but listen man, the only intellectually rigorous way to study a subject is to independently reproduce it from first principles.

It's too bad that humanity hasn't figured out a way to record and share and pool knowledge yet, but them's the breaks.

I don't think the author adequately considers changes to the local environment of the thermometer, changes in the equipment itself (eg replacement, movement) possible changes in recording methodology and so on.

There was no real effort to understand the possible sources of noise or error in the measurements.

But local changes of environment would have been expected to increase temperature readings? More asphalt, more buildings...

Not necessarily, it could just as easily go the other way (thermal sink dropping the average).

Huh? https://en.wikipedia.org/wiki/Urban_heat_island

Also, 1920 is a very arbitrary starting year. Why then?

In 1920 the Industrial Revolution has been going on for over 100 years, the US petroleum industry was already big enough to have been affected by antitrust action, and Henry Ford's assembly line has been enabling mass motorization for the better part of a decade.

1920 is 100 years ago, so I don't think it's an arbitrary starting year. Also the older you start, the worst the data quality will be.

What if existing literature and study is somewhat biased by 'green' funding?

That would be a testable hypothesis that you have not tested. Anybody can do whataboutism but it isn't a meaningful argument. If it's your belief that the literature is biased by 'green' funding, prove it.

how would this be done, without being dismissed as being "just a bunch of plots with no effort to engage with the existing literature and study"?

Engaging with the existing literature would be a good start.

If you were interested in studying the relationship between bias and funding you might do a survey of published papers and articles on the subject.

If you can identify some measurable criteria that can be used to rate how "green" a paper's funding is then you can use that as an axis and compare the surveyed papers to reveal trends.

Additionally, since one is already doing that, check out what kind of funding Fossil Fuel companies have done in the past and present.

>and if necessary, turn off Fox News

Quips like this aren't very productive if you want to convince others of your viewpoint.