To account for non climate related impacts on the recorded temperatures.
So what "non climate related impacts" have there been on the Rutherglen site,
RickNRoll?
None.
This is why that site is in such sharp focus. Unlike most other sites, it has never been moved. Also unlike most other sites, it has never had an encroachment of urbanisation on it.
So why the warming trend at Rutherglen when the raw data - which would have to be one of the most pristine temperature records in Australia - shows a cooling trend?