Global sea levels rose faster in the 20th century than in any of the other 27 in 2,800 years, according to a Rutgers University-led study published Monday in the United States. Moreover, without global warming, global sea levels would have risen by less than half the observed 20th century increase and might even have fallen.

 

Instead, global sea level rose by about 14 centimeters, or 5.5 inches, from 1900 to 2000 — a significant increase, especially for vulnerable, low-lying coastal areas.

“The 20th-century rise was extraordinary in the context of the last three millennia  — and the rise over the last two decades has been even faster,” said Robert Kopp, the lead author and an associate professor in Rutgers’ Department of Earth and Planetary Sciences.

The new study, the culmination of a decade of work by three teams of scientists, has charted what they called an “acceleration” in sea level rise that’s triggering and worsening flooding in coastlines around the world.

“During the past millennia, sea level has never risen nearly as fast as during the last century,” said Stefan Rahmstorf, a physics professor at Potsdam University in Germany, one of 10 authors of the paper. “That was to be expected, since global warming inevitably leads to rising seas.”

The scientists reported in a paper published Monday in Proceedings of the National Academy of Sciences that they have greater than 95% certainty that at least half of more than 5 inches of sea level rise they detected during the 20th century was directly caused by global warming.

In a separate report published also on Monday, Climate Central of Princeton, New Jersey — which publishes climate change research — reported that it used the new findings to calculate that roughly three-quarters of the tidal flood days now occurring in towns along the East Coast of the US would not be happening in the absence of the rise in the sea level caused by human emissions.

Climate Central says that globally, average temperatures have risen about 1°C (nearly 2°F) since the 1800s. Last year was the hottest recorded, easily surpassing the mark set one year earlier. The expansion of warming ocean water was blamed in a recent study for about half of sea level rise during the past decade.

Changes in sea level vary around the world and over time, because of the effects of ocean cycles, volcanic eruptions and other phenomenon. But the hastening pace of sea level rise is being caused by climate change.

“The new sea level data confirm once again just how unusual the age of modern global warming, due to our greenhouse gas emissions, is,” Rahmstorf said. “They also demonstrate that one of the most dangerous impacts of global warming, namely rising seas, is well underway.”

Rutgers says that the database included records from 24 locations around the world and the analysis also tapped 66 tide-gauge records from the last 300 years.

Scientists at the following institutions contributed to the study: Rutgers, The State University of New Jersey; Tufts University; Potsdam Institute for Climate Impact Research in Germany; Woods Hole Oceanographic Institution; University of York in the United Kingdom; and Harvard University. The research was funded by the National Science Foundation, the National Oceanic and Atmospheric Administration, the New Jersey Sea Grant Consortium, the Strategic Environmental Research and Development Group, the U.K. National Environmental Research Council, the Royal Society, and Harvard University.

See satellite view of this scene Photo/Graphic: Climate Central