> I'm a bit dubious about this

What exactly are you dubious about? That the paper predicts lower sea level rise than previous models, or that either way the sea level rise will be enough to have serious consequences?

Your phrasing makes it seem like you're disagreeing with me, but I don't see which part you're disagreeing with.

> Now, it could be a matter of timing - it might take 1000 years or so for the full ice-sheet response - but it's not exactly reassuring.

There's a massive difference between "20m of sea level rise in 80 years" and "20m of sea level rise in 1,000 years".

In particular, my understanding is that paleographic studies are generally of the form "temperature went up 5C and sea level went up 20m over the course of 10ky", meaning sustained temperature increase led to large sea level rise. There's not really any hope of seeing temperatures 80 years from now back to pre-industrial levels, but IPCC scenarios like SSP1-2.6 see temperature starting to fall by then, meaning it could be back to pre-industrial levels within a century or two.

As a result, if a certain amount of sea level rise requires only 80 years of sustained temperature increase of 1.5-2C, we have little hope of avoiding that. By contrast, if that amount of sea level rise requires 1,000+ years of sustained temperature increase of 1.5-2C, there's quite good odds of avoiding some, most, or potentially even virtually all of that.

In general, the known ice melt tipping points take thousands of years. I extracted a list of those tipping points from a paper previously discussed on r/science, and the timescale for 10m+ of sea level rise looks to be about 2,000 years (mainly West Antarctic ice sheet and East Antarctic subglacial basins).

If the water rises slow enough, we might get lucky and find lots of it falling on land and recharging aquifers, which would reduce the amount in the ocean and contributing to the rise. Not by much though