Scientists are envisioning giant but risky
engineering projects to undo climate change
If fossil fuel technologies got us into the global
warming crisis, can technology get us out? Scientists say massive, planet-saving
interventions are possible, but they aren't for the faint of heart. Efforts to
"geo-engineer" earth, they warn, will incur staggering costs and pose risks as
unpredictable as global warming itself. "Cutting carbon must come first," says
David Keith, an energy expert at the University of Calgary. "To think of
geo-engineering as a solution is ludicrous." Still, even Keith agrees that, in a
worst-case scenario, big fixes may be needed. Arctic temperatures in recent
years have risen about three times faster than the world average, stoking fears
that sea levels might climb rapidly. The looming costs of climate change in
terms of lives, land, and infrastructure lost could eventually justify
extraordinary acts. Here are some proposals--and risks:
1 SOLAR
SHADE Scientists have long toyed with the idea of
orbiting a huge mirror around the earth to block the sun's rays. Any such
contraption would be too heavy to loft, so J. Roger P. Angel, a professor of
optics at the University of Arizona, envisions shooting trillions of ultrathin,
lightweight glass "fliers" into space instead. The discs would be aimed at a
sweet spot where the gravitational pull of the sun is equal to that of the
earth. They would refract just 2% of sunlight--too little to notice on the
ground, but enough to offset a doubling of CO2 levels. Angel proposes using
exotic magnetic launchers to shoot bins of fliers into orbit. Risks: Huge costs,
plus it would be impossible to turn off the shading effect.
2 ALGAE FARMING In
the same way that trees are planted to capture CO2, algae growth could be
stimulated in the oceans. As the mass of plankton grew, it would mop up CO2;
when the little plants died, they would sink to the ocean floor. The missing
ingredient to trigger one of these blooms is iron, which is scarce in some
otherwise mineral-rich waters around the globe. But in experiments researchers
have shown that a spritz of iron can spawn algae blooms even in fairly barren
waters. Risks: Unlike a solar shade, this approach would take a long time to
lower global temperatures, and huge blooms might harm sea life by depleting
waters of vital minerals.
3
CLOUD FACTORIES Some of the sun's rays are
reflected back into space by clouds, ice, snow, and dust. The impact can be
significant. A single, big volcanic eruption can spew enough fine matter into
the air to lower the earth's surface temperatures. To replicate this effect,
Stephen Salter at the University of Edinburgh ponders a fleet of floating cloud
generators. Mounted on active or retired freighters and powered by wind or wave
energy, the vessels would use vertical turbines to spin ocean water into a fine
salty mist. Once airborne, the salt molecules would seed the formation of big
banks of white, highly reflective clouds. Risks: This approach could cause
unwanted increases in rainfall in many areas. The size and cost of deploying a
mammoth cloud fleet is also unknown.
4 MOVING OCEANS If the seas rise too
high, why not relocate the waters to low-lying deserts? Futurist Kim Stanley
Robinson explores this idea in his upcoming novel Sixty Days and
Counting. Engineers might construct sprawling nuclear-powered waterworks to
pump the oceans into desert basins such as Death Valley or the Arabian Desert.
Risks: In principle, this isn't so different from rerouting rivers to thirsty
cities, but the energy expenditure would be enormous. And the impact of the new
bodies of water on nearby regions is hard to predict.
5 SALTING THE
SEAS Scientists worry that freshwater from melting
Arctic ice and Greenland's glaciers will dilute and disrupt the Gulf Stream as
it loops through the North Atlantic. In the past, when this conveyor belt of
warm water has stalled, Northern Europe was sent into a mini-Ice Age. To keep
the current flowing, Robinson suggests that tanker loads of mineral salt could
be dumped into the sea at key points along the Gulf Stream. Since saltier,
denser water sinks, staggered deliveries of salt could jolt the cycle and keep
the current going. Risks: Altering ocean chemistry on this scale could have
catastrophic effects on sea life. Will we have a choice, though? "I'm as dubious
about geo-engineering as anyone else," says Robinson. "But the fact is, with
climate change we're already doing it."
