Posts Tagged ‘climate’

ACORN-SAT 2.0: New South Wales- What a mess

April 10, 2019

This is the seventh in a series of posts in which I directly compare the most recent version of Australia’s temperature record, ACORN-SAT 2, with that of the previous version, ACORN-SAT 1.  Daily data are directly downloaded from the Bureau of Meteorology. I do not analyse against raw data (available at Climate Data Online), except for particular examples, as I am interested in how different Acorn 2 is from Acorn 1.  The basis for the new version is in the Research Report.  The Bureau has published a new station catalogue with more detailed information, the adjustment summary for each station, plus lists of comparative stations for adjustments and all comparison stations for each site, with explanations of adjustment terminology.  Well worth a look.

See my previous posts for Western Australia, the Northern TerritoryQueensland,  South Australia, Tasmania, and Victoria for a general introduction.  It is important to highlight this paragraph on the new ACORN-SAT home page:

The purpose of updating datasets like ACORN-SAT is principally to incorporate data that has been recorded since the last analysis was released, as well as historical paper records that have been recently digitised. ACORN-SAT version 2 also incorporates the findings and recommendations of the Technical Advisory Forum, applies the latest scientific research and understanding and, where applicable, introduces new methodologies. The overall aim of the update to ACORN-SAT is to provide improved estimates of historical changes in climate.

As well, in the ACORN-SAT FAQs, the Bureau says:

“… The important question is not which one (version) represents the absolute truth, but whether those estimates produce wildly different results, and whether the range of estimates provides a reasonable guide to what has actually occurred.”

Therefore, the Bureau has set their own criterion for whether Acorn 1 and Acorn 2 are at all useful and valuable.  To repeat:

“whether those estimates produce wildly different results, and whether the range of estimates provides a reasonable guide to what has actually occurred.”

The Context – New South Wales

Figure 1 is a map of Australia showing all of the Bureau’s ACORN-SAT climate monitoring stations.  New South Wales is the oldest and most populous state with climates varying from semi-desert to montaine.

Figure 1:  Australian ACORN-SAT stations

NSW map all

There are 25 Acorn stations in the NSW BOM database.  Differences between Acorn 1 and Acorn 2 are summarized in the following sections.

Additional data

An extra 27 years of data have been digitised for Canberra, and 45 years for Moree, which has had an enormous effect on annual temperature trends (see below).  Some locations had changes to new sites, with Acorn 1 data merged to Acorn 2 data, including Tibooburra and Wilcannia.

Largest temperature differences

In maxima, changes to Acorn 1 daily data ranged from +8.3 ℃ at Scone in 1996 to -9.6 ℃ at Cabramurra in 1998 applied to individual daily figures.

Remarkably, there were NO changes from Acorn 1 to Acorn 2 at Gunnedah.

Figure 2:  Daily changes in maxima from Acorn 1 to Acorn 2 at Cabramurra

Cabramurra max adj

Minima adjustments ranged from -13.4 ℃ at Wagga Wagga in 1946 to +9.6 ℃ at Scone in 1996 on individual days but with many days adjusted by -2 ℃ or greater.

Figure 3:  Daily changes in minima from Acorn 1 to Acorn 2 at Wagga Wagga:

Wagga min diffs

(Remember, these are adjustments to Acorn 1, which was supposed to be “world’s best practice” seven years ago.  How did the Bureau get it so wrong the first time?  Has world’s best practice changed so much in seven years?)

Record temperatures

New record maxima were established at nine stations, with the highest at Bourke (48.9 ℃) while other stations’ record highs were unchanged or reduced.  There were two notable changes.  Figure 4 shows maxima at Sydney in 1939, where the record was increased by 2.5 ℃ to 47.9 ℃.

Figure 4:  Three versions of maxima at Sydney in 1939

Sydney record max

(The temperature was below 20 ℃ on 16th and 17th.)

Figure 5 shows Port Macquarie, whose record maximum was reduced by -4.1 ℃ from 48.1 ℃ to 44 ℃ in 1944.

Figure 5:  Two versions of maxima at Port Macquarie in 1944

PtMcquarie record max

There is NO daily raw data for any Port Macquarie site from 1921 to 1956 at Climate Data Online, so there is no way of replicating these adjustments.

Such “wildly different results” are beyond rational explanation.

New record low temperatures were established at 15 stations, and a new record low for Acorn stations was set, not at Cabramurra in the Snowy Mountains, but at Inverell in the north: -13 ℃.  Canberra’s minimum was reduced by 2.9 ℃ to -11.5 ℃.

Figure 6:  Three versions of minima at Inverell

Inverell record min

Raw minimum of -10 ℃ is cold enough.  Acorn version 1 had cooled this further by 1.4 ℃, but version 2 cools version 1 by another 1.6 ℃, making it three degrees cooler than the raw figure.  Strange things happen in the past!

Quality Control: especially minimum temperatures higher than maximum.

In Acorn 1, 15 out of the 25 stations had at least one example of minimum higher than maximum- including 12 times at Bourke and Sydney, 15 at Tibooburra, and 212 times at Cabramurra.  The worst example was minimum 2.2 ℃ above maximum in October 1913 at Tibooburra.  Blair Trewin claims he has “fixed” this problem (which he concedes was “physically unrealistic”) by adjusting temperatures in Acorn 2 so that the maximum and minimum are the same, so that DTR for the day is zero.  In his words:

A procedure was therefore adopted under which, if a day had a negative diurnal range in the adjusted data, the maximum and minimum temperatures were each corrected to the mean of the original adjusted maximum and adjusted minimum, creating no change in the daily mean.

That is almost how he “corrected” the worst NSW example in Acorn 1 (minimum 2.2 ℃ above maximum at Tibooburra).  Here is a plot of the raw data and changes made by Acorn 1 and Acorn 2 at Tibooburra in 1913.

Figure 7:  Tibooburra temperatures October-November 1913

Tibooburra DTR 1913

Acorn 1 maxima (orange line) were reduced too far below Raw (brown). Acorn 1 minima (grey) were too far above raw minima (light blue).  Result: garbage. Acorn 2 has changed maxima (dark red) back to 0.1 ℃ below the raw value, and reduced minima (dark blue) from 17 ℃ to 16 ℃.  This is not the “mean of the original adjusted maximum and adjusted minimum”- but at least the DTR is not negative.

The problem was caused by far too large adjustments to both maxima and minima, and was fixed by more arbitrary adjustments.

Not all Acorn 2 adjustments resulted in an increase in warming- in several, the warming trend was reduced.  For example, Figure 8 shows annual temperature trends at Sydney.

Figure 8:  Maxima Trends in Sydney 1910-2017

Sydney max ann trends

The warming rate of +1 ℃ per 100 years in Acorn 1 has been reduced to +0.79 ℃ in Acorn 2.

However, at Coffs Harbour the warming trend in minima was more than doubled, from +1.47 ℃ to +3.17 ℃ per 100 years.

Figure 9:  Minima trends at Coffs Harbour 1952-2017

CoffsHbr min ann trends

Figure 10 shows the effect of including an extra 27 years of data on annual trends at Canberra, with Acorn 1 adjusted downwards from 2011.

Figure 10:  Trends in Canberra minima 1914-2017

Canberra min ann trends

Acorn 1 starts in 1940.  Canberra’s warming trend has been increased from +1.48 ℃ to +2.18 ℃ per 100 years.

Conclusion:

There are no additional stations, but additional digitised data at several stations has a large impact on annual trends.  As well, several Acorn 1 stations closed and their data merged with data from new sites in Acorn 2.

Large differences between Acorn 1 and Acorn 2 daily data of many degrees Celsius are found at several stations.  Interestingly, no changes were made to Version 1 in Gunnedah maxima, and only a few in minima.

