By Fred Guteri, Source: ScientificAmerican

“We [seem to] have a 100-year flood every two years now,” New York Governor Andrew Cuomo says he told President Barack Obama during his tour of the damage from Hurricane Sandy on Tuesday. The remark is in the spirit of what climate scientists have been saying about the rise in “extreme weather events,” sea level rise and the vulnerability of New York and other coastal cities to flooding.  The arrival of Sandy has, at least temporarily, focused people’s minds on climate change and its implications. Two studies in particular—both pre-dating Sandy—paint a sobering picture of what the future might hold if worst-case scenarios of climate change come to pass.

The details in the first study on the kind of damage that a big storm could cause in New York eerily match what damage Sandy in fact did cause. The report, which was published by the Cuomo administration, is a hypothetical case study of how a “100-year storm”—the kind of deluge that is supposed to occur only once every 100 years, which Gov. Cuomo refers to—would play out. It includes maps showing extensive flooding of transport tunnels on the East River and Hudson River. (It also estimates that restoring the electrical grid from storm damage would take 15 days. So far New York city hasn’t given a timetable for Sandy–let’s hope the report is wrong on that score.) With a two-foot rise in sea levels, the report says, flooding levels in the tunnels would have been five times worse.

The second report is a longer-range look at what might play out in the worst-case scenarios of rapid sea-level rise. Researchers in Germany and Holland focused on what a five-meter rise in sea level over the next century would mean to the cities of London and Rotterdam and elsewhere in Northern Europe. Five meters, consistent with a collapse of the West Antarctic Ice Sheet, is on the extreme end of what climate scientists expect over the next century, to say the least, but the report is intended more as a thought experiment in how societies would respond to sea level rise than as a climate prediction. Think of it as a visitation from the ghost of Christmas past.

Rotterdam, one of the great shipping capitals of the world, is in the Dutch lowlands, one of the most vulnerable regions to flooding. The Dutch have currently designed their flood protection on the assumption that sea level will rise 0.8 meters over the next century—which is well above the mainstream predictions. Should sea rise exceed those estimates, most likely the rises would be ignored for several years, or perhaps a decade, before the public could be persuaded to do something about the problem, and the government acted to bolster its defenses against water.

In the meantime, as shippers began to have problems managing the flow of goods or protecting ships from the weather, Rotterdam would lose business to other cities. Nearby Amsterdam, already the “Venice of the North,” would grow even more watery. Buildings that were built alongside canals and waterways would be prone to flooding. The city would get a reputation for being moldy and wet and unpleasant, to the detriment of tourism. In the government, indecision would set in, and steps taken to support evacuees would be too little, too late. The result would be growing economic disruption, poverty, and social chaos.

The city of London doesn’t fare much better, under the researchers scenario. London years ago built the Thames Barrier, a series of gates that can be raised at high tide to prevent a storm surge from raising the level of the Thames upstream and to protect the floodplain upon which much of London stands. Engineers built the barrier after years of flood damage. Since the barrier was inaugurated in 1984, engineers have been upgrading it to handle a one-meter sea-level rise in coming years, in line with conventional climate-change projections. But an Antarctic event would make those plans wholly inadequate, and this would become apparent over a few decades.

It might start with a big storm that breaches the Thames Barrier. That would the hasten UK’s plans to upgrade it, but sooner or later another storm would breach the upgrade. London would experience its Hurricane Katrina. Waters would rise and inundate the Houses of Parliament and Victoria, and they’d lap up against the walls of Buckingham Palace. The damage would be counted in the tens of billions of pounds. Sea level rise would outrace the ability of engineers to protect the London floodplain. Eventually, the UK would have to abandon large swaths of central London and relocate to higher ground. Or the city would have to rebuild itself as a twenty-first-century Venice, with canals and gondoliers with Cockney accents.

After his trip surveying damage to New Jersey on Tuesday, Governor Chris Christie said, “The Jersey shore of my youth is gone.” He vowed to rebuild. If there is a silver lining to Sandy, it would be to renew our appreciation for rebuilding with an eye to the future.