[JimRed]

But our current rise is 120 and growing at 2ppm per year with no apparent rise in volcanic activity.

And you believe those figures because...? Haven't they lied to us about almost everything before?

[palmer]

I believe those figures because they have been replicated in various locations since the 1950's. There is no doubt that the CO2 has risen to 400+, little doubt that it was never higher in the last 20k years and little doubt that the rise is from fossil.

That said, the main reason it is probably fossil is that there are no other viable explanations or combination of explanations. New volcanic activity has not been observed to correlate with the rise, and ocean outgassing from ocean warming is not large enough to cause the rise. If the rise were from warming, we would need 12C of ocean warming in the last few centuries. That's not plausible.