New record maxima were established at nine stations, with the remaining stations’ records being reduced or unchanged.  The largest increase was of +2.5 ℃ at Sydney, and the largest decrease was at Port Macquarie where the record high was reduced by -4.1 ℃.

The issue of instances of minima being higher than maxima caused by too vigorous adjustments at 15 stations (including 12 times at Bourke and Sydney, 15 at Tibooburra, and 212 times at Cabramurra) has been “fixed”- only seven years after the problem was pointed out.

Not all Acorn 2 adjustments resulted in an increase in warming- in several, the warming trend was reduced.  However, excessive adjustments have resulted in Coffs Harbour’s Acorn 1 minima trend of +1.47 ℃ per 100 years being more than doubled to +3.17 ℃ in Acorn 2.

The size of the adjustments only seven years after the “world’s best practice” dataset was launched, is incredible, and demands explanation.  The explanation that Acorn Version 2 “applies the latest scientific research and understanding and, where applicable, introduces new methodologies”, is beyond belief, as most datasets so far examined are vastly different from Acorn Version 1.  This is not incremental improvement.

In the ACORN-SAT FAQs, in the answer to:

“Why should the adjustments change, weren’t they correct the first time?”

the Bureau says:

“… The important question is not which one (version) represents the absolute truth, but whether those estimates produce wildly different results, and whether the range of estimates provides a reasonable guide to what has actually occurred.”

By their own words they have condemned themselves- “wildly different results” is exactly what has been produced.  Adjustments made in Version 1 were apparently made in error as they have been “corrected” by adjustments in version 2.  Will these adjustments be in error and corrected in version 3?

The Bureau officers responsible for Acorn version 2 appear to be blissfully unaware that they have made adjustments of up to 13.4 ℃ to temperatures in the dataset they proudly claimed to be world’s best practice just seven years ago.

What a mess.

I will next show a summary of Version 2 changes across the whole network, and then look at annual trends at all stations.

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ACORN-SAT 2.0: Victoria- A comedy of errors

April 5, 2019

This is the sixth in a series of posts in which I directly compare the most recent version of Australia’s temperature record, ACORN-SAT 2, with that of the previous version, ACORN-SAT 1.  Daily data are directly downloaded from the Bureau of Meteorology. I do not analyse against raw data (available at Climate Data Online), except for particular examples, as I am interested in how different Acorn 2 is from Acorn 1.  The basis for the new version is in the Research Report.  The Bureau has published a new station catalogue with more detailed information, the adjustment summary for each station, plus lists of comparative stations for adjustments and all comparison stations for each site, with explanations of adjustment terminology.  Well worth a look.

See my previous posts for Western Australia, the Northern TerritoryQueensland,  South Australia, and Tasmania for a general introduction.  It is important to highlight this paragraph on the new ACORN-SAT home page:

The purpose of updating datasets like ACORN-SAT is principally to incorporate data that has been recorded since the last analysis was released, as well as historical paper records that have been recently digitised. ACORN-SAT version 2 also incorporates the findings and recommendations of the Technical Advisory Forum, applies the latest scientific research and understanding and, where applicable, introduces new methodologies. The overall aim of the update to ACORN-SAT is to provide improved estimates of historical changes in climate.

As well, in the ACORN-SAT FAQs, the Bureau says:

“… The important question is not which one (version) represents the absolute truth, but whether those estimates produce wildly different results, and whether the range of estimates provides a reasonable guide to what has actually occurred.”

Therefore, the Bureau has set their own criterion for whether Acorn 1 and Acorn 2 are at all useful and valuable.  To repeat:

“whether those estimates produce wildly different results, and whether the range of estimates provides a reasonable guide to what has actually occurred.”

The Context – Victoria

Figure 1 is a map of Australia showing all of the Bureau’s ACORN-SAT climate monitoring stations.  Victoria is a small state with climates varying from semi-desert to montaine.

Figure 1:  Australian ACORN-SAT stations

Vic map

There are eleven Acorn stations in the Victorian BOM database.  Differences between Acorn 1 and Acorn 2 are summarized in the following sections.

Additional data

An extra 36 years of data have been digitised for Sale, which has had an enormous effect on annual temperature trends (see below).  Melbourne Regional Office observations ceased on 6 January 2015, but Acorn 2 continues the series with Olympic Park, with an overlap of 19 months.

Largest temperature differences

In maxima, changes to Acorn 1 daily data ranged from +14.6 ℃ at Orbost in 2012 to -4.4 ℃ at Sale in 2013 applied to individual daily figures.

Figure 2:  Daily changes in maxima from Acorn 1 to Acorn 2 at Orbost

Orbost max adj

Minima adjustments ranged from -7.4 ℃ at Orbost to +6.2 ℃ at Rutherglen in 1926 on individual days but with many days adjusted by -2℃ or greater.   Most changes were small but numerous, for example at Rutherglen where the changes to Acorn 1 ranged between -1 ℃ and +2 ℃ for many years.

Figure 3:  Daily changes in minima from Acorn 1 to Acorn 2 at Rutherglen:

Rutherglen min diffs

(Remember, these are adjustments to Acorn 1, which was supposed to be “world’s best practice” seven years ago.  How did the Bureau get it so wrong the first time?  Has world’s best practice changed so much in seven years?)

Record temperatures

New record maxima were established at Cape Otway, Gabo Island, and Mildura, while other stations’ record highs were unchanged or reduced.

Figure 4:  Three versions of maxima at Mildura in 1960

Mildura record max

That eclipses Mildura’s record in raw temperatures of 46.9 ℃.

New record low temperatures were established at Cape Otway, Laverton, Melbourne R.O., Nhill, Rutherglen, and Wilson’s Promontory.  Melbourne’s minima was reduced by 1.1 ℃ to -1.5 ℃.

Figure 5:  Three versions of minima at Melbourne Regional Office

Melbourne record min

Acorn version 1 had warmed the minima by 0.5 ℃, but version 2 cools version 1 by 1.2 ℃, making it 0.7 ℃ cooler than the raw figure.  Strange things happen in the past!

Quality Control: especially minimum temperatures higher than maximum.

In Acorn 1, eight out of the eleven stations had at least one example of minimum higher than maximum- including 48 times at Orbost, 63 at Cape Otway, and 79 times at Wilson’s Promontory.  The worst example was minimum 1.8 ℃ above maximum in February 1946 at Orbost.  Blair Trewin claims he has “fixed” this problem (which he concedes was “physically unrealistic”) by adjusting temperatures in Acorn 2 so that the maximum and minimum are the same, so that DTR for the day is zero.  In his words:

A procedure was therefore adopted under which, if a day had a negative diurnal range in the adjusted data, the maximum and minimum temperatures were each corrected to the mean of the original adjusted maximum and adjusted minimum, creating no change in the daily mean.

That is not how he “corrected” the worst Victoria example in Acorn 1 (minimum 1.8 ℃ above maximum at Orbost).  Here is a plot of the raw data and changes made by Acorn 1 and Acorn 2 at Orbost in 1946.

Figure 6:  Orbost temperatures January – February 1946

Orbost DTR

Acorn 1 maxima (orange line) were reduced below Raw (brown). Acorn 1 minima (grey) were too far above raw minima (light blue).  Result: garbage. Acorn 2 has changed maxima (dark red) back to approximately raw values, and reduced minima (dark blue) markedly.  This is not the “mean of the original adjusted maximum and adjusted minimum”.

The problem was caused by far too large adjustments to both maxima and minima, and was fixed by reducing the minimum, and raising the maximum, on all days to almost the same as the raw figures.

