Global sea levels could rise 10 feet in 50 years if the Antarctic and Greenland ice caps rapidly melt, a new study suggests.
Analysis of coral beds formed in Mexico's Yucatan peninsula found that during the last warm period between ice ages more than 100,000 years ago, an entire layer of corals suddenly died, only to be replaced decades later by a new, smaller layer.
That indicates that sea levels had risen between 2 and 3 meters (6.6 to 10 feet) fairly rapidly — over 50 to 100 years. And the only thing that could cause that would be a substantial melting of the continental ice sheets.
"Scientists have tended to assume that sea level reached a maximum during the last interglacial very slowly, over several millennia," study leader Paul Blanchon of the National University of Mexico told Agence France-Presse. "What we are saying is 'No, they didn't.'"
The previous interglacial period, the Eemian, lasted from 130,000 to 115,000 years ago. It was warmer than the current interglacial, the Holocene, with hardwood forests well north of the Arctic Circle and, presumably, smaller ice caps.
Blanchon's sudden coral die-off occurred about 121,000 years ago, which means the Eemian may have continued to get warmer as it went on.
"The potential for sustained rapid ice loss and catastrophic sea-level rise in the near future is confirmed by our discovery of sea-level instability," he and his co-authors write in Friday's issue of the journal Nature.
Blanchon's work illustrates that sea levels can rise very quickly, but doesn't ascribe a cause for the rising temperatures back then.
People skeptical of the theory of man-made global warming could use the paper as evidence the Earth warms up suddenly on its own, without any explanation.
Of course, that would also mean that the planet can rapidly cool down and slide into another ice age — as will likely happen within the next 5,000 years without man-made global warming.