May 13, 2011 - By Charles Q. Choi - Ancient trees reveal that the El Niño and La Niña events that wreak havoc on climate worldwide have been even more extreme than anyone knew, a revelation that suggests wilder swings in the future as the world gets warmer. El Niño and La Niña are the warm and cold phases, respectively, of the pattern known as the El Niño Southern Oscillation (ENSO) in the eastern half of the tropical Pacific. Forecasting how this pattern will behave a few months in advance is now routine. However, the task of predicting its long-term behavior is hampered by the relatively short history scientists have of monitoring it. Now an international team of scientists has peered back into the history of this climate pattern by analyzing trees up to 1,100 years old.
http://www.ouramazingplanet.com/tree-ring-el-nino-records-climate-change-1516/