This assumes sea level change is the largest hazard of climate change. An increase in severe weather and changes in the climate of arable regions seems like a much larger hazard. Adaptation isn't necessarily the hardest part either - our world order is already in flux with migrants leaving the Middle East and Northern Africa - if people start leaving other regions it's going to be a challenge to maintain order. If people start fleeing countries like India, Pakistan, Indonesia, or Bangladesh en mass due to climate change there will be massive implications for the stability of the region.