Exporting calamity: Katrinas for everyone; Coming soon to a coast near you.

When the malevolent waters of Hurricane Katrina destroyed most of New Orleans, Americans across the country began asking two basic questions. How in the world did this disaster happen? And, Can the same thing happen where I live?

Surprisingly, in all the coverage since the storm, the media have answered the first question largely incorrectly and the second question not at all.

The main reason Katrina became a mega-disaster was not because of flawed hurricane levees and poor evacuation plans. These were just symptoms of a larger disease. Katrina destroyed New Orleans because, over the past 100 years, the Gulf of Mexico moved about one meter higher in relation to the city. The land itself, thanks to human activities, sank about two-thirds of a meter in relation to the Gulf while the Gulf waters rose-again because of human actions--about 30 centimeters.

That one-meter rise over the last 100 years wiped out a staggering 400,000 hectares of coastal wetlands and barrier islands between New Orleans and the Gulf. A land mass larger than Rhode Island simply turned to water. The result, by August 29, 2005, was to create a watery flight path for Katrina to slam into New Orleans, like a plane into the World Trade Center. The old landforms that had traditionally slowed down the surge tides of past hurricanes in Louisiana--the marsh grasses, the coastal islands--were almost all gone. Without them, only a fantastic fortresslike city could hold back such assaults. Sooner or later New Orleans was bound to lose, no matter how big the levees grew or how much bottled water was stored at the Superdome.

So why did the land sink in the first place, and the ocean rise? Because of something I call the Law of Unintended Consequences. The land sank because the lower Mississippi River no longer flows free. After 7,000 years of annual flooding at its mouth, which deposited along the Louisiana coast staggering amounts of sediments and nutrients drained from two-thirds of the continental United States, the lower Mississippi River doesn't flood anymore. From the crude early levees of the French settlers to the massive control structures of the Army Corps of Engineers, the lower Mississippi has been utterly tamed. It obediently stays within its banks all the way to the continental shelf and deposits its soil into the deep water of the Gulf of Mexico rather than along the Louisiana coast.

The pre-existing coastal land, meanwhile, then does something seemingly strange: it sinks, in a natural process geologists call "subsidence." The land is composed of old and fragile alluvial soils that contract in volume over time, leaving the coastal areas starved for counterbalancing deposits of new sediments. This sinking is happening so fast that 20 hectares of land turn to water every day in south Louisiana even without hurricanes.

No one intended this. The original French settlers and everyone else for the past 300 years simply wanted to stay dry and keep their children from drowning and keep their crops from being washed away by the Mississippi's spring floods. So they built huge levees along her banks. But everything in nature is connected to everything else. If you profoundly disrupt one major aspect of an ecosystem as huge as the lower Mississippi (i.e., the flooding), you profoundly disrupt all major aspects of that ecosystem: the land itself turns to water.

But this is only part of the equation. Why did the Gulf of Mexico itself rise? Again, it was an accident. In 1712, British blacksmith Thomas Newcomen had no intention of harming anyone or anything when he invented the world's first workable steam engine powered by coal. All he knew was that this one contraption could do the work of 500 horses. So began the industrial revolution, launched by an engine first called, ironically, an "atmospheric" machine.

Today, we human beings set fire to 15.9 million short tons of coal every day to power everything from subway cars to iPods. We also torch 7.4 billion cubic meters of natural gas and ignite 82.4 million barrels of oil. One byproduct of this combustion, of course, is carbon dioxide, a dangerous greenhouse gas. It flows up into the atmosphere where it remains for about a century, trapping heat. The atmosphere is warming as a result and, since everything is connected to everything, so are the world's great stores of land-based ice. Glaciers everywhere are melting, sending water into the oceans at the same time that the ocean water itself is heating up and expanding in volume. Hence, over the last 100 years, the Gulf of Mexico rose a third of a meter, a huge problem for low-lying New Orleans.

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But unfortunately the story of global warming doesn't end there. It would be nice to simply shake our heads for poor, inundated New Orleans, write a check, and go about our business. But the changing climate that contributed to a meter of relative sea-level rise along the Louisiana Gulf coast during the 20th century is now projected to have the very same impact on every coastline in the world during the 21st century. The Intergovernmental Panel on Climate Change projects up to one meter of "absolute" sea-level rise worldwide by 2100 unless drastic cuts are made in greenhouse gas emissions. If the Greenland Ice Sheet continues its rapid disintegration, that rise could be closer to six meters.

Consequently, if you want to know what all the world's great coastal cities will be fighting against 25 and 50 and 75 years from now, just look at New Orleans today. Shanghai and Gdansk and Mumbai and Miami and Baltimore--they'll all be huddled behind levees, living below sea-level, pumping out rainwater, and trying to keep their drinking water from turning salty, just like New Orleans today.

