Over on WUWT (http://wattsupwiththat.com/2010/07/13/calculating-global-temperature/), Zeke Hausfarther and Steven Mosher have been discussing the calculation of global temperature from station data. They list several methods of combining records, noting that most of the major indices use the Common Anomalies Method (CAM). They mention, but do not discuss, the First Differences Method (FDM). In fact, FDM is … Continue reading The First Difference Method