“Local factors such as land subsidence are primarily responsible for the differences.”
This last sentence basically says that the sinking of coastal land is happening at different rates. I think someone told the global warming crowd that nobody believes the sea level is rising more in Venice Italy than in other parts of the world because it defies logic; when I fill my tub the end by the spigot doesn’t fill before the other end.
Cyrrently sea level is “higher” in the west pacific than along the west coast. The difference is due to the trade winds blowing west and mounding up warm water. When the trade winds relax that warm water spills east and we get El Nino. The differences caused by wind make it difficult to measure sea level.