Update: see below.
Once again we are drawn into the "making up stuff for the sake of a bad yarn" territory at WUWT (archived here) .
Anthony Watts has written about articles by science denier and "environment" writer for the Australian, Graham Lloyd and one of Australia's resident deniers, Jennifer Marohasy. They are raising a big kerfuffle about the record of temperature trends from the agricultural research centre at DEPI Rutherglen.
I'd normally leave it up to Nick Stokes of Moyhu to analyse denialist claims like this, but he hasn't done so yet. So I'll give it a shot myself.
Rutherglen is wine-grape country just north west of the Great Dividing Range in north eastern Victoria. As well as wine grapes there is dryland farming - animals and cropping, among other things. There has been an agricultural research centre there since the year dot. Well, since the late 1800s - doing viticultural research and education (from 1880), as well as other agricultural research from the early 20th century. (There used to be two research centres, now one.)
My family has lived in the region since the 1950s. I worked for the Victorian Department of Agriculture in the early 1980s, was on the agriculture faculty at Melbourne Uni in the 1990s, headed the Victorian branch of the ag science professional body for a while, and have since done work with the Victorian primary industries department (including its research arm) so the research centre at Rutherglen is not unfamiliar territory, although I've never worked on site there.
Picking cherries in Rutherglen
Now what the deniers are complaining about this time isn't the mean temperature, nor the maximum daily. Nor is it the climatology of Australia or Victoria or even of the region. What they are talking about is the minimum temperature and in particular, the minimum temperatures up to around the mid-1960s early 1970s recorded at Rutherglen. That's more than forty years ago. A single weather station. The ultimate cherry pick.
I couldn't find another weather station close by that has records going back to the turn of the century, so Rutherglen is about it as far as I can tell. Here is a chart of raw average annual temperatures (from daily). I've included the raw records from Corowa, which is not far away on the Murray as well as Benalla and Wangaratta. Click to view larger.
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| Data sources: Bureau of Meteorology - Raw as recorded and ACORN-SAT |
As you can see from the above, the raw records are shown as lower than the ACORN-SAT (adjusted/corrected) records for the period prior to the gap between 1959 and 1965. I'm not in a position to say why that is the case. I will say that the proper explanation is not nefarious intent. You can leave the conspiracy ideation to deniers who congregate at WUWT. There are any number of plausible explanations for why an algorithm would have detected a break in the record and made an adjustment, some of which I've described below.
One thing you'll notice is where Benalla overlaps with Rutherglen in the earliest records for Benalla, the difference in raw minimum temperature is much less than later on (I've highlighted the two bits to look at). This suggests that BoM was not in error in regard to Rutherglen.


