Hiding something? BOM throws out Bourke’s hot historic data, changes long cooling trend to warming

Hello Soviet style weather service? On January 3, 1909, an extremely hot 51.7C (125F) was recorded at Bourke. It’s possibly the hottest ever temperature recorded in a Stevenson Screen in Australia, but the BOM has removed it as a clerical error. There are legitimate questions about the accuracy of records done so long ago — standards were different. But there are very legitimate questions about the BOMs treatment of this historic data. ‘The BOM has also removed the 40 years of weather recorded before 1910, which includes some very hot times. Now we find out the handwritten original notes from 62 years of the mid 20th Century were supposed to be dumped in 1996 as well. Luckily, these historic documents were saved from the dustbin and quietly kept in private hands instead.

Bourke has one of the longest datasets in Australia — but the BOM, supposedly so concerned about the long term climate trends, appears to have little curiosity in the hot weather of the 1880′s and 1890′s (I talked about the amazing heatwave of 1896 here where hundreds died and people in Bourke escaped on special trains). If it had been a cool spell then, would the BOM feel more inclined to put some effort into analyzing them? All of the 50+ temperatures recorded do have a story to tell, yet they lie invisible in news reports of the 21st Century.

Perhaps most seriously, the regular BOM press releases of hottest ever records now rarely give any indication that these earlier hot records existed at all.

Ian Cole lives in Bourke, and runs the local radio station. For years, his father Neville used to do the meticulous recordings every three hours. Ian Cole feels very frustrated that he can’t broadcast any of that information to listeners in weather reports — the BOM won’t supply any data before the year 2000 to the official Weatherzone service provider. He remarked that “We keep on being told about records that are not actually records and averages that are not quite right”.

Bourke got new automated weather recorders in 1994, with a two year overlap of manual and new equipment.

Bourke raw Maxima trend: was 1.7C cooling, now increased to a slight warming trend

Bourke raw Minima trend: was 0.53C warming, now increased to 1.64C warming trend

–These trends, calculated by Jennifer Marohasy have not been disputed by the BOM

Graham Lloyd at The Australian continues to ask the questions the BOM should have been asked for the last ten years.

Where is the respect for historic records?

Weatherman’s records detail heat that ’didn’t happen’

AS a child, Ian Cole would watch his father Neville take meticulous readings from the Bureau of Meteorology thermometer at the old post office in the western NSW town of Bourke and send the results through by teleprinter.

The temperature was recorded every three hours, including at night when the mercury sometimes plunged to freezing, and the data was logged in handwritten journals that included special notes to help explain the results.

For Mr Cole it is a simple matter of trusting the care and attention of his father. “Why should you change manually created records?” Mr Cole said. “At the moment they (BOM) are saying we have a warming climate but if the old figures are used we have a cooling climate.”

Thank goodness someone saved the original notes:

The Stevenson Screen went to the dump and, but for fate, the handwritten notes could have gone there too. But without instruction, the records were kept and are now under lock and key, held as physical evidence of what the weather was really doing in the mid-20th century.

Amazingly Bourke residents are told only of records since the year 2000? (This almost seems too hard to believe. Very Soviet.)

The records are also important in an ongoing row that frustrates Mr Cole. The Bourke cotton farmer may be managing director of the local radio station 2WEB but Mr Cole can only broadcast temperature records that date back to 2000 because the Bureau of Meteorology won’t supply historic records to service provider Weatherzone.

As a result “hottest day on record” doesn’t really mean what it seems. “We keep on being told about records that are not actually records and averages that are not quite right,” Mr Cole said.

Again it’s the homogenization practice which changes the trends:

Worse still there are concerns about what has happened to the precision of those handwritten records in the earlier years. Bourke now forms part of a network of weather stations used to make up the national record known as ACORN-SAT. The raw temperature records are “homogenised”, a method BOM says has been peer-reviewed as world’s best practice and is used by equivalent meteorological organisations across the world.

Independent research, the ­results of which have not been disputed by BOM, has shown that, after homogenisation, a 0.53C warming in the minimum temperature trend has been increased to a 1.64C warming trend. A 1.7C cooling trend in the maximum temperature series in the raw data for Bourke has been changed to a slight warming.

The Australian is doing a remarkable job.

The BOM explained Bourke in their reply to Graham Lloyd (discussed a few days ago here).

Bourke: the major adjustments (none of them more than 0.5 degrees Celsius) relate to site moves in 1994 (the instrument was moved from the town to the airport), 1999 (moved within the airport grounds) and 1938 (moved within the town), as well as 1950s inhomogeneities that were detected by neighbour comparisons which, based on station photos before and after, may be related to changes in vegetation (and therefore exposure of the instrument) around the site.

We will be discussing this record more in future, along with the “worlds best practice” of using thermometers hundreds of kilometers away as a reason to change the original data with rationalization of what “may” have happened.

Jennifer Marohasy has written this up on her blog. She also talked about old weather records changing at other sites, in a 7 minute podcast from Melbourne radio station 3AW yesterday.

No doubt some adjustments were required in Bourke, because there are station moves in the record. But again we find the warming trend is larger because of the adjustments, and Ken Stewart’s work shows that across the whole Australian ACORN dataset the warming adjustments to minima are larger than the cooling adjustments. Changes this large need to be carefully documented and explained.

Australians might just see Climate Change, renewable energy and carbon taxes differently if they also knew how meaningless most of the Headlines of Hottest Ever Weather really are.

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