comprise the other great sink of greenhouse gases; some researchers estimate that they absorb 40 percent of fossil- fuel emissions.
In coastal waters rich in runoff, plankton can swarm densely, a million in a drop of water. They color the sea brown and green
where deltas form from big rivers, or cities dump their sewage. Tiny yet hugely important, plankton govern how well the sea
harvests the sun's bounty, and so are the foundation of the ocean's food chain. Far offshore, the sea returns to its plankton-starved
are huge drivers in the environmental equations, because within them the plankton process vast stores of gases. Though cause
and effect are not quite clear, we do know that in ice ages, carbon dioxide levels dropped 30 percent.
we do this today? Driving carbon dioxide down should lower temperatures, certainly. But how?
may lie not in the tropics but in the polar oceans, where huge reserves of key ingredients for plant growth--nitrates and
phosphates--drift unused. The problem is not weak sunlight or bitter cold, but lack of iron. Electrons move readily in its
presence, playing a leading role in trapping sunlight.
fix would be to seed these oceans with dissolved iron dust. This may have been the trigger that caused the big carbon dioxide
drop in the ice ages: The continents dried, so more dust blew into the oceans, carrying iron and stimulating plankton to absorb
carbon dioxide. Mother Nature can be subtle.
an idea crosses the momentous boundary between quasi-natural mitigation such as tree planting and self-evidently artificial
means. Here is the nub of it, the conceptual chasm. With a boast that may cost his cause dearly, the inventor of the idea,
John Martin of the Moss Landing Marine Laboratories in California, said, "Give me half a tanker full of iron, and I'll give
you another ice age."
carbon gets tied up in a "standing crop" of plankton. These tiny creatures dwell within a few meters of the surface. To truly
bury the gas, they must somehow carry it into the vast bulk of the whole ocean. Some biologists believe that from the plankton
the carbon dioxide should slowly dissolve into the lower waters, though we are uncertain of this. Perhaps the carbon dioxide
eventually is deposited on the seabed. This last process no one has checked. Somehow, though, a good deal of carbon does end up in the deep ocean sinks.
proposed by Martin in 1988, the "Geritol solution" of adding iron to the ocean had a rocky history. Many derided it automatically
as foolish, arrogant, and politically risky. But in 1996 the idea finally got tested by the U.S. government, and it performed well. Near the Galapagos Islands lies
a fairly biologically barren area. Over 28 square miles of blue sea, scientists poured 990 pounds of iron during a week of
testing. Immediately the waters bloomed with tiny phytoplankton, which finally covered 200 square miles, suddenly green. Plankton
production peaked nine days after the experiment started. One thousand pounds of iron dust stimulated over 2,000 times its
own weight in plant growth, far greater than the performance of any fertilizer on land. The plankton soaked up carbon dioxide,
reducing its concentration in nearby sea water by 15 percent. It quickly made up this deficiency by drawing carbon dioxide
from the air.
show that since this process would affect only about 16 percent of the ocean area, a full-bore campaign to dump megatons of
iron into the polar oceans probably would suck somewhere between 6 percent and 21 percent of the carbon dioxide from the atmosphere,
with most recent estimates settling around 10 percent. Such scary, big-time tinkering is the extreme; the method would have
to be tested at far lower levels. Still, this mitigation could dent the greenhouse problem, though not solve it entirely.
such partial solutions attract firm opponents. Geoengineering carries the strong scent of hubris. What is best described as
eco-virtue reared its head immediately after the 1988 proposal, even before any experiments took place. Following the Puritan
model that any deviation from abstinence is itself a further indulgence, many scientists and ecologists saw in Martin's plan
an incentive for polluters. "A lot of us have an automatic horror at the thought," commented atmospheric authority Ralph Cicerone
of the University of California at Irvine.
specialists retaliated. Russell Seitz of Harvard said the Galapagos experimenters were afraid to seem politically incorrect.
"If this approach proves to be environmentally benign," Seitz said, "it would appear to be highly economic relative to a Luddite
program of declaring war against fire globally."
uncertainties remain: How would the iron affect the deeper ecosystems, of which we know little? Will the carbon truly end
up on the seabed? Can the polar oceans carry the absorbed carbon away fast enough to not block the process? Would the added
plankton stimulate fish and whale numbers in the great Antarctic Ocean? Or would some side effect damage the entire food pyramid? Even if the idea worked, who should run such a program?
