According to the study, the next Ice Age is due between 10,000 and 100,000 years from now - but global warming may step in to prevent it.

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PARIS: Scheduled shifts in Earth's orbit are due to plunge the planet into an Ice Age perhaps 10,000 years from now, but the event may be averted by man-made greenhouse gases, say scientists.

They caution, though, in a study reporting the find in the British journal Nature, that this news is not an argument in favour of global warming, which is driving imminent and potentially far-reaching damage to the climate system.

Big freeze

Earth has experienced long periods of extreme cold over the billions of years of its history. The big freezes are interspersed with "interglacial" periods of relative warmth, of the kind we have experienced since the end of the last Ice Age, around 11,000 years ago.

These climate swings have natural causes, believed to be rooted particularly in changes in Earth's orbit and axis that, while minute, have a powerful effect on how much solar heat falls on the planet.

The two researchers behind the study built a high-powered computer model to take a closer look at these intriguing phases of cooling and warmth.

In addition to the planetary shifts, they also factored in levels of carbon dioxide (CO₂), found in tiny bubbles in ice cores, that provide an indicator of temperature spanning hundreds of thousands of years.

The model revealed dramatic swings in climate, including changes when Earth flipped from one state to the other over a relatively short time, said one of the authors, geoscientist Thomas Crowley of the University of Edinburgh in Scotland.

Abrupt bifurcations

These shifts, called "bifurcations," appear to happen in abrupt series, which is counter-intuitive to the idea that the planet cools or warms gradually.

"You had a big change about a million years ago; then a second change around 650,000 years ago, when you had bigger glaciations; then 450,000 years ago, when you started to get more repeated glaciations," said Crowley. "What's also interesting is that the inter-glaciations also became warmer."

According to the model, authored by Crowley and physicist William Hyde of Toronto University in Canada, the next "bifurcation" would normally be due between 10,000 and 100,000 years from now.