A recent discovery may update sea level rise models. The 3 foot rise expected over the next few decades is now seen as only possible under the most optimistic scenarios. Added to that base level of concern are recently discovered phenomena called Marine Ice-Cliff Instability. Ice cliffs can enter a period of accelerated calving and shedding when the weight of the ice exceeds the strength of the ice sheet. Instead of taking millennia to melt, new evidence suggests the sheets can melt in as little as 20-50 years. Two antarctic sheets in particular are vulnerable and could rapidly rise the oceans about 11 feet. If marine ice-cliff instabilities occur they may trigger marine ice-sheet instabilities. Other ice sheets, including ones in Greenland could raise the level another 20 feet.
“Ice Apocalypse” – Grist
As recently mentioned, the last time the planet had this much atmospheric greenhouse gas the sea levels were 33-66 feet higher, so there is precedent.
Pretending Not To Panic 
Pingback: Data That Matters November 2017 | Pretending Not To Panic