Additionally, there is some evidence that little of the newly fixed carbon in the Galapagos experiment actually sank.
seems to have come back into chemical equilibrium with the air. Controversy surrounds this essential point; clearly, here
is where more research could tell us much.
much seems certain (and should allay many fears): If we decide to stop the Geritol solution because of unforeseen side effects,
control is easy. The standing crop will die off within a week, providing a quick correction.
too, are easy to figure. There is nothing very high-tech about dumping iron. Martin estimated that the job would take about
half a million tons per year. Depending on what sort of iron proves best at prodding plankton, and implementation methods,
the iron costs range between $10 million and $1 billion a year. Throwing in 15 ships steaming across the polar oceans all
year long, dumping iron dust in lanes, brings the total to around $10 billion. This would soak up about a third of our global
fossil-fuel-generated carbon dioxide emissions each year.
mitigation efforts need take place on land or sea. In fact, the most intuitive approach may be simply to reflect more sunlight
back into space, before it can be emitted in heat radiation and then absorbed by carbon dioxide. People understand the basic
concept readily enough: Black T-shirts are warmer in summer than white ones. We already know that simply painting buildings
white makes them cooler. We could compensate for the effect of all greenhouse gas emissions since the Industrial Revolution
by reflecting less than 1 percent more of the sunlight.
0.5 percent change in Earth's net reflectivity, or albedo, would solve the greenhouse problem completely. The big problem
is the oceans, which comprise about 70 percent of our surface area and absorb more light because they are darker than land.
it comes to increasing albedo, it would be wise to begin the discussion by introducing positive measures that can be easily
understood and are close at hand. Reflecting sunlight is not a deep technical idea, after all. Simply adding sand or glass
to ordinary asphalt ("glassphalt") doubles its albedo. This is one mitigation measure everyone could see--a clean, passive
way to Do Something.
UCLA study showed that Los
Angeles is 5 degrees
Fahrenheit warmer than the surrounding areas, mostly due to dark roofs and asphalt. Cars and power plants contribute, but
only a bit; at high noon, the sun delivers to each square mile the power equivalent of a billion-watt electrical plant.
urban "heat island" effect is common. But white roofs, concrete-colored pavements, and about $10 billion in new shade trees
could cool the city below the countryside, cutting air conditioning costs by 18 percent. Cooler roads lessen tire erosion,
too. About 1 percent of the United States is covered by human constructions, mostly paving, suggesting that we may already control enough of the land to get
at the job.
such homegrown solutions, we could make the leap to space. The most environmentally benign proposal for increasing the planet's
albedo is very high-tech (and expensive): a massive orbiting white screen, about 2,000 kilometers on a side. Even if such
parasols were broken into small pieces, putting them up would cost about $120 billion, a bit steep. We would also have to
pay a lot to take them down if they caused some undesirable side effects. (One is certain: a night sky permanently light-polluted,
irritating astronomers and moonstruck lovers.)
more-innocuous dust to reflect sunlight does not work; it drifts away, driven off by the sun's light pressure. But the upper
atmosphere is still a good place to intervene, because much sunlight gets absorbed in the atmosphere on its way to us. Also,
measures far above our heads trouble us less.
sorts of reflectors at high altitudes are promising. Spreading dust in the stratosphere appears workable because at those
heights tiny particles stay aloft for several years. This is why volcanoes spewing dust affect weather strongly. The tiny
motes that redden our sundowns reflect more sunlight than they trap infrared.
better than dust are microscopic droplets of sulfuric acid, which reflects light more effectively. Sulfate aerosols can also
raise the number of droplets that make clouds condense, further increasing overall reflectivity. This could then be a local
cooling, easier to monitor than carbon dioxide's global warming. We could perform such small, controllable experiments now.
The amount of droplets or dust needed is a hundredth of the amount already blown into the atmosphere by natural processes,
so we would not be venturing big dislocations. And we would get some spectacular sunsets in the bargain.
there are human-centered concerns. The Environmental Protection Agency hammers away at particulate levels, blaming them for
lung disorders. Luckily, high- altitude dust would come down mostly in raindrops, not making us cough. The cheapest way of
delivering dust to the stratosphere is to shoot it up, not fly it. Big naval guns fired straight up can put a one-ton shell
20 kilometers high, where it would explode and spread the dust. This costs only a hundredth as much as the space-parasol idea.
But booming naval guns that rattle windows for miles around are likely to provoke more than a few Not in My Backyard reactions.
there is a ready alternative to dust in any form: jet fuel. Changing the fuel mixture in a jet engine to burn rich can leave
a ribbon of fog behind for up to three months, though as it spreads it becomes invisible to the eye. These motes would also
come down mostly in rain, not troubling the brow of the EPA. Fuel costs about 15 percent of airlines' cash operating expenses,
and running rich increases costs by only a few percent. For about $10 million, this method would offset the 1990 U.S. greenhouse emissions. Adding this to the cost of an airline ticket would boost prices
perhaps 1 percent. An added asset is that quietly running rich on airline fuel will attract little notice, doesn't even change
sunsets, and is hard to muster a media-saturated demonstration against.
are, as always, side effects. Dust or sulfuric acid would heat the stratosphere, too, with unknown impact. Some scientists
suspect the ozone layer could be affected. If a widespread experiment showed this, we could turn off the effect within roughly
a year as the dust settled down and got rained out. (Smaller experiments should show this first, of course.)
ideas envision doing what natural clouds do already as the major players in the total albedo picture. A 4 percent increase
in stratocumulus over the oceans would offset global carbon dioxide emission. Land reflects sunlight much better than the
wine-dark seas, so putting clouds far out from land, and preferably in the tropics, gets the greatest leverage.
condense around microscopic nuclei, often the kind of sulfuric acid droplets the geoengineers want to spread in the stratosphere.
