Ken Stewart, May 2010
“All thermometers are equal, but some thermometers are more equal than others.”
(Apologies to George Orwell)
Australia’s Northern territory in the remote outback is home to the tourist meccas of Ayers Rock and Kakadu, spectacular scenery, miles of desert and savannah, and a population of 219,800. It covers 1,349,129 square kilometres, or roughly 17.5% of the Australian landmass.
This vast area, like the rest of Australia, has a network of weather stations managed by the Bureau of Meteorology (BOM). BOM produces climate information for the public and the government. The official climate record is presented as trend maps and time series graphs for Australia as a whole, various regions, and each State and territory. This official record is produced from the High Quality Data Sites- 100 non-urban sites across Australia.
the HQ series has some inherent problems:
- It is based on data that has been subjectively and manually adjusted.
- It makes no allowance for Urban Heat island (UHI) effects.
- In Queensland, it produces a trend in mean temperatures that is 0.2 degrees Celsius greater than the raw data does.
Now, how many HQ stations were used to build the Northern Territory’s climate record? 2. That’s right, TWO. Alice Springs Airport and Tennant Creek Airport. Darwin isn’t used because it is urban.
Note the big red section around Alice Springs!
And the time series:The Northern Territory has a warming trend of 1.1 degrees Celsius per 100 years, so a lot depends on those two sites, because as you can see from the table below, the trend has been increased from 0.98 degrees to 1.13 degrees per 100 years.
Round all figures to tenths, 1 degree C to 1.1C. No, no other sites were used. A 10% warming bias- and all due to Alice Springs, as you can see.
When you look at the individual records, the arbitrary nature of the adjustments becomes apparent.
There were actually a number of sites used at Alice Springs. The Old Telegraph Station from 1878 to 1932; the town Post Office from 1932 to 1989; the old airport (Connellan’s), the new Airport (The Seven Mile) from 1941 but with several changes in position there. Note the cooling trend to 1950, and the similarity (though slightly warmer) of Airport to PO 1943-1953. By the way, the mid 70s dip is reflected in several other sites. Compare the splice with HQ:
Warming increased from 0.95 to 1.65. No nearby stations have a complete record. Only one (Charlotte Waters) covers the early decades, and it shows cooling. So the adjustment must be based on records from many hundreds of kilometres away- like Tennant Creek, which shows less warming! The nearest long term station in Queensland showing similar warming is Boulia (raw trend 1.1 degrees, adjusted to >1.6 degrees!) Further south, Oodnadatta has records only from 1941, showing considerable warming since then, but there is no evidence that this warming started in 1910. Therefore, the HQ record for Alice Springs, subjectively and manually adjusted, is arguably highly suspect. It follows that the time series for the Northern Territory is also incorrect.
By the way, Darwin Airport, which is urban and not included, is an interesting site: The Post Office records to 1940, and the Airport from 1941. The Post Office measurements apparently were based on dodgy practices, like no Stevenson screen. Raw data:
Note the airport shows a warming of about 0.8C- if the trend is extrapolated back to 1910, which is not good practice.
Darwin’s trend: 0.5C, and a good mirror of Daly Waters. Note the 1970s dip, common throughout the inland. BOM’s adjustment does not stand up.
The climate record for the Northern Territory is based on very limited data. Very few stations have long records, much data is missing, and the Trend Maps and Time Series Graphs thus depend on only two sites. Both of them showed about 1 degree of warming, but Alice Springs has been manually adjusted to give extra warming which cannot be justified. Similarly, Darwin’s extra warming (though not used in the record) cannot be justified.
The official BOM record for the Northern Territory is guesswork. BOM would have been better off leaving the record as is, and saying “We don’t know enough to show any trends for the Northern Territory.”
Progress Report on the HQ series:
BOM assertion: “On the issue of adjustments you find that these have a near zero impact on the all Australian temperature because these tend to be equally positive and negative across the network (as would be expected given they are adjustments for random station changes).”
After 30 stations (30%): Raw trend: +0.79C HQ trend: +0.96C Warming bias 21.5% (in Celsius terms)