What was done
The authors studied characteristics of wind speed and direction over the North Sea based on NCEP/NCAR reanalysis data for the 40-year period 1958-1997.

What was learned
In the words of the authors, "the annual mean wind speed for the North Sea shows a rising trend of ~10% during the last 40 years, mainly restricted to the period from October to March."  They also note that "since the early 1970s 'strong wind' events are more frequent than in the 1960s," and "since the mid-1980s, the strong wind events are increasingly found in February and March."

What it means
Winter weather over the North Sea seems to be getting more blustery.  With respect to this phenomenon, the authors say their data "may suggest an anthropogenic origin, but this hypothesis can neither be supported nor disproved by analyzing such short time series."  They do, however, present data indicating a link to the simultaneous increase observed in the North Atlantic Oscillation, which some have suggested to be an expected consequence of CO2-induced global warming.  At the end of the day, however, all is still speculation.