Biology of Business

The definition of El Niño

Kevin E. Trenberth

Bulletin of the American Meteorological Society (1997)

TL;DR

Everyone knows El Niño is coming—the effects are predictable, the timing isn't. ENSO operates on 2-7 year cycles with certain disruption at uncertain times.

By Alex Denne

Standard scientific reference defining El Niño—establishing measurement thresholds for a 2-7 year climate cycle that creates predictable effects (droughts, floods) at unpredictable times. Explains the paradox of known cycles with uncertain timing.

Key Findings from Trenberth (1997)

  • ENSO operates on 2-7 year irregular cycles—predictable pattern, unpredictable timing
  • Defined specific temperature thresholds for El Niño classification
  • Primary driver of short-term climate variability globally
  • Creates droughts in Australia/Indonesia, floods in Peru, disrupted monsoons
  • Effects are known but timing cannot be precisely forecast