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History keeps getting colder — ACORN2 raises Australia’s warming rate by over 20%

More warming adjustments from ACORN2

Once again we find that the oldest thermometers were apparently reading artificially high even though many were newish in 1910 and placed in approved Stevenson screens.)  This is also despite the additional urban warming effect of a population that grew 400% since then. What are the odds?!

Fortunately, gifted craftsmen, sorry scientists have uncovered the true readings from the old biased thermometers which they explain carefully in a 67 page impenetrable document.

Chris Gillham has soldiered through the new “ACORN 2” adjustments that the Australian Bureau of Meteorology has o-so-quietly released and Australians are just waking up to find that our coldest mornings back in 1910 were even colder than anyone realized at the time. Graham Lloyd is  reporting in The Australian how the second rewrite in six years increases the warming by 23% . (Where was the ABC announcement?)

The ACORN series of the Bureau of Meteorology includes 112 stations. Their report lists the warming trends per decade in Table 9. I converted that into the total warming since 1910 and graphed that below.

About one third of the warming of our mean temperature is due to man-made adjustments

Comparing AWAP (semi-raw) to the latest ACORN2, the mean temp is up from 0.08C up to 0.123C per decade. That’s a 50% increase.

To slow Australia’s warming it’d be much cheaper to replace the BOM rather than our electricity grid. Just a thought.

Adjustments at the 57 longest stations in Australia, ACORN2 BOM, Max and Min. Graph.

The Australian BOM uses 112 Stations for the ACORN series. These are the full adjustments to the min, mean and max across all stations for the full range of 1910 – 2016.

As Chris points out AWAP is not exactly raw — but it is at least the unhomogenised Australian Water Availability Project dataset.

The biggest changes are in the old minima

The new ACORN version has nearly doubled the rate of warming in the minima of the longest running stations.

About half of the stations in the ACORN list are newer and start recording sometime after 1910. The last station added was in 1975. Chris Gillham reasons that this is not really good practice and so he identified the 57 stations which do have data all the way back.  He laboriously calculated the decadal trends, and again I converted them to the total warming and graphed the changes below, and we can see that  most of the action comes from the oldest early morning records.

Suddenly, one hundred years later, frosts got far worse during World War I.

It would be very helpful if the Bureau could explain why these particularly were measuring too high.

The historical cooling will presumably stop Australia setting some new “coldest ever records” and make it a bit easier to set “hottest ever” ones.

Records were smashed in all kinds of ways the week ACORN2 was released, but nobody knew…

Adjustments at the 57 longest stations in Australia, ACORN2 BOM, Max and Min. Graph.

In the 57 longest running sites the rate of warming nearly doubled in the minima.

 No, the homogenisation methods of the BOM have not been found to be “sound”

Graham Lloyd, The Australian:

A number of reviews of the ­bureau’s network equipment and its temperature data handling have been carried out. A technical panel found the homogenisation methods used were largely sound.

Actually, the The BOM Technical Advisory Forum was never tasked with replicating the homogenization process. Task members were mostly hand picked statisticians. They agreed homogenisation was necessary, “best practice” and they read “the unsolicited complaints”, and concluded that they were not enough to worry about. The only definitive news that came out of that forum was the admission from the BoM that absolutely no one outside of their sacred guild would ever get all the information and training to to recreate their dataset. The BoM method remains a secret black box technique to this day. If it can’t be replicated (because no one can explain the full methodology) it isn’t science.

Three years and $1.3 billion dollars later and still no error bars?

Graham Lloyd reports that progress is slow:

But a key recommendation, to include confidence levels or error margins in the data, remains ­unfulfilled. A BoM spokesman said work was under way on a number of scientific papers looking at uncertainty and confidence intervals for temperature data ­observations, adjustments and national averages.

“This work will be made available to the public following ­thorough peer review,” the spokesman said.

The Australian BOM get one million dollars a day but 1,339 days since the report was released and $1.3 billion dollars of taxpayer funds later, they still can’t do error bars.

Is this, or is this not the “Best Ever” dataset?

I mentioned a few days ago that the new rewrite created a new all time hottest Australian temperature record — a day that reached 51 degrees C. The question is whether the BOM will recognize this officially, or whether, like the last ACORN record in Albany, they simply pretend it doesn’t exist. ACORN 2 is now considered the official national average temperature record, but is the Carnarvon record from 1953 real, or just an anomaly accidentally created by sweeping changes?

Do the BoM team believe in ACORN? With no press release it doesn’t appear so.

Chris Gillham (and others) has done a mountain of work and there is much more yet to discuss. More soon…


Bureau of Meteorology, ACORN 2, October 2019, Bureau Research Report – 032

WA Climate, Chris Gillham, ACORN2 influence on Australian temperature trends.

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