Contact: Gisela Speidel
University of Hawaii at Manoa
Caption: This graph shows El Niņo amplitude derived from North American tree rings (blue) and instrumental measurements (red). The green curve represents the long-term trend in El Nino strength. (Individual El Niņo events occur typically at intervals of 2-7 years.) Periods of strong El Niņo activity are indicated by amplitudes above 1.0. Superimposed on a general rising trend, cycles of strong activity occurred about every 50-90 years.
Credit: International Pacific Research Center
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Related news release: Tree rings tell a 1,100-year history of El Niño