A new study suggests that sea levels are rising at an unprecedented rate and that the problem will continue well into this century.
"Sea level rise in the 20th century was truly extraordinary by historical standards," says Bob Kopp, an associate professor of Earth and planetary sciences at Rutgers University, and who is lead author on the study, which appears in the journal Proceedings of the National Academy of Sciences.
Sea levels rose by roughly 5½ inches in the past hundred years, Kopp says, noting, "That's faster than any century since at least 800 B.C., since the founding of Rome."
Kopp's team based its findings on dozens of earlier studies carried out around the world. Those studies determined past sea levels by looking at everything from microbial fossils to the locations of ancient Roman ruins along the Italian coast.
The results show sea levels remained largely unchanged for more than two millennia — except for one period around 1000 A.D., in which the oceans dropped slightly due to a brief medieval cold snap.
Looking forward, Kopp and his co-authors predict things are going to get worse. The team's findings suggest sea levels will rise between 1 to 4 feet by 2100.
Kopp says those kinds of increases will put many coastal cities at risk of frequent flooding. Although cutting carbon emissions could help in the future, rising seas now appear inevitable. Sea level rise "is going to be something we have to prepare for," he says.