Sea levels are rising at their fastest rate in 2000 years

http://www.sciencemag.org/news/2016/02/sea-levels-are-rising-their-fastest-rate-2000-years

By Warren CornwallFeb. 22, 2016
Science Magazine

Global sea levels appear exquisitely sensitive to changes in temperature and greenhouse gas levels, according to a set of new studies that examines up to 6 million years of climate change data. The four papers, published today in the Proceedings of the National Academy of Sciences (PNAS), illustrate the growing power of computers to simulate complex interactions between climate, polar ice, and the planet’s oceans. They also underscore the effects that rising greenhouse gases and global temperatures could have on future sea level.

“The big takeaway is that the modern rate of sea level rise in the 20th century is faster than anything we’ve seen in the previous two millennia (2,000 years),” says Benjamin Horton, a Rutgers University, New Brunswick, in New Jersey geologist who helped direct one of the studies. “This isn’t a model. This is data.”

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They [the studies] also add to a growing body of research that suggests sea level can change more dramatically over a short time than previously suspected, says Andrea Dutton, a University of Florida in Gainesville geologist and a leading expert on reconstructing ancient sea levels.

The first study found that small temperature fluctuations have led to measurable changes in ocean levels over the past 3000 years. As the global thermostat turned down just 0.2°C between 1000 and 1400 B.C.E., for example, the world’s seas dropped an estimated 8 centimeters. By contrast, they have risen about 14 centimeters [5.5 inches] in the 20th century. At least half of that increase is due to human-induced climate change, say the researchers, who add that sea levels are very likely to rise another 0.24 [9.4 inches] to 1.3 meters [51.2 inches = 4.3 feet] during this century.

The study’s results come in part from measurements of past sea levels gathered at 24 sites around the world.

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Looking to the future, the results of the new model suggest that changes in Antarctic ice might cause sea level to rise even more rapidly than current studies indicate, DeConto says. “It may be that the Kopp approach and the IPCC are both wrong,” he says. “Once we start seeing a lot of meltwater on the ice shelves around Antarctica, what’s that going to do?”