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In the past few decades, a handful of scientists have come up with
big, futuristic ways to fight global warming: Build sunshades in
orbit to cool the planet. Tinker with clouds to make them reflect
more sunlight back into space. Trick oceans into soaking up more
heat-trapping greenhouse gases.
Their proposals were relegated to the fringes of climate science.
Few journals would publish them. Few government agencies would pay
for feasibility studies. Environmentalists and mainstream scientists
said the focus should be on reducing greenhouse gases and preventing
global warming in the first place.
But now, in a major reversal, some of the world's most prominent
scientists say the proposals deserve a serious look because of
growing concerns about global warming.
Worried about a potential planetary crisis, these leaders are
calling on governments and scientific groups to study exotic ways to
reduce global warming, seeing them as possible fallback positions if
the planet eventually needs a dose of emergency cooling.
Graphic: Science Fiction?

"We should treat these ideas like any other research and get into
the mind-set of taking them seriously," said Ralph J. Cicerone,
president of the National Academy of Sciences in Washington.
The plans and proposed studies are part of a controversial field
known as geoengineering, which means rearranging the earth's
environment on a large scale to suit human needs and promote
habitability. Dr. Cicerone, an atmospheric chemist, will detail his
arguments in favor of geoengineering studies in the August issue of
the journal Climatic Change.
Practicing what he preaches, Dr. Cicerone is also encouraging
leading scientists to join the geoengineering fray. In April, at his
invitation, Roger P. Angel, a noted astronomer at the University of
Arizona, spoke at the academy's annual meeting. Dr. Angel outlined a
plan to put into orbit small lenses that would bend sunlight away
from earth — trillions of lenses, he now calculates, each about two
feet wide, extraordinarily thin and weighing little more than a
butterfly.
In addition, Dr. Cicerone recently joined a bitter dispute over
whether a Nobel laureate's geoengineering ideas should be aired, and
he helped get them accepted for publication. The laureate, Paul J.
Crutzen of the Max Planck Institute for Chemistry in Germany, is a
star of atmospheric science who won his Nobel in 1995 for showing
how industrial gases damage the earth's ozone shield. His paper
newly examines the risks and benefits of trying to cool the planet
by injecting sulfur into the stratosphere.
The paper "should not be taken as a license to go out and pollute,"
Dr. Cicerone said in an interview, emphasizing that most scientists
thought curbing greenhouse gases should be the top priority. But he
added, "In my opinion, he's written a brilliant paper."
Geoengineering is no magic bullet, Dr. Cicerone said. But done
correctly, he added, it will act like an insurance policy if the
world one day faces a crisis of overheating, with repercussions like
melting icecaps, droughts, famines, rising sea levels and coastal
flooding.
"A lot of us have been saying we don't like the idea" of
geoengineering, he said. But he added, "We need to think about it"
and learn, among other things, how to distinguish sound proposals
from ones that are ineffectual or dangerous.
Many scientists still deride geoengineering as an irresponsible
dream with more risks and potential bad side effects than benefits;
they call its extreme remedies a good reason to redouble efforts at
reducing heat-trapping gases like carbon dioxide. And skeptics of
human-induced global warming dismiss geoengineering as a costly
effort to battle a mirage.
Even so, many analysts say the prominence of its new advocates is
giving the field greater visibility and credibility and adding to
the likelihood that global leaders may one day consider taking such
emergency steps.
"People used to say, 'Shut up, the world isn't ready for this,' "
said Wallace S. Broecker, a geoengineering pioneer at Columbia.
"Maybe the world has changed."
Michael C. MacCracken, chief scientist of the Climate Institute, a
private research group in Washington, said he was resigned to the
need to take geoengineering seriously.
"It's really too bad," Dr. MacCracken said, "that the United States
and the world cannot do much more so that it's not necessary to
consider getting addicted to one of these approaches."
Martin A. Apple, president of the Council of Scientific Society
Presidents, said of geoengineering at a recent meeting in
Washington, "Let's talk about research funding with enough zeroes on
it so we can make a dent."
The study of futuristic countermeasures began quietly in the 1960's,
as scientists theorized that global warming caused by
human-generated emissions might one day pose a serious threat. But
little happened until the 1980's, when global temperatures started
to rise.
Some scientists noted that the earth reflected about 30 percent of
incoming sunlight back into space and absorbed the rest. Slight
increases of reflectivity, they reasoned, could easily counteract
heat-trapping gases, thereby cooling the planet.
