It may be hard to imagine the world getting so hot that scientists and
engineers would design a fleet of 55,000 mirrors, each bigger than Manhattan,
and send them into space to deflect sunlight away from Earth.
Or that they would mimic a major volcanic eruption in order to cool the melting
Arctic, shooting dust and other particles into the upper atmosphere where they
would scatter the sun's light away from Earth.
Using geoengineering, the large-scale manipulation of the environment, to combat
global warming has been proposed by scientists like Lowell Wood at Lawrence
Livermore National Laboratory in California.
He argues that simulating a volcanic winter -- the cooling that follows major
volcanic eruptions like Mount Pinatubo in 1991 -- is the most practical approach
to managing global warming.
"It appears, of all the things I have heard discussed, to be the most economical
and readily implemented," Dr. Wood says.
The idea of interfering with nature in such an aggressive and intentional way is
seen as irresponsible by many other scientists and environmentalists. They worry
that focusing on high-tech fixes will distract politicians and ordinary citizens
from the measures that could be taken today to reduce the world's dependence on
fossil fuels, which produce carbon dioxide when they are burned. Carbon dioxide
and other greenhouse gases act like a solar blanket, trapping heat in the
"If we really knew we could do this, there is no question it would lessen
efforts to push politicians to reduce carbon dioxide levels," says David Keith,
an expert on geoengineering who holds the Canada Research Chair in Energy and
the Environment at the University of Calgary.
But what if global warming is more severe or happens more quickly than
scientists predict? The worst-case scenarios are bad enough, and would see
cities like Vancouver, New York and Shanghai swamped by rising sea levels caused
by melting Greenland and Antarctic ice. Other parts of the world could be
periodically devastated by more severe droughts, hurricanes and other weather.
"You would like to have a backup system to try. To have an alternative," Mike
MacCracken, with the Climate Institute in Washington, said.
Research needs to done, both to determine if geoengineering schemes would work
and what unintended consequences they might have, said Dr. Keith, who recently
moved to the University of Calgary from the Carnegie Mellon University in
He is working on what may turn out to be an economical way to capture carbon
dioxide from the air and store it underground. It sounds more like tinkering
than large-scale manipulation, but Dr. Keith considers his work to be
But he worries that if he is successful, it will give people a false sense of
"You don't want people to jump to conclusions that everything can be solved," he
When the time comes to make a decision, in 30 or 50 years, Dr. Keith said,
politicians will need to know which geoengineering proposals will work and which
won't, how much they will cost and what the risks are.
"It is essentially a statement of fact, that whatever we do now, people in 2050
are going to think about this. I'm not saying they are going to do it, but they
are going to think about this."
He has written a number of articles about the options.
Mimicking a volcano by shooting particles that scatter light into the upper
atmosphere could damage the ozone layer.
Using mirrors in space would cause the sun's light to flicker.
"That would be distracting," Dr. MacCracken said. To avoid brief, repeated
eclipses, one giant mirror would have to be built, but Dr. MacCracken said that
would require a manufacturing base on the moon.
John Bennett of the Sierra Club of Canada wondered if it wouldn't be easier to
reduce our use of fossil fuels.
Edward Teller didn't think so. The father of the hydrogen bomb was also one of
the most prominent early proponents of using geoengineering to fight global
Dr. Teller, who died in 2003, argued that humans were generally weak and
self-serving, said Ken Caldeira, a Carnegie Institution researcher at Stanford
University in California who worked at the same laboratory -- Lawrence Livermore
- as Dr. Teller for 12 years.
Dr. Teller didn't believe that human beings would avoid wars unless there was a
weapon so terrible they wouldn't want to use it, Dr. Caldeira said. And he
didn't think they were going to stop using fossil fuels. The best solution to
global warming, Dr. Teller argued in a number of papers, might be a scientific
Dr. Caldeira, however, doesn't like the notion of interfering with the planet
any more than we already have, and he set out to show that the idea of
deflecting sunlight away from Earth -- either with mirrors or tiny particles --
wouldn't work. His hypothesis was that reducing the amount of sunlight might
slightly cool some parts of the world, like the equator, but wouldn't have much
of an impact overall.
Much to his chagrin, his climate modelling produced evidence that it could work.
"The reason why it works has a lot to do with sea ice," he said.
Ice acts as an insulator for the Arctic Ocean. If it melts, heat rushes out and
the atmosphere becomes warmer. Deflecting sunlight would cool Earth just enough
to keep the sea ice in the north frozen.
