Externalities are emergent.
The benefit of computers, AI, medicin, the ability to save life by being able to drive patients to hospitals and keep babies alive in incubators and I could go on. The ability to produce fertilizers which is why we can keep 3-4billion people alive and who wouldn't be around if it wasn't for that.
The ability to produce steel, concrete and plastic and the resillience that provides us.
The world is greener, we can produce food more places.
Moden life is 100% depending on the burning of fossile fuel and while it creates it's own problems, these are better problems to have than those it solved.
That's too expensive a target to be realistic right now, so the real question is what's a level of taxation that won't cause social unrest, but that will change behaviour?