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Earth Relief MapAugust 29, 2000 — El Niño, La Niña, move over. NOAA scientists and their colleagues are looking at another pattern in the world's climate, this one focused in the North Atlantic and lasting about seven decades.

In a paper to be published in the September issue of the journal Climate Dynamics, scientists at NOAA's Geophysical Fluid Dynamics Laboratory in Princeton, N.J., and the University of Virginia explain their work with computer models trying to simulate observed changes in the sea surface temperatures over the North Atlantic.

"The results from our computer models agree with what can be seen in the observed climate system," said Thomas Delworth, a GFDL meteorologist. "There appears to be a distinct temperature swing that lasts about 70 years. What we still need to look at is how this affects the ocean-atmosphere relationship and ultimately, our climate and its future changes."

Observed records, or data gathered from instruments, exist for only the last 150 years, and are thus of limited value for studying climate changes on the multidecadal to centennial time scale. To overcome this limitation, scientists use proxy records—such as ice cores, tree rings, and coral growth—to look for deviations in temperature records over longer time scales.

Delworth and colleague Michael Mann of the University of Virginia in Charlottesville, used proxy records of temperature changes over the last 330 years. What they found was a distinct oscillation or swing in temperature around the North Atlantic Ocean that lasts about 70 years.

"We also ran two versions of a computer model that came up with the same variability and the same pattern," Mann said. "The similarity between the pattern of the surface temperature variability produced by the model and that observed in climate reconstructions based on long-term ‘proxy' climate data is striking."

Delworth said this is significant because it adds another level of understanding about how our climate works and will help in long-range climate forecasting.

"We are also looking at the effect such events may have on the circulation of the oceans," Delworth said. "Changes in ocean circulation can have a substantial impact on climate by altering how much heat is moved from the warm tropical regions to colder higher latitudes. We also need to look at what effects, if any, this may have on other climate patterns, such as the frequency of hurricanes.

"If you think of climate as a puzzle with many pieces making up the whole, what we have found is another important piece of that puzzle."

Relevant Web Sites
NOAA's Geophysical Fluid Dynamics Laboratory

NOAA's Revised Relief Globe Slide Set

NOAA's Climate Page

Media Contact:
Jana Goldman, NOAA Research, (301) 713-2483 ext. 181.