Strong El Niño Continues

El Niño in a Warming World

Did You Know?

  • The strongest El Niño on record occurred between 1997 and 1998.
  • The August 2015 average sea surface temperature in the Pacific Ocean was the second highest on record (1.49°C above normal). The highest on record occurred in 1997 (1.74°C above normal).

The El Niño-Southern Oscillation (ENSO) is the periodic warming and cooling of the central and eastern tropical Pacific Ocean. This warming and cooling changes how air in the upper-atmosphere moves, which in turn affects global and regional temperature, precipitation, and wind patterns. The term El Niño describes warming of the central and eastern tropical Pacific and the term La Niña describes cooling of waters in the same region.

El Niño events occur every two to seven years on average. Currently, one of the strongest El Niño events on record is occurring – it is expected to peak in winter and begin to weaken through spring 2016. In the United States, El Niño conditions in the Pacific are usually associated with increased rainfall and flooding in the Southwest and decreased rainfall in the Northwest. For instance, California and other regions of the Southwest experienced historic flooding and landslides during the 1997-1998 El Niño event. Along with changes in precipitation, El Niño years also tend to be warmer than average globally.

Scientific studies suggest that ENSO activity has been highest over the last 100 years compared to the previous 500 years. In a recent study published in Nature Climate Change, researchers show that the occurrence of El Niño events could double in the future due to a warming climate.

Scientists study satellite sea surface height data to determine sea surface temperatures. Higher sea heights indicate warmer temperatures because warmer water expands to fill more volume. The NASA image below compares the sea surface height in the Pacific in July 1997 and 2015.

The video below demonstrates how warm water in the central Pacific can influence prevailing pressure and precipitation patterns.

Learn More:


  • Cai, Wenu, Simon Borlace, Matthieu Lengaigne, Peter van Rensch, Mat Collins, Gabriel Vecchi, Axel Timmermann, Agus Santoso, Michael J. McPhaden, Lixin Wu, Matthew H. England, Guojian Wang, Eric Guilyardi and Fei-Fei Jin. 2014. "Increase Frequency of Extreme El Niño Events Due to Greenhous Warming." Nature Climate Change 4: 111-116.
  • Melillo, Jerry M., Terese (T.C.) Richmond, and Gary W. Yohe, Eds. 2014. Climate Change Impacts in the United States: The Third National Climate Assessment. Washington: U.S. Global Change Research Program.
  • NASA. 2015. "El Niño Conditions are Growing Stronger." Accessed October 8.
  • NOAA.2014. "What is the El Niño-Southern Oscillation (ENSO) in a nutshell?" Accesesed October 8, 2015.
  • NOAA. 2015. "September 2015 El Niño Update and Q&A." Accessed October 8.