Rising seas threaten many islands, cities and coasts
Rising seas threaten many islands, cities and coasts
Alister Doyle, Reuters/Oslo
It sounds insignificant alongside the Indian Ocean tsunami, yet
an almost imperceptible annual rise in the world's oceans may
pose a huge threat to ports, coasts and islands by 2100.
Leaders of 37 small island states meet in Mauritius from Jan.
10 to Jan. 14 to discuss an early warning system to protect
against tsunamis and a creeping rise in ocean levels, blamed
widely global warming.
Rising sea levels, now about two mm per year, could swamp low-
lying countries like Tuvalu in the Pacific or the Maldives in the
Indian Ocean if temperatures keep rising.
They could also lead to hugely expensive damage worldwide.
"It's often presented as a problem only for developing nations,"
said Mike MacCracken, chief scientist for climate change
programs at the Climate Institute, a Washington think-tank.
"(But) developed countries will be very much at risk because
so much infrastructure is at sea level."
Many of the world's biggest cities are near coasts --
including Calcutta, Dhaka, Lagos, London, New York, Shanghai and
Tokyo. Flooding could cause billions of dollars of damage. In
Bangladesh, 17 million people live less than one metre (three
feet) above sea level.
McCracken and some other experts say that recent evidence of a
faster-than-expected melt of Greenland and Antarctic ice indicate
that the rise in sea levels would be in the upper half of a 9
centimeter to 88 cm range projected by the UN's climate panel by
2100.
Seas rose by 10 cm to 20 cm in the 20th century, according to
the UN scientists. Thermal expansion -- water gets bigger as it
warms -- would be the main cause of rising seas while melting
glaciers and ice caps would add volume.
CO2 rises
The UN panel projects that overall temperatures will rise by 1.4
degrees Celsius to 5.8 degrees Celsius by 2100, mainly because of
a build-up of carbon dioxide from cars, factories and power
plants.
Some scientists say UN models are scaremongering.
"We have no reason to believe, as suggested by most global
warming scenarios, that massive flooding will occur due to an
increase in sea levels," Nils Axel-Morner of the University of
Stockholm wrote in a report.
He predicted oceans would gain 10 cm by 2100, avoiding the
need for extra measures like those to protect Venice, where the
city is sinking, or dykes like those to shield the Netherlands.
Others say the world can adapt -- fossil seashells have been
found high in the Himalayas and continents are almost always
rising or falling.
Still, many countries favor caution.
The UN's 128-nation Kyoto protocol, which seeks to curb
emissions of carbon dioxide, will come into force on Feb. 16. The
United States pulled out in 2001, saying it was too costly and
that its targets to 2012 wrongly excluded poor countries.
"The cost of defending cities would be enormous but the value
at stake is also enormous so protection makes sense," said
Richard Klein, a senior researcher at the Potsdam Institute for
Climate Impact Research.
"It makes less sense to defend agricultural land," he said.
Poor countries would be least able to build defenses,
exacerbating the impact of rising seas, he added. "Vulnerability
to rising seas has as much a social dimension as an environmental
one," he said.
New road design?
McCracken said countries needed to consider whether to build
roads parallel to the coast on levies in low-lying areas or
further back, with spurs towards the sea. And they needed to
stop, for instance, building sewage farms at sea level.
He said a gradual rise in sea levels often caused erosion
because, over time, it made coasts more vulnerable to hurricanes
or cyclones.
"It doesn't happen gradually. People stay on the coast and
then there is a big event like a storm or a tsunami. Then the
coastline changes dramatically," he said.
More than 145,000 people died in the Dec. 26 earthquake and
ensuing huge waves which hit coasts from Indonesia to Somalia.
Scientific evidence from the past varies widely.
Yossi Mart, of Israel's University of Haifa, said that based
on structures like Roman aqueducts and the sluice gates of a
Herodian harbor, sea levels 2,000 years ago in the eastern
Mediterranean were similar to those now.
"In the Crusader times, during the 12th and 13th centuries,
the principal jetty was built for a sea level which is lower than
the present by more than 50 cm," he said.
Conrad Neumann, professor of marine sciences at the University
of North Carolina, said sea levels jumped inexplicably by four
metres about 120,000 years ago, based on surveys in the Bahamas.
They dropped again almost as rapidly.
"There was no man-made effect on the climate then," he said.
"But we shouldn't mess with the climate; it can change in a
hurry. If it's a sleeping dragon don't poke it with a stick: Our
stick might be carbon dioxide."