MIAMI • Say goodbye to Miami and New Orleans. No matter what we do to curb global warming, these and other beloved US cities will sink below rising seas, says a study.
But making extreme carbon cuts and moving to renewable energy could save millions of people living in iconic coastal areas of the United States, say the findings in the Oct 12 edition of the Proceedings of the National Academy of Sciences, a peer-reviewed US journal.
Scientists have already established that if we do nothing to reduce our burning of fossil fuels up to the year 2100, the planet will face sea level rise of 4.3m to 9.9m, said the study's lead author Ben Strauss, vice-president for sea level and climate impacts at Climate Central.
The big uncertainty is the issue of when.
"Some of this could happen as early as next century," Dr Strauss told Agence France-Presse. "But it might also take many centuries."
"Just think of a pile of ice in a warm room. You know it is going to melt, but it is harder to say how quickly," he added.
To bring this issue home for people in the US, the study pinpoints at-risk land where more than 20 million people reside.
The authors projected business- as-usual carbon emissions, in addition to the complication of the melting West Antarctic ice sheet, a process some experts fear is irreversible. They also considered what might happen if the world were to make a big turnaround, reaching peak carbon emissions by 2020, a radical shift from the current aim of some world powers to peak by 2050, said Dr Strauss.
An online tool shows which US cities may face "lock-in dates beyond which the cumulative effects of carbon emissions likely commit them to long-term sea-level rise that could submerge land under more than half of the city's population".
"Norfolk, Virginia, for example, faces a lock-in date of 2045 under a scenario of unabated carbon emissions," the study says. For cities such as Miami and New Orleans, the limits are already exceeded.
"In our analysis, a lot of cities have futures that depend on our carbon choices but some appear to be already lost," Dr Strauss said.
New York is also in peril, and under a worst-case scenario, the city could be un-livable by the year 2085, according to the study.
But strong action - the kind that would reduce carbon emissions in 2050 to levels that more closely resemble those seen in 1950 - could make a difference.
Fourteen cities with more than 100,000 residents each could avoid locking in this century, including Jacksonville, Florida; Chesapeake in Virginia; and Sacramento and Stockton in California.
The online tool at http:// choices.climatecentral.org allows users to see the impacts on various US cities. A global version is expected in the next month, Dr Strauss said.