I just hope Bangladesh is still habitable in 20 years.

Well before it is inundated by rising seas, rising temperatures (in the hottest times of year) and high humidity can make it impossible for humans to sweat enough to maintain a livable body temperature, even sitting still in the shade.

This will be a problem in other areas, particularly Sub-Saharan west Africa, much of Central America, and in and around Indonesia. Hundreds of millions of people live in those areas now. They will not sit down and die; they will try to move to where they can live, but there are borders in the way, and people blocking those borders.

It has already started.