, policy makers, the media, and the general public.” [the OP].

    For evidence of this, see #6. (“What is the level for total accumulated emissions of CO2. The graph above seems to indicate that it is less than 200 gt…”) It’s a graph of a multiplier, front and center: the most critical takeaway of the article (an excellent one, for all of that, and thank you Mr. Gerlach). But it took me a minute. Speaking as a more-or-less scientifically literate member of the public, without context it’s not something the general public will wrap their heads around easily or intuitively.

    * sigh * Everything I read these days, I read through the lens of Tom Curtis’ comment – almost a year ago, here:

    “Whenever your simplify the explanation of a significant theory sufficiently to make it understandable to high school graduates of average education, you also make it misrepresent the science sufficiently that unscrupulous people can make a plausible case that you are wrong. This is particularly true of descriptions of complex systems such as climate.”

    …the most striking and disheartening word-bite I can recall ever having read on the internet.

  13. 13
    Hans Kiesewetter says:

    I’m missing a “line of defence”.

    Yes, volcanic CO2 emissions are small compared to the emissions from human activities. We can proof that. But that has no meaning. Central point is that human emissions are additional. Even if volcanic emisions were twice the amount we emit, it would not matter. There is no indication that volcanic activity has increased the last few centuries, so they can not be an explanation for present rising CO2 levels.
    Just imagine that we can convince the deniers (no, we can not) about the vulcanos, they can easely switch to an other natural source. At the end, the human emissions are still small compared to the total natural carbon cycle. See this graph. For example, the emissions by oceans are 10 times larger than antropogenic emission. But these large emissions by the oceans are not the problemen because they are part of a well balanced system, in balance for thousends of years.
    Nevertheless it is good to have articles like this available to educate the journalist who shoud educate the public. (And I can use it too. Thanks).

  14. 14
    Hansi Singh says:

    Thanks for publishing this. An excellent article that I will direct my learned comrades to in the event of ignorance or misunderstanding of the scientific consensus.

    The whole issue of anthropogenic climate change is one that should remind us that we, as a scientific community desiring a well-educated populace, need to push for better science and math education in the public schools. I agree that this is NOT an article that is accessible to the lay reader, though portions of it SHOULD be. It is the relative opacity of scientific literature, combined with scientific illiteracy in the general population, that has enabled so many charlatans to put doubt and denial into the public psyche regarding ACC. Ignorance does not respond well to reason.

    Great article, nonetheless.

  15. 15
    Dikran Marsupial says:

    regarding eric’s comment about different types of volcanos: IIRC the skeptic claim (e.g. Plimer) seems to be that the official figures don’t include underwater volcanic activity (which appears not to be true anyway). However, I would have thought that they would be the low CO2 type of eruptions as they would be less likely to be bringing up magma from subducted crust (I am thinking here of e.g. the mid-Atlantic ridge)?

  16. 16
    Edward Greisch says:

    9 Gordon McGrew: The coal seam or petroleum source could be above and the magma source below. Then the magma would flow through the fossil fuel. I read somewhere about that happening in the Siberian traps [volcanic “stairsteps” region] 250 million years ago.

  17. 17
    Ian says:

    In your opening paragraph you comment:

    “TV screen images of erupting and exploding volcanoes spewing forth emissions are typically spectacular, awesome, and vividly suggestive of huge additions of gas to the atmosphere. By comparison, the smokestack and exhaust pipe venting of anthropogenic emissions is comparatively unexciting, unimpressive, and commonplace”.

    In australia at least and possibly in other countries, the media when discussing carbon dioxide and anthropogenic global warming invariably decorate their piece with pictures of “smoke” plumes from cooling towers That these are plumes of water vapour and not smoke is never mentioned. Perhaps this is because such pictures are not “comparatively unexciting, unimpressive, and commonplace” even though they may be misleading

  18. 18
    tamino says:

    Thanks for the RC post, and especially for your article in EOS. Back in June I used it as a basis to refute yet another of the foolish claims about volcanic activity dominating the growth of atmospheric CO2:

  19. 19
    Jim Eager says:

    Hans @13 wrote: “For example, the emissions by oceans are 10 times larger than antropogenic emission.”

    But note that there are two arrows for the ocean in that graph (and for vegetation and land), one for emission, and one for absorption, and that the one for absorption is larger than the one for emission.

    That means emission from the ocean is more than offset by absorption of CO2 by the ocean. The ‘sceptics’ aka deniers never mention the absorption arrow.

