Cassley DCNN0343 – The ” Indisputable Truth” behind Met Office failures?

58.16818 -4.72721 Met Office CIMO Assessed FORMERLY Class 1 now assessed Class 3 – So what changed?

For the benefit of new readers and to bring others up to speed, when I restarted the Surface Station Project in August 2024, I queried the CIMO assessments of both Hastings and Edenbridge weather stations which were local enough for me to visit personally. Both sites had been rated as Class 1 but I discovered that this excellent status was actually the default position for the Met Office unless adjusted otherwise. Subsequently the Met Office officially reassessed both sites as Class 4 with their internationally recognised attendant “Class 4 (additional estimated uncertainty added by siting up to 2 °C).

I then moved on to query Cassley (the only claimed Class 1 site in Scotland) and so began a trail of “varying” information from the Met Office

Firstly to confirm that this is not “Disinformation” regarding CIMO ratings and automatic default positions of “Excellent”, I repeat the details straight from the “horses mouth” regarding Hastings.

“Dear Mr Sanders

Thank you very much for your enquiry. This has highlighted an issue in our database. My original recorded inspection data was ‘CIMO Class 4’ (and I’ve reviewed the exposure diagram, which confirms), with the Stevenson screen exposure recorded as ‘Acceptable’ (and Satisfactory overall, taking into account the CIMO 4 rating).

The default CIMO rating is 1 on our site visit application (and Met O ‘Excellent’), so it looks like the class hasn’t been entered correctly, human error.

I trust this answers your question.

Sincerely

Angus Bruce BSc MIET“

You cannot get much more specific than that.

In going on to query Edenbridge’s Cass 1 rating I encountered a Met Office senior manager, Karl Shepherdson whose view on science extended to matters being beyond discussion (“Settled Science?”) in his authorship of the “Indisputable Truth“. Begrudgingly it seemed he had to accept that Edenbridge was similarly wrongly classified.

“Dear Mr Sanders,

I have checked the CIMO classification at Edenbridge, and it is indeed still CIMO 4 for screen air temperatures. The class 4 is due to occasional shading by trees.

The classification has now been corrected in our database. Thank you for bringing this to my attention.

Regards,

Karl.

Karl Shepherdson BSc(Hons) Cert. Ed. FRMetS    Pronouns: he/him/his.“

It did strike me as odd to claim “still CIMO Class 4” when it had been shown as Class 1 but I let that point go.

There seemed to me to be many more sites that were shown as Class 1 that simply did not meet requirements. I decided to test whether internet only investigations were adequate to contest classifications and noted that the Sutherland Cassley site clearly was not Class 1 and queried it. Seemingly Civil Servants feel they are above reproach and the public are only allowed a limited number of queries no matter how successful their challenges may actually be. Karl, having offered me the option of discussing matters either by telephone or video conference, then reneged on his offer and bluntly answered as below.

“Dear Mr Saunders, (editor’s note:yes incorrect spelling)

Thank you for your email last Friday. I can confirm the classification of Cassely Screen Air Temperatures is correct.

It may be worth a read of some of our online resources to give a broader understanding of our wider approach to inspection and quality management at our weather stations, please see here: https://www.metoffice.gov.uk/weather/learn-about/how-forecasts-are-made/observations/observation-site-classification  

In order to ensure any future queries receive our fullest attention, the most appropriate route will be to correspond via enquiries@metoffice.gov.uk  

Best regards,

Karl.”

So for the avoidance of any doubt, the CIMO Class 1 was claimed to be “correct” though Karl did not actually state that it was Class 1. However, his email dates from August 2024 and when I received an updated CIMO list in February 2025 (almost 6 months later) it was still shown as below to be rated Class 1.

Around this time the Met Office enquiries desk deemed that they did not have to answer questions from a tax paying member of the public who both contributed to their salaries AND was proving them wrong. Undeterred I carried on the Surface Stations Project without their assistance having to resort to Freedom of Information requests which subsequently resulted in me being deemed “Vexatious” and that angle of inquiry being similarly closed to me. For those who may not have seen this podcast I further explain the issues in conversation with James Corbett.

Cassley though did continue to interest me and with the valuable assistance of retired auditor Dave Woolcock we demonstrated some alarmingly large discrepancies caused by the automation of readings form previous manual observation. The Cassley addendum data displayed up to double digit differences from the overlapping periods of different reporting systems.

