Global warming solutions that would earn a laugh from many of us are getting some serious attention by scientists.

With the impacts of global warming being felt around the globe, an insurance policy of sorts may be needed in case the effects are faster and more dramatic that what can be fought with more traditional methods like efficiency, renewable power, etc. Here’s a sample of the more interesting scenarios that are being considered and studied:

• A man-made "volcano" that shoots gigatons of sulfur high into the air, creating a "sun shade" made of trillions of little reflectors between Earth and the sun and slightly lowering the planet's temperature, mimicking what has happened during large natural volcanic eruptions. Scientists with the Center for Atmospheric Research have put this idea into a climate model, but the results aren’t cheap or promising. It would take tens of thousands of tons of sulfate to have a persistent effect, and some scientists point out that shooting sulfate into the atmosphere doesn’t do anything to fix the initial problem of humans emitting too much carbon dioxide (CO2) pollution. Furthermore, it doesn’t address the dramatic increase in acidity of the world’s oceans, a predicted impact of global warming.
• A forest of artificial "trees" that suck carbon dioxide out of the air. Looking more like a 200 foot high “radiator on a stick” than a tree, these contraptions use air filters that grab the CO2 and use chemical absorbers to compress it into a liquid or gas that can be shipped and stored elsewhere. Columbia University professor Klaus Lackner’s middle school daughter was able to do this on a tiny scale for a school science fair, but now Lackner – inspired by Richard Branson’s $25 million prize offer - is looking at it on a global scale. Hurdles include the need for a huge amount of energy to power the air capture devices and the cost of CO2 disposal.
• Dumping iron dust into the ocean to increase the natural plankton and algae system that would drink up the CO2 from the atmosphere. The Intergovernmental Panel on Climate Change has cited this as a possible way to fight global warming, but also warned against the “large-scale fertilization of the ocean,” causing harmful temperature differences between the surface water and deeper waters and having a dramatic effect on marine life. This has been tried out several times on a small scale since the 1990s, and earlier this month Planktos Inc. of Foster City, CA launched the Weatherbird II to dump 50 tons of iron dust in the Pacific Ocean. Planktos Inc. CEO Russ George assured the Associated Press that his company has consulted with governments around the world and is dropping the iron in open international seas that don't require permits. He argues that the amount of iron dust is small compared to the ocean volume and so poses no threat. Scientists continue to debate the effectiveness of this.

Of course, many scientists are wary of such drastic solutions. From the AP:

Scientists in the recent past have been reluctant to consider such concepts. Many fear there will be unintended side effects; others worry such schemes might prevent the type of reduction in greenhouse gas emissions that scientists say are the only real way to fight global warming. These approaches are not an alternative to cutting pollution, said University of Calgary professor David Keith, a top geoengineering researcher.

NASA is finishing up a report summarizing ideas like the ones listed above, and the National Center for Atmospheric Research has spent the last six weeks running computer simulations of the man-made volcano scenario.

Associated Press, via WPVI-TV