A Tale of Two Records

The Bureau of Meteorology, in its recent media release, accepted and repeated by the media, made an astonishing claim:

Bureau of Meteorology confirms it’s been the hottest summer on record

Where did they get the data to make this claim?  Well, in their media release they said:

“Of the 112 locations used in long-term climate monitoring, 14 had their hottest day on record during the summer of 2012/13..”

112.  Not the 700+ of the AWAP (Australian Water Availability Project) used to make the claim about January 7 being the hottest day on record.  112 is the number of sites in the ACORN dataset.

So I’m sure all journalists reporting this claim would have referred to the BOM’s Time Series Graphs on their website, which use the ACORN data, to confirm just where this summer was the hottest on record.  Forgive the sarcasm- they plainly didn’t.  Let’s take a look.

First, here is the plot for the summer mean temperatures for all of Australia 1910-2012 (which includes January and February 2013):summer1213austYep, the 2012-13 summer mean was definitely the highest on (this) record.  There are 6 regions and 7 states/territories in Australia:summer1213  regionsLet’s see how each of these performed.

Northern Australia:summer1213  N austNope!

Southern Australia:summer1213  S austNope!

Eastern Australia:summer1213  E austSouth Western Australia:summer1213  SW austSouth Eastern Australia:summer1213  SE austMurray-Darling Basin:summer1213  MDBWhat’s going on?

I am reminded that one way of calculating mean temperature is to average the minimum and the maximum.  Here’s the summer maximum for Australia:summer 1213 max austAs expected.  Now the minimum:summer 1213 min austSo we can blame the record mean on the record maximum temperatures.  Let’s look at the different regions.

Not Northern Australia.summer 1213 max N austIt’s Southern Australia:summer 1213 max S austBut not Eastern Australia.summer 1213 max east austNot South Western Australia.summer 1213 max SW austNot South Australia (the State):summer 1213 max SANot Western Australia (the State):summer 1213 max WASo the only part of Australia left that could be responsible for the summer maximum record, and consequently the mean, is this bottom part of WA not in the south west corner, or perhaps as well the southern portion of Queensland:summer1213  regions responsibleIt must have been a tad warmer than average there!summer max map

It doesn’t look to be hotter than South Australia or Victoria. By the way, this is Victoria:summer 1213 max VicThe problem:

The summer mean temperature for all of Australia, according to BOM, was the highest on record.  They confirm this with their graph of ACORN data.

The summer minimum was not a record by a long way.

Only Southern Australia’s maximum temperatures show this record.  No other regions were hotter this summer.  And this includes none of the smaller regions within Southern Australia.

Therefore we can conclude that BOM is flicking between two methods of calculating temperature and two datasets to find the “record” that fits their global warming mantra.

Please explain.


h/t Andrew Barnham


7 Responses to “A Tale of Two Records”

  1. r k bradstock BE civil SU '63 Says:

    well done! BoM must be mocked 4 rejecting data pre 1910, and ‘adjusting’ early data. bring on the cooling period…

  2. Ian Says:

    r k
    An example of what you claim – one of the records broken was Walgett, NSW. It reached 48.5C in Jan 2013 breaking a 48C in 1973. However, according to their own records, Walgett had a 49.2C on 3rd Jan, 1903.

    What do you make of this? 2009 is now the 3rd warmest year after being 2nd last year (replaced by 1998). Look at the annual summaries (2011 and 2012) now before they are ‘corrected’. Also shows up on the time series graphs.

    1998 has risen from 0.73 to 0.85C and 2009 has gone from 0.90C down to 0.81C.

  3. AGW – A Tale of Two Records – Misadventure with temperature records | The GOLDEN RULE Says:

    […] the complete article ” A Tale of Two Records”,  here, to find out how the public are being […]

  4. Sou Says:

    Ken, while the actual calculations used by BoM would be more complex the concept is fairly simple.

    If you look at the summer temperature charts, the highest years you’ve circled have all been different years, so for all Australia the regions with lower summer maxima would have dragged down the Australia-wide.

    This year, and in particular that amazing fortnight in January, everywhere – all over the continent, was amazingly hot at the same time. If you missed it and want to see a gif animation of part of the heat wave, visit my website here:


    So even though individual regions or states might have been hotter in one or other years, in the same year one state had its hottest year, other states would not have.

    This time they were all hot at the same time, even if no individual state had a ‘hottest year’ for that state. Hence the hottest year overall.

    I might not have explained it well. Try using matchsticks of different heights and line them up with the different years – then put all the match sticks in any one year end to end. The longest line is the hottest year.

    Or think of it this way (you can try different combinations of numbers):
    10 + 5 + 5 + 6=26;
    5 + 10 + 6 + 6 = 27
    8 + 8 + 7 + 8 = 31 – the hottest year, even though no one number is as high as the 10 in other years.

    BoM would most likely use smaller sized grids than is available in the summer maxima charts but the principle is the same.

    Even just eyeballing the charts, at the very coarse level of State summer maxima, it’s pretty obvious which was the hottest year for the continent overall.

    Hope that helps.

    • Ken Stewart Says:

      Thank you Sou for your polite and reasoned comment. As you are aware from my comments at another site, I agree that it is possible to have a record across the whole without individual component records. The area I highlighted in southern WA is worth watching however. It has a large influence across a wide area (because of the scarcity of stations) and any errors are magnified. Watch this space.

  5. Sou Says:

    Hi Ken,
    Have you ever looked at a temperature chart (map)? That might give you a better understanding of how the Bureau is able to deal with large areas. It’s a bit like a contour map. Similar temperature ranges can spread over very large areas. If, it’s hot in Alice Springs and it’s hot in Broome and the Pilbara – it’s likely to be just as hot in between. These days satellites help a lot as well as looking at pressure gradients, rain bands, wind etc.

    Temperature calculations would be fairly straightforward.

    • Ken Stewart Says:

      Yes Sou, I am quite familiar with them. And a small error in one remote location can therefore “be spread over very large areas”. One of the problems identified by the review of ACORN. I will be posting about this very topic in a few weeks’ time.

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