Wednesday, March 21, 2001

Axel Timmermann, post-doctoral researcher at UH,
is a specialist on the earth's climate.

German physicist
contemplates the
harmony of
weather cycles

He is forming a research group
to continue work he started
here on El Nino events

By Helen Altonn

Axel Timmermann studied church music as a youth and hoped to become a famous organist. At age 30, however, his vision has shifted to physical forces. His goal: To understand Pacific climate changes.

Timmermann is finishing six months of collaboration with University of Hawaii meteorologist Fei-Fei Jin at the International Pacific Research Center.

He began looking at evidence that large El Nino events occur with regularity while earning a doctorate degree in theoretical physics in Hamburg, Germany, and doing postdoctoral work at the Royal Dutch Weather Service in the Netherlands.

He is forming a research group in Kiel, Germany, to continue the work after leaving in about two months.

Timmermann said it appears that there are episodes of strong El Ninos for five to eight years followed by periods of calm. He doesn't think El Ninos can be predicted but believes there is some kind of predictability to the ENSO (El Nino/Southern Oscillation) cycle.

ENSO refers to fluctuations in the ocean-atmosphere dynamics that lead to opposite extremes in eastern tropical Pacific sea surface temperatures -- warmer with El Ninos and abnormally cold with La Ninas.

Klaus Wyrtki, 76, retired University of Hawaii scientist regarded as the "grand old man" of physical oceanography, said climate prediction isn't a black-and-white matter.

Prediction involves many different aspects, he said, "and one has to be quite specific when one wants to predict something. You can say the summer season on the West Coast will be rainy -- that's probably predictable. But when the storm comes is not predictable."

Timmermann is looking at "a completely different kind of predictability" based on old and new data fed into computer models. He's interested in paleoclimatology research studying climate changes over centuries from ice cores, ocean corals and other ancient records.

"In Kiel, we will try to come up with a computer model which simulates both paleo stages and present (global) warming stages," he said.

Three groups in Europe are doing computer modeling, working in the same direction, he said.

He hopes to improve on a model and do "sensitivity studies," switching off different components, such as the ice sheet, to see how the ocean circulation behaves.

"We will see what is the role of the ice sheet, then the role of the atmosphere in generating very quick and rapid transitions" such as occurred in the last glacial period, he said.

"These are changes that have a time scale of about 1,500 years. They are so interesting because the climate over Europe warmed by 10 degrees Fahrenheit in 10 years."

Isotope measurements in Greenland ice cores show very rapid sawtooth-like changes occurred, he said.

He cites four theories for the transitions: Ice sheet instability, coupling of the ocean-atmosphere system, a change in the solar radiation output and very long tides in the ocean. He noted an "exotic theory" suggesting the ocean circulation was changed through mixing of warm and cold water in ocean for 1,800 years.

He favors the solar variability theory, explaining, "There is at least evidence from cosmosgenic isotope records that there is change in the solar energy output."

But there is some regularity in extreme interannual changes in El Ninos and La Ninas, he said. "There is predictability beyond the classic predictability scale -- six to 12 months for an El Nino, then most people give up and say they can't predict any further.

"In a way they're right. I'm not predicting the next El Nino but the next strong ENSO era, which can be done eight to 10 years in advance."

A significant change occurred in the ENSO between the 1970s and 1980s, with periods stronger and longer in the 1980s, he said. "At the same time, the temperature pattern in the ocean was different, and timing was different when the ENSO started."

No picture completely repeats itself.

Timmermann added, "It may be that small deviations are important to kick off something in the ocean which may lead to a turnaround.

Wyrtki, who joined UH-Manoa in 1950 from the University of Kiel, said scientists "are basically in the beginning phases of serious climate prediction. Science is always advancing, and in 20 or 50 years we will know a lot more.

However, climate is such a complex process, he said, the conclusion may be "that certain things are not predictable."

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