During the current heat wave, the Bureau of Meteorology (BOM) have been speculating about the likelihood of maximum temperature records being broken, including Queensland’s record of 49.5 degrees Celsius set in Birdsville on 24/12/1972.
Birdsville is a tiny but well known outpost in the far south west of Queensland. The nearest other site is Bedourie 170 km away, but it has no data from before 1998. There are no records for comparison on CDO within 290 km.
The Acorn record starts from 10/5/54, which according to the metadata is when observations commenced. On Climate Data Online Birdsville Police Station record starts on 1/1/57. Where is the missing data? It’s no excuse to say it hasn’t been digitised from the paper records because it obviously has been digitised into Acorn. It should be fairly straightforward to copy it from Acorn into CDO. By contrast, Brisbane has CDO data from the old Regional Office from 1887 yet Acorn’s creators have chosen to exclude this early data before 1948.
Acorn uses Police Station data exactly until the Airport site opens on 29 June 2000 when it adopts the Airport data exactly, with no adjustment despite good overlap- with occasional exceptions. (Airport data is slightly less than Police Station data by on average 0.1 C.)
Before 1 September 1972 Police Station data was recorded in whole degrees Fahrenheit, therefore the uncertainty is +/- 0.3 C. In the months following 1 September 1972, the date of metrication, temperatures are recorded in whole and half degrees Celsius, so the uncertainty is +/- 0.25 C. Queensland’s “record” maximum temperature was recorded at Birdsville on 24 December 1972, so the actual temperature on this day could have been between 49.2 and 49.8C.
When the Airport site opened and its data used by Acorn, it was recording temperatures in whole degrees Celsius only, and the uncertainty then was +/- 0.5C.
Second highest temperature was 49C on 6/12/1981.
The next highest temperatures were 48.8 on 22/12/1990, and 48.7 on 17/11/90.
Interestingly, there are 5 other recordings of the next highest temperature, 48.5C, on 23/12/1973, 5/12/1981, 5 and 6 January 2004, and 30/11/2006. Despite having an Airport recording of 47.9C on 5 January 2004, Acorn has chosen to use the higher Police Station recording instead of the Airport.
So the more extreme temperature was chosen!
Despite all expectations of the record being broken, the highest BOM could get out of Birdsville this summer has been 47.3C on 4 January. That’s 19th, and not even close to the record.
To put this in context, taking 35 C as BOM’s latest standard for heatwave conditions, 34.4% of Birdsville’s maxima are 35C or more. Birdsville’s January mean is 40.2 degrees.
They’re hoping temperatures will get back up to where they’re supposed to be, otherwise that trend line of nearly 0.25C per decade will change a bit.
Conclusion? They’re desperate and dateless.