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Giant Ocean Tubes Proposed as Global Warming Fix

Kate Ravilious
for National Geographic News
September 26, 2007
 
Imagine an ocean full of giant pipes that pump up cold, nutrient-rich water from deep below, encouraging surface algae to bloom and suck carbon dioxide from the atmosphere.

That's the controversial new vision of James Lovelock, the independent British scientist best known for proposing the Gaia hypothesis, and Chris Rapley, a space physicist and director of London's Science Museum.

The pair claims that such climate engineering solutions may be the only way to hold global warming at bay given its current progress. (See a global warming interactive.)

"Global warming appears to be an irreversible process, and if we don't do anything then the world will just heat up to a stable, hot state," Lovelock said. "The stakes are now so high that we have to act."

But other experts are skeptical, pointing out that the scheme could release more carbon than it absorbs while putting fragile marine life in danger. (Related: "Plan to Dump Iron in Ocean as Climate Fix Attracts Debate" [July 25, 2007].)

Wave-Powered

Lovelock and Rapley say their proposal is the oceanic equivalent of planting trees. But with more than two-thirds of Earth covered in ocean, the plan could be applied on a much grander scale.

The pair's preliminary calculations indicate that an array of between 10,000 and 100,000 pipes would be required, with each pipe around 33 feet (10 meters) wide and 330 feet (100 meters) long.

Wave energy would make the pipes bob up and down. One-way valves inside the pipes would then force water to circulate, bringing nutrient-rich water up to the surface.

"This would stimulate algal growth and help to draw down carbon dioxide," Lovelock said.

A further benefit from the increased algal blooms is that they would produce dimethyl sulfide, a chemical that helps sunlight-reflecting clouds to form, the scientists say.

The idea is outlined in this week's issue of the journal Nature.

"In principle this idea should work, and it should definitely be examined further," said John Latham, an atmospheric scientist at the University Corporation for Atmospheric Research in Boulder, who is also developing engineering solutions to mitigate climate change.

Preliminary laboratory tests using cylindrical pipes in a tank of water have shown that the concept has potential, at least on a small scale, Lovelock and Rapley point out.

Making the Problem Worse?

But there are a number of issues with such a proposal, other researchers say.

"Pumping deep water to the surface not only pumps nutrients up, but also carbon dioxide," said Penny Chisholm, an environmental engineer at the Massachusetts Institute of Technology in Cambridge.

Initially the deep waters might "exhale" carbon dioxide into atmosphere, adding to the global warming problem.

"Only after the outgassing is complete will the surface ocean start to take up carbon dioxide, and it is unclear whether there will actually be a net transfer of carbon dioxide to the deep ocean," said Eric Achterberg, an oceanographer at the University of Southampton in England.

Another concern is that meddling with oceanic water circulation might be damaging to ocean life.

"If done on a large enough scale then problems with oxygen depletion could occur in subsurface waters, which would probably have knock-on effects for ecosystems," said Toby Tyrrell, an ocean ecology expert at the University of Southampton.

Time to Test

Lovelock and Rapley acknowledge that there could be problems but still think that the idea deserves to be tested.

The problem of global warming is so serious, they say, that we may have to resort to climate-engineering solutions and accept some of the unwanted consequences.

"Even if we stopped emitting carbon dioxide tomorrow we are still committed to significant temperature rise," Rapley said.

"We don't think that scrubbing carbon dioxide out of chimneys and driving energy efficient cars will be sufficient. We need to draw carbon dioxide out of the atmosphere too."

The pair is already working with an anonymous sponsor on building an oceanic prototype.

"We can do a small-scale trial and discover any problems, giving us opportunity to back off if need be," Rapley said.

If all goes well the scientists envision situating their pipes in areas where they would have a dual purpose, such as the Gulf of Mexico and the Coral Sea off northeast Australia.

Cooler surface waters in such locations could help take the oomph out of Atlantic hurricanes and revitalize coral in the Great Barrier Reef.

Cleansing Earth

The new proposal ties back to Lovelock's best-known work, the Gaia hypothesis.

In the 1960s Lovelock formulated the idea that Earth functions like a living organism, with both living and nonliving parts interacting to regulate the planet's environment. (Related: "New Technologies Emerge in Search for Alien Life" [February 7, 2003].)

Lovelock and Rapley see today's global warming as a disease of Earth caused by human actions.

"Our idea is to stimulate the Earth's immune system," Rapley said, "and help it to cure itself of its current infection."

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