RE: CO2 has no effect on global warming.
I wouldn't say I worry about them, I don't try to pretend they don't exist or that I am unaware of them.
millions of volcanoes? I couldn't find a number for the ocean floor but I think you may want to revisit your source for that
There are approximately 500 active volcanoes in the world today, not including those underneath the oceans. In fact, as you read these words, there are probably 20 volcanoes erupting right now. Between 50-70 volcanoes are erupting every year, 160 have erupted in the last decade.
So there are 20 volcanoes erupting, obviously they have an impact, but why would you think burning close 3 to billion gallons a day of petroleum based fuels has none?
Yes the buffalo also had an effect except they didn't extract CO2 that they emitted from deep within the earth like we do at the rate of almost a trillion gallons a year.
If those pigeons still did that they would certainly have an effect on the climate.
If an estimate of 4,000 volcanoes per million square kilometers on the floor of the Pacific Ocean is extrapolated for all the oceans than there are more than a million submarine (underwater) volcanoes
the pacific is where most surface volcanoes are too, the ring of fire, so I don't know why we would extrapolate that. The good thing about underwater volcanoes is that their effect, if any, on the atmosphere is hard to measure because they don't shoot any clouds of ash gasses or whatever directly into it.