Climate buffer: The remarkable data set comes from 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.
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PARIS: The world's oceans may be losing their ability to soak up extra CO2 from the atmosphere, with the potential to exacerbate global warming, say new studies.
Absorption of atmospheric CO2 by the North Atlantic plunged by half between the mid-1990s and the period from 2002 to 2005, British researchers say in the November 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.
Oceanic buffer
The discovery touches on a key aspect of the global warming question, because for decades the ocean has been acting as a buffer, 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," she said.
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, however. "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."
Economic growth
In another study, published on Monday, researchers said that economic growth had caused levels of atmospheric CO2 to increase 35 per cent faster than expected since 2000.
Eighteen per cent 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 kg 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 U.S. journal the Proceedings of the National Academy of Sciences.
