By SIMON COLLINS
The winner of one of New Zealand's top science medals, Professor Peter Barrett, has backed off a controversial claim that humanity faces extinction within 100 years because of global warming.
Dr Barrett, who was presented with the Royal Society's Marsden Medal in Christchurch last night, gave the Christchurch Press notes for his acceptance speech in which he planned to say: "If we continue our present growth path we are facing extinction - not in millions of years, or even millennia, but by the end of this century."
After a storm of criticism, he changed the word "extinction" in his speech last night to "the end of civilisation as we know it".
Dr Barrett, 64, the director of Victoria University's Antarctic Research Centre, has used ancient air particles trapped in Antarctic ice to show changes in carbon dioxide are linked with changes in the polar ice sheets and the Earth's climate. His work has been widely cited in the world's scientific journals.
But his own colleagues were embarrassed yesterday after his initial speech notes were reported.
"I certainly wouldn't be using that language," said Dr Jim Salinger, the lead author for the Australia and New Zealand chapter of the next global assessment by the Intergovernmental Panel on Climate Change.
Dr Tim Naish of the Institute of Geological and Nuclear Sciences, who has worked with Dr Barrett in Antarctica for many years, said he talked to him at length after his speech notes were reported and said, "I don't think he meant to say that in 100 years we'll all be gone.
"I personally, and I think the majority of scientists, would find his comments, as they were reported, hard to defend from a scientific basis," Dr Naish said.
Auckland engineer Bryan Leyland, a climate change sceptic, said small ice sheets had melted but there was no evidence the rest of Antarctica was warming.
Dr Salinger said Antarctic ice showed that carbon dioxide ranged between 180 and 280 parts per million during natural cycles caused by changes in the Earth's orbit over the past 400,000 years, but had now reached 374 ppm.
Dr Barrett said smaller climatic changes had destroyed past civilisations and humanity could not run the risk of rising carbon dioxide levels.
"The last time carbon dioxide levels were this high was before humans evolved," he said.