Homogenisation: The Magical system which uses thermometers in Victoria to correct the temperature in Tasmania

Trying to fix past mistakes through homogenization

Lots of things can muck up a perfect thermometer spot, like shade, new roads, new screens, or old paint. In order to remove these annoying non-climatic effects, the BOM compares each station to those around it to look for odd changes. In theory this sounds like a good idea. In practice it’s more like hepatitis – bad news that spreads. It’s a rogue code, sweeping through records, trying to find undocumented changes, and enabling any amount of revisionism.

The BOM “detects” these mysterious shifts at each site through thermometers that may be hundreds of kilometers away, even across a mountain range or the Bass Strait.

Among other sites, Cape Bruny in far south Tasmania has been corrected with the help of Ballarat 812 km away on the mainland, over mountains and across the Bass Strait. In 1991 Cape Bruny was found to be “statistically” wrong, and adjusted down by over half a degree.

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All these sites marked in red were used to correct the record at least once at Cape Bruny, a distant island in the far south of Tasmania.

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