Average annual output of CO2 from volcanoes is 130-230 million metric tons per year:
The great 1991 eruption of Mt. Pinatubo released CO2 to an extent estimated to be 42 to 234 million metric tons:
The most recent 1-year figure I can find so far for CO2 from fossil fuel combustion is 8.05 petagrams of carbon, meaning 29.5 billion metric tons of CO2. That is from an estimate by BP, which has turned out to be reasonably accurate. The most recent estimate from the Carbon Dioxide Information Analysis Center is from 2005, and is probably the one in the line with the year labelled as "2005.5". That figure is 7.61 PgC, which is 27.9 billion metric tons of CO2. The one for the year before that is 7.34 PgC, which is 26.9 billion metric tons of CO2.
Looks like fossil fuel combustion is adding CO2 to the atmosphere at an annual rate 100-200 times that of that of volcanoes.
- Don Klipstein ( snipped-for-privacy@misty.com)