Climate Change

While the debate over global climate change and its causes rages on, no one really knows what the climate will do in the next 10, 50, or 100 years.

Now scientists think important clues to climate change lie in water circulation patterns in the deep ocean. Ocean currents play a key role in creating climate by redistributing heat from the earth’s equator toward the poles. By studying the ocean, they say, we may one day be able to make long-range predictions of global climate change that could be worth billions of dollars to society.

”We do know that the ocean is capable of changing the climate,” says Carl Wunsch, Cecil and Ida Green Professor of Physical Oceanography. ”El Niño, the warm water phenomenon in the Pacific, shows this on a rather short time scale.”

Wunsch says climate change is inevitable and that we must plan for it. ”Just knowing what variety of wheat to plant, given that you’re going to have 30 percent less rainfall one year, would be enormously valuable,” he says, adding that the oil and electricity industries could also use such information to plan their supplies more efficiently.

Constant change

”We know the climate has been very different in the past,” Wunsch says. ”And we strongly suspect one of the reasons is that the ocean has done something quite different in the past also.” Wunsch says the ocean is constantly changing, much like the atmosphere, and that the two systems interact to produce climate.

Observing changes in the ocean is difficult, says Wunsch, because its surface is largely impenetrable to the human or satellite eye and its salt content makes it inhospitable to radio signals. ”The real problem with the ocean is that because we don’t live there, we’re not normally aware of the changes that take place,” he explains. ”And until recently, the only way to study the ocean was to go there physically aboard a ship, which is tremendously expensive.”

Wunsch, who has spent plenty of time aboard ships, says he knew the solution had to be technological. ”I’ve spent the past 20 years trying to solve this observational problem with the ocean, in part because of these increasingly urgent questions about climate change,” he says, adding that the ultimate goal would be a global ocean observation system that could aid in climate prediction.

Recently Wunsch and his colleagues successfully tested a promising new high-tech system of ocean observation. The system combines a computer model of fluid motion, satellite measurements of the shape of the ocean’s surface, and acoustic data from a fixed array of sensors under the water.

”We had critics who said it would never work,” says Wunsch. ”But we managed to make sense of all the data.” The resulting maps, colorful and covered with tiny arrows, offer a detailed picture of the flow and temperature profile of huge expanses of deep ocean. Wunsch says the technology could be expanded to a global scale, providing continuous information about the entire ocean.

”This is an oceanographer’s dream,” he says of the data.

Predicting climate

Wunsch says that despite this breakthrough, the kinds of long-term climate predictions that could save society billions of dollars are still a long way off. ”The research is not at the stage of making predictions, but rather asking whether predictions are possible in principle,” he says. He points out that meteorologists can only make accurate weather predictions about eight days into the future.

”No weather center in the world would attempt to forecast weather two or three weeks out because it has been proven that you can’t do it. We don’t yet know whether we can forecast the climate one year or 10 years or 100 years out,” he says, adding that climate is largely an average of the day-to-day weather. ”However, last fall some forecasters did successfully predict increased rainfall in California this winter due to El Niño,” Wunsch says, pointing out that some climate phenomena may be more predictable than others.

Wunsch envisions a day when oceanographers will monitor the ocean’s circulation like the weather service does for the atmosphere. ”We will be able to say what went on in the North Pacific last week at 3,000 meters deep and 5,000 kilometers from shore,” he says. ”We might predict, for instance, that colder water at the ocean’s surface could create a change in weather systems.”

Predicting climate change is such an important goal, says Wunsch, because our climate will change no matter what we do. ”There’s no reason to think climate change will stop just because there are people around who don’t like it,” he says. ”The system has always changed in the past; it is surely changing now; it will surely change in the future. We have to plan for global climate change.”

by Eve Downing

On Topic: earth+atmospheric sciences, environment, faculty