If you think about it, thermometers did not become a mainstream instrument until the Victorian industrial revolution. So that is going on to roughly 140-180 years or so, ago. Hardly enough data to predict any sort of trend. Even sun-spot records are longer than that - and those relied on expensively, hand-polished glass lenses belonging to some elite star-gazer, before that same industrial revolution.

And there was still an issue for thermometers, with calibrating, and regulating the measuring environment etc., which is actually still an issue, TBH.

So historical max-heat or cold records, shmishtorical. As an alternative methodology, look for studies using ice cores, or tree-bark, or even lichen records, or even lake verves, which are subsequently integrated via software that will be more accurate than historical thermometer records.

If you think about it, thermometers did not become a mainstream instrument until the Victorian industrial revolution. So that is going on to roughly 140-180 years or so, ago. Hardly enough data to predict any sort of trend. Even sun-spot records are longer than that - and those relied on expensively, hand-polished glass lenses belonging to some elite star-gazer, before that same industrial revolution.

And there was still an issue for thermometers, with calibrating, and regulating the measuring environment etc., which is actually still an issue, TBH.

So historical max-heat or cold records, shmishtorical. As an alternative methodology, look for studies using ice cores, or tree-bark, or even lichen records, or even lake verves, which are subsequently integrated via software that will be more accurate than historical thermometer records.