Cassley was then put on the “back burner” whilst I continued reviewing all the approximately 400 Met office sites until I received an unsolicited email from a Talkshop reader who had followed the whole Cassley saga. They pointed out to me that in my report on Syerston I had posted a newer CIMO classification listing from 2026 (obtained by someone else) comprising purely Class 1 and 2 sites and that it did NOT include Cassley. {A failure on my part to have not noticed that I have to admit to!}

The poster had chosen to directly contact the Met Office themselves as follows:

“I have noted from an online blogger that the Cassley Weather Station was rated as Class 1 under CIMO Regulations from this published  list gained under FOI on 19/2/2025.  

Updated Met Office CIMO Classification List – not getting Better.

The blogger goes on to say in another post that he queried this rating but a Met office employee upheld the Class 1 rating.

Cassley DCNN 0343 – Foehn (and other) Effects.

What is now most concerning is that the latest listing, also available to view online, does not show Cassley as either Class 1 nor 2 implying it is Class 3 or lower.

https://www.whatdotheyknow.com/request/annual_mean_temperature_data_fro#incoming-3287286

Can you confirm please the current CIMO rating of Cassley Weather station and, if it has recently changed, when the date of the inspection was that actually re-assessed the site?”

On receiving this email I genuinely doubted a reply would be forthcoming from the Met Office but to my surprise my reader (several days later) forwarded me a quite amazing response.

“The air temperature and humidity elements at Cassley were assessed as CIMO class 3 on 06/05/2025.

Understanding Site Classifications and the Integrity of the UK Climate Record
The Met Office is committed to transparency and scientific rigour in all aspects of our observational work. We operate a long-standing site grading scheme in accordance with international best practices defined by the World Meteorological Organization (WMO) Guide to Instruments and Methods of Observation (WMO-No.8)https://community.wmo.int/en/activity-areas/imop/cimo-guide>. This methodology is referenced within our own Met Office site grading scheme.

These classifications form part of a broader, internationally recognised system of quality assurance. The WMO CIMO classifications are designed as a global assessment scheme to provide a broad indicator of how well an instrument meets WMO siting recommendations and the degree to which it is representative of the surrounding geographical area. Importantly, the WMO emphasises that CIMO classifications should not be used to rank station quality. Sites in higher latitudes, for example, may receive lower CIMO scores due to minor shading-an acknowledged and well-documented limitation of the classification system, as reported by the Norwegian Meteorological Institutehttps://www.met.no/publikasjoner/met-report/met-report-2016/_/attachment/download/ece77c3c-90a7-4013-bf1d-c50acf5b41fb:35bb6ec95375a950cb518b75842109e6c2e4d555/MET-report-16-2016.pdf>.

It is misleading and inappropriate to use these classifications in isolation to question the integrity of the UK’s climate record or the quality of our observing network. The Met Office applies robust, peer-reviewed scientific methods consistent with international best practices to ensure the continuity and accuracy of long-term climate datasets.

We remain committed to correcting any misrepresentations of our data or processes. For more information on our classification of observation sites and our data quality maintenance, please visit the Met Office Observation Site Classification pagehttps://weather.metoffice.gov.uk/learn-about/how-forecasts-are-made/observations/observation-site-classification> and In depth: Classifying land-based observationshttps://weather.metoffice.gov.uk/learn-about/how-forecasts-are-made/observations/in-depth-classifying-land-based-observations>. 

I trust this answers your query.

Kind regards,

Anoushka

Service Desk“

Leaving aside all the unnecessary deflections, huffing, puffing and unsubstantiated bluster, the most obvious and relevant point is that Cassley weather station has not moved nor is there likely to have been any changes to this remote site – CASSLEY WAS NEVER CLASS 1…………..but I was assured it was.

In all fairness it is quite possible that Karl Shepherdson referred to others who confirmed to him the alleged status of Cassley. Thus again, for the avoidance of any doubt, I shall forward this report MYSELF to the Met Office enquiries for confirmation of the exact details. Any refusal to respond to my inquiry will, may I say, not be good “optics” for them. To be continued…………

Source: https://tallbloke.wordpress.com/2026/05/23/cassley-dcnn0343-the-indisputable-truth-behind-met-office-failures/