Adaptation by extinction, the best one. Except people can adapt to living in very warm areas and will adapt even more by using science. e.g. better (GMO) crop,

Adaptation by extinction, the best one. Except people can adapt to living in very warm areas and will adapt even more by using science. e.g. better (GMO) crop, bioreactors, solar powered desalinators, huge water pipes (why not? when we can have huge oil pipes) and so on