Plot of time (1950 to 2015) versus sea surface temperature anomalies (-2.5 to +2.5 degrees C)
Sea surface temperature anomalies (SSTA) from NOAA are used to determine when El Nino and La Nina conditions have occurred. This visualization shows a plot over time of SSTAs over a region of the Pacific Ocean called "Oceanic Nino Index Region 3.4". An El Nino happens when the SSTA is greater than 0.5 degrees C (shown in red); a La Nina happens when SSTA is less than -0.5 degrees C (shown in blue).
Over this period, several El Nino events occurred including: 1957-1958, 1972-1973, 1982-1983, and 1997-1998.
GCMD keywords can be found on the Internet with the following citation:
Olsen, L.M., G. Major, K. Shein, J. Scialdone, S. Ritz, T. Stevens, M. Morahan, A. Aleman, R. Vogel, S. Leicester, H. Weir, M. Meaux, S. Grebas, C.Solomon, M. Holland, T. Northcutt, R. A. Restrepo, R. Bilodeau, 2013. NASA/Global Change Master Directory (GCMD) Earth Science Keywords. Version 126.96.36.199.0