The unimaginable devastation of Hurricane Katrina emphatically affirmed the frightening future of tropical storms.

If you follow climate issues, you are aware of the debate over what impact worldwide warming had on Katrina in 2005 and what it means for the hurricane seasons to come, a subject we touched on two weeks ago. We will leave that debate to the scientists, whom we are loath to pit against each other.

We can say with some certainty, however, that even if global warming slows, stops or reverses tomorrow, hurricane seasons will become ever more destructive and expensive along the coasts, from Texas to Florida to New Jersey to Cape Cod.

It is a direct result of human activity - oceanside development, that is.

Very simply, more is in the way than ever before.

In raw dollars, Katrina was the costliest hurricane on record, causing more than $80 billion in damages. That price tag was the result not only of the storm's power, but the fact that it occurred in 2005.

But what if the same storm had hit the same areas 35 years earlier, in 1970? We mention that year because it was the beginning of a hurricane-lull period that lasted until 1995. That calm coincided with an incredible building boom along the nation's coasts.

A 1970 Katrina would have cost $32 billion in inflation-adjusted dollars - 2½ times less damage. That figure is based on an analysis, performed at The Inquirer's request, by disaster specialist Roger Pielke Jr.

Pielke, who works out of the University of Colorado, uses changes in inflation, population and wealth to "normalize" hurricane damages. He estimates what past storms would cost if they hit in the modern era. He updates his rankings periodically; a new edition is due this summer.

His most recent list, published in 2004, has the 1926 hurricane that struck Miami as the most expensive - close to $100 billion (a figure that will rise slightly on the new list). So even on this adjusted ranking, Katrina won't be No. 1.

In other words, if a 1926-style hurricane made a direct hit on Miami today, it would be a certifiable disaster not only for Miamians but for all American taxpayers.

The entire Florida peninsula, dangling into one of the world's busiest hurricane corridors, is particularly endangered. Its population growth has been stunning. From 1970 to 2000, it swelled from 6.8 million to 16 million. That's close to 6,000 more people a week, 840 a day.

That's a lot of folks in harm's way, and the outlook is not promising. National Hurricane Center scientist Christopher Landsea and a team of researchers have warned that the Atlantic Basin is in the middle of a busy hurricane period that could last 25 more years.

Kerry Emanuel, a professor at the Massachusetts Institute of Technology, holds that punishing hurricane seasons are now a permanent condition because of global warming.

And Emanuel and Landsea have found common ground on the issue of coastal development. Both their names appear on a statement about global warming that was presented to Congress and is posted on Emanuel's Web site. The document warns of what it terms an "urgent" challenge: "Our lemming-like march to the sea requires immediate and sustained attention."

In short, the explosion of people and buildings bodes ominous for the nation's hurricane-prone regions.

Said Frank Marks, director of the National Oceanic and Atmospheric Administration's Hurricane Research Division: "That drawfs any other signal."

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Contact staff writer Anthony R. Wood at 610-313-8210 or twood@phillyenws.com.