Some weird science is getting serious looks by leading climate experts who say it would be folly not to prepare emergency measures to try to stop global warming in its tracks. This is going on despite the well known risk of unintended consequences whenever humans meddle with nature.
The scientists' worry is that global temperatures are now rising steadily and the process may get beyond any hope of being stopped by cutting greenhouse gas emissions alone.
"These 'geo-engineering' ideas are something any serious scientist approaches with extreme caution," NASA earth studies expert James Hansen told ABC News.
"But we're at the hairy edge," he said. "We 've only got about 10 years to turn the carbon emissions around, and so you're finding more scientists thinking about these things."
Some astonishing ideas are popping up -- like a monster sunshade for planet Earth.
NASA has asked University of Arizona professor Roger Angel to flesh out his idea for a gigantic sunshade in space.
For only $3 trillion, says Angel, a "solar shield" could be made of mirrors that would span 1,200 miles of space, 950,000 miles away from the earth, to block some of the sun, making the earth cooler.
Angel argues that while $3 trillion may sound like a lot, it's less than 2 percent of the world's gross national product.
But what if the mirrors' tilt controls fail? Could mankind really build the necessary space vehicles needed to repair something so huge in time? And if runaway warming starts, would there even be enough time to build such a massive structure anyway? There are no clear answers.
Some scientists suggest turning the earth's blue skies a yellowish grey by injecting sulphur dioxide into the atmosphere with a vast fleet of planes.
The sulphur dioxide would reflect warming sunlight back into space.
But the psychological effect on humanity of a world without blue skies -- to say nothing of the effect on earth's plants and animals -- is clearly incalculable.
And what would all that sulphur dioxide do to the oceans into which it would soon settle?
Even though that part hasn't been worked out yet, climate scientist Tom Wigley of the National Center for Atmospheric Research is promoting the sulphur skies idea in the premier research journal Science.
Blanketing the Deserts
A number of scientists have suggested blanketing enormous sections of the planet 's deserts with plastic sheets to reflect sunlight straight back into space, preventing it from warming the earth.
That might work because sunlight, coming in or reflected back out to space, passes right through greenhouse gasses -- unlike the infrared heat a warmed earth gives off, which gets trapped in those gasses.
But scientists admit they're not sure how to maintain such immense reflectivity: would a few good dust storms -- already increasingly common on our warming planet -- dull the giant reflective sheets, requiring a huge cleaning staff ? How many vacuum cleaners would they need?
Sowing the Waves... But What About the Bugs?
Another idea being seriously debated among scientists is to send a fleet of ships into the world's oceans to sow the waves with iron particles.
The iron would stimulate massive growth of the sea's myriad tiny plankton, which flourish on a diet of iron.
The plankton, which also love carbon dioxide, would then suck up huge chunks of it -- the same CO2 which causes global warming.
Just a couple of problems for some scientists: When they die and sink to the ocean floor, will the plankton keep the CO2 there, or in dying will the plankton give up the CO2 along with their ghosts, releasing it back into the air?
Then there are the sea bugs.
Professor Eduoard Bard of the College de France in Paris points out that if the CO2 did sink with the dead plankton but then get released, it would turn some parts of the ocean acidic, starving it of oxygen.
That would create conditions loved by tiny sea bugs, different species of bacteria that would then proliferate, releasing untold tonnage of nitrous oxide which, as Bard told the French news agency AFP, "is a more powerful greenhouse gas that CO2."
That is to say, sowing the seas with iron might make the planet cooler -- at first -- then warmer.
Eye Grabbing Contraptions
Eye-grabbing artist's renderings of huge "geo-engineering" contraptions to battle global warming are appearing more frequently now in popular science magazines.
One showed a landscape dotted with skyscraper-sized, pitchfork-like structures whose louver panels, according to the caption, would capture carbon from the air and somehow hide it underground.
Impossibly expensive, according to some climate experts, several of whom added that it might reassure readers who assume technology will somehow just whisk the problem away, but it is only wishful thinking for now.
Experts say the problem of scale is one of the main obstacles -- the massive size of that space mirror array, the number of boats or planes needed to seed the sea or the sky.
But human daring is famous for disregarding such obstacles -- at least in fantasy.
Former NOAA Hurricane research chief Hugh Willoughby recently reviewed for ABC News some of the "wild and crazy ideas" he received in the mail for stopping hurricanes.
One man suggested strategically placing a circular series of nuclear bombs in an advancing hurricane's eye-wall.
"It wouldn't work," Willoughby says. "And all you'd get would be a radioactive hurricane."
Such unintended consequences notwithstanding, preeminent climate scientists are now contemplating fast technological fixes for a problem far bigger than a hurricane.
NASA's James Hansen and several colleagues recently suggested, in Publications Of The National Academy of Sciences, that "seeding of clouds by ships plying selected ocean regions deserves investigation" -- because the particle-bearing "aerosols" they recommend using have already been shown to reflect sunlight back into space.
All these ideas are enormously controversial, and it's hard, say sceintists, to imagine how humanity could ever be convinced to shell out the resources in time -- especially given unintended consequences.
Think of that famous example in Australia.
Records tell of 13 domestic rabbits brought from England in 1859 to improve the quality of the hunting on one estate. A few escaped the gunshots, escaped, and bred like, well, rabbits.
The entire continent was soon covered with billions of them -- what Autralians call simply "the gray blanket."
A thousand-mile long "rabbit fence" was built in the early 1900s, but it did little good, and now Australia suffers $720 million a year in crop damage.