Climate Science: Interannual Scale
ENSO's Irregular Pulse
There is ongoing debate within the research community on whether or not ENSO and other climate patterns such as the Pacific Decadal Oscillation are in fact really oscillations or something else. The term oscillation suggests a regular frequency like a pendulum swing, but ENSO events exhibit a chaotic quality and are difficult to predict even though they can occur several times a decade. Once an event begins to clearly emerge, however, its impacts can be fairly well forecast.

This animation of recent Sea Surface Temperature (SST) is provided by the NOAA-CIRES Climate Diagnostics Center. (See details below.)

Research is recently being focused on why ENSO is irregular in its nature. Some suggest it is internal noise such as weather (Suarez, 1988 , Penland, 1993), while others are exploring to determine if there is an inherent nonlinearity of the coupled atmosphere/ocean system (Mantua, 1994 ). Others are exploring how changes in the external forcing, such as carbon dioxide concentrations could be contributing to ENSO events (Knutson, 1994 ), while some researchers are exploring the relationships between ENSO and annual and interannual events (Tziperman, 1994).

Reynolds SST data provided by the NOAA-CIRES Climate Diagnostics Center, Boulder, Colorado, USA.

Return to Climate Science 10 Years