Released two months before 9/11 made its special-effects rendering of Lower Manhattan chillingly obsolete—the Twin Towers were prominent in the movie’s skyline—Steven Spielberg’s futuristic A.I. Artificial Intelligence imagined New York and other coastal cities engulfed by the oceans. Global warming was the culprit, narrator Ben Kingsley informed us in a voice-over.

Hollywood tends to exaggerate the speed and extent of climate change. A more recent (and far poorer-quality) movie titled The Day After Tomorrow had North America become a sprawling suburb of the Arctic in what seemed like a matter of minutes. This time, it was snow and ice, not seawater, that finally buried Manhattan, although the flick also depicted citywide oceanic floods just before the deep freeze set in. (A.I. at least allowed a breather of several centuries between flooding and freezing.)

In real (as opposed to reel) life, the near-term scenario isn’t so drastic. Barring the mega-tsunami that’s theoretically possible should the Cumbre Vieja volcano in the Canary Islands erupt catastrophically and send half a trillion metric tons of rock and earth crashing into the Atlantic, New York City probably isn’t going to be submerged all at once.

More immediately threatening, scientists say, is an acceleration of the rise in sea levels. Between 1993 and 2008, according to US Environmental Protection Agency data, that rise—while still small at 0.11 to 0.13 inches per year—was double that of the longer-term trend globally. Assuming the trend toward acceleration continues, the yearly rise may increase to more than a half an inch within a couple of decades. It adds up, whether it’s man-made or occurring naturally.

In the case of New York City, that doesn’t mean Central Park will become an aquarium in our lifetimes, or even our grandchildren’s lifetimes. It does increase the size of the city’s flood-prone zone and therefore the risk of large-scale damage from storms, even those that fall well short of hurricane strength, according to a New York Times piece earlier this week exploring the city’s preparation, or lack thereof. With 520 miles of shoreline, the city should be putting sea gates and other defenses into place, Douglas Hill, an engineer with the Storm Surge Research Group at Stony Brook University, told the Times.

Naturally, the cost of such preparation would be enormous—upwards of $10 billion for sea gates—and the expenditure would be for an event that isn’t likely to happen. The Empire State Building reportedly swayed four inches during the Category 3 hurricane that made landfall on Long Island in 1938, but the last time a hurricane hit the city at full strength, the year was 1821.

Even if you count the 1893 storm that swallowed up Hog Island just over the border into Nassau County, we’re not talking about frequent hurricanes in these parts. With colder waters off our shores, the conditions to sustain—let alone generate—such a storm aren’t right. The odds of one striking here in the next 50 years are just 6.6%, compared to 95.5% for Miami, according to landfall tables from Colorado State University.

In August 2011, it looked as though the city might get its second full-bore hurricane in two centuries. The Bloomberg administration shut down all subway service, and ordered nearly 400,000 city residents to evacuate, as Hurricane Irene approached. Both moves were unprecedented locally, although they’re routine farther down the East Coast.

Yet Irene had weakened to a tropical storm by the time it made landfall in Brooklyn. “Yawn,” said some New Yorkers. The feeling wasn’t so much that the city had dodged a bullet as one of much hysteria over nothing. (North and west of the city, it was a different story, with upwards of $6 billion in damage.)

But in that 1821 hurricane, the East and Hudson rivers converged across Lower Manhattan. Consider the consequences in terms of property damage if that happened today. A June study from CoreLogic ranked the New York City metro area at the top of the list for financial risk of hurricane-related damage, estimating that $168 billion worth of property would be in harm’s way. 

To date, this year’s Atlantic hurricane season has been relatively low-key. Irene is ancient history. And all those waterfront developments aren’t going anywhere. Yet earthquakes don’t happen everyday, which doesn’t mean that building codes for cities along seismic faults should ignore the risk. Similarly, maybe it’s time to stop assuming that the oceans will stay put merely because we’d like them to. Nature abhors a vacuum, and it’s not too crazy about complacency, either.