[ben_w]

People plant loads of trees for lumber, but you're right, it's an economics question in the end.

This actually means I'm also worried about something currently impossible: that when we do develop the tech sufficiently to be useful, if it's cheap enough to be profitable, nothing would seem to stop extraction. So CO2 goes down to, what, 300ppm? Pre-industrial? Ice age? Same coin, other side. We want to flip a coin and have it land on the edge.

A single world government could organise to fix this either way, but as all leadership roles come with the risk of the leader being fundamentally bad, this isn't something I'd advocate for either.

[myrmidon]

> that when we do develop the tech sufficiently to be useful, if it's cheap enough to be profitable, nothing would seem to stop extraction. So CO2 goes down to, what, 300ppm?

This is an extremely improbable scenario, for several reasons:

1) If you actually use the extracted CO2, then it gets re-emitted on use, and the atmospheric concentration is virtually unaffected.

2) Concentration difference alone makes it very unlikely that we'll ever extract CO2 as cheaply as O2 from ambient air (or carbon from a mine), and CO2 is not really an appealing ressource compared to its components, either (so demand would presumable be pretty low for centuries, even if the price comes down a lot).

[ben_w]

> 1) If you actually use the extracted CO2, then it gets re-emitted on use, and the atmospheric concentration is virtually unaffected.

Depends what you use it for, e.g. synthetic diamond windows won't re-emit unless they catch fire.

> 2) Concentration difference alone makes it very unlikely that we'll ever extract CO2 as cheaply as O2 from ambient air (or carbon from a mine), and CO2 is not really an appealing ressource compared to its components, either (so demand would presumable be pretty low for centuries, even if the price comes down a lot).

Underestimating how big an industry would get is the mistake Svante Arrhenius initially made, thinking it would take millennia to emit enough CO2 to cause noticeable global warming.

And remember, with this concern I'm inherently presuming tech (mainly energy) that makes it sufficiently cheap that business and/or governments are willing and able to remove in the order of at least one teratonne of the stuff (but hopefully not two or more teratonnes) — because less than that, it's not solving global warming.