The study, which resulted from a detailed analysis of a continuous 10,000-year record of El Nino events from a lake in southern Ecuador, is the first documented evidence that such a millennial cycle exists for El Nino. The researchers found that the frequency of El Nino events peaked about 1,200 years ago, or during the early Middle Ages. If the pattern continues into the future, there should be an increase in El Nino events in the early part of the 22nd century, the scientists say.

"El Nino operates within its own kind of 2,000-year rhythm, and because of that, we believe these periodic changes have had a major impact on global climate conditions over the past 10,000 years," says Christopher Moy G'00, the lead author of the study and a 2000 graduate of Syracuse University. "El Nino is one of the primary forces that can alter climate around the globe during a short period of time."

The study is the result of work Moy did as a graduate student in the Department of Earth Sciences in Syracuse University's College of Arts and Sciences for his master's thesis. His advisor was Prof. Geoffrey Seltzer. In a 1999 study published in Science, Seltzer and Donald T. Rodbell, who was Moy's undergraduate advisor at Union College, discovered the first continuous record of El Nino events that dated back more than 5,000 years. That study was based on sediment samples taken in 1993 from the same lake in southern Ecuador--Lake Pallcacocha--as part of a larger global climate study on which they were collaborating.

This new study of El Nino events is based on another set of sediment cores taken in 1999 from Lake Pallcacocha, which is located in the Andes Mountains. The National Science Foundation funded the research.

Characterized by warm sea surface temperatures that appear off the western coast of South America, modern El Nino events cause dramatic changes in the weather systems across both the North and South American continents--from tumultuous rainfall in northern Peru and southern Ecuador to unusually warm and dry conditions in the northeastern United States.

Like the 1993 sediment core samples, the new core samples contain a series of light-colored sediment layers that contain the type of debris that would flow into the lake during periods of intense precipitation. In his analysis of the sediment layers, Moy confirmed results from the first study--that scattered El Nino events began about 10,000 years ago and steadily increased in frequency beginning about 7,000 years ago. In addition to that, he uncovered high-frequency clusters of El Nino events occurring on a 2,000-year cycle.

"About every 2,000 years, we see a lot of El Nino activity," says Moy, who is currently a graduate student at Stanford University and plans to pursue a Ph.D. in geology and environmental science. "This oscillation has not been seen in any other study of climate records of this area of the world, which makes this study unique. El Nino is an important part of our modern-day climate system. Likewise, our study shows it was also an important part of the earth's climate system 7,000 years ago. Understanding the past will help us to better understand future climate changes."

Seltzer says that Moy's study sheds new light on a tropical phenomenon that can radically alter climate conditions in a relatively short period of time. "We are extremely excited and pleased that the research Chris did as a Syracuse University graduate student is now being published in a premier, international journal and that he is moving toward greater accomplishments in the field. It's the ultimate outcome for our program and of a student-centered research university like Syracuse University."

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