Computer modeling is as much an art as it is a science and much depends upon the assumptions that are made, consciously and otherwise. Additionally there is far more to consider when you consider the entire Earth as a single but ever-changing environment. It is no accident that meteorologists need the very best and most powerful computing platforms just to do 3-5 day forecasts. The interplay of factors in a column of atmosphere extending from ground level to space is almost unbelievable.
In this prediction of a 3+ foot rise in mean sea level, I wonder what compensating factors do their computer models take into account for the following factors; increase in solar bounce-back from an increase in iceberg coverage, where the increased water evaporation from the increased water surface will be deposited and so on? Are these scientist more competent than I? Yes without a doubt. Are they more competent than the 'dissenters' who, despite Al Gore's risible protestations, are becoming an increasingly significant protest movement against anthropocentric global climate change? I have most considerable DOUBTS!
Why do you call them scientists? They are modelers. I started my career as a scientist. The scientific method shaped my knowledge. In the 70’s I got into computing. The only science in the computer is the actual manufactured parts. Programs can do anything.
Do you realize that you can come up with a single equation that will pass exactly through N distinct data points? The equation will be of order N-1.
It will pass through all, but there is no guarantee where it goes between these points or beyond them.