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Comparing volcanic CO2 to human CO2

Posted on 27 August 2010 by Andy Skuce

The solid Earth contains a huge quantity of carbon, far more than scientists estimate is present in the atmosphere or oceans. As an important part of the global carbon cycle, some of this carbon is slowly released from the rocks in the form of carbon dioxide, through vents at volcanoes and hot springs. Published reviews of the scientific literature by Moerner and Etiope (2002) and Kerrick (2001) report a minimum-maximum range of emission of 65 to 319 million tonnes of CO2 per year. Counter claims that volcanoes, especially submarine volcanoes, produce vastly greater amounts of CO2 than these estimates are not supported by any papers published by the scientists who study the subject.

The burning of fossil fuels results in the emission into the atmosphere of approximately 30 billion tonnes of carbon dioxide per year worldwide, according to the EIA. The fossil fuels emissions numbers are about 100 times bigger than even the maximum estimated volcanic CO2 fluxes. Our understanding of volcanic discharges would have to be shown to be very mistaken before volcanic CO2 discharges could be considered anything but a bit player in contributing to the recent changes observed in the concentration of CO2 in the Earth's atmosphere.

Volcanoes can--and do--influence the global climate over time periods of a few years but this is achieved through the injection of sulfate aerosols into the high reaches of the atmosphere during the very large volcanic eruptions that occur sporadically each century. But that's another story...

Recommended further reading on CO2 and volcanoes can be found here: Terry Gerlach in Earth Magazine ; USGS

This post is the Basic version (written by Andy S) of the skeptic argument "Volcanoes emit more CO2 than humans". We're currently writing plain English versions of all the skeptic rebuttals. If you're interested in helping with this effort, please contact me.

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Comments 1 to 23:

