Date: 20-Feb-09
Country: CANADA
Author: Alister Doyle, Environment Correspondent
OSLO - Abrupt shifts in the climate such as the end of Ice Ages could provide an early warning system for modern changes such as prolonged droughts, a leading scientist said on Monday.
The sudden desertification of North Africa 5,500 years ago or a warming at the end of the last Ice Age 11,000 years ago were preceded by signs of a less stable climate, according to Marten Scheffer of Wageningen University in the Netherlands.
That insight, reported last year, is now being applied to try to detect shifts in the modern climate that might herald ever more droughts and other changes in nature.
"It's a whole rich field that's opening," Scheffer told Reuters, adding it could have applications for predicting when irreversible shifts, or "tipping points," were approaching.
"We are working on the recent climate now as well," said Scheffer, head of Aquatic Ecology and Water Management group at the University.
Scheffer will present the ideas at a meeting in Copenhagen on March 10-12 that that is meant to help more than 190 governments work out a new treaty by December to fight global warming blamed on manmade greenhouse gases.
Under the findings, temperature fluctuations and other climate factors slowed down before tipping points in the ancient climate, such as 34 million years ago when the world shifted from a warm "greenhouse" to a far colder state.
ELASTIC
Scheffer likened the slowdowns to a rubber band that loses elasticity before suddenly snapping.
"It looks like droughts have some of the characteristics we're looking for," he said of preliminary findings that could help detect subtle changes that can predict droughts that could lead to desertification.
"General conditions may change, ocean temperatures may change, cloudiness may change in gradual ways," he said. "It may push a regional system to a tipping point."
"There are massive databases of precipitation, of heatwaves," he said. "We have begun filtering these data to see if there is some systematic change before the onset of droughts."
Farmers could shift to less intensive land uses -- away from grazing cattle, for instance -- if scientists were able to predict that a region was vulnerable to drought.
Other applications could include examining the recovery rates of natural systems -- such as coral reefs or lakes -- to see how resilient they are to change.
If they take longer to recover after damage than in the past "the system may be close to a tipping point" he said.
Other potential climate "tipping points" in nature include a shrinking of the Arctic ice in summer that could herald the disappearance of the ice cap. Dark ground and water soak up far more heat than reflective snow and ice -- accelerating the warming. Arctic ice reached a record low in September 2007.
(Editing by Alison Williams)
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