Weather – October 2007, Vol. 62, No. 10

291

Met Office

Have other readers noticed that the MetOffice have recently changed the historicalcontext in which unusual months and sea-sons are viewed?

They have drawn a line at 1914, and nowpretend that all records taken before thatsimply does not exist. There may be goodin-house reasons for this, although it isunlikely that they are relevant to the mediaor the general public. However, the decisionis not (and has never to my knowledgebeen) explained.

New records are now, by this method,much easier to obtain, but if events arelabelled “the wettest since records began”or “unprecedented”, then the people wepay to keep our infrastructure running havea ready-made excuse for failure. “It’s neverhappened before, so how could we beexpected to plan for it?”

By so doing they have - probably uncon-sciously, though I could easily be persuadedotherwise – made my job as first port of callfor many journalists on weather storiesmuch more difficult than it ought to be.

Philip EdenWhipsnade,

BedfordshireDOI: 10.1002/wea.131

Belief in records

If the Met Office no longer believes recordsprior to 1914 are acceptable, thus makingJune 2007 the ‘wettest on record’, shouldwe discount the global and regional warm-ing trend identified in the instrumentalrecords since the mid-nineteenth century?Can we strike the ‘Little Ice Age’ from thetextbooks? Was the meticulous work ofobservers in the eighteenth and nineteenthcentury (with often beautifully made, accu-rate equipment) a waste of time? Is myadmiration for Professor Manley’s work onthe Central England Temperature series,extending back to 1659, misplaced?

Michael DukesChesham

Buckinghamshire

DOI: 10.1002/wea.132

Reply from John Prior, NationalClimate Information Centre, MetOffice, Exeter These letters concern the areal series thatmay be used to place a UK weather eventinto context, so their main features will bedescribed to help explain choices that aremade for individual events and, in particu-lar, the significance of 1914.

The series include the historic CentralEngland Temperature (CET) and UK precipi-tation (HadUKP) series. The CET series hasvalues representative of an area from theSouth Midlands to Lancashire, on a monthlybasis from 1659 and daily from 1772. TheHadUKP series represent England andWales, Scotland and Northern Ireland,together with 8 sub-regions, with variousstarting dates e.g. 1766 for England andWales (combined) and 1931 for Scotlandand Northern Ireland. These historic serieshave been calculated using a limited set oflong period stations, with the intention ofpreserving homogeneity.

A further type of series has been devel-oped by the Met Office more recently,based upon all station data that are avail-able electronically. For a given element,these have been interpolated to 5km gridpoints and then areal values produced byaveraging the relevant gridded values. Inthis way it has been possible to produceareal series for the UK, constituent coun-tries, climate districts and counties. In gen-eral, these series start in 1961 but, as a resultof a programme of digitising data publishedin the Monthly Weather Report (MWR), thesunshine series extends back to 1929 andthe temperature and precipitation ones to1914. Why these particular years? A relative-ly dense, even station network is needed forcreating gridded data sets, and 1929 is theearliest year with a suitable sunshine stationnetwork. 1914 is the year when the formatof the MWR changed to one that allowedefficient digitization for the period to 1960.The feasibility of further extending the grid-ded series will be investigated, e.g. to 1900or even to 1884 when the MWR was firstpublished. In addition, a homogeneousmerger of the gridded and historic(HadUKP) precipitation series is being pur-sued for some of the areas, to enable only

the gridded type to be maintained fromnow on. The intention is to publish a peer-reviewed paper about this work.

Whilst being shorter than most of the his-toric series, the gridded series have theadvantage of being available for many moresub-divisions of the UK - from individualcounties upwards. So when the heat of amonth such as July 2006 needs to be placedinto context, that may be done for all partsof the UK not just central England and whenflooding occurs in Yorkshire as it did in June2007, a ranking in the Yorkshire precipita-tion series can be referred to. The griddedseries have been quoted regularly in theannual and seasonal summaries publishedin Weather, beginning with those for 2005and winter 2005/06 (Weather, 61:4), and areused in parts of Weather Log.

The UK temperature and precipitationseries from 1914 may be used to satisfymedia demand for a greater range of infor-mation, particularly about local areas. Theseseries also enable the weather to be placedin a ‘within living memory’ context. Howev-er, when a weather event warrants it, thelonger series are also used. Recent examplesinclude April 2007 being the warmest Aprilin the 349-year CET series (Met Office NewsRelease, 2 May 2007) and May to July 2007being the wettest such period over Englandand Wales in the 241-year HadUKP series(Met Office News Release, 26 July 2007).

Further information about the two types of series is available at http://www.metoff ice .gov.uk/c l imate/uk/about/methods.html

John PriorExeter

DOI:10.1002/wea.161

The Met Office News Release of 5 July 2007entitled ‘Record breaking June rainfallfigures’ stated ‘the month of June has beenthe wettest since records began in 1914’.This date refers to the start date of the MetOffice areal rainfall series rather than thestation-based England and Wales Rainfallseries that starts in 1766. The Met OfficeSeasonal Weather Summary for summer2007 which appears on page 276 of thisissue refers to both rainfall series. (Ed.)

Letters