Hollywood time is not geological time

The cataclysmic ice age scenario depicted in "The Day After Tomorrow" gets the mechanics of global warming mostly correct, but wildly exaggerates the speed at which it might occur, reveals a Duke University, Durham, 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 abruptly plunges the world into a new ice age--possibly could happen in real life, "but it would take many, many decades or even a century or more," assures Susan Lozier, Truman and Nellie Semans/Alex Brown & Sons Associate Professor of Earth and Oceans Sciences at the Nicholas School of the Environment and Earth Sciences. "Hollywood time is not, obviously, the same as geological time."

Despite its inaccuracies, Loziar thinks "The Day After Tomorrow" may prove beneficial to the policy debate about global warming by raising public awareness of the oceans' role in climate and weather fluctuations. "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."

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 explains. 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 salt and fresh water. Alter any of these factors, Lozier indicates, and a current's path will change, modifying over time the climate of lands in or near its path. Her research has identified subtle fluctuations 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. 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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