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NOAA-Funded Research Probes Effect of Climate Change on El Niño

Scientists Note Possible Connection of 1918/1919 El Niño to Flu Pandemic

By any account, 1918 was a difficult year. It saw the end of World War I, a flu pandemic that claimed millions, severe drought in India, and revolutions in four countries. With so much turmoil, it is no wonder the mundane collection of ocean temperature data was not a high priority.

El Niño returns in 2009: A satellite image of the climate phenomenon called El Niño in 2009. Characterized by higher sea-surface temperatures and low ocean surface winds in the Equatorial Pacific, a strong El Niño in 1918 and an ensuing drought in India may have contributed to a higher death rate in Asia from the flu pandemic that swept the world that year, according to NOAA scientists conducting a reanalysis of past weather and climate.

Nonetheless, by the scant measurements that were made that year, scientists have known that 1918 was also an El Niño year. Spanish for "the child", El Niño is the name climate scientists have given the occasional periods of Pacific Ocean warming that play havoc with global weather patterns. For example, El Niño is known to intensify winter storms for residents of the West Coast, Gulf states, and southeast United States. El Niño also dampens Atlantic hurricane formation and can increase the number of Pacific hurricanes.

Scientists today are trying to learn more about El Niño because its disruption of global weather patterns has broad consequences for agriculture, energy consumption, and public safety. Some have proposed that global warming is intensifying El Niño and its influence on weather. The strong El Niño events of 1982/1983 and 1997/1998 support this idea. To explore the possibility more closely, Benjamin Giese, Ph.D., at Texas A&M University, recently led a team of scientists in a reanalysis of the 1918/1919 El Niño.

This NOAA Climate Program Office-funded study shows that the 1918/1919 El Niño was one of the strongest of the 20th century, a finding counter to earlier analyses that viewed it as weak. This research could ultimately lead to a better understanding of how El Niño events impact weather in the United States and globally.

Photo Credit: National Library of Medicine
More American died from the influenza pandemic in 1918 than were killed in World War I, and as many as 18 million people in India, already suffering from hunger and lack of potable water, may have perished from flu virus.

And although improving our understanding El Niño was the team’s principal aim, the scientists also made an observation that El Niño might have influenced the high death rate of the 1918 influenza pandemic in India. Giese points out that when El Niño is located in the central Pacific, as it was in 1918, its has a strong influence on the summer monsoon rains in India.

In 1918, the summer monsoon rains – so necessary for India’s agriculture – failed to develop. Severe drought ensued and coincided with the flu pandemic that was sweeping the globe at that time. Tragically, influenza killed an estimated 18 million people in India. Globally, the 1918 pandemic is thought to have claimed about 50 million lives.

"1918 was one of the worst droughts of the 20th century in India. There was famine and a lack of potable water, thus a compromised population," says Giese, careful to point out that he is an oceanographer and not an epidemiologist. "It is clear that climate played a role in the mortality of people in India. This is an example of how climate can impact human health. I think it raises intriguing questions."

The influence of climate on human health is a concern today as scientists try to predict how global climate change will impact weather patterns and also expand the range of disease-causing organisms. Giese’s observation about the 1918/1919 El Niño and flu mortality is also drawing attention as his team’s study coincides with an El Niño and flu pandemic in 2009. However, while his team raises intriguing questions on climate and health, it provides solid new information about the 1918/1919 El Niño.

Just how did they do that with a dearth of ocean temperature data from the World War I era?

The research team relied on a newly available atmospheric circulation dataset covering 1908 through 1958 to draw a more complete picture of the 1918/1919 El Niño. During World War I, ocean and atmospheric observations were sparse. The lack of direct observations has hampered understanding of the 1918/1919 El Niño.

The new atmospheric dataset, produced by NOAA and University of Colorado scientists through the 20th Century Reanalysis Project, filled in missing atmospheric data needed to produce a computer model of ocean conditions for that time period.

Drought conditions like this could have been caused in India by a strong El Niño in 1918. The Indian drought led to crop failures, which in turn compromised the nutrition of the population and their ability to withstand the flu virus.

"What people have been doing to look at past El Niños is to use very sparse datasets and extrapolate based on patterns we know about during recent years," Giese explains. "But those patterns can change."

The team discovered that the pattern of the 1918/1919 El Niño was quite different than those observed in recent years. It was strong in the central Pacific but not along the South American coast. Since most of the observations in 1918 were along the coast, those observations missed the region of greatest warming.

The study refines our understanding of El Niño and climate change. The results from the scientific team’s "hindcast" portray El Niño events as stronger at the beginning and end of the 20th century with weaker events in the middle. The scientists say that their method could be applied to other El Niño events for which observed measurements were sparse.

Co-authors include Gilbert Compo, Prashant Sardeshmukh, and Jeffrey Whitaker of NOAA’s Earth System Research Laboratory; Niall Slowey and Sulagna Ray of Texas A&M University; and James Carton of the University of Maryland. Compo and Sardeshmukh are also affiliated with CIRES, the Cooperative Institute for Research in Environmental Sciences, a joint institute of the University of Colorado at Boulder and NOAA.

The study, "The 1918/1919 El Niño," is published in the Bulletin of the American Meteorological Society and is available online at http://dx.doi.org/10.1175/2009BAMS2903.1.

January 14, 2010

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