Rising Seas Threaten Islands, Cities, Coasts
Reuters News Service, Jan. 11, 2005
OSLO (Reuters) - 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 this week to discuss an early warning system to protect against tsunamis and a creeping rise in ocean levels, blamed widely on global warming.
Rising sea levels, now about 0.08 inch a 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 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 3.5-34.5 inch range projected by the U.N.'s climate panel by 2100.
Seas rose by 3.9-7.8 inches in the 20th century, according to the U.N. 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.
The U.N. panel projects that overall temperatures will rise by 2.5-10.5 degrees Fahrenheit by 2100, mainly because of a build-up of carbon dioxide from cars, factories and power plants. Some scientists say U.N. models are scare-mongering.
"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 3.9 inches 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 U.N.'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 toward 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-13th centuries, the principal jetty was built for a sea level which is lower than the present by more than 50 cm (19.7 inches)," he said.
Conrad Neumann, professor of marine sciences at the University of North Carolina, said sea levels jumped inexplicably by 12 feet 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."
Will Rising Seas Swamp Some Small Island States?
PORT LOUIS - Small island nations meet in Mauritius from Jan. 10-14 for talks about threats including a creeping rise in sea levels blamed by most scientists on global warming.
The meeting is likely to be dominated by calls for early warning systems for natural disasters after Asia's Dec. 26 tsunami that killed more than 150,000 people. It will separately look at a feared slow rise of ocean levels in a warmer world.
A UN panel of more than 2,000 scientists predicted in its latest report in 2001 that average sea levels are likely to rise by 9-88 cms (3.5-35 inches) by 2100, mainly because of a build-up of heat-trapping gases in the atmosphere from human burning of fossil fuels.
"If the higher end of that scale is reached, the sea could overflow the heavily populated coastlines of such countries as Bangladesh, cause the disappearance of some nations entirely (such as the island state of the Maldives), foul freshwater supplies for billions of people and spur mass migrations," according to a UN statement.
The 2001 report said that seas rose by 10-20 cms in the 20th century, far faster than the century average for the past few thousand years.
Many scientists say that a 50 cm sea rise can typically cause a 50 metre retreat of the coastline where the land is relatively flat. Erosion can often happen in surges after cyclones, hurricanes or tsunamis.
A minority of scientists dismiss the UN findings about global warming and say they are based on erroneous climate models. Some others say they may underestimate risks from a melting of ice-caps in Antarctica and Greenland.
WHAT ISLANDS WOULD BE MOST AT RISK?
In the Pacific, island states barely above sea level include Kiribati, the Marshall Islands, Tonga and Tuvalu. In the Atlantic, Angigua and Nevis are vulnerable, as are the Maldives in the Indian Ocean.
WHAT EVIDENCE IS THERE?
The UN Environment Programme said on Thursday that Kiribati, the Marshall Islands and Tuvalu have already lost islets to sea level rise.
TUVALU - In February 2004, the nine islands of the Pacific atoll were submerged by "king tides", washing over much of the nation whose highest point is 4.5 metres over sea level. Once rare, king tides happen now once every two years and damage crops and freshwater sources, according to inhabitants.
NIUE - Cyclone Heta devastated the South Pacific island in January 2004, causing damage to houses and infrastructure estimated at eight times the island's gross domestic product.
Devastating storms have happened throughout history but the UN models predict that they will become more frequent in a warmer world.
HOW ABOUT ELSEWHERE?
About 17 million people live less than one metre above sea level in Bangladesh. Large areas of US states southern Florida or Louisiana would also be flooded if seas rose by a metre. Venice and London are among cities built in regions where the land is sinking, adding to the problems.
The United Nations projects that 80 percent of the world's population will live within 100 miles (60 km) of coastlines by 2010.
Huge cities just above sea level include Tokyo, Osaka, Bombay, Madras, Calcutta, Seoul, Bangkok, Dhaka, Karachi, Jakarta, Manila, Shanghai, Tianjin, Lagos, Cairo, Istanbul, London, New York, Los Angeles, Buenos Aires and Lima.