Temperature anomalies during the 1997-1998 El Niño event. Image: NASA
Last updated June 17, 2019
Mar 5, 2015
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Jun 9, 2016

Extreme El Niño 2015 - 2016

Niño 3.4 region

The 2015-2016 El Niño officially tied the 1997-1998 event as the strongest El Niño on record, the National Oceanic and Atmospheric Administration announced the first week of January 2016.

Research has shown that the exceptional warmth observed during the event was unlikely to have occurred entirely naturally, and appears to reflect an anthropogenically forced trend.[1]

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Central Pacific warmth during the 2015-2016 El Niño was unprecedented

The 2015-2016 El Niño was not wholly unexpected. For years, the oceans have absorbed most of the added heat trapped by greenhouse gases. What we saw during the 2015-2016 El Niño was some of this heat reemerging.

The strength of an El Niño is measured by the surface temperature of the Pacific Ocean, and from October through December 2015, the water temperature was 2.3°C above average, tying the temperature departure during these months for the 1997-1998 event.

A 2017 study found that the warmth in the central equatorial Pacific was unprecedented in nearly all SST reconstruction datasets, and the warmth seen in the eastern equatorial Pacific could be expected roughly once every 40 years.[1]


Extreme El Niños and global warming

Predicting how El Niños evolve in a warming planet is extremely challenging. The factors involved are far from well understood. However, the most recent model projections tell us that we may expect extreme El Niños (and La Niñas) to happen more frequently. Records tend to be broken when natural variation runs in the same direction as climate change, and this El Niño event moved along on a record-breaking path.


Extreme El Niño Impacts

There are features of the climate system that can complicate the complex work of predicting El Niño-driven global weather patterns. One such example is the “the cold blob” in the north Atlantic that appears to be caused by ice water running off the melting Greenland ice sheet and is affecting ocean currents.


Changes to El Niño increase risk in the United states

Predicting exactly what this El Niño will do to extreme weather in the United States is challenging. We are now in uncharted territory. The 2015-2016 El Niño was not only warmer, but its effect reached much further west than El Niños in the past. It may also be connected to record-breaking ocean temperatures along the west coast of Baja and further north.

The regional features of our climate system are becoming harder to predict due to climate change. Disaster usually strikes when a threshold is crossed. Our economic infrastructure has been built to withstand the known historical extremes; similarly, our natural ecosystems have evolved to cope with those same extremes. When faced with new extremes, however, these systems often collapse. The rising unpredictability of regional changes like El Niño magnifies the risks we face from extreme events.