Figure 3.4: Time series of Southern Oscillation Index (SOI, upper panel) and Interdecadal Pacific Oscillation (IPO, lower panel) from 1900
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Text description of figure
The upper panel in this figure displays a time series of the Southern Oscillation Index for the period from 1900 to 2006. The figure shows this index persists below about minus one for the years of El Niño events, and persists above plus one during La Niña events. The Southern Oscillation Index varies between about three and seven years and large variability exists in the intensity of individual events.
The lower panel shows a time series of the Interdecadal Pacific Oscillation from the period from 1900 to 2006. There was a positive phase from 1925 to 1943 and again from 1978 to 1999, and a negative phase from 1944 to 1977.
