Antarctic melt may push sea levels to 1.4 metres: study

Marlowe Hood Yahoo News 1 Dec 09;

PARIS (AFP) – Quickening ice loss in West Antarctica will likely contribute heavily to a projected sea level rise of up to 1.4 metres (4.5 feet) by 2100, according to a major scientific report released Tuesday.

Scientists long held that most of Antarctica's continent-sized ice sheet was highly resistant to global warming, and that the more vulnerable West Antarctic ice block would remain intact for thousands of years to come.

The Intergovernmental Panel on Climate Change (IPCC) -- whose 2007 report is the scientific benchmark for the UN December 7-18 Copenhagen climate summit -- did not even factor melting ice sheets into its forecasts for rising seas.

But studies since then show huge loss of ice mass, mainly as a result of warmer ocean temperatures, according to the review by more than 100 experts on the Scientific Committee on Antarctic Research.

The new evidence suggests that West Antarctica in particular will add "tens of centimetres" to the global ocean watermark, which is predicted to go up two to nine times higher than the IPCC forecast, according to the report.

Even the relatively modest IPCC projection of a 18-59 centimetre (7-23 inch) increase by 2100 would render several island nations unlivable and wreak havoc in low-lying deltas home to hundreds of millions.

Ironically, the impact of global warming on the region is set to intensify over the next century due to the successful effort to repair another kind of damage to the environment -- depletion of the ozone layer.

A hole in the ozone layer caused by the release of CFC (chlorofluorocarbon) gases has cooled temperatures and shielded most of Antarctica from global warming, the report found.

"The most astonishing evidence is the way that one man-made environmental impact -- the ozone hole -- has shielded most of Antarctica from another, global warming," said John Turner, head of climate research for the British Antarctic Survey and lead editor or the review.

The stable temperatures -- and in some areas additional cooling -- over much of the vast Antarctic continent during the last 30 years has been offered as evidence by climate skeptics that global warming trends were exaggerated or simply false.

But with measures to control the CFC gases, the scientists said they expected the hole to "heal" in around 50 to 60 years, leading to additional warming of about 3.0 Celsius (5.4 Fahrenheit) by century's end.

Already today, 90 percent of the Antarctic Peninsula's glaciers have retreated in the last few decades, though the bulk of the continent's ice sheet has so far shown little change.

The 550-page report highlights several other recent findings:

-- Earth's most powerful ocean current, the Antarctic Circumpolar Current, has warmed faster than the global ocean as a whole. This is set to disrupt the region's ecosystems, including the rise of alien species that compete with and replace native Antarctic inhabitants.

That process has already begun on the Antarctic Peninsula, where rapid warming has resulted in the expansion of plant, animal and microbial communities -- many of them introduced by humans -- on newly thawed land.

-- Sea ice loss and ocean acidification are directly affecting wildlife, and could reduce Antarctica's rich biodiversity, from the bottom to the top of the food chain.

Tiny krill have declined significantly, and in some areas Adelie penguin populations have dropped due to reduced sea ice and prey. In other regions, however, notably Ross Sea and East Antarctica, populations of the flightless birds have remained stable or gone up.

-- Levels of carbon dioxide and methane, the two main greenhouse gases, are higher and increasing faster than at any time in the last 800,000 years. At the same time, recent studies show that small changes in climate over the last 11,000 years -- the last ice age -- has caused rapid ice loss along with shifts in ocean and atmospheric circulation.

Antarctic to feed major sea rise
Richard Black, BBC News 1 Dec 09;

Sea levels are likely to rise by about 1.4m (4ft 6in) globally by 2100 as polar ice melts, according to a major review of climate change in Antarctica.

Conducted by the Scientific Committee on Antarctic Research (SCAR), it says that warming seas are accelerating melting in the west of the continent.

Ozone loss has cooled the region, it says, shielding it from global warming.

Rising temperatures in the Antarctic Peninsula are making life suitable for invasive species on land and sea.

The report - Antarctic Climate Change and the Environment - was written using contributions from 100 leading scientists in various disciplines, and reviewed by a further 200.

SCAR's executive director Dr Colin Summerhayes said it painted a picture of "the creeping global catastrophe that we face".

"The temperature of the air is increasing, the temperature of the ocean is increasing, sea levels are rising - and the Sun appears to have very little influence on what we see," he said.

SCAR's report comes 50 years to the day after the Antarctic Treaty, the international agreement regulating use of the territory, was opened for signing, and a week before the opening of the potentially seminal UN climate summit in Copenhagen.

High rise

Two years ago, the Intergovernmental Panel on Climate Change (IPCC) projected that the global average sea level would probably rise by 28-43 cm (11-16in) by the end of the century.

But it acknowledged this figure was almost certainly too low, because it was impossible to model "ice dynamics" - the acceleration in ice melting projected to occur as air and water temperatures rise.

Launching the SCAR report in London, lead editor John Turner from the British Antarctic Survey (BAS) suggested that observations on the ground had changed that picture, especially in parts of the West Antarctic ice sheet.

"Warmer water is getting under the edges of the West Antarctic ice sheet and accelerating the flow of ice into the ocean," he said.

By the end of the century, he said, the sheet will probably have lost enough ice alone to raise sea levels globally by "tens of centimetres".

The remainder of the projected rise would come from melting of the Greenland cap, melting of mountain glaciers in the Himalayas and Andes, and the expansion of seawater as it warms.