    However, there is only one arrow for the burning of fossil fuels. Our power plants and automobiles don’t absorb any CO2.

    That is to say, the ocean absorbs as much CO2 as it emits, plus more than a quarter of what we humans emit each year, which is why the pH of seawater is falling.

    Similarly, CO2 emission by volcanic activity is roughly offset by geologic absorption of CO2 through carbonate shell deposition and silicate rock weathering.

    Those who bring up CO2 emission from the ocean and volcanoes are misleading people, often deliberately, by using only half the truth.

  20. 20

    Neither link in the posting seems to work.

    [Response: Possibly related to today being the deadline for abstract submission to Fall AGU. I have put another copy of the main file here. – gavin]

  21. 21
    Slioch says:

    #6 wili

    Between 1850 and 2000 the total recorded human caused emissions of CO2 amounted to 1620 billion tons CO2. The increase in atmospheric CO2 was 640 billion tons. Most of the difference (about 1 trillion tons CO2) has been absorbed by the oceans and terrestrial sinks. The oceans are a net sink of CO2 at present, ie. they are not expelling net CO2, even though they are warming, because the effect of the increase in partial pressure of CO2 in the atmosphere more than compensates for the warming.

    [Info. from the Carbon Dioxide Information Analysis Centre: with masses C converted to CO2 by multiplying by 44/12)]

    As for the total accumulated emissions of CO2, each increase of 1ppmv of CO2 represents an extra 7.81Gtons CO2 in the atmosphere (see cdiac above), so the increase from c.280ppmv pre-industrial levels to the present 394ppmv means an extra 890Gtons CO2 in the atmosphere. This does not, of course, represent the total human emissions, since rather more than half of anthropogenic emissions have been absorbed by oceans and land.

  22. 22
    Jim Eager says:

    Yes Ian (@17), the use of images of power pant condensing/cooling towers in media stories is a common and misleading occurrence, especially when those towers are actually at a nuclear plant, but they are also used at some fossil fuel thermal plants, so it’s hardly the same as deliberately misleading people about the size of volcanic emissions, which are in fact less than 1% as large as those from the burning of fossil carbon fuels, now is it?

  23. 23
    Peter Boyer says:

    Thanks Terry for a useful weapon in the battle against misinformation. (I come from the land of Ian Plimer, so I know something about that.) A small technical matter which I found frustrating – I tried to access your paper using the URL supplied, but whichever link I used (including Googling the paper title) I kept getting redirected to the AGU Fall meeting flyer – . Is there a bug in the system or am I missing something? (No, I’m not paranoid.)

  24. 24
    thomas hine says:

    The mass balance margin of error is what is laughable, eh CSU carbon-cycle physicist?

    Texas is praying for hurricanes – come on NOAA, deliver.

  25. 25
    Geoff Wexler says:

    Useful article.

    Plimer states: “Over the past 250 years, humans have added just one part of CO2 in 10,000 to the atmosphere. One volcanic cough can do this in a day.”

    This hyped version of his own claim, came out close to an important debate in the Australian Parliament. It was also on Plimer’s web site. When I asked a geologist about it, he suggested that the solubility of CO2 in magma under pressure would probably be too low to make this possible. But it was not a definitive reply.

    Plimer’s assertion was also on the ABC.
    Points of possible confusion result from the need to learn more than one point.

    People who have been encouraged to trust the experts have problems with being told that Ian Plimer , described as a geologist, can possibly be so wrong about a geological topic like this. This can be a major stumbling block.

    If they can get their head round that one, they are then surprised to discover that volcanoes actually cool the planet in the short term. But it doesn’t end there. They have to learn that the emergence of life required that the Earth should be able to boot itself out of a snowball state and that the best explanation is that this was due to the warming caused by the very slow emission of CO2 over geological time.

  26. 26
    Patrick 027 says:

    Re 3 Russell – I remember thinking that the Discovery Channel movie “Supervolcano” was not particularly unrealistic (except perhaps for the low probability that it would go off in any one time period (but they weren’t saying ‘this will happen now’)- but it easily could happen again someday, possibly when there are still technologically-advanced humans about) – certainly more realistic than either “Armageddon” or “The Day After Tomorrow”, and way way way more realistic than “The Core” (all good movies, though). There were no claims made about the CO2 emissions from the volcano – that I can recall. The movie depicted global cooling, which would certainly happen – about the duration and magnitude, I’m not sure (about reality or the movie).

    The problem perhaps is that there aren’t enough realistic AGW movies (I’d recommend “Earth 2100” (the only one I know of) – very very depressing).

    [Response: If you want to be really depressed, go to the unforced variations thread, and read about Judith Curry’s latest incredible jump into unscience….–eric]

  27. 27
    Bryan S says:

    “though the idea of a volcano ‘over’ a gas field doesn’t make sense. The roots of a volcano are deep — so if there’s a volcano around, you can be sure there are no oil and gas deposits right underneath it”

    You can’t be so sure, since there are in fact a few oilfields beneath volcanos. They are rare, but occur where the a non-vertical magma vent and relatively shallow chamber produces a volcano at the surface which overlies sedimentary rocks in the subsurface. Quite a geologic novelty, but yes, they do occur.

    [Response: Fair enough. Thanks! –eric]

  28. 28
    M says:

    “Such a volcano [presumably] emits far more CO2 that others, but there are only a handful of these”

    Is Mt. Etna of this category? I’m fairly sure I remember reading that Mt. Etna by itself accounts for a significant percentage of the total volcanic emissions worldwide…

    [Response: No, Etna is a regular old stratovolcano, like Mt. Rainier.–eric]

  29. 29
    Thomas says:

    Volcanoes represent a recycling of the silicate carbonate cycle. Silicate rock (I think these are of volcanic origin) weather into quartz and carbonate, absorbing CO2 in the process. When the carbonates are subducted and heat up enough the reaction revereses. This in combination with the sensitivity of erosion rate to global temperature over geologic timescales is the proposed thermostat that has keep the earth livable over billions of years.

  30. 30
    Vincent says:

    “TV screen images of erupting and exploding volcanoes spewing forth emissions are typically spectacular, awesome, and vividly suggestive of huge additions of gas to the atmosphere. By comparison, the smokestack and exhaust pipe venting of anthropogenic emissions is comparatively unexciting, unimpressive, and commonplace.”
    In cognitive psychology, this is known as the “availability heuristic”, first empirically studied by Tversky and Kahneman: .

  31. 31
    Rick Pikul says:

    For a discussion elsewhere, in response to such a volcano claim, I did a ballpark calculation of how much stuff was put out by Pinatubo.

    It looked to be a bit less than human CO2 emissions, but that was everything sent up by Pinatubo combined. Everyone here should know where most of that stuff ended up: On the ground within sight of the volcano, it’s not like rocks stay in the atmosphere for very long.

  32. 32
    Rick Pikul says:

    That should be “annual human CO2 emissions”.

  33. 33
    janama says:

    You may wish to read this article on Volcanic CO2

  34. 34
    E.L. says:

    Good post, and hopefully, it will clear up some common misconceptions.

  35. 35
    Nick Rouse says:

    ** Yes we are aware that CO2 is colorless and that the plumes in the figures are mostly steam. – Eds.
    Steam is also colorless. The clouds in both cases are mainly fine droplets of liquid water

    [Response: Water vapour is indeed colourless, and indeed, these plumes are made up of droplets of liquid water. But steam colloquially can refer to both. – gavin]

  36. 36
    EFS_Junior says:

    (I don’t know if this should be posted in this thread or the current Open Variations thread)
    This infamous E&E paper;
    (consider the publication in E&E and the site location where posted, as both are highly biased with intent)
    claims that there is no lag between the NH and the SH with respect to CO2 concentrations, and therefore concludes (incorrectly I might add) that atmospheric CO2 concentrations can’t be anthropogenic in origin.
    However, anyone can go to the Scripps CO2 site;
    And download the entire MLO and SPO monthly datasets (two flask datasets, one each for SPO and MLO), and one atmospheric air in situ dataset (MLO) (NOTE: I’m using the last column of data from these three files (seasonally adjusted filled)).
    These are the two sites where direct CO2 measurements have the longest records (March 1961 to February 2011 (flask based comparison, 50 years of record) or March 1958 to February 2011 (flask vs air in situ, 53 years of record).
    I get the following results when plotting SPO vs MLO (no lag), SPO = 0.961*MLO +11.6 (spo (flask) vs mlo (air in situ)), R^2 = 0.99953 (autocorrelation)

    I get the following results when plotting SPO vs MLO (no lag), SPO = 0.962*MLO +11.2 (spo (flask) vs mlo (flask)), R^2 = 0.99933 (autocorrelation)

    Note the close agreement between these two results, one with flasks and one with two different measurement systems, the coefficients and constants, as well as the very high R^2 (yes, there is bound to be a lot of autocorrelation regardless), and note that the linear coefficients are less than one.

