It might sound like I'm being flippant, but I'm not: that's what you get for living on a sandbar.
My serious point is this: NOBODY, ever, (except perhaps the Egyptians and their pyramids) built cities on the basis of "what's the safest place for us to build this to withstand millennia of the cycles of climate?" This is a relevant discussion no matter where you stand on AGW; it's *ultimately* an issue to everyone, the only thing that will matter depending on your climate-change stance is the urgency.
Cities are built in places of convenience, which almost always means water nearby, often large amounts (because boats are a shitload easier to move cargo than by hand in a horse-drawn wagon) like oceans. These locations in particular are subject to the vagaries of climate.
Further, the growth of human population and concomitant urban sprawl heedless of such concerns has caused major populated areas to end up in danger zones even if the original core city wasn't (New Orleans would be a prime example: the oldest parts weren't endangered by Katrina-flooding).
So now we have massive collections of human dwellings and urban areas on city sites that were likely selected by neolithic humans THOUSANDS of years ago because of a fortuitous mix of convenience, safety, and food sources...and now we're saying "oh, wait, these city sites are vulnerable"? Seriously? Of COURSE they are.
It's just staggeringly naive or disingenuous to be surprised about this. Nothing lasts forever. if climate was going the other direction, it would be like complaining that Edmonton's going to get wiped out by glaciers - yeah, if you build a city in the distant north, eventually, that's its fate. And yes, "eventually" comes someday.