climate change wa

Bureau of Meteorology database bug


With temperatures in Western Australia and across the country in 2009/2010 reported by the Bureau of Meteorology to be among the hottest ever recorded, it's worth being aware of database adjustments made by the BOM during that period.

BOM data indicates that Australia’s annual mean temperature for 2009 was .9°C above the 1961/90 average, making it the country’s second warmest year since "high quality" records began in 1910. WA's average temperature during the 12 months to the end of June 2010 was 23.55°C, matching the previous record.

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I maintain a 100 year temperature comparison on my site at waclimate.net based on 32 locations in WA with fairly consistent BOM records dating to the late 1800s / early 1900s.

The 32 locations in WA are Albany, Balladonia, Bridgetown, Broome, Bunbury, Busselton, Cape Leeuwin, Cape Naturaliste, Carnarvon, Derby, Donnybrook, Esperance, Eucla, Eyre, Geraldton, Halls Creek, Kalgoorlie, Katanning, Kellerberrin, Laverton, Marble Bar, Merredin, Mt Barker, Northam, Onslow, Perth, Rottnest Island, Southern Cross, Wandering, Wiluna, Wyndham and York.

In summary, my calculation of the BOM data records shows that, based on these 32 locations, the average annual minimum around the year 1900 was 12.96C and the average annual maximum was 25.12C.

Other analyses of the BOM's historic data for these 32 locations might calculate the averages a few points of a degree higher or lower, dependent upon different criteria, but it is irrelevant in the context of this discussion as 12.96C and 25.12C are the fixed baselines for all my minimum and maximum comparisons since 2008.

I update my website each month with the latest BOM data and when doing my update in December 2009 I noticed the mean minimum and maximum temperatures had all been adjusted up by about half a degree from the temperatures that had previously been recorded on the BOM website database for August 2009.

Below are the 32 locations with their original data in the top green row as posted by the BOM from September 1 to November 17, and their new adjusted data in the red row below:


August 2009:

Min Max Min Max Min Max Min Max
Albany 9 16.2 Balladonia 5 20.7 Bridgetown 5.7 15.7 Broome 14.6 29.2
9.4 16.6 5.5 21.1 6.2 16.1 15.1 29.7
Bunbury 8.2 16.7 Busselton 8.7 17 Cape Leeuwin 11.8 16.2 Cape Naturaliste 10.5 16.7
8.7 17.2 9.2 17.4 12.2 16.6 11 17.1
Carnarvon 11.4 23.2 Derby 15 32.7 Donnybrook 6.7 17.2 Esperance 8.3 17.7
11.8 23.6 15.6 33.2 7.2 17.6 8.8 18.1
Eucla 7.9 21.5 Eyre 4.3 21.6 Geraldton 9.5 20 Halls Creek 16.1 32.6
8.4 21.9 4.5 22 10 20.5 16.6 33
Kalgoorlie 6.8 20.3 Katanning 6.1 14.7 Kellerberrin 5.3 18.6 Laverton 7.5 22.4
7.2 20.7 6.5 15.1 5.6 18.9 7.9 22.9
Marble Bar 13.8 31.1 Merredin 6.1 17.7 Mt Barker 6.8 15.6 Northam 6.2 18.4
14.3 31.5 6.5 18.1 7 15.8 6.6 18.7
Onslow 13.8 27.7 Perth 8.8 18.5 Rottnest Island 12.4 17.3 Southern Cross 4.6 18.1
14.3 28.1 9.3 18.9 12.9 17.7 5 18.6
Wandering 5.3 16.1 Wiluna 7.5 24.8 Wyndham 18.3 34 York 5.6 17.9
5.6 16.6 7.7 25.2 18.8 34.4 5.9 18.3



As recorded from September 1 to November 17 2009 on BOM web database
As recorded since November 17 2009 following correction to BOM database bug


I questioned the BOM as to what had happened and on December 7 2009 received this reply …

"Thanks for pointing this problem out to us. Yes, there was a bug in the Daily Weather Observations (DWO) on the web, when the updated version replaced the old one around mid November. The program rounded temperatures to the nearest degree, resulting in mean maximum/minimum temperature being higher. The bug has been fixed since and the means for August 2009 on the web are corrected."

