Australia ACORN-SAT series precise station audit
Australia ACORN-SAT temperature fraction audit
Within the ACORN-SAT series of minimum and maximum temperature records at 112 locations comprising 201 Australian weather stations, 30.1% of all raw temperatures were logged by observers as whole .0 Fahrenheit degrees before Celsius metrication on 1 September 1972.
This compares with 31.04% of all Australian temperatures recorded as .0 Fahrenheit before September 1972 in the High Quality temperature series and 25.5% in New Zealand's Seven Station series. The correct proportion should be around 10%.
Within the ACORN-SAT weather station records, 17.7% of all raw temperatures were logged as a whole .0 Celsius degree since Celsius metrication from 1 September 1972 to 31 December 2011.
This compares with 19.47% of all Australian temperatures recorded as .0 Celsius since September 1972 in the High Quality temperature series and 13.2% in New Zealand's Seven Station series. The correct proportion should be around 10%.
The Australian Climate Observations Reference Network – Surface Air Temperature (ACORN- SAT) dataset is a long-term record of Australian daily air temperature, covering the period from 1910 to the present at 112 locations comprising 201 weather stations.
The ACORN-SAT dataset estimates that for temperatures across 1911-2010, Australia's average annual maximum increased by 0.75C, its annual minimum by 1.14C and its annual mean by 0.94C.
This audit analyses the fractional proportion of Fahrenheit and Celsius degrees recorded before and after September 1972 metrication, based upon the exact timeframes of temperature data at each of the 201 weather station records within the ACORN-SAT dataset. A separate audit of entire temperature records, including before 1910, is available.
The raw temperature source of the ACORN-SAT dataset audited in this presentation includes 3,212,142 minimum and maximum Fahrenheit temperatures recorded at 138 weather stations before September 1972 and 3,306,309 minimum and maximum Celsius temperatures recorded at 195 weather stations from 1 September 1972 to 31 December 2011, totalling 6,518,451 temperature recordings.
In the technical report Techniques involved in developing the Australian Climate Observations Reference Network – Surface Air Temperature dataset (pages 25, 65, 70) published with Australia's ACORN-SAT temperature dataset in March 2012, the BoM says that tests show metrication in 1972 caused a .1C warming breakpoint that year.
The precise anomaly is unknown and unadjusted in the ACORN-SAT dataset due to record wet, cloudy La Nina weather conditions from 1973 to 1977 which complicated the data influence of Celsius conversion. See extracts from technical report.
This adds weight to evidence that rather than an even distribution of rounding up and down to .0 by weather station observers who ignored BoM instructions to record precise fractions on Fahrenheit thermometers before 1972, there was a greater proportion of temperature truncation down to .0.
In turn, this suggests that long-term data averages underestimate actual temperatures before Celsius metrication with consequent artificial warming in Australia's climate record.
In compiling the ACORN-SAT dataset, the Centre for Australian Weather and Climate Research had access to more digitised temperature data than is available publicly for this audit through the BoM national database.
The following blocks of data were unavailable and not audited over the full duration of the ACORN-SAT timelines:
All these unavailable station records include Fahrenheit temperatures back to 1910 which, based on proportions at other sites, would suggest the ratio of .0F before 1972 would be greater than 30.1% if the missing data were included.
A preliminary analysis of the ACORN-SAT dataset is available at Ken's Kingdom.
In the Fahrenheit era before September 1972, 30.1% of all temperatures recorded at the 138 relevant weather stations were logged as .0F degrees (rather than a tenth fraction such as .3 or .8).
The combined 31% of temperatures recorded as .9F and .1F infers an actual .0F ratio above 40%.
In the Celsius era from 1 September 1972 to 31 December 2011, 17.7% of all temperatures recorded at all 195 relevant weather stations within the ACORN-SAT dataset were recorded as .0C degrees.
This compares with 19.5% of all Australian temperatures recorded as .0 Celsius since September 1972 in the High Quality temperature series. The correct proportion should be around 10%.
Some of these consecutive blocks extend over months or years and contribute to the high .0C and above average .5C proportions in the Celsius era. The longest block is 1,308 consecutive days of .0C and .5C minima and maxima recorded at Nhill 78031 from 1 September 1972 to 31 March 1976.
In extracts from technical reports published with ACORN-SAT, note the chart which is an example of fraction and whole maximum degree recordings below 15C at Eddystone Point from 1959 to 2008, detailed in this audit of site 92045. The audit shows the similar number of converted Celsius fractions and whole degrees before 1972 represented a high proportion of .0 Fahrenheit recordings (28.4%) before conversion. Their divergence after 1972 is related to .0C being 35.4% of all Celsius fractions recorded since that year at Eddystone Point.
Click temperatures for tenth fractional charts in Fahrenheit or Celsius
Note: This audit of Australian weather station temperature records was possible due to the Excel programming skills of former ABS statistician Ian Hill and chemical engineer Ed Thurstan.
Western Australia ACORN-SAT audit
New Zealand Seven
New Zealand Eleven