By Steve Goddard
As Bob Tisdale pointed out, Tom Karl’s NCDC trend claims don’t match his graph. The trend line is less than either of the claimed V2 or V3 trends in the graph below.
But beyond this blatant error, there are other problems with his graph. Why did it start in 1900? NCDC has data going back to 1880. As you can see below, temperatures dropped from 1880 for about 30 years, which reduces the long term slope considerably.
Now let’s compare his graph vs. Had-Crut, which goes back to 1850. Had-Crut is shown in green, and NCDC V3 is shown in red, at the same scale. Note that there is a huge divergence over the last ten years vs. Had-Crut. The Had-Crut long term trend is 0.45C/century, about half of what Tom Karl is claiming.
It appears that someone is hiding the decline at both ends of the graph.
UPDATE from Steve Goddard:
When I wrote the article I did not recognize that the “global” data presented to the Senate in slide 21 was land only. Thanks to Bob Tisdale for pointing it out. The land only data has diverged from global data over the last decade and explains the discrepancy at the right side of the graph. It does not explain why the slide is marked as “global” or why the land only data set was presented to Congress as “unequivocal” evidence of “global” warming. My apologies to Tom Karl for not recognizing which data set he was presenting to Congress in that particular slide.