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The worst drought in over a thousand years of California’s history finally ended in the winter of 2014 when a series of storms poured millions of gallons of water over its drought-stricken coast.

This outpouring of water is referred to as an atmospheric river, and was caused in part by El Niño. El Niño refers to the phase of the natural three-to-five-year El Niño Southern Oscillation (ENSO) cycle, when east winds are weaker, and water in the Pacific warms. During an El Niño year, the west coast of the United States tends to receive more rainfall, however El Niño (and its opposite La Niña) have varying effects on global weather patterns.

  • What do scientists look for, and where, when determining whether it’s an El Niño, La Niña or normal year?
  • Which El Niño Southern Oscillation (ENSO) cycle is happening now?
  • What about last year?
  • Who and where is most affected by ENSO?
  • Does ENSO affect every part of the world the same way?
  • Why is ENSO considered one of the most important climatic phenomena on Earth?

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Sea Surface Temperature Anomaly - Real-time

Because El Niño is a shift in the temperature in the ocean, anomalies in sea surface temperature indicate the current status of the ENSO cycle. Look for cooler water off the Western coast of South America during El Niño events.