Hurricane Activity High In Medieval Warm Period, Study Shows

The Atlantic Ocean and Caribbean experienced a large number of hurricanes from 900 to 1200 AD, a period when air and sea temperatures were high, according to a new study. After examining sediment deposits in coastal lagoons at seven sites in the U.S. and one in Puerto Rico, meteorologist Michael Mann of Penn State University and colleagues determined that up to 15 hurricanes a year struck the western Atlantic about 1,000 years ago — roughly equal to the number recorded in the past 15 years. But Mann said that the current spate of hurricanes is due primarily to higher ocean temperatures in the Atlantic and Caribbean, while the greater incidence of hurricanes a millennium ago was attributable both to warmer Atlantic temperatures and anomalous conditions in the Pacific that weakened the jet stream and allowed more hurricanes to form in the Atlantic. Mann said his study indicated rising ocean temperatures will likely lead to more frequent and intense hurricanes. Meanwhile, a study by researchers at the National Oceanic and Atmospheric Administration suggests that one reason more hurricanes have been reported in recent decades is because storm detection techniques have improved markedly.