The Bureau of Meteorology, in its recent media release, accepted and repeated by the media, made an astonishing claim:
Bureau of Meteorology confirms it’s been the hottest summer on record
Where did they get the data to make this claim? Well, in their media release they said:
“Of the 112 locations used in long-term climate monitoring, 14 had their hottest day on record during the summer of 2012/13..”
112. Not the 700+ of the AWAP (Australian Water Availability Project) used to make the claim about January 7 being the hottest day on record. 112 is the number of sites in the ACORN dataset.
So I’m sure all journalists reporting this claim would have referred to the BOM’s Time Series Graphs on their website, which use the ACORN data, to confirm just where this summer was the hottest on record. Forgive the sarcasm- they plainly didn’t. Let’s take a look.
First, here is the plot for the summer mean temperatures for all of Australia 1910-2012 (which includes January and February 2013):Yep, the 2012-13 summer mean was definitely the highest on (this) record. There are 6 regions and 7 states/territories in Australia:Let’s see how each of these performed.
I am reminded that one way of calculating mean temperature is to average the minimum and the maximum. Here’s the summer maximum for Australia:As expected. Now the minimum:So we can blame the record mean on the record maximum temperatures. Let’s look at the different regions.
Not Northern Australia.It’s Southern Australia:But not Eastern Australia.Not South Western Australia.Not South Australia (the State):Not Western Australia (the State):So the only part of Australia left that could be responsible for the summer maximum record, and consequently the mean, is this bottom part of WA not in the south west corner, or perhaps as well the southern portion of Queensland:It must have been a tad warmer than average there!
The summer mean temperature for all of Australia, according to BOM, was the highest on record. They confirm this with their graph of ACORN data.
The summer minimum was not a record by a long way.
Only Southern Australia’s maximum temperatures show this record. No other regions were hotter this summer. And this includes none of the smaller regions within Southern Australia.
Therefore we can conclude that BOM is flicking between two methods of calculating temperature and two datasets to find the “record” that fits their global warming mantra.
h/t Andrew Barnham