Well with all due respect to all in this conversation the most likely point of no return was around 1980. This is not used in general conversation around the subject as the “we can still save ourselves” v the “**** it, it’s too late” has more kerb appeal.
It’s inevitable that we will need a technology to save us, as abstinence is a very hard sell particularly in less well off parts of the world.
Also water as in too much and too little is a more immediate problem. Covid was a very big near miss, it might not have felt like that but it was – that view came directly from a virologist at Porten Down.