I.e. about the "extra 20ft of risen sea"
The recent studies I've explored predict around 50-130cm by 2100. However, I have seen discussions of ~20ft by 2200 and 26ft by 2300 (https://www.theatlantic.com/science/archive/2019/01/sea-leve...), alongside more alarming figures (https://www.annualreviews.org/doi/10.1146/annurev-environ-10...).
You might be interested to read The Myth of the 1970s Global Cooling Scientific Consensus: http://nora.nerc.ac.uk/id/eprint/11584/1/2008bams2370%252E1....
Excerpt: "There was no scientific consensus in the 1970s that the Earth was headed into an imminent ice age. Indeed, the possibility of anthropogenic warming dominated the peer-reviewed literature even then."