 Polar bears only have to hold out for 10,000 more years until the new Ice Age rescues them.
November 13, 2008 4:17 PM
By Alister Doyle
OSLO - The planet could face a freeze worse than an Ice Age starting in as little as 10,000 years, giving future societies a headache the opposite of coping with global warming, scientists say.
The researchers, based in Britain and Canada, said that now-vilified greenhouse gases might help in future to avert a chill that could smother much of Canada and the United States, Europe and Russia in permanent ice.
They said the study, based on records of tiny marine fossils and the earth's shifting orbit, did not mean the world should stop fighting warming, stoked by human emissions of heat-trapping gases from burning fossil fuels.
"We're saying: 'don't push the panic button'," said Thomas Crowley, an American scientist at Edinburgh University who shared authorship of the study in the journal Nature with a colleague at Toronto University.
"There's no excuse for saying 'we've got to keep pumping carbon dioxide (CO2) into the atmosphere", he told Reuters by telephone, adding that the cooling was projected to start in 10,000 to 100,000 years.
"Geologically it's tomorrow," he said. "But we have a lot of time to argue about the appropriate level of greenhouse gases."
The projected build-up of vast ice sheets across
the Northern Hemisphere and over seas around
Antarctica would also lower sea levels by perhaps
300metres (980ft) - connecting Russia to Alaska
by land.
FALLING, RISING
In the last Ice Age, sea levels fell about 130 metres
and much of Russia escaped a big ice sheet. Scientists
can build sea level records from fossils because ocean
chemistry varies; salt, for instance, is more
concentrated when there is less sea water.
"Presumably, future society could prevent this
transition indefinitely with very modest adjustments
to the atmospheric CO2 level," they wrote. Greenhouse
gases are widely blamed as the main cause of current
warming that may bring more heatwaves, droughts,
food shortages and rising seas.
A shift to a bigger blanket of ice would mark the end
of a period of warming that began 50 million years ago,
when even Antarctica was almost ice-free.
The scientists said the recent swings between Ice
Ages and warmer periods such as the present, over
the past 900,000 years, were getting sharper. Models
suggested that instability could herald a shift to a new,
far colder and stable state.
A similar shift happened more than 34 million years
ago when Antarctica was first covered by ice, the
scientists said. A trigger could be a slight growth of
polar ice sheets, with ice and snow reflecting more of
the sun's heat back into space. That could accelerate
a cooling.
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