A significant number of people in 1,700 American cities are at greater risk of living below sea level than previously thought
Suzanne Goldenberg guardian.co.uk 30 Jul 13;
US sea levels rising : Florida Coast Line At Greatest Risk Of Rising Sea Level
For nearly 80 US cities, the watery future would come much sooner, within the next decade. Photograph: Joe Raedle/Getty Images
More than 1,700 American cities and towns – including Boston, New York, and Miami – are at greater risk from rising sea levels than previously feared, a new study has found.
The future of these 1,700 locations is "locked in" by greenhouse gas emissions already built up in the atmosphere, the analysis published in the Proceedings of the National Academy of Sciences on Monday found.
The survey does not specify a date by which these cities would actually fall under water. Instead, it specifies a "locked-in" date, by which time a future under water would be certain. In other words, a point of no return.
Because of the inertia built into the climate system, even if all carbon emissions stopped immediately, it would take some time for the global temperature rises to ease off. That means the fate of some cities is already sealed, the study says.
"Even if we could just stop global emissions tomorrow on a dime, Fort Lauderdale, Miami Gardens, Hoboken, New Jersey will be under sea level," said Benjamin Strauss, a researcher at Climate Central, and author of the paper. Dramatic cuts in emissions – much greater than Barack Obama and other world leaders have so far agreed – could save nearly 1,000 of those towns, by averting the sea-level rise, the study found.
"Hundreds of American cities are already locked into watery futures and we are growing that group very rapidly," Strauss said. "We are locking in hundreds more as we continue to emit carbon into the atmosphere."
A recent study, also published in PNAS by the climate scientist Anders Levermann found each 1C rise in atmospheric warming would lead eventually to 2.3m of sea-level rise. The latest study takes those figures, and factors in the current rate of carbon emissions, as well as the best estimate of global temperature sensitivity to pollution.
This shows that the list of cities at risk of being "locked in" by 2100 spans Sacramento, California – which lies far from the sea but would be vulnerable to flooding in the San Joaquin delta – and Norfolk, Virginia. The latter town is home of America's largest navy base, whose miles of waterfront installations would be at risk of being locked in to future sea level rises by the 2040s. The Pentagon has already begun actively planning for a future under climate change, including relocating bases.
About half the population of Cambridge, Massachusetts, across the Charles River from Boston and home to Harvard and MIT, could be locked in to a future below sea level by the early 2060s, the study found. Several coastal cities in Texas were also vulnerable.
But the region at highest risk was Florida, which has dozens of towns which will be locked by century's end. The date of no-return for much of Miami would be 2041, the study found. Half of Palm Beach with its millionaires' estates along the sea front would be beyond saving by the 2060s. The point of no return for other cities such as Fort Lauderdale would come before that.
"Pretty much everywhere it seems you are going to be under water unless you build a massive system of dykes and levees," Strauss said. The study drew on current research on sea-level rise, now growing at 1ft per decade.