The temperatures for all WA locations in the BOM web database remain at the higher adjusted temperatures for August 2009 and there was no change from the adjustment made on November 17 prior to my correspondence.

I was confused by this so I sent another question to the BOM, as below and with the response on December 9 ...

"Thanks for the reply but I'm still a bit puzzled. Below are August 2009 min and max data for 32 WA sites I keep an eye on, the top temps being those recorded on the BoM website from Sep 1 to Nov 17, and the bottom temps the updated version since Nov 17. The rounded temperature bug seems to have only affected August as there has been no adjustment to any other month including September. I've just checked the BoM site and there's no change to the August data. Can you please let me know which of the temps below are correct?"

Reply: "The bottom ones are correct. The bug only affected averages for August 2009."

Since then I have continued to update my site each month with BOM data to compare the ongoing 12 month average at 32 WA locations with my fixed 1900 baseline of minimum 12.96C and maximum 25.12C ...


Year to March 2009 Year to April 2009 Year to May 2009 Year to June 2009
min .29 C above the early 1900s min .33 C above the early 1900s min .25 C above the early 1900s min .29 C above the early 1900s
max .68 C above the early 1900s max .79 C above the early 1900s max .75 C above the early 1900s max .69 C above the early 1900s
Year to July 2009 Year to August 2009 Year to September 2009 Year to October 2009
min .31 C above the early 1900s min .51 C above the early 1900s min .44 C above the early 1900s min .39 C above the early 1900s
max .64 C above the early 1900s max .72 C above the early 1900s max .60 C above the early 1900s max .60 C above the early 1900s
Year to November 2009 Year to December 2009 Year to January 2010 Year to February 2010
min .53 C above the early 1900s min .59 C above the early 1900s min .54 C above the early 1900s min .60 C above the early 1900s
max .92 C above the early 1900s max 1.09 C above the early 1900s max 1.16 C above the early 1900s max 1.28 C above the early 1900s
Year to March 2010 Year to April 2010 Year to May 2010 Year to June 2010
min .75 C above the early 1900s min .80 C above the early 1900s min .85 C above the early 1900s min .80 C above the early 1900s
max 1.37 C above the early 1900s max 1.35 C above the early 1900s max 1.29 C above the early 1900s max 1.31 C above the early 1900s
Year to July 2010 Year to August 2010 Year to September 2010 Year to October 2010
min .74 C above the early 1900s min .63 C above the early 1900s min .63 C above the early 1900s min .56 C above the early 1900s
max 1.32 C above the early 1900s max 1.27 C above the early 1900s max 1.34 C above the early 1900s max 1.34 C above the early 1900s
Year to November 2010 Year to December 2010 Year to January 2011 Year to February 2011
min .56 C above the early 1900s min .61 C above the early 1900s min .68 C above the early 1900s min .72 C above the early 1900s
max 1.37 C above the early 1900s max 1.23 C above the early 1900s max 1.17 C above the early 1900s max 1.02 C above the early 1900s
Year to March 2011 Year to April 2011 Year to May 2011 Year to June 2011
min .69 C above the early 1900s min .67 C above the early 1900s min .69 C above the early 1900s min .75 C above the early 1900s
