/ 30 January 2007

Antarctica — a test bed for global warming

As top scientists meet in the comfort of Paris to hammer out a major report on climate change, a handful of their confreres hunker down on a frozen plateau in the middle of Antarctica, painstakingly gathering warning signs of global warming.

A century ago, Antarctica was deemed a forbidding frozen wilderness, a place irredeemably hostile to settlement or even human life itself. Today, the fringes of this great white wilderness are valued by scientists as a store of unique wildlife, and its heart is prized as a precious barometer of Earth’s fevers and chills.

By digging deep — more than 3km deep — into the crust of ice that blankets the world’s least hospitable continent, a rotating commune of French and Italian researchers is tracing the history of the planet’s climate going back nearly a million years.

Getting the samples is a straightforward if technically daunting procedure. Using 3m lengths of 9,8cm-diameter aluminium tubing, the scientists drill in increments, preserving samples to be analysed in laboratories on site and in France or Italy.

Particles of dust and air bubbles trapped in the ice make it possible to establish links between the presence of greenhouse gases in the atmosphere — especially carbon dioxide — and shifts in weather patterns across the millennia.

“It’s of huge importance for understanding the climate machine,” says Dominique Raymond, of the Laboratory for Glaciology and Environmental Geophysics, based in Grenoble, southeastern France.

These invisible signatures in the ice can reveal the atmospheric nuclear tests of the 1940s, 1950s and 1960s as well as the eruption of Krakatoa in 1883 — and other climate events that go far beyond the brief history of Homo sapiens.

The data will yield “a succession of hot and cold cycles” going back 875 000 years, the first time such an ancient record has been established, explains Olivier Cattani, a glaciologist from the Climate Science and Environment Laboratory in Saclay outside Paris.

It took researchers nearly 10 years to drill through 3 270m of ice to within 5m of bedrock. “At Concordia, the deep glaciology is finished,” he says. “But the science is just beginning.”

Carbon dioxide

The results from studies here and other research centres at both extremities of the planet are set to confirm that carbon-dioxide levels are higher now than at any time in the past 800 000 years.

Significantly, Cattani says, the measurements have shown only a meagre difference, of about eight degrees Celsius, between the last warm period (the Holocene, our present era) and the last ice age, about 21 000 years ago.

The 500-odd scientists in Paris comprising the United Nations Intergovernmental Panel on Climate Change (IPCC) will release a report on Friday that will summarise the most recent research and predict temperature rises over the next century.

In its previous report in 2001, the body forecast that by 2100 the global atmospheric temperature would have risen between 1,4 and 5,8 degrees Celsius compared with its 1990 level, depending on how much greenhouse gas is emitted.

The French first set up a scientific base at Concordia, about 1 100km inland toward the South Pole from the Indian Ocean, in 1992, and were soon joined by Italy. In 1996, under the auspices of European Project for Ice Coring in Antarctica, they established the year-round habitat called Dome C and began digging into the ice plateau.

In the summer months of November to March, when temperatures hit a balmy -30 degrees Celsius, the station — a pair of snow-white, three-storey cylinders connected by a passageway along with several technical structures — can accommodate more than 30 scientists and staff.

But the PhDs can only reach the base by an arduous voyage, through wave-tossed, iceberg-infested seas, aboard the supply ship Astrolabe, and then overland by helicopter and snow tractor.

In winter — with average thermometer readings of -60 degrees Celsius — the population plummets to 16 or fewer. — AFP