SUMMARY

The wind speed data appears to have been heavily affected by the changing location of the recording equipment and it may be unsafe to draw conclusions.

However, there does seem to be a downwards trend in the measurements from around the early 1970s which is contrary to climate change modelling predictions.

There is also a hint that a ten-year cycle may be operating.

ANALYSIS

Climate Modellers predict that Britain will get stormier as the global temperature rises [1]. The evidence presented below shows the opposite to apparently be true for Weymouth.

Geoff Jenkins, Head of the Hadley Centre, has said that Britain has become twice as stormy in the past 50 years as climate change has forced the deep depressions that used to hit Iceland to move further south. Whilst low pressure areas which bring high wind and rain are getting deeper, the high pressure areas which bring calm, settled periods are getting stronger. The increased gradients between the two make for more dramatic weather - and for insurance companies, expensive claims for damaged buildings and fences.

The Environment Agency predicts [2]

"... the climate predictions also indicate that Britain will be windier. One study suggests 30 percent more gales in Wales and southern England in winter, increasing the risk of another storm like that in 1987, which left £2 billion of damage in its wake. Greater windiness in summer could also add to the desiccation of the landscape."

So, is it getting more windy in Weymouth as climate modellers are predicting?

Figure 1

Figure 1 shows the wind speed record at the same time each day from 1949 averaged over a one-year moving window. Before 1949 wind speeds were recorded as Beaufort Numbers which cannot accurately be related to actual wind speeds. 

It can be seen that there is an overall downwards trend in wind speed with a dramatic drop between 1969 and 1992 as indicated by the red arrows. This change is almost certainly due to the change in location of the recording equipment in these years. In 1969 the recorders were moved from the Corporation Yard on Westwey Road to Westhaven Hospital. The latter is near the crest of a hill on the outskirts of the town whereas the Corporation Yard is in the centre of the town. One might expect the winds to be stronger on the new site. However, the above chart shows the winds recorded as being about 4 mph lower.

In 1982 and 1983 the recorder was moved within the hospital grounds and this probably accounts for the sudden rise in mean wind speed seen in the chart at around that time.

In 1992 the equipment was moved because of vandalism which had been a big problem since the 1950s - this type of crime is not a recent phenomenon! The next location is a secret but is significantly different from the Westhaven site. This move almost certainly accounts for the jump in mean annual wind speed recorded in 1992.

Despite these discontinuities in the data caused by location changes, there does seem to be two trends in operation in figure 1.

Firstly, there is an overall trend downwards of about 2 - 3 mph per decade which is seen in periods where the recorder was in the same location, i.e., the 1970 - 1979 and the 1995 - 2005 decades.

Secondly, there seem to be peaks in the data approximately every 10 - 11 years. It is possible that this is tied up with the 11-year sunspot cycle which is known to affect some aspects of weather and climate.

1.  The Guardian Unlimited, 'Climate change doubles Britain's stormy weather' http://www.guardian.co.uk/uk_news/story/0,3604,1103539,00.html