Re: Trends. You can compute it if you like. People have done that. I don't recall the results but they were close enough to zero to be equivalent. Re: ClimDiv. Yes, but from my comment:

"they have kept on using the old broken network which they now adjust via models"

So indeed you'd expect them to follow each other closely now.

There's no attempt to dupe you - a full treatment of the problems with temperature data is a book sized topic, that's all. The reason for the selection of years is simply because that's all the data that has been collected by the new network. By all means, treat this as a good faith attempt to provoke questions and further research. The CRN is just an example - the problem I'm getting at here is what it reveals about the methodologies and culture. Specifically, how do we know that people who claim to be scientists are actually using the scientific method? That's the topic I responded to.

For decades the US data collection system was degrading in ways that created false warming, but it wasn't the people who are paid to study climate who raised the alarm. It was volunteers. That should be a serious problem for any rational person who wants to know true things; scientists are meant to care about measurement error and take steps to minimize it. So you'd want at least some sort of post-mortem process to identify the root causes of this collective institutional failure, but, it didn't happen. Instead data accuracy became politicized and now researchers refuse to use the CRN even though it was built specifically to resolve disputes over data quality!

The problem here is actually more severe than this one case. Climatologists were well aware of other problems with temperature data! Data quality problems are common in science so that's not inherently an issue. But the scientific approach is to quantify and then communicate the flaws in data through CIs/error bars, then propagate those through any statistical derivation you do, and finally be honest about what the CIs are telling you even if that's "we can't say much". That's the point you were making originally and we agree. Climatologists don't do this. Instead they think up reasons the data must be flawed, "fix" it via post-processing and then issue new dataset versions without error bars. They don't only do this for data collected long ago. Once they opened that pandora's box they couldn't stop and now temperature readings collected even just 5 years ago are subject to large scale revisions post-hoc. These revisions don't just change individual data points. Entire trends appear or disappear due to the revisions.

https://retractionwatch.com/2021/08/16/will-the-real-hottest...

https://www.nature.com/articles/nature.2015.17700

http://www.climate4you.com/images/NCDC%20Jan1915%20and%20Jan...

That behavior is considered fraud in other fields and for good reason: the temptation to change the data to confirm your theory is too great if you allow that. Climatologists though, don't consider it fraud, they think it's normal and fine. Sure enough, there are problems like temperatures as measured by satellites and weather balloons not matching the modified temperature timeseries from ground based weather stations. This is the sort of thing you'd expect to see if the ground station data was corrupted but pointing out this divergence is considered "denialism" and verboten.

All this opens up lots of meta-scientific questions like, is the scientific method objective? Do the institutions attempt to enforce the usage of it? What even is the scientific method anyway, can you write it down in a way nobody will object to? Clearly here we have a major disconnect: if you did what climatologists do in a physics experiment, your papers would be retracted and you'd be booted out in disgrace. Yet both fields claim to be scientific.

the vast majority of climate change deniers takes are along the lines I described - "it's snowing, ergo suck it libs"

Sure, and that's indeed not a useful rebuttal to claims of long term trends. I don't know about "vast majority" because I don't know of any surveys that could be used to check that claim. But unfortunately it's also no longer particularly meaningful to check. Climatologists, governments and media are now all too happy to attribute individual forest fires, cold years, hot years etc to climate change. If they can do it then "it's snowing ergo suck it libs" is in fact a valid argument by the scientific institution's own standards. Hence my point: are they really scientific?