Since I read about it a few years back, I've been intrigued by Ian Plimer's suggestion that subsea volcanoes may be emitting very large quantities of carbon dioxide into the atmosphere, thus being responsible for a (presumably) significant proportion of the rise in atmospheric concentrations. This idea has been broadly poo-poohed by mainstream scientivists because of lack of evidence, although the idea that one should assume a figure close to zero because we didn't know what was going on at the bottom of the oceans was never one that gave me a warm feeling.
Over the weekend Anthony Watts described an interesting new study which has put a new and much higher estimate on just how much carbon dioxide is being emitted in this way.
We now know that the CO2 released during volcanic eruptions is almost insignificant compared with what happens after the camera crews get bored. The emissions that really matter are concealed. The silent, silvery plumes which are currently winding their way skyward above the 150 or so active volcanoes on our planet also carry with them the bulk of its carbon dioxide. Their coughing fits might catch the eye — but in between tantrums, the steady breathing of volcanoes quietly sheds upwards of a quarter of a billion tons of CO2 every year.
The quantities of carbon dioxide involved are still relatively small with respect to anthropogenic emissions, but the increase over earlier estimates is startling. Given how little we know about the ocean depths, this may not be the end of the story.
Anthony's article is here.