Exactly, AND they had to be read manually (potential inaccuracy), AND hand recorded (another point of potential inaccuracy), AND then there would also be the issue of legibility (some people's handwriting is almost unreadable).Most accurate thermometer in 1880, was only to the one tenth of a degree! And considering we’re talking about Great Britain, that was in Fahrenheit in 1880’s…
So at most we have SOME records of questionable accuracy for a very short period. Sounds like a great basis for changing society's whole direction and upending everything that western civilization has accomplished.