Recent trends in the seasonal and temporal behaviour of the El Niño–Southern Oscillation

Trends in the seasonal and temporal behaviour of the El Niño–Southern Oscillation over the period 1958–2007 have been assessed using two indices of the phenomenon, NINO3.4 and a non‐standardised Southern Oscillation Index (SOI). There is no evidence of trends in the variability or the persistence of the indices, nor in their seasonal patterns. There is a trend towards what might be considered more “El Niño‐like” behaviour in the SOI (and more weakly in NINO3.4), but only through the period March–September and not in November–February, the season when El Niño and La Niña events typically peak. The trend in the SOI reflects only a trend in Darwin pressures, with no trend in Tahiti pressures. Apart from this trend, the temporal/seasonal nature of the El Niño–Southern Oscillation has been remarkably consistent through a period of strong global warming.