RHS Wisley DCNN 5237 – The damning case of the second station….with different temperatures!

51.31071 -0.47638 Met Office assessed CIMO Class 4 & Excellent Data from 1/1/1904

The Met Office’s ill defined and unique assessment of this site is “Excellent” despite their official CIMO assessment classification of Class 4 with an error margin of 2°C. Set in an orchard of the botanic gardens of the Royal Horticultural Society this site clearly does not represent the natural environment. It is specifically designed to elevate temperatures, reduce winds and create an artificial micro climate. The Met Office uses numerous sites in such locations to contribute to the historic temperature record in the full knowledge these sites do not represent their natural environs. Most reasonable people would consider that an unacceptable practise.

However, that is not my headline story here. The real issue is actually about another Wisley Met Office weather station just 102 metres away …..

RHS Wisley No 2 DCNN 5238- The Ghost Station recording differently.

51.31017 -0.47534 No Met Office site assessments known. Installed 8/5/2018 Closed 31/3.2021

This small second station was established in mid 2018 – image from Google Earth Pro is dated April 2020. I can find no information why this unit was set up, however, its records were archived on the CEDA database in addition to the main station archived here.

The main site looks like this.

Though I can find no close up images of the current No 2 site, the BING Maps “Birds Eye” view is sufficiently old to include both stations with the handy ability of a “measuring” tool. As evidenced below just 333 feet/102 metres separates the two sites which are at the same quoted elevation of 38 metres amsl.

Although the No 2 site is not particularly better sited, it is further from the orchard surroundings and towards the edge of the overall gardens and less subject to warming effects. Building works taking place at the time were nearer the new screen than the old. Realistically, two such close sites should not differ to any noticeable degree if neither site were not, in some way, artificially compromised. The weather does not change much over such a short distance in flat Surrey terrain. The temperature reading instruments would have been equally accurate and calibrated.

I have only just uncovered this second site and not yet fully analysed the data – any readers willing to take on that task will be able to download figures from the CEDA links above. {Please let me know in comments below if anyone chooses to accept the task} I did however, opt for a brief scan and detail the surprising findings below. N.B. This is not a “cherry pick”. Simply for speed I chose to compare a notably hot period i.e. the few days before and after the 2019 July hot weather event when Cambridge Botanic Gardens “claimed” the then UK National high of 38.7°C.

Firstly for Wisley (original)

Then for Wisley No 2

Comparing daily maximum air temperatures reveals the following.

Date Wisley Wisley No 2 Variation Wisley over Wisley no 2

20/7/2019 24.5°C 24.6°C -0.1°C 21/7 23.2 23.1 +0.1 22/7 26.5 25.6 +0.9 23/7 32.5 32.1 +0.4 24/7 32.3 31.4 +0.9 25/7 36.7 36.2 +0.4 26/7 26.1 25.6 +0.5 27/7 19.4 19.4 Level 28.7 23.9 23.6 +0.3 29.7 24.7 24.1 +0.6

Obviously there is a significant variation over the 10 day period with surprisingly only 1 day’s readings being the same, one day showing Wisley cooler by just 0.1°C and 8 days showing Wisley running hotter by almost 1 degree on 2 occasions. One could infer there were artificial cooling influences on the No 2 site but if so what on earth would those be? Much more logically the discrepancy can be explained by ongoing artificial warming to the modified climate that the Wisley station experiences.

Further number crunching is required but I am confident this opportunity to compare 2 extremely close sites demonstrates the significant artificial variations caused by siting – EXACTLY what the CIMO regulations were intended to eradicate. I contend that all sites not meeting Class 1 or 2 status must not be used for reporting data to the historic climate record. The “flagship” Wisley site and literally hundreds of over similarly low grade poor sites should be withdrawn.

Source: https://tallbloke.wordpress.com/2024/10/23/rhs-wisley-dcnn-5237-the-damning-case-of-the-second-station-with-different-temperatures/