    Now I forward lag SPO relative to MLO by N months (forward lagging brings a later part of the SPO monthly time series in line with the untouched MLO time series), forcing the lagged plot through zero at the origin, and lag until N yields a slope of the line of approximately one (cross-correlation).

    I get the following results when plotting SPO vs MLO (N = 16 month lag), SPO = 0.999895*MLO (spo (flask) vs mlo (air in situ)), R^2 = 0.99897 (cross-correlation). (the linear coefficient is slightly less than 1, thus lag is actually somewhat greater than N = 16).

    I get the following results when plotting SPO vs MLO (N = 17 month lag), SPO = 1.00016*MLO (spo (flask) vs mlo (flask)), R^2 = 0.99888 (cross-correlation). (the linear coefficient is slightly greater than 1, thus lag is actually somewhat less than N = 17).

    NOTE: I did this aboot a year ago and updated the spreadsheet today with the annual Scripps update for 2011 that was released a few months ago.

    Anyways, tha lag in SPO relative to MLO is quite obvious and unambiguous, consistent with the majority of anthropogenic CO2 emissions being sourced predominantly from the NH, thus one would expect a significant lag in CO2 concentrations at the SPO versus all other higher latitude CO2 measurement sites.

    Therefore, the author of this infamous E&E paper does not know what all they are even talking aboot.

  37. 37
    Terry Gerlach says:

    #2 (Slioch)
    I have searched through the BGS publication you mention (Hards, 2005) 3 or 4 times in the past. It reports various estimates by others for various aggregates of volcano types, but I have never found a place where it lays out a global volcanic CO2 emission estimate of it brings them together into a global estimate. Its 0.3-Gt/y estimate is for terrestrial (i.e., subaerial) volcanic degassing only, and this is at least a factor of 2 greater than other subaerial estimates. Further, it is taken from the subaerial volcanic CO2 emission estimate of 0.3 Gt/y by Morner and Etiope (2002), which is an assumed estimate rather than an empirical estimate, as I point out in my supplement. It was obtained by first assuming (dubiously) a plume CO2 output of 0.25 Gt/y for 500 historically active subaerial volcanoes—a lot of CO2 output for a group of volcanoes that are presently mostly inactive (each one would be emitting about 20% of what a very active volcano like Kilauea in Hawaii emits each year); next, it is assumed that the diffusive flux of CO2 from the volcano flanks is 20 percent of this value to get an additional 0.05 Gt/y. Until these assumptions (particularly the first one!) are verified, this estimate is highly speculative and suspect. Neither Morner nor Etioipe have subsequently published measurements supporting either of these assumptions. This estimate was published in Global and Planetary Change, not exactly a mainline journal for volcanology, petrology, and high-temperature geochemistry, which is probably how it survived the review process.
    #6 (wili)
    No, non-CO2 GHGs are not included. The 35 Gt includes CO2 from fossil fuel combustion, land use changes, cement production, and waste gas flaring. This information is stated in the figure caption along with reference and URL sources (sorry, probably not the best choice for it).
    If you click on the graph in comment #1 and magnify it so you can read the y-axis label and caption, you will see it is not about total accumulated anthropogenic CO2 emissions. As noted by #12 (Jaime), it shows the anthropogenic CO2 multiplier (ACM)—defined in the paper as the ratio of anthropogenic to volcanic CO2—over time rising gradually from 1900 to 1950 and then rapidly to the present. The figure shows anthropogenic CO2 is increasingly dominant over volcanic CO2.
    #13 (Hans), #19 (Jim)
    Interesting discussions. A volcanic analogy to the anthropogenic “addition” may be a period of accelerating volcanism during plate tectonic reorganization or breakup of supercontinents.
    #14 (Hansi)
    Excellent critical comment. I’ll remember this!
    #15 (Dikran)
    The estimates for global submarine volcanic CO2 were the earliest global scale estimates to be made, thanks to isotope and tracer techniques that made this possible for the submarine environment. There are some words in the supplement about techniques that allow estimates of submarine volcanic CO2 without needing to count submarine volcanoes or measure gases from individual volcanoes. For example, much of the work has been done on glass samples from dredged lavas coupled with He isotope fluxes for the oceans. I think Plimer understands this (or at least could understand it), but he typically makes diverting commentary about all the many uncounted volcanoes on the seafloor—nearly all of which are extinct, but he never points that out.
    #17 (Ian)
    The gas emitted by erupting volcanoes is typically about 90 percent water vapor (mole basis).
    #18 (Tamino)
    Thank you for the link. I look forward to reading the comments. Do you think Plimer is the source of the Pinatubo quote? I’ve been looking for evidence that clearly ties it to him. Do you have anything?
    Thanks for all your comments.

