An international team of scientists has developed a new method of measuring CO2 absorption by the oceans and mapped CO2 uptake for the entire North Atlantic for the first time.

Appearing tomorrow in the journal Science, the study could greatly improve our understanding of the natural ocean 'sinks' and enable more accurate predictions about how the global climate is changing.

The new technique could also lead to the development of an 'early-warning system' to detect any weakening of the ocean sinks – seen by some scientists as the first sign of more pronounced climate change.

 The researchers used a network of commercial ships carrying chemical sensors in their engine rooms - combined with other information such as satellite observations of sea surface temperature - to map the uptake of atmospheric CO2 by the entire North Atlantic Ocean.

The results suggest that the North Atlantic absorption of CO2 varies substantially over periods of several years and is sensitive to regional changes in climate.

"These exciting results from our new co-ordinated network represent the first time scientists have observed CO2 uptake over any large region of the world - either land or ocean - with such accuracy," said Prof Watson.

"Our new method estimates the flux and how it varies from year to year and season to season, showing patterns of uptake with a detail never before realized."

 It is hoped that similar networks could be established in other major ocean basins well-covered by shipping, making it possible to observe carbon uptake over most of the world's oceans. The networks could be used to give early warning of any weakening in the uptake of carbon dioxide by the global oceans.

This uptake is very important in slowing the rise of CO2 in the atmosphere, and some scientists have warned that such a weakening of the sink could be beginning to occur as climate change becomes more pronounced.