Oceans may be losing ability to absorb CO2
The world`s oceans may be losing their ability to soak up extra carbon dioxide (CO2) from the atmosphere, with the risk that this will help stoke global warming, two new studies say.
Absorption of atmospheric CO2 by the North Atlantic plunged by half between the mid-1990s and 2002-5, British researchers say in a paper published in the November issue of the Journal of Geophysical Research.
The data comes from sensors lowered by a container ship carrying bananas, which makes a round trip from the West Indies to Britain every month. It has generated more than 90,000 measurements of ocean CO2.
The finding touches on a key aspect of the global warming question, because for decades the ocean has been absorbing much of the CO2 released into the atmosphere from the burning of fossil fuels.
If the sea performs less well as a carbon sponge, or "sink" according to the technical jargon, more CO2 will remain in the atmosphere, thus accelerating the greenhouse effect.
Ute Schuster, who led the research with Professor Andrew Watson of the University of East Anglia`s School of Environmental Sciences, admitted she was astonished by the data.
"Such large changes are a tremendous surprise. We expected that the uptake would change only slowly because of the ocean`s great mass," Schuster was quoted by the university in a press release Monday as saying.
Research last year pointed to rising acidification of the oceans as a result of CO2 uptake, highlighting the risk of carbon saturation as well as a looming peril for biodiversity.
Schuster was cautious about drawing too swift a conclusion from the new research.
"Perhaps this is partly a natural oscillation or perhaps it is a response to the recent rapid climate warming," she said.
"In either case, we now know that the sink can change quickly and we need to continue to monitor the ocean uptake."
In another study also published on Monday, the researchers said that economic growth had caused levels of atmospheric CO2 to increase 35 percent faster than expected since 2000.
Eighteen percent of the increase could be attributed to a decline in the efficiency of sinks -- the oceans as well as forests -- in soaking up airborne CO2. The remainder came from fossil fuels.
"Fifty years ago, for every tonne of CO2 emitted, 600 kilograms (1,300 pounds) were removed by natural sinks. In 2006, only 550 kilograms were removed per tonne and that amount is falling," said lead author Pep Canadell of the Global Carbon Project.
The findings were published in the Proceedings of the National Academy of Sciences, which like the Journal of Geophysical Research is published in the United States.
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