But there's more. Two separate things conspired to destroy New Orleans. The first was the meter of relative sea-level rise. The second was the storm itself. When it finally came, it was gigantic. Katrina boasted wind gusts up to 280 kilometers per hour at her peak, and her six-meter surge tide was by far the highest Louisiana had ever seen.

But amazingly, Katrina was not the most powerful hurricane of 2005. Somehow, two other storms beat her for sheer strength. Indeed, of the six most powerful hurricanes ever recorded in the Atlantic Basin (the Gulf, Caribbean, and Atlantic combined), three of them (Katrina, Wilma, and Rita) occurred within the eye-blink of a 52-day period in 2005. It took 153 years of human record keeping to identify one half of that A-list of top-six hurricanes. It took 52 days to record the other half.

This seemingly impossible coincidence makes sense once you realize that the same global warming that's causing the oceans to rise is also cooking hurricanes into increasingly huge monsters. No fewer than six peer-reviewed scientific studies, all published in the past year, point to the same thing: warming sea-surface temperatures linked to global warming are making hurricanes more powerful. Warm water is the very fuel that makes hurricanes go, and more warmth means more power. The most authoritative of these recent studies, published by Kerry Emanuel of the Massachusetts Institute of Technology, reveals that over the past 50 years hurricanes and cyclones worldwide have experienced a 50-percent increase in both wind speed and lifespan.

Whether one hurricane in particular, Katrina, was made more intense by global warming is impossible to say. What is certain is that the 2005 hurricane season was so violent and fraught with such weird storm behavior that scientists increasingly point to it as the possible "new normal" for hurricane activity in an increasingly overheated world.

And here's a stark fact: most Americans haven't even begun to comprehend the extraordinary nature of the 2005 hurricane season and what it portends. To say the 2005 season was unusually "active" or "powerful" is like saying a nuclear explosion is "active" compared to a conventional TNT bomb. The truth is there's no adequate way to describe what happened last summer and fall. One thinks of the Inupiat people of Alaska, faced with rapid Arctic warming, who have no word in their language for the barn owls and wasps arriving in recent years because they've simply never seen such creatures before. The 2005 hurricane season was our tropical barn owl. It shattered so many records and brought such unprecedented storm behavior, that the season as a whole is simply unrecognizable compared to all previous storm years.

It began with Tropical Storm Arlene, forming unusually early (June 9) in the lower Caribbean without inflicting meaningful harm. It ended seven long months later when Hurricane Zeta took shape on December 30, a full month after the official close of the Atlantic hurricane season. In between came a veritable traffic pile-up of records. Never before in the Atlantic Basin had 27 named storms formed in one season. (The old record was 21, set in 1933.) Never before had 14 full-blown hurricanes formed in a single season (old record: 12 in 1969). Never before had four major hurricanes hit the United States (old record: three in 2004), or three Category 5 hurricanes formed in a single season (old record: two in 1960 and 1961), or seven tropical storms formed before August 1st (old record: five in 1977).

This is global warming. It fits the pattern and characteristics scientists describe for a warmer world, and it all comes on the heels of the record storm season of 2004, when four major hurricanes slammed into Florida.

But amid it all, Katrina stands out. She crossed over unusually warm Gulf waters, grew into a monster, and came ashore to claim at least 1,836 lives and inflict over $100 billion in damage. Now, as a nation, we're exporting to the rest of the world the same basic ingredients that created this disaster. Through our destructive addiction to fossil fuels we are sharing the sea-level rise and the heightened storm power with the rest of the world, turning every shoreline on every continent into a version of New Orleans.

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Somehow, a full year after Katrina hit, Americans continue to ignore the storm's biggest lesson. In the same way we ignored pleas to bolster the New Orleans levees and rebuild the barrier islands prior to Katrina, we are now ignoring pleas from scientists and leaders worldwide to get off fossil fuels or else enter a permanent "era of Katrina." History is now repeating itself on the largest scale imaginable, and the price goes up with each curtain call.

There is a plan to get us out of this mess. It involves the aid of hybrid cars and modern windmills and solarized homes and government policies that move us forward instead of backward. Clean energy is the solution to global warming, and clean energy is as widely available to us today as the dirt below our feet for filling sandbags. We just have to pitch in and pick up our shovels and get to work, right now.

We have but one planet and it is not just another watery Louisiana parish we can evacuate and return to when the danger's gone. Our days of running from the problem are simply running out. It's time to stay and finally rescue New Orleans--and ourselves.

Mike Tidwell is the author of The Ravaging Tide: Strange Weather, Future Katrinas, and the Coming Death of America's Coastal Cities.