Tuesday, 25 September 2012

Taking the temperature


I have a digital thermometer thingy bought for £10 from Lidl. It has an internal digital thermometer and a separate, battery-powered temperature sensor connected via a short range radio link.

I hang the external thermometer on a rusty nail in the brick outbuilding attached to the garage. As the place has a pitched, tiled roof, one smallish west-facing window glazed with Stippolyte and isn’t heated, I reckon it gives me a reasonable outside temperature measurement without being exposed to the elements, including direct sunlight. It agrees well with the Met Office anyway.

It’s not a complex device, but I get max and min recordings inside the house and outside, in the outbuilding.

I don’t record the temperatures in a log or anything nerdy like that, I’m just interested in how the temperatures wanders up and down as seasons change. I’ve no idea how accurate my thermometer is apart from the crude Met Office checks, but as a former environmental scientist, I don’t really care – approximate will do. I’m not going in for NPL calibration for something so casual.

I also have an outside temperature display in the car and again I don’t know how accurate it is, but I suspect it’s near enough. It gives an anxious little ping and shows a snowflake symbol when the temperature outside the car drops to 4 °C or below. Presumably it’s warning me about the potential for icy roads.

Anyway, as I drive around the lanes of Derbyshire, particularly on early mornings when we’re setting off for a walk, I tend to notice how the temperature changes as we drive through the countryside. Warmer at low level and cooler if you climb into the hills, as you’d expect.

Sometimes it’s cooler in the hollows, especially during the winter months where conditions are right for inversions. The air temperature can easily change by 3°C over a short distance. In fact I’ve seen changes as high as 5°C over a few miles, driving out of a valley up into the hills.

So how would I measure the temperature of Derbyshire? Where would I put the thermometers and how many of them would I need? What would I measure - daily maximum and minimum or continuous recordings? How would I account for the differences between hills and valleys? How high off the ground should my thermometers be, or should I bury some of them to measure the temperature of the ground? Surely ground temperature is important?

How would I calibrate the thermometers and check that all readings had been taken correctly? How would I deal with faulty thermometers? How would I know when they were giving biased readings? How would I check for calibration drift?

And given I could sort out all of this, how would I check my network of Derbyshire thermometers? How would I compare them to another network which doesn’t actually exist? And how would I build a rationale to cope with the obvious fact that Derbyshire doesn’t have a temperature, that it all depends on how you measure it?

Because I’d need that rationale, wouldn’t I?

I’m not making an obscure scientific point here. I’m just pointing out some well-known problems behind the apparently simple issue of taking temperature measurements. Environmental field measurements, including temperature, used to be an important aspect of my job. I know how difficult it is – even with simple measures such as temperature.

I’m also interested in how climate moonbats (is that the correct term?) claim to measure global temperatures to a tenth of a degree, because I know it’s impossible. And by the way, the BBC won't tell you this, but there is no such thing as a global temperature. That is to say, it could only ever be a convention, yet still there is no agreement as to what that convention might be.

Environmental temperatures are conventions.


RMcGeddon said...

When I did hill walking we used to calculate that temperatures would fall by 1C for every 100metres we climbed. And rose by the same amount as we descended. But this would vary for wet weather and windy weather etc. It was only a rough estimate for dry calm weather. Which was rare on the hills.
So if you see the temperature for your area mentioned on the tv then you have to adjust it according to how high you are above sea level.
The climate science scammers use temperature monitors that are in urban environments so that they can get higher readings due to urban heating. Despite this cheating the temperatures refuse to rise and the junk scientists just try and 'hide the decline' in temperatures by omitting any evidence that points to the coming mini ice age when making up their graphs. Many of the monitors were originally out in the sticks but have been surrounded by urban sprawl over the years and not been re sited for better accuracy.

A K Haart said...

RM - hill walking soon puts you right on temperatures, doesn't it?

In the seventies I knew of a Met Office temperature station sited near a sewage works gas flare-off point.

James Higham said...

in the brick outbuilding

Is this an actual outbuilding or a euphemism for a smaller building?

A K Haart said...

James - it's a euphemism for a brick building added to the end of the garage. Added before our time.