Yes, You Can Do This At Home

AG(data)W Begins In 1990
E.M.Smith
So What About The Graph?

"Well, first off, notice that a trend line fit to the annual data is just about dead flat right up until about 1990. (That is the very thin blue line at near the zero line) The change of “duplicate numbers” or “modification history flag” on thermometers starts to hit in about 1986-1987 but those records have a matching entry from the prior “duplicate number” until about 1990 when “the reveal” is done and the older series of “duplicate numbers” are dropped. You could put the segment break at 1987 and get similar results, but I chose 1990 as that is when the data series are left to stand on their own.

At that point we see a dramatic increase in the slope of the trend line as “AGW suddenly begins”. But, IMHO, it’s not the world that’s warming, it’s the data…

That is the most striking thing I see. Just look at the slope of that thin Hot Pink trend line! We go from nearly flat trend up to 1990 (the thin blue line) to dramatic warming (thin hot pink line) just as the “modification history” or “duplicate number” change indicates a change of processing of the data. Hmmmm.

But wait, there is more… "