Readers must exercise some caution in reading the analysis of the Weymouth weather records as the recording equipment has been moved several times since 1927 which is when the full daily recording was started. However, with the exception of the sunshine and wind speed, there is no evidence that these moves have biased the data.

ACCURACY OF BBC WEATHER FORECASTS

A scheme for testing the accuracy of BBC five-day online weather forecasts for Weymouth has been used based on the weather symbols displayed on the website [1].

This shows that forecasts are correct on only about one day in four irrespective of time ahead of the forecast from one day to four.

About half the forecasts are unacceptable in the sense that the weather is annoyingly different from that forecast, e.g., forecasting a sunny day when it actually rains.

Choosing weather symbols at random and taking this as a 'forecast' works acceptable on about one day in five - not as good as professional forecasting. 

Assuming that the weather four days ahead will be broadly the same as today produces acceptable forecasts more frequently than professional forecasters' predictions!

The Meteorological Office tests its forecasting performance by measuring the accuracy of the forecasts for daily maximum temperature. The accuracy is better than persistence (e.g., assuming that tomorrow will be the same as today) but only by about 10 - 15%.

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SEA LEVEL RISE AND FLOODING RISKS

The best forecast of sea level rise for Weymouth Harbour is about 250 mm by 2050 and 650 mm by 2100. However, some forecasts give higher figures nearer 350 mm by 2050 and 850 mm by 2100.

By 2050, tidal heights of three metres will become 'three-times-a-decade' events. The top of the new harbour wall is about three metres above chart datum so that this will be over-topped and the 'Park District' and the western half of the Town Centre will be prone to direct flooding from the sea pouring over the present harbour wall.

By 2100, three metre tides will become monthly occurrences. 

Clearly, remedial work and new harbour defences will need to be installed before the second half of the 21st century arrives.

By 2100, the harbour wall must be at least 500 mm - and preferably one metre - higher than the recently built wall and a more extensive system of pumping will be needed to prevent backflow through the town's drainage system. Weymouth Town Centre and 'Park District' must then be protected by an extensive wall or even a substantial dyke possibly extending to the northern end of Radipole Lake.

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TEMPERATURE

The averaged minimum temperature in Weymouth has been rising since about 1985 and is now higher than at any time since records started in 1927. Average maximum temperatures have also risen but are still lower than temperatures experienced in the 1940s.

The rates of rise seen in Weymouth's temperature curves in the 1990s was about 1.0 degree Centigrade compared with a global rate of rise of about 0.2 degree Centigrade. 

This suggests that any rises seen in Weymouth's temperature records are not directly linked to changes in global temperature. If the rises are due to climate change then something is greatly amplifying the global heating on a local basis.

Looking at the changes in average temperatures over seasons of the year, minimum temperatures have steadily been rising in the first half of the year and falling in the second half. Spring average temperatures have risen by an incredible five degrees since 1927.

Average maximum temperatures have risen in the first half of the year but fallen in the second half of the year. Indeed, average maximum summer temperatures are now, on average, four degrees lower than in the 1930s.

In brief, Winter and Spring are getting warmer and Summer and Autumn are getting cooler - contrary to the predictions of climate modellers.

There has been a slight rise in the number of frosty days each year.

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SUNSHINE

However, since 1927, the average sunshine has increased steadily in the quarter October, November and December and fallen slowly in the half-year from January to June.

In the third quarter, July to September, there has been no significant trend in the data.

Summer days were slightly more overcast in the 1940s and 1970s but there is not a strong overall trend.

The sunshine recording instrument has been moved several times, vandalised and replaced in the period 1927 - 2005 so the analysis may be fraught with uncertainty.

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RAINFALL

Climate modelling experts predict changing rainfall patterns in southern UK with wetter winters and drier summers and more days having intense rainfall in the winter than now.

The Weymouth weather record show no overall change in annual rainfall. 

However, average rainfall shows a decreasing trend in the second half of each year. This broadly agrees with the predictions by climate modellers but this is coincidental. There was an increase in summer and autumn rainfall before about 1958. As a result, summer and autumn rainfall now is much the same as in the 1930s with no long-term increase. 

The number of days each year when rain falls has increased by 50 days since 1990 but the number of days on which it rains hard has not changed. This means that there are more days with light rain. 

This trend for more wet days affects every season with April, May and June showing slightly greater increase than other quarters.

However, this increase in the number of wet days since 1990 follows a prolonged period of decreasing number of wet days since about 1940. The figures for wet days are now about the same as in the late 1920s and 1930 strongly suggesting that global warming is not the cause of these changes but that they are due to a long-term natural cycle.

Thus, the long-term changes in rainfall are almost certainly due to long-term natural weather cycles and not due to global warming.

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CLOUD

Cloud was recorded as tenths of sky area until end of February 1949 and recorded in eighths after this date. In this analysis, all the data have been converted to percentage of sky clouded.

There is no significant change in cloud cover either for the annual average or for the average over the four quarters of each year.

There is certainly no evidence of increased stormy weather, as predicted by climate change modellers and which we would expect to see as increasing cloud cover.

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BAROMETRIC PRESSURE

Despite climate modellers forecasting wider extremes of barometric pressure over southern England, there is no evidence for any such change in Weymouth's eighty-year barometric pressure record. 

There has, however, been a fall in the number of days experiencing pressures below 1,000 mB since 1975 and this is contrary to the claims that global warming is increasing the occurrence of low pressure storm systems. 

In fact Weymouth's records suggest a cycle of about fifty years length in the record. If this cycle is valid then we should see an increase in the number of low pressure days between 2008 until around 2030.

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WIND SPEEDS

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 broad downwards trend in the measurements from around the early 1970s which is contrary to climate change modelling predictions that the Southern coast of the UK is getting stormier.

There is a hint in the data that a ten-year cycle is operating.

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