Figure 7 shows the effect Acorn version 2 tinkering adjustments have on annual temperature trends at Nhill.

Figure 7:  Trends in Nhill minima 1944-2017

Nhill min ann trends

Acorn 1 had this series cooling very slightly at -0.13 ℃ per 100 years but Acorn 2 has reversed the Acorn 1 trend to +0.67 ℃ per 100 years.  (This is restored to about 0.13 ℃ above what the “raw” trend showed.)

Figure 8 shows the effect of including an extra 36 years of data on annual trends at Sale.

Figure 8:  Trends in Sale maxima 1910-2017

Sale max ann trends

The arrow shows where Acorn 1 starts in 1946.

Conclusion:

There are no additional stations, but an extra 36 years of data at Sale has a large impact on annual trends.  Melbourne Regional Office is now amalgamated with Olympic Park, despite having only 19 months of overlap.

Large differences between Acorn 1 and Acorn 2 daily data of several degrees Celsius are found at Orbost, Sale, and Rutherglen.

New record maxima were established at Cape Otway, Gabo Island, and Mildura. New record low temperatures were established Cape Otway, Laverton, Melbourne R.O., Nhill, Rutherglen, and Wilson’s Promontory.

The issue of instances of minima being higher than maxima caused by too vigorous adjustments at eight stations (including 48 instances at Orbost, 63 at Cape Otway, and 79 at Wilson’s Promontory) has been “fixed”- only seven years after the problem was pointed out.

Excessive adjustments have resulted in Nhill’s Acorn 1 minima trend of -0.13℃ per 100 years being changed to +0.67 ℃ in Acorn 2.

The size of the adjustments only seven years after the “world’s best practice” dataset was launched, is incredible, and demands explanation.  The explanation that Acorn Version 2 “applies the latest scientific research and understanding and, where applicable, introduces new methodologies”, is beyond belief, as nearly every dataset so far examined is vastly different from Acorn Version 1.  This is not incremental improvement.

In the ACORN-SAT FAQs, in the answer to:

“Why should the adjustments change, weren’t they correct the first time?”

the Bureau says:

“… The important question is not which one (version) represents the absolute truth, but whether those estimates produce wildly different results, and whether the range of estimates provides a reasonable guide to what has actually occurred.”

By their own words they have condemned themselves- “wildly different results” is exactly what has been produced.  Adjustments made in Version 1 were apparently made in error as they have been “corrected” by adjustments in version 2.  Will these adjustments be in error and corrected in version 3?

It’s a joke, a continuing comedy of errors.

I have so far looked at 87 of the 112 Acorn stations.  Next up: New South Wales.

ACORN-SAT 2.0: Tasmania- May the Farce be with you

April 1, 2019

This is the fifth in a series of posts in which I directly compare the most recent version of Australia’s temperature record, ACORN-SAT 2, with that of the previous version, ACORN-SAT 1.  Daily data are directly downloaded from the Bureau of Meteorology. I do not analyse against raw data (available at Climate Data Online), except for particular examples, as I am interested in how different Acorn 2 is from Acorn 1.  The basis for the new version is in the Research Report.  The Bureau has published a new station catalogue with more detailed information, the adjustment summary for each station, plus lists of comparative stations for adjustments and all comparison stations for each site, with explanations of adjustment terminology.  Well worth a look.

See my previous posts for Western Australia, the Northern Territory, Queensland, and South Australia for a general introduction.  An important addition to this general introduction is this paragraph on the ACORN-SAT home page:

The purpose of updating datasets like ACORN-SAT is principally to incorporate data that has been recorded since the last analysis was released, as well as historical paper records that have been recently digitised. ACORN-SAT version 2 also incorporates the findings and recommendations of the Technical Advisory Forum, applies the latest scientific research and understanding and, where applicable, introduces new methodologies. The overall aim of the update to ACORN-SAT is to provide improved estimates of historical changes in climate.

The Context – Tasmania

Figure 1 is a map of Australia showing all of the Bureau’s ACORN-SAT climate monitoring stations.  Tasmania is an island state with a cool marine climate.

Figure 1:  Australian ACORN-SAT stations

Tas map

There are seven Acorn stations in the Tasmanian BOM database.  Differences between Acorn 1 and Acorn 2 are summarized in the following sections.

Largest temperature differences

In maxima, changes to Acorn 1 daily data ranged from +5.4 ℃ at Larapuna (Eddystone Point) to -7.3 ℃ in 1946 at Butlers Gorge applied to individual daily figures.

Figure 2:  Daily changes in maxima from Acorn 1 to Acorn 2 at Butlers Gorge

ButlersGorge max adj

Minima adjustments ranged from -9.7 ℃ to +11.3 ℃ at Butlers Gorge on individual days but with many days adjusted by -2℃ or greater.   Most changes were small but numerous, for example at Launceston where the changes to Acorn 1 ranged between -1 ℃ and +2 ℃ for many years.

Figure 3:  Daily changes in minima from Acorn 1 to Acorn 2 at Launceston:

Launceston min diffs

(Remember, these are adjustments to Acorn 1, which was supposed to be “world’s best practice” seven years ago.  How did the Bureau get it so wrong the first time?  Has world’s best practice changed so much in seven years?)

Record temperatures

New record maxima were established at Butlers Gorge, Cape Bruny Lighthouse, Larapuna (Eddystone Point), and Low Head.

Figure 4:  Three versions of maximum at Low Head 3 February 1912

LowHd record max

New record low temperatures were established at all stations except Butlers Gorge.  Low Head’s minima was reduced by 0.7 ℃ to -2.9 ℃.

Figure 5:  Three versions of minima at Low Head July 1944

LowHd record min

Acorn version 1 had warmed the minima by 0.6 ℃, but version 2 cools version 1 by 0.7 ℃, making it 0.1 ℃ cooler than the raw figure.  Strange things happen in the past!

Quality Control: especially minimum temperatures higher than maximum.

In Acorn 1, five out of the seven stations had at least one example of minimum higher than maximum- including 37 times at Butlers Gorge and 39 times at Low Head (again), where the worst example was minimum 2.1 ℃ above maximum in December 1926.  Blair Trewin claims he has “fixed” this problem (which he concedes was “physically unrealistic”) by adjusting temperatures in Acorn 2 so that the maximum and minimum are the same, so that DTR for the day is zero.  In his words:

A procedure was therefore adopted under which, if a day had a negative diurnal range in the adjusted data, the maximum and minimum temperatures were each corrected to the mean of the original adjusted maximum and adjusted minimum, creating no change in the daily mean.

That is not how he “corrected” the worst Tasmanian example in Acorn 1 (minimum 2.1 ℃ above maximum at Low Head).  Here is a plot of the raw data and changes made by Acorn 1 and Acorn 2 at Low Head in December 1926.

Figure 6:  Low Head temperatures December 1926

LowHd DTR

Acorn 1 maxima (orange line) were reduced too far below Raw (brown). Acorn 1 minima (grey) were too far above raw minima (light blue).  Result: garbage. Acorn 2 has changed maxima (dark red) back above raw, and reduced minima (dark blue) almost to the same value as raw, except on the 17th when it has been made the same as the Acorn 2 maximum.  This is not the “mean of the original adjusted maximum and adjusted minimum”.

The problem was caused by far too large adjustments to maxima, and was fixed by arbitrarily making the minimum on the 17th the same as the maximum, unusually higher than other minima adjustments.

Figure 7 shows the effect Acorn tinkering adjustments have on annual temperature trends at Butlers Gorge.

Figure 7:  Trends in Butlers Gorge minima 1944-2017

ButlersGorge min ann trends

Acorn 1 had this series cooling very slightly at -0.12 ℃ per 100 years but Acorn 2 has reversed the Acorn 1 trend to +0.54 ℃ per 100 years.  (This is restored to what the “raw” trend showed, from a messy record with huge data gaps.)

