Not only has siting of weather stations near urban heat sources have been a real issue for weather measurement stations worldwide, but so maybe has the recently implemented automatic electronic weather measurement instrumentation.
Now we find another example, this one coming from the Alice Springs, Australia station.
According to the Australian ABC news site, the new electronic thermometer measured a scorching 46°C (an all time high) last Tuesday. However an adjacent mercury thermometer showed only 41.5°C, i.e. a huge 4.5°C less! It turns out that the 46°C reading was a “spike” that lasted only a minute before disappearing.
As a consequence, the ABC writes, the “Bureau of Meteorology (BoM) has withdrawn its advice Alice Springs recorded its hottest day on Tuesday, blaming a faulty thermometer for an incorrect temperature reading.”
The old record of 45.2°C was set 55 years ago, in 1960. The ABC quotes climatologist Joel Lisonbee:
It looks like we had an instrument fault with our automatic weather station at the Alice Springs Airport. […] We have some mercury and glass thermometers that did not show that spike to 46C. […]
They showed the maximum temperature yesterday to be only 41.5C.”
According to the ABC, the station is located right next to a “scorching” airport tarmac. So how could the new automatic thermometer produce such a faulty reading?
It seems that these new automatic systems are highly sensitive. As reported here at NTZ, one German weather instrumentation expert conducted an 8.5 year side-by-side comparison test of the new automatic electronic temperature measurement system and the former mercury glass thermometer. That test showed that the new automatic thermometers produced a mean temperature for the period that was a whopping 0.9°C warmer than the mercury thermometer. That result could possibly in part explain why Germany’s annual mean temperature jumped by a similar amount from 1985 to 2000, i.e. the period that Germany transitioned over to automatic measurement.
The Alice Springs inflated reading is an indication that the new measurement system indeed may be overstating temperature readings all over the world, thus adding uncertainties on top of those created by the urban heat island effect.
With the Alice Springs Station, the error was caught and the “record high” was withdrawn. Yet the question remains if this is the case all over the world. How many recent records are in fact not records at all, but rather are merely faulty readings produced from instrumentation and siting issues?