For The Record

I regularly see the claim from climate denialists that volcanoes dump much more CO2 into the atmosphere than human activities. Only rarely do I see it pointed out that this is simply false.  The Guardian does so today:

If you have been a victim of the rumour, persistent in some circles, that volcanic CO2 emissions dwarf those of human activity, now is the time to be liberated.
According to the British Geological Survey:

The contribution to the present day atmospheric CO2 loading from volcanic emissions is, however, relatively insignificant, and it has been estimated that subaerial volcanism releases around 300 Mt/yr CO2.

The US Geological Survey estimate is lower still:

Volcanoes emit … about 130–230 million tonnes of CO2 into the atmosphere every year. This estimate includes both subaerial and submarine volcanoes, about in equal amounts.

What I hadn't seen before was the estimate that human CO2 production was on the order of 100 times that of volcanoes.  Wow.