Net Zero

Australia’s Broken Temperature Record (Part 1)

Written by
26 January 2022
Jennifer at Goulburn weather station in August
Originally appeared in

The feature image, at the very top of this blog post, shows me at the Goulburn weather station in August a few years back.

It could be that the last 26-years of temperature recordings by the Australian Bureau of Meteorology will be found not fit for purpose and will eventually need to be discarded. This would make for a rather large hole in the calculation of global warming – given the size of Australia.

The Australian Bureau of Meteorology undertakes industrial-scale remodelling of historic temperatures in ways that generate more global warming for the same weather through the process of homogenisation, remember the work I did some years ago on Rutherglen.  The process is neither transparent nor scientific and lacks consistency with the Bureau’s own policies.  Also of concern, since 1996 the Bureau has converted to custom-made electronic probes for temperature recording, and rather than averaging temperatures over one or five minutes as is standard practice around the world from such equipment, the Australian Bureau is recording one second extrema. To be clear a ‘hottest temperature’ record is now a one second automatic download from a supersensitive electronic probe rather than a reading from a more inert mercury thermometer.  This is another way the Bureau gets more global warming for the same weather – with its own third generation probes. I am going to explain all of this in more detail in a book I’m sketching out, to write this year.

Theoretically the probes would also bias the minima downwards, except remember Thredbo? How I showed a few years ago that the Bureau has placed limits on how cold an individual weather station can record temperatures, so most of the bias is going to be warmer.

Journalist Graham Lloyd, ignoring all the problems that I’ve documented in such detail over the years, was arguably somewhat premature when he published uncritically for the Bureau on 14th January.

… according to the Bureau of Meteorology annual climate statement, 2021 was the coolest year in nearly a decade and wettest since 2016. By the end of 2021 – and for the first time in five years – no large parts of the country were experiencing rainfall deficits and drought conditions.

Announcing BoM’s 2021 temperature data, climatologist Dr Simon Grainger says: ‘After three years of drought from 2017 to 2019, above-average rainfall last year resulted in a welcome recharge of our water storages but also some significant flooding to eastern Australia.’

In 2021, Australia’s mean temperature was 0.56C above the 1961-1990 climate reference period. It was the 19th-warmest year since national records began in 1910, but also the coolest year since 2012. Rainfall was 9 per cent above the 1961-1990 average, making 2021 the wettest year since 2016, with November the wettest on record.

I went looking for the Annual Climate Statement, and the supporting data.  There was a note at the Bureau’s website saying the Annual Climate Statement wouldn’t be published until February.  There was no data published on 14th January, just the promise.

I am keen to see which few years they have put before 2021; as being hotter.   But alas I will have to wait until February.  Of more concern, in February the dilemma will remain that many of the earlier annual average temperatures have been calculated with a different mix of weather stations.

Very few people realise – though I have explained all of this multiple times including to multiple journalists – that when the Bureau of Meteorology transitioned in 2011 to the new Australian Climate Observation Reference Network – Surface Air Temperatures (ACORN-SAT) system for calculating the national average temperature it removed 57 stations from its calculations, replacing them with 36 on-average hotter stations.  This had the effect of increasing the recorded Australian average temperature by 0.42 degree Celsius, independently of any actual change in the weather.

Of the 57 stations removed from the calculation of the national average temperature, only 3 of these had closed as weather stations.   I will explain all of this in my book.  You should be able to order it for Christmas.

There are so many problems with Australia’s official temperature record including the changing combination of stations, the use of custom-designed probes without averaging, not to mention all the homogenisation.


Australia has reliable historical temperature data for the period from about 1889 until 1996 measured using liquid-in-glass thermometers – mercury for maxima and alcohol for minima.  Averaging the maxima and minima gives a mean temperature.   In some of the records there is a cooling trend to about 1960, and then warming to the present.  This is particularly the case at inland locations.  Within the longer trend there are short cycles with temperatures generally trending up during drought, and down during wetter years.

When the longest continuous temperature series are combined, with a transparent system of area weighting, as I did in an analysis of temperature trends for south-eastern Australia published as a book chapter by Elsevier in 2016, the overall warming trend is only 0.3 degrees Celsius per century (1887 – 2013).   This is significantly less than the Australian Bureau of Meteorology 0.7 degrees Celsius for the same region but a shorter period (1910 – 2016).  NASA recently announced a rate of 1.1 degrees Celsius since the late 19th century average, the start of the industrial revolution.

