Climate scientists in Germany based their predictions, which appear in the latest issue of British journal Nature, on what they believe is an impending change in the Gulf Stream - the conveyor belt that transports warm surface water from the tropical Atlantic to the northern Atlantic and returns cold water southwards at depth.

The Gulf Stream will temporarily weaken over the next decade, in line with what has been happening regularly in the past, the researchers say.

This will lead to slightly cooler temperatures in the North Atlantic and in North America and Europe, and also help the temperatures in the tropical Pacific to remain stable, they suggest.

Last year, scientists on the United Nations' Intergovernmental Panel on Climate Change (IPCC) said that in the next 20 years alone, the global climate would warm by around 0.2 deg C per decade.

These calculations are based on atmospheric concentrations of carbon gases - the 'greenhouse effect' in which solar heat is stored in the air rather than released into space. The heat is eventually transferred to the sea and land, ultimately disrupting Earth's climate system.

The authors of the new study stress that they do not dispute the IPCC's figures.

'Just to make things clear, we are not stating that anthropogenic (man-made) climate change won't be as bad as previously thought,' said Professor Mojib Latif of the Leibniz Institute of Marine Sciences in Kiel, northern Germany.

'What we are saying is that, on top of the warming trend, there is a long-periodic oscillation that will probably lead to a lower temperature increase than we would expect from the current trend during the next years.'

Climate experts have long warned that global warming is unlikely to be a gradual process, but a movement in stops and starts.

The main reason for this is that the oceans - the biggest store of heat - go through natural cycles of circulation.

The long churning of the seas can have a far-reaching effect, sometimes delaying for years the moment when the stored warmth is released at the surface.

Fellow author Johann Jungclaus of the Max Planck Institute for Meteorology in Hamburg likened the trend to 'driving from the coast to a mountainous area and crossing some hills and valleys before you reach the top'.

In some years, the natural long-term variation in ocean circulation would work in the other direction, temporarily pushing on the warming accelerator, he warned.

AGENCE FRANCE-PRESSE