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By RANDOLPH E. SCHMID, AP Science Writer
      


WASHINGTON (AP) - Sea level has been rising significantly over
the past century of global warming, according to a study that
offers the most detailed look yet at the changes in ocean levels
during the last 2,100 years.


      The researchers found that since the late 19th century - as the
world became industrialized - sea level has risen more than 2
millimeters per year, on average. That's a bit less than one-tenth
of an inch, but it adds up over time.


      It will lead to land loss, more flooding and saltwater invading
bodies of fresh water, said lead researcher Benjamin Horton, whose
team examined sediment from North Carolina's Outer Banks. He
directs the Sea Level Research Laboratory at the University of
Pennsylvania.


      The predicted effects he cites aren't new and are predicted by
many climate scientists. But outside experts say the research
verifies increasing sea level rise compared to previous centuries.


      Kenneth Miller, chairman of the Department of Earth and
Planetary Sciences at Rutgers University, called the new report
significant.


      "This is a very important contribution because it firmly
establishes that the rise in sea level in the 20th century is
unprecedented for the recent geologic past," said Miller, who was
not part of the research team. 


Miller said he recently advised New
Jersey Gov. Chris Christie that the state needs to plan for a sea
level rise of about 3 feet by the end of the century.

      Horton said rising temperatures are the reason behind the higher
sea level.


      Looking back in history, the researchers found that sea level
was relatively stable from 100 B.C. to A.D. 950. Then, during a
warm climate period beginning in the 11th century, sea level rose
by about half a millimeter per year for 400 years. 


That was
followed by a second period of stable sea level associated with a
cooler period, known as the Little Ice Age, which persisted until
the late 19th century.


      Rising sea levels are among the hazards that concern
environmentalists and governments with increasing global
temperatures caused by "greenhouse" gases like carbon dioxide
from burning fossil fuels like coal and oil over the last century
or so.


      Although melting icebergs floating on the sea won't change sea
level, there are millions of tons of ice piled up on land in
Greenland, Antarctica and elsewhere. Melting that ice would have a
major impact by raising ocean levels.


      The result could include flooding in highly populated coastal
cities and greater storm damage in oceanfront communities.


      While the new study does not predict the future, Horton pointed
out that it does show "there is a very close link between sea
level and temperature. So for the 21st century when temperatures
will rise, so will sea level."


      Two of his co-authors calculated in an earlier paper that sea
level could rise by between 30 and 75 inches by the end of this
century. And it might even rise faster than that, Martin Vermeer of
Aalto University in Finland and Stefan Rahmstorf of Germany's
Potsdam Institute for Climate Impact reported in 2009.


      "Accurate estimates of past sea-level variability provide a
context for such projections," co-author Andrew Kemp of Yale
University's Climate and Energy Institute said in a statement.


      Horton's team studied sediment cores from salt marshes at Sand
Point and Tump Point on the North Carolina coast to develop their
calculations of sea-level change over the two millennia. They
analyzed microfossils in the cores and the age of the cores was
estimated using radiocarbon dating and other methods.


      For the years since tide gauges have been installed, those
findings closely track the results from the study, the researchers
noted.


      While Horton's report is the first to produce a continuous
record of the past 2,000 years "other studies show similar
changes, especially concerning the acceleration in sea level rise
in the 20th century," Miller said.

Gallery

Environmental News

Sea level has been rising significantly over
the past century of global warming, according to a study that
offers the most detailed look yet at the changes in ocean levels
during the last 2,100 years.

Study details significant rise in sea level

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