I just wrote...
144-million-upwards inhabitants
Sorry. For _all_ of Bangladesh to go under for good (except for the
mountains in eastern Chittagong -- certainly not a place where you can
stuff tens of millions of people), the sea level would have to rise by 6
m. That would require most of Greenland to melt. Sure, this has begun, but
it's still going to take a few hundred years.
Still, a sea-level rise by 1 m would flood 10 % of the country.
Oh, and some say 146 million rather than 144.3.
http://en.wikipedia.org/wiki/Bangladesh