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Graeme Inkster Says:
January 17th, 2011 at 3:02 pm
What sort of thermometers do they use? Sorry to ask but I’m new to this.
You can get calibrated (mercury) thermometers to 0.1 deg C, but they are quite expensive. I can’t see the typical Govt. Purchasing Dept. buying them [even at less than $150 each in bulk] when they could buy the “equivalent” at $1. Unless the respective BOM’s bought them themselves, or kept instructing each new Purchasing Officer on what to buy, then the cheap ones would be bought.
Use (or substitution/replacement) with ordinary thermometers introduces an error of over 0.5 deg. [if you've ever checked a box of them you'd know]. If they use thermocouples and automatic recording, how well are these calibrated at the start, and after time?
And then there is the well known problem of getting people to read them accurately. It is well known that in the USSR the colder the temperature reported, the more heating oil was allocated by the Central Bureau. A certain tendency to “underestimate” developed, but disappeared after the breakup when there was no point in doing so. But have those records ever been corrected? So from 1985 to 1995 there would have been a jump in the supposed temperature regardless of any actual trend.
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Pat Frank Says:
January 18th, 2011 at 5:18 am
#13, Graeme, most 20th century readings were made using specialized mercury-style thermometers inside a shelter — typically a Stevenson screen (aka Cotton Regional Shelter). Over the last twenty years or so, these have been systematically replaced in North America and Europe with precision resistance thermometers inside gilled chambers, often aspirated. There’s a good run-down here of the various types of thermometers and shelters in use.
In the laboratory, the best thermometers can be calibrated to (+/-)0.1 C, although the older mercury thermometers varied in precision and may not have markings every 0.1 C. However, the real question is precision and accuracy in the field, rather than in the lab.
The screens and shelters help prevent sun and wind (among other factors) from distorting the temperature readings. But they’re not perfect, and there is systematic error in the temperature measurements.
It’s pretty clear that climate scientists have just assumed that all the measurement errors just average away. But they’ve never surveyed the thermometers and sensors in the field to test this assumption and demonstrate its validity. After my own look at published material, the evidence is that this assumption doesn’t hold at all. But in any case, such negligence is hardly the way to do experimental science, and certainly no way to justify forcing huge economic dislocations.