Hurricanes Growing More Fierce Over Past 30 Years

In his new analysis of tropical hurricane records, which he reportsonline today in the journal Nature, Emanuel finds that both theduration of the storms and their maximum wind speeds have increased byabout 50 per cent since the mid-1970s. Moreover, this marked increasein the energy release has occurred in both the north Atlantic and thenorth Pacific Oceans.

Unlike previous studies, which have focused on whether hurricanesare becoming more frequent, Emanuel's study is one of the first to askwhether they are becoming more fierce.

"It's an innovative application of a theoretical concept, and hasproduced a new analysis of hurricanes' strength and destructivepotential," says Jay Fein, director of the National Science Foundation(NSF)'s climate dynamics program, which funded the research. And thatanalysis, in turn, "has resulted in an important measure of thepotential impact of hurricanes on social, economic and ecologicalsystems,"

Indeed, as Emanuel himself says, "the near doubling of hurricane'spower over the period of record should be a matter of some concern, asit's a measure of the [future] destructive potential of these storms."

Also of concern, he says, is that the increases in storm intensityare mirrored by increases in the average temperatures at the surface ofthe tropical oceans, suggesting that this warming is responsible forthe hurricanes' greater power. Since hurricanes depend on warm water toform and build, Emanuel warns that global climate change might increasethe effect of hurricanes still further in coming years.

In addition, he says, recent research suggests that global tropicalhurricane activity may play a role in driving the oceans' circulation,which in turn has important "feedbacks" to regional and global climate.

Fluctuations in tropical hurricane activity "are of obviousimportance to society," he adds, "especially as populations of affectedareas increase. Hurricanes account for a significant fraction ofdamage, injury and loss of life from natural hazards, and are thecostliest natural catastrophes in the United States. As the humanpopulation in coastal regions gets denser, the damage and casualtiesproduced by more intense storms could increase considerably in thefuture."