DESCRIPTION: Warm (red) and cold (blue) episodes based on a threshold
of +/- 0.5oC for the Oceanic Niño Index (ONI) [3 month running mean of ERSST.v3b SST anomalies in the Niño 3.4
region (5oN-5oS, 120o-170oW)], based on the 1971-2000 base period. For historical purposes cold and warm episodes
(blue and red colored numbers) are defined when the threshold is met for a minimum of 5 consecutive over-lapping seasons.