Some blame global warming. Others say such climatic conditions have always occurred in cycles. And still others argue that, well, no one quite knows for sure.

So far, seven hurricanes have hit the northern hemisphere this year. By far the most devastating have been Charley, Frances, Ivan and Jeanne.

Hurricane Jeanne landed in Florida early Sunday, with early reports showing it was faster and doing more damage than Hurricane Frances three weeks ago. The same storm has caused massive devastation in the poor Caribbean nation of Haiti, where the toll of those either dead or missing is expected to top 2,200.

In between Frances and Jeanne was Hurricane Ivan, which last week killed more than 130 people in the eastern United States and Caribbean nations.

Before that, Hurricane Charley also left a trail of death and destruction. Other storms often occur at sea but are not so newsworthy as they do not make landfall.

Olivier Talagrand, the director of research at France's National Centre for Scientific Research, said that he was "strongly tempted to link the number and intensity (of this year's storms) to global warming."

Warmer than usual waters are a pre-requisite for hurricanes, and Talagrand said the sea temperature in the Caribbean region was "particularly high" this year.

"It's not proof of global warming but tends in that direction," he added.

A tropical cyclone that matures to intensity is called a hurricane when it occurs in the Atlantic Ocean or adjacent seas; a typhoon in the Pacific Ocean; or simply a cyclone in the Indian Ocean region.

The number of storms in the 2004 northern hemisphere cyclone season, which ends in early November, is above the annual average of 5.4 recorded since the 1960s.

That is not unusual -- according to Dominique Escale of Meteo-France, these things go in cycles of 20 to 30 years.

"In the years 1950 to 1969 the frequency of cyclones was above the average for the northern hemisphere," she told AFP.

The years 1970 to 1994 were quieter. "Since 1995, one can detect a cyclonic upswing, but not necessarily any more than from 1950 to 1969."

Only two hurricanes were registered in the region in 1982, while the years 1969 and 1995 boast the most, with 12 and 11 respectively.

She refused to speculate on whether the above-average number of storms this year was down to global warming, a term used to describe a gradual heating of the Earth's surface by "greenhouse" gases which trap the Sun's heat instead of letting it radiate back out into space.

She said there was too little data available and that storms developed for many reasons, not just warmer seas.

Michel Petit of the Intergovernmental Panel on Climate Change, a group set up by the United Nations and World Meteorological Organisation, agreed that it would be "excessive" to blame the storms on global warming.

Escale did not want to predict whether hurricanes would increase in number but said she did expect them to increase in intensity.

"The only consensus (among weather experts) is about the violence of these phenomena," with stronger winds and heavier rainfall, she added.

Talagrand was more pessimistic. He expects both the number and intensity to rise, and is adamant that "it's because of global warming."

Petit, for his part, disagreed on both counts.

He said that based on analysis of existing studies, "we cannot say that we expect cyclones to be stronger in 2050," and prediction models "don't seem to be suggesting any more cyclones."

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