About 3.7 million Americans
live within a few feet of high tide and risk being hit by more frequent coastal
flooding in coming decades because of the sea level rise caused by global
warming, according to new research.
By far the most
vulnerable state is Florida Louisiana , California , New York and
New Jersey
“Sea level rise is
like an invisible tsunami, building force while we do almost nothing,” said
Benjamin H. Strauss, an author, with other scientists, of two new papers
outlining the research. “We have a closing window of time to prevent the worst
by preparing for higher seas.”
The project on sea
level rise led by Dr. Strauss for the nonprofit organization Climate Central
appears to be the most elaborate effort in decades to estimate the proportion
of the national population at risk from the rising sea. The papers are
scheduled for publication on Wednesday by the journal Environmental Research
Letters. The work is based on the 2010 census and on improved estimates,
compiled by federal agencies, of the land elevation near coastlines and of
tidal levels throughout the country.
Climate
Central, of Princeton ,
N.J.
While some coastal
governments have previously assessed their risk, most have not, and
national-level analyses have also been rare. The new package of material may
therefore give some communities and some citizens their first solid sense of
the threat.
Dr. Strauss said he
hoped this would spur fresh efforts to prepare for the ocean’s rise, and help
make the public more aware of the risks society is running by pumping
greenhouse gases into the air. Scientists say those gases are causing the
planet to warm and its land ice to melt into the sea. The sea itself is
absorbing most of the extra heat, which causes the water to expand and thus
contributes to the rise.
The ocean has been
rising slowly and relentlessly since the late 19th century, one of the hallmark
indicators that the climate of the earth is changing. The average global rise
has been about eight inches since 1880, but the local rise has been higher in
some places where the land is also sinking, as in Louisiana
and the Chesapeake Bay region.
The rise appears to
have accelerated lately, to a rate of about a foot per century, and many
scientists expect a further acceleration as the warming of the planet
continues. One estimate that communities are starting to use for planning
purposes suggests the ocean could rise a foot over the next 40 years, though
that calculation is not universally accepted among climate scientists.
The handful of climate
researchers who question the scientific consensus about global warming do not
deny that the ocean is rising. But they often assert that the rise is a result
of natural climate variability, they dispute that the pace is likely to
accelerate, and they say that society will be able to adjust to a continuing
slow rise.
Myron Ebell, a climate
change skeptic at the Competitive Enterprise Institute, a Washington
Experts say a few
inches of sea level rise can translate to a large incursion by the ocean onto
shallow coastlines. Sea level rise has already cost governments and private
landowners billions of dollars as they have pumped sand onto eroding beaches
and repaired the damage from storm surges.
Insurance companies
got out of the business of writing flood insurance decades ago, so much of the
risk from sea level rise is expected to fall on the financially troubled
National Flood Insurance Program, set up by Congress, or on state insurance
pools. Federal taxpayers also heavily subsidize coastal development when the
government pays to rebuild infrastructure destroyed in storm surges and picks
up much of the bill for private losses not covered by insurance.
For decades, coastal
scientists have argued that these policies are foolhardy, and that the nation
must begin planning an orderly retreat from large portions of its coasts, but
few politicians have been willing to embrace that message or to warn the public
of the rising risks.
Organizations like Mr.
Ebell’s, even as they express skepticism about climate science, have sided with
the coastal researchers on one issue. They argue that Congress should stop
subsidizing coastal development, regarding it as a waste of taxpayers’ money
regardless of what the ocean might do in the future.
“If people want to
build an expensive beach house on the Florida
or Carolina
The new research
calculates the size of the population living within one meter, or 3.3 feet, of
the mean high tide level, as estimated in a new tidal data set from the
National Oceanic and Atmospheric Administration. In the lower 48 states, that
zone contains 3.7 million people today, the papers estimate, a figure exceeding
1 percent of the nation’s population.
Under current coastal
policies, the population and the value of property at risk in that zone are
expected to continue rising. The land below the 3.3-foot line is expected to be
permanently inundated someday, possibly as early as 2100, except in places
where extensive fortifications are built to hold back the sea. One of the new
papers calculates that long before inundation occurs, life will become more
difficult in the low-lying zone because the rising sea will make big storm
surges more likely.
Only in a handful of
places have modest steps been taken to prepare. New York City Long Island , Connecticut
and New Jersey
