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Study says El Nino slows Earth's rotation
Reuters, Wednesday May 27 6:51 AM EDT

If you have noticed the days are getting a little longer, you are right - and it's not just the change of season - scientists said Tuesday. Researchers gathered in Boston for a meeting of the American Geophysical Union blamed El Nino and its effects on the atmosphere for slowing the Earth's rotation by almost a thousandth of a second. "The energy is going from the Earth into the atmosphere. The Earth is slowing down," NASA's Goddard Space Flight Center scientist Dr. John Gipson told reporters. He estimated that at its peak in July 1997, El Nino slowed the Earth's rotation by 800 microseconds. Throughout the El Nino period, which is expected to taper off later this summer or in the fall, the Earth's rotation has slowed by an average of 300 to 400 microseconds, Gipson said. "My guess is that following the current El Nino, we're going to through one of those periods where the Earth speeds up and makes the days shorter" in a La Nina episode, Gipson said.

This is not the first time an El Nino has made the days longer. The 1982-83 El Nino also slowed the Earth's rotation, but not by such a large amount, the scientists said. During an El Nino, the ocean temperature is raised in the eastern Pacific and reduced in the western Pacific. The phenomenon, which has been blamed for floods in Ecuador, droughts in Indonesia and ice storms in Quebec and the U.S. northeast, changes the ocean currents and the intensity and direction of atmospheric winds. This large scale shift in winds and currents changes the length of day by an amount measurable by sophisticated space-based methods. La Nina is the opposite phenomenon with the water temperature in the western Pacific rising, while the eastern Pacific gets colder. It too affects the Earth's rotation causing it to speed up, but "only about three-quarters as much" as El Nino slowed it down, Gipson said.

Dr. Jean Dickey of NASA's Jet Propulsion Laboratory said that while the average person would probably not be affected by such a small shift in the Earth's rotation, "it plays a very important role in inter-planetary navigation." She called it a "critical factor in the success of the Pathfinder mission to Mars." University of Texas at Austin Professor Byron Tapley added the speed of the Earth's rotation was also key to the functioning of the Global Positioning System (GPS) used by ships, planes and the military.