Tropical Cyclones Bury CO2: Study

Monday, 20 October 2008 Alister Doyle Reuters

Cyclones could have a significant role in the transfer of carbon dioxide to the deep ocean, say the study's authors (Source: NASA) Tropical cyclones may be slowing global warming by washing large amounts of vegetation and soil containing greenhouse gases into the sea, say scientists.

A study of the LiWu river in Taiwan showed that floods caused by typhoon Mindulle in 2004 swept into the Pacific Ocean an estimated 0.05% of carbon stored in leaves, branches, roots and soil on the hillsides being studied. The carbon sank to the seabed.

"Tropical cyclones could have a significant role in the transfer of atmospheric carbon dioxide to long-term deposits in the deep ocean," according to the study's findings, published in the journal Nature Geoscience.

Plants soak up carbon dioxide and store it as carbon as they grow. The carbon usually gets released back to the air when vegetation rots or is burnt.

"50 to 90 million tonnes of carbon a year is thought to enter the oceans from islands of the west Pacific alone," mainly during cyclones, according to the scientists, based in Britain and Taiwan.

Tiny effect

But the scientists say the mechanism would not do much to slow global warming, believed to be the result of burning fossil fuels.

"The current amount of carbon dioxide building up from manmade sources is about 100 to 1000 times faster than this carbon (burial) from the interaction between the cyclones, erosion and forests," says study co-author Professor Robert Hilton of Cambridge University.

"In terms of the manmade carbon cycle this is not going to save us. But it illustrates that the earth has natural ways of dealing with carbon dioxide," he says.

And the scientists say more than half of the carbon might be from fossils in rocks washed down rivers by floods, rather than recent vegetation.

Hilton says the findings from Taiwan were likely to be similar to the impact of Atlantic hurricanes on Caribbean islands.

The experts included Meng-Chiang Chen of the Taroko National Park, who had the risky job of going out during cyclones, tied to a harness, to gather water from the LiWu river in containers dangling from a pole.

The United Nation's Intergovernmental Panel on Climate Change predicts that tropical cyclones are likely to get more powerful because of global warming that would also cause more heatwaves, droughts, floods and raise sea levels.

The carbon burial mechanism might fractionally offset the trend to more powerful storms, says Hilton. But more powerful cyclones would have other damaging effects such as washing away more topsoil, threatening farms.

Source: http://www.abc.net.au/