The Associated Press is reporting that President Barack Obama's science advisor John Holdren has brought up the idea of using geo-engineering as an emergency measure for cooling the planet should man-made global warming get out of hand. The AP says:
One such extreme option includes shooting pollution particles into the upper atmosphere to reflect the sun's rays. Holdren said such an experimental measure would only be used as a last resort.
"It's got to be looked at," he said. "We don't have the luxury of taking any approach off the table." …
…Holdren noted that shooting particles into the air — making an artificial volcano as one Nobel laureate has suggested — could have grave side effects and would not completely solve all the problems from soaring greenhouse gas emissions. So such actions could not be taken lightly, he said.
Still, "we might get desperate enough to want to use it," he added.
Another geoengineering option he mentioned was the use of so-called artificial trees to suck carbon dioxide — the chief human-caused greenhouse gas — out of the air and store it. At first that seemed prohibitively expensive, but a re-examination of the approach shows it might be less costly, he said.
Naturally, Reason was ahead of the curve on the issue of geo-engineering the climate. In his 1997 article "Climate Controls," Gregory Benford outlined a number of possible technical fixes for cooling the planet including putting reflective dust or sulfur particles in the upper atmosphere and growing more trees to soak up carbon dioxide. On upper atmosphere particles, Benford wrote:
Spreading dust in the stratosphere appears workable because at those heights tiny particles stay aloft for several years. This is why volcanoes spewing dust affect weather strongly. The tiny motes that redden our sundowns reflect more sunlight than they trap infrared.
Even better than dust are microscopic droplets of sulfuric acid, which reflects light more effectively. Sulfate aerosols can also raise the number of droplets that make clouds condense, further increasing overall reflectivity. This could then be a local cooling, easier to monitor than carbon dioxide's global warming. We could perform such small, controllable experiments now. The amount of droplets or dust needed is a hundredth of the amount already blown into the atmosphere by natural processes, so we would not be venturing big dislocations. And we would get some spectacular sunsets in the bargain.
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