Effect of solar activity

Mendoza et al. (1991) analyzed the occurrence of El Niño events in coastal Peru as related to sunspot numbers (rule 57). They found that, between 1700 and 1985, more El Niños (63%) occurred in sunspot minima or with negative gradients (descending phase) of the solar cycle, than in maxima or in the ascending phase (37%). Our research indicates that during the ascending phase of the solar cycle the odds are shifted in favor of La Niña events (rule 485).

Solar Cycle 24, which officially started in January 2008, has been a subject of much debate due to competing forecasts on whether it will be a highly active or a quiet low cycle. Both camps agree, however, that the sooner the new cycle takes over the waning previous cycle, the more likely it will be a strong one. As of this writing (May 2008), solar activity remains at a very low level, with just a few sunspots, which some believe still belong to the “never ending Cycle 23” (see here). Solar cycle 24 is expected to peak in late 2011 or mid-2012.  If the patterns described in rules 57 and 485 hold true, the probability of La Niña events will remain relatively high and the background SST will be relatively low until about 2014. However, the next El Niña event (and possibly a strong one) is currently brewing (see below).