There seems to be a cottage industry of old people sending around crazy emails, and my MIL sometimes forwards them to me. They usually blame all the evils of the world on either (a) muslims or (b) the government* … but the latest target is volcanoes.
Specifically, the claim was that the Iceland volcano eruption (when was that? A year or two ago?) produced enough CO2 to negate the effects of all human attempts to reduce CO2 over the past 5 years.
Well, first of all, that could simply mean that the human attempts were so pathetic that a small amount of volcano CO2 was enough to negate them. But, for sake of argument, I found a seemingly reputable analysis here:
Here is the tl,dr:
Globally, volcanoes release a total of about 200 million tonnes of CO2 annually. The global fossil fuel CO2 emissions for 2003 tipped the scales at 26.8 billion tonnes. Thus, volcanic CO2 comprises less than 1 percent of that value.
I’d be interested (DAVE) to see more thoughts on this.
* Of course, I am not entirely unsympathetic to the government-evil theory …