The Atlantic Seaboard and the Caribbean face 10 to 40 years of stronger and more frequent hurricanes, a new analysis of weather data shows.
As a result, crowded coastlines and islands are confronted with the greatest risk of devastation in a generation, said the scientists who conducted the study.
Many meteorologists said the new analysis provided the firmest evidence yet that cycles in ocean and atmospheric conditions that suppressed big storms from 1971 to 1994 had shifted into a storm-spawning state.
The number and power of storms first jumped in 1995, but only now have enough years passed to measure a significant trend, the researchers said.
In a paper in today's issue of Science, they say the driving force is a periodic warming of the Atlantic north of the equator and a simultaneous drop in wind shear, the difference between trade winds near the surface and winds at higher altitudes.
Tropical storms thrive on energy and moisture supplied by warmer water. In addition, the lack of clashing winds aloft allows the resulting cyclones to mushroom miles high, the researchers reported.
Conditions were similar from the 1920s through the 1960s, the study said.
But coasts that were sparsely populated then are now dense with people and homes, said Stanley B. Goldenberg, the lead author of the study and a meteorologist at the National Oceanographic and Atmospheric Administration's hurricane research center in Miami.