Conclusion:

There are no additional stations, so Tasmania has only seven stations.

There is no more additional digitized data, except for the period 2012 to 2017.

Large differences between Acorn 1 and Acorn 2 daily data of several degrees Celsius are found at Larapuna and Butlers Gorge.

New record maxima were set at Butlers Gorge, Cape Bruny, Larapuna, and Low Head.  New record low temperatures were established at all stations except Butlers Gorge.

The issue of instances of minima being higher than maxima caused by too vigorous adjustments (37 times at Butlers Gorge and 39 times at Low Head has been “fixed” by arbitrary adjustments.

Excessive adjustments have resulted in Butler Gorge’s Acorn 1 minima trend of -0.12℃ per 100 years being changed to +0.54 ℃ in Acorn 2.

The size of the adjustments only seven years after the “world’s best practice” dataset was launched, is incredible, and demands explanation.  The explanation that Acorn Version 2 “applies the latest scientific research and understanding and, where applicable, introduces new methodologies”, is beyond belief, as nearly every dataset so far examined is vastly different from Acorn Version 1.  This not incremental improvement.

In the ACORN-SAT FAQs, in the answer to:

“Why should the adjustments change, weren’t they correct the first time?”

the Bureau spokesman says:

“… The important question is not which one (version) represents the absolute truth, but whether those estimates produce wildly different results, and whether the range of estimates provides a reasonable guide to what has actually occurred.”

By their own words they have condemned themselves- “wildly different results”  is exactly what has been produced.

 

What a farce.

I have so far looked at 76 of the 112 Acorn stations.  Next up: Victoria.

ACORN-SAT 2.0: South Australia- Science Fiction

March 28, 2019

This is the fourth in a series of posts in which I directly compare the most recent version of Australia’s temperature record, ACORN-SAT 2, with that of the previous version, ACORN-SAT 1.  Daily data are directly downloaded from the Bureau of Meteorology. I do not analyse against raw data (available at Climate Data Online), except for particular examples, as I am interested in how different Acorn 2 is from Acorn 1.  The basis for the new version is in the Research Report.

See my previous posts for Western Australia, the Northern Territory and Queensland for a general introduction.

The Context – South Australia

Figure 1 is a map of Australia showing all of the Bureau’s ACORN-SAT climate monitoring stations.  South Australia has a narrow band of arable country in the south with cool wet winters and hot dry summers, but most of the state is desert.  South Australia achieved notoriety 18 months ago when the whole state endured an electricity blackout- but of course large scale adoption of renewable energy was blameless.

Figure 1:  Australian ACORN-SAT stations

SA map

There are thirteen Acorn stations in the South Australian BOM database.  Differences between Acorn 1 and Acorn 2 are summarized in the following sections.

Largest temperature differences

In maxima, changes to Acorn 1 daily data ranged from +9.7 ℃ in 1996 to -7.6 ℃ in 1993 at Port Lincoln, with changes of +8.5 ℃ on many occasions, applied to individual daily figures.

Figure 2:  Daily changes in maxima from Acorn 1 to Acorn 2 at Port Lincoln

PortLincoln diffs max

Minima adjustments ranged from -5.5 ℃ again at Port Lincoln to +9.1 ℃ at Snowtown, and there were many other large adjustments at other stations as well.  Most changes were small but numerous, for example at Mount Gambier where the changes to Acorn 1 ranged between -2.2 ℃ and +0.5 ℃ for many years.

Figure 3:  Daily changes in minima from Acorn 1 to Acorn 2 at Mount Gambier:

MtGambier diffs min

(Remember, these are adjustments to Acorn 1, which was supposed to be “world’s best practice” seven years ago.  How did the Bureau get it so wrong the first time?  Has world’s best practice changed so much in seven years?)

Record temperatures

Most stations had their record highs actually reduced.  New record maxima were established at two stations, Port Lincoln increased from 46.7 ℃ to 47.9 ℃, and Oodnadatta set a new record of 51.1 degrees Celsius, which is a new record for all of Australia, pipping Carnarvon in WA by 0.1 ℃.

Figure 4:  New version of maxima at Oodnadatta December 1959 – January 1960

Oodnadatta record max

New record low temperatures were established at Cape Borda, Nuriootpa, and Mount Gambier.  Mount Gambier shows the Bureau at its silliest:

Figure 5:  Three versions of minima at Mt Gambier June 1950

MtGambier record min

Acorn version 1 had warmed the minima by 0.4 ℃, but version 2 cools version 1 by 0.6 ℃, making it cooler than the raw figures.

Up, down- what was the ‘correct’ temperature?.

Quality Control: especially minimum temperatures higher than maximum.

In Acorn 1, eight out of the thirteen stations had at least one example of minimum higher than maximum.  Blair Trewin claims he has “fixed” this problem (which he concedes was “physically unrealistic”) by adjusting temperatures in Acorn 2 so that the maximum and minimum are the same, so that DTR for the day is zero.  In his words:

A procedure was therefore adopted under which, if a day had a negative diurnal range in the adjusted data, the maximum and minimum temperatures were each corrected to the mean of the original adjusted maximum and adjusted minimum, creating no change in the daily mean.

That is how he “corrected” the worst South Australian example in Acorn 1 (minimum 2.4 ℃ above maximum at Tarcoola).  Here is a plot of the raw data and changes made by Acorn 1 and Acorn 2 at Tarcoola from 26 April to 5 May 1923.

Figure 6:  Tarcoola temperatures 26 April – 5 May 1923

Tarcoola DTR

Acorn 1 maxima (orange line) were slightly reduced below Raw (brown). Acorn 1 minima (grey) were far above raw minima (light blue).  Result: garbage.  Acorn 2 has made minima (dark blue) about two degrees less than Acorn 1.

The problem was caused by far too large adjustments, as Figure 7 shows:

Figure 7:  Adjustments to raw Tarcoola minima 26 April – 5 May 1923

Tarcoola adjustments

Acorn 1 adjustments to raw minima were as much as 4.4 degrees; Acorn 2 has introduced variety- sometimes lower, sometimes higher.

Figure 8 shows the effect Acorn adjustments have on annual temperature trends.

Figure 8:  Trends in Tarcoola minima 1922-2017

Tarcoola min ann trends

I spliced the old Tarcoola record with Tarcoola Aero which overlapped  from 1998 to 2000 to create a “minimally adjusted” series, shown in blue.  This series is cooling at -0.46 ℃ per 100 years.  Acorn 1 reversed this trend, showing warming at 0.67 ℃ per 100 years, but Acorn 2 has increased the Acorn 1 trend more than three times to +2.43 ℃ per 100 years.

Conclusion:

There are no additional stations, so the network is still extremely sparse.

There is no more additional digitized data.

Large differences between Acorn 1 and Acorn 2 daily data of several degrees Celsius are found at Port Lincoln, Snowtown, Tarcoola, and Mount Gambier.

A new Australian record maximum temperature has been set at 51.1 ℃ at Oodnadatta, Port Lincoln also has a new record, but other locations had record maxima reduced.  New record low temperatures were established at Cape Borda, Nuriootpa, and Mount Gambier.

The issue of instances of minima being higher than maxima caused by too vigorous adjustments has been “fixed” by arbitrary adjustments.

Excessive adjustments have resulted in Tarcoola’s raw minima trend of -0.46℃ per 100 years being changed to +0.67 ℃ in Acorn 1 and an incredible +2.43 ℃ in Acorn 2, an increase of 262% over Acorn 1.

