Yeah, that one is always brought up, but the issues weren't widespread as someone inferred earlier. Again, it would be obvious in the overall temperature record if that was the case. Looking at a temp map from the early 1900s and assuming it's "off" because of overexposure doesn't make any sense.
Improper siting, maintenance, sensor drift, differences in how old data was collected vs modern data...these have all been issues for a long time, but I doubt any are as widespread as UHI/land changes is currently. In terms of comparing modern records to historic ones.
This reminds me of my sister’s BC from back in the day. That dog was wicked smart and herded everything from cars, kids, me, toys, global warming. We dog sat for a few extended periods about 20 years ago and I specifically remember having her during the July 2006 mega ridge. Good times. She also had some of the weirdest triggers too. For no apparent reason if you looked at her and said the word “Alaska” she would go absolutely ape . She’d never been to Alaska and no other state would work. “Starburst” and “Skittles” were also equally effective.