Cirencester DCNN 4972 – A case study in how not to derive an “average”.

51.70892 -1.99589 Met Office CIMO Assessed Class 4 Digital Temperature archives from 1/1/1959

There has been a weather station in the Cirencester area since at least 1883 though at a different location in the main town at Claremont Place. The Royal Horticultural Society opened this current station at their out of town college in at least 1915 for which there are stored hand written records. Readings have been converted to digital archives from 1/1/1959 and the site is now known as the Royal Agricultural University with the claim of being the UK’s smallest public university. Still a manual reporting station with no apparent site relocation this should be a good option for providing 30 year rolling “climate averages” covering the period 1960 to 2020 – if only life were that simple.

The site itself is in flat open country alongside the Rugby pitch and agricultural fields. Again this is one of those confusing Met Office severe downgrades to Class 4. The hedge fencing alongside is minimal and I find it remarkably improbable that an agricultural university would object to the correct maintenance or removal of it for the benefit of accuracy of readings. Here is a prime example of the university’s advertised interest in weather relative to agricultural research.

Given the sports pitch is advantageous to area maintenance, this site should really have no difficulty in meeting a very respectable Class 2 as delineated in the 30 metre radius area below.

Going to the location specific long term averages and for once, Cirencester is shown with very definite operating period data for the entire 60 years. What does this “data” show? An upward trend over the 60 year period as per these examples below. First example from 1960 to 1990.

A second example for 1990 to 2020 clearly demonstrates a significant “average” temperature increase.

Well surely even I cannot dispute this. The site is pretty good and the figures say it all…….or do they?

The important thing about manually reporting stations is that somebody actually makes the effort to take readings. The absence of readings is astonishingly common with most Met Office manual stations being often dependent on amateur volunteers. However, this is the Royal Agricultural University and as demonstrated above, weather records are critically important to them – aren’t they? Just 32 km/20 miles from Cirencester is another agricultural college at Hartpury that displays “Mean Measurement Mayhem”. Despite an appallingly bad readings-taking record the Met Office still impossibly derived “annual averages” for the station which they seemed unembarrassed to release under FOI.

The 30 year “climate averages” the Met Office publishes are (according to them) not specific to any named single site but an “homogenised” average of groups of stations representative of that area. The station figures for Hartpury are solely for that site but, of course, under that same FOI the Met Office released individual site data for Cirencester itself.

Whilst in 2023 Hartpury only managed 144 days readings with an “average” of 11.1°C, Cirencester was not a great deal better at just 255 readings giving a concocted “annual average” of 12.6°C. I make that anthropogenic global warming of 1.5°C in just 20 miles!

The omission of 110 day’s readings at Cirencester renders any interpretation of the remaining day’s data as an annual representation as a completely nonsensical exercise – a GCSE level abject failure. The reality, however, is that this is quite the norm for both the Met Office and, sadly, The Royal Agricultural University, Cirencester – an allegedly highly respected educational establishment that somehow fails to take adequate data essential for its primary function.

is this a one off aberration? Unfortunately not. They were a bit better in 2022 “only” missing 52 days readings but this time managed a 2.7°C discrepancy with the paltry 97 days worth of Hartpury readings from 20 miles away.

I can go on – in 2021 54 readings were missed and the differential with Hartpury reached a staggering 3.8°C

Throughout the modern history of Cirencester weather station the object of the exercise – taking the readings – seems to be a part time exercise. This renders the entirety of its data quite meaningless but nothing seems to stop the Met Office fulfilling its function of producing figures, any figures, regardless of their relevance. For further prior years of lack of readings consult downloads available here.

I am often accused, by those who seem to find themselves having to disagree with my position on this subject, of peddling misinformation even to the extent of alleged “fact checkers” claiming to debunk me. I would like to take this opportunity of responding by pointing out that precisely NONE of the data I present is mine and 100% of the information I present (as above) is directly from the Met Office.

The conclusions regarding Cirencester is that it is not a particularly poorly located site but one whose husbandry is typical of the extremely poor standards of the Met Office. The site itself is not quite junk but the use of what passes for its data is far worse.

Source: https://tallbloke.wordpress.com/2025/03/28/cirencester-dcnn-4972-a-case-study-in-how-not-to-derive-an-average/