August 27, 2010 - A relatively new type of El Nino, which has its warmest waters in the central-equatorial Pacific Ocean, rather than in the eastern-equatorial Pacific, is becoming more common and progressively stronger, according to a new study by NASA and NOAA.

The research may improve our understanding of the relationship between El Ninos and climate change, and has potential significant implications for long-term weather forecasting. 

Lead author Tong Lee of NASA?s Jet Propulsion Laboratory, Pasadena, Calif., and Michael McPhaden of NOAA?s Pacific Marine Environmental Laboratory in Seattle measured changes in El Nino intensity since 1982. They analyzed NOAA satellite observations of sea surface temperature, checked against and blended with directly-measured ocean temperature data.

El Nino (Spanish for ?the little boy?) is the oceanic component of a climate pattern called the El Nino-Southern Oscillation, which appears in the tropical Pacific Ocean on average every three to five years. The most dominant year-to-year fluctuating pattern in Earth?s climate system, El Ninos have a powerful impact on the ocean and atmosphere, as well as important socioeconomic consequences. 

They can influence global weather patterns and the occurrence and frequency of hurricanes, droughts and floods; and can even raise or lower global temperatures by as much as 0.2 degrees Celsius (0.4 degrees Fahrenheit). 

During a ?classic? El Nino episode, the normally strong easterly trade winds in the tropical eastern Pacific weaken. That weakening suppresses the normal upward movement of cold subsurface waters and allows warm surface water from the central Pacific to shift toward the Americas. In these situations, unusually warm surface water occupies much of the tropical Pacific, with the maximum ocean warming remaining in the eastern-equatorial Pacific. 

Since the early 1990s, however, scientists have noted a new type of El Nino that has been occurring with greater frequency. Known variously as ?central-Pacific El Nino,? ?warm-pool El Nino,? ?dateline El Nino? or ?El Nino Modoki? (Japanese for ?similar but different?), the maximum ocean warming from such El Ninos is found in the central-equatorial, rather than eastern, Pacific. Such central Pacific El Nino events were observed in 1991-92, 1994-95, 2002-03, 2004-05 and 2009-10. 

Studies have hypothesized that global warming due to human-produced greenhouse gases could shift the warming center of El Ninos from the eastern to the central Pacific, further increasing the frequency of such events in the future.