Stephen Salter and John Latham cloud seeding spray ship
The Atlantic, July/August 2009
Edited by Andy Ross
On a future Earth ravaged by catastrophic climate change, we might pull fire
hoses up into the sky, attached to zeppelins hovering 20 km high. Factories on
the ground would pump sulfur dioxide up through those hoses continuously, day
and night. The hoses would puff a sulfurous pall into the sky. At sunset on some
parts of the planet, the aerosol would glow a dramatic red. During the day, it
would shield the planet from the sunís full force.
Within a few years we could cool the Earth to average temperatures not seen for
over 200 years. For less than $100 billion, we could reverse anthropogenic
climate change entirely. To stop global warming directly, by cutting carbon
emissions, would cost maybe $1 trillion yearly. President Obamaís science
adviser, John Holdren, said in April that he thought the administration would
consider the sulfur solution, "if we get desperate enough."
Big geo-engineering projects are among the boldest ideas being considered today
to combat climate change. Some scientists see geo-engineering as a last-ditch
option to prevent us from cooking the planet to death. Others fear the
Stephen Salter, a Scottish engineer, has an idea for a fleet of hundreds of
ships that suck up seawater and spray it high enough for the wind to carry it
into the clouds. The spray would make the clouds whiter and fluffier, and hence
better at bouncing sunlight back into space. Salter estimates the cost for the
enough ships to turn back the climate clock two centuries to be $600 million to
start plus $100 million a year from then on.
Roger Angel, a professor at the University of Arizona, would build a giant
sunshade in space. He would use a battery of electromagnetic guns, each more
than a mile long and built on high ground, to shoot Frisbee-size ceramic disks.
Each gun would launch 10 million disks per hour for 10 years. The guns would aim
at the gravitational midpoint between the Earth and the sun, so that the disks
would hang in space, scattering sunlight and shading the Earth. The scheme would
cost several trillion dollars.
Thomas Schelling, who won the 2005 Nobel Prize in economics, points out how
difficult it is to get vast international agreements such as the Kyoto Protocol
to stick. He says a geo-engineering strategy like the sulfur aerosol changes
everything. Instead of a situation where any one country can foil efforts to
curb global warming, any one country can curb global warming all on its own.
Pumping sulfur into the atmosphere is a lot easier than trying to orchestrate
the actions of 200 countries, each of whom has strong incentives to cheat.
But there are big drawbacks to the sulfur strategy. Opponents say it might
produce acid rain and decimate plant and fish life. It would likely trigger
radical shifts in the climate that would hit the globe unevenly. And we'd risk
calamity as son as we stopped pumping: the aerosols would rain down and the
accumulated carbon dioxide would make temperatures soar. We would suffer the
full force of postponed warming in just a few catastrophic years.
Since 1977, Freeman Dyson has explored how plants affect the planet's
carbon-dioxide concentrations. Every summer, plants absorb about a tenth of the
carbon dioxide in the atmosphere. In the fall, when they stop growing or shed
their leaves, they release most of it back into the air. Dyson proposed creating
forests of trees engineered to suck carbon ravenously from the air, and to fix
in thick roots that would decay into topsoil, trapping the carbon. He estimates
that we could offset our carbon emissions with just a few mm of additional
topsoil worldwide per year.
David Keith, at the University of Calgary, proposes to capture carbon from the
air by building structures resembling industrial cooling towers. These would
funnel air through grids coated with a chemical solution that binds to
carbon-dioxide molecules. The grids would be scrubbed chemically to separate the
carbon dioxide, which would then be buried by pumping it into the caverns left
by oil drilling.
We might also store carbon dioxide in the oceans. On the ocean surface, clouds
of blooming plankton ingest amounts of carbon dioxide comparable to those taken
in by trees. Climos, a company based in San Francisco, is trying to cultivate
ever-bigger plankton blooms that would suck in lots of carbon. When the plankton
died, the carbon would end up on the sea floor. Plankton need plenty of iron to
grow. If you spread powdered iron over the surface of the ocean, you soon get a
massive bloom of plankton. But seeding the ocean with iron and creating vast
undersea forests could have a terrible price. When the dead algae decay, they
Even staunch environmentalists and eminent scientists are discussing
geo-engineering. But with growing acceptance comes another danger. If you
promise that in a future emergency you can chill the Earth in a matter of
months, cutting emissions today will seem far less urgent.
Geo-engineering is so cheap that a single rogue nation could afford to change
the climate. Industrialized governments may need to regulate and monopolize the
technology, rather like the International Atomic Energy Agency now regulates
We should keep investigating these geo-engineering solutions, but be quite clear
that most of them are dreadful.
AR I like these ideas — bold
and fearless! But not on my planet, thank you. Except maybe the fluffy white
clouds one, which sounds rather nice.