Saturday, December 2, 2006

by Margot Habiby

USA (Bloomberg), DALLAS: The Atlantic hurricane season sputtered to an official end on Thursday, flouting forecasts it would approach last year's record activity and complicating arguments about global warming's role in storms.

The final tally in this below-normal season: nine named storms, including five hurricanes. That compares with a record 28 storms in 2005, including Hurricane Katrina, which devastated New Orleans and caused more than 1,800 deaths and $40.6 billion in damage.

None of this year's hurricanes made landfall in the US, though three tropical storms did, including Ernesto, which caused $100 million in damage and power outages in parts of eastern North Carolina and southeastern Virginia on September 1.

"Certainly, those who were pointing to last season being indicative of global warming have some explaining to do as to why this season was below normal," said Ken Reeves, senior meteorologist and director of forecasting operations at AccuWeather.com. "It's not that simple."

Forecasters at the National Hurricane Center in Miami, at State College, Pennsylvania-based AccuWeather Inc. and at Colorado State University say a late El Nino weather pattern in the Pacific Ocean -- in which equatorial waters warm and affect patterns of air circulation across a wide area -- and dryness in the tropical Atlantic curtailed what would have been an intense hurricane season.

"There are clearly other factors in modulating Atlantic-basin hurricane activity besides Atlantic sea-surface temperatures, since they were still pretty warm this year," Colorado State researcher Phil Klotzbach said in an e-mail. He publishes the university's closely followed hurricane forecasts with William Gray, developer of the first seasonal forecasts for tropical storms in the 1980s.

Former US Vice President Al Gore became the standard-bearer this year for the argument that more intense and destructive storms, among other global climate changes, are caused by man-made emissions of carbon dioxide and other greenhouse gases. Many scientists say global warming is melting glaciers and raising sea levels as well as intensifying storms.

"The power of storms is increasing in both the Atlantic and the Pacific since the 1970s because the top 200 feet of the oceans have been warmed by man-made global warming," Gore said in a June interview with television host Charlie Rose about Gore's film, "An Inconvenient Truth."

Dan Becker, director of the Sierra Club's global-warming program, said the mild hurricane season doesn't diminish the argument that global warming is occurring, as El Nino patterns are well documented as mitigating hurricanes' intensity.

"It unfortunately doesn't mean that we're not having global warming," he said. "The force of the El Nino diminished the number of hurricanes despite the warmer seas caused by global warming." He said he would expect to see an increase in the frequency of hurricanes in a non-El Nino year.

Kevin Trenberth, head of the climate analysis section of the National Center for Atmospheric Research, a Boulder, Colorado-based cooperative for U.S. universities, said that Atlantic basin waters were warmer than normal in 2005 and that about half of the increase could be attributed to global warming and the rest to other factors.

"We still think the global warming contribution is there," he said. "On average, as we go into the future, the sea temperature will be higher."

Whatever the underlying factors, it was the first time since 2001 and the 11th time since 1945 that no hurricane made a US landfall.

The 2005 hurricanes cost $57.3 billion in total, according to the Jersey City, New Jersey-based Insurance Services Office Inc., which surveys insurers.

The US National Hurricane Center initially predicted 13 to 16 named storms would form in the Atlantic this season, with as many as 10 of them strengthening to hurricanes, which have sustained winds of at least 74 miles an hour.

Colorado State University's Klotzbach and Gray forecast in April and May that the season would produce 17 named storms and nine hurricanes. The AccuWeather.com Hurricane Center said May 15 that it was forecasting six tropical storms to make US landfall, five of them hurricanes and three of them major hurricanes, with sustained winds of more than 111 mph.

While the Atlantic hurricane season was less active than normal, the separate eastern Pacific hurricane season was more active than usual, according to the US hurricane center.

Hurricane Sergio this month became the 10th hurricane and the 18th named storm of the Pacific season when it formed off Mexico's west coast. That compares with an average of about 15 named storms and eight hurricanes, according to Chris Landsea, a meteorologist at the Miami center.

When Sergio formed, it was the first time in 45 years that two named storms were christened in the eastern Pacific basin in November. Sergio also was the most powerful storm on record to form this late in the year, according to data from the center.

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