Thursday, September 11, 2014

Bureau BOMS out on history

Thought a summary version of our FACT checking of BOM records might be of interest:

In recent weeks The Australian newspaper has exposed serious issues with the manner in which the Bureau of Meteorology analyse Australia’s temperature records. (See articles HERE, and HERE). BOM’s ACORN dataset is the result of a statistical homogenisation process. This sometimes produces warming trends from data collected at high quality stations where the station records themselves often show cooling trends. It seems some of the adjustments made are justified but some it seems are not.
While the meteorological community continue to debate the details over the validity of BOM’s analytical processes in adjusting historical records I thought readers might be interested to know how BOM treat some of its historical data.
In January this year eastern Australia experienced a heatwave. This was similar to past heatwaves. It seems it was not as severe or widespread as heatwaves in 1960 or in 1939. Nonetheless the episode was out of the ordinary and worthy of the attention of our weather experts. BOM dutifully reported on the heatwave and released a “Special climate statement”: number 48titled “One of southeast Australia’s most significant heatwaves”.
According to the Bureau Special Climate Statements:  provide a detailed summary of significant weather and climate events. They are produced on an occasional basis for weather/climate events which are unusual in the context of the climatology of the affected region. Their purpose is to document major events. In doing so, they serve as a historical record, inform the public on the broader historical and climatological context for events, and give easy access to data and information which is in high demand from the media and the public.
On page 5 of statement number 48 BOM state: "Canberra also set a record with four consecutive days of 39°C." The “record” was also picked up by ABC’s weather guru Graham Creed in his ABC Weather Man blog. This “record” set my sceptical senses tingling and I set about a little fact checking.
After a brief check through the National Library Newspaper Archive I came across a few headlines from the Canberra Times that indicated the BOM had got things wrong. In fact the newspaper records showed that in a remarkable 7 day stint from the 8th of January 1939 to the 14th of January the BOM’s ACTON weather station in Canberra recorded 7 days over 39 degrees, including 4 days over 40, along with ACT’s record maximum temperature of 42.8 degrees on January 11, 1939. The ACTON station was closed in late January 1939 and a weather new station was opened at Canberra Airport.
I passed this advice on the ABC’s weather guru who corrected his blog to indicate the 4 consecutive days were in fact recorded at BOM’s newer Canberra Airport Station. The blog was not updated to reference the newspaper stories or the 1939 weather records.
I requested the daily records for ACTON from the Bureau but for some reason this station in our nation’s capital only had monthly data.  It’s only the nation’s Capital! After contacting the minister, the Bureau indicated it would as a matter of priority, collate the data and place it on its website. This was back in January.
Earlier last week, about 8 months after my request, I received an email from the Bureau to indicate the maximum temperature readings for ACTON were now online. I checked and they confirmed the Newspaper reports. Not wanting the historical record to be in error I requested BOM correct its Climate Statement. This is the response:
The record referenced in Special Climate Statement 48 is a station record for Canberra Airport (station numbers 70014 and 70351), as is stated in Table 3. 
It seems the historical record will be forever tainted! According to the Bureau’s climate statement the record heatwave of 1939 did not happen in Canberra. This despite the Bureau’s own data showing it did.

BOM’s homogenisation process may be valid or not, but it seems its handling of the nation’s weather records, based on its handling of ACTON, leaves much to be desired. 

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