For months we have been told how this is a strong El Nino, similar to the “Super El Nino” of 1997-98. How does it really stack up?
As data for sea surface temperatures are not available before 1950, the Southern Oscillation Index (SOI) data from 1876 are the best for long term analysis. In this post I am using SOI data from the BOM archive.
The Bureau uses sustained (three month mean) SOI values of 7 or less as an indication of El Nino conditions. This plot shows three month mean SOI values from 1876:
Fig. 1: Three month mean SOI values from 1876
It is plain that as of November 2015 the three month mean is still nowhere near as low as it has been in several past El Ninos (and 1997-98 was not the lowest either!)
The next graph compares the length of El Ninos.
Fig. 2: El…
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