Can we combat climate change by changing the climate? It's worth a try, say advocates of geoengineering—manipulating the climate to reduce the effects of heat-trapping greenhouse gases in Earth's atmosphere. (See: "5 Last-Ditch Schemes to Avert Warming Disaster.")
This and other emergency measures are under the microscope this week as part of the first Asilomar International Conference on Climate Intervention Technologies in Pacific Grove, California. The meeting will attempt to draft the world's first voluntary guidelines for ethical behavior in geoengineering schemes, most of which are still no more than ideas.
That's not to say any of the schemes will be deployed in the near future, noted Samuel Thernstrom, co-director of the Geoengineering Project at the American Enterprise Institute, a Washington, D.C.-based policy-research institute.
But experts should seriously consider all options, Thernstrom said, including altering the climate: "There is no argument for ignorance—we should know more about geoengineering."
Photograph by Emory Kristof, National Geographic
2. Greening the Desert
Greening the desert may be a way to trap more atmospheric greenhouse gases such as carbon dioxide, experts say—a geoengineering idea already taking root in Africa.
If greenhouse gas emissions continue to skyrocket, however, a green desert likely wouldn't have enough carbon-trapping heft to make a dent, said Michael MacCracken, chief scientist for climate programs at the nonprofit Climate Institute, a Washington, D.C.-based climate-advocacy organization.
But in a lower-carbon world, he said, green deserts could be a good strategy for keeping emissions down.
Photograph by Naftall Hilger, ArabianEye, Photolibrary
3. "Biochar" in Soils
It may be old as dirt, but the Amazonian practice of making "biochar" could be a climate saver, experts say (pictured, a farmer holds biochar in West Virginia in 2008).
When returned to the soil, biochar—a rich, highly porous charcoal made by heating agricultural waste—can trap carbon in soils for hundreds to thousands of years, according to the International Biochar Initiative. By contrast, the carbon-holding powers of trees are limited, because greenhouse gases escape if a tree is cut down or dies.
The American Enterprise Institute's Thernstrom puts biochar in his "deserves to be explored" category, as does the Climate Institute's MacCracken, who noted that the substance has the added benefit of improving soil quality. (See "Superdirt Made Lost Amazon Cities Possible?")
Photograph by Jeff Hutchens, Getty Images
4. Seaweed Farms
It may be a cousin to pond scum, but seaweed has attained a more noble status among scientists advocating seaweed farms as carbon sinks (above, a woman in Bali, Indonesia, harvests seaweed in an undated photo).
Half of the world's photosynthesis—a process that uses sunlight to convert carbon dioxide into energy—takes place in the oceans. But most of that occurs in tiny marine plants called phytoplankton, which can't be farmed, according to the Seaweed Clean Development Mechanism Project at Korea's Pusan National University.
As a bonus, farmed seaweed can be harvested and turned into a renewable fuel—"a joint benefit," said the Climate Institute's MacCracken.
Photograph by Jason Edwards, Bio-Images, National Geographic Stock
5. Cloud-making Ships
With a design reminiscent of an oceangoing pogo stick, this "cloud ship" may give some bounce to geoengineering efforts to combat climate change.
The wind-powered devices take in ocean water and spray a fine mist of sea salt, which generates ocean clouds. Such clouds are denser and whiter than regular clouds, so they reflect more of the sun's heat back into space.
Deploying about 1,500 of these relatively inexpensive vessels could have an immediate cooling effect, said the American Enterprise Institute's Thernstrom.
"We're a long way from knowing for sure whether that would work," he said. "But it's a plausible theory that does deserve serious investigation."
Illustration by John MacNeill
6. White Roofs
Fighting climate change is hardly black-and-white. But making roofs more reflective by painting them white—like these rooftops in Hamilton, Bermuda—may be one of the simplest geoengineering fixes.
Scientists have already conducted about a dozen preliminary iron-seeding experiments around the world, with varying degrees of success. In one test, the iron-stimulated plants were promptly gobbled up by shrimplike animals, negating any carbon-absorbing benefits.
Regardless of the method, finding a way forward for geoengineering is crucial, since many schemes would be long-lasting—"imposing an obligation on future generations," the Climate Institute's MacCracken said. "And that's a huge issue."