Highly speculative. Full of conjecture. Based on flimsy evidence. Not supported by mainstream science. Not peer reviewed. Not suitable for basing policy on.
It sounds like climate scientists are talking about the claims of climate deniers. But this time they are talking about a 23 July discussion paper by James Hansen, the most famous and respected climate scientist on the planet.
In it, Hansen starts by arguing that the ice melting on and around Greenland and Antarctica will cause rises in sea level that are much faster than mainstream predictions, meaning that we are likely to see several metres of sea level rise this century. It is an argument he has been making for a long time: for instance in his 2007 feature for New Scientist.