Just a few days ago (February 19), I posted part XX of this series. The subject of that post was a new compilation of historical temperatures for Australia (going back to 1910), known as ACORN2, just out from the Australian Bureau of Meteorology. The effect of ACORN2 was to increase the reported rate of climatic warming in Australia by 0.2 deg C per century over the previous compilation known as ACORN1, which had only been issued about 6+ years ago and had itself also increased the reported rate of warming as against the previous official records by about 0.2 deg C per century. The increased rate of warming is entirely accomplished by adjusting earlier-year temperatures downward.
Could there possibly be anything honest about what is going on? My source for the February 19 post — independent Australian researcher and blogger Joanne Nova — provided a link to the the BoM’s 57-page Research Report that supposedly justified the changes. That document appeared “impenetrable” both to Nova and to me, but maybe some much cleverer person could figure out what they were doing?
Well, now we move to the next step. Another hard-working Australian independent researcher and blogger, Jennifer Marohasy, decided to get the detailed records for a particular station, just to see what adjustments had been made, and whether any possible legitimate explanation could support them. The station that Marohasy selected is Darwin. For those unfamiliar with the geography of Australia, Darwin is the biggest city (not very big — about 150,000 people) in the vast northern areas of the country. Marohasy’s February 23 post is titled “Changes to Darwin’s Climate History are Not Logical.” A version of Marohasy’s post was also published on Watts Up With That on February 22.
Basically, Marohasy documents that Australia’s BoM has shortened Darwin’s temperature record to begin in 1910 (records actually exist back to 1895), and then adjusted the earliest temperatures downward by a full degree and more C, just since the previous set of downward adjustments only 6 years ago. For example, here is what has happened on the first day of the series as it now exists:
[O]n 1st January 1910 the maximum temperature recorded at the Darwin post office was 34.2 degrees Celsius. A few years ago [in ACORN1], the Bureau changed this to 33.8 degrees Celsius, cooling the recorded temperature by 0.4 degrees. In its most recent re-revision of Darwin’s climate history the temperature on this day has been further reduced, and is now just 32.8.
And of course, it’s not just the one day. Let’s look at the first six days of January 1910:
All of them got adjusted down by something in the range of 0.8 to 1.2 deg C, even after prior downward adjustments just 6+ years ago. The environmental reporter for the newspaper The Australian asked the BoM for an explanation, and here is what he got:
For the case of Darwin, a downward adjustment to older records is applied to account for differences between the older sites and the current site, and differences between older thermometers and the current automated sensor. In other words, the adjustments estimate what historical temperatures would look like if they were recorded with today’s equipment at the current site.
But here’s the problem, idiots: this is the same explanation you gave six years ago for the 0.4 deg C downward adjustment then. What about temperatures in the year 1910, or the equipment in 1910, or the site in 1910, changed between ACORN1 in 2012 and ACORN2 in 2019 to justify further downward adjustments averaging a full deg C? Nothing. Marohasy:
Neither the equipment, nor the site has changed since ACORN-SAT Version 1 was published in 2012. Yet another 1 degree has been shaven from the historical temperature record! To be clear, the weather station has been at the airport since February 1941, and an automatic weather station was installed on 1 October 1990. A Stevenson screen was first installed at the post office site in 1894, and has always been used at the airport site. So, why was the temperature dropped down by a further one degree for 1 January 1910 in the most recent revision – undertaken just a few months ago? There is no logical or reasonable explanation.
Are you still wondering if there is anything honest about this? Marohasy compiles a graph of the raw mean maximum annual temperatures as recorded at Darwin, versus the “adjusted” ACORN2 series that is now Australia’s official temperature record. Note that the site did move in 1941, from the post office in downtown Darwin out to the airport. To indicate the discontinuity, Marohasy graphs the post office series in green, and the airport in blue. Here is her graph:
Is the post office site systematically warmer than the airport site? Note that the last several years at the post office were considerably cooler than the first years at the airport. But the BoM has made the executive decision to replace the temperatures recorded at the post office in the period 1910 to 1941 with temperatures that average about 1.5 deg C cooler. Pre-adjustments, 1906 looks like the year with the hottest mean maximum temperature, and by a wide margin; and number two is also pre-1910. Post-adjustments, the warmest is 2016. This is how you get to have “hottest year ever” press releases every year or two.
Conclusion, from Marohasy:
What the Bureau has done to the historical temperature record for Darwin is indefensible. The Bureau has artificially shortened and cooled Darwin’s climate history to make it consistent with the theory of human-caused global warming.
It’s completely dishonest and fraudulent.
For all 21 posts in this series, go to this link.