Iron versus the Greenhouse
Oceanographers cautiously explore a global warming therapy
By RICHARD MONASTERSKY
from Science News, vol. 148, p. 220, September 30, 1995
Nothing had prepared Kenneth Coale or his shipmates for the color of
the water. The oceanographers watched in awe as the R. V. Melville
plied Pacific waves dyed a soupy green by a bumper crop of tiny ocean
plants.
The tint was abnormal. Only a day before, this patch of water
near the Galapagos Islands had sparkled with electric blue clarity,
a quality owed to the general absence of microscopic plants called
phytoplankton. Coale and his colleagues had transformed this marine
desert into a garden simply by sprinkling a dilute solution of iron
into the water.
"We had predicted the response, but none of us was really
prepared for what it would look or feel like," says Coale, a
researcher at the Moss Landing (Calif.) Marine Laboratories. "There
were some of us who were quite pleased and others of us who would walk
out on the fantail and burst into tears. It was a profoundly
disturbing experience for me. We had deckhands come up to us and ask,
`Did we do this?'"
Indeed they had, and some of the scientists feared that the
repercussions would ripple far beyond this small sector of water.
Although designed to test basic theories about marine ecology, the
Pacific experiment had demonstrated all too dramatically the effects
of adding iron to the oceanÑa scheme known as the Geritol solution to
global warming. By spreading just half a ton of iron across 100
square kilometers of the Pacific, the oceanographers had stimulated
enough plant growth to sop up some 350,000 kilograms of carbon dioxide
from the seawater. If performed on a grand scale, iron fertilization
of ocean water could absorb billions of tons of carbon dioxide from
the air, enough to slow the rate of greenhouse warming, according to
some rough estimates.
The Geritol solution, named for the venerable iron supplement,
represents only one of many geoengineering quick-fixes dreamed up to
stave off global environmental problems. The proposals range from
low-tech to Star Trek, from planting trees to stationing a huge
filtering screen between Earth and the sun. Some people promote
these megaprojects as a planetary salve, easing the pain of global
warming without requiring society to address the root cause, its
dependence on fossil fuels. Others view them as last-ditch efforts
that could save Earth should efforts to reduce pollution prove
ineffective.
Coale and many others who witnessed iron's tremendous greening
effect loathe the idea of tinkering with the globe in such a
heavy-handed way. But he admits that the overwhelming success of the
iron experiment could well generate a wave of support for
geoengineering proposals.
"We have demonstrated that we have the key now for turning
this system on and off," says Coale. "I think some will be encouraged
by these findings. Therein lies the dilemma."
The idea of stimulating plankton growth with iron grew out of the
fertile mind of the late John H. Martin, an oceanographer at Moss
Landing. Martin sought originally to explain a long-standing mystery
concerning barren waters in the Antarctic, subarctic, and equatorial
Pacific Oceans. With the abundant concentrations of nutritious
nitrate and phosphorus in all three regions, phytoplankton should
thrive. But it doesn't. Martin became convinced in the late
1980s that lack of iron keeps the phytoplankton from making use of
the nutrients and that a little extra iron would trigger rapid
growth of the plants. He calculated that it would be feasible to
fertilize the ocean on a massive scale, eventually drawing carbon
dioxide out of the atmosphere and deep-sixing the greenhouse gas into
the nether reaches of the ocean. Want to slow global warming? Just
add iron. He announced this possibility somewhat facetiously in July
1988 at a lecture at the Woods Hole (Mass.) Oceanographic Institution.
"Putting on my best Dr. Strangelove accent, I suggested that with half
a shipload of Fe [iron] . . . I could give you an ice age," he
recalled 2 years later in the newsletter of the Joint Ocean Global
Flux Study.
Martin lobbied extensively for conducting a field experiment
of iron fertilization--a plan that some oceanographers considered
anathema. Nonetheless, the National Research Council's Board on
Biology backed Martin's call for field research to test the iron
hypothesis. It estimated that iron fertilization could remove 2
billion tons of carbon in the form of carbon dioxide from the
atmosphere each year. That's about 1.5 times the U.S. carbon dioxide
emissions each year.
