Coral fossils show sea levels can rise rapidly

Evidence from fossil coral reefs in Mexico underlines the potential for a sudden jump in sea levels because of global warming, scientists report in a new study.The study, published in the journal Nature, suggests that a sudden rise of 6.5 feet to 10 feet occurred within a span of 50 to 100 years about 121,000 years ago, at the end of the last warm interval between ice ages."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" in that period, the authors write.Yet other experts on corals and climate are faulting the work, saying that big questions about coastal risks in a warming world remain unresolved.One of the most momentous and enduring questions related to human-caused global warming is how fast and far seas may rise.Studies of past climate shifts, particularly warm-ups at the ends of ice ages, show that fast-eroding ice sheets have sometimes raised sea levels worldwide in bursts of up to several yards in a century.A question facing scientists is whether such a rise can occur when the world has less polar ice and is already warm, as it is now, and getting warmer.Citing the evidence from fossil coral reefs, the authors of the new study say with conviction that the answer is yes.The study focuses on a set of fossil reef remains exposed in excavations for channels at a resort and water park, Xcaret, about 40 miles south of Cancun on the east coast of the Yucatan peninsula in Mexico.