Dr. Broecker of Columbia proposed doing so by lacing the
stratosphere with tons of sulfur dioxide, as erupting volcanoes
occasionally do. The injections, he calculated in the 80's, would
require a fleet of hundreds of jumbo jets and, as a byproduct, would
increase acid rain.
By 1997, such futuristic visions found a prominent advocate in
Edward Teller, a main inventor of the hydrogen bomb. "Injecting
sunlight-scattering particles into the stratosphere appears to be a
promising approach," Dr. Teller wrote in The Wall Street Journal.
"Why not do that?"
But government agencies usually balked at paying researchers to
study such far-out ideas, and even ones that were more down to
earth. John Latham, an atmospheric physicist at the National Center
for Atmospheric Research in Colorado, told how he and his colleagues
had unsuccessfully sought for many years to test whether spraying
saltwater mists into low ocean clouds might increase their
reflectivity.
"We haven't found a way in," Dr. Latham said of government
financing. "It's been a bit dispiriting."
Other plans called for reflective films to be laid over deserts or
white plastic islands to be floated on the world's oceans, both as
ways to reflect more sunlight into space.
Another idea was to fertilize the sea with iron, creating vast
blooms of plants that would gulp down tons of carbon dioxide and, as
the plants died, drag the carbon into the abyss.
The general reaction to such ideas, said Alvia Gaskill, president of
Environmental Reference Materials Inc., a consulting firm in North
Carolina that advocates geoengineering, "has been dismissive and
sometimes frightened — afraid that we don't know what the
consequences will be of making large-scale changes to the
environment."
Dr. Gaskill said small experiments would let researchers quickly
pull the plug if such tinkering started to go awry.
Critics of geoengineering argued that it made more sense to avoid
global warming than to gamble on risky fixes. They called for
reducing energy use, developing alternative sources of power and
curbing greenhouse gases.
But international efforts like the Kyoto Protocol — which the United
States never ratified, and which China and India as members of the
developing world never had to obey, freeing the current and
projected leaders in greenhouse gas emissions from its restrictions
— have so far failed to diminish the threat. Scientists estimate
that the earth's surface temperature this century may rise as much
as 10 degrees Fahrenheit.
Geoengineering's advocates say humankind is already vastly altering
the global environment and simply needs to do so more intelligently.
Dr. Angel, the University of Arizona astronomer, told members of the
science academy of his idea for an orbital sunshade, calling the
proposal less important than the goal of encouraging bold thought.
"This could engage a whole generation," he said in an interview.
"All I'm saying is, let's start thinking about these kinds of things
in case we need them one day." Such visionary plans are still far
from winning universal acclaim. James E. Hansen of the NASA Goddard
Institute for Space Studies in New York, who attended the talk and
strongly advocates curbing emissions, belittled the orbital sunshade
as "incredibly difficult and impractical."
Dr. Crutzen, the Nobel laureate from the Max Planck Institute, has
also drawn fire for his paper about injecting sulfur into the
stratosphere. "There was a passionate outcry by several prominent
scientists claiming that it is irresponsible," recalled Mark G.
Lawrence, an American scientist who is also at the institute.
The stratospheric plan called for fighting one kind of pollution
(excess greenhouse gases like carbon dioxide) with another (sulfur
dioxide), though it appeared that any increase in sulfur at the
earth's surface would be small compared with the tons already being
emitted from the smokestacks of coal-fueled plants.
Dr. Cicerone of the science academy helped broker a compromise: Dr.
Crutzen's paper would be published, but with several commentaries,
including his own. They will appear in the August issue of Climatic
Change. The other authors are Dr. Lawrence of the German chemistry
institute, Dr. MacCracken of the Climate Institute, Jeffrey T. Kiehl
of the National Center for Atmospheric Research, and Lennart
Bengtsson of the Max Planck Institute for Meteorology in Germany.
In a draft of his paper, Dr. Crutzen estimates the annual cost of
his sulfur proposal at up to $50 billion, or about 5 percent of the
world's annual military spending.
"Climatic engineering, such as presented here, is the only option
available to rapidly reduce temperature rises" if international
efforts fail to curb greenhouse gases, Dr. Crutzen wrote.
"So far," he added, "there is little reason to be optimistic."
Andrew C. Revkin contributed reporting for this article.
Source.
The New York Times
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