Always one to inspire controversy and debate, Martin remained
vague about his feelings on actually using iron fertilization to
limit global warming. Oceanographer Sallie W. Chisholm of the
Massachusetts Institute of Technology often argued with him about
the ethics of geoengineering, or even of conducting research toward
that goal.
"He was cynical about humankind," she says. "He felt that
obviously this would be a foolish way to go, that humans should get
their act together and stop emitting so much carbon dioxide. But he
didn't believe that we would get our act together."
Whatever his thoughts about actually implementing the Geritol
solution, Martin used the idea to his advantage. The controversial
notion attracted interest to his pet hypothesis about iron deficiency
in phytoplankton, which other oceanographers roundly criticized as
too simplistic. At the time, prevailing theories held that various
combinations of light limitations, cold temperatures, and predator
populations kept the phytoplankton from using up the ready supply of
nutrients. When Martin broached the issue of geoengineering, what
had been basic science instantly acquired social relevance.
The charismatic oceanographer convinced his colleagues and the
National Science Foundation to stage a small-scale experiment that
would add iron to 64 square kilometers of ocean near the Galapagos
Islands. Though Martin died of cancer shortly before the expedition,
his colleagues carried out the first iron addition in the fall of 1993.
The experiment vindicated Martin's hypothesis. As predicted,
the iron supplement stimulated plant growth, verifying that at
least some phytoplankton species suffered from iron deficiency.
But the anticipated drawdown of carbon dioxide never
materialized. Tiny animals known as zooplankton flocked to the
region and consumed the new plant growth, releasing the carbon dioxide
before it could sink into the deep ocean. Other factors also limited
the iron's effectiveness (SN: 3/5/94, p.148).
In June, Coale and company ventured back out to the eastern
Pacific to fertilize another parcel of ocean, this time spreading the
iron additions out over a week's time. Given the results of the first
experiment, the oceanographers were not prepared for the overwhelming
bloom they created in the normally barren ocean. "It would be like
driving through the Mojave Desert and coming on a rain forest," says
Coale.
Phytoplankton grew so successfully that concentrations of the
photosynthetic pigment chlorophyll increased by a factor of 30 to 40
in the water, accounting for the green color. This time, scientists
measured a marked decrease in the carbon dioxide concentration of
the water. Because this part of the Pacific normally vents carbon
dioxide into the atmosphere, the experiment reduced the natural
flow of the greenhouse gas into the air (SN: 7/22/95, p.53).
The second fertilization produced a much more powerful
response because of slight changes in experimental procedure and
natural conditions. In 1993, the oceanographers added all the iron at
once, whereas in the more recent outing, they split the supplement
into three doses, prolonging the time it took the iron to
sink. Ocean currents also kept the iron-doped water at the surface
longer during the second experiment, giving phytoplankton more time
to grow and absorb carbon dioxide.
Coale is quick to distance the iron experiments from the topic
of geoengineering, noting that the team set out only to test the
validity of Martin's basic hypothesis. But he acknowledges that the
recent results could help those who want to pursue large-scale iron
fertilization.
"We are conducting research that may be used toward
geoengineering and that does make me feel a bit uncomfortable. I don't
feel we have the same dilemma as the scientists who worked on the Man-
hattan Project [building the first atomic bomb], but there are some
similarities," he says.
Despite Coale's personal feelings, his lab at Moss Landing has
turned into a mecca for geoengineering supporters. Sitting on a shelf
in his office is a bottle of Japanese scotch, a present from visiting
researchers connected with the Japanese electric power industry,
which seeks to conduct experiments aimed at iron fertilization. The
benefits are clear for producers of electricity, who face the specter
of increased regulation and potential limits on profits should nations
start imposing controls on greenhouse gas pollution.
Coale has yet to open the bottle. "It's sort of ironic that
the scotch is sitting there unopened after two experiments, and we
don't know whether it would be a good idea to toast these results or
not."
Coale and others associated with the more recent experiment argue
vigorously against using these findings to support the Geritol
solution to global warming. For starters, they raise the issue of
efficacy. No one knows exactly where the carbon dioxide goes once
incorporated into the phytoplankton tissue. The gas could stay in
the ocean, or it could leak out into the atmosphere just as quickly as
it is absorbed.
