May 3 - Here are five facts about the science of hurricanes and global warming:
*Hurricanes are engines that require warm, moist air as fuel and need ocean temperatures of at least 80 degrees Fahrenheit (26.5 degrees C) to form and grow. That warm water must be present to a depth of about 150 feet (50 m).
*While scientists generally agree sea-surface temperatures have gone up -- perhaps 1 degree Fahrenheit in the last 30 years -- there is disagreement as to whether human-caused greenhouse gases are responsible and whether warmer water is affecting the formation and intensity of hurricanes. Some scientists believe the increased number of storms in the Atlantic and Caribbean since 1995 is due to a natural cycle rather than global warming.
*Hurricane intensity is measured by the atmospheric pressure at their core -- the lower the pressure, the more powerful the storm. Last year's Hurricane Wilma, with an estimated central pressure of 882 millibars, was the most intense Atlantic hurricane ever recorded. Wilma, Katrina, Rita and Emily were all Category 5 hurricanes; the first time a single season produced four Category 5s.
*A recent study by Georgia Institute of Technology researchers found that the number of Category 4 and 5 hurricanes around the world has nearly doubled over the past 35 years.
*According to a study by Kerry Emanuel, a professor of atmospheric science at the Massachusetts Institute of Technology, the duration and strength of hurricanes have increased by about 50 percent over the last three decades.
REUTERS NEWS SERVICE
