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: