A different perspective on atmospheric CO2

Something I don't usually try to talk about too me, since it seems so contra. I read a terrific book a few years ago about the evolution of the atmosphere (Oxygen: A Four Billion Year History by Donald E. Canfield) which pointed out something that had never occurred to me. The rock cycle, which is the transition of rocks in the crust from various processes, mostly related to plate tectonics, is what makes our planet the really extraordinary geological system that it is. And it includes the sequestration as carbonate rocks resulting from biological processes, of a truly enormous amount of carbon dioxide. Mars' and Venus' atmospheres are mostly Carbon dioxide. But Earth's is almost all rock. Think how finely balanced that is. Without that little bit of carbon dioxide, it would be very very chilly on this planet and life would be much constrained. Thing is, for the last 50 million years or so, up until about 1780, that little bit was mostly slowly but surely falling towards zero. This is one of the main reasons that for the last 2 ½ million years (a fairly short time, so a recent paradigm shift), the Earth has been mostly glaciated down to about 50° latitude. (The arrangement of continents and ocean currents is the other principal reason). The rock cycle is failing, or better to say, the carbon sequestration in the crust is nearing totality. This is bad for life in any number of ways, not least of which is organisms cannot make either food or oxygen in the absence of CO2 in the atmosphere. Along comes humanity and upsets the applecart. CO2 levels start to RISE. The earth warms (returning to mean if you look at the last 50 million years). Any threat of insufficient CO2 for metabolism and photosynthesis averted! Yay! Humanity learns that it can, and must, steward the atmosphere so the great carbon depletion extinction is averted forever! Hurrah!

Well, that doesn't square well with the climate message, which is, too fast! too poisonous! crisis! slow down!... but somehow that message is hard enough to convey without complicating the issue with the simple fact that in the long run, stabilizing and maybe even living with a somewhat higher level of CO2 is optimal, and we really probably have permanently averted what would have been, based on precedent, a fairly rapid progression of the next ice age in the relatively near future. Of course, that doesn't change one bit the urgency with which humanity must act to avert the catastrophic instability and possible collapse that could result in allowing the levels to rapidly rise to extreme levels. And in this, although the greatly reduced cost recently of renewable energy is certainly a plus, it remains the fact that our race to net zero is being lost, and we are likely to have to pull out stops which are themselves chaotic and unpredictable, including direct mitigation efforts. But one way or another, I think it likely that there will be a path forward. We will always have to pay attention to our emissions, but the science is pretty clear, and people, after reality has bitten them squarely on the ass, do eventually do what is optimal.