Background
The authors write that "one area of growing concern in climate science is the impact that global warming could have through modulations of the nature and characteristics of naturally occurring extreme events, such as severe mid-latitude storms," and that a recent study of a 47-year storm database (Alexander et al., 2005) "showed an increase in the number of severe storms in the 1990s in the United Kingdom," but that "it was not possible to say with any certainty that this was either indicative of climatic change or unusual unless it was seen in a longer-term context."

What was done
To provide that longer-term context, Allan et al. (2009) extended the database of Alexander et al. back to 1920, almost doubling the length of the record, after which they reanalyzed the expanded dataset for the periods of boreal autumn (October, November, December) and winter (January, February, March).

What was learned
Both databases exhibited peaks in storminess in the 1920s and 1990s, with boreal autumn storms being more numerous in the 1920s and winter storms being more numerous in the 1990s. In the figure below, therefore, we have plotted the total storm numbers for each decade; and as can be seen there, both the beginning and end decades of the record experienced nearly identical numbers of storms.

Number of extreme storms impacting the British Isles in each of eight decadal periods. Created from results reported by Allan et al. (2009).

What it means
It should be clear to everyone from the results obtained by Allan et al. that the number of extreme storms impacting the British Isles over the last eight decades of the 20th century were not in any way related to the global warming of that period, which climate alarmists claim was unprecedented over the prior millennium or more.

Reference
Alexander, L.V., Tett, S.F.B. and Jonsson, T. 2005. Recent observed changes in severe storms over the United Kingdom and Iceland. Geophysical Research Letters 32: 10.1029/2005GL022371.