I suggest that this headline means that the level of presumed danger X has increased to 1.0001X in the past fifty years.
We have added 2.75 inches over the past twenty two years and that is during a warm phase in our climate of which we have had many in the past ten thousand years.
Trouble is that all the easy ice has been melted and this is not a linear process. Progressively more heat needs to be applied.
In the meantime water expansion has also been acknowledged and that applied to the top six hundred feet. That is a huge mass and it can absorb a lot of heat.