Readers here (and elsewhere) have noted the release of a new version of the UAH satellite-derived tropospheric temperature record by John Christy and Roy Spencer. As noted by Spencer on March 5, version 5.3 seeks to remove, or at least mitigate, a spurious annual cycle that was apparently exacerbated in the changeover from the older MSU sensors to the newer AMSUs back in 1998.
The new data set is now available, so I’ll show some graphs that highlight the differences between the two versions. But first I’ll give a brief background on the matter, including my role.
[Update, March 10: It appears that John Christy was first notified of the annual cycle issue in October 2008, although it is unclear whether he understood the implications at that time. ]