c) Regardless, if #2, #3, #8 & #12 are accurate; do we even need to worry about it, since peak everything will ultimately result in the tapering off of fossil fuel emissions for economic reasons & a catastrophic 'tipping point' is impossible since all of the carbon in fossil fuels was once in the atmosphere prior to the Great Oxygen Catastrophe anyway?
I'm sure I could think of more, but that's what I have right now...
Good post. Right. So. I can speak to alot of this. But I'll talk about (c) because it's the easiest to explain and understand.
Lets think about one possibility, that CO2 was here on the planet. Life evolved that could use that CO2 with light to create...call it sugar. So that was going on.
Millions of years. There was the great oxygenation event and all that, yes. What's missing from your thinking is the rates.
So photosynthesizing plants are using up a lot of CO2. I mean, like, craptons. Over and over, year after year, all over the planet (little bit on land, tons and tons in the oceans). This process is absolutely
cooking. And then it reached a relative equilibrium. So CO2 was getting used up, and it should've disappeared entirely right? I mean maybe a little bit from animals, but the notion that animal life was using up enough plants and oxygen to create enough CO2 to keep the process going is wrong.
So where was the CO2 coming from? The answer is complicated, but it's from a bunch of places. One huge source is volcanoes. Lets just say for simplicity that this is the only source. So volcanoes put CO2 into the atmosphere, and plants take it out. And the various levels go up and down. Periodically, something happens and manages to bury a massive amount of plants and other life, which eventually turns into sweet sweet fossil fuels.
Along come humans, and in 150 years we manage to turn millions of years of sequestered carbon back into atmospheric CO2. Now, we haven't managed to get all of it back up there, and some of it never really left, because it was part of plants that got eaten and then animals, *ahem* exhausted it, but we're definitely trying hard to find the rest of it and burn it. So it isn't that it's in the atmosphere and that's where it came from, it's that instead of being released over millions of years, it's been released essentially instantaneously.
There's really no way to know exactly what the effect will be, but it's sort of hard to wrap your head around exactly what this looks like. The only reason the effect hasn't been massive and worse, is that there are some other sequestration effects that kick in to help knock some of it down, and that the planet was a little on the cold side.
And because the sequestration process that took it out takes geological timescales to work, it's likely that the higher concentration is with us for awhile, so if it does tip the energy balance, then we get a warming trend, as opposed to a warming value (10 degrees total not too bad, 10 degrees per millennium forever...well...not awesome (not my problem either)).