How much energy does it take to turn CO2 back into oil? Is there a viable synthesis pathway? Carbon neutral oil would be fabulous. I'm guessing you have to spend a significant amount of energy to turn it back into oil, but is it 1.01x? 1.5x? 10x? 200x? The lower range would be viable to work with other kinds of renewables.

Can't store solar at night? Turn atmospheric carbon into oil. It doesn't have to be cheaper than oil (it almost certainly can't be unless it gets too hard to drill), but we can subsidize it within some kind of range.

EDIT: Oh cool, some people are trying this.

https://www.technologyreview.com/s/407748/making-gasoline-fr...

https://www.sciencemag.org/news/2015/09/feature-there-s-too-...

I very much want to believe this. But how?

It cannot be achieved through reduced consumption. Humans won't allow it. It's technology or bust.

I think the idea is that humanity itself dies off in large numbers due to lack of food, potable water, wars, etc. There's how you get your reduced consumption. The earth itself is just fine with this natural cycle.

> electricity generation also has significant environmental impact

Hydropower? The primary materials used are concrete and steel, and dams last for centuries with minimal upkeep. As long as appropriate measures (such as fish ladders) are taken, the local and global environmental impact is negligible.

Maybe, but we at least need to buy time until we otherwise solve the problems using technology.

Here's your technological solution: Use more efficient, less polluting (and slower) turbofan engines instead of less efficient, more polluting (and faster) turbojects.

And here's the attendant public policy: Tax the turbojects' users enough to offset the negative ecological externalities incurred by their use. That will likely make commercial SST unprofitable.

As far as I know, and according to Wikipedia, most commercial airliners already use turbofans [1], which are high-bypass turbojets [2]. Unless you were referring to turboprops?

[1]: https://en.wikipedia.org/wiki/Turbofan

Almost nobody uses turbojets anymore. Certainly not airliners. Even fighter jets use turbofans.

Exactly my point.