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Tuesday, January 13, 2009

Scientists seek clues in historic global warming

Climate experts today began a major conference in Wellington canvassing evidence of climate change before humans .

The conference at Te Papa, organised by GNS Science, is probing evidence of greenhouse effects in the climate of the Paleogene period, 65 to 35 million years ago.

This is thought to be the most recent time the Earth experienced global warming on a scale similar to what is now being projected as a result of human activity.

On Wednesday, leading scientists will stage a one-day symposium to showcase the role that research into the ancient greenhouse world can play in advancing understanding of modern climate change.

Speakers will explore the role of greenhouse gases in driving Paleogene episodes of extreme global warming, the effects that warming had on biological systems, how natural feedback systems modulate climate and atmospheric greenhouse gas levels and the effectiveness of climate models in simulating greenhouse climate states.

Conference organiser Chris Hollis said there was growing evidence that temperatures in high latitude places like New Zealand have been far higher than previously thought.

In a paper on global temperature over the past 100 million years, Professor Peter Barrett, of Victoria University, said the "greenhouse world" was 6degC to 7degC warmer than today with only small ice sheets in the interior of Antarctica.

Antarctic ice core records from relatively recent times showed a close association between atmospheric carbon dioxide levels and temperature over the past 800,000 years.

"It seems that from a geological perspective, without concerted intervention now, there is a credible risk of Earth's climate, by the end of the century, reverting to greenhouse world temperature, but with `residual' polar ice sheets," he said.

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