The size of the adjustments only seven years after the “world’s best practice” dataset was launched, is incredible, and demands explanation.

Acorn 2’s adjustments are science fiction.

Next up: Tasmania.

 

ACORN-SAT 2.0: Queensland: Welcome to Dreamworld

February 28, 2019

This is the third in a series of posts in which I directly compare the most recent version of Australia’s temperature record, ACORN-SAT 2, with that of the previous version, ACORN-SAT 1.  Daily data are directly downloaded from the Bureau of Meteorology. I do not analyse against raw data (available at Climate Data Online), except for particular examples, as I am interested in how different Acorn 2 is from Acorn 1.  The basis for the new version is in the Research Report.

See my previous posts for Western Australia and the Northern Territory for a general introduction.

The Context – Queensland

Figure 1 is a map of Australia showing all of the Bureau’s ACORN-SAT climate monitoring stations.  Queensland is in the north-east from monsoonal tropics to mountain temperate to savannah and desert.

Figure 1:  Australian ACORN-SAT stations

Qld map

There are 26 Acorn stations in the Queensland BOM database.  Differences between Acorn 1 and Acorn 2 are summarized in the following sections.

Largest temperature differences

In maxima, changes to Acorn 1 daily data ranged from +7.2C at Burketown in 2003 to -5.2C at Georgetown on many occasions, applied to individual daily figures.

Figure 2:  Daily changes in maxima from Acorn 1 to Acorn 2 at Georgetown

Georgetown diffs

Minima adjustments ranged from -9.1C at Thargomindah to +6.3C at Charleville, and there were many other large adjustments at other stations as well.  Most changes were small but there were many still substantial changes, for example at Longreach where there were some very large changes to Acorn 1, with large numbers between -4C and +2C.

Figure 3:  Daily changes in minima from Acorn 1 to Acorn 2 at Longreach:

Longreach diffs

(Remember, these are adjustments to Acorn 1, which was supposed to be “world’s best practice” seven years ago.  How did the Bureau get it so wrong the first time?  Has world’s best practice changed so much in seven years?)

Record temperatures

New record maxima were established at 10 stations.  These were +0.8C higher than the previous record in Acorn 1 at Burketown (previous record 44.7C to 45.5C).

Figure 4:  Three versions of maxima at Burketown December 1934

Burketown max 1934

A new record low temperature was established at Palmerville, way up north in tropical Cape Yorke Peninsula, where the ridiculous Acorn 1 temperature of -2.4C was reduced even further to -3.1C.  Unbelievable- the record low at Charters Towers, 500km south, is 1.1C.  The record low at Rockhampton, 1,000 km south, is -1C.

Figure 5:  Three versions of minima at Palmerville June 1913

Palmerville min 1913

New lows were also established at 10 other stations.

Apparently the adjustments made to raw data in Acorn 1 weren’t big enough.

Quality Control: especially minimum temperatures higher than maximum.

In Acorn 1, 15 out of the 26 stations had at least one example of minimum higher than maximum.  Blair Trewin has “fixed” this problem (which he concedes was “physically unrealistic”) by adjusting temperatures in Acorn 2 so that the maximum and minimum are the same, so that DTR for the day is zero.  In his words:

A procedure was therefore adopted under which, if a day had a negative diurnal range in the adjusted data, the maximum and minimum temperatures were each corrected to the mean of the original adjusted maximum and adjusted minimum, creating no change in the daily mean.

That is how he “corrected” the worst Queensland example in Acorn 1 (minimum 2.8C above maximum at tropical Mackay).  Here is a plot of the raw data and changes made by Acorn 1 and Acorn 2 at Mackay from 25 to 31 August 1953.

Figure 6:  Mackay Aerodrome data 25-31 August 1953

Mackay August 1953

Acorn 1 maxima (brown line) were slightly reduced below Raw (bright green) until 27 August but had a major adjustment on the 28th, far below Raw minima (olive) and Acorn 1 minima (blue).  Result: garbage.  Acorn 2 has made minima (purple) less than Acorn 1.  Acorn 2 maxima (red) are slightly less than Acorn 1 except on the 28th when the maximum has been made the same as minimum.

The problem was caused by far too large adjustments.

The problem has been “fixed” by making more arbitrary adjustments, but large adjustments remain.

Amberley:

Amberley came under scrutiny after Acorn 1 because of a major adjustment to minima to account for a discontinuity in the 1980s.  I compare before and after annual data.

Figure 7:  Amberley Minima

Amberley min annual

There is a discontinuity in the raw data, so the negative trend is probably too steep.  However, the adjustments in Acorn 1 were far too great.  Acorn 2 is a slight improvement: the trend is now +2.11C per 100 years instead of +2.62C.

Barcaldine:

Barcaldine’s raw data was not supposed to be adjusted in Acorn 1- at least that was claimed in the Table guidance notes of the Table of Adjustments released in 2014.  However, there were some small one-off adjustments to maxima in Acorn 1: +0.1C in 1962, 1995, and 1996, and -0.1C in 2011. However, both maxima and minima have been strongly adjusted in Acorn 2.  Here is Barcaldine’s Tmax:

Figure 8:  Barcaldine Maxima

Barcaldine max annual

That’s a 52% increase in annual trends!

Conclusion:

There are no additional stations, so the network is still extremely sparse.

There is a very small amount of additional digitized data.

Burketown, Georgetown, Longreach, Normanton, and Richmond all had large differences in maxima between Acorn 1 and Acorn 2 daily data of over five degrees Celsius.  Charters Towers, Longreach, Normanton, Palmerville, and Thargomindah had greater than five degree differences in minima.

New record maximum and minimum temperatures have been set.  Palmerville’s new recod low is especially preposterous.

The issue of instances of minima being higher than maxima caused by too vigorous adjustments has been “fixed” by arbitrary adjustments.

Amberley’s minima adjustments have been reduced.

Barcaldine’s raw data was not adjusted in Acorn 1, but both maxima and minima have been  adjusted in Acorn 2.

The size of the adjustments only seven years after the “world’s best practice” dataset was launched, is incredible, and demands explanation.

You don’t have to go to the Gold Coast to see Dreamworld- it’s in the Acorn 2 adjustments.

I will be concentrating on another project for a few weeks so may not post for a while, but when I do, next will be South Australia.

ACORN 2: Rutherglen-Digging a Deeper Hole

February 26, 2019

Rutherglen is back in the news again, so here’s my two bob’s worth.

Acorn 2 has increased the warming trend in annual minima from +1.71C per 100 years to +1.8C per 100 years:

Figure 1:  Rutherglen annual minima

Rutherglen annuals min

Rutherglen’s lowest minimum has been reduced from -7.9C to -8C.

The “corrections” to Acorn 1 are now from 31 December 2010:

Figure 2: Acorn 2 minus Acorn 1 daily values

Rutherglen Tmin diffs

Who knew thermometers were reading a much as 1.2 degrees too warm in 2010?  (The annual mean differences between Acorn 1 and Acorn 2 for the years before 2011 are from 0.5C to 0.7C).

So, is the new version of Acorn an improvement on the homogenization in Acorn 1 from seven years ago?

As a result of the media interest in Rutherglen, in 2014 the Bureau published this plot, showing Rutherglen’s raw data compared with the homogenized data from Wagga Wagga, Deniliquin, and Kerang.

Figure 3:  BOM justification for adjustments

Rutherglen BOM comparison chart

Comparing raw data from one station with adjusted data from other stations is hardly a valid argument.

Back in 2014, I posited a test for the validity of adjustments.  The aim of homogenizing is to adjust the temperature record to make a “best estimate” of what the temperature should have been.  This is achieved by pairwise comparison between the candidate site and 10 reference sites.