A number of research teams have come up with similar projections.

But this is the first time that an international body such as SCAR has endorsed the likelihood that sea levels will rise enough to threaten some of the world's biggest cities by the end of the century.

Cold store

The Antarctic Peninsula - the strip of land that points towards the southern tip of South America - has warmed by about 3C over the last 50 years, the fastest rise seen anywhere in the southern hemisphere, according to the report.

But the rest of the continent has remained largely immune from the global trend of rising temperatures.

Indeed, the continent's largest portion, East Antarctica, appears to have cooled, bringing a 10% increase in the sea ice extent since 1980.

This report backs the theory that it has bucked the global trend largely because of ozone depletion - the chemical havoc wrought over 30 years by chlorofluorocarbons (CFCs) and other agents in the stratosphere above the polar region.

"We used to have a big blanket of ozone, and when we took it away we saw a cooling," said Professor Turner.

"The Antarctic has been shielded from the impacts of global warming."

But, the report concludes, that will not last forever.

The ozone hole is expected to repair itself in about 50 years, now that the Montreal Protocol has curbed the use of ozone-destroying substances.

As it does so, the SCAR team predicts that greenhouse warming will come to dominate the temperature change across Antarctica, as in other parts of the planet.

Doubling of greenhouse gas concentrations in the atmosphere would warm the continent by 3-4C, it says.

The majority of Antarctica is so cold that a rise of this magnitude in air temperature would have little impact.

But more warming of the oceans would speed ice loss still further, the report concludes.

On the basis of declines seen around the Antarctic Peninsula, it would also be expected to bring significant reductions in the abundance of krill, a key foodstuff for baleen whales and other animals.

Among humankind, the frozen continent was once a preserve of explorers and scientists.

But now, about 30,000 tourists a year visit, some setting foot on outlying parts of the peninsula.

This increased human traffic, plus the warming on land and sea, are going to change the region's ecology, according to Julian Gutt, allowing organisms to enter and survive that were previously excluded through climate or simple geography.

"A good candidate is the stone crab (aka king crab) such as those found throughout Norwegian waters - they're more than a metre across from toe to toe.

"There are hints of it hopping across from South America - and that could completely change the ecosystem on the sea floor," said the Alfred Wegener Institute researcher.

About one third of one percent of Antarctica's land surface is ice-free; but already, non-native species are competing with native mosses for this meagre resource, Dr Gutt noted.

Major cities at risk from rising sea level threat
Hannah Devlin and Robin Pagnamenta, The Times Online 1 Dec 09;

Sea levels will rise by twice as much as previously predicted as a result of global warming, an important international study has concluded.

The Scientific Committee on Antarctic Research (SCAR) calculated that if temperatures continued to increase at the present rate, by 2100 the sea level would rise by up to 1.4 metres — twice that predicted two years ago.

Such a rise in sea levels would engulf island nations such as the Maldives in the Indian Ocean and Tuvalu in the Pacific, devastate coastal cities such as Calcutta and Dhaka and force London, New York and Shanghai to spend billions on flood defences.

Even if the average global temperature increases by only 2C — the target set for next week’s Copenhagen summit — sea levels could still rise by 50cm, double previous forecasts, according to the report.

SCAR, a partnership of 35 of the world’s leading climate research institutions, made the prediction in the report Antarctic Climate Change and Climate. It far exceeds the 0.59 metre rise by the end of the century quoted by the Intergovernmental Panel on Climate Change (IPCC) in 2007. This was based on a “business as usual” approach by governments that allowed temperatures to rise by 4 degrees. It will underpin the negotiations in Copenhagen.

SCAR scientists said that the IPCC underestimated grossly how much the melting of the Antarctic and Greenland ice sheets would contribute to total sea-level rises.

One of the world’s leading experts on climate science has called for the world to intensify efforts to control global warming by actively removing carbon dioxide from the atmosphere.

In an interview with The Times, Dr Rajendra Pachauri, chairman of the IPCC, said that geo-engineering, where carbon is stripped from the atmosphere using specialist technologies, would be necessary to control runaway damage to the climate. “At some point we will have to cross over and start sucking some of those gases out of the atmosphere.”

He added that world leaders meeting in Copenhagen should aim for a tighter target of no more than a 1.5C rise in global temperatures.

The IPCC report predicted that the melting of ice sheets would contribute about 20 per cent of the total rise in sea levels, with the majority coming from the melting of glaciers and the expansion of the water as it warms. It said that it was not able to predict the impact of melting ice sheets, but suggested this could add 10-20cm.

The SCAR report uses detailed climate observations over the past century linking temperature to sea levels to produce a more sophisticated estimate. It puts the likely contribution from ice sheets at more than 50 per cent.

The calculations were carried out by Stefan Rahmstorf, Professor of Physics of the Oceans at the Potsdam Institute for Climate Impact Research in Germany. Sceptics seized upon his figures as further evidence of the unreliability of climate change predictions.

“It’s 50cm, 60cm, 100cm — 60m if you ask James Hansen from Nasa,” said Benny Peiser, director of the Global Warming Policy Foundation . “The predictions come in thick and fast, but we take them all with a pinch of salt. We look out of the window and it’s very cold, it doesn’t seem to be warming. We’re very concerned that 100-year policies are being made on the basis of these predictions”