  38. 38
    Icarus says:

    If I understand it correctly, Plimer has been making a slightly more subtle argument than “volcanoes produce more CO2 than human activity”. His argument is that one volcanic eruption could produce more CO2 than the amount we’ve *avoided emitting* by instituting emissions reduction measures… and for all I know, that could be true. It’s certainly not as obviously false as the “volcanoes produce more CO2 than human activity” claim, but it is without a doubt intended to mislead and to be misinterpreted (wilfully or otherwise) as minimising the significance of human emissions. It’s also entirely irrelevant to the issue of emissions reductions, for a couple of the reasons already raised here, plus other reasons.

  39. 39
    Dave says:

    The end is near.

    CO2 follows warmth.

    [Response: Well done. You have discovered the positive carbon-cycle feedback. Now think about what happens when you put human CO2 in the air, which warms the planet and which then releases more CO2 into the air and ….. The end may indeed be a bit nearer. – gavin]

  40. 40
    Jim Eager says:

    janama @33, why on earth would we disregard what the US Geological Survey and the British Geological Survey say about volcanic CO2 and instead accept the pseudo-paper published by a petroleum geologist on his website?

    That’s right, Timothy Casey’s lively hood depends on the petroleum industry.

    But let’s assume for a moment that he’s correct that CO2 emissions from volcanic activity is larger than thought. Let’s assume it’s double the estimates. It would still amount to less than 2% as much annually as from burning fossil carbon fuels.

    Please, get a clue.

  41. 41
    Russell says:


    Fast forwarding geological time to advertise eschatology is not limited to televangelists seeking to cash in on the end times before the end of the fiscal year.

    Environmental PR firms can photoshop the apocalypse as well as anybody in the business.

  42. 42
    Susan Anderson says:

    I’m mildly addicted to Russell’s writing, a brilliant conservative unwilling to mess with the truth (and a witness for the existence of same), otherwise I would have used this time elsewhere. (If he reads this, I do not expect him to return the favor; that’s OK by me.) Daniel Curewitz (@5) also makes a good point – volcano had less effect than not flying planes. I remember at the time of the post about Glory somebody linked to the satellite site, and I fossicked around, finding highest CO2 emissions somewhere in the neighborhood of Greenland, 298 at the time. I know data over time and space is different from point sources, but it was interesting nonetheless.

    Definitely check out Earth 2100; at the time somebody mentioned the “look” was Soviet era graphics which was against it. I wish Podesta and his institute and some other good people would find better PR. As time trickles through our lives, leaving us in progressively worse case, oil is being given a makeover – love your oil and gas, smart molecules – which to my eye is very effective (likewise with coal, but this is recent). On every level, fakery does a better job of promoting its mischief than those who know what they are talking about outside the political position.

  43. 43
    Mike says:

    Any thoughts on the Salby talk/paper being touted elsewhere?

  44. 44
    Hank Roberts says:

    Mike, wrong topic, asked and answered.

    The very same question has been repeatedly posted around the site, off topic — likely by people who try to bump it up in search results.

    When that happens, often it gets ignored after a while.

    There’s a way to avoid being confused with those copypastebotpeople, though.

    You do know how to use the Search tool.

    Try it. White rectangle, upper right corner of every page.

    Click the option for Site Search and type “salby” into the white space.

    See? Easy.

  45. 45
    Jim Eager says:

    Terry Gerlach @37 “A volcanic analogy to the anthropogenic “addition” may be a period of accelerating volcanism during plate tectonic reorganization or breakup of supercontinents.”

    Yes, something that I often point out when discussing the interaction of CO2 and temperature, particularly the slow build up in CO2 and temperature at the end of the Paleocene as the Indian subcontinent moved northward, forcing the subduction of the shallow carbonate-rich seabed between it and Asia, which triggered the PETM on the way to the peak of that warming in the early Eocene.

