John said

> Okay - anomaly it is!

Hmmm. Now I'm beginning to go off the way the authors use this word. Ref 33 is also their work. I think "seasonally adjusted" would be a better term for what they doing: "actual temperature value minus climatological average for each calendar day".

There is a positive correlation between temperatures in Turkey during March to May in 1960 and those in New Zealand during September to November in 1990. I haven't checked, but I know, because it was spring in both cases. Obviously, this is not of interest for predicting El Nino events. At the moment I'm leaning towards using absolute temperatures (in Kelvin, no messing about) and talking about "seasonally adjusted correlations/covariances".