In the couple of games I’ve played so far the population got upto around 8.5billion but then famines caused by drought started killing people off by 2070 so by 2100 it had dropped back to 7.5billion.

I tried as hard as I could to help, but the population kept falling. On the plus side the economic collapse that went along with it meant emissions fell sufficiently to only have a 2.5C temperature rise by the end of the century, rather than the 3.5C it was heading to.