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Australian Extreme Temperature Trends

October 7, 2016

By Paul Homewood


The Australian Bureau of Meterology have quite a lot of useful tools on their website (take note, Met Office!)

Among them are graphs for “climate extremes”, (I think they mean “weather”, BTW!). The link is here. 



Starting with temperature, we have the average number of very hot days, defined as days over 40C. (There is a full explanation of the definitions and how they are calculated here. In this case, it seems that they work on an average of all stations with sufficiently long data, across the country)




Clearly there is no increase in very hot days.


The chart below shows that the average temperature of the hottest day may have crept up a little bit in 2013, but for all other recent years, again, nothing unusual has occurred.




However, when we look at very cold days, there is a very definite reduction in the number, and average temperatures are also not as low now.







You may recall I looked at Spring temperature trends in the UK, and came to very similar conclusions – that rising average temperatures were due to there being less very cold days, rather than more, or warmer, hot days.

I have not seen any real attempt to explain this phenomenon, which is, of course, highly inconvenient for those paid to scare us about “record heat”, “parched earth” and the rest.


There is also a very noticeable drop in the length of cold spells:




There is no graph for hot spell duration, but I’ll finish with growing season length, defined as:

Annual (1st July to 30th June) count between first span of 6 or more days with daily mean temperature > 15°C and first span of 6 or more days with daily mean temperature < 15°C




As far as temperatures are concerned, all of this looks to be very good news for Aussies.

I’ll take a look at rainfall extremes shortly.

  1. October 7, 2016 4:25 pm

    UHI effect?

    • Mickey permalink
      October 7, 2016 4:34 pm

      Exactly what I was thinking.

      • October 7, 2016 5:58 pm

        A contributory factor if nothing else I would guess

    • Tom Roche permalink
      October 7, 2016 5:50 pm

      Same phenomenon to be seen in central England temperature record. No UHI effect I presume.

    • October 9, 2016 10:50 pm

      The Australian BoM has reduced rural thermometers and relies more on those in the cities and airports. Jennifer Mahorasy has shown that, apart from “homogenisation”‘ UHI has had a marked effect on “average” temperatures. The BoM only talks about max temperatures when there is a.very high one, preferring to use the average as it is higher because of the elevated minimums.

  2. Joe Public permalink
    October 7, 2016 6:03 pm

    Do those charts use original or adjusted temperatures such as you’ve reported in the past?

    • A C Osborn permalink
      October 7, 2016 6:08 pm

      I think it is probably their Acorn Dataset.

    • October 7, 2016 9:52 pm

      The tampering with temperatures takes place with monthly means.

      As far as I can see, these are based on actual daily readings, although the BOM don’t give their database

  3. October 7, 2016 6:07 pm

    I think that most “climate change” over the 20th century in Australia was a rise in minimum temperatures, which might explain the reducing number of cold days. Thus, the temperature of choice for alarmists is the average, since “OMG the nights are getting warmer” is not very scary, so they say “Australia is getting hotter”, which most people assume means that days are getting hotter, but that is not so.

    • A C Osborn permalink
      October 7, 2016 6:09 pm

      And yet this was one of the coldest periods in Australia with very high Snow & Rain Falls.

      • A C Osborn permalink
        October 7, 2016 6:10 pm

        That should say “in some areas”, because Australia is a very big place.

  4. October 7, 2016 6:46 pm

    The increase in length of the growing season is not all good news. The BBC and Met Office manage to squeeze bad news from it:
    “The Met Office recently issued a report which states that the growing season in the UK is now one month longer than it was in the 1960’s. Keen gardeners may notice that spring bulbs are coming up much earlier and that fruit like apples are flowering sooner in the year whilst some farmers can now bring in their harvest before the end of the summer. Peter Gibbs discovers that whilst there are opportunities for growers in more Northerly latitudes rapid changes globally may put yields of vital crops at risk. The UK’s gardeners, crop scientists and farmers are not simply sitting back and admitting defeat though. A changing climate is a challenge which many growers are busy preparing for.”
    See ‘Costing the Earth’:

  5. richard verney permalink
    October 7, 2016 7:02 pm

    I recall reading something (possibly on Jo Nova’s site) that the 1880s was the warmest period in Australia, and BOM deliberately chose to start its data sets in the early 1900s so as to hide that unfortunate fact.

    Would be worth checking.

    • Graeme No.3 permalink
      October 7, 2016 7:58 pm

      Good luck finding the data. The BoM insists that Australian records only started in 1910, the year they started. Any records before that from the States are ignored as inaccurate, unreliable (and unadjusted?). Lack of Stephenson screens is one justification despite Melbourne having one before 1869. In 1880 Clement Wragge in Adelaide published a paper on observations in Stephenson screens at the original West Terrace site and on Mt. Lofty.

      Clement (a wild colonial boy though born in England) then moved to Queensland and set up a network of stations and later, with data from across Australia, attempted long range weather forecasting with no more success than the current lot with supercomputers.

    • October 7, 2016 8:12 pm

      There has been some academic work on using data prior to 1910, but AFAIK the BoM has not (yet?) adopted it:

  6. Oliver K. Manuel permalink
    October 7, 2016 7:31 pm

    I agree with Professor Michael Kelley on the inherent danger of lock-step consensus science promoted by FRS, NAS, etc.:

  7. Get Real permalink
    October 7, 2016 7:35 pm

    The highest temperature recorded by my weather station here on the east coast of NSW in the last 12 months was 40.4 degrees C on October 5th 2015. The next closest was 40.2 degrees during January 2016. Methinks an Ice age approaches.

  8. Ian George permalink
    October 7, 2016 7:57 pm

    NSW had its first +30C day yesterday (Oct 7th) – the latest start for post-winter temp above 30C on record.

  9. October 7, 2016 11:54 pm

    More GHG’s equal more MODERATION of temps. Keep driving those SUV’s and flying those jets please!!

    UHI should increase max temps a little as you would start a hot day at a higher temp requiring less energy to reach the peak…

  10. October 7, 2016 11:57 pm

    Reblogged this on Climatism and commented:
    Australia used to be much hotter, which is why BOM hides the pre -1910 data:

    NASA complicit in Australia’s temperature adjustment fraud, to fit the global warming narrative:

    • AndyG55 permalink
      October 8, 2016 2:07 am

      Yep, you would have to lengthen the vertical axis is you used pre-1910 data.

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