Central England Temperature Update (part 4)

I’m very fond of the Central England Temperature record. For one thing you can pull down the monthly mean temperature for as far back as January 1659 (3°C). That’s kinda freaky: we’re talking 368 years ago, with Richard Cromwell on the throne serving as Lord Protector. His dad was the rabid puritan Oliver Cromwell (of roundheads fame), and one of the blokes who decided to bring the axe down on King Charles I. Nasty business!

Now, the first device capable of detecting temperature changes - known as a thermoscope - was developed by Galileo Galilei around 1592–1593. However, this instrument lacked a numerical scale and was affected by air pressure. The first true thermometer (defined as a device with a calibrated scale to measure specific temperatures) was created by Santorio Santorio in 1612 (with clear diagrams published in 1625).

In 1629, Joseph Solomon Delmedigo, a student of Galileo and Santorio in Padua, published what is possibly the first description and illustration of a sealed liquid-in-glass thermometer. This was described as having a bulb at the bottom of a sealed tube partially filled with brandy – now that’s my kind of thermometer! Interestingly enough, Delmedigo did not claim to have invented this instrument; he simply described what he had seen somewhere. But then, in 1654 or thereabouts, Ferdinando II de’ Medici (Grand Duke of Tuscany) went and actually manufactured the first sealed liquid-in-glass thermometer using alcohol. The key here is that seal, which renders the instrument independent of changes in atmospheric pressure. Good one Ferdinando!

The use of two references for graduating a thermometer is said to have been introduced by Joachim Dalence in 1668, although Christiaan Huygens in 1665 had already suggested the use of graduations based on the melting and boiling points of water as standards. In 1694, Carlo Rinaldini proposed using them as fixed points along a universal scale divided into degrees. Now, this is interesting coz it means that that first monthly mean temperature back in January of 1659 would have been recorded using a sealed liquid-in-glass jobby (I like the thought of it being brandy), but with possibly only the freezing point of water used as a single reference mark and a nominal scale of sorts. Quite so, for our modern-day use of the Fahrenheit scale didn’t come about until Daniel Gabriel Fahrenheit got going in 1724, with Anders Celsius adding to the pot in 1742. Quite how Hadley Centre bods have reconciled those very early records dating back to 1659 is beyond my ken, but maybe some keen reader might dig out a dusty paper or two.

So there you go, but since I tend to use HadCET daily data dating back to just 1878, then I’m well clear of early teething troubles and into the precision gauge era with mercury and whatnot. This leaves the tricky question of where you stick your thermometer. Out in the blaze of direct sunshine is not a good idea, hence the use of the protected enclosure designed by Thomas Stevenson (father of author Robert Louis Stevenson). The development of a screen with double-louvered walls on all sides and no floor was reported in 1864. Modifications by Edward Mawley of the Royal Meteorological Society in 1884 included a double roof, a floor with slanted boards, and a modification of the double louvers; this being the standard design adopted by the British Meteorological Office. This means those early daily HadCET records dating back to 1878 were likely taken using a basic form of Stevenson screen, with the full Monty arriving within a decade.

This leaves us with the fundamental issue of screen location, and this is the bit I want to get my teeth into today. As one sharp-as-razors reader has already commented, the weather station sample going to make-up the HadCET daily record has flipped around a bit since its inception. And there are other problems, besides. Those who are super-keen ought to read this paper by Parker et al detailing the development of the HadCET dataset.

Back to those stations…

You can pull down an ASCII file called cet_station_active_flags.txt from here, and if you do you’ll find a simple log of binary codes for the following eight stations:

• Radcliffe

• Rothamsted

• Ross-on-Wye

• Stonyhurst

• Malvern

• Squires Gate

• Ringway

• Pershore College

If I had time I’d run a little report on each station with a little piccy summary collage showing you where they have shoved their central England thermometers. But I ain’t got that time – business before pleasure, as they say - and these days I have to earn my crust elsewhere before I mess around with Substack owing to the microscopic following of paying subscribers. Such are the lives of statisticians.

The data comes with an explanatory note that we need to be aware of…

Note: Where a station observation is unavailable but the station is active, a backup station is used.

…OK, so they’re happy to flip around flippantly, and I guess I better flag those occasions when an unknown backup station would have entered the frame. The fly in the ointment here is that the datafile doesn’t distinguish between those occasions when a station is active but with data unavailable, and those occasions when a station is inactive with data unavailable. This means we’ll need to assume that backup stations were used each time the unavailable flag shows its face. When it comes to climate science it’s never straightforward!

And now for some basic plots…