Volcanic CO2 .vs. Man Made CO2

Burning fossil fuels puts 150 times as much CO2 into the atmosphere as volcanoes do annually.

http://www.gaspig.com/volcano.htm

We know exactly how much fuel we're burning, and it's easy to calculate that this burning puts 26 billion tons of CO2 into the atmosphere each year. We know that the atmosphere contains about 2800 billion tons of CO2.

Yet I have seen global warming deniers claim that volcanoes spew hundreds of times more CO2 into the atmosphere than humans. If that were true, then we would expect volcanic CO2 production to exceed 2600 billion tons - little less than the current amount of atmospheric CO2 each year.

Clearly this is a mind-bogglingly ridiculous argument. Even if volcanoes put out the same amount of CO2 as people do, then they would have already put out the equivalent of the current atmospheric CO2 over the past 108 years!

This might be reasonable if there were some sink into which that much CO2 would go, sequestering it and taking it out of the atmosphere much like what happened to the fossil fuels we are now burning. But there isn't, at least not one that big.