    But I also point out the subsequent long, slow draw down of both CO2 and temperature as the resulting uplift of the Himalaya and Tibetan plateau led to accelerated silicate weathering, both excellent examples where the change in CO2 clearly preceded the change in temperature.

  46. 46
    EFS_Junior says:

    #43 Any thoughts on the Salby talk/paper being touted elsewhere?

    Hm, no.

    So far, all we have is an audio podcast, no slides even. Go figure.

    Typical denier MO though, circle j**k fantasies litter the denial-o-sphere, waiting for jolly old St. Nick.

    The paper will appear at some future date TBD, perhaps E&E, or some other obscure 3rd tier publication totally unrelated to climate science.

    You will also get to buy the book BEFORE the paper is published though, with hints of inclusion of some of this proported “bombshell” of a revelation.

    In the good old days (three days before The Day After Tomorrow), we got the PR just slightly ahead (by a few days) of the peer reviewed paper, now we’ve had the BEST pre-pre-pre announcements, and now this pre-pre-pre-pre-pre-pre- …, ad infinitum ad nauseum.


  47. 47
    Geoff Wexler says:

    Re # 38. Your remark is interesting, but I have a question:

    Plimer has been making a slightly more subtle argument,

    I wonder if he has ever withdrawn the less subtle versions such as the one in #25 ?

    He doesn’t usually make an argument. Unless he has reformed recently, he has a whole encylopedia of them, which can be used one at a time or all together in a gish gallup.

  48. 48
    Brian Dodge says:

    @ janama — 5 Aug 2011 @ 1:17 AM

    Don’t you think it’s too much of a coincidence that Casey’s “1000 potentially active subaerial volcanoes worldwide” have been hypothetically increasing their emissions, starting around 1850, precisely matching the rate of anthropogenic fossil fuel emissions? Something that has never happened in the last 400000 years, according to the Vostok CO2 record.

    Casey is also wrong in his assertion that volcanic CO2 is indistinguishable from fossil fuel emissions. Concentrations and isotope ratios of carbon, nitrogen and sulfur in ocean-floor basalts SARAI et. al 1984 found “The isotopic ratios of indigenous carbon and nitrogen are in very narrow ranges, -6.2 [per mil; symbol didn’t paste] relative to PDB and +0.2 & 0.6460 relative to atmospheric nitrogen, respectively.”
    This is less negative than the atmospheric ratio, which declined from -7.6 in 1980 to -8.2 in 2008. The Mid Ocean Ridge is the largest volcanic structure on earth, 65,000 miles long. Its erupted basalt created the ocean floor, average age ~70 million years, thickness ~2km, area ~1.8e8 km^2. The volume is therefore 3.6e8 km^3, and the eruption rate is ~5km^3 per year. The is equivalent to one Mount Pinatubo every 2 years – Pinatubo was the largest eruption since Novarupta in 1912, and caused no measurable change in atmospheric carbon isotope ratios. FÜRI ET AL.: CARBON RELEASE AT THE COSTA RICA FORE ARC
    “We estimate that the carbon flux (CO2 plus methane) through submarine fluid venting at the outer fore arc is 8.0 × 105 g C km−1 yr−1, which is virtually negligible compared to the total sedimentary carbon input to the margin, …the implication is that most of the carbon being subducted in Costa Rica must be transferred to the (deeper) mantle, i.e., beyond the depth of arc magma generation.”

    The ocean ridge carbon has the wrong isotope ratio to account for atmospheric CO2 rise. Plate margin subduction zone volcanism removes more carbon than it emits. Even if you accept Casey’s glorified guesswork that Toba emitted 494 Mt of carbon, that is a small fraction (<2%) of the 26 Gt of carbon from fossil fuels and other human activities. We can't possibly be missing 50 Toba scale eruptions per year, (or 500 Tambora scale eruptions). Pinatubo didn't even make Casey's scale, and most of us noticed that eruption and its effect on climate.

  49. 49
    Clippo (UK) says:

    Hiding a smirk, I’m afraid to say both opinions on the source of CO2 are wrong here. Apparently, in the current WUWT article,
    a Prof. Salby ‘proves’ the current CO2 rise is due to Warming, i.e. the old ‘800 year’ lag. (and therefore AGW must be hoax)

  50. 50
    Jim Eager says:

    Clippo, you are late to the party and in the wrong thread.