Scientists generally agree that sea level has risen eight inches since the 1880s and that it is rising about an inch every 10 years.
The big question is how high can it go. The answer has major importance for Costa Rica which has oceans on both coasts.
A new study in the journal Nature estimates the seas rose 20 to 43 feet higher than today during a warm period between ice ages 440,000 years ago.
That estimate is up to a third less than previous estimates, but still a drastic change, according to the Earth Institute at New York’s Columbia University.
The increase in sea level is driven by thermal expansion of seawater and melting of glaciers and ice sheets, including the still mostly intact ice sheets of Greenland and West Antarctica, the institute noted.
Meanwhile another study of the coastal United States said that nearly 4 million persons and 32,000 square kilometers (about 12,300 square miles) are at risk by sea level rise in the next century. That study was published in Environmental Research Letters and bases its estimates on a sea one meter higher than today. A meter is about 3 feet, 3.4 inches.
The Colombia University study was based on cliff tops in Eleuthera, Bahamas, that are nearly 70 feet above the present sea level. Since there are marine fossils at the top, the first assumption is that the sea rose that much.
The study says this is incorrect because the island has been pushed up and down by the weight the Ice Age put on North America.
Costa Rican coastal residents do not need to buy a boat just yet. Other scientists say that an estimated sea level rise of 20 to 43 feet would take hundreds to thousands of years, noted the university.
Of more immediate concern is the prediction by the Intergovernmental Panel on Climate Change which estimated that the seas could rise up to two feet by 2100. That could have major impact on coastal areas. The Instituto Meteorológical Nacional already has done a study to show the impact that amount of sea level rise would have on the Puntarenas Centro peninsula. Anywhere from a third to half the land area would be under water.
The U.S. study was by researchers at Climate Central and the University of Arizona.