"tony sayer" wrote in message
...

Much has been written re the long term temp variation of the climate but
as it appears were talking about around 1 deg C change over quite a long
time, pre industrial era, just how absolute accurate where the
thermometers in use?.

Very accurate with the max min thermometers used in stevenson screens
when they were still read manually 3 times a day. But the other problem
is that so many of them were where suburbia encroached and the usual
heat island effect made the accuracy of the thermometer itself irrelevant.

Course these days there are some very accurate ones around but back then
in the 1800's how accurate was a standard one back then anyone any idea?.

Those were just as accurate as they are now.

Lets not take into account as to where the measurement was made either
in town out in the country at the sea side etc, but the gear in use to
measure?.