By most people’s criteria I feel your link isn’t independent Matt and it didn’t actually answer my question. So, I have been forced to google ‘Carbon dioxide emissions from volcanoes'.
(I have left out animal & plant emissions because they aren’t ‘fossil’ emissions – they are the normal equilibrium of emission /absorption and even typical of pre-industrialisation. I’ve left out your ‘oceans’ emissions because they absorb, not emit CO2). See
http://www.bbc.co.uk/climate/evidenc..._dioxide.shtml for support for these omissions.
The first reference on my googled list was :-
http://volcanoes.usgs.gov/Hazards/Wh...as/volgas.html
an extract is :-
Quote:
Comparison of CO2 emissions from volcanoes vs. human activities.
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, 1992). 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 22 billion tonnes per year (24 billion tons) [ ( Marland, et al., 1998) - The reference gives the amount of released carbon (C), rather than CO2.]. Human activities release more than 150 times the amount of CO2 emitted by volcanoes--the equivalent of nearly 17,000 additional volcanoes like Kilauea (Kilauea emits about 13.2 million tonnes/year)!
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(My bolding).
Now, I have no idea whether this site is independent – all I can say it doesn’t have extreme rhetoric of other websites on either side of the debate. It seems to be a US government website (the geological service ?). It also gives a direct reference to CO2 emissions from volcanoes :-
Gerlach, T.M., 1992, Present-day CO2 emissions from volcanoes: Eos, Transactions, American Geophysical Union, Vol. 72, No. 23, June 4, 1991, pp. 249, and 254-255.
I have looked closely at the next 20+ google hits but most either refer to this US site as I’m assuming, or don’t deal with my question. One turned out to be an engineering discussion forum – but like this one there were wild unsubstantiated claims on either side.
I tried to look at the Gerlach original paper but it’s off the bottom of the AGU list. However, he/she is still active (get it!) in volcanic gas measurements and in the abstract of a paper in 2002, they found CO2 emissions 2-3 times higher than previously at Mt kileau – (but nowhere near 150 times).
So, I’m still really am trying to be scientifically dispassionate about this question but my undeniable conclusion, (unless you can show me otherwise) is:-
Human activities release far, far more CO2 into the atmosphere that so-called natural sources.