Nick
You say
‘… on the account you’ve given, it makes no sense. You’d only want a modified estimate of the temperature at some time/place for a purpose – to fit some theoretical postulate.’
The postualte is that there is a warming bias in early instrumental records and they weant to identify and correct it.
https://springerlink3.metapress.com/content/g111046235jnv572/resource-secured/?target=fulltext.pdf&sid=3zjnwhmsywiatam5ynntvs13&sh=www.springerlink.com
tonyb