max .95 C above the early 1900s max .95 C above the early 1900s max .93 C above the early 1900s max .94 C above the early 1900s
Year to July 2011 Year to August 2011 Year to September 2011 Year to October 2011
min .88 C above the early 1900s min .97 C above the early 1900s min .96 C above the early 1900s min 1.07 C above the early 1900s
max .96 C above the early 1900s max 1.05 C above the early 1900s max 1.06 C above the early 1900s max .99 C above the early 1900s
Year to November 2011 Year to December 2011 Year to January 2012 Year to February 2012
min 1.04 C above the early 1900s min 1.10 C above the early 1900s min 1.09 C above the early 1900s min 0.99 C above the early 1900s
max .84 C above the early 1900s max .88 C above the early 1900s max .81 C above the early 1900s max .85 C above the early 1900s
Year to March 2012 Year to April 2012 Year to May 2012 Year to June 2012
min .99 C above the early 1900s min .86 C above the early 1900s min .79 C above the early 1900s min .78 C above the early 1900s
max .86 C above the early 1900s max .89 C above the early 1900s max .95 C above the early 1900s max .95 C above the early 1900s
Year to July 2012 Year to August 2012 Year to September 2012 Year to October 2012
min .57 C above the early 1900s min .48 C above the early 1900s min .54 C above the early 1900s .54C above the early 1900s
max .96 C above the early 1900s max .97 C above the early 1900s max 1.06 C above the early 1900s 1.22C above the early 1900s
Year to November 2012 Year to December 2012 Year to January 2013 Year to February 2013
min .52 C above the early 1900s min .53 C above the early 1900s min .54 C above the early 1900s min .56 C above the early 1900s
max 1.25 C above the early 1900s max 1.35 C above the early 1900s max 1.44 C above the early 1900s max 1.56 C above the early 1900s
Year to March 2013 Year to April 2013 Year to May 2013 Year to June 2013
min .61 C above the early 1900s min .79 C above the early 1900s min .92 C above the early 1900s min .89 C above the early 1900s
max 1.46 C above the early 1900s max 1.56 C above the early 1900s max 1.49 C above the early 1900s max 1.49 C above the early 1900s
Year to July 2013 Year to August 2013 Year to September 2013 Year to October 2013
min 1.01 C above the early 1900s min 1.14 C above the early 1900s min 1.24 C above the early 1900s min 1.21 C above the early 1900s
max 1.51 C above the early 1900s max 1.53 C above the early 1900s max 1.46 C above the early 1900s max 1.42 C above the early 1900s
Year to November 2013 Year to December 2013 Year to January 2014 Year to February 2014
min 1.31 C above the early 1900s min 1.23 C above the early 1900s min 1.17 C above the early 1900s min 1.12 C above the early 1900s
max 1.51 C above the early 1900s max 1.47 C above the early 1900s max 1.43 C above the early 1900s max 1.29 C above the early 1900s
Year to March 2014 Year to April 2014 Year to May 2014 Year to June 2014
min 1.17 C above the early 1900s min 1.01 C above the early 1900s min 1.08 C above the early 1900s min 1.03 C above the early 1900s
max 1.31 C above the early 1900s max 1.19 C above the early 1900s max 1.22 C above the early 1900s max 1.24 C above the early 1900s
Year to July 2014 Year to August 2014
min 1.07 C above the early 1900s min 1.03 C above the early 1900s
max 1.22 C above the early 1900s max 1.29 C above the early 1900s