He also set out to prove that blocking sunlight would be bad for global
agriculture. But again, his climate models showed the opposite. When plants take
in more carbon dioxide, they can use water more efficiently, so they grow
faster. This would offset the slower growth that less sunlight would bring.
Dr. Caldeira now finds himself in the awkward position of having done science
that contributes to the case for geoengineering, even though he is opposed to
"I think geoengineering is a terrible the idea. It just seems the Earth system
is so complicated, the more we interfere, the more we screw it up.
"The goal was to show it wouldn't work. The results suggested it would work."
Many scientists are uneasy with the notion of monkeying with a climate system so
complicated they are still working to understand it. In 1992, when a U.S.
National Academy of Sciences panel looked at the policy implications of global
warming, there was a serious debate over whether geoengineering should be
included, said Stephen Schneider, a climate expert at Stanford University. Some
members of the panel feared it could be used as an excuse to continue pollution.
In the end, they decided to lay out some of the options in a carefully worded
Some were shockingly expensive.
Putting 55,000 mirrors in space would cost at least $120-billion (U.S.), and
replacing the mirrors over time could cost as much 40 times more.
Others came with a smaller price tag. Dust or other particles could be fired
into the upper atmosphere with naval guns, rockets or balloons at small fraction
of the cost of launching space mirrors.
This proposal seems the most feasible and a number of researchers are looking at
it. Dr. MacCracken said that Dutch researcher Paul Crutzen, who won the Nobel
Prize in chemistry in 1995 for work on the depletion of the ozone layer, is
publishing an article in a respected journal in August about the idea.
There are legal questions as well as scientific ones about deliberately causing
a volcanic winter or implementing other geoengineering plans.
International treaties would apply in some cases. There would also need to be a
plan in place to compensate country or individuals whose interests were hurt by
a geoengineering scheme, experts say.
It might be best, Dr. Caldeira said, to focus on more benign kinds of
geoengineering, like making our roads white, instead of black, and installing
roofs that would reflect light instead of absorb it. Planting more trees in
urban areas would make cities cooler, and reduce the use of air conditioners, he
"Small-scale geoengineering is probably a very good idea."
Dr. Keith said focus should be put on reducing greenhouse-gas emissions while
remaining open to other options.
"But I can imagine conditions, say 50 years in the future, where I think it
might make sense to contemplate geoengineering, not as a substitute for reducing
our emissions, but as a way to take the edge off the worst of their effects."
A number of high tech solutions have been proposed to fight global warming and
some involve the large-scale manipulation of the environment . Many scientist
worry they will have unintended consequences and distract politicians and
citizens from taking less risky steps such as reducing their use of fossil
1. Giant mirrors in space
The upside: The mirrors each 100 square kilometres in area, weld reflect
sunlight away from earth.
The downside: Would cause the light from the sun to flicker. Could cost $120
billion (U.S.) and replacing the mirrors over time could cost 40 times more.
2. dust or aerosols in the stratosphere.
The upside: Scientists would mimic the cooling effect of volcanoes by sending
dust or other particles into the upper atmosphere
The downside: It might damage the ozone layer.
3. Fertilizing the ocean.
The upside: Scattering iron in the sea around Antarctica to increase the growth
of carbon-absorbing plankton.
The downside: It would require 15 ships, each steaming at 10 knots for 300 days
a year, and could cost between $10-billion (U.S.) and $100-billion a year. Might
increase the release of methane, a potent greenhouse gas.
4. Planting more trees.
The upside: this is considered benign from a geoengineering standpoint. Trees
absorb carbon dioxide, and they also evaporate water to the atmosphere, which
helps to cool the planet.
The downside: Forests are also dark, and absorb a lot of sunlight, which warms
Earth. In temperate regions, such as Canada, research suggests it may not have a
5. Pump liquid carbon dioxide into rocks.
The upside: The greenhouse gas would be captured in the atmosphere, compressed
onto a liquid and stored underground.
The downside: It might be expensive to do, and to regulate.
6. Pump liquid carbon dioxide into the deep ocean.
The upside: Carbon dioxide would be collected at smokestacks, and injected into
currents that would carry it deep into the ocean.
The downside: There is some uncertainty about the fate of carbon dioxide in the
SOURCES: U.S. NATIONAL ACADEMY OF SCIENCES, DAVID KEITH, UNIVERSITY OF CALGARY,
KEN CALDEIRA, CARNEGIE INSTITUTION AT STANFORD UNIVERSITY, STEPHEN SCHNEIDER,