Hurricanes getting stronger due to global warming says study

Dramatic Satellite Photo: Hurricane Katrina moved ashore over southeast Louisiana and southern Mississippi early on August 29, 2005, as an extremely dangerous Category 4 storm.

With winds of 135 miles per hour (217 kilometers per hour), a powerful storm surge, and heavy rains, Katrina pounded the U.S. Gulf Coast, triggering extensive life-threatening flooding.

This GOES image shows the storm as it moved over southern Mississippi at 9:02 a.m. The eye of the storm was due east of New Orleans, Louisiana. Katrina moved north into Mississippi, and was expected to track quickly northeast across the United States into Eastern Canada over the first part of the week. (Image courtesy of the NASA Earth Observatory.)

SUMMARY

Late last month an atmospheric scientist at Massachusetts Institute of Technology released a study in Nature that found hurricanes have grown significantly more powerful and destructive over the past three decades.

Kerry Emanuel, the author of the study, warns that since hurricanes depend on warm water to form and build, global climate change might increase the effect of hurricanes still further in coming years.


Hurricanes Growing More Fierce Over Past 30 Years
National Science Foundation release

Hurricanes have grown significantly more powerful and destructive over the past three decades, according to atmospheric scientist Kerry Emanuel of the Massachusetts Institute of Technology.

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

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

"It's an innovative application of a theoretical concept, and has produced a new analysis of hurricanes' strength and destructive potential," says Jay Fein, director of the National Science Foundation (NSF)'s climate dynamics program, which funded the research.

"And that analysis, in turn, "has resulted in an important measure of the potential impact of hurricanes on social, economic and ecological systems,"

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

Also of concern, he says, is that the increases in storm intensity are mirrored by increases in the average temperatures at the surface of the tropical oceans, suggesting that this warming is responsible for the hurricanes' greater power.

Since hurricanes depend on warm water to form and build, Emanuel warns that global climate change might increase the effect of hurricanes still further in coming years.

In addition, he says, recent research suggests that global tropical hurricane 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 obvious importance to society," he adds, "especially as populations of affected areas increase.

"Hurricanes account for a significant fraction of damage, injury and loss of life from natural hazards, and are the costliest natural catastrophes in the United States.

"As the human population in coastal regions gets denser, the damage and casualties produced by more intense storms could increase considerably in the future.

"My results suggest that future warming may lead to an upward trend in [hurricanes'] destructive potential, and--taking into account an increasing coastal population--a substantial increase in hurricane-related losses in the 21st century."

Theories and computer simulations of climate indicate that warming should generate an increase in storm intensity. In other words, they should hit harder, produce higher winds and last longer.

To explore that premise, Emanuel analyzed records of tropical cyclones--commonly called hurricanes or typhoons--since the middle of the 20th century.

He found that the amount of energy released in these events in both the North Atlantic and the North Pacific oceans has increased markedly since the mid-1970s.

Both the duration of the cyclones and the largest wind speeds they produce have increased by about 50 percent over the past 50 years.

He further reports that these increases in storm intensity are mirrored by increases in the average temperature at the surface of the tropical oceans, suggesting that this warming--some of which can be ascribed to global warming--is responsible for the greater power of the cyclones.

Mongabay