The discovery in a core of ancient polar ice of evidence of a sudden Antarctic temperature rise thousands of years ago has added fuel to the debate on global warming.
The find, by scientists working on an ice core taken several km (miles) beneath the surface, is the first evidence of rapid warming in the Antarctic and matches existing evidence of warmer bouts in past aeons in the north pole region.
It suggests a temperature spike of around four degrees Celsius took place in the south pole region over about a decade 19,000 years ago.
"That's a significant temperature change (over) about a decade... Pretty phenomenal," said Dr David Etheridge, a scientist with Australia's Commonwealth Scientific and Industrial Research Organisation (CSIRO).
The discovery, by University of Colorado Associate Professor James White towards the end of last year, is sending Australian scientists back to examine their own drill cores of Antarctic ice, taken from Australia's East Antarctic Territory.
Scientific interest in White's discovery, from cores taken from coastal West Antarctica, has been heightened by a correlation between the time of the temperature spike and an abrupt rise in sea levels at about the same time, as documented by Australian National University research.
"It is fuel for the argument that climate change can be rapid, even in the southern hemisphere, and ice sheets can melt," Etheridge said.
Not everyone agrees. White's discovery, which all scientists caution needs verification, is providing as much fuel for sceptics as for committed believers in greenhouse warming.
Professor Pat Quilty, former chief scientist with the Australian government-funded Australian Antarctic Division and now an academic with the University of Tasmania, says the Antarctic temperature spike counters doomsday theories of melting Antarctic ice sheets.
Belying the beliefs of those on the global climate change bandwagon, the new Antarctic readings showed natural change could be as dramatic as anything produced by man, he said.
"This is taking a more reasoned view," Quilty said. "Nature imposes some pretty dramatic changes."
Etheridge says ancient Antarctic ice is proving that warming thousands of years ago took place after changing orbital tilts of the earth triggered a release of the greenhouse gas, carbon dioxide, from the oceans.
Greenhouse gas was part of the cause of warming even then, long before industrialisation increased the amount of gas clogging the atmosphere, he said.
Now ancient Antarctic ice could help predict modern climate change, he said.
"It is the historical record which constrains our understanding of the climate system. The 19,000 year shift is another piece of the jigsaw into understanding how things change," Etheridge said.
SEARCH FOR NEW EVIDENCE
Further evidence of White's warming could be hidden in a 10 cm (four inch) section of a core sample of ice in Australia.
"It's worth looking," said Vin Morgan, principal research scientist with the Australian Antarctic Division (AAD), the government-funded body responsible for logistics and research at Australia's Antarctic Territory.
AAD will re-examine a core covering an 80,000 years timespan drilled around 10 years ago at Law Dome, inland from Casey Station.
The real question was what made rapid climate changes occur, Morgan said. Nobody knows, despite the unlocking of some of the secrets of Antarctic ice.
Also, nobody definitely knows how Antarctic ice sheets are responding to global warming and changes in sea level, he said.
The West Antarctic ice sheet contains enough ice to raise global sea levels by five to six metres. The entire Antarctic ice is about equivalent to 70 metres of sea level.
But new snow was generally compensating for ice loss, leaving the Antarctic in approximate balance between accumulation and outflow of Antarctic ice, Morgan said.
If anything, atmospheric warming should initially increase the Antarctic ice sheet through increased snowfall, with the rate of outfall taking thousands of years to react to temperature change, he said.
Australian ice cores clearly record increased atmospheric buildup of greenhouse gases through the industrial age, in association with a temperature rise of about 1.5 degrees celsius over the last 150 years.
Global warming was expected to continue as modern economies pumped out greenhouse gases, Etheridge said. Antarctic ice would therefore be a key part of science's attempts to maintain a habitable climate on earth.
"The ice is a detective story, I guess," Etheridge mused.