HADCRUT4 is the new Met Office dataset designed to replaced HADCRUT3. Why do they need to replace HADCRUT3?
Because the trend for the last 15 years in HADCRUT3 is negative and therefore it must be exterminated – like the Medieval Warming Period.
The following graph compares HADCRUT4 to HADCRUT3. (Click for a larger version)
Take note of the following:
1) HADCRUT3 and HADCRUT4 overlaps until about 2002 with minor differences.
2) For some reason, after 2002, there appears to be corrections of .1 to .2C. Why was the data ok in 1997-2002 and suddenly it was so bad it had to be “corrected”.
3) What justifies a .2C adjustment up in 2007? Thats 40% higher!
4) Every place a red line is well above the blue they have adjusted up to make the the “new dataset” hotter.
5) HADCRUT3 trend (the dashed line) was negative (-.016C/Decade). HADCRUT4 is positive (.033C/Decade).