Research conducted at Texas A&M University casts doubts on the notion that El Ni-o has been getting stronger because of global warming and raises interesting questions about the relationship between El Ni-o and a severe flu pandemic 91 years ago. The findings are based on analysis of the 1918 El Ni-o, which the new research shows to be one of the strongest of the 20th century.
El Ni-o occurs when unusually warm surface waters form over vast stretches of the eastern Pacific Ocean and can affect weather systems worldwide. Using advanced computer models, Benjamin Giese, a professor of oceanography who specializes in ocean modeling, and his co-authors conducted a simulation of the global oceans for the first half of the 20th century and they find that, in contrast with prior descriptions, the 1918-19 El Ni-o was one of the strongest of the century.
Giese's work will be published in the current "Bulletin of the American Meteorological Society," and the research project was funded by NOAA (National Oceanic and Atmospheric Administration) and the National Science Foundation.
Giese says there were few measurements of the tropical Pacific Ocean in 1918, the last year of World War I, and the few observations that are available from 1918 are mostly along the coast of South America. "But the model results show that the El Ni-o of 1918 was stronger in the central Pacific, with a weaker signature near the coast," Giese explains. "Thus the limited measurements likely missed detecting the 1918 El Ni-o."
Giese adds, "The most commonly used indicator of El Ni-o is the ocean temperature anomaly in the central Pacific Ocean. By that standard, the 1918-19 El Ni-o is as strong as the events in 1982-83 and 1997-98, considered to be two of the strongest events on record, causing some researchers to conclude that El Ni-o has been getting stronger because of global warming. Since the 1918-19 El Ni-o occurred before significant warming from greenhouse gasses, it makes it difficult to argue that El Ni-o s have been getting stronger."
The El Ni-o of 1918 coincided with one of the worst droughts in India, he adds. "It is well known that there is a connection between El Ni-o and the failure of the Indian monsoon, just as there is a well-established connection between El Ni-o and Atlantic hurricane intensity," Giese says. In addition to drought in India and Australia, 1918 was also a year in which there were few Atlantic hurricanes.