It's The Data

clipped from chiefio.wordpress.com GHCN V2 All Data Anomalies 1800 to Date Segmented at 1990 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…