Almost assuredly extremely poor non-Americans who contribute very little to greenhouse gas emissions.

The rich people who are still buying ocean-front property?

If that stuff is ever truly condemned a level of government will pay them fair market rate (1), and there will be finagling to ensure that rate is appropriate. You forget that this is a country that has seen the mississippi flood its banks for three centuries, and rather than not develop these flood prone areas we opt to develop them, allow them to be destroyed, and offer federally subsidized flood insurance to rebuild them to be inevitably destroyed again in the future.

1. https://en.wikipedia.org/wiki/The_Sunken_City

Yes, but only because they have a ton of overlap with the much broader group of "people who will get shot in the hole they just dug for shortsightedly causing exactly the kind of societal instability that resulted in them getting shot in the hole they just dug."

Humans can survive and thrive in very extreme climates. We can grow enough food for everybody. What we can't do is figure out ways for both of those things to happen without preventing people's standard of living from going so far backwards they get shooty.

I had a business professor joke that his house that was off the beach would be worth a fortune for his grand kids because it would end up being waterfront.