Siberia and Northern Canada would become warm enough for people to live in, so that the earth could hold a much larger population.
Most of the Siberia and the Canadian Arctic will become uninhabitable if global warming persists. When the permafrost melts, the solid soil will be converted to a semi-solid state, leading to the formation of swamps and marshes. It will be almost impossible to undertake agriculture or human settlement in these areas.
No relation to the question of the OP.
Side note, "swamps and marshes" tend to be prolific generators of life, although perhaps rather unpleasant to humans....Hello, Arctic crocodiles....
lol...