A team of two British scientists have conceptualised a radical plan that calls for placing giant pumps in the ocean to pump up cold, nutrient-rich water from deep below, encouraging surface algae to bloom and suck carbon dioxide from the atmosphere.
James Lovelock and Chris Rapley claim that such climate engineering solutions might be the only way to hold global warming at bay given its current progress.
"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. The stakes are now so high that we have to act," said Lovelock.
Other experts are however, sceptical, and have pointed out that the scheme could release more carbon than it absorbs while putting fragile marine life in danger.
The duo, nevertheless, say their proposal is the oceanic equivalent of planting trees.
With more than two-thirds of Earth covered in ocean, the plan could be applied on a much grander scale, they add.
They say their 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," the scientists write in their study in the journal Nature.
"This would stimulate algal growth and help to draw down carbon dioxide," says Lovelock.
They say preliminary laboratory tests using cylindrical pipes in a tank of water have shown that the concept has potential, at least on a small scale.
They say a further benefit from the increased algal blooms would be that they would produce dimethyl sulfide, a chemical that helps sunlight-reflecting clouds to form.
"In principle this idea should work, and it should definitely be examined further," says John Latham, an atmospheric scientist at the University Corporation for Atmospheric Research in Boulder, who is also developing engineering solutions to mitigate climate change.
However, "pumping deep water to the surface would not only pump nutrients up, but also carbon dioxide," adds 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, Chisholm says.
"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," says Eric Achterberg, an oceanographer at the University of Southampton in England.
Scientists say 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," says Toby Tyrrell, an ocean ecology expert at the University of Southampton.