The world's oceans are rising at a faster rate than any time in the past 2,800 years, and might even have fallen without the influence of human-driven climate change, researchers say.

Sea levels rose globally by about 5.5 inches (14 centimeters) from 1900 to 2000, said the study led by Rutgers University, published in Proceedings of the National Academy of Sciences.

In the absence of global warming, the change in sea level would have been far less -- ranging between a 1.2 inch (three centimeters) drop in the last century, to a rise of about 2.8 inches (seven centimeters).

"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 lead author Robert Kopp, an associate professor in Rutgers University's Department of Earth and Planetary Sciences.

The study also predicted that global sea level will rise by 1.7 to 4.3 feet (50 to 130 centimeters) in the 21st century if the world continues to rely heavily upon fossil fuels.

Even if fossil fuels were phased out, the seas would likely mount between 0.8 and two feet by century's end, it said.

Average global temperature today is about 1.8 degrees Fahrenheit (one degree Celsius) higher than it was in the late 19th century.

The Rutgers-led study -- with co-authors from Harvard University, the Woods Hole Oceanographic Institution and the Potsdam Institute for Climate Impact Research in Germany -- was based on a database that included records from 24 locations around the world, and 66 tide-gauge records from the last 300 years.

Scientists say the planet is incredibly sensitive to small changes in temperature, with today's average climate about 1.8 degrees Fahrenheit (one degree Celsius) warmer than it was in the 19th century.

"During the past millennia sea-level has never risen nearly as fast as during the last century," said co-author Stefan Rahmstorf, co-Chair of the Potsdam-Institute for Climate Impact Research's (PIK) research domain Earth System Analysis.

"The new sea-level data confirm once again just how unusual the age of modern global warming due to our greenhouse gas emissions is -- and they demonstrate that one of the most dangerous impacts of global warming, rising seas, is well underway."

A second report issued to Monday by Climate Central found that without the global warming, more than half of the 8,000 coastal nuisance floods seen in the United States since 1950 would not have occurred.