  1. A nice and simple explanation, but might the impact of the Terry Gerlach article in Earth Magazine be somewhat diluted by its footnote?
    Gerlach is an emeritus geologist at the U.S. Geological Survey, Cascades Volcano Observatory, in Vancouver, Wash. E-mail: The views expressed are his own.
    Of course, any that proceed to read the USGS reference will see that essentially the exact same observations are made, but with more references to the science. I'm ambivalent concerning the best approach, because I liked the Gerlach article and it's vitally important to hammer-home that Plimer's factually challenged book is useless as a guide to the science. But I'm glad that you provided the USGS as confirmation. Might a one sentence Gerlach biography might be useful?
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  2. This is nice, especially the graphic. The obvious reply to the Plimer madness is to observe how remarkable it is that the postulated increase in invisible volcanic activity, gradually, decade by decade over the last 40 years, should so precisely match the known increase in CO2 from industrial activity.
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  3. Great article. Maybe now the disinformation Rush Limbaugh inflicted on the public will finally die the slow, agonizing death it deserves.
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  4. The presentation is straighforward and informative, yet something seems to be missing.. (i.e., another cloud graphic that represents some other major, yet natural source(s) of CO2). Supposedly, pre-Industrial Revolution CO2 levels were around 250 ppm, whereas now they are around 380 ppm, an increment ratio of 1.5:1. On the otherhand, according to the above, man-made fossil fuel emission is around 100 times that of volcanos. If one assumes nature is only equipped to absorb the CO2 emitted by volcanos, one would expect current CO2 ppm to be much higher. What exactly is not being explained here?
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  5. RSVP: Total emissions since 1750 from fossil fuels and cement production are 337 GT carbon (from ORNL-DAAC). Note that this is equivalent to 92 GT of CO2. If all of this accumulated in the atmosphere, it would represent an increase of 158 ppmv CO2 (2.13 GT carbon per 1 ppmv CO2). However, quite a bit goes into the ocean, so the actual rise has only been about 112 ppmv so far. It's still quite an increase over the pre-industrial conditions: Figure 1: CO2 levels (parts per million) over the past 10,000 years. Blue line from Taylor Dome ice cores (NOAA). Green line from Law Dome ice core (CDIAC). Red line from direct measurements at Mauna Loa, Hawaii (NOAA).
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  6. RSVP, also 250 ppm was indeed the 'pre-Industrial Revolution' CO2 level... if you are talking about ~13,000 years before the Industrial Revolution. Immediately before industrialization began it was around 280 ppm.
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  7. #5 Ned at 21:23 PM on 27 August, 2010 Total emissions since 1750 from fossil fuels and cement production are 337 GT carbon (from ORNL-DAAC). Note that this is equivalent to 92 GT of CO2. No. 337 Gt carbon is equivalent to 1236 Gt of CO2. Currently we have about 3000 Gt of the stuff in the atmosphere. That's equivalent to 823 Gt carbon. At the same time there is about 40,000 Gt carbon dissolved in the oceans in the form of various carbon compounds. That's equivalent to 145,000 Gt of CO2. We also have several tens of million Gt carbon buried in carbonate rocks.
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  8. BP writes: No. 337 Gt carbon is equivalent to 1236 Gt of CO2. You are of course right -- I reversed the conversion. Sorry about that. However, it doesn't affect the rest of the calculations in my comment. 337 GT carbon is approximately equivalent to 158 ppmv in the atmosphere. Comparing this to the observed 112 ppmv increase in the atmosphere shows that, in answer to RSVP's question, there's nothing really large that needs to be explained -- most of the CO2 increase from fossil fuels is still in the atmosphere, but a fraction of it has gone into the oceans. Anyway, thanks for the correction, Berényi Péter. It's been a long week.
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  9. Speaking of C12/C13 ratio. This is an analysis of Spencer that clearly shows its imcompetency. Check the comments, there are as coherent ;)
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  10. Berényi Péter writes: At the same time there is about 40,000 Gt carbon dissolved in the oceans in the form of various carbon compounds. That's equivalent to 145,000 Gt of CO2. We also have several tens of million Gt carbon buried in carbonate rocks. Yes ... so? What's the point, BP? CO2 has been remarkably stable over the past 800,000 years, ranging from ~180 ppmv at glacial maxima to ~280 ppmv during interglacials. But since 1850 we have raised the atmospheric CO2 concentration by 112 ppmv, roughly equivalent to the maximum fluctuation in the entire ice-core record ... but starting at what was already a high point. Over the course of this century we will almost certainly be adding another 150 to 300 ppmv on top of today's level. Nothing like this has happened any time in the past 800,000 years. Figure 1: CO2 concentration over the past 800,000 years from ice cores at Dome C, Vostok, Taylor Dome, and Law Dome.
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  11. In regards to the link {Moerner and Etiope (2002)}, it does not exist nor was I able to find a joint paper by these authors via Scifinder. However, there is a 2002 article by Etiope on "Geologic emissions of methane to the atmosphere" in Chemosphere Volume 49, Issue 8, December 2002, Pages 777-789 0 0
  • thpritch: Thanks, I have fixed the link. Andy
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  • Ned Thank you. The graphs you provide show that the natural sources and sinks of CO2 effect cycles of 100,000 years, or so. This explains how with emissions 100 times found in nature, you get that verticle spike at the end, and I suppose that if this were to continue for 100,000 years, the atmosphere would reach 30% CO2, however this is actually not possible since all the oxygen would be used up way before this. :) Seriously,... it looks like we are up a creek...
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  • Wow! RSVP are you trying to be sarcastic or are you putting down your "skeptic" mantle long enough to admit we have some serious issues ahead of us?!
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  • Thanks, RSVP. If we tried to keep this up over the long term, I think the first limit we'd run into would be a shortage of burnable carbon. But in any case, yes, I agree that the graphs show that we (or, more particularly the next couple of generations) are in for a wild ride. I wish we had started dealing with this problem two decades ago. Somehow it just seems intuitive to me that when you're trying to change a system with a lot of momentum, it's easier to start early with a more gradual change than to wait until the last minute and have to make more radical adjustments. Right now the line on the far-right side of those two graphs seems to be headed implacably upward.
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  • Ned, Before reading your reply #15, (and as I was driving around town), I realized that while fossil fuels are bad news, they will ironically be counted on for transitioning to alternative technologies, and that this situation may not even be something that could have been avoided. actually thoughtfull No sarcasm intended... lets not confuse a little global warming with assured oxygen deprivation.
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  • Further to Ned and RSVP's thoughts, I think of fossil fuels somewhat as a class 1 lever with the advantage end becoming shorter even as the load becomes heavier. Maybe the GHG problem is the fulcrum being moved in a way that makes supporting the load even more difficult? "Snap" goes the metaphor but we should acknowledge we need to slip something else under the load, soon, or it'll fall. The fossil fuel lever is a tool to be used for temporary application, best put away, it's not a cantilever we can use for permanent structural support.
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  • Cloarec, M.-F. L. and Marty, B. (1991), Volatile fluxes from volcanoes. Terra Nova, 3: 17–27. doi: 10.1111/j.1365-3121.1991.tb00839.x Feedback between deglaciation and volcanic emissions of CO2 [PDF]P Huybers, C Langmuir - … Letters, v286 (3-4), p479-491, 2009 - EMEP/EEA air pollutant emission inventory guidebook 2009
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  • The second article TOP referred to can be downloaded here. The paper discusses how deglaciation can temporarily speed up the rates of volcanic activity, as a result of the reduced ice load on the volcano. The concluding sentences of the paper help put the magnitude of this effect into the perspective of modern, man-made changes in atmospheric CO2 concentrations. Finally, we estimate that volcanoes emit an excess 0.1 to 0.5 Gt of CO2 during deglaciation. Humans presently emit ~30 Gt of CO2 per year. If volcanic emissions influence the course of glacial/interglacial climates, it gives us pause that the accumulated volcanic CO2 emissions during ~10,000 years of deglaciation would, at current rates, be replicated by only a century of anthropogenic emissions.
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  • If every man, woman and child on the planet plants 5 trees a year the fossil fuel CO2 problem is fixed. Consider that each tree grows to 1 ton in ten years.
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  • Great, TOP. How many trees have you planted? Your immediate family? Friends? Coworkers? Out of your first circle of acquainted men, women and children, how many or what fraction have planted 5 trees this year?
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  • TOP: According to NASA there are about 400 billion trees on the planet. If 7 billion of us each planted 5 trees per year, then over 12 years, we'd have doubled that figure. That's a lot of grazing land, crop land or desert to convert to forest in such a short time. And I wish that each of the trees I planted recently would grow to be a ton in ten years - and I live in a temperate rainforest climate zone. For now.
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  • I planted eight trees about 15 years ago. Only one of these is still alive. Meanwhile, two or three autochthonous species sprang up where nature dictated. The "CO2 problem" is the unnatural "population problem" that CO2 has amplified. Arguments based on per capita oil consumption are only part of the story. Its not an issue about energy or heat, as much as taking stock in what nature is able to deliver.
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