I would use caution throwing around ultimatums. I'm sure pocket-sized digital supercomputers or a global near-instant communications network didn't seem likely within the lifetime of people born in the Great Depression, but here we are.
These exponential advances in technology are difficult to predict with human brains. I try to stay cautiously optimistic.
This of course depends on the time frame one wants to achieve, but assuming we want to remove carbon dioxide as quickly as we added it, that means we would need some operation comparable in size to the global coal, oil and gas industry extracting carbon dioxide from the atmosphere around the clock. And while I agree with you, exponential growth is in some sense hard to predict, I don't really see us starting such a gigantic endeavor unless we are absolutely forced to by the consequences of climate change.
Today's computers were perfectly obvious to Gordon Moore in his 1965 paper. By contrast nobody today is writing papers about the inevitable expansion of carbon-free energy production.
Various forms of next generation nuclear would meet that requirement right? People are certainly writing papers on building better nuclear power plants. Doesn't even have to be something exotic like fusion.
> Don't forget that you'd have to do that in an entirely carbon free way and cease all current carbon emissions
Plenty of carbon is naturally removed from the environment, at least partly by photosynthesis; that's how an equilibrium was maintained before we humans in wealthy countries started releasing so much more carbon into the atmosphere. We don't need zero emissions.
Carbon is generally not removed from the environment by photosynthesis.
In photosynthesis, CO2 is converted into sugar [0], storing the solar energy in the chemical bonds of the sugar molecule. Later, the energy is released through the reverse reaction where the sugar is converted back into CO2 [1].
Carbon is also used in biology for things other than sugar production, but in general the carbon that gets consumed by an organism eventually gets released when that organism (and the organism that ate it, and so on up the food chain) decays. This is refered to as the carbon cycle.
Under some circumstances, the carbon cycle is broken, and dead organisms end up sequestering their carbon in a place that does not allow it to return to the general environment (eg. fossil fuels).
TL;RD when we burn fossil fuels we are adding carbon to the environment. When plants consume carbon, they are moving it from the atmosphere to another part of the environment, and it almost always ends up back in the atmosphere.
[0] The full reaction is CO2 + Water -> Sugar + Oxygen, or 6(CO2) + 6(H2O) -> C6H12O6 + 6(O2)
Yes, good point. I knew that but somehow it escaped me when I wrote the post. My point was, the global ecosystem can handle the release of some carbon by human activity without a problem; we don't need to go to zero.
However, the sooner and farther we reduce carbon output, the faster we reduce excess carbon in the atmosphere. There's nothing magic about zero; negative output would help too.
These exponential advances in technology are difficult to predict with human brains. I try to stay cautiously optimistic.