The winter season 2008-2009 - how does it compare with past cold winters?  End of winter update.                    

My last blog entry was an attempt to put the winter in perspective – a rash pursuit as it was written in mid-February but people wanted to know!  The last two weeks of February were quite a bit milder than expected so here are the tables revised according to the confirmed Central England Temperature figures (I’ve retained in the table the original estimate for February and also updated the January figure according to the Hadley Centre data shown at http://hadobs.metoffice.com/hadcet/cetml1659on.dat ).    

CET values from October 2008 to February 2009. 

Winter is defined in climatology as December to February. The average CET for winter 2008-09 is 3.533°C. The next table compares this with past winters since 1950. This shows that it was the equal 4th coldest winter since that of 1984/85 and the equal 16^th coldest since 1950 – hardly earth-shattering!  As there is a three-way tie for 16^th place, it would be sensible to mention that we should take any such data to two decimal places with a hefty pinch of salt – there have been changes in the composition of the observing stations used.   

The coldest winters (Dec. to Jan.) since 1950

Finally, in view of the cold weather in late October that necessitated salting activity in many areas, the following table compares the October to February mean temperature, encompassing the salting season (to date).   Not surprisingly, the ranking of 2008/09 rises to 13^th (down from an original estimate of 10^th and an estimated value of  5.2°).

The coldest October to February periods since 1950

So, an average February puts a dent in the claims that winter had any ‘freak’ weather, but all the same, it does stand out from those of the last two decades, especially when viewed over the longer winter half-year.

Just to confuse matters, it should be noted that there are two versions of the CET series. The figures quoted here are the estimates made in the Hadley Centre. The climate historian Philip Eden keeps his own CET series and this usually tallies closely with the Hadley Centre data. However, Philip’s figures for winter 2008-09 are slightly warmer for each month (3.59° in December, 3.16° in January and 4.19° in February but the values fro previous winters are also slightly different too. His figures, and those of the Hadley Centre, go back to 1974 (http://www.climate-uk.com/provisional.htm) ; before that the monthly values were calculated by Gordon Manley himself.

While using Philip’s data, I noticed that he mentions that the greatest level snow depth on 2 February was as much as 41cm at the Royal Horticultural Society’s gardens at Wisley in Surrey (http://www.climate-uk.com/page2.html).

Gordon Manley’s article on the CET series was published in the Quarterly Journal of the Royal Meteorological Society in 1953 and 1974, his ‘magnum opus’ as Philip Eden described it. The Society has thoughtfully put pdf versions on their website for all to read at http://www.rmets.org/about/history/classics.php (scroll down to ‘M’). Well worth reading either article if you have never done so – a real insight into why so many of us miss such writing and regard him as the leading climatologist of the 20^th century. Not all world-class research in the last 50 years involved computers or models! 

Julian Mayes, 6th March 2009. 

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