It is not as if the flooding of Venice has been unknown, but it is instead a function of the intensity of these events and how much recovery time exists between them.
The city is flooding at a much higher rate. There will be valiant efforts to save it as the frequency rises, but ultimately these will become to expensive and too difficult.
The same, I think is true of New Orleans, and for that matter, New York and indeed many
nations around the world.
As others have noted, none of these events are totally a function of climate change, but climate change is what will make them irredeemable.
Climate Change / Four Battlefronts : A global threat laps at the gates of Venice
...Intensified storm activity associated with global warming is likely to aggravate the impact. An increase in siroccos, the winds that sweep in from the Sahara, has already raised the frequency of surge tides that flood sidewalks and ground floors here.
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"One can expect high waters that are very destructive, very frequent and perhaps almost permanent at certain times" in Venice, according to Pierre Lasserre, a marine biologist who directs the offices here of the UN Educational, Scientific and Educational Organization.
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Venice's battles with climate change offer a glimpse of what other low-lying cities will face in coming decades, according to environmental experts...
...Other major cities that risk troubles with rising water include New York and Miami. Tens of millions of people, especially in Bangladesh and Southeast Asia, face serious or permanent flooding of their land if the climate change predictions become reality. In Europe, storm surges in the North Sea or the Baltic could eventually make it too expensive to preserve low-lying regions along the Dutch, German and Danish coasts...
JUST THE BEGINNING? —There's no question that the problem has worsened and the threat is real. Last year alone, high waters inundated St. Mark's Square, the city's main piazza and lowest point, more than 90 times. That compares to fewer than 60 occasions during the entire decade of the 1920s.
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Paintings by the Venetian master Canaletto, which show the waterline on buildings, indicate that the tides now lap the walls 80 centimeters, or 31 inches, higher than two centuries ago. Marble steps leading down to the canals, above water at the beginning of the 20th century, are now submerged except at low tide.
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That could just be the beginning...
http://www.iht.com/articles/2002/03/23/t1_86.php