It’s worse than we thought. Gee, it’s getting hot.
All the models show it and according to the consensus we all know it.
The thermometer, however, has been uncooperative. To counter this Australian thermometer readings have been homogenised, that is adjusted.
The Bureau of Meteorology have published the improved temperatures as the ACORN data set. The result – an increase in temperature of 0.9 °C over a century. QED.
Two issues cloud the matter somewhat. One is the urban heat island (UHI) effect. Increase the bitumen and the buildings around weather stations and you expect a warming bias in the record. The second issue is the adjustment process. One would expect that, for urban weather stations, either the modern records would be corrected downwards or older records to be corrected upwards, in order to compensate for the UHI. The mechanism the BoM uses for temperature adjustment has not been published. But trust us, we are from the government and are here to help. As was said of another government “the future is certain, only the past is subject to change”.
The past has left a record. In 1933 what was then called CSIR published 74 years of weather records. Twenty years later The Commonwealth Bureau of Census and Statistics published an Official Year Book of Australia which included the mean temperature readings from 1911 to 1940 at 44 locations.
One Chris Gillham has been working very hard to compare the historical records with the ACORN set. And guess what … the older records have been adjusted downwards. Almost half of the vaunted warming has been due entirely to changes in the record. My guess is that the rest is due to the UHI.
My source is Jo Nova where you can find far more detail.