El Nino and variations in climate

The pattern of variations in climate from year to year may appear, at first glance, to be essentially random. However, a careful examination of the historical data reveals a remarkably coherent global pattern of oceanic and atmospheric anomalies that reappears every few years in approximately the same sequence and form. This recurrent fluctuation, now referred to as the El Nino-Southern Oscillation phenomenon, involves major dislocations of the rainfall regimes of the tropics, bringing drought to productive agricultural areas and torrential rains to otherwise arid regions. The related anomalies in atmospheric circulation extend deep into the temperate zones, where they are related to unusual wintertime conditions over regions as far apart as the United States and New Zealand.