After the recent Pacific experiment, the waters returned
quickly to their natural condition. This indicates that any
geoengineering plan would have to add iron to the water quite
frequently, says Coale. Even if the technique worked, it would offset
only about one-third of global carbon dioxide emissions.
Then there is the question of side effects. Promoting the
growth of certain phytoplankton species on a massive scale will alter
the ecology of these ocean areas, with unknown consequences, says
Chisholm. Considering that most researchers laughed off the iron
hypothesis as recently as 8 years ago, oceanographers feel wholly
unprepared to predict how the ocean will respond to iron
fertilization.
To succeed, a geoengineering scheme would have to spike an
area of ocean the size of Asia, nearly 500,000 times the size of the
experimental patch. The bloom of plants could enrich the whole
ecosystem.But the decay of all that organic matter could rob the
surface waters of oxygen, generating huge anoxic zones--the equivalent
of a giant swampy layer in the ocean--that would kill marine life
there. It is even possible that the organic matter could exacerbate
global warming by generating methane, a greenhouse gas much more
potent than carbon dioxide.
"I think it's folly. It would just cause another environmental
problem," says Chisholm. "It's so naive to think that we can do one
thing and it's going to have a predictable effect. The arrogance of
human beings is just astounding."
A controversial report by the National Academy of Sciences in
1992 looked at iron fertilization, among other geoengineering
options. Although the NAS noted some caveats, it concluded that iron
fertilization does have one attractive feature: a relatively cheap
price tag. Running 360 ships full-time to fertilize 46 million
square kilometers of ocean would cost somewhere between $10 billion
and $110 billion a year.
Not much for altering the global climate. In comparison, the
United States spends close to $2 billion each year on global change
research.
But would the money be well spent? Michael MacCracken,
director of the Office of the U.S. Global Change Research Program in
Washington, D.C., examined geoengineering schemes for the upcoming
report by the Intergovernmental Panel on Climate Change. He argues
that society would benefit more from investing in new energy
technologies than from manipulating the environment.
"The trouble with most geoengineering options is that it's
sort of money down the drain," says MacCracken. "If you are going to
go to all of this effort, why don't you just build some alternative
power sources? Why not use the same amount of money to build
solar-powered satellites and beam the energy back?"
MacCracken also warns that, once started, the geoengineering
path would become an addiction. "All of these become a continuing
commitment for society in order to keep temperatures down. And if you
ever stopped doing that for some reason, you suddenly get this very
large warming influence upon you."
But society may need geoengineering options, no matter how
unpalatable, says Gregg Marland of the Oak Ridge (Tenn.) National
Laboratory, who worked on the NAS report. He also helped organize a
symposium on the topic at last year's annual meeting of the American
Association for the Advancement of Science.
Marland says his jobÑcompiling the global inventory of carbon
dioxide emissions--has made him skeptical about the prospects of
making deep cuts in green-house gas pollution. "Per capita emis-
sions in the U.S. are 5 tons per year of carbon. The global average
per capita emissions are 1.1 tons per year. It's inconceivable in any
kind of an equitable world that those emissions won't
increase. Population is increasing, for one thing. The growth taking
place in Asia right now is phenomenal."
Society may simply lack the political will to reduce
greenhouse gas emissions, says Marland. "If we don't, somewhere down
the line geoengineering may be our only choice.... l think we'd be
foolish to walk away from geoengineering, and we'd be equally foolish
to count on it right now or to start trying it."
Against this backdrop of divergent options and emotionally
charged arguments, many scientists take the safe route, calling for
more basic research on climate. In a book submitted for publication,
The Engineering Response to Global Climate Change, a panel of
scientists and engineers, which includes Marland and MacCracken,
argues that scientists must learn how the climate works and develop
the skill to predict it before evaluating strategies to control
nature.
To that end, Coale and his colleagues are trying to secure
funding for a small-scale fertilization experiment in the Antarctic
Ocean, another area seemingly affected by iron limitations. Although
he has conflicting feelings about how people might use the results of
this research, Coale believes the issue won't disappear.
Oceanographers should therefore explore the iron hypothesis further so
society will have the necessary information for making sound
judgments.
"As John Martin once said, 'The cat's out of the bag.' I feel
compelled to carry out this research in a way which is environmentally
responsible," Coale says.
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