Historic storms live again

摘要

In september 1813, a major hurricane destroyed US gunboats and ships that were defending St Mary's, Georgia, from the British. Fifty sailors drowned. In a letter to the US secretary of the navy, the commodore of the naval task force wrote that a privateer named Saucy Jack had been deposited so high on the marshes that the sea must have risen nearly 6 metres above its low water mark. Other letters of the time accurately described the passage of the eye of the storm and the timing of events. Such historical records are proving invaluable to researchers trying to understand long-term patterns in the frequency and intensity of the hurricanes that lash the US mainland. Last week, Isabel became the 15th hurricane to strike since 1990, feeding dire predictions that hurricanes are on the increase. But a historical analysis completed six weeks ago, combined with sophisticated computer models and modern hurricane-monitoring technology, has confirmed there is no such trend. Instead, hurricanes in the Atlantic come and go in cycles lasting a few decades. While that is good news for some, it is also a warning for coastal communities that may have seen no storms for a generation or more.