Date: Mon, 9 Dec 2002 13:14:04 -0800 From: NASANEWS@mail.arc.nasa.gov To: Subject: NASA TREE-RING STUDY REVEALS LONG HISTORY OF EL NIŅO John Bluck Dec. 9, 2002 NASA Ames Research Center, Moffett Field, Calif. Phone: 650/604-5026 or 650/604-9000 E-mail: jbluck@mail.arc.nasa.gov RELEASE: 02-131AR NASA TREE-RING STUDY REVEALS LONG HISTORY OF EL NIŅO El Niņo is not a new weather phenomenon, according to a recent NASA study that looks 750 years into the past using tree-ring records. Utilizing special computer techniques, a NASA scientist has linked tree-ring widths -- a natural record of local and regional climate conditions -- with sea surface temperatures (SST) to compile a record that looks back three-quarters of a millennium, indicating that El Niņo caused heavy rain in some places in South America and droughts in other areas. "We feed the computer model with past tree-ring data, and this model 'hind casts' past sea surface temperatures," said Hector D'Antoni, a scientist at NASA Ames Research Center in California's Silicon Valley. "We can go back in time and reconstruct some of the factors controlling ecosystems." An ecosystem is a system composed of living organisms and their environment. "The hypothesis I had all along was that the El Niņo Southern Oscillation (ENSO) is not a new component of the global climate system, and that ENSO effects on South America were not new or negligible," he said. "Sea surface temperatures of both the Atlantic and Pacific oceans in tropical and subtropical locations have a strong influence on the temperate forests of South America. Therefore, one can expect to find some 'signal' of these drivers in the collection of tree rings over a period of time."