Apr 06 2009

Geoengineering: Salvation or Suicide?

Posted by: Jonathan Marshall

In 1988, NASA climate expert James Hansen riveted the country with his Senate testimony about the dangers of global warming. Two decades later, in a letter to President-elect Obama, Hansen reflected on how little progress has been made and warned of the "profound disconnect between actions that policy circles are considering and what the science demands for preservation of the planet."

As we document here almost every week in the feature Climate Changes, scientists now see frightening signs that climate feedback effects from the melting of polar ice and tundra appear much worse than predicted just a few years ago, and could accelerate the devastating effects of global warming on the environment and human society.

Even so, there's no guarantee that Congress will take the tough measures necessary to drastically reduce greenhouse gas emissions. The specter of political leaders seemingly fiddling while the Earth burns has prompted some otherwise sober scientists to propose a radical Plan B: geoengineering.

Geoengineering is the idea of intervening on a planetary scale to modify the earth's environment, in this case to prevent runaway global warming. Instead of (or in addition to)  dealing with the cause--overproduction of greenhouse gases--typical geoengineering solutions would cool the earth one of two ways: either reducing incoming solar radiation or by capturing and storing greenhouse gases after they are produced.

Hardly anyone admits to being a cheerleader for geoengineering; it smacks too much of the kind of hubris that got our planet into this mess in the first place. But more and more experts are quietly concluding that humankind had better keep the option open lest a worse evil overtake us.

As the futurist Jamais Cascio put in in a guest essay on Gristmill, "Geoengineering is risky, likely to provoke international tension, certain to have unanticipated consequences, and pretty much inevitable."

Creative minds have proposed an astonishing array of proposals for planetary-scale environmental engineering, some hairbrained and some remarkably clever.

One idea is to launch trillions of sunshades into orbit to offset greenhouse warming. Unfortunately, this "solution" would require 135,000 rocket launches a year to put 31,000 square kilometers of sunshades into space. It will probably be cheaper just to relocate Disney World to Fairbanks, Alaska.

Then there's a proposal from Ohio State University climate scientist Jason Box to cover Greenland's ice sheets with giant rolls of white plastic to reflect the sun and slow the rate of melting. He's testing his idea over a 10,000 square meter patch of ice. No word yet from the plastics industry's lobbyists about federal support for this idea.

Another idea that's won much wider currency and ongoing testing is fertilizing the oceans with iron to promote the growth of tiny algae to increase their uptake of carbon dioxide. As they die, they will drift to the seabed, locking that carbon away for millennia. With one apparent exception, however, recent ocean tests have thrown cold water on the prospects for this solution. The results from one German-Indian test found that iron did promote algae growth, but animals came along and ate the blooms, preventing them from falling to the ocean floor. The amount of carbon locked up was "a small amount, almost negigible," according to one scientist.

Perhaps the most widely analyzed proposal--advanced by Nobel laureate Paul Crutzen--is to mimic nature by injecting sulfate particles into the upper atmosphere to reflect just enough sunlight to keep the earth from overheating. Without any political consultation, Mount Pinatubo did just that in 1991, releasing 15 million tonnes of sulfur dioxide clouds that cut average global temperatures more than half a degree Celsius over a period of about 15 months. A recent study published in Atmospheric Chemisty and Physics found that this method would have the greatest potential of any proposed to date to cool the globe.

Unfortunately, sulfur dioxide reacts to create sulfuric acid, falling as acid rain to harm terrestrial ecosystems. Worse yet, sulfates might eat a much bigger hole in the earth's ozone layer, exposing us all to dangerous UV radiation and aggravating global warming in the southern hemisphere. Oh, well, back to the drawing board.

Tomorrow: A novel scheme to cool the planet by seeding clouds.

 

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