Upton Sinclair said
“It is difficult to get a man to understand something when his salary depends on his not understanding it.”
Let’s just try to understand a fairly straightforward question. I don’t mean straightforward as in ‘easy to determine’ , but as in ‘you’d think it might have a definite, clear answer’. Here it is:
How much carbon dioxide do volcanoes emit?
This seems exactly the kind of question we should be able to answer if we want to be able to say anything serious about climate change (see the top left box of the diagram). It also seems to be the kind of thing that scientific observation and measurement ought to be able to help us with.
Furthermore, it would in principle be perfectly reasonable to conclude that we don’t actually have an answer yet because it’s just too hard to measure volcanoes with existing methods and technology. A little humility never hurt anyone.
So here goes with the answer.
First, the United States Geological Survey claims:
“Human activities release more than 130 times the amount of CO2 emitted by volcanoes.”
Second, Ian Plimer’s book Heaven and Earth states:
“Volcanoes produce more CO2 than the world’s cars and industries combined”. (p. 413)
Since there is a difference of a factor of around 130, it’s reasonable to suppose that these contrasting answers cannot both be correct. Inconveniently, however, the Plimer source does not actually state how much carbon dioxide is produced by volcanoes.
When challenged on this discrepancy in an interview, Ian Plimer did not deny the USGS figures but claimed they were only measuring terrestrial, not oceanic volcanoes: “85% of the world’s volcanoes we neither see nor measure… They leak out huge amounts of carbon dioxide… That does not come into the USGS figures nor does it come into the Intergovernmental Panel on Climate Change’s figures.”
Is this correct? Vulcanologist for the USGC, Dr Terrence Gerlach replied:
“I can confirm to you that the “130 times” figure on the USGS website is an estimate that includes all volcanoes – submarine as well as subaerial … Geoscientists have two methods for estimating the CO2 output of the mid-oceanic ridges. There were estimates for the CO2 output of the mid-oceanic ridges before there were estimates for the global output of subaerial volcanoes.”
The USCG site actually lays out the figures:
“Scientists have calculated that volcanoes emit between about 130-230 million tonnes (145-255 million tons) of CO2 into the atmosphere every year (Gerlach, 1999, 1991). This estimate includes both subaerial and submarine volcanoes, about in equal amounts. Emissions of CO2 by human activities, including fossil fuel burning, cement production, and gas flaring, amount to about 27 billion tonnes per year (30 billion tons) [ ( Marland, et al., 2006) – The reference gives the amount of released carbon (C), rather than CO2, through 2003.]. Human activities release more than 130 times the amount of CO2 emitted by volcanoes–the equivalent of more than 8,000 additional volcanoes like Kilauea (Kilauea emits about 3.3 million tonnes/year)! (Gerlach et. al., 2002)”
Human CO2 emissions relating to energy are also detailed in the EIA Energy Outlook 2009 (using figures from the Energy Annual 2006), with the similar result of 29bn metric tons in 2006.
The IPPC reports tend to refer to radiative forcing (RF) and it is in these terms that they describe the impact on the climate of volcanoes:
“Because of its episodic and transitory nature, it is difficult to give a best estimate for the volcanic RF, unlike the other agents. Neither a best estimate nor a level of scientific understanding was given in the TAR [Third Assesment Report]. For the well-documented case of the explosive 1991 Mt. Pinatubo eruption, there is good scientific understanding.However, the limited knowledge of the RF associated with prior episodic, explosive events indicates a low level of scientific understanding (section2.9, Table 2.11)” (Forster et al. p. 195)
It seems strange that rather than refer to the low level of scientific understanding about volcanic radiative forcing, which the IPPC report concedes, Plimer would make unreferenced assertions about volcanic emissions of carbon dioxide. He is, after all, a professional geologist. Would such a person not know that scientific claims are supposed to be backed up with data, or references or… anything at all? Would he not also be able to work out that even if terrestrial volcanoes were only 15% of all volcanoes, as he seemed to claim, the total CO2 emissions of these plus the ‘85%’ of volcanoes supposedly not included by Gerlach and the USGS would still amount to nowhere near the amount emitted ‘by the world’s cars and industries combined’?
The volcano issue is just one of many climate change ‘facts’ that are contested by Plimer, and then re-contested by others, including Ian Enting’s fairly detailed critique of Plimer’s book.
So, would a reasonable person be entitled to conclude that Prof Plimer’s figures are organised on the basis of the preconceived desire to deny anthropic climate forcing? This may or may not have something to do with the fact that he is the director of three mining companies – which we might dub the Sinclair effect (remember the salary that depends on not understanding). Or he may have convinced himself on other grounds, such as an entirely novel and undocumented understanding of the carbon dioxide emissions of volcanoes.
He doesn’t seem to think the directorships could influence his opinions in any way, since science is science whoever does it. But it is clear that Plimer’s book has been used to support climate change denial and has bolstered the positions of a number of influential people.
We should scarcely bother with Plimer’s book – after all, it has been said of it:
“It is not “merely” atmospheric scientists that would have to be wrong for Plimer to be right. It would require a rewriting of biology, geology, physics, oceanography, astronomy and statistics”.
The point of this little polemic is to note how even something as seemingly straightforward (though hardly simple) as the amount of carbon dioxide emitted by volcanoes is the subject of contestation.
We don’t primarily argue about the interpretation of facts, as many would like to believe. We argue about the facts themselves.
Even though to me and to others it appears Prof Plimer has failed to give any reference for his assertion that volcanoes produce more CO2 than the world’s cars and industries combined, he still manages to influence the climate change debate by appealing to people who either already agree with his general view, or who aren’t in a position to query his detailed working (lack of it, that is). It’s interesting that a number of commentators on Plimer’s book have been impressed with the large number of references it contains. Would one more, detailing all those gassy undersea volcanoes no one else knows anything about have been all that hard to provide?
Forster, P., V. Ramaswamy, P. Artaxo, T. Berntsen, R. Betts, D.W. Fahey, J. Haywood, J. Lean, D.C. Lowe, G. Myhre, J. Nganga, R. Prinn, G. Raga, M. Schulz and R. Van Dorland, 2007: Changes in Atmospheric Constituents and in Radiative Forcing. In: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M.Tignor and H.L. Miller (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.
Gerlach, T.M., 1991, Present-day CO2 emissions from volcanoes: Eos, Transactions, American Geophysical Union, Vol. 72, No. 23, June 4, 1991, pp. 249, and 254-255.
Gerlach, T.M., McGee, K.A., Elias, T., Sutton, A.J., and Doukas, M.P., 2002, Carbon dioxide emission rate of Kilauea Volcano: Implications for primary magma and the summit reservoir, Journal of Geophysical Research, Vol. 107, No. B9, 2189, doi:10.1029/2001JB000407.
Plimer, Ian. 2009 Heaven and Earth. Connor Court Press.