Meltdown

It was rather hot a month ago. In fact, the temperature record for the UK was clearly broken on the 16th of July 2022. Even with my ten gallon sceptics’ hat on, I could not dispute that. On the face of it, the 40.3°C recorded on the 19th of July this year was quite remarkable.

Now, in Denierland I did dispute the previous record of 38.7°C, set in July 2019 at the Cambridge Botanic Garden – sort of. I accepted it as a true record of how hot it was that day where people live – but questioned whether the record could be a true representation of how hot the UK would have been that day, in the presence of anthropogenic CO2but in the absence of anthropogenic habitat alteration. That is to say, I doubted whether a temperature station in that very location but set in the original wildwood that covered the UK from stem to stern would have recorded the same value as the temperature station in the real Cambridge Botanic Garden in the real UK in 2019.

The same applies to the new 40°C record. It’s a true representation of what people experienced that day. It is not necessarily a direct measurement of climate change via CO2 emissions.

The record, it should be noted, was taken by RAF Coningsby in Lincolnshire. But five places recorded 40°C, as reported by Paul Homewood on the day itself (these records may have been revised, I do not know).

I would have been more than happy to let this stand without saying a word, right up until the point when the BBC began to browbeat us once again. Their headline:

UK heatwave: Five common myths debunked

“Debunked” is a kind of arrogant word that should not be used casually. If your intent is to demean your opponent, and you really have no sense of honour, then by all means use it. In any case its usage here is spare. “UK heatwave: five common myths” was sufficient. And if you debunk, you had better be sure your debunk is correct. Otherwise you end up showing that your priority is winning the argument, not ensuring that the facts are known. The article has already been mentioned at Cliscep, by John here and Mark in Open Mic.

Of the five “myths” presented by the BBC, I want to concentrate on #2, which like the others is enclosed in snark quotes just in case the reader might think the proposition is believed by the writer:

‘Runway temperatures are making it hotter’

The Met Office was accused of manufacturing and manipulating the record-breaking temperatures, because some were recorded at Heathrow. Some suggested heat emitted from the airport’s runway had skewed temperatures.

Temperature readings in the UK are taken from standardised weather stations, which have to meet specific criteria and are maintained and inspected by specialist teams.

Although some weather stations are located at airports, temperature readings are taken from thermometers in a Stevenson screen, which is a white slatted box with its door facing north.

The locations of these are also standardised, positioned over level grass and away from concrete or hardstanding wherever possible, which minimises the influence of man-made surfaces, like airport runways.

The Met Office also measures temperatures of the soil, ground and water in places too.

Now, if you want to argue that runways are not skewing the readings, it would be better to simply point to the fact that the records are not at runways. However, of the top 5, one is Heathrow and the other two are RAF bases with runways. That’s quite a strike rate.

What about those “specific criteria”? Perhaps the BBC debunker could have actually investigated, in an open-minded way, whether those 5 stations do in fact fulfil those criteria? Ya know, engage in a disinterested search for truth rather than a search for ways to get the deniers to shut the **** up once and for all?

Luckily this correspondent decided to do the work of the BBC’s debunker for them. So: just how good are these sites? One would hope that those crowing about records would first make damn sure that the sites where the records were made were beyond reproach, even by the most denialist deniers, the ones with the ten gallon sceptics’ hats. Are they?

WMO siting classification

The WMO classifies weather stations based on a range of criteria, from Class 1 (very good) to Class 5 (terrible). The criteria can be obtained here.

To summarise the relevant criteria:

Class 1

A source of heat (or expanse of water) is considered to have an impact if it occupies more than 10% of the surface within a circular radius of 100 m surrounding the screen, makes up 5% of an annulus of 10–30 m, or covers 1% of a 10 m radius area.

Class 2

A source of heat (or expanse of water) is considered to have an impact if it occupies more than 10% of the surface within a radius of 30 m surrounding the screen, makes up 5% of an annulus of 5–10 m, or covers 1% of a 5 m radius area.

Class 3 (additional estimated uncertainty added by siting up to 1 °C)

A source of heat (or expanse of water) is considered to have an impact if it occupies more than 10% of the surface within a radius of 10 m surrounding the screen or makes up 5% of a 5 m radius area.

Class 4 (additional estimated uncertainty added by siting up to 2 °C)

(a) Close, artificial heat sources and reflective surfaces (buildings, concrete surfaces, car parks, etc.) or expanse of water (unless significant of the region), occupying:
(i) Less than 50% of the surface within a 10 m radius around the screen;
(ii) Less than 30% of the surface within a 3 m radius around the screen;

Class 5 (additional estimated uncertainty added by siting up to 5 °C)

Site not meeting the requirements of class 4.

Coningsby

Here is the met station (these and subsequent snips from Google), with 10, 30 and 100 m rings (relevant to defining Class 1 and Class 2 sites):

Conclusion: Class 3. Fails Class 2 because of the hardstanding within the 30m radius.

St James’s Park

Conclusion: Class 4. The metalled path is within 10 m.

Heathrow:

Conclusion: Class 3. Significant hardstanding within 30 m. Note: it looks as if the weather station has been surrounded by a solid fence.

Kew

Conclusion: Close to Class 1, definitely not worse than 2. The children’s play area at lower left looks to be astroturf. There’s a cafe and some metalled paths. Putting it together the artificial surfaces total >10% within a 100 m radius, which would make it Class 2. Note: the children’s play area is fairly recent, and replaced natural ground with trees. This therefore has slightly contaminated the station.

Northolt

Conclusion: Class 3. Significant hardstanding within 30 m. The empty square at bottom looks like the former location of the weather station, but I can’t be sure. If so it was better before.

Of the five stations exceeding 40°C, only one is close to being “pristine” – Kew Gardens. And it is perhaps unnecessary to add that even Kew is in the middle of a large urban area. Caveat: I might have have mistaken the locations of the weather stations. Google Earth is very good, but it’s sometimes not obvious where the weather station is.

Harpenden

At this stage it is worth making a comparison with another site, this one that ticks the boxes and definitely meets the WMO criteria for Class 1: Harpenden. This site replaced the Cambridge Botanic Garden as a representative station for the Central England Temperature series. There are no buildings and no hardstanding within 100 m.

A sceptic might quibble about the qualities even of Harpenden, despite it qualifying as a Class 1 station. That is (i) because a set of arable fields are not representative of the pristine island that existed before wholesale forest clearance and (ii) the site is not far north of the great metropolis, and might receive pre-warmed air from there on a southerly breeze. However, the difference in temperature achieved is notable. I took these snips quite shortly after the record was announced, as you can tell from the time that the data is cut off. Both taken from the Met Office’s WOW. First, Coningsby, capping out at 40.3°C:

Next, Harpenden (the Rothamsted research station there), capping out at 37.8°C:

The day before the record, Radio 4’s The World at One was trailing, not 40°C, but 43°C. First the figure was given as a forecast, but that nuance was soon forgotten as Sarah Montague began asking learned guests: is this the new normal?

43°C, it need not be said, was way off the mark, and the time to discuss the record was after it had been achieved, not before.

Conclusion

The top score of 40.3°C came from a site of Class 3, with a 1°C variation from true. The question remains as to exactly how valid that record is.

Finally, I present the Met Office’s conception of what a weather station is supposed to look like. Doesn’t look a lot like an airport.

Featured image:

A frame from the BBC forecast of 16th July, showing climate change over the UK and Western Europe, and nothing much to see happening to the east of there.

via Climate Scepticism

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August 15, 2022 at 10:36AM

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