Dear Felix, We looked at the trends in our 2011 paper (see Fig AM3 under "Supporting Information" in http://dx.doi.org/10.1029/2011GL047364). You're right in that there is a warming trend in E that makes the two extreme El Niño larger relative to older El Niño, but this does not change the fact that they stand out, way outside of the cluster of the other El Niño. On the other hand, trends in the variability (standard deviation) and warm/cold asymmetry (skewness) in E change sign if we recalculate them after removing these two events. They are so large that the statistics of 60 years are very affected by only these two. A more robust and perhaps more interesting result is that the positive trend in the mean C index and its variability is accompanied by an increasingly negative asymmetry. That is, the central Pacific is warming but the extreme La Niñas are getting bigger there. This is consistent with a recent study I coauthored (http://dx.doi.org/10.1038/nclimate2492) that shows this trend in future climate scenarios. Cheers Ken