A recent article on the BBC website said:
The UK has experienced its “weirdest” weather on record in the past few months, scientists say.
The question today is then, is this true?
Firstly, you need to define “weird”. The BBC article suggests that the spring-summer rainfall changes were “weird”, and it certainly was a year of two halves in 2012. However, we need a more objective measure for “weirdness”.
Following the article, I used the England and Wales precipitation (EWP) timeseries (available here), and calculated the daily anomalies by subtracting off a smoothed annual cycle of precipitation. This leaves the ‘weather’, and the variance of these daily anomalies from April to September is one way of objectively defining ‘weird’. But, there may be others.
The figure below shows this index, and demonstrates that 2012 is the second weirdest year in the record (since 1931), just behind 2007. There is a positive trend in the index, which is significant at the 95% level. So, UK rainfall has been very weird this year, and has been getting “weirder”, but 2012 was not the weirdest on record, at least by this definition.
The BBC article refers largely due to the change in river flows, which are also dependent on the temporal distribution of rainfall anomalies, as well as many other factors (weather related and not) which are not captured by this simple analysis.
UPDATE: (from CEH) The original material used for the BBC article is here, which does not use the word “weird”, except in the title bar of the webpage.