How does the amount of CO2 that we create compare to the amount of CO2 that a volcano creates?

Answer 1

Humans emit much more CO2 than volcanoes. I know it is a key bit of climate-change denier mythology that the reverse is true but it isn't.

Volcano's emit between 150-250 million tons of CO2 per year (first source). Humans emit about 25 billions tons (second source).

Both of these numbers are very rough estimates, and it's good to be skeptical about them. The best evidence that volcano's are not a significant source of CO2 is from the level of CO2 in the air over the last 50 years. (third source). The level goes up smoothly, year after year. If a major part of this increase was due to volcanoes, you'd see the chart jump in years with major eruptions. As it is, you can't tell at all which years volcano's went off in.