El Nino is a periodic climatic phenomenon initiated by the reversal of oceanic and atmospheric circulations in the equatorial Pacific, but its effects are global. Severe ENSO events may have catastrophic consequences. Several major famines in India and China have been attributed to ENSO. It is likely that multiple ENSO events were responsible for the demise of the Maya in Central America, the Moche, Chimu and Nazca in South America and the Anasazi in the Chaco Canyon area of the US southwest