Emily Beament Global temperatures may not increase over the next decade because of natural variations in the climate which will offset man-made warming, scientists predicted yesterday.

Researchers attempting to model what might happen to the climate of the North Atlantic over a period of decades suggest that the temperature of the sea and Europe and North America may cool slightly.

The researchers said the North Atlantic had variability on a 70 to 80-year cycle and the meridional overturning circulation (MOC) - a giant "conveyor belt" that brings warm water northwards into the area - had an important role to play in driving those fluctuations. When the circulation is strong, it creates warmer temperatures.

The study created a model that used sea surface temperatures and attempted to simulate the variability of the MOC in a bid to predict climate over coming decades.

The model - tested by comparing retrospective "predictions" against what has actually happened - suggests the MOC may weaken towards a long-term average, leading to slightly cooler temperatures in the North Atlantic.

Sea surface temperatures in the tropical Pacific will remain unchanged, the scientists led by Noel Keenlyside of Leibniz Institute of Marine Sciences, Kiel, Germany, said.

Writing in Nature, they said: "Our results suggest that global surface temperature may not increase over the next decade, as natural climate variations in the North Atlantic and tropical Pacific temporarily offset the projected anthropogenic warming."

Commenting on the study, Richard Wood of the Met Office, Hadley Centre, said the model suggested the weakening of the MOC would have a cooling effect around the North Atlantic.

"Such a cooling could temporarily offset the longer-term warming trend from increasing levels of greenhouse gases in the atmosphere.

"That emphasises once again the need to consider climate variability and climate change together when making predictions over timescales of decades."

But he said the use of just sea surface temperatures may not accurately reflect the state of the MOC, which is several kilometres deep and dependent on factors besides temperatures, such as salt content.

If the model could accurately forecast other variables besides temperature, such as rainfall, it would be increasingly useful, but climate predictions for a decade ahead would always be to some extent uncertain, he added.