The data shows averaged annual temperature across WA rose sharply from November 2009, the month the BOM software bug was corrected to adjust August 2009 average temperatures up by about half a degree. The above data is graphed below:

bom database bug graph


This baseline early 1900s comparison shows the average maximum in January 2014 remained about .6C higher than before November 2009, with the average minimum about .8C higher.

BOM monthly data is available for all WA recording locations with historic averages which can be used to verify the trend I calculate from 32 locations compared to 1900 baseline temperatures.

The sharp upward trend compared with the 1900 average is reflected in BOM data below (BOM website source) which shows the overall WA mean temperature jumped by almost 1 degree C beginning in the spring of 2009 between August and November, broken into seasons to give some averaged time perspective.

Spring 2008 - 23.4C average Summer 2008/09 - 28.6C average
Sep 2008 - 20.99C - 1.3C above average Dec 2008 - 27.4C - .5C below average
July 2008 - 14.39C - 0.42C above average Oct 2008 - 24.57C - 1.43C above average Jan 2009 - 29.7C - 1C above average
Aug 2008 - 16.52C - 0.64C below average Nov 2008 - 24.6C - 1.3C below average Feb 2009 - 28.7C - .6C above average
Autumn 2009 - 23.1C average Winter 2009 - 16.9C average Spring 2009 - 23.6C average
Mar 2009 - 26.7C - 0.1C above average Jun 2009 - 16.2C - 0.3C above average Sep 2009 - 20C - 0.3C above average
Apr 2009 - 23.8C - 0.6C above average Jul 2009 - 15.6C - 0.6C above average Oct 2009 - ?? but above average
May 2009 - 18.7C - 0.2C below average Aug 2009 - 18.9C - 1.7C above average Nov 2009 - 27.2C - 1.3C above average
Summer 2009/10 - 29.6C average Autumn 2010 - 24C average Winter 2010 - 16.2C average
Dec 2009 - 29C - 1C above average Mar 2010 - 27.6C - 1C above average Jun 2010 - 16.6C - 0.7C above average
Jan 2010 - 29.9C - 1.2C above average Apr 2010 - 25C - 1.8C above average Jul 2010 - 15.3C - 0.3C above average
Feb 2010 - 29.8C - 1.7C above average May 2010 - 19.4C - 0.5C above average Aug 2010 - 16.6C - 0.1C above average
Spring 2010 - 22.9C average Summer 2010/11 - 28.5C average Autumn 2011 - 22.1C average
Sep 2010 - 19C - 0.7C below average Dec 2010 - 27.9C - long-term average Mar 2011 - 25.3C - 1.3C below average
Oct 2010 - 23.1C - long-term average Jan 2011 - 29.7C - 1C above average Apr 2011 - 23.1C - 0.1C below average
Nov 2010 - 26.6C - 0.7C above average Feb 2011 - 27.9C - 0.9C below average May 2011 - 18C - 0.9C below average
Winter 2011 - 16.3C average Spring 2011 - 22.8C average Summer 2011/12 - 27.9C average
Jun 2011 - 15.5C - 0.4C below average Sep 2011 - 19.6C - 0.1C above average Dec 2011 - 27.9C - 0.1C below average
Jul 2011 - 15.9C - 1C above average Oct 2011 - 23.4C - 0.2C above average Jan 2012 - 27.8C - 0.9C below average
Aug 2011 - 17.6C - 1.1C above average Nov 2011 - 25.3C - 0.6C below average Feb 2012 - 27.9C - 0.2C below average
Autumn 2012 - 22.5C average Winter 2012 - 15.9C average Spring 2012 - 24.2C average
Mar 2012 - 25.4C - 1.2C below average Jun 2012 - 15.8C - 0.1C below average Sep 2012 - 21.2C - 1.5C above average
Apr 2012 - 23.2C - long-term average Jul 2012 - 14.3C - 0.7C below average Oct 2012 - 24.8C - 1.7C above average
May 2012 - 18.8C - 0.1C below average Aug 2012 - 17.7C - 1.1C above average Nov 2012 - 26.7C - 0.8C above average

Note: the ACORN-SAT dataset is being used by the BoM for temperature area averages from December 2012 onwards. For this reason, all averages tabulated above are from a different set of weather stations and in many cases their mean temperatures bear no relation to the mean temperatures listed below.

Summer 2012/13 - 29.1C average Autumn 2013 - 26.0C average Winter 2013 - 18.4C average
Dec 2012 - 28.5C - 0.60C above average Mar 2013 - 33.2C - 0.02C above average Jun 2013 - 21.65C - 0.43C below average
Jan 2013 - 30.1C - 1.20C above average Apr 2013 - 25.16C - 1.96C above average Jul 2013 - 15.61C - 0.61C above average
Feb 2013 - 28.71C - 0.62C above average May 2013 - 19.78C - 0.86C above average Aug 2013 - 18.1C - 1.56C above average
Spring 2013 - 24.3C average Summer 2013/14 - 28.2C average Autumn 2014 - 23.9C average
Sep 2013 - 21.1C - 1.37C above average Dec 2013 - 28.2C - 0.32C above average Mar 2014 - 27.63 - 1.03C above average
Oct 2013 - 24.9C - 1.77C above average Jan 2014 - 28.9C - 0.16C above average Apr 2014 - 23.7C - 0.50C above average
Nov 2013 - 26.8 - 0.90C above average Feb 2014 - 27.63 - 0.47C below average May 2014 - 20.28C - 1.38C above average
Winter 2014
Jun 2014 - 15.85C - 0.05C below average
Jul 2014 - 15.21C - 0.21C above average


