This article doesn't mention carbon at all much less CO2:
http://gsa.confex.com/gsa/inqu/finalpro ... _55669.htm
This one makes a passing reference to CH4:
http://www.pnas.org/content/107/15/6594.full
Again no mention in this one:
http://www.sciencedirect.com/science?_o ... 77fd9e23e4
Now it could be because this just isn't an area studied but the scientific literature doesn't seem to support any sort of massive CO2 release with volcanoes. Sulfer and various halogen compounds yes but CO2 no.
I did find this one:
http://www.sciencedirect.com/science?_o ... 1d08bd88a7
Looks like the numbers didn't copy. They were both on the order of 30,000,000,000,000 grams/year. I make that as 30,000,000 metric tons/year. Now how much is due to this one volcano is another matter. It could be significantly in excess of that from yearly average emissions.Abstract
Global emission of carbon dioxide by subaerial volcanoes is calculated, using from volcanic gas analyses and SO2 flux, to be from passive degassing and from eruptions. Volcanic CO2 presently represents only 0.22% of anthropogenic emissions but may have contributed to significant “greenhouse” effects at times in Earth history. Models of climate response to CO2 increases may be tested against geological data.
A bunch more of possible interest of this google:
http://scholar.google.com/scholar?hl=en ... =&as_vis=1
In particular this one suggest I was wrong:
http://geology.geoscienceworld.org/cgi/ ... /28/10/915
and this one:Although CO2 and H2O account for more than 90 mol% of volcanic gases, the rates at which these gases are emitted from volcanoes are difficult to determine because of their high atmospheric background levels. We report the first precise field measurements of volcanic CO2, and H2O, in addition to HCl, HF, and SO2, in the plume of Masaya volcano, Nicaragua, a basaltic volcano with a record of Plinian activity. The molar ratios for CO2: SO2 (2.3–2.5) and H2O: SO2 (66–69) observed in February–March 1998 and March 1999 show no significant variation over the 12 month period. The molar composition of the gas is similar to other basaltic arc volcanoes in Central America. Emission rates of SO2 from the summit crater, determined by correlation spectroscopy, averaged 21 kg s–1 during the study periods, indicating CO2, H2O, HCl, and HF emission rates of 32–36, 380–420, 7.0–7.8, and 0.86–0.95 kg s–1, respectively. At these rates it takes only a few years to emit the equivalent volatiles associated with Masaya's prehistoric Plinian eruptions.
http://www.sciencedirect.com/science?_o ... e0dd2fd9d3