I am not well versed at all in the multiple disciplines one needs to talk about this in technical detail, but I guess 500.000 people per habitable continent should be enough?
I do realize this is impossible to enforce top down or get the people to do bottom up. As the evolutionary greedy animals we are, we will continue to procreate.
After all this rambling my short, personal answer: The only possible thing is becomming true eco terrorists and genociding 99% of the world population somehow. Boom. 99% of the ecological/climate foot print humanity has evaporated!
To the appalled reader: I‘d prefer reasonable counter arguments over downvotes and flags...
Ideological capture.
You have been convinced to act against your own self interest.
I do not care about the future of humanity and nature, I try to live as hedonistic as I can and do not desire being a father. Also, I do not wish for the mentioned genocide. I‘d only care about it to the degree it impacts me: I do not want to die as part of the 99% and I do not want the amount of potential lovers to be reduced.
Perhaps I'm being presumptuous but it sounds like you are in a state of hopelessness.
I will pray for you.
I mean, if every ton of CO2 emitted had to be offset by certificates for 1.1 tons of CO2, that were truly removed from the atmosphere, the climate problem would be solved over time and we could switch to 1:1 once we got the atmosphere back to pre-industrial levels. While this would surely reduce quality of living, I would be surprised if this meant that only 500k people per continent could survive. Surely, we could do better.
Lol sound like impossible for many practical and social raisons. Thinking about how temper the overkill proposition is more realistic than keep on lying ourself to the impossible one.