Figure from Po-Chedley & Fu's Correction to UAH Trend

Update 4:25 pm PDT: John Christy and Roy Spencer has a response here. 


Update 3:04 pm PDT: John Christy tells me they are preparing a response to the Po-Chedley & Fu paper and will post it soon:

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I have a not-final version of the Po-Chedley & Fu paper claiming an error in UAH middle troposphere temperatures. Here's their figure that shows a difference in how UAH handled the NOAA-9 satellite, which was used from about 1985-1987 (Change 2:54 pm PDT: new, corrected version of the figure):

The "warm target" calibration corrects for the effect of the satellite body that the instrument resides in. The authors write:

We find that the difference between any two teams’ TMT anomaly series is significantly correlated (95% confidence) with the global mean NOAA-9 warm target temperature from January 1985 to February 1987 (26 months). For example, the correlation coefficient (r) for UAH–NOAA and UAH–RSS versus TTARGET is -0.90 and -0.83, respectively. This implies that the warm target calibration does explain some of the differences betweenthe MSU datasets. As a result of the warm target temperature drift during NOAA-9’s operational life, these differences will also affect the merged TMT trends. In this study, we utilize radiosondes as references to find biases in the warm target factor α_i.

(Edit 3:00 pm PDT - correlation coefficients corrected from a cut-and-paste error that had them displayed as "20.90" and "20.83".)