The daily maximum and minimum values in ‘the national temperature dataset’ (the homogenised ACORN-SAT data) are different from the actual recorded historical values, often by several degrees, usually cooler.  The further back you go in time, the more significant the cooling thus making what was a modest temperature increase over the period appear greater than it is.

This remodelling is in a different category to correcting for outlier that might have been caused by transcription errors or faulty equipment.  The remodelling cannot be confused with legitimate data-hygiene/quality assurance.

Furthermore since 1996, at an increasing number of weather stations platinum electronic probes have replaced the traditional mercury and alcohol thermometers.   For example, the Rutherglen agricultural research station has a long, continuous, temperature record with minimum and maximum temperatures first recorded using standard and calibrated equipment in a Stevenson Screen back in November 1912. Considering the first 85 years of summer temperatures – unadjusted/not homogenized – the very hottest summer on record at Rutherglen is the summer of 1938/1939.

At Rutherglen, the first significant equipment change happened on 29 January 1998. That is when the mercury and alcohol thermometers were replaced with an electronic probe – custom built to the Australian Bureau of Meteorology’s own standard, with the specifications still yet to be made public.

According to Bureau policy, when such a major equipment change occurs there should be at least three years (preferably five) of overlapping/parallel temperature recordings. However,  the mercury and alcohol thermometers (used to measure maximum and minimum temperatures, respectively) were removed on the same day the custom-built probe was placed into the Stevenson screen at Rutherglen, in direct contravention of this policy.

In 2011, the Bureau made further changes in that it stopped averaging one- second readings from the probe at Rutherglen over one minute. The maximum temperature as recorded each day at Rutherglen is now the highest one-second spot reading from the custom-built probe. That is correct – a spot reading.

So, to reiterate, we now have a non-standard method of measuring (spot readings) from non-standard equipment (custom-built probes) making it impossible to establish the equivalence of recent temperatures from Rutherglen with historical data.

At Rutherglen, a modest rate of warming in the historical maximum temperatures of 0.7 degrees Celsius per Century was changed to 1.3 degrees Celsius in ACORN-SAT Version 2. Changes to the minimum temperature trend are more dramatic: a slight cooling trend of 0.3 degrees Celsius in the historic dataset was changed to warming of 1.9 degrees in ACORN-SAT Version 2 for Rutherglen.

There is much more detail concerning temperatures at Rutherglen and surrounding stations in a report I wrote a few years ago, that can be downloaded by clicking here.


The number of weather stations with electronic probes has slowly increased since 1996, and the bureau now has a network of about 700, referred to as automatic weather stations (AWS). In a report released in September 2017 it acknowledged issues with the performance of just two of these: Goulburn Airport (Goulburn) and Thredbo Top Station (Thredbo). These are the same two weather stations that I reported in blog posts on the 5th and 18th July 2017 as not recording temperatures measured below minus 10 degrees, respectively.

While the Bureau strenuously denied it was setting limits, Minister Josh Frydenberg nevertheless insisted on a review of the entire AWS network.

When the report was published the Bureau’s investigations confirmed that Goulburn and Thredbo were the only sites where temperature records had been affected by the inability of some Bureau AWS to read low temperatures.  What are the chances? Of the nearly 700 weather stations, I stumbled across the only two with problems.

Goulburn was discovered because my friend Lance Pidgeon lives nearby and was up early on the morning of 2 July concerned his pipes were going to freeze and burst – while watching the live AWS temperature readings tick-over on that weather station, then letting me know when the record for July of minus 10.4 was reached: only to see it rounded up to minus 10.0.

Thredbo was discovered because, after making a fuss about Goulburn, I wanted to check that the Bureau had lifted the limits on readings below minus 10. So, two weeks later I decided to get up early and watch the one-second reading at one of the stations in the snow fields on the Sunday morning of 16th July thinking it might be a cold morning. Why did I choose Thredbo – of all the weather stations in the Australian Alps? Simply because my school friend Diane Ainsworth died in the landslide there twenty years ago.

I wrote this all up some years ago, at my blog, and it was republished by The Spectator Australia online, you can read more by clicking here.


When the Australian Bureau of Meteorology announce how much hotter last year was relative to earlier years, which they usually do at the beginning of each year, a reasonable person might assume they had just added-up and averaged recorded temperature measurements, perhaps adding an area weighting.   But it’s much more complicated than that.  In an article in the Weekend Australian on January 22-23 entitled, ‘BoM cools the past, warms present’ Graham Lloyd explains that the Bureau has remodelled Australia’s official temperature record for a third time in nine years.  He wrote this the week after announcing to readers of The Australian that the Bureau had published the data for 2021, when it hadn’t.