The statewide data above shows temperatures dropped in the summer of 2011 to 0.4C below the long-term average, although this moderating of temperatures is not reflected in the historic baseline comparison for the 32 major centres.

The BOM explains its baseline for the above anomalies thus: The climatological averages shown in the text and tables are generally long-term means based on observations from all available years of record, which vary widely from site to site. They are not shown for sites with less than 30 years of record, as they cannot then be calculated reliably. Climatological extremes are generally taken from available observations from all available years of record. The number of years can vary substantially from site to site.

The BOM also compares temperatures with the baseline average of 22.5C from 1961 to 1990. The BoM's portrayal of WA's temperature history is not static. The animation below shows the difference between the anomaly charts published in 2010 and 2013, the ACORN dataset of 2012 a probable reason for the early years cooling and temperatures warming since about 1930:


historic temperature anomalies wa

It is worth noting that, according to the BOM, the statewide mean maximum temperature for the three months October to December 2009 was the highest on record. August 2009 had the second highest mean maximum and the fifth warmest mean minimum since records began in 1950.

According to the BOM's Annual Australian Climate Statement 2009: An unusual winter-time heatwave occurred during August over large parts of inland Australia and resulted in Australia’s warmest August on record. A third prolonged heatwave occurred during November across central and southeast Australia, leading to a record 8 consecutive days of maximum temperatures above 35°C in Adelaide, and numerous maximum temperature records across southern and eastern Australia, especially in South Australia and New South Wales. Based on the analysis of daily (maximum and minimum) temperature data above and below set thresholds, there are clear upward trends in the number of hot events and downward trends in the number of cold events (over the period 1960 to date), consistent with the background of global warming.

The mean minimum and maximum across WA in autumn 2010 were the fourth and sixth highest respectively. January 2010 had the third highest average maximum and the second highest average minimum on record. February 2010 had the 4th hottest average minimum and maximum ever recorded.

The summer months of 2009/2010 were the hottest on record in WA and the national average in 2010 has been biased by temperatures well above average in the western half of the continent.

So has the weather been exceptionally hot across WA in the 12 months to July 2010 or did a BOM database adjustment in November 2009 influence subsequent temperature readings?

It is worth noting the frequency of adjustments on the BOM database as presented on the web.

In July 2010 I checked every month back to June 2009 in all 32 locations within my records against the BOM database as currently presented on the web. I found 43 adjustments by the BOM, the most consistent being January 2010 wherein most but not all locations saw a small reduction in their mean maximum:


