Ocean currents may offset global warming over coming decade

• Ian Sample
• guardian.co.uk,
• Thursday May 1 2008

This article was first published on guardian.co.uk on Thursday May 01 2008.

Global warming is set to stall over the next 10 years as natural variations in ocean currents counteract manmade climate change.

Researchers modelling the climate of Europe and North America found that a major ocean current that brings warm water northwards is set to weaken, potentially offsetting temperature rises caused by human activity.

A team led by Noel Keenlyside at the Leibniz Institute for Marine Science in Germany focused on an ocean current known as the meridional overturning current or MOC. The current acts as a huge conveyor belt, bringing warm water into the North Atlantic and returning cold water to the south.

Scientists believe the ocean current strengthens and weakens on a natural cycle with a 70 to 80-year period. When the current is strong, it brings warmer water and a milder climate to northern regions.

The team's models, which were checked against historical temperature changes, suggest the current will weaken enough to cool the North Atlantic, while temperatures in the tropical Pacific are unlikely to change.

The study appears in the journal Nature today.

"Our results show that global mean temperatures may plateau or cool weakly over the next 10 years because of natural fluctuations, but in the long term temperatures will continue to rise," said Dr Keenlyside. "This doesn't change the bottom line on global warming."

Reports from the UN Intergovernmental Panel on Climate Change suggest carbon emissions could drive global temperatures up by as much as 0.2C each decade.