Jennifer Marohasy. Remember that name, especially if you’re Australian.
In a recent blog post she decides to name names:
It is not disputed that Blair Trewin under the supervision of David Jones (both working at the Australian Bureau of Meteorology) remodel all the historical temperature data generating trends and statistics that look quite different from the actual measurements.
Yes they do. My opinion: either she doesn’t understand why they do, or she does but she doesn’t care because she wants to slander climate scientists and the data they produce.
She highlights this graph of multiple versions of yearly average temperature at Wagga Wagga, Australia:
It looks kind of like a mess, doesn’t it? Well it should, because they’re all for “Wagga Wagga” but they’re not for the same location. The lines marked “Raw: Wagga Wagga (Kooringal) and “Raw: Wagga Wagga AMO” are yearly averages of thermometer readings taken at different locations about five miles apart. We already know that they won’t give the same readings — there is likely (almost inevitably) a difference between their average readings, they are essentiall on a different scale. But we also know they will show the same trend over time with extremely high precision. This means we can combine them to estimate the trend at Wagga Wagga, but we can’t combine them to get the actual temperature unless we adjust one of them to be on the same scale as the other. Unless, of course, you want to get the wrong answer. My opinion: Jennifer Marohasy doesn’t just want to get the wrong answer, she wants all of Australia to get it wrong.
Neither record covers the time span Australia’s BoM (Bureau of Meteorology) is mainly interested in: from 1910 to the present. Hence the BoM has combined them to make a single record for “Wagga Wagga” covering the whole episode. Therefore they adjust the data before combining it — because they want to get the right answer. They’ll make adjustments for other reasons too, but always with good reasons.
My guess: What Jennifer Marohasy really wants readers to think is that if you use the two sets of data as is, not “remodel” the data, then the trend you get is nothing like the trend claimed for Wagga Wagga by the BoM, so the BoM data must be wrong, maybe they’re perpetrating a hoax.
What Jennifer Marohasy doesn’t do — in spite of the fact that it’s oh, so easy — is show why Australia’s BoM “remodels” things.
Allow me, using the exact example pointed to by Jennifer Marohasy.
The BoM wants to understand Australia’s temperature history back to at least 1910, and one clue is the temperature from Wagga Wagga, Australia, because there’s a weather station there, Wagga Wagga AMO. Unfortunately, the data only go back to 1942.
Fortunately there’s another station nearby — less than 5 miles away — which has prior data, extending from 1871 up to 1950, at Kooringal. It’s not the same location, but we can count on the fact that the weather there will follow the weather at Wagga Wagga AMO quite closely. If it’s hot, or cold, or rainy, or sunny five miles away, it probably is where you are too.
Let’s see for ourselves. I retrieved daily data for high temperature (the “actual measurements,” without any “remodel” adjustments) for both locations, then computed yearly averages from 1910 through 2019 (as above). My graph is quite similar, but (I think) less cluttered and clearer.
Let’s zoom in on the time span from 1942 through 1951:
Obviously, they show the same changes over time. This means that we can use the temperature changes at Kooringal as a good estimate of the temperature changes at Wagga Wagga AMO, for those times from 1910 to 1942 when there isn’t direct information.
Another thing is obvious: that they show the same changes over time but are offset from each other. The yearly average temperature at Kooringal is about 1°C hotter than at Wagga Wagga AMO, consistently and persistently. It’s not always 1°C hotter, they are not the same location! But for climate purposes, they are so nearby that their monthly and yearly averages will track each other precisely, if you adjust the Kooringal data to be at the same “zero point level” as the Wagga Wagga AMO data. Since we can estimate the temperature at Wagga Wagga AMO by subtracting 1°C from the temperature at Wagga Wagga Kooringal, we’ll have an estimate all the way back to 1910!
If you don’t do this — if you deliberately omit this “remodel” adjustment — then you are deliberately misrepresenting the temperature changes at Wagga Wagga. That’s a fact.
If we just glue together the data from both locations to form a combined record for Wagga Wagga with no allowance for the consistent, persistent difference between the data from the two locations, we would know that the early stuff is too hot. You would only do that if you are so amazingly stupid that you don’t get this, or if you are so dishonest you don’t care.
If you do “remodel” the data, by subtracting 1°C from the Kooringal data (0.994°C, to be precise), you get this picture of temperature change at Wagga Wagga since 1910:
Compare that to the 2nd graph in this post (the first one produced by me).
Ms. Marohasy goes on to say:
So, when Michael Mann and David Karoly tell you it’s getting hotter and hotter, this is their interpretation of Blair Trewin’s statistics, not their interpretation of the actual data.
When I say there needs to be more scrutiny of what Blair does to the actual measurements, I’m simply making a request.
My opinion: this is obviously a lie. Tell us, Jennifer Marohasy, do you still beat your kids? Do you still torture animals? When I say there needs to be more scrutiny of what you do to children and animals, I’m simply making a request.
What is not opinion, but a fact, is that the BoM has been transparent about their methods and results, everything is available for public scrutiny, they have offered detailed explanations, in short, they have already answered Jennifer Marohasy’s question.
Jennifer Marohasy is doing everything she can to prevent Australia from dealing with the climate crisis and preparing for the consequences — too many of which have already hit. She is one of the sources of misinformation for those have crippled any attempt to save Australia from the coming (and present) conflagration.
Also my opinion: Australians should remember the name Jennifer Marohasy, and should definitely hold her accountable.
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