From what I have observed as to how surface air temperatures are now measured at many weather stations, I will admit to being more than a little sceptical.
As a result of the economic and political changes that occured 15 - 20 years ago, many weather stations were shut down and much of the skills base was lost. Some new weather stations were established, but often by people who had little idea of what they were doing.
So that today's temperature reading can be compared with that taken tomorrow and on all subsequent days, thermometers are supposed to be housed in a ventilated, white painted wooden box - known as a "Stevenson Screen."
This box should be mounted four feet off the ground, away from all buldings, and over a grass lawn:
- direct sunlight on the thermometer, and also heat reflected off the ground or radiated off buildings will greatly affect the thermometer reading.
Yet in all too many instances in recent times, this knowledge seems to have been lost when new weather stations have been established :
- partly to blame, I feel, are the full "Weather Station" kits that are readlily obtainable from any electronic store.
- invariably, the instructions come with no reference made to the need to shade the thermometer.
(Yet none of this is rocket science - I recall these things being covered in detail during Grade 9 geography at high school).
I saw a classic back in 2006:
- A Platinum Resistance Thermometer (PRT) was mounted directly above a long run iron roof, totally exposed to the full heat of the tropical sun.
- Then, to further add to the heating effect, this thermometer was in the direct path of the exhaust gases of eight 10 500 hp gas turbine engines.
As a result, the climate statistics for the Tari Valley area of Papua New Guinea WILL be showing a marked "warming trend" since 2006!
(The most disappointing thing of the lot about the establishment of this "weather station" was that nobody was at all interested when I attempted to explain to them about the use of a Stevenson Screen - and about mounting it over the grass lawn on the other side of the building.)
My thoughts, anyway!
Bill.