By comparing Rutherglen’s raw and adjusted data with that of each of the stations used in the homogenizing process, we can see how the Rutherglen record compares with its neighbours before and after homogenising.

Subtracting the mean of neighbours’ temperature anomalies from those of Rutherglen, we can tell how well the raw data compare, and how well the adjusted data compare.

Figure 4:  2014 comparison of differences

2014 plot

Back then, it was obvious that Rutherglen minima were cooling at about the same rate as the neighbours, and that the Acorn 1 adjustments were much too great.

Applying exactly the same methodology now, with complete dataset extended to 2017, we see that Rutherglen is cooling very slightly more than neighbours, while Acorn 2 is even more out of touch with the regional reality.

Figure 5:  Rutherglen differences 2019

Rutherglen tmin avg comps

The Acorn 2 adjustments are much too large, and have created an even stronger warming trend.

FAIL.

ACORN-SAT 2: Eucla: The Devil in the detail

February 18, 2019

I’m having a break from looking at Acorn 2 data from Queensland.  I’ve been wondering:  what’s going on?  What’s beneath these changes?  In particular, I was struck by statements in the accompanying Research Paper that

In total, there were 966 adjustments applied in version 2 of the ACORN-SAT dataset, 463 for maximum temperature and 503 for minimum temperature.”

The Bureau is referring to breakpoints in the data where adjustments are applied to all previous years.  In the daily data, there are tens of thousands of adjustments at each station.

For example, in Eucla’s Tmax record, there are 34,145 daily datapoints; 34,144 in Acorn 1; and 33,858 in Acorn 2.  There are  10,190 instances where Acorn 1 makes no change to raw data, and 9,312 in Acorn 2.  Most of the instances of no adjustments are since 1995.  Before then almost every day has been adjusted.

And the devil is in the detail.

The following plots show how adjustments are applied to the range of raw maxima.  First Acorn 1.

Figure 1:  Acorn 1 adjustments as applied to raw maxima at Eucla

Ac1 raw adj

Figure 2:  Acorn 2 adjustments as applied to raw maxima

Ac2 raw adj

Acorn 2 removes the large negative adjustments for temperatures in the high 30s, and the spread is wider for very high temperatures.  So far so good.

Figure 3 shows where many of these adjustments are made.

Figure 3:  Acorn 2 and  raw maxima

Eucla 1913-2017

Between 1930 and 1995 many high temperature spikes are reduced by 5 degrees and more.

For example, here is November 1960.

Figure 4:  Raw, Acorn 1, and Acorn 2 in November 1960

Eucla Nov 1960

The Bureau can truthfully claim that there is a balance between positive and negative adjustments.

However, note how all temperatures over 35C have been reduced by five degrees.  This is common across these years.

Perhaps temperatures on very hot days at Eucla in the 1960s were exaggerated?  Perhaps they were not read accurately?

If this pattern of hot day reductions is generally followed at stations across large regions, e.g. southern Australia, the effect will be that climate analysis based on Acorn 2 will show that past extremes were generally not as high as nowadays.

And that can’t be a bad thing for the meme.

ACORN-SAT 2.0: The Northern Territory- Alice in Wonderland

February 15, 2019

(UPDATE 17/02/2019:

I have corrected a glitch in trend calculations which are now as shown.  I have deleted all Diurnal Temperature Range plots and discussion as well.)

This is the second in a series of posts in which I directly compare the most recent version of Australia’s temperature record, ACORN-SAT 2, with that of the previous version, ACORN-SAT 1.  Daily data are directly downloaded from the Bureau of Meteorology. I do not analyse against raw data (available at Climate Data Online), except for particular examples, as I am interested in how different Acorn 2 is from Acorn 1.  The basis for the new version is in the Research Report.

See my previous post for Western Australia for a general introduction.

The Context – The Northern Territory

Figure 1 is a map of Australia showing all of the Bureau’s ACORN-SAT climate monitoring stations.  The Northern Territory is right in the Outback, from the monsoonal north to the desert centre. Most of it is savannah or desert, and there are vast distances between settlements and thermometers.

Figure 1:  Australian ACORN-SAT stations

map NT

There are five Acorn stations in the Northern Territory BOM database.  Differences between Acorn 1 and Acorn 2 are summarized in the following sections.

Trend changes

Trends in maximum temperature have changed a lot at individual stations, but on average there has been little change  (+1.29C to +1.27C per 100 years).  (Even though an average of such wildly different stations across such vast territory is meaningless.)

Figure 2:  Maxima trend changes from Acorn 1 to Acorn 2

NT max trend

The “average” change in minima is -33.3%  (+0.55C to +0.37C per 100 years).    This however is mainly due to Rabbit Flat’s short history with much missing data.

Figure 3:  Minima trend changes from Acorn 1 to Acorn 2

NT min trend

Largest temperature differences

In maxima, changes to Acorn 1 daily data were mostly small, except at Alice Springs which had adjustments ranging from -9.2C to +10.1C applied to individual daily figures, but only on a few days.  The +10.1C adjustment was to correct what could only have been a typographical error in Acorn 1, which recorded 26.8C instead of 36.8C on 28 January 1944.  The -9.2C is less easily explained and may be the opposite, Acorn 2 recording 24.1C instead perhaps of 34.1C on 6 March 1943.  Acorn 2 made many other large corrections around these dates, as Figure 4 shows.

Figure 4:  Daily changes in maxima from Acorn 1 to Acorn 2 at Alice Springs

max diff alice

Minima adjustments ranged from -11.5C to +11C also at Alice, and there were many other large adjustments as well.  At the other stations the range was much less, though still substantial changes (-3.6C to +4.6C) to Acorn 1.  Here is Alice Springs again:

Figure 5:  Daily changes in minima from Acorn 1 to Acorn 2 at Alice Springs

min diff alice

(Remember, these are adjustments to Acorn 1, which was supposed to be “world’s best practice” seven years ago.  How did Blair Trewin get it so wrong the first time?  Has world’s best practice changed so much in seven years?)

Record temperatures

A new record maximum was established at Darwin, whose record on 18 October 1982 (unchanged from raw to Acorn 1) increased from 38.9C to 39.5C in Acorn 2.

Figure 6:  Three versions of maxima at Darwin 18 October 1982

Darwin max 1982

A slightly higher record was also set at Victoria River Downs.

A new record low temperature on 21 June 1925 was also established at Alice Springs, where the Acorn 1 temperature of -6.7C was reduced to -9.4C.   (The temperature in the Post Office raw data was -5.6C.)  New lows were established at Darwin and Tennant Creek as well, but on nothing like the same scale.

Apparently the adjustments made to raw data in Acorn 1 weren’t big enough.

Quality Control: especially minimum temperatures higher than maximum.

In Acorn 1, 3 out of the 5 stations had at least one example of minimum higher than maximum.  Blair Trewin claims he has “fixed” this problem (which he concedes was “physically unrealistic”) by adjusting temperatures in Acorn 2 so that the maximum and minimum are the same, so that DTR for the day is zero.  In his words:

A procedure was therefore adopted under which, if a day had a negative diurnal range in the adjusted data, the maximum and minimum temperatures were each corrected to the mean of the original adjusted maximum and adjusted minimum, creating no change in the daily mean.

But that is not how he “corrected” the worst NT examples in Acorn 1 (minimum 4.8C above maximum at Alice Springs, and a 3.9C difference at Tennant Creek).  Here is a plot of the raw data and changes made by Acorn 1 and Acorn 2 at Alice Springs for 11 to 21 June 1932.

