It kind of seems like this article is saying that if we (in 1989) slow global warming by the year 2000, the worst effects of sea level rise will not happen. It's not saying that those effects will happen in the year 2000.

My understanding in 2021 is that much of that stuff is already happening, since we obviously didn't halt warming. And that it's also too late to prevent more of it from happening, because there is a lag time between prevention measures happening, and having an effect.

We are past the point where just reducing emissions will be enough, and instead will need to also harden the world against inevitable effects of climate change. This is even harder and more expensive than it would have been if we had stopped emitting earlier.