Home' Technology Review : January February 2010 Contents FEATURE STORY
Rivers fed by melting snow and glaciers supply water to
over one-sixth of the world's population---well over a
billion people. But these sources of water are quickly
disappearing: the Himalayan glaciers that feed rivers in
India, China, and other Asian countries could be gone in 25 years.
Such e ects of climate change no longer surprise scientists. But
the speed at which they're happening does. "The earth appears to
be changing faster than the climate models predicted," says Daniel
Schrag, a professor of earth and planetary sciences at Harvard
University, who advises President Obama on climate issues.
Atmospheric levels of carbon dioxide have already climbed to
385 parts per million, well over the 350 parts per million that many
scientists say is the upper limit for a relatively stable climate. And
despite government-led e orts to limit carbon emissions in many
countries, annual emissions from fossil-fuel combustion are going
up, not down: over the last two decades, they have increased 41
percent. In the last 10 years, the concentration of carbon dioxide
in the atmosphere has increased by nearly two parts per million
every year. At this rate, they'll be twice preindustrial levels by the
end of the century. Meanwhile, researchers are growing convinced
that the climate might be more sensitive to greenhouse gases at
this level than once thought. "The likelihood that we're going to
avoid serious damage seems quite low," says Schrag. "The best
we're going to do is probably not going to be good enough."
This shocking realization has caused many influential scientists,
including Obama advisors like Schrag, to fundamentally change
their thinking about how to respond to climate change. They have
begun calling for the government to start funding research into
geoengineering---large-scale schemes for rapidly cooling the earth.
Strategies for geoengineering vary widely, from launching tril-
lions of sun shields into space to triggering vast algae blooms in
oceans. The one that has gained the most attention in recent years
involves injecting millions of tons of sulfur dioxide high into the
atmosphere to form microscopic particles that would shade the
planet. Many geoengineering proposals date back decades, but
until just a few years ago, most climate scientists considered them
something between high-tech hubris and science fiction. Indeed,
the subject was "forbidden territory," says Ronald Prinn, a profes-
sor of atmospheric sciences at MIT. Not only is it unclear how such
engineering feats would be accomplished and whether they would,
in fact, moderate the climate, but most scientists worry that they
could have disastrous unintended consequences. What's more,
relying on geoengineering to cool the earth, rather than cutting
greenhouse-gas emissions, would commit future generations to
maintaining these schemes indefinitely. For these reasons, mere
discussion of geoengineering was considered a dangerous distrac-
tion for policy makers considering how to deal with global warm-
ing. Prinn says that until a few years ago, he thought its advocates
were "o the deep end."
It's not just a fringe idea anymore. The United Kingdom's Royal
Society issued a report on geoengineering in September that
outlined the research and policy challenges ahead. The National
Academies in the United States are working on a similar study.
And John Holdren, the director of the White House O ce of Sci-
ence and Technology Policy, broached the idea soon after he was
appointed. "Climate change is happening faster than anyone pre-
viously predicted," he said during one talk. "If we get su ciently
desperate, we may try to engage in geoengineering to try to create
cooling e ects." To prepare ourselves, he said, we need to under-
stand the possibilities and the possible side e ects. Even the U.S.
Congress has now taken an interest, holding its first hearings on
geoengineering in November.
Geoengineering might be "a terrible idea," but it might be better
than doing nothing, says Schrag. Unlike many past advocates, he
doesn't think it's an alternative to reducing greenhouse-gas emis-
sions. "It's not a techno-fix. It's not a Band-Aid. It's a tourniquet,"
The Geoengineering Gambit
For years, radical thinkers have proposed risky technologies that
they say could rapidly cool the earth and o set global warming.
Now a growing number of mainstream climate scientists say we
may have to consider extreme action despite the dangers.
By KEVIN BULLIS
Photographs by MAURICIO ALEJO
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