Figure 7:  Alice Springs Post Office data for 11-21 June 1932

Alice june 32 min2

Acorn 1 made no change to raw maxima, but was supposed to cool raw minima (the purple line) substantially  (the blue line).  Unfortunately, it is likely that instead of 8.1C, 18.1C was entered, human error resulting in garbage.  Acorn 2 has fixed this, but not by making minima and maxima equal to the Acorn 1 mean (15.7C), and neither is the DTR zero.  Instead there were more arbitrary adjustments.

(At Tennant Creek, to correct negative DTR of -3.9C,  minimum and maximum were both set to 22.9C, which is one degree less than the Acorn 1 mean of 23.9C).

 “Square wave” pattern in adjustments

The peculiar repeating pattern of adjustments to Perth in Acorn 1 also occurs at Darwin, but the pattern is even more bizarre.

Figure 8:  Darwin Acorn 1 daily maxima differences (pre-World War 2)

sq wave Darwin acorn 1

In every month, every day of the month was adjusted in Acorn 1 by exactly the same amount, which is the reason only 1917 is visible- the others are exactly the same.  Blair Trewin has taken notice of the criticism, and adjusted Acorn 2 with a little more intelligence, but the monthly pattern is still visible.  Adjustments are still applied month by month, especially in the Dry months.

Figure 9:  Darwin Acorn 2 daily maxima differences 

sq wave Darwin acorn 2

Conclusion:

There are no additional stations, so the network is still extremely sparse.

There is a very small amount of additional digitized data.

The average trend in maxima for NT has not changed very much, even though there is a large range across individual stations.  There was a reduction in the minima trend of -33.3%, mainly from the large impact of Rabbit Flat’s poor data.

Alice Springs had large differences between Acorn 1 and Acorn 2 daily data of over 11 degrees Celsius.

New record maximum and minimum temperatures have been set.

The issue of instances of minima being higher than maxima caused by too vigorous adjustments or human error has been “fixed” by arbitrary adjustments, and not as described in the research paper.

The bizarre “square wave” pattern in adjustments in Darwin has been largely rectified, at least in the Wet months.

With only five Acorn stations in the Territory, each one has a large impact on the climate record.  Alice Springs, which is said to contribute 7 to 10 percent of the national climate signal, has had extremely large adjustments made to Acorn 1.  VRD and Rabbit Flat, stations with short histories and incomplete data, also have a large impact on the national climate signal.

The size of the adjustments (made by comparison with stations up to 1,300 km away) only seven years after the “world’s best practice” dataset was launched, is incredible, and demands explanation.

Otherwise, it would appear that the temperature record of the Northern Territory, especially at The Alice,but also at other stations, has fallen down a rabbit hole, and appears to be out of a chapter from Alice in Wonderland.

Next: Queensland.

 

ACORN-SAT 2.0: Western Australia- A State of Confusion

February 14, 2019

(UPDATE 17/02/2019:

I have corrected a glitch in trend calculations which are now as shown.  I have deleted all Diurnal Temperature Range plots and discussion as well.)

This is the first in a series of posts in which I directly compare the most recent version of Australia’s temperature record, ACORN-SAT 2, with that of the previous version, ACORN-SAT 1.  Daily data are directly downloaded from the Bureau of Meteorology. I do not analyse against raw data (available at Climate Data Online), except for particular examples, as I am interested in how different Acorn 2 is from Acorn 1.  The basis for the new version is in the Research Report.

I start with Western Australia, and must thank Chris Gillham for his outstanding work and for allowing me to use data from stations he has used for his annual analysis.

Introduction:

The Bureau of Meteorology has released its latest revision of the Australian temperature record back to 1910.  Previous versions of our historic temperatures included “High Quality”, which I revealed in 2010 to have major flaws, not least being the strong warming bias; and ACORN-SAT 1, released in March 2012, proudly touted as being “World’s Best Practice”, which I (along with others) found to have very many severe problems.  (If you like, check these posts, here, here, here, and here.  There are many others.)

Stung by the public and media criticism which this generated, the Bureau set up a supposedly independent Technical Advisory Forum, which met on one day per year for three years and basically rubber-stamped Acorn.  They did, however, make some recommendations, particularly about transparency.  In the light of this recommendation, this latest release without any publicity at all is perplexing.

Nearly all of Australia’s climate analysis and modelling is based on the previous version, Acorn 1, including monthly, seasonal, and annual means, extremes, and trends.  Sometime in the near future, this will be based on Acorn 2 data.

As this an upgrade to an existing dataset, we might expect there would be a few small tweaks of maybe a few tenths of a degree in some records and any changes to temperature trends would be fairly small.  Perhaps there might be some extra stations in remote areas to improve the density of the sparse network, perhaps some records starting earlier because of newly digitized data, hopefully a sensible fix for the dreadful situation of many daily minimum temperatures being higher than the maximum.

Not so.

No wonder the Bureau has released Acorn 2 so quietly- it is a confusing mess, and completely alters Acorn 1.  Trends are vastly different, some temperatures altered by more than 10 degrees Celsius, and new records established.

The Context – Western Australia

Figure 1 is a map of Australia showing all of the Bureau’s ACORN-SAT climate monitoring stations.  Western Australia occupies the western third of the continent.  Most of it is desert, and there are vast distances between settlements and thermometers.

Figure 1:  Australian ACORN-SAT stations

Acorn map WA

There are 25 Acorn stations in the Western Australian BOM database.  One (Kalumburu 001019) has the latest version data for minima but not for maxima, so complete analysis is not possible.  Differences between Acorn 1 and Acorn 2 are summarized in the following sections.

Trend changes

Trends in maximum temperature have increased by an average of +0.25 degrees Celsius per 100 years (from +1.17C to 1.42C), which is an increase of 21.7% over the trend produced by Acorn 1.  (Click on each graphic to enlarge.)

Figure 2:  Maxima trend changes from Acorn 1 to Acorn 2

WA Max trend chart

The largest increase in trend is at Wittenoom.

Trends in minimum temperature have increased by an average of nearly +0.22 degrees Celsius per 100 years (from +1.04C to +1.27C), which is an increase of 21.53%.

Figure 3:  Minima trend changes from Acorn 1 to Acorn 2

WA Min trend chart

The largest increase  (+1.06C per 100 years- from +0.55C to +1.61C).  The largest decrease in trend was at Halls Creek: -1.31C per 100 years.

Largest temperature differences

In maxima, changes to Acorn 1 daily data were often very large.  Wandering gets the gong for greatest adjustments, ranging from -10.9C to +10.9C applied to individual daily figures, but only on a few days.  Eucla has many large changes made to Acorn 1 data.

Figure 4:  Daily changes in maxima from Acorn 1 to Acorn 2 at Eucla

Diff Tmax Eucla

Minima adjustments ranged from -10.8C at Esperance to +7.8C at Halls Creek for a few adjustments, but at most stations the range was much less, though still substantial changes to Acorn 1.  Here is Perth:

Figure 5:  Daily changes in minima from Acorn 1 to Acorn 2 at Perth

Diff Tmin Perth

(Remember, these are adjustments to Acorn 1, which was supposed to be “world’s best practice” seven years ago.  How did Blair Trewin get it so wrong the first time?  Has world’s best practice changed so much in seven years?)

Record temperatures

A new record maximum was established at Carnarvon, whose already homogenized record increased from 48.5C to 51C.  This is now the record for all of Australia, apparently (although I have 87 more stations to check).   Additional large adjustments are the cause:

Figure 6:  Three versions of maxima at Carnarvon 23 January 1953

Carnarvon Max

The previous “record”, held by Albany in the cool south, after much ridicule was reduced from 51.2C to 49.5C.  New records were also established at Bridgetown, Dalwallinu, Eucla, Kalgoorlie, Katanning, Marble Bar, Merredin, Perth, and Port Hedland.

