I've been arguing at WUWT, eg here. More and more I find people saying that all surface measures are totally corrupt. Of course, they give no evidence or rational argument. And when sceptics do mount an effort to actually investigate, eg here, it falls in a heap. BEST was actually one such effort that was followed through, but ended up confirming the main indices. So of course that is corrupt too.
As linked, I do sometimes point out that I have been tracking for six years with an index, TempLS, which uses unadjusted GHCN and gets very similar results to GISS and others. I have posted the code, which is only about 200 lines, and I have posted monthly predictions (ahead of GISS and all) for about six years. But no, they say, GHCN unadjusted is corrupted too. All rigged by Hansen or someone before you see it.
The proper way to deal with this is for some such sceptic to actually follow through the quite transparent recording process, and try to find some error. But I see no inclination there to do that. Just shout louder.
So here I'll track through the process whereby readings in my country, from BoM, go through the WMO collection in CLIMAT forms, and so into the GHCN repository. That's partly to show how it can be done, if a sceptic ever was inclined to stop ranting and start investigating.
I'll illustrate from my home town, Melbourne. For the state (and others), BoM posts half-hourly AWS readings, within a few minutes of measurement. The statewide site is here. Here is the line (as of now) which shows current temps, and ringed min/max.
Actually, this isn't quite so useful for my demo, because while the max is OK for today, the min is basically the min since then; it will show the proper min in the morning. But in a day or so, you'll be able to check. If you drill down to the Melbourne page, you'll see the last few days of half hour readings (and also daily max/min). These are the numbers that are quoted in news reports, etc. If someone says it was 35° yesterday, that is what they are quoting.
So firstly, on the "corrupted" issue, that doesn't work here. Firstly, it would go against other people's experience and measurement if it was fiddled. And second, there is just no way that the process could have human intervention. There are thousands of figures posted every half hour.
Those numbers are entered into the curent month file. Here is a brief extract:
Today's numbers aren't yet entered, but will appear in a few hours. When the month is done, a page for that month is posted - last 13 months available. Here is the page for October for Melbourne Airport. The summary numbers are here; I have red ringed the relevant numbers:
Now those are the numbers that are sent off on the Climat form to WMO. If you follow through there, you'll see 100 entries for Australia. Here is an extract for Melbourne Airport for October 2016. I have redringed the min/max which you can see corresponds to the BoM posted file. It adds a calc of the average (13.2), which I have brown-ringed.
If you are really hankering for authenticity, you can scroll down to see the actual code they send. And finally, you can find the unadjusted GHCN data here. It's a big file, and you have to gunzip and untar. You can also get a file for max and min. Then you have a text file, which, if you search for 501948660002016TAVG you see this line:
It has the monthly numbers for 2016 (as integer, multiplied by 100) for Melb Airport, with some letter flags. I have ringed the corresponding number 1320. These are the data I use in TempLS unadjusted.
So you can see for Australia at least, the numbers can be followed through from the posted reports every 1/2 hour to the GHCN unadjusted monthly. Of course, it is just one month. But the pattern is there, and anyone who wants to say the process is corrupted should follow through other months to see if they can find a discrepancy. I bet they won't.