What was done
The authors examined "the issue of a possible tide gauge datum discontinuity at Brest [France], caused by the bombing of the city in August 1944," via "a detailed analysis of historical leveling information, and comparison of sea level data between adjacent stations."

What was learned
Woppelmann et al. determined, in their words, that the Brest tide gauge "is 'stable' over the 1889-1996 period," and they say that their work "led to an accurate datum connection between recently rediscovered 18th century sea level data (back to 1711) and those of the present day." In addition, they note that what they call "an interesting by-product" of their work is "the close matching of the Brest and Liverpool [UK] time series over more than 200 years." Both instrumental records, as they continue, "show a roughly coincident increase in the rate of relative sea-level rise around the end of the 19th century," as does the sea-level record of Newlyn in the UK. In fact, from 1890 to the ends of the records, which appear to extend to about 2007, all three data sets define similar linear increases with time.

What it means
If one splits the period of linear sea-level rise into two equal 57-year parts centered on the middle of the 20th century -- 1893 to 1950 and 1950 to 2007 -- it can be determined from various atmospheric trace gas records that the air's CO2 concentration rose about 3.8 times faster over the last of these periods than it did over the first period. Consequently, since mean sea-level rose at a constant rate over the entire 114 years, it seems highly unlikely that the historical increase in the atmosphere's CO2 content -- which accelerated dramatically over this time interval -- could have been the ultimate cause of the steady mean sea-level rise.