Science Story

08 January 2009 19:56 BST

CO2 ocean sink 'declining'

One of the world's major sources for absorbing carbon dioxide (CO2) is not taking up as much of the gas as it used to, prompting increasing climate change fears.

Scientists report today that they have discovered the Southern Ocean has been absorbing less CO2 since 1981. They propose that this is likely to be due to increased windiness as a result of human activities.

The international team of researchers collected atmospheric CO2 data from 11 stations in the Southern Ocean and 40 stations across the world.

They found that the fall in CO2 absorption equates to five to 30 per cent less per decade.

Due to the Southern Ocean's crucial role, the decrease means that levels of CO2 in the world's atmosphere will be higher in the future than predicted, the researchers claim in the journal Science.

This could then increase climate change as increased CO2 traps more of the Sun's energy in the atmosphere, causing global warming. It is thought the higher levels of CO2 will occur for hundreds of years.

"Climate models project a continued intensification in the Southern Ocean winds throughout the 21st century if atmospheric CO2 continues to increase," the researchers write.

"The ocean CO2 sink will persist as long as atmospheric CO2 increases, but the fraction of the CO2 emissions that the ocean is able to absorb may decrease if the observed intensification of the Southern Ocean winds continues in the future, and the level at which atmospheric CO2 will stabilise on a multi-century time scale may be higher if natural CO2 is out-gassed from the Southern Ocean."