Subjective interpretations arrived at by motivated reasoning or raw empirical measurements?

From The hottest summer on record except for the ones that we’ve changed by Jennifer Marohasy. I lived in Australia from 1997-2002 and they were already all over this issue of retroactive readjustments of the temperature records. And it is still going on apparently.

This last summer has been hot in south-eastern Australia. But was it the hottest ever? Summer 80 years ago was arguably as hot, if not hotter.

Australia’s Environment Minister, Melissa Price, also recently claimed this summer’s bushfires as a consequence of climate change. I grew up with stories from my late father of terrible bushfires – infernos – back in 1939. The Black Friday firestorm of 13 January 1939 destroyed four times the area of farmland and forest as the devastating February 2009 fires – and twenty times as much as burnt this last summer.

But it is actually now near impossible to know which summer was the hottest ever summer – because of the extensive remodelling of our temperature history.

The extensive remodelling is not denied by the Australian Bureau of Meteorology. Rather it is justified on the basis that temperatures are now measured using a non-standard method (spot readings) from non-standard equipment (custom built probes in automatic weather stations). Apparently, we need to know how hot it was back then, relative to the equipment used now – so temperature are remodelled. To be clear, there are three factors that potentially confound how hot it was back then – or now: the equipment, how it is used, and the remodelling, which is often referred to as homogenisation.

The largest single change in the new ACORN-SAT Version 2 temperature database is a drop of more than 13 degrees Celsius at the town of Wagga on 27 November 1946.

But let’s begin with Rutherglen. The Rutherglen agricultural research station has one of the longest, continuous, temperature records for anywhere in rural Victoria. Minimum and maximum temperatures were first recorded at Rutherglen using standard and calibrated equipment 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.

While this last summer of 2018/2019 was hotter according to Minister Price, such a claim would not pass scrutiny if assessed for the Guinness Book of records – because of all the changes to the way temperatures are now measured at Rutherglen relative to back in 1938/1939.

At Rutherglen, the first big change happened 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, except the mercury and alcohol thermometers (used to measure maximum and minimum temperatures, respectively) were removed on exactly 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 – 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 – or any of the Bureau’s other 695 probes in automatic weather stations spread across the landmass of Australia – with historical data.

There are plenty of similar reports from across the country. I saw a similar one a month or so ago regarding the temperature records for the Northern Territory.

No one denies that it is important that there are changes in the technology for recording temperatures and that there are necessary calibrations and that adjustments need to be made for built environment issues. The problem is that it appears, given the secrecy and transparency, as if these legitimate needs are being used as a cover for wholesale and purpose-driven changes in the temperature record.

It is interesting that the same thing is happening elsewhere in the world but I do not see near the coverage as I do out of Australia. I do not know why that should be the case but it appears to be.

The whole AGW argument is in perilous condition enough with recent, patchy, incomplete temperature records across inconsistent and poorly calibrated measurement mechanisms. Past poor data quality management practices such as revealed by the East Anglia University leak/hack makes the issue worse. In an environment where there needs to be a premium on trust in order to move the investigation forward, it helps not a jot that these shenanigans seem to be common and extensive.