The Bureau are not saying how much the most recent remodelling (December 2020) has warmed the overall trend.  They acknowledged back in November 2018 that the second remodelling added 23% to the overall warming trend.

The Bureau claims the changes are necessary because of changes in the location of recording equipment, abrupt warming or cooling relative to other sites in the region. The article concludes with assurances from the Bureau that what they do is World’s Best Practice.

In June 2014 I gave a presentation to the Sydney Institute entitled ‘Modelling Australian and Global Temperatures: What’s Wrong? Bourke and Amberley as Case Studies’.  I choose Amberley because this is a military base with temperatures recorded by military personnel.   Temperatures have always been recorded at this same location since 1941.  My analysis was of the ACORN-SAT version 1 dataset for this location, and for the period to 2013.

At Amberley the historic minimum temperatures showed cooling at a rate of about 1 degree per century from 1970.  The Bureau changed this to warming after first determined there were two statistical discontinuities in the data in 1980 and 1996, and to correct for these changed all the historical temperatures back from 1996 to 1941 were changed creating a warming trend of 2.5 degrees Celsius per century.   A combined absolute temperature increase of 1.5 degrees Celsius.    This is a very large adjustment.

According to various peer-reviewed papers, and technical reports, homogenization is a technique that enables non-climatic factors to be eliminated from temperature series. It is often done when there is a site change (for example from a post office to an airport), or equipment change (from a Glaisher Stand to a Stevenson screen). But at Amberley neither of these criteria can be applied. The temperatures have been recorded at the same well-maintained site within the perimeter of the air force base since 1941.

My criticisms were published in Issue 26 of The Sydney Papers Online.  The Bureau has a policy of not responding to my enquiries, submissions, or peer-reviewed journal articles.  However, interestingly Gavin Schmidt then the new Director of NASA’s Goddard Institute for Space Studies in New York came to the Bureau’s defence – on Twitter.

Dr Schmidt was quite blunt about what had been done to the Amberley minimum temperature series, ‘@jennmarohasy There is an inhomogenity detected (~1980) and based on continuity w/nearby stations it is corrected. #notrocketscience’.

When I sought clarification regarding what was meant by “nearby” stations I was provided with a link to a list of 310 localities used by climate scientists at Berkeley when homogenizing the Amberley data. The inclusion of Berkeley scientists was perhaps to make the point that all the key institutions working on temperature series (the Australian Bureau, NASA, and also scientists at Berkeley) appreciated the need to adjust up the temperatures at Amberley.

But these 310 ‘nearby’ stations stretch to a radius of 974 kilometres and include Frederick Reef in the Coral Sea, Quilpie post office and even Bourke post office.

Considering the unhomogenized data for the six nearest stations that are part of the Bureau’s ACORN-SAT network (old Brisbane aero, Cape Moreton Lighthouse, Gayndah post office, Bundaberg post office, Miles post office and Yamba pilot station) the Bureau’s jump-up for Amberley creates an increase for the official temperature trend of 0.75 degree C per century. Temperatures at old Brisbane aero, the closest station that is also part of the ACORN-SAT network, also shows a long-term cooling trend. Indeed, perhaps the cooling at Amberley is real. Why not consider this, particularly in the absence of real physical evidence to the contrary?

In the Twitter conversation with Dr Schmidt we suggested it was nonsense to use temperature data from radically different climatic zones to homogenize Amberley, and repeated our original question asking why it was necessary to change the original temperature record in the first place. Dr Schmidt replied, ‘@jennmarohasy Your question is ill-posed. No-one changed the trend directly. Instead procedures correct for a detected jump around ~1980.’

If Twitter was around at the time George Orwell was writing the dystopian fiction Nineteen Eighty-Four, I wonder whether he might have borrowed some text from Dr Schmidt’s tweets, particularly when words like, ‘procedures correct’ refer to mathematical algorithms reaching out to ‘nearby’ locations that are across the Coral Sea and beyond the Great Dividing Range to change what was a mild cooling trend, into dramatic warming, for an otherwise politically incorrect temperature series.

There is more in the article published by the Sydney Institute following the presentation that I gave there a few years ago, you can read it by clicking here.

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Jennifer Marohasy

Jennifer Marohasy is a Senior Fellow at the Institute of Public Affairs

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