The cataclysmic ice age scenario depicted in the upcoming movie, "The Day After Tomorrow," gets the mechanics of global warming mostly right, but wildly exaggerates the speed at which it might occur, says a Duke University oceanographer who studies North Atlantic ocean currents.
The type of global climate change that happens in the movie -- where global warming diverts warm ocean currents and plunges the world abruptly into a new ice age -- could possibly happen in real life, "but it would take many, many decades or even a century or more," said Susan Lozier, the Truman and Nellie Semans/Alex Brown & Sons Associate Professor of Earth and Oceans Sciences at Duke's Nicholas School of the Environment and Earth Sciences.
"Hollywood time is not, obviously, the same as geological time," Lozier said.
Lozier is a principal investigator in a five-year, National Science Foundation-funded study of the circulation pathways of North Atlantic currents, and has published findings from her work in Science, the Journal of Physical Oceanography and other leading journals.
Despite its inaccuracies, Lozier thinks "The Day After Tomorrow," slated to open May 28, may prove beneficial to the policy debate about global warming by raising public awareness of the oceans' role in climate and climate change.
"When people think about global warming, they think about the whole world getting warmer due to greenhouse gases. They may not realize that some parts will get warmer and some will get colder, some will get wetter and some will get drier, due in part to changes in ocean currents," Lozier said.
The oceans store a tremendous amount of heat from the sun, and their currents act like a giant conveyor belt, redistributing that heat around the globe, she explained. The Gulf Stream, for example, carries tropical warmth far into the North Atlantic, giving western Europe a mild, moist climate despite its northerly latitude.
Current paths are driven by the prevailing winds and density differences that exist between cold and warm water, and salty and fresh water. Alter any of these factors, Lozier said, and a current's path will change, altering over time the climate of lands in or near its path.
Her research -- including a paper in the January 2004 issue of Geophysical Research Letters that documents the warming and salinification of Mediterranean waters -- has identified subtle changes taking place in North Atlantic waters over the past 50 years. Waters at high latitudes, such as in the subpolar regions, are becoming colder, less salty and slightly less dense, while waters at low latitudes, such as those nearer the equator, are growing warmer, saltier and slightly denser.
"If this continues, it could, in theory, disrupt the circulation of North Atlantic currents and cause them to slow or eventually shut down," Lozier said. "Earth goes in and out of ice ages, and this is a process that continues today. Only it doesn't happen anywhere nearly as suddenly as it does in the movie. That's pretty far-fetched. It's like saying someone can run the mile in less than a second."
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