More than seven years have passed since the publication of our earlier monograph on historical and paleoclimatic aspects of the El Niño/Southern Oscillation (ENSO) phenomenon. El Niño is now not only a household word but is used to sell everything from snowblowers to ski vacation packages! This entry of the term “El Niño” into the vernacular is partly the result of our “media culture” taking advantage of a catchy term to get myriad messages across, but it also derives from significant advances in our understanding and ability to predict aspects of this natural phenomenon months, or even seasons, in advance. At the same time, interpretations of the paleorecord from a variety of indices lead us to conclude that the ENSO phenomenon contributes the lion's share of the higher frequency variability in these records.

Events since 1992 – the year our previous book was published – have shown that improvements in our knowledge of various aspects of the long-term variability of ENSO are still needed. In the 1990s, events such as the persistent El Niño pattern from 1991 to 1994, and the recent development of another major El Niño episode in 1997–98 (only fifteen years after the great El Nino of 1982–83 first catapulted this phenomenon into the consciousness of the general public), underscore the need to understand longterm aspects of ENSO variability. A major theme of this volume is concerned with the relationship between global-scale climatic patterns, operating on different timescales, and the space-time behavior of the higher frequency ENSO system itself.