A major consideration is that as the climate warms, the water mass absorbs much of that heat increase and "disguises" the effects until the water reaches a critical mass at which time there is a greater increase in expansion of that water mass which leads to ocean rise. Another real concern is that the monitoring of the gulf stream seems to indicate that it could be reaching a point where it will stop flowing north and if that should happen, although the planet will still "warm" the land mass serviced by the gulf stream will be covered in masses of ice, creating a very different world i.e. an ice age in the northern hemisphere and droughts and deserts in the southern?