The El Ni o/Southern Oscillation (ENSO) phenomenon is a recurrent feature of the climate in tropical regions. In this volume leading experts summarize information gained over the past decade on diverse aspects of ENSO, which have led to marked improvements in forecasting. This volume compares ENSO's modern morphology and variability with its recent historic and prehistoric behavior. It expands and updates Diaz and Markgraf's earlier volume El Ni o: Historical and Paleoclimatic Aspects of the Southern Oscillation (Cambridge University Press, 1992). Key features include new paleoclimate records and new information that links ENSO variability to aspects of human health.