“Every record has been destroyed or falsified, every book has been rewritten, every picture has been repainted, every statue and street building has been renamed, every date has been altered. And that process is continuing day be day and minute by minute. History has stopped. Nothing exists except the endless present in which the party is always right.”
In estimates I asked the BOM if ACORN 3 was going to be released anytime soon as it’s been a number of years since ACORN 2 was released.
For those of you not familiar with the BOM’s record keeping techniques they homogenise weather records. I.e. change them. Scientifically of course.
The “homogenised” weather records are called the ACORN series.
I was surprised to hear that rather than release a whole new data set which may bring unwanted attention about their modifications, they now surreptitiously update record sets using decimal points.
The Ministry of Truth would be very proud of this lot.
Economics Legislation Committee
29/05/2024
Estimates
CLIMATE CHANGE, ENERGY, THE ENVIRONMENT AND WATER PORTFOLIO
Bureau of Meteorology
Senator RENNICK: Are there any plans for an updated dataset of homogenised figures? You’ve got ACORN 1 and ACORN 2. Is there going to be an ACORN 3 out anytime soon.
Dr Johnson: As you know, we update our reference dataset regularly. I don’t have a specific date on when the next update will be, but we updated it recently as you know.
Senator RENNICK: I only know of two updates. I’m happy to be corrected. ACORN 1 and ACORN 2.
Dr Johnson: If you bear with me I might be able to get you an update. I’ll ask Dr Braganza to join us. He’s manager at our climate services and may be able to give you that number more quickly than I can.
Dr Braganza: The ACORN-SAT dataset is effectively added to every year. While there’s version 1 and 2, you will have version 1.3 and 1.4, version 2.4, for example, as we do small incremental updates. We would generally wait till we get sufficient data to look back at the homogenisation. We need sufficient data to understand whether network changes, for example, have affected any biases in the record. We would be expecting to have an update within the next several years to be released.
Senator RENNICK: In the next several years? Is there going to be an actual end date to updating past records by this homogenisation. Is this homogenisation ever going to end? I suppose I’m looking for a fixed reference point here and if you keep changing it or updating it, people are going to lose track of the original dataset because there’s multiple homogenised datasets.
Dr Braganza: The reason for having an homogenised dataset is to analyse change over time. The network is never stationary. I think that’s something that is the experience of meteorological agencies around the world. It’s very hard to keep a fixed network. If you imagine sites at an airport. We don’t control the built environment, so sites will move.
Senator RENNICK: That’s a good question, and I’ve raised this in the past: why don’t you put the weather stations out in national parks, right away from urbanisation and the heat island effect, so the conditions around the weather station don’t change or aren’t subject to as much change? I accept they’d probably change eventually.
Dr Braganza: I think our experience and those of our international partners is it’s virtually impossible to keep a fixed network in time where technology and sites are never changed. It’s our due diligence to look at whether network changes have biased change over time. We don’t have datasets that recast what happened in the past. If you want to know what the temperature was at a particular location at a point in history, that is fixed in time; it is a baseline. In order to understand how things have changed over time, we would be criticised if we didn’t look with due diligence at what changes in the network might have done to influence change.
Senator RENNICK: In regard to the classic Sydney Observatory, have you homogenised that dataset down, given it’s quite apparent it’s gotten hotter there? It is right in the heart of Sydney, with all the concrete surrounding it. Was that homogenised, step one, and was that temperature homogenised downward to take the urban island effect into account?
Dr Braganza: The first thing to note about the Sydney record is it doesn’t contribute to our national average calculation because we consider it to be affected by urbanisation to the point that we can’t disentangle urbanisation from climate change. The Sydney record has been homogenised for changes that have occurred at that site in the past; most recently that was a slight change due to the built environment changing.
Senator RENNICK: What was the result of that? Did you adjust downwards, given it was probably recording higher temperatures?
Dr Braganza: I would have to take that detail on notice.
Senator RENNICK: If you could, please. How many staff do you have working on the homogenisation process at any one time? Do you have a full department that does that? What is the process for that?
Dr Braganza: As with anything at the bureau, there is a very large set of dependencies on data collection modelling and then what we do with our reports at the final end. I would have to take on notice how many people would be working on homogenisation.
Senator RENNICK: Thank you.
