Sea level rise can be extremely nonlinear. There are glaciers in Antarctica that are like the cork in the wine bottle. If the "gatekeeper glacier" is gone, the sea water gets into the basin that's below sea level and will melt all the multi kilometer thick ice in that basin.

Each can provide meters of sea level rise. You can check out Eric Rignot's presentations from youtube.

We don't know if the melting of such a gatekeeper glacier will take ten, fifty or a hundred years. But it has started.

You can't extrapolate this effect from just looking at recent past temperature and sea level rise - it's a whole different mechanism.