The sea level rise issue comes from ignorance on the part of some, deception by others, and invalid and incorrect assumptions by some so called “scientists” regarding when oceans & ice evaporates due to greater warming, where will all that water go.
While I do not support their thesis, their own error is in how much the greater evaporation of seas and ice will return to the seas. Yes, all rivers do eventually flow to the seas. But what they vastly under estimate is (a) how much water can and will be retained in existing and possibly new land-locked lakes and (b) how much water will be added to the land-based water table and underground reservoirs and aquifers. They also under estimate how a greener planet will have a greater abundance of green plants which will absorb great amounts of water also.
That is only to suggests, that there is every possibility that the greater warmth they predict, even if it nears that prediction (not saying it will), could conceivably NOT produce all the calamities they claim it will. Changes yes, but not necessarily calamities.
There simply isn't enough of the essential plant nutrient CO2 in the current atmosphere to feed twice the greenery as we have now.