I would bet that even under worst case scenarios + some black swan events 20 feet above sea level is still perfectly safe from sea level rise until 2100, but th

I would bet that even under worst case scenarios + some black swan events 20 feet above sea level is still perfectly safe from sea level rise until 2100, but then you still have increased flooding from extreme rainfall events, draughts, heatwaves, ocean acidification, soil depletion, mass migration, and a number of other future problems that can wreak havok on people just about everywhere.