I have figured out the main reason why I was getting only negligible correlation between link strength and nino34 anomaly,
even though Graham was able to reproduce the Ludascher results.
Maplotlib's xcorr and acorr function do not subtract the means from the signals before doing the rolling dot products.
This was fine for the nino34 anomaly since that is mean 0 by design, but link strength is all positive so it is badly affected by this.
Once the mean is subtracted from the anomaly, the 0 time lag correlation remain negligible,
but there a small but noticable peak in the xcorr plot at -4 coresponding to a correlation
with the anomaly 4 month after the corresponding link strength.
The correlation with 6 months later is almost the same,
but it is still lower than the 6-month lag autocorrelation of the anomaly itself
and significantly lower than the other models I have posted here.
I have updated the [notebook](https://www.googledrive.com/host/0B4cyIPgV_VxrX0lxSUxHU2VLN28/link-anom.html) to subtract the mean from the anomaly prior to the analysis.