ACORN-SAT 2.0: Victoria- A comedy of errors

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.

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6 Responses to “ACORN-SAT 2.0: Victoria- A comedy of errors”

  1. Bill in Oz Says:

    Ken, homogenisation is just another word for doubting the actual data recorded by people over decades & decades all over Australia.

    It is NOT data.

    It is FAKE misinformation

    And must be treated as such.

    Knowing the extent of the fakery can only be shown by the comparison of the actual readings taken at each station with the purported fake non data of the ACORN SAT’s 1 & 2

    Otherwise too much is hidden.

    And that is playing the BOM’s invented game.

  2. kenskingdom Says:

    I agree with you that Acorn 1 and 2 are fake, built on dodgy adjustments. I have showed how much garbage Acorn 1 is (was) and how badly it mangled raw data in numerous posts. Check them out, starting from May 2012. This current series of posts is merely to record the idiocy of both versions (especially that they produce “wildly different results”) while we still have access to version 1, as it is about to be replaced by version 2.

    • Bill in Oz Says:

      Thanks Ken for your reply.
      I appreciate that we agree on the fake nature of the ACORN Sat’s 1& 2.
      But surely that is why it is important to do the comparison between the ra/actual data recorded AND ACORN 2

  3. John in Oz Says:

    Ken,

    All communication with ministers/politicians results in no response or the tired mantra of ‘the scientists tell us” or similar appeal to authority.

    No questioning by any of them of the veracity of the info they are provided with.

    One never knows if the pollies are seeing our communications (other than my local state member who rings me personally) or if a staffer is filtering what the pollie sees.

    Thanks for your analyses as I refer to them often

  4. ACORN-SAT 2.0: New South Wales- What a mess | kenskingdom Says:

    […] A Reality Check on Global Warming « ACORN-SAT 2.0: Victoria- A comedy of errors […]

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