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January 23, 1999

Long-term forecasting could give nations tools to survive climate change

News and Information

ANAHEIM, Calif. – Long-term climate phenomena like the one that triggered the Dust Bowl have happened throughout history, sometimes toppling entire civilizations. But scientists increasingly are able to peer into the future to see how cycles such as the El Ni?outhern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO) might affect weather a year or even a decade from now.

That ability can give developed nations time to mitigate the effects of a potential climate catastrophe, a University of Washington climatologist said today at the annual meeting of the American Association for the Advancement of Science.

“We assume the next 10 years will be like the last 10 years, and that’s not true,” said Edward Sarachik, an atmospheric sciences and oceanography professor. He was among six scientists addressing an AAAS symposium on the Frontiers of the Physical Sciences.

There are indications that decadal climate variability has been a constant feature of Earth’s environment but happens so slowly that humans are only dimly aware of it, Sarachik said.

Research shows the world has long been subject to prolonged climate cycles. For instance, the Dust Bowl that plagued North America’s Great Plains in the 1930s, devastating the nation’s breadbasket and driving thousands of people from their farms, paled in comparison to severe and longer droughts in the same region before A.D. 1200. Long-term drought also is believed to have been significant in the collapse of the Mayan culture of Central America between 750 and 900.

Evidence of climate events long past has helped in understanding cycles that can span years or even decades, Sarachik said. Underdeveloped nations could be severely crippled with just one bad year of drought or flooding. For instance, Peru’s fishing industry was battered by the effects of El Ni?wo years ago, severely curtailing the nation’s food supply.

Developed nations such as the United States can withstand one or two years of severe conditions, but long-term affects such as the Dust Bowl could cause havoc in what has become the breadbasket of the world, Sarachik said. If public and private agencies correctly use long-term information, they could lessen the impacts of climate change, possibly even ensure cultural survival. But they must ask the right questions. For example, with growing evidence of global warming – either caused by man or resulting from natural cycles – policy makers should focus more on mitigating the effects rather than trying to reverse the trend, he said.

“It may turn out that in 100 years that’s the difference between the United States being a great nation and a nothing nation,” he said. Reversing the trend might not even be possible, he added, particularly if society is unwilling to take the needed steps, which could be quite severe.

Sarachik is among atmospheric scientists researching climate cycles for the Joint Institute for the Study of Atmosphere and Ocean at the University of Washington. That research has brought understanding to the mechanisms by which ENSO triggers El Ni?uring its positive phase and La Ni?uring its negative phase, and has led to greater ability to forecast the phenomena. It also has pinpointed the much-longer-term PDO cycles, and scientists are beginning to understand how the PDO influences ENSO to magnify the effects of El Ni?r La Ni?In fact, effects of the current La Ni?re being heightened because the PDO is in its positive, or cold, phase, Sarachik said.

Long-term climate variations also have been identified in other parts of the world. Scientists are beginning to understand how they can have wide impacts by themselves and even wider effects when they operate in concert with each other. Sarachik expects forecasting arrays, making measurements above and beneath the ocean’s surface, eventually to be installed where there currently is little data, such as the South Atlantic and the Indian Ocean.

“There is a decadal oscillation out in the Pacific and it matters,” Sarachik said. “It affects temperature and precipitation all across the United States. There is a decadal oscillation in the North Atlantic that affects temperature and rainfall in Europe and Asia.” When those decadal oscillations synchronize with each other, the effects can be severe throughout the Northern Hemisphere and can be made worse by other climate cycles, he said.

Crucial to properly using long-term climate forecasts, Sarachik said, is understanding how climate, nature and people interrelate. Without that understanding, policy makers could pursue ways to protect people that ultimately would harm nature, or protect nature at the expense of people. An emerging discipline called “end-to-end forecasting” combines physical and social sciences to consider the scientific data that foretells climate change, the probable impacts of that change on people and nature, and possibilities for lessening the impact of the change or taking advantage of it.

“The more I think about the future, the more I think of it in terms of risk management and risk avoidance,” he said. “The fact that we can now peer slightly into the future – and as time goes by, more and more – offers an exciting opportunity for humankind to affect its own destiny.”


For more information, contact Sarachik at (206) 543-6720 or by e-mail at From Thursday through Saturday, during the AAAS convention, he can be reached by leaving a message at the Anaheim Hilton, (714) 750-4321, or at the AAAS press room, (714) 750-4321.