UNITED STATES - It is late afternoon inside the low-ceilinged room on the edge of Miami and a bank of computer monitors is showing a mass of throbbing colours - green and blue and yellow - steadily marching north-east across Florida.

This swirling mass is Alberto, the first tropical storm of this year's season, and it has moved across the western Caribbean and the Gulf of Mexico, deluging Cuba and Grand Cayman and blasting them with winds of 112km/h, tracked by the experts from the National Weather Service's Tropical Prediction Centre.

Hunched over a telephone, Richard Pasch is on a conference call with colleagues. It is clear that Alberto's power is falling and they discuss whether it should be downgraded from the status of tropical storm. They decide to maintain the warning for a few hours longer.

After last year's hurricane season, the busiest on record, unprecedented attention is now given to warnings about tropical storms. With more people moving to coastal communities, never have so many lives, and so much money, been at stake.

And yet never before has the science of tropical weather prediction been riddled by such disagreement. The debate is part of a broader discussion about the extent and implications of climate change and whether storms are getting stronger as a result of man-made global warming. Some say there is no convincing evidence, others that the evidence is obvious.

A year ago, Katrina made people question if global warming could be to blame.

Among the science cited to back such a claim was a report in Nature magazine by Professor Kerry Emanuel, a Massachusetts climatologist, which argued that the strength of hurricanes had increased in recent years and that this was linked to climate change.

Although sea temperatures had increased only by around half a degree over 30 years, the destructive power of hurricanes had doubled in that period, he said.

Emanuel had statistics dating back to 1930 relating to the power of hurricanes and - having made adjustments to counter what was widely considered an inaccuracy in some earlier measurements - worked out a figure to measure their annual destructive power, which he called the Power Dissipation Index (PDI). He set these figures against data showing the average September sea-surface temperature for each of those years, and claimed a remarkable link between the two.

He also showed that storms lasted longer and were more intense. He wrote: "My results suggest that future warming [of the oceans] may lead to an upward trend in tropical cyclone destructive potential."

In 2004 George Trenberth, of the National Centre for Atmospheric Research in Colorado, also argued that "trends in human-influenced environment changes are now evident in hurricane regions".

A third piece of evidence came from Peter Webster and Greg Holland, who said their research suggested the number of category-four and category-five hurricanes worldwide had nearly doubled over 35 years. "Our work is consistent with the concept that there is a relationship between increasing sea surface temperature and hurricane intensity," said Webster.