CO2 emissions per capita (tons/person/year):
Canada 18.72
United States 15.32
China 7.44
Brazil 2.24
Indonesia 2.02
India 1.89
Canada 18.72
United States 15.32
China 7.44
Brazil 2.24
Indonesia 2.02
India 1.89
There is also the delta to take into account. Industrialized countries are decarbonizing and switching to renewables, while industrializing countries are building new coal plants.
The ethical solution would be for industrialized nations to subsidize the development and decarbonization of developing nations.
You make a good point though: what is and what isn't habitable will change and as a result there will be substantial movement of people, displaced either by choice or by need.
Looks like Niagara falls only produces about 16 billion BTUs or 4.9 Million kWs.