Dr Henry F. Diaz is a Research Meteorologist in the Earth System Research Laboratory at the National Oceanic and Atmospheric Administration (NOAA). He has worked on a variety of climate issues at NOAA over the last 15 years, particularly the impact of climatic variation on water resources of the western United States. He is recognized as an expert on the El Ni o Southern Oscillation (ENSO) phenomenon and coedited El Ni o: Historical and Paleoclimatic Aspects of the Southern Oscillation, also published by Cambridge University Press (1992).