Tropical cyclones can bury greenhouse gases: study
Sun Oct 19, 2008 1:01pm EDT
By Alister Doyle, Environment Correspondent
OSLO (Reuters) – Tropical cyclones may be a tiny help in slowing global warming by
washing large amounts of vegetation and soil containing greenhouse gases into the
sea, scientists said on Sunday.
A study in Taiwan of the LiWu river showed that floods caused by typhoon Mindulle in
2004 swept into the Pacific Ocean an estimated 0.05 percent 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 findings
in the journal Nature Geoscience.
Plants soak up carbon dioxide, a natural greenhouse gas also emitted by burning
fossil fuels, and store it as carbon as they grow. The carbon usually gets released
back to the air when vegetation rots or is burned.
“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.
But the scientists said the mechanism would not do much to slow warming caused by
mankind, led by burning of fossil fuels.
“The current amount of carbon dioxide building up from manmade sources is about
100-1,000 times faster than this carbon (burial) from the
interaction between the cyclones, erosion and forests,” said Robert Hilton of
Cambridge University who was one of the authors.
“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
said.
And the scientists said more than half of the carbon might be from fossils in rocks
washed down rivers by floods, rather than recent vegetation.
Hilton said 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
Headquarters, 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 U.N. Climate Panel predicted last year that tropical cyclones were likely to get
more powerful because of global warming that would also cause more heatwaves,
droughts, floods and raise world sea levels.
The carbon burial mechanism might fractionally offset the trend to more powerful
storms, Hilton said. But more powerful cyclones would have other damaging effects
such as washing away more topsoil, threatening farms.
(Editing by Charles Dick)
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