A few critical points;
First:
We're already past the tipping point in terms of CO2 emissions; unless we find a way to scrub it out of the atmosphere (all proposals with any chance of having an effect are priced in, literally, tens of trillions of dollars or more) or reduce sunlight hitting the Earth (big orbital mirrors or something, again, MASSIVE investment cost, and huge secondary effects on plant growth to boot), without something like that, warming will continue, and it will tend to accelerate, since there are exacerbating factors that pile on;
- Reduced ice caps mean that the poles are less "white" and thus less reflective, and absorb more solar energy, increasing warming (particularly in the oceans).
- Melting permafrost generally releases trapped methane pockets; methane is a FAR stronger greenhouse gas in the short term than CO2, though it only lasts in the atmosphere for a decade or two after release
Etc. So it's a snowball effect, and the accelerating sea level rise reflects that, basically. It should continue to accelerate, so it won't be at 3.3mm/year in 2090, it'll be higher.
Second:
There's two measures to be aware of, when evaluating sea level rise; the basic sea level (which is what you're talking about) and the storm surge level. Storms are low-pressure areas, and between pushing the ocean ahead of them with winds and the low pressure tending to "suck" the ocean up, you can get significant temporary increases in sea level rise. The case study I'm using in my thesis work had a storm in 1999 that saw nearly 4 meters of storm surge;
If you see the pole on the right (apologies for the quality; took this with my camera while I was there), the line you can see on it is the high water mark during that storm. The water level you see there is a normal high tide level. That line's about shoulder-high if you're standing next to it. That isn't a possible extreme; that's where the water actually
was in 1999, during that storm, due to storm surge. It caused a lot of flooding, obviously. And that's not the highest wave point, either; that's the resting water level, wave action is on top of that.
Coastal cities are already mostly built right on the limits they could have expected with storm surges in the past. Even 6 inches of additional sea level, especially combined with stronger storms, and you get significant flooding of the city when the storm hits at high tide, which is a matter of time.
If you've never done this kind of flood mapping, you'd be
shocked by how quickly this scales up, in terms of impacts.