Are the Climate Commission's claims of a hot summer correct?

However the BOM also lists the summer temperature anomalies for all Australian States, Territories and Regions. Researcher Ken Stewart has done an analysis of these States, Territories and Regions. None of these 13 component areas of the Australian continent show a summer temperature record.

How can there be a continent wide summer record when no part of the continent had a record?

The problem is the BOM has not released the methodology of how it reached its conclusion that the summer was the hottest; or what climatic and weather causes were responsible for it, other than saying that AGW has caused it.

A possible explanation is put forward by Ken Stewart in his post. The summer record is based on the mean temperature which is the average of the combined maximum and minimum temperatures for the period. In his analysis Ken notes that no region had a summer record minimum temperature and only one region had a summer record maximum temperature, Southern Australia.

Southern Australia covers this part of Australia:

However when the temperature results at a State level are combined with the Regional results only a relatively small part of Southern Australian Region is left as being a possible source of the whole Southern Region's maximum temperature record:

The point Ken makes is that a record maximum in one part of Australia may have produced an overall summer mean record. If this is the case the summer temperature record is not based on a Nation-wide mean temperature heating event; it is based instead on a statistical extrapolation of a different temperature type which only has correlation with weather and climate causes in the area where the record occurred.

The BOM and the CC could make the point that there does not have to be a record in all the constituent parts of the nation; it is sufficient that it be hot enough everywhere for the record to be broken. Any particular records would be a bonus. To this end they list 123 alleged records during the summer covering temperature, rainfall, river heights and other "extreme events".

Ken Stewart has examined a few of the alleged records and discovered some dubious book-keeping. Ken refers to the 23 records shown in the eye-catching graph on page 3 of the report. He notes the CC appears to have specified 4 flood records including 2 from the Burnett River [Walla and Bundaberg 50 Km apart which would mean 2 records are claimed for the one event!]. The others are Laidley Creek, and the Clarence which produced the Grafton floods.

In the Brisbane River catchment alone, there are 40 separate streams, one of which is Laidley Creek. So, 1 out of 40 streams had a record height. And this was in the wet season. All the larger streams [Warrill, Lockyer, Bremer, Stanley, Brisbane] were not just below record but also below predicted heights.