February 28, 2007
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A Guide to Information on Greenhouse Gases and Ozone Depletion
Published July 1988 through June 1999
FROM VOLUME 9, NUMBER 12, DECEMBER 1996
results in a major ocean field experiment have oceanographers
looking forward to follow-up experiments, and have renewed
controversy over a geoengineering scheme. Last summer, in
"IronEx II," iron was added to areas of the tropical
Pacific Ocean, triggering a massive bloom of phytoplankton that
removed CO2 from the air. The results confirm that
lack of iron is a controlling factor in this part of the carbon
cycle, and support the hypothesis that iron reaching the oceans
in the form of windblown dust accounts for the reduced levels of
CO2 during the ice ages that kept the planet cool.
Stimulation of plankton also increased emissions of dimethyl
sulfide (DMS), a gas which oxidizes in the atmosphere to form
sulfate particles. These particles further contribute to cooling,
by shielding the Earth from solar heating and by enhancing the
formation of clouds. (See New Scientist, p. 4, Oct. 12,
1996; Chem. Eng. News, p. 10, Oct. 14; and papers in Prof.
Pubs./Ocean Fertilization, this Global Climate Change Digest issue--Dec.
The next experimental phase will investigate the mechanism in
the Southern Ocean, where its impact on atmospheric CO2
is likely to be the most permanent, because carbon incorporated
into phytoplankton would be carried to the ocean floor and locked
away for centuries. (See Chem. Eng. News, pp. 40-41, Nov.
4, 1996.) According to British oceanographer Andrew Watson,
putting iron in the Southern Ocean could theoretically reduce
atmospheric CO2 by 17 percent within a century.
Another line of research has shown that ocean bacteria also
need iron, and stimulating bacteria with iron would also remove
CO2 from the atmosphere. (See Science News, p.
197, Sep. 28, and papers in Prof. Pubs./Ocean Fertilization, this Global
Climate Change Digest issue--Dec. 1996.)
Ever since the iron fertilization theory was proposed a few
years ago, some have grasped at the concept as a solution to
global warming, while others are leery of this and other
geoengineering schemes, particularly because of possible
unintended consequences. The controversy is discussed thoroughly
in The New York Times (pp. C1, C6, Nov. 12, 1996).
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