Min Max Min Max Min Max Min Max
Albany 16.4 23.1 Balladonia 16.1 34.4 Balladonia 4.3 21.7 Bridgetown 12.1 30.5
Jan 2010 16.4 23 Jan 2010 16.1 34.1 Sep 2009 4.4 21.7 Jan 2010 12.1 30.4
Min Max Min Max Min Max Min Max
Broome 26.6 33.1 Bunbury 15.5 31.7 Busselton 14.7 30.6 Busselton 11.4 23.3
Jan 2010 26.6 33 Jan 2010 15.5 31.6 Jan 2010 14.7 30.5 Apr 2009 11.3 23.3
Min Max Min Max Min Max Min Max
Cape Leeuwin 17.3 23.2 Cape Naturaliste 15.2 27.7 Carnarvon 22.5 30.8 Derby 25 39.4
Jan 2010 17.3 23.1 Jan 2010 15.2 27.6 Jan 2010 22.5 30.9 Nov 2009 25 39.5
Min Max Min Max Min Max Min Max
Derby 26.5 36.5 Donnybrook 15.9 33.1 Esperance 16.1 27.8 Esperance Airport 15 29.4
Feb 2010 26.4 36.5 Jan 2010 15.9 33 Jan 2010 16.1 27.6 Jan 2010 15 29.2
Min Max Min Max Min Max Min Max
Eucla 18.2 30.3 Eyre 14.3 30.9 Geraldton 18.3 33 Halls Creek
Jan 2010 18.2 30.1 Jan 2010 14.3 30.7 Jan 2010 18.3 32.9 * *
Min Max Min Max Min Max Min Max
Kalgoorlie 19.8 36.8 Katanning 13.1 31.2 Kellerberrin 8.3 26.8 Kellerberrin 14.7 34.4
Jan 2010 19.8 36.6 Jan 2010 13.1 31.1 Oct 2009 8.9 27.2 Dec 2009 14.5 34.4
Min Max Min Max Min Max Min Max
Kellerberrin 16.5 38 Kellerberrin 17.5 35.8 Kellerberrin 10.6 27.9 Laverton
Jan 2010 16.3 37.8 Feb 2010 17.6 36 Apr 2009 10.6 27.8 * *
Min Max Min Max Min Max Min Max
Marble Bar 26.8 41.9 Merredin 18.5 37.6 Mt Barker 7 14.8 Mt Barker 11.8 27.9
Jan 2010 26.8 42 Feb 2010 18.5 37.4 Sep 2009 6.3 14.9 Jan 2010 11.8 28.3
Min Max Min Max Min Max Min Max
Northam 17.7 37.4 Onslow 24 36.3 Perth Metro 18.9 33.5 Rottnest Island 16 23.6
Jan 2010 17.7 37.3 Jan 2010 24 36.6 Jan 2010 18.9 33.4 Nov 2009 16 23.7
Min Max Min Max Min Max Min Max
Rottnest Island 19.5 27.3 Southern Cross 18.2 37.4 Southern Cross 18.7 36.1 Wandering 14.3 34.7
Jan 2010 19.5 27.2 Jan 2010 18.2 37.3 Feb 2010 18.6 36 Jan 2010 14.3 34.6
Min Max Min Max Min Max Min Max
Wandering 13.4 30.1 Wiluna 14.7 33.6 Wiluna 23.1 38.3 Wiluna 25.2 41.1
Mar 2010 13.4 29.9 Oct 2009 14.9 33.8 Dec 2009 23.1 38.1 Jan 2010 24.8 41.2
Min Max Min Max
Wyndham York 16.5 36.7
* * Jan 2010 16.5 36.6

* No change




As originally posted on BOM website database
As recorded on August 10 2010

When all the BOM adjustments are calibrated into my averages for the 12 months to July 2010, there is no change at all to the overall minimum and maximum averages ... i.e within adjustments by the BOM to its database since November to its monthly records since September 2009, the upward adjustments almost perfectly counter the downward adjustments. The consistency of adjustments made to January 2010 records suggests a database bug correction was again responsible for the "incorrect" original recording.

The increase in WA average temperatures coinciding with the month that a BOM database bug was corrected does not necessarily mean the Daily Weather Observations on the BOM website are inaccurate. It may well have been a very hot year across Western Australia.

However, the presence of software bugs for extended periods, as well as sporadic adjustments without a seeming pattern, raise questions about the reliability of data from the BOM website for research purposes.

Similar questions surround the reliability of Australian temperature recordings by the Goddard Institute of Space Studies.


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This website produced by Scribeworks 2009/11

Albany
Balladonia
Bridgetown
Broome
Bunbury
Busselton
Cape Leeuwin
Cape Naturaliste
Carnarvon
Derby
Donnybrook
Esperance
Eucla
Eyre
Geraldton
Halls Creek
Kalgoorlie
Katanning
Kellerberrin
Laverton
Marble Bar
Merredin
Mt Barker
Northam
Onslow
Perth
Rottnest Island
Southern Cross
Wandering
Wiluna
Wyndham
York

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