First world countries already have 1 child per family with the rest of the world also moving that direction as they grow wealthier. This policy wouldn't actually do much to help and would likely cause massive unintended consequences like China is dealing with right now.
Yes I know putting it into practice by law is not practical or even wanted. I just don't believe climate changes significantly improves by having electric cars and replacing old light bulbs with led. We need more deepcutting measures.
Either have less kids or power the world nuclear and all eat vegan (no methane producing animals), or accept the new climate reality and deal with the heat or whatever. Just don't pretend we are doing a good job at the moment because we don't.
Obviously putting humanity below replacement reproduction eventually causes it to disappear, then the planet will recover from whatever we did after a few million years.
But I don’t see how that will make it a better place to live for us. We know that birth rates already fall with higher standards of living, so if you want fewer kids just develop those countries where the birth rate is still high.
A world wide one-child policy like it used to exist in China [1] would be a real solution in keeping earth a pleasant place to live.
[1] https://en.wikipedia.org/wiki/One-child_policy