World sea levels to rise 1.5m by 2100: scientists

Karin Strohecker, Reuters 15 Apr 08;

VIENNA (Reuters) - Melting glaciers, disappearing ice sheets and warming water could lift sea levels by as much as 1.5 meters (4.9 feet) by the end of this century, displacing tens of millions of people, new research showed on Tuesday.

Presented at a European Geosciences Union conference, the research forecasts a rise in sea levels three times higher than that predicted by the Intergovernmental Panel on Climate Change (IPCC) last year.

The U.N. climate panel shared the 2007 Nobel Peace Prize with former U.S. Vice President Al Gore.

Svetlana Jevrejeva of the Proudman Oceanographic Laboratory in Britain said the estimate was based on a new model allowing accurate reconstruction of sea levels over the past 2,000 years.

"For the past 2,000 years, the sea level was very stable," she told journalists on the margins of the Vienna meeting.

But the pace at which sea levels are rising is accelerating, and they will be 0.8-1.5 meters higher by next century, researchers including Jevrejeva said in a statement.

Sea levels rose 2 cm in the 18th century, 6 cm in the 19th century and 19 cm last century, she said, adding: "It seems that rapid rise in the 20th century is from melting ice sheets".

Scientists fiercely debate how much sea levels will rise, with the IPCC predicting increases of between 18 cm and 59 cm.

"The IPCC numbers are underestimates," said Simon Holgate, also of the Proudman Laboratory.

The researchers said the IPCC had not accounted for ice dynamics -- the more rapid movement of ice sheets due to melt water which could markedly speed up their disappearance and boost sea levels.

But this effect is set to generate around one-third of the future rise in sea levels, according to Steve Nerem from the University of Colorado in the United States.

"There is a lot of evidence out there that we will see around one meter in 2100," said Nerem, adding the rise would not be uniform around the globe, and that more research was needed to determine the effects on single regions.

Scientists might debate the levels, but they agree on who will be hardest hit -- developing nations in Africa and Asia who lack the infrastructural means to build up flood defenses. They include countries like Bangladesh, almost of all of whose land surface is a within a meter of the current sea level.

"If (the sea level) rises by one meter, 72 million Chinese people will be displaced, and 10 percent of the Vietnamese population," said Jevrejeva.

(Reporting by Karin Strohecker; Editing by Catherine Evans)

Forecast for big sea level rise
Richard Black, BBC News 15 Apr 08;

Sea levels could rise by up to one-and-a-half metres by the end of this century, according to a new scientific analysis.

This is substantially more than the Intergovernmental Panel on Climate Change (IPCC) forecast in last year's landmark assessment of climate science.

Sea level rise of this magnitude would have major impacts on low-lying countries such as Bangladesh.

The findings were presented at a major science conference in Vienna.

The research group is not the first to suggest that the IPCC's forecast of an average rise in global sea levels of 28-43cm by 2100 is too conservative.

The IPCC was unable to include the contribution from "accelerated" melting of polar ice sheets as water temperatures warm because the processes involved were not yet understood.

Melt water

The new analysis comes from a UK/Finnish team which has built a computer model linking temperatures to sea levels for the last two millennia.

"For the past 2,000 years, the [global average] sea level was very stable, it only varied by about 20cm," said Svetlana Jevrejeva from the Proudman Oceanographic Laboratory (POL), near Liverpool, UK.

"But by the end of the century, we predict it will rise by between 0.8m and 1.5m.

"The rapid rise in the coming years is associated with the rapid melting of ice sheets."

The model, she told reporters here at the European Geosciences Union (EGU) annual meeting, is able to mimic accurately sea levels reliably observed by tide gauges over the last 300 years.

There is little concrete evidence on sea levels for the thousands of years before that, explained POL's Simon Holgate, who was not involved in the new study.

"There is some limited archaeological evidence [based on] the sill heights of fish enclosures that the Romans used, that's probably the strongest evidence that there hasn't been any significant change in sea level over the last 2,000 years."

Against that, he said, the currently observed rise of about three mm per year is significant, and many scientists working in the field expect to see an acceleration.

Last year, German researcher Stefan Rahmstorf used different methodology but reached a similar conclusion to Dr Jevrejeva's group, projecting a sea level rise of between 0.5m and 1.4m by 2100.

Space-eye view

The latest satellite data indicates that the Greenland and West Antarctic ice sheets are losing mass, though the much bigger East Antarctic sheet may be gaining mass.

A full melting of Greenland and West Antarctica would raise sea levels by many metres; but the process, if it happened, would take centuries.

"We know what's happening today from satellite data, but trying to predict what that means in the future is very difficult science," noted Steve Nerem from the University of Colorado, whose own research concerns global sea levels.

"There's a lot of evidence out there that we're going to see at least a metre of sea level rise by 2100," he said.

"We're seeing big changes in Greenland, we're seeing big changes in West Antarctica, so we're expecting this to show up in the sea level data as an increase in the rate we've been observing."

However, a rise of even a metre could have major implications for low-lying countries - especially, noted Dr Holgate, those whose economies are not geared up to build sophisticated sea defence systems.

"Eighty to 90% of Bangladesh is within a metre or so of sea level," he said, "so if you live in the Ganges delta you're in a lot of trouble; and that's an awful lot of people."

Dr Jevrejeva's projections have been submitted for publication in the scientific journal Proceedings of the National Academy of Sciences.

Climate change scientists 'underestimating impact on sea levels'
The Telegraph 16 Apr 08;

Sea levels could rise much more dramatically than previously thought affecting millions of people, scientists have warned.

The rise could be as much as 1.5 metres (4.9 feet) by the end of the century which would have devastating consequences for low-lying countries.

The findings - from a UK/Finnish team presented at a Geosciences conference in Vienna - are far higher than climate scientists have previously predicted.

Svetlana Jevrejeva of the UK’s Proudman Oceanographic Laboratory said the estimate was based on a new model which allowed for accurate reconstruction of sea levels over the past 2,000 years.

She said the sea level had been stable throughout two millennia but the pace at which they were rising was now accelerating.

Sea levels had risen by two cms (three-quarters of an inch) in the 18th century, six cms (2.3 inches) in the 19th century and by 19 cms (7.4 inches) in the last century.

She said: “It seems that rapid rise in the 20th century is from melting ice sheets”.

The predictions are substantially higher than estimates from the Intergovernmental Panel on Climate Change (IPCC) which has talked of a 28-43cm (11-17 inches) rise by 2100.

The IPCC did not take into account the melting of the polar ice sheets because the processes were not fully understood.

The researchers said the IPCC had not allowed for ice dynamics - the more rapid movement of ice sheets due to melt water which could markedly speed up their disappearance and boost sea levels.

According to Steve Nerem from the University of Colorado in the United States, who is also involved in sea level research, this effect is set to generate around one-third of the future rise in sea levels.

“There is a lot of evidence out there that we will see around one metre in 2100,” he said although the rise would be different around the world.

“We’re seeing big changes in Greenland, we’re seeing big changes in West Antarctica, so we’re expecting this to show up in the sea level data as an increase in the rate we’ve been observing.”

Worst hit would be nations, particularly in Africa, who do not have adequate flood defences and countries such as Bangladesh most of whose land is within one metre of current sea levels.

Dr Jevrejeva added: “If the sea level rises by one metre, 72m Chinese people will be displaced, as well as 10 percent of the Vietnamese population.”

Her projections have been submitted for publication in the scientific journal Proceedings of the National Academy of Sciences.