In 100 years our technology would be so advanced that people would be much much more prosperous. Ok sure a few cities drown but people move and adapt.
I still hold ground on the fact that people will be more prosperous in 100 years with sea level rising - in the sense that a person would prefer to live then rather than now
Some places are going to lose their sources of drinking water and others will face deadly heat. Either way millions of people are going to get displaced every year.
The point of view changes according to the sets of people one belongs to while still being alive, eg living in a warming Denver or attempting not drown in NYC?
Look at America/Trump right now with economic immigrants alone. This caused half the country to go "Yea, locking up people in cages and letting losers with guns shoot whoever they want while supporting an authoritarian regime is perfectly ok". Just what do you think it's going to look like when the numbers are 10x that from inside the country alone (a huge amount of the population lives close to the ocean).
Advanced technology has nothing to do with wealth equality and with the costs of making said technology it may be even further reverse correlated in the future.