New record low temperatures were established at Bridgetown, Cape Leeuwin, Cunderdin, Dalwallinu, Esperance, Eucla, Forrest, Geraldton, Halls Creek, Kalgoorlie, Learmonth, Marble Bar, Meekatharra, Perth, and Wittenoom.

Apparently the adjustments made to raw data in Acorn 1 weren’t good enough.

Quality Control: especially minimum temperatures higher than maximum.

In Acorn 1, 16 out of 25 stations had at least one example of minimum higher than maximum.  Blair Trewin has “fixed” this problem (which he concedes was “physically unrealistic”) by adjusting temperatures in Acorn 2 so that the maximum and minimum are the same, so that DTR for the day is zero.  In his words:

A procedure was therefore adopted under which, if a day had a negative diurnal range in the adjusted data, the maximum and minimum temperatures were each corrected to the mean of the original adjusted maximum and adjusted minimum, creating no change in the daily mean.

But that is not how he “corrected” the worst Western Australian example in Acorn 1 (minimum 2.1C above maximum) at Kalgoorlie.  Here is a plot of the raw data for 14th to 18th November 1914.

Figure 7:  Kalgoorlie Post Office data for 14-18 November 1914

Kalgoorlie raw

The 16th was a cold rainy day, with only 0.1C separating minimum (15.5C) and maximum (15.6C).  But temperatures in 1914 were read from a Fahrenheit thermometer.  Both 60F and 60.1F convert to 15.6C; 15.5C is 59.9F.  It is likely the temperature ranged from just under 60F to just over 60F.

Acorn 1 adjustments were made with brute force rather than finesse.  The maximum was reduced by 1.3C to 14.3C, and the minimum was raised by 0.9C to 16.4C, resulting in nonsense.

Figure 8:  Kalgoorlie Post Office and Acorn 1 data for 14-18 November 1914

Kalgoorlie Ac1

In Fahrenheit, 57.7F maximum and 61.5F minimum.

The solution in Acorn 2?  Even more brutal adjustments- and not to the mean of the Acorn 1 adjustments (which would have been 15.35C):

Figure 9:  Kalgoorlie Post Office and Acorn 2 data for 14-18 November 1914

Kalgoorlie Ac2

The Acorn 1 minima is decreased (by 3.4C) to 13C, and Acorn 1 maxima decreased by another 1.3C to 13C (or 55.4F), making it 2.6C below the raw temperature as read in 1914.  Now there is no problem with minimum exceeding maximum, but at the cost of raw data tortured beyond recognition.

“Square wave” pattern in adjustments

Bob Fernley-Jones first noticed a peculiar repeating pattern of adjustments to Perth in Acorn 1 monthly data.  I can replicate this in dailies.

Figure 10:  Perth Acorn 1 daily maxima differences 1983-1986

sq wave perth acorn 1

This pattern is still visible in Acorn 2, but is much reduced.  Adjustments are still applied month by month, but they are not as rigid.

Figure 11:  Perth Acorn 2 daily maxima differences 1983-1986

sq wave perth acorn 2

This is how it was changed:

Figure 12:  Perth Acorn 2 minus Acorn 1 daily maxima differences 1983-1986

sq wave perth acorn 2- acorn1

A new square wave- almost a mirror image of Figure 11.  It is good to see that the Bureau has taken notice of criticisms!

Conclusion:

Comparison of Acorn2 versus Acorn 1 data for Western Australia does not encourage confidence in the Bureau’s methods:-

There are no additional stations, so the network is still extremely sparse.

There is a very small amount of additional digitized data.

The average trend in maxima for WA has been increased by 21.7%, and in minima by 21.5%.

Differences between Acorn 1 and Acorn 2 daily data can be up to nearly 11 degrees Celsius.

New record maximum temperatures have been set.

The issue of instances of minima being higher than maxima caused by too vigorous adjustments has been “fixed” by further vigorous adjustments.

The “square wave” pattern in adjustments in Perth has been largely rectified.  The square wave is now in the difference between Acorn 1 and Acorn 2.

It beggars belief that a dataset that was proudly described as “world’s best practice” just seven years ago has needed to be adjusted by so much.  Has “best practice” changed so much?  How was Acorn 1 so wrong?  How can we be sure that the new version is better, and will itself not be changed again in a few years?

There are now four versions of WA temperature:  Raw; High Quality (no longer available); Acorn 1; and Acorn 2.  All are different.

The record for Western Australia reveals a state, not of excitement, but of confusion.

 

Next: the Northern Territory.

Townsville Rainfall In Context

February 11, 2019

The rain event which caused massive floods in Townsville (and fearful stock losses in the north-west) has now ended.  There have been some who have made further political capital out of this disaster by linking it to climate change.

According to Independent Australia, a “progressive journal”,

The City of Townsville, with some 20% of its suburban zones under water today (6 February 2019), might now be a model for the world — for possible climate change impacts and handling them. 

These days, the very heavy falls have been happening more frequently — for example, in 2007, 2009 and then in 2010.

Time for a reality check.

This has indeed been a record breaking event for Townsville.  A few graphs will illustrate.  Townsville airport has had its wettest 14 day period since 1941, averaging over 100mm per day.

Fig. 1:  14 day rainfall

Tville 14d rainfall

It has also broken the record for rainfall over 31 days:

Fig. 2:  31 day rainfall

Tville 31d rainfall

And with the wet season far from over, it is very likely to break the 121 day rainfall record.

Fig. 3:  121 day rainfall

Tville 121d rainfall

Townsville’s rain is very seasonal.  Annual rainfall averages about 1127mm, and half of that falls in January and February, with another quarter in December and March, so a plot of 121 day rainfall captures the relative strength of wet seasons over the years.  There doesn’t appear to be any recent increase in wet season strength.  What is interesting is there are periods of wetter and drier years, which is more plainly seen in a plot of decadal rainfall.

 Fig. 4:  Decadal rainfall at Townsville

Tville decadal rainfall

Rainfall appears to be in a decreasing trend.

But what about the claim for greater frequency of very heavy rain events?  Heavy rain events are usually short and intense, so three day rainfall will also show relative frequency and intensity.

Fig. 5:  Three day rainfall

Tville 3d rainfall

The “Night of Noah” in 1998 is obvious, and there was another intense event in 1953.  But there is NO trend.  (The calculated trend is zero.)  Intense events are not more frequent.  Similarly, the number of days per year recording 100mm of rain shows zero trend, even though there have been eight already this year.

Fig. 6:  Count of days per year with over 100mm of rain

Tville days over 100mm

There is no climate change signal in Townsville’s rain record.

Now, to show how different locations can lead to completely different interpretations of trends in climate, I turn to two locations in wetter parts of the tropics that I have some knowledge of.  I lived for many years not far from Pleystowe and Sarina Sugar Mills near Mackay, which are about 30 km apart.  Sarina appears to have an increasing trend in rainfall:

Fig. 7:  Decadal rainfall at Sarina

Sarina decadal rainfall

While Pleystowe shows no trend.

Fig. 8:  Decadal rainfall at Pleystowe

Pleystowe decadal rainfall

Notice the similar patterns of wetter and drier periods in Townsville, Pleystowe, and Sarina.

And incidentally, the most intense and highest rainfall events in these locations occurred many years ago, in 1990-91, the 1970s, the 1950s, and 1918.  As with the recent Townsville flood, these occurred when the monsoon trough, with embedded decaying cyclones, lingered overhead for many days or even weeks.

The Townsville flood was not due to climate change, but to a frequent North Queensland phenomenon- an intense monsoon trough stuck in one place for too long.  This was an unusually intense and long lasting example, but such events are not more frequent or more intense.