Changing El Nino making hurricanes more frequent, research suggests

Changes in the nature of global weather phenomenon El Nio may be causing an increase in the total number of hurricanes as well as their likelihood of hitting land, new research suggests.

El Nio forms in the Pacific, but it affects circulation patterns across the globe from drought in Australia, to the Indian monsoon and the number and severity of hurricanes in the Atlantic.

Conventional El Nio events involve warming in the eastern Pacific. But a new wrinkle might be emerging as a phenomenon dubbed El Nio Modoki (from the Japanese meaning "similar, but different") shows warming in the Central Pacific similar to that which is seen during La Nina years.

"Normally, El Nio results in diminished hurricanes in the Atlantic," said Peter Webster, a professor at Georgia Tech's School of Earth and Atmospheric Sciences, who led a research team studying the issue. "But this new type is resulting in a greater number of hurricanes with greater frequency and more potential to make landfall."

Warming in the central Pacific Ocean is associated with a greater-than-average frequency and increasing landfall potential along the Gulf of Mexico coast and Central America, the report said.

The study's findings are published in the July 3 issue of Science.

The value of hurricane-related damages averages $800 million during El Nio years, and as much as $1.6 billion during La Nina years, the report said.

Forecasters predicted lower than average hurricane activity in 2004, which was expected to be an El Nio year. But the season ended up being unusually higha total of 15 tropical cyclones developed in the North Atlantic, of which 12 were named storms. Cylcones caused a total of $40 billion in damages and led to the loss of 3,000 lives that year.

Changes in the characteristics of El Nio could have huge ramifications for the insurance industry, as well as making storm-ravaged areas better able to avert catastrophe.

"This new type of El Nio is more predictable," said Webster. "We're not sure why, but this could mean that we get greater warning of hurricanes, probably by a number of months."

As to why the form of El Nio is changing to El Nio Modoki, that's not entirely clear yet either, Webster said.

"This could be part of a natural oscillation of El Nio," he said. "Or it could be El Nio's response to a warming atmosphere. There are hints that the trade winds of the Pacific have become weaker with time and this may lead to the warming occurring further to the west. We need more data before we know for sure."

The research team is currently looking at changes in La Nina, which is showing signs of changing its structure as well.