Well, according to New Scientist, who have definitely swallowed the Kool Aid and are handing it out to passer's by, volcanoes aren't a very significant source of CO2
"Fossil fuels also contain less carbon-13 than carbon-12, compared with the atmosphere, because the fuels derive from plants, which preferentially take up the more common carbon-12. The ratio of carbon-13 to carbon-12 in the atmosphere and ocean surface waters is steadily falling, showing that more carbon-12 is entering the atmosphere.
Finally, claims that volcanoes emit more CO2 than human activities are simply not true. In the very distant past, there have been volcanic eruptions so massive that they covered vast areas in lava more than a kilometre thick and appear to have released enough CO2 to warm the planet after the initial cooling caused by the dust (see Wipeout). But even with such gigantic eruptions, most of subsequent warming may have been due to methane released when lava heated coal deposits, rather than from CO2 from the volcanoes (see also Did the North Atlantic's 'birth' warm the world?).
Measurements of CO2 levels over the past 50 years do not show any significant rises after eruptions. Total emissions from volcanoes on land are estimated to average just 0.3 Gt of CO2 each year - about a hundredth of human emissions (pdf document).
While volcanic emissions are negligible in the short term, over tens of millions of years they do release massive quantities of CO2. But they are balanced by the loss of carbon in ocean sediments subducted under continents through tectonic plate movements. Ultimately, this carbon will be returned to the atmosphere by volcanoes."
Note assorted irrelevancies, weasel words and straw men.
actually includes some numbers. Looks like volcanoes aren't huge emitters.
Cheers
Greg Locock
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