The oceans make such droplets as sea algae decays, and the natural production rate sets the limit on how many clouds form
over the seas. Clouds cover about 31 percent of our globe already, so a 4 percent increase is not going to noticeably ruin
with such a mammoth natural process is daunting, but in fact about 400 medium-sized coal-fired power plants give off enough
sulfur in a year to do the job for the whole Earth. (This in itself suggests just how much we are already perturbing the planet.)
There are problems with using coal: Arguing that more air pollution is good for Mother Earth sounds intuitively wrong. Coal
plants sit on land, and the clouds would be most effective over the oceans. A savvy international strategy leaps to mind:
Subsidize electricity-dependent industry on isolated Pacific islands, and ship them the messiest, sulfur-rich coal. The plants'
plumes would stretch far downwind, and the manufactured goods could revitalize the tropical ocean states, paying them for
being global good neighbors. The wealthy states would then get their mitigation carried out far from home and far from vexatious
neighborhood committees, using labor purchased at low rates. And nobody has to take the plants; prices will mediate the demand.
boring approach, worked out by the National Academy of Sciences panel, envisions a fleet of coal-burning ships which heap sulfur directly
into their furnaces. (Maybe some collaboration would work here. Freighters burning sulfur could also spread iron dust, combining
the approaches, with some economies.) The ships spew great ribbons of sulfur vapor far out at sea, where nobody can complain,
and cloud corridors form obediently behind. It would be best to use these sulfur clouds to augment the edges of existing overcast
regions, swelling them and increasing the lifetime of natural clouds. The continuously burning sulfur freighters would follow
weather patterns, guided by weather satellite data.
these could operate as regional experiments, to work out a good model of how the ocean's cloud system responds. This low-tech
method would cost about $2 billion per year, including amortizing the ships.
political risk here lies with shifts in the weather. The entire campaign would increase the sulfur droplet content in our
air by about 25 percent. Probably this would cause no significant trouble, with most of the sulfur raining out into the oceans,
which have enormous buffering capacity. Keeping the freighters a week's sailing distance from land would probably save us
from scare headlines about sudden acid rains on farmers' heads, since about 30 percent of the sulfur should rain out each
panel found that "one of the surprises of this analysis is the relatively low cost" of implementing some significant geoengineering.
It might take only a few billion dollars to mitigate the U.S. emission of carbon dioxide. Compared with stopping people in China from burning coal, this is nothing.
not take the 1992 panel report, thick with footnotes and layers of qualifiers, to be a road map to a blissful future. The
NAS estimates are simple, linear, and made with poorly known parameters. They also ignore many secondary effects. For example,
forests promote clouds above them, since the water vapor they exhale condenses quickly. Those lovely cumulus puffs reflect
sunlight. So growing trees to sop up carbon dioxide also increases albedo, a positive feedback bonus. But is that the end
of the chain? No, because water vapor itself is a greenhouse gas. Thick clouds absorb infrared as well. If forests respire
a lot, they can partially trap their own heat. Understanding this, and calculating it in detail, will take a generation of
the greatest unknown is social: How will the politically aware public react--those who vote, anyway? If geoengineers are painted
early and often as Dr. Strangeloves of the air, they will fail. Properly portrayed as allies of science--and true environmentalism--they
could become heroes. Not letting the radical greens set the terms of discussion will matter crucially.
factor here will be whether mitigation looks like yet another top-down contrivance, another set of orders from the elite.
Draconian policing of fuel burning will certainly look that way, a frowning Aunt Bessie elbowing into daily details, calculating
your costs of commuting to work and setting your thermostat level. In contrast, mitigation does not have to push a new camel's
nose into our tents. Technical solutions can play out far from people's lives, on the sea or high in the air.
widespread acceptance of mitigation strategies could lead to an albedo chic--ostentatious flaunting of white roofs, the Mediterranean
look, silvered cars, the return of the ice-cream suit in fashion circles. White could be appropriate after Labor Day again.
seriously, every little bit would indeed help. This is crucial: Mitigation wears the white hat. It asks simple, clear measures
of everyone, before going to larger-scale interventions. Grassroots involvement should be integral from the very beginning.
Local efforts should go apace with those at the nation-state level, especially since mitigation intertwines deeply with diplomacy.
Here appearances are even more critical, given the levels of animosity between the big burners (especially the United States) and the tropical world.
solutions should stay within the NAS panel's sober guidelines. Learning more is the crucial first step, of course. This is
not just the usual academic call for more funded research; nobody wants to try global experiments on a wing and a prayer.
more studies and reports, we must soon begin thinking of controlled experiments. Climate scientists so far have studied passively,
much like astronomers. They have a bias toward this mode, especially since the discernible changes we have made in our climate
generally have been pernicious. Such mental sets ebb slowly. The reek of hubris also restrains many. But a time for many limited
experiments like the iron-dumping one will come. This will be the second great step as we ponder whether to become geoengineers.
Constraints must be severe to ensure clear results.
important, perturbations in climate must be local and reversible--and not merely to quiet environmentalist fears. Only controlled
experiments, well designed and well analyzed, will be convincing to all sides in this debate. Indeed, the green plume near
the Galapagos Islands showed this. Its larger features were best studied by
satellite, which picked up the green splotch strongly against the dark blue sea. But the crucial issue of whether the carbon
stayed tied up in ocean waters was poorly addressed. Satellites were of no help. Slightly better funding and more scientists
in dispersed, small craft could have told us a lot more.
climate modeling must closely parallel every experiment. Few doubt that our climate stands in a class by itself in terms of
complexity. Though much is made of how wondrous our minds are, perhaps the most complex entity known is our biosphere, in
which we are mere mayflies. Absent a remotely useful theory of complexity in systems, we must proceed cautiously.
computer studies are notorious for revealing mostly what was sought, confirming the prejudices of their programmers, methods
are improving quickly. They can explore the many side avenues of small-scale geoengineering experiments. Invoking computer
models as crucial watchdogs in every experiment will calm fears, at least among those who read beyond the headlines.
in the end? Political pressure may well compel nations to comply with some target goals. A crucial factor will be what ratio
to use in assessing a nation's (or region's) rectitude: net fossil-fuel consumption divided by what? Population? This favors
the poor and populous nations. Economic value created with the fuels? The United States would fare reasonably well. Some weighted mean between the two?
descending into pure power politics and making policy sausage in public, a World Warming Authority could copy our fledgling
pollution-voucher methods, bringing some market forces into play. But instead of simply trading the right to burn more--a
negative unit--one could use a positive Mitigation Unit as well. Industries amassing them by, say, paying for rich-burning
jet fuel could then burn more oil themselves. A market-driven dynamic equilibrium could then minimize costs for a given anti-warming
approaches might drive the emergence of suites of methods, which regions could choose among to their best advantage. Deserts
reflect light well (though their roads are usually dark), so added cloud cover is less effective there overall; the whitewashing
of cities could be measured by their average decrease in the heat-island effect; lands with high rainfall may favor forestation.
Any such policy calculus should hover over the intricacies of markets, which
will move faster and with more ingenuity than any committee. Rigid mandates will inevitably fail.
going from the local to the global is fraught with uncertainty--and sure to inspire much anxiety. We will always be ambivalent
stewards of the Earth. And greenhouse gas emissions certainly will not be our last problem, either. We are doing many things
to our environment, with our numbers expected to reach 10 billion by 2050. What new threats will emerge? Catastrophes may
come at a quickening pace, springing from the many synergistic effects that we must trace through the geophysical labyrinth.
begin correcting for our inadvertent insults to Mother Earth, we should realize that it's forever. Once we become caretakers,
we cannot stop. The large tasks confronting humanity, especially the uplifting of the majority to some semblance of prosperity,
must be carried forward in the shadow of our stewardship.
even among the able nations, those who have the foresight to grasp solutions, an odd reluctance pervades the policy classes.
As the atmospheric physicist Ralph Cicerone has noted, "Many who envision environmental problems foresee doom and have little
faith in technology, and therefore propose strong limits on industrialization, while most optimists refuse to believe that
there is an environmental problem at all."
sinned against Mother Nature inadvertently, many are keenly reluctant to intervene knowingly. Sherwood Rowland, a chemist
at the University of California at Irvine who predicted, with Mario Molina, the depletion of the ozone layer, declared, "I
am unalterably opposed to global mitigation." This added considerable weight to the abstention cause. At root, such people
see mankind as the problem; only by behaving humbly, living lightly upon our Earth, can we atone. Here most scientists and
theologians agree, at least for now.
century will see a protracted battle between the prophets who would intervene and the moralists who see all grand-scale human
measures as tainted. Even now, many argue that even to speak of geoengineering encourages the unwashed to more excess, since
the masses will think that once again science has a remedy at hand.
though, will say quietly, persistently, Well, maybe science does....
Gregory Benford is a professor of physics at the University of California at Irvine and the
author of Timescape.
Reason on Line:
(GLOBAL WARMING, TECHNOLOGY)