Tarcoola- A Cooling Outlier

In a previous post I looked at the warming outliers in the Acorn network– those sites that had homogenisation adjustments that created a difference of more than +2 degrees Celsius between the Acorn trend and the raw trend in minima.  In all of these six examples, the adjustments had created trends that were not just greater than the raw trends at each site, not just the mean of their Acorn neighbours raw data trends, but greater than the Acorn trends of their neighbours, and in all but one, greater than each of the individual Acorn trends of their neighbours.

In this post I consider the opposite scenario.  I look at one cooling outlier, Tarcoola in South Australia, where the cooling adjustments have created a difference in trend of -2.81C per 100 years.  There is one other, Forrest in W.A., with an enormous cooling adjustment of around -2.14C, but I have little faith in the accuracy of the data there.  Greg Geegman suggested in a comment that if a site that is adjusted downwards is cooled relative to the neighbour group, this may indicate the Percentile Matching algorithm operates iteratively, although Technical Report No. 49 does not mention this.  An alternative explanation might be that the algorithm is too sensitive and exaggerates necessary adjustments.

All data may be downloaded from the BOM website: Site networks and Climate Data Online.

Tarcoola is in the centre of South Australia:Tarcoola map

As before, I compare Tarcoola with its neighbours in the Acorn network, using anomalies from the 1961-1990 mean.

Fig. 1:  Tarcoola Acorn vs ‘Raw’ minimaTarcoola tmin

Cooler trend than raw.  Note the spurious data pre-1930.

Fig. 2: Tarcoola raw vs mean of Acorn neighbours’ rawtarcoola raw v reg mean raw

Tarcoola appears to need cooling.

Fig. 3: Tarcoola Acorn vs mean of neighbours’ meantarcoola acorn v reg raw

Cooler trend than neighbours’ raw

Fig. 4: Tarcoola Acorn vs mean of neighbours’ Acorntarcoola acorn v reg acorn

Cooler trend than neighbours Acorn

Tarcoola Acorn trend is also cooler than each of the neighbours’ individual Acorn trends.

So which neighbours were used to make the Tarcoola adjustments?


Both warming and cooling outliers show Acorn adjustments outperforming those of the neighbours. This suggests that the algorithm exaggerates adjustments, both warming and cooling, and needs serious re-examination.

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5 Responses to “Tarcoola- A Cooling Outlier”

  1. Geoff Sherrington Says:

    “This suggests that the algorithm exaggerates adjustments, both warming and cooling, and needs serious re-examination.”

    Seconded. There seems to be reliance on relationships between the separation distance of sites and the correlation coefficients between them. This is also done by BEST. I’ve never been comfortable with the data presented to justify this relation in extrapolation. Trouble is, I cannot deduce what, if anything, is wrong with it. (There are good geostatistical methods to estimate range that do not depend on correlation coefficients).
    Has anyone tried to fault the distance/r^2 relationship? I suspect it is a key to the problem, especially if the correlation coefficients are derived from smoothed or averaged data.

  2. DaveR Says:

    This post, and a number of recent posts, again raises the question of whether a new “premium” group of station records should be put together to form an Australian temperature index.

    The key requirements would be : 100-150 years of unbroken records, no siting moves, away from obvious urbanisation encroachment and UHI effects.

    And of course we would use raw, unadjusted data.

    I have been asking BOM and CSIRO for 5 years to consider putting this combination together, with no response. It is now clear that it has to be done outside of these scientifically-compromised, rotten departments.

  3. Truthseeker Says:


    You will want to have a closer look at this.


    Maybe you could do the same analysis with BOM data?

  4. My Submission to the BOM Review Panel | kenskingdom Says:

    […] (For further information and full explanation see https://kenskingdom.wordpress.com/2014/07/